SPACE PROPULSION SYSTEM PHASED-MISSION PROBABILITY ANALYSIS USING CONVENTIONAL PRA METHODS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Curtis Smith; James Knudsen

As part of a series of papers on the topic of advance probabilistic methods, a benchmark phased-mission problem has been suggested. This problem consists of modeling a space mission using an ion propulsion system, where the mission consists of seven mission phases. The mission requires that the propulsion operate for several phases, where the configuration changes as a function of phase. The ion propulsion system itself consists of five thruster assemblies and a single propellant supply, where each thruster assembly has one propulsion power unit and two ion engines. In this paper, we evaluate the probability of mission failure usingmore » the conventional methodology of event tree/fault tree analysis. The event tree and fault trees are developed and analyzed using Systems Analysis Programs for Hands-on Integrated Reliability Evaluations (SAPHIRE). While the benchmark problem is nominally a "dynamic" problem, in our analysis the mission phases are modeled in a single event tree to show the progression from one phase to the next. The propulsion system is modeled in fault trees to account for the operation; or in this case, the failure of the system. Specifically, the propulsion system is decomposed into each of the five thruster assemblies and fed into the appropriate N-out-of-M gate to evaluate mission failure. A separate fault tree for the propulsion system is developed to account for the different success criteria of each mission phase. Common-cause failure modeling is treated using traditional (i.e., parametrically) methods. As part of this paper, we discuss the overall results in addition to the positive and negative aspects of modeling dynamic situations with non-dynamic modeling techniques. One insight from the use of this conventional method for analyzing the benchmark problem is that it requires significant manual manipulation to the fault trees and how they are linked into the event tree. The conventional method also requires editing the resultant cut sets to obtain the correct results. While conventional methods may be used to evaluate a dynamic system like that in the benchmark, the level of effort required may preclude its use on real-world problems.« less

Relating phylogenetic trees to transmission trees of infectious disease outbreaks.

PubMed

Ypma, Rolf J F; van Ballegooijen, W Marijn; Wallinga, Jacco

2013-11-01

Transmission events are the fundamental building blocks of the dynamics of any infectious disease. Much about the epidemiology of a disease can be learned when these individual transmission events are known or can be estimated. Such estimations are difficult and generally feasible only when detailed epidemiological data are available. The genealogy estimated from genetic sequences of sampled pathogens is another rich source of information on transmission history. Optimal inference of transmission events calls for the combination of genetic data and epidemiological data into one joint analysis. A key difficulty is that the transmission tree, which describes the transmission events between infected hosts, differs from the phylogenetic tree, which describes the ancestral relationships between pathogens sampled from these hosts. The trees differ both in timing of the internal nodes and in topology. These differences become more pronounced when a higher fraction of infected hosts is sampled. We show how the phylogenetic tree of sampled pathogens is related to the transmission tree of an outbreak of an infectious disease, by the within-host dynamics of pathogens. We provide a statistical framework to infer key epidemiological and mutational parameters by simultaneously estimating the phylogenetic tree and the transmission tree. We test the approach using simulations and illustrate its use on an outbreak of foot-and-mouth disease. The approach unifies existing methods in the emerging field of phylodynamics with transmission tree reconstruction methods that are used in infectious disease epidemiology.

Modeling time-to-event (survival) data using classification tree analysis.

PubMed

Linden, Ariel; Yarnold, Paul R

2017-12-01

Time to the occurrence of an event is often studied in health research. Survival analysis differs from other designs in that follow-up times for individuals who do not experience the event by the end of the study (called censored) are accounted for in the analysis. Cox regression is the standard method for analysing censored data, but the assumptions required of these models are easily violated. In this paper, we introduce classification tree analysis (CTA) as a flexible alternative for modelling censored data. Classification tree analysis is a "decision-tree"-like classification model that provides parsimonious, transparent (ie, easy to visually display and interpret) decision rules that maximize predictive accuracy, derives exact P values via permutation tests, and evaluates model cross-generalizability. Using empirical data, we identify all statistically valid, reproducible, longitudinally consistent, and cross-generalizable CTA survival models and then compare their predictive accuracy to estimates derived via Cox regression and an unadjusted naïve model. Model performance is assessed using integrated Brier scores and a comparison between estimated survival curves. The Cox regression model best predicts average incidence of the outcome over time, whereas CTA survival models best predict either relatively high, or low, incidence of the outcome over time. Classification tree analysis survival models offer many advantages over Cox regression, such as explicit maximization of predictive accuracy, parsimony, statistical robustness, and transparency. Therefore, researchers interested in accurate prognoses and clear decision rules should consider developing models using the CTA-survival framework. © 2017 John Wiley & Sons, Ltd.

A novel method of fuzzy fault tree analysis combined with VB program to identify and assess the risk of coal dust explosions

PubMed Central

Li, Jia; Wang, Deming; Huang, Zonghou

2017-01-01

Coal dust explosions (CDE) are one of the main threats to the occupational safety of coal miners. Aiming to identify and assess the risk of CDE, this paper proposes a novel method of fuzzy fault tree analysis combined with the Visual Basic (VB) program. In this methodology, various potential causes of the CDE are identified and a CDE fault tree is constructed. To overcome drawbacks from the lack of exact probability data for the basic events, fuzzy set theory is employed and the probability data of each basic event is treated as intuitionistic trapezoidal fuzzy numbers. In addition, a new approach for calculating the weighting of each expert is also introduced in this paper to reduce the error during the expert elicitation process. Specifically, an in-depth quantitative analysis of the fuzzy fault tree, such as the importance measure of the basic events and the cut sets, and the CDE occurrence probability is given to assess the explosion risk and acquire more details of the CDE. The VB program is applied to simplify the analysis process. A case study and analysis is provided to illustrate the effectiveness of this proposed method, and some suggestions are given to take preventive measures in advance and avoid CDE accidents. PMID:28793348

A novel method of fuzzy fault tree analysis combined with VB program to identify and assess the risk of coal dust explosions.

PubMed

Wang, Hetang; Li, Jia; Wang, Deming; Huang, Zonghou

2017-01-01

Coal dust explosions (CDE) are one of the main threats to the occupational safety of coal miners. Aiming to identify and assess the risk of CDE, this paper proposes a novel method of fuzzy fault tree analysis combined with the Visual Basic (VB) program. In this methodology, various potential causes of the CDE are identified and a CDE fault tree is constructed. To overcome drawbacks from the lack of exact probability data for the basic events, fuzzy set theory is employed and the probability data of each basic event is treated as intuitionistic trapezoidal fuzzy numbers. In addition, a new approach for calculating the weighting of each expert is also introduced in this paper to reduce the error during the expert elicitation process. Specifically, an in-depth quantitative analysis of the fuzzy fault tree, such as the importance measure of the basic events and the cut sets, and the CDE occurrence probability is given to assess the explosion risk and acquire more details of the CDE. The VB program is applied to simplify the analysis process. A case study and analysis is provided to illustrate the effectiveness of this proposed method, and some suggestions are given to take preventive measures in advance and avoid CDE accidents.

Preventing medical errors by designing benign failures.

PubMed

Grout, John R

2003-07-01

One way to successfully reduce medical errors is to design health care systems that are more resistant to the tendencies of human beings to err. One interdisciplinary approach entails creating design changes, mitigating human errors, and making human error irrelevant to outcomes. This approach is intended to facilitate the creation of benign failures, which have been called mistake-proofing devices and forcing functions elsewhere. USING FAULT TREES TO DESIGN FORCING FUNCTIONS: A fault tree is a graphical tool used to understand the relationships that either directly cause or contribute to the cause of a particular failure. A careful analysis of a fault tree enables the analyst to anticipate how the process will behave after the change. EXAMPLE OF AN APPLICATION: A scenario in which a patient is scalded while bathing can serve as an example of how multiple fault trees can be used to design forcing functions. The first fault tree shows the undesirable event--patient scalded while bathing. The second fault tree has a benign event--no water. Adding a scald valve changes the outcome from the undesirable event ("patient scalded while bathing") to the benign event ("no water") Analysis of fault trees does not ensure or guarantee that changes necessary to eliminate error actually occur. Most mistake-proofing is used to prevent simple errors and to create well-defended processes, but complex errors can also result. The utilization of mistake-proofing or forcing functions can be thought of as changing the logic of a process. Errors that formerly caused undesirable failures can be converted into the causes of benign failures. The use of fault trees can provide a variety of insights into the design of forcing functions that will improve patient safety.

An object-oriented approach to risk and reliability analysis : methodology and aviation safety applications.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dandini, Vincent John; Duran, Felicia Angelica; Wyss, Gregory Dane

2003-09-01

This article describes how features of event tree analysis and Monte Carlo-based discrete event simulation can be combined with concepts from object-oriented analysis to develop a new risk assessment methodology, with some of the best features of each. The resultant object-based event scenario tree (OBEST) methodology enables an analyst to rapidly construct realistic models for scenarios for which an a priori discovery of event ordering is either cumbersome or impossible. Each scenario produced by OBEST is automatically associated with a likelihood estimate because probabilistic branching is integral to the object model definition. The OBEST methodology is then applied to anmore » aviation safety problem that considers mechanisms by which an aircraft might become involved in a runway incursion incident. The resulting OBEST model demonstrates how a close link between human reliability analysis and probabilistic risk assessment methods can provide important insights into aviation safety phenomenology.« less

Impacts of age-dependent tree sensitivity and dating approaches on dendrogeomorphic time series of landslides

NASA Astrophysics Data System (ADS)

Šilhán, Karel; Stoffel, Markus

2015-05-01

Different approaches and thresholds have been utilized in the past to date landslides with growth ring series of disturbed trees. Past work was mostly based on conifer species because of their well-defined ring boundaries and the easy identification of compression wood after stem tilting. More recently, work has been expanded to include broad-leaved trees, which are thought to produce less and less evident reactions after landsliding. This contribution reviews recent progress made in dendrogeomorphic landslide analysis and introduces a new approach in which landslides are dated via ring eccentricity formed after tilting. We compare results of this new and the more conventional approaches. In addition, the paper also addresses tree sensitivity to landslide disturbance as a function of tree age and trunk diameter using 119 common beech (Fagus sylvatica L.) and 39 Crimean pine (Pinus nigra ssp. pallasiana) trees growing on two landslide bodies. The landslide events reconstructed with the classical approach (reaction wood) also appear as events in the eccentricity analysis, but the inclusion of eccentricity clearly allowed for more (162%) landslides to be detected in the tree-ring series. With respect to tree sensitivity, conifers and broad-leaved trees show the strongest reactions to landslides at ages comprised between 40 and 60 years, with a second phase of increased sensitivity in P. nigra at ages of ca. 120-130 years. These phases of highest sensitivities correspond with trunk diameters at breast height of 6-8 and 18-22 cm, respectively (P. nigra). This study thus calls for the inclusion of eccentricity analyses in future landslide reconstructions as well as for the selection of trees belonging to different age and diameter classes to allow for a well-balanced and more complete reconstruction of past events.

Fault-Tree Compiler Program

NASA Technical Reports Server (NTRS)

Butler, Ricky W.; Martensen, Anna L.

1992-01-01

FTC, Fault-Tree Compiler program, is reliability-analysis software tool used to calculate probability of top event of fault tree. Five different types of gates allowed in fault tree: AND, OR, EXCLUSIVE OR, INVERT, and M OF N. High-level input language of FTC easy to understand and use. Program supports hierarchical fault-tree-definition feature simplifying process of description of tree and reduces execution time. Solution technique implemented in FORTRAN, and user interface in Pascal. Written to run on DEC VAX computer operating under VMS operating system.

Can Religious Beliefs be a Protective Factor for Suicidal Behavior? A Decision Tree Analysis in a Mid-Sized City in Iran, 2013.

PubMed

Baneshi, Mohammad Reza; Haghdoost, Ali Akbar; Zolala, Farzaneh; Nakhaee, Nouzar; Jalali, Maryam; Tabrizi, Reza; Akbari, Maryam

2017-04-01

This study aimed to assess using tree-based models the impact of different dimensions of religion and other risk factors on suicide attempts in the Islamic Republic of Iran. Three hundred patients who attempted suicide and 300 age- and sex-matched patient attendants with other types of disease who referred to Kerman Afzalipour Hospital were recruited for this study following a convenience sampling. Religiosity was assessed by the Duke University Religion Index. A tree-based model was constructed using the Gini Index as the homogeneity criterion. A complementary discrimination analysis was also applied. Variables contributing to the construction of the tree were stressful life events, mental disorder, family support, and religious belief. Strong religious belief was a protective factor for those with a low number of stressful life events and those with a high mental disorder score; 72 % of those who formed these two groups had not attempted suicide. Moreover, 63 % of those with a high number of stressful life events, strong family support, strong problem-solving skills, and a low mental disorder score were less likely to attempt suicide. The significance of four other variables, GHQ, problem-coping skills, friend support, and neuroticism, was revealed in the discrimination analysis. Religious beliefs seem to be an independent factor that can predict risk for suicidal behavior. Based on the decision tree, religious beliefs among people with a high number of stressful life events might not be a dissuading factor. Such subjects need more family support and problem-solving skills.

Fault-Tree Compiler

NASA Technical Reports Server (NTRS)

Butler, Ricky W.; Boerschlein, David P.

1993-01-01

Fault-Tree Compiler (FTC) program, is software tool used to calculate probability of top event in fault tree. Gates of five different types allowed in fault tree: AND, OR, EXCLUSIVE OR, INVERT, and M OF N. High-level input language easy to understand and use. In addition, program supports hierarchical fault-tree definition feature, which simplifies tree-description process and reduces execution time. Set of programs created forming basis for reliability-analysis workstation: SURE, ASSIST, PAWS/STEM, and FTC fault-tree tool (LAR-14586). Written in PASCAL, ANSI-compliant C language, and FORTRAN 77. Other versions available upon request.

Boolean logic tree of graphene-based chemical system for molecular computation and intelligent molecular search query.

PubMed

Huang, Wei Tao; Luo, Hong Qun; Li, Nian Bing

2014-05-06

The most serious, and yet unsolved, problem of constructing molecular computing devices consists in connecting all of these molecular events into a usable device. This report demonstrates the use of Boolean logic tree for analyzing the chemical event network based on graphene, organic dye, thrombin aptamer, and Fenton reaction, organizing and connecting these basic chemical events. And this chemical event network can be utilized to implement fluorescent combinatorial logic (including basic logic gates and complex integrated logic circuits) and fuzzy logic computing. On the basis of the Boolean logic tree analysis and logic computing, these basic chemical events can be considered as programmable "words" and chemical interactions as "syntax" logic rules to construct molecular search engine for performing intelligent molecular search query. Our approach is helpful in developing the advanced logic program based on molecules for application in biosensing, nanotechnology, and drug delivery.

Application of fault tree approach for the causation mechanism of urban haze in Beijing--Considering the risk events related with exhausts of coal combustion.

PubMed

Huang, Weiqing; Fan, Hongbo; Qiu, Yongfu; Cheng, Zhiyu; Qian, Yu

2016-02-15

Haze weather has become a serious environmental pollution problem which occurs in many Chinese cities. One of the most critical factors for the formation of haze weather is the exhausts of coal combustion, thus it is meaningful to figure out the causation mechanism between urban haze and the exhausts of coal combustion. Based on above considerations, the fault tree analysis (FAT) approach was employed for the causation mechanism of urban haze in Beijing by considering the risk events related with the exhausts of coal combustion for the first time. Using this approach, firstly the fault tree of the urban haze causation system connecting with coal combustion exhausts was established; consequently the risk events were discussed and identified; then, the minimal cut sets were successfully determined using Boolean algebra; finally, the structure, probability and critical importance degree analysis of the risk events were completed for the qualitative and quantitative assessment. The study results proved that the FTA was an effective and simple tool for the causation mechanism analysis and risk management of urban haze in China. Copyright © 2015 Elsevier B.V. All rights reserved.

Fault and event tree analyses for process systems risk analysis: uncertainty handling formulations.

PubMed

Ferdous, Refaul; Khan, Faisal; Sadiq, Rehan; Amyotte, Paul; Veitch, Brian

2011-01-01

Quantitative risk analysis (QRA) is a systematic approach for evaluating likelihood, consequences, and risk of adverse events. QRA based on event (ETA) and fault tree analyses (FTA) employs two basic assumptions. The first assumption is related to likelihood values of input events, and the second assumption is regarding interdependence among the events (for ETA) or basic events (for FTA). Traditionally, FTA and ETA both use crisp probabilities; however, to deal with uncertainties, the probability distributions of input event likelihoods are assumed. These probability distributions are often hard to come by and even if available, they are subject to incompleteness (partial ignorance) and imprecision. Furthermore, both FTA and ETA assume that events (or basic events) are independent. In practice, these two assumptions are often unrealistic. This article focuses on handling uncertainty in a QRA framework of a process system. Fuzzy set theory and evidence theory are used to describe the uncertainties in the input event likelihoods. A method based on a dependency coefficient is used to express interdependencies of events (or basic events) in ETA and FTA. To demonstrate the approach, two case studies are discussed. © 2010 Society for Risk Analysis.

Fire safety in transit systems fault tree analysis

DOT National Transportation Integrated Search

1981-09-01

Fire safety countermeasures applicable to transit vehicles are identified and evaluated. This document contains fault trees which illustrate the sequences of events which may lead to a transit-fire related casualty. A description of the basis for the...

Reliability computation using fault tree analysis

NASA Technical Reports Server (NTRS)

Chelson, P. O.

1971-01-01

A method is presented for calculating event probabilities from an arbitrary fault tree. The method includes an analytical derivation of the system equation and is not a simulation program. The method can handle systems that incorporate standby redundancy and it uses conditional probabilities for computing fault trees where the same basic failure appears in more than one fault path.

Fault tree analysis for urban flooding.

PubMed

ten Veldhuis, J A E; Clemens, F H L R; van Gelder, P H A J M

2009-01-01

Traditional methods to evaluate flood risk generally focus on heavy storm events as the principal cause of flooding. Conversely, fault tree analysis is a technique that aims at modelling all potential causes of flooding. It quantifies both overall flood probability and relative contributions of individual causes of flooding. This paper presents a fault model for urban flooding and an application to the case of Haarlem, a city of 147,000 inhabitants. Data from a complaint register, rainfall gauges and hydrodynamic model calculations are used to quantify probabilities of basic events in the fault tree. This results in a flood probability of 0.78/week for Haarlem. It is shown that gully pot blockages contribute to 79% of flood incidents, whereas storm events contribute only 5%. This implies that for this case more efficient gully pot cleaning is a more effective strategy to reduce flood probability than enlarging drainage system capacity. Whether this is also the most cost-effective strategy can only be decided after risk assessment has been complemented with a quantification of consequences of both types of events. To do this will be the next step in this study.

Using Boosting Decision Trees in Gravitational Wave Searches triggered by Gamma-ray Bursts

NASA Astrophysics Data System (ADS)

Zuraw, Sarah; LIGO Collaboration

2015-04-01

The search for gravitational wave bursts requires the ability to distinguish weak signals from background detector noise. Gravitational wave bursts are characterized by their transient nature, making them particularly difficult to detect as they are similar to non-Gaussian noise fluctuations in the detector. The Boosted Decision Tree method is a powerful machine learning algorithm which uses Multivariate Analysis techniques to explore high-dimensional data sets in order to distinguish between gravitational wave signal and background detector noise. It does so by training with known noise events and simulated gravitational wave events. The method is tested using waveform models and compared with the performance of the standard gravitational wave burst search pipeline for Gamma-ray Bursts. It is shown that the method is able to effectively distinguish between signal and background events under a variety of conditions and over multiple Gamma-ray Burst events. This example demonstrates the usefulness and robustness of the Boosted Decision Tree and Multivariate Analysis techniques as a detection method for gravitational wave bursts. LIGO, UMass, PREP, NEGAP.

Monte Carlo sensitivity analysis of unknown parameters in hazardous materials transportation risk assessment.

PubMed

Pet-Armacost, J J; Sepulveda, J; Sakude, M

1999-12-01

The US Department of Transportation was interested in the risks associated with transporting Hydrazine in tanks with and without relief devices. Hydrazine is both highly toxic and flammable, as well as corrosive. Consequently, there was a conflict as to whether a relief device should be used or not. Data were not available on the impact of relief devices on release probabilities or the impact of Hydrazine on the likelihood of fires and explosions. In this paper, a Monte Carlo sensitivity analysis of the unknown parameters was used to assess the risks associated with highway transport of Hydrazine. To help determine whether or not relief devices should be used, fault trees and event trees were used to model the sequences of events that could lead to adverse consequences during transport of Hydrazine. The event probabilities in the event trees were derived as functions of the parameters whose effects were not known. The impacts of these parameters on the risk of toxic exposures, fires, and explosions were analyzed through a Monte Carlo sensitivity analysis and analyzed statistically through an analysis of variance. The analysis allowed the determination of which of the unknown parameters had a significant impact on the risks. It also provided the necessary support to a critical transportation decision even though the values of several key parameters were not known.

A review for identification of initiating events in event tree development process on nuclear power plants

NASA Astrophysics Data System (ADS)

Riyadi, Eko H.

2014-09-01

Initiating event is defined as any event either internal or external to the nuclear power plants (NPPs) that perturbs the steady state operation of the plant, if operating, thereby initiating an abnormal event such as transient or loss of coolant accident (LOCA) within the NPPs. These initiating events trigger sequences of events that challenge plant control and safety systems whose failure could potentially lead to core damage or large early release. Selection for initiating events consists of two steps i.e. first step, definition of possible events, such as by evaluating a comprehensive engineering, and by constructing a top level logic model. Then the second step, grouping of identified initiating event's by the safety function to be performed or combinations of systems responses. Therefore, the purpose of this paper is to discuss initiating events identification in event tree development process and to reviews other probabilistic safety assessments (PSA). The identification of initiating events also involves the past operating experience, review of other PSA, failure mode and effect analysis (FMEA), feedback from system modeling, and master logic diagram (special type of fault tree). By using the method of study for the condition of the traditional US PSA categorization in detail, could be obtained the important initiating events that are categorized into LOCA, transients and external events.

A Fault Tree Approach to Analysis of Behavioral Systems: An Overview.

ERIC Educational Resources Information Center

Stephens, Kent G.

Developed at Brigham Young University, Fault Tree Analysis (FTA) is a technique for enhancing the probability of success in any system by analyzing the most likely modes of failure that could occur. It provides a logical, step-by-step description of possible failure events within a system and their interaction--the combinations of potential…

How different are the results acquired from mathematical and subjective methods in dendrogeomorphology? Insights from landslide movements

NASA Astrophysics Data System (ADS)

Šilhán, Karel

2016-01-01

Knowledge of past landslide activity is crucial for understanding landslide behaviour and for modelling potential future landslide occurrence. Dendrogeomorphic approaches represent the most precise methods of landslide dating (where trees annually create tree-rings in the timescale of up to several hundred years). Despite the advantages of these methods, many open questions remain. One of the less researched uncertainties, and the focus of this study, is the impact of two common methods of geomorphic signal extraction on the spatial and temporal results of landslide reconstruction. In total, 93 Norway spruce (Picea abies (L.) Karst.) trees were sampled at one landslide location dominated by block-type movements in the forefield of the Orlické hory Mts., Bohemian Massif. Landslide signals were examined by the classical subjective method based on reaction (compression) wood analysis and by a numerical method based on eccentric growth analysis. The chronology of landslide movements obtained by the mathematical method resulted in twice the number of events detected compared to the subjective method. This finding indicates that eccentric growth is a more accurate indicator for landslide movements than the classical analysis of reaction wood. The reconstructed spatial activity of landslide movements shows a similar distribution of recurrence intervals (Ri) for both methods. The differences (maximally 30% of the total Ri ranges) in results obtained by both methods may be caused by differences in the ability of trees to react to tilting of their stems by a specific growth response (reaction wood formation or eccentric growth). Finally, the ability of trees to record tilting events (by both growth responses) in their tree-ring series was analysed for different decades of tree life. The highest sensitivity to external tilting events occurred at tree ages from 70 to 80 years for reaction wood formation and from 80 to 90 years for eccentric growth response. This means that the ability of P. abies to record geomorphic signals varies with not only eccentric growth responses but also with age.

Improving the flash flood frequency analysis applying dendrogeomorphological evidences

NASA Astrophysics Data System (ADS)

Ruiz-Villanueva, V.; Ballesteros, J. A.; Bodoque, J. M.; Stoffel, M.; Bollschweiler, M.; Díez-Herrero, A.

2009-09-01

Flash floods are one of the natural hazards that cause major damages worldwide. Especially in Mediterranean areas they provoke high economic losses every year. In mountain areas with high stream gradients, floods events are characterized by extremely high flow and debris transport rates. Flash flood analysis in mountain areas presents specific scientific challenges. On one hand, there is a lack of information on precipitation and discharge due to a lack of spatially well distributed gauge stations with long records. On the other hand, gauge stations may not record correctly during extreme events when they are damaged or the discharge exceeds the recordable level. In this case, no systematic data allows improvement of the understanding of the spatial and temporal occurrence of the process. Since historic documentation is normally scarce or even completely missing in mountain areas, tree-ring analysis can provide an alternative approach. Flash floods may influence trees in different ways: (1) tilting of the stem through the unilateral pressure of the flowing mass or individual boulders; (2) root exposure through erosion of the banks; (3) injuries and scars caused by boulders and wood transported in the flow; (4) decapitation of the stem and resulting candelabra growth through the severe impact of boulders; (5) stem burial through deposition of material. The trees react to these disturbances with specific growth changes such as abrupt change of the yearly increment and anatomical changes like reaction wood or callus tissue. In this study, we sampled 90 cross sections and 265 increment cores of trees heavily affected by past flash floods in order to date past events and to reconstruct recurrence intervals in two torrent channels located in the Spanish Central System. The first study site is located along the Pelayo River, a torrent in natural conditions. Based on the external disturbances of trees and their geomorphological position, 114 Pinus pinaster (Ait.) influenced by flash flood events were sampled using an increment borer. For each tree sampled, additional information were recorded including the geographical position (GPS measure), the geomorphological situation based on a detailed geomorphological map, the social position within neighbouring trees, a description of the external disturbances and information on tree diameter, tree height and the position of the cores extracted. 265 cores were collected. In the laboratory, the 265 samples were analyzed using the standard methods: surface preparation, counting of tree rings as well as measuring of ring widths using a digital LINTAB positioning table and TSAP 4.6 software. Increment curves of the disturbed trees were then crossdated with a reference chronology in order to correct faulty tree-ring series derived from disturbed samples and to determine initiation of abrupt growth suppression or release. The age of the trees in this field site is between 50 and 100 years old. In the field most of the trees were tilted (93 %) and showed exposed roots (64 %). In the laboratory, growth suppressions were detected in 165 samples. Based on the number of trees showing disturbances, the intensity of the disturbance and the spatial distribution of the trees in the field, seven well represented events were dated for the last 50 years: 2005, 2000, 1996, 1976, 1973, 1966 and 1963. The second field site was a reach of 2 km length along the Arenal River, where the stream is channelized. Here stumps from previously felled trees could be analyzed directly in the field. 100 Alnus glutinosa (L.) Gaertn. and Fraxinus angustifolia (Vahl.) cross sections were investigated in order to date internal wounds. Different carpenter tools, sanding paper and magnifying glasses were used to count tree rings and to date the wounds in the field. In addition to the dating in the field, 22 cross sections were sampled and analyzed in the laboratory using the standard methods. The age of the trees ranges between 30 and 50 years. Based on the injuries dated in the field and in the laboratory, and based on the location of the trees, 8 main events were dated for the last 30 years: 2005, 2003, 2000, 1998, 1997, 1995, 1993 and 1978. Additional results are in progress, such as the amount of rainfall responsible for the triggering of the events, estimation of the magnitude, and the influence of the channelization in the case of the Arenal River. The strength of Dendrogeomorphology in flood analysis has been demonstrated, especially in areas where the lack of historical documents, rainfall and flow data limits the use of traditional methods.

Graphical fault tree analysis for fatal falls in the construction industry.

PubMed

Chi, Chia-Fen; Lin, Syuan-Zih; Dewi, Ratna Sari

2014-11-01

The current study applied a fault tree analysis to represent the causal relationships among events and causes that contributed to fatal falls in the construction industry. Four hundred and eleven work-related fatalities in the Taiwanese construction industry were analyzed in terms of age, gender, experience, falling site, falling height, company size, and the causes for each fatality. Given that most fatal accidents involve multiple events, the current study coded up to a maximum of three causes for each fall fatality. After the Boolean algebra and minimal cut set analyses, accident causes associated with each falling site can be presented as a fault tree to provide an overview of the basic causes, which could trigger fall fatalities in the construction industry. Graphical icons were designed for each falling site along with the associated accident causes to illustrate the fault tree in a graphical manner. A graphical fault tree can improve inter-disciplinary discussion of risk management and the communication of accident causation to first line supervisors. Copyright © 2014 Elsevier Ltd. All rights reserved.

Dendrogeomorphological analysis of a slope near Lago, Calabria (Italy)

NASA Astrophysics Data System (ADS)

Fantucci, Rosanna; Sorriso-Valvo, Marino

1999-10-01

The dendrogeomorphological analysis has been used to investigate the periods of disturbance on a slope affected by deep-seated gravitational movements. The method proved to be of great help in determining the temporal sequence of diffused slope movement in the study area, and, though to a lesser extent, to find out the possible causes of triggering the mass-movement. In general, leaning trees indicate that the movement is active. The visual growth analysis indicates that anomalies consisted of sudden decreases of the growth (suppression of tree-rings) induced by stress consequent on ground disturbance, followed in some cases by sudden increases of tree-ring width induced by the higher moisture content in the landslide body. By anomaly analysis, an increase of the anomaly index (It) occurred between 1840 and 1860; subsequently, a period of strongly oscillating values of It occurred that levelled off around 1950. It also appears that mass-movements began to affect this zone soon after 1850s, thus, we can tentatively assume that they have been the cause of the growth anomalies, with a maximum influence in the period between 1860 and 1895. As regards the causes for mass-movement, we inquired about timing of extreme meteorological events and earthquakes. The meteorological data obtained from raingauging stations are not so well related to mass-movement reactivation as the seismic data are. However, only a minority of extreme meteorological events may produce such a disturbance that can be recorded in the tree-ring record. Indeed, only 30% of anomalies can be explained in terms of extreme events. On the other hand, the continuous creeping of the sackung might irregularly trigger the movement of shallower landslides in non extreme-events years. We obtained, instead, a higher degree of coincidence between disturbing causes and anomalous tree growth using archive reports on extreme rainfall periods.

Using inventory data to determine the impact of drought on tree mortality

Treesearch

Greg C. Liknes; Christopher W. Woodall; Charles H. Perry

2012-01-01

Drought has been the subject of numerous recent studies that hint at an acceleration of tree mortality due to climate change. In particular, a recent global survey of tree mortality events implicates drought as the cause of quaking aspen mortality in Minnesota, USA in 2007. In this study, data from the Forest Inventory and Analysis program of the USDA Forest Service...

A review for identification of initiating events in event tree development process on nuclear power plants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riyadi, Eko H., E-mail: e.riyadi@bapeten.go.id

2014-09-30

Initiating event is defined as any event either internal or external to the nuclear power plants (NPPs) that perturbs the steady state operation of the plant, if operating, thereby initiating an abnormal event such as transient or loss of coolant accident (LOCA) within the NPPs. These initiating events trigger sequences of events that challenge plant control and safety systems whose failure could potentially lead to core damage or large early release. Selection for initiating events consists of two steps i.e. first step, definition of possible events, such as by evaluating a comprehensive engineering, and by constructing a top level logicmore » model. Then the second step, grouping of identified initiating event's by the safety function to be performed or combinations of systems responses. Therefore, the purpose of this paper is to discuss initiating events identification in event tree development process and to reviews other probabilistic safety assessments (PSA). The identification of initiating events also involves the past operating experience, review of other PSA, failure mode and effect analysis (FMEA), feedback from system modeling, and master logic diagram (special type of fault tree). By using the method of study for the condition of the traditional US PSA categorization in detail, could be obtained the important initiating events that are categorized into LOCA, transients and external events.« less

Fault tree analysis of the causes of waterborne outbreaks.

PubMed

Risebro, Helen L; Doria, Miguel F; Andersson, Yvonne; Medema, Gertjan; Osborn, Keith; Schlosser, Olivier; Hunter, Paul R

2007-01-01

Prevention and containment of outbreaks requires examination of the contribution and interrelation of outbreak causative events. An outbreak fault tree was developed and applied to 61 enteric outbreaks related to public drinking water supplies in the EU. A mean of 3.25 causative events per outbreak were identified; each event was assigned a score based on percentage contribution per outbreak. Source and treatment system causative events often occurred concurrently (in 34 outbreaks). Distribution system causative events occurred less frequently (19 outbreaks) but were often solitary events contributing heavily towards the outbreak (a mean % score of 87.42). Livestock and rainfall in the catchment with no/inadequate filtration of water sources contributed concurrently to 11 of 31 Cryptosporidium outbreaks. Of the 23 protozoan outbreaks experiencing at least one treatment causative event, 90% of these events were filtration deficiencies; by contrast, for bacterial, viral, gastroenteritis and mixed pathogen outbreaks, 75% of treatment events were disinfection deficiencies. Roughly equal numbers of groundwater and surface water outbreaks experienced at least one treatment causative event (18 and 17 outbreaks, respectively). Retrospective analysis of multiple outbreaks of enteric disease can be used to inform outbreak investigations, facilitate corrective measures, and further develop multi-barrier approaches.

Origin and Possible Genetic Recombination of the Middle East Respiratory Syndrome Coronavirus from the First Imported Case in China: Phylogenetics and Coalescence Analysis

PubMed Central

Wang, Yanqun; Liu, Di; Shi, Weifeng; Lu, Roujian; Wang, Wenling; Zhao, Yanjie; Deng, Yao; Zhou, Weimin; Ren, Hongguang; Wu, Jun; Wang, Yu; Wu, Guizhen

2015-01-01

ABSTRACT The Middle East respiratory syndrome coronavirus (MERS-CoV) causes a severe acute respiratory tract infection with a high fatality rate in humans. Coronaviruses are capable of infecting multiple species and can evolve rapidly through recombination events. Here, we report the complete genomic sequence analysis of a MERS-CoV strain imported to China from South Korea. The imported virus, provisionally named ChinaGD01, belongs to group 3 in clade B in the whole-genome phylogenetic tree and also has a similar tree topology structure in the open reading frame 1a and -b (ORF1ab) gene segment but clusters with group 5 of clade B in the tree constructed using the S gene. Genetic recombination analysis and lineage-specific single-nucleotide polymorphism (SNP) comparison suggest that the imported virus is a recombinant comprising group 3 and group 5 elements. The time-resolved phylogenetic estimation indicates that the recombination event likely occurred in the second half of 2014. Genetic recombination events between group 3 and group 5 of clade B may have implications for the transmissibility of the virus. PMID:26350969

The weakest t-norm based intuitionistic fuzzy fault-tree analysis to evaluate system reliability.

PubMed

Kumar, Mohit; Yadav, Shiv Prasad

2012-07-01

In this paper, a new approach of intuitionistic fuzzy fault-tree analysis is proposed to evaluate system reliability and to find the most critical system component that affects the system reliability. Here weakest t-norm based intuitionistic fuzzy fault tree analysis is presented to calculate fault interval of system components from integrating expert's knowledge and experience in terms of providing the possibility of failure of bottom events. It applies fault-tree analysis, α-cut of intuitionistic fuzzy set and T(ω) (the weakest t-norm) based arithmetic operations on triangular intuitionistic fuzzy sets to obtain fault interval and reliability interval of the system. This paper also modifies Tanaka et al.'s fuzzy fault-tree definition. In numerical verification, a malfunction of weapon system "automatic gun" is presented as a numerical example. The result of the proposed method is compared with the listing approaches of reliability analysis methods. Copyright © 2012 ISA. Published by Elsevier Ltd. All rights reserved.

Fault trees for decision making in systems analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lambert, Howard E.

1975-10-09

The application of fault tree analysis (FTA) to system safety and reliability is presented within the framework of system safety analysis. The concepts and techniques involved in manual and automated fault tree construction are described and their differences noted. The theory of mathematical reliability pertinent to FTA is presented with emphasis on engineering applications. An outline of the quantitative reliability techniques of the Reactor Safety Study is given. Concepts of probabilistic importance are presented within the fault tree framework and applied to the areas of system design, diagnosis and simulation. The computer code IMPORTANCE ranks basic events and cut setsmore » according to a sensitivity analysis. A useful feature of the IMPORTANCE code is that it can accept relative failure data as input. The output of the IMPORTANCE code can assist an analyst in finding weaknesses in system design and operation, suggest the most optimal course of system upgrade, and determine the optimal location of sensors within a system. A general simulation model of system failure in terms of fault tree logic is described. The model is intended for efficient diagnosis of the causes of system failure in the event of a system breakdown. It can also be used to assist an operator in making decisions under a time constraint regarding the future course of operations. The model is well suited for computer implementation. New results incorporated in the simulation model include an algorithm to generate repair checklists on the basis of fault tree logic and a one-step-ahead optimization procedure that minimizes the expected time to diagnose system failure.« less

Method and system for dynamic probabilistic risk assessment

NASA Technical Reports Server (NTRS)

Dugan, Joanne Bechta (Inventor); Xu, Hong (Inventor)

2013-01-01

The DEFT methodology, system and computer readable medium extends the applicability of the PRA (Probabilistic Risk Assessment) methodology to computer-based systems, by allowing DFT (Dynamic Fault Tree) nodes as pivot nodes in the Event Tree (ET) model. DEFT includes a mathematical model and solution algorithm, supports all common PRA analysis functions and cutsets. Additional capabilities enabled by the DFT include modularization, phased mission analysis, sequence dependencies, and imperfect coverage.

Reliability analysis of a wastewater treatment plant using fault tree analysis and Monte Carlo simulation.

PubMed

Taheriyoun, Masoud; Moradinejad, Saber

2015-01-01

The reliability of a wastewater treatment plant is a critical issue when the effluent is reused or discharged to water resources. Main factors affecting the performance of the wastewater treatment plant are the variation of the influent, inherent variability in the treatment processes, deficiencies in design, mechanical equipment, and operational failures. Thus, meeting the established reuse/discharge criteria requires assessment of plant reliability. Among many techniques developed in system reliability analysis, fault tree analysis (FTA) is one of the popular and efficient methods. FTA is a top down, deductive failure analysis in which an undesired state of a system is analyzed. In this study, the problem of reliability was studied on Tehran West Town wastewater treatment plant. This plant is a conventional activated sludge process, and the effluent is reused in landscape irrigation. The fault tree diagram was established with the violation of allowable effluent BOD as the top event in the diagram, and the deficiencies of the system were identified based on the developed model. Some basic events are operator's mistake, physical damage, and design problems. The analytical method is minimal cut sets (based on numerical probability) and Monte Carlo simulation. Basic event probabilities were calculated according to available data and experts' opinions. The results showed that human factors, especially human error had a great effect on top event occurrence. The mechanical, climate, and sewer system factors were in subsequent tier. Literature shows applying FTA has been seldom used in the past wastewater treatment plant (WWTP) risk analysis studies. Thus, the developed FTA model in this study considerably improves the insight into causal failure analysis of a WWTP. It provides an efficient tool for WWTP operators and decision makers to achieve the standard limits in wastewater reuse and discharge to the environment.

A comparative critical study between FMEA and FTA risk analysis methods

NASA Astrophysics Data System (ADS)

Cristea, G.; Constantinescu, DM

2017-10-01

Today there is used an overwhelming number of different risk analyses techniques with acronyms such as: FMEA (Failure Modes and Effects Analysis) and its extension FMECA (Failure Mode, Effects, and Criticality Analysis), DRBFM (Design Review by Failure Mode), FTA (Fault Tree Analysis) and and its extension ETA (Event Tree Analysis), HAZOP (Hazard & Operability Studies), HACCP (Hazard Analysis and Critical Control Points) and What-if/Checklist. However, the most used analysis techniques in the mechanical and electrical industry are FMEA and FTA. In FMEA, which is an inductive method, information about the consequences and effects of the failures is usually collected through interviews with experienced people, and with different knowledge i.e., cross-functional groups. The FMEA is used to capture potential failures/risks & impacts and prioritize them on a numeric scale called Risk Priority Number (RPN) which ranges from 1 to 1000. FTA is a deductive method i.e., a general system state is decomposed into chains of more basic events of components. The logical interrelationship of how such basic events depend on and affect each other is often described analytically in a reliability structure which can be visualized as a tree. Both methods are very time-consuming to be applied thoroughly, and this is why it is oftenly not done so. As a consequence possible failure modes may not be identified. To address these shortcomings, it is proposed to use a combination of FTA and FMEA.

Two-dimensional fuzzy fault tree analysis for chlorine release from a chlor-alkali industry using expert elicitation.

PubMed

Renjith, V R; Madhu, G; Nayagam, V Lakshmana Gomathi; Bhasi, A B

2010-11-15

The hazards associated with major accident hazard (MAH) industries are fire, explosion and toxic gas releases. Of these, toxic gas release is the worst as it has the potential to cause extensive fatalities. Qualitative and quantitative hazard analyses are essential for the identification and quantification of these hazards related to chemical industries. Fault tree analysis (FTA) is an established technique in hazard identification. This technique has the advantage of being both qualitative and quantitative, if the probabilities and frequencies of the basic events are known. This paper outlines the estimation of the probability of release of chlorine from storage and filling facility of chlor-alkali industry using FTA. An attempt has also been made to arrive at the probability of chlorine release using expert elicitation and proven fuzzy logic technique for Indian conditions. Sensitivity analysis has been done to evaluate the percentage contribution of each basic event that could lead to chlorine release. Two-dimensional fuzzy fault tree analysis (TDFFTA) has been proposed for balancing the hesitation factor involved in expert elicitation. Copyright © 2010 Elsevier B.V. All rights reserved.

Wood anatomical analysis of Alnus incana and Betula pendula injured by a debris-flow event.

PubMed

Arbellay, Estelle; Stoffel, Markus; Bollschweiler, Michelle

2010-10-01

Vessel chronologies in ring-porous species have been successfully employed in the past to extract the climate signal from tree rings. Environmental signals recorded in vessels of ring-porous species have also been used in previous studies to reconstruct discrete events of drought, flooding and insect defoliation. However, very little is known about the ability of diffuse-porous species to record environmental signals in their xylem cells. Moreover, time series of wood anatomical features have only rarely been used to reconstruct former geomorphic events. This study was therefore undertaken to characterize the wood anatomical response of diffuse-porous Alnus incana (L.) Moench and Betula pendula Roth to debris-flow-induced wounding. Tree microscopic response to wounding was assessed through the analysis of wood anatomical differences between injured rings formed in the debris-flow event year and uninjured rings formed in the previous year. The two ring types were examined close and opposite to the injury in order to determine whether wound effects on xylem cells decrease with increasing tangential distance from the injury. Image analysis was used to measure vessel parameters as well as fiber and parenchyma cell (FPC) parameters. The results of this study indicate that injured rings are characterized by smaller vessels as compared with uninjured rings. By contrast, FPC parameters were not found to significantly differ between injured and uninjured rings. Vessel and FPC parameters mainly remained constant with increasing tangential distance from the injury, except for a higher proportion of vessel lumen area opposite to the injury within A. incana. This study highlights the existence of anatomical tree-ring signatures-in the form of smaller vessels-related to past debris-flow activity and addresses a new methodological approach to date injuries inflicted on trees by geomorphic processes.

Fault tree analysis: NiH2 aerospace cells for LEO mission

NASA Technical Reports Server (NTRS)

Klein, Glenn C.; Rash, Donald E., Jr.

1992-01-01

The Fault Tree Analysis (FTA) is one of several reliability analyses or assessments applied to battery cells to be utilized in typical Electric Power Subsystems for spacecraft in low Earth orbit missions. FTA is generally the process of reviewing and analytically examining a system or equipment in such a way as to emphasize the lower level fault occurrences which directly or indirectly contribute to the major fault or top level event. This qualitative FTA addresses the potential of occurrence for five specific top level events: hydrogen leakage through either discrete leakage paths or through pressure vessel rupture; and four distinct modes of performance degradation - high charge voltage, suppressed discharge voltage, loss of capacity, and high pressure.

Methodology for Collision Risk Assessment of an Airspace Flow Corridor Concept

NASA Astrophysics Data System (ADS)

Zhang, Yimin

This dissertation presents a methodology to estimate the collision risk associated with a future air-transportation concept called the flow corridor. The flow corridor is a Next Generation Air Transportation System (NextGen) concept to reduce congestion and increase throughput in en-route airspace. The flow corridor has the potential to increase throughput by reducing the controller workload required to manage aircraft outside the corridor and by reducing separation of aircraft within corridor. The analysis in this dissertation is a starting point for the safety analysis required by the Federal Aviation Administration (FAA) to eventually approve and implement the corridor concept. This dissertation develops a hybrid risk analysis methodology that combines Monte Carlo simulation with dynamic event tree analysis. The analysis captures the unique characteristics of the flow corridor concept, including self-separation within the corridor, lane change maneuvers, speed adjustments, and the automated separation assurance system. Monte Carlo simulation is used to model the movement of aircraft in the flow corridor and to identify precursor events that might lead to a collision. Since these precursor events are not rare, standard Monte Carlo simulation can be used to estimate these occurrence rates. Dynamic event trees are then used to model the subsequent series of events that may lead to collision. When two aircraft are on course for a near-mid-air collision (NMAC), the on-board automated separation assurance system provides a series of safety layers to prevent the impending NNAC or collision. Dynamic event trees are used to evaluate the potential failures of these layers in order to estimate the rare-event collision probabilities. The results show that the throughput can be increased by reducing separation to 2 nautical miles while maintaining the current level of safety. A sensitivity analysis shows that the most critical parameters in the model related to the overall collision probability are the minimum separation, the probability that both flights fail to respond to traffic collision avoidance system, the probability that an NMAC results in a collision, the failure probability of the automatic dependent surveillance broadcast in receiver, and the conflict detection probability.

Selective Tree-ring Models: A Novel Method for Reconstructing Streamflow Using Tree Rings

NASA Astrophysics Data System (ADS)

Foard, M. B.; Nelson, A. S.; Harley, G. L.

2017-12-01

Surface water is among the most instrumental and vulnerable resources in the Northwest United States (NW). Recent observations show that overall water quantity is declining in streams across the region, while extreme flooding events occur more frequently. Historical streamflow models inform probabilities of extreme flow events (flood or drought) by describing frequency and duration of past events. There are numerous examples of tree-rings being utilized to reconstruct streamflow in the NW. These models confirm that tree-rings are highly accurate at predicting streamflow, however there are many nuances that limit their applicability through time and space. For example, most models predict streamflow from hydrologically altered rivers (e.g. dammed, channelized) which may hinder our ability to predict natural prehistoric flow. They also have a tendency to over/under-predict extreme flow events. Moreover, they often neglect to capture the changing relationships between tree-growth and streamflow over time and space. To address these limitations, we utilized national tree-ring and streamflow archives to investigate the relationships between the growth of multiple coniferous species and free-flowing streams across the NW using novel species-and site-specific streamflow models - a term we coined"selective tree-ring models." Correlation function analysis and regression modeling were used to evaluate the strengths and directions of the flow-growth relationships. Species with significant relationships in the same direction were identified as strong candidates for selective models. Temporal and spatial patterns of these relationships were examined using running correlations and inverse distance weighting interpolation, respectively. Our early results indicate that (1) species adapted to extreme climates (e.g. hot-dry, cold-wet) exhibit the most consistent relationships across space, (2) these relationships weaken in locations with mild climatic variability, and (3) some species appear to be strong candidates for predicting high flow events, while others may be better at pridicting drought. These findings indicate that selective models may outperform traditional models when reconstructing distinctive aspects of streamflow.

Direct evaluation of fault trees using object-oriented programming techniques

NASA Technical Reports Server (NTRS)

Patterson-Hine, F. A.; Koen, B. V.

1989-01-01

Object-oriented programming techniques are used in an algorithm for the direct evaluation of fault trees. The algorithm combines a simple bottom-up procedure for trees without repeated events with a top-down recursive procedure for trees with repeated events. The object-oriented approach results in a dynamic modularization of the tree at each step in the reduction process. The algorithm reduces the number of recursive calls required to solve trees with repeated events and calculates intermediate results as well as the solution of the top event. The intermediate results can be reused if part of the tree is modified. An example is presented in which the results of the algorithm implemented with conventional techniques are compared to those of the object-oriented approach.

Predicting Tree Mortality Die-off Events Associated with Hotter Drought and Assessing Their Global Consequences via Ecoclimate Teleconnections.

NASA Astrophysics Data System (ADS)

Breshears, D. D.; Allen, C. D.; McDowell, N. G.; Adams, H. D.; Barnes, M.; Barron-Gafford, G.; Bradford, J. B.; Cobb, N.; Field, J. P.; Froend, R.; Fontaine, J. B.; Garcia, E.; Hardy, G. E. S. J.; Huxman, T. E.; Kala, J.; Lague, M. M.; Martinez-Yrizar, A.; Matusick, G.; Minor, D. M.; Moore, D. J.; Ng, M.; Ruthrof, K. X.; Saleska, S. R.; Stark, S. C.; Swann, A. L. S.; Villegas, J. C.; Williams, A. P.; Zou, C.

2017-12-01

Evidence that tree mortality is increasingly likely occur in extensive die-off events across the terrestrial biosphere continues to mount. The consequences of such extensive mortality events are potentially profound, not only for the locations where die-off events occur, but also for other locations that could be impacted via ecoclimate teleconnections, whereby the land surface changes associated with die-off in one location could alter atmospheric circulation patterns and affect vegetation elsewhere. Here, we (1) recap the background of tree mortality as an emerging environmental issue, (2) highlight recent advances that could help us improve predictions of the vulnerability to tree mortality, including the underlying importance of hydraulic failure, the potential to develop climatic envelopes specific to tree mortality events, and consideration of the role of heat waves; and (3) initial bounding simulations that indicate the potential for tree die-off events in different locations to alter ecoclimate teleconnections. As we move toward globally coordinated carbon accounting and management, the high vulnerability to tree die-off events and the potential for such events to affect vegetation elsewhere will both need to be accounted for.

Vegetation optical depth measured by microwave radiometry as an indicator of tree mortality risk

NASA Astrophysics Data System (ADS)

Rao, K.; Anderegg, W.; Sala, A.; Martínez-Vilalta, J.; Konings, A. G.

2017-12-01

Increased drought-related tree mortality has been observed across several regions in recent years. Vast spatial extent and high temporal variability makes field monitoring of tree mortality cumbersome and expensive. With global coverage and high temporal revisit, satellite remote sensing offers an unprecedented tool to monitor terrestrial ecosystems and identify areas at risk of large drought-driven tree mortality events. To date, studies that use remote sensing data to monitor tree mortality have focused on external climatic thresholds such as temperature and evapotranspiration. However, this approach fails to consider internal water stress in vegetation - which can vary across trees even for similar climatic conditions due to differences in hydraulic behavior, soil type, etc - and may therefore be a poor basis for measuring mortality events. There is a consensus that xylem hydraulic failure often precedes drought-induced mortality, suggesting depleted canopy water content shortly before onset of mortality. Observations of vegetation optical depth (VOD) derived from passive microwave are proportional to canopy water content. In this study, we propose to use variations in VOD as an indicator of potential tree mortality. Since VOD accounts for intrinsic water stress undergone by vegetation, it is expected to be more accurate than external climatic stress indicators. Analysis of tree mortality events in California, USA observed by airborne detection shows a consistent relationship between mortality and the proposed VOD metric. Although this approach is limited by the kilometer-scale resolution of passive microwave radiometry, our results nevertheless demonstrate that microwave-derived estimates of vegetation water content can be used to study drought-driven tree mortality, and may be a valuable tool for mortality predictions if they can be combined with higher-resolution variables.

Modification of the SAS4A Safety Analysis Code for Integration with the ADAPT Discrete Dynamic Event Tree Framework.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jankovsky, Zachary Kyle; Denman, Matthew R.

It is difficult to assess the consequences of a transient in a sodium-cooled fast reactor (SFR) using traditional probabilistic risk assessment (PRA) methods, as numerous safety-related sys- tems have passive characteristics. Often there is significant dependence on the value of con- tinuous stochastic parameters rather than binary success/failure determinations. One form of dynamic PRA uses a system simulator to represent the progression of a transient, tracking events through time in a discrete dynamic event tree (DDET). In order to function in a DDET environment, a simulator must have characteristics that make it amenable to changing physical parameters midway through themore » analysis. The SAS4A SFR system analysis code did not have these characteristics as received. This report describes the code modifications made to allow dynamic operation as well as the linking to a Sandia DDET driver code. A test case is briefly described to demonstrate the utility of the changes.« less

Uncertainty analysis in fault tree models with dependent basic events.

PubMed

Pedroni, Nicola; Zio, Enrico

2013-06-01

In general, two types of dependence need to be considered when estimating the probability of the top event (TE) of a fault tree (FT): "objective" dependence between the (random) occurrences of different basic events (BEs) in the FT and "state-of-knowledge" (epistemic) dependence between estimates of the epistemically uncertain probabilities of some BEs of the FT model. In this article, we study the effects on the TE probability of objective and epistemic dependences. The well-known Frèchet bounds and the distribution envelope determination (DEnv) method are used to model all kinds of (possibly unknown) objective and epistemic dependences, respectively. For exemplification, the analyses are carried out on a FT with six BEs. Results show that both types of dependence significantly affect the TE probability; however, the effects of epistemic dependence are likely to be overwhelmed by those of objective dependence (if present). © 2012 Society for Risk Analysis.

[Impact of water pollution risk in water transfer project based on fault tree analysis].

PubMed

Liu, Jian-Chang; Zhang, Wei; Wang, Li-Min; Li, Dai-Qing; Fan, Xiu-Ying; Deng, Hong-Bing

2009-09-15

The methods to assess water pollution risk for medium water transfer are gradually being explored. The event-nature-proportion method was developed to evaluate the probability of the single event. Fault tree analysis on the basis of calculation on single event was employed to evaluate the extent of whole water pollution risk for the channel water body. The result indicates, that the risk of pollutants from towns and villages along the line of water transfer project to the channel water body is at high level with the probability of 0.373, which will increase pollution to the channel water body at the rate of 64.53 mg/L COD, 4.57 mg/L NH4(+) -N and 0.066 mg/L volatilization hydroxybenzene, respectively. The measurement of fault probability on the basis of proportion method is proved to be useful in assessing water pollution risk under much uncertainty.

Forest tree responses to extreme drought and some biotic events: Towards a selection according to hazard tolerance?

NASA Astrophysics Data System (ADS)

Bréda, Nathalie; Badeau, Vincent

2008-09-01

The aim of this paper is to illustrate how some extreme events could affect forest ecosystems. Forest tree response can be analysed using dendroecological methods, as tree-ring widths are strongly controlled by climatic or biotic events. Years with such events induce similar tree responses and are called pointer years. They can result from extreme climatic events like frost, a heat wave, spring water logging, drought or insect damage… Forest tree species showed contrasting responses to climatic hazards, depending on their sensitivity to water shortage or temperature hardening, as illustrated from our dendrochronological database. For foresters, a drought or a pest disease is an extreme event if visible and durable symptoms are induced (leaf discolouration, leaf loss, perennial organs mortality, tree dieback and mortality). These symptoms here are shown, lagging one or several years behind a climatic or biotic event, from forest decline cases in progress since the 2003 drought or attributed to previous severe droughts or defoliations in France. Tree growth or vitality recovery is illustrated, and the functional interpretation of the long lasting memory of trees is discussed. A coupled approach linking dendrochronology and ecophysiology helps in discussing vulnerability of forest stands, and suggests management advices in order to mitigate extreme drought and cope with selective mortality.

Interim reliability evaluation program, Browns Ferry 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mays, S.E.; Poloski, J.P.; Sullivan, W.H.

1981-01-01

Probabilistic risk analysis techniques, i.e., event tree and fault tree analysis, were utilized to provide a risk assessment of the Browns Ferry Nuclear Plant Unit 1. Browns Ferry 1 is a General Electric boiling water reactor of the BWR 4 product line with a Mark 1 (drywell and torus) containment. Within the guidelines of the IREP Procedure and Schedule Guide, dominant accident sequences that contribute to public health and safety risks were identified and grouped according to release categories.

Testing for Independence between Evolutionary Processes.

PubMed

Behdenna, Abdelkader; Pothier, Joël; Abby, Sophie S; Lambert, Amaury; Achaz, Guillaume

2016-09-01

Evolutionary events co-occurring along phylogenetic trees usually point to complex adaptive phenomena, sometimes implicating epistasis. While a number of methods have been developed to account for co-occurrence of events on the same internal or external branch of an evolutionary tree, there is a need to account for the larger diversity of possible relative positions of events in a tree. Here we propose a method to quantify to what extent two or more evolutionary events are associated on a phylogenetic tree. The method is applicable to any discrete character, like substitutions within a coding sequence or gains/losses of a biological function. Our method uses a general approach to statistically test for significant associations between events along the tree, which encompasses both events inseparable on the same branch, and events genealogically ordered on different branches. It assumes that the phylogeny and themapping of branches is known without errors. We address this problem from the statistical viewpoint by a linear algebra representation of the localization of the evolutionary events on the tree.We compute the full probability distribution of the number of paired events occurring in the same branch or in different branches of the tree, under a null model of independence where each type of event occurs at a constant rate uniformly inthephylogenetic tree. The strengths andweaknesses of themethodare assessed via simulations;we then apply the method to explore the loss of cell motility in intracellular pathogens. © The Author(s) 2016. Published by Oxford University Press, on behalf of the Society of Systematic Biologists. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Probability and possibility-based representations of uncertainty in fault tree analysis.

PubMed

Flage, Roger; Baraldi, Piero; Zio, Enrico; Aven, Terje

2013-01-01

Expert knowledge is an important source of input to risk analysis. In practice, experts might be reluctant to characterize their knowledge and the related (epistemic) uncertainty using precise probabilities. The theory of possibility allows for imprecision in probability assignments. The associated possibilistic representation of epistemic uncertainty can be combined with, and transformed into, a probabilistic representation; in this article, we show this with reference to a simple fault tree analysis. We apply an integrated (hybrid) probabilistic-possibilistic computational framework for the joint propagation of the epistemic uncertainty on the values of the (limiting relative frequency) probabilities of the basic events of the fault tree, and we use possibility-probability (probability-possibility) transformations for propagating the epistemic uncertainty within purely probabilistic and possibilistic settings. The results of the different approaches (hybrid, probabilistic, and possibilistic) are compared with respect to the representation of uncertainty about the top event (limiting relative frequency) probability. Both the rationale underpinning the approaches and the computational efforts they require are critically examined. We conclude that the approaches relevant in a given setting depend on the purpose of the risk analysis, and that further research is required to make the possibilistic approaches operational in a risk analysis context. © 2012 Society for Risk Analysis.

Assessment of tree response to drought: validation of a methodology to identify and test proxies for monitoring past environmental changes in trees.

PubMed

Tene, A; Tobin, B; Dyckmans, J; Ray, D; Black, K; Nieuwenhuis, M

2011-03-01

A thinning experiment stand at Avoca, Ballinvalley, on the east coast of the Republic of Ireland was used to test a developed methodology aimed at monitoring drought stress, based on the analysis of growth rings obtained by coring. The stand incorporated six plots representing three thinning regimes (light, moderate and heavy) and was planted in the spring of 1943 on a brown earth soil. Radial growth (early- and latewood) was measured for the purpose of this study. A multidisciplinary approach was used to assess historic tree response to climate: specifically, the application of statistical tools such as principal component and canonical correlation analysis to dendrochronology, stable isotopes, ring density proxy, blue reflectance and forest biometrics. Results showed that radial growth was a good proxy for monitoring changes to moisture deficit, while maximum density and blue reflectance were appropriate for assessing changes in accumulated temperature for the growing season. Rainfall also influenced radial growth changes but not significantly, and was a major factor in stable carbon and oxygen discrimination, mostly in the latewood formation phase. Stable oxygen isotope analysis was more accurate than radial growth analysis in drought detection, as it helped detect drought signals in both early- and latewood while radial growth analysis only detected the drought signal in earlywood. Many studies have shown that tree rings provide vital information for marking past climatic events. This work provides a methodology to better identify and understand how commonly measured tree proxies relate to environmental parameters, and can best be used to characterize and pinpoint drought events (variously described using parameters such as like moisture deficit, accumulated temperature, rainfall and potential evaporation).

Risk Analysis of Earth-Rock Dam Failures Based on Fuzzy Event Tree Method

PubMed Central

Fu, Xiao; Gu, Chong-Shi; Su, Huai-Zhi; Qin, Xiang-Nan

2018-01-01

Earth-rock dams make up a large proportion of the dams in China, and their failures can induce great risks. In this paper, the risks associated with earth-rock dam failure are analyzed from two aspects: the probability of a dam failure and the resulting life loss. An event tree analysis method based on fuzzy set theory is proposed to calculate the dam failure probability. The life loss associated with dam failure is summarized and refined to be suitable for Chinese dams from previous studies. The proposed method and model are applied to one reservoir dam in Jiangxi province. Both engineering and non-engineering measures are proposed to reduce the risk. The risk analysis of the dam failure has essential significance for reducing dam failure probability and improving dam risk management level. PMID:29710824

Gene-Tree Reconciliation with MUL-Trees to Resolve Polyploidy Events.

PubMed

Gregg, W C Thomas; Ather, S Hussain; Hahn, Matthew W

2017-11-01

Polyploidy can have a huge impact on the evolution of species, and it is a common occurrence, especially in plants. The two types of polyploids-autopolyploids and allopolyploids-differ in the level of divergence between the genes that are brought together in the new polyploid lineage. Because allopolyploids are formed via hybridization, the homoeologous copies of genes within them are at least as divergent as orthologs in the parental species that came together to form them. This means that common methods for estimating the parental lineages of allopolyploidy events are not accurate, and can lead to incorrect inferences about the number of gene duplications and losses. Here, we have adapted an algorithm for topology-based gene-tree reconciliation to work with multi-labeled trees (MUL-trees). By definition, MUL-trees have some tips with identical labels, which makes them a natural representation of the genomes of polyploids. Using this new reconciliation algorithm we can: accurately place allopolyploidy events on a phylogeny, identify the parental lineages that hybridized to form allopolyploids, distinguish between allo-, auto-, and (in most cases) no polyploidy, and correctly count the number of duplications and losses in a set of gene trees. We validate our method using gene trees simulated with and without polyploidy, and revisit the history of polyploidy in data from the clades including both baker's yeast and bread wheat. Our re-analysis of the yeast data confirms the allopolyploid origin and parental lineages previously identified for this group. The method presented here should find wide use in the growing number of genomes from species with a history of polyploidy. [Polyploidy; reconciliation; whole-genome duplication.]. © The Author(s) 2017. Published by Oxford University Press, on behalf of the Society of Systematic Biologists. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Fault tree analysis for system modeling in case of intentional EMI

NASA Astrophysics Data System (ADS)

Genender, E.; Mleczko, M.; Döring, O.; Garbe, H.; Potthast, S.

2011-08-01

The complexity of modern systems on the one hand and the rising threat of intentional electromagnetic interference (IEMI) on the other hand increase the necessity for systematical risk analysis. Most of the problems can not be treated deterministically since slight changes in the configuration (source, position, polarization, ...) can dramatically change the outcome of an event. For that purpose, methods known from probabilistic risk analysis can be applied. One of the most common approaches is the fault tree analysis (FTA). The FTA is used to determine the system failure probability and also the main contributors to its failure. In this paper the fault tree analysis is introduced and a possible application of that method is shown using a small computer network as an example. The constraints of this methods are explained and conclusions for further research are drawn.

Analysis of transcripts differentially expressed between fruited and deflowered 'Gala' adult trees: a contribution to biennial bearing understanding in apple.

PubMed

Guitton, B; Kelner, J J; Celton, J M; Sabau, X; Renou, J P; Chagné, D; Costes, E

2016-02-29

The transition from vegetative to floral state in shoot apical meristems (SAM) is a key event in plant development and is of crucial importance for reproductive success. In perennial plants, this event is recurrent during tree life and subject to both within-tree and between-years heterogeneity. In the present study, our goal was to identify candidate processes involved in the repression or induction of flowering in apical buds of adult apple trees. Genes differentially expressed (GDE) were examined between trees artificially set in either 'ON' or 'OFF' situation, and in which floral induction (FI) was shown to be inhibited or induced in most buds, respectively, using qRT-PCR and microarray analysis. From the period of FI through to flower differentiation, GDE belonged to four main biological processes (i) response to stimuli, including response to oxidative stress; (ii) cellular processes, (iii) cell wall biogenesis, and (iv) metabolic processes including carbohydrate biosynthesis and lipid metabolic process. Several key regulator genes, especially TEMPRANILLO (TEM), FLORAL TRANSITION AT MERISTEM (FTM1) and SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) were found differentially expressed. Moreover, homologs of SPL and Leucine-Rich Repeat proteins were present under QTL zones previously detected for biennial bearing. This data set suggests that apical buds of 'ON' and 'OFF' trees were in different physiological states, resulting from different metabolic, hormonal and redox status which are likely to contribute to FI control in adult apple trees. Investigations on carbohydrate and hormonal fluxes from sources to SAM and on cell detoxification process are expected to further contribute to the identification of the underlying physiological mechanisms of FI in adult apple trees.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarrack, A.G.

The purpose of this report is to document fault tree analyses which have been completed for the Defense Waste Processing Facility (DWPF) safety analysis. Logic models for equipment failures and human error combinations that could lead to flammable gas explosions in various process tanks, or failure of critical support systems were developed for internal initiating events and for earthquakes. These fault trees provide frequency estimates for support systems failures and accidents that could lead to radioactive and hazardous chemical releases both on-site and off-site. Top event frequency results from these fault trees will be used in further APET analyses tomore » calculate accident risk associated with DWPF facility operations. This report lists and explains important underlying assumptions, provides references for failure data sources, and briefly describes the fault tree method used. Specific commitments from DWPF to provide new procedural/administrative controls or system design changes are listed in the ''Facility Commitments'' section. The purpose of the ''Assumptions'' section is to clarify the basis for fault tree modeling, and is not necessarily a list of items required to be protected by Technical Safety Requirements (TSRs).« less

Fault tree analysis for integrated and probabilistic risk analysis of drinking water systems.

PubMed

Lindhe, Andreas; Rosén, Lars; Norberg, Tommy; Bergstedt, Olof

2009-04-01

Drinking water systems are vulnerable and subject to a wide range of risks. To avoid sub-optimisation of risk-reduction options, risk analyses need to include the entire drinking water system, from source to tap. Such an integrated approach demands tools that are able to model interactions between different events. Fault tree analysis is a risk estimation tool with the ability to model interactions between events. Using fault tree analysis on an integrated level, a probabilistic risk analysis of a large drinking water system in Sweden was carried out. The primary aims of the study were: (1) to develop a method for integrated and probabilistic risk analysis of entire drinking water systems; and (2) to evaluate the applicability of Customer Minutes Lost (CML) as a measure of risk. The analysis included situations where no water is delivered to the consumer (quantity failure) and situations where water is delivered but does not comply with water quality standards (quality failure). Hard data as well as expert judgements were used to estimate probabilities of events and uncertainties in the estimates. The calculations were performed using Monte Carlo simulations. CML is shown to be a useful measure of risks associated with drinking water systems. The method presented provides information on risk levels, probabilities of failure, failure rates and downtimes of the system. This information is available for the entire system as well as its different sub-systems. Furthermore, the method enables comparison of the results with performance targets and acceptable levels of risk. The method thus facilitates integrated risk analysis and consequently helps decision-makers to minimise sub-optimisation of risk-reduction options.

A synthesis of radial growth patterns preceding tree mortality

USGS Publications Warehouse

Cailleret, Maxime; Jansen, Steven; Robert, Elisabeth M.R.; Desoto, Lucia; Aakala, Tuomas; Antos, Joseph A.; Beikircher, Barbara; Bigler, Christof; Bugmann, Harald; Caccianiga, Marco; Cada, Vojtech; Camarero, Jesus J.; Cherubini, Paolo; Cochard, Herve; Coyea, Marie R.; Cufar, Katarina; Das, Adrian J.; Davi, Hendrik; Delzon, Sylvain; Dorman, Michael; Gea-Izquierdo, Guillermo; Gillner, Sten; Haavik, Laurel J.; Hartmann, Henrik; Heres, Ana-Maria; Hultine, Kevin R.; Janda, Pavel; Kane, Jeffrey M.; Kharuk, Vyacheslav I.; Kitzberger, Thomas; Klein, Tamir; Kramer, Koen; Lens, Frederic; Levanic, Tom; Calderon, Juan C. Linares; Lloret, Francisco; Lobo-Do-Vale, Raquel; Lombardi, Fabio; Lopez Rodriguez, Rosana; Makinen, Harri; Mayr, Stefan; Meszaros, IIona; Metsaranta, Juha M.; Minunno, Francesco; Oberhuber, Walter; Papadopoulos, Andreas; Peltoniemi, Mikko; Petritan, Any M.; Rohner, Brigitte; Sanguesa-Barreda, Gabriel; Sarris, Dimitrios; Smith, Jeremy M.; Stan, Amanda B.; Sterck, Frank; Stojanovic, Dejan B.; Suarez, Maria L.; Svoboda, Miroslav; Tognetti, Roberto; Torres-Ruiz, Jose M.; Trotsiuk, Volodymyr; Villalba, Ricardo; Vodde, Floor; Westwood, Alana R.; Wyckoff, Peter H.; Zafirov, Nikolay; Martinez-Vilalta, Jordi

2017-01-01

Tree mortality is a key factor influencing forest functions and dynamics, but our understanding of the mechanisms leading to mortality and the associated changes in tree growth rates are still limited. We compiled a new pan-continental tree-ring width database from sites where both dead and living trees were sampled (2970 dead and 4224 living trees from 190 sites, including 36 species), and compared early and recent growth rates between trees that died and those that survived a given mortality event. We observed a decrease in radial growth before death in ca. 84% of the mortality events. The extent and duration of these reductions were highly variable (1–100 years in 96% of events) due to the complex interactions among study species and the source(s) of mortality. Strong and long-lasting declines were found for gymnosperms, shade- and drought-tolerant species, and trees that died from competition. Angiosperms and trees that died due to biotic attacks (especially bark-beetles) typically showed relatively small and short-term growth reductions. Our analysis did not highlight any universal trade-off between early growth and tree longevity within a species, although this result may also reflect high variability in sampling design among sites. The intersite and interspecific variability in growth patterns before mortality provides valuable information on the nature of the mortality process, which is consistent with our understanding of the physiological mechanisms leading to mortality. Abrupt changes in growth immediately before death can be associated with generalized hydraulic failure and/or bark-beetle attack, while long-term decrease in growth may be associated with a gradual decline in hydraulic performance coupled with depletion in carbon reserves. Our results imply that growth-based mortality algorithms may be a powerful tool for predicting gymnosperm mortality induced by chronic stress, but not necessarily so for angiosperms and in case of intense drought or bark-beetle outbreaks.

A synthesis of radial growth patterns preceding tree mortality.

PubMed

Cailleret, Maxime; Jansen, Steven; Robert, Elisabeth M R; Desoto, Lucía; Aakala, Tuomas; Antos, Joseph A; Beikircher, Barbara; Bigler, Christof; Bugmann, Harald; Caccianiga, Marco; Čada, Vojtěch; Camarero, Jesus J; Cherubini, Paolo; Cochard, Hervé; Coyea, Marie R; Čufar, Katarina; Das, Adrian J; Davi, Hendrik; Delzon, Sylvain; Dorman, Michael; Gea-Izquierdo, Guillermo; Gillner, Sten; Haavik, Laurel J; Hartmann, Henrik; Hereş, Ana-Maria; Hultine, Kevin R; Janda, Pavel; Kane, Jeffrey M; Kharuk, Vyacheslav I; Kitzberger, Thomas; Klein, Tamir; Kramer, Koen; Lens, Frederic; Levanic, Tom; Linares Calderon, Juan C; Lloret, Francisco; Lobo-Do-Vale, Raquel; Lombardi, Fabio; López Rodríguez, Rosana; Mäkinen, Harri; Mayr, Stefan; Mészáros, Ilona; Metsaranta, Juha M; Minunno, Francesco; Oberhuber, Walter; Papadopoulos, Andreas; Peltoniemi, Mikko; Petritan, Any M; Rohner, Brigitte; Sangüesa-Barreda, Gabriel; Sarris, Dimitrios; Smith, Jeremy M; Stan, Amanda B; Sterck, Frank; Stojanović, Dejan B; Suarez, Maria L; Svoboda, Miroslav; Tognetti, Roberto; Torres-Ruiz, José M; Trotsiuk, Volodymyr; Villalba, Ricardo; Vodde, Floor; Westwood, Alana R; Wyckoff, Peter H; Zafirov, Nikolay; Martínez-Vilalta, Jordi

2017-04-01

Tree mortality is a key factor influencing forest functions and dynamics, but our understanding of the mechanisms leading to mortality and the associated changes in tree growth rates are still limited. We compiled a new pan-continental tree-ring width database from sites where both dead and living trees were sampled (2970 dead and 4224 living trees from 190 sites, including 36 species), and compared early and recent growth rates between trees that died and those that survived a given mortality event. We observed a decrease in radial growth before death in ca. 84% of the mortality events. The extent and duration of these reductions were highly variable (1-100 years in 96% of events) due to the complex interactions among study species and the source(s) of mortality. Strong and long-lasting declines were found for gymnosperms, shade- and drought-tolerant species, and trees that died from competition. Angiosperms and trees that died due to biotic attacks (especially bark-beetles) typically showed relatively small and short-term growth reductions. Our analysis did not highlight any universal trade-off between early growth and tree longevity within a species, although this result may also reflect high variability in sampling design among sites. The intersite and interspecific variability in growth patterns before mortality provides valuable information on the nature of the mortality process, which is consistent with our understanding of the physiological mechanisms leading to mortality. Abrupt changes in growth immediately before death can be associated with generalized hydraulic failure and/or bark-beetle attack, while long-term decrease in growth may be associated with a gradual decline in hydraulic performance coupled with depletion in carbon reserves. Our results imply that growth-based mortality algorithms may be a powerful tool for predicting gymnosperm mortality induced by chronic stress, but not necessarily so for angiosperms and in case of intense drought or bark-beetle outbreaks. © 2016 John Wiley & Sons Ltd.

Bow-tie diagrams for risk management in anaesthesia.

PubMed

Culwick, M D; Merry, A F; Clarke, D M; Taraporewalla, K J; Gibbs, N M

2016-11-01

Bow-tie analysis is a risk analysis and management tool that has been readily adopted into routine practice in many high reliability industries such as engineering, aviation and emergency services. However, it has received little exposure so far in healthcare. Nevertheless, its simplicity, versatility, and pictorial display may have benefits for the analysis of a range of healthcare risks, including complex and multiple risks and their interactions. Bow-tie diagrams are a combination of a fault tree and an event tree, which when combined take the shape of a bow tie. Central to bow-tie methodology is the concept of an undesired or 'Top Event', which occurs if a hazard progresses past all prevention controls. Top Events may also occasionally occur idiosyncratically. Irrespective of the cause of a Top Event, mitigation and recovery controls may influence the outcome. Hence the relationship of hazard to outcome can be viewed in one diagram along with possible causal sequences or accident trajectories. Potential uses for bow-tie diagrams in anaesthesia risk management include improved understanding of anaesthesia hazards and risks, pre-emptive identification of absent or inadequate hazard controls, investigation of clinical incidents, teaching anaesthesia risk management, and demonstrating risk management strategies to third parties when required.

Tree ring-based chronology of hydro-geomorphic processes as a fundament for identification of hydro-meteorological triggers in the Hrubý Jeseník Mountains (Central Europe).

PubMed

Tichavský, Radek; Šilhán, Karel; Tolasz, Radim

2017-02-01

Hydro-geomorphic processes have significantly influenced the recent development of valley floors, river banks and depositional forms in mountain environments, have caused considerable damage to manmade developments and have disrupted forest management. Trees growing along streams are affected by the transported debris mass and provide valuable records of debris flow/flood histories in their tree-ring series. Dendrogeomorphic approaches are currently the most accurate methods for creating a chronology of the debris flow/flood events in forested catchments without any field-monitoring or a stream-gauging station. Comprehensive studies focusing on the detailed chronology of hydro-geomorphic events and analysis of meteorological triggers and weather circulation patterns are still lacking for the studied area. We provide a spatio-temporal reconstruction of hydro-geomorphic events in four catchments of the Hrubý Jeseník Mountains, Czech Republic, with an analysis of their triggering factors using meteorological data from four nearby rain gauges. Increment cores from 794 coniferous trees (Picea abies [L.] Karst.) allowed the identification of 40 hydro-geomorphic events during the period of 1889-2013. Most of the events can be explained by extreme daily rainfalls (≥50mm) occurring in at least one rain gauge. However, in several cases, there was no record of extreme precipitation at rain gauges during the debris flow/flood event year, suggesting extremely localised rainstorms at the mountain summits. We concluded that the localisation, intensity and duration of rainstorms; antecedent moisture conditions; and amount of available sediments all influenced the initiation, spatial distribution and characteristics of hydro-geomorphic events. The most frequent synoptic situations responsible for the extreme rainfalls (1946-2015) were related to the meridional atmospheric circulation pattern. Our results enhance current knowledge of the occurrences and triggers of debris flows/floods in the Central European mountains in transition between temperate oceanic and continental climatic conditions and may prompt further research of these phenomena in the Eastern Sudetes in general. Copyright © 2016 Elsevier B.V. All rights reserved.

STRIDE: Species Tree Root Inference from Gene Duplication Events.

PubMed

Emms, David M; Kelly, Steven

2017-12-01

The correct interpretation of any phylogenetic tree is dependent on that tree being correctly rooted. We present STRIDE, a fast, effective, and outgroup-free method for identification of gene duplication events and species tree root inference in large-scale molecular phylogenetic analyses. STRIDE identifies sets of well-supported in-group gene duplication events from a set of unrooted gene trees, and analyses these events to infer a probability distribution over an unrooted species tree for the location of its root. We show that STRIDE correctly identifies the root of the species tree in multiple large-scale molecular phylogenetic data sets spanning a wide range of timescales and taxonomic groups. We demonstrate that the novel probability model implemented in STRIDE can accurately represent the ambiguity in species tree root assignment for data sets where information is limited. Furthermore, application of STRIDE to outgroup-free inference of the origin of the eukaryotic tree resulted in a root probability distribution that provides additional support for leading hypotheses for the origin of the eukaryotes. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Origin and Possible Genetic Recombination of the Middle East Respiratory Syndrome Coronavirus from the First Imported Case in China: Phylogenetics and Coalescence Analysis.

PubMed

Wang, Yanqun; Liu, Di; Shi, Weifeng; Lu, Roujian; Wang, Wenling; Zhao, Yanjie; Deng, Yao; Zhou, Weimin; Ren, Hongguang; Wu, Jun; Wang, Yu; Wu, Guizhen; Gao, George F; Tan, Wenjie

2015-09-08

The Middle East respiratory syndrome coronavirus (MERS-CoV) causes a severe acute respiratory tract infection with a high fatality rate in humans. Coronaviruses are capable of infecting multiple species and can evolve rapidly through recombination events. Here, we report the complete genomic sequence analysis of a MERS-CoV strain imported to China from South Korea. The imported virus, provisionally named ChinaGD01, belongs to group 3 in clade B in the whole-genome phylogenetic tree and also has a similar tree topology structure in the open reading frame 1a and -b (ORF1ab) gene segment but clusters with group 5 of clade B in the tree constructed using the S gene. Genetic recombination analysis and lineage-specific single-nucleotide polymorphism (SNP) comparison suggest that the imported virus is a recombinant comprising group 3 and group 5 elements. The time-resolved phylogenetic estimation indicates that the recombination event likely occurred in the second half of 2014. Genetic recombination events between group 3 and group 5 of clade B may have implications for the transmissibility of the virus. The recent outbreak of MERS-CoV in South Korea has attracted global media attention due to the speed of spread and onward transmission. Here, we present the complete genome of the first imported MERS-CoV case in China and demonstrate genetic recombination events between group 3 and group 5 of clade B that may have implications for the transmissibility of MERS-CoV. Copyright © 2015 Wang et al.

77 FR 61024 - Notice of Public Meeting and Request for Comments

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-05

... public meeting and public comments--The National Christmas Tree Lighting and the subsequent 26-day event... National Christmas Tree Lighting and the subsequent 26-day event. The general plan and theme for the event... comments and suggestions on the planning of the 2012 National Christmas Tree Lighting and the subsequent 26...

Remnant Pachira quinata pasture trees have greater opportunities to self and suffer reduced reproductive success due to inbreeding depression.

PubMed

Rymer, P D; Sandiford, M; Harris, S A; Billingham, M R; Boshier, D H

2015-08-01

Habitat fragmentation is extensive throughout the world, converting natural ecosystems into fragments of varying size, density and connectivity. The potential value of remnant trees in agricultural landscapes as seed sources and in connecting fragments has formed a fertile area of debate. This study contrasted the mating patterns of bat-pollinated Pachira quinata trees in a continuous forest to those in pasture through microsatellite-based paternity analysis of progeny. The breeding system was determined by analysis of pollen tube growth and seed production from controlled pollinations. Fitness of selfed and outcrossed seed was compared by germination and seedling growth. There was more inbreeding within pasture trees (outcrossing=0.828±0.015) compared with forest trees (0.926±0.005). Pasture trees had fewer sires contributing to mating events, but pollen dispersal distances were greater than those in the forest. Paternity analysis showed variation in outcrossing rates among pasture trees with high proportions of external and self pollen sources detected. A leaky self-incompatibility system was found, with self pollen having reduced germination on stigmas and slower growth rate through the style. Controlled pollinations also showed a varied ability to self among trees, which was reflected in the selfing rates among pasture trees shown by the paternity analysis (0-80% selfing). Self pollination resulted in lower seed set, germination and seedling growth compared with outcrossing. While remnant trees in agricultural landscapes are involved in broader mating patterns, they show increased but varied levels of inbreeding, which result in reduced fitness.

Remnant Pachira quinata pasture trees have greater opportunities to self and suffer reduced reproductive success due to inbreeding depression

PubMed Central

Rymer, P D; Sandiford, M; Harris, S A; Billingham, M R; Boshier, D H

2015-01-01

Habitat fragmentation is extensive throughout the world, converting natural ecosystems into fragments of varying size, density and connectivity. The potential value of remnant trees in agricultural landscapes as seed sources and in connecting fragments has formed a fertile area of debate. This study contrasted the mating patterns of bat-pollinated Pachira quinata trees in a continuous forest to those in pasture through microsatellite-based paternity analysis of progeny. The breeding system was determined by analysis of pollen tube growth and seed production from controlled pollinations. Fitness of selfed and outcrossed seed was compared by germination and seedling growth. There was more inbreeding within pasture trees (outcrossing=0.828±0.015) compared with forest trees (0.926±0.005). Pasture trees had fewer sires contributing to mating events, but pollen dispersal distances were greater than those in the forest. Paternity analysis showed variation in outcrossing rates among pasture trees with high proportions of external and self pollen sources detected. A leaky self-incompatibility system was found, with self pollen having reduced germination on stigmas and slower growth rate through the style. Controlled pollinations also showed a varied ability to self among trees, which was reflected in the selfing rates among pasture trees shown by the paternity analysis (0–80% selfing). Self pollination resulted in lower seed set, germination and seedling growth compared with outcrossing. While remnant trees in agricultural landscapes are involved in broader mating patterns, they show increased but varied levels of inbreeding, which result in reduced fitness. PMID:23963342

The Imprint of Extreme Climate Events in Century-Long Time Series of Wood Anatomical Traits in High-Elevation Conifers

PubMed Central

Carrer, Marco; Brunetti, Michele; Castagneri, Daniele

2016-01-01

Extreme climate events are of key importance for forest ecosystems. However, both the inherent infrequency, stochasticity and multiplicity of extreme climate events, and the array of biological responses, challenges investigations. To cope with the long life cycle of trees and the paucity of the extreme events themselves, our inferences should be based on long-term observations. In this context, tree rings and the related xylem anatomical traits represent promising sources of information, due to the wide time perspective and quality of the information they can provide. Here we test, on two high-elevation conifers (Larix decidua and Picea abies sampled at 2100 m a.s.l. in the Eastern Alps), the associations among temperature extremes during the growing season and xylem anatomical traits, specifically the number of cells per ring (CN), cell wall thickness (CWT), and cell diameter (CD). To better track the effect of extreme events over the growing season, tree rings were partitioned in 10 sectors. Climate variability has been reconstructed, for 1800–2011 at monthly resolution and for 1926–2011 at daily resolution, by exploiting the excellent availability of very long and high quality instrumental records available for the surrounding area, and taking into account the relationship between meteorological variables and site topographical settings. Summer temperature influenced anatomical traits of both species, and tree-ring anatomical profiles resulted as being associated to temperature extremes. Most of the extreme values in anatomical traits occurred with warm (positive extremes) or cold (negative) conditions. However, 0–34% of occurrences did not match a temperature extreme event. Specifically, CWT and CN extremes were more clearly associated to climate than CD, which presented a bias to track cold extremes. Dendroanatomical analysis, coupled to high-quality daily-resolved climate records, seems a promising approach to study the effects of extreme events on trees, but further investigations are needed to improve our comprehension of the critical role of such elusive events in forest ecosystems. PMID:27242880

FTC - THE FAULT-TREE COMPILER (SUN VERSION)

NASA Technical Reports Server (NTRS)

Butler, R. W.

1994-01-01

FTC, the Fault-Tree Compiler program, is a tool used to calculate the top-event probability for a fault-tree. Five different gate types are allowed in the fault tree: AND, OR, EXCLUSIVE OR, INVERT, and M OF N. The high-level input language is easy to understand and use. In addition, the program supports a hierarchical fault tree definition feature which simplifies the tree-description process and reduces execution time. A rigorous error bound is derived for the solution technique. This bound enables the program to supply an answer precisely (within the limits of double precision floating point arithmetic) at a user-specified number of digits accuracy. The program also facilitates sensitivity analysis with respect to any specified parameter of the fault tree such as a component failure rate or a specific event probability by allowing the user to vary one failure rate or the failure probability over a range of values and plot the results. The mathematical approach chosen to solve a reliability problem may vary with the size and nature of the problem. Although different solution techniques are utilized on different programs, it is possible to have a common input language. The Systems Validation Methods group at NASA Langley Research Center has created a set of programs that form the basis for a reliability analysis workstation. The set of programs are: SURE reliability analysis program (COSMIC program LAR-13789, LAR-14921); the ASSIST specification interface program (LAR-14193, LAR-14923), PAWS/STEM reliability analysis programs (LAR-14165, LAR-14920); and the FTC fault tree tool (LAR-14586, LAR-14922). FTC is used to calculate the top-event probability for a fault tree. PAWS/STEM and SURE are programs which interpret the same SURE language, but utilize different solution methods. ASSIST is a preprocessor that generates SURE language from a more abstract definition. SURE, ASSIST, and PAWS/STEM are also offered as a bundle. Please see the abstract for COS-10039/COS-10041, SARA - SURE/ASSIST Reliability Analysis Workstation, for pricing details. FTC was originally developed for DEC VAX series computers running VMS and was later ported for use on Sun computers running SunOS. The program is written in PASCAL, ANSI compliant C-language, and FORTRAN 77. The TEMPLATE graphics library is required to obtain graphical output. The standard distribution medium for the VMS version of FTC (LAR-14586) is a 9-track 1600 BPI magnetic tape in VMSINSTAL format. It is also available on a TK50 tape cartridge in VMSINSTAL format. Executables are included. The standard distribution medium for the Sun version of FTC (LAR-14922) is a .25 inch streaming magnetic tape cartridge in UNIX tar format. Both Sun3 and Sun4 executables are included. FTC was developed in 1989 and last updated in 1992. DEC, VAX, VMS, and TK50 are trademarks of Digital Equipment Corporation. UNIX is a registered trademark of AT&T Bell Laboratories. SunOS is a trademark of Sun Microsystems, Inc.

FTC - THE FAULT-TREE COMPILER (VAX VMS VERSION)

NASA Technical Reports Server (NTRS)

Butler, R. W.

1994-01-01

FTC, the Fault-Tree Compiler program, is a tool used to calculate the top-event probability for a fault-tree. Five different gate types are allowed in the fault tree: AND, OR, EXCLUSIVE OR, INVERT, and M OF N. The high-level input language is easy to understand and use. In addition, the program supports a hierarchical fault tree definition feature which simplifies the tree-description process and reduces execution time. A rigorous error bound is derived for the solution technique. This bound enables the program to supply an answer precisely (within the limits of double precision floating point arithmetic) at a user-specified number of digits accuracy. The program also facilitates sensitivity analysis with respect to any specified parameter of the fault tree such as a component failure rate or a specific event probability by allowing the user to vary one failure rate or the failure probability over a range of values and plot the results. The mathematical approach chosen to solve a reliability problem may vary with the size and nature of the problem. Although different solution techniques are utilized on different programs, it is possible to have a common input language. The Systems Validation Methods group at NASA Langley Research Center has created a set of programs that form the basis for a reliability analysis workstation. The set of programs are: SURE reliability analysis program (COSMIC program LAR-13789, LAR-14921); the ASSIST specification interface program (LAR-14193, LAR-14923), PAWS/STEM reliability analysis programs (LAR-14165, LAR-14920); and the FTC fault tree tool (LAR-14586, LAR-14922). FTC is used to calculate the top-event probability for a fault tree. PAWS/STEM and SURE are programs which interpret the same SURE language, but utilize different solution methods. ASSIST is a preprocessor that generates SURE language from a more abstract definition. SURE, ASSIST, and PAWS/STEM are also offered as a bundle. Please see the abstract for COS-10039/COS-10041, SARA - SURE/ASSIST Reliability Analysis Workstation, for pricing details. FTC was originally developed for DEC VAX series computers running VMS and was later ported for use on Sun computers running SunOS. The program is written in PASCAL, ANSI compliant C-language, and FORTRAN 77. The TEMPLATE graphics library is required to obtain graphical output. The standard distribution medium for the VMS version of FTC (LAR-14586) is a 9-track 1600 BPI magnetic tape in VMSINSTAL format. It is also available on a TK50 tape cartridge in VMSINSTAL format. Executables are included. The standard distribution medium for the Sun version of FTC (LAR-14922) is a .25 inch streaming magnetic tape cartridge in UNIX tar format. Both Sun3 and Sun4 executables are included. FTC was developed in 1989 and last updated in 1992. DEC, VAX, VMS, and TK50 are trademarks of Digital Equipment Corporation. UNIX is a registered trademark of AT&T Bell Laboratories. SunOS is a trademark of Sun Microsystems, Inc.

CytoSPADE: high-performance analysis and visualization of high-dimensional cytometry data

PubMed Central

Linderman, Michael D.; Simonds, Erin F.; Qiu, Peng; Bruggner, Robert V.; Sheode, Ketaki; Meng, Teresa H.; Plevritis, Sylvia K.; Nolan, Garry P.

2012-01-01

Motivation: Recent advances in flow cytometry enable simultaneous single-cell measurement of 30+ surface and intracellular proteins. CytoSPADE is a high-performance implementation of an interface for the Spanning-tree Progression Analysis of Density-normalized Events algorithm for tree-based analysis and visualization of this high-dimensional cytometry data. Availability: Source code and binaries are freely available at http://cytospade.org and via Bioconductor version 2.10 onwards for Linux, OSX and Windows. CytoSPADE is implemented in R, C++ and Java. Contact: michael.linderman@mssm.edu Supplementary Information: Additional documentation available at http://cytospade.org. PMID:22782546

To live or to die? Evidence of variable drivers of wood d13C reveal different responses to disturbance in co-occurring oaks

NASA Astrophysics Data System (ADS)

Reed, A. S.; Stephen, F. M.; Billings, S. A.

2011-12-01

A major oak decline event in recent decades in Northwest Arkansas permits insight into disturbance impacts on forests, which is important for understanding global carbon, nutrient and climate cycles given projections of increasing disturbance event frequency in the future. The decline event, associated with an increase in population of a native, wood-boring insect, followed a cycle of droughts and resulted in a mosaic of apparently healthy red oaks (Quercus rubra) neighboring severely declining trees of the same species. Tree-ring evidence suggests decreased growth rates following increases in the insect's population decades prior to visible external decline symptoms (i.e. decreased crown coverage, mortality), but only in trees destined to die during the insect outbreak. Reasons why some trees experienced mortality and some remained healthy are unclear. Through analysis of stable isotopes of carbon (δ13C) and oxygen (δ18O) in wood and leaf δ13C and nitrogen among co-occurring trees, we can infer differential responses of red oaks to disturbance and associated resilience to mortality. Tree-ring a-cellulose δ13C varied from -27.3to -23.0%, and δ18O values varied from 27.5 to 31.8%. Neither δ13C nor δ18O exhibited signficant differences between healthy and declining trees. However, declining trees exhibited a significant, positive relationship between δ13C and δ18O (p <0.05, r2=0.15) prior to peak insect infestation. In contrast, apparently healthy individuals did not exhibit a significant relationship between these parameters, but exhibited significant, positive relationships between current year leaf δ13C and nitrogen content (p<0.05, r2=0.77). These results suggest that healthy and declining trees had different strategies for coping with insect infestation. Correlation between tree-ring δ13C and δ18O in dying trees suggests that trees destined to die during the infestation regulated their δ13C values primarily via stomatal conductance, a mechanism that influences both δ13C and δ18O. In contrast, δ13C values in apparently healthy trees did not vary with δ18O, indicating that stomatal conductance was not an important regulator of δ13C. The linkage between δ13C and nitrogen availability in these trees suggests that carbon sink strength, typically associated with plant nutrient status, may have played a more important role than carbon source strength (i.e. stomatal conductance) in governing tree-ring δ13C. These results suggest that 1) responses to disturbance of co-occurring trees of the same species can diverge in ways discernable decades later via stable isotopic analysis, and 2) the primary driver of wood δ13C values, whether carbon source (stomatal conductance) or sink (fixation capacity) strength, is linked to its fate.

Application of fuzzy fault tree analysis based on modified fuzzy AHP and fuzzy TOPSIS for fire and explosion in the process industry.

PubMed

Yazdi, Mohammad; Korhan, Orhan; Daneshvar, Sahand

2018-05-09

This study aimed at establishing fault tree analysis (FTA) using expert opinion to compute the probability of an event. To find the probability of the top event (TE), all probabilities of the basic events (BEs) should be available when the FTA is drawn. In this case, employing expert judgment can be used as an alternative to failure data in an awkward situation. The fuzzy analytical hierarchy process as a standard technique is used to give a specific weight to each expert, and fuzzy set theory is engaged for aggregating expert opinion. In this regard, the probability of BEs will be computed and, consequently, the probability of the TE obtained using Boolean algebra. Additionally, to reduce the probability of the TE in terms of three parameters (safety consequences, cost and benefit), the importance measurement technique and modified TOPSIS was employed. The effectiveness of the proposed approach is demonstrated with a real-life case study.

Onboard Classifiers for Science Event Detection on a Remote Sensing Spacecraft

NASA Technical Reports Server (NTRS)

Castano, Rebecca; Mazzoni, Dominic; Tang, Nghia; Greeley, Ron; Doggett, Thomas; Cichy, Ben; Chien, Steve; Davies, Ashley

2006-01-01

Typically, data collected by a spacecraft is downlinked to Earth and pre-processed before any analysis is performed. We have developed classifiers that can be used onboard a spacecraft to identify high priority data for downlink to Earth, providing a method for maximizing the use of a potentially bandwidth limited downlink channel. Onboard analysis can also enable rapid reaction to dynamic events, such as flooding, volcanic eruptions or sea ice break-up. Four classifiers were developed to identify cryosphere events using hyperspectral images. These classifiers include a manually constructed classifier, a Support Vector Machine (SVM), a Decision Tree and a classifier derived by searching over combinations of thresholded band ratios. Each of the classifiers was designed to run in the computationally constrained operating environment of the spacecraft. A set of scenes was hand-labeled to provide training and testing data. Performance results on the test data indicate that the SVM and manual classifiers outperformed the Decision Tree and band-ratio classifiers with the SVM yielding slightly better classifications than the manual classifier.

Fault tree analysis of fire and explosion accidents for dual fuel (diesel/natural gas) ship engine rooms

NASA Astrophysics Data System (ADS)

Guan, Yifeng; Zhao, Jie; Shi, Tengfei; Zhu, Peipei

2016-09-01

In recent years, China's increased interest in environmental protection has led to a promotion of energy-efficient dual fuel (diesel/natural gas) ships in Chinese inland rivers. A natural gas as ship fuel may pose dangers of fire and explosion if a gas leak occurs. If explosions or fires occur in the engine rooms of a ship, heavy damage and losses will be incurred. In this paper, a fault tree model is presented that considers both fires and explosions in a dual fuel ship; in this model, dual fuel engine rooms are the top events. All the basic events along with the minimum cut sets are obtained through the analysis. The primary factors that affect accidents involving fires and explosions are determined by calculating the degree of structure importance of the basic events. According to these results, corresponding measures are proposed to ensure and improve the safety and reliability of Chinese inland dual fuel ships.

Risk assessment techniques with applicability in marine engineering

NASA Astrophysics Data System (ADS)

Rudenko, E.; Panaitescu, F. V.; Panaitescu, M.

2015-11-01

Nowadays risk management is a carefully planned process. The task of risk management is organically woven into the general problem of increasing the efficiency of business. Passive attitude to risk and awareness of its existence are replaced by active management techniques. Risk assessment is one of the most important stages of risk management, since for risk management it is necessary first to analyze and evaluate risk. There are many definitions of this notion but in general case risk assessment refers to the systematic process of identifying the factors and types of risk and their quantitative assessment, i.e. risk analysis methodology combines mutually complementary quantitative and qualitative approaches. Purpose of the work: In this paper we will consider as risk assessment technique Fault Tree analysis (FTA). The objectives are: understand purpose of FTA, understand and apply rules of Boolean algebra, analyse a simple system using FTA, FTA advantages and disadvantages. Research and methodology: The main purpose is to help identify potential causes of system failures before the failures actually occur. We can evaluate the probability of the Top event.The steps of this analize are: the system's examination from Top to Down, the use of symbols to represent events, the use of mathematical tools for critical areas, the use of Fault tree logic diagrams to identify the cause of the Top event. Results: In the finally of study it will be obtained: critical areas, Fault tree logical diagrams and the probability of the Top event. These results can be used for the risk assessment analyses.

Enhancing the Possibility of Success by Measuring the Probability of Failure in an Educational Program.

ERIC Educational Resources Information Center

Brookhart, Susan M.; And Others

1997-01-01

Process Analysis is described as a method for identifying and measuring the probability of events that could cause the failure of a program, resulting in a cause-and-effect tree structure of events. The method is illustrated through the evaluation of a pilot instructional program at an elementary school. (SLD)

Assembly and analysis of a male sterile rubber tree mitochondrial genome reveals DNA rearrangement events and a novel transcript.

PubMed

Shearman, Jeremy R; Sangsrakru, Duangjai; Ruang-Areerate, Panthita; Sonthirod, Chutima; Uthaipaisanwong, Pichahpuk; Yoocha, Thippawan; Poopear, Supannee; Theerawattanasuk, Kanikar; Tragoonrung, Somvong; Tangphatsornruang, Sithichoke

2014-02-10

The rubber tree, Hevea brasiliensis, is an important plant species that is commercially grown to produce latex rubber in many countries. The rubber tree variety BPM 24 exhibits cytoplasmic male sterility, inherited from the variety GT 1. We constructed the rubber tree mitochondrial genome of a cytoplasmic male sterile variety, BPM 24, using 454 sequencing, including 8 kb paired-end libraries, plus Illumina paired-end sequencing. We annotated this mitochondrial genome with the aid of Illumina RNA-seq data and performed comparative analysis. We then compared the sequence of BPM 24 to the contigs of the published rubber tree, variety RRIM 600, and identified a rearrangement that is unique to BPM 24 resulting in a novel transcript containing a portion of atp9. The novel transcript is consistent with changes that cause cytoplasmic male sterility through a slight reduction to ATP production efficiency. The exhaustive nature of the search rules out alternative causes and supports previous findings of novel transcripts causing cytoplasmic male sterility.

Missing Rings in Pinus halepensis – The Missing Link to Relate the Tree-Ring Record to Extreme Climatic Events

PubMed Central

Novak, Klemen; de Luis, Martin; Saz, Miguel A.; Longares, Luis A.; Serrano-Notivoli, Roberto; Raventós, Josep; Čufar, Katarina; Gričar, Jožica; Di Filippo, Alfredo; Piovesan, Gianluca; Rathgeber, Cyrille B. K.; Papadopoulos, Andreas; Smith, Kevin T.

2016-01-01

Climate predictions for the Mediterranean Basin include increased temperatures, decreased precipitation, and increased frequency of extreme climatic events (ECE). These conditions are associated with decreased tree growth and increased vulnerability to pests and diseases. The anatomy of tree rings responds to these environmental conditions. Quantitatively, the width of a tree ring is largely determined by the rate and duration of cell division by the vascular cambium. In the Mediterranean climate, this division may occur throughout almost the entire year. Alternatively, cell division may cease during relatively cool and dry winters, only to resume in the same calendar year with milder temperatures and increased availability of water. Under particularly adverse conditions, no xylem may be produced in parts of the stem, resulting in a missing ring (MR). A dendrochronological network of Pinus halepensis was used to determine the relationship of MR to ECE. The network consisted of 113 sites, 1,509 trees, 2,593 cores, and 225,428 tree rings throughout the distribution range of the species. A total of 4,150 MR were identified. Binomial logistic regression analysis determined that MR frequency increased with increased cambial age. Spatial analysis indicated that the geographic areas of south-eastern Spain and northern Algeria contained the greatest frequency of MR. Dendroclimatic regression analysis indicated a non-linear relationship of MR to total monthly precipitation and mean temperature. MR are strongly associated with the combination of monthly mean temperature from previous October till current February and total precipitation from previous September till current May. They are likely to occur with total precipitation lower than 50 mm and temperatures higher than 5°C. This conclusion is global and can be applied to every site across the distribution area. Rather than simply being a complication for dendrochronology, MR formation is a fundamental response of trees to adverse environmental conditions. The demonstrated relationship of MR formation to ECE across this dendrochronological network in the Mediterranean basin shows the potential of MR analysis to reconstruct the history of past climatic extremes and to predict future forest dynamics in a changing climate. PMID:27303421

Missing Rings in Pinus halepensis - The Missing Link to Relate the Tree-Ring Record to Extreme Climatic Events.

PubMed

Novak, Klemen; de Luis, Martin; Saz, Miguel A; Longares, Luis A; Serrano-Notivoli, Roberto; Raventós, Josep; Čufar, Katarina; Gričar, Jožica; Di Filippo, Alfredo; Piovesan, Gianluca; Rathgeber, Cyrille B K; Papadopoulos, Andreas; Smith, Kevin T

2016-01-01

Climate predictions for the Mediterranean Basin include increased temperatures, decreased precipitation, and increased frequency of extreme climatic events (ECE). These conditions are associated with decreased tree growth and increased vulnerability to pests and diseases. The anatomy of tree rings responds to these environmental conditions. Quantitatively, the width of a tree ring is largely determined by the rate and duration of cell division by the vascular cambium. In the Mediterranean climate, this division may occur throughout almost the entire year. Alternatively, cell division may cease during relatively cool and dry winters, only to resume in the same calendar year with milder temperatures and increased availability of water. Under particularly adverse conditions, no xylem may be produced in parts of the stem, resulting in a missing ring (MR). A dendrochronological network of Pinus halepensis was used to determine the relationship of MR to ECE. The network consisted of 113 sites, 1,509 trees, 2,593 cores, and 225,428 tree rings throughout the distribution range of the species. A total of 4,150 MR were identified. Binomial logistic regression analysis determined that MR frequency increased with increased cambial age. Spatial analysis indicated that the geographic areas of south-eastern Spain and northern Algeria contained the greatest frequency of MR. Dendroclimatic regression analysis indicated a non-linear relationship of MR to total monthly precipitation and mean temperature. MR are strongly associated with the combination of monthly mean temperature from previous October till current February and total precipitation from previous September till current May. They are likely to occur with total precipitation lower than 50 mm and temperatures higher than 5°C. This conclusion is global and can be applied to every site across the distribution area. Rather than simply being a complication for dendrochronology, MR formation is a fundamental response of trees to adverse environmental conditions. The demonstrated relationship of MR formation to ECE across this dendrochronological network in the Mediterranean basin shows the potential of MR analysis to reconstruct the history of past climatic extremes and to predict future forest dynamics in a changing climate.

Debris-flow activity in abandoned channels of the Manival torrent reconstructed with LiDAR and tree-ring data

NASA Astrophysics Data System (ADS)

Lopez Saez, J.; Corona, C.; Stoffel, M.; Gotteland, A.; Berger, F.; Liébault, F.

2011-05-01

Hydrogeomorphic processes are a major threat in many parts of the Alps, where they periodically damage infrastructure, disrupt transportation corridors or even cause loss of life. Nonetheless, past torrential activity and the analysis of areas affected during particular events remain often imprecise. It was therefore the purpose of this study to reconstruct spatio-temporal patterns of past debris-flow activity in abandoned channels on the forested cone of the Manival torrent (Massif de la Chartreuse, French Prealps). A Light Detecting and Ranging (LiDAR) generated Digital Elevation Model (DEM) was used to identify five abandoned channels and related depositional forms (lobes, lateral levees) in the proximal alluvial fan of the torrent. A total of 156 Scots pine trees (Pinus sylvestris L.) with clear signs of debris flow events was analyzed and growth disturbances (GD) assessed, such as callus tissue, the onset of compression wood or abrupt growth suppression. In total, 375 GD were identified in the tree-ring samples, pointing to 13 debris-flow events for the period 1931-2008. While debris flows appear to be very common at Manival, they have only rarely propagated outside the main channel over the past 80 years. Furthermore, analysis of the spatial distribution of disturbed trees contributed to the identification of four patterns of debris-flow routing and led to the determination of three preferential breakout locations. Finally, the results of this study demonstrate that the temporal distribution of debris flows did not exhibit significant variations since the beginning of the 20th century.

Project delay analysis of HRSG

NASA Astrophysics Data System (ADS)

Silvianita; Novega, A. S.; Rosyid, D. M.; Suntoyo

2017-08-01

Completion of HRSG (Heat Recovery Steam Generator) fabrication project sometimes is not sufficient with the targeted time written on the contract. The delay on fabrication process can cause some disadvantages for fabricator, including forfeit payment, delay on HRSG construction process up until HRSG trials delay. In this paper, the author is using semi quantitative on HRSG pressure part fabrication delay with configuration plant 1 GT (Gas Turbine) + 1 HRSG + 1 STG (Steam Turbine Generator) using bow-tie analysis method. Bow-tie analysis method is a combination from FTA (Fault tree analysis) and ETA (Event tree analysis) to develop the risk matrix of HRSG. The result from FTA analysis is use as a threat for preventive measure. The result from ETA analysis is use as impact from fabrication delay.

A Multi-stakeholder Approach to Moving Beyond Tree Mortality in the Sierra Nevada

NASA Astrophysics Data System (ADS)

Balachowski, J.; Buluc, L.; Fischer, C.; Ko, J.; Ostoja, S.

2017-12-01

The US Forest Service has estimated that 102 million trees have died in California since 2010. This die off event has been attributed to the combined effects of historical land management practices, fire suppression, insect outbreaks, and climate-related stressors. This tree mortality event represents the largest and most significant ecological disturbance in California in centuries, if not longer. Both scientists and managers recognize the need to rethink our approach to forest management in the face of a changing climate and increasingly frequent, uncharacteristically large wildfires, while budgets and staffing capacity continue to decrease. Addressing the uncertainly in managing under climate change with fewer financial resources will require multiple partners and stakeholders—including federal and state agencies, local governments, and non-governmental organizations—to work together to identify common goals and paths moving forward. The USDA California Climate Hub and USFS Region 5 convened a symposium on drought and tree mortality in July 2017. With nearly 170 attendees across a wide range of sectors, the event provided a meaningful opportunity for reflection, analysis, and consideration of next steps. Among the outcomes of this symposium was the identification of areas in which our capacity for individual and synergistic action is stronger, and those in which it is lacking that will thus require additional attention and effort. From this symposium, which included a series of smaller, stakeholder and partner working groups, we collectively identified research and information needs, possible policy adjustments, future management actions, and funding needs and opportunities. Here, we present these findings and suggest approaches for addressing the current tree mortality event based on the shared interests of multiple, diverse stakeholder groups.

Extreme Drought Events Revealed in Amazon Tree Ring Records

NASA Astrophysics Data System (ADS)

Jenkins, H. S.; Baker, P. A.; Guilderson, T. P.

2010-12-01

The Amazon basin is a center of deep atmospheric convection and thus acts as a major engine for global hydrologic circulation. Yet despite its significance, a full understanding of Amazon rainfall variability remains elusive due to a poor historical record of climate. Temperate tree rings have been used extensively to reconstruct climate over the last thousand years, however less attention has been given to the application of dendrochronology in tropical regions, in large part due to a lower frequency of tree species known to produce annual rings. Here we present a tree ring record of drought extremes from the Madre de Dios region of southeastern Peru over the last 190 years. We confirm that tree ring growth in species Cedrela odorata is annual and show it to be well correlated with wet season precipitation. This correlation is used to identify extreme dry (and wet) events that have occurred in the past. We focus on drought events identified in the record as drought frequency is expected to increase over the Amazon in a warming climate. The Cedrela chronology records historic Amazon droughts of the 20th century previously identified in the literature and extends the record of drought for this region to the year 1816. Our analysis shows that there has been an increase in the frequency of extreme drought (mean recurrence interval = 5-6 years) since the turn of the 20th century and both Atlantic and Pacific sea surface temperature (SST) forcing mechanisms are implicated.

Review: Evaluation of Foot-and-Mouth Disease Control Using Fault Tree Analysis.

PubMed

Isoda, N; Kadohira, M; Sekiguchi, S; Schuppers, M; Stärk, K D C

2015-06-01

An outbreak of foot-and-mouth disease (FMD) causes huge economic losses and animal welfare problems. Although much can be learnt from past FMD outbreaks, several countries are not satisfied with their degree of contingency planning and aiming at more assurance that their control measures will be effective. The purpose of the present article was to develop a generic fault tree framework for the control of an FMD outbreak as a basis for systematic improvement and refinement of control activities and general preparedness. Fault trees are typically used in engineering to document pathways that can lead to an undesired event, that is, ineffective FMD control. The fault tree method allows risk managers to identify immature parts of the control system and to analyse the events or steps that will most probably delay rapid and effective disease control during a real outbreak. The present developed fault tree is generic and can be tailored to fit the specific needs of countries. For instance, the specific fault tree for the 2001 FMD outbreak in the UK was refined based on control weaknesses discussed in peer-reviewed articles. Furthermore, the specific fault tree based on the 2001 outbreak was applied to the subsequent FMD outbreak in 2007 to assess the refinement of control measures following the earlier, major outbreak. The FMD fault tree can assist risk managers to develop more refined and adequate control activities against FMD outbreaks and to find optimum strategies for rapid control. Further application using the current tree will be one of the basic measures for FMD control worldwide. © 2013 Blackwell Verlag GmbH.

The Tunguska event in 1908: evidence from tree-ring anatomy.

PubMed

Vaganov, Evgenii A; Hughes, Malcolm K; Silkin, Pavel P; Nesvetailo, Valery D

2004-01-01

We analyzed tree rings in wood samples collected from some of the few surviving trees found close to the epicenter (within 4-5 km) of the Tunguska event that occurred on the last day of June 1908. Tree-ring growth shows a depression starting in the year after the event and continuing during a 4-5-year period. The most remarkable traces of the event were found in the rings' anatomical structure: (1) formation of "light" rings and a reduction of maximum density in 1908; (2) non-thickened tracheids (the cells that make up most of the wood volume) in the transition and latewood zones (the middle and last-formed parts of the ring, respectively); and (3) deformed tracheids, which are located on the 1908 annual ring outer boundary. In the majority of samples, normal earlywood and latewood tracheids were formed in all annual rings after 1908. The observed anomalies in wood anatomy suggest two main impacts of the Tunguska event on surviving trees--(1) defoliation and (2) direct mechanical stress on active xylem tissue. The mechanical stress needed to fell trees is less than the stress needed to cause the deformation of differentiating tracheids observed in trees close to the epicenter. In order to resolve this apparent contradiction, work is suggested on possible topographic modification of the overpressure experienced by these trees, as is an experimental test of the effects of such stresses on precisely analogous growing trees.

Logic flowgraph methodology - A tool for modeling embedded systems

NASA Technical Reports Server (NTRS)

Muthukumar, C. T.; Guarro, S. B.; Apostolakis, G. E.

1991-01-01

The logic flowgraph methodology (LFM), a method for modeling hardware in terms of its process parameters, has been extended to form an analytical tool for the analysis of integrated (hardware/software) embedded systems. In the software part of a given embedded system model, timing and the control flow among different software components are modeled by augmenting LFM with modified Petrinet structures. The objective of the use of such an augmented LFM model is to uncover possible errors and the potential for unanticipated software/hardware interactions. This is done by backtracking through the augmented LFM mode according to established procedures which allow the semiautomated construction of fault trees for any chosen state of the embedded system (top event). These fault trees, in turn, produce the possible combinations of lower-level states (events) that may lead to the top event.

Monitoring of environmental conditions in the Alaskan forests using ERS-1 SAR data

NASA Technical Reports Server (NTRS)

Rignot, Eric; Way, Jobea; Mcdonald, Kyle; Viereck, Leslie; Adams, Phyllis

1992-01-01

Preliminary results from an analysis of the multitemporal radar backscatter signatures of tree species acquired by European Remote Sensing Satellite (ERS-1) synthetic aperture radar (SAR) data are presented. Significant changes in radar backscatter are detected. Correlation of these differences with ground truth observations indicate that these are due to changes in soil and liquid water content as a result of freeze/thaw events. C-band observations acquired by the NASA/Jet Propulsion Laboratory Airborne SAR (JPL AIRSAR) instrument demonstrate the potential of a C-band radar instrument to monitor drought/flood events. The potential of ERS-1 for monitoring phenologic changes in the forest and for classifying tree species is less promising.

Inferring phylogenetic trees from the knowledge of rare evolutionary events.

PubMed

Hellmuth, Marc; Hernandez-Rosales, Maribel; Long, Yangjing; Stadler, Peter F

2018-06-01

Rare events have played an increasing role in molecular phylogenetics as potentially homoplasy-poor characters. In this contribution we analyze the phylogenetic information content from a combinatorial point of view by considering the binary relation on the set of taxa defined by the existence of a single event separating two taxa. We show that the graph-representation of this relation must be a tree. Moreover, we characterize completely the relationship between the tree of such relations and the underlying phylogenetic tree. With directed operations such as tandem-duplication-random-loss events in mind we demonstrate how non-symmetric information constrains the position of the root in the partially reconstructed phylogeny.

Development and application of the dynamic system doctor to nuclear reactor probabilistic risk assessments.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kunsman, David Marvin; Aldemir, Tunc; Rutt, Benjamin

2008-05-01

This LDRD project has produced a tool that makes probabilistic risk assessments (PRAs) of nuclear reactors - analyses which are very resource intensive - more efficient. PRAs of nuclear reactors are being increasingly relied on by the United States Nuclear Regulatory Commission (U.S.N.R.C.) for licensing decisions for current and advanced reactors. Yet, PRAs are produced much as they were 20 years ago. The work here applied a modern systems analysis technique to the accident progression analysis portion of the PRA; the technique was a system-independent multi-task computer driver routine. Initially, the objective of the work was to fuse the accidentmore » progression event tree (APET) portion of a PRA to the dynamic system doctor (DSD) created by Ohio State University. Instead, during the initial efforts, it was found that the DSD could be linked directly to a detailed accident progression phenomenological simulation code - the type on which APET construction and analysis relies, albeit indirectly - and thereby directly create and analyze the APET. The expanded DSD computational architecture and infrastructure that was created during this effort is called ADAPT (Analysis of Dynamic Accident Progression Trees). ADAPT is a system software infrastructure that supports execution and analysis of multiple dynamic event-tree simulations on distributed environments. A simulator abstraction layer was developed, and a generic driver was implemented for executing simulators on a distributed environment. As a demonstration of the use of the methodological tool, ADAPT was applied to quantify the likelihood of competing accident progression pathways occurring for a particular accident scenario in a particular reactor type using MELCOR, an integrated severe accident analysis code developed at Sandia. (ADAPT was intentionally created with flexibility, however, and is not limited to interacting with only one code. With minor coding changes to input files, ADAPT can be linked to other such codes.) The results of this demonstration indicate that the approach can significantly reduce the resources required for Level 2 PRAs. From the phenomenological viewpoint, ADAPT can also treat the associated epistemic and aleatory uncertainties. This methodology can also be used for analyses of other complex systems. Any complex system can be analyzed using ADAPT if the workings of that system can be displayed as an event tree, there is a computer code that simulates how those events could progress, and that simulator code has switches to turn on and off system events, phenomena, etc. Using and applying ADAPT to particular problems is not human independent. While the human resources for the creation and analysis of the accident progression are significantly decreased, knowledgeable analysts are still necessary for a given project to apply ADAPT successfully. This research and development effort has met its original goals and then exceeded them.« less

Tracing footprints of environmental events in tree ring chemistry using neutron activation analysis

NASA Astrophysics Data System (ADS)

Sahin, Dagistan

The aim of this study is to identify environmental effects on tree-ring chemistry. It is known that industrial pollution, volcanic eruptions, dust storms, acid rain and similar events can cause substantial changes in soil chemistry. Establishing whether a particular group of trees is sensitive to these changes in soil environment and registers them in the elemental chemistry of contemporary growth rings is the over-riding goal of any Dendrochemistry research. In this study, elemental concentrations were measured in tree-ring samples of absolutely dated eleven modern forest trees, grown in the Mediterranean region, Turkey, collected and dated by the Malcolm and Carolyn Wiener Laboratory for Aegean and Near Eastern Dendrochronology laboratory at Cornell University. Correlations between measured elemental concentrations in the tree-ring samples were analyzed using statistical tests to answer two questions. Does the current concentration of a particular element depend on any other element within the tree? And, are there any elements showing correlated abnormal concentration changes across the majority of the trees? Based on the detailed analysis results, the low mobility of sodium and bromine, positive correlations between calcium, zinc and manganese, positive correlations between trace elements lanthanum, samarium, antimony, and gold within tree-rings were recognized. Moreover, zinc, lanthanum, samarium and bromine showed strong, positive correlations among the trees and were identified as possible environmental signature elements. New Dendrochemistry information found in this study would be also useful in explaining tree physiology and elemental chemistry in Pinus nigra species grown in Turkey. Elemental concentrations in tree-ring samples were measured using Neutron Activation Analysis (NAA) at the Pennsylvania State University Radiation Science and Engineering Center (RSEC). Through this study, advanced methodologies for methodological, computational and experimental NAA were developed to ensure an acceptable accuracy and certainty in the elemental concentration measurements in tree-ring samples. Two independent analysis methods of NAA were used; the well known k-zero method and a novel method developed in this study, called the Multi-isotope Iterative Westcott (MIW) method. The MIW method uses reaction rate probabilities for a group of isotopes, which can be calculated by a neutronic simulation or measured by experimentation, and determines the representative values for the neutron flux and neutron flux characterization parameters based on Westcott convention. Elemental concentration calculations for standard reference material and tree-ring samples were then performed using the MIW and k-zero analysis methods of the NAA and the results were cross verified. In the computational part of this study, a detailed burnup coupled neutronic simulation was developed to analyze real-time neutronic changes in a TRIGA Mark III reactor core, in this study, the Penn State Breazeale Reactor (PSBR) core. To the best of the author`s knowledge, this is the first burnup coupled neutronic simulation with realistic time steps and full fuel temperature profile for a TRIGA reactor using Monte Carlo Utility for Reactor Evolutions (MURE) code and Monte Carlo Neutral-Particle Code (MCNP) coupling. High fidelity and flexibility in the simulation was aimed to replicate the real core operation through the day. This approach resulted in an enhanced accuracy in neutronic representation of the PSBR core with respect to previous neutronic simulation models for the PSBR core. An important contribution was made in the NAA experimentation practices employed in Dendrochemistry studies at the RSEC. Automated laboratory control and analysis software for NAA measurements in the RSEC Radionuclide Applications Laboratory was developed. Detailed laboratory procedures were written in this study comprising preparation, handling and measurements of tree-ring samples in the Radionuclide Applications Laboratory.

The analysis of rapidly developing fog at the Kennedy Space Center

NASA Technical Reports Server (NTRS)

Wheeler, Mark M.; Atchison, Michael K.; Schumann, Robin; Taylor, Greg E.; Yersavich, Ann; Warburton, John D.

1994-01-01

This report documents fog precursors and fog climatology at Kennedy Space Center (KSC) Florida from 1986 to 1990. The major emphasis of this report focuses on rapidly developing fog events that would affect the less than 7-statute mile visibility rule for End-Of-Mission (EOM) Shuttle landing at KSC (Rule 4-64(A)). The Applied Meteorology Unit's (AMU's) work is to: develop a data base for study of fog associated weather conditions relating to violations of this landing constraint; develop forecast techniques or rules-of-thumb to determine whether or not current conditions are likely to result in an acceptable condition at landing; validate the forecast techniques; and transition techniques to operational use. As part of the analysis the fog events were categorized as either advection, pre-frontal or radiation. As a result of these analyses, the AMU developed a fog climatological data base, identified fog precursors and developed forecaster tools and decision trees. The fog climatological analysis indicates that during the fog season (October to April) there is a higher risk for a visibility violation at KSC during the early morning hours (0700 to 1200 UTC), while 95 percent of all fog events have dissipated by 1600 UTC. A high number of fog events are characterized by a westerly component to the surface wind at KSC (92 percent) and 83 percent of the fog events had fog develop west of KSC first (up to 2 hours). The AMU developed fog decision trees and forecaster tools that would help the forecaster identify fog precursors up to 12 hours in advance. Using the decision trees as process tools ensures the important meteorological data are not overlooked in the forecast process. With these tools and a better understanding of fog formation in the local KSC area, the Shuttle weather support forecaster should be able to give the Launch and Flight Directors a better KSC fog forecast with more confidence.

The chordate proteome history database.

PubMed

Levasseur, Anthony; Paganini, Julien; Dainat, Jacques; Thompson, Julie D; Poch, Olivier; Pontarotti, Pierre; Gouret, Philippe

2012-01-01

The chordate proteome history database (http://ioda.univ-provence.fr) comprises some 20,000 evolutionary analyses of proteins from chordate species. Our main objective was to characterize and study the evolutionary histories of the chordate proteome, and in particular to detect genomic events and automatic functional searches. Firstly, phylogenetic analyses based on high quality multiple sequence alignments and a robust phylogenetic pipeline were performed for the whole protein and for each individual domain. Novel approaches were developed to identify orthologs/paralogs, and predict gene duplication/gain/loss events and the occurrence of new protein architectures (domain gains, losses and shuffling). These important genetic events were localized on the phylogenetic trees and on the genomic sequence. Secondly, the phylogenetic trees were enhanced by the creation of phylogroups, whereby groups of orthologous sequences created using OrthoMCL were corrected based on the phylogenetic trees; gene family size and gene gain/loss in a given lineage could be deduced from the phylogroups. For each ortholog group obtained from the phylogenetic or the phylogroup analysis, functional information and expression data can be retrieved. Database searches can be performed easily using biological objects: protein identifier, keyword or domain, but can also be based on events, eg, domain exchange events can be retrieved. To our knowledge, this is the first database that links group clustering, phylogeny and automatic functional searches along with the detection of important events occurring during genome evolution, such as the appearance of a new domain architecture.

CUTSETS - MINIMAL CUT SET CALCULATION FOR DIGRAPH AND FAULT TREE RELIABILITY MODELS

NASA Technical Reports Server (NTRS)

Iverson, D. L.

1994-01-01

Fault tree and digraph models are frequently used for system failure analysis. Both type of models represent a failure space view of the system using AND and OR nodes in a directed graph structure. Fault trees must have a tree structure and do not allow cycles or loops in the graph. Digraphs allow any pattern of interconnection between loops in the graphs. A common operation performed on digraph and fault tree models is the calculation of minimal cut sets. A cut set is a set of basic failures that could cause a given target failure event to occur. A minimal cut set for a target event node in a fault tree or digraph is any cut set for the node with the property that if any one of the failures in the set is removed, the occurrence of the other failures in the set will not cause the target failure event. CUTSETS will identify all the minimal cut sets for a given node. The CUTSETS package contains programs that solve for minimal cut sets of fault trees and digraphs using object-oriented programming techniques. These cut set codes can be used to solve graph models for reliability analysis and identify potential single point failures in a modeled system. The fault tree minimal cut set code reads in a fault tree model input file with each node listed in a text format. In the input file the user specifies a top node of the fault tree and a maximum cut set size to be calculated. CUTSETS will find minimal sets of basic events which would cause the failure at the output of a given fault tree gate. The program can find all the minimal cut sets of a node, or minimal cut sets up to a specified size. The algorithm performs a recursive top down parse of the fault tree, starting at the specified top node, and combines the cut sets of each child node into sets of basic event failures that would cause the failure event at the output of that gate. Minimal cut set solutions can be found for all nodes in the fault tree or just for the top node. The digraph cut set code uses the same techniques as the fault tree cut set code, except it includes all upstream digraph nodes in the cut sets for a given node and checks for cycles in the digraph during the solution process. CUTSETS solves for specified nodes and will not automatically solve for all upstream digraph nodes. The cut sets will be output as a text file. CUTSETS includes a utility program that will convert the popular COD format digraph model description files into text input files suitable for use with the CUTSETS programs. FEAT (MSC-21873) and FIRM (MSC-21860) available from COSMIC are examples of programs that produce COD format digraph model description files that may be converted for use with the CUTSETS programs. CUTSETS is written in C-language to be machine independent. It has been successfully implemented on a Sun running SunOS, a DECstation running ULTRIX, a Macintosh running System 7, and a DEC VAX running VMS. The RAM requirement varies with the size of the models. CUTSETS is available in UNIX tar format on a .25 inch streaming magnetic tape cartridge (standard distribution) or on a 3.5 inch diskette. It is also available on a 3.5 inch Macintosh format diskette or on a 9-track 1600 BPI magnetic tape in DEC VAX FILES-11 format. Sample input and sample output are provided on the distribution medium. An electronic copy of the documentation in Macintosh Microsoft Word format is included on the distribution medium. Sun and SunOS are trademarks of Sun Microsystems, Inc. DEC, DeCstation, ULTRIX, VAX, and VMS are trademarks of Digital Equipment Corporation. UNIX is a registered trademark of AT&T Bell Laboratories. Macintosh is a registered trademark of Apple Computer, Inc.

Adaptation of Chain Event Graphs for use with Case-Control Studies in Epidemiology.

PubMed

Keeble, Claire; Thwaites, Peter Adam; Barber, Stuart; Law, Graham Richard; Baxter, Paul David

2017-09-26

Case-control studies are used in epidemiology to try to uncover the causes of diseases, but are a retrospective study design known to suffer from non-participation and recall bias, which may explain their decreased popularity in recent years. Traditional analyses report usually only the odds ratio for given exposures and the binary disease status. Chain event graphs are a graphical representation of a statistical model derived from event trees which have been developed in artificial intelligence and statistics, and only recently introduced to the epidemiology literature. They are a modern Bayesian technique which enable prior knowledge to be incorporated into the data analysis using the agglomerative hierarchical clustering algorithm, used to form a suitable chain event graph. Additionally, they can account for missing data and be used to explore missingness mechanisms. Here we adapt the chain event graph framework to suit scenarios often encountered in case-control studies, to strengthen this study design which is time and financially efficient. We demonstrate eight adaptations to the graphs, which consist of two suitable for full case-control study analysis, four which can be used in interim analyses to explore biases, and two which aim to improve the ease and accuracy of analyses. The adaptations are illustrated with complete, reproducible, fully-interpreted examples, including the event tree and chain event graph. Chain event graphs are used here for the first time to summarise non-participation, data collection techniques, data reliability, and disease severity in case-control studies. We demonstrate how these features of a case-control study can be incorporated into the analysis to provide further insight, which can help to identify potential biases and lead to more accurate study results.

36 CFR 292.46 - Timber harvesting activities.

Code of Federal Regulations, 2010 CFR

2010-07-01

... hazard trees; or to respond to natural events such as wildfire, flood, earthquake, volcanic eruption, high winds, and disease or insect infestation. (2) Where authorized, trees may be harvested by... trees, or to respond to natural events provided that the activity is consistent with the Wild and Scenic...

Distributed Events in Sentinel: Design and Implementation of a Global Event Detector

DTIC Science & Technology

1999-01-01

local event detector and a global event detector to detect events. Global event detector in this case plays the role of a message sending/receiving than...significant in this case . The system performance will decrease with increase in the number of applications involved in global event detection. Yet from a...Figure 8: A Global event tree (2) 1. Global composite event is detected at the GED In this case , the whole global composite event tree is sent to the

Inferring duplications, losses, transfers and incomplete lineage sorting with nonbinary species trees.

PubMed

Stolzer, Maureen; Lai, Han; Xu, Minli; Sathaye, Deepa; Vernot, Benjamin; Durand, Dannie

2012-09-15

Gene duplication (D), transfer (T), loss (L) and incomplete lineage sorting (I) are crucial to the evolution of gene families and the emergence of novel functions. The history of these events can be inferred via comparison of gene and species trees, a process called reconciliation, yet current reconciliation algorithms model only a subset of these evolutionary processes. We present an algorithm to reconcile a binary gene tree with a nonbinary species tree under a DTLI parsimony criterion. This is the first reconciliation algorithm to capture all four evolutionary processes driving tree incongruence and the first to reconcile non-binary species trees with a transfer model. Our algorithm infers all optimal solutions and reports complete, temporally feasible event histories, giving the gene and species lineages in which each event occurred. It is fixed-parameter tractable, with polytime complexity when the maximum species outdegree is fixed. Application of our algorithms to prokaryotic and eukaryotic data show that use of an incomplete event model has substantial impact on the events inferred and resulting biological conclusions. Our algorithms have been implemented in Notung, a freely available phylogenetic reconciliation software package, available at http://www.cs.cmu.edu/~durand/Notung. mstolzer@andrew.cmu.edu.

When All the Ducks Line Up

NASA Technical Reports Server (NTRS)

Henwood, Bart E.

2007-01-01

This viewgraph presentation gives an overview of the N2NA Pylon overheat mishap. The contents include: 1) Investigation Process; 2) Bottom Line; 3) Event Description / Damage; 4) Causal Tree Analysis; 5) Significant Observations; and 6) Major Recommendations.

Coronal Mass Ejection Data Clustering and Visualization of Decision Trees

NASA Astrophysics Data System (ADS)

Ma, Ruizhe; Angryk, Rafal A.; Riley, Pete; Filali Boubrahimi, Soukaina

2018-05-01

Coronal mass ejections (CMEs) can be categorized as either “magnetic clouds” (MCs) or non-MCs. Features such as a large magnetic field, low plasma-beta, and low proton temperature suggest that a CME event is also an MC event; however, so far there is neither a definitive method nor an automatic process to distinguish the two. Human labeling is time-consuming, and results can fluctuate owing to the imprecise definition of such events. In this study, we approach the problem of MC and non-MC distinction from a time series data analysis perspective and show how clustering can shed some light on this problem. Although many algorithms exist for traditional data clustering in the Euclidean space, they are not well suited for time series data. Problems such as inadequate distance measure, inaccurate cluster center description, and lack of intuitive cluster representations need to be addressed for effective time series clustering. Our data analysis in this work is twofold: clustering and visualization. For clustering we compared the results from the popular hierarchical agglomerative clustering technique to a distance density clustering heuristic we developed previously for time series data clustering. In both cases, dynamic time warping will be used for similarity measure. For classification as well as visualization, we use decision trees to aggregate single-dimensional clustering results to form a multidimensional time series decision tree, with averaged time series to present each decision. In this study, we achieved modest accuracy and, more importantly, an intuitive interpretation of how different parameters contribute to an MC event.

Early changes in physical tree characteristics during an oak decline event in the Ozark highlands

Treesearch

Martin A. Spetich

2006-01-01

An oak decline event is severely affecting up to 120 000 ha in the Ozark National Forest of Arkansas. Results of early changes in physical tree characteristics during that event are presented. In the fall and winter of 1999 and 2000, we established research plots on a site that would become a center of severe oak decline. In August 2000, standing trees > 14 cm in...

A computational framework for prime implicants identification in noncoherent dynamic systems.

PubMed

Di Maio, Francesco; Baronchelli, Samuele; Zio, Enrico

2015-01-01

Dynamic reliability methods aim at complementing the capability of traditional static approaches (e.g., event trees [ETs] and fault trees [FTs]) by accounting for the system dynamic behavior and its interactions with the system state transition process. For this, the system dynamics is here described by a time-dependent model that includes the dependencies with the stochastic transition events. In this article, we present a novel computational framework for dynamic reliability analysis whose objectives are i) accounting for discrete stochastic transition events and ii) identifying the prime implicants (PIs) of the dynamic system. The framework entails adopting a multiple-valued logic (MVL) to consider stochastic transitions at discretized times. Then, PIs are originally identified by a differential evolution (DE) algorithm that looks for the optimal MVL solution of a covering problem formulated for MVL accident scenarios. For testing the feasibility of the framework, a dynamic noncoherent system composed of five components that can fail at discretized times has been analyzed, showing the applicability of the framework to practical cases. © 2014 Society for Risk Analysis.

Dissecting the space-time structure of tree-ring datasets using the partial triadic analysis.

PubMed

Rossi, Jean-Pierre; Nardin, Maxime; Godefroid, Martin; Ruiz-Diaz, Manuela; Sergent, Anne-Sophie; Martinez-Meier, Alejandro; Pâques, Luc; Rozenberg, Philippe

2014-01-01

Tree-ring datasets are used in a variety of circumstances, including archeology, climatology, forest ecology, and wood technology. These data are based on microdensity profiles and consist of a set of tree-ring descriptors, such as ring width or early/latewood density, measured for a set of individual trees. Because successive rings correspond to successive years, the resulting dataset is a ring variables × trees × time datacube. Multivariate statistical analyses, such as principal component analysis, have been widely used for extracting worthwhile information from ring datasets, but they typically address two-way matrices, such as ring variables × trees or ring variables × time. Here, we explore the potential of the partial triadic analysis (PTA), a multivariate method dedicated to the analysis of three-way datasets, to apprehend the space-time structure of tree-ring datasets. We analyzed a set of 11 tree-ring descriptors measured in 149 georeferenced individuals of European larch (Larix decidua Miller) during the period of 1967-2007. The processing of densitometry profiles led to a set of ring descriptors for each tree and for each year from 1967-2007. The resulting three-way data table was subjected to two distinct analyses in order to explore i) the temporal evolution of spatial structures and ii) the spatial structure of temporal dynamics. We report the presence of a spatial structure common to the different years, highlighting the inter-individual variability of the ring descriptors at the stand scale. We found a temporal trajectory common to the trees that could be separated into a high and low frequency signal, corresponding to inter-annual variations possibly related to defoliation events and a long-term trend possibly related to climate change. We conclude that PTA is a powerful tool to unravel and hierarchize the different sources of variation within tree-ring datasets.

Quantification of source uncertainties in Seismic Probabilistic Tsunami Hazard Analysis (SPTHA)

NASA Astrophysics Data System (ADS)

Selva, J.; Tonini, R.; Molinari, I.; Tiberti, M. M.; Romano, F.; Grezio, A.; Melini, D.; Piatanesi, A.; Basili, R.; Lorito, S.

2016-06-01

We propose a procedure for uncertainty quantification in Probabilistic Tsunami Hazard Analysis (PTHA), with a special emphasis on the uncertainty related to statistical modelling of the earthquake source in Seismic PTHA (SPTHA), and on the separate treatment of subduction and crustal earthquakes (treated as background seismicity). An event tree approach and ensemble modelling are used in spite of more classical approaches, such as the hazard integral and the logic tree. This procedure consists of four steps: (1) exploration of aleatory uncertainty through an event tree, with alternative implementations for exploring epistemic uncertainty; (2) numerical computation of tsunami generation and propagation up to a given offshore isobath; (3) (optional) site-specific quantification of inundation; (4) simultaneous quantification of aleatory and epistemic uncertainty through ensemble modelling. The proposed procedure is general and independent of the kind of tsunami source considered; however, we implement step 1, the event tree, specifically for SPTHA, focusing on seismic source uncertainty. To exemplify the procedure, we develop a case study considering seismic sources in the Ionian Sea (central-eastern Mediterranean Sea), using the coasts of Southern Italy as a target zone. The results show that an efficient and complete quantification of all the uncertainties is feasible even when treating a large number of potential sources and a large set of alternative model formulations. We also find that (i) treating separately subduction and background (crustal) earthquakes allows for optimal use of available information and for avoiding significant biases; (ii) both subduction interface and crustal faults contribute to the SPTHA, with different proportions that depend on source-target position and tsunami intensity; (iii) the proposed framework allows sensitivity and deaggregation analyses, demonstrating the applicability of the method for operational assessments.

Dendrogeomorphic analysis of flash floods in a small ungauged mountain catchment (Central Spain)

NASA Astrophysics Data System (ADS)

Ruiz-Villanueva, Virginia; Díez-Herrero, Andrés; Stoffel, Markus; Bollschweiler, Michelle; Bodoque, José M.; Ballesteros, Juan A.

2010-06-01

Flash floods represent one of the most significant natural hazards with serious death tolls and economic damage at a worldwide level in general and in Mediterranean mountain catchments in particular. In these environments, systematic data is often lacking and analyses have to be based on alternative approaches such as dendrogeomorphology. In this study, we focus on the identification of flash floods based on growth disturbances (GD) observed in 98 heavily affected Mediterranean pine trees ( Pinus pinaster Ait.) located in or next to the torrential channel of the Pelayo River in the Spanish Central System. Flash floods are quite common in this catchment and are triggered by heavy storms, with high discharge and debris transport rates favoured by high stream gradients. Comparison of the anomalies in tree morphology and the position of the trees in the channel showed that the intensity of the disturbance clearly depends on geomorphology. The dating of past flash flood events was based on the number and intensity of GD observed in the tree-ring series and on the spatial distribution of affected trees along the torrent, thus allowing seven flash flood events during the last 50 years to be dated, namely in 1963, 1966, 1973, 1976, 1996, 2000, and 2005.

Dendrogeomorphic analysis of Flash Floods in a small ungauged mountain catchment (Central Spain)

NASA Astrophysics Data System (ADS)

Ruiz-Villanueva, Virginia; Díez-Herrero, Andrés.; Stoffel, Markus; Bollschweiler, Michelle; María Bodoque, José; Ballesteros, Juan Antonio

2010-05-01

Flash floods represent one of the most significant natural hazards with serious death tolls and economic damage at a worldwide level in general and in Mediterranean mountain catchments in particular. In these environments, systematic data is often lacking and analyses have to be based on alternative approaches such as dendrogeomorphology. In this study, we focus on the identification of flash floods based on growth disturbances (GD) observed in 98 heavily affected Mediterranean pine trees (Pinus pinaster Ait.) located in or next to the torrential channel of the Pelayo River in the Spanish Central System. Flash floods are quite common in this catchment and are triggered by heavy storms, with high discharge and debris transport rates favoured by high stream gradients. Comparison of the anomalies in tree morphology and the position of the trees in the channel showed that the intensity of the disturbance clearly depends on geomorphology. The dating of past flash-flood events was based on the number and intensity of GD observed in the tree-ring series, and on the spatial distribution of affected trees along the torrent, thus allowing seven flash-flood events during the last ~50 years to be dated, namely in 1963, 1966, 1973, 1976, 1996, 2000, and 2005.

Putative recombination events and evolutionary history of five economically important viruses of fruit trees based on coat protein-encoding gene sequence analysis.

PubMed

Boulila, Moncef

2010-06-01

To enhance the knowledge of recombination as an evolutionary process, 267 accessions retrieved from GenBank were investigated, all belonging to five economically important viruses infecting fruit crops (Plum pox, Apple chlorotic leaf spot, Apple mosaic, Prune dwarf, and Prunus necrotic ringspot viruses). Putative recombinational events were detected in the coat protein (CP)-encoding gene using RECCO and RDP version 3.31beta algorithms. Based on RECCO results, all five viruses were shown to contain potential recombination signals in the CP gene. Reconstructed trees with modified topologies were proposed. Furthermore, RECCO performed better than the RDP package in detecting recombination events and exhibiting their evolution rate along the sequences of the five viruses. RDP, however, provided the possible major and minor parents of the recombinants. Thus, the two methods should be considered complementary.

Universal artifacts affect the branching of phylogenetic trees, not universal scaling laws.

PubMed

Altaba, Cristian R

2009-01-01

The superficial resemblance of phylogenetic trees to other branching structures allows searching for macroevolutionary patterns. However, such trees are just statistical inferences of particular historical events. Recent meta-analyses report finding regularities in the branching pattern of phylogenetic trees. But is this supported by evidence, or are such regularities just methodological artifacts? If so, is there any signal in a phylogeny? In order to evaluate the impact of polytomies and imbalance on tree shape, the distribution of all binary and polytomic trees of up to 7 taxa was assessed in tree-shape space. The relationship between the proportion of outgroups and the amount of imbalance introduced with them was assessed applying four different tree-building methods to 100 combinations from a set of 10 ingroup and 9 outgroup species, and performing covariance analyses. The relevance of this analysis was explored taking 61 published phylogenies, based on nucleic acid sequences and involving various taxa, taxonomic levels, and tree-building methods. All methods of phylogenetic inference are quite sensitive to the artifacts introduced by outgroups. However, published phylogenies appear to be subject to a rather effective, albeit rather intuitive control against such artifacts. The data and methods used to build phylogenetic trees are varied, so any meta-analysis is subject to pitfalls due to their uneven intrinsic merits, which translate into artifacts in tree shape. The binary branching pattern is an imposition of methods, and seldom reflects true relationships in intraspecific analyses, yielding artifactual polytomies in short trees. Above the species level, the departure of real trees from simplistic random models is caused at least by two natural factors--uneven speciation and extinction rates; and artifacts such as choice of taxa included in the analysis, and imbalance introduced by outgroups and basal paraphyletic taxa. This artifactual imbalance accounts for tree shape convergence of large trees. There is no evidence for any universal scaling in the tree of life. Instead, there is a need for improved methods of tree analysis that can be used to discriminate the noise due to outgroups from the phylogenetic signal within the taxon of interest, and to evaluate realistic models of evolution, correcting the retrospective perspective and explicitly recognizing extinction as a driving force. Artifacts are pervasive, and can only be overcome through understanding the structure and biological meaning of phylogenetic trees. Catalan Abstract in Translation S1.

Assembly and analysis of a male sterile rubber tree mitochondrial genome reveals DNA rearrangement events and a novel transcript

PubMed Central

2014-01-01

Background The rubber tree, Hevea brasiliensis, is an important plant species that is commercially grown to produce latex rubber in many countries. The rubber tree variety BPM 24 exhibits cytoplasmic male sterility, inherited from the variety GT 1. Results We constructed the rubber tree mitochondrial genome of a cytoplasmic male sterile variety, BPM 24, using 454 sequencing, including 8 kb paired-end libraries, plus Illumina paired-end sequencing. We annotated this mitochondrial genome with the aid of Illumina RNA-seq data and performed comparative analysis. We then compared the sequence of BPM 24 to the contigs of the published rubber tree, variety RRIM 600, and identified a rearrangement that is unique to BPM 24 resulting in a novel transcript containing a portion of atp9. Conclusions The novel transcript is consistent with changes that cause cytoplasmic male sterility through a slight reduction to ATP production efficiency. The exhaustive nature of the search rules out alternative causes and supports previous findings of novel transcripts causing cytoplasmic male sterility. PMID:24512148

Estimating phylogenetic relationships despite discordant gene trees across loci: the species tree of a diverse species group of feather mites (Acari: Proctophyllodidae).

PubMed

Knowles, Lacey L; Klimov, Pavel B

2011-11-01

With the increased availability of multilocus sequence data, the lack of concordance of gene trees estimated for independent loci has focused attention on both the biological processes producing the discord and the methodologies used to estimate phylogenetic relationships. What has emerged is a suite of new analytical tools for phylogenetic inference--species tree approaches. In contrast to traditional phylogenetic methods that are stymied by the idiosyncrasies of gene trees, approaches for estimating species trees explicitly take into account the cause of discord among loci and, in the process, provides a direct estimate of phylogenetic history (i.e. the history of species divergence, not divergence of specific loci). We illustrate the utility of species tree estimates with an analysis of a diverse group of feather mites, the pinnatus species group (genus Proctophyllodes). Discord among four sequenced nuclear loci is consistent with theoretical expectations, given the short time separating speciation events (as evident by short internodes relative to terminal branch lengths in the trees). Nevertheless, many of the relationships are well resolved in a Bayesian estimate of the species tree; the analysis also highlights ambiguous aspects of the phylogeny that require additional loci. The broad utility of species tree approaches is discussed, and specifically, their application to groups with high speciation rates--a history of diversification with particular prevalence in host/parasite systems where species interactions can drive rapid diversification.

COMCAN: a computer program for common cause analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burdick, G.R.; Marshall, N.H.; Wilson, J.R.

1976-05-01

The computer program, COMCAN, searches the fault tree minimal cut sets for shared susceptibility to various secondary events (common causes) and common links between components. In the case of common causes, a location check may also be performed by COMCAN to determine whether barriers to the common cause exist between components. The program can locate common manufacturers of components having events in the same minimal cut set. A relative ranking scheme for secondary event susceptibility is included in the program.

75 FR 66125 - Notice of Public Meeting and Request for Comments

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-27

...--The National Christmas Tree Lighting and the subsequent 23 day event. SUMMARY: The National Park Service is seeking public comments and suggestions on the planning of the 2010 National Christmas Tree... Christmas Tree Lighting and the subsequent 23 day event, which opens on December 9, 2010, on the Ellipse...

Identifying influential factors of business process performance using dependency analysis

NASA Astrophysics Data System (ADS)

Wetzstein, Branimir; Leitner, Philipp; Rosenberg, Florian; Dustdar, Schahram; Leymann, Frank

2011-02-01

We present a comprehensive framework for identifying influential factors of business process performance. In particular, our approach combines monitoring of process events and Quality of Service (QoS) measurements with dependency analysis to effectively identify influential factors. The framework uses data mining techniques to construct tree structures to represent dependencies of a key performance indicator (KPI) on process and QoS metrics. These dependency trees allow business analysts to determine how process KPIs depend on lower-level process metrics and QoS characteristics of the IT infrastructure. The structure of the dependencies enables a drill-down analysis of single factors of influence to gain a deeper knowledge why certain KPI targets are not met.

The influence of tree traits and storm event characteristics on stemflow production from isolated deciduous trees in an urban park

NASA Astrophysics Data System (ADS)

Carlyle-Moses, D. E.; Schooling, J. T.

2014-12-01

Urban tree canopy processes affect the volume and biogeochemistry of inputs to the hydrological cycle in cities. We studied stemflow from 37 isolated deciduous trees in an urban park in Kamloops, British Columbia which has a semi-arid climate dominated by small precipitation events. Precipitation and stemflow were measured on an event basis from June 12, 2012 to November 3, 2013. To clarify the effect of canopy traits on stemflow thresholds, rates, yields, percent, and funneling ratios, we analyzed branch angles, bark roughness, tree size, cover, leaf size, and branch and leader counts. High branch angles promoted stemflow in all trees, while bark roughness influenced stemflow differently for single- and multi-leader trees. The association between stemflow and numerous leaders deserves further study. Columnar-form trees often partitioned a large percentage of precipitation into stemflow, with event-scale values as high as 27.9 % recorded for an Armstrong Freeman Maple (Acer x freemanii 'Armstrong'). Under growing-season conditions funneling ratios as high as 196.9 were derived for an American Beech (Fagus grandifolia) individual. Among meteorological variables, rain depth was strongly correlated with stemflow yields; intra-storm break duration, rainfall intensity, rainfall inclination, wind speed, and vapour pressure deficit also played roles. Greater stemflow was associated with leafless canopies and with rain or mixed events versus snow. Results can inform climate-sensitive selection and siting of urban trees towards integrated rainwater management. For example, previous studies suggest that the reduction in storm-water generation by urban trees is accomplished through canopy interception loss alone. However, trees that partition large quantities of precipitation canopy-drainage as stemflow to the base of their trunks, where it has the potential to infiltrate into the soil media rather than fall on impervious surfaces as throughfall, may assist in reducing stormwater flow.

Evidence of solar activity and El Niño signals in tree rings of Araucaria araucana and A. angustifolia in South America

NASA Astrophysics Data System (ADS)

Perone, A.; Lombardi, F.; Marchetti, M.; Tognetti, R.; Lasserre, B.

2016-10-01

Tree rings reveal climatic variations through years, but also the effect of solar activity in influencing the climate on a large scale. In order to investigate the role of solar cycles on climatic variability and to analyse their influences on tree growth, we focused on tree-ring chronologies of Araucaria angustifolia and Araucaria araucana in four study areas: Irati and Curitiba in Brazil, Caviahue in Chile, and Tolhuaca in Argentina. We obtained an average tree-ring chronology of 218, 117, 439, and 849 years for these areas, respectively. Particularly, the older chronologies also included the period of the Maunder and Dalton minima. To identify periodicities and trends observable in tree growth, the time series were analysed using spectral, wavelet and cross-wavelet techniques. Analysis based on the Multitaper method of annual growth rates identified 2 cycles with periodicities of 11 (Schwebe cycle) and 5.5 years (second harmonic of Schwebe cycle). In the Chilean and Argentinian sites, significant agreement between the time series of tree rings and the 11-year solar cycle was found during the periods of maximum solar activity. Results also showed oscillation with periods of 2-7 years, probably induced by local environmental variations, and possibly also related to the El-Niño events. Moreover, the Morlet complex wavelet analysis was applied to study the most relevant variability factors affecting tree-ring time series. Finally, we applied the cross-wavelet spectral analysis to evaluate the time lags between tree-ring and sunspot-number time series, as well as for the interaction between tree rings, the Southern Oscillation Index (SOI) and temperature and precipitation. Trees sampled in Chile and Argentina showed more evident responses of fluctuations in tree-ring time series to the variations of short and long periodicities in comparison with the Brazilian ones. These results provided new evidence on the solar activity-climate pattern-tree ring connections over centuries.

Average Stand Age from Forest Inventory Plots Does Not Describe Historical Fire Regimes in Ponderosa Pine and Mixed-Conifer Forests of Western North America.

PubMed

Stevens, Jens T; Safford, Hugh D; North, Malcolm P; Fried, Jeremy S; Gray, Andrew N; Brown, Peter M; Dolanc, Christopher R; Dobrowski, Solomon Z; Falk, Donald A; Farris, Calvin A; Franklin, Jerry F; Fulé, Peter Z; Hagmann, R Keala; Knapp, Eric E; Miller, Jay D; Smith, Douglas F; Swetnam, Thomas W; Taylor, Alan H

Quantifying historical fire regimes provides important information for managing contemporary forests. Historical fire frequency and severity can be estimated using several methods; each method has strengths and weaknesses and presents challenges for interpretation and verification. Recent efforts to quantify the timing of historical high-severity fire events in forests of western North America have assumed that the "stand age" variable from the US Forest Service Forest Inventory and Analysis (FIA) program reflects the timing of historical high-severity (i.e. stand-replacing) fire in ponderosa pine and mixed-conifer forests. To test this assumption, we re-analyze the dataset used in a previous analysis, and compare information from fire history records with information from co-located FIA plots. We demonstrate that 1) the FIA stand age variable does not reflect the large range of individual tree ages in the FIA plots: older trees comprised more than 10% of pre-stand age basal area in 58% of plots analyzed and more than 30% of pre-stand age basal area in 32% of plots, and 2) recruitment events are not necessarily related to high-severity fire occurrence. Because the FIA stand age variable is estimated from a sample of tree ages within the tree size class containing a plurality of canopy trees in the plot, it does not necessarily include the oldest trees, especially in uneven-aged stands. Thus, the FIA stand age variable does not indicate whether the trees in the predominant size class established in response to severe fire, or established during the absence of fire. FIA stand age was not designed to measure the time since a stand-replacing disturbance. Quantification of historical "mixed-severity" fire regimes must be explicit about the spatial scale of high-severity fire effects, which is not possible using FIA stand age data.

Average Stand Age from Forest Inventory Plots Does Not Describe Historical Fire Regimes in Ponderosa Pine and Mixed-Conifer Forests of Western North America

PubMed Central

Stevens, Jens T.; Safford, Hugh D.; North, Malcolm P.; Fried, Jeremy S.; Gray, Andrew N.; Brown, Peter M.; Dolanc, Christopher R.; Dobrowski, Solomon Z.; Falk, Donald A.; Farris, Calvin A.; Franklin, Jerry F.; Fulé, Peter Z.; Hagmann, R. Keala; Knapp, Eric E.; Miller, Jay D.; Smith, Douglas F.; Swetnam, Thomas W.; Taylor, Alan H.

2016-01-01

Quantifying historical fire regimes provides important information for managing contemporary forests. Historical fire frequency and severity can be estimated using several methods; each method has strengths and weaknesses and presents challenges for interpretation and verification. Recent efforts to quantify the timing of historical high-severity fire events in forests of western North America have assumed that the “stand age” variable from the US Forest Service Forest Inventory and Analysis (FIA) program reflects the timing of historical high-severity (i.e. stand-replacing) fire in ponderosa pine and mixed-conifer forests. To test this assumption, we re-analyze the dataset used in a previous analysis, and compare information from fire history records with information from co-located FIA plots. We demonstrate that 1) the FIA stand age variable does not reflect the large range of individual tree ages in the FIA plots: older trees comprised more than 10% of pre-stand age basal area in 58% of plots analyzed and more than 30% of pre-stand age basal area in 32% of plots, and 2) recruitment events are not necessarily related to high-severity fire occurrence. Because the FIA stand age variable is estimated from a sample of tree ages within the tree size class containing a plurality of canopy trees in the plot, it does not necessarily include the oldest trees, especially in uneven-aged stands. Thus, the FIA stand age variable does not indicate whether the trees in the predominant size class established in response to severe fire, or established during the absence of fire. FIA stand age was not designed to measure the time since a stand-replacing disturbance. Quantification of historical “mixed-severity” fire regimes must be explicit about the spatial scale of high-severity fire effects, which is not possible using FIA stand age data. PMID:27196621

IDHEAS – A NEW APPROACH FOR HUMAN RELIABILITY ANALYSIS

DOE Office of Scientific and Technical Information (OSTI.GOV)

G. W. Parry; J.A Forester; V.N. Dang

2013-09-01

This paper describes a method, IDHEAS (Integrated Decision-Tree Human Event Analysis System) that has been developed jointly by the US NRC and EPRI as an improved approach to Human Reliability Analysis (HRA) that is based on an understanding of the cognitive mechanisms and performance influencing factors (PIFs) that affect operator responses. The paper describes the various elements of the method, namely the performance of a detailed cognitive task analysis that is documented in a crew response tree (CRT), and the development of the associated time-line to identify the critical tasks, i.e. those whose failure results in a human failure eventmore » (HFE), and an approach to quantification that is based on explanations of why the HFE might occur.« less

Initiating Event Analysis of a Lithium Fluoride Thorium Reactor

NASA Astrophysics Data System (ADS)

Geraci, Nicholas Charles

The primary purpose of this study is to perform an Initiating Event Analysis for a Lithium Fluoride Thorium Reactor (LFTR) as the first step of a Probabilistic Safety Assessment (PSA). The major objective of the research is to compile a list of key initiating events capable of resulting in failure of safety systems and release of radioactive material from the LFTR. Due to the complex interactions between engineering design, component reliability and human reliability, probabilistic safety assessments are most useful when the scope is limited to a single reactor plant. Thus, this thesis will study the LFTR design proposed by Flibe Energy. An October 2015 Electric Power Research Institute report on the Flibe Energy LFTR asked "what-if?" questions of subject matter experts and compiled a list of key hazards with the most significant consequences to the safety or integrity of the LFTR. The potential exists for unforeseen hazards to pose additional risk for the LFTR, but the scope of this thesis is limited to evaluation of those key hazards already identified by Flibe Energy. These key hazards are the starting point for the Initiating Event Analysis performed in this thesis. Engineering evaluation and technical study of the plant using a literature review and comparison to reference technology revealed four hazards with high potential to cause reactor core damage. To determine the initiating events resulting in realization of these four hazards, reference was made to previous PSAs and existing NRC and EPRI initiating event lists. Finally, fault tree and event tree analyses were conducted, completing the logical classification of initiating events. Results are qualitative as opposed to quantitative due to the early stages of system design descriptions and lack of operating experience or data for the LFTR. In summary, this thesis analyzes initiating events using previous research and inductive and deductive reasoning through traditional risk management techniques to arrive at a list of key initiating events that can be used to address vulnerabilities during the design phases of LFTR development.

Ecohydrology of Lodgepole Pine Forests: Connecting Transpiration to Subsurface Flow Paths and Storage within a Subalpine Catchment

NASA Astrophysics Data System (ADS)

Byers, A.; Harpold, A. A.; Barnard, H. R.

2011-12-01

The hydrologic cycle plays a central role in regulating ecosystem structure and function. Linked studies of both subsurface and aboveground processes are needed to improve understanding of ecosystem changes that could result from climate change and disturbance in Colorado's subalpine forests. Here, we present data from plots dominated by lodgepole pine (Pinus contorta) at the Niwot Ridge LTER site on the Colorado Front Range that improves the process-level understanding of the source and fate of water between subsurface storage and plant uptake. This study utilized event-based sampling during the 2011 growing season to investigate a paradox between water sources and rooting depth in lodgepole pine. Findings from Niwot Ridge have shown that lodgepole, typically believed to be a shallow-rooted species, appear to be strongly dependent on water from snowmelt for the entire growing season. These results suggested that conifer species were accessing water from deeper in the soil than summer monsoon rain typically penetrated. In our study, the relationship between precipitation event size and depth of infiltration on a seasonal and event basis, the effective rooting depth of lodgepole pine, and hysteretic responses of transpiration to soil moisture over a growing season were examined using measurements of tree physiological processes (sap flux and water stress) and hydrological parameters (precipitation, soil moisture) as well as stable water isotope composition of xylem water, mobile and immobile soil water, snow, precipitation, and stream water. Analysis of data shows that soil moisture in deep layers (60 and 70 cm) responds to large summer rain events of 0.7 mm and greater, and that lodgepole sap flux increases by 15-30% within 24 hours of monsoon events and decreases over 72 hours or until subsequent rain. Water isotope analysis will further elucidate the source and event response of these trees. This research helps us understand whether processes known to occur in Mediterranean climate regimes, such as the "two water worlds" theory that tightly bound water in soil is available to trees but is separate from mobile water that drains to streams, also applies to continental mountainous climates. Furthermore, understanding the mediation of hydrologic processes by trees like lodgepole pine will improve modeling of hydrological and ecological processes and knowledge of forest susceptibility to climate change and other disturbance impacts.

Impacts of a water stress followed by an early frost event on beech (Fagus sylvatica L.) susceptibility to Scolytine ambrosia beetles - Research strategy and first results

NASA Astrophysics Data System (ADS)

La Spina, Sylvie; de Cannière, Charles; Molenberg, Jean-Marc; Vincke, Caroline; Deman, Déborah; Grégoire, Jean-Claude

2010-05-01

Climate change tends to induce more frequent abiotic and biotic extreme events, having large impacts on tree vitality. Weakened trees are then more susceptible to secondary insect outbreaks, as it happened in Belgium in the early 2000s: after an early frost event, secondary Scolytine ambrosia beetles attacks were observed on beech trees. In this study, we test if a combination of stress, i.e. a soil water deficit preceding an early frost, could render trees more attractive to beetles. An experimental study was set in autumn 2008. Two parcels of a beech forest were covered with plastic tents to induce a water stress by rain interception. The parcels were surrounded by 2-meters depth trenches to avoid water supply by streaming. Soil water content and different indicators of tree water use (sap flow, predawn leaf water potential, tree radial growth) were followed. In autumn 2010, artificial frost injuries will be inflicted to trees using dry ice. Trees attractivity for Scolytine insects, and the success of insect colonization will then be studied. The poster will focus on experiment setting and first results (impacts of soil water deficit on trees).

Biogeochemical hotspots following a simulated tree mortality event of southern pine beetle

NASA Astrophysics Data System (ADS)

Siegert, C. M.; Renninger, H. J.; Karunarathna, S.; Hornslein, N.; Riggins, J. J.; Clay, N. A.; Tang, J. D.; Chaney, B.; Drotar, N.

2017-12-01

Disturbances in forest ecosystems can alter functions like productivity, respiration, and nutrient cycling through the creation of biogeochemical hotspots. These events occur sporadically across the landscape, leading to uncertainty in terrestrial biosphere carbon models, which have yet to capture the full complexity of biotic and abiotic factors driving ecological processes in the terrestrial environment. Given the widespread impact of southern pine beetle on forest ecosystems throughout the southeastern United States, it is critical to management and planning activities to understand the role of these disturbances. As such, we hypothesize that bark beetle killed trees create biogeochemical hotspots in the soils surrounding their trunk as they undergo mortality due to (1) increased soil moisture from reductions in plant water uptake and increased stemflow production, (2) enhanced canopy-derived inputs of carbon and nitrogen, and (3) increased microbial activity and root mortality. In 2015, a field experiment to mimic a southern pine beetle attack was established by girdling loblolly pine trees. Subsequent measurements of throughfall and stemflow for water quantity and quality, transpiration, stem respiration, soil respiration, and soil chemistry were used to quantify the extent of spatial and temporal impacts of tree mortality on carbon budgets. Compared to control trees, girdled trees exhibited reduced water uptake within the first 6 months of the study and succumbed to mortality within 18 months. Over two years, the girdled trees generated 33% more stemflow than control trees (7836 vs. 5882 L m-2). Preliminary analysis of carbon and nitrogen concentrations and dissolved organic matter quality are still pending. In the surrounding soils, C:N ratios were greater under control trees (12.8) than under girdled trees (12.1), which was driven by an increase in carbon around control trees (+0.13 mg C mg-1 soil) and not a decrease around girdled trees (-0.01 mg C mg-1 soil), with no observed differences in N concentrations. Although data from the remaining of the 2017 growing season are still pending, we have thus far demonstrated how tree mortality from southern pine beetle changes single tree hydrologic and biogeochemical cycles.

Validation of criteria for the definition of transient lower esophageal sphincter relaxations using high-resolution manometry.

PubMed

Roman, S; Holloway, R; Keller, J; Herbella, F; Zerbib, F; Xiao, Y; Bernard, L; Bredenoord, A J; Bruley des Varannes, S; Chen, M; Fox, M; Kahrilas, P J; Mittal, R K; Penagini, R; Savarino, E; Sifrim, D; Wu, J; Decullier, E; Pandolfino, J E; Mion, F

2017-02-01

Criteria for transient lower esophageal sphincter relaxations (TLESRs) are well-defined for Dentsleeve manometry. As high-resolution manometry (HRM) is now the gold standard to assess esophageal motility, our aim was to propose a consensus definition of TLESRs using HRM. Postprandial esophageal HRM combined with impedance was performed in 10 patients with gastroesophageal reflux disease. Transient lower esophageal sphincter relaxations identification was performed by 17 experts using a Delphi process. Four investigators then characterized TLESR candidates that achieved 100% agreement (TLESR events) and those that achieved less than 25% agreement (non-events) after the third round. Logistic regression and decision tree analysis were used to define optimal diagnostic criteria. All diagnostic criteria were more frequently encountered in the 57 TLESR events than in the 52 non-events. Crural diaphragm (CD) inhibition and LES relaxation duration >10 seconds had the highest predictive value to identify TLESR. Based on decision tree analysis, reflux on impedance, esophageal shortening, common cavity, upper esophageal sphincter relaxation without swallow and secondary peristalsis were alternate diagnostic criteria. Using HRM, TLESR might be defined as LES relaxation occurring in absence of swallowing, lasting more than 10 seconds and associated with CD inhibition. © 2016 John Wiley & Sons Ltd.

Water uptake of trees in a montane forest catchment and the geomorphological potential of root growth in Boulder Creek Critical Zone Observatory, Rocky Mountains, Colorado

NASA Astrophysics Data System (ADS)

Skeets, B.; Barnard, H. R.; Byers, A.

2011-12-01

The influence of vegetation on the hydrological cycle and the possible effect of roots in geomorphological processes are poorly understood. Gordon Gulch watershed in the Front Range of the Rocky Mountains, Colorado, is a montane climate ecosystem of the Boulder Creek Critical Zone Observatory whose study adds to the database of ecohydrological work in different climates. This work sought to identify the sources of water used by different tree species and to determine how trees growing in rock outcrops may contribute to the fracturing and weathering of rock. Stable isotopes (18O and 2H) were analyzed from water extracted from soil and xylem samples. Pinus ponderosa on the south-facing slope consumes water from deeper depths during dry periods and uses newly rain-saturated soils, after rainfall events. Pinus contorta on the north -facing slope shows a similar, expected response in water consumption, before and after rain. Two trees (Pinus ponderosa) growing within rock outcrops demonstrate water use from cracks replenished by new rains. An underexplored question in geomorphology is whether tree roots growing in rock outcrops contribute to long-term geomorphological processes by physically deteriorating the bedrock. The dominant roots of measured trees contributed approximately 30 - 80% of total water use, seen especially after rainfall events. Preliminary analysis of root growth rings indicates that root growth is capable of expanding rock outcrop fractures at an approximate rate of 0.6 - 1.0 mm per year. These results demonstrate the significant role roots play in tree physiological processes and in bedrock deterioration.

Record of the Solar Activity and of Other Geophysical Phenomenons in Tree Ring

NASA Astrophysics Data System (ADS)

Rigozo, Nivaor Rodolfo

1999-01-01

Tree ring studies are usually used to determine or verify climatic factors which prevail in a given place or region and may cause tree ring width variations. Few studies are dedicated to the geophysical phenomena which may underlie these tree ring width variations. In order to look for periodicities which may be associated to the solar activity and/or to other geophysical phenomena which may influence tree ring growth, a new interactive image analysis method to measure tree ring width was developed and is presented here. This method makes use of a computer and a high resolution flatbed scanner; a program was also developed in Interactive Data Language (IDL 5.0) to study ring digitized images and transform them into time series. The main advantage of this method is the tree ring image interactive analysis without needing complex and high cost instrumentation. Thirty-nine samples were collected: 12 from Concordia - S. C., 9 from Canela - R. S., 14 from Sao Francisco de Paula - R. S., one from Nova Petropolis - R. S., 2 from Sao Martinho da Serra - R. S. e one from Chile. Fit functions are applied to ring width time series to obtain the best long time range trend (growth rate of every tree) curves and are eliminated through a standardization process that gives the tree ring index time series from which is performed spectral analysis by maximum entropy method and iterative regression. The results obtained show periodicities close to 11 yr, 22 yr Hale solar cycles and 5.5 yr for all sampling locations 52 yr and Gleissberg cycles for Concordia - S. C. and Chile samples. El Nino events were also observed with periods around 4 e 7 yr.

Oncogenetic tree model of somatic mutations and DNA methylation in colon tumors.

PubMed

Sweeney, Carol; Boucher, Kenneth M; Samowitz, Wade S; Wolff, Roger K; Albertsen, Hans; Curtin, Karen; Caan, Bette J; Slattery, Martha L

2009-01-01

Our understanding of somatic alterations in colon cancer has evolved from a concept of a series of events taking place in a single sequence to a recognition of multiple pathways. An oncogenetic tree is a model intended to describe the pathways and sequence of somatic alterations in carcinogenesis without assuming that tumors will fall in mutually exclusive categories. We applied this model to data on colon tumor somatic alterations. An oncogenetic tree model was built using data on mutations of TP53, KRAS2, APC, and BRAF genes, methylation at CpG sites of MLH1 and TP16 genes, methylation in tumor (MINT) markers, and microsatellite instability (MSI) for 971 colon tumors from a population-based series. Oncogenetic tree analysis resulted in a reproducible tree with three branches. The model represents methylation of MINT markers as initiating a branch and predisposing to MSI, methylation of MHL1 and TP16, and BRAF mutation. APC mutation is the first alteration in an independent branch and is followed by TP53 mutation. KRAS2 mutation was placed a third independent branch, implying that it neither depends on, nor predisposes to, the other alterations. Individual tumors were observed to have alteration patterns representing every combination of one, two, or all three branches. The oncogenetic tree model assumptions are appropriate for the observed heterogeneity of colon tumors, and the model produces a useful visual schematic of the sequence of events in pathways of colon carcinogenesis.

Reliability analysis of airship remote sensing system

NASA Astrophysics Data System (ADS)

Qin, Jun

1998-08-01

Airship Remote Sensing System (ARSS) for obtain the dynamic or real time images in the remote sensing of the catastrophe and the environment, is a mixed complex system. Its sensor platform is a remote control airship. The achievement of a remote sensing mission depends on a series of factors. For this reason, it is very important for us to analyze reliability of ARSS. In first place, the system model was simplified form multi-stage system to two-state system on the basis of the result of the failure mode and effect analysis and the failure tree failure mode effect and criticality analysis. The failure tree was created after analyzing all factors and their interrelations. This failure tree includes four branches, e.g. engine subsystem, remote control subsystem, airship construction subsystem, flying metrology and climate subsystem. By way of failure tree analysis and basic-events classing, the weak links were discovered. The result of test running shown no difference in comparison with theory analysis. In accordance with the above conclusions, a plan of the reliability growth and reliability maintenance were posed. System's reliability are raised from 89 percent to 92 percent with the reformation of the man-machine interactive interface, the augmentation of the secondary better-groupie and the secondary remote control equipment.

Missing rings in Pinus halepensis – the missing link to relate the tree-ring record to extreme climatic events

Treesearch

Klemen Novak; Martin de Luis; Miguel A. Saz; Luis A. Longares; Roberto Serrano-Notivoli; Josep Raventos; Katarina Cufar; Jozica Gricar; Alfredo Di Filippo; Gianluca Piovesan; Cyrille B.K. Rathgeber; Andreas Papadopoulos; Kevin T. Smith

2016-01-01

Climate predictions for the Mediterranean Basin include increased temperatures, decreased precipitation, and increased frequency of extreme climatic events (ECE). These conditions are associated with decreased tree growth and increased vulnerability to pests and diseases. The anatomy of tree rings responds to these environmental conditions. Quantitatively, the width of...

A diagnosis system using object-oriented fault tree models

NASA Technical Reports Server (NTRS)

Iverson, David L.; Patterson-Hine, F. A.

1990-01-01

Spaceborne computing systems must provide reliable, continuous operation for extended periods. Due to weight, power, and volume constraints, these systems must manage resources very effectively. A fault diagnosis algorithm is described which enables fast and flexible diagnoses in the dynamic distributed computing environments planned for future space missions. The algorithm uses a knowledge base that is easily changed and updated to reflect current system status. Augmented fault trees represented in an object-oriented form provide deep system knowledge that is easy to access and revise as a system changes. Given such a fault tree, a set of failure events that have occurred, and a set of failure events that have not occurred, this diagnosis system uses forward and backward chaining to propagate causal and temporal information about other failure events in the system being diagnosed. Once the system has established temporal and causal constraints, it reasons backward from heuristically selected failure events to find a set of basic failure events which are a likely cause of the occurrence of the top failure event in the fault tree. The diagnosis system has been implemented in common LISP using Flavors.

Simple street tree sampling

Treesearch

David J. Nowak; Jeffrey T. Walton; James Baldwin; Jerry Bond

2015-01-01

Information on street trees is critical for management of this important resource. Sampling of street tree populations provides an efficient means to obtain street tree population information. Long-term repeat measures of street tree samples supply additional information on street tree changes and can be used to report damages from catastrophic events. Analyses of...

Event Classification and Identification Based on the Characteristic Ellipsoid of Phasor Measurement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Jian; Diao, Ruisheng; Makarov, Yuri V.

2011-09-23

In this paper, a method to classify and identify power system events based on the characteristic ellipsoid of phasor measurement is presented. The decision tree technique is used to perform the event classification and identification. Event types, event locations and clearance times are identified by decision trees based on the indices of the characteristic ellipsoid. A sufficiently large number of transient events were simulated on the New England 10-machine 39-bus system based on different system configurations. Transient simulations taking into account different event types, clearance times and various locations are conducted to simulate phasor measurement. Bus voltage magnitudes and recordedmore » reactive and active power flows are used to build the characteristic ellipsoid. The volume, eccentricity, center and projection of the longest axis in the parameter space coordinates of the characteristic ellipsoids are used to classify and identify events. Results demonstrate that the characteristic ellipsoid and the decision tree are capable to detect the event type, location, and clearance time with very high accuracy.« less

Adaptive Sampling using Support Vector Machines

DOE Office of Scientific and Technical Information (OSTI.GOV)

D. Mandelli; C. Smith

2012-11-01

Reliability/safety analysis of stochastic dynamic systems (e.g., nuclear power plants, airplanes, chemical plants) is currently performed through a combination of Event-Tress and Fault-Trees. However, these conventional methods suffer from certain drawbacks: • Timing of events is not explicitly modeled • Ordering of events is preset by the analyst • The modeling of complex accident scenarios is driven by expert-judgment For these reasons, there is currently an increasing interest into the development of dynamic PRA methodologies since they can be used to address the deficiencies of conventional methods listed above.

Reliability Analysis of Main-axis Control System of the Equatorial Antarctica Astronomical Telescope Based on Fault Tree

NASA Astrophysics Data System (ADS)

LI, Y.; Yang, S. H.

2017-05-01

The Antarctica astronomical telescopes work chronically on the top of the unattended South Pole, and they have only one chance to maintain every year. Due to the complexity of the optical, mechanical, and electrical systems, the telescopes are hard to be maintained and need multi-tasker expedition teams, which means an excessive awareness is essential for the reliability of the Antarctica telescopes. Based on the fault mechanism and fault mode of the main-axis control system for the equatorial Antarctica astronomical telescope AST3-3 (Antarctic Schmidt Telescopes 3-3), the method of fault tree analysis is introduced in this article, and we obtains the importance degree of the top event from the importance degree of the bottom event structure. From the above results, the hidden problems and weak links can be effectively found out, which will indicate the direction for promoting the stability of the system and optimizing the design of the system.

Conversion of Questionnaire Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Powell, Danny H; Elwood Jr, Robert H

During the survey, respondents are asked to provide qualitative answers (well, adequate, needs improvement) on how well material control and accountability (MC&A) functions are being performed. These responses can be used to develop failure probabilities for basic events performed during routine operation of the MC&A systems. The failure frequencies for individual events may be used to estimate total system effectiveness using a fault tree in a probabilistic risk analysis (PRA). Numeric risk values are required for the PRA fault tree calculations that are performed to evaluate system effectiveness. So, the performance ratings in the questionnaire must be converted to relativemore » risk values for all of the basic MC&A tasks performed in the facility. If a specific material protection, control, and accountability (MPC&A) task is being performed at the 'perfect' level, the task is considered to have a near zero risk of failure. If the task is performed at a less than perfect level, the deficiency in performance represents some risk of failure for the event. As the degree of deficiency in performance increases, the risk of failure increases. If a task that should be performed is not being performed, that task is in a state of failure. The failure probabilities of all basic events contribute to the total system risk. Conversion of questionnaire MPC&A system performance data to numeric values is a separate function from the process of completing the questionnaire. When specific questions in the questionnaire are answered, the focus is on correctly assessing and reporting, in an adjectival manner, the actual performance of the related MC&A function. Prior to conversion, consideration should not be given to the numeric value that will be assigned during the conversion process. In the conversion process, adjectival responses to questions on system performance are quantified based on a log normal scale typically used in human error analysis (see A.D. Swain and H.E. Guttmann, 'Handbook of Human Reliability Analysis with Emphasis on Nuclear Power Plant Applications,' NUREG/CR-1278). This conversion produces the basic event risk of failure values required for the fault tree calculations. The fault tree is a deductive logic structure that corresponds to the operational nuclear MC&A system at a nuclear facility. The conventional Delphi process is a time-honored approach commonly used in the risk assessment field to extract numerical values for the failure rates of actions or activities when statistically significant data is absent.« less

Using incident response trees as a tool for risk management of online financial services.

PubMed

Gorton, Dan

2014-09-01

The article introduces the use of probabilistic risk assessment for modeling the incident response process of online financial services. The main contribution is the creation of incident response trees, using event tree analysis, which provides us with a visual tool and a systematic way to estimate the probability of a successful incident response process against the currently known risk landscape, making it possible to measure the balance between front-end and back-end security measures. The model is presented using an illustrative example, and is then applied to the incident response process of a Swedish bank. Access to relevant data is verified and the applicability and usability of the proposed model is verified using one year of historical data. Potential advantages and possible shortcomings are discussed, referring to both the design phase and the operational phase, and future work is presented. © 2014 Society for Risk Analysis.

Simulation-Based Evaluation of Hybridization Network Reconstruction Methods in the Presence of Incomplete Lineage Sorting

PubMed Central

Kamneva, Olga K; Rosenberg, Noah A

2017-01-01

Hybridization events generate reticulate species relationships, giving rise to species networks rather than species trees. We report a comparative study of consensus, maximum parsimony, and maximum likelihood methods of species network reconstruction using gene trees simulated assuming a known species history. We evaluate the role of the divergence time between species involved in a hybridization event, the relative contributions of the hybridizing species, and the error in gene tree estimation. When gene tree discordance is mostly due to hybridization and not due to incomplete lineage sorting (ILS), most of the methods can detect even highly skewed hybridization events between highly divergent species. For recent divergences between hybridizing species, when the influence of ILS is sufficiently high, likelihood methods outperform parsimony and consensus methods, which erroneously identify extra hybridizations. The more sophisticated likelihood methods, however, are affected by gene tree errors to a greater extent than are consensus and parsimony. PMID:28469378

Efficient Exploration of the Space of Reconciled Gene Trees

PubMed Central

Szöllősi, Gergely J.; Rosikiewicz, Wojciech; Boussau, Bastien; Tannier, Eric; Daubin, Vincent

2013-01-01

Gene trees record the combination of gene-level events, such as duplication, transfer and loss (DTL), and species-level events, such as speciation and extinction. Gene tree–species tree reconciliation methods model these processes by drawing gene trees into the species tree using a series of gene and species-level events. The reconstruction of gene trees based on sequence alone almost always involves choosing between statistically equivalent or weakly distinguishable relationships that could be much better resolved based on a putative species tree. To exploit this potential for accurate reconstruction of gene trees, the space of reconciled gene trees must be explored according to a joint model of sequence evolution and gene tree–species tree reconciliation. Here we present amalgamated likelihood estimation (ALE), a probabilistic approach to exhaustively explore all reconciled gene trees that can be amalgamated as a combination of clades observed in a sample of gene trees. We implement the ALE approach in the context of a reconciliation model (Szöllősi et al. 2013), which allows for the DTL of genes. We use ALE to efficiently approximate the sum of the joint likelihood over amalgamations and to find the reconciled gene tree that maximizes the joint likelihood among all such trees. We demonstrate using simulations that gene trees reconstructed using the joint likelihood are substantially more accurate than those reconstructed using sequence alone. Using realistic gene tree topologies, branch lengths, and alignment sizes, we demonstrate that ALE produces more accurate gene trees even if the model of sequence evolution is greatly simplified. Finally, examining 1099 gene families from 36 cyanobacterial genomes we find that joint likelihood-based inference results in a striking reduction in apparent phylogenetic discord, with respectively. 24%, 59%, and 46% reductions in the mean numbers of duplications, transfers, and losses per gene family. The open source implementation of ALE is available from https://github.com/ssolo/ALE.git. [amalgamation; gene tree reconciliation; gene tree reconstruction; lateral gene transfer; phylogeny.] PMID:23925510

Using Fault Trees to Advance Understanding of Diagnostic Errors.

PubMed

Rogith, Deevakar; Iyengar, M Sriram; Singh, Hardeep

2017-11-01

Diagnostic errors annually affect at least 5% of adults in the outpatient setting in the United States. Formal analytic techniques are only infrequently used to understand them, in part because of the complexity of diagnostic processes and clinical work flows involved. In this article, diagnostic errors were modeled using fault tree analysis (FTA), a form of root cause analysis that has been successfully used in other high-complexity, high-risk contexts. How factors contributing to diagnostic errors can be systematically modeled by FTA to inform error understanding and error prevention is demonstrated. A team of three experts reviewed 10 published cases of diagnostic error and constructed fault trees. The fault trees were modeled according to currently available conceptual frameworks characterizing diagnostic error. The 10 trees were then synthesized into a single fault tree to identify common contributing factors and pathways leading to diagnostic error. FTA is a visual, structured, deductive approach that depicts the temporal sequence of events and their interactions in a formal logical hierarchy. The visual FTA enables easier understanding of causative processes and cognitive and system factors, as well as rapid identification of common pathways and interactions in a unified fashion. In addition, it enables calculation of empirical estimates for causative pathways. Thus, fault trees might provide a useful framework for both quantitative and qualitative analysis of diagnostic errors. Future directions include establishing validity and reliability by modeling a wider range of error cases, conducting quantitative evaluations, and undertaking deeper exploration of other FTA capabilities. Copyright © 2017 The Joint Commission. Published by Elsevier Inc. All rights reserved.

Extreme Drought Event and Shrub Invasion Reduce Oak Trees Functioning and Resilience on Water-Limited Ecosystems

NASA Astrophysics Data System (ADS)

Caldeira, M. C.; Lobo-do-Vale, R.; Lecomte, X.; David, T. S.; Pinto, J. G.; Bugalho, M. N.; Werner, C.

2016-12-01

Extreme droughts and plant invasions are major drivers of global change that can critically affect ecosystem functioning. Shrub encroachment is increasing in many regions worldwide and extreme events are projected to increase in frequency and intensity, namely in the Mediterranean region. Nevertheless, little is known about how these drivers may interact and affect ecosystem functioning and resilience Using a manipulative shrub removal experiment and the co-occurrence of an extreme drought event in a Mediterranean oak woodland, we show that the combination of native shrub invasion and extreme drought reduced ecosystem transpiration and the resilience of the key-stone oak tree species. We established six 25 x 25 m paired plots in a shrub (Cistus ladanifer L.) encroached Mediterranean cork-oak (Quercus suber L.) woodland. We measured sapflow and pre-dawn leaf water potential of trees and shrubs and soil water content in all plots during four years. We determined the resilience of tree transpiration to evaluate to what extent trees recovered from the extreme drought event. From February to November 2011 we conducted baseline measurements for plot comparison. In November 2011 all the shrubs from one of all the paired plots were cut and removed. Ecosystem transpiration was dominated by the water use of the invasive shrub, which further increased after the extreme drought. Simultaneously, tree transpiration in invaded plots declined more sharply (67 ± 13 %) than in plots cleared from shrubs (31 ± 11%) relative to the pre-drought year (2011). Trees in invaded plots were not able to recover in the following wetter year showing lower resilience to the extreme drought event. Our results imply that in Mediterranean-type of climates invasion by water spending species coupled with the projected recurrent extreme droughts will cause critical drought tolerance thresholds of trees to be overcome, thus increasing the probability of tree mortality.

Nonbinary Tree-Based Phylogenetic Networks.

PubMed

Jetten, Laura; van Iersel, Leo

2018-01-01

Rooted phylogenetic networks are used to describe evolutionary histories that contain non-treelike evolutionary events such as hybridization and horizontal gene transfer. In some cases, such histories can be described by a phylogenetic base-tree with additional linking arcs, which can, for example, represent gene transfer events. Such phylogenetic networks are called tree-based. Here, we consider two possible generalizations of this concept to nonbinary networks, which we call tree-based and strictly-tree-based nonbinary phylogenetic networks. We give simple graph-theoretic characterizations of tree-based and strictly-tree-based nonbinary phylogenetic networks. Moreover, we show for each of these two classes that it can be decided in polynomial time whether a given network is contained in the class. Our approach also provides a new view on tree-based binary phylogenetic networks. Finally, we discuss two examples of nonbinary phylogenetic networks in biology and show how our results can be applied to them.

Stand-structural effects on Heterobasidion abietinum-related mortality following drought events in Abies pinsapo.

PubMed

Linares, Juan Carlos; Camarero, Jesús Julio; Bowker, Matthew A; Ochoa, Victoria; Carreira, José Antonio

2010-12-01

Climate change may affect tree-pathogen interactions. This possibility has important implications for drought-prone forests, where stand dynamics and disease pathogenicity are especially sensitive to climatic stress. In addition, stand structural attributes including density-dependent tree-to-tree competition may modulate the stands' resistance to drought events and pathogen outbreaks. To assess the effects of stand structure on root-rot-related mortality after severe droughts, we focused on Heterobasidion abietinum mortality in relict Spanish stands of Abies pinsapo, a drought-sensitive fir. We compared stand attributes and tree spatial patterns in three plots with H. abietinum root-rot disease and three plots without root-rot. Point-pattern analyses were used to investigate the scale and extent of mortality patterns and to test hypotheses related to the spread of the disease. Dendrochronology was used to date the year of death and to assess the association between droughts and growth decline. We applied a structural equation modelling approach to test if tree mortality occurs more rapidly than predicted by a simple distance model when trees are subjected to high tree-to-tree competition and following drought events. Contrary to expectations of drought mortality, the effect of precipitation on the year of death was strong and negative, indicating that a period of high precipitation induced an earlier tree death. Competition intensity, related to the size and density of neighbour trees, also induced an earlier tree death. The effect of distance to the disease focus was negligible except in combination with intensive competition. Our results indicate that infected trees have decreased ability to withstand drought stress, and demonstrate that tree-to-tree competition and fungal infection act as predisposing factors of forest decline and mortality.

Fuzzy fault tree assessment based on improved AHP for fire and explosion accidents for steel oil storage tanks.

PubMed

Shi, Lei; Shuai, Jian; Xu, Kui

2014-08-15

Fire and explosion accidents of steel oil storage tanks (FEASOST) occur occasionally during the petroleum and chemical industry production and storage processes and often have devastating impact on lives, the environment and property. To contribute towards the development of a quantitative approach for assessing the occurrence probability of FEASOST, a fault tree of FEASOST is constructed that identifies various potential causes. Traditional fault tree analysis (FTA) can achieve quantitative evaluation if the failure data of all of the basic events (BEs) are available, which is almost impossible due to the lack of detailed data, as well as other uncertainties. This paper makes an attempt to perform FTA of FEASOST by a hybrid application between an expert elicitation based improved analysis hierarchy process (AHP) and fuzzy set theory, and the occurrence possibility of FEASOST is estimated for an oil depot in China. A comparison between statistical data and calculated data using fuzzy fault tree analysis (FFTA) based on traditional and improved AHP is also made. Sensitivity and importance analysis has been performed to identify the most crucial BEs leading to FEASOST that will provide insights into how managers should focus effective mitigation. Copyright © 2014 Elsevier B.V. All rights reserved.

Real-Time and Delayed Analysis of Tree and Shrub Cores as Indicators of Subsurface Volatile Organic Compound Contamination, Durham Meadows Superfund Site, Durham, Connecticut, August 29, 2006

USGS Publications Warehouse

Vroblesky, Don A.; Willey, Richard E.; Clifford, Scott; Murphy, James J.

2008-01-01

This study examined volatile organic compound concentrations in cores from trees and shrubs for use as indicators of vadose-zone contamination or potential vapor intrusion by volatile organic compounds into buildings at the Durham Meadows Superfund Site, Durham, Connecticut. The study used both (1) real-time tree- and shrub-core analysis, which involved field heating the core samples for 5 to 10 minutes prior to field analysis, and (2) delayed analysis, which involved allowing the gases in the cores to equilibrate with the headspace gas in the sample vials unheated for 1 to 2 days prior to analysis. General correspondence was found between the two approaches, indicating that preheating and field analysis of vegetation cores is a viable approach to real-time monitoring of subsurface volatile organic compounds. In most cases, volatile organic compounds in cores from trees and shrubs at the Merriam Manufacturing Company property showed a general correspondence to the distribution of volatile organic compounds detected in a soil-gas survey, despite the fact that most of the soil-gas survey data in close proximity to the relevant trees were collected about 3 years prior to the tree-core collection. Most of the trees cored at the Durham Meadows Superfund Site, outside of the Merriam Manufacturing Company property, contained no volatile organic compounds and were in areas where indoor air sampling and soil-gas sampling showed little or no volatile organic compound concentrations. An exception was tree DM11, which contained barely detectable concentrations of trichloroethene near a house where previous investigations found low concentrations of trichloroethene (0.13 to 1.2 parts per billion by volume) in indoor air and 7.7 micrograms per liter of trichloroethene in the ground water. The barely detectable concentration of trichloroethene in tree DM11 and the lack of volatile organic compound detection in nearby tree DM10 (adjacent to the well having 7.7 micrograms of trichloroethene) may be attributable to the relatively large depth to water (17.6 feet), the relatively low soil-vapor trichloroethene concentration, and the large amount of rainfall during and preceding the tree-coring event. The data indicate that real-time and delayed analyses of tree cores are viable approaches to examining subsurface volatile organic compound soil-gas or vadose-zone contamination at the Durham Meadows Superfund Site and other similar sites. Thus, the methods may have application for determining the potential for vapor intrusion into buildings.

Attribution of Disturbances Causing Tree Mortality for the Continental U.S.

NASA Astrophysics Data System (ADS)

Wang, M.; Xu, C.; Allen, C. D.; McDowell, N. G.

2016-12-01

Broad-scale tree mortality has been frequently reported and documented to increase with warming climate and human activities. However, there is so far no general method to quantify the relative contributions of different disturbances on observed broad-scale tree mortality. In this study, we presented a framework to investigate the contribution of various disturbances causing tree mortality for 2000-2014 in the continental US. Our work is based on the high-resolution forest-loss data developed by Hansen et al. (2013). Firstly, fire-driven mortality was determined using the data from Monitoring Trends in Burn Severity (MTBS) project. Secondly, a landscape-pattern-recognition approach focusing on the differences of boundary complexity caused by natural and anthropogenic disturbances was developed to attribute harvest-driven mortality patches. Then, a drought threshold was determined through conducting an intensive literature survey for attribution of drought-driven mortality. Our results showed that we can correctly attribute 85% harvest-driven mortality as compared to Forest Inventory and Analysis (FIA) data. Based on Evaporative Stress Index (ESI), our literature survey suggests that most mortality events happened at extreme drought (37.7%), then severe (31.4%) and moderate (23.4%) drought. In total, 92.6% of drought-induced mortality events observed during 2000-2014 occurred at drought conditions of moderate or worse with corresponding ESI values ranging from -0.9 -2.49. Therefore, -0.9 will be used as the threshold to attribute drought-driven tree mortality. Overall, these results imply a great potential for using these methods to identify and attribute disturbances driving tree death at broad spatial scales.

Are trees long-lived?

Treesearch

Kevin T. Smith

2009-01-01

Trees and tree care can capture the best of people's motivations and intentions. Trees are living memorials that help communities heal at sites of national tragedy, such as Oklahoma City and the World Trade Center. We mark the places of important historical events by the trees that grew nearby even if the original tree, such as the Charter Oak in Connecticut or...

The role of hybridization in facilitating tree invasion

USDA-ARS?s Scientific Manuscript database

Hybridization events can generate additional genetic diversity on which natural selection can act and at times enhance invasiveness of the species. Invasive tree species are a growing ecological concern worldwide, and some of these invasions involve hybridization events pre- or post-introduction. Th...

Solar-Terrestrial Signal Record in Tree Ring Width Time Series from Brazil

NASA Astrophysics Data System (ADS)

Rigozo, Nivaor Rodolfo; Lisi, Cláudio Sergio; Filho, Mário Tomazello; Prestes, Alan; Nordemann, Daniel Jean Roger; de Souza Echer, Mariza Pereira; Echer, Ezequiel; da Silva, Heitor Evangelista; Rigozo, Valderez F.

2012-12-01

This work investigates the behavior of the sunspot number and Southern Oscillation Index (SOI) signal recorded in the tree ring time series for three different locations in Brazil: Humaitá in Amazônia State, Porto Ferreira in São Paulo State, and Passo Fundo in Rio Grande do Sul State, using wavelet and cross-wavelet analysis techniques. The wavelet spectra of tree ring time series showed signs of 11 and 22 years, possibly related to the solar activity, and periods of 2-8 years, possibly related to El Niño events. The cross-wavelet spectra for all tree ring time series from Brazil present a significant response to the 11-year solar cycle in the time interval between 1921 to after 1981. These tree ring time series still have a response to the second harmonic of the solar cycle (5.5 years), but in different time intervals. The cross-wavelet maps also showed that the relationship between the SOI x tree ring time series is more intense, for oscillation in the range of 4-8 years.

Underground riparian wood: Reconstructing the processes influencing buried stem and coarse root structures of Black Poplar (Populus nigra L.)

NASA Astrophysics Data System (ADS)

Holloway, James V.; Rillig, Matthias C.; Gurnell, Angela M.

2017-02-01

Following analysis of morphological (including dendrochronological and sedimentological) aspects of buried stem and coarse root structures of eight mature P. nigra individuals located within two sites along the middle to lower Tagliamento River, Italy (Holloway et al., 2017), this paper introduces information on the historical processes of vegetation development and river flow and links this to the form of these eight trees. Aerial images and flow time series are assembled to reconstruct the flood history, potential recruitment periods, and vegetation cover development in the vicinity of the studied trees. This information is combined with previous morphological evidence to reconstruct the development history of each tree via three-element summary diagrams showing (i) a time series of floods, aerial imagery dates, and potential recruitment periods, with colour-coded bars indicating likely key stages in the development of the tree; (ii) colour-coded overlays on an SfM photogrammetric model of each tree; and (iii) colour-coded text boxes providing explanatory annotations. The combined morphology-process analysis reveals complex three-dimensional underground structures, incorporating buried stems, shoots, and adventitious roots that are sometimes joined by grafting, linking the standing tree with the buried gravel surface on which it was recruited. Analysis of process data provides a firm basis for identifying and dating influential flow disturbance events and recruitment windows and shows that a relatively small number of flood events have significantly impacted the studied trees, which are mainly but not exclusively the largest floods in the record. Nevertheless, we stress that all suggested dates are best estimates in the light of the combined evidence. There is undoubted potential for building different interpretations of belowground woody structure development in light of such evidence, but we feel that the form and timing of the developmental trajectories we have proposed are reasonable and give balanced insights into the many possible ways in which this hidden component of riparian trees may develop. Our results are relevant to river research and management issues concerning riparian woodland, fluvial wood dynamics, and wood budgets, as they indicate (i) a large hidden volume of wood that is often ignored; (ii) complex, deep, coarse anchorage structures that have relevance for rates of fluvial wood recruitment associated with lateral bank erosion/stability or wind throw; and (iii) a wood element that may significantly affect wood transport and retention within fluvial systems.

A Passive System Reliability Analysis for a Station Blackout

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brunett, Acacia; Bucknor, Matthew; Grabaskas, David

2015-05-03

The latest iterations of advanced reactor designs have included increased reliance on passive safety systems to maintain plant integrity during unplanned sequences. While these systems are advantageous in reducing the reliance on human intervention and availability of power, the phenomenological foundations on which these systems are built require a novel approach to a reliability assessment. Passive systems possess the unique ability to fail functionally without failing physically, a result of their explicit dependency on existing boundary conditions that drive their operating mode and capacity. Argonne National Laboratory is performing ongoing analyses that demonstrate various methodologies for the characterization of passivemore » system reliability within a probabilistic framework. Two reliability analysis techniques are utilized in this work. The first approach, the Reliability Method for Passive Systems, provides a mechanistic technique employing deterministic models and conventional static event trees. The second approach, a simulation-based technique, utilizes discrete dynamic event trees to treat time- dependent phenomena during scenario evolution. For this demonstration analysis, both reliability assessment techniques are used to analyze an extended station blackout in a pool-type sodium fast reactor (SFR) coupled with a reactor cavity cooling system (RCCS). This work demonstrates the entire process of a passive system reliability analysis, including identification of important parameters and failure metrics, treatment of uncertainties and analysis of results.« less

RecPhyloXML - a format for reconciled gene trees.

PubMed

Duchemin, Wandrille; Gence, Guillaume; Arigon Chifolleau, Anne-Muriel; Arvestad, Lars; Bansal, Mukul S; Berry, Vincent; Boussau, Bastien; Chevenet, François; Comte, Nicolas; Davín, Adrián A; Dessimoz, Christophe; Dylus, David; Hasic, Damir; Mallo, Diego; Planel, Rémi; Posada, David; Scornavacca, Celine; Szöllosi, Gergely; Zhang, Louxin; Tannier, Éric; Daubin, Vincent

2018-05-14

A reconciliation is an annotation of the nodes of a gene tree with evolutionary events-for example, speciation, gene duplication, transfer, loss, etc-along with a mapping onto a species tree. Many algorithms and software produce or use reconciliations but often using different reconciliation formats, regarding the type of events considered or whether the species tree is dated or not. This complicates the comparison and communication between different programs. Here, we gather a consortium of software developers in gene tree species tree reconciliation to propose and endorse a format that aims to promote an integrative-albeit flexible-specification of phylogenetic reconciliations. This format, named recPhyloXML, is accompanied by several tools such as a reconciled tree visualizer and conversion utilities. http://phylariane.univ-lyon1.fr/recphyloxml/. wandrille.duchemin@univ-lyon1.fr. There is no supplementary data associated with this publication.

Application of decision tree model for the ground subsidence hazard mapping near abandoned underground coal mines.

PubMed

Lee, Saro; Park, Inhye

2013-09-30

Subsidence of ground caused by underground mines poses hazards to human life and property. This study analyzed the hazard to ground subsidence using factors that can affect ground subsidence and a decision tree approach in a geographic information system (GIS). The study area was Taebaek, Gangwon-do, Korea, where many abandoned underground coal mines exist. Spatial data, topography, geology, and various ground-engineering data for the subsidence area were collected and compiled in a database for mapping ground-subsidence hazard (GSH). The subsidence area was randomly split 50/50 for training and validation of the models. A data-mining classification technique was applied to the GSH mapping, and decision trees were constructed using the chi-squared automatic interaction detector (CHAID) and the quick, unbiased, and efficient statistical tree (QUEST) algorithms. The frequency ratio model was also applied to the GSH mapping for comparing with probabilistic model. The resulting GSH maps were validated using area-under-the-curve (AUC) analysis with the subsidence area data that had not been used for training the model. The highest accuracy was achieved by the decision tree model using CHAID algorithm (94.01%) comparing with QUEST algorithms (90.37%) and frequency ratio model (86.70%). These accuracies are higher than previously reported results for decision tree. Decision tree methods can therefore be used efficiently for GSH analysis and might be widely used for prediction of various spatial events. Copyright © 2013. Published by Elsevier Ltd.

A survival tree method for the analysis of discrete event times in clinical and epidemiological studies.

PubMed

Schmid, Matthias; Küchenhoff, Helmut; Hoerauf, Achim; Tutz, Gerhard

2016-02-28

Survival trees are a popular alternative to parametric survival modeling when there are interactions between the predictor variables or when the aim is to stratify patients into prognostic subgroups. A limitation of classical survival tree methodology is that most algorithms for tree construction are designed for continuous outcome variables. Hence, classical methods might not be appropriate if failure time data are measured on a discrete time scale (as is often the case in longitudinal studies where data are collected, e.g., quarterly or yearly). To address this issue, we develop a method for discrete survival tree construction. The proposed technique is based on the result that the likelihood of a discrete survival model is equivalent to the likelihood of a regression model for binary outcome data. Hence, we modify tree construction methods for binary outcomes such that they result in optimized partitions for the estimation of discrete hazard functions. By applying the proposed method to data from a randomized trial in patients with filarial lymphedema, we demonstrate how discrete survival trees can be used to identify clinically relevant patient groups with similar survival behavior. Copyright © 2015 John Wiley & Sons, Ltd.

Large-scale wind disturbances promote tree diversity in a Central Amazon forest.

PubMed

Marra, Daniel Magnabosco; Chambers, Jeffrey Q; Higuchi, Niro; Trumbore, Susan E; Ribeiro, Gabriel H P M; Dos Santos, Joaquim; Negrón-Juárez, Robinson I; Reu, Björn; Wirth, Christian

2014-01-01

Canopy gaps created by wind-throw events, or blowdowns, create a complex mosaic of forest patches varying in disturbance intensity and recovery in the Central Amazon. Using field and remote sensing data, we investigated the short-term (four-year) effects of large (>2000 m(2)) blowdown gaps created during a single storm event in January 2005 near Manaus, Brazil, to study (i) how forest structure and composition vary with disturbance gradients and (ii) whether tree diversity is promoted by niche differentiation related to wind-throw events at the landscape scale. In the forest area affected by the blowdown, tree mortality ranged from 0 to 70%, and was highest on plateaus and slopes. Less impacted areas in the region affected by the blowdown had overlapping characteristics with a nearby unaffected forest in tree density (583 ± 46 trees ha(-1)) (mean ± 99% Confidence Interval) and basal area (26.7 ± 2.4 m(2) ha(-1)). Highly impacted areas had tree density and basal area as low as 120 trees ha(-1) and 14.9 m(2) ha(-1), respectively. In general, these structural measures correlated negatively with an index of tree mortality intensity derived from satellite imagery. Four years after the blowdown event, differences in size-distribution, fraction of resprouters, floristic composition and species diversity still correlated with disturbance measures such as tree mortality and gap size. Our results suggest that the gradients of wind disturbance intensity encompassed in large blowdown gaps (>2000 m(2)) promote tree diversity. Specialists for particular disturbance intensities existed along the entire gradient. The existence of species or genera taking an intermediate position between undisturbed and gap specialists led to a peak of rarefied richness and diversity at intermediate disturbance levels. A diverse set of species differing widely in requirements and recruitment strategies forms the initial post-disturbance cohort, thus lending a high resilience towards wind disturbances at the community level.

Large-Scale Wind Disturbances Promote Tree Diversity in a Central Amazon Forest

PubMed Central

Marra, Daniel Magnabosco; Chambers, Jeffrey Q.; Higuchi, Niro; Trumbore, Susan E.; Ribeiro, Gabriel H. P. M.; dos Santos, Joaquim; Negrón-Juárez, Robinson I.; Reu, Björn; Wirth, Christian

2014-01-01

Canopy gaps created by wind-throw events, or blowdowns, create a complex mosaic of forest patches varying in disturbance intensity and recovery in the Central Amazon. Using field and remote sensing data, we investigated the short-term (four-year) effects of large (>2000 m2) blowdown gaps created during a single storm event in January 2005 near Manaus, Brazil, to study (i) how forest structure and composition vary with disturbance gradients and (ii) whether tree diversity is promoted by niche differentiation related to wind-throw events at the landscape scale. In the forest area affected by the blowdown, tree mortality ranged from 0 to 70%, and was highest on plateaus and slopes. Less impacted areas in the region affected by the blowdown had overlapping characteristics with a nearby unaffected forest in tree density (583±46 trees ha−1) (mean±99% Confidence Interval) and basal area (26.7±2.4 m2 ha−1). Highly impacted areas had tree density and basal area as low as 120 trees ha−1 and 14.9 m2 ha−1, respectively. In general, these structural measures correlated negatively with an index of tree mortality intensity derived from satellite imagery. Four years after the blowdown event, differences in size-distribution, fraction of resprouters, floristic composition and species diversity still correlated with disturbance measures such as tree mortality and gap size. Our results suggest that the gradients of wind disturbance intensity encompassed in large blowdown gaps (>2000 m2) promote tree diversity. Specialists for particular disturbance intensities existed along the entire gradient. The existence of species or genera taking an intermediate position between undisturbed and gap specialists led to a peak of rarefied richness and diversity at intermediate disturbance levels. A diverse set of species differing widely in requirements and recruitment strategies forms the initial post-disturbance cohort, thus lending a high resilience towards wind disturbances at the community level. PMID:25099118

Large-Scale Wind Disturbances Promote Tree Diversity in a Central Amazon Forest

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marra, Daniel Magnabosco; Chambers, Jeffrey Q.; Higuchi, Niro

Canopy gaps created by wind-throw events, or blowdowns, create a complex mosaic of forest patches varying in disturbance intensity and recovery in the Central Amazon. Using field and remote sensing data, we investigated the short-term (four-year) effects of large (>2000 m 2) blowdown gaps created during a single storm event in January 2005 near Manaus, Brazil, to study (i) how forest structure and composition vary with disturbance gradients and (ii) whether tree diversity is promoted by niche differentiation related to wind-throw events at the landscape scale. In the forest area affected by the blowdown, tree mortality ranged from 0 tomore » 70%, and was highest on plateaus and slopes. Less impacted areas in the region affected by the blowdown had overlapping characteristics with a nearby unaffected forest in tree density (583±46 trees ha -1) (mean±99% Confidence Interval) and basal area (26.7±2.4 m 2 ha -1). Highly impacted areas had tree density and basal area as low as 120 trees ha -1 and 14.9 m 2 ha -1, respectively. In general, these structural measures correlated negatively with an index of tree mortality intensity derived from satellite imagery. Four years after the blowdown event, differences in size-distribution, fraction of resprouters, floristic composition and species diversity still correlated with disturbance measures such as tree mortality and gap size. Our results suggest that the gradients of wind disturbance intensity encompassed in large blowdown gaps (>2000 m 2) promote tree diversity. Specialists for particular disturbance intensities existed along the entire gradient. The existence of species or genera taking an intermediate position between undisturbed and gap specialists led to a peak of rarefied richness and diversity at intermediate disturbance levels. A diverse set of species differing widely in requirements and recruitment strategies forms the initial post-disturbance cohort, thus lending a high resilience towards wind disturbances at the community level.« less

Large-Scale Wind Disturbances Promote Tree Diversity in a Central Amazon Forest

DOE PAGES

Marra, Daniel Magnabosco; Chambers, Jeffrey Q.; Higuchi, Niro; ...

2014-08-06

Canopy gaps created by wind-throw events, or blowdowns, create a complex mosaic of forest patches varying in disturbance intensity and recovery in the Central Amazon. Using field and remote sensing data, we investigated the short-term (four-year) effects of large (>2000 m 2) blowdown gaps created during a single storm event in January 2005 near Manaus, Brazil, to study (i) how forest structure and composition vary with disturbance gradients and (ii) whether tree diversity is promoted by niche differentiation related to wind-throw events at the landscape scale. In the forest area affected by the blowdown, tree mortality ranged from 0 tomore » 70%, and was highest on plateaus and slopes. Less impacted areas in the region affected by the blowdown had overlapping characteristics with a nearby unaffected forest in tree density (583±46 trees ha -1) (mean±99% Confidence Interval) and basal area (26.7±2.4 m 2 ha -1). Highly impacted areas had tree density and basal area as low as 120 trees ha -1 and 14.9 m 2 ha -1, respectively. In general, these structural measures correlated negatively with an index of tree mortality intensity derived from satellite imagery. Four years after the blowdown event, differences in size-distribution, fraction of resprouters, floristic composition and species diversity still correlated with disturbance measures such as tree mortality and gap size. Our results suggest that the gradients of wind disturbance intensity encompassed in large blowdown gaps (>2000 m 2) promote tree diversity. Specialists for particular disturbance intensities existed along the entire gradient. The existence of species or genera taking an intermediate position between undisturbed and gap specialists led to a peak of rarefied richness and diversity at intermediate disturbance levels. A diverse set of species differing widely in requirements and recruitment strategies forms the initial post-disturbance cohort, thus lending a high resilience towards wind disturbances at the community level.« less

Probabilistic Risk Assessment of Hydraulic Fracturing in Unconventional Reservoirs by Means of Fault Tree Analysis: An Initial Discussion

NASA Astrophysics Data System (ADS)

Rodak, C. M.; McHugh, R.; Wei, X.

2016-12-01

The development and combination of horizontal drilling and hydraulic fracturing has unlocked unconventional hydrocarbon reserves around the globe. These advances have triggered a number of concerns regarding aquifer contamination and over-exploitation, leading to scientific studies investigating potential risks posed by directional hydraulic fracturing activities. These studies, balanced with potential economic benefits of energy production, are a crucial source of information for communities considering the development of unconventional reservoirs. However, probabilistic quantification of the overall risk posed by hydraulic fracturing at the system level are rare. Here we present the concept of fault tree analysis to determine the overall probability of groundwater contamination or over-exploitation, broadly referred to as the probability of failure. The potential utility of fault tree analysis for the quantification and communication of risks is approached with a general application. However, the fault tree design is robust and can handle various combinations of regional-specific data pertaining to relevant spatial scales, geological conditions, and industry practices where available. All available data are grouped into quantity and quality-based impacts and sub-divided based on the stage of the hydraulic fracturing process in which the data is relevant as described by the USEPA. Each stage is broken down into the unique basic events required for failure; for example, to quantify the risk of an on-site spill we must consider the likelihood, magnitude, composition, and subsurface transport of the spill. The structure of the fault tree described above can be used to render a highly complex system of variables into a straightforward equation for risk calculation based on Boolean logic. This project shows the utility of fault tree analysis for the visual communication of the potential risks of hydraulic fracturing activities on groundwater resources.

Exposure of trees to drought-induced die-off is defined by a common climatic threshold across different vegetation types

PubMed Central

Mitchell, Patrick J; O'Grady, Anthony P; Hayes, Keith R; Pinkard, Elizabeth A

2014-01-01

Increases in drought and temperature stress in forest and woodland ecosystems are thought to be responsible for the rise in episodic mortality events observed globally. However, key climatic drivers common to mortality events and the impacts of future extreme droughts on tree survival have not been evaluated. Here, we characterize climatic drivers associated with documented tree die-off events across Australia using standardized climatic indices to represent the key dimensions of drought stress for a range of vegetation types. We identify a common probabilistic threshold associated with an increased risk of die-off across all the sites that we examined. We show that observed die-off events occur when water deficits and maximum temperatures are high and exist outside 98% of the observed range in drought intensity; this threshold was evident at all sites regardless of vegetation type and climate. The observed die-off events also coincided with at least one heat wave (three consecutive days above the 90th percentile for maximum temperature), emphasizing a pivotal role of heat stress in amplifying tree die-off and mortality processes. The joint drought intensity and maximum temperature distributions were modeled for each site to describe the co-occurrence of both hot and dry conditions and evaluate future shifts in climatic thresholds associated with the die-off events. Under a relatively dry and moderate warming scenario, the frequency of droughts capable of inducing significant tree die-off across Australia could increase from 1 in 24 years to 1 in 15 years by 2050, accompanied by a doubling in the occurrence of associated heat waves. By defining commonalities in drought conditions capable of inducing tree die-off, we show a strong interactive effect of water and high temperature stress and provide a consistent approach for assessing changes in the exposure of ecosystems to extreme drought events. PMID:24772285

Dendrogeochronologic and Anatomic Analysis of Excavated Plains Cottonwoods Determine Overbank Sedimentation Rates and Historical Channel Positions Along the Interior of a Migrating Meander Bend, Powder River, Montana

NASA Astrophysics Data System (ADS)

Metzger, T. L.; Pizzuto, J. E.; Schook, D. M.; Hasse, T. R.; Affinito, R. A.

2017-12-01

Dendrochronological dating of buried trees precisely determines the germination year and identifies the stratigraphic context of germination for the trees. This recently developed application of dendrochronology provides accurate time-averaged sedimentation rates of overbank deposition along floodplains and can be used to identify burial events. Previous studies have demonstrated that tamarisk (Tamarix ramosissima) and sandbar willow (Salix exigua) develop anatomical changes within the tree rings (increased vessel size and decreased ring widths) on burial, but observations of plains cottonwood (Populus deltoides ssp. monilifera) are lacking. In September 2016 and June 2017, five buried plains cottonwoods were excavated along a single transect of the interior of a meander bend of the Powder River, Montana. Sediment samples were obtained near each tree for 210Pb and 137Cs dating, which will allow for comparison between dendrochronological and isotopic dating methods. The plains cottonwood samples collected exhibit anatomical changes associated with burial events that are observed in other species. All trees germinated at the boundary between thinly bedded fine sand and mud and coarse sand underlain by sand and gravel, indicating plains cottonwoods germinate on top of point bars prior to overbank deposition. The precise germination age and depth provide elevations and minimum age constraints for the point bar deposits and maximum ages for the overlying sediment, helping constrain past channel positions and overbank deposition rates. Germination years of the excavated trees, estimated from cores taken 1.5 m above ground level, range from 2014 to 1862. Accurate establishment years determined by cross-dating the buried section of the tree can add an additional 10 years to the cored age. The sedimentation rate and accumulation thickness varied with tree age. The germination year, total sediment accumulation, and average sedimentation rate at the five sampled trees is: 2011, 35 cm, 7.0 cm/year; 1973, 77 cm, 1.8 cm/year; 1962, 140 cm, 2.6 cm/year; 1960, 123 cm, 2.2 cm/year; and 1862, 112 cm, 0.7 cm/year. These sedimentation rates indicate that the cumulative sedimentation decreases as a power law with increasing tree age.

Monitoring of Freezing Dynamics in Trees: A Simple Phase Shift Causes Complexity1[OPEN

PubMed Central

Charra-Vaskou, Katline

2017-01-01

During winter, trees have to cope with harsh conditions, including extreme freeze-thaw stress. This study focused on ice nucleation and propagation, related water shifts and xylem cavitation, as well as cell damage and was based on in situ monitoring of xylem (thermocouples) and surface temperatures (infrared imaging), ultrasonic emissions, and dendrometer analysis. Field experiments during late winter on Picea abies growing at the alpine timberline revealed three distinct freezing patterns: (1) from the top of the tree toward the base, (2) from thin branches toward the main stem’s top and base, and (3) from the base toward the top. Infrared imaging showed freezing within branches from their base toward distal parts. Such complex freezing causes dynamic and heterogenous patterns in water potential and probably in cavitation. This study highlights the interaction between environmental conditions upon freezing and thawing and demonstrates the enormous complexity of freezing processes in trees. Diameter shrinkage, which indicated water fluxes within the stem, and acoustic emission analysis, which indicated cavitation events near the ice front upon freezing, were both related to minimum temperature and, upon thawing, related to vapor pressure deficit and soil temperature. These complex patterns, emphasizing the common mechanisms between frost and drought stress, shed new light on winter tree physiology. PMID:28242655

Widespread Amazon forest tree mortality from a single cross-basin squall line event

NASA Astrophysics Data System (ADS)

Negrón-Juárez, Robinson I.; Chambers, Jeffrey Q.; Guimaraes, Giuliano; Zeng, Hongcheng; Raupp, Carlos F. M.; Marra, Daniel M.; Ribeiro, Gabriel H. P. M.; Saatchi, Sassan S.; Nelson, Bruce W.; Higuchi, Niro

2010-08-01

Climate change is expected to increase the intensity of extreme precipitation events in Amazonia that in turn might produce more forest blowdowns associated with convective storms. Yet quantitative tree mortality associated with convective storms has never been reported across Amazonia, representing an important additional source of carbon to the atmosphere. Here we demonstrate that a single squall line (aligned cluster of convective storm cells) propagating across Amazonia in January, 2005, caused widespread forest tree mortality and may have contributed to the elevated mortality observed that year. Forest plot data demonstrated that the same year represented the second highest mortality rate over a 15-year annual monitoring interval. Over the Manaus region, disturbed forest patches generated by the squall followed a power-law distribution (scaling exponent α = 1.48) and produced a mortality of 0.3-0.5 million trees, equivalent to 30% of the observed annual deforestation reported in 2005 over the same area. Basin-wide, potential tree mortality from this one event was estimated at 542 ± 121 million trees, equivalent to 23% of the mean annual biomass accumulation estimated for these forests. Our results highlight the vulnerability of Amazon trees to wind-driven mortality associated with convective storms. Storm intensity is expected to increase with a warming climate, which would result in additional tree mortality and carbon release to the atmosphere, with the potential to further warm the climate system.

A Mid-Layer Model for Human Reliability Analysis: Understanding the Cognitive Causes of Human Failure Events

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stacey M. L. Hendrickson; April M. Whaley; Ronald L. Boring

The Office of Nuclear Regulatory Research (RES) is sponsoring work in response to a Staff Requirements Memorandum (SRM) directing an effort to establish a single human reliability analysis (HRA) method for the agency or guidance for the use of multiple methods. As part of this effort an attempt to develop a comprehensive HRA qualitative approach is being pursued. This paper presents a draft of the method’s middle layer, a part of the qualitative analysis phase that links failure mechanisms to performance shaping factors. Starting with a Crew Response Tree (CRT) that has identified human failure events, analysts identify potential failuremore » mechanisms using the mid-layer model. The mid-layer model presented in this paper traces the identification of the failure mechanisms using the Information-Diagnosis/Decision-Action (IDA) model and cognitive models from the psychological literature. Each failure mechanism is grouped according to a phase of IDA. Under each phase of IDA, the cognitive models help identify the relevant performance shaping factors for the failure mechanism. The use of IDA and cognitive models can be traced through fault trees, which provide a detailed complement to the CRT.« less

A mid-layer model for human reliability analysis : understanding the cognitive causes of human failure events.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Song-Hua; Chang, James Y. H.; Boring,Ronald L.

2010-03-01

The Office of Nuclear Regulatory Research (RES) at the US Nuclear Regulatory Commission (USNRC) is sponsoring work in response to a Staff Requirements Memorandum (SRM) directing an effort to establish a single human reliability analysis (HRA) method for the agency or guidance for the use of multiple methods. As part of this effort an attempt to develop a comprehensive HRA qualitative approach is being pursued. This paper presents a draft of the method's middle layer, a part of the qualitative analysis phase that links failure mechanisms to performance shaping factors. Starting with a Crew Response Tree (CRT) that has identifiedmore » human failure events, analysts identify potential failure mechanisms using the mid-layer model. The mid-layer model presented in this paper traces the identification of the failure mechanisms using the Information-Diagnosis/Decision-Action (IDA) model and cognitive models from the psychological literature. Each failure mechanism is grouped according to a phase of IDA. Under each phase of IDA, the cognitive models help identify the relevant performance shaping factors for the failure mechanism. The use of IDA and cognitive models can be traced through fault trees, which provide a detailed complement to the CRT.« less

The Legacy of Episodic Climatic Events in Shaping Temperate, Broadleaf Forests

NASA Technical Reports Server (NTRS)

Pederson, Neil; Dyer, James M.; McEwan, Ryan W.; Hessl, Amy E.; Mock, Cary J.; Orwig, David A.; Rieder, Harald E.; Cook, Benjamin I.

2015-01-01

In humid, broadleaf-dominated forests where gap dynamics and partial canopy mortality appears to dominate the disturbance regime at local scales, paleoecological evidence shows alteration at regional-scales associated with climatic change. Yet, little evidence of these broad-scale events exists in extant forests. To evaluate the potential for the occurrence of large-scale disturbance, we used 76 tree-ring collections spanning approx. 840 000 sq km and 5327 tree recruitment dates spanning approx. 1.4 million sq km across the humid eastern United States. Rotated principal component analysis indicated a common growth pattern of a simultaneous reduction in competition in 22 populations across 61 000 km2. Growth-release analysis of these populations reveals an intense and coherent canopy disturbance from 1775 to 1780, peaking in 1776. The resulting time series of canopy disturbance is so poorly described by a Gaussian distribution that it can be described as ''heavy tailed,'' with most of the years from 1775 to 1780 comprising the heavy-tail portion of the distribution. Historical documents provide no evidence that hurricanes or ice storms triggered the 1775-1780 event. Instead, we identify a significant relationship between prior drought and years with elevated rates of disturbance with an intense drought occurring from 1772 to 1775. We further find that years with high rates of canopy disturbance have a propensity to create larger canopy gaps indicating repeated opportunities for rapid change in species composition beyond the landscape scale. Evidence of elevated, regional-scale disturbance reveals how rare events can potentially alter system trajectory: a substantial portion of old-growth forests examined here originated or were substantially altered more than two centuries ago following events lasting just a few years. Our recruitment data, comprised of at least 21 species and several shade-intolerant species, document a pulse of tree recruitment at the subcontinental scale during the late-1600s suggesting that this event was severe enough to open large canopy gaps. These disturbances and their climatic drivers support the hypothesis that punctuated, episodic, climatic events impart a legacy in broadleaf-dominated forests centuries after their occurrence. Given projections of future drought, these results also reveal the potential for abrupt, meso- to large-scale forest change in broadleaf-dominated forests over future decades.

Synergy of extreme drought and shrub invasion reduce ecosystem functioning and resilience in water-limited climates

PubMed Central

Caldeira, Maria C.; Lecomte, Xavier; David, Teresa S.; Pinto, Joaquim G.; Bugalho, Miguel N.; Werner, Christiane

2015-01-01

Extreme drought events and plant invasions are major drivers of global change that can critically affect ecosystem functioning and alter ecosystem-atmosphere exchange. Invaders are expanding worldwide and extreme drought events are projected to increase in frequency and intensity. However, very little is known on how these drivers may interact to affect the functioning and resilience of ecosystems to extreme events. Using a manipulative shrub removal experiment and the co-occurrence of an extreme drought event (2011/2012) in a Mediterranean woodland, we show that native shrub invasion and extreme drought synergistically reduced ecosystem transpiration and the resilience of key-stone oak tree species. Ecosystem transpiration was dominated by the water use of the invasive shrub Cistus ladanifer, which further increased after the extreme drought event. Meanwhile, the transpiration of key-stone tree species decreased, indicating a competitive advantage in favour of the invader. Our results suggest that in Mediterranean-type climates the invasion of water spending species and projected recurrent extreme drought events may synergistically cause critical drought tolerance thresholds of key-stone tree species to be surpassed, corroborating observed higher tree mortality in the invaded ecosystems. Ultimately, this may shift seasonally water limited ecosystems into less desirable alternative states dominated by water spending invasive shrubs. PMID:26461978

Synergy of extreme drought and shrub invasion reduce ecosystem functioning and resilience in water-limited climates.

PubMed

Caldeira, Maria C; Lecomte, Xavier; David, Teresa S; Pinto, Joaquim G; Bugalho, Miguel N; Werner, Christiane

2015-10-13

Extreme drought events and plant invasions are major drivers of global change that can critically affect ecosystem functioning and alter ecosystem-atmosphere exchange. Invaders are expanding worldwide and extreme drought events are projected to increase in frequency and intensity. However, very little is known on how these drivers may interact to affect the functioning and resilience of ecosystems to extreme events. Using a manipulative shrub removal experiment and the co-occurrence of an extreme drought event (2011/2012) in a Mediterranean woodland, we show that native shrub invasion and extreme drought synergistically reduced ecosystem transpiration and the resilience of key-stone oak tree species. Ecosystem transpiration was dominated by the water use of the invasive shrub Cistus ladanifer, which further increased after the extreme drought event. Meanwhile, the transpiration of key-stone tree species decreased, indicating a competitive advantage in favour of the invader. Our results suggest that in Mediterranean-type climates the invasion of water spending species and projected recurrent extreme drought events may synergistically cause critical drought tolerance thresholds of key-stone tree species to be surpassed, corroborating observed higher tree mortality in the invaded ecosystems. Ultimately, this may shift seasonally water limited ecosystems into less desirable alternative states dominated by water spending invasive shrubs.

Synergy of extreme drought and shrub invasion reduce ecosystem functioning and resilience in water-limited climates

NASA Astrophysics Data System (ADS)

Caldeira, Maria C.; Lecomte, Xavier; David, Teresa S.; Pinto, Joaquim G.; Bugalho, Miguel N.; Werner, Christiane

2015-10-01

Extreme drought events and plant invasions are major drivers of global change that can critically affect ecosystem functioning and alter ecosystem-atmosphere exchange. Invaders are expanding worldwide and extreme drought events are projected to increase in frequency and intensity. However, very little is known on how these drivers may interact to affect the functioning and resilience of ecosystems to extreme events. Using a manipulative shrub removal experiment and the co-occurrence of an extreme drought event (2011/2012) in a Mediterranean woodland, we show that native shrub invasion and extreme drought synergistically reduced ecosystem transpiration and the resilience of key-stone oak tree species. Ecosystem transpiration was dominated by the water use of the invasive shrub Cistus ladanifer, which further increased after the extreme drought event. Meanwhile, the transpiration of key-stone tree species decreased, indicating a competitive advantage in favour of the invader. Our results suggest that in Mediterranean-type climates the invasion of water spending species and projected recurrent extreme drought events may synergistically cause critical drought tolerance thresholds of key-stone tree species to be surpassed, corroborating observed higher tree mortality in the invaded ecosystems. Ultimately, this may shift seasonally water limited ecosystems into less desirable alternative states dominated by water spending invasive shrubs.

Patterns of drought tolerance in major European temperate forest trees: climatic drivers and levels of variability.

PubMed

Zang, Christian; Hartl-Meier, Claudia; Dittmar, Christoph; Rothe, Andreas; Menzel, Annette

2014-12-01

The future performance of native tree species under climate change conditions is frequently discussed, since increasingly severe and more frequent drought events are expected to become a major risk for forest ecosystems. To improve our understanding of the drought tolerance of the three common European temperate forest tree species Norway spruce, silver fir and common beech, we tested the influence of climate and tree-specific traits on the inter and intrasite variability in drought responses of these species. Basal area increment data from a large tree-ring network in Southern Germany and Alpine Austria along a climatic cline from warm-dry to cool-wet conditions were used to calculate indices of tolerance to drought events and their variability at the level of individual trees and populations. General patterns of tolerance indicated a high vulnerability of Norway spruce in comparison to fir and beech and a strong influence of bioclimatic conditions on drought response for all species. On the level of individual trees, low-growth rates prior to drought events, high competitive status and low age favored resilience in growth response to drought. Consequently, drought events led to heterogeneous and variable response patterns in forests stands. These findings may support the idea of deliberately using spontaneous selection and adaption effects as a passive strategy of forest management under climate change conditions, especially a strong directional selection for more tolerant individuals when frequency and intensity of summer droughts will increase in the course of global climate change. © 2014 John Wiley & Sons Ltd.

Usefulness of Beta2-Microglobulin as a Predictor of All-Cause and Nonculprit Lesion-Related Cardiovascular Events in Acute Coronary Syndromes (from the PROSPECT Study).

PubMed

Möckel, Martin; Muller, Reinhold; Searle, Julia; Slagman, Anna; De Bruyne, Bernard; Serruys, Patrick; Weisz, Giora; Xu, Ke; Holert, Fabian; Müller, Christian; Maehara, Akiko; Stone, Gregg W

2015-10-01

In the Providing Regional Observations to Study Predictors of Events in the Coronary Tree (PROSPECT) study, plaque burden, plaque composition, and minimal luminal area were associated with an increased risk of adverse cardiovascular events arising from untreated atherosclerotic lesions (vulnerable plaques) in patients with acute coronary syndromes (ACS). We sought to evaluate the utility of biomarker profiling and clinical risk factors to predict 3-year all-cause and nonculprit lesion-related major adverse cardiac events (MACEs). Of 697 patients who underwent successful percutaneous coronary intervention (PCI) for ACS, an array of 28 baseline biomarkers was analyzed. Median follow-up was 3.4 years. Beta2-microglobulin displayed the strongest predictive power of all variables assessed for all-cause and nonculprit lesion-related MACE. In a classification and regression tree analysis, patients with beta2-microglobulin >1.92 mg/L had an estimated 28.7% 3-year incidence of all-cause MACE; C-peptide <1.32 ng/ml was associated with a further increase in MACE to 51.2%. In a classification and regression tree analysis for untreated nonculprit lesion-related MACE, beta2-microglobulin >1.92 mg/L identified a cohort with a 3-year rate of 18.5%, and C-peptide <2.22 ng/ml was associated with a further increase to 25.5%. By multivariable analysis, beta2-microglobulin was the strongest predictor of all-cause and nonculprit MACE during follow-up. High-density lipoprotein (HDL), transferrin, and history of angina pectoris were also independent predictors of all-cause MACE, and HDL was an independent predictor of nonculprit MACE. In conclusion, in the PROSPECT study, beta2-microglobulin strongly predicted all-cause and nonculprit lesion-related MACE within 3 years after PCI in ACS. C-peptide and HDL provided further risk stratification to identify angiographically mild nonculprit lesions prone to future MACE. Copyright © 2015 Elsevier Inc. All rights reserved.

The genome of black cottonwood, Populus trichocarpa (Torr. & Gray)

Treesearch

G.A. Tuskan; S. DiFazio; S. Jansson; J. Bohlmann; I. Grigoriev; U. Hellsten; N. Putnam; S. Ralph; S. Rombauts; A. Salamov; J. Schein; L. Sterck; A. Aerts; R.R. Bhalerao; R.P. Bhalerao; D. Blaudez; W. Boerjan; A. Brun; A. Brunner; V. Busov; M. Campbell; J. Carlson; M. Chalot; J. Chapman; G.-L. Chen; D. Cooper; P.M. Coutinho; J. Couturier; S. Covert; Q. Cronk; R. Cunningham; J. Davis; S. Degroeve; A. Dejardin; C. dePamphilis; J. Detter; B. Dirks; U. Dubchak; S. Duplessis; J. Ehlting; B. Ellis; K. Gendler; D. Goodstein; M. Gribskov; J. Grimwood; A. Groover; L. Gunter; B. Hamberger; B. Heinze; Y. Helariutta; B. Henrissat; D. Holligan; R. Holt; W. Huang; N. Islam-Faridi; S. Jones; M. Jones-Rhoades; R. Jorgensen; C. Joshi; J. Kangasjarvi; J. Karlsson; C. Kelleher; R. Kirkpatrick; M. Kirst; A. Kohler; U. Kalluri; F. Larimer; J. Leebens-Mack; J.-C. Leple; P. Locascio; Y. Lou; S. Lucas; F. Martin; B. Montanini; C. Napoli; D.R. Nelson; C. Nelson; K. Nieminen; O. Nilsson; V. Pereda; G. Peter; R. Philippe; G. Pilate; A. Poliakov; J. Razumovskaya; P. Richardson; C. Rinaldi; K. Ritland; P. Rouze; D. Ryaboy; J. Schumtz; J. Schrader; B. Segerman; H. Shin; A. Siddiqui; F. Sterky; A. Terry; C.-J. Tsai; E. Uberbacher; P. Unneberg; J. Vahala; K. Wall; S. Wessler; G. Yang; T. Yin; C. Douglas; M. Marra; G. Sandberg; Y. Van de Peer; D. Rokhsar

2006-01-01

We report the draft genome of the black cottonwood tree, Populus trichocarpa. Integration of shotgun sequence assembly with genetic mapping enabled chromosome-scale reconstruction of the genome. More than 45,000 putative protein-coding genes were identified. Analysis of the assembled genome revealed a whole-genome duplication event; about 8000 pairs...

DOE Office of Scientific and Technical Information (OSTI.GOV)

A. Alfonsi; C. Rabiti; D. Mandelli

The Reactor Analysis and Virtual control ENviroment (RAVEN) code is a software tool that acts as the control logic driver and post-processing engine for the newly developed Thermal-Hydraulic code RELAP-7. RAVEN is now a multi-purpose Probabilistic Risk Assessment (PRA) software framework that allows dispatching different functionalities: Derive and actuate the control logic required to simulate the plant control system and operator actions (guided procedures), allowing on-line monitoring/controlling in the Phase Space Perform both Monte-Carlo sampling of random distributed events and Dynamic Event Tree based analysis Facilitate the input/output handling through a Graphical User Interface (GUI) and a post-processing data miningmore » module« less

Modeling flash floods in ungauged mountain catchments of China: A decision tree learning approach for parameter regionalization

NASA Astrophysics Data System (ADS)

Ragettli, S.; Zhou, J.; Wang, H.; Liu, C.; Guo, L.

2017-12-01

Flash floods in small mountain catchments are one of the most frequent causes of loss of life and property from natural hazards in China. Hydrological models can be a useful tool for the anticipation of these events and the issuing of timely warnings. One of the main challenges of setting up such a system is finding appropriate model parameter values for ungauged catchments. Previous studies have shown that the transfer of parameter sets from hydrologically similar gauged catchments is one of the best performing regionalization methods. However, a remaining key issue is the identification of suitable descriptors of similarity. In this study, we use decision tree learning to explore parameter set transferability in the full space of catchment descriptors. For this purpose, a semi-distributed rainfall-runoff model is set up for 35 catchments in ten Chinese provinces. Hourly runoff data from in total 858 storm events are used to calibrate the model and to evaluate the performance of parameter set transfers between catchments. We then present a novel technique that uses the splitting rules of classification and regression trees (CART) for finding suitable donor catchments for ungauged target catchments. The ability of the model to detect flood events in assumed ungauged catchments is evaluated in series of leave-one-out tests. We show that CART analysis increases the probability of detection of 10-year flood events in comparison to a conventional measure of physiographic-climatic similarity by up to 20%. Decision tree learning can outperform other regionalization approaches because it generates rules that optimally consider spatial proximity and physical similarity. Spatial proximity can be used as a selection criteria but is skipped in the case where no similar gauged catchments are in the vicinity. We conclude that the CART regionalization concept is particularly suitable for implementation in sparsely gauged and topographically complex environments where a proximity-based regionalization concept is not applicable.

Treelink: data integration, clustering and visualization of phylogenetic trees.

PubMed

Allende, Christian; Sohn, Erik; Little, Cedric

2015-12-29

Phylogenetic trees are central to a wide range of biological studies. In many of these studies, tree nodes need to be associated with a variety of attributes. For example, in studies concerned with viral relationships, tree nodes are associated with epidemiological information, such as location, age and subtype. Gene trees used in comparative genomics are usually linked with taxonomic information, such as functional annotations and events. A wide variety of tree visualization and annotation tools have been developed in the past, however none of them are intended for an integrative and comparative analysis. Treelink is a platform-independent software for linking datasets and sequence files to phylogenetic trees. The application allows an automated integration of datasets to trees for operations such as classifying a tree based on a field or showing the distribution of selected data attributes in branches and leafs. Genomic and proteonomic sequences can also be linked to the tree and extracted from internal and external nodes. A novel clustering algorithm to simplify trees and display the most divergent clades was also developed, where validation can be achieved using the data integration and classification function. Integrated geographical information allows ancestral character reconstruction for phylogeographic plotting based on parsimony and likelihood algorithms. Our software can successfully integrate phylogenetic trees with different data sources, and perform operations to differentiate and visualize those differences within a tree. File support includes the most popular formats such as newick and csv. Exporting visualizations as images, cluster outputs and genomic sequences is supported. Treelink is available as a web and desktop application at http://www.treelinkapp.com .

Geologic events coupled with Pleistocene climatic oscillations drove genetic variation of Omei treefrog (Rhacophorus omeimontis) in southern China.

PubMed

Li, Jun; Zhao, Mian; Wei, Shichao; Luo, Zhenhua; Wu, Hua

2015-12-21

Pleistocene climatic oscillations and historical geological events may both influence current patterns of genetic variation, and the species in southern China that faced unique climatic and topographical events have complex evolutionary histories. However, the relative contributions of climatic oscillations and geographical events to the genetic variation of these species remain undetermined. To investigate patterns of genetic variation and to test the hypotheses about the factors that shaped the distribution of this genetic variation in species of southern China, mitochondrial genes (cytochrome b and NADH dehydrogenase subunit 2) and nine microsatellite loci of the Omei tree frog (Rhacophorus omeimontis) were amplified in this study. The genetic diversity in the populations of R. omeimontis was high. The phylogenetic trees reconstructed from the mitochondrial DNA (mtDNA) haplotypes and the Bayesian genetic clustering analysis based on microsatellite data both revealed that all populations were divided into three lineages (SC, HG and YN). The two most recent splitting events among the lineages coincided with recent geological events (including the intense uplift of the Qinghai-Tibet Plateau, QTP and the subsequent movements of the Yun-Gui Plateau, YGP) and the Pleistocene glaciations. Significant expansion signals were not detected in mismatch analyses or neutrality tests. And the effective population size of each lineage was stable during the Pleistocene. Based on the results of this study, complex geological events (the recent dramatic uplift of the QTP and the subsequent movements of the YGP) and the Pleistocene glaciations were apparent drivers of the rapid divergence of the R. omeimontis lineages. Each diverged lineages survived in situ with limited gene exchanges, and the stable demographics of lineages indicate that the Pleistocene climatic oscillations were inconsequential for this species. The analysis of genetic variation in populations of R. omeimontis contributes to the understanding of the effects of changes in climate and of geographical events on the dynamic development of contemporary patterns of genetic variation in the species of southern China.

Dynamic event tree analysis with the SAS4A/SASSYS-1 safety analysis code

DOE PAGES

Jankovsky, Zachary K.; Denman, Matthew R.; Aldemir, Tunc

2018-02-02

The consequences of a transient in an advanced sodium-cooled fast reactor are difficult to capture with the traditional approach to probabilistic risk assessment (PRA). Numerous safety-relevant systems are passive and may have operational states that cannot be represented by binary success or failure. In addition, the specific order and timing of events may be crucial which necessitates the use of dynamic PRA tools such as ADAPT. The modifications to the SAS4A/SASSYS-1 sodium-cooled fast reactor safety analysis code for linking it to ADAPT to perform a dynamic PRA are described. A test case is used to demonstrate the linking process andmore » to illustrate the type of insights that may be gained with this process. Finally, newly-developed dynamic importance measures are used to assess the significance of reactor parameters/constituents on calculated consequences of initiating events.« less

Dynamic event tree analysis with the SAS4A/SASSYS-1 safety analysis code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jankovsky, Zachary K.; Denman, Matthew R.; Aldemir, Tunc

The consequences of a transient in an advanced sodium-cooled fast reactor are difficult to capture with the traditional approach to probabilistic risk assessment (PRA). Numerous safety-relevant systems are passive and may have operational states that cannot be represented by binary success or failure. In addition, the specific order and timing of events may be crucial which necessitates the use of dynamic PRA tools such as ADAPT. The modifications to the SAS4A/SASSYS-1 sodium-cooled fast reactor safety analysis code for linking it to ADAPT to perform a dynamic PRA are described. A test case is used to demonstrate the linking process andmore » to illustrate the type of insights that may be gained with this process. Finally, newly-developed dynamic importance measures are used to assess the significance of reactor parameters/constituents on calculated consequences of initiating events.« less

A divide and conquer approach to cope with uncertainty, human health risk, and decision making in contaminant hydrology

NASA Astrophysics Data System (ADS)

de Barros, Felipe P. J.; Bolster, Diogo; Sanchez-Vila, Xavier; Nowak, Wolfgang

2011-05-01

Assessing health risk in hydrological systems is an interdisciplinary field. It relies on the expertise in the fields of hydrology and public health and needs powerful translation concepts to provide decision support and policy making. Reliable health risk estimates need to account for the uncertainties and variabilities present in hydrological, physiological, and human behavioral parameters. Despite significant theoretical advancements in stochastic hydrology, there is still a dire need to further propagate these concepts to practical problems and to society in general. Following a recent line of work, we use fault trees to address the task of probabilistic risk analysis and to support related decision and management problems. Fault trees allow us to decompose the assessment of health risk into individual manageable modules, thus tackling a complex system by a structural divide and conquer approach. The complexity within each module can be chosen individually according to data availability, parsimony, relative importance, and stage of analysis. Three differences are highlighted in this paper when compared to previous works: (1) The fault tree proposed here accounts for the uncertainty in both hydrological and health components, (2) system failure within the fault tree is defined in terms of risk being above a threshold value, whereas previous studies that used fault trees used auxiliary events such as exceedance of critical concentration levels, and (3) we introduce a new form of stochastic fault tree that allows us to weaken the assumption of independent subsystems that is required by a classical fault tree approach. We illustrate our concept in a simple groundwater-related setting.

Implementation of Tree and Butterfly Barriers with Optimistic Time Management Algorithms for Discrete Event Simulation

NASA Astrophysics Data System (ADS)

Rizvi, Syed S.; Shah, Dipali; Riasat, Aasia

The Time Wrap algorithm [3] offers a run time recovery mechanism that deals with the causality errors. These run time recovery mechanisms consists of rollback, anti-message, and Global Virtual Time (GVT) techniques. For rollback, there is a need to compute GVT which is used in discrete-event simulation to reclaim the memory, commit the output, detect the termination, and handle the errors. However, the computation of GVT requires dealing with transient message problem and the simultaneous reporting problem. These problems can be dealt in an efficient manner by the Samadi's algorithm [8] which works fine in the presence of causality errors. However, the performance of both Time Wrap and Samadi's algorithms depends on the latency involve in GVT computation. Both algorithms give poor latency for large simulation systems especially in the presence of causality errors. To improve the latency and reduce the processor ideal time, we implement tree and butterflies barriers with the optimistic algorithm. Our analysis shows that the use of synchronous barriers such as tree and butterfly with the optimistic algorithm not only minimizes the GVT latency but also minimizes the processor idle time.

Effects of soil water table regime on tree community species richness and structure of alluvial forest fragments in Southeast Brazil.

PubMed

Silva, A C; Higuchi, P; van den Berg, E

2010-08-01

In order to determine the influence of soil water table fluctuation on tree species richness and structure of alluvial forest fragments, 24 plots were allocated in a point bar forest and 30 plots in five forest fragments located in a floodplain, in the municipality of São Sebastião da Bela Vista, Southeast Brazil, totalizing 54, 10 X 20 m, plots. The information recorded in each plot were the soil water table level, diameter at breast height (dbh), total height and botanical identity off all trees with dbh > 5 cm. The water table fluctuation was assessed through 1 m deep observation wells in each plot. Correlations analysis indicated that sites with shallower water table in the flooding plains had a low number of tree species and high tree density. Although the water table in the point bar remained below the wells during the study period, low tree species richness was observed. There are other events taking place within the point bar forest that assume a high ecological importance, such as the intensive water velocity during flooding and sedimentation processes.

Triggered surface slips in the Coachella Valley area associated with the 1992 Joshua Tree and Landers, California, Earthquakes

USGS Publications Warehouse

Rymer, M.J.

2000-01-01

The Coachella Valley area was strongly shaken by the 1992 Joshua Tree (23 April) and Landers (28 June) earthquakes, and both events caused triggered slip on active faults within the area. Triggered slip associated with the Joshua Tree earthquake was on a newly recognized fault, the East Wide Canyon fault, near the southwestern edge of the Little San Bernardino Mountains. Slip associated with the Landers earthquake formed along the San Andreas fault in the southeastern Coachella Valley. Surface fractures formed along the East Wide Canyon fault in association with the Joshua Tree earthquake. The fractures extended discontinuously over a 1.5-km stretch of the fault, near its southern end. Sense of slip was consistently right-oblique, west side down, similar to the long-term style of faulting. Measured offset values were small, with right-lateral and vertical components of slip ranging from 1 to 6 mm and 1 to 4 mm, respectively. This is the first documented historic slip on the East Wide Canyon fault, which was first mapped only months before the Joshua Tree earthquake. Surface slip associated with the Joshua Tree earthquake most likely developed as triggered slip given its 5 km distance from the Joshua Tree epicenter and aftershocks. As revealed in a trench investigation, slip formed in an area with only a thin (<3 m thick) veneer of alluvium in contrast to earlier documented triggered slip events in this region, all in the deep basins of the Salton Trough. A paleoseismic trench study in an area of 1992 surface slip revealed evidence of two and possibly three surface faulting events on the East Wide Canyon fault during the late Quaternary, probably latest Pleistocene (first event) and mid- to late Holocene (second two events). About two months after the Joshua Tree earthquake, the Landers earthquake then triggered slip on many faults, including the San Andreas fault in the southeastern Coachella Valley. Surface fractures associated with this event formed discontinuous breaks over a 54-km-long stretch of the fault, from the Indio Hills southeastward to Durmid Hill. Sense of slip was right-lateral; only locally was there a minor (~1 mm) vertical component of slip. Measured dextral displacement values ranged from 1 to 20 mm, with the largest amounts found in the Mecca Hills where large slip values have been measured following past triggered-slip events.

The Inference of Gene Trees with Species Trees

PubMed Central

Szöllősi, Gergely J.; Tannier, Eric; Daubin, Vincent; Boussau, Bastien

2015-01-01

This article reviews the various models that have been used to describe the relationships between gene trees and species trees. Molecular phylogeny has focused mainly on improving models for the reconstruction of gene trees based on sequence alignments. Yet, most phylogeneticists seek to reveal the history of species. Although the histories of genes and species are tightly linked, they are seldom identical, because genes duplicate, are lost or horizontally transferred, and because alleles can coexist in populations for periods that may span several speciation events. Building models describing the relationship between gene and species trees can thus improve the reconstruction of gene trees when a species tree is known, and vice versa. Several approaches have been proposed to solve the problem in one direction or the other, but in general neither gene trees nor species trees are known. Only a few studies have attempted to jointly infer gene trees and species trees. These models account for gene duplication and loss, transfer or incomplete lineage sorting. Some of them consider several types of events together, but none exists currently that considers the full repertoire of processes that generate gene trees along the species tree. Simulations as well as empirical studies on genomic data show that combining gene tree–species tree models with models of sequence evolution improves gene tree reconstruction. In turn, these better gene trees provide a more reliable basis for studying genome evolution or reconstructing ancestral chromosomes and ancestral gene sequences. We predict that gene tree–species tree methods that can deal with genomic data sets will be instrumental to advancing our understanding of genomic evolution. PMID:25070970

Reconciliation of Gene and Species Trees

PubMed Central

Rusin, L. Y.; Lyubetskaya, E. V.; Gorbunov, K. Y.; Lyubetsky, V. A.

2014-01-01

The first part of the paper briefly overviews the problem of gene and species trees reconciliation with the focus on defining and algorithmic construction of the evolutionary scenario. Basic ideas are discussed for the aspects of mapping definitions, costs of the mapping and evolutionary scenario, imposing time scales on a scenario, incorporating horizontal gene transfers, binarization and reconciliation of polytomous trees, and construction of species trees and scenarios. The review does not intend to cover the vast diversity of literature published on these subjects. Instead, the authors strived to overview the problem of the evolutionary scenario as a central concept in many areas of evolutionary research. The second part provides detailed mathematical proofs for the solutions of two problems: (i) inferring a gene evolution along a species tree accounting for various types of evolutionary events and (ii) trees reconciliation into a single species tree when only gene duplications and losses are allowed. All proposed algorithms have a cubic time complexity and are mathematically proved to find exact solutions. Solving algorithms for problem (ii) can be naturally extended to incorporate horizontal transfers, other evolutionary events, and time scales on the species tree. PMID:24800245

The space of ultrametric phylogenetic trees.

PubMed

Gavryushkin, Alex; Drummond, Alexei J

2016-08-21

The reliability of a phylogenetic inference method from genomic sequence data is ensured by its statistical consistency. Bayesian inference methods produce a sample of phylogenetic trees from the posterior distribution given sequence data. Hence the question of statistical consistency of such methods is equivalent to the consistency of the summary of the sample. More generally, statistical consistency is ensured by the tree space used to analyse the sample. In this paper, we consider two standard parameterisations of phylogenetic time-trees used in evolutionary models: inter-coalescent interval lengths and absolute times of divergence events. For each of these parameterisations we introduce a natural metric space on ultrametric phylogenetic trees. We compare the introduced spaces with existing models of tree space and formulate several formal requirements that a metric space on phylogenetic trees must possess in order to be a satisfactory space for statistical analysis, and justify them. We show that only a few known constructions of the space of phylogenetic trees satisfy these requirements. However, our results suggest that these basic requirements are not enough to distinguish between the two metric spaces we introduce and that the choice between metric spaces requires additional properties to be considered. Particularly, that the summary tree minimising the square distance to the trees from the sample might be different for different parameterisations. This suggests that further fundamental insight is needed into the problem of statistical consistency of phylogenetic inference methods. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

A classification tree based modeling approach for segment related crashes on multilane highways.

PubMed

Pande, Anurag; Abdel-Aty, Mohamed; Das, Abhishek

2010-10-01

This study presents a classification tree based alternative to crash frequency analysis for analyzing crashes on mid-block segments of multilane arterials. The traditional approach of modeling counts of crashes that occur over a period of time works well for intersection crashes where each intersection itself provides a well-defined unit over which to aggregate the crash data. However, in the case of mid-block segments the crash frequency based approach requires segmentation of the arterial corridor into segments of arbitrary lengths. In this study we have used random samples of time, day of week, and location (i.e., milepost) combinations and compared them with the sample of crashes from the same arterial corridor. For crash and non-crash cases, geometric design/roadside and traffic characteristics were derived based on their milepost locations. The variables used in the analysis are non-event specific and therefore more relevant for roadway safety feature improvement programs. First classification tree model is a model comparing all crashes with the non-crash data and then four groups of crashes (rear-end, lane-change related, pedestrian, and single-vehicle/off-road crashes) are separately compared to the non-crash cases. The classification tree models provide a list of significant variables as well as a measure to classify crash from non-crash cases. ADT along with time of day/day of week are significantly related to all crash types with different groups of crashes being more likely to occur at different times. From the classification performance of different models it was apparent that using non-event specific information may not be suitable for single vehicle/off-road crashes. The study provides the safety analysis community an additional tool to assess safety without having to aggregate the corridor crash data over arbitrary segment lengths. Copyright © 2010. Published by Elsevier Ltd.

Extreme drought event and shrub invasion combine to reduce ecosystem functioning and resilience in water-limited climates

NASA Astrophysics Data System (ADS)

Caldeira, Maria; Lecomte, Xavier; David, Teresa; Pinto, Joaquim; Bugalho, Miguel; Werner, Christiane

2016-04-01

Extreme droughts and plant invasions are major drivers of global change that can critically affect ecosystem functioning. Shrub encroachment is increasing in many regions worldwide and extreme events are projected to increase in frequency and intensity, namely in the Mediterranean region. Nevertheless, little is known about how these drivers may interact and affect ecosystem functioning and resilience to extreme droughts. Using a manipulative shrub removal experiment and the co-occurrence of an extreme drought event (2011/2012) in a Mediterranean woodland, we show that the native shrub invasion and extreme drought combined to reduce ecosystem transpiration and the resilience of the key-stone oak tree species. We established six 25 x 25 m paired plots in a shrub (Cistus ladanifer L.) encroached Mediterranean cork-oak (Quercus suber L.) woodland. We measured sapflow and pre-dawn leaf water potential of trees and shrubs and soil water content in all plots during three years. We determined the resilience of tree transpiration to evaluate to what extent trees recovered from the extreme drought event. From February to November 2011 we conducted baseline measurements for plot comparison. In November 2011 all the shrubs from one of all the paired plots were cut and removed. Ecosystem transpiration was dominated by the water use of the invasive shrub, which further increased after the extreme drought. Simultaneously, tree transpiration in invaded plots declined much stronger (67 ± 13 %) than in plots cleared from shrubs (31 ± 11%) relative to the pre-drought year. Trees in invaded plots were not able to recover in the following wetter year showing lower resilience to the extreme drought event. Our results imply that in Mediterranean-type of climates invasion by water spending species can combine with projected recurrent extreme droughts causing critical drought tolerance thresholds of trees to be overcome increasing the probability of tree mortality (Caldeira et.al. 2015). Caldeira M.C., Lecomte X., David T.S., Pinto J.G., Bugalho M.N. & Werner C. (2015). Synergy of extreme drought and shrub invasion reduce ecosystem functioning and resilience in water-limited climates. Scientific Reports, 5, 15110.

GIGA: a simple, efficient algorithm for gene tree inference in the genomic age

PubMed Central

2010-01-01

Background Phylogenetic relationships between genes are not only of theoretical interest: they enable us to learn about human genes through the experimental work on their relatives in numerous model organisms from bacteria to fruit flies and mice. Yet the most commonly used computational algorithms for reconstructing gene trees can be inaccurate for numerous reasons, both algorithmic and biological. Additional information beyond gene sequence data has been shown to improve the accuracy of reconstructions, though at great computational cost. Results We describe a simple, fast algorithm for inferring gene phylogenies, which makes use of information that was not available prior to the genomic age: namely, a reliable species tree spanning much of the tree of life, and knowledge of the complete complement of genes in a species' genome. The algorithm, called GIGA, constructs trees agglomeratively from a distance matrix representation of sequences, using simple rules to incorporate this genomic age information. GIGA makes use of a novel conceptualization of gene trees as being composed of orthologous subtrees (containing only speciation events), which are joined by other evolutionary events such as gene duplication or horizontal gene transfer. An important innovation in GIGA is that, at every step in the agglomeration process, the tree is interpreted/reinterpreted in terms of the evolutionary events that created it. Remarkably, GIGA performs well even when using a very simple distance metric (pairwise sequence differences) and no distance averaging over clades during the tree construction process. Conclusions GIGA is efficient, allowing phylogenetic reconstruction of very large gene families and determination of orthologs on a large scale. It is exceptionally robust to adding more gene sequences, opening up the possibility of creating stable identifiers for referring to not only extant genes, but also their common ancestors. We compared trees produced by GIGA to those in the TreeFam database, and they were very similar in general, with most differences likely due to poor alignment quality. However, some remaining differences are algorithmic, and can be explained by the fact that GIGA tends to put a larger emphasis on minimizing gene duplication and deletion events. PMID:20534164

GIGA: a simple, efficient algorithm for gene tree inference in the genomic age.

PubMed

Thomas, Paul D

2010-06-09

Phylogenetic relationships between genes are not only of theoretical interest: they enable us to learn about human genes through the experimental work on their relatives in numerous model organisms from bacteria to fruit flies and mice. Yet the most commonly used computational algorithms for reconstructing gene trees can be inaccurate for numerous reasons, both algorithmic and biological. Additional information beyond gene sequence data has been shown to improve the accuracy of reconstructions, though at great computational cost. We describe a simple, fast algorithm for inferring gene phylogenies, which makes use of information that was not available prior to the genomic age: namely, a reliable species tree spanning much of the tree of life, and knowledge of the complete complement of genes in a species' genome. The algorithm, called GIGA, constructs trees agglomeratively from a distance matrix representation of sequences, using simple rules to incorporate this genomic age information. GIGA makes use of a novel conceptualization of gene trees as being composed of orthologous subtrees (containing only speciation events), which are joined by other evolutionary events such as gene duplication or horizontal gene transfer. An important innovation in GIGA is that, at every step in the agglomeration process, the tree is interpreted/reinterpreted in terms of the evolutionary events that created it. Remarkably, GIGA performs well even when using a very simple distance metric (pairwise sequence differences) and no distance averaging over clades during the tree construction process. GIGA is efficient, allowing phylogenetic reconstruction of very large gene families and determination of orthologs on a large scale. It is exceptionally robust to adding more gene sequences, opening up the possibility of creating stable identifiers for referring to not only extant genes, but also their common ancestors. We compared trees produced by GIGA to those in the TreeFam database, and they were very similar in general, with most differences likely due to poor alignment quality. However, some remaining differences are algorithmic, and can be explained by the fact that GIGA tends to put a larger emphasis on minimizing gene duplication and deletion events.

Object-oriented fault tree evaluation program for quantitative analyses

NASA Technical Reports Server (NTRS)

Patterson-Hine, F. A.; Koen, B. V.

1988-01-01

Object-oriented programming can be combined with fault free techniques to give a significantly improved environment for evaluating the safety and reliability of large complex systems for space missions. Deep knowledge about system components and interactions, available from reliability studies and other sources, can be described using objects that make up a knowledge base. This knowledge base can be interrogated throughout the design process, during system testing, and during operation, and can be easily modified to reflect design changes in order to maintain a consistent information source. An object-oriented environment for reliability assessment has been developed on a Texas Instrument (TI) Explorer LISP workstation. The program, which directly evaluates system fault trees, utilizes the object-oriented extension to LISP called Flavors that is available on the Explorer. The object representation of a fault tree facilitates the storage and retrieval of information associated with each event in the tree, including tree structural information and intermediate results obtained during the tree reduction process. Reliability data associated with each basic event are stored in the fault tree objects. The object-oriented environment on the Explorer also includes a graphical tree editor which was modified to display and edit the fault trees.

Phylogenetic inference under varying proportions of indel-induced alignment gaps

PubMed Central

Dwivedi, Bhakti; Gadagkar, Sudhindra R

2009-01-01

Background The effect of alignment gaps on phylogenetic accuracy has been the subject of numerous studies. In this study, we investigated the relationship between the total number of gapped sites and phylogenetic accuracy, when the gaps were introduced (by means of computer simulation) to reflect indel (insertion/deletion) events during the evolution of DNA sequences. The resulting (true) alignments were subjected to commonly used gap treatment and phylogenetic inference methods. Results (1) In general, there was a strong – almost deterministic – relationship between the amount of gap in the data and the level of phylogenetic accuracy when the alignments were very "gappy", (2) gaps resulting from deletions (as opposed to insertions) contributed more to the inaccuracy of phylogenetic inference, (3) the probabilistic methods (Bayesian, PhyML & "MLε, " a method implemented in DNAML in PHYLIP) performed better at most levels of gap percentage when compared to parsimony (MP) and distance (NJ) methods, with Bayesian analysis being clearly the best, (4) methods that treat gapped sites as missing data yielded less accurate trees when compared to those that attribute phylogenetic signal to the gapped sites (by coding them as binary character data – presence/absence, or as in the MLε method), and (5) in general, the accuracy of phylogenetic inference depended upon the amount of available data when the gaps resulted from mainly deletion events, and the amount of missing data when insertion events were equally likely to have caused the alignment gaps. Conclusion When gaps in an alignment are a consequence of indel events in the evolution of the sequences, the accuracy of phylogenetic analysis is likely to improve if: (1) alignment gaps are categorized as arising from insertion events or deletion events and then treated separately in the analysis, (2) the evolutionary signal provided by indels is harnessed in the phylogenetic analysis, and (3) methods that utilize the phylogenetic signal in indels are developed for distance methods too. When the true homology is known and the amount of gaps is 20 percent of the alignment length or less, the methods used in this study are likely to yield trees with 90–100 percent accuracy. PMID:19698168

Application of the FTA and ETA Method for Gas Hazard Identification for the Performance of Safety Systems in the Industrial Department

NASA Astrophysics Data System (ADS)

Ignac-Nowicka, Jolanta

2018-03-01

The paper analyzes the conditions of safe use of industrial gas systems and factors influencing gas hazards. Typical gas installation and its basic features have been characterized. The results of gas threat analysis in an industrial enterprise using FTA error tree method and ETA event tree method are presented. Compares selected methods of identifying hazards gas industry with respect to the scope of their use. The paper presents an analysis of two exemplary hazards: an industrial gas catastrophe (FTA) and an explosive gas explosion (ETA). In both cases, technical risks and human errors (human factor) were taken into account. The cause-effect relationships of hazards and their causes are presented in the form of diagrams in the drawings.

Twenty five years long survival analysis of an individual shortleaf pine trees

Treesearch

Pradip Saud; Thomas B. Lynch; James M. Guldin

2016-01-01

A semi parametric cox proportion hazard model is preferred when censored data and survival time information is available (Kleinbaum and Klein 1996; Alison 2010). Censored data are observations that have incomplete information related to survival time or event time of interest. In repeated forest measurements, usually observations are either right censored or...

Enumerating all maximal frequent subtrees in collections of phylogenetic trees

PubMed Central

2014-01-01

Background A common problem in phylogenetic analysis is to identify frequent patterns in a collection of phylogenetic trees. The goal is, roughly, to find a subset of the species (taxa) on which all or some significant subset of the trees agree. One popular method to do so is through maximum agreement subtrees (MASTs). MASTs are also used, among other things, as a metric for comparing phylogenetic trees, computing congruence indices and to identify horizontal gene transfer events. Results We give algorithms and experimental results for two approaches to identify common patterns in a collection of phylogenetic trees, one based on agreement subtrees, called maximal agreement subtrees, the other on frequent subtrees, called maximal frequent subtrees. These approaches can return subtrees on larger sets of taxa than MASTs, and can reveal new common phylogenetic relationships not present in either MASTs or the majority rule tree (a popular consensus method). Our current implementation is available on the web at https://code.google.com/p/mfst-miner/. Conclusions Our computational results confirm that maximal agreement subtrees and all maximal frequent subtrees can reveal a more complete phylogenetic picture of the common patterns in collections of phylogenetic trees than maximum agreement subtrees; they are also often more resolved than the majority rule tree. Further, our experiments show that enumerating maximal frequent subtrees is considerably more practical than enumerating ordinary (not necessarily maximal) frequent subtrees. PMID:25061474

Enumerating all maximal frequent subtrees in collections of phylogenetic trees.

PubMed

Deepak, Akshay; Fernández-Baca, David

2014-01-01

A common problem in phylogenetic analysis is to identify frequent patterns in a collection of phylogenetic trees. The goal is, roughly, to find a subset of the species (taxa) on which all or some significant subset of the trees agree. One popular method to do so is through maximum agreement subtrees (MASTs). MASTs are also used, among other things, as a metric for comparing phylogenetic trees, computing congruence indices and to identify horizontal gene transfer events. We give algorithms and experimental results for two approaches to identify common patterns in a collection of phylogenetic trees, one based on agreement subtrees, called maximal agreement subtrees, the other on frequent subtrees, called maximal frequent subtrees. These approaches can return subtrees on larger sets of taxa than MASTs, and can reveal new common phylogenetic relationships not present in either MASTs or the majority rule tree (a popular consensus method). Our current implementation is available on the web at https://code.google.com/p/mfst-miner/. Our computational results confirm that maximal agreement subtrees and all maximal frequent subtrees can reveal a more complete phylogenetic picture of the common patterns in collections of phylogenetic trees than maximum agreement subtrees; they are also often more resolved than the majority rule tree. Further, our experiments show that enumerating maximal frequent subtrees is considerably more practical than enumerating ordinary (not necessarily maximal) frequent subtrees.

TU-AB-BRD-03: Fault Tree Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dunscombe, P.

2015-06-15

Current quality assurance and quality management guidelines provided by various professional organizations are prescriptive in nature, focusing principally on performance characteristics of planning and delivery devices. However, published analyses of events in radiation therapy show that most events are often caused by flaws in clinical processes rather than by device failures. This suggests the need for the development of a quality management program that is based on integrated approaches to process and equipment quality assurance. Industrial engineers have developed various risk assessment tools that are used to identify and eliminate potential failures from a system or a process before amore » failure impacts a customer. These tools include, but are not limited to, process mapping, failure modes and effects analysis, fault tree analysis. Task Group 100 of the American Association of Physicists in Medicine has developed these tools and used them to formulate an example risk-based quality management program for intensity-modulated radiotherapy. This is a prospective risk assessment approach that analyzes potential error pathways inherent in a clinical process and then ranks them according to relative risk, typically before implementation, followed by the design of a new process or modification of the existing process. Appropriate controls are then put in place to ensure that failures are less likely to occur and, if they do, they will more likely be detected before they propagate through the process, compromising treatment outcome and causing harm to the patient. Such a prospective approach forms the basis of the work of Task Group 100 that has recently been approved by the AAPM. This session will be devoted to a discussion of these tools and practical examples of how these tools can be used in a given radiotherapy clinic to develop a risk based quality management program. Learning Objectives: Learn how to design a process map for a radiotherapy process Learn how to perform failure modes and effects analysis analysis for a given process Learn what fault trees are all about Learn how to design a quality management program based upon the information obtained from process mapping, failure modes and effects analysis and fault tree analysis. Dunscombe: Director, TreatSafely, LLC and Center for the Assessment of Radiological Sciences; Consultant to IAEA and Varian Thomadsen: President, Center for the Assessment of Radiological Sciences Palta: Vice President of the Center for the Assessment of Radiological Sciences.« less

Species tree inference by minimizing deep coalescences.

PubMed

Than, Cuong; Nakhleh, Luay

2009-09-01

In a 1997 seminal paper, W. Maddison proposed minimizing deep coalescences, or MDC, as an optimization criterion for inferring the species tree from a set of incongruent gene trees, assuming the incongruence is exclusively due to lineage sorting. In a subsequent paper, Maddison and Knowles provided and implemented a search heuristic for optimizing the MDC criterion, given a set of gene trees. However, the heuristic is not guaranteed to compute optimal solutions, and its hill-climbing search makes it slow in practice. In this paper, we provide two exact solutions to the problem of inferring the species tree from a set of gene trees under the MDC criterion. In other words, our solutions are guaranteed to find the tree that minimizes the total number of deep coalescences from a set of gene trees. One solution is based on a novel integer linear programming (ILP) formulation, and another is based on a simple dynamic programming (DP) approach. Powerful ILP solvers, such as CPLEX, make the first solution appealing, particularly for very large-scale instances of the problem, whereas the DP-based solution eliminates dependence on proprietary tools, and its simplicity makes it easy to integrate with other genomic events that may cause gene tree incongruence. Using the exact solutions, we analyze a data set of 106 loci from eight yeast species, a data set of 268 loci from eight Apicomplexan species, and several simulated data sets. We show that the MDC criterion provides very accurate estimates of the species tree topologies, and that our solutions are very fast, thus allowing for the accurate analysis of genome-scale data sets. Further, the efficiency of the solutions allow for quick exploration of sub-optimal solutions, which is important for a parsimony-based criterion such as MDC, as we show. We show that searching for the species tree in the compatibility graph of the clusters induced by the gene trees may be sufficient in practice, a finding that helps ameliorate the computational requirements of optimization solutions. Further, we study the statistical consistency and convergence rate of the MDC criterion, as well as its optimality in inferring the species tree. Finally, we show how our solutions can be used to identify potential horizontal gene transfer events that may have caused some of the incongruence in the data, thus augmenting Maddison's original framework. We have implemented our solutions in the PhyloNet software package, which is freely available at: http://bioinfo.cs.rice.edu/phylonet.

Proceedings of the Conference on Flight Mechanics and System Design Lessons from Operational Experience Held at Athens, Greece on 10-13 May 1983.

DTIC Science & Technology

1983-10-01

of facts and allowed the tail rotor surrounding this mishap. to strike tree branches Particular attention should during night landing. be focused on...aeroplane. Attention was drawn particularly to the event shown in Figure 9 because of its magnitude. An analysis of the event carried out by W. Pinsker at...the JT9, so that the 747-236 with RB 211s suffered a greater deceleration than the 747-136 when the throttles were closed. When the pilots attention

Monotone Boolean approximation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hulme, B.L.

1982-12-01

This report presents a theory of approximation of arbitrary Boolean functions by simpler, monotone functions. Monotone increasing functions can be expressed without the use of complements. Nonconstant monotone increasing functions are important in their own right since they model a special class of systems known as coherent systems. It is shown here that when Boolean expressions for noncoherent systems become too large to treat exactly, then monotone approximations are easily defined. The algorithms proposed here not only provide simpler formulas but also produce best possible upper and lower monotone bounds for any Boolean function. This theory has practical application formore » the analysis of noncoherent fault trees and event tree sequences.« less

Remote Detection and Modeling of Abrupt and Gradual Tree Mortality in the Southwestern USA

NASA Astrophysics Data System (ADS)

Muss, J. D.; Xu, C.; McDowell, N. G.

2014-12-01

Current climate models predict a warming and drying trend that has a high probability of increasing the frequency and spatial extent of tree mortality events. Field surveys can be used to identify, date, and attribute a cause of mortality to specific trees, but monetary and time constraints prevent broad-scale surveys, which are necessary to establish regional or global trends in tree mortality. This is significant because widespread forest mortality will likely lead to radical changes in evapotranspiration and surface albedo, which could compound climate change. While understanding the causes and mechanisms of tree mortality events is crucial, it is equally important to be able to detect and monitor mortality and subsequent changes to the ecosystem at broad spatial- and temporal-scales. Over the past five years our ability to remotely detect abrupt forest mortality events has improved greatly, but gradual events—such as those caused by drought or certain types of insects—are still difficult to identify. Moreover, it is virtually impossible to quantify the amount of mortality that has occurred within a mixed pixel. We have developed a system that fuses climate and satellite-derived spectral data to identify both the date and the agent of forest mortality events. This system has been used with Landsat time series data to detect both abrupt and general trends in tree loss that have occurred during the past quarter-century in northern New Mexico. It has also been used with MODIS data to identify pixels with a high likelihood of drought-caused tree mortality in the Southwestern US. These candidate pixels were then fed to ED-FRT, a coupled forest dynamics-radiative transfer model, to generate estimates of drought-induced. We demonstrate a multi-scale approach that can produce results that will be instrumental in advancing our understanding of tree mortality-climate feedbacks, and improve our ability to predict what forests could look like in the future.

Applying fault tree analysis to the prevention of wrong-site surgery.

PubMed

Abecassis, Zachary A; McElroy, Lisa M; Patel, Ronak M; Khorzad, Rebeca; Carroll, Charles; Mehrotra, Sanjay

2015-01-01

Wrong-site surgery (WSS) is a rare event that occurs to hundreds of patients each year. Despite national implementation of the Universal Protocol over the past decade, development of effective interventions remains a challenge. We performed a systematic review of the literature reporting root causes of WSS and used the results to perform a fault tree analysis to assess the reliability of the system in preventing WSS and identifying high-priority targets for interventions aimed at reducing WSS. Process components where a single error could result in WSS were labeled with OR gates; process aspects reinforced by verification were labeled with AND gates. The overall redundancy of the system was evaluated based on prevalence of AND gates and OR gates. In total, 37 studies described risk factors for WSS. The fault tree contains 35 faults, most of which fall into five main categories. Despite the Universal Protocol mandating patient verification, surgical site signing, and a brief time-out, a large proportion of the process relies on human transcription and verification. Fault tree analysis provides a standardized perspective of errors or faults within the system of surgical scheduling and site confirmation. It can be adapted by institutions or specialties to lead to more targeted interventions to increase redundancy and reliability within the preoperative process. Copyright © 2015 Elsevier Inc. All rights reserved.

A Hierarchical Analysis of Tree Growth and Environmental Drivers Across Eastern US Temperate Forests

NASA Astrophysics Data System (ADS)

Mantooth, J.; Dietze, M.

2014-12-01

Improving predictions of how forests in the eastern United States will respond to future global change requires a better understanding of the drivers of variability in tree growth rates. Current inventory data lack the temporal resolution to characterize interannual variability, while existing growth records lack the extent required to assess spatial scales of variability. Therefore, we established a network of forest inventory plots across ten sites across the eastern US, and measured growth in adult trees using increment cores. Sites were chosen to maximize climate space explored, while within sites, plots were spread across primary environmental gradients to explore landscape-level variability in growth. Using the annual growth record available from tree cores, we explored the responses of trees to multiple environmental covariates over multiple spatial and temporal scales. We hypothesized that within and across sites growth rates vary among species, and that intraspecific growth rates increase with temperature along a species' range. We also hypothesized that trees show synchrony in growth responses to landscape-scale climatic changes. Initial analyses of growth increments indicate that across sites, trees with intermediate shade tolerance, e.g. Red Oak (Quercus rubra), tend to have the highest growth rates. At the site level, there is evidence for synchrony in response to large-scale climatic events (e.g. prolonged drought and above average temperatures). However, growth responses to climate at the landscape scale have yet to be detected. Our current analysis utilizes hierarchical Bayesian state-space modeling to focus on growth responses of adult trees to environmental covariates at multiple spatial and temporal scales. This predictive model of tree growth currently incorporates observed effects at the individual, plot, site, and landscape scale. Current analysis using this model shows a potential slowing of growth in the past decade for two sites in the northeastern US (Harvard Forest and Bartlett Experimental Forest), however more work is required to determine the robustness of this trend. Finally, these observations are being incorporated into ecosystem models using the Brown Dog informatics tools and the Predictive Ecosystem Analyzer (PEcAn) data assimilation workflow.

A simulation model for probabilistic analysis of Space Shuttle abort modes

NASA Technical Reports Server (NTRS)

Hage, R. T.

1993-01-01

A simulation model which was developed to provide a probabilistic analysis tool to study the various space transportation system abort mode situations is presented. The simulation model is based on Monte Carlo simulation of an event-tree diagram which accounts for events during the space transportation system's ascent and its abort modes. The simulation model considers just the propulsion elements of the shuttle system (i.e., external tank, main engines, and solid boosters). The model was developed to provide a better understanding of the probability of occurrence and successful completion of abort modes during the vehicle's ascent. The results of the simulation runs discussed are for demonstration purposes only, they are not official NASA probability estimates.

Priority Queues for Computer Simulations

NASA Technical Reports Server (NTRS)

Steinman, Jeffrey S. (Inventor)

1998-01-01

The present invention is embodied in new priority queue data structures for event list management of computer simulations, and includes a new priority queue data structure and an improved event horizon applied to priority queue data structures. ne new priority queue data structure is a Qheap and is made out of linked lists for robust, fast, reliable, and stable event list management and uses a temporary unsorted list to store all items until one of the items is needed. Then the list is sorted, next, the highest priority item is removed, and then the rest of the list is inserted in the Qheap. Also, an event horizon is applied to binary tree and splay tree priority queue data structures to form the improved event horizon for event management.

Climate changes effects on vegetation in Mediterranean areas

NASA Astrophysics Data System (ADS)

Viola, F.; Pumo, D.; Noto, L. V.

2009-04-01

The Mediterranean ecosystems evolved under climatic conditions characterized by precipitations markedly out of phase with the growing period for the vegetation there established. In such environments, deep and shallow rooted species cohabit and compete each other. The formers, being characterized by deeper root, are able to utilize the water stored during the dormant season, while the conditions of shallow rooted plant are closely related to the intermittence of the precipitations. A numerical model has been here used in order to carry out an analysis of the potential climate changes influence on the vegetation state in a typical Mediterranean environment, such as Sicilian one. The most important consequences arising from climate changes in the Mediterranean area, due to the CO2 increase, are the temperatures raise and the contemporaneous rainfall reduction. Probably, this reduction could be accompanied by an increase in events intensity and, at the same time, by a decrease in the number of annual events. There are very few information about possible changes in the distribution of the rainfall events over the year. However, according to the analysis of the recorded trend, it is possible to predict that the rainfall reduction will be mainly concentrated during the autumnal and wintry months. The goal of this work is a quantitative evaluation of the effects due to the climatic forcing changes, on vegetation water stress. In particular, great attention is paid to the effects that rainfall decrease may have on vegetation, by itself or coupled with the temperature increase. A detailed investigation on the influence of the variations in rainfall seasonality, frequency and intensity is carried out. In this work two vegetation covers, with shallow and deep rooting depth (grass and tree) laying on three different soil types (loamy sand, sandy loam and clay) are considered. Simulations on Mediterranean ecosystems have lead to recognize the role of the rainfall amount, frequency and temporal distribution. Rainfall decrease increases the vegetation water stress much more than temperature increase do. Intense and rare rainfall events, as they are expected to be, could attenuate the effects of rainfall reduction because of the less interception correlated to them. The future rainfall distribution over the year is also crucial for vegetation water stress. If the current ratio between the growing season and the dormant season rainfall will be kept, trees and grasses will suffer a common increase of water stress, which seems more severe for trees than for grasses. Otherwise, if the rainfall reduction will be concentrated during the wintry periods, as emerges from literature, grasses will have some advantages over the trees species. In this conditions grasses will keep the water stress similar to the nowadays value, while trees will suffer for the lack of the winter recharge increasing their water stress.

Pedologic and geomorphic impacts of a tornado blowdown event in a mixed pine-hardwood forest

Treesearch

Jonathan D. Phillips; Daniel A. Marion; Alice V. Turkington

2008-01-01

Biomechanical effects of trees on soils and surface processes may be extensive in forest environments. Two blowdown sites caused by a November 2005 tornado in the Ouachita National Forest, Arkansas allowed a case study examination of bioturbation associated with a specific forest blowdown event, as well as detailed examination of relationships between tree root systems...

A fast bottom-up algorithm for computing the cut sets of noncoherent fault trees

DOE Office of Scientific and Technical Information (OSTI.GOV)

Corynen, G.C.

1987-11-01

An efficient procedure for finding the cut sets of large fault trees has been developed. Designed to address coherent or noncoherent systems, dependent events, shared or common-cause events, the method - called SHORTCUT - is based on a fast algorithm for transforming a noncoherent tree into a quasi-coherent tree (COHERE), and on a new algorithm for reducing cut sets (SUBSET). To assure sufficient clarity and precision, the procedure is discussed in the language of simple sets, which is also developed in this report. Although the new method has not yet been fully implemented on the computer, we report theoretical worst-casemore » estimates of its computational complexity. 12 refs., 10 figs.« less

From Gene Trees to a Dated Allopolyploid Network: Insights from the Angiosperm Genus Viola (Violaceae)

PubMed Central

Marcussen, Thomas; Heier, Lise; Brysting, Anne K.; Oxelman, Bengt; Jakobsen, Kjetill S.

2015-01-01

Allopolyploidization accounts for a significant fraction of speciation events in many eukaryotic lineages. However, existing phylogenetic and dating methods require tree-like topologies and are unable to handle the network-like phylogenetic relationships of lineages containing allopolyploids. No explicit framework has so far been established for evaluating competing network topologies, and few attempts have been made to date phylogenetic networks. We used a four-step approach to generate a dated polyploid species network for the cosmopolitan angiosperm genus Viola L. (Violaceae Batch.). The genus contains ca 600 species and both recent (neo-) and more ancient (meso-) polyploid lineages distributed over 16 sections. First, we obtained DNA sequences of three low-copy nuclear genes and one chloroplast region, from 42 species representing all 16 sections. Second, we obtained fossil-calibrated chronograms for each nuclear gene marker. Third, we determined the most parsimonious multilabeled genome tree and its corresponding network, resolved at the section (not the species) level. Reconstructing the “correct” network for a set of polyploids depends on recovering all homoeologs, i.e., all subgenomes, in these polyploids. Assuming the presence of Viola subgenome lineages that were not detected by the nuclear gene phylogenies (“ghost subgenome lineages”) significantly reduced the number of inferred polyploidization events. We identified the most parsimonious network topology from a set of five competing scenarios differing in the interpretation of homoeolog extinctions and lineage sorting, based on (i) fewest possible ghost subgenome lineages, (ii) fewest possible polyploidization events, and (iii) least possible deviation from expected ploidy as inferred from available chromosome counts of the involved polyploid taxa. Finally, we estimated the homoploid and polyploid speciation times of the most parsimonious network. Homoploid speciation times were estimated by coalescent analysis of gene tree node ages. Polyploid speciation times were estimated by comparing branch lengths and speciation rates of lineages with and without ploidy shifts. Our analyses recognize Viola as an old genus (crown age 31 Ma) whose evolutionary history has been profoundly affected by allopolyploidy. Between 16 and 21 allopolyploidizations are necessary to explain the diversification of the 16 major lineages (sections) of Viola, suggesting that allopolyploidy has accounted for a high percentage—between 67% and 88%—of the speciation events at this level. The theoretical and methodological approaches presented here for (i) constructing networks and (ii) dating speciation events within a network, have general applicability for phylogenetic studies of groups where allopolyploidization has occurred. They make explicit use of a hitherto underexplored source of ploidy information from chromosome counts to help resolve phylogenetic cases where incomplete sequence data hampers network inference. Importantly, the coalescent-based method used herein circumvents the assumption of tree-like evolution required by most techniques for dating speciation events. PMID:25281848

Knowledge Representation Standards and Interchange Formats for Causal Graphs

NASA Technical Reports Server (NTRS)

Throop, David R.; Malin, Jane T.; Fleming, Land

2005-01-01

In many domains, automated reasoning tools must represent graphs of causally linked events. These include fault-tree analysis, probabilistic risk assessment (PRA), planning, procedures, medical reasoning about disease progression, and functional architectures. Each of these fields has its own requirements for the representation of causation, events, actors and conditions. The representations include ontologies of function and cause, data dictionaries for causal dependency, failure and hazard, and interchange formats between some existing tools. In none of the domains has a generally accepted interchange format emerged. The paper makes progress towards interoperability across the wide range of causal analysis methodologies. We survey existing practice and emerging interchange formats in each of these fields. Setting forth a set of terms and concepts that are broadly shared across the domains, we examine the several ways in which current practice represents them. Some phenomena are difficult to represent or to analyze in several domains. These include mode transitions, reachability analysis, positive and negative feedback loops, conditions correlated but not causally linked and bimodal probability distributions. We work through examples and contrast the differing methods for addressing them. We detail recent work in knowledge interchange formats for causal trees in aerospace analysis applications in early design, safety and reliability. Several examples are discussed, with a particular focus on reachability analysis and mode transitions. We generalize the aerospace analysis work across the several other domains. We also recommend features and capabilities for the next generation of causal knowledge representation standards.

Mechanisms of piñon pine mortality after severe drought: a retrospective study of mature trees.

PubMed

Gaylord, Monica L; Kolb, Thomas E; McDowell, Nate G

2015-08-01

Conifers have incurred high mortality during recent global-change-type drought(s) in the western USA. Mechanisms of drought-related tree mortality need to be resolved to support predictions of the impacts of future increases in aridity on vegetation. Hydraulic failure, carbon starvation and lethal biotic agents are three potentially interrelated mechanisms of tree mortality during drought. Our study compared a suite of measurements related to these mechanisms between 49 mature piñon pine (Pinus edulis Engelm.) trees that survived severe drought in 2002 (live trees) and 49 trees that died during the drought (dead trees) over three sites in Arizona and New Mexico. Results were consistent over all sites indicating common mortality mechanisms over a wide region rather than site-specific mechanisms. We found evidence for an interactive role of hydraulic failure, carbon starvation and biotic agents in tree death. For the decade prior to the mortality event, dead trees had twofold greater sapwood cavitation based on frequency of aspirated tracheid pits observed with scanning electron microscopy (SEM), smaller inter-tracheid pit diameter measured by SEM, greater diffusional constraints to photosynthesis based on higher wood δ(13)C, smaller xylem resin ducts, lower radial growth and more bark beetle (Coleoptera: Curculionidae) attacks than live trees. Results suggest that sapwood cavitation, low carbon assimilation and low resin defense predispose piñon pine trees to bark beetle attacks and mortality during severe drought. Our novel approach is an important step forward to yield new insights into how trees die via retrospective analysis. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Research frontiers for improving our understanding of drought‐induced tree and forest mortality

USGS Publications Warehouse

Hartmann, Henrik; Moura, Catarina; Anderegg, William R. L.; Ruehr, Nadine; Salmon, Yann; Allen, Craig D.; Arndt, Stefan K.; Breshears, David D.; Davi, Hendrik; Galbraith, David; Ruthrof, Katinka X.; Wunder, Jan; Adams, Henry D.; Bloemen, Jasper; Cailleret, Maxime; Cobb, Richard; Gessler, Arthur; Grams, Thorsten E. E.; Jansen, Steven; Kautz, Markus; Lloret, Francisco; O’Brien, Michael

2018-01-01

Accumulating evidence highlights increased mortality risks for trees during severe drought, particularly under warmer temperatures and increasing vapour pressure deficit (VPD). Resulting forest die‐off events have severe consequences for ecosystem services, biophysical and biogeochemical land–atmosphere processes. Despite advances in monitoring, modelling and experimental studies of the causes and consequences of tree death from individual tree to ecosystem and global scale, a general mechanistic understanding and realistic predictions of drought mortality under future climate conditions are still lacking. We update a global tree mortality map and present a roadmap to a more holistic understanding of forest mortality across scales. We highlight priority research frontiers that promote: (1) new avenues for research on key tree ecophysiological responses to drought; (2) scaling from the tree/plot level to the ecosystem and region; (3) improvements of mortality risk predictions based on both empirical and mechanistic insights; and (4) a global monitoring network of forest mortality. In light of recent and anticipated large forest die‐off events such a research agenda is timely and needed to achieve scientific understanding for realistic predictions of drought‐induced tree mortality. The implementation of a sustainable network will require support by stakeholders and political authorities at the international level.

Construction of phylogenetic trees by kernel-based comparative analysis of metabolic networks.

PubMed

Oh, S June; Joung, Je-Gun; Chang, Jeong-Ho; Zhang, Byoung-Tak

2006-06-06

To infer the tree of life requires knowledge of the common characteristics of each species descended from a common ancestor as the measuring criteria and a method to calculate the distance between the resulting values of each measure. Conventional phylogenetic analysis based on genomic sequences provides information about the genetic relationships between different organisms. In contrast, comparative analysis of metabolic pathways in different organisms can yield insights into their functional relationships under different physiological conditions. However, evaluating the similarities or differences between metabolic networks is a computationally challenging problem, and systematic methods of doing this are desirable. Here we introduce a graph-kernel method for computing the similarity between metabolic networks in polynomial time, and use it to profile metabolic pathways and to construct phylogenetic trees. To compare the structures of metabolic networks in organisms, we adopted the exponential graph kernel, which is a kernel-based approach with a labeled graph that includes a label matrix and an adjacency matrix. To construct the phylogenetic trees, we used an unweighted pair-group method with arithmetic mean, i.e., a hierarchical clustering algorithm. We applied the kernel-based network profiling method in a comparative analysis of nine carbohydrate metabolic networks from 81 biological species encompassing Archaea, Eukaryota, and Eubacteria. The resulting phylogenetic hierarchies generally support the tripartite scheme of three domains rather than the two domains of prokaryotes and eukaryotes. By combining the kernel machines with metabolic information, the method infers the context of biosphere development that covers physiological events required for adaptation by genetic reconstruction. The results show that one may obtain a global view of the tree of life by comparing the metabolic pathway structures using meta-level information rather than sequence information. This method may yield further information about biological evolution, such as the history of horizontal transfer of each gene, by studying the detailed structure of the phylogenetic tree constructed by the kernel-based method.

Phylogeny of the cycads based on multiple single-copy nuclear genes: congruence of concatenated parsimony, likelihood and species tree inference methods.

PubMed

Salas-Leiva, Dayana E; Meerow, Alan W; Calonje, Michael; Griffith, M Patrick; Francisco-Ortega, Javier; Nakamura, Kyoko; Stevenson, Dennis W; Lewis, Carl E; Namoff, Sandra

2013-11-01

Despite a recent new classification, a stable phylogeny for the cycads has been elusive, particularly regarding resolution of Bowenia, Stangeria and Dioon. In this study, five single-copy nuclear genes (SCNGs) are applied to the phylogeny of the order Cycadales. The specific aim is to evaluate several gene tree-species tree reconciliation approaches for developing an accurate phylogeny of the order, to contrast them with concatenated parsimony analysis and to resolve the erstwhile problematic phylogenetic position of these three genera. DNA sequences of five SCNGs were obtained for 20 cycad species representing all ten genera of Cycadales. These were analysed with parsimony, maximum likelihood (ML) and three Bayesian methods of gene tree-species tree reconciliation, using Cycas as the outgroup. A calibrated date estimation was developed with Bayesian methods, and biogeographic analysis was also conducted. Concatenated parsimony, ML and three species tree inference methods resolve exactly the same tree topology with high support at most nodes. Dioon and Bowenia are the first and second branches of Cycadales after Cycas, respectively, followed by an encephalartoid clade (Macrozamia-Lepidozamia-Encephalartos), which is sister to a zamioid clade, of which Ceratozamia is the first branch, and in which Stangeria is sister to Microcycas and Zamia. A single, well-supported phylogenetic hypothesis of the generic relationships of the Cycadales is presented. However, massive extinction events inferred from the fossil record that eliminated broader ancestral distributions within Zamiaceae compromise accurate optimization of ancestral biogeographical areas for that hypothesis. While major lineages of Cycadales are ancient, crown ages of all modern genera are no older than 12 million years, supporting a recent hypothesis of mostly Miocene radiations. This phylogeny can contribute to an accurate infrafamilial classification of Zamiaceae.

A new Bayesian Event Tree tool to track and quantify volcanic unrest and its application to Kawah Ijen volcano

NASA Astrophysics Data System (ADS)

Tonini, Roberto; Sandri, Laura; Rouwet, Dmitri; Caudron, Corentin; Marzocchi, Warner; Suparjan

2016-07-01

Although most of volcanic hazard studies focus on magmatic eruptions, volcanic hazardous events can also occur when no migration of magma can be recognized. Examples are tectonic and hydrothermal unrest that may lead to phreatic eruptions. Recent events (e.g., Ontake eruption on September 2014) have demonstrated that phreatic eruptions are still hard to forecast, despite being potentially very hazardous. For these reasons, it is of paramount importance to identify indicators that define the condition of nonmagmatic unrest, in particular for hydrothermal systems. Often, this type of unrest is driven by movement of fluids, requiring alternative monitoring setups, beyond the classical seismic-geodetic-geochemical architectures. Here we present a new version of the probabilistic BET (Bayesian Event Tree) model, specifically developed to include the forecasting of nonmagmatic unrest and related hazards. The structure of the new event tree differs from the previous schemes by adding a specific branch to detail nonmagmatic unrest outcomes. A further goal of this work consists in providing a user-friendly, open-access, and straightforward tool to handle the probabilistic forecast and visualize the results as possible support during a volcanic crisis. The new event tree and tool are here applied to Kawah Ijen stratovolcano, Indonesia, as exemplificative application. In particular, the tool is set on the basis of monitoring data for the learning period 2000-2010, and is then blindly applied to the test period 2010-2012, during which significant unrest phases occurred.

The fundamental theorem of asset pricing under default and collateral in finite discrete time

NASA Astrophysics Data System (ADS)

Alvarez-Samaniego, Borys; Orrillo, Jaime

2006-08-01

We consider a financial market where time and uncertainty are modeled by a finite event-tree. The event-tree has a length of N, a unique initial node at the initial date, and a continuum of branches at each node of the tree. Prices and returns of J assets are modeled, respectively, by a R2JxR2J-valued stochastic process . In this framework we prove a version of the Fundamental Theorem of Asset Pricing which applies to defaultable securities backed by exogenous collateral suffering a contingent linear depreciation.

The impact of within-herd genetic variation upon inferred transmission trees for foot-and-mouth disease virus.

PubMed

Valdazo-González, Begoña; Kim, Jan T; Soubeyrand, Samuel; Wadsworth, Jemma; Knowles, Nick J; Haydon, Daniel T; King, Donald P

2015-06-01

Full-genome sequences have been used to monitor the fine-scale dynamics of epidemics caused by RNA viruses. However, the ability of this approach to confidently reconstruct transmission trees is limited by the knowledge of the genetic diversity of viruses that exist within different epidemiological units. In order to address this question, this study investigated the variability of 45 foot-and-mouth disease virus (FMDV) genome sequences (from 33 animals) that were collected during 2007 from eight premises (10 different herds) in the United Kingdom. Bayesian and statistical parsimony analysis demonstrated that these sequences exhibited clustering which was consistent with a transmission scenario describing herd-to-herd spread of the virus. As an alternative to analysing all of the available samples in future epidemics, the impact of randomly selecting one sequence from each of these herds was used to assess cost-effective methods that might be used to infer transmission trees during FMD outbreaks. Using these approaches, 85% and 91% of the resulting topologies were either identical or differed by only one edge from a reference tree comprising all of the sequences generated within the outbreak. The sequence distances that accrued during sequential transmission events between epidemiological units was estimated to be 4.6 nucleotides, although the genetic variability between viruses recovered from chronic carrier animals was higher than between viruses from animals with acute-stage infection: an observation which poses challenges for the use of simple approaches to infer transmission trees. This study helps to develop strategies for sampling during FMD outbreaks, and provides data that will guide the development of further models to support control policies in the event of virus incursions into FMD free countries. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

The vestigial olfactory receptor subgenome of odontocete whales: phylogenetic congruence between gene-tree reconciliation and supermatrix methods.

PubMed

McGowen, Michael R; Clark, Clay; Gatesy, John

2008-08-01

The macroevolutionary transition of whales (cetaceans) from a terrestrial quadruped to an obligate aquatic form involved major changes in sensory abilities. Compared to terrestrial mammals, the olfactory system of baleen whales is dramatically reduced, and in toothed whales is completely absent. We sampled the olfactory receptor (OR) subgenomes of eight cetacean species from four families. A multigene tree of 115 newly characterized OR sequences from these eight species and published data for Bos taurus revealed a diverse array of class II OR paralogues in Cetacea. Evolution of the OR gene superfamily in toothed whales (Odontoceti) featured a multitude of independent pseudogenization events, supporting anatomical evidence that odontocetes have lost their olfactory sense. We explored the phylogenetic utility of OR pseudogenes in Cetacea, concentrating on delphinids (oceanic dolphins), the product of a rapid evolutionary radiation that has been difficult to resolve in previous studies of mitochondrial DNA sequences. Phylogenetic analyses of OR pseudogenes using both gene-tree reconciliation and supermatrix methods yielded fully resolved, consistently supported relationships among members of four delphinid subfamilies. Alternative minimizations of gene duplications, gene duplications plus gene losses, deep coalescence events, and nucleotide substitutions plus indels returned highly congruent phylogenetic hypotheses. Novel DNA sequence data for six single-copy nuclear loci and three mitochondrial genes (> 5000 aligned nucleotides) provided an independent test of the OR trees. Nucleotide substitutions and indels in OR pseudogenes showed a very low degree of homoplasy in comparison to mitochondrial DNA and, on average, provided more variation than single-copy nuclear DNA. Our results suggest that phylogenetic analysis of the large OR superfamily will be effective for resolving relationships within Cetacea whether supermatrix or gene-tree reconciliation procedures are used.

Performance analysis of distributed applications using automatic classification of communication inefficiencies

DOEpatents

Vetter, Jeffrey S.

2005-02-01

The method and system described herein presents a technique for performance analysis that helps users understand the communication behavior of their message passing applications. The method and system described herein may automatically classifies individual communication operations and reveal the cause of communication inefficiencies in the application. This classification allows the developer to quickly focus on the culprits of truly inefficient behavior, rather than manually foraging through massive amounts of performance data. Specifically, the method and system described herein trace the message operations of Message Passing Interface (MPI) applications and then classify each individual communication event using a supervised learning technique: decision tree classification. The decision tree may be trained using microbenchmarks that demonstrate both efficient and inefficient communication. Since the method and system described herein adapt to the target system's configuration through these microbenchmarks, they simultaneously automate the performance analysis process and improve classification accuracy. The method and system described herein may improve the accuracy of performance analysis and dramatically reduce the amount of data that users must encounter.

Risk assessment for enterprise resource planning (ERP) system implementations: a fault tree analysis approach

NASA Astrophysics Data System (ADS)

Zeng, Yajun; Skibniewski, Miroslaw J.

2013-08-01

Enterprise resource planning (ERP) system implementations are often characterised with large capital outlay, long implementation duration, and high risk of failure. In order to avoid ERP implementation failure and realise the benefits of the system, sound risk management is the key. This paper proposes a probabilistic risk assessment approach for ERP system implementation projects based on fault tree analysis, which models the relationship between ERP system components and specific risk factors. Unlike traditional risk management approaches that have been mostly focused on meeting project budget and schedule objectives, the proposed approach intends to address the risks that may cause ERP system usage failure. The approach can be used to identify the root causes of ERP system implementation usage failure and quantify the impact of critical component failures or critical risk events in the implementation process.

Effects of biotic and abiotic factors on resistance versus resilience of Douglas fir to drought.

PubMed

Carnwath, Gunnar; Nelson, Cara

2017-01-01

Significant increases in tree mortality due to drought-induced physiological stress have been documented worldwide. This trend is likely to continue with increased frequency and severity of extreme drought events in the future. Therefore, understanding the factors that influence variability in drought responses among trees will be critical to predicting ecosystem responses to climate change and developing effective management actions. In this study, we used hierarchical mixed-effects models to analyze drought responses of Pseudotsuga menziesii in 20 unmanaged forests stands across a broad range of environmental conditions in northeastern Washington, USA. We aimed to 1) identify the biotic and abiotic attributes most closely associated with the responses of individual trees to drought and 2) quantify the variability in drought responses at different spatial scales. We found that growth rates and competition for resources significantly affected resistance to a severe drought event in 2001: slow-growing trees and trees growing in subordinate canopy positions and/or with more neighbors suffered greater declines in radial growth during the drought event. In contrast, the ability of a tree to return to normal growth when climatic conditions improved (resilience) was unaffected by competition or relative growth rates. Drought responses were significantly influenced by tree age: older trees were more resistant but less resilient than younger trees. Finally, we found differences between resistance and resilience in spatial scale: a significant proportion (approximately 50%) of the variability in drought resistance across the study area was at broad spatial scales (i.e. among different forest types), most likely due to differences in the total amount of precipitation received at different elevations; in contrast, variation in resilience was overwhelmingly (82%) at the level of individual trees within stands and there was no difference in drought resilience among forest types. Our results suggest that for Pseudotsuga menziesii resistance and resilience to drought are driven by different factors and vary at different spatial scales.

Effects of biotic and abiotic factors on resistance versus resilience of Douglas fir to drought

PubMed Central

Nelson, Cara

2017-01-01

Significant increases in tree mortality due to drought-induced physiological stress have been documented worldwide. This trend is likely to continue with increased frequency and severity of extreme drought events in the future. Therefore, understanding the factors that influence variability in drought responses among trees will be critical to predicting ecosystem responses to climate change and developing effective management actions. In this study, we used hierarchical mixed-effects models to analyze drought responses of Pseudotsuga menziesii in 20 unmanaged forests stands across a broad range of environmental conditions in northeastern Washington, USA. We aimed to 1) identify the biotic and abiotic attributes most closely associated with the responses of individual trees to drought and 2) quantify the variability in drought responses at different spatial scales. We found that growth rates and competition for resources significantly affected resistance to a severe drought event in 2001: slow-growing trees and trees growing in subordinate canopy positions and/or with more neighbors suffered greater declines in radial growth during the drought event. In contrast, the ability of a tree to return to normal growth when climatic conditions improved (resilience) was unaffected by competition or relative growth rates. Drought responses were significantly influenced by tree age: older trees were more resistant but less resilient than younger trees. Finally, we found differences between resistance and resilience in spatial scale: a significant proportion (approximately 50%) of the variability in drought resistance across the study area was at broad spatial scales (i.e. among different forest types), most likely due to differences in the total amount of precipitation received at different elevations; in contrast, variation in resilience was overwhelmingly (82%) at the level of individual trees within stands and there was no difference in drought resilience among forest types. Our results suggest that for Pseudotsuga menziesii resistance and resilience to drought are driven by different factors and vary at different spatial scales. PMID:28973008

Using transportation accident databases to investigate ignition and explosion probabilities of flammable spills.

PubMed

Ronza, A; Vílchez, J A; Casal, J

2007-07-19

Risk assessment of hazardous material spill scenarios, and quantitative risk assessment in particular, make use of event trees to account for the possible outcomes of hazardous releases. Using event trees entails the definition of probabilities of occurrence for events such as spill ignition and blast formation. This study comprises an extensive analysis of ignition and explosion probability data proposed in previous work. Subsequently, the results of the survey of two vast US federal spill databases (HMIRS, by the Department of Transportation, and MINMOD, by the US Coast Guard) are reported and commented on. Some tens of thousands of records of hydrocarbon spills were analysed. The general pattern of statistical ignition and explosion probabilities as a function of the amount and the substance spilled is discussed. Equations are proposed based on statistical data that predict the ignition probability of hydrocarbon spills as a function of the amount and the substance spilled. Explosion probabilities are put forth as well. Two sets of probability data are proposed: it is suggested that figures deduced from HMIRS be used in land transportation risk assessment, and MINMOD results with maritime scenarios assessment. Results are discussed and compared with previous technical literature.

Evaluating the risk of industrial espionage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bott, T.F.

1998-12-31

A methodology for estimating the relative probabilities of different compromise paths for protected information by insider and visitor intelligence collectors has been developed based on an event-tree analysis of the intelligence collection operation. The analyst identifies target information and ultimate users who might attempt to gain that information. The analyst then uses an event tree to develop a set of compromise paths. Probability models are developed for each of the compromise paths that user parameters based on expert judgment or historical data on security violations. The resulting probability estimates indicate the relative likelihood of different compromise paths and provide anmore » input for security resource allocation. Application of the methodology is demonstrated using a national security example. A set of compromise paths and probability models specifically addressing this example espionage problem are developed. The probability models for hard-copy information compromise paths are quantified as an illustration of the results using parametric values representative of historical data available in secure facilities, supplemented where necessary by expert judgment.« less

Windthrown trees on the Kings River Ranger District, Sierra National Forest: meteorological aspects

Treesearch

Michael A. Fosberg

1986-01-01

Blowdown in shelterwood, sanitation cuts, and other partial cuts on the Kings River Ranger District, Sierra National Forest, are due to Mono winds. Both winter storm and Mono winds were considered as causes of winter blowdown. All evidence, e.g., direction of tree-fall and occurrence of high wind events, point to Mono wind events as the cause of blowdown. Only 12...

Object-Oriented Algorithm For Evaluation Of Fault Trees

NASA Technical Reports Server (NTRS)

Patterson-Hine, F. A.; Koen, B. V.

1992-01-01

Algorithm for direct evaluation of fault trees incorporates techniques of object-oriented programming. Reduces number of calls needed to solve trees with repeated events. Provides significantly improved software environment for such computations as quantitative analyses of safety and reliability of complicated systems of equipment (e.g., spacecraft or factories).

Fuel treatment effects on tree mortality following wildfire in dry mixed conifer forests, Washington State, USA

Treesearch

Susan J. Prichard; Maureen C. Kennedy

2012-01-01

Fuel reduction treatments are increasingly used to mitigate future wildfire severity in dry forests, but few opportunities exist to assess their effectiveness. We evaluated the influence of fuel treatment, tree size and species on tree mortality following a large wildfire event in recent thin-only, thin and prescribed burn (thin-Rx) units. Of the trees that died within...

Precipitation thresholds and drought-induced tree die-off: Insights from patterns of Pinus edulis mortality along an environmental stress gradient

Treesearch

Michael J. Clifford; Patrick D. Royer; Neil S. Cobb; David D. Breshears; Paulette L. Ford

2013-01-01

Recent regional tree die-off events appear to have been triggered by a combination of drought and heat - referred to as 'global-change-type drought'. To complement experiments focused on resolving mechanisms of drought-induced tree mortality, an evaluation of how patterns of tree die-off relate to highly spatially variable precipitation is needed....

A new fast method for inferring multiple consensus trees using k-medoids.

PubMed

Tahiri, Nadia; Willems, Matthieu; Makarenkov, Vladimir

2018-04-05

Gene trees carry important information about specific evolutionary patterns which characterize the evolution of the corresponding gene families. However, a reliable species consensus tree cannot be inferred from a multiple sequence alignment of a single gene family or from the concatenation of alignments corresponding to gene families having different evolutionary histories. These evolutionary histories can be quite different due to horizontal transfer events or to ancient gene duplications which cause the emergence of paralogs within a genome. Many methods have been proposed to infer a single consensus tree from a collection of gene trees. Still, the application of these tree merging methods can lead to the loss of specific evolutionary patterns which characterize some gene families or some groups of gene families. Thus, the problem of inferring multiple consensus trees from a given set of gene trees becomes relevant. We describe a new fast method for inferring multiple consensus trees from a given set of phylogenetic trees (i.e. additive trees or X-trees) defined on the same set of species (i.e. objects or taxa). The traditional consensus approach yields a single consensus tree. We use the popular k-medoids partitioning algorithm to divide a given set of trees into several clusters of trees. We propose novel versions of the well-known Silhouette and Caliński-Harabasz cluster validity indices that are adapted for tree clustering with k-medoids. The efficiency of the new method was assessed using both synthetic and real data, such as a well-known phylogenetic dataset consisting of 47 gene trees inferred for 14 archaeal organisms. The method described here allows inference of multiple consensus trees from a given set of gene trees. It can be used to identify groups of gene trees having similar intragroup and different intergroup evolutionary histories. The main advantage of our method is that it is much faster than the existing tree clustering approaches, while providing similar or better clustering results in most cases. This makes it particularly well suited for the analysis of large genomic and phylogenetic datasets.

Tanglegrams for rooted phylogenetic trees and networks

PubMed Central

Scornavacca, Celine; Zickmann, Franziska; Huson, Daniel H.

2011-01-01

Motivation: In systematic biology, one is often faced with the task of comparing different phylogenetic trees, in particular in multi-gene analysis or cospeciation studies. One approach is to use a tanglegram in which two rooted phylogenetic trees are drawn opposite each other, using auxiliary lines to connect matching taxa. There is an increasing interest in using rooted phylogenetic networks to represent evolutionary history, so as to explicitly represent reticulate events, such as horizontal gene transfer, hybridization or reassortment. Thus, the question arises how to define and compute a tanglegram for such networks. Results: In this article, we present the first formal definition of a tanglegram for rooted phylogenetic networks and present a heuristic approach for computing one, called the NN-tanglegram method. We compare the performance of our method with existing tree tanglegram algorithms and also show a typical application to real biological datasets. For maximum usability, the algorithm does not require that the trees or networks are bifurcating or bicombining, or that they are on identical taxon sets. Availability: The algorithm is implemented in our program Dendroscope 3, which is freely available from www.dendroscope.org. Contact: scornava@informatik.uni-tuebingen.de; huson@informatik.uni-tuebingen.de PMID:21685078

Tree-ring dating of meteorite fall in Sikhote-Alin, Eastern Siberia - Russia

NASA Astrophysics Data System (ADS)

Fantucci, R.; Di Martino, Mario; Serra, Romano

2012-01-01

This research deals with the fall of the Sikhote-Alin iron meteorite on the morning of 12 February 1947, at about 00:38 h Utrecht, in a remote area in the territory of Primorsky Krai in Eastern Siberia (46°09‧36″N, 134°39‧22″E). The area engulfed by the meteoritic fall was around 48 km2, with an elliptic form and thousands of craters. Around the large craters the trees were torn out by the roots and laid radially to the craters at a distance of 10-20 m; the more distant trees had broken tops. This research investigated through dendrocronology n.6 Scots pine trees (Pinus Sibirica) close to one of the main impact craters. The analysis of growth anomalies has shown a sudden decrease since 1947 for 4-8 years after the meteoritic impact. Tree growth stress, detected in 1947, was analysed in detail through wood microsection that confirmed the winter season (rest vegetative period) of the event. The growth stress is mainly due to the lost crown (needle lost) and it did not seem to be caused due to direct damages on trunk and branches (missing of resin ducts).

Radial growth of Qilian juniper on the Northeast Tibetan Plateau and potential climate associations.

PubMed

Qin, Chun; Yang, Bao; Melvin, Thomas M; Fan, Zexin; Zhao, Yan; Briffa, Keith R

2013-01-01

There is controversy regarding the limiting climatic factor for tree radial growth at the alpine treeline on the northeastern Tibetan Plateau. In this study, we collected 594 increment cores from 331 trees, grouped within four altitude belts spanning the range 3550 to 4020 m.a.s.l. on a single hillside. We have developed four equivalent ring-width chronologies and shown that there are no significant differences in their growth-climate responses during 1956 to 2011 or in their longer-term growth patterns during the period AD 1110-2011. The main climate influence on radial growth is shown to be precipitation variability. Missing ring analysis shows that tree radial growth at the uppermost treeline location is more sensitive to climate variation than that at other elevations, and poor tree radial growth is particularly linked to the occurrence of serious drought events. Hence water limitation, rather than temperature stress, plays the pivotal role in controlling the radial growth of Sabina przewalskii Kom. at the treeline in this region. This finding contradicts any generalisation that tree-ring chronologies from high-elevation treeline environments are mostly indicators of temperature changes.

Radial Growth of Qilian Juniper on the Northeast Tibetan Plateau and Potential Climate Associations

PubMed Central

Qin, Chun; Yang, Bao; Melvin, Thomas M.; Fan, Zexin; Zhao, Yan; Briffa, Keith R.

2013-01-01

There is controversy regarding the limiting climatic factor for tree radial growth at the alpine treeline on the northeastern Tibetan Plateau. In this study, we collected 594 increment cores from 331 trees, grouped within four altitude belts spanning the range 3550 to 4020 m.a.s.l. on a single hillside. We have developed four equivalent ring-width chronologies and shown that there are no significant differences in their growth-climate responses during 1956 to 2011 or in their longer-term growth patterns during the period AD 1110–2011. The main climate influence on radial growth is shown to be precipitation variability. Missing ring analysis shows that tree radial growth at the uppermost treeline location is more sensitive to climate variation than that at other elevations, and poor tree radial growth is particularly linked to the occurrence of serious drought events. Hence water limitation, rather than temperature stress, plays the pivotal role in controlling the radial growth of Sabina przewalskii Kom. at the treeline in this region. This finding contradicts any generalisation that tree-ring chronologies from high-elevation treeline environments are mostly indicators of temperature changes. PMID:24244488

Root Cause Analysis: Learning from Adverse Safety Events.

PubMed

Brook, Olga R; Kruskal, Jonathan B; Eisenberg, Ronald L; Larson, David B

2015-10-01

Serious adverse events continue to occur in clinical practice, despite our best preventive efforts. It is essential that radiologists, both as individuals and as a part of organizations, learn from such events and make appropriate changes to decrease the likelihood that such events will recur. Root cause analysis (RCA) is a process to (a) identify factors that underlie variation in performance or that predispose an event toward undesired outcomes and (b) allow for development of effective strategies to decrease the likelihood of similar adverse events occurring in the future. An RCA process should be performed within the environment of a culture of safety, focusing on underlying system contributors and, in a confidential manner, taking into account the emotional effects on the staff involved. The Joint Commission now requires that a credible RCA be performed within 45 days for all sentinel or major adverse events, emphasizing the need for all radiologists to understand the processes with which an effective RCA can be performed. Several RCA-related tools that have been found to be useful in the radiology setting include the "five whys" approach to determine causation; cause-and-effect, or Ishikawa, diagrams; causal tree mapping; affinity diagrams; and Pareto charts. © RSNA, 2015.

Increase in platinum group elements in Mexico City as revealed from growth rings of Taxodium mucronatum ten.

PubMed

Morton-Bermea, Ofelia; Beramendi-Orosco, Laura; Martínez-Reyes, Ángeles; Hernández-Álvarez, Elizabeth; González-Hernández, Galia

2016-02-01

Tree rings may be used as indicators of contamination events providing information on the chronology and the elemental composition of the contamination. In this framework, we report PGEs enrichment in growth rings of Taxodium mucronatum ten for trees growing in the central area of Mexico City as compared to trees growing in a non-urban environment. Concentrations of PGE were determined by ICP-MS analysis on microwave-digested tree rings. The element found in higher concentrations was Pd (1.13-87.98 μg kg(-1)), followed by Rh (0.28-36.81 μg kg(-1)) and Pt (0.106-7.21 μg kg(-1)). The concentration trends of PGEs in the tree-ring sequences from the urban area presented significant correlation values when comparing between trees (r between 0.618 and 0.98, P < 0.025) and between elements within individual trees (r between 0.76 and 0.994, P < 0.01). Furthermore, a clear increase was observed for rings after 1997, with enrichment of up to 60 times the mean concentration found for the sequence from the non-urban area and up to 40 times the mean concentration for the pre-1991 period in the urban trees. These results also demonstrate the feasibility of applying T. mucronatum ten to be used as a bioindicator of the increase in PGE in urban environments.

Tree mortality in the eastern Mediterranean, causes and implications under climatic change

NASA Astrophysics Data System (ADS)

Sarris, Dimitrios; Iacovou, Valentina; Hoch, Guenter; Vennetier, Michel; Siegwolf, Rolf; Christodoulakis, Dimitrios; Koerner, Christian

2015-04-01

The eastern Mediterranean has experienced repeated incidents of forest mortality related to drought in recent decades. Such events may become more frequent in the future as drought conditions are projected to further intensify due to global warming. We have been investigating the causes behind such forest mortality events in Pinus halepensis, (the most drought tolerant pine in the Mediterranean). We cored tree stems and sampled various tissue types from dry habitats close to sea level and explored growth responses, stable isotope signals and non-structural carbohydrate (NSC) concentrations. Under intense drought that coincided with pine desiccation events in natural populations our result indicate a significant reduction in tree growth, the most significant in more than a century despite the increase in atmospheric CO2 concentrations in recent decades. This has been accompanied by a lengthening in the integration periods of rainfall needed for pine growth, reaching even 5-6 years before and including the year of mortality occurrence. Oxygen stable isotopes indicate that these signals were associated with a shift in tree water utilization from deeper moisture pools related to past rainfall events. Furthermore, where the driest conditions occur, pine carbon reserves were found to increase in stem tissue, indicating that mortality in these pines cannot be explained by carbon starvation. Our findings suggest that for pine populations that are already water limited (i) a further atmospheric CO2 increase will not compensate for the reduction in growth because of a drier climate, (ii) hydraulic failure appears as the most likely cause of pine desiccation, as no shortage occurs in tree carbon reserves, (iii) a further increase in mortality events may cause these systems to become carbon sources.

El Niño-southern oscillation effect on a fire regime in northeastern Mexico has changed over time.

PubMed

Yocom, Larissa L; Fulé, Peter Z; Brown, Peter M; Cerano, Julian; Villanueva-Díaz, José; Falk, Donald A; Cornejo-Oviedo, Eladio

2010-06-01

The El Niño Southern Oscillation (ENSO) is a climate-forcing mechanism that has been shown to affect precipitation and the occurrence of wildfires in many parts of the world. In the southern United States and northern Mexico, warm events (El Niño) are associated with moist winter conditions and fewer fires, while cool events (La Niñia) tend to favor dry winters and more fires. We tested this relationship in a region of northeastern Mexico by characterizing the historical fire regime and climatic influences: Fire regimes were reconstructed from fire-scar samples collected from 100 trees in three high-elevation sites on Peña Nevada in southern Nuevo Le6n. The sites were approximately 25 ha each, and the site centers were approximately 1 km apart. The earliest recorded fire occurred in 1521 and the time period we used for analysis was 1645-1929. The sites were characterized by frequent surface fires before the 1920s. In the three sites, mean fire intervals ranged from 8.6 to 9.6 years (all fires) and 11.9 to 18.6 years (fires that scarred > or = 25% of recording trees). The per-tree mean fire return interval was 17 years, and all three sites burned in the same year seven times between 1774 and 1929. After 1929, fires were nearly eliminated in all sites, likely due to human causes. We found a temporal change in the association between ENSO events and fires; before the 1830s La Niña events were significantly associated with fire years, while after the 1830s this association was not significant. In 1998, when the most severe El Niño event of the past century occurred, the three sites experienced severe, stand-replacing fires that killed many trees that had survived multiple surface fires in the past. Prior to the 1830s, fires tended to occur during dry La Niña years, but since then both La Niña and El Niño have been associated with dry years in this region, especially during the last three decades. This result suggests that ENSO effects have changed over time in this location and that phases of ENSO are not consistent indicators of precipitation, fire occurrence, or fire behavior in this area of northeastern Mexico.

Manned space flight nuclear system safety. Volume 3: Reactor system preliminary nuclear safety analysis. Part 2: Accident Model Document (AMD)

NASA Technical Reports Server (NTRS)

1972-01-01

The Accident Model Document is one of three documents of the Preliminary Safety Analysis Report (PSAR) - Reactor System as applied to a Space Base Program. Potential terrestrial nuclear hazards involving the zirconium hydride reactor-Brayton power module are identified for all phases of the Space Base program. The accidents/events that give rise to the hazards are defined and abort sequence trees are developed to determine the sequence of events leading to the hazard and the associated probabilities of occurence. Source terms are calculated to determine the magnitude of the hazards. The above data is used in the mission accident analysis to determine the most probable and significant accidents/events in each mission phase. The only significant hazards during the prelaunch and launch ascent phases of the mission are those which arise form criticality accidents. Fission product inventories during this time period were found to be very low due to very limited low power acceptance testing.

VESGEN Software for Mapping and Quantification of Vascular Regulators

NASA Technical Reports Server (NTRS)

Parsons-Wingerter, Patricia A.; Vickerman, Mary B.; Keith, Patricia A.

2012-01-01

VESsel GENeration (VESGEN) Analysis is an automated software that maps and quantifies effects of vascular regulators on vascular morphology by analyzing important vessel parameters. Quantification parameters include vessel diameter, length, branch points, density, and fractal dimension. For vascular trees, measurements are reported as dependent functions of vessel branching generation. VESGEN maps and quantifies vascular morphological events according to fractal-based vascular branching generation. It also relies on careful imaging of branching and networked vascular form. It was developed as a plug-in for ImageJ (National Institutes of Health, USA). VESGEN uses image-processing concepts of 8-neighbor pixel connectivity, skeleton, and distance map to analyze 2D, black-and-white (binary) images of vascular trees, networks, and tree-network composites. VESGEN maps typically 5 to 12 (or more) generations of vascular branching, starting from a single parent vessel. These generations are tracked and measured for critical vascular parameters that include vessel diameter, length, density and number, and tortuosity per branching generation. The effects of vascular therapeutics and regulators on vascular morphology and branching tested in human clinical or laboratory animal experimental studies are quantified by comparing vascular parameters with control groups. VESGEN provides a user interface to both guide and allow control over the users vascular analysis process. An option is provided to select a morphological tissue type of vascular trees, network or tree-network composites, which determines the general collections of algorithms, intermediate images, and output images and measurements that will be produced.

Divide and Conquer: A Valid Approach for Risk Assessment and Decision Making under Uncertainty for Groundwater-Related Diseases

NASA Astrophysics Data System (ADS)

Sanchez-Vila, X.; de Barros, F.; Bolster, D.; Nowak, W.

2010-12-01

Assessing the potential risk of hydro(geo)logical supply systems to human population is an interdisciplinary field. It relies on the expertise in fields as distant as hydrogeology, medicine, or anthropology, and needs powerful translation concepts to provide decision support and policy making. Reliable health risk estimates need to account for the uncertainties in hydrological, physiological and human behavioral parameters. We propose the use of fault trees to address the task of probabilistic risk analysis (PRA) and to support related management decisions. Fault trees allow decomposing the assessment of health risk into individual manageable modules, thus tackling a complex system by a structural “Divide and Conquer” approach. The complexity within each module can be chosen individually according to data availability, parsimony, relative importance and stage of analysis. The separation in modules allows for a true inter- and multi-disciplinary approach. This presentation highlights the three novel features of our work: (1) we define failure in terms of risk being above a threshold value, whereas previous studies used auxiliary events such as exceedance of critical concentration levels, (2) we plot an integrated fault tree that handles uncertainty in both hydrological and health components in a unified way, and (3) we introduce a new form of stochastic fault tree that allows to weaken the assumption of independent subsystems that is required by a classical fault tree approach. We illustrate our concept in a simple groundwater-related setting.

Growth and reproduction respond differently to climate in three Neotropical tree species.

PubMed

Alfaro-Sánchez, Raquel; Muller-Landau, Helene C; Wright, S Joseph; Camarero, J Julio

2017-06-01

The response of tropical forests to anthropogenic climate change is critically important to future global carbon budgets, yet remains highly uncertain. Here, we investigate how precipitation, temperature, solar radiation and dry- and wet-season lengths are related to annual tree growth, flower production, and fruit production in three moist tropical forest tree species using long-term datasets from tree rings and litter traps in central Panama. We also evaluated how growth, flower, and fruit production were interrelated. We found that growth was positively correlated with wet-season precipitation in all three species: Jacaranda copaia (r = 0.63), Tetragastris panamensis (r = 0.39) and Trichilia tuberculata (r = 0.39). Flowering and fruiting in Jacaranda were negatively related to current-year dry-season rainfall and positively related to prior-year dry-season rainfall. Flowering in Tetragastris was negatively related to current-year annual mean temperature while Trichilia showed no significant relationships of reproduction with climate. Growth was significantly related to reproduction only in Tetragastris, where it was positively related to previous year fruiting. Our results suggest that tree growth in moist tropical forest tree species is generally reduced by drought events such as those associated with strong El Niño events. In contrast, interannual variation in reproduction is not generally associated with growth and has distinct and species-specific climate responses, with positive effects of El Niño events in some species. Understanding these contrasting climate effects on tree growth and reproduction is critical to predicting changes in tropical forest dynamics and species composition under climate change.

Radiocarbon dating with annual-resolution of subfossil trees from the Younger Dryas event in the southern French Alps

NASA Astrophysics Data System (ADS)

Capano, Manuela; Miramont, Cécile; Guibal, Frédéric; Kromer, Bernd; Tuna, Thibaut; Fagault, Yoann; Bard, Edouard

2017-04-01

Tree rings are an important archive for the calibration of radiocarbon data. The younger part of the IntCal curve is based essentially on tree-ring chronologies, absolutely dated by dendrochronological analysis. For the Northern Hemisphere (NH), a gap still exists between the absolutely dated sequences and a floating chronology. Based on the Southern Hemisphere (SH) tree-ring chronologies a link has been previously proposed (Reimer et al. 2013, Radiocarbon; see also update in Hogg et al. 2016, Radiocarbon). By measuring radiocarbon at annual resolution in French subfossil pines (Pinus sylvestris L.) we propose to improve the connection between the absolute chronology and the floating chronology. Several subfossil pines have been found in the Southern French Alps; they were buried by flood deposits, allowing their preservation. Some trees discovered in the Barbier riverbed were dated to the Younger Dryas periods by previous decadal radiocarbon measurements, performed in Heidelberg and Mannheim. The trees selected for our new study are Barb12 and Barb17 (analyzed sequences of 163 and 152 rings, respectively). These sequences were sampled at annual resolution when permitted by the ring width. As a first step, every third ring was pretreated for radiocarbon analysis. These samples were sliced in small pieces and pretreated by using the ABA-B method before being combusted, graphitized with the AGE system and measured with AixMICADAS (Bard et al. 2015, Nucl. Instr. Meth. B). From the comparison with the kauri sequence, the Barb12-17 sequence can be dated from about 12835 to 12606 cal. BP. It can also be used to calculate the interhemispheric gradient (IHG) over the overlapping period. In order to reduce the inter-annual variability, the Barb12-17 record was smoothed, grouped and averaged over the same decades as in the Kauri record. On the basis of twenty values, a mean IHG value of ca. 60 years was calculated. Quantification of the IHG around 50 yr is particularly robust during the two "age plateaux" corresponding to the time intervals 12820-12760 and 12660-12630 cal. BP. Overall, the IHG stayed relatively high throughout the studied period corresponding to the beginning of the Younger Dryas climatic event.

Tree mortality from a short-duration freezing event and global-change-type drought in a Southwestern piñon-juniper woodland, USA

PubMed Central

2014-01-01

This study documents tree mortality in Big Bend National Park in Texas in response to the most acute one-year drought on record, which occurred following a five-day winter freeze. I estimated changes in forest stand structure and species composition due to freezing and drought in the Chisos Mountains of Big Bend National Park using permanent monitoring plot data. The drought killed over half (63%) of the sampled trees over the entire elevation gradient. Significant mortality occurred in trees up to 20 cm diameter (P < 0.05). Pinus cembroides Zucc. experienced the highest seedling and tree mortality (P < 0.0001) (55% of piñon pines died), and over five times as many standing dead pines were observed in 2012 than in 2009. Juniperus deppeana vonSteudal and Quercus emoryi Leibmann also experienced significant declines in tree density (P < 0.02) (30.9% and 20.7%, respectively). Subsequent droughts under climate change will likely cause even greater damage to trees that survived this record drought, especially if such events follow freezes. The results from this study highlight the vulnerability of trees in the Southwest to climatic change and that future shifts in forest structure can have large-scale community consequences. PMID:24949231

Risk Analysis of a Fuel Storage Terminal Using HAZOP and FTA

PubMed Central

Baixauli-Pérez, Mª Piedad

2017-01-01

The size and complexity of industrial chemical plants, together with the nature of the products handled, means that an analysis and control of the risks involved is required. This paper presents a methodology for risk analysis in chemical and allied industries that is based on a combination of HAZard and OPerability analysis (HAZOP) and a quantitative analysis of the most relevant risks through the development of fault trees, fault tree analysis (FTA). Results from FTA allow prioritizing the preventive and corrective measures to minimize the probability of failure. An analysis of a case study is performed; it consists in the terminal for unloading chemical and petroleum products, and the fuel storage facilities of two companies, in the port of Valencia (Spain). HAZOP analysis shows that loading and unloading areas are the most sensitive areas of the plant and where the most significant danger is a fuel spill. FTA analysis indicates that the most likely event is a fuel spill in tank truck loading area. A sensitivity analysis from the FTA results show the importance of the human factor in all sequences of the possible accidents, so it should be mandatory to improve the training of the staff of the plants. PMID:28665325

Risk Analysis of a Fuel Storage Terminal Using HAZOP and FTA.

PubMed

Fuentes-Bargues, José Luis; González-Cruz, Mª Carmen; González-Gaya, Cristina; Baixauli-Pérez, Mª Piedad

2017-06-30

The size and complexity of industrial chemical plants, together with the nature of the products handled, means that an analysis and control of the risks involved is required. This paper presents a methodology for risk analysis in chemical and allied industries that is based on a combination of HAZard and OPerability analysis (HAZOP) and a quantitative analysis of the most relevant risks through the development of fault trees, fault tree analysis (FTA). Results from FTA allow prioritizing the preventive and corrective measures to minimize the probability of failure. An analysis of a case study is performed; it consists in the terminal for unloading chemical and petroleum products, and the fuel storage facilities of two companies, in the port of Valencia (Spain). HAZOP analysis shows that loading and unloading areas are the most sensitive areas of the plant and where the most significant danger is a fuel spill. FTA analysis indicates that the most likely event is a fuel spill in tank truck loading area. A sensitivity analysis from the FTA results show the importance of the human factor in all sequences of the possible accidents, so it should be mandatory to improve the training of the staff of the plants.

78 FR 66762 - Notice of Public Meeting and Request for Comments

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-06

... of request for public meeting and public comments on the planning of the National Christmas Tree... and suggestions on the planning of the 2013 National Christmas Tree Lighting and the subsequent 26-day... on the planning of the 2013 National Christmas Tree Lighting and the subsequent 26-day event, which...

76 FR 66082 - Notice of Public Meeting and Request for Comments

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-25

... for Public Meeting and Public Comments--The National Christmas Tree Lighting and the subsequent 31 day... the 2011 National Christmas Tree Lighting and the subsequent 31 day event. DATES: The meeting will be... and suggestions on the planning of the 2011 National Christmas Tree Lighting and the subsequent 31 day...

Tasting the Tree of Life: Development of a Collaborative, Cross-Campus, Science Outreach Meal Event.

PubMed

Clement, Wendy L; Elliott, Kathryn T; Cordova-Hoyos, Okxana; Distefano, Isabel; Kearns, Kate; Kumar, Raagni; Leto, Ashley; Tumaliuan, Janis; Franchetti, Lauren; Kulesza, Evelyn; Tineo, Nicole; Mendes, Patrice; Roth, Karen; Osborn, Jeffrey M

2018-01-01

Communicating about science with the public can present a number of challenges, from participation to engagement to impact. In an effort to broadly communicate messages regarding biodiversity, evolution, and tree-thinking with the campus community at The College of New Jersey (TCNJ), a public, primarily undergraduate institution, we created a campus-wide, science-themed meal, "Tasting the Tree of Life: Exploring Biodiversity through Cuisine." We created nine meals that incorporated 149 species/ingredients across the Tree of Life. Each meal illustrated a scientific message communicated through interactions with undergraduate biology students, informational signs, and an interactive website. To promote tree-thinking, we reconstructed a phylogeny of all 149 ingredients. In total, 3,262 people attended the meal, and evaluations indicated that participants left with greater appreciation for the biodiversity and evolutionary relatedness of their food. A keynote lecture and a coordinated social media campaign enhanced the scientific messages, and media coverage extended the reach of this event. "Tasting the Tree of Life" highlights the potential of cuisine as a valuable science communication tool.

Tropical forest carbon balance: effects of field- and satellite-based mortality regimes on the dynamics and the spatial structure of Central Amazon forest biomass

NASA Astrophysics Data System (ADS)

Di Vittorio, Alan V.; Negrón-Juárez, Robinson I.; Higuchi, Niro; Chambers, Jeffrey Q.

2014-03-01

Debate continues over the adequacy of existing field plots to sufficiently capture Amazon forest dynamics to estimate regional forest carbon balance. Tree mortality dynamics are particularly uncertain due to the difficulty of observing large, infrequent disturbances. A recent paper (Chambers et al 2013 Proc. Natl Acad. Sci. 110 3949-54) reported that Central Amazon plots missed 9-17% of tree mortality, and here we address ‘why’ by elucidating two distinct mortality components: (1) variation in annual landscape-scale average mortality and (2) the frequency distribution of the size of clustered mortality events. Using a stochastic-empirical tree growth model we show that a power law distribution of event size (based on merged plot and satellite data) is required to generate spatial clustering of mortality that is consistent with forest gap observations. We conclude that existing plots do not sufficiently capture losses because their placement, size, and longevity assume spatially random mortality, while mortality is actually distributed among differently sized events (clusters of dead trees) that determine the spatial structure of forest canopies.

A method for investigating relative timing information on phylogenetic trees.

PubMed

Ford, Daniel; Matsen, Frederick A; Stadler, Tanja

2009-04-01

In this paper, we present a new way to describe the timing of branching events in phylogenetic trees. Our description is in terms of the relative timing of diversification events between sister clades; as such it is complementary to existing methods using lineages-through-time plots which consider diversification in aggregate. The method can be applied to look for evidence of diversification happening in lineage-specific "bursts", or the opposite, where diversification between 2 clades happens in an unusually regular fashion. In order to be able to distinguish interesting events from stochasticity, we discuss 2 classes of neutral models on trees with relative timing information and develop a statistical framework for testing these models. These model classes include both the coalescent with ancestral population size variation and global rate speciation-extinction models. We end the paper with 2 example applications: first, we show that the evolution of the hepatitis C virus deviates from the coalescent with arbitrary population size. Second, we analyze a large tree of ants, demonstrating that a period of elevated diversification rates does not appear to have occurred in a bursting manner.

Poster - Thur Eve - 05: Safety systems and failure modes and effects analysis for a magnetic resonance image guided radiation therapy system.

PubMed

Lamey, M; Carlone, M; Alasti, H; Bissonnette, J P; Borg, J; Breen, S; Coolens, C; Heaton, R; Islam, M; van Proojen, M; Sharpe, M; Stanescu, T; Jaffray, D

2012-07-01

An online Magnetic Resonance guided Radiation Therapy (MRgRT) system is under development. The system is comprised of an MRI with the capability of travel between and into HDR brachytherapy and external beam radiation therapy vaults. The system will provide on-line MR images immediately prior to radiation therapy. The MR images will be registered to a planning image and used for image guidance. With the intention of system safety we have performed a failure modes and effects analysis. A process tree of the facility function was developed. Using the process tree as well as an initial design of the facility as guidelines possible failure modes were identified, for each of these failure modes root causes were identified. For each possible failure the assignment of severity, detectability and occurrence scores was performed. Finally suggestions were developed to reduce the possibility of an event. The process tree consists of nine main inputs and each of these main inputs consisted of 5 - 10 sub inputs and tertiary inputs were also defined. The process tree ensures that the overall safety of the system has been considered. Several possible failure modes were identified and were relevant to the design, construction, commissioning and operating phases of the facility. The utility of the analysis can be seen in that it has spawned projects prior to installation and has lead to suggestions in the design of the facility. © 2012 American Association of Physicists in Medicine.

Informational Gene Phylogenies Do Not Support a Fourth Domain of Life for Nucleocytoplasmic Large DNA Viruses

PubMed Central

Williams, Tom A.; Embley, T. Martin; Heinz, Eva

2011-01-01

Mimivirus is a nucleocytoplasmic large DNA virus (NCLDV) with a genome size (1.2 Mb) and coding capacity ( 1000 genes) comparable to that of some cellular organisms. Unlike other viruses, Mimivirus and its NCLDV relatives encode homologs of broadly conserved informational genes found in Bacteria, Archaea, and Eukaryotes, raising the possibility that they could be placed on the tree of life. A recent phylogenetic analysis of these genes showed the NCLDVs emerging as a monophyletic group branching between Eukaryotes and Archaea. These trees were interpreted as evidence for an independent “fourth domain” of life that may have contributed DNA processing genes to the ancestral eukaryote. However, the analysis of ancient evolutionary events is challenging, and tree reconstruction is susceptible to bias resulting from non-phylogenetic signals in the data. These include compositional heterogeneity and homoplasy, which can lead to the spurious grouping of compositionally-similar or fast-evolving sequences. Here, we show that these informational gene alignments contain both significant compositional heterogeneity and homoplasy, which were not adequately modelled in the original analysis. When we use more realistic evolutionary models that better fit the data, the resulting trees are unable to reject a simple null hypothesis in which these informational genes, like many other NCLDV genes, were acquired by horizontal transfer from eukaryotic hosts. Our results suggest that a fourth domain is not required to explain the available sequence data. PMID:21698163

Responses of tree species to heat waves and extreme heat events.

PubMed

Teskey, Robert; Wertin, Timothy; Bauweraerts, Ingvar; Ameye, Maarten; McGuire, Mary Anne; Steppe, Kathy

2015-09-01

The number and intensity of heat waves has increased, and this trend is likely to continue throughout the 21st century. Often, heat waves are accompanied by drought conditions. It is projected that the global land area experiencing heat waves will double by 2020, and quadruple by 2040. Extreme heat events can impact a wide variety of tree functions. At the leaf level, photosynthesis is reduced, photooxidative stress increases, leaves abscise and the growth rate of remaining leaves decreases. In some species, stomatal conductance increases at high temperatures, which may be a mechanism for leaf cooling. At the whole plant level, heat stress can decrease growth and shift biomass allocation. When drought stress accompanies heat waves, the negative effects of heat stress are exacerbated and can lead to tree mortality. However, some species exhibit remarkable tolerance to thermal stress. Responses include changes that minimize stress on photosynthesis and reductions in dark respiration. Although there have been few studies to date, there is evidence of within-species genetic variation in thermal tolerance, which could be important to exploit in production forestry systems. Understanding the mechanisms of differing tree responses to extreme temperature events may be critically important for understanding how tree species will be affected by climate change. © 2014 John Wiley & Sons Ltd.

Air blasts generated by rockfall impacts: Analysis of the 1996 Happy Isles event in Yosemite National Park

USGS Publications Warehouse

Morrissey, M.M.; Savage, W.Z.; Wieczorek, G.F.

1999-01-01

The July 10, 1996, Happy Isles rockfall in Yosemite National Park, California, released 23,000 to 38,000 m3 of granite in four separate events. The impacts of the first two events which involved a 550-m free fall, generated seismic waves and atmospheric pressure waves (air blasts). We focus on the dynamic behavior of the second air blast that downed over 1000 trees, destroyed a bridge, demolished a snack bar, and caused one fatality and several injuries. Calculated velocities for the air blast from a two-phase, finite difference model are compared to velocities estimated from tree damage. From tornadic studies of tree damage, the air blast is estimated to have traveled <108-120 m/s within 50 m from the impact and decreased to <10-20 m/s within 500 m from the impact. The numerical model simulates the two-dimensional propagation of an air blast through a dusty atmosphere with initial conditions defined by the impact velocity and pressure. The impact velocity (105-107 m/s) is estimated from the Colorado Rockfall Simulation Program that simulates rockfall trajectories. The impact pressure (0.5 MPa) is constrained by the kinetic energy of the impact (1010-1012 J) estimated from the seismic energy generated by the impact. Results from the air blast simulations indicate that the second Happy Isles air blast (weak shock wave) traveled with an initial velocity above the local sound speed. The size and location of the first impact are thought to have injected <50 wt % dust into the atmosphere. This amount of dust lowered the local atmospheric sound speed to ???220 m/s. The discrepancy between calculated velocity data and field estimated velocity data (???220 m/s versus ???110 m/s) is attributed to energy dissipated by the downing of trees and additional entrainment of debris into the atmosphere not included in the calculations. Copyright 1999 by the American Geophysical Union.

Air blasts generated by rockfall impacts: Analysis of the 1996 Happy Isles event in Yosemite National Park

NASA Astrophysics Data System (ADS)

Morrissey, M. M.; Savage, W. Z.; Wieczorek, G. F.

1999-10-01

The July 10, 1996, Happy Isles rockfall in Yosemite National Park, California, released 23,000 to 38,000 m3 of granite in four separate events. The impacts of the first two events which involved a 550-m free fall, generated seismic waves and atmospheric pressure waves (air blasts). We focus on the dynamic behavior of the second air blast that downed over 1000 trees, destroyed a bridge, demolished a snack bar, and caused one fatality and several injuries. Calculated velocities for the air blast from a two-phase, finite difference model are compared to velocities estimated from tree damage. From tornadic studies of tree damage, the air blast is estimated to have traveled <108-120 m/s within 50 m from the impact and decreased to <10-20 m/s within 500 m from the impact. The numerical model simulates the two-dimensional propagation of an air blast through a dusty atmosphere with initial conditions defined by the impact velocity and pressure. The impact velocity (105-107 m/s) is estimated from the Colorado Rockfall Simulation Program that simulates rockfall trajectories. The impact pressure (0.5 MPa) is constrained by the kinetic energy of the impact (1010-1012 J) estimated from the seismic energy generated by the impact. Results from the air blast simulations indicate that the second Happy Isles air blast (weak shock wave) traveled with an initial velocity above the local sound speed. The size and location of the first impact are thought to have injected <50 wt% dust into the atmosphere. This amount of dust lowered the local atmospheric sound speed to ˜220 m/s. The discrepancy between calculated velocity data and field estimated velocity data (˜220 m/s versus ˜110 m/s) is attributed to energy dissipated by the downing of trees and additional entrainment of debris into the atmosphere not included in the calculations.

Resolving Evolutionary Relationships in Closely Related Species with Whole-Genome Sequencing Data

PubMed Central

Nater, Alexander; Burri, Reto; Kawakami, Takeshi; Smeds, Linnéa; Ellegren, Hans

2015-01-01

Using genetic data to resolve the evolutionary relationships of species is of major interest in evolutionary and systematic biology. However, reconstructing the sequence of speciation events, the so-called species tree, in closely related and potentially hybridizing species is very challenging. Processes such as incomplete lineage sorting and interspecific gene flow result in local gene genealogies that differ in their topology from the species tree, and analyses of few loci with a single sequence per species are likely to produce conflicting or even misleading results. To study these phenomena on a full phylogenomic scale, we use whole-genome sequence data from 200 individuals of four black-and-white flycatcher species with so far unresolved phylogenetic relationships to infer gene tree topologies and visualize genome-wide patterns of gene tree incongruence. Using phylogenetic analysis in nonoverlapping 10-kb windows, we show that gene tree topologies are extremely diverse and change on a very small physical scale. Moreover, we find strong evidence for gene flow among flycatcher species, with distinct patterns of reduced introgression on the Z chromosome. To resolve species relationships on the background of widespread gene tree incongruence, we used four complementary coalescent-based methods for species tree reconstruction, including complex modeling approaches that incorporate post-divergence gene flow among species. This allowed us to infer the most likely species tree with high confidence. Based on this finding, we show that regions of reduced effective population size, which have been suggested as particularly useful for species tree inference, can produce positively misleading species tree topologies. Our findings disclose the pitfalls of using loci potentially under selection as phylogenetic markers and highlight the potential of modeling approaches to disentangle species relationships in systems with large effective population sizes and post-divergence gene flow. PMID:26187295

Tree-growth analyses to estimate tree species' drought tolerance.

PubMed

Eilmann, Britta; Rigling, Andreas

2012-02-01

Climate change is challenging forestry management and practices. Among other things, tree species with the ability to cope with more extreme climate conditions have to be identified. However, while environmental factors may severely limit tree growth or even cause tree death, assessing a tree species' potential for surviving future aggravated environmental conditions is rather demanding. The aim of this study was to find a tree-ring-based method suitable for identifying very drought-tolerant species, particularly potential substitute species for Scots pine (Pinus sylvestris L.) in Valais. In this inner-Alpine valley, Scots pine used to be the dominating species for dry forests, but today it suffers from high drought-induced mortality. We investigate the growth response of two native tree species, Scots pine and European larch (Larix decidua Mill.), and two non-native species, black pine (Pinus nigra Arnold) and Douglas fir (Pseudotsuga menziesii Mirb. var. menziesii), to drought. This involved analysing how the radial increment of these species responded to increasing water shortage (abandonment of irrigation) and to increasingly frequent drought years. Black pine and Douglas fir are able to cope with drought better than Scots pine and larch, as they show relatively high radial growth even after irrigation has been stopped and a plastic growth response to drought years. European larch does not seem to be able to cope with these dry conditions as it lacks the ability to recover from drought years. The analysis of trees' short-term response to extreme climate events seems to be the most promising and suitable method for detecting how tolerant a tree species is towards drought. However, combining all the methods used in this study provides a complete picture of how water shortage could limit species.

[Extreme Climatic Events in the Altai Republic According to Dendrochronological Data].

PubMed

Barinov, V V; Myglan, V S; Nazarov, A N; Vaganov, E A; Agatova, A R; Nepop, R K

2016-01-01

The results of dating of extreme climatic events by damage to the anatomical structure and missing tree rings of the Siberian larch in the upper forest boundary of the Altai Republic are given. An analysis of the spatial distribution of the revealed dates over seven plots (Kokcy, Chind, Ak-ha, Jelo, Tute, Tara, and Sukor) allowed us to distinguish the extreme events on interregional (1700, 1783, 1788, 1812, 1814, 1884), regional (1724, 1775, 1784, 1835, 1840, 1847, 1850, 1852, 1854, 1869, 1871, 1910, 1917, 1927, 1938, 1958, 1961), and local (1702, 1736, 1751, 1785, 1842, 1843,1874, 1885, 1886, 1919, 2007, and 2009) scales. It was shown that the events of an interregional scale correspond with the dates of major volcanic eruptions (Grimsvotn, Lakagigar, Etna, Awu, Tambora, Soufriere St. Vinsent, Mayon, and Krakatau volcanos) and extreme climatic events, crop failures, lean years, etc., registered in historical sources.

Mistletoe infection alters the transpiration flow path and suppresses water regulation of host trees during extreme events

NASA Astrophysics Data System (ADS)

Griebel, A.; Maier, C.; Barton, C. V.; Metzen, D.; Renchon, A.; Boer, M. M.; Pendall, E.

2017-12-01

Mistletoe is a globally distributed group of parasitic plants that infiltrates the vascular tissue of its host trees to acquire water, carbon and nutrients, making it a leading agent of biotic disturbance. Many mistletoes occur in water-limited ecosystems, thus mistletoe infection in combination with increased climatic stress may exacerbate water stress and potentially accelerate mortality rates of infected trees during extreme events. This is an emerging problem in Australia, as mistletoe distribution is increasing and clear links between mistletoe infection and mortality have been established. However, direct observations about how mistletoes alter host physiological processes during extreme events are rare, which impedes our understanding of mechanisms underlying increased tree mortality rates. We addressed this gap by continuously monitoring stem and branch sap flow and a range of leaf traits of infected and uninfected trees of two co-occurring eucalypt species during a severe heatwave in south-eastern Australia. We demonstrate that mistletoes' leaf water potentials were maintained 30% lower than hosts' to redirect the trees' transpiration flow path towards mistletoe leaves. Eucalypt leaves reduced water loss through stomatal regulation when atmospheric dryness exceeded 2 kPa, but the magnitude of stomatal regulation in non-infected eucalypts differed by species (between 40-80%). Remarkably, when infected, sap flow rates of stems and branches of both eucalypt species remained unregulated even under extreme atmospheric dryness (>8 kPa). Our observations indicate that excessive water use of mistletoes likely increases xylem cavitation rates in hosts during prolonged droughts and supports that hydraulic failure contributes to increased mortality of infected trees. Hence, in order to accurately model the contribution of biotic disturbances to tree mortality under a changing climate, it will be crucial to increase our process-based understanding of the interaction between biotic and abiotic dynamics, especially to establish thresholds of critical cavitation rates of infected trees.

Microbial-based evaluation of foaming events in full-scale wastewater treatment plants by microscopy survey and quantitative image analysis.

PubMed

Leal, Cristiano; Amaral, António Luís; Costa, Maria de Lourdes

2016-08-01

Activated sludge systems are prone to be affected by foaming occurrences causing the sludge to rise in the reactor and affecting the wastewater treatment plant (WWTP) performance. Nonetheless, there is currently a knowledge gap hindering the development of foaming events prediction tools that may be fulfilled by the quantitative monitoring of AS systems biota and sludge characteristics. As such, the present study focuses on the assessment of foaming events in full-scale WWTPs, by quantitative protozoa, metazoa, filamentous bacteria, and sludge characteristics analysis, further used to enlighten the inner relationships between these parameters. In the current study, a conventional activated sludge system (CAS) and an oxidation ditch (OD) were surveyed throughout a period of 2 and 3 months, respectively, regarding their biota and sludge characteristics. The biota community was monitored by microscopic observation, and a new filamentous bacteria index was developed to quantify their occurrence. Sludge characteristics (aggregated and filamentous biomass contents and aggregate size) were determined by quantitative image analysis (QIA). The obtained data was then processed by principal components analysis (PCA), cross-correlation analysis, and decision trees to assess the foaming occurrences, and enlighten the inner relationships. It was found that such events were best assessed by the combined use of the relative abundance of testate amoeba and nocardioform filamentous index, presenting a 92.9 % success rate for overall foaming events, and 87.5 and 100 %, respectively, for persistent and mild events.

Twisted trees and inconsistency of tree estimation when gaps are treated as missing data - The impact of model mis-specification in distance corrections.

PubMed

McTavish, Emily Jane; Steel, Mike; Holder, Mark T

2015-12-01

Statistically consistent estimation of phylogenetic trees or gene trees is possible if pairwise sequence dissimilarities can be converted to a set of distances that are proportional to the true evolutionary distances. Susko et al. (2004) reported some strikingly broad results about the forms of inconsistency in tree estimation that can arise if corrected distances are not proportional to the true distances. They showed that if the corrected distance is a concave function of the true distance, then inconsistency due to long branch attraction will occur. If these functions are convex, then two "long branch repulsion" trees will be preferred over the true tree - though these two incorrect trees are expected to be tied as the preferred true. Here we extend their results, and demonstrate the existence of a tree shape (which we refer to as a "twisted Farris-zone" tree) for which a single incorrect tree topology will be guaranteed to be preferred if the corrected distance function is convex. We also report that the standard practice of treating gaps in sequence alignments as missing data is sufficient to produce non-linear corrected distance functions if the substitution process is not independent of the insertion/deletion process. Taken together, these results imply inconsistent tree inference under mild conditions. For example, if some positions in a sequence are constrained to be free of substitutions and insertion/deletion events while the remaining sites evolve with independent substitutions and insertion/deletion events, then the distances obtained by treating gaps as missing data can support an incorrect tree topology even given an unlimited amount of data. Copyright © 2015 Elsevier Inc. All rights reserved.

Effects of the 2015/16 ENSO event on tropical trees in regrowing secondary forests in Central Panama

NASA Astrophysics Data System (ADS)

Bretfeld, M.; Ewers, B. E.; Hall, J. S.; Ogden, F. L.

2016-12-01

The 2015/16 El Niño-Southern Oscillation (ENSO) event ranks amongst the driest and hottest periods on record in Panama, with severe drought conditions reported for over 90% of the country. A predicted long-term transition into a drier climatic period makes this event an ideal opportunity to study the effects of drought on tropical tree species in secondary forests of central Panama. These forests are associated with desirable hydrological ecosystem services, characterized by reduced peak runoff during high precipitation events in the rainy season and increased base flow during the dry season ("sponge-effect"), making these forest invaluable for water provisioning for the Panama Canal's $2 billion business and Panama's thriving capital city. Starting in February 2015, we installed heat-ratio sap flow sensors in 76 trees (representing 42 different species) in secondary forests of three different ages (8, 25, and 80+ years) in the 15 km2 Agua Salud study area, located in the Panama Canal Watershed. Within each site, trees were selected to represent local tree size distribution. Additional sensors were installed on the roots of a subset of trees. Sap flow data were logged every 30 minutes and soil moisture was measured every 3 minutes at 10, 30, 50, and 100 cm depth. Pre-dawn, mid-day, and pre-dusk leaf water potentials were measured during the dry season (March 2016) and rainy season (July 2016). Meteorological data were taken from a nearby met-station ("Celestino"). Primary drivers of transpiration were vapor pressure deficit and solar radiation. Trees of the 25 and 80+ year old forests appear not water limited during the dry season following ENSO while reduced sap flow rates of trees in the 8 year old forest are indicative of a regulatory response to the drought. Younger understory trees in the 80+ year old forest showed no signs of a drought response. Throughout most of the dry season, volumetric water content at 30 and 50 cm depths was 8% lower in the 8 year old forest than in the 80+ year old forest. Our data indicate higher resilience to drought in older forest and support that hydrological properties improve as secondary forests mature in central Panama.

Impacts of short-term heatwaves on sun-induced chlorophyll fluorescence(SiF) in temperate tree species

NASA Astrophysics Data System (ADS)

Wang, F.; Gu, L.; Guha, A.; Han, J.; Warren, J.

2017-12-01

The current projections for global climate change forecast an increase in the intensity and frequency of extreme climatic events, such as droughts and short-term heat waves. Understanding the effects of short-term heat wave on photosynthesis process is of critical importance to predict global impacts of extreme weather event on vegetation. The diurnal and seasonal characteristics of SIF emitted from natural vegetation, e.g., forest and crop, have been studied at the ecosystem-scale, regional-scale and global-scale. However, the detailed response of SIF from different plant species under extremely weather event, especially short-term heat wave, have not been reported. The purpose of this study was to study the response of solar-induced chlorophyll fluorescence, gas exchange and continuous fluorescence at leaf scale for different temperate tree species. The short-term heatwave experiment was conducted using plant growth chamber (CMP6050, Conviron Inc., Canada). We developed an advanced spectral fitting method to obtain the plant SIF in the plant growth chamber. We compared SIF variation among different wavelength and chlorophyll difference among four temperate tree species. The diurnal variation of SIF signals at leaf-scales for temperate tree species are different under heat stress. The SIF response at leaf-scales and their difference for four temperate tree species are different during a cycle of short-term heatwave stress. We infer that SIF be used as a measure of heat tolerance for temperate tree species.

Assessment of Methods to Determine Tree Ring Response to Large Magnitude Mississippi River Floods

NASA Astrophysics Data System (ADS)

Therrell, M. D.; Meko, M. D.; Bialecki, M.; Remo, J. W.

2017-12-01

Riparian trees that experience prolonged inundation can record major flood events as inter-and intra-annual variability in size, shape and arrangement of vessels in the annual xylem growth increment. As part of an NSF-funded project to develop tree-ring records of past flooding, we have made collections of several oak species (e.g., Quercus lyrata, Q. macrocarpa) at six sites in the Mississippi River Basin. At each of these sites sampled trees exhibit notably anomalous anatomy of growth increments formed in years coinciding with major recorded floods. We have used these "flood rings" to develop individual site chronologies as well as a regional chronology of spring flood events in the basin for the past several hundred years. We have also analyzed earlywood vessel diameter as a proxy for flooding and find that although this variable reflects only a fraction of the annual-growth increment it strongly reflects tree response to flooding at all the sites so far examined. We compare both these chronologies with the instrumental and historical record of flooding and find that our chronologies are recording nearly all large observed Mississippi River floods in the 20th century, and provide a new record of similar events in the 18th and 19th centuries. These results suggest that tree-rings can be effectively used to develop and improve pre-instrumental flood records throughout the basin and potentially other similar systems.

Bayesian analysis of biogeography when the number of areas is large.

PubMed

Landis, Michael J; Matzke, Nicholas J; Moore, Brian R; Huelsenbeck, John P

2013-11-01

Historical biogeography is increasingly studied from an explicitly statistical perspective, using stochastic models to describe the evolution of species range as a continuous-time Markov process of dispersal between and extinction within a set of discrete geographic areas. The main constraint of these methods is the computational limit on the number of areas that can be specified. We propose a Bayesian approach for inferring biogeographic history that extends the application of biogeographic models to the analysis of more realistic problems that involve a large number of areas. Our solution is based on a "data-augmentation" approach, in which we first populate the tree with a history of biogeographic events that is consistent with the observed species ranges at the tips of the tree. We then calculate the likelihood of a given history by adopting a mechanistic interpretation of the instantaneous-rate matrix, which specifies both the exponential waiting times between biogeographic events and the relative probabilities of each biogeographic change. We develop this approach in a Bayesian framework, marginalizing over all possible biogeographic histories using Markov chain Monte Carlo (MCMC). Besides dramatically increasing the number of areas that can be accommodated in a biogeographic analysis, our method allows the parameters of a given biogeographic model to be estimated and different biogeographic models to be objectively compared. Our approach is implemented in the program, BayArea.

Divergence in strategies for coping with winter embolism among co-occurring temperate tree species: the role of positive xylem pressure, wood type and tree stature

Treesearch

Cun-Yang Niu; Frederick C. Meinzer; Guang-You Hao

2017-01-01

1. In temperate ecosystems, freeze-thaw events are an important environmental stress that can induce severe xylem embolism (i.e. clogging of conduits by air bubbles) in overwintering organs of trees. However, no comparative studies of different adaptive strategies among sympatric tree species for coping with winter embolism have examined the potential role of the...

Qualitative Importance Measures of Systems Components - A New Approach and Its Applications

NASA Astrophysics Data System (ADS)

Chybowski, Leszek; Gawdzińska, Katarzyna; Wiśnicki, Bogusz

2016-12-01

The paper presents an improved methodology of analysing the qualitative importance of components in the functional and reliability structures of the system. We present basic importance measures, i.e. the Birnbaum's structural measure, the order of the smallest minimal cut-set, the repetition count of an i-th event in the Fault Tree and the streams measure. A subsystem of circulation pumps and fuel heaters in the main engine fuel supply system of a container vessel illustrates the qualitative importance analysis. We constructed a functional model and a Fault Tree which we analysed using qualitative measures. Additionally, we compared the calculated measures and introduced corrected measures as a tool for improving the analysis. We proposed scaled measures and a common measure taking into account the location of the component in the reliability and functional structures. Finally, we proposed an area where the measures could be applied.

Persistence of long-distance, insect-mediated pollen movement for a tropical canopy tree species in remnant forest patches in an urban landscape.

PubMed

Noreen, A M E; Niissalo, M A; Lum, S K Y; Webb, E L

2016-12-01

As deforestation and urbanization continue at rapid rates in tropical regions, urban forest patches are essential repositories of biodiversity. However, almost nothing is known about gene flow of forest-dependent tree species in urban landscapes. In this study, we investigated gene flow in the insect-pollinated, wind-dispersed tropical tree Koompassia malaccensis in and among three remnant forest patches in the urbanized landscape of Singapore. We genotyped the vast majority of adults (N=179) and a large number of recruits (N=2103) with 8 highly polymorphic microsatellite markers. Spatial genetic structure of the recruit and adult cohorts was significant, showing routine gene dispersal distances of ~100-400 m. Parentage analysis showed that 97% of recruits were within 100 m of their mother tree, and a high frequency of relatively short-distance pollen dispersal (median ~143-187 m). Despite routine seed and pollen dispersal distances of within a few hundred meters, interpatch gene flow occurred between all patches and was dominated by pollen movement: parentage analysis showed 76 pollen versus 2 seed interpatch dispersal events, and the seedling neighborhood model estimated ~1-6% seed immigration and ~21-46% pollen immigration rates, depending on patch. In addition, the smallest patch (containing five adult K. malaccensis trees) was entirely surrounded by >2.5 km of 'impervious' substrate, yet had the highest proportional pollen and seed immigration estimates of any patch. Hence, contrary to our hypothesis, insect-mediated gene flow persisted across an urban landscape, and several of our results also parallel key findings from insect-pollinated canopy trees sampled in mixed agricultural-forest landscapes.

Strip-Bark Morphology and Radial Growth Trends in Ancient Pinus sibirica Trees From Central Mongolia

NASA Astrophysics Data System (ADS)

Leland, Caroline; Cook, Edward R.; Andreu-Hayles, Laia; Pederson, Neil; Hessl, Amy; Anchukaitis, Kevin J.; Byambasuren, Oyunsanaa; Nachin, Baatarbileg; Davi, Nicole; D'Arrigo, Rosanne; Griffin, Kevin; Bishop, Daniel A.; Rao, Mukund Palat

2018-03-01

Some of the oldest and most important trees used for dendroclimatic reconstructions develop strip-bark morphology, in which only a portion of the stem contains living tissue. Yet the ecophysiological factors initiating strip bark and the potential effect of cambial dieback on annual ring widths and tree-ring estimates of past climate remain poorly understood. Using a combination of field observations and tree-ring data, we investigate the causes and timing of cambial dieback events in Pinus sibirica strip-bark trees from central Mongolia and compare the radial growth rates and trends of strip-bark and whole-bark trees over the past 515 years. Results indicate that strip bark is more common on the southern aspect of trees, and dieback events were most prevalent in the 19th century, a cold and dry period. Further, strip-bark and whole-bark trees have differing centennial trends, with strip-bark trees exhibiting notably large increases in ring widths at the beginning of the 20th century. We find a steeper positive trend in the strip-bark chronology relative to the whole-bark chronology when standardizing with age-dependent splines. We hypothesize that localized warming on the southern side of stems due to solar irradiance results in physiological damage and dieback and leads to increasing tree-ring increment along the living portion of strip-bark trees. Because the impact of cambial dieback on ring widths likely varies depending on species and site, we suggest conducting a comparison of strip-bark and whole-bark ring widths before statistically treating ring-width data for climate reconstructions.

The use of minimal spanning trees in particle physics

DOE PAGES

Rainbolt, J. Lovelace; Schmitt, M.

2017-02-14

Minimal spanning trees (MSTs) have been used in cosmology and astronomy to distinguish distributions of points in a multi-dimensional space. They are essentially unknown in particle physics, however. We briefly define MSTs and illustrate their properties through a series of examples. We show how they might be applied to study a typical event sample from a collider experiment and conclude that MSTs may prove useful in distinguishing different classes of events.

The use of minimal spanning trees in particle physics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rainbolt, J. Lovelace; Schmitt, M.

Minimal spanning trees (MSTs) have been used in cosmology and astronomy to distinguish distributions of points in a multi-dimensional space. They are essentially unknown in particle physics, however. We briefly define MSTs and illustrate their properties through a series of examples. We show how they might be applied to study a typical event sample from a collider experiment and conclude that MSTs may prove useful in distinguishing different classes of events.

A Search for the tt¯H (H → bb) Large Hadron Collider with the atlas detector using a matrix element method

NASA Astrophysics Data System (ADS)

Basye, Austin T.

A matrix element method analysis of the Standard Model Higgs boson, produced in association with two top quarks decaying to the lepton-plus-jets channel is presented. Based on 20.3 fb--1 of s=8 TeV data, produced at the Large Hadron Collider and collected by the ATLAS detector, this analysis utilizes multiple advanced techniques to search for ttH signatures with a 125 GeV Higgs boson decaying to two b -quarks. After categorizing selected events based on their jet and b-tag multiplicities, signal rich regions are analyzed using the matrix element method. Resulting variables are then propagated to two parallel multivariate analyses utilizing Neural Networks and Boosted Decision Trees respectively. As no significant excess is found, an observed (expected) limit of 3.4 (2.2) times the Standard Model cross-section is determined at 95% confidence, using the CLs method, for the Neural Network analysis. For the Boosted Decision Tree analysis, an observed (expected) limit of 5.2 (2.7) times the Standard Model cross-section is determined at 95% confidence, using the CLs method. Corresponding unconstrained fits of the Higgs boson signal strength to the observed data result in the measured signal cross-section to Standard Model cross-section prediction of mu = 1.2 +/- 1.3(total) +/- 0.7(stat.) for the Neural Network analysis, and mu = 2.9 +/- 1.4(total) +/- 0.8(stat.) for the Boosted Decision Tree analysis.

From gene trees to a dated allopolyploid network: insights from the angiosperm genus Viola (Violaceae).

PubMed

Marcussen, Thomas; Heier, Lise; Brysting, Anne K; Oxelman, Bengt; Jakobsen, Kjetill S

2015-01-01

Allopolyploidization accounts for a significant fraction of speciation events in many eukaryotic lineages. However, existing phylogenetic and dating methods require tree-like topologies and are unable to handle the network-like phylogenetic relationships of lineages containing allopolyploids. No explicit framework has so far been established for evaluating competing network topologies, and few attempts have been made to date phylogenetic networks. We used a four-step approach to generate a dated polyploid species network for the cosmopolitan angiosperm genus Viola L. (Violaceae Batch.). The genus contains ca 600 species and both recent (neo-) and more ancient (meso-) polyploid lineages distributed over 16 sections. First, we obtained DNA sequences of three low-copy nuclear genes and one chloroplast region, from 42 species representing all 16 sections. Second, we obtained fossil-calibrated chronograms for each nuclear gene marker. Third, we determined the most parsimonious multilabeled genome tree and its corresponding network, resolved at the section (not the species) level. Reconstructing the "correct" network for a set of polyploids depends on recovering all homoeologs, i.e., all subgenomes, in these polyploids. Assuming the presence of Viola subgenome lineages that were not detected by the nuclear gene phylogenies ("ghost subgenome lineages") significantly reduced the number of inferred polyploidization events. We identified the most parsimonious network topology from a set of five competing scenarios differing in the interpretation of homoeolog extinctions and lineage sorting, based on (i) fewest possible ghost subgenome lineages, (ii) fewest possible polyploidization events, and (iii) least possible deviation from expected ploidy as inferred from available chromosome counts of the involved polyploid taxa. Finally, we estimated the homoploid and polyploid speciation times of the most parsimonious network. Homoploid speciation times were estimated by coalescent analysis of gene tree node ages. Polyploid speciation times were estimated by comparing branch lengths and speciation rates of lineages with and without ploidy shifts. Our analyses recognize Viola as an old genus (crown age 31 Ma) whose evolutionary history has been profoundly affected by allopolyploidy. Between 16 and 21 allopolyploidizations are necessary to explain the diversification of the 16 major lineages (sections) of Viola, suggesting that allopolyploidy has accounted for a high percentage-between 67% and 88%-of the speciation events at this level. The theoretical and methodological approaches presented here for (i) constructing networks and (ii) dating speciation events within a network, have general applicability for phylogenetic studies of groups where allopolyploidization has occurred. They make explicit use of a hitherto underexplored source of ploidy information from chromosome counts to help resolve phylogenetic cases where incomplete sequence data hampers network inference. Importantly, the coalescent-based method used herein circumvents the assumption of tree-like evolution required by most techniques for dating speciation events. © The Author(s) 2014. Published by Oxford University Press, on behalf of the Society of Systematic Biologists.

Probabilistic sensitivity analysis for decision trees with multiple branches: use of the Dirichlet distribution in a Bayesian framework.

PubMed

Briggs, Andrew H; Ades, A E; Price, Martin J

2003-01-01

In structuring decision models of medical interventions, it is commonly recommended that only 2 branches be used for each chance node to avoid logical inconsistencies that can arise during sensitivity analyses if the branching probabilities do not sum to 1. However, information may be naturally available in an unconditional form, and structuring a tree in conditional form may complicate rather than simplify the sensitivity analysis of the unconditional probabilities. Current guidance emphasizes using probabilistic sensitivity analysis, and a method is required to provide probabilistic probabilities over multiple branches that appropriately represents uncertainty while satisfying the requirement that mutually exclusive event probabilities should sum to 1. The authors argue that the Dirichlet distribution, the multivariate equivalent of the beta distribution, is appropriate for this purpose and illustrate its use for generating a fully probabilistic transition matrix for a Markov model. Furthermore, they demonstrate that by adopting a Bayesian approach, the problem of observing zero counts for transitions of interest can be overcome.

Temporal Association Between Nonfatal Self-Directed Violence and Tree and Grass Pollen Counts.

PubMed

Jeon-Slaughter, Haekyung; Claassen, Cynthia A; Khan, David A; Mihalakos, Perry; Lee, Kevin B; Brown, E Sherwood

2016-09-01

Prior research suggests a possible association between pollen and suicide. No studies have examined the relationship between pollen and attempted suicide. This study examines the temporal association between airborne pollen counts and nonfatal suicidal and nonsuicidal self-directed violence (SDV) requiring an emergency department visit. Data on daily emergency department visits due to nonfatal SDV as identified by ICD-9 diagnosis criteria were extracted from emergency department medical records of Parkland Memorial Hospital in Dallas, Texas, between January 2000 and December 2003. Concurrent daily airborne tree, grass, and ragweed pollen data from the city of Dallas were extracted from the National Allergy Bureau online database. The data were analyzed using the time series method of generalized autoregressive conditional heteroskedasticity. There were statistically significant and positive temporal associations between tree pollen counts and the number of nonfatal SDV events among women (P = .04) and between grass pollen counts and number of nonfatal SDV events among both men (P = .03) and women (P < .0001). There was no significant temporal association found between ragweed pollen counts and number of nonfatal SDV events. The study findings suggest that an increase in nonfatal SDV is associated with changes in tree and grass pollen counts. This is the first study that has examined an association between seasonal variation in tree and grass pollen levels and nonfatal SDV event data. The study also used a narrowly defined geographic area and temporal window. The findings suggest that pollen count may be a factor influencing seasonal patterns in suicidal behavior. © Copyright 2016 Physicians Postgraduate Press, Inc.

Bayesian Analysis of Biogeography when the Number of Areas is Large

PubMed Central

Landis, Michael J.; Matzke, Nicholas J.; Moore, Brian R.; Huelsenbeck, John P.

2013-01-01

Historical biogeography is increasingly studied from an explicitly statistical perspective, using stochastic models to describe the evolution of species range as a continuous-time Markov process of dispersal between and extinction within a set of discrete geographic areas. The main constraint of these methods is the computational limit on the number of areas that can be specified. We propose a Bayesian approach for inferring biogeographic history that extends the application of biogeographic models to the analysis of more realistic problems that involve a large number of areas. Our solution is based on a “data-augmentation” approach, in which we first populate the tree with a history of biogeographic events that is consistent with the observed species ranges at the tips of the tree. We then calculate the likelihood of a given history by adopting a mechanistic interpretation of the instantaneous-rate matrix, which specifies both the exponential waiting times between biogeographic events and the relative probabilities of each biogeographic change. We develop this approach in a Bayesian framework, marginalizing over all possible biogeographic histories using Markov chain Monte Carlo (MCMC). Besides dramatically increasing the number of areas that can be accommodated in a biogeographic analysis, our method allows the parameters of a given biogeographic model to be estimated and different biogeographic models to be objectively compared. Our approach is implemented in the program, BayArea. [ancestral area analysis; Bayesian biogeographic inference; data augmentation; historical biogeography; Markov chain Monte Carlo.] PMID:23736102

Historical vegetation change in Oakland and its implications for urban forest management

Treesearch

David J. Nowak

1993-01-01

The history of Oakland, California's urban forest was researched to determine events that could influence future urban forests. Vegetation in Oakland has changed drastically from a preurbanized area with approximately 2% tree cover to a present tree cover of 19%. Species composition of trees was previously dominated by coast live oak (Quercus agrifolia...

Patterns of conifer tree regeneration following an autumn wildfire event in the western Oregon Cascade Range, USA.

Treesearch

Andrew J. Larson; Jerry F. Franklin

2005-01-01

We investigated the effect of fire severity and environmental conditions on conifer tree regeneration 11 years after an autumn wildfire in the western Oregon Cascade Range. Conifer tree seedlings, including those of Pseudotsuga menziesii, established promptly and at high densities following fire, in contrast to long establishment periods documented...

A framework for adapting urban forests to climate change

Treesearch

Leslie Brandt; Abigail Derby Lewis; Robert Fahey; Lydia Scott; Lindsay Darling; Chris Swanston

2016-01-01

Planting urban trees and expanding urban forest canopy cover are often considered key strategies for reducing climate change impacts in urban areas. However, urban trees and forests can also be vulnerable to climate change through shifts in tree habitat suitability, changes in pests and diseases, and changes in extreme weather events. We developed a three-step...

Survival and ecophysiology of tree seedlings during El Nino drought in a tropical moist forest in Panama

Treesearch

Betinna M.J. Engelbrecht; S. Joseph Wright; Diane De Steven

2002-01-01

In tropical forests, severe droughts caused by El Nino events may strongly influence the water relations of tree seedlings and thereby increase their mortality. Data on known-aged seedlings of three common shade-tolerant canopy tree species (Trichilia tuberculata, Tetragastris panamensis and Quararibea asterolepis) in a Panamanian...

How does tree age influence damage and recovery in forests impacted by freezing rain and snow?

PubMed

Zhu, LiRong; Zhou, Ting; Chen, BaoMing; Peng, ShaoLin

2015-05-01

The response and recovery mechanisms of forests to damage from freezing rain and snow events are a key topic in forest research and management. However, the relationship between the degree of damage and tree age, i.e., whether seedlings, young trees, or adult trees are most vulnerable, remains unclear and is rarely reported. We investigated the effect of tree age on the degrees of vegetation damage and subsequent recovery in three subtropical forest types-coniferous, mixed, and broad-leaved-in the Tianjing Mountains, South China, after a series of rare icy rain and freezing snow events in 2008. The results showed that damage and recovery rates were both dependent on tree age, with the proportion of damaged vegetation increasing with age (estimated by diameter at breast height, DBH) in all three forest types and gradually plateauing. Significant variation occurred among forest types. Young trees in the coniferous forest were more vulnerable than those in the broad-leaved forest. The type of damage also varied with tree age in different ways in the three forest types. The proportion of young seedlings that were uprooted (the most severe type of damage) was highest in the coniferous forest. In the mixed forest, young trees were significantly more likely to be uprooted than seedlings and adult trees, while in the broad-leaved forest, the proportion of uprooted adult trees was significantly higher than that of seedlings and young trees. There were also differences among forest types in how tree age affected damage recovery. In the coniferous forest, the recovery rate of trees with broken trunks or crowns (DBH > 2.5 cm) increased with tree age. However, in the mixed and broad-leaved forests, no obvious correlation between the recovery rate of trees with broken trunks or crowns and tree age was observed. Trees with severe root damage did not recover; they were uprooted and died. In these forests, vegetation damage and recovery showed tree age dependencies, which varied with tree shape, forest type, and damage type. Understanding this dependency will guide restoration after freezing rain and snow disturbances.

Tree mortality across biomes is promoted by drought intensity, lower wood density and higher specific leaf area.

PubMed

Greenwood, Sarah; Ruiz-Benito, Paloma; Martínez-Vilalta, Jordi; Lloret, Francisco; Kitzberger, Thomas; Allen, Craig D; Fensham, Rod; Laughlin, Daniel C; Kattge, Jens; Bönisch, Gerhard; Kraft, Nathan J B; Jump, Alistair S

2017-04-01

Drought events are increasing globally, and reports of consequent forest mortality are widespread. However, due to a lack of a quantitative global synthesis, it is still not clear whether drought-induced mortality rates differ among global biomes and whether functional traits influence the risk of drought-induced mortality. To address these uncertainties, we performed a global meta-analysis of 58 studies of drought-induced forest mortality. Mortality rates were modelled as a function of drought, temperature, biomes, phylogenetic and functional groups and functional traits. We identified a consistent global-scale response, where mortality increased with drought severity [log mortality (trees trees -1  year -1 ) increased 0.46 (95% CI = 0.2-0.7) with one SPEI unit drought intensity]. We found no significant differences in the magnitude of the response depending on forest biomes or between angiosperms and gymnosperms or evergreen and deciduous tree species. Functional traits explained some of the variation in drought responses between species (i.e. increased from 30 to 37% when wood density and specific leaf area were included). Tree species with denser wood and lower specific leaf area showed lower mortality responses. Our results illustrate the value of functional traits for understanding patterns of drought-induced tree mortality and suggest that mortality could become increasingly widespread in the future. © 2017 John Wiley & Sons Ltd/CNRS.

Evaluation of growth disturbances of Picea abies (L.) Karst. to disturbances caused by landslide movements

NASA Astrophysics Data System (ADS)

Šilhán, Karel

2017-01-01

Dendrogeomorphic methods are frequently used in landslide analyses. Although methods of landslide dating based on tree rings are well developed, they still indicated many questions. The aim of this study was to evaluate the frequently used theoretical scheme based on the event-response relationship. Seventy-four individuals of Norway spruce (Picea abies (L.) Karst.) exhibiting visible external disturbance, were sampled on the Girová landslide (the largest historical flow-like landslide in the Czech Republic). This landslide reactivated in May 2010, and post-landslide tree growth responses were studied in detail. These growth responses were compared with the intensity and occurrence of visible external tree disturbance: tilted stems, damaged root systems, and decapitation. Twenty-nine trees (39.2%) died within one to four years following the 2010 landslide movement. The trees that died following the landslide movement were significantly younger and displayed significantly greater stem tilting than the live trees. Abrupt growth suppression was a more-frequent response among the dead trees, whereas growth release dominated among the live trees. Only two trees (2.7%) created no reaction wood in response to the landslide movement. Forty-four percent of the trees started to produce reaction wood structure after a delay, which generally spanned one year. Some eccentric growth was evident in the tree rings of the landslide year and was significant in the first years following the landslide movement. Missing rings were observed only on the upper sides of the stems, and no false tree rings were observed. The results confirm the general validity of event-response relationship, nevertheless this study points out the limitations and uncertainties of this generally accepted working scheme.

400 Years of summer hydroclimate from stable isotopes in Iberian trees

NASA Astrophysics Data System (ADS)

Andreu-Hayles, Laia; Ummenhofer, Caroline C.; Barriendos, Mariano; Schleser, Gerhard H.; Helle, Gerhard; Leuenberger, Markus; Gutiérrez, Emilia; Cook, Edward R.

2017-07-01

Tree rings are natural archives that annually record distinct types of past climate variability depending on the parameters measured. Here, we use ring-width and stable isotopes in cellulose of trees from the northwestern Iberian Peninsula (IP) to understand regional summer hydroclimate over the last 400 years and the associated atmospheric patterns. Correlations between tree rings and climate data demonstrate that isotope signatures in the targeted Iberian pine forests are very sensitive to water availability during the summer period, and are mainly controlled by stomatal conductance. Non-linear methods based on extreme events analysis allow for capturing distinct seasonal climatic variability recorded by tree-ring parameters and asymmetric signals of the associated atmospheric features. Moreover, years with extreme high (low) values in the tree-ring records were characterised by coherent large-scale atmospheric circulation patterns with reduced (enhanced) moisture transport onto the northwestern IP. These analyses of extremes revealed that high/low proxy values do not necessarily correspond to mirror images in the atmospheric anomaly patterns, suggesting different drivers of these patterns and the corresponding signature recorded in the proxies. Regional hydroclimate features across the broader IP and western Europe during extreme wet/dry summers detected by the northwestern IP trees compare favourably to independent multicentury sea level pressure and drought reconstructions for Europe. Historical records also validate our findings that attribute non-linear moisture signals recorded by extreme tree-ring values to distinct large-scale atmospheric patterns and allow for 400-year reconstructions of the frequency of occurrence of extreme conditions in late spring and summer hydroclimate.

400 years of summer hydroclimate from stable isotopes in Iberian trees

NASA Astrophysics Data System (ADS)

Andreu-Hayles, Laia; Ummenhofer, Caroline C.; Barriendos, Mariano; Schleser, Gerhard H.; Helle, Gerhard; Leuenberger, Markus; Gutierrez, Emilia; Cook, Edward R.

2017-04-01

Tree rings are natural archives that annually record distinct types of past climate variability depending on the parameters measured. Here, we use ring-width and stable isotopes in cellulose of trees from the northwestern Iberian Peninsula (IP) to understand regional summer hydroclimate over the last 400 years and the associated atmospheric patterns. Correlations between tree rings and climate data demonstrate that isotope signatures in the targeted Iberian pine forests are very sensitive to water availability during the summer period, and are mainly controlled by stomatal conductance. Non-linear methods based on extreme events analysis allow for capturing distinct seasonal climatic variability recorded by tree-ring parameters and asymmetric signals of the associated atmospheric features. Moreover, years with extreme high (low) values in the tree-ring records were characterised by coherent large-scale atmospheric circulation patterns with reduced (enhanced) moisture transport onto the northwestern IP. These analyses of extremes revealed that high/low proxy values do not necessarily correspond to mirror images in the atmospheric anomaly patterns, suggesting different drivers of these patterns and the corresponding signature recorded in the proxies. Regional hydroclimate features across the broader IP and western Europe during extreme wet/dry summers detected by the northwestern IP trees compare favourably to an independent multicentury sea level pressure and drought reconstruction for Europe. Historical records also validate our findings that attribute non-linear moisture signals recorded by extreme tree-ring values to distinct large-scale atmospheric patterns and allow for 400-yr reconstructions of the frequency of occurrence of extreme conditions in summer hydroclimate. We will discuss how the results for Lillo compare with other records.

Patterns of mortality in a montane mixed-conifer forest in San Diego County, California.

PubMed

Freeman, Mary Pyott; Stow, Douglas A; An, Li

2017-10-01

We examine spatial patterns of conifer tree mortality and their changes over time for the montane mixed-conifer forests of San Diego County. These forest areas have recently experienced extensive tree mortality due to multiple factors. A spatial contextual image processing approach was utilized with high spatial resolution digital airborne imagery to map dead trees for the years 1997, 2000, 2002, and 2005 for three study areas: Palomar, Volcan, and Laguna mountains. Plot-based fieldwork was conducted to further assess mortality patterns. Mean mortality remained static from 1997 to 2002 (4, 2.2, and 4.2 trees/ha for Palomar, Volcan, and Laguna) and then increased by 2005 to 10.3, 9.7, and 5.2 trees/ha, respectively. The increase in mortality between 2002 and 2005 represents the temporal pattern of a discrete disturbance event, attributable to the 2002-2003 drought. Dead trees are significantly clustered for all dates, based on spatial cluster analysis, indicating that they form distinct groups, as opposed to spatially random single dead trees. Other tests indicate no directional shift or spread of mortality over time, but rather an increase in density. While general temporal and spatial mortality processes are uniform across all study areas, the plot-based species and quantity distribution of mortality, and diameter distributions of dead vs. living trees, vary by study area. The results of this study improve our understanding of stand- to landscape-level forest structure and dynamics, particularly by examining them from the multiple perspectives of field and remotely sensed data. © 2017 by the Ecological Society of America.

Multiple dendrochronological responses to the eruption of Cinder Cone, Lassen Volcanic National Park, California

USGS Publications Warehouse

Sheppard, P.R.; Ort, M.H.; Anderson, K.C.; Clynne, M.A.; May, E.M.

2009-01-01

Two dendrochronological properties – ring width and ring chemistry – were investigated in trees near Cinder Cone in Lassen Volcanic National Park, northeastern California, for the purpose of re-evaluating the date of its eruption. Cinder Cone is thought to have erupted in AD 1666 based on ring-width evidence, but interpreting ring-width changes alone is not straightforward because many forest disturbances can cause changes in ring width. Old Jeffrey pines growing in Cinder Cone tephra and elsewhere for control comparison were sampled. Trees growing in tephra show synchronous ring-width changes at AD 1666, but this ring-width signal could be considered ambiguous for dating the eruption because changes in ring width can be caused by other events. Trees growing in tephra also show changes in ring phosphorus, sulfur, and sodium during the late 1660s, but inter-tree variability in dendrochemical signals makes dating the eruption from ring chemistry alone difficult. The combination of dendrochemistry and ring-width signals improves confidence in dating the eruption of Cinder Cone over the analysis of just one ring-growth property. These results are similar to another case study using dendrochronology of ring width and ring chemistry at Parícutin, Michoacán, Mexico, a cinder cone that erupted beginning in 1943. In both cases, combining analysis with ring width and ring chemistry improved confidence in the dendro-dating of the eruptions.

Drought-induced changes in Amazon forest structure from repeat airborne lidar

NASA Astrophysics Data System (ADS)

Morton, D. C.; Leitold, V.; Longo, M.; Keller, M.; dos-Santos, M. N.; Scaranello, M. A., Sr.

2017-12-01

Drought events in tropical forests, including the 2015-2016 El Niño, may reduce net primary productivity and increase canopy tree mortality, thereby altering the short and long-term net carbon balance of tropical forests. Given the broad extent of drought impacts, forest inventory plots or eddy flux towers may not capture regional variability in forest response to drought. Here, we analyzed repeat airborne lidar data to evaluate canopy turnover from branch and tree fall before (2013-2014) and during (2014-2016) the recent El Niño drought in the eastern and central Brazilian Amazon. Coincident field surveys for a 16-ha subset of the lidar coverage provided complementary information to classify turnover areas by mechanism (branch, multiple branch, tree fall, multiple tree fall) and estimate the total coarse woody debris volume from canopy and understory tree mortality. Annualized rates of canopy turnover increased by 50%, on average, during the drought period in both intact and fragmented forests near Santarém, Pará. Turnover increased uniformly across all size classes, and there was limited evidence that taller trees contributed a greater proportion of turnover events in any size class in 2014-2016 compared to 2013-2014. This short-term increase in canopy turnover differs from findings in multi-year rainfall exclusion experiments that large trees were more sensitive to drought impacts. Field measurements confirmed the separability of the smallest (single branch) and largest damage classes (multiple tree falls), but single tree and multiple branch fall events generated similar coarse woody debris production and lidar-derived changes in canopy volume. Large-scale sampling possible with repeat airborne lidar data also captured strong local and regional gradients in canopy turnover. Differences in slope partially explained the north-south gradient in canopy turnover dynamics near Santarém, with larger increases in turnover on flatter terrain. Regional variability in canopy turnover in response to drought conditions highlights the need for a mechanistic representation of branch and tree fall dynamics in ecosystem models to resolve changes in net carbon balance from the increase in coarse woody debris production and reorganization of canopy light environments during drought years.

Dendrometric measurements reveal stages leading to tree mortality in a semiarid pine forest

NASA Astrophysics Data System (ADS)

Tatarinov, Fyodor; Preisler, Yakir; Klein, Tamir; Rotenberg, Eyal; Yakir, Dan

2017-04-01

Increasing frequency and intensity of climatic extreme events, such as droughts may lead to increasing vulnerability of forests, especially in semi-arid regions. In the spring of 2016 mortality was observed among trees used for sap flow (SF) and dendrometry measurements in the semi-arid Fluxnet pine forest site of Yatir in Israel (280mm annual mean precipitation). This was accompanied by bark-beetle attack, and with visual drying of needles starting in April 2016. Comparative analysis of dendrometry and sap flux (SF) measurements in 31 trees of which 7 died and 24 survived permitted identification of the stages leading to tree mortality. Distinction between dying and surviving trees was identified in the dendrometric measurements from Nov. 2015, about five months before visual mortality signs: First, clear decline in diameter (DBH) was observed in all dying trees, whereas DBH of living trees remained constant until the first rain in January 2016 followed by growth. Second, the diurnal patterns in DBH showed a gradual shift of the diurnal DBH maximum from noon-time to early morning from the summer of 2015 to the spring of 2016 in surviving trees, whereas in dying trees it remained stable around noontime. Third, the diurnal swelling/shrinkage dynamics, assumed to reflect water use and storage dynamics, showed clear decline in magnitude, down to near zero, in the dying trees while regular daily cycle continued in the surviving trees. In September 2015 Shoot measurements showed midnight minimum of leaf water potential, lower than in living trees (-4.5 vs. -3.6 MPa respectively). Sap flow measurements were not sufficiently sensitive during the non-active season (fall and early winter) and indicated changes only after the first rain in January 2016. At this time, SF showed dramatic increase in SF with typical midday maximum in the surviving trees, whereas in dying trees SF remained low and irregular. The results show that indicators of mortality can be detected at least 5 months before visual signs are observed, and demonstrate the interacting effects of carbon economy (growth) and tree water management (radial water movement and storage) on the development of mortality in Aleppo pine trees.

Modeling flash floods in ungauged mountain catchments of China: A decision tree learning approach for parameter regionalization

NASA Astrophysics Data System (ADS)

Ragettli, S.; Zhou, J.; Wang, H.; Liu, C.

2017-12-01

Flash floods in small mountain catchments are one of the most frequent causes of loss of life and property from natural hazards in China. Hydrological models can be a useful tool for the anticipation of these events and the issuing of timely warnings. Since sub-daily streamflow information is unavailable for most small basins in China, one of the main challenges is finding appropriate parameter values for simulating flash floods in ungauged catchments. In this study, we use decision tree learning to explore parameter set transferability between different catchments. For this purpose, the physically-based, semi-distributed rainfall-runoff model PRMS-OMS is set up for 35 catchments in ten Chinese provinces. Hourly data from more than 800 storm runoff events are used to calibrate the model and evaluate the performance of parameter set transfers between catchments. For each catchment, 58 catchment attributes are extracted from several data sets available for whole China. We then use a data mining technique (decision tree learning) to identify catchment similarities that can be related to good transfer performance. Finally, we use the splitting rules of decision trees for finding suitable donor catchments for ungauged target catchments. We show that decision tree learning allows to optimally utilize the information content of available catchment descriptors and outperforms regionalization based on a conventional measure of physiographic-climatic similarity by 15%-20%. Similar performance can be achieved with a regionalization method based on spatial proximity, but decision trees offer flexible rules for selecting suitable donor catchments, not relying on the vicinity of gauged catchments. This flexibility makes the method particularly suitable for implementation in sparsely gauged environments. We evaluate the probability to detect flood events exceeding a given return period, considering measured discharge and PRMS-OMS simulated flows with regionalized parameters. Overall, the probability of detection of an event with a return period of 10 years is 62%. 44% of all 10-year flood peaks can be detected with a timing error of 2 hours or less. These results indicate that the modeling system can provide useful information about the timing and magnitude of flood events at ungauged sites.

Quantitative assessment of building fire risk to life safety.

PubMed

Guanquan, Chu; Jinhua, Sun

2008-06-01

This article presents a quantitative risk assessment framework for evaluating fire risk to life safety. Fire risk is divided into two parts: probability and corresponding consequence of every fire scenario. The time-dependent event tree technique is used to analyze probable fire scenarios based on the effect of fire protection systems on fire spread and smoke movement. To obtain the variation of occurrence probability with time, Markov chain is combined with a time-dependent event tree for stochastic analysis on the occurrence probability of fire scenarios. To obtain consequences of every fire scenario, some uncertainties are considered in the risk analysis process. When calculating the onset time to untenable conditions, a range of fires are designed based on different fire growth rates, after which uncertainty of onset time to untenable conditions can be characterized by probability distribution. When calculating occupant evacuation time, occupant premovement time is considered as a probability distribution. Consequences of a fire scenario can be evaluated according to probability distribution of evacuation time and onset time of untenable conditions. Then, fire risk to life safety can be evaluated based on occurrence probability and consequences of every fire scenario. To express the risk assessment method in detail, a commercial building is presented as a case study. A discussion compares the assessment result of the case study with fire statistics.

Impact of Deforestation and Recovery on Streamflow Recession Statistics

NASA Astrophysics Data System (ADS)

Krapu, C.; Kumar, M.

2016-12-01

Deforestation is known to influence streamflow and baseflow in particular in sub-humid environments. Baseflow contributions to the recession limb of a flood hydrograph convey information about subsurface stores from which trees also draw water. Recent works based on the assumptions outlined by Brutsaert and Nieber (1977) have proposed analyzing streamflow recession curves on a per-event basis. In this framework, each event's recession curve is governed by a power law relation with per-event scale and shape coefficients. As streamflow recession depends in part upon evapotranspiration demand from trees, these coefficients are hypothesized to contain useful information about catchment vegetation. Analysis was conducted of 13 small experimental catchments in the eastern United States with known forest treatment histories to determine whether or not streamflow recession behavior as observed from daily discharge records could serve as an indicator of deforestation in the drainage basin. Power-law scale coefficients were calculated for each major stormflow event at each test site and a statistical comparison of distribution of fitted coefficients was made between pre-treatment and post-treatment events as well as between pre-treatment and post-recovery events. A second method using these fitted coefficients in conjunction with Gaussian process regression was employed to track the change in the scale coefficient in the 13 catchments described previously as well as two medium-sized catchments in the North Carolina portion of the American Piedmont which did not have extensive records of forest cover. A linear trend analysis of precipitation was performed to determine whether nonstationarity in rainfall could be a confounding cause of changes in event scale coefficients. These results show a statistically significant difference in scale coefficient values in 5/8 treatment catchments and 0/5 control catchments. This suggests that lesser alterations to forest cover may not be detectable but that this method is robust against changes in precipitation. Additionally, we found clear evidence that forest regrowth in the Piedmont sites continued from 1940-1970. As a proof-of-concept, this work suggests that major alterations to forest cover can be inferred from daily data of stream discharge.

Drought frequency in central California since 101 B.C. recordered in giant sequoia tree rings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hughes, M.K.; Brown, P.M.

1992-01-01

Well replicated tree-ring width index chronologies have been developed for giant sequoia at three sites in the Sierra Nevada, California. Extreme low-growth events in these chronologies correspond with regional drought events in the twentieth century in the San Joaquin drainage, in which the giant sequoia sites are located. This relationship is based upon comparison of tree-ring indices with August Palmer Drought Severity Indices for California Climate Division 5. Ring-width indices in the lowest decile from each site were compared. The frequency of low-growth events which occurred at all three sites in the same year is reconstructed from 101 B.C. tomore » A.D. 1988. The inferred frequency of severe drought events changes through time, sometimes suddenly. The period from roughly 1850 to 1950 had one of the lowest frequencies of drought of any one hundred year period in the 2089 year record. The twentieth century so far has had a below-average frequency of extreme droughts. 26 refs., 6 figs., 1 tab.« less

Vulnerability of Amazon forests to storm-driven tree mortality

NASA Astrophysics Data System (ADS)

Negrón-Juárez, Robinson I.; Holm, Jennifer A.; Magnabosco Marra, Daniel; Rifai, Sami W.; Riley, William J.; Chambers, Jeffrey Q.; Koven, Charles D.; Knox, Ryan G.; McGroddy, Megan E.; Di Vittorio, Alan V.; Urquiza-Muñoz, Jose; Tello-Espinoza, Rodil; Alegria Muñoz, Waldemar; Ribeiro, Gabriel H. P. M.; Higuchi, Niro

2018-05-01

Tree mortality is a key driver of forest community composition and carbon dynamics. Strong winds associated with severe convective storms are dominant natural drivers of tree mortality in the Amazon. Why forests vary with respect to their vulnerability to wind events and how the predicted increase in storm events might affect forest ecosystems within the Amazon are not well understood. We found that windthrows are common in the Amazon region extending from northwest (Peru, Colombia, Venezuela, and west Brazil) to central Brazil, with the highest occurrence of windthrows in the northwest Amazon. More frequent winds, produced by more frequent severe convective systems, in combination with well-known processes that limit the anchoring of trees in the soil, help to explain the higher vulnerability of the northwest Amazon forests to winds. Projected increases in the frequency and intensity of convective storms in the Amazon have the potential to increase wind-related tree mortality. A forest demographic model calibrated for the northwestern and the central Amazon showed that northwestern forests are more resilient to increased wind-related tree mortality than forests in the central Amazon. Our study emphasizes the importance of including wind-related tree mortality in model simulations for reliable predictions of the future of tropical forests and their effects on the Earth’ system.

How Much Water Trees Access and How It Determines Forest Response to Drought

NASA Astrophysics Data System (ADS)

Berdanier, A. B.; Clark, J. S.

2015-12-01

Forests are transformed by drought as water availability drops below levels where trees of different sizes and species can maintain productivity and survive. Physiological studies have provided detailed understanding of how species differences affect drought vulnerability but they offer almost no insights about the amount of water different trees can access beyond general statements about rooting depth. While canopy architecture provides strong evidence for light availability aboveground, belowground moisture availability remains essentially unknown. For example, do larger trees always have greater access to soil moisture? In temperate mixed forests, the ability to access a large soil moisture pool could minimize damage during drought events and facilitate post-drought recovery, potentially at the expense of neighboring trees. We show that the pool of accessible soil moisture can be estimated for trees with data on whole-plant transpiration and that this data can be used to predict water availability for forest stands. We estimate soil water availability with a Bayesian state-space model based on a simple water balance, where cumulative depressions in water use below potential transpiration indicate soil resource depletion. We compare trees of different sizes and species, extend these findings to the entire stand, and connect them to our recent research showing that tree survival after drought depends on post-drought growth recovery and local moisture availability. These results can be used to predict competitive abilities for soil water, understand ecohydrological variation within stands, and identify trees that are at risk of damage from future drought events.

Temporal Dynamics in the Concentration, Flux, and Optical Properties of Tree-derived Dissolved Organic Matter (Tree-DOM) in an Epiphyte-laden Oak-cedar Forest.

NASA Astrophysics Data System (ADS)

Whitetree, A.; Van Stan, J. T., II; Wagner, S.; Guillemette, F.; Lewis, J.; Silva, L.; Stubbins, A.

2017-12-01

Studies on the fate and transport of dissolved organic matter (DOM) along the rainfall-to-discharge flow pathway typically begin in streams or soils, neglecting the initial enrichment of rainfall with DOM during contact with plant canopies. However, rain water can gather significant amounts of tree-derived DOM (tree-DOM) when it drains from the canopy, as throughfall, and down the stem, as stemflow. We examined the temporal variability of event-scale tree-DOM concentrations, yield, and optical (light absorbance and fluorescence) characteristics from an epiphyte-laden Quercus virginiana-Juniperus virginiana forest on Skidaway Island, Savannah, Georgia (USA). All tree-DOM fluxes were highly enriched compared to rainfall and epiphytes further increased concentrations. Stemflow DOC concentrations were greater than throughfall across study species, yet larger throughfall water yields produced greater DOC yields versus stemflow. Tree-DOM optical characteristics indicate it is aromatic-rich with FDOM dominated by humic-like fluorescence, containing 10-20% protein-like (tryptophan-like) fluorescence. Storm size was the only storm condition that strongly correlated with tree-DOM concentration and flux; however, throughfall and stemflow optical characteristics varied little across a wide range of storm conditions (from low magnitude events to intense tropical storms). Annual tree-DOM yields from the study forest (0.8-46 g-C m-2 yr-1) compared well to other yields along the rainfall-to- discharge flow pathway, exceeding DOM yields from some river watersheds.

Preliminary evaluation of the potential of tree-ring cellulose content as a novel supplementary proxy in dendroclimatology

NASA Astrophysics Data System (ADS)

Ziehmer, Malin M.; Nicolussi, Kurt; Schlüchter, Christian; Leuenberger, Markus

2018-02-01

Cellulose content (CC (%)) in tree rings is usually utilised as a tool to control the quality of the α-cellulose extraction from tree rings in the preparation of stable-isotope analysis in wooden tissues. Reported amounts of CC (%) are often limited to mean values per tree. For the first time, CC (%) series from two high-Alpine species, Larix decidua Mill. (European Larch, LADE) and Pinus cembra L. (Swiss stone pine, PICE) are investigated in modern wood samples and Holocene wood remains from the Early and mid-Holocene. Modern CC (%) series reveal a species-specific low-frequency trend independent of their sampling site over the past 150 years. Climate-cellulose relationships illustrate the ability of CC (%) to record temperature in both species but for slightly different periods within the growing season. The Holocene CC (%) series illustrate diverging low-frequency trends in both species, independent of sampling site characteristics (latitude, longitude and elevation). Moreover, potential age trends are not apparent in the two coniferous species. The arithmetic mean of CC (%) series in the Early and mid-Holocene indicate low CC (%) succeeding cold events. In conclusion, CC (%) in tree rings show high potential to be established as novel supplementary proxy in dendroclimatology.

Evaluating phylogenetic congruence in the post-genomic era.

PubMed

Leigh, Jessica W; Lapointe, François-Joseph; Lopez, Philippe; Bapteste, Eric

2011-01-01

Congruence is a broadly applied notion in evolutionary biology used to justify multigene phylogeny or phylogenomics, as well as in studies of coevolution, lateral gene transfer, and as evidence for common descent. Existing methods for identifying incongruence or heterogeneity using character data were designed for data sets that are both small and expected to be rarely incongruent. At the same time, methods that assess incongruence using comparison of trees test a null hypothesis of uncorrelated tree structures, which may be inappropriate for phylogenomic studies. As such, they are ill-suited for the growing number of available genome sequences, most of which are from prokaryotes and viruses, either for phylogenomic analysis or for studies of the evolutionary forces and events that have shaped these genomes. Specifically, many existing methods scale poorly with large numbers of genes, cannot accommodate high levels of incongruence, and do not adequately model patterns of missing taxa for different markers. We propose the development of novel incongruence assessment methods suitable for the analysis of the molecular evolution of the vast majority of life and support the investigation of homogeneity of evolutionary process in cases where markers do not share identical tree structures.

Evaluating Phylogenetic Congruence in the Post-Genomic Era

PubMed Central

Leigh, Jessica W.; Lapointe, François-Joseph; Lopez, Philippe; Bapteste, Eric

2011-01-01

Congruence is a broadly applied notion in evolutionary biology used to justify multigene phylogeny or phylogenomics, as well as in studies of coevolution, lateral gene transfer, and as evidence for common descent. Existing methods for identifying incongruence or heterogeneity using character data were designed for data sets that are both small and expected to be rarely incongruent. At the same time, methods that assess incongruence using comparison of trees test a null hypothesis of uncorrelated tree structures, which may be inappropriate for phylogenomic studies. As such, they are ill-suited for the growing number of available genome sequences, most of which are from prokaryotes and viruses, either for phylogenomic analysis or for studies of the evolutionary forces and events that have shaped these genomes. Specifically, many existing methods scale poorly with large numbers of genes, cannot accommodate high levels of incongruence, and do not adequately model patterns of missing taxa for different markers. We propose the development of novel incongruence assessment methods suitable for the analysis of the molecular evolution of the vast majority of life and support the investigation of homogeneity of evolutionary process in cases where markers do not share identical tree structures. PMID:21712432

PHYLOGEOrec: A QGIS plugin for spatial phylogeographic reconstruction from phylogenetic tree and geographical information data

NASA Astrophysics Data System (ADS)

Nashrulloh, Maulana Malik; Kurniawan, Nia; Rahardi, Brian

2017-11-01

The increasing availability of genetic sequence data associated with explicit geographic and environment (including biotic and abiotic components) information offers new opportunities to study the processes that shape biodiversity and its patterns. Developing phylogeography reconstruction, by integrating phylogenetic and biogeographic knowledge, provides richer and deeper visualization and information on diversification events than ever before. Geographical information systems such as QGIS provide an environment for spatial modeling, analysis, and dissemination by which phylogenetic models can be explicitly linked with their associated spatial data, and subsequently, they will be integrated with other related georeferenced datasets describing the biotic and abiotic environment. We are introducing PHYLOGEOrec, a QGIS plugin for building spatial phylogeographic reconstructions constructed from phylogenetic tree and geographical information data based on QGIS2threejs. By using PHYLOGEOrec, researchers can integrate existing phylogeny and geographical information data, resulting in three-dimensional geographic visualizations of phylogenetic trees in the Keyhole Markup Language (KML) format. Such formats can be overlaid on a map using QGIS and finally, spatially viewed in QGIS by means of a QGIS2threejs engine for further analysis. KML can also be viewed in reputable geobrowsers with KML-support (i.e., Google Earth).

Phylogenetic framework for coevolutionary studies: a compass for exploring jungles of tangled trees.

PubMed

Martínez-Aquino, Andrés

2016-08-01

Phylogenetics is used to detect past evolutionary events, from how species originated to how their ecological interactions with other species arose, which can mirror cophylogenetic patterns. Cophylogenetic reconstructions uncover past ecological relationships between taxa through inferred coevolutionary events on trees, for example, codivergence, duplication, host-switching, and loss. These events can be detected by cophylogenetic analyses based on nodes and the length and branching pattern of the phylogenetic trees of symbiotic associations, for example, host-parasite. In the past 2 decades, algorithms have been developed for cophylogetenic analyses and implemented in different software, for example, statistical congruence index and event-based methods. Based on the combination of these approaches, it is possible to integrate temporal information into cophylogenetical inference, such as estimates of lineage divergence times between 2 taxa, for example, hosts and parasites. Additionally, the advances in phylogenetic biogeography applying methods based on parametric process models and combined Bayesian approaches, can be useful for interpreting coevolutionary histories in a scenario of biogeographical area connectivity through time. This article briefly reviews the basics of parasitology and provides an overview of software packages in cophylogenetic methods. Thus, the objective here is to present a phylogenetic framework for coevolutionary studies, with special emphasis on groups of parasitic organisms. Researchers wishing to undertake phylogeny-based coevolutionary studies can use this review as a "compass" when "walking" through jungles of tangled phylogenetic trees.

Phylogenetic framework for coevolutionary studies: a compass for exploring jungles of tangled trees

PubMed Central

2016-01-01

Abstract Phylogenetics is used to detect past evolutionary events, from how species originated to how their ecological interactions with other species arose, which can mirror cophylogenetic patterns. Cophylogenetic reconstructions uncover past ecological relationships between taxa through inferred coevolutionary events on trees, for example, codivergence, duplication, host-switching, and loss. These events can be detected by cophylogenetic analyses based on nodes and the length and branching pattern of the phylogenetic trees of symbiotic associations, for example, host–parasite. In the past 2 decades, algorithms have been developed for cophylogetenic analyses and implemented in different software, for example, statistical congruence index and event-based methods. Based on the combination of these approaches, it is possible to integrate temporal information into cophylogenetical inference, such as estimates of lineage divergence times between 2 taxa, for example, hosts and parasites. Additionally, the advances in phylogenetic biogeography applying methods based on parametric process models and combined Bayesian approaches, can be useful for interpreting coevolutionary histories in a scenario of biogeographical area connectivity through time. This article briefly reviews the basics of parasitology and provides an overview of software packages in cophylogenetic methods. Thus, the objective here is to present a phylogenetic framework for coevolutionary studies, with special emphasis on groups of parasitic organisms. Researchers wishing to undertake phylogeny-based coevolutionary studies can use this review as a “compass” when “walking” through jungles of tangled phylogenetic trees. PMID:29491928

Comparing Phylogenetic Trees by Matching Nodes Using the Transfer Distance Between Partitions.

PubMed

Bogdanowicz, Damian; Giaro, Krzysztof

2017-05-01

Ability to quantify dissimilarity of different phylogenetic trees describing the relationship between the same group of taxa is required in various types of phylogenetic studies. For example, such metrics are used to assess the quality of phylogeny construction methods, to define optimization criteria in supertree building algorithms, or to find horizontal gene transfer (HGT) events. Among the set of metrics described so far in the literature, the most commonly used seems to be the Robinson-Foulds distance. In this article, we define a new metric for rooted trees-the Matching Pair (MP) distance. The MP metric uses the concept of the minimum-weight perfect matching in a complete bipartite graph constructed from partitions of all pairs of leaves of the compared phylogenetic trees. We analyze the properties of the MP metric and present computational experiments showing its potential applicability in tasks related to finding the HGT events.

Flash floods in the Tatra Mountain streams: frequency and triggers.

PubMed

Ballesteros-Cánovas, J A; Czajka, B; Janecka, K; Lempa, M; Kaczka, R J; Stoffel, M

2015-04-01

Flash floods represent a frequently recurring natural phenomenon in the Tatra Mountains. On the northern slopes of the mountain chain, located in Poland, ongoing and expected future changes in climate are thought to further increase the adverse impacts of flash floods. Despite the repeat occurrence of major floods in the densely populated foothills of the Polish Tatras, the headwaters have been characterized by a surprising lack of data, such that any analysis of process variability or hydrometeorological triggers has been largely hampered so far. In this study, dendrogeomorphic techniques have been employed in four poorly-gauged torrential streams of the northern slope of the Tatra Mountains to reconstruct temporal and spatial patterns of past events. Using more than 1100 increment cores of trees injured by past flash floods, we reconstruct 47 events covering the last 148 years and discuss synoptic situations leading to the triggering of flash floods with the existing meteorological and flow gauge data. Tree-ring analyses have allowed highlighting the seasonality of events, providing new insights about potential hydrometeorological triggers as well as a differentiating flash flood activity between catchments. Results of this study could be useful to design future strategies to deal with flash flood risks at the foothills of the Polish Tatras and in the Vistula River catchment. Copyright © 2014. Published by Elsevier B.V.

Evolution of the SOUL Heme-Binding Protein Superfamily Across Eukarya.

PubMed

Fortunato, Antonio Emidio; Sordino, Paolo; Andreakis, Nikos

2016-06-01

SOUL homologs constitute a heme-binding protein superfamily putatively involved in heme and tetrapyrrole metabolisms associated with a number of physiological processes. Despite their omnipresence across the tree of life and the biochemical characterization of many SOUL members, their functional role and the evolutionary events leading to such remarkable protein repertoire still remain cryptic. To explore SOUL evolution, we apply a computational phylogenetic approach, including a relevant number of SOUL homologs, to identify paralog forms and reconstruct their genealogy across the tree of life and within species. In animal lineages, multiple gene duplication or loss events and paralog functional specializations underlie SOUL evolution from the dawn of ancestral echinoderm and mollusc SOUL forms. In photosynthetic organisms, SOUL evolution is linked to the endosymbiosis events leading to plastid acquisition in eukaryotes. Derivative features, such as the F2L peptide and BH3 domain, evolved in vertebrates and provided innovative functionality to support immune response and apoptosis. The evolution of elements such as the N-terminal protein domain DUF2358, the His42 residue, or the tetrapyrrole heme-binding site is modern, and their functional implications still unresolved. This study represents the first in-depth analysis of SOUL protein evolution and provides novel insights in the understanding of their obscure physiological role.

Five centuries of Central European temperature extremes reconstructed from tree-ring density and documentary evidence

NASA Astrophysics Data System (ADS)

Battipaglia, G.; Frank, D.; Buentgen, U.; Dobrovolný, P.; Brázdil, R.; Pfister, C.; Esper, J.

2009-09-01

In this project three different summer temperature sensitive tree-ring chronologies across the European Alpine region were compiled and analyzed to make a calendar of extreme warm and cold summers. We identified 100 extreme events during the past millennium from the tree ring data, and 44 extreme years during the 1550-2003 period based upon tree-ring, documentary and instrumental evidence. Comparisons with long instrumental series and documentary evidence verify the tree-ring extremes and indicate the possibility to use this dataset towards a better understanding of the characteristics prior to the instrumental period. Potential links between the occurrence of extreme events over Alps and anomalous large-scale patterns were explored and indicate that the average pattern of the 20 warmest summers (over the 1700-2002 period) describes maximum positive anomalies over Central Europe, whereas the average pattern of the 20 coldest summers shows maximum negative anomalies over Western Europe. Challenges with the present approach included determining an appropriate classification scheme for extreme events and the development of a methodology able to identify and characterize the occurrence of extreme episodes back in time. As a future step, our approach will be extended to help verify the sparse documentary data from the beginning of the past millennium and will be used in conjunction with climate models to assess model capabilities in reproducing characteristics of temperature extremes.

Tree rings reveal a major episode of forest mortality in the late 18th century on the Tibetan Plateau

NASA Astrophysics Data System (ADS)

Fang, Ouya; Alfaro, René I.; Zhang, Qi-Bin

2018-04-01

There is a growing research interest on studying forest mortality in relation to ongoing climate warming, but little is known about such events in past history. The study of past forest mortality provides valuable information for determining baselines that establish the normal parameters of functioning in forest ecosystems. Here we report a major episode of previously undocumented forest mortality in the late 18th century on the northern Tibetan Plateau, China. The event was not spatially uniform, in which a more severe mortality happened in dryer sites. We used dendrochronology to compare radial growth trajectories of individual trees from 11 sites in the region, and found that many trees showed positive growth trend, or growth release, during 1796-1800 CE. Growth releases are a proxy indicator of stand thinning caused by tree mortality. The growth release was preceded by an almost two-decade long growth reduction. Long-term drought related to weakened North Atlantic Oscillation and frequent El Niño events are the likely factors causing the tree mortality in a large area of the plateau. Our findings suggest that, besides the effect of drought in the late 18th century, large-scale forest mortality may be an additional factor that further deteriorated the environment and increased the intensity of dust storms.

Updated precipitation reconstruction (AD 1482-2012) for Huashan, north-central China

NASA Astrophysics Data System (ADS)

Chen, Feng; Zhang, Ruibo; Wang, Huiqin; Qin, Li; Yuan, Yujiang

2016-02-01

We developed a tree-ring width chronology from pine trees ( Pinus tabulaeformis and Pinus armandii) stand near the peaks of Huashan, Shaanxi, north-central China. Growth-climate response analyses showed that the radial growth of pine trees is mainly influenced by April-June precipitation. A model to reconstruct precipitation based on tree widths was constructed, accounting for 55 % of the instrumental variance during the period 1953-2012. Spatial correlation analyses between the reconstruction and observed gridded precipitation data shows that the seasonal precipitation reconstruction captures regional climatic variations over north China. Compared with the historical archives and other tree-ring records in north China, many large-scale drought events, linked to the El Niño-Southern Oscillation (ENSO), were found. Many of these events have had profound impacts on the people of north China over the past several centuries. Composite maps of sea surface temperatures and 500 hPa geopotential heights for selected extremely dry and wet years in Huashan show characteristics similar to those related to the ENSO patterns, particularly with regard to ocean and atmospheric conditions in the equatorial and north Pacific. Our 531-year precipitation reconstruction for Huashan provides a long-term perspective on current and 20th century wet and dry events in north China, and is useful to guide expectations of future variability, and helps us to address climate change.

Assessing the stability of tree ranges and influence of disturbance in eastern US forests

Treesearch

C.W. Woodall; K. Zhu; J.A. Westfall; C.M. Oswalt; A.W. D' Amato; B.F. Walters; H.E. Lintz

2013-01-01

Shifts in tree species ranges may occur due to global climate change, which in turn may be exacerbated by natural disturbance events. Within the context of global climate change, developing techniques to monitor tree range dynamics as affected by natural disturbances may enable mitigation/adaptation of projected impacts. Using a forest inventory across the eastern U.S...

Biological control reduces growth, and alters water relations of the saltcedar tree (Tamarix spp.) in western Nevada, USA

Treesearch

R.R. Pattison; C.M. D' Antonio; T.L. Dudley

2011-01-01

We monitored the impacts of a biological control agent, the saltcedar leaf beetle (Diorhabda carinulata), on the saltcedar tree (Tamarix spp.) at two sites (Humboldt and Walker rivers) in Nevada, USA. At the Humboldt site trees that had experienced three to four defoliation events had more negative water potentials and lower...

Vernal freeze damage and genetic variation alter tree growth, chemistry, and insect interactions.

PubMed

Rubert-Nason, Kennedy F; Couture, John J; Gryzmala, Elizabeth A; Townsend, Philip A; Lindroth, Richard L

2017-11-01

Anticipated consequences of climate change in temperate regions include early spring warmup punctuated by intermittent hard freezes. Warm weather accelerates leaf flush in perennial woody species, potentially exposing vulnerable young tissues to damaging frosts. We employed a 2 × 6 randomized factorial design to examine how the interplay of vernal (springtime) freeze damage and genetic variation in a hardwood species (Populus tremuloides) influences tree growth, phytochemistry, and interactions with an insect herbivore (Chaitophorus stevensis). Acute effects of freezing included defoliation and mortality. Surviving trees exhibited reduced growth and altered biomass distribution. Reflushed leaves on these trees had lower mass per area, lower lignin concentrations, and higher nitrogen concentrations, altered chemical defence profiles, and supported faster aphid population growth. Many effects varied among plant genotypes and were related with herbivore performance. This study suggests that a single damaging vernal freeze event can alter tree-insect interactions through effects on plant growth and chemistry. Differential responses of various genotypes to freeze damage suggest that more frequent vernal freeze events could also influence natural selection, favouring trees with greater freeze hardiness, and more resistance or tolerance to herbivores following damage. © 2017 John Wiley & Sons Ltd.

The role of hybridization in facilitating tree invasion

PubMed Central

2017-01-01

Abstract Hybridization events can generate additional genetic diversity upon which natural selection can act and at times enhance invasiveness of the species. Invasive tree species are a growing ecological concern worldwide, and some of these invasions involve hybridization events pre- or post-introduction. There are 20 hybrid invasive tree taxa in 15 genera (11 plant families) discussed here. When reported, abundance of hybrids comprised 10–100 % of an invasion, the remainder being parental taxa. In seven hybrid taxa, researchers identified phenotypes that may make hybrids better invaders. Twelve hybrid tree taxa involved introgression and more hybrids involved all non-native taxa than native × non-native taxa. Three hybrid tree taxa were the result of intentional crosses, and all hybrid taxa involved intentional introduction of either one or more parental taxon or the hybrid itself. The knowledge gaps present in some hybrid tree taxa can weaken our effectiveness in predicting and controlling invasions, as hybrids can add a level of complexity to an invasion by being morphologically cryptic, causing genetic pollution of a native parental taxon, presenting novel genotypes for which there may not be coevolved biological control agents, or evolving adaptive traits through increased genetic variation. PMID:28028055

Cognitive Support During High-Consequence Episodes of Care in Cardiovascular Surgery.

PubMed

Conboy, Heather M; Avrunin, George S; Clarke, Lori A; Osterweil, Leon J; Christov, Stefan C; Goldman, Julian M; Yule, Steven J; Zenati, Marco A

2017-03-01

Despite significant efforts to reduce preventable adverse events in medical processes, such events continue to occur at unacceptable rates. This paper describes a computer science approach that uses formal process modeling to provide situationally aware monitoring and management support to medical professionals performing complex processes. These process models represent both normative and non-normative situations, and are validated by rigorous automated techniques such as model checking and fault tree analysis, in addition to careful review by experts. Context-aware Smart Checklists are then generated from the models, providing cognitive support during high-consequence surgical episodes. The approach is illustrated with a case study in cardiovascular surgery.

Categorizing accident sequences in the external radiotherapy for risk analysis

PubMed Central

2013-01-01

Purpose This study identifies accident sequences from the past accidents in order to help the risk analysis application to the external radiotherapy. Materials and Methods This study reviews 59 accidental cases in two retrospective safety analyses that have collected the incidents in the external radiotherapy extensively. Two accident analysis reports that accumulated past incidents are investigated to identify accident sequences including initiating events, failure of safety measures, and consequences. This study classifies the accidents by the treatments stages and sources of errors for initiating events, types of failures in the safety measures, and types of undesirable consequences and the number of affected patients. Then, the accident sequences are grouped into several categories on the basis of similarity of progression. As a result, these cases can be categorized into 14 groups of accident sequence. Results The result indicates that risk analysis needs to pay attention to not only the planning stage, but also the calibration stage that is committed prior to the main treatment process. It also shows that human error is the largest contributor to initiating events as well as to the failure of safety measures. This study also illustrates an event tree analysis for an accident sequence initiated in the calibration. Conclusion This study is expected to provide sights into the accident sequences for the prospective risk analysis through the review of experiences. PMID:23865005

Tree-ring δ13C and δ18O, leaf δ13C and wood and leaf N status demonstrate tree growth strategies and predict susceptibility to disturbance

PubMed Central

Billings, S.A.; Boone, A.S.; Stephen, F.M.

2016-01-01

Understanding how tree growth strategies may influence tree susceptibility to disturbance is an important goal, especially given projected increases in diverse ecological disturbances this century. We use growth responses of tree rings to climate, relationships between tree-ring stable isotopic signatures of carbon (δ13C) and oxygen (δ18O), wood nitrogen concentration [N], and contemporary leaf [N] and δ13C values to assess potential historic drivers of tree photosynthesis in dying and apparently healthy co-occurring northern red oak (Quercus rubra L. (Fagaceae)) during a region-wide oak decline event in Arkansas, USA. Bole growth of both healthy and dying trees responded negatively to drought severity (Palmer Drought Severity Index) and temperature; healthy trees exhibited a positive, but small, response to growing season precipitation. Contrary to expectations, tree-ring δ13C did not increase with drought severity. A significantly positive relationship between tree-ring δ13C and δ18O was evident in dying trees (P < 0.05) but not in healthy trees. Healthy trees’ wood exhibited lower [N] than that of dying trees throughout most of their lives (P < 0.05), and we observed a significant, positive relationship (P < 0.05) in healthy trees between contemporary leaf δ13C and leaf N (by mass), but not in dying trees. Our work provides evidence that for plants in which strong relationships between δ13C and δ18O are not evident, δ13C may be governed by plant N status. The data further imply that historic photosynthesis in healthy trees was linked to N status and, perhaps, C sink strength to a greater extent than in dying trees, in which tree-ring stable isotopes suggest that historic photosynthesis was governed primarily by stomatal regulation. This, in turn, suggests that assessing the relative dominance of photosynthetic capacity vs stomatal regulation as drivers of trees’ C accrual may be a feasible means of predicting tree responses to some disturbance events. Our work demonstrates that a dual isotope, tree-ring approach can be integrated with tree N status to begin to unravel a fundamental question in forest ecology: why do some trees die during a disturbance, while other conspecifics with apparently similar access to resources remain healthy? PMID:26960389

Drug safety data mining with a tree-based scan statistic.

PubMed

Kulldorff, Martin; Dashevsky, Inna; Avery, Taliser R; Chan, Arnold K; Davis, Robert L; Graham, David; Platt, Richard; Andrade, Susan E; Boudreau, Denise; Gunter, Margaret J; Herrinton, Lisa J; Pawloski, Pamala A; Raebel, Marsha A; Roblin, Douglas; Brown, Jeffrey S

2013-05-01

In post-marketing drug safety surveillance, data mining can potentially detect rare but serious adverse events. Assessing an entire collection of drug-event pairs is traditionally performed on a predefined level of granularity. It is unknown a priori whether a drug causes a very specific or a set of related adverse events, such as mitral valve disorders, all valve disorders, or different types of heart disease. This methodological paper evaluates the tree-based scan statistic data mining method to enhance drug safety surveillance. We use a three-million-member electronic health records database from the HMO Research Network. Using the tree-based scan statistic, we assess the safety of selected antifungal and diabetes drugs, simultaneously evaluating overlapping diagnosis groups at different granularity levels, adjusting for multiple testing. Expected and observed adverse event counts were adjusted for age, sex, and health plan, producing a log likelihood ratio test statistic. Out of 732 evaluated disease groupings, 24 were statistically significant, divided among 10 non-overlapping disease categories. Five of the 10 signals are known adverse effects, four are likely due to confounding by indication, while one may warrant further investigation. The tree-based scan statistic can be successfully applied as a data mining tool in drug safety surveillance using observational data. The total number of statistical signals was modest and does not imply a causal relationship. Rather, data mining results should be used to generate candidate drug-event pairs for rigorous epidemiological studies to evaluate the individual and comparative safety profiles of drugs. Copyright © 2013 John Wiley & Sons, Ltd.

Development of quantitative security optimization approach for the picture archives and carrying system between a clinic and a rehabilitation center

NASA Astrophysics Data System (ADS)

Haneda, Kiyofumi; Kajima, Toshio; Koyama, Tadashi; Muranaka, Hiroyuki; Dojo, Hirofumi; Aratani, Yasuhiko

2002-05-01

The target of our study is to analyze the level of necessary security requirements, to search for suitable security measures and to optimize security distribution to every portion of the medical practice. Quantitative expression must be introduced to our study, if possible, to enable simplified follow-up security procedures and easy evaluation of security outcomes or results. Using fault tree analysis (FTA), system analysis showed that system elements subdivided into groups by details result in a much more accurate analysis. Such subdivided composition factors greatly depend on behavior of staff, interactive terminal devices, kinds of services provided, and network routes. Security measures were then implemented based on the analysis results. In conclusion, we identified the methods needed to determine the required level of security and proposed security measures for each medical information system, and the basic events and combinations of events that comprise the threat composition factors. Methods for identifying suitable security measures were found and implemented. Risk factors for each basic event, a number of elements for each composition factor, and potential security measures were found. Methods to optimize the security measures for each medical information system were proposed, developing the most efficient distribution of risk factors for basic events.

Environmental controls in the water use patterns of a tropical cloud forest tree species, Drimys brasiliensis (Winteraceae).

PubMed

Eller, Cleiton B; Burgess, Stephen S O; Oliveira, Rafael S

2015-04-01

Trees from tropical montane cloud forest (TMCF) display very dynamic patterns of water use. They are capable of downwards water transport towards the soil during leaf-wetting events, likely a consequence of foliar water uptake (FWU), as well as high rates of night-time transpiration (Enight) during drier nights. These two processes might represent important sources of water losses and gains to the plant, but little is known about the environmental factors controlling these water fluxes. We evaluated how contrasting atmospheric and soil water conditions control diurnal, nocturnal and seasonal dynamics of sap flow in Drimys brasiliensis (Miers), a common Neotropical cloud forest species. We monitored the seasonal variation of soil water content, micrometeorological conditions and sap flow of D. brasiliensis trees in the field during wet and dry seasons. We also conducted a greenhouse experiment exposing D. brasiliensis saplings under contrasting soil water conditions to deuterium-labelled fog water. We found that during the night D. brasiliensis possesses heightened stomatal sensitivity to soil drought and vapour pressure deficit, which reduces night-time water loss. Leaf-wetting events had a strong suppressive effect on tree transpiration (E). Foliar water uptake increased in magnitude with drier soil and during longer leaf-wetting events. The difference between diurnal and nocturnal stomatal behaviour in D. brasiliensis could be attributed to an optimization of carbon gain when leaves are dry, as well as minimization of nocturnal water loss. The leaf-wetting events on the other hand seem important to D. brasiliensis water balance, especially during soil droughts, both by suppressing tree transpiration (E) and as a small additional water supply through FWU. Our results suggest that decreases in leaf-wetting events in TMCF might increase D. brasiliensis water loss and decrease its water gains, which could compromise its ecophysiological performance and survival during dry periods. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sattison, M.B.

The Idaho National Engineering Laboratory (INEL) over the three years has created 75 plant-specific Accident Sequence Precursor (ASP) models using the SAPHIRE suite of PRA codes. Along with the new models, the INEL has also developed a new module for SAPHIRE which is tailored specifically to the unique needs of ASP evaluations. These models and software will be the next generation of risk tools for the evaluation of accident precursors by both the U.S. Nuclear Regulatory Commission`s (NRC`s) Office of Nuclear Reactor Regulation (NRR) and the Office for Analysis and Evaluation of Operational Data (AEOD). This paper presents an overviewmore » of the models and software. Key characteristics include: (1) classification of the plant models according to plant response with a unique set of event trees for each plant class, (2) plant-specific fault trees using supercomponents, (3) generation and retention of all system and sequence cutsets, (4) full flexibility in modifying logic, regenerating cutsets, and requantifying results, and (5) user interface for streamlined evaluation of ASP events. Future plans for the ASP models is also presented.« less

Species Tree Inference Using a Mixture Model.

PubMed

Ullah, Ikram; Parviainen, Pekka; Lagergren, Jens

2015-09-01

Species tree reconstruction has been a subject of substantial research due to its central role across biology and medicine. A species tree is often reconstructed using a set of gene trees or by directly using sequence data. In either of these cases, one of the main confounding phenomena is the discordance between a species tree and a gene tree due to evolutionary events such as duplications and losses. Probabilistic methods can resolve the discordance by coestimating gene trees and the species tree but this approach poses a scalability problem for larger data sets. We present MixTreEM-DLRS: A two-phase approach for reconstructing a species tree in the presence of gene duplications and losses. In the first phase, MixTreEM, a novel structural expectation maximization algorithm based on a mixture model is used to reconstruct a set of candidate species trees, given sequence data for monocopy gene families from the genomes under study. In the second phase, PrIME-DLRS, a method based on the DLRS model (Åkerborg O, Sennblad B, Arvestad L, Lagergren J. 2009. Simultaneous Bayesian gene tree reconstruction and reconciliation analysis. Proc Natl Acad Sci U S A. 106(14):5714-5719), is used for selecting the best species tree. PrIME-DLRS can handle multicopy gene families since DLRS, apart from modeling sequence evolution, models gene duplication and loss using a gene evolution model (Arvestad L, Lagergren J, Sennblad B. 2009. The gene evolution model and computing its associated probabilities. J ACM. 56(2):1-44). We evaluate MixTreEM-DLRS using synthetic and biological data, and compare its performance with a recent genome-scale species tree reconstruction method PHYLDOG (Boussau B, Szöllősi GJ, Duret L, Gouy M, Tannier E, Daubin V. 2013. Genome-scale coestimation of species and gene trees. Genome Res. 23(2):323-330) as well as with a fast parsimony-based algorithm Duptree (Wehe A, Bansal MS, Burleigh JG, Eulenstein O. 2008. Duptree: a program for large-scale phylogenetic analyses using gene tree parsimony. Bioinformatics 24(13):1540-1541). Our method is competitive with PHYLDOG in terms of accuracy and runs significantly faster and our method outperforms Duptree in accuracy. The analysis constituted by MixTreEM without DLRS may also be used for selecting the target species tree, yielding a fast and yet accurate algorithm for larger data sets. MixTreEM is freely available at http://prime.scilifelab.se/mixtreem/. © The Author 2015. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Recent Mega-Thrust Tsunamigenic Earthquakes and PTHA

NASA Astrophysics Data System (ADS)

Lorito, S.

2013-05-01

The occurrence of several mega-thrust tsunamigenic earthquakes in the last decade, including but not limited to the 2004 Sumatra-Andaman, the 2010 Maule, and 2011 Tohoku earthquakes, has been a dramatic reminder of the limitations in our capability of assessing earthquake and tsunami hazard and risk. However, the increasingly high-quality geophysical observational networks allowed the retrieval of most accurate than ever models of the rupture process of mega-thrust earthquakes, thus paving the way for future improved hazard assessments. Probabilistic Tsunami Hazard Analysis (PTHA) methodology, in particular, is less mature than its seismic counterpart, PSHA. Worldwide recent research efforts of the tsunami science community allowed to start filling this gap, and to define some best practices that are being progressively employed in PTHA for different regions and coasts at threat. In the first part of my talk, I will briefly review some rupture models of recent mega-thrust earthquakes, and highlight some of their surprising features that likely result in bigger error bars associated to PTHA results. More specifically, recent events of unexpected size at a given location, and with unexpected rupture process features, posed first-order open questions which prevent the definition of an heterogeneous rupture probability along a subduction zone, despite of several recent promising results on the subduction zone seismic cycle. In the second part of the talk, I will dig a bit more into a specific ongoing effort for improving PTHA methods, in particular as regards epistemic and aleatory uncertainties determination, and the computational PTHA feasibility when considering the full assumed source variability. Only logic trees are usually explicated in PTHA studies, accounting for different possible assumptions on the source zone properties and behavior. The selection of the earthquakes to be actually modelled is then in general made on a qualitative basis or remains implicit, despite different methods like event trees have been used for different applications. I will define a quite general PTHA framework, based on the mixed use of logic and event trees. I will first discuss a particular class of epistemic uncertainties, i.e. those related to the parametric fault characterization in terms of geometry, kinematics, and assessment of activity rates. A systematic classification in six justification levels of epistemic uncertainty related with the existence and behaviour of fault sources will be presented. Then, a particular branch of the logic tree is chosen in order to discuss just the aleatory variability of earthquake parameters, represented with an event tree. Even so, PTHA based on numerical scenarios is a too demanding computational task, particularly when probabilistic inundation maps are needed. For trying to reduce the computational burden without under-representing the source variability, the event tree is first constructed by taking care of densely (over-)sampling the earthquake parameter space, and then the earthquakes are filtered basing on their associated tsunami impact offshore, before calculating inundation maps. I'll describe this approach by means of a case study in the Mediterranean Sea, namely the PTHA for some locations of Eastern Sicily coasts and Southern Crete coast due to potential subduction earthquakes occurring on the Hellenic Arc.

Mitochondrial genomes and avian phylogeny: complex characters and resolvability without explosive radiations.

PubMed

Gibb, Gillian C; Kardailsky, Olga; Kimball, Rebecca T; Braun, Edward L; Penny, David

2007-01-01

We improve the taxon sampling for avian phylogeny by analyzing 7 new mitochondrial genomes (a toucan, woodpecker, osprey, forest falcon, American kestrel, heron, and a pelican). This improves inference of the avian tree, and it supports 3 major conclusions. The first is that some birds (including a parrot, a toucan, and an osprey) exhibit a complete duplication of the control region (CR) meaning that there are at least 4 distinct gene orders within birds. However, it appears that there are regions of continued gene conversion between the duplicate CRs, resulting in duplications that can be stable for long evolutionary periods. Because of this stable duplicated state, gene order can eventually either revert to the original order or change to the new gene order. The existence of this stable duplicate state explains how an apparently unlikely event (finding the same novel gene order) can arise multiple times. Although rare genomic changes have theoretical advantages for tree reconstruction, they can be compromised if these apparently rare events have a stable intermediate state. Secondly, the toucan and woodpecker improve the resolution of the 6-way split within Neoaves that has been called an "explosive radiation." An explosive radiation implies that normal microevolutionary events are insufficient to explain the observed macroevolution. By showing the avian tree is, in principle, resolvable, we demonstrate that the radiation of birds is amenable to standard evolutionary analysis. Thirdly, and as expected from theory, additional taxa breaking up long branches stabilize the position of some problematic taxa (like the falcon). In addition, we report that within the birds of prey and allies, we did not find evidence pairing New World vultures with storks or accipitrids (hawks, eagles, and osprey) with Falconids.

Phylogenomics reveals an extensive history of genome duplication in diatoms (Bacillariophyta).

PubMed

Parks, Matthew B; Nakov, Teofil; Ruck, Elizabeth C; Wickett, Norman J; Alverson, Andrew J

2018-03-01

Diatoms are one of the most species-rich lineages of microbial eukaryotes. Similarities in clade age, species richness, and primary productivity motivate comparisons to angiosperms, whose genomes have been inordinately shaped by whole-genome duplication (WGD). WGDs have been linked to speciation, increased rates of lineage diversification, and identified as a principal driver of angiosperm evolution. We synthesized a large but scattered body of evidence that suggests polyploidy may be common in diatoms as well. We used gene counts, gene trees, and distributions of synonymous divergence to carry out a phylogenomic analysis of WGD across a diverse set of 37 diatom species. Several methods identified WGDs of varying age across diatoms. Determining the occurrence, exact number, and placement of events was greatly impacted by uncertainty in gene trees. WGDs inferred from synonymous divergence of paralogs varied depending on how redundancy in transcriptomes was assessed, gene families were assembled, and synonymous distances (Ks) were calculated. Our results highlighted a need for systematic evaluation of key methodological aspects of Ks-based approaches to WGD inference. Gene tree reconciliations supported allopolyploidy as the predominant mode of polyploid formation, with strong evidence for ancient allopolyploid events in the thalassiosiroid and pennate diatom clades. Our results suggest that WGD has played a major role in the evolution of diatom genomes. We outline challenges in reconstructing paleopolyploid events in diatoms that, together with these results, offer a framework for understanding the impact of genome duplication in a group that likely harbors substantial genomic diversity. © 2018 The Authors. American Journal of Botany is published by Wiley Periodicals, Inc. on behalf of the Botanical Society of America.

Changes in El Nino - Southern Oscillation (ENSO) conditions during the Younger Dryas revealed by New Zealand tree-rings.

NASA Astrophysics Data System (ADS)

Palmer, Jonathan; Turney, Chris; Cook, Edward; Fenwick, Pavla; Thomas, Zoë; Helle, Gerhard; Jones, Richard; Clement, Amy; Hogg, Alan; Southon, John; Bronk Ramsey, Christopher; Staff, Richard; Muscheler, Raimund; Corrège, Thierry; Hua, Quan

2017-04-01

The warming trend at the end of the last glacial was disrupted by rapid cooling clearly identified in Greenland (Greenland Stadial 1 or GS-1) and Europe (Younger Dryas Stadial or YD). This reversal to glacial-like conditions is one of the best known examples of abrupt change but the exact timing and global spatial extent remains uncertain. Whilst the wider Atlantic region has a network of high-resolution proxy records spanning the YD, the Pacific Ocean suffers from a scarcity of sub-decadally resolved sequences. Here we report the results from an investigation into a tree-ring chronology from northern New Zealand aimed at addressing the paucity of data. The conifer tree species kauri (Agathis australis) is known from contemporary studies to be sensitive to regional climate changes. An analysis of a 'historic' 452-year kauri chronology confirms a tropical-Pacific teleconnection via the El Niño - Southern Oscillation (ENSO). We then focus our study to a 1010-year subfossil kauri chronology that has been precisely dated by comprehensive radiocarbon dating and contains a striking ring-width downturn between 12,500 to 12,380 cal BP within the YD. Wavelet analysis shows a marked increase in ENSO-like periodicities occurring after the downturn event. Comparison to low- and mid-latitude Pacific records suggests a coherency in the changes to ENSO and Southern Hemisphere westerly airflow during this period. The drivers for this climate event remain unclear but may be related to solar changes that subsequently led to establishment and/or increased expression of ENSO across the mid-latitudes of the Pacific, seemingly independent of the Atlantic and polar regions.

Changes in El Niño - Southern Oscillation (ENSO) conditions during the Greenland Stadial 1 (GS-1) chronozone revealed by New Zealand tree-rings

NASA Astrophysics Data System (ADS)

Palmer, Jonathan G.; Turney, Chris S. M.; Cook, Edward R.; Fenwick, Pavla; Thomas, Zoë; Helle, Gerhard; Jones, Richard; Clement, Amy; Hogg, Alan; Southon, John; Bronk Ramsey, Christopher; Staff, Richard; Muscheler, Raimund; Corrège, Thierry; Hua, Quan

2016-12-01

The warming trend at the end of the last glacial was disrupted by rapid cooling clearly identified in Greenland (Greenland Stadial 1 or GS-1) and Europe (Younger Dryas Stadial or YD). This reversal to glacial-like conditions is one of the best known examples of abrupt change but the exact timing and global spatial extent remain uncertain. Whilst the wider Atlantic region has a network of high-resolution proxy records spanning GS-1, the Pacific Ocean suffers from a scarcity of sub-decadally resolved sequences. Here we report the results from an investigation into a tree-ring chronology from northern New Zealand aimed at addressing the paucity of data. The conifer tree species kauri (Agathis australis) is known from contemporary studies to be sensitive to regional climate changes. An analysis of a 'historic' 452-year kauri chronology confirms a tropical-Pacific teleconnection via the El Niño - Southern Oscillation (ENSO). We then focus our study on a 1010-year sub-fossil kauri chronology that has been precisely dated by comprehensive radiocarbon dating and contains a striking ring-width downturn between ∼12,500 and 12,380 cal BP within GS-1. Wavelet analysis shows a marked increase in ENSO-like periodicities occurring after the downturn event. Comparison to low- and mid-latitude Pacific records suggests a coherency with ENSO and Southern Hemisphere atmospheric circulation change during this period. The driver(s) for this climate event remain unclear but may be related to solar changes that subsequently led to establishment and/or increased expression of ENSO across the mid-latitudes of the Pacific, seemingly independent of the Atlantic and polar regions.

Risk Management in Complex Construction Projects that Apply Renewable Energy Sources: A Case Study of the Realization Phase of the Energis Educational and Research Intelligent Building

NASA Astrophysics Data System (ADS)

Krechowicz, Maria

2017-10-01

Nowadays, one of the characteristic features of construction industry is an increased complexity of a growing number of projects. Almost each construction project is unique, has its project-specific purpose, its own project structural complexity, owner’s expectations, ground conditions unique to a certain location, and its own dynamics. Failure costs and costs resulting from unforeseen problems in complex construction projects are very high. Project complexity drivers pose many vulnerabilities to a successful completion of a number of projects. This paper discusses the process of effective risk management in complex construction projects in which renewable energy sources were used, on the example of the realization phase of the ENERGIS teaching-laboratory building, from the point of view of DORBUD S.A., its general contractor. This paper suggests a new approach to risk management for complex construction projects in which renewable energy sources were applied. The risk management process was divided into six stages: gathering information, identification of the top, critical project risks resulting from the project complexity, construction of the fault tree for each top, critical risks, logical analysis of the fault tree, quantitative risk assessment applying fuzzy logic and development of risk response strategy. A new methodology for the qualitative and quantitative risk assessment for top, critical risks in complex construction projects was developed. Risk assessment was carried out applying Fuzzy Fault Tree analysis on the example of one top critical risk. Application of the Fuzzy sets theory to the proposed model allowed to decrease uncertainty and eliminate problems with gaining the crisp values of the basic events probability, common during expert risk assessment with the objective to give the exact risk score of each unwanted event probability.

Beyond the extreme: Recovery dynamics following heat and drought stress in trees

NASA Astrophysics Data System (ADS)

Ruehr, N.; Duarte, A. G.; Arneth, A.

2016-12-01

Plant recovery processes following extreme events can have profound impacts on forest carbon and water cycling. However, large knowledge gaps persist on recovery dynamics of tree physiological processes following heat and drought stress. To date, few experimental studies exist that include recovery responses in stress research. We synthesized recent research on tree recovery processes related to carbon and water exchange following heat and drought stress, and show that the intensity of stress can affect the pace of recovery with large variations among tree species and processes. Following stress release, leaf water potential recovers instantaneously upon rewatering as found in most studies. Transpiration (T), stomatal conductance (gs) and photosynthesis (A) often lag behind, with lowest recovery following severe stress. Interestingly, the patterns in heat and drought stress recovery apparently differ. While A recovers generally more quickly than gs following drought, which increases water-use-efficiency, both gs and A tend to remain reduced following heat events. The pace of recovery following heat events likely depends on water availability during stress and temperature maxima reached (photosynthetic impairment at temperatures > 40°C). Slow recovery during the initial post-stress days might result from hydraulic limitation and elevated levels of abscisic acid. The mechanisms resulting in a continued impairment of T and gs during a later stage of the recovery period (from weeks up to months) are still elusive. Feedback loops from the photosynthetic machinery, reduced mesophyll conductance or leaf morphological changes may play an important role. In summary, post-stress recovery can substantially affect tree carbon and water cycling. Thus, in order to estimate the impacts of extreme climate events on forest ecosystems in the long-term, we need a better understanding of recovery dynamics and their limitations in terms of stress timing, intensity and duration.

Tree species' responses to throughfall removal experiments superimposed on a natural drought event in two contrasting humid temperate forests in New Hampshire, USA

NASA Astrophysics Data System (ADS)

Jennings, Katie; McIntire, Cameron; Coble, Adam; Vandeboncoeur, Matthew; Rustad, Lindsay; Templer, Pamela; Absbjornsen, Heidi

2017-04-01

Climate change is likely to affect Northeastern U.S. forests through the increased frequency and severity of drought events. However, our understanding of how these humid temperate forests will respond to moderate to extreme droughts is limited. Given the important role that these forests play in providing ecosystem services and in supplying forest products, enhancing our knowledge about the impacts of drought is critical to guiding forest management and climate change adaptation efforts. We conducted 50% throughfall removal experiments at two contrasting sites in the Northeastern US (Hubbard Brook Experimental Forest and Thompson Farm, NH, USA), which were superimposed on the severe natural drought occurring in August-September 2016. Preliminary analysis suggests that the two sites respond differently to simulated drought. Pinus strobus trees at Thompson Farm reduced their transpiration rates in response to both the natural and experimental drought, particularly evident during a 5-day period at the height of the drought were transpiration nearly ceased. Both P. strobus and Quercus rubra trees increased their water use efficiency in response to reduced soil water availability, with Q. rubra allowing its midday water potential to reach more negative values, consistent with its more drought tolerant strategy compared to P. strobus. In contrast, we did not detect any significant differences in tree transpiration rates or growth in the dominant tree species, Acer rubrum, in response to the experimental drought treatment at Hubbard Brook. However, both soil respiration and fine root biomass production were lower in the drought treatment plots relative to the control plots at Hubbard Brook. We plan to continue these throughfall removal experiments for at least two more years to better understand the implications of future drought in these humid temperate forests and identify differences in species' physiological adaptations and threshold responses.

Correlation Between the System Capabilities Analytic Process (SCAP) and the Missions and Means Framework (MMF)

DTIC Science & Technology

2013-05-01

specifics of the correlation will be explored followed by discussion of new paradigms— the ordered event list (OEL) and the decision tree — that result from...4.2.1  Brief Overview of the Decision Tree Paradigm ................................................15  4.2.2  OEL Explained...6  Figure 3. A depiction of a notional fault/activation tree . ................................................................7

Predicting post-fire tree mortality for 14 conifers in the Pacific Northwest, USA: Model evaluation, development, and thresholds

Treesearch

Lindsay M. Grayson; Robert A. Progar; Sharon M. Hood

2017-01-01

Fire is a driving force in the North American landscape and predicting post-fire tree mortality is vital to land management. Post-fire tree mortality can have substantial economic and social impacts, and natural resource managers need reliable predictive methods to anticipate potential mortality following fire events. Current fire mortality models are limited to a few...

Continental-scale consequences of tree die-offs in North America: identifying where forest loss matters most

NASA Astrophysics Data System (ADS)

Swann, Abigail L. S.; Laguë, Marysa M.; Garcia, Elizabeth S.; Field, Jason P.; Breshears, David D.; Moore, David J. P.; Saleska, Scott R.; Stark, Scott C.; Villegas, Juan Camilo; Law, Darin J.; Minor, David M.

2018-05-01

Regional-scale tree die-off events driven by drought and warming and associated pests and pathogens have occurred recently on all forested continents and are projected to increase in frequency and extent with future warming. Within areas where tree mortality has occurred, ecological, hydrological and meteorological consequences are increasingly being documented. However, the potential for tree die-off to impact vegetation processes and related carbon dynamics in areas remote to where die-off occurs has rarely been systematically evaluated, particularly for multiple distinct regions within a given continent. Such remote impacts can occur when climate effects of local vegetation change are propagated by atmospheric circulation—the phenomena of ‘ecoclimate teleconnections’. We simulated tree die-off events in the 13 most densely forested US regions (selected from the 20 US National Ecological Observatory Network [NEON] domains) and found that tree die-off even for smaller regions has potential to affect climate and hence Gross Primary Productivity (GPP) in disparate regions (NEON domains), either positively or negatively. Some regions exhibited strong teleconnections to several others, and some regions were relatively sensitive to tree loss regardless of what other region the tree loss occurred in. For the US as a whole, loss of trees in the Pacific Southwest—an area undergoing rapid tree die-off—had the largest negative impact on remote US GPP whereas loss of trees in the Mid-Atlantic had the largest positive impact. This research lays a foundation for hypotheses that identify how the effects of tree die-off (or other types of tree loss such as deforestation) can ricochet across regions by revealing hot-spots of forcing and response. Such modes of connectivity have direct applicability for improving models of climate change impacts and for developing more informed and coordinated carbon accounting across regions.

A Case Study of a Combat Helicopter’s Single Unit Vulnerability.

DTIC Science & Technology

1987-03-01

22 2.6 Generic Fault Tree Diagram ----------------------- 24 2.7 Example Kill Diagram ----------------------------- 25 2.8 Example EEA Summary...that of the vulnerability program, a susceptibility program is subdivided into three major tasks. First is an essential elements analysis ( EEA ...which leads to the 27 i final undesired event in much the same manner as a FTA. An example EEA is provided in Figure 2.8. [Ref.l:p226] The

Large Scale Data Analysis and Knowledge Extraction in Communication Data

DTIC Science & Technology

2017-03-31

this purpose, we developed a novel method the " Correlation Density Ran!C’ which finds probability density distribution of related frequent event on all...which is called " Correlation Density Rank", is developed to derive the community tree from the network. As in the real world, where a network is...Community Structure in Dynamic Social Networks using the Correlation Density Rank," 2014 ASE BigData/SocialCom/Cybersecurity Conference, Stanford

The carbon balance of reducing wildfire risk and restoring process: an analysis of 10-year post-treatment carbon dynamics in a mixed-conifer forest

Treesearch

Morgan L. Wiechmann; Matthew D. Hurteau; Malcolm P. North; George W. Koch; Lucie Jerabkova

2015-01-01

Forests sequester carbon from the atmosphere, helping mitigate climate change. In fire-prone forests, burn events result in direct and indirect emissions of carbon. High fire-induced tree mortality can cause a transition from a carbon sink to source, but thinning and prescribed burning can reduce fire severity and carbon loss when wildfire occurs. However, treatment...

Disentangling factors that control the vulnerability of forests to catastrophic wind damage

NASA Astrophysics Data System (ADS)

Dracup, E.; Taylor, A.; MacLean, D.; Boulanger, Y.

2017-12-01

Wind is an important driver of forest dynamics along North America's north-eastern coastal forests, but also damages many commercially managed forests which society relies as an important source of wood fiber. Although the influence of wind on north-eastern forests is well recognized, knowledge of factors predisposing trees to wind damage is less known, especially in the context of large, powerful wind storm events. This is of particular concern as climate change is expected to alter the frequency and severity of strong wind storms affecting this region. On 29 September 2003, Hurricane Juan made landfall over Nova Scotia, Canada as a Category 2 hurricane with sustained winds of 158 km/h, and gusts of up to 185 km/h. Hurricane Juan variously damaged a swath of over 600,000 ha of forest. The damaged forest area was surveyed using aerial photography and LandSAT imagery and categorized according to level of wind damage sustained (none, low, moderate, severe) at a resolution of 15 x 15 m square cells. We used Random Forest to analyze and compare level of wind damage in each cell with a myriad of abiotic (exposure, depth to water table, soil composition, etc.) and biotic (tree species composition, canopy closure, canopy height, etc.) factors known or expected to predispose trees to windthrow. From our analysis, we identified topographic exposure, precipitation, and maximum gust speed as the top predictors of windthrow during Hurricane Juan. To our surprise, forest stand factors, such as tree species composition and height, had minimal effects on level of windthrow. These results can be used to construct predictive risk maps which can help society to assess the vulnerability of forests to future wind storm events.

Designing efficient nitrous oxide sampling strategies in agroecosystems using simulation models

NASA Astrophysics Data System (ADS)

Saha, Debasish; Kemanian, Armen R.; Rau, Benjamin M.; Adler, Paul R.; Montes, Felipe

2017-04-01

Annual cumulative soil nitrous oxide (N2O) emissions calculated from discrete chamber-based flux measurements have unknown uncertainty. We used outputs from simulations obtained with an agroecosystem model to design sampling strategies that yield accurate cumulative N2O flux estimates with a known uncertainty level. Daily soil N2O fluxes were simulated for Ames, IA (corn-soybean rotation), College Station, TX (corn-vetch rotation), Fort Collins, CO (irrigated corn), and Pullman, WA (winter wheat), representing diverse agro-ecoregions of the United States. Fertilization source, rate, and timing were site-specific. These simulated fluxes surrogated daily measurements in the analysis. We ;sampled; the fluxes using a fixed interval (1-32 days) or a rule-based (decision tree-based) sampling method. Two types of decision trees were built: a high-input tree (HI) that included soil inorganic nitrogen (SIN) as a predictor variable, and a low-input tree (LI) that excluded SIN. Other predictor variables were identified with Random Forest. The decision trees were inverted to be used as rules for sampling a representative number of members from each terminal node. The uncertainty of the annual N2O flux estimation increased along with the fixed interval length. A 4- and 8-day fixed sampling interval was required at College Station and Ames, respectively, to yield ±20% accuracy in the flux estimate; a 12-day interval rendered the same accuracy at Fort Collins and Pullman. Both the HI and the LI rule-based methods provided the same accuracy as that of fixed interval method with up to a 60% reduction in sampling events, particularly at locations with greater temporal flux variability. For instance, at Ames, the HI rule-based and the fixed interval methods required 16 and 91 sampling events, respectively, to achieve the same absolute bias of 0.2 kg N ha-1 yr-1 in estimating cumulative N2O flux. These results suggest that using simulation models along with decision trees can reduce the cost and improve the accuracy of the estimations of cumulative N2O fluxes using the discrete chamber-based method.

What determines tree mortality in dry environments? A multi-perspective approach.

PubMed

Dorman, Michael; Svoray, Tal; Perevolotsky, Avi; Moshe, Yitzhak; Sarris, Dimitrios

2015-06-01

Forest ecosystems function under increasing pressure due to global climate changes, while factors determining when and where mortality events will take place within the wider landscape are poorly understood. Observational studies are essential for documenting forest decline events, understanding their determinants, and developing sustainable management plans. A central obstacle towards achieving this goal is that mortality is often patchy across a range of spatial scales, and characterized by long-term temporal dynamics. Research must therefore integrate different methods, from several scientific disciplines, to capture as many relevant informative patterns as possible. We performed a landscape-scale assessment of mortality and its determinants in two representative Pinus halepensis planted forests from a dry environment (~300 mm), recently experiencing an unprecedented sequence of two severe drought periods. Three data sources were integrated to analyze the spatiotemporal variation in forest performance: (1) Normalized Difference Vegetation Index (NDVI) time-series, from 18 Landsat satellite images; (2) individual dead trees point-pattern, based on a high-resolution aerial photograph; and (3) Basal Area Increment (BAI) time-series, from dendrochronological sampling in three sites. Mortality risk was higher in older-aged sparse stands, on southern aspects, and on deeper soils. However, mortality was patchy across all spatial scales, and the locations of patches within "high-risk" areas could not be fully explained by the examined environmental factors. Moreover, the analysis of past forest performance based on NDVI and tree rings has indicated that the areas affected by each of the two recent droughts do not coincide. The association of mortality with lower tree densities did not support the notion that thinning semiarid forests will increase survival probability of the remaining trees when facing extreme drought. Unique information was obtained when merging dendrochronological and remotely sensed performance indicators, in contrast to potential bias when using a single approach. For example, dendrochronological data suggested highly resilient tree growth, since it was based only on the "surviving" portion of the population, thus failing to identify past demographic changes evident through remote sensing. We therefore suggest that evaluation of forest resilience should be based on several metrics, each suited for detecting transitions at a different level of organization.

Snow avalanche activity in the High Tatras Mountains: new data achieved by means of dendrogeomorphic methods

NASA Astrophysics Data System (ADS)

Tichavsky, R.

2016-12-01

The High Tatras Mountains are permanently affected by the occurrence of hazardous geomorphic processes. Snow avalanches represent a common hazard that threatens the infrastructure and humans living and visiting the mountains. So far, the spatio-temporal reconstruction of snow avalanche histories was based only on existing archival records, orthophoto interpretation and lichenometric dating in the High Tatras Mountains. Dendrogeomorphic methods allow for the intra-seasonal dating of scars on tree stems and branches and have been broadly used for the dating of snow avalanche events all over the world. We extracted the increment cores and cross sections from 189 individuals of Pinus mugo var. mugo growing on four tali in the Great Cold Valley and dated all the past scars that could correspond with the winter to early spring occurrence of snow avalanches. The dating was supported by the visual analysis of three orthophoto images from 2004, 2009 and 2014. In total, nineteen event years of snow avalanches (10 certain events, and 9 probable events) were identified since 1959. Historical archives provided evidence only for nine event years since 1987, and three of them were confirmed dendrogeomorphically. Geomorphic effect of recent snow avalanches identified by the spatial distribution of scarred trees in individual years corresponds with the extent of events visible from the orthophotos. We can confirm higher frequency of snow avalanche events since 1980s (17 out of 19 events) and significant increase during the last ten years. The future expected climatic changes associated with the changes in temperature and precipitation regime could significantly influence on the frequency of snow avalanches. Therefore, our results can become the starting line for more extensive dendrogeomorphic survey in the High Tatras Mountains in order to create a catalogue of all natural hazards for the future prediction and modelling of these phenomena in context of environmental changes.

Hydrological states and the resilience of deltaic forested wetlands

NASA Astrophysics Data System (ADS)

Keim, R.; Allen, S. T.

2017-12-01

The flooding regime constitutes a set of chronic disturbances that are largely responsible for ecosystem structure. However, disturbances do not always constitute stresses to plants that survive because of adaptations to flooded conditions. We examine baldcypress-water tupelo forested wetlands in the delta of the Mississippi River as a case study in mechanisms by which hydrologic change shapes wetland ecosystem change, supported by experimental evidence from remote sensing, tree-ring and other field studies, and meta-analysis across the literature. Decreased hydrologic variability caused by water control structures has reduced the frequency of flood events that increase growth of baldcypress and favor its establishment by reducing competition from other species. Hydrologic modifications that lead to semi-permanent, stagnant flooding constitute semi-permanent disturbance that prevents regeneration of any trees, reduces growth of established trees, and reduces stand density by causing mortality of some trees. However, baldcypress trees in low-density stands appear to be generally adapted for long-term survival in stagnant conditions. Thus, initial decreases in stand density after impoundment do not necessarily portend continued conversion away from forest because reduced inter-tree competition is a negative feedback on mortality. Overall, a natural hydrologic regime with high variability in riverine flooding favors denser stands with greater diversity of tree species, and the present, controlled hydrologic regime that has largely eliminated riverine flooding favors open stands. Sea-level rise will increase salinity that quickly leads to forest conversion to marsh, but will also increase stagnant, freshwater flooding further inland. These drivers of hydrologic change reduce carbon assimilation by forests, both by reduced stand-level productivity and decreased forested area.

Clustering Genes of Common Evolutionary History

PubMed Central

Gori, Kevin; Suchan, Tomasz; Alvarez, Nadir; Goldman, Nick; Dessimoz, Christophe

2016-01-01

Phylogenetic inference can potentially result in a more accurate tree using data from multiple loci. However, if the loci are incongruent—due to events such as incomplete lineage sorting or horizontal gene transfer—it can be misleading to infer a single tree. To address this, many previous contributions have taken a mechanistic approach, by modeling specific processes. Alternatively, one can cluster loci without assuming how these incongruencies might arise. Such “process-agnostic” approaches typically infer a tree for each locus and cluster these. There are, however, many possible combinations of tree distance and clustering methods; their comparative performance in the context of tree incongruence is largely unknown. Furthermore, because standard model selection criteria such as AIC cannot be applied to problems with a variable number of topologies, the issue of inferring the optimal number of clusters is poorly understood. Here, we perform a large-scale simulation study of phylogenetic distances and clustering methods to infer loci of common evolutionary history. We observe that the best-performing combinations are distances accounting for branch lengths followed by spectral clustering or Ward’s method. We also introduce two statistical tests to infer the optimal number of clusters and show that they strongly outperform the silhouette criterion, a general-purpose heuristic. We illustrate the usefulness of the approach by 1) identifying errors in a previous phylogenetic analysis of yeast species and 2) identifying topological incongruence among newly sequenced loci of the globeflower fly genus Chiastocheta. We release treeCl, a new program to cluster genes of common evolutionary history (http://git.io/treeCl). PMID:26893301

Seasonality and Disturbance Events in the Carbon Isotope Record of Pinus elliottii Tree Rings from Big Pine Key, Florida

NASA Astrophysics Data System (ADS)

Rebenack, C.; Anderson, W. T.; Cherubini, P.

2012-12-01

The South Florida coastal ecosystem is among the world's subtropical coastlines which are threatened by the potential effects of climate change. A well-developed localized paleohistory is essential in the understanding of the role climate variability/change has on both hydrological dynamics and disturbance event frequency and intensity; this understanding can then aid in the development of better predictive models. High resolution paleoclimate proxies, such as those developed from tree-ring archives, may be useful tools for extrapolating actual climate trends over time from the overlapping long-term and short-term climate cycles, such as the Atlantic Multidecadal Oscillation (AMO) and the El Niño-Southern Oscillation (ENSO). In South Florida, both the AMO and ENSO strongly influence seasonal precipitation, and a more complete grasp of how these cycles have affected the region in the past could be applied to future freshwater management practices. Dendrochronology records for the terrestrial subtropics, including South Florida, are sparse because seasonality for this region is precipitation-driven; this is in contrast to the drastic temperature changes experienced in the temperate latitudes. Subtropical seasonality may lead to the complete lack of visible rings or to the formation of ring structures that may or may not represent annual growth. Fortunately, it has recently been demonstrated that Pinus elliottii trees in South Florida produce distinct annual growth rings; however ring width was not found to significantly correlate with either the AMO or ENSO. Dendrochronology studies may be taken a step beyond the physical tree-ring proxies by using the carbon isotope ratios to infer information about physiological controls and environmental factors that affect the distribution of isotopes within the plant. It has been well established that the stable isotope composition of cellulose can be related to precipitation, drought, large-scale ocean/atmospheric oscillations, and disturbance events, such as tropical cyclone impacts. Because slash pine growth is dependent on water availability, a chronology developed using carbon isotopes may provide greater insight into plant stress over time and ultimately may lead to better correlations with climate oscillations. The work presented here is the result of a carbon-isotope study of four slash pine trees located across a freshwater gradient on Big Pine Key, Florida. A site chronology has been developed by cross-dating the δ13C records for each of the trees. The tree located on the distal edge of the freshwater gradient shows an overall enriched isotopic signature over time compared to the trees growing over a deeper part of the local freshwater lens, indicating that these trees are sensitive to water stress. In addition, the carbon isotope data show seasonal stomatal activity in the trees and indicate the timing of two disturbance events.

Signatures of cosmic-ray increase attributed to exceptional solar storms inferred from multiple cosmogenic radionuclide records

NASA Astrophysics Data System (ADS)

Mekhaldi, Florian; Muscheler, Raimund; Adolphi, Florian; Svensson, Anders; Aldahan, Ala; Possnert, Göran; McConnell, Joseph R.; Sigl, Michael; Welten, Kees C.; Woodruff, Thomas E.

2014-05-01

Miyake et al. (2012, 2013) discovered rapid increases of 14C content in tree rings dated to AD 774-5 and AD 993-4 which they have attributed to cosmic-ray events. These extreme particle events have no counterparts in the instrumental record and have been tentatively associated with solar proton events, supernovae and short gamma-ray bursts, which have very different energy spectra. Cosmogenic radionuclides such as 14C, 10Be and 36Cl arise from the interaction of cosmic rays with atmospheric nitrogen, oxygen and argon. These radio-isotopes are produced through different reaction pathways and vary with different energy dependencies of the production rate cross section. Owing to this, yield functions can be used to determine the energy level of incident particles. However, only 14C has been measured at high resolution to quantify the energy and thus the origin of the outbursts. We present an annually resolved record of 10Be from the NGRIP ice core for the two events. In addition, we also utilized the GRIP ice core 36Cl record in our analysis. Our results show that the differential production of cosmogenic 14C, 10Be and 36Cl is consistent with a solar energy spectrum. Considering the notable increase in radionuclides, the solar storms would have had to be substantially greater than the largest recorded geomagnetic storm, the so-called Carrington event. This challenges our understanding of the sun's dynamics. Furthermore, the events could possibly be of interest for the investigation of potential cosmic ray-cloud linkages (Svensmark & Friis-Christensen, 1997). Alternatively, such outbursts of energetic particles have the potential to deplete atmospheric ozone and alter atmospheric circulation. Ultimately, the magnitude of such particle events draws attention to the perhaps underestimated potential of the sun to cause great damage to modern technologies. References Miyake, F., Masuda, K. & Nakamura, T. Another rapid event in the carbon-14 content of tree rings. Nature Communications 4:1748, DOI: 10.1038/ncomms2783 (2013). Miyake, F., Nagaya, K., Masuda, K. & Nakamura, T. A signature of cosmic-ray increase in AD 774-775 from tree rings in Japan. Nature 486, 240-242, DOI: 210.1038/nature11123 (2012). Svensmark, H., & Friis-Christensen, E. Variation of cosmic ray flux and global cloud coverage - A missing link in solar-climate relationships. J. Atmos. Sol., Terr. Phys., 59, 225-1232, DOI: 10.1029/1998JD200091 (1997).

Evolution of aminoacyl-tRNA synthetases--analysis of unique domain architectures and phylogenetic trees reveals a complex history of horizontal gene transfer events.

PubMed

Wolf, Y I; Aravind, L; Grishin, N V; Koonin, E V

1999-08-01

Phylogenetic analysis of aminoacyl-tRNA synthetases (aaRSs) of all 20 specificities from completely sequenced bacterial, archaeal, and eukaryotic genomes reveals a complex evolutionary picture. Detailed examination of the domain architecture of aaRSs using sequence profile searches delineated a network of partially conserved domains that is even more elaborate than previously suspected. Several unexpected evolutionary connections were identified, including the apparent origin of the beta-subunit of bacterial GlyRS from the HD superfamily of hydrolases, a domain shared by bacterial AspRS and the B subunit of archaeal glutamyl-tRNA amidotransferases, and another previously undetected domain that is conserved in a subset of ThrRS, guanosine polyphosphate hydrolases and synthetases, and a family of GTPases. Comparison of domain architectures and multiple alignments resulted in the delineation of synapomorphies-shared derived characters, such as extra domains or inserts-for most of the aaRSs specificities. These synapomorphies partition sets of aaRSs with the same specificity into two or more distinct and apparently monophyletic groups. In conjunction with cluster analysis and a modification of the midpoint-rooting procedure, this partitioning was used to infer the likely root position in phylogenetic trees. The topologies of the resulting rooted trees for most of the aaRSs specificities are compatible with the evolutionary "standard model" whereby the earliest radiation event separated bacteria from the common ancestor of archaea and eukaryotes as opposed to the two other possible evolutionary scenarios for the three major divisions of life. For almost all aaRSs specificities, however, this simple scheme is confounded by displacement of some of the bacterial aaRSs by their eukaryotic or, less frequently, archaeal counterparts. Displacement of ancestral eukaryotic aaRS genes by bacterial ones, presumably of mitochondrial origin, was observed for three aaRSs. In contrast, there was no convincing evidence of displacement of archaeal aaRSs by bacterial ones. Displacement of aaRS genes by eukaryotic counterparts is most common among parasitic and symbiotic bacteria, particularly the spirochaetes, in which 10 of the 19 aaRSs seem to have been displaced by the respective eukaryotic genes and two by the archaeal counterpart. Unlike the primary radiation events between the three main divisions of life, that were readily traceable through the phylogenetic analysis of aaRSs, no consistent large-scale bacterial phylogeny could be established. In part, this may be due to additional gene displacement events among bacterial lineages. Argument is presented that, although lineage-specific gene loss might have contributed to the evolution of some of the aaRSs, this is not a viable alternative to horizontal gene transfer as the principal evolutionary phenomenon in this gene class.

The Probability of a Gene Tree Topology within a Phylogenetic Network with Applications to Hybridization Detection

PubMed Central

Yu, Yun; Degnan, James H.; Nakhleh, Luay

2012-01-01

Gene tree topologies have proven a powerful data source for various tasks, including species tree inference and species delimitation. Consequently, methods for computing probabilities of gene trees within species trees have been developed and widely used in probabilistic inference frameworks. All these methods assume an underlying multispecies coalescent model. However, when reticulate evolutionary events such as hybridization occur, these methods are inadequate, as they do not account for such events. Methods that account for both hybridization and deep coalescence in computing the probability of a gene tree topology currently exist for very limited cases. However, no such methods exist for general cases, owing primarily to the fact that it is currently unknown how to compute the probability of a gene tree topology within the branches of a phylogenetic network. Here we present a novel method for computing the probability of gene tree topologies on phylogenetic networks and demonstrate its application to the inference of hybridization in the presence of incomplete lineage sorting. We reanalyze a Saccharomyces species data set for which multiple analyses had converged on a species tree candidate. Using our method, though, we show that an evolutionary hypothesis involving hybridization in this group has better support than one of strict divergence. A similar reanalysis on a group of three Drosophila species shows that the data is consistent with hybridization. Further, using extensive simulation studies, we demonstrate the power of gene tree topologies at obtaining accurate estimates of branch lengths and hybridization probabilities of a given phylogenetic network. Finally, we discuss identifiability issues with detecting hybridization, particularly in cases that involve extinction or incomplete sampling of taxa. PMID:22536161

Comparison of rainfall and stemflow peak intensities and infiltration patterns for a mature coastal forest in British Columbia, Canada

NASA Astrophysics Data System (ADS)

van Meerveld, Ilja; Spencer, Sheena

2017-04-01

Most studies on stemflow have focused on the amount of stemflow in different forests or for different rainfall events. So far, few studies have looked at how stemflow intensity varies during rainfall events and how peak stemflow intensities compare to peak rainfall intensities. High stemflow intensities at the base of the tree, where roots and other preferential flow pathways are prevalent, may lead to faster and deeper infiltration of stemflow than rainfall and thus affect soil moisture dynamics and potentially also subsurface stormflow generation. We measured stemflow intensities for three Western hemlock, two Western red cedar, two Douglas-fir and one Birch tree in a mature coniferous forest in coastal British Columbia to determine how stemflow intensities were related to rainfall intensity. We sprayed a blue dye tracer on two Western hemlock trees (29 and 52 cm diameter at breast height (DBH)) to determine how stemflow water flows through the soil and to what depth it infiltrates. We also applied the blue dye tracer to an area between the trees to compare infiltration of stemflow with rainfall. Stemflow increased linearly with event total precipitation for all trees. The larger trees almost exclusively had funneling ratios (i.e. the volume of stemflow per unit basal area divided by the rainfall) smaller than one, regardless of species and event size. The funneling ratios for the small trees were generally larger for larger events (up to a funneling ratio of 20) but there was considerable scatter in this relation. Trees with a DBH <35 cm, which represent 24% of the total basal area of the study site, contributed 72% of the estimated total stemflow amount. Stemflow intensities (volume of stemflow per unit basal area per hour) often increased in a stepwise manner. When there were two precipitation bursts, stemflow intensity was usually highest during the second precipitation burst. However, when there were several hours of very low rainfall intensity between consecutive precipitation bursts, stemflow intensity was lower during the first burst after the break in rainfall. Peak stemflow intensities were higher than the maximum precipitation intensity. The blue dye that was applied to the tree stems was found more frequently at depth than near the soil surface. Stemflow flowed primarily through the 10 cm organic rich upper layer of the soil around the tree before flowing between or along live and dead roots, inside dead roots, around rocks and boulders deeper into the soil. Lateral flow was observed above a dense clay layer but where roots were able to penetrate the clay layer, the infiltrating water flowed deeper into the soil and (almost) reached the soil-bedrock interface. Stemflow appeared to infiltrate deeper (122 cm) than rainfall (85 cm) but this difference was in part due to variations in maximum soil depth. These results suggest that even though stemflow is only a minor component of the water balance, the double funnelling of stemflow may significantly affect soil moisture, recharge and runoff generation.

Unique haplotypes of cacao trees as revealed by trnH-psbA chloroplast DNA

PubMed Central

Gutiérrez-López, Nidia; Ovando-Medina, Isidro; Salvador-Figueroa, Miguel; Molina-Freaner, Francisco; Avendaño-Arrazate, Carlos H.

2016-01-01

Cacao trees have been cultivated in Mesoamerica for at least 4,000 years. In this study, we analyzed sequence variation in the chloroplast DNA trnH-psbA intergenic spacer from 28 cacao trees from different farms in the Soconusco region in southern Mexico. Genetic relationships were established by two analysis approaches based on geographic origin (five populations) and genetic origin (based on a previous study). We identified six polymorphic sites, including five insertion/deletion (indels) types and one transversion. The overall nucleotide diversity was low for both approaches (geographic = 0.0032 and genetic = 0.0038). Conversely, we obtained moderate to high haplotype diversity (0.66 and 0.80) with 10 and 12 haplotypes, respectively. The common haplotype (H1) for both networks included cacao trees from all geographic locations (geographic approach) and four genetic groups (genetic approach). This common haplotype (ancient) derived a set of intermediate haplotypes and singletons interconnected by one or two mutational steps, which suggested directional selection and event purification from the expansion of narrow populations. Cacao trees from Soconusco region were grouped into one cluster without any evidence of subclustering based on AMOVA (FST = 0) and SAMOVA (FST = 0.04393) results. One population (Mazatán) showed a high haplotype frequency; thus, this population could be considered an important reservoir of genetic material. The indels located in the trnH-psbA intergenic spacer of cacao trees could be useful as markers for the development of DNA barcoding. PMID:27076998

Phenology of Pacific Northwest tree species

Treesearch

Connie Harrington; Kevin Ford; Brad St. Clair

2016-01-01

Phenology is the study of the timing of recurring biological events. For foresters, the most commonly observed phenological events are budburst, flowering, and leaf fall, but other harder to observe events, such as diameter-growth initiation, are also important. Most events that occur in the spring are influenced by past exposure to cool (chilling) temperatures and...

Unified framework for triaxial accelerometer-based fall event detection and classification using cumulants and hierarchical decision tree classifier.

PubMed

Kambhampati, Satya Samyukta; Singh, Vishal; Manikandan, M Sabarimalai; Ramkumar, Barathram

2015-08-01

In this Letter, the authors present a unified framework for fall event detection and classification using the cumulants extracted from the acceleration (ACC) signals acquired using a single waist-mounted triaxial accelerometer. The main objective of this Letter is to find suitable representative cumulants and classifiers in effectively detecting and classifying different types of fall and non-fall events. It was discovered that the first level of the proposed hierarchical decision tree algorithm implements fall detection using fifth-order cumulants and support vector machine (SVM) classifier. In the second level, the fall event classification algorithm uses the fifth-order cumulants and SVM. Finally, human activity classification is performed using the second-order cumulants and SVM. The detection and classification results are compared with those of the decision tree, naive Bayes, multilayer perceptron and SVM classifiers with different types of time-domain features including the second-, third-, fourth- and fifth-order cumulants and the signal magnitude vector and signal magnitude area. The experimental results demonstrate that the second- and fifth-order cumulant features and SVM classifier can achieve optimal detection and classification rates of above 95%, as well as the lowest false alarm rate of 1.03%.

Fire-mediated dieback and compositional cascade in an Amazonian forest.

PubMed

Barlow, Jos; Peres, Carlos A

2008-05-27

The only fully coupled land-atmosphere global climate model predicts a widespread dieback of Amazonian forest cover through reduced precipitation. Although these predictions are controversial, the structural and compositional resilience of Amazonian forests may also have been overestimated, as current vegetation models fail to consider the potential role of fire in the degradation of forest ecosystems. We examine forest structure and composition in the Arapiuns River basin in the central Brazilian Amazon, evaluating post-fire forest recovery and the consequences of recurrent fires for the patterns of dominance of tree species. We surveyed tree plots in unburned and once-burned forests examined 1, 3 and 9 years after an unprecedented fire event, in twice-burned forests examined 3 and 9 years after fire and in thrice-burned forests examined 5 years after the most recent fire event. The number of trees recorded in unburned primary forest control plots was stable over time. However, in both once- and twice-burned forest plots, there was a marked recruitment into the 10-20cm diameter at breast height tree size classes between 3 and 9 years post-fire. Considering tree assemblage composition 9 years after the first fire contact, we observed (i) a clear pattern of community turnover among small trees and the most abundant shrubs and saplings, and (ii) that species that were common in any of the four burn treatments (unburned, once-, twice- and thrice-burned) were often rare or entirely absent in other burn treatments. We conclude that episodic wildfires can lead to drastic changes in forest structure and composition, with cascading shifts in forest composition following each additional fire event. Finally, we use these results to evaluate the validity of the savannization paradigm.

Quantifying tree mortality in a mixed species woodland using multitemporal high spatial resolution satellite imagery

USGS Publications Warehouse

Garrity, Steven R.; Allen, Craig D.; Brumby, Steven P.; Gangodagamage, Chandana; McDowell, Nate G.; Cai, D. Michael

2013-01-01

Widespread tree mortality events have recently been observed in several biomes. To effectively quantify the severity and extent of these events, tools that allow for rapid assessment at the landscape scale are required. Past studies using high spatial resolution satellite imagery have primarily focused on detecting green, red, and gray tree canopies during and shortly after tree damage or mortality has occurred. However, detecting trees in various stages of death is not always possible due to limited availability of archived satellite imagery. Here we assess the capability of high spatial resolution satellite imagery for tree mortality detection in a southwestern U.S. mixed species woodland using archived satellite images acquired prior to mortality and well after dead trees had dropped their leaves. We developed a multistep classification approach that uses: supervised masking of non-tree image elements; bi-temporal (pre- and post-mortality) differencing of normalized difference vegetation index (NDVI) and red:green ratio (RGI); and unsupervised multivariate clustering of pixels into live and dead tree classes using a Gaussian mixture model. Classification accuracies were improved in a final step by tuning the rules of pixel classification using the posterior probabilities of class membership obtained from the Gaussian mixture model. Classifications were produced for two images acquired post-mortality with overall accuracies of 97.9% and 98.5%, respectively. Classified images were combined with land cover data to characterize the spatiotemporal characteristics of tree mortality across areas with differences in tree species composition. We found that 38% of tree crown area was lost during the drought period between 2002 and 2006. The majority of tree mortality during this period was concentrated in piñon-juniper (Pinus edulis-Juniperus monosperma) woodlands. An additional 20% of the tree canopy died or was removed between 2006 and 2011, primarily in areas experiencing wildfire and management activity. -Our results demonstrate that unsupervised clustering of bi-temporal NDVI and RGI differences can be used to detect tree mortality resulting from numerous causes and in several forest cover types.

Managing Risk to Ensure a Successful Cassini/Huygens Saturn Orbit Insertion (SOI)

NASA Technical Reports Server (NTRS)

Witkowski, Mona M.; Huh, Shin M.; Burt, John B.; Webster, Julie L.

2004-01-01

I. Design: a) S/C designed to be largely single fault tolerant; b) Operate in flight demonstrated envelope, with margin; and c) Strict compliance with requirements & flight rules. II. Test: a) Baseline, fault & stress testing using flight system testbeds (H/W & S/W); b) In-flight checkout & demos to remove first time events. III. Failure Analysis: a) Critical event driven fault tree analysis; b) Risk mitigation & development of contingencies. IV) Residual Risks: a) Accepted pre-launch waivers to Single Point Failures; b) Unavoidable risks (e.g. natural disaster). V) Mission Assurance: a) Strict process for characterization of variances (ISAs, PFRs & Waivers; b) Full time Mission Assurance Manager reports to Program Manager: 1) Independent assessment of compliance with institutional standards; 2) Oversight & risk assessment of ISAs, PFRs & Waivers etc.; and 3) Risk Management Process facilitator.

Growth-mortality relationships in piñon pine (Pinus edulis) during severe droughts of the past century: shifting processes in space and time.

PubMed

Macalady, Alison K; Bugmann, Harald

2014-01-01

The processes leading to drought-associated tree mortality are poorly understood, particularly long-term predisposing factors, memory effects, and variability in mortality processes and thresholds in space and time. We use tree rings from four sites to investigate Pinus edulis mortality during two drought periods in the southwestern USA. We draw on recent sampling and archived collections to (1) analyze P. edulis growth patterns and mortality during the 1950s and 2000s droughts; (2) determine the influence of climate and competition on growth in trees that died and survived; and (3) derive regression models of growth-mortality risk and evaluate their performance across space and time. Recent growth was 53% higher in surviving vs. dying trees, with some sites exhibiting decades-long growth divergences associated with previous drought. Differential growth response to climate partly explained growth differences between live and dead trees, with responses wet/cool conditions most influencing eventual tree status. Competition constrained tree growth, and reduced trees' ability to respond to favorable climate. The best predictors in growth-mortality models included long-term (15-30 year) average growth rate combined with a metric of growth variability and the number of abrupt growth increases over 15 and 10 years, respectively. The most parsimonious models had high discriminatory power (ROC>0.84) and correctly classified ∼ 70% of trees, suggesting that aspects of tree growth, especially over decades, can be powerful predictors of widespread drought-associated die-off. However, model discrimination varied across sites and drought events. Weaker growth-mortality relationships and higher growth at lower survival probabilities for some sites during the 2000s event suggest a shift in mortality processes from longer-term growth-related constraints to shorter-term processes, such as rapid metabolic decline even in vigorous trees due to acute drought stress, and/or increases in the attack rate of both chronically stressed and more vigorous trees by bark beetles.

Phytomonitoring of chlorinated ethenes in trees: a four-year study of seasonal chemodynamics in planta.

PubMed

Limmer, Matt A; Holmes, Amanda J; Burken, Joel G

2014-09-16

Long-term monitoring (LTM) of groundwater remedial projects is costly and time-consuming, particularly when using phytoremediation, a long-term remedial approach. The use of trees as sensors of groundwater contamination (i.e., phytoscreening) has been widely described, although the use of trees to provide long-term monitoring of such plumes (phytomonitoring) has been more limited due to unexplained variability of contaminant concentrations in trees. To assess this variability, we developed an in planta sampling method to obtain high-frequency measurements of chlorinated ethenes in oak (Quercus rubra) and baldcypress (Taxodium distichum) trees growing above a contaminated plume during a 4-year trial. The data set revealed that contaminant concentrations increased rapidly with transpiration in the spring and decreased in the fall, resulting in perchloroethene (PCE) and trichloroethene (TCE) sapwood concentrations an order of magnitude higher in late summer as compared to winter. Heartwood PCE and TCE concentrations were more buffered against seasonal effects. Rainfall events caused negligible dilution of contaminant concentrations in trees after precipitation events. Modeling evapotranspiration potential from meteorological data and comparing the modeled uptake and transport with the 4 years of high frequency data provides a foundation to advance the implementation of phytomonitoring and improved understanding of plant contaminant interactions.

Drivers and mechanisms of tree mortality in moist tropical forests.

PubMed

McDowell, Nate; Allen, Craig D; Anderson-Teixeira, Kristina; Brando, Paulo; Brienen, Roel; Chambers, Jeff; Christoffersen, Brad; Davies, Stuart; Doughty, Chris; Duque, Alvaro; Espirito-Santo, Fernando; Fisher, Rosie; Fontes, Clarissa G; Galbraith, David; Goodsman, Devin; Grossiord, Charlotte; Hartmann, Henrik; Holm, Jennifer; Johnson, Daniel J; Kassim, Abd Rahman; Keller, Michael; Koven, Charlie; Kueppers, Lara; Kumagai, Tomo'omi; Malhi, Yadvinder; McMahon, Sean M; Mencuccini, Maurizio; Meir, Patrick; Moorcroft, Paul; Muller-Landau, Helene C; Phillips, Oliver L; Powell, Thomas; Sierra, Carlos A; Sperry, John; Warren, Jeff; Xu, Chonggang; Xu, Xiangtao

2018-02-16

Tree mortality rates appear to be increasing in moist tropical forests (MTFs) with significant carbon cycle consequences. Here, we review the state of knowledge regarding MTF tree mortality, create a conceptual framework with testable hypotheses regarding the drivers, mechanisms and interactions that may underlie increasing MTF mortality rates, and identify the next steps for improved understanding and reduced prediction. Increasing mortality rates are associated with rising temperature and vapor pressure deficit, liana abundance, drought, wind events, fire and, possibly, CO 2 fertilization-induced increases in stand thinning or acceleration of trees reaching larger, more vulnerable heights. The majority of these mortality drivers may kill trees in part through carbon starvation and hydraulic failure. The relative importance of each driver is unknown. High species diversity may buffer MTFs against large-scale mortality events, but recent and expected trends in mortality drivers give reason for concern regarding increasing mortality within MTFs. Models of tropical tree mortality are advancing the representation of hydraulics, carbon and demography, but require more empirical knowledge regarding the most common drivers and their subsequent mechanisms. We outline critical datasets and model developments required to test hypotheses regarding the underlying causes of increasing MTF mortality rates, and improve prediction of future mortality under climate change. No claim to original US government works New Phytologist © 2018 New Phytologist Trust.

Widespread crown condition decline, food web disruption, and amplified tree mortality with increased climate change-type drought

PubMed Central

Carnicer, Jofre; Coll, Marta; Ninyerola, Miquel; Pons, Xavier; Sánchez, Gerardo; Peñuelas, Josep

2011-01-01

Climate change is progressively increasing severe drought events in the Northern Hemisphere, causing regional tree die-off events and contributing to the global reduction of the carbon sink efficiency of forests. There is a critical lack of integrated community-wide assessments of drought-induced responses in forests at the macroecological scale, including defoliation, mortality, and food web responses. Here we report a generalized increase in crown defoliation in southern European forests occurring during 1987–2007. Forest tree species have consistently and significantly altered their crown leaf structures, with increased percentages of defoliation in the drier parts of their distributions in response to increased water deficit. We assessed the demographic responses of trees associated with increased defoliation in southern European forests, specifically in the Iberian Peninsula region. We found that defoliation trends are paralleled by significant increases in tree mortality rates in drier areas that are related to tree density and temperature effects. Furthermore, we show that severe drought impacts are associated with sudden changes in insect and fungal defoliation dynamics, creating long-term disruptive effects of drought on food webs. Our results reveal a complex geographical mosaic of species-specific responses to climate change–driven drought pressures on the Iberian Peninsula, with an overwhelmingly predominant trend toward increased drought damage. PMID:21220333

Widespread crown condition decline, food web disruption, and amplified tree mortality with increased climate change-type drought.

PubMed

Carnicer, Jofre; Coll, Marta; Ninyerola, Miquel; Pons, Xavier; Sánchez, Gerardo; Peñuelas, Josep

2011-01-25

Climate change is progressively increasing severe drought events in the Northern Hemisphere, causing regional tree die-off events and contributing to the global reduction of the carbon sink efficiency of forests. There is a critical lack of integrated community-wide assessments of drought-induced responses in forests at the macroecological scale, including defoliation, mortality, and food web responses. Here we report a generalized increase in crown defoliation in southern European forests occurring during 1987-2007. Forest tree species have consistently and significantly altered their crown leaf structures, with increased percentages of defoliation in the drier parts of their distributions in response to increased water deficit. We assessed the demographic responses of trees associated with increased defoliation in southern European forests, specifically in the Iberian Peninsula region. We found that defoliation trends are paralleled by significant increases in tree mortality rates in drier areas that are related to tree density and temperature effects. Furthermore, we show that severe drought impacts are associated with sudden changes in insect and fungal defoliation dynamics, creating long-term disruptive effects of drought on food webs. Our results reveal a complex geographical mosaic of species-specific responses to climate change-driven drought pressures on the Iberian Peninsula, with an overwhelmingly predominant trend toward increased drought damage.

Environment and paleoecology of a 12 ka mid-North American Younger Dryas forest chronicled in tree rings

USGS Publications Warehouse

Panyushkina, Irina P.; Leavitt, Steven W.; Thompson, Todd A.; Schneider, Allan F.; Lange, Todd

2008-01-01

Until now, availability of wood from the Younger Dryas abrupt cooling event (YDE) in N. America ca. 12.9 to 11.6 ka has been insufficient to develop high-resolution chronologies for refining our understanding of YDE conditions. Here we present a multi-proxy tree-ring chronology (ring widths, “events” evidenced by microanatomy and macro features, stable isotopes) from a buried black spruce forest in the Great Lakes area (Liverpool East site), spanning 116 yr at ca. 12,000 cal yr BP. During this largely cold and wet period, the proxies convey a coherent and precise forest history including frost events, tilting, drowning and burial in estuarine sands as the Laurentide Ice Sheet deteriorated. In the middle of the period, a short mild interval appears to have launched the final and largest episode of tree recruitment. Ultimately the tops of the trees were sheared off after death, perhaps by wind-driven ice floes, culminating an interval of rising water and sediment deposition around the base of the trees. Although relative influences of the continental ice sheet and local effects from ancestral Lake Michigan are indeterminate, the tree-ring proxies provide important insight into environment and ecology of a N. American YDE boreal forest stand.

TU-AB-BRD-02: Failure Modes and Effects Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huq, M.

2015-06-15

Current quality assurance and quality management guidelines provided by various professional organizations are prescriptive in nature, focusing principally on performance characteristics of planning and delivery devices. However, published analyses of events in radiation therapy show that most events are often caused by flaws in clinical processes rather than by device failures. This suggests the need for the development of a quality management program that is based on integrated approaches to process and equipment quality assurance. Industrial engineers have developed various risk assessment tools that are used to identify and eliminate potential failures from a system or a process before amore » failure impacts a customer. These tools include, but are not limited to, process mapping, failure modes and effects analysis, fault tree analysis. Task Group 100 of the American Association of Physicists in Medicine has developed these tools and used them to formulate an example risk-based quality management program for intensity-modulated radiotherapy. This is a prospective risk assessment approach that analyzes potential error pathways inherent in a clinical process and then ranks them according to relative risk, typically before implementation, followed by the design of a new process or modification of the existing process. Appropriate controls are then put in place to ensure that failures are less likely to occur and, if they do, they will more likely be detected before they propagate through the process, compromising treatment outcome and causing harm to the patient. Such a prospective approach forms the basis of the work of Task Group 100 that has recently been approved by the AAPM. This session will be devoted to a discussion of these tools and practical examples of how these tools can be used in a given radiotherapy clinic to develop a risk based quality management program. Learning Objectives: Learn how to design a process map for a radiotherapy process Learn how to perform failure modes and effects analysis analysis for a given process Learn what fault trees are all about Learn how to design a quality management program based upon the information obtained from process mapping, failure modes and effects analysis and fault tree analysis. Dunscombe: Director, TreatSafely, LLC and Center for the Assessment of Radiological Sciences; Consultant to IAEA and Varian Thomadsen: President, Center for the Assessment of Radiological Sciences Palta: Vice President of the Center for the Assessment of Radiological Sciences.« less

Drought timing influences the legacy of tree growth recovery.

PubMed

Huang, Mengtian; Wang, Xuhui; Keenan, Trevor F; Piao, Shilong

2018-05-04

Whether and how the timing of extreme events affects the direction and magnitude of legacy effects on tree growth is poorly understood. In this study, we use a global database of Ring-Width Index (RWI) from 2,500 sites to examine the impact and legacy effects (the departure of observed RWI from expected RWI) of extreme drought events during 1948-2008, with a particular focus on the influence of drought timing. We assessed the recovery of stem radial growth in the years following severe drought events with separate groupings designed to characterize the timing of the drought. We found that legacies from extreme droughts during the dry season (DS droughts) lasted longer and had larger impacts in each of the 3 years post drought than those from extreme droughts during the wet season (WS droughts). At the global scale, the average integrated legacy from DS droughts (0.18) was about nine times that from WS droughts (0.02). Site-level comparisons also suggest stronger negative impacts or weaker positive impacts of DS droughts on tree growth than WS droughts. Our results, therefore, highlight that the timing of drought is a crucial factor determining drought impacts on tree recovery. Further increases in baseline aridity could therefore exacerbate the impact of punctuated droughts on terrestrial ecosystems. © 2018 John Wiley & Sons Ltd.

Reduced transpiration response to precipitation pulses precedes mortality in a piñon-juniper woodland subject to prolonged drought.

PubMed

Plaut, Jennifer A; Wadsworth, W Duncan; Pangle, Robert; Yepez, Enrico A; McDowell, Nate G; Pockman, William T

2013-10-01

Global climate change is predicted to alter the intensity and duration of droughts, but the effects of changing precipitation patterns on vegetation mortality are difficult to predict. Our objective was to determine whether prolonged drought or above-average precipitation altered the capacity to respond to the individual precipitation pulses that drive productivity and survival. We analyzed 5 yr of data from a rainfall manipulation experiment in piñon-juniper (Pinus edulis-Juniperus monosperma) woodland using mixed effects models of transpiration response to event size, antecedent soil moisture, and post-event vapor pressure deficit. Replicated treatments included irrigation, drought, ambient control and infrastructure control. Mortality was highest under drought, and the reduced post-pulse transpiration in the droughted trees that died was attributable to treatment effects beyond drier antecedent conditions and reduced event size. In particular, trees that died were nearly unresponsive to antecedent shallow soil moisture, suggesting reduced shallow absorbing root area. Irrigated trees showed an enhanced response to precipitation pulses. Prolonged drought initiates a downward spiral whereby trees are increasingly unable to utilize pulsed soil moisture. Thus, the additive effects of future, more frequent droughts may increase drought-related mortality. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

[The Application of the Fault Tree Analysis Method in Medical Equipment Maintenance].

PubMed

Liu, Hongbin

2015-11-01

In this paper, the traditional fault tree analysis method is presented, detailed instructions for its application characteristics in medical instrument maintenance is made. It is made significant changes when the traditional fault tree analysis method is introduced into the medical instrument maintenance: gave up the logic symbolic, logic analysis and calculation, gave up its complicated programs, and only keep its image and practical fault tree diagram, and the fault tree diagram there are also differences: the fault tree is no longer a logical tree but the thinking tree in troubleshooting, the definition of the fault tree's nodes is different, the composition of the fault tree's branches is also different.

36 CFR 292.46 - Timber harvesting activities.

Code of Federal Regulations, 2014 CFR

2014-07-01

... hazard trees; or to respond to natural events such as wildfire, flood, earthquake, volcanic eruption, high winds, and disease or insect infestation. (2) Where authorized, trees may be harvested by... landscape to the extent practicable. (b) Wild and Scenic Rivers. The following standards and guidelines...

36 CFR 292.46 - Timber harvesting activities.

Code of Federal Regulations, 2011 CFR

2011-07-01

... hazard trees; or to respond to natural events such as wildfire, flood, earthquake, volcanic eruption, high winds, and disease or insect infestation. (2) Where authorized, trees may be harvested by... landscape to the extent practicable. (b) Wild and Scenic Rivers. The following standards and guidelines...

36 CFR 292.46 - Timber harvesting activities.

Code of Federal Regulations, 2013 CFR

2013-07-01

... hazard trees; or to respond to natural events such as wildfire, flood, earthquake, volcanic eruption, high winds, and disease or insect infestation. (2) Where authorized, trees may be harvested by... landscape to the extent practicable. (b) Wild and Scenic Rivers. The following standards and guidelines...

36 CFR 292.46 - Timber harvesting activities.

Code of Federal Regulations, 2012 CFR

2012-07-01

... hazard trees; or to respond to natural events such as wildfire, flood, earthquake, volcanic eruption, high winds, and disease or insect infestation. (2) Where authorized, trees may be harvested by... landscape to the extent practicable. (b) Wild and Scenic Rivers. The following standards and guidelines...

Reliability analysis of the solar array based on Fault Tree Analysis

NASA Astrophysics Data System (ADS)

Jianing, Wu; Shaoze, Yan

2011-07-01

The solar array is an important device used in the spacecraft, which influences the quality of in-orbit operation of the spacecraft and even the launches. This paper analyzes the reliability of the mechanical system and certifies the most vital subsystem of the solar array. The fault tree analysis (FTA) model is established according to the operating process of the mechanical system based on DFH-3 satellite; the logical expression of the top event is obtained by Boolean algebra and the reliability of the solar array is calculated. The conclusion shows that the hinges are the most vital links between the solar arrays. By analyzing the structure importance(SI) of the hinge's FTA model, some fatal causes, including faults of the seal, insufficient torque of the locking spring, temperature in space, and friction force, can be identified. Damage is the initial stage of the fault, so limiting damage is significant to prevent faults. Furthermore, recommendations for improving reliability associated with damage limitation are discussed, which can be used for the redesigning of the solar array and the reliability growth planning.

Integrated Safety Risk Reduction Approach to Enhancing Human-Rated Spaceflight Safety

NASA Astrophysics Data System (ADS)

Mikula, J. F. Kip

2005-12-01

This paper explores and defines the current accepted concept and philosophy of safety improvement based on a Reliability enhancement (called here Reliability Enhancement Based Safety Theory [REBST]). In this theory a Reliability calculation is used as a measure of the safety achieved on the program. This calculation may be based on a math model or a Fault Tree Analysis (FTA) of the system, or on an Event Tree Analysis (ETA) of the system's operational mission sequence. In each case, the numbers used in this calculation are hardware failure rates gleaned from past similar programs. As part of this paper, a fictional but representative case study is provided that helps to illustrate the problems and inaccuracies of this approach to safety determination. Then a safety determination and enhancement approach based on hazard, worst case analysis, and safety risk determination (called here Worst Case Based Safety Theory [WCBST]) is included. This approach is defined and detailed using the same example case study as shown in the REBST case study. In the end it is concluded that an approach combining the two theories works best to reduce Safety Risk.

Applications of High Resolution Laser Induced Breakdown Spectroscopy for Environmental and Biological Samples

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martin, Madhavi Z; Labbe, Nicole; Wagner, Rebekah J.

2013-01-01

This chapter details the application of LIBS in a number of environmental areas of research such as carbon sequestration and climate change. LIBS has also been shown to be useful in other high resolution environmental applications for example, elemental mapping and detection of metals in plant materials. LIBS has also been used in phytoremediation applications. Other biological research involves a detailed understanding of wood chemistry response to precipitation variations and also to forest fires. A cross-section of Mountain pine (pinceae Pinus pungen Lamb.) was scanned using a translational stage to determine the differences in the chemical features both before andmore » after a fire event. Consequently, by monitoring the elemental composition pattern of a tree and by looking for abrupt changes, one can reconstruct the disturbance history of a tree and a forest. Lastly we have shown that multivariate analysis of the LIBS data is necessary to standardize the analysis and correlate to other standard laboratory techniques. LIBS along with multivariate statistical analysis makes it a very powerful technology that can be transferred from laboratory to field applications with ease.« less

Seasonality of weather and tree phenology in a tropical evergreen mountain rain forest.

PubMed

Bendix, J; Homeier, J; Cueva, E Ortiz; Emck, P; Breckle, S-W; Richter, M; Beck, E

2006-07-01

Flowering and fruiting as phenological events of 12 tree species in an evergreen tropical mountain rain forest in southern Ecuador were examined over a period of 3-4 years. Leaf shedding of two species was observed for 12 months. Parallel to the phenological recordings, meteorological parameters were monitored in detail and related to the flowering and fruiting activity of the trees. In spite of the perhumid climate of that area, a high degree of intra- and inter-specific synchronisation of phenological traits was apparent. With the exception of one species that flowered more or less continuously, two groups of trees could be observed, one of which flowered during the less humid months (September to October) while the second group started to initiate flowers towards the end of that phase and flowered during the heavy rains (April to July). As reflected by correlation coefficients, the all-time series of meteorological parameters showed a distinct seasonality of 8-12 months, apparently following the quasi-periodic oscillation of precipitation and related cloudiness. As revealed by power spectrum analysis and Markov persistence, rainfall and minimum temperature appear to be the only parameters with a periodicity free of long-term variations. The phenological events of most of the plant species showed a similar periodicity of 8-12 months, which followed the annual oscillation of relatively less and more humid periods and thus was in phase or in counter-phase with the oscillations of the meteorological parameters. Periods of unusual cold or dryness, presumably resulting from underlying longer-term trends or oscillations (such as ENSO), affected the homogeneity of quasi-12-month flowering events, fruit maturation and also the production of germinable seeds. Some species show underlying quasi-2-year-oscillations, for example that synchronise with the development of air temperature; others reveal an underlying decrease or increase in flowering activity over the observation period, influenced for instance by solar irradiance. As Ecuador suffers the highest rate of deforestation in South America, there is an urgent need for indigenous plant material for reforestation. A detailed knowledge of the biology of reproduction in relation to governing external factors (mainly climate) is thus required.

Tree mortality across biomes is promoted by drought intensity, lower wood density and higher specific leaf area

USGS Publications Warehouse

Greenwood, Sarah; Ruiz-Benito, Paloma; Martinez-Vilalta, Jordi; Lloret, Francisco; Kitzberger, Thomas; Allen, Craig D.; Fensham, Rod; Laughlin, Daniel C.; Kattge, Jens; Bönisch, Gerhard; Kraft, Nathan J. B.; Jump, Alistair S.

2017-01-01

Drought events are increasing globally, and reports of consequent forest mortality are widespread. However, due to a lack of a quantitative global synthesis, it is still not clear whether drought-induced mortality rates differ among global biomes and whether functional traits influence the risk of drought-induced mortality. To address these uncertainties, we performed a global meta-analysis of 58 studies of drought-induced forest mortality. Mortality rates were modelled as a function of drought, temperature, biomes, phylogenetic and functional groups and functional traits. We identified a consistent global-scale response, where mortality increased with drought severity [log mortality (trees trees−1 year−1) increased 0.46 (95% CI = 0.2–0.7) with one SPEI unit drought intensity]. We found no significant differences in the magnitude of the response depending on forest biomes or between angiosperms and gymnosperms or evergreen and deciduous tree species. Functional traits explained some of the variation in drought responses between species (i.e. increased from 30 to 37% when wood density and specific leaf area were included). Tree species with denser wood and lower specific leaf area showed lower mortality responses. Our results illustrate the value of functional traits for understanding patterns of drought-induced tree mortality and suggest that mortality could become increasingly widespread in the future.

A novel, highly divergent ssDNA virus identified in Brazil infecting apple, pear and grapevine.

PubMed

Basso, Marcos Fernando; da Silva, José Cleydson Ferreira; Fajardo, Thor Vinícius Martins; Fontes, Elizabeth Pacheco Batista; Zerbini, Francisco Murilo

2015-12-02

Fruit trees of temperate and tropical climates are of great economical importance worldwide and several viruses have been reported affecting their productivity and longevity. Fruit trees of different Brazilian regions displaying virus-like symptoms were evaluated for infection by circular DNA viruses. Seventy-four fruit trees were sampled and a novel, highly divergent, monopartite circular ssDNA virus was cloned from apple, pear and grapevine trees. Forty-five complete viral genomes were sequenced, with a size of approx. 3.4 kb and organized into five ORFs. Deduced amino acid sequences showed identities in the range of 38% with unclassified circular ssDNA viruses, nanoviruses and alphasatellites (putative Replication-associated protein, Rep), and begomo-, curto- and mastreviruses (putative coat protein, CP, and movement protein, MP). A large intergenic region contains a short palindromic sequence capable of forming a hairpin-like structure with the loop sequence TAGTATTAC, identical to the conserved nonanucleotide of circoviruses, nanoviruses and alphasatellites. Recombination events were not detected and phylogenetic analysis showed a relationship with circo-, nano- and geminiviruses. PCR confirmed the presence of this novel ssDNA virus in field plants. Infectivity tests using the cloned viral genome confirmed its ability to infect apple and pear tree seedlings, but not Nicotiana benthamiana. The name "Temperate fruit decay-associated virus" (TFDaV) is proposed for this novel virus. Copyright © 2015 Elsevier B.V. All rights reserved.

Using of bayesian networks to estimate the probability of "NATECH" scenario occurrence

NASA Astrophysics Data System (ADS)

Dobes, Pavel; Dlabka, Jakub; Jelšovská, Katarína; Polorecká, Mária; Baudišová, Barbora; Danihelka, Pavel

2015-04-01

In the twentieth century, implementation of Bayesian statistics and probability was not much used (may be it wasn't a preferred approach) in the area of natural and industrial risk analysis and management. Neither it was used within analysis of so called NATECH accidents (chemical accidents triggered by natural events, such as e.g. earthquakes, floods, lightning etc.; ref. E. Krausmann, 2011, doi:10.5194/nhess-11-921-2011). Main role, from the beginning, played here so called "classical" frequentist probability (ref. Neyman, 1937), which rely up to now especially on the right/false results of experiments and monitoring and didn't enable to count on expert's beliefs, expectations and judgements (which is, on the other hand, one of the once again well known pillars of Bayessian approach to probability). In the last 20 or 30 years, there is possible to observe, through publications and conferences, the Renaissance of Baysssian statistics into many scientific disciplines (also into various branches of geosciences). The necessity of a certain level of trust in expert judgment within risk analysis is back? After several decades of development on this field, it could be proposed following hypothesis (to be checked): "We couldn't estimate probabilities of complex crisis situations and their TOP events (many NATECH events could be classified as crisis situations or emergencies), only by classical frequentist approach, but also by using of Bayessian approach (i.e. with help of prestaged Bayessian Network including expert belief and expectation as well as classical frequentist inputs). Because - there is not always enough quantitative information from monitoring of historical emergencies, there could be several dependant or independant variables necessary to consider and in generally - every emergency situation always have a little different run." In this topic, team of authors presents its proposal of prestaged typized Bayessian network model for specified NATECH scenario (heavy rainfalls AND/OR melting snow OR earthquake -> landslides AND/OR floods -> major chemical accident), comparing it with "Black Box approach" and with so called "Bow-tie approach" (ref. C. A. Brebbia, Risk Analysis VIII, p.103-111 , WIT Press, 2012) - visualisation of development of the scenario with possibility to calculate frequencies (TOP event of the scenario, developed both ways down to initation events and upwards to end accidental events, using Fault Tree Analysis and Event Tree Analysis methods). This model can include also possible terrorist attack on the chemical facility with potential of major release of chemical into the environmental compartments (water, soil, air), with the goal to threaten environmental safety in the specific area. The study was supported by the project no. VG20132015128 "Increasing of the Environmental Safety & Security by the Prevention of Industrial Chemicals Misuse to the Terrorism", supported by the Ministry of the Interior of the Czech Republic through Security Research Programme, 2013-2015.

Mapping mountain pine beetle mortality through growth trend analysis of time-series landsat data

USGS Publications Warehouse

Liang, Lu; Chen, Yanlei; Hawbaker, Todd J.; Zhu, Zhi-Liang; Gong, Peng

2014-01-01

Disturbances are key processes in the carbon cycle of forests and other ecosystems. In recent decades, mountain pine beetle (MPB; Dendroctonus ponderosae) outbreaks have become more frequent and extensive in western North America. Remote sensing has the ability to fill the data gaps of long-term infestation monitoring, but the elimination of observational noise and attributing changes quantitatively are two main challenges in its effective application. Here, we present a forest growth trend analysis method that integrates Landsat temporal trajectories and decision tree techniques to derive annual forest disturbance maps over an 11-year period. The temporal trajectory component successfully captures the disturbance events as represented by spectral segments, whereas decision tree modeling efficiently recognizes and attributes events based upon the characteristics of the segments. Validated against a point set sampled across a gradient of MPB mortality, 86.74% to 94.00% overall accuracy was achieved with small variability in accuracy among years. In contrast, the overall accuracies of single-date classifications ranged from 37.20% to 75.20% and only become comparable with our approach when the training sample size was increased at least four-fold. This demonstrates that the advantages of this time series work flow exist in its small training sample size requirement. The easily understandable, interpretable and modifiable characteristics of our approach suggest that it could be applicable to other ecoregions.

The Source of Adult Age Differences in Event-Based Prospective Memory: A Multinomial Modeling Approach

ERIC Educational Resources Information Center

Smith, Rebekah E.; Bayen, Ute J.

2006-01-01

Event-based prospective memory involves remembering to perform an action in response to a particular future event. Normal younger and older adults performed event-based prospective memory tasks in 2 experiments. The authors applied a formal multinomial processing tree model of prospective memory (Smith & Bayen, 2004) to disentangle age differences…

Methodology development for quantitative optimization of security enhancement in medical information systems -Case study in a PACS and a multi-institutional radiotherapy database-.

PubMed

Haneda, Kiyofumi; Umeda, Tokuo; Koyama, Tadashi; Harauchi, Hajime; Inamura, Kiyonari

2002-01-01

The target of our study is to establish the methodology for analyzing level of security requirements, for searching suitable security measures and for optimizing security distribution to every portion of medical practice. Quantitative expression must be introduced to our study as possible for the purpose of easy follow up of security procedures and easy evaluation of security outcomes or results. Results of system analysis by fault tree analysis (FTA) clarified that subdivided system elements in detail contribute to much more accurate analysis. Such subdivided composition factors very much depended on behavior of staff, interactive terminal devices, kinds of service, and routes of network. As conclusion, we found the methods to analyze levels of security requirements for each medical information systems employing FTA, basic events for each composition factor and combination of basic events. Methods for searching suitable security measures were found. Namely risk factors for each basic event, number of elements for each composition factor and candidates of security measure elements were found. Method to optimize the security measures for each medical information system was proposed. Namely optimum distribution of risk factors in terms of basic events were figured out, and comparison of them between each medical information systems became possible.

DG TO FT - AUTOMATIC TRANSLATION OF DIGRAPH TO FAULT TREE MODELS

NASA Technical Reports Server (NTRS)

Iverson, D. L.

1994-01-01

Fault tree and digraph models are frequently used for system failure analysis. Both types of models represent a failure space view of the system using AND and OR nodes in a directed graph structure. Each model has its advantages. While digraphs can be derived in a fairly straightforward manner from system schematics and knowledge about component failure modes and system design, fault tree structure allows for fast processing using efficient techniques developed for tree data structures. The similarities between digraphs and fault trees permits the information encoded in the digraph to be translated into a logically equivalent fault tree. The DG TO FT translation tool will automatically translate digraph models, including those with loops or cycles, into fault tree models that have the same minimum cut set solutions as the input digraph. This tool could be useful, for example, if some parts of a system have been modeled using digraphs and others using fault trees. The digraphs could be translated and incorporated into the fault trees, allowing them to be analyzed using a number of powerful fault tree processing codes, such as cut set and quantitative solution codes. A cut set for a given node is a group of failure events that will cause the failure of the node. A minimum cut set for a node is any cut set that, if any of the failures in the set were to be removed, the occurrence of the other failures in the set will not cause the failure of the event represented by the node. Cut sets calculations can be used to find dependencies, weak links, and vital system components whose failures would cause serious systems failure. The DG TO FT translation system reads in a digraph with each node listed as a separate object in the input file. The user specifies a terminal node for the digraph that will be used as the top node of the resulting fault tree. A fault tree basic event node representing the failure of that digraph node is created and becomes a child of the terminal root node. A subtree is created for each of the inputs to the digraph terminal node and the root of those subtrees are added as children of the top node of the fault tree. Every node in the digraph upstream of the terminal node will be visited and converted. During the conversion process, the algorithm keeps track of the path from the digraph terminal node to the current digraph node. If a node is visited twice, then the program has found a cycle in the digraph. This cycle is broken by finding the minimal cut sets of the twice visited digraph node and forming those cut sets into subtrees. Another implementation of the algorithm resolves loops by building a subtree based on the digraph minimal cut sets calculation. It does not reduce the subtree to minimal cut set form. This second implementation produces larger fault trees, but runs much faster than the version using minimal cut sets since it does not spend time reducing the subtrees to minimal cut sets. The fault trees produced by DG TO FT will contain OR gates, AND gates, Basic Event nodes, and NOP gates. The results of a translation can be output as a text object description of the fault tree similar to the text digraph input format. The translator can also output a LISP language formatted file and an augmented LISP file which can be used by the FTDS (ARC-13019) diagnosis system, available from COSMIC, which performs diagnostic reasoning using the fault tree as a knowledge base. DG TO FT is written in C-language to be machine independent. It has been successfully implemented on a Sun running SunOS, a DECstation running ULTRIX, a Macintosh running System 7, and a DEC VAX running VMS. The RAM requirement varies with the size of the models. DG TO FT is available in UNIX tar format on a .25 inch streaming magnetic tape cartridge (standard distribution) or on a 3.5 inch diskette. It is also available on a 3.5 inch Macintosh format diskette or on a 9-track 1600 BPI magnetic tape in DEC VAX FILES-11 format. Sample input and sample output are provided on the distribution medium. An electronic copy of the documentation in Macintosh Microsoft Word format is provided on the distribution medium. DG TO FT was developed in 1992. Sun, and SunOS are trademarks of Sun Microsystems, Inc. DECstation, ULTRIX, VAX, and VMS are trademarks of Digital Equipment Corporation. UNIX is a registered trademark of AT&T Bell Laboratories. Macintosh is a registered trademark of Apple Computer, Inc. System 7 is a trademark of Apple Computers Inc. Microsoft Word is a trademark of Microsoft Corporation.

Improving the water use efficiency of olive trees growing in water harvesting systems

NASA Astrophysics Data System (ADS)

Berliner, Pedro; Leake, Salomon; Carmi, Gennady; Agam, Nurit

2017-04-01

Water is a primary limiting factor for agricultural development in many arid and semi-arid regions in which a runoff generation is a rather frequent event. If conveyed to dyke surrounded plots and ponded, runoff water can thereafter be used for tree production. One of the most promising runoff collection configurations is that of micro-catchments in which water is collected close to the area in which runoff was generated and stored in adjacent shallow pits. The objective of this work was to assess the effect of the geometry of runoff water collection area (shallow pit or trench) on direct evaporative water losses and on the water use efficiency of olive trees grown in them. The study was conducted during the summer of 2013 and 2014. In this study regular micro-catchments with basins of 9 m2 (3 x 3 m) by 0.1 m deep were compared with trenches of one meter deep and one meter wide. Each configuration was replicated three times. One tree was planted in each shallow basin and the distance between trees in the 12 m long trench was four meters. Access tubes for neutron probes were installed in the micro-catchments and trenches (four and seven, respectively) to depths of 2.5 m. Soil water content in the soil profile was monitored periodically throughout drying periods in between simulated runoff events. Transpiration of the trees was estimated from half-hourly sap flow measurements using a Granier system. Total transpiration fluxes were computed for time intervals corresponding to consecutive soil water measurements. During the first year, a large runoff event was simulated by applying once four cubic meters to each plot; and in the second year the same volume of water was split into four applications, simulating a series of small runoff events. In both geometries, trees received the same amount of water per tree. Evaporation from trenches and micro-catchments was estimated as the difference between evapotranspiration obtained computing the differences in total soil water content between two consecutive measurements and transpiration for this interval estimated from sap flow measurements. In both years the evaporation from micro-catchments was significantly larger than that of trenches. The fractional loss due to evaporation from the total applied water for the second year for example, was 53% and 22% for micro-catchments and trenches, respectively. This indicates that a trench geometry reduces the amount of water lost to direct evaporation from the soil, and is thus more efficient in utilizing harvested runoff water.

Deduction of probable events of lateral gene transfer through comparison of phylogenetic trees by recursive consolidation and rearrangement

PubMed Central

MacLeod, Dave; Charlebois, Robert L; Doolittle, Ford; Bapteste, Eric

2005-01-01

Background When organismal phylogenies based on sequences of single marker genes are poorly resolved, a logical approach is to add more markers, on the assumption that weak but congruent phylogenetic signal will be reinforced in such multigene trees. Such approaches are valid only when the several markers indeed have identical phylogenies, an issue which many multigene methods (such as the use of concatenated gene sequences or the assembly of supertrees) do not directly address. Indeed, even when the true history is a mixture of vertical descent for some genes and lateral gene transfer (LGT) for others, such methods produce unique topologies. Results We have developed software that aims to extract evidence for vertical and lateral inheritance from a set of gene trees compared against an arbitrary reference tree. This evidence is then displayed as a synthesis showing support over the tree for vertical inheritance, overlaid with explicit lateral gene transfer (LGT) events inferred to have occurred over the history of the tree. Like splits-tree methods, one can thus identify nodes at which conflict occurs. Additionally one can make reasonable inferences about vertical and lateral signal, assigning putative donors and recipients. Conclusion A tool such as ours can serve to explore the reticulated dimensionality of molecular evolution, by dissecting vertical and lateral inheritance at high resolution. By this, we mean that individual nodes can be examined not only for congruence, but also for coherence in light of LGT. We assert that our tools will facilitate the comparison of phylogenetic trees, and the interpretation of conflicting data. PMID:15819979

Temporal Dynamics in the Concentration, Flux, and Optical Properties of Tree-Derived Dissolved Organic Matter in an Epiphyte-Laden Oak-Cedar Forest

NASA Astrophysics Data System (ADS)

Van Stan, John T.; Wagner, Sasha; Guillemette, François; Whitetree, Ansley; Lewis, Julius; Silva, Leticia; Stubbins, Aron

2017-11-01

Studies on the fate and transport of dissolved organic matter (DOM) along the rainfall-to-discharge flow pathway typically begin in streams or soils, neglecting the initial enrichment of rainfall with DOM during contact with plant canopies. However, rain water can gather significant amounts of tree-derived DOM (tree-DOM) when it drains from the canopy, as throughfall, and down the stem, as stemflow. We examined the temporal variability of event-scale tree-DOM concentrations, yield, and optical (light absorbance and fluorescence) characteristics from an epiphyte-laden Quercus virginiana-Juniperus virginiana forest on Skidaway Island, Savannah, Georgia (USA). All tree-DOM fluxes were highly enriched in dissolved organic carbon (DOC) compared to rainfall, and epiphytes further increased concentrations. Stemflow DOC concentrations were greater than throughfall across study species, yet larger throughfall water yields produced greater DOC yields versus stemflow. Tree-DOM optical characteristics indicate it is aromatic-rich with fluorescent DOM dominated by humic-like fluorescence, containing 10-20% protein-like (tryptophan-like) fluorescence. Storm size was the only storm condition that strongly correlated with tree-DOM concentration and flux; however, throughfall and stemflow optical characteristics varied little across a wide range of storm conditions (from low magnitude events to intense tropical storms). Annual tree-DOM yields from the study forest (0.8-46 g C m-2 yr-1) were similar to other yields from discrete down-gradient fluxes (litter leachates, soil leachates, and stream discharge) along the rainfall-to-discharge flow path.

Conversion events in gene clusters

PubMed Central

2011-01-01

Background Gene clusters containing multiple similar genomic regions in close proximity are of great interest for biomedical studies because of their associations with inherited diseases. However, such regions are difficult to analyze due to their structural complexity and their complicated evolutionary histories, reflecting a variety of large-scale mutational events. In particular, conversion events can mislead inferences about the relationships among these regions, as traced by traditional methods such as construction of phylogenetic trees or multi-species alignments. Results To correct the distorted information generated by such methods, we have developed an automated pipeline called CHAP (Cluster History Analysis Package) for detecting conversion events. We used this pipeline to analyze the conversion events that affected two well-studied gene clusters (α-globin and β-globin) and three gene clusters for which comparative sequence data were generated from seven primate species: CCL (chemokine ligand), IFN (interferon), and CYP2abf (part of cytochrome P450 family 2). CHAP is freely available at http://www.bx.psu.edu/miller_lab. Conclusions These studies reveal the value of characterizing conversion events in the context of studying gene clusters in complex genomes. PMID:21798034

Growth-Mortality Relationships in Piñon Pine (Pinus edulis) during Severe Droughts of the Past Century: Shifting Processes in Space and Time

PubMed Central

Macalady, Alison K.; Bugmann, Harald

2014-01-01

The processes leading to drought-associated tree mortality are poorly understood, particularly long-term predisposing factors, memory effects, and variability in mortality processes and thresholds in space and time. We use tree rings from four sites to investigate Pinus edulis mortality during two drought periods in the southwestern USA. We draw on recent sampling and archived collections to (1) analyze P. edulis growth patterns and mortality during the 1950s and 2000s droughts; (2) determine the influence of climate and competition on growth in trees that died and survived; and (3) derive regression models of growth-mortality risk and evaluate their performance across space and time. Recent growth was 53% higher in surviving vs. dying trees, with some sites exhibiting decades-long growth divergences associated with previous drought. Differential growth response to climate partly explained growth differences between live and dead trees, with responses wet/cool conditions most influencing eventual tree status. Competition constrained tree growth, and reduced trees’ ability to respond to favorable climate. The best predictors in growth-mortality models included long-term (15–30 year) average growth rate combined with a metric of growth variability and the number of abrupt growth increases over 15 and 10 years, respectively. The most parsimonious models had high discriminatory power (ROC>0.84) and correctly classified ∼70% of trees, suggesting that aspects of tree growth, especially over decades, can be powerful predictors of widespread drought-associated die-off. However, model discrimination varied across sites and drought events. Weaker growth-mortality relationships and higher growth at lower survival probabilities for some sites during the 2000s event suggest a shift in mortality processes from longer-term growth-related constraints to shorter-term processes, such as rapid metabolic decline even in vigorous trees due to acute drought stress, and/or increases in the attack rate of both chronically stressed and more vigorous trees by bark beetles. PMID:24786646

Examining the Relationship Between Edaphic Variables and the Rooting System of Abies concolor in the southern Sierra Nevada

NASA Astrophysics Data System (ADS)

Wilson, A.; Jackson, R. B.; Tumber-Davila, S. J.

2017-12-01

An increase in the frequency and severity of droughts has been associated with the changing climate. These events have the potential to alter the composition and biogeography of forests, as well as increase tree mortality related to climate-induced stress. Already, an increase in tree mortality has been observed throughout the US. The recent drought in California led to millions of tree mortalities in the southern Sierra Nevada alone. In order to assess the potential impacts of these events on forest systems, it is imperative to understand what factors contribute to tree mortality. As plants become water-stressed, they may invest carbon more heavily belowground to reach a bigger pool of water, but their ability to adapt may be limited by the characteristics of the soil. In the Southern Sierra Critical Zone Observatory, a high tree mortality zone, we have selected both dead and living trees to examine the factors that contribute to root zone variability and belowground biomass investment by individual plants. A series of 15 cores surrounding the tree were taken to collect root and soil samples. These were then used to compare belowground rooting distributions with soil characteristics (texture, water holding capacity, pH, electric conductivity). Abies concolor is heavily affected by drought-induced mortality, therefore the rooting systems of dead Abies concolor trees were examined to determine the relationship between their rooting systems and environmental conditions. Examining the relationship between soil characteristics and rooting systems of trees may shed light on the plasticity of rooting systems and how trees adapt based on the characteristics of its environment. A better understanding of the factors that contribute to tree mortality can improve our ability to predict how forest systems may be impacted by climate-induced stress. Key words: Root systems, soil characteristics, drought, adaptation, terrestrial carbon, forest ecology

Applications of Hobbyist Electronics in Monitoring Stemflow Processes: Preliminary Insights and Results

NASA Astrophysics Data System (ADS)

Carlyle-Moses, D. E.; Turner, B.; Hill, D. J.

2016-12-01

Leveraging the power and adaptability of inexpensive, accessible hobbyist electronics it has been possible to gain insights into the processes governing stemflow. The sensor platform utilizes an Arduino® microcontroller equipped with an ultrasonic sensor and wetness sensor as well as a GPS unit for accurate timestamps. The wetness sensor, which is attached to the terminus of a collection tube diverting water entering the stemflow collar to a collection vessel, provides the precise time in which stemflow commences. In turn, this time can be compared with the time stamp record of a high precision tipping-bucket rain gauge so that the rain depth required for stemflow generation can be derived. In addition, the ultrasonic sensor mounted above the stemflow collection vessel monitors changes in water depth over time. The changes in water depth are then converted to volumetric changes allowing for reasonable approximations of stemflow flow rates throughout the storm event. As a trial, the stemflow monitoring platform was deployed from May 1 to June 30, 2016 on an ornamental Green Ash (Fraxinus pennsylvanica Marsh.) tree on the grounds of Thompson Rivers University in Kamloops, British Columbia, Canada (500 40' 25" N, 1200 21' 50" W). The tree was in full-leaf condition, was 7.4 m in height and had a diameter at breast height of 10.8 cm. Rain totaled 77.2 mm during the study and was distributed over 15 events (mean = 5.1 mm, range = 0.2 - 14.3 mm), with the five smallest rain events (0.2 - 1.3 mm) not producing stemflow. The study period funneling ratio was 14.0 (event range = 0.0 - 40.0). Regression analysis revealed that for events in which stemflow was produced, rainfall depth explained only 50.2 percent of the variation in event stemflow volumes. The variant nature of stemflow in our study was a consequence of both highly variable mean event flow rates once stemflow had commenced (mean = 0.197 L / mm of rain, coefficient of variation = 0.67, range = 0.009 - 0.444 L / mm), as well as widely differing rain depth thresholds required for stemflow generation (mean = 2.4 mm, coefficient of variation = 0.58, range = 0.8 - 5.2 mm). Future work, including expanding the study (longer study period and more trees) and examining the role of storm meteorology on both threshold rain depths and stemflow rates will be discussed.

Water-Tree Modelling and Detection for Underground Cables

NASA Astrophysics Data System (ADS)

Chen, Qi

In recent years, aging infrastructure has become a major concern for the power industry. Since its inception in early 20th century, the electrical system has been the cornerstone of an industrial society. Stable and uninterrupted delivery of electrical power is now a base necessity for the modern world. As the times march-on, however, the electrical infrastructure ages and there is the inevitable need to renew and replace the existing system. Unfortunately, due to time and financial constraints, many electrical systems today are forced to operate beyond their original design and power utilities must find ways to prolong the lifespan of older equipment. Thus, the concept of preventative maintenance arises. Preventative maintenance allows old equipment to operate longer and at better efficiency, but in order to implement preventative maintenance, the operators must know minute details of the electrical system, especially some of the harder to assess issues such water-tree. Water-tree induced insulation degradation is a problem typically associated with older cable systems. It is a very high impedance phenomenon and it is difficult to detect using traditional methods such as Tan-Delta or Partial Discharge. The proposed dissertation studies water-tree development in underground cables, potential methods to detect water-tree location and water-tree severity estimation. The dissertation begins by developing mathematical models of water-tree using finite element analysis. The method focuses on surface-originated vented tree, the most prominent type of water-tree fault in the field. Using the standard operation parameters of North American electrical systems, the water-tree boundary conditions are defined. By applying finite element analysis technique, the complex water-tree structure is broken down to homogeneous components. The result is a generalized representation of water-tree capacitance at different stages of development. The result from the finite element analysis is used to model water-tree in large system. Both empirical measurements and the mathematical model show that the impedance of early-stage water-tree is extremely large. As the result, traditional detection methods such Tan-Delta or Partial Discharge are not effective due to the excessively high accuracy requirement. A high-frequency pulse detection method is developed instead. The water-tree impedance is capacitive in nature and it can be reduced to manageable level by high-frequency inputs. The method is able to determine the location of early-stage water-tree in long-distance cables using economically feasible equipment. A pattern recognition method is developed to estimate the severity of water-tree using its pulse response from the high-frequency test method. The early-warning system for water-tree appearance is a tool developed to assist the practical implementation of the high-frequency pulse detection method. Although the equipment used by the detection method is economically feasible, it is still a specialized test and not designed for constant monitoring of the system. The test also place heavy stress on the cable and it is most effective when the cable is taken offline. As the result, utilities need a method to estimate the likelihood of water-tree presence before subjecting the cable to the specialized test. The early-warning system takes advantage of naturally occurring high-frequency events in the system and uses a deviation-comparison method to estimate the probability of water-tree presence on the cable. If the likelihood is high, then the utility can use the high-frequency pulse detection method to obtain accurate results. Specific pulse response patterns can be used to calculate the capacitance of water-tree. The calculated result, however, is subjected to margins of error due to limitations from the real system. There are both long-term and short-term methods to improve the accuracy. Computation algorithm improvement allows immediate improvement on accuracy of the capacitance estimation. The probability distribution of the calculation solution showed that improvements in waveform time-step measurement allow fundamental improves to the overall result.

TU-AB-BRD-00: Task Group 100

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

2015-06-15

Current quality assurance and quality management guidelines provided by various professional organizations are prescriptive in nature, focusing principally on performance characteristics of planning and delivery devices. However, published analyses of events in radiation therapy show that most events are often caused by flaws in clinical processes rather than by device failures. This suggests the need for the development of a quality management program that is based on integrated approaches to process and equipment quality assurance. Industrial engineers have developed various risk assessment tools that are used to identify and eliminate potential failures from a system or a process before amore » failure impacts a customer. These tools include, but are not limited to, process mapping, failure modes and effects analysis, fault tree analysis. Task Group 100 of the American Association of Physicists in Medicine has developed these tools and used them to formulate an example risk-based quality management program for intensity-modulated radiotherapy. This is a prospective risk assessment approach that analyzes potential error pathways inherent in a clinical process and then ranks them according to relative risk, typically before implementation, followed by the design of a new process or modification of the existing process. Appropriate controls are then put in place to ensure that failures are less likely to occur and, if they do, they will more likely be detected before they propagate through the process, compromising treatment outcome and causing harm to the patient. Such a prospective approach forms the basis of the work of Task Group 100 that has recently been approved by the AAPM. This session will be devoted to a discussion of these tools and practical examples of how these tools can be used in a given radiotherapy clinic to develop a risk based quality management program. Learning Objectives: Learn how to design a process map for a radiotherapy process Learn how to perform failure modes and effects analysis analysis for a given process Learn what fault trees are all about Learn how to design a quality management program based upon the information obtained from process mapping, failure modes and effects analysis and fault tree analysis. Dunscombe: Director, TreatSafely, LLC and Center for the Assessment of Radiological Sciences; Consultant to IAEA and Varian Thomadsen: President, Center for the Assessment of Radiological Sciences Palta: Vice President of the Center for the Assessment of Radiological Sciences.« less

TU-AB-BRD-01: Process Mapping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palta, J.

2015-06-15

Current quality assurance and quality management guidelines provided by various professional organizations are prescriptive in nature, focusing principally on performance characteristics of planning and delivery devices. However, published analyses of events in radiation therapy show that most events are often caused by flaws in clinical processes rather than by device failures. This suggests the need for the development of a quality management program that is based on integrated approaches to process and equipment quality assurance. Industrial engineers have developed various risk assessment tools that are used to identify and eliminate potential failures from a system or a process before amore » failure impacts a customer. These tools include, but are not limited to, process mapping, failure modes and effects analysis, fault tree analysis. Task Group 100 of the American Association of Physicists in Medicine has developed these tools and used them to formulate an example risk-based quality management program for intensity-modulated radiotherapy. This is a prospective risk assessment approach that analyzes potential error pathways inherent in a clinical process and then ranks them according to relative risk, typically before implementation, followed by the design of a new process or modification of the existing process. Appropriate controls are then put in place to ensure that failures are less likely to occur and, if they do, they will more likely be detected before they propagate through the process, compromising treatment outcome and causing harm to the patient. Such a prospective approach forms the basis of the work of Task Group 100 that has recently been approved by the AAPM. This session will be devoted to a discussion of these tools and practical examples of how these tools can be used in a given radiotherapy clinic to develop a risk based quality management program. Learning Objectives: Learn how to design a process map for a radiotherapy process Learn how to perform failure modes and effects analysis analysis for a given process Learn what fault trees are all about Learn how to design a quality management program based upon the information obtained from process mapping, failure modes and effects analysis and fault tree analysis. Dunscombe: Director, TreatSafely, LLC and Center for the Assessment of Radiological Sciences; Consultant to IAEA and Varian Thomadsen: President, Center for the Assessment of Radiological Sciences Palta: Vice President of the Center for the Assessment of Radiological Sciences.« less

TU-AB-BRD-04: Development of Quality Management Program

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomadsen, B.

2015-06-15

Current quality assurance and quality management guidelines provided by various professional organizations are prescriptive in nature, focusing principally on performance characteristics of planning and delivery devices. However, published analyses of events in radiation therapy show that most events are often caused by flaws in clinical processes rather than by device failures. This suggests the need for the development of a quality management program that is based on integrated approaches to process and equipment quality assurance. Industrial engineers have developed various risk assessment tools that are used to identify and eliminate potential failures from a system or a process before amore » failure impacts a customer. These tools include, but are not limited to, process mapping, failure modes and effects analysis, fault tree analysis. Task Group 100 of the American Association of Physicists in Medicine has developed these tools and used them to formulate an example risk-based quality management program for intensity-modulated radiotherapy. This is a prospective risk assessment approach that analyzes potential error pathways inherent in a clinical process and then ranks them according to relative risk, typically before implementation, followed by the design of a new process or modification of the existing process. Appropriate controls are then put in place to ensure that failures are less likely to occur and, if they do, they will more likely be detected before they propagate through the process, compromising treatment outcome and causing harm to the patient. Such a prospective approach forms the basis of the work of Task Group 100 that has recently been approved by the AAPM. This session will be devoted to a discussion of these tools and practical examples of how these tools can be used in a given radiotherapy clinic to develop a risk based quality management program. Learning Objectives: Learn how to design a process map for a radiotherapy process Learn how to perform failure modes and effects analysis analysis for a given process Learn what fault trees are all about Learn how to design a quality management program based upon the information obtained from process mapping, failure modes and effects analysis and fault tree analysis. Dunscombe: Director, TreatSafely, LLC and Center for the Assessment of Radiological Sciences; Consultant to IAEA and Varian Thomadsen: President, Center for the Assessment of Radiological Sciences Palta: Vice President of the Center for the Assessment of Radiological Sciences.« less

Potential utility of tree ring δ18O series for reconstructing precipitation records from the lower reaches of the Yangtze River, southeast China

NASA Astrophysics Data System (ADS)

Xu, Chenxi; Ge, Junyi; Nakatsuka, Takeshi; Yi, Liang; Zheng, Huaizhou; Sano, Masaki

2016-04-01

In this study, we investigated the interannual and intraannual variabilities in the oxygen isotope composition (δ18O) preserved in the tree ring cellulose of Pinus taiwanensis in the lower reaches of the Yangtze River, southeast China, to explore its potential utility for precipitation reconstruction over the period of 1855-2013. Intraannual variations of tree ring cellulose δ18O show distinct annual cycles that are characterized by δ18O maxima in the early growth near the ring boundary and δ18O minima in the middle and late portions of the ring. Seasonal patterns of tree ring δ18O were influenced by August-October typhoons. The tree ring cellulose δ18O was measured in both young and old trees to test for the juvenile effect. The results revealed no significant differences in the mean values and long-term trends in δ18O in the old and young trees. A response analysis indicated that tree ring δ18O correlated significantly with precipitation and relative humidity between May and October, and the δ18O chronology accounted for 37.4% of the actual variation in the May-October precipitation between 1951 and 2013. The extremely dry and wet years revealed by the tree ring δ18O-based reconstructed precipitation also corresponded to actual local drought and flood events from the documentary records. Reconstructed precipitation showed significant relationship with central tropical Pacific sea surface temperature, which indicated that El Niño-Southern Oscillation (ENSO) exerted influences on May-October precipitation in the lower reaches of the Yangtze River. In addition, the relationship between ENSO and precipitation weakened between 1920 and 1940, and low variance of ENSO from 1920 to 1940 may result in the damped ENSO's influences on precipitation in southeast China.

Reconstruction of glacial lake outburst floods in northern Tien Shan: Implications for hazard assessment

NASA Astrophysics Data System (ADS)

Zaginaev, V.; Ballesteros-Cánovas, J. A.; Erokhin, S.; Matov, E.; Petrakov, D.; Stoffel, M.

2016-09-01

Glacier lake outburst floods (GLOFs) and related debris flows are among the most significant natural threats in the Tien Shan Mountains of Kyrgyzstan and have even caused the loss of life and damage to infrastructure in its capital Bishkek. An improved understanding of the occurrence of this process is essential so as to be able to design reliable disaster risk reduction strategies, even more so in view of ongoing climate change and scenarios of future evolutions. Here, we apply a dendrogeomorphic approach to reconstruct past debris-flow activity on the Aksay cone (Ala-Archa valley, Kyrgyz range), where outbursting glacier lakes and intense rainfalls have triggered huge debris flows over the past decades. A total of 96 Picea abies (L.) Karst. trees growing on the cone and along the main channel have been selected based on the evidence of past debris-flow damage in their trunks; these trees were then sampled using increment borers. The dating of past events was based on the assessment of growth disturbances (GD) in the tree-ring records and included the detection of injuries, tangential rows of traumatic resin ducts, reaction wood, and abrupt growth changes. In total, 320 GD were identified in the tree-ring samples. In combination with aerial imagery and geomorphic recognition in the field, reactions in trees and their position on the cone have allowed reconstruction of the main spatial patterns of past events on the Aksay cone. Our findings suggest that at least 27 debris flows have occurred on the site between 1877 and 2015 and point to the occurrence of at least 17 events that were not documented prior to this study. We also observe high process activity during the 1950s and 1960s, with major events on the cone in 1950, 1966, and 1968, coinciding with phases of slight glacier advance. The spatial analyses of events also point to two different spatial patterns, suggesting that quite dissimilar magnitudes probably occurred during glacier lake outburst floods and rainfall-induced debris-flow events. The results presented here represent the longest, annually resolved GLOF series in the region, which in turn has key implications on risk assessment, not just in the Ala-Archa valley, but also in the entire Kyrgyz range (northern Tien Shan).

Mortality in Subalpine Forests of the Sierra Nevada, California, USA: Differential Response of Pines (Pinus albicaulis and P. flexilis) to Climate Variability

NASA Astrophysics Data System (ADS)

Millar, C. I.; Westfall, R. D.; Delany, D. L.

2010-12-01

Widespread forest mortality in high-elevation forests has been increasing across western North American mountains in recent years, with climate, insects, and disease the primary causes. Subalpine forests in the eastern Sierra Nevada, by contrast, have experienced far less mortality than other ranges, and mortality events have been patchy and episodic. This situation, and lack of significant effect of non-native white-pine blister rust, enable investigation of fine-scale response of two subalpine Sierran species, whitebark pine (Pinus albicaulis, PiAl) and limber pine (P. flexilis, PiFl), to climate variability. We report similarities and differences between the two major mortality events in these pines in the last 150 years: 1988-1992 for PiFl and 2006-ongoing for PiAl. In both species, the events occurred within monotypic, closed-canopy, relatively young stands (< 200 yrs PiAl, < 300 yrs in PiFl); were localized to central-eastern Sierra Nevada; and occurred at 2740-2840 m along the eastern edge of the escarpment on north/northeast aspects with slopes > 40%. Mortality patches averaged 40-80 ha in both species, with mean stand mortality of trees > 10 cm diameter 91% in PiAl and 60% in PiFl. The ultimate cause of tree death was mountain pine beetle (Dendroctonus ponderosae) in both species, with increasing 20th/21st C minimum temperatures combined with drought the pre-conditioning factors. Overall growth in the past 150 years suggests that PiFl is more drought hardy than PiAl but responds sensitively to the combined effects of drought and increasing warmth. After the 1988-1992 drought, surviving PiFl recovered growth. PiAl trees grew very poorly during that drought, and continued poor growth in the years until 2006 when the mortality event occurred in PiAl. A significant species effect is the apparent difference in levels of within-stand genetic diversity for climate factors. Differential growth between 19th C (cool, wet) and 20th/21st C (warming, drying) of PiFl trees that died versus survivors indicates that considerable within-stand genetic diversity for climate existed in PiFl. For PiFl, the late 20th C mortality event acted as strong natural selection to improve within-stand fitness for warmer and drier conditions. PiFl trees that survived the 1988-1992 drought remained healthy through subsequent droughts, including the drought that is currently causing PiAl mortality. By contrast, the PiAl stands do not appear to have contained adaptive genetic diversity for drought and warmth, and PiAl trees growth behavior over the past 150 years was similar in pattern to the PiFl trees that died. As a result, the mortality event in PiAl is creating forest openings, with unknown future stand conditions, rather than rapid within-species adaptation that occurred in PiFl.

Bounding the Resource Availability of Partially Ordered Events with Constant Resource Impact

NASA Technical Reports Server (NTRS)

Frank, Jeremy

2004-01-01

We compare existing techniques to bound the resource availability of partially ordered events. We first show that, contrary to intuition, two existing techniques, one due to Laborie and one due to Muscettola, are not strictly comparable in terms of the size of the search trees generated under chronological search with a fixed heuristic. We describe a generalization of these techniques called the Flow Balance Constraint to tightly bound the amount of available resource for a set of partially ordered events with piecewise constant resource impact We prove that the new technique generates smaller proof trees under chronological search with a fixed heuristic, at little increase in computational expense. We then show how to construct tighter resource bounds but at increased computational cost.

Genetic diversity-seeing the forest through the trees

Treesearch

M. Thompson Conkle

1992-01-01

Forest trees, populations, races, species, and taxonomic groups above the species level display rich variation in biochemical markers. The variation stems from inherited modifications that trace back in time, through converging ancestries, towards common progenitors. Past movements of continents, mountain building events, and climate changes isolated forest populations...

30 CFR 250.618 - Tubing and wellhead equipment.

Code of Federal Regulations, 2011 CFR

2011-07-01

... following requirements during well-workover operations with the tree removed: (a) No tubing string shall be... pressure integrity and is otherwise suitable for its intended use. (b) In the event of prolonged operations... Manager. (c) When reinstalling the tree, you must: (1) Equip wells to monitor for casing pressure...

Application Research of Fault Tree Analysis in Grid Communication System Corrective Maintenance

NASA Astrophysics Data System (ADS)

Wang, Jian; Yang, Zhenwei; Kang, Mei

2018-01-01

This paper attempts to apply the fault tree analysis method to the corrective maintenance field of grid communication system. Through the establishment of the fault tree model of typical system and the engineering experience, the fault tree analysis theory is used to analyze the fault tree model, which contains the field of structural function, probability importance and so on. The results show that the fault tree analysis can realize fast positioning and well repairing of the system. Meanwhile, it finds that the analysis method of fault tree has some guiding significance to the reliability researching and upgrading f the system.

Genetic recombination events between sympatric Clade A and Clade C lice in Africa.

PubMed

Veracx, Aurélie; Boutellis, Amina; Raoult, Didier

2013-09-01

Human head and body lice have been classified into three phylogenetic clades (Clades A, B, and C) based on mitochondrial DNA. Based on nuclear markers (the 18S rRNA gene and the PM2 spacer), two genotypes of Clade A head and body lice, including one that is specifically African (Clade A2), have been described. In this study, we sequenced the PM2 spacer of Clade C head lice from Ethiopia and compared these sequences with sequences from previous works. Trees were drawn, and an analysis of genetic diversity based on the cytochrome b gene and the PM2 spacer was performed for African and non-African lice. In the tree drawn based on the PM2 spacer, the African and non-African lice formed separate clusters. However, Clade C lice from Ethiopia were placed within the African Clade A subcluster (Clade A2). This result suggests that recombination events have occurred between Clade A2 lice and Clade C lice, reflecting the sympatric nature of African lice. Finally, the PM2 spacer and cytochrome b gene sequences of human lice revealed a higher level of genetic diversity in Africa than in other regions.

Interim Reliability Evaluation Program: analysis of the Browns Ferry, Unit 1, nuclear plant. Main report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mays, S.E.; Poloski, J.P.; Sullivan, W.H.

1982-07-01

A probabilistic risk assessment (PRA) was made of the Browns Ferry, Unit 1, nuclear plant as part of the Nuclear Regulatory Commission's Interim Reliability Evaluation Program (IREP). Specific goals of the study were to identify the dominant contributors to core melt, develop a foundation for more extensive use of PRA methods, expand the cadre of experienced PRA practitioners, and apply procedures for extension of IREP analyses to other domestic light water reactors. Event tree and fault tree analyses were used to estimate the frequency of accident sequences initiated by transients and loss of coolant accidents. External events such as floods,more » fires, earthquakes, and sabotage were beyond the scope of this study and were, therefore, excluded. From these sequences, the dominant contributors to probable core melt frequency were chosen. Uncertainty and sensitivity analyses were performed on these sequences to better understand the limitations associated with the estimated sequence frequencies. Dominant sequences were grouped according to common containment failure modes and corresponding release categories on the basis of comparison with analyses of similar designs rather than on the basis of detailed plant-specific calculations.« less

The ethnobotany of Christ's Thorn Jujube (Ziziphus spina-christi) in Israel.

PubMed

Dafni, Amots; Levy, Shay; Lev, Efraim

2005-09-28

This article surveys the ethnobotany of Ziziphus spina-christi (L.) Desf. in the Middle East from various aspects: historical, religious, philological, literary, linguistic, as well as pharmacological, among Muslims, Jews, and Christians. It is suggested that this is the only tree species considered "holy" by Muslims (all the individuals of the species are sanctified by religion) in addition to its status as "sacred tree " (particular trees which are venerated due to historical or magical events related to them, regardless of their botanical identity) in the Middle East. It has also a special status as "blessed tree" among the Druze.

Dendrogeomorphic reconstruction of lahar activity and triggers: Shiveluch volcano, Kamchatka Peninsula, Russia

NASA Astrophysics Data System (ADS)

Salaorni, E.; Stoffel, M.; Tutubalina, O.; Chernomorets, S.; Seynova, I.; Sorg, A.

2017-01-01

Lahars are highly concentrated, water-saturated volcanic hyperconcentrated flows or debris flows containing pyroclastic material and are a characteristic mass movement process on volcanic slopes. On Kamchatka Peninsula (Russian Federation), lahars are widespread and may affect remote settlements. Historical records of past lahar occurrences are generally sparse and mostly limited to events which damaged infrastructure on the slopes or at the foot of volcanoes. In this study, we present a tree-ring-based reconstruction of spatiotemporal patterns of past lahar activity at Shiveluch volcano. Using increment cores and cross sections from 126 Larix cajanderi trees, we document 34 events covering the period AD 1729-2012. Analyses of the seasonality of damage in trees reveal that 95% of all lahars occurred between October and May and thus point to the predominant role of the sudden melt of the snow cover by volcanic material. These observations suggest that most lahars were likely syn-eruptive and that lahar activity is largely restricted to periods of volcanic activity. By contrast, rainfall events do not seem to play a significant role in lahar triggering.

Rapid increase in cosmogenic 14C in AD 775 measured in New Zealand kauri trees indicates short-lived increase in 14C production spanning both hemispheres

NASA Astrophysics Data System (ADS)

Güttler, D.; Adolphi, F.; Beer, J.; Bleicher, N.; Boswijk, G.; Christl, M.; Hogg, A.; Palmer, J.; Vockenhuber, C.; Wacker, L.; Wunder, J.

2015-02-01

In 2012, Miyake et al. reported a sudden and strong increase of the atmospheric radiocarbon (14C) content in Japanese cedar trees of 1.2% between AD 774 and 775. While their findings were quickly confirmed by a German oak chronology for the Northern Hemisphere (NH), the question remained if the effect was seen in both hemispheres. Here we present the first annually resolved Southern Hemisphere (SH) 14C record spanning the interval AD 760-787, using New Zealand kauri (Agathis australis) chronology wood. An almost identical distinct increase compared to Northern Hemisphere data was observed, suggesting a cosmic event with globally uniform impact as a potential cause for the increase. Deploying a carbon cycle box model a worldwide averaged net 14C production of 2.2 ×108 14C atoms cm-2 was estimated, which is 3.7 times higher than the average annual 14C production. The immediate appearance of the event in tree rings on both hemispheres suggests a short duration event of significantly less than 1 yr.

Application of Decision Tree to Obtain Optimal Operation Rules for Reservoir Flood Control Considering Sediment Desilting-Case Study of Tseng Wen Reservoir

NASA Astrophysics Data System (ADS)

ShiouWei, L.

2014-12-01

Reservoirs are the most important water resources facilities in Taiwan.However,due to the steep slope and fragile geological conditions in the mountain area,storm events usually cause serious debris flow and flood,and the flood then will flush large amount of sediment into reservoirs.The sedimentation caused by flood has great impact on the reservoirs life.Hence,how to operate a reservoir during flood events to increase the efficiency of sediment desilting without risk the reservoir safety and impact the water supply afterward is a crucial issue in Taiwan. 　Therefore,this study developed a novel optimization planning model for reservoir flood operation considering flood control and sediment desilting,and proposed easy to use operating rules represented by decision trees.The decision trees rules have considered flood mitigation,water supply and sediment desilting.The optimal planning model computes the optimal reservoir release for each flood event that minimum water supply impact and maximum sediment desilting without risk the reservoir safety.Beside the optimal flood operation planning model,this study also proposed decision tree based flood operating rules that were trained by the multiple optimal reservoir releases to synthesis flood scenarios.The synthesis flood scenarios consists of various synthesis storm events,reservoir's initial storage and target storages at the end of flood operating. 　Comparing the results operated by the decision tree operation rules(DTOR) with that by historical operation for Krosa Typhoon in 2007,the DTOR removed sediment 15.4% more than that of historical operation with reservoir storage only8.38×106m3 less than that of historical operation.For Jangmi Typhoon in 2008,the DTOR removed sediment 24.4% more than that of historical operation with reservoir storage only 7.58×106m3 less than that of historical operation.The results show that the proposed DTOR model can increase the sediment desilting efficiency and extend the reservoir life.

Large Wood recruitment and transport along a piedmont gravel bed river

NASA Astrophysics Data System (ADS)

Picco, Lorenzo; Tonon, Alessia; Ravazzolo, Diego; Aristide Lenzi, Mario

2015-04-01

In recent years an increasing attention has been devoted on Large Wood (LW), focusing to its role and impact along riverine systems. However there is still a lack of knowledge about many aspects of its recruitment and displacement from the vegetated patches (e.g. floodplain and island) of a riverine environment. This research aims to analyse and consider the differences in LW recruitment during a flood event along a reach of a piedmont gravel bed river. The study has been carried out along a 3 km - long study reach located into the middle course of the gravel bed Piave River (North-Eastern Italian Alps). A buffer zone of 20 m - wide was considered along the floodplains and islands. Into this stripe every standing tree, with diameter ≥ 0.10 m, was measured manually (Diameter Breast Height-DBH; Height). Moreover, for each tree the GPS position was recorded and a numbered tag was installed to simplify the post event recovery. In November 2014 an over bankfull flood (Q=1039 m3 s-1; R.I=3.5 years) occurred. Preliminary results shows that 668 trees were recruited during the flood event thanks to both bank erosion processes along the floodplain banks and along the island shores. Analysing the origin, it is possible to define as 401 (60.03 %) trees were recruited from the floodplain, 244 (36.53%) from fluvial islands and, finally, 23 (3.44%) trees were not completely moved into the active channel area and recruited by the flood, but were just uprooted. Thanks to the accurate dendrometric measurements, it has been possible to define the dimensions for both category of LW, recruited from floodplain and island respectively. Looking to the minimum, maximum and mean height detected were defined values of 2.00, 20.00 and 8.98 m, and 2.20, 15.00 and 6.64 m, for floodplain and island, respectively. The DBH show minimum, maximum and mean values of about 0.10, 0.54 and 0.14 m, and 0.10, 0.44 and 0.14 m for floodplain and island, respectively. These dendrometric measurements permitted us to define the input volume of LW from floodplain and island, 75.59 m3 (0.19 m3/tree) and 39.66 m3 (0.16 m3/tree), respectively. It is worth to focus on the greater input of LW from floodplain, due to the recruitment of an higher number of trees and the bigger dimension of these plants. Post flood field survey permitted also to detect the displacement length of recruited trees along the study area, obtaining values of about 2.50 km, that is consistent with similar results obtained in the same study reach. Further analysis will permit to investigate more in detail the LW origin, its displacement and to link it with flood condition and the morphological settings of the study reach. This research is funded within, the University of Padova research Project CPDA149091- "WoodAlp: linking large Wood and morphological dynamics of gravel bed rivers of Eastern Italian Alps"- 2014-16 and the Project "SedAlp: sediment management in Alpine basins, integrating sediment continuum, risk mitigation and hydropower", 83-4-3-AT, in the framework of the European Territorial Cooperation Program "Alpine Space" 2007-13.

Simulation-Based Model Checking for Nondeterministic Systems and Rare Events

DTIC Science & Technology

2016-03-24

year, we have investigated AO* search and Monte Carlo Tree Search algorithms to complement and enhance CMU’s SMCMDP. 1 Final Report, March 14... tree , so we can use it to find the probability of reachability for a property in PRISM’s Probabilistic LTL. By finding the maximum probability of...savings, particularly when handling very large models. 2.3 Monte Carlo Tree Search The Monte Carlo sampling process in SMCMDP can take a long time to

Sequence evidence for the symbiotic origins of chloroplasts and mitochondria

NASA Technical Reports Server (NTRS)

George, D. G.; Hunt, L. T.; Dayhoff, M. O.

1983-01-01

The origin of mitochondria and chloroplasts is investigated on the basis of prokaryotic and early-eukaryotic evolutionary trees derived from protein and nucleic-acid sequences by the method of Dayhoff (1979). Trees for bacterial ferrodoxins, 5S ribosomal RNA, c-type cytochromes, the lipid-binding subunit of ATPase, and dihydrofolate reductase are presented and discussed. Good agreement among the trees is found, and it is argued that the mitochondria and chloroplasts evolved by multiple symbiotic events.

Novel Hydraulic Vulnerability Proxies for a Boreal Conifer Species Reveal That Opportunists May Have Lower Survival Prospects under Extreme Climatic Events.

PubMed

Rosner, Sabine; Světlík, Jan; Andreassen, Kjell; Børja, Isabella; Dalsgaard, Lise; Evans, Robert; Luss, Saskia; Tveito, Ole E; Solberg, Svein

2016-01-01

Top dieback in 40-60 years old forest stands of Norway spruce [Picea abies (L.) Karst.] in southern Norway is supposed to be associated with climatic extremes. Our intention was to learn more about the processes related to top dieback and in particular about the plasticity of possible predisposing factors. We aimed at (i) developing proxies for P 50 based on anatomical data assessed by SilviScan technology and (ii) testing these proxies for their plasticity regarding climate, in order to (iii) analyze annual variations of hydraulic proxies of healthy looking trees and trees with top dieback upon their impact on tree survival. At two sites we selected 10 tree pairs, i.e., one healthy looking tree and one tree with visual signs of dieback such as dry tops, needle shortening and needle yellowing (n = 40 trees). Vulnerability to cavitation (P 50) of the main trunk was assessed in a selected sample set (n = 19) and we thereafter applied SilviScan technology to measure cell dimensions (lumen (b) and cell wall thickness (t)) in these specimen and in all 40 trees in tree rings formed between 1990 and 2010. In a first analysis step, we searched for anatomical proxies for P 50. The set of potential proxies included hydraulic lumen diameters and wall reinforcement parameters based on mean, radial, and tangential tracheid diameters. The conduit wall reinforcement based on tangential hydraulic lumen diameters ((t/b ht)(2)) was the best estimate for P 50. It was thus possible to relate climatic extremes to the potential vulnerability of single annual rings. Trees with top dieback had significantly lower (t/b ht)(2) and wider tangential (hydraulic) lumen diameters some years before a period of water deficit (2005-2006). Radial (hydraulic) lumen diameters showed however no significant differences between both tree groups. (t/b ht)(2) was influenced by annual climate variability; strongest correlations were found with precipitation in September of the previous growing season: high precipitation in previous September resulted in more vulnerable annual rings in the next season. The results are discussed with respect to an "opportunistic behavior" and genetic predisposition to drought sensitivity.

On the typology and the worship status of sacred trees with a special reference to the Middle East.

PubMed

Dafni, Amots

2006-05-15

This article contains the reasons for the establishment of sacred trees in Israel based on a field study. It includes 97 interviews with Muslim and Druze informants. While Muslims (Arabs and Bedouins) consider sacred trees especially as an abode of righteous figures' (Wellis') souls or as having a connection to their graves, the Druze relate sacred trees especially to the events or deeds in the lives of prophets and religious leaders. A literary review shows the existence of 24 known reasons for the establishment of sacred trees worldwide, 11 of which are known in Israel one of these is reported here for the first time. We found different trends in monotheistic and polytheistic religions concerning their current worship of sacred trees.

On the typology and the worship status of sacred trees with a special reference to the Middle East

PubMed Central

Dafni, Amots

2006-01-01

This article contains the reasons for the establishment of sacred trees in Israel based on a field study. It includes 97 interviews with Muslim and Druze informants. While Muslims (Arabs and Bedouins) consider sacred trees especially as an abode of righteous figures' (Wellis') souls or as having a connection to their graves, the Druze relate sacred trees especially to the events or deeds in the lives of prophets and religious leaders. A literary review shows the existence of 24 known reasons for the establishment of sacred trees worldwide, 11 of which are known in Israel one of these is reported here for the first time. We found different trends in monotheistic and polytheistic religions concerning their current worship of sacred trees. PMID:16700917

A Trichosporonales genome tree based on 27 haploid and three evolutionarily conserved 'natural' hybrid genomes.

PubMed

Takashima, Masako; Sriswasdi, Sira; Manabe, Ri-Ichiroh; Ohkuma, Moriya; Sugita, Takashi; Iwasaki, Wataru

2018-01-01

To construct a backbone tree consisting of basidiomycetous yeasts, draft genome sequences from 25 species of Trichosporonales (Tremellomycetes, Basidiomycota) were generated. In addition to the hybrid genomes of Trichosporon coremiiforme and Trichosporon ovoides that we described previously, we identified an interspecies hybrid genome in Cutaneotrichosporon mucoides (formerly Trichosporon mucoides). This hybrid genome had a gene retention rate of ~55%, and its closest haploid relative was Cutaneotrichosporon dermatis. After constructing the C. mucoides subgenomes, we generated a phylogenetic tree using genome data from the 27 haploid species and the subgenome data from the three hybrid genome species. It was a high-quality tree with 100% bootstrap support for all of the branches. The genome-based tree provided superior resolution compared with previous multi-gene analyses. Although our backbone tree does not include all Trichosporonales genera (e.g. Cryptotrichosporon), it will be valuable for future analyses of genome data. Interest in interspecies hybrid fungal genomes has recently increased because they may provide a basis for new technologies. The three Trichosporonales hybrid genomes described in this study are different from well-characterized hybrid genomes (e.g. those of Saccharomyces pastorianus and Saccharomyces bayanus) because these hybridization events probably occurred in the distant evolutionary past. Hence, they will be useful for studying genome stability following hybridization and speciation events. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Neoendemism in Madagascan scaly tree ferns results from recent, coincident diversification bursts.

PubMed

Janssen, Thomas; Bystriakova, Nadia; Rakotondrainibe, France; Coomes, David; Labat, Jean-Noël; Schneider, Harald

2008-08-01

More than 80% of Madagascar's 12,000 plant species are endemic with the degree of endemism reaching as much as 95% in the scaly tree ferns, an important species rich component of Madagascar's evergreen rainforests. Predominantly African or Asian ancestry and divergence times usually postdating the separation of Madagascar from the Gondwanan landmasses have been demonstrated for several Madagascan animal and angiosperm groups. However, evolutionary studies of rainforest-specific lineages are scarce and the ecological context of radiation events has rarely been investigated. Here, we examine the evolution of Madagascan tree ferns as a rainforest-specific model family, integrate results from bioclimatic niche analysis with a dated phylogenetic framework, and propose an evolutionary scenario casting new light on our knowledge of the evolution of large island endemic clades. We show that Madagascar's extant tree fern diversity springs from three distinct ancestors independently colonizing Madagascar in the Miocene and that these three monophyletic clades diversified in three coincident radiation bursts during the Pliocene, reaching exceptionally high diversification rates and most likely responding to a common climatic trigger. Recent diversification bursts may thus have played a major role in the evolution of the extant Madagascan rainforest biome, which hence contains a significant number of young, neoendemic taxa.

Domino effect in chemical accidents: main features and accident sequences.

PubMed

Darbra, R M; Palacios, Adriana; Casal, Joaquim

2010-11-15

The main features of domino accidents in process/storage plants and in the transportation of hazardous materials were studied through an analysis of 225 accidents involving this effect. Data on these accidents, which occurred after 1961, were taken from several sources. Aspects analyzed included the accident scenario, the type of accident, the materials involved, the causes and consequences and the most common accident sequences. The analysis showed that the most frequent causes are external events (31%) and mechanical failure (29%). Storage areas (35%) and process plants (28%) are by far the most common settings for domino accidents. Eighty-nine per cent of the accidents involved flammable materials, the most frequent of which was LPG. The domino effect sequences were analyzed using relative probability event trees. The most frequent sequences were explosion→fire (27.6%), fire→explosion (27.5%) and fire→fire (17.8%). Copyright © 2010 Elsevier B.V. All rights reserved.

Tree-ring based reconstruction of rockfalls at Cofre de Perote volcano, Mexico

NASA Astrophysics Data System (ADS)

Franco-Ramos, Osvaldo; Stoffel, Markus; Vázquez-Selem, Lorenzo

2017-08-01

In this study, dendrogeomorphic techniques are employed to analyse the temporal frequency and spatial distribution of rockfalls on a talus slope of La Teta valley, located on the NW slopes of Cofre de Perote volcano at 4000 m above sea level. Based on the interpretation of disturbance signals in growth rings of old-growth Pinus hartwegii Lindl. trees, we identify 100 growth disturbances related with rockfall events dated between 1780 and 2011, with slightly more than half of these events being dated to the last 50 years. The sectors most susceptible to rockfall correspond with the young rock lobes located at the foot of scarps. Roughly three in ten events has been triggered by regional, M > 6 earthquakes, whereas half of the events activity coincides with periods characterized by severe, prolonged summer rainfalls such as the ones occurred in 1995, 1998, 2005 and 2011.

META: Multi-resolution Framework for Event Summarization

DTIC Science & Technology

2014-05-01

designated by other documentation. 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS ( ES ) U.S. Army Research Office P.O. Box 12211 Research Triangle...storage by removing the lower lev- els of the description nodes. The pruned tree still contains enough details for analysis, and an analyst who analyzes a...similar to the ‘projec- tion’ in relational algebra . It is a unary operator written as Πe(1),e(2),...,e(k)(F). The operation is defined as picking the

Phylogenetic analysis and victim contact tracing of rabies virus from humans and dogs in Bali, Indonesia.

PubMed

Mahardika, G N K; Dibia, N; Budayanti, N S; Susilawathi, N M; Subrata, K; Darwinata, A E; Wignall, F S; Richt, J A; Valdivia-Granda, W A; Sudewi, A A R

2014-06-01

The emergence of human and animal rabies in Bali since November 2008 has attracted local, national and international interest. The potential origin and time of introduction of rabies virus to Bali is described. The nucleoprotein (N) gene of rabies virus from dog brain and human clinical specimens was sequenced using an automated DNA sequencer. Phylogenetic inference with Bayesian Markov Chain Monte Carlo (MCMC) analysis using the Bayesian Evolutionary Analysis by Sampling Trees (BEAST) v. 1.7.5 software confirmed that the outbreak of rabies in Bali was caused by an Indonesian lineage virus following a single introduction. The ancestor of Bali viruses was the descendant of a virus from Kalimantan. Contact tracing showed that the event most likely occurred in early 2008. The introduction of rabies into a large unvaccinated dog population in Bali clearly demonstrates the risk of disease transmission for government agencies and should lead to an increased preparedness and efforts for sustained risk reduction to prevent such events from occurring in future.

Quantitative risk assessment system (QRAS)

NASA Technical Reports Server (NTRS)

Tan, Zhibin (Inventor); Mosleh, Ali (Inventor); Weinstock, Robert M (Inventor); Smidts, Carol S (Inventor); Chang, Yung-Hsien (Inventor); Groen, Francisco J (Inventor); Swaminathan, Sankaran (Inventor)

2001-01-01

A quantitative risk assessment system (QRAS) builds a risk model of a system for which risk of failure is being assessed, then analyzes the risk of the system corresponding to the risk model. The QRAS performs sensitivity analysis of the risk model by altering fundamental components and quantifications built into the risk model, then re-analyzes the risk of the system using the modifications. More particularly, the risk model is built by building a hierarchy, creating a mission timeline, quantifying failure modes, and building/editing event sequence diagrams. Multiplicities, dependencies, and redundancies of the system are included in the risk model. For analysis runs, a fixed baseline is first constructed and stored. This baseline contains the lowest level scenarios, preserved in event tree structure. The analysis runs, at any level of the hierarchy and below, access this baseline for risk quantitative computation as well as ranking of particular risks. A standalone Tool Box capability exists, allowing the user to store application programs within QRAS.

Genetic Diversity of the Ordinary Strain of Potato virus Y (PVY) and Origin of Recombinant PVY Strains

PubMed Central

Karasev, Alexander V.; Hu, Xiaojun; Brown, Celeste J.; Kerlan, Camille; Nikolaeva, Olga V.; Crosslin, James M.; Gray, Stewart M.

2011-01-01

The ordinary strain of Potato virus Y (PVY), PVYO, causes mild mosaic in tobacco and induces necrosis and severe stunting in potato cultivars carrying the Ny gene. A novel substrain of PVYO was recently reported, PVYO-O5, which is spreading in the United States and is distinguished from other PVYO isolates serologically (i.e., reacting to the otherwise PVYN-specific monoclonal antibody 1F5). To characterize this new PVYO-O5 subgroup and address possible reasons for its continued spread, we conducted a molecular study of PVYO and PVYO-O5 isolates from a North American collection of PVY through whole-genome sequencing and phylogenetic analysis. In all, 44 PVYO isolates were sequenced, including 31 from the previously defined PVYO-O5 group, and subjected to whole-genome analysis. PVYO-O5 isolates formed a separate lineage within the PVYO genome cluster in the whole-genome phylogenetic tree and represented a novel evolutionary lineage of PVY from potato. On the other hand, the PVYO sequences separated into at least two distinct lineages on the whole-genome phylogenetic tree. To shed light on the origin of the three most common PVY recombinants, a more detailed phylogenetic analysis of a sequence fragment, nucleotides 2,406 to 5,821, that is present in all recombinant and nonrecombinant PVYO genomes was conducted. The analysis revealed that PVYN:O and PVYN-Wi recombinants acquired their PVYO segments from two separate PVYO lineages, whereas the PVYNTN recombinant acquired its PVYO segment from the same lineage as PVYN:O. These data suggest that PVYN:O and PVYN-Wi recombinants originated from two separate recombination events involving two different PVYO parental genomes, whereas the PVYNTN recombinants likely originated from the PVYN:O genome via additional recombination events. PMID:21675922

Five centuries of Central European temperature extremes reconstructed from tree-ring density and documentary evidence

NASA Astrophysics Data System (ADS)

Battipaglia, Giovanna; Frank, David; Büntgen, Ulf; Dobrovolný, Petr; Brázdil, Rudolf; Pfister, Christian; Esper, Jan

2010-06-01

Future climate change will likely influence the frequency and intensity of weather extremes. As such events are by definition rare, long records are required to understand their characteristics, drivers, and consequences on ecology and society. Herein we provide a unique perspective on regional-scale temperature extremes over the past millennium, using three tree-ring maximum latewood density (MXD) chronologies from higher elevations in the European Alps. We verify the tree-ring-based extremes using documentary evidences from Switzerland, the Czech Republic, and Central Europe that allowed the identification of 44 summer extremes over the 1550-2003 period. These events include cold temperatures in 1579, 1628, 1675, and 1816, as well as warm ones in 1811 and 2003. Prior to 1550, we provide new evidence for cold (e.g., 1068 and 1258) and warm (e.g., 1333) summers derived from the combined MXD records and thus help to characterize high-frequency temperature variability during medieval times. Spatial coherence of the reconstructed extremes is found over Switzerland, with most signatures even extending across Central Europe. We discuss potential limitations of the tree-ring and documentary archives, including the ( i) ability of MXD to particularly capture extremely warm temperatures, ( ii) methodological identification and relative definition of extremes, and ( iii) placement of those events in the millennium-long context of low-frequency climate change.

Using multiple data sets to populate probabilistic volcanic event trees

USGS Publications Warehouse

Newhall, C.G.; Pallister, John S.

2014-01-01

The key parameters one needs to forecast outcomes of volcanic unrest are hidden kilometers beneath the Earth’s surface, and volcanic systems are so complex that there will invariably be stochastic elements in the evolution of any unrest. Fortunately, there is sufficient regularity in behaviour that some, perhaps many, eruptions can be forecast with enough certainty for populations to be evacuated and kept safe. Volcanologists charged with forecasting eruptions must try to understand each volcanic system well enough that unrest can be interpreted in terms of pre-eruptive process, but must simultaneously recognize and convey uncertainties in their assessment. We have found that use of event trees helps to focus discussion, integrate data from multiple sources, reach consensus among scientists about both pre-eruptive process and uncertainties and, in some cases, to explain all of this to officials. Figure 1 shows a generic volcanic event tree from Newhall and Hoblitt (2002) that can be modified as needed for each specific volcano. This paper reviews how we and our colleagues have used such trees during a number of volcanic crises worldwide, for rapid hazard assessments in situations in which more formal expert elicitations could not be conducted. We describe how Multiple Data Sets can be used to estimate probabilities at each node and branch. We also present case histories of probability estimation during crises, how the estimates were used by public officials, and some suggestions for future improvements.

Searching for events in Chinese ancient records to explain the increase in 14C from AD 774-775 and AD 993-994

NASA Astrophysics Data System (ADS)

Chai, Ya-Ting; Zou, Yuan-Chuan

2015-09-01

According to analysis of the 14C content in two Japanese trees, that grew over a period of approximately 3000 years, with high time resolution, Miyake et al. found a rapid increase at AD 774-775 and another one at AD 993-994. These increases correspond to high-energy events that happened within those years and radiated γ-ray energy of about 7×1024 erg toward the Earth. The origin of these events is a mystery. Such strong events should have an unusual optical counterpart, and have been recorded in historical literatures. We searched Chinese historical materials around AD 744-775 and AD 993-994, but no remarkable event was found except for a violent thunderstorm in AD 775. However, the possibility of a thunderstorm containing so much energy is unlikely. We conclude that the events, which caused the 14C increase, are still unclear. These events most probably had no optical counterpart, and a short gamma-ray burst, giant flare of a soft gamma-ray repeater or a terrestrial γ-ray flash could all be candidates.

The fault-tree compiler

NASA Technical Reports Server (NTRS)

Martensen, Anna L.; Butler, Ricky W.

1987-01-01

The Fault Tree Compiler Program is a new reliability tool used to predict the top event probability for a fault tree. Five different gate types are allowed in the fault tree: AND, OR, EXCLUSIVE OR, INVERT, and M OF N gates. The high level input language is easy to understand and use when describing the system tree. In addition, the use of the hierarchical fault tree capability can simplify the tree description and decrease program execution time. The current solution technique provides an answer precise (within the limits of double precision floating point arithmetic) to the five digits in the answer. The user may vary one failure rate or failure probability over a range of values and plot the results for sensitivity analyses. The solution technique is implemented in FORTRAN; the remaining program code is implemented in Pascal. The program is written to run on a Digital Corporation VAX with the VMS operation system.

Uranium mobility across annual growth rings in three deciduous tree species

DOE Office of Scientific and Technical Information (OSTI.GOV)

McHugh, Kelly C.; Widom, Elisabeth; Spitz, Henry B.

Black walnut (Juglans nigra), slippery elm (Ulmus rubra), and white ash (Fraxinus americana) trees were evaluated as potential archives of past uranium (U) contamination. Like other metals, U mobility in annual growth rings of trees is potentially dependent on the tree species. Uranium concentrations and isotopic compositions (masses 234, 235, 236, and 238) were analyzed by thermal ionization mass spectrometry to test the efficacy of using tree rings to retroactively monitor U pollution from the FFMPC, a U purification facility operating from 1951 to 1989. This study found non-natural U (depleted U and detectable 236U) in growth rings of allmore » three tree species that pre-dated the start of operations at FFMPC and compositional trends that did not correspond with known contamination events. Therefore, the annual growth rings of these tree species cannot be used to reliably monitor the chronology of U contamination.« less

Uranium mobility across annual growth rings in three deciduous tree species.

PubMed

McHugh, Kelly C; Widom, Elisabeth; Spitz, Henry B; Wiles, Gregory C; Glover, Sam E

2018-02-01

Black walnut (Juglans nigra), slippery elm (Ulmus rubra), and white ash (Fraxinus americana) trees were evaluated as potential archives of past uranium (U) contamination. Like other metals, U mobility in annual growth rings of trees is dependent on the tree species. Uranium concentrations and isotopic compositions (masses 234, 235, 236, and 238) were analyzed by thermal ionization mass spectrometry to test the efficacy of using tree rings to retroactively monitor U pollution from the FFMPC, a U purification facility operating from 1951 to 1989. This study found non-natural U (depleted U and detectable 236 U) in growth rings of all three tree species that pre-dated the start of operations at FFMPC and compositional trends that did not correspond with known contamination events. Therefore, the annual growth rings of these tree species cannot be used to reliably monitor the chronology of U contamination. Copyright © 2017 Elsevier Ltd. All rights reserved.

The Fault Tree Compiler (FTC): Program and mathematics

NASA Technical Reports Server (NTRS)

Butler, Ricky W.; Martensen, Anna L.

1989-01-01

The Fault Tree Compiler Program is a new reliability tool used to predict the top-event probability for a fault tree. Five different gate types are allowed in the fault tree: AND, OR, EXCLUSIVE OR, INVERT, AND m OF n gates. The high-level input language is easy to understand and use when describing the system tree. In addition, the use of the hierarchical fault tree capability can simplify the tree description and decrease program execution time. The current solution technique provides an answer precisely (within the limits of double precision floating point arithmetic) within a user specified number of digits accuracy. The user may vary one failure rate or failure probability over a range of values and plot the results for sensitivity analyses. The solution technique is implemented in FORTRAN; the remaining program code is implemented in Pascal. The program is written to run on a Digital Equipment Corporation (DEC) VAX computer with the VMS operation system.

A metabolomic, geographic, and seasonal analysis of the contribution of pollen-derived adenosine to allergic sensitization.

PubMed

Mueller, Geoffrey A; Thompson, Peter M; DeRose, Eugene F; O'Connell, Thomas M; London, Robert E

2016-12-01

Studies on ragweed and birch pollen extracts suggested that the adenosine content is an important factor in allergic sensitization. However, exposure levels from other pollens and considerations of geographic and seasonal factors have not been evaluated. This study compared the metabolite profile of pollen species important for allergic disease, specifically measured the adenosine content, and evaluated exposure to pollen-derived adenosine. An NMR metabolomics approach was used to measure metabolite concentrations in twenty-six pollen extracts. Pollen count data was analyzed from five cities to model exposure. A principal component analysis of the various metabolites identified by NMR showed that pollen extracts could be differentiated primarily by sugar content: glucose, fructose, sucrose, and myo-inositol. In extracts of 10 mg of pollen/ml, the adenosine was highest for grasses (45 μM) followed by trees (23 μM) and weeds (19 μM). Pollen count data showed that tree pollen was typically 5-10 times the amount of other pollens. At the daily peaks of tree, grass, and weed season the pollen-derived adenosine exposure per day is likely to only be 1.1, 0.11, and 0.12 μg, respectively. Seasonal models of pollen exposure and respiration suggest that it would be a rare event limited to tree pollen season for concentrations of pollen-derived adenosine to approach physiological levels. Sugar content and other metabolites may be useful in classifying pollens. Unless other factors create localized exposures that are very different from these models, pollen-derived adenosine is unlikely to be a major factor in allergic sensitization.

Trade Studies of Space Launch Architectures using Modular Probabilistic Risk Analysis

NASA Technical Reports Server (NTRS)

Mathias, Donovan L.; Go, Susie

2006-01-01

A top-down risk assessment in the early phases of space exploration architecture development can provide understanding and intuition of the potential risks associated with new designs and technologies. In this approach, risk analysts draw from their past experience and the heritage of similar existing systems as a source for reliability data. This top-down approach captures the complex interactions of the risk driving parts of the integrated system without requiring detailed knowledge of the parts themselves, which is often unavailable in the early design stages. Traditional probabilistic risk analysis (PRA) technologies, however, suffer several drawbacks that limit their timely application to complex technology development programs. The most restrictive of these is a dependence on static planning scenarios, expressed through fault and event trees. Fault trees incorporating comprehensive mission scenarios are routinely constructed for complex space systems, and several commercial software products are available for evaluating fault statistics. These static representations cannot capture the dynamic behavior of system failures without substantial modification of the initial tree. Consequently, the development of dynamic models using fault tree analysis has been an active area of research in recent years. This paper discusses the implementation and demonstration of dynamic, modular scenario modeling for integration of subsystem fault evaluation modules using the Space Architecture Failure Evaluation (SAFE) tool. SAFE is a C++ code that was originally developed to support NASA s Space Launch Initiative. It provides a flexible framework for system architecture definition and trade studies. SAFE supports extensible modeling of dynamic, time-dependent risk drivers of the system and functions at the level of fidelity for which design and failure data exists. The approach is scalable, allowing inclusion of additional information as detailed data becomes available. The tool performs a Monte Carlo analysis to provide statistical estimates. Example results of an architecture system reliability study are summarized for an exploration system concept using heritage data from liquid-fueled expendable Saturn V/Apollo launch vehicles.

Factors impacting stemflow generation in a European beech forest: Individual tree versus neighborhood properties

NASA Astrophysics Data System (ADS)

Metzger, Johanna Clara; Germer, Sonja; Hildebrandt, Anke

2017-04-01

The redistribution of precipitation by canopies changes the water flow dynamics to the forest floor. The spatial pattern of throughfall has been researched in a number of studies in different ecosystems. Yet, also stemflow substantially influences water input patterns, constituting a mean of 12% of gross precipitation for European beech as one of the most abundant tree species in Central Europe. While the initiation of stemflow depends mostly on precipitation event properties, stemflow amounts are strongly shaped by canopy structure. Stemflow research has mainly addressed the impact of single tree morphological variables. In previous studies, the impact of forest structure on area-based stemflow was studied comparing plots with different properties using few exemplary stemflow measurements. In non-homogeneous stands, this approach might not be accurate, as the variation of stand properties like tree density could change tree individual stemflow fluxes. To investigate this, a total measurement of all trees per plot is required. We hypothesize, that in addition to individual tree metrics, tree neighborhood relations have a significant impact on stemflow generation in a heterogeneous beech forest. Our study site is located in the pristine forest of the National Park Hainich, central Germany. It is heterogeneous in respect to tree density, species composition and tree age. We measured stemflow in an areal approach, for all trees on 11 subplots (each 10 m x 10 m) spaced evenly throughout a 1 ha plot. This involved overall 65 trees, which is 11% of the plot's trees. 27 precipitation events were recorded in spring and early summer of 2015 and 2016. Stand properties were surveyed, including diameter at breast height, height, position and species of a tree. From this data, we calculated neighborhood properties for each tree, as number, basal area, and relative height of neighboring trees within a radius of the plot's mean tree distance. Using linear mixed effects models, we identified the different factors, individual and neighborhood, which significantly explain stemflow amount per tree. Preliminary results show, that the main impact on stemflow in our heterogeneous beech forest is due to individual tree diameter at breast height, while neighborhood factors have a smaller influence. This work defines the most important factors for stemflow fluxes, using easy-to-acquire tree and stand information, which allows the robust extrapolation of stemflow measurements and the generation of a spatially discrete pattern of stemflow input to the soil. Because of the high local and temporal concentration of precipitation, stemflow fluxes could be a key factor in forest soil water dynamics. On the long run, the results shall enable us to directly link soil water content measurements with estimated stemflow volumes for individual trees to trace stemflow fluxes into and through the soil.

Health Management Applications for International Space Station

NASA Technical Reports Server (NTRS)

Alena, Richard; Duncavage, Dan

2005-01-01

Traditional mission and vehicle management involves teams of highly trained specialists monitoring vehicle status and crew activities, responding rapidly to any anomalies encountered during operations. These teams work from the Mission Control Center and have access to engineering support teams with specialized expertise in International Space Station (ISS) subsystems. Integrated System Health Management (ISHM) applications can significantly augment these capabilities by providing enhanced monitoring, prognostic and diagnostic tools for critical decision support and mission management. The Intelligent Systems Division of NASA Ames Research Center is developing many prototype applications using model-based reasoning, data mining and simulation, working with Mission Control through the ISHM Testbed and Prototypes Project. This paper will briefly describe information technology that supports current mission management practice, and will extend this to a vision for future mission control workflow incorporating new ISHM applications. It will describe ISHM applications currently under development at NASA and will define technical approaches for implementing our vision of future human exploration mission management incorporating artificial intelligence and distributed web service architectures using specific examples. Several prototypes are under development, each highlighting a different computational approach. The ISStrider application allows in-depth analysis of Caution and Warning (C&W) events by correlating real-time telemetry with the logical fault trees used to define off-nominal events. The application uses live telemetry data and the Livingstone diagnostic inference engine to display the specific parameters and fault trees that generated the C&W event, allowing a flight controller to identify the root cause of the event from thousands of possibilities by simply navigating animated fault tree models on their workstation. SimStation models the functional power flow for the ISS Electrical Power System and can predict power balance for nominal and off-nominal conditions. SimStation uses realtime telemetry data to keep detailed computational physics models synchronized with actual ISS power system state. In the event of failure, the application can then rapidly diagnose root cause, predict future resource levels and even correlate technical documents relevant to the specific failure. These advanced computational models will allow better insight and more precise control of ISS subsystems, increasing safety margins by speeding up anomaly resolution and reducing,engineering team effort and cost. This technology will make operating ISS more efficient and is directly applicable to next-generation exploration missions and Crew Exploration Vehicles.

Characterization of Extreme Deposition of Air Pollutants in MT. Mitchell State Park: Potential for Forest Decline and Opportunity for Cloud Deacidification

NASA Astrophysics Data System (ADS)

Defelice, Thomas Peter

The decline of forests has long been attributed to various natural (e.g. drought), man-made (e.g. logging), and perhaps, combinations of these (eg. fires caused by loggers) causes. A new type of forest decline (attributed to the deposition of air pollutants and other natural causes) has become apparent at high elevation sites in western Europe and North America; especially for above cloudbase forests like those in the Mt. Mitchell State Park. Investigations of air pollutant deposition are plentiful and laboratory studies have shown extreme deposition of these pollutants to be potentially harmful to forests. However, no field study has concentrated on these events. The primary objective of this study is to characterize (i.e., meterologically, microphysically, chemically) extreme episodes of air pollutant deposition. This study defines extreme aqueous events as having a pH < 3.1. pH's of this order are known to reduce laboratory tree growth depending on their age and species. On the average, one out of three aqueous events, sampled in the park during the 1986-1988 growing seasons (mid-May through mid-September), was extreme. Their occurrence over time may lead to the death of infant and 'old' trees, and to the reduced vigor of trees in their prime, as a result of triggering the decline mechanisms of these trees. These events usually last ~ 4.0 h, form during extended periods of high atmospheric pressure, have a liquid water content of ~ 0.10 gm^{-3}, and near typical cloud droplet sizes (~ 8.0 μm). Extreme aqueous events deposit most of their acid at their end. The deposition from the infrequent occurrences of very high ozone ( >=q100 ppb) and sulfur dioxide (>=q 5 ppb) concentrations in conjunction with these cloud events may be even more detrimental to the canopy, then that by extreme aqueous events alone. The physical characteristics of these combined events appear to include those of mature, precipitating clouds. Their occurrence may provide a clue as to how very low pH clouds might be deacidified. That is, base gases (eg. ammonia) locally introduced into such clouds at the proper time may render them harmless upon impact with the forest canopy, and beneficial to regional water supply users.

30 CFR 250.619 - Tubing and wellhead equipment.

Code of Federal Regulations, 2013 CFR

2013-07-01

... during well-workover operations with the tree removed: (a) No tubing string shall be placed in service or... otherwise suitable for its intended use. (b) In the event of prolonged operations such as milling, fishing... the tree, you must: (1) Equip wells to monitor for casing pressure according to the following chart...

30 CFR 250.618 - Tubing and wellhead equipment.

Code of Federal Regulations, 2012 CFR

2012-07-01

... during well-workover operations with the tree removed: (a) No tubing string shall be placed in service or... otherwise suitable for its intended use. (b) In the event of prolonged operations such as milling, fishing... the tree, you must: (1) Equip wells to monitor for casing pressure according to the following chart...

30 CFR 250.619 - Tubing and wellhead equipment.

Code of Federal Regulations, 2014 CFR

2014-07-01

... during well-workover operations with the tree removed: (a) No tubing string shall be placed in service or... otherwise suitable for its intended use. (b) In the event of prolonged operations such as milling, fishing... the tree, you must: (1) Equip wells to monitor for casing pressure according to the following chart...

High-resolution climate signals in the Bølling Allerød Interstadial (Greenland Interstadial 1) as reflected in European tree-ring chronologies compared to marine varves and ice-core records

NASA Astrophysics Data System (ADS)

Friedrich, Michael; Kromer, Bernd; Kaiser, Klaus F.; Spurk, Marco; Hughen, Konrad A.; Johnsen, Sigfus J.

2001-05-01

Lateglacial and Holocene tree-ring chronologies are unique archives, which provide various information on past environments on a true annual time scale. Changes in ring-width can be related to past climate anomalies and dendrodated wood provides an ideal source for radiocarbon calibration. We present a 1051 year tree-ring chronology from the Late Glacial, built from subfossil Scots pines (Pinus sylvestris) that grew in different regions of Central and Southern Europe. Through a series of high-precision radiocarbon measurements we obtained a floating radiocarbon chronology, which allowed accurate wiggle-matching to the INTCAL98 calibration curve. The trees show a coherent pattern in ring-width variations throughout Central Europe, and extending into the Mediterranean, which indicates a strong external climatic factor, most probably temperature during the growing season. We identified major growth events, which appear synchronous with events seen in isotopic and tracer signals in the Greenland ice cores and with changes in the strength of upwelling in the Cariaco Basin.

A practical approximation algorithm for solving massive instances of hybridization number for binary and nonbinary trees.

PubMed

van Iersel, Leo; Kelk, Steven; Lekić, Nela; Scornavacca, Celine

2014-05-05

Reticulate events play an important role in determining evolutionary relationships. The problem of computing the minimum number of such events to explain discordance between two phylogenetic trees is a hard computational problem. Even for binary trees, exact solvers struggle to solve instances with reticulation number larger than 40-50. Here we present CycleKiller and NonbinaryCycleKiller, the first methods to produce solutions verifiably close to optimality for instances with hundreds or even thousands of reticulations. Using simulations, we demonstrate that these algorithms run quickly for large and difficult instances, producing solutions that are very close to optimality. As a spin-off from our simulations we also present TerminusEst, which is the fastest exact method currently available that can handle nonbinary trees: this is used to measure the accuracy of the NonbinaryCycleKiller algorithm. All three methods are based on extensions of previous theoretical work (SIDMA 26(4):1635-1656, TCBB 10(1):18-25, SIDMA 28(1):49-66) and are publicly available. We also apply our methods to real data.

Seasonally Resolved Oxygen Isotope Paleoclimate Proxy in Tree-Ring Cellulose from the Southeastern U.S.

NASA Astrophysics Data System (ADS)

Miller, D. L.; Mora, C. I.; Grissino-Mayer, H. D.; Mock, C. J.

2004-12-01

Stable isotopes in precipitation reflect changes in climate, moisture source, and extreme events such as tropical cyclones, and an oxygen isotope proxy record of these changes through time and space is preserved in tree-ring cellulose. Extreme climate events such as droughts and hurricanes are formidable natural disasters in the southeastern United States, and considerable efforts have been made to understand factors controlling their frequency, whether natural or anthropogenic. Tree rings offer an unusually well-resolved, dateable record of climate events extending beyond modern or historical (documentary) records. Oxygen isotopes in alpha-cellulose of shallowly-rooted conifers predominately reflect the composition of precipitation. Tropical storm convection results in marked 18O depletion in storm precipitation, to -15‰ relative to source seawater (~0‰ ). The depletion increases towards the eyewall of the cyclone, however, isotopically depleted precipitation may extend outward many 100's of km. Storm water 18O depletion translates to soil water 18O depletion that may persist for many weeks until ameliorated by soil water evaporation. Tree growth during that time will take up the anomalous isotopic compositions. Distinctive earlywood (EW ~March-June) versus latewood (LW ~July-October) growth allows the rings to be resolved at an intra-annual (seasonal) scale. By comparison to average soil water, droughts result in 18O-enriched soil water compositions. Seasonal drought or years of continued drought will be similarly captured in the isotope compositions of tree-ring cellulose. A 227-year (1770-1997) seasonally-resolved record of tropical cyclone and drought activity was obtained from cross-sections of felled slash pines (Pinus elliottii Engelm.) and remnant longleaf pines (Pinus palustris Mill.) from southern Georgia. Interpretations of drought or hurricane events were tested by comparison with recent, detailed meteorological records. The 227-year record reveals most previously established hurricane events, including Florence (1953) and the Great Hurricane of 1780. Newly recognized tropical storms such as 1857 are also evident. Significant seasonal droughts such as 1955, 1927, 1904 and 1896, are observed for southeastern Georgia. Larger-scale climate oscillations appear to overprint the EW and LW isotope series, displaying periods of relatively large or small differences in EW and LW δ 18O values. The oscillations are interpreted to reflect dominant climate modes that influence moisture source or seasonal temperature variation. The tree-ring record potentially extends many centuries. A preliminary record through a portion of the North American "Little Ice Age" (1580-1650) indicates a significant reduction in tropical cyclone activity.

Tree-ring analysis of ancient baldcypress trees and subfossil wood

NASA Astrophysics Data System (ADS)

Stahle, David W.; Burnette, Dorian J.; Villanueva, Jose; Cerano, Julian; Fye, Falko K.; Griffin, R. Daniel; Cleaveland, Malcolm K.; Stahle, Daniel K.; Edmondson, Jesse R.; Wolff, Kathryn P.

2012-02-01

Ancient baldcypress trees found in wetland and riverine environments have been used to develop a network of exactly dated annual ring-width chronologies extending from the southeastern United States, across Mexico, and into western Guatemala. These chronologies are sensitive to growing season precipitation in spite of frequently flooded site conditions, and have been used to reconstruct moisture levels the southeastern United States and Mexico for over 1000 years. The El Nino/Southern Oscillation (ENSO) is a major influence on the climate reconstructions derived from these baldcypress chronologies, especially in Mexico where some of the most extreme reconstructed droughts occurred during El Nino events. In the Southeast, the ENSO influence on climate and tree growth changes sign from spring to summer, and this change in dynamical forcing is recorded by sub-seasonal chronologies of earlywood and latewood width. Most existing baldcypress chronologies have been extended with tree-ring data from "subfossil" wood recovered from surface and submerged deposits. Well-preserved subfossil logs have also been recovered in quantity from buried deposits of great age, and may permit development of long continuously dated Holocene chronologies and discontinuous "floating" Pleistocene chronologies. The extensive subfossil baldcypress swamp discovered 6 m below the streets of Washington D.C. was overrun by a transgression of the Potomac estuary, possibly during the previous super interglacial (marine OIS 5e), and provides direct evidence for one potential impact of unmitigated anthropogenic warming and sea level rise.

Multilocus inference of species trees and DNA barcoding.

PubMed

Mallo, Diego; Posada, David

2016-09-05

The unprecedented amount of data resulting from next-generation sequencing has opened a new era in phylogenetic estimation. Although large datasets should, in theory, increase phylogenetic resolution, massive, multilocus datasets have uncovered a great deal of phylogenetic incongruence among different genomic regions, due both to stochastic error and to the action of different evolutionary process such as incomplete lineage sorting, gene duplication and loss and horizontal gene transfer. This incongruence violates one of the fundamental assumptions of the DNA barcoding approach, which assumes that gene history and species history are identical. In this review, we explain some of the most important challenges we will have to face to reconstruct the history of species, and the advantages and disadvantages of different strategies for the phylogenetic analysis of multilocus data. In particular, we describe the evolutionary events that can generate species tree-gene tree discordance, compare the most popular methods for species tree reconstruction, highlight the challenges we need to face when using them and discuss their potential utility in barcoding. Current barcoding methods sacrifice a great amount of statistical power by only considering one locus, and a transition to multilocus barcodes would not only improve current barcoding methods, but also facilitate an eventual transition to species-tree-based barcoding strategies, which could better accommodate scenarios where the barcode gap is too small or inexistent.This article is part of the themed issue 'From DNA barcodes to biomes'. © 2016 The Authors.

Exact Algorithms for Duplication-Transfer-Loss Reconciliation with Non-Binary Gene Trees.

PubMed

Kordi, Misagh; Bansal, Mukul S

2017-06-01

Duplication-Transfer-Loss (DTL) reconciliation is a powerful method for studying gene family evolution in the presence of horizontal gene transfer. DTL reconciliation seeks to reconcile gene trees with species trees by postulating speciation, duplication, transfer, and loss events. Efficient algorithms exist for finding optimal DTL reconciliations when the gene tree is binary. In practice, however, gene trees are often non-binary due to uncertainty in the gene tree topologies, and DTL reconciliation with non-binary gene trees is known to be NP-hard. In this paper, we present the first exact algorithms for DTL reconciliation with non-binary gene trees. Specifically, we (i) show that the DTL reconciliation problem for non-binary gene trees is fixed-parameter tractable in the maximum degree of the gene tree, (ii) present an exponential-time, but in-practice efficient, algorithm to track and enumerate all optimal binary resolutions of a non-binary input gene tree, and (iii) apply our algorithms to a large empirical data set of over 4700 gene trees from 100 species to study the impact of gene tree uncertainty on DTL-reconciliation and to demonstrate the applicability and utility of our algorithms. The new techniques and algorithms introduced in this paper will help biologists avoid incorrect evolutionary inferences caused by gene tree uncertainty.

Estimation on rubber tree disturbance caused by typhoon Damery (200518) with Landsat and MODIS data in Hainan Island of China

NASA Astrophysics Data System (ADS)

Tan, Chenyan; Fang, Weihua; Li, Jian

2016-04-01

In 2005, Typhoon Damery (200518) caused severe damage to the rubber trees in Hainan Island with its destructive winds and rainfall. Selection of proper vegetation indices using multi-source remote sensing data is critical to the assessment of forest disturbance and damage loss for this event. In this study, we will compare the performance of seven vegetation indices derived from MODIS and Landsat TM imageries prior to and after typhoon Damery, in order to select an optimal index for identifying rubber tree disturbance. The indices to be compared are normalized difference vegetation index (NDVI), Normalized Difference Water Index (NDWI), Normalized Difference Infrared Index (NDII), Enhanced vegetation index (EVI), Leaf area index (LAI), forest z-score (IFZ), and Disturbance Index (DI). The ground truth data of rubber tree damage collected through field investigation was used to verify and compare the results. Our preliminary result for the area with ground-truth data shows that DI has the most significant performance for disturbance detection for this typhoon event. This index DI is then applied to all the areas in Hainan Island hit by Darmey to evaluate the overall forest damage severity. At last, rubber tree damage severity is analyzed with other typhoon hazard factors such as wind, topography, soil and precipitation.

Tree diversity does not always improve resistance of forest ecosystems to drought.

PubMed

Grossiord, Charlotte; Granier, André; Ratcliffe, Sophia; Bouriaud, Olivier; Bruelheide, Helge; Chećko, Ewa; Forrester, David Ian; Dawud, Seid Muhie; Finér, Leena; Pollastrini, Martina; Scherer-Lorenzen, Michael; Valladares, Fernando; Bonal, Damien; Gessler, Arthur

2014-10-14

Climate models predict an increase in the intensity and frequency of drought episodes in the Northern Hemisphere. Among terrestrial ecosystems, forests will be profoundly impacted by drier climatic conditions, with drastic consequences for the functions and services they supply. Simultaneously, biodiversity is known to support a wide range of forest ecosystem functions and services. However, whether biodiversity also improves the resistance of these ecosystems to drought remains unclear. We compared soil drought exposure levels in a total of 160 forest stands within five major forest types across Europe along a gradient of tree species diversity. We assessed soil drought exposure in each forest stand by calculating the stand-level increase in carbon isotope composition of late wood from a wet to a dry year (Δδ(13)CS). Δδ(13)CS exhibited a negative linear relationship with tree species diversity in two forest types, suggesting that species interactions in these forests diminished the drought exposure of the ecosystem. However, the other three forest types were unaffected by tree species diversity. We conclude that higher diversity enhances resistance to drought events only in drought-prone environments. Managing forest ecosystems for high tree species diversity does not necessarily assure improved adaptability to the more severe and frequent drought events predicted for the future.

Computing all hybridization networks for multiple binary phylogenetic input trees.

PubMed

Albrecht, Benjamin

2015-07-30

The computation of phylogenetic trees on the same set of species that are based on different orthologous genes can lead to incongruent trees. One possible explanation for this behavior are interspecific hybridization events recombining genes of different species. An important approach to analyze such events is the computation of hybridization networks. This work presents the first algorithm computing the hybridization number as well as a set of representative hybridization networks for multiple binary phylogenetic input trees on the same set of taxa. To improve its practical runtime, we show how this algorithm can be parallelized. Moreover, we demonstrate the efficiency of the software Hybroscale, containing an implementation of our algorithm, by comparing it to PIRNv2.0, which is so far the best available software computing the exact hybridization number for multiple binary phylogenetic trees on the same set of taxa. The algorithm is part of the software Hybroscale, which was developed specifically for the investigation of hybridization networks including their computation and visualization. Hybroscale is freely available(1) and runs on all three major operating systems. Our simulation study indicates that our approach is on average 100 times faster than PIRNv2.0. Moreover, we show how Hybroscale improves the interpretation of the reported hybridization networks by adding certain features to its graphical representation.

Testing for Polytomies in Phylogenetic Species Trees Using Quartet Frequencies.

PubMed

Sayyari, Erfan; Mirarab, Siavash

2018-02-28

Phylogenetic species trees typically represent the speciation history as a bifurcating tree. Speciation events that simultaneously create more than two descendants, thereby creating polytomies in the phylogeny, are possible. Moreover, the inability to resolve relationships is often shown as a (soft) polytomy. Both types of polytomies have been traditionally studied in the context of gene tree reconstruction from sequence data. However, polytomies in the species tree cannot be detected or ruled out without considering gene tree discordance. In this paper, we describe a statistical test based on properties of the multi-species coalescent model to test the null hypothesis that a branch in an estimated species tree should be replaced by a polytomy. On both simulated and biological datasets, we show that the null hypothesis is rejected for all but the shortest branches, and in most cases, it is retained for true polytomies. The test, available as part of the Accurate Species TRee ALgorithm (ASTRAL) package, can help systematists decide whether their datasets are sufficient to resolve specific relationships of interest.

Testing for Polytomies in Phylogenetic Species Trees Using Quartet Frequencies

PubMed Central

Sayyari, Erfan

2018-01-01

Phylogenetic species trees typically represent the speciation history as a bifurcating tree. Speciation events that simultaneously create more than two descendants, thereby creating polytomies in the phylogeny, are possible. Moreover, the inability to resolve relationships is often shown as a (soft) polytomy. Both types of polytomies have been traditionally studied in the context of gene tree reconstruction from sequence data. However, polytomies in the species tree cannot be detected or ruled out without considering gene tree discordance. In this paper, we describe a statistical test based on properties of the multi-species coalescent model to test the null hypothesis that a branch in an estimated species tree should be replaced by a polytomy. On both simulated and biological datasets, we show that the null hypothesis is rejected for all but the shortest branches, and in most cases, it is retained for true polytomies. The test, available as part of the Accurate Species TRee ALgorithm (ASTRAL) package, can help systematists decide whether their datasets are sufficient to resolve specific relationships of interest. PMID:29495636

Probabilistic short-term volcanic hazard in phases of unrest: A case study for tephra fallout

NASA Astrophysics Data System (ADS)

Selva, Jacopo; Costa, Antonio; Sandri, Laura; Macedonio, Giovanni; Marzocchi, Warner

2014-12-01

During volcanic crises, volcanologists estimate the impact of possible imminent eruptions usually through deterministic modeling of the effects of one or a few preestablished scenarios. Despite such an approach may bring an important information to the decision makers, the sole use of deterministic scenarios does not allow scientists to properly take into consideration all uncertainties, and it cannot be used to assess quantitatively the risk because the latter unavoidably requires a probabilistic approach. We present a model based on the concept of Bayesian event tree (hereinafter named BET_VH_ST, standing for Bayesian event tree for short-term volcanic hazard), for short-term near-real-time probabilistic volcanic hazard analysis formulated for any potential hazardous phenomenon accompanying an eruption. The specific goal of BET_VH_ST is to produce a quantitative assessment of the probability of exceedance of any potential level of intensity for a given volcanic hazard due to eruptions within restricted time windows (hours to days) in any area surrounding the volcano, accounting for all natural and epistemic uncertainties. BET_VH_ST properly assesses the conditional probability at each level of the event tree accounting for any relevant information derived from the monitoring system, theoretical models, and the past history of the volcano, propagating any relevant epistemic uncertainty underlying these assessments. As an application example of the model, we apply BET_VH_ST to assess short-term volcanic hazard related to tephra loading during Major Emergency Simulation Exercise, a major exercise at Mount Vesuvius that took place from 19 to 23 October 2006, consisting in a blind simulation of Vesuvius reactivation, from the early warning phase up to the final eruption, including the evacuation of a sample of about 2000 people from the area at risk. The results show that BET_VH_ST is able to produce short-term forecasts of the impact of tephra fall during a rapidly evolving crisis, accurately accounting for and propagating all uncertainties and enabling rational decision making under uncertainty.

Effects of protection forests on rockfall risks: implementation in the Swiss risk concept

NASA Astrophysics Data System (ADS)

Trappmann, Daniel; Moos, Christine; Fehlmann, Michael; Ernst, Jacqueline; Sandri, Arthur; Dorren, Luuk; Stoffel, Markus

2016-04-01

Forests growing on slopes below active rockfall cliffs can provide effective protection for human lives and infrastructures. The risk-based approach for natural hazards in Switzerland shall take such biological measures just like existing technical protective measures into account, provided that certain criteria regarding condition, maintenance and durability are met. This contribution describes a project in which we are investigating how the effects of protection forests can be considered in rockfall risk analyses in an appropriate way. In principle, protection forests reduce rockfall risks in three different ways: (i) reduction of the event magnitude (energy) due to collisions with tree stems; (ii) reduction of frequency of occurrence of a given scenario (block volume arriving at the damage potential); (iii) reduction of spatial probability of occurrence (spread and runout) of a given scenario in case of multiple fragments during one event. The aim of this work is to develop methods for adequately implementing these three effects of rockfall protection forests in risk calculations. To achieve this, we use rockfall simulations taking collisions with trees into account and detailed field validation. On five test sites, detailed knowledge on past rockfall activity is gathered by combining investigations of impacted trees, analysis of documented historical events, and deposits in the field. Based on this empirical data on past rockfalls, a methodology is developed that allows transferring real past rockfall activity to simulation results obtained with the three-dimensional, process-based model Rockyfor3D. Different ways of quantifying the protective role of forests will be considered by comparing simulation results with and without forest cover. Combining these different research approaches, systematic considerations shall lead to the development of methods for adequate inclusion of the protective effects of forests in risk calculations. The applicability of the developed methods will be tested on the case study slopes in order to ensure practical applicability to a broad range of rockfall situations on forested slopes.

Constraining the timing of the Great Oxidation Event within the Rubisco phylogenetic tree.

PubMed

Kacar, B; Hanson-Smith, V; Adam, Z R; Boekelheide, N

2017-09-01

Ribulose 1,5-bisphosphate (RuBP) carboxylase/oxygenase (RuBisCO, or Rubisco) catalyzes a key reaction by which inorganic carbon is converted into organic carbon in the metabolism of many aerobic and anaerobic organisms. Across the broader Rubisco protein family, homologs exhibit diverse biochemical characteristics and metabolic functions, but the evolutionary origins of this diversity are unclear. Evidence of the timing of Rubisco family emergence and diversification of its different forms has been obscured by a meager paleontological record of early Earth biota, their subcellular physiology and metabolic components. Here, we use computational models to reconstruct a Rubisco family phylogenetic tree, ancestral amino acid sequences at branching points on the tree, and protein structures for several key ancestors. Analysis of historic substitutions with respect to their structural locations shows that there were distinct periods of amino acid substitution enrichment above background levels near and within its oxygen-sensitive active site and subunit interfaces over the divergence between Form III (associated with anoxia) and Form I (associated with oxia) groups in its evolutionary history. One possible interpretation is that these periods of substitutional enrichment are coincident with oxidative stress exerted by the rise of oxygenic photosynthesis in the Precambrian era. Our interpretation implies that the periods of Rubisco substitutional enrichment inferred near the transition from anaerobic Form III to aerobic Form I ancestral sequences predate the acquisition of Rubisco by fully derived cyanobacterial (i.e., dual photosystem-bearing, oxygen-evolving) clades. The partitioning of extant lineages at high clade levels within our Rubisco phylogeny indicates that horizontal transfer of Rubisco is a relatively infrequent event. Therefore, it is possible that the mutational enrichment periods between the Form III and Form I common ancestral sequences correspond to the adaptation of key oxygen-sensitive components of Rubisco prior to, or coincident with, the Great Oxidation Event. © 2017 The Authors. Geobiology Published by John Wiley & Sons Ltd.

Temperature response surfaces for mortality risk of tree species with future drought

DOE PAGES

Adams, Henry D.; Barron-Gafford, Greg A.; Minor, Rebecca L.; ...

2017-11-17

Widespread, high levels of tree mortality, termed forest die-off, associated with drought and rising temperatures, are disrupting forests worldwide. Drought will likely become more frequent with climate change, but even without more frequent drought, higher temperatures can exacerbate tree water stress. The temperature sensitivity of drought-induced mortality of tree species has been evaluated experimentally for only single-step changes in temperature (ambient compared to ambient + increase) rather than as a response surface (multiple levels of temperature increase), which constrains our ability to relate changes in the driver with the biological response. Here we show that time-to-mortality during drought for seedlingsmore » of two western United States tree species, Pinus edulis (Engelm.) and Pinus ponderosa (Douglas ex C. Lawson), declined in continuous proportion with increasing temperature spanning a 7.7 °C increase. Although P. edulis outlived P. ponderosa at all temperatures, both species had similar relative declines in time-to-mortality as temperature increased (5.2% per °C for P. edulis; 5.8% per °C for P. ponderosa). When combined with the non-linear frequency distribution of drought duration—many more short droughts than long droughts—these findings point to a progressive increase in mortality events with global change due to warming alone and independent of additional changes in future drought frequency distributions. As such, dire future forest recruitment patterns are projected assuming the calculated 7–9 seedling mortality events per species by 2100 under business-as-usual warming occur, congruent with additional vulnerability predicted for adult trees from stressors like pathogens and pests. Our progressive projection for increased mortality events was driven primarily by the non-linear shape of the drought duration frequency distribution, a common climate feature of drought-affected regions. These results illustrate profound benefits for reducing emissions of carbon to the atmosphere from anthropogenic sources and slowing warming as rapidly as possible to maximize forest persistence.« less

Temperature response surfaces for mortality risk of tree species with future drought

NASA Astrophysics Data System (ADS)

Adams, Henry D.; Barron-Gafford, Greg A.; Minor, Rebecca L.; Gardea, Alfonso A.; Bentley, Lisa Patrick; Law, Darin J.; Breshears, David D.; McDowell, Nate G.; Huxman, Travis E.

2017-11-01

Widespread, high levels of tree mortality, termed forest die-off, associated with drought and rising temperatures, are disrupting forests worldwide. Drought will likely become more frequent with climate change, but even without more frequent drought, higher temperatures can exacerbate tree water stress. The temperature sensitivity of drought-induced mortality of tree species has been evaluated experimentally for only single-step changes in temperature (ambient compared to ambient + increase) rather than as a response surface (multiple levels of temperature increase), which constrains our ability to relate changes in the driver with the biological response. Here we show that time-to-mortality during drought for seedlings of two western United States tree species, Pinus edulis (Engelm.) and Pinus ponderosa (Douglas ex C. Lawson), declined in continuous proportion with increasing temperature spanning a 7.7 °C increase. Although P. edulis outlived P. ponderosa at all temperatures, both species had similar relative declines in time-to-mortality as temperature increased (5.2% per °C for P. edulis; 5.8% per °C for P. ponderosa). When combined with the non-linear frequency distribution of drought duration—many more short droughts than long droughts—these findings point to a progressive increase in mortality events with global change due to warming alone and independent of additional changes in future drought frequency distributions. As such, dire future forest recruitment patterns are projected assuming the calculated 7-9 seedling mortality events per species by 2100 under business-as-usual warming occur, congruent with additional vulnerability predicted for adult trees from stressors like pathogens and pests. Our progressive projection for increased mortality events was driven primarily by the non-linear shape of the drought duration frequency distribution, a common climate feature of drought-affected regions. These results illustrate profound benefits for reducing emissions of carbon to the atmosphere from anthropogenic sources and slowing warming as rapidly as possible to maximize forest persistence.

Temperature response surfaces for mortality risk of tree species with future drought

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adams, Henry D.; Barron-Gafford, Greg A.; Minor, Rebecca L.

Widespread, high levels of tree mortality, termed forest die-off, associated with drought and rising temperatures, are disrupting forests worldwide. Drought will likely become more frequent with climate change, but even without more frequent drought, higher temperatures can exacerbate tree water stress. The temperature sensitivity of drought-induced mortality of tree species has been evaluated experimentally for only single-step changes in temperature (ambient compared to ambient + increase) rather than as a response surface (multiple levels of temperature increase), which constrains our ability to relate changes in the driver with the biological response. Here we show that time-to-mortality during drought for seedlingsmore » of two western United States tree species, Pinus edulis (Engelm.) and Pinus ponderosa (Douglas ex C. Lawson), declined in continuous proportion with increasing temperature spanning a 7.7 °C increase. Although P. edulis outlived P . ponderosa at all temperatures, both species had similar relative declines in time-to-mortality as temperature increased (5.2% per °C for P. edulis; 5.8% per °C for P. ponderosa). When combined with the non-linear frequency distribution of drought duration—many more short droughts than long droughts—these findings point to a progressive increase in mortality events with global change due to warming alone and independent of additional changes in future drought frequency distributions. As such, dire future forest recruitment patterns are projected assuming the calculated 7-9 seedling mortality events per species by 2100 under business-as-usual warming occurs, congruent with additional vulnerability predicted for adult trees from stressors like pathogens and pests. Our progressive projection for increased mortality events was driven primarily by the non-linear shape of the drought duration frequency distribution, a common climate feature of drought-affected regions. These results illustrate profound benefits for reducing emissions of carbon to the atmosphere from anthropogenic sources and slowing warming as rapidly as possible to maximize forest persistence.« less

Temperature response surfaces for mortality risk of tree species with future drought

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adams, Henry D.; Barron-Gafford, Greg A.; Minor, Rebecca L.

Widespread, high levels of tree mortality, termed forest die-off, associated with drought and rising temperatures, are disrupting forests worldwide. Drought will likely become more frequent with climate change, but even without more frequent drought, higher temperatures can exacerbate tree water stress. The temperature sensitivity of drought-induced mortality of tree species has been evaluated experimentally for only single-step changes in temperature (ambient compared to ambient + increase) rather than as a response surface (multiple levels of temperature increase), which constrains our ability to relate changes in the driver with the biological response. Here we show that time-to-mortality during drought for seedlingsmore » of two western United States tree species, Pinus edulis (Engelm.) and Pinus ponderosa (Douglas ex C. Lawson), declined in continuous proportion with increasing temperature spanning a 7.7 °C increase. Although P. edulis outlived P. ponderosa at all temperatures, both species had similar relative declines in time-to-mortality as temperature increased (5.2% per °C for P. edulis; 5.8% per °C for P. ponderosa). When combined with the non-linear frequency distribution of drought duration—many more short droughts than long droughts—these findings point to a progressive increase in mortality events with global change due to warming alone and independent of additional changes in future drought frequency distributions. As such, dire future forest recruitment patterns are projected assuming the calculated 7–9 seedling mortality events per species by 2100 under business-as-usual warming occur, congruent with additional vulnerability predicted for adult trees from stressors like pathogens and pests. Our progressive projection for increased mortality events was driven primarily by the non-linear shape of the drought duration frequency distribution, a common climate feature of drought-affected regions. These results illustrate profound benefits for reducing emissions of carbon to the atmosphere from anthropogenic sources and slowing warming as rapidly as possible to maximize forest persistence.« less

Comparing Phylogenetic Trees by Matching Nodes Using the Transfer Distance Between Partitions

PubMed Central

Giaro, Krzysztof

2017-01-01

Abstract Ability to quantify dissimilarity of different phylogenetic trees describing the relationship between the same group of taxa is required in various types of phylogenetic studies. For example, such metrics are used to assess the quality of phylogeny construction methods, to define optimization criteria in supertree building algorithms, or to find horizontal gene transfer (HGT) events. Among the set of metrics described so far in the literature, the most commonly used seems to be the Robinson–Foulds distance. In this article, we define a new metric for rooted trees—the Matching Pair (MP) distance. The MP metric uses the concept of the minimum-weight perfect matching in a complete bipartite graph constructed from partitions of all pairs of leaves of the compared phylogenetic trees. We analyze the properties of the MP metric and present computational experiments showing its potential applicability in tasks related to finding the HGT events. PMID:28177699

Mapping tree density in forests of the southwestern USA using Landsat 8 data

USGS Publications Warehouse

Humagain, Kamal; Portillo-Quintero, Carlos; Cox, Robert D.; Cain, James W.

2017-01-01

The increase of tree density in forests of the American Southwest promotes extreme fire events, understory biodiversity losses, and degraded habitat conditions for many wildlife species. To ameliorate these changes, managers and scientists have begun planning treatments aimed at reducing fuels and increasing understory biodiversity. However, spatial variability in tree density across the landscape is not well-characterized, and if better known, could greatly influence planning efforts. We used reflectance values from individual Landsat 8 bands (bands 2, 3, 4, 5, 6, and 7) and calculated vegetation indices (difference vegetation index, simple ratios, and normalized vegetation indices) to estimate tree density in an area planned for treatment in the Jemez Mountains, New Mexico, characterized by multiple vegetation types and a complex topography. Because different vegetation types have different spectral signatures, we derived models with multiple predictor variables for each vegetation type, rather than using a single model for the entire project area, and compared the model-derived values to values collected from on-the-ground transects. Among conifer-dominated areas (73% of the project area), the best models (as determined by corrected Akaike Information Criteria (AICc)) included Landsat bands 2, 3, 4, and 7 along with simple ratios, normalized vegetation indices, and the difference vegetation index (R2 values for ponderosa: 0.47, piñon-juniper: 0.52, and spruce-fir: 0.66). On the other hand, in aspen-dominated areas (9% of the project area), the best model included individual bands 4 and 2, simple ratio, and normalized vegetation index (R2 value: 0.97). Most areas dominated by ponderosa, pinyon-juniper, or spruce-fir had more than 100 trees per hectare. About 54% of the study area has medium to high density of trees (100–1000 trees/hectare), and a small fraction (4.5%) of the area has very high density (>1000 trees/hectare). Our results provide a better understanding of tree density for identifying areas in need of treatment and planning for more effective treatment. Our analysis also provides an integrated method of estimating tree density across complex landscapes that could be useful for further restoration planning.

Description of an establishment event by the invasive Asian longhorned beetle (Anoplophora glabripennis) in a suburban landscape in the northeastern United States

PubMed Central

Pepper, Eugene; Davis, Kevin; Trotter, Robert Talbot

2017-01-01

The establishment of non-native species is commonly described as occurring in three phases: arrival, establishment, and dispersal. Both arrival and dispersal by the Asian longhorned beetle (Anoplophora glabripennis Motschulsky), a xylophagous Cerambycid native to China and the Korean peninsula, has been documented for multiple locations in both North America and Europe, however the transitional phase, establishment, is not well understood for this species due to the need to rapidly remove populations to prevent dispersal and assist eradication, and the evident variation in the behavior of populations. Here we describe the dynamics of an establishment event for the Asian longhorned beetle in a small, isolated population within the regulated quarantine zone near Worcester, Massachusetts, USA. These data were collected during an opportunity afforded by logistical limits on the Cooperative Asian Longhorned Beetle Eradication Program administered by state, federal, and local government partners. Seventy-one infested red maple (Acer rubrum) trees and 456 interspersed un-infested trees were surveyed in an isolated, recently established population within a ~0.29 ha stand in a suburban wetland conservation area in which nearly 90% of the trees were host species, and nearly 80% were Acer rubrum. Tree-ring analyses show that within this establishing population, Asian longhorned beetles initially infested one or two A. rubrum, before moving through the stand to infest additional A. rubrum based not on distance or direction, but on tree size, with infestation biased towards trees with larger trunk diameters. Survey data from the larger landscape suggest this population may have generated long-distance dispersers (~1400 m), and that these dispersal events occurred before the originally infested host trees were fully exploited by the beetle. The distribution and intensity of damage documented in this population suggest dispersal here may have been spatially more rapid and diffuse than in other documented infestations. Dispersal at these larger spatial scales also implies that when beetles move beyond the closed canopy of the stand, the direction of dispersal may be linked to prevailing winds. PMID:28727772

Abrupt Increases in Amazonian Tree Mortality Due to Drought-Fire Interactions

NASA Technical Reports Server (NTRS)

Brando, Paulo Monteiro; Balch, Jennifer K.; Nepstad, Daniel C.; Morton, Douglas C.; Putz, Francis E.; Coe, Michael T.; Silverio, Divino; Macedo, Marcia N.; Davidson, Eric A.; Nobrega, Caroline C.;

Abrupt increases in Amazonian tree mortality due to drought-fire interactions.

PubMed

Brando, Paulo Monteiro; Balch, Jennifer K; Nepstad, Daniel C; Morton, Douglas C; Putz, Francis E; Coe, Michael T; Silvério, Divino; Macedo, Marcia N; Davidson, Eric A; Nóbrega, Caroline C; Alencar, Ane; Soares-Filho, Britaldo S

2014-04-29

Interactions between climate and land-use change may drive widespread degradation of Amazonian forests. High-intensity fires associated with extreme weather events could accelerate this degradation by abruptly increasing tree mortality, but this process remains poorly understood. Here we present, to our knowledge, the first field-based evidence of a tipping point in Amazon forests due to altered fire regimes. Based on results of a large-scale, long-term experiment with annual and triennial burn regimes (B1yr and B3yr, respectively) in the Amazon, we found abrupt increases in fire-induced tree mortality (226 and 462%) during a severe drought event, when fuel loads and air temperatures were substantially higher and relative humidity was lower than long-term averages. This threshold mortality response had a cascading effect, causing sharp declines in canopy cover (23 and 31%) and aboveground live biomass (12 and 30%) and favoring widespread invasion by flammable grasses across the forest edge area (80 and 63%), where fires were most intense (e.g., 220 and 820 kW ⋅ m(-1)). During the droughts of 2007 and 2010, regional forest fires burned 12 and 5% of southeastern Amazon forests, respectively, compared with <1% in nondrought years. These results show that a few extreme drought events, coupled with forest fragmentation and anthropogenic ignition sources, are already causing widespread fire-induced tree mortality and forest degradation across southeastern Amazon forests. Future projections of vegetation responses to climate change across drier portions of the Amazon require more than simulation of global climate forcing alone and must also include interactions of extreme weather events, fire, and land-use change.

Estimating drought induced tree mortality in the Amazon rainforest: A simulation study with a focus on plant hydraulic processes

NASA Astrophysics Data System (ADS)

Papastefanou, P.; Fleischer, K.; Hickler, T.; Grams, T.; Lapola, D.; Quesada, C. A.; Zang, C.; Rammig, A.

2017-12-01

The Amazon basin was recently hit by severe drought events that were unprecedented in their severity and spatial extent, e.g. during 2005, 2010 and 2015/2016. Significant amounts of biomass were lost, turning large parts of the rainforest from a carbon sink into a carbon source. It is assumed that drought-induced tree mortality from hydraulic failure played an important role during these events and may become more frequent in the Amazon region in the future. Many state-of-the-art dynamic vegetation models do not include plant hydraulic processes and fail to reproduce observed rainforest responses to drought events, such as e.g. increased tree mortality. We address this research gap by developing a simple plant-hydraulic module for the dynamic vegetation model LPJ-GUESS. This plant-hydraulic module uses leaf water potential and cavitation as baseline processes to simulate tree mortality under drought stress. Furthermore, we introduce different plant strategies in the model, which describe e.g. differences in the stomatal regulation under drought stress. To parameterize and evaluate our hydraulic module, we use a set of available observational data from the Amazon region. We apply our model to the Amazon Basin and highlight similarities and differences across other measured and predicted drought responses, e.g. extrapolated observations and data derived from satellite measurements. Our results highlight the importance of including plant hydraulic processes in dynamic vegetation models to correctly predict vegetation dynamics under drought stress and show major differences on the vegetation dynamics depending on the selected plant strategies. We also identify gaps in process understanding of the triggering factors, the extent and the consequences of drought responses that hampers our ability to predict potential impact of future drought events on the Amazon rainforest.

Abrupt increases in Amazonian tree mortality due to drought–fire interactions

PubMed Central

Brando, Paulo Monteiro; Balch, Jennifer K.; Nepstad, Daniel C.; Morton, Douglas C.; Putz, Francis E.; Coe, Michael T.; Silvério, Divino; Macedo, Marcia N.; Davidson, Eric A.; Nóbrega, Caroline C.; Alencar, Ane; Soares-Filho, Britaldo S.

2014-01-01

Interactions between climate and land-use change may drive widespread degradation of Amazonian forests. High-intensity fires associated with extreme weather events could accelerate this degradation by abruptly increasing tree mortality, but this process remains poorly understood. Here we present, to our knowledge, the first field-based evidence of a tipping point in Amazon forests due to altered fire regimes. Based on results of a large-scale, long-term experiment with annual and triennial burn regimes (B1yr and B3yr, respectively) in the Amazon, we found abrupt increases in fire-induced tree mortality (226 and 462%) during a severe drought event, when fuel loads and air temperatures were substantially higher and relative humidity was lower than long-term averages. This threshold mortality response had a cascading effect, causing sharp declines in canopy cover (23 and 31%) and aboveground live biomass (12 and 30%) and favoring widespread invasion by flammable grasses across the forest edge area (80 and 63%), where fires were most intense (e.g., 220 and 820 kW⋅m−1). During the droughts of 2007 and 2010, regional forest fires burned 12 and 5% of southeastern Amazon forests, respectively, compared with <1% in nondrought years. These results show that a few extreme drought events, coupled with forest fragmentation and anthropogenic ignition sources, are already causing widespread fire-induced tree mortality and forest degradation across southeastern Amazon forests. Future projections of vegetation responses to climate change across drier portions of the Amazon require more than simulation of global climate forcing alone and must also include interactions of extreme weather events, fire, and land-use change. PMID:24733937

Effect of simulated monsoon failure on the carbon balance of mountain forests, Bhutan, eastern Himalayas

NASA Astrophysics Data System (ADS)

Wangdi, Norbu; Ahmed, Iftekhar; Zangmo, Norbu; Gratzer, Georg; Jandl, Robert; Schindlbacher, Andreas

2017-04-01

Extreme climatic events leading to severe disturbances in ecosystems are expected to increase globally. Such events carry strong potentials for severe reductions or whole losses of ecosystem services. This is particularly true for the Himalayas: they are located in a region forming a tipping element in the Earth's climate system. At a millennial time scale, complete breakdowns of the summer monsoon circulation and a resulting failure of the Indian summer monsoon rains have occurred several times during the last 1000 years. Climate change potentially increases the frequency of such monsoon failures and related mega-droughts. Given the significance of the region, the knowledge on the effects of climate change on forest ecosystem C dynamics is strikingly limited. While the effects of droughts are studied experimentally in Europe and North America, no precipitation manipulation experiments have been carried out in the Himalayas yet. We make use of natural forests with coexisting conifer and broadleaf as well as deciduous and evergreen species at slopes of stark environmental gradients for conducting a replicated large-scale five year throughfall exclosure experiment. We study drought response at individual tree and ecosystem levels. We present the effects of the experimental drought on the ecosystem carbon balance, integrating above- and belowground pools and fluxes such as heterotrophic and autotrophic soil respiration, litter fall and root turnover as well as above- and belowground tree growth. A preliminary assessment indicates that soil microbes were primarily affected during the first three years of simulated drought, whereas trees altered allocation patterns but survived the experimental drought. A detailed analysis will be presented at the conference.

Case study: Rainfall partitioning across a natural-to-urban forest gradient during an extreme rain event

NASA Astrophysics Data System (ADS)

Akin, B. H.; Van Stan, J. T., II; Cote, J. F.; Jarvis, M. T.; Underwood, J.; Friesen, J.; Hildebrandt, A.; Maldonado, G.

2017-12-01

Trees' partitioning of rainfall is an important first process along the rainfall-to-runoff pathway that has economically significant influences on urban stormwater management. However, important knowledge gaps exist regarding (1) its role during extreme storms and (2) how this role changes as forest structure is altered by urbanization. Little research has been conducted on canopy rainfall partitioning during large, intense storms, likely because canopy water storage is rapidly overwhelmed (i.e., 1-3 mm) by short duration events exceeding, for example, 80 mm of rainfall. However, canopy structure controls more than just storage; it also affects the time for rain to drain to the surface (becoming throughfall) and the micrometeorological conditions that drive wet canopy evaporation. In fact, observations from an example extreme ( 100 mm with maximum 5-minute intensities exceeding 55 mm/h) storm across a urban-to-natural gradient in pine forests in southeast Georgia (USA), show that storm intensities were differentially dampened by 33% (tree row), 28% (forest fragment), and 17% (natural forests). In addition, maximum wet canopy evaporation rates were higher for the exposed tree row (0.18 mm/h) than for the partially-enclosed fragment canopy (0.14 mm/h) and the closed canopy natural forest site (0.11). This resulted in interception percentages decreasing from urban-to-natural stand structures (25% to 16%). A synoptic analysis of the extreme storm in this case study also shows that the mesoscale meteorological conditions that developed the heavy rainfall is expected to occur more often with projected climate changes.

The ethnobotany of Christ's Thorn Jujube (Ziziphus spina-christi) in Israel

PubMed Central

Dafni, Amots; Levy, Shay; Lev, Efraim

2005-01-01

This article surveys the ethnobotany of Ziziphus spina-christi (L.) Desf. in the Middle East from various aspects: historical, religious, philological, literary, linguistic, as well as pharmacological, among Muslims, Jews, and Christians. It is suggested that this is the only tree species considered "holy" by Muslims (all the individuals of the species are sanctified by religion) in addition to its status as "sacred tree " (particular trees which are venerated due to historical or magical events related to them, regardless of their botanical identity) in the Middle East. It has also a special status as "blessed tree" among the Druze. PMID:16270941

The importance of drought-pathogen interactions in driving oak mortality events in the Ozark Border Region

NASA Astrophysics Data System (ADS)

Wood, Jeffrey D.; Knapp, Benjamin O.; Muzika, Rose-Marie; Stambaugh, Michael C.; Gu, Lianhong

2018-01-01

Forests are expected to become more vulnerable to drought-induced tree mortality owing to rising temperatures and changing precipitation patterns that amplify drought lethality. There is a crucial knowledge gap regarding drought-pathogen interactions and their effects on tree mortality. The objectives of this research were to examine whether stand dynamics and ‘background’ mortality rates were affected by a severe drought in 2012; and to evaluate the importance of drought-pathogen interactions within the context of a mortality event that killed 10.0% and 26.5% of white (Quercus alba L.) and black (Q. velutina Lam.) oak stems, respectively, in a single year. We synthesized (i) forest inventory data (24 years), (ii) 11 years of ecosystem flux data with supporting biological data including predawn leaf water potential and annual forest inventories, (iii) tree-ring analyses of individual white oaks that were alive and ones that died in 2013, and (iv) documentation of a pathogen infection. This forest displayed stand dynamics consistent with expected patterns of decreasing tree density and increasing basal area. Continued basal area growth outpaced mortality implying a net accumulation of live biomass, which was supported by eddy covariance ecosystem carbon flux observations. Individual white and black oaks that died in 2013 displayed historically lower growth with the majority of dead trees exhibiting Biscogniauxia cankers. Our observations point to the importance of event-based oak mortality and that drought-Biscogniauxia interactions are important in shaping oak stand dynamics in this region. Although forest function has not been significantly impaired, these drought-pathogen interactions could amplify mortality under future climate conditions and thus warrant further investigation.

Dendrogeomorphic Assessment of the Rattlesnake Gulf Landslide in the Tully Valley, Onondaga County, New York

USGS Publications Warehouse

Tamulonis, Kathryn L.; Kappel, William M.

2009-01-01

Dendrogeomorphic techniques were used to assess soil movement within the Rattlesnake Gulf landslide in the Tully Valley of central New York during the last century. This landslide is a postglacial, slow-moving earth slide that covers 23 acres and consists primarily of rotated, laminated, glaciolacustrine silt and clay. Sixty-two increment cores were obtained from 30 hemlock (Tsuga canadensis) trees across the active part of the landslide and from 3 control sites to interpret the soil-displacement history. Annual growth rings were measured and reaction wood was identified to indicate years in which ring growth changed from concentric to eccentric, on the premise that soil movement triggered compensatory growth in displaced trees. These data provided a basis for an 'event index' to identify years of landslide activity over the 108 years of record represented by the oldest trees. Event-index values and total annual precipitation increased during this time, but years with sudden event-index increases did not necessarily correspond to years with above-average precipitation. Multiple-regression and residual-values analyses indicated a possible correlation between precipitation and movement within the landslide and a possible cyclic (decades-long) tree-ring response to displacement within the landslide area from the toe upward to, and possibly beyond, previously formed landslide features. The soil movement is triggered by a sequence of factors that include (1) periods of several months with below-average precipitation followed by persistent above-average precipitation, (2) the attendant increase in streamflow, which erodes the landslide toe and results in an upslope propagation of slumping, and (3) the harvesting of mature trees within this landslide during the last century and continuing to the present.

Simultaneous inference of phylogenetic and transmission trees in infectious disease outbreaks

PubMed Central

2017-01-01

Whole-genome sequencing of pathogens from host samples becomes more and more routine during infectious disease outbreaks. These data provide information on possible transmission events which can be used for further epidemiologic analyses, such as identification of risk factors for infectivity and transmission. However, the relationship between transmission events and sequence data is obscured by uncertainty arising from four largely unobserved processes: transmission, case observation, within-host pathogen dynamics and mutation. To properly resolve transmission events, these processes need to be taken into account. Recent years have seen much progress in theory and method development, but existing applications make simplifying assumptions that often break up the dependency between the four processes, or are tailored to specific datasets with matching model assumptions and code. To obtain a method with wider applicability, we have developed a novel approach to reconstruct transmission trees with sequence data. Our approach combines elementary models for transmission, case observation, within-host pathogen dynamics, and mutation, under the assumption that the outbreak is over and all cases have been observed. We use Bayesian inference with MCMC for which we have designed novel proposal steps to efficiently traverse the posterior distribution, taking account of all unobserved processes at once. This allows for efficient sampling of transmission trees from the posterior distribution, and robust estimation of consensus transmission trees. We implemented the proposed method in a new R package phybreak. The method performs well in tests of both new and published simulated data. We apply the model to five datasets on densely sampled infectious disease outbreaks, covering a wide range of epidemiological settings. Using only sampling times and sequences as data, our analyses confirmed the original results or improved on them: the more realistic infection times place more confidence in the inferred transmission trees. PMID:28545083

Effects of a natural dam-break flood on geomorphology and vegetation on the Elwha River, Washington, U.S.A.

USGS Publications Warehouse

Acker, S.A.; Beechie, T.J.; Shafroth, P.B.

2008-01-01

Ephemeral dams caused by landslides have been observed around the world, yet little is known about the effects of their failure on landforms and vegetation. In 1967, a landslide-dam-break flood in a pristine reach of the Elwha River valley filled the former channel and diverted the river. The reach is a reference site for restoration following the planned removal of dams on the river. We identified five surfaces on the 25 ha debris fan deposited by the flood. Based on tree ages and historic air photos, three of the surfaces formed in 1967, while two formed later. The surfaces varied in substrate (silt and sand, to boulders), and height above the river channel. Tree mortality resulted from tree removal and burial by sediment, the latter leaving snags and some surviving trees. Tree species composition was generally consistent within each surface. Dominant species included red alder (Alnus rubra) and Sitka willow (Salix sitchensis), alone or in combination, a combination of Douglas-fir (Pseudotsuga menziesii) and black cottonwood (Populus balsamifera ssp. trichocarpa), or a combination of alder and Cottonwood. There were significant differences between surfaces in stem density, basal area, and rate of basal area growth. The large degree of heterogeneity in forest structure, composition, and productivity within a relatively small floodplain feature is in part due to spatial variability in the intensity of a single disturbance event, and in part due to the occurrence of subsequent, smaller events. To recreate natural diversity of riparian forests may require mimicking the variety of physical and biotic habitats that a single, complex disturbance event may create.

The importance of drought–pathogen interactions in driving oak mortality events in the Ozark Border Region

DOE PAGES

Wood, Jeffrey D.; Knapp, Benjamin O.; Muzika, Rose-Marie; ...

2017-10-20

Forests are expected to become more vulnerable to drought-induced tree mortality owing to rising temperatures and changing precipitation patterns that amplify drought lethality. There is a crucial knowledge gap regarding drought–pathogen interactions and their effects on tree mortality. The objectives of this research were to examine whether stand dynamics and 'background' mortality rates were affected by a severe drought in 2012; and to evaluate the importance of drought–pathogen interactions within the context of a mortality event that killed 10.0% and 26.5% of white (Quercus alba L.) and black (Q. velutina Lam.) oak stems, respectively, in a single year. We synthesizedmore » (i) forest inventory data (24 years), (ii) 11 years of ecosystem flux data with supporting biological data including predawn leaf water potential and annual forest inventories, (iii) tree-ring analyses of individual white oaks that were alive and ones that died in 2013, and (iv) documentation of a pathogen infection. This forest displayed stand dynamics consistent with expected patterns of decreasing tree density and increasing basal area. Continued basal area growth outpaced mortality implying a net accumulation of live biomass, which was supported by eddy covariance ecosystem carbon flux observations. Individual white and black oaks that died in 2013 displayed historically lower growth with the majority of dead trees exhibiting Biscogniauxia cankers. Our observations point to the importance of event-based oak mortality and that drought–Biscogniauxia interactions are important in shaping oak stand dynamics in this region. Although forest function has not been significantly impaired, these drought–pathogen interactions could amplify mortality under future climate conditions and thus warrant further investigation.« less

Simultaneous inference of phylogenetic and transmission trees in infectious disease outbreaks.

PubMed

Klinkenberg, Don; Backer, Jantien A; Didelot, Xavier; Colijn, Caroline; Wallinga, Jacco

2017-05-01

Whole-genome sequencing of pathogens from host samples becomes more and more routine during infectious disease outbreaks. These data provide information on possible transmission events which can be used for further epidemiologic analyses, such as identification of risk factors for infectivity and transmission. However, the relationship between transmission events and sequence data is obscured by uncertainty arising from four largely unobserved processes: transmission, case observation, within-host pathogen dynamics and mutation. To properly resolve transmission events, these processes need to be taken into account. Recent years have seen much progress in theory and method development, but existing applications make simplifying assumptions that often break up the dependency between the four processes, or are tailored to specific datasets with matching model assumptions and code. To obtain a method with wider applicability, we have developed a novel approach to reconstruct transmission trees with sequence data. Our approach combines elementary models for transmission, case observation, within-host pathogen dynamics, and mutation, under the assumption that the outbreak is over and all cases have been observed. We use Bayesian inference with MCMC for which we have designed novel proposal steps to efficiently traverse the posterior distribution, taking account of all unobserved processes at once. This allows for efficient sampling of transmission trees from the posterior distribution, and robust estimation of consensus transmission trees. We implemented the proposed method in a new R package phybreak. The method performs well in tests of both new and published simulated data. We apply the model to five datasets on densely sampled infectious disease outbreaks, covering a wide range of epidemiological settings. Using only sampling times and sequences as data, our analyses confirmed the original results or improved on them: the more realistic infection times place more confidence in the inferred transmission trees.

The importance of drought–pathogen interactions in driving oak mortality events in the Ozark Border Region

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wood, Jeffrey D.; Knapp, Benjamin O.; Muzika, Rose-Marie

Forests are expected to become more vulnerable to drought-induced tree mortality owing to rising temperatures and changing precipitation patterns that amplify drought lethality. There is a crucial knowledge gap regarding drought–pathogen interactions and their effects on tree mortality. The objectives of this research were to examine whether stand dynamics and 'background' mortality rates were affected by a severe drought in 2012; and to evaluate the importance of drought–pathogen interactions within the context of a mortality event that killed 10.0% and 26.5% of white (Quercus alba L.) and black (Q. velutina Lam.) oak stems, respectively, in a single year. We synthesizedmore » (i) forest inventory data (24 years), (ii) 11 years of ecosystem flux data with supporting biological data including predawn leaf water potential and annual forest inventories, (iii) tree-ring analyses of individual white oaks that were alive and ones that died in 2013, and (iv) documentation of a pathogen infection. This forest displayed stand dynamics consistent with expected patterns of decreasing tree density and increasing basal area. Continued basal area growth outpaced mortality implying a net accumulation of live biomass, which was supported by eddy covariance ecosystem carbon flux observations. Individual white and black oaks that died in 2013 displayed historically lower growth with the majority of dead trees exhibiting Biscogniauxia cankers. Our observations point to the importance of event-based oak mortality and that drought–Biscogniauxia interactions are important in shaping oak stand dynamics in this region. Although forest function has not been significantly impaired, these drought–pathogen interactions could amplify mortality under future climate conditions and thus warrant further investigation.« less

Complete genome analysis of porcine kobuviruses from the feces of pigs in Japan.

PubMed

Akagami, Masataka; Ito, Mika; Niira, Kazutaka; Kuroda, Moegi; Masuda, Tsuneyuki; Haga, Kei; Tsuchiaka, Shinobu; Naoi, Yuki; Kishimoto, Mai; Sano, Kaori; Omatsu, Tsutomu; Aoki, Hiroshi; Katayama, Yukie; Oba, Mami; Oka, Tomoichiro; Ichimaru, Toru; Yamasato, Hiroshi; Ouchi, Yoshinao; Shirai, Junsuke; Katayama, Kazuhiko; Mizutani, Tetsuya; Nagai, Makoto

2017-08-01

Porcine kobuviruses (PoKoVs) are ubiquitously distributed in pig populations worldwide and are thought to be enteric viruses in swine. Although PoKoVs have been detected in pigs in Japan, no complete genome data for Japanese PoKoVs are available. In the present study, 24 nearly complete or complete sequences of the PoKoV genome obtained from 10 diarrheic feces and 14 non-diarrheic feces of Japanese pigs were analyzed using a metagenomics approach. Japanese PoKoVs shared 85.2-100% identity with the complete coding nucleotide (nt) sequences and the closest relationship of 85.1-98.3% with PoKoVs from other countries. Twenty of 24 Japanese PoKoVs carried a deletion of 90 nt in the 2B coding region. Phylogenetic tree analyses revealed that PoKoVs were not grouped according to their geographical region of origin and the phylogenetic trees of the L, P1, P2, and P3 genetic regions showed topologies different from each other. Similarity plot analysis using strains from a single farm revealed partially different similarity patterns among strains from identical farm origins, suggesting that recombination events had occurred. These results indicate that various PoKoV strains are prevalent and not restricted geographically on pig farms worldwide and the coexistence of multiple strains leads to recombination events of PoKoVs and contributes to the genetic diversity and evolution of PoKoVs.

The floral transcriptomes of four bamboo species (Bambusoideae; Poaceae): support for common ancestry among woody bamboos.

PubMed

Wysocki, William P; Ruiz-Sanchez, Eduardo; Yin, Yanbin; Duvall, Melvin R

2016-05-20

Next-generation sequencing now allows for total RNA extracts to be sequenced in non-model organisms such as bamboos, an economically and ecologically important group of grasses. Bamboos are divided into three lineages, two of which are woody perennials with bisexual flowers, which undergo gregarious monocarpy. The third lineage, which are herbaceous perennials, possesses unisexual flowers that undergo annual flowering events. Transcriptomes were assembled using both reference-based and de novo methods. These two methods were tested by characterizing transcriptome content using sequence alignment to previously characterized reference proteomes and by identifying Pfam domains. Because of the striking differences in floral morphology and phenology between the herbaceous and woody bamboo lineages, MADS-box genes, transcription factors that control floral development and timing, were characterized and analyzed in this study. Transcripts were identified using phylogenetic methods and categorized as A, B, C, D or E-class genes, which control floral development, or SOC or SVP-like genes, which control the timing of flowering events. Putative nuclear orthologues were also identified in bamboos to use as phylogenetic markers. Instances of gene copies exhibiting topological patterns that correspond to shared phenotypes were observed in several gene families including floral development and timing genes. Alignments and phylogenetic trees were generated for 3,878 genes and for all genes in a concatenated analysis. Both the concatenated analysis and those of 2,412 separate gene trees supported monophyly among the woody bamboos, which is incongruent with previous phylogenetic studies using plastid markers.

Constellation Probabilistic Risk Assessment (PRA): Design Consideration for the Crew Exploration Vehicle

NASA Technical Reports Server (NTRS)

Prassinos, Peter G.; Stamatelatos, Michael G.; Young, Jonathan; Smith, Curtis

2010-01-01

Managed by NASA's Office of Safety and Mission Assurance, a pilot probabilistic risk analysis (PRA) of the NASA Crew Exploration Vehicle (CEV) was performed in early 2006. The PRA methods used follow the general guidance provided in the NASA PRA Procedures Guide for NASA Managers and Practitioners'. Phased-mission based event trees and fault trees are used to model a lunar sortie mission of the CEV - involving the following phases: launch of a cargo vessel and a crew vessel; rendezvous of these two vessels in low Earth orbit; transit to th$: moon; lunar surface activities; ascension &om the lunar surface; and return to Earth. The analysis is based upon assumptions, preliminary system diagrams, and failure data that may involve large uncertainties or may lack formal validation. Furthermore, some of the data used were based upon expert judgment or extrapolated from similar componentssystemsT. his paper includes a discussion of the system-level models and provides an overview of the analysis results used to identify insights into CEV risk drivers, and trade and sensitivity studies. Lastly, the PRA model was used to determine changes in risk as the system configurations or key parameters are modified.

Tree-space statistics and approximations for large-scale analysis of anatomical trees.

PubMed

Feragen, Aasa; Owen, Megan; Petersen, Jens; Wille, Mathilde M W; Thomsen, Laura H; Dirksen, Asger; de Bruijne, Marleen

2013-01-01

Statistical analysis of anatomical trees is hard to perform due to differences in the topological structure of the trees. In this paper we define statistical properties of leaf-labeled anatomical trees with geometric edge attributes by considering the anatomical trees as points in the geometric space of leaf-labeled trees. This tree-space is a geodesic metric space where any two trees are connected by a unique shortest path, which corresponds to a tree deformation. However, tree-space is not a manifold, and the usual strategy of performing statistical analysis in a tangent space and projecting onto tree-space is not available. Using tree-space and its shortest paths, a variety of statistical properties, such as mean, principal component, hypothesis testing and linear discriminant analysis can be defined. For some of these properties it is still an open problem how to compute them; others (like the mean) can be computed, but efficient alternatives are helpful in speeding up algorithms that use means iteratively, like hypothesis testing. In this paper, we take advantage of a very large dataset (N = 8016) to obtain computable approximations, under the assumption that the data trees parametrize the relevant parts of tree-space well. Using the developed approximate statistics, we illustrate how the structure and geometry of airway trees vary across a population and show that airway trees with Chronic Obstructive Pulmonary Disease come from a different distribution in tree-space than healthy ones. Software is available from http://image.diku.dk/aasa/software.php.

Landscape-scale consequences of differential tree mortality from catastrophic wind disturbance in the Amazon.

PubMed

Rifai, Sami W; Urquiza Muñoz, José D; Negrón-Juárez, Robinson I; Ramírez Arévalo, Fredy R; Tello-Espinoza, Rodil; Vanderwel, Mark C; Lichstein, Jeremy W; Chambers, Jeffrey Q; Bohlman, Stephanie A

2016-10-01

Wind disturbance can create large forest blowdowns, which greatly reduces live biomass and adds uncertainty to the strength of the Amazon carbon sink. Observational studies from within the central Amazon have quantified blowdown size and estimated total mortality but have not determined which trees are most likely to die from a catastrophic wind disturbance. Also, the impact of spatial dependence upon tree mortality from wind disturbance has seldom been quantified, which is important because wind disturbance often kills clusters of trees due to large treefalls killing surrounding neighbors. We examine (1) the causes of differential mortality between adult trees from a 300-ha blowdown event in the Peruvian region of the northwestern Amazon, (2) how accounting for spatial dependence affects mortality predictions, and (3) how incorporating both differential mortality and spatial dependence affect the landscape level estimation of necromass produced from the blowdown. Standard regression and spatial regression models were used to estimate how stem diameter, wood density, elevation, and a satellite-derived disturbance metric influenced the probability of tree death from the blowdown event. The model parameters regarding tree characteristics, topography, and spatial autocorrelation of the field data were then used to determine the consequences of non-random mortality for landscape production of necromass through a simulation model. Tree mortality was highly non-random within the blowdown, where tree mortality rates were highest for trees that were large, had low wood density, and were located at high elevation. Of the differential mortality models, the non-spatial models overpredicted necromass, whereas the spatial model slightly underpredicted necromass. When parameterized from the same field data, the spatial regression model with differential mortality estimated only 7.5% more dead trees across the entire blowdown than the random mortality model, yet it estimated 51% greater necromass. We suggest that predictions of forest carbon loss from wind disturbance are sensitive to not only the underlying spatial dependence of observations, but also the biological differences between individuals that promote differential levels of mortality. © 2016 by the Ecological Society of America.

Air flow analysis in the upper Río Negro Valley (Argentina)

NASA Astrophysics Data System (ADS)

Cogliati, M. G.; Mazzeo, N. A.

2006-06-01

The so called Upper Río Negro Valley in Argentina is one of the most important fruit and vegetable production regions of the country. It comprises the lower valleys of the Limay and Neuquén rivers and the upper Negro river valley. Out of the 41,671 cultivated hectares, 84.6% are cultivated with fruit trees, especially apple, pear and stone fruit trees. Late frosts occurring when trees are sensitive to low temperatures have a significant impact on the regional production. This study presents an analysis of air flow characteristics in the Upper Río Negro Valley and its relationship with ambient air flow. To such effect, observations made when synoptic-scale weather patterns were favorable for radiative frosts (light wind and clear sky) or nocturnal temperature inversion in the lower layer were used. In the Negro river valley, both wind channeling and downward horizontal momentum transport from ambient wind were observed; in nighttime, very light wind events occurred, possibly associated with drainage winds from the nearby higher levels of the barda. In the Neuquén river valley, the prevailing effect appeared to be forced channeling, consistent with the results obtained in valleys where the synoptic scale wind crossed the axis of the valley. In the Limay river valley, the flow was observed to blow parallel to the longitudinal valley axis, possibly influenced by pressure gradient and forced channeling.

Monitoring drought impact on Mediterranean oak savanna vegetation using remote sensing

NASA Astrophysics Data System (ADS)

González-Dugo, Maria P.; Carpintero, Elisabet; Andreu, Ana

2015-04-01

A holm oak savanna, known as dehesa in Spain and montado in Portugal, is the largest agroforest ecosystem in Europe, covering about 3 million hectares in the Iberian Peninsula and Greece (Papanastasis et al., 2004). It is considered an example of sustainable land use, supporting a large number of species and diversity of habitats and for its importance in rural development and economy (Plieninger et al., 2001). It is a combination between an agricultural and a naturally vegetated ecosystem, consisting of widely-spaced oak trees (mostly Quercus Ilex and Quercus suber) combined with a sub-canopy composed by crops, annual grassland and/or shrubs. It has a Mediterranean climate with severe periodic droughts. In the last decades, this system is being exposed to multiple threats derived from socio-economic changes and intensive agricultural use, which have caused environmental degradation, including tree decline, changes in soil properties and hydrological processes, and an increase of soil erosion (Coelho et al., 2004). Soil water dynamics plays a central role in the current decline and reduction of forested areas that jeopardizes the preservation of the system. In this work, a series of remotely sensed images since 1990 to present was used to evaluate the effect of several drought events occurred in the study area (1995, 2009, 2010/2011) on the tree density and water status. Data from satellites Landsat and field measurements have been combined in a spectral mixture model to assess separately the evolution of tree, dry grass and bare soil ground coverage. Only summer images have been used to avoid the influence of the green herbaceous layer on the analysis. Thermal data from the same sensors and meteorological information are integrated in a two source surface energy balance model to compute the Evaporative Stress Index (ESI) and evaluate the vegetation water status. The results have provided insights about the severity of each event and the spatial distribution of their impacts.

Earthquake signals in tree-ring data from the New Madrid seismic zone and implications for paleoseismicity

NASA Astrophysics Data System (ADS)

van Arsdale, Roy B.; Stahle, David W.; Cleaveland, Malcolm K.; Guccione, Margaret J.

1998-06-01

Severe ground shaking and the formation of Reelfoot Lake during the great New Madrid earthquakes of a.d. 1811 1812 had a profound effect on baldcypress trees that still survive in Reelfoot Lake of northwestern Tennessee. Inundation greatly increased baldcypress radial growth from 1812 to 1819 and permanently decreased wood density after 1811. Ground shaking fractured the baldcypress stems that were present during the 1811 1812 event, but fractures are absent in the post-1811 growth. In contrast, the growth of old baldcypress trees in the St. Francis sunkland of northeastern Arkansas was severely suppressed for almost 50 yr following the 1811 1812 New Madrid earthquakes. Thus, there are two opposite but profound growth responses to the same earthquake events preserved in baldcypress trees of the New Madrid seismic zone. The tree-ring chronology at Reelfoot Lake extends from a.d. 1682 to 1990, but the 1812 1819 growth surge was the only extreme growth anomaly in this 309 yr period. The St. Francis sunkland chronology extends from a.d. 1321 to 1990, and the 1812 1857 growth suppression is the most severe and prolonged growth anomaly of this entire 670 year period. Thus, the tree-ring record indicates that there was not a great earthquake during the 129 yr prior to 1811 in the Reelfoot Lake basin, nor during the 490 yr prior to 1811 in the St. Francis sunkland.

Measuring and modelling interception loss by an isolated olive tree in a traditional olive grove - pasture system

NASA Astrophysics Data System (ADS)

Nóbrega, Cristina; Pereira, Fernando L.; Valente, Fernanda

2015-04-01

Water losses associated to the rainfall interception process by trees can be an important component of the local hydrologic balance and must be accounted for when implementing any sustainable water management programme. In many dry areas of the Mediterranean region where agro-forestry systems are common, those programmes are crucial to foster adequate water conservation measures. Recent studies have shown that the evaluation of interception loss in sparse forests or tree plantations should be made for individual trees, being the total value determined as the sum of the individual contributions. Following this approach, rainfall interception was measured and modelled over two years, in an isolated Olea europeaea L. tree, in a traditional low-density olive grove in Castelo Branco, central Portugal. Total interception loss over the experimental period was 243.5 mm, on a tree crown projected area basis, corresponding to 18.0% of gross rainfall (Pg). Modelling made for each rainfall event using the sparse version of the Gash model, slightly underestimated interception loss with a value of 240.5 mm, i.e., 17.8 % ofPg. Modelling quality, evaluated according to a number of criteria, was good, allowing the conclusion that the methodology used was adequate. Modelling was also made on a daily basis, i.e., assuming a single storm per rainday. In this case, interception loss was overestimated by 12%, mostly because 72% of all rainfall events lasted for more than a day.

The critical amplifying role of increasing atmospheric moisture demand on tree mortality and associated regional die-off

DOE PAGES

Breshears, David D.; Adams, Henry D.; Eamus, Derek; ...

2013-08-02

Drought-induced tree mortality, including large-scale die-off events and increases in background rates of mortality, is a global phenomenon (Allen et al., 2010) that can directly impact numerous earth system properties and ecosystem goods and services (Adams et al., 2010; Breshears et al., 2011; Anderegg et al., 2013). Tree mortality is particularly of concern because of the likelihood that it will increase in frequency and extent with climate change (McDowell et al., 2008, 2011; Adams et al., 2009; McDowell, 2011; Williams et al., 2013). Recent plant science advances related to drought have focused on understanding the physiological mechanisms that not onlymore » affect plant growth and associated carbon metabolism, but also the more challenging issue of predicting plant mortality thresholds (McDowell et al., 2013). Although some advances related to mechanisms of mortality have been made and have increased emphasis on interrelationships between carbon metabolism and plant hydraulics (McDowell et al., 2011), notably few studies have specifically evaluated effects of increasing atmospheric demand for moisture (i.e., vapour pressure deficit; VPD) on rates of tree death. In this opinion article we highlight the importance of considering the key risks of future large-scale tree die-off and other mortality events arising from increased VPD. Here we focus on mortality of trees, but our point about the importance of VPD is also relevant to other vascular plants.« less

Integrated Approach To Design And Analysis Of Systems

NASA Technical Reports Server (NTRS)

Patterson-Hine, F. A.; Iverson, David L.

1993-01-01

Object-oriented fault-tree representation unifies evaluation of reliability and diagnosis of faults. Programming/fault tree described more fully in "Object-Oriented Algorithm For Evaluation Of Fault Trees" (ARC-12731). Augmented fault tree object contains more information than fault tree object used in quantitative analysis of reliability. Additional information needed to diagnose faults in system represented by fault tree.

Spatial contagiousness of canopy disturbance in tropical rain forest: an individual-tree-based test.

PubMed

Jansen, Patrick A; van der Meer, Peter J; Bongers, Frans

2008-12-01

Spatial contagiousness of canopy dynamics-the tendency of canopy disturbances to occur nearby existing canopy openings due to an elevated risk of tree fall around gaps-has been demonstrated in many temperate-zone forests, but only inferentially for tropical forests. Hypothesized mechanisms increasing the risk of tree fall around tropical forest gaps are (1) increased tree exposure to wind around gaps, (2) reduced stability of trees alongside gaps due to crown asymmetry, or (3) reduced tree health around gaps due to damage from prior disturbances. One hypothesized consequence of elevated disturbance levels around gaps would be that gap-edge zones offer relatively favorable prospects for seedling recruitment, growth, and survival. We tested whether disturbance levels are indeed elevated around natural canopy gaps in a neotropical rain forest in French Guiana, and more so as gaps are larger. We followed the fate of 5660 trees >10 cm stem diameter over five years across 12 ha of old-growth forest and analyzed the risk and magnitude of canopy disturbance events in relation to tree diameter and the proximity and size of natural canopy gaps. We found that the cumulative incidence of disturbance over the five-year survey was not significantly elevated around preexisting gaps, and only weakly related to gap size. Also, neither the risk nor the magnitude of canopy disturbances increased significantly with the proximity of gaps. Moreover, canopy disturbance risk around gaps was independent of gap size, while the magnitude of disturbance events around gaps was weakly related to gap size. Tree size was the major driver of disturbance risk as well as magnitude. We did find an elevated incidence of disturbance inside preexisting gaps, but this "repeat disturbance" was due to an elevated disturbance risk inside gaps, not around gaps. Overall, we found no strong evidence for canopy dynamics in this rain forest being spatially contagious. Our findings are consistent with the traditional view of tropical rain forests as mosaics of patches with predictable regeneration cycles.

Type A Accident Investigation Board report on the January 17, 1996, electrical accident with injury in Technical Area 21 Tritium Science and Fabrication Facility Los Alamos National Laboratory. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1996-04-01

An electrical accident was investigated in which a crafts person received serious injuries as a result of coming into contact with a 13.2 kilovolt (kV) electrical cable in the basement of Building 209 in Technical Area 21 (TA-21-209) in the Tritium Science and Fabrication Facility (TSFF) at Los Alamos National Laboratory (LANL). In conducting its investigation, the Accident Investigation Board used various analytical techniques, including events and causal factor analysis, barrier analysis, change analysis, fault tree analysis, materials analysis, and root cause analysis. The board inspected the accident site, reviewed events surrounding the accident, conducted extensive interviews and document reviews,more » and performed causation analyses to determine the factors that contributed to the accident, including any management system deficiencies. Relevant management systems and factors that could have contributed to the accident were evaluated in accordance with the guiding principles of safety management identified by the Secretary of Energy in an October 1994 letter to the Defense Nuclear Facilities Safety Board and subsequently to Congress.« less

Tree-ring 14C links seismic swarm to CO2 spike at Yellowstone, USA

USGS Publications Warehouse

Evans, William C.; Bergfeld, D.; McGeehin, J.P.; King, J.C.; Heasler, H.

2010-01-01

Mechanisms to explain swarms of shallow seismicity and inflation-deflation cycles at Yellowstone caldera (western United States) commonly invoke episodic escape of magma-derived brines or gases from the ductile zone, but no correlative changes in the surface efflux of magmatic constituents have ever been documented. Our analysis of individual growth rings in a tree core from the Mud Volcano thermal area within the caldera links a sharp ~25% drop in 14C to a local seismic swarm in 1978. The implied fivefold increase in CO2 emissions clearly associates swarm seismicity with upflow of magma-derived fluid and shows that pulses of magmatic CO2 can rapidly traverse the 5-kmthick brittle zone, even through Yellowstone's enormous hydrothermal reservoir. The 1978 event predates annual deformation surveys, but recognized connections between subsequent seismic swarms and changes in deformation suggest that CO2 might drive both processes. ?? 2010 Geological Society of America.

Complete Sequence and Comparative Analysis of the Chloroplast Genome of Coconut Palm (Cocos nucifera)

PubMed Central

Huang, Ya-Yi; Matzke, Antonius J. M.; Matzke, Marjori

2013-01-01

Coconut, a member of the palm family (Arecaceae), is one of the most economically important trees used by mankind. Despite its diverse morphology, coconut is recognized taxonomically as only a single species (Cocos nucifera L.). There are two major coconut varieties, tall and dwarf, the latter of which displays traits resulting from selection by humans. We report here the complete chloroplast (cp) genome of a dwarf coconut plant, and describe the gene content and organization, inverted repeat fluctuations, repeated sequence structure, and occurrence of RNA editing. Phylogenetic relationships of monocots were inferred based on 47 chloroplast protein-coding genes. Potential nodes for events of gene duplication and pseudogenization related to inverted repeat fluctuation were mapped onto the tree using parsimony criteria. We compare our findings with those from other palm species for which complete cp genome sequences are available. PMID:24023703

A fault tree model to assess probability of contaminant discharge from shipwrecks.

PubMed

Landquist, H; Rosén, L; Lindhe, A; Norberg, T; Hassellöv, I-M; Lindgren, J F; Dahllöf, I

2014-11-15

Shipwrecks on the sea floor around the world may contain hazardous substances that can cause harm to the marine environment. Today there are no comprehensive methods for environmental risk assessment of shipwrecks, and thus there is poor support for decision-making on prioritization of mitigation measures. The purpose of this study was to develop a tool for quantitative risk estimation of potentially polluting shipwrecks, and in particular an estimation of the annual probability of hazardous substance discharge. The assessment of the probability of discharge is performed using fault tree analysis, facilitating quantification of the probability with respect to a set of identified hazardous events. This approach enables a structured assessment providing transparent uncertainty and sensitivity analyses. The model facilitates quantification of risk, quantification of the uncertainties in the risk calculation and identification of parameters to be investigated further in order to obtain a more reliable risk calculation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Complete sequence and comparative analysis of the chloroplast genome of coconut palm (Cocos nucifera).

PubMed

Huang, Ya-Yi; Matzke, Antonius J M; Matzke, Marjori

2013-01-01

Coconut, a member of the palm family (Arecaceae), is one of the most economically important trees used by mankind. Despite its diverse morphology, coconut is recognized taxonomically as only a single species (Cocos nucifera L.). There are two major coconut varieties, tall and dwarf, the latter of which displays traits resulting from selection by humans. We report here the complete chloroplast (cp) genome of a dwarf coconut plant, and describe the gene content and organization, inverted repeat fluctuations, repeated sequence structure, and occurrence of RNA editing. Phylogenetic relationships of monocots were inferred based on 47 chloroplast protein-coding genes. Potential nodes for events of gene duplication and pseudogenization related to inverted repeat fluctuation were mapped onto the tree using parsimony criteria. We compare our findings with those from other palm species for which complete cp genome sequences are available.

Rene Saldana's "The Jumping Tree": Exploring Childhood Universals through a Hispanic Novel

ERIC Educational Resources Information Center

Newman, Beatrice Mendez

2006-01-01

In "The Jumping Tree", set in Nuevo Penitas, an actual South Texas town, 12-year-old Rey Castaneda recounts landmark events in his journey toward becoming a man. Rey's stories of his childhood escapades, adventures, and everyday experiences could be anyone's childhood stories. When readers have finished the last page, they have relived the…

Basic tree-ring sample preparation techniques for aging aspen

Treesearch

Lance A. Asherin; Stephen A. Mata

2001-01-01

Aspen is notoriously difficult to age because of its light-colored wood and faint annual growth rings. Careful preparation and processing of aspen ring samples can overcome these problems, yield accurate age and growth estimates, and concisely date disturbance events present in the tree-ring record. Proper collection of aspen wood is essential in obtaining usable ring...

Seasonality and Disturbance Events in the Carbon Isotope Record of Slash Pine (Pinus elliottii) Tree Rings from Big Pine Key, Florida

NASA Astrophysics Data System (ADS)

Rebenack, C.; Anderson, W. T.; Cherubini, P.

2011-12-01

The South Florida coastal ecosystem is among the world's subtropical coastlines which are threatened by the potential effects of climate change. A well-developed localized paleohistory is essential in the understanding of the role climate variability/change has on both hydrological dynamics and disturbance event frequency and intensity; this understanding can then aid in the development of better predictive models. High resolution paleoclimate proxies, such as those developed from tree-ring archives, may be useful tools for extrapolating actual climate trends over time from the overlapping long-term and short-term climate cycles, such as the Atlantic Multidecadal Oscillation (AMO) and the El Niño-Southern Oscillation (ENSO). In South Florida, both the AMO and ENSO strongly influence seasonal precipitation, and a more complete grasp of how these cycles have affected the region in the past could be applied to future freshwater management practices. Dendrochronology records for the terrestrial subtropics, including South Florida, are sparse because seasonality for this region is precipitation driven; this is in contrast to the drastic temperature changes experienced in the temperate latitudes. Subtropical seasonality may lead to the complete lack of visible rings or to the formation of ring structures that may or may not represent annual growth. Fortunately, it has recently been demonstrated that Pinus elliottii trees in South Florida produce distinct annual growth rings; however ring width was not found to significantly correlate with either the AMO or ENSO. Dendrochronology studies may be taken a step beyond the physical tree-ring proxies by using the carbon isotope ratios to infer information about physiological controls and environmental factors that affect the distribution of isotopes within the plant. It has been well established that the stable isotope composition of cellulose can be related to precipitation, drought, large-scale ocean/atmospheric oscillations, and disturbance events. Because slash pine growth is dependent on water availability, a chronology developed using carbon isotopes may provide greater insight into plant stress over time and ultimately may lead to better correlations with climate oscillations. The work presented here is the preliminary result of a carbon-isotope study of four slash pine trees from Big Pine Key, Florida. Initial δ13C data show seasonal stomatal activity in the trees and indicate the timing of possible disturbance events.

45 years of non-stationary hydrology over a forest plantation growth cycle, Coalburn catchment, Northern England

NASA Astrophysics Data System (ADS)

Birkinshaw, Stephen J.; Bathurst, James C.; Robinson, Mark

2014-11-01

The Coalburn research catchment (1.5 km2) in Kielder Forest, Northern England, is a long-term project to study the effect of upland afforestation on hydrology. There is now a unique 45-year record; making it Britain's longest running forest hydrology research catchment. The site was instrumented in 1967, ploughed and planted in 1972/73 and the trees have now reached maturity. Hourly meteorological data have been measured since 1993 and these have enabled hydrological simulations to be carried out using the Shetran model for the period 1993-2011. The results from this work show that after ploughing there was an increase of around 50-100 mm in annual streamflow compared with the original upland grassland vegetation. However, the mature trees now show a decrease of around 250-300 mm in the annual streamflow compared with the original vegetation and a decrease of around 350 mm in the annual streamflow compared with when the site was ploughed. The simulation results show very clearly the non-stationary nature of the catchment during 1993-2011 with an annual increase in intercepted evaporation and a decrease in discharge as the trees grow. Simulation results also show that peak discharges are higher for a cover of smaller trees compared with taller trees. However, the results suggest that the bigger the event the smaller is the difference, i.e. there is absolute convergence for the two different tree scenarios at higher discharges. The study shows how modelling can compensate for data deficiencies, to maximise outcomes. As a rare example of long-term analysis of non-stationary catchment behaviour it also provides real evidence of change that would otherwise have had to be inferred theoretically.