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Sample records for pressure risk model

  1. Dynamic prediction model and risk assessment chart for cardiovascular disease based on on-treatment blood pressure and baseline risk factors.

    PubMed

    Teramukai, Satoshi; Okuda, Yasuyuki; Miyazaki, Shigeru; Kawamori, Ryuzo; Shirayama, Masayuki; Teramoto, Tamio

    2016-02-01

    For patients with hypertension, an individual risk prediction tool for cardiovascular disease based on on-treatment blood pressure is needed and would be useful. The objective of this study was to establish a 3-year risk prediction model for cardiovascular disease based on data from 13 052 patients with no history of cardiovascular disease in the Olmesartan Mega study to determine the relationship between Cardiovascular Endpoints and Blood Pressure Goal Achievement study. To develop dynamic prediction models including on-treatment blood pressure, a Cox proportional hazard model using the sliding landmarking method with three landmark points (6, 12 and 18 months from baseline) was used. The prediction model included blood pressure (<130/85 mm Hg, ⩾130/85  to <140/90 mm Hg, ⩾140/90 to <160/100 mm Hg and ⩾160/100 mm Hg) as a time-dependent covariate and well-known baseline risk factors (sex, age, smoking, family history of coronary artery disease and diabetes) as covariates. The 3-year risk assessment chart was constructed using the combination of all risk factors in the prediction model, and six different colors were displayed on each chart corresponding to the predicted probability of cardiovascular disease. Judging from the chart, if an elderly man with diabetes and other risk factors had a blood pressure of <130/85 mm Hg at 6 months, the risk of cardiovascular disease would be 8.0%, whereas the risk would be 8.6% if he had a blood pressure of ⩾130/85 to <140/90 mm Hg. The risk assessment chart developed from the large-scale observational study data would help physicians to more easily assess the cardiovascular disease risk for hypertensive patients on antihypertensive treatments. PMID:26606874

  2. Risk Factors for High Blood Pressure

    MedlinePlus

    ... the NHLBI on Twitter. Risk Factors for High Blood Pressure Anyone can develop high blood pressure; however, age, ... can increase your risk for developing high blood pressure. Age Blood pressure tends to rise with age. About 65 ...

  3. Blood Pressure Patterns May Predict Stroke Risk

    MedlinePlus

    ... fullstory_158731.html Blood Pressure Patterns May Predict Stroke Risk Odds increase with rapid rise in middle ... overall pattern to predict a patient's risk of stroke or early death, new research suggests. "Our study ...

  4. Visual Impairment/Intracranial Pressure Risk Assessment

    NASA Technical Reports Server (NTRS)

    Fogarty, Jennifer A.; Durham, T.; Otto, C.; Grounds, D.; Davis, J. R.

    2010-01-01

    Since 2006 there have been 6 reported cases of altered visual acuity and intracranial pressure (ICP) in long duration astronauts. In order to document this risk and develop an integrated approach to its mitigation, the NASA Space Life Sciences Directorate (SLSD) and Human Research Program (HRP) have chosen to use the Human System Risk Board (HSRB) and the risk management analysis tool (RMAT). The HSRB is the venue in which the stakeholders and customers discuss and vet the evidence and the RMAT is the tool that facilitates documentation and comparison of the evidence across mission profiles as well as identification of risk factors, and documentation of mitigation strategies. This process allows for information to be brought forward and dispositioned so that it may be properly incorporated into the RMAT and contribute to the design of the research and mitigation plans. The evidence thus far has resulted in the identification of a visual impairment/intracranial pressure (VIIP) project team, updating of both short and long duration medical requirements designed to assess visual acuity, and a research plan to characterize this issue further. In order to understand this issue more completely, a plan to develop an Accelerated Research Collaboration (ARC) has been approved by the HSRB. The ARC is a novel research model pioneered by the Myelin Repair Foundation. It is a patient centered research model that brings together researchers and clinicians, under the guidance of a scientific advisory panel, to collaborate and produce results much quickly than accomplished through traditional research models. The data and evidence from the updated medical requirements and the VIIP ARC will be reviewed at the HSRB on a regular basis. Each review package presented to the HSRB will include an assessment and recommendation with respect to continuation of research, countermeasure development, occupational surveillance modalities, selection criteria, etc. This process will determine the

  5. Blood Pressure Patterns May Predict Stroke Risk

    MedlinePlus

    ... at Erasmus University Medical Center in Rotterdam, the Netherlands. High blood pressure is the number one risk ... of epidemiology, Erasmus University Medical Center, Rotterdam, the Netherlands; Andrew Rogove, M.D., Ph.D., medical director, ...

  6. Radiation risk estimation models

    SciTech Connect

    Hoel, D.G.

    1987-11-01

    Cancer risk models and their relationship to ionizing radiation are discussed. There are many model assumptions and risk factors that have a large quantitative impact on the cancer risk estimates. Other health end points such as mental retardation may be an even more serious risk than cancer for those with in utero exposures. 8 references.

  7. Blood pressure targets and absolute cardiovascular risk.

    PubMed

    Odutayo, Ayodele; Rahimi, Kazem; Hsiao, Allan J; Emdin, Connor A

    2015-08-01

    In the Eighth Joint National Committee guideline on hypertension, the threshold for the initiation of blood pressure-lowering treatment for elderly adults (≥60 years) without chronic kidney disease or diabetes mellitus was raised from 140/90 mm Hg to 150/90 mm Hg. However, the committee was not unanimous in this decision, particularly because a large proportion of adults ≥60 years may be at high cardiovascular risk. On the basis of Eighth Joint National Committee guideline, we sought to determine the absolute 10-year risk of cardiovascular disease among these adults through analyzing the National Health and Nutrition Examination Survey (2005-2012). The primary outcome measure was the proportion of adults who were at ≥20% predicted absolute cardiovascular risk and above goals for the Seventh Joint National Committee guideline but reclassified as at target under the Eighth Joint National Committee guideline (reclassified). The Framingham General Cardiovascular Disease Risk Score was used. From 2005 to 2012, the surveys included 12 963 adults aged 30 to 74 years with blood pressure measurements, of which 914 were reclassified based on the guideline. Among individuals reclassified as not in need of additional treatment, the proportion of adults 60 to 74 years without chronic kidney disease or diabetes mellitus at ≥20% absolute risk was 44.8%. This corresponds to 0.8 million adults. The proportion at high cardiovascular risk remained sizable among adults who were not receiving blood pressure-lowering treatment. Taken together, a sizable proportion of reclassified adults 60 to 74 years without chronic kidney disease or diabetes mellitus was at ≥20% absolute cardiovascular risk. PMID:26056340

  8. Melanoma Risk Prediction Models

    Cancer.gov

    Developing statistical models that estimate the probability of developing melanoma cancer over a defined period of time will help clinicians identify individuals at higher risk of specific cancers, allowing for earlier or more frequent screening and counseling of behavioral changes to decrease risk.

  9. Modeling of Intracranial Pressure Dynamics

    PubMed Central

    Griffith, Richard L.; Sullivan, Humbert G.; Miller, J. Douglas

    1978-01-01

    Digital computer simulation is utilized to test hypotheses regarding poorly understood mechanisms of intracranial pressure change. The simulation produces graphic output similar to records from polygraph recorders used in patient monitoring and in animal experimentation. The structure of the model is discussed. The mathematic model perfected by the comparison between simulation and experiment will constitute a formulation of medical information applicable to automated clinical monitoring and treatment of intracranial hypertension.

  10. Biosafety Risk Assessment Model

    SciTech Connect

    2011-05-27

    Software tool based on a structured methodology for conducting laboratory biosafety risk assessments by biosafety experts. Software is based upon an MCDA scheme and uses peer reviewed criteria and weights. The software was developed upon Microsoft’s .net framework. The methodology defines likelihood and consequence of a laboratory exposure for thirteen unique scenarios and provides numerical relative risks for each of the relevant thirteen. The software produces 2-d graphs reflecting the relative risk and a sensitivity analysis which highlights the overall importance of each factor. The software works as a set of questions with absolute scales and uses a weighted additive model to calculate the likelihood and consequence.

  11. ''Swiss cheese'' models with pressure

    SciTech Connect

    Bona, C.; Stela, J.

    1987-11-15

    Local spherically symmetric inhomogeneities are matched to a spatially flat Robertson-Walker background with pressure. In the cases in which the background evolves to an Einstein--de Sitter dust universe, the interior metrics tend with time either to the vacuum Schwarzschild solution or to the spatially flat Tolman dust metrics. The whole construction may be interpreted as the history of the dust-filled ''Swiss cheese'' models.

  12. Blood pressure variability: a novel and important risk factor.

    PubMed

    Floras, John S

    2013-05-01

    Blood pressure is a continuous, not a static, variable. Individuals exhibiting similar clinic or home blood pressure can differ considerably with respect to their average day and nighttime values, beat-by-beat blood pressure variation during wakefulness and sleep, responses to mental and physical stimuli, and intersession and seasonal variation. There now is evidence that several such representations of blood pressure variability, if augmented, increase cardiovascular risk independent of the average of conventionally acquired blood pressure readings. As well, recent retrospective analyses of published trial data have concluded that antihypertensive drug classes differ in their effects on intersession blood pressure variability and associated risk of stroke. If the goal of the hypertension community is to optimize personalized cardiovascular risk assessment and to attenuate fully such risk, future efforts should be directed at determining which representation of blood pressure variability estimates individual cardiovascular risk best, establishing "normal" and "high- risk" variability distributions, testing the hypothesis that attenuating such variability specifically through drug or device therapy reduces cardiovascular risk more than blood pressure reduction per se, and integrating such data into clinical practice. PMID:23618505

  13. General Pressurization Model in Simscape

    NASA Technical Reports Server (NTRS)

    Servin, Mario; Garcia, Vicky

    2010-01-01

    System integration is an essential part of the engineering design process. The Ares I Upper Stage (US) is a complex system which is made up of thousands of components assembled into subsystems including a J2-X engine, liquid hydrogen (LH2) and liquid oxygen (LO2) tanks, avionics, thrust vector control, motors, etc. System integration is the task of connecting together all of the subsystems into one large system. To ensure that all the components will "fit together" as well as safety and, quality, integration analysis is required. Integration analysis verifies that, as an integrated system, the system will behave as designed. Models that represent the actual subsystems are built for more comprehensive analysis. Matlab has been an instrument widely use by engineers to construct mathematical models of systems. Simulink, one of the tools offered by Matlab, provides multi-domain graphical environment to simulate and design time-varying systems. Simulink is a powerful tool to analyze the dynamic behavior of systems over time. Furthermore, Simscape, a tool provided by Simulink, allows users to model physical (such as mechanical, thermal and hydraulic) systems using physical networks. Using Simscape, a model representing an inflow of gas to a pressurized tank was created where the temperature and pressure of the tank are measured over time to show the behavior of the gas. By further incorporation of Simscape into model building, the full potential of this software can be discovered and it hopefully can become a more utilized tool.

  14. The risk of establishment of aquatic invasive species: joining invasibility and propagule pressure

    PubMed Central

    Leung, Brian; Mandrak, Nicholas E

    2007-01-01

    Invasive species are increasingly becoming a policy priority. This has spurred researchers and managers to try to estimate the risk of invasion. Conceptually, invasions are dependent both on the receiving environment (invasibility) and on the ability to reach these new areas (propagule pressure). However, analyses of risk typically examine only one or the other. Here, we develop and apply a joint model of invasion risk that simultaneously incorporates invasibility and propagule pressure. We present arguments that the behaviour of these two elements of risk differs substantially—propagule pressure is a function of time, whereas invasibility is not—and therefore have different management implications. Further, we use the well-studied zebra mussel (Dreissena polymorpha) to contrast predictions made using the joint model to those made by separate invasibility and propagule pressure models. We show that predictions of invasion progress as well as of the long-term invasion pattern are strongly affected by using a joint model. PMID:17711834

  15. Biosafety Risk Assessment Model

    Energy Science and Technology Software Center (ESTSC)

    2011-05-27

    Software tool based on a structured methodology for conducting laboratory biosafety risk assessments by biosafety experts. Software is based upon an MCDA scheme and uses peer reviewed criteria and weights. The software was developed upon Microsoft’s .net framework. The methodology defines likelihood and consequence of a laboratory exposure for thirteen unique scenarios and provides numerical relative risks for each of the relevant thirteen. The software produces 2-d graphs reflecting the relative risk and a sensitivitymore » analysis which highlights the overall importance of each factor. The software works as a set of questions with absolute scales and uses a weighted additive model to calculate the likelihood and consequence.« less

  16. Non-invasive model-based estimation of aortic pulse pressure using suprasystolic brachial pressure waveforms.

    PubMed

    Lowe, A; Harrison, W; El-Aklouk, E; Ruygrok, P; Al-Jumaily, A M

    2009-09-18

    Elevated central arterial (aortic) blood pressure is related to increased risk of cardiovascular disease. Methods of non-invasively estimating this pressure would therefore be helpful in clinical practice. To achieve this goal, a physics-based model is derived to correlate the arterial pressure under a suprasystolic upper-arm cuff to the aortic pressure. The model assumptions are particularly applicable to the measurement method and result in a time-domain relation with two parameters, namely, the wave propagation transit time and the reflection coefficient at the cuff. Central pressures estimated by the model were derived from completely automatic, non-invasive measurement of brachial blood pressure and suprasystolic waveform and were compared to simultaneous invasive catheter measurements in 16 subjects. Systolic blood pressure agreement, mean (standard deviation) of difference was -1 (7)mmHg. Diastolic blood pressure agreement was 4 (4)mmHg. Correlation between estimated and actual central waveforms was greater than 90%. Individualization of model parameters did not significantly improve systolic and diastolic pressure agreement, but increased waveform correlation. Further research is necessary to confirm that more accurate brachial pressure measurement improves central pressure estimation. PMID:19665136

  17. Pressure ulcer risk of patient handling sling use.

    PubMed

    Peterson, Matthew J; Kahn, Julie A; Kerrigan, Michael V; Gutmann, Joseph M; Harrow, Jeffrey J

    2015-01-01

    Patient handling slings and lifts reduce the risk of musculoskeletal injuries for healthcare providers. However, no published evidence exists of their safety with respect to pressure ulceration for vulnerable populations, specifically persons with spinal cord injury, nor do any studies compare slings for pressure distribution. High-resolution interface pressure mapping was used to describe and quantify risks associated with pressure ulceration due to normal forces and identify at-risk anatomical locations. We evaluated 23 patient handling slings with 4 nondisabled adults. Sling-participant interface pressures were recorded while participants lay supine on a hospital bed and while suspended during typical patient transfers. Sling-participant interface pressures were greatest while suspended for all seated and supine slings and exceeded 200 mm Hg for all seated slings. Interface pressures were greatest along the sling seams (edges), regardless of position or sling type. The anatomical areas most at risk while participants were suspended in seated slings were the posterior upper and lower thighs. For supine slings, the perisacral area, ischial tuberosities, and greater trochanters were most at risk. The duration of time spent in slings, especially while suspended, should be limited. PMID:26237005

  18. Acute radiation risk models

    NASA Astrophysics Data System (ADS)

    Smirnova, Olga

    Biologically motivated mathematical models, which describe the dynamics of the major hematopoietic lineages (the thrombocytopoietic, lymphocytopoietic, granulocytopoietic, and erythropoietic systems) in acutely/chronically irradiated humans are developed. These models are implemented as systems of nonlinear differential equations, which variables and constant parameters have clear biological meaning. It is shown that the developed models are capable of reproducing clinical data on the dynamics of these systems in humans exposed to acute radiation in the result of incidents and accidents, as well as in humans exposed to low-level chronic radiation. Moreover, the averaged value of the "lethal" dose rates of chronic irradiation evaluated within models of these four major hematopoietic lineages coincides with the real minimal dose rate of lethal chronic irradiation. The demonstrated ability of the models of the human thrombocytopoietic, lymphocytopoietic, granulocytopoietic, and erythropoietic systems to predict the dynamical response of these systems to acute/chronic irradiation in wide ranges of doses and dose rates implies that these mathematical models form an universal tool for the investigation and prediction of the dynamics of the major human hematopoietic lineages for a vast pattern of irradiation scenarios. In particular, these models could be applied for the radiation risk assessment for health of astronauts exposed to space radiation during long-term space missions, such as voyages to Mars or Lunar colonies, as well as for health of people exposed to acute/chronic irradiation due to environmental radiological events.

  19. Mental Models of Security Risks

    NASA Astrophysics Data System (ADS)

    Asgharpour, Farzaneh; Liu, Debin; Camp, L. Jean

    In computer security, risk communication refers to informing computer users about the likelihood and magnitude of a threat. Efficacy of risk communication depends not only on the nature of the risk, but also on the alignment between the conceptual model embedded in the risk communication and the user's mental model of the risk. The gap between the mental models of security experts and non-experts could lead to ineffective risk communication. Our research shows that for a variety of the security risks self-identified security experts and non-experts have different mental models. We propose that the design of the risk communication methods should be based on the non-expert mental models.

  20. Pressure Systems Stored-Energy Threshold Risk Analysis

    SciTech Connect

    Paulsen, Samuel S.

    2009-08-25

    Federal Regulation 10 CFR 851, which became effective February 2007, brought to light potential weaknesses regarding the Pressure Safety Program at the Pacific Northwest National Laboratory (PNNL). The definition of a pressure system in 10 CFR 851 does not contain a limit based upon pressure or any other criteria. Therefore, the need for a method to determine an appropriate risk-based hazard level for pressure safety was identified. The Laboratory has historically used a stored energy of 1000 lbf-ft to define a pressure hazard; however, an analytical basis for this value had not been documented. This document establishes the technical basis by evaluating the use of stored energy as an appropriate criterion to establish a pressure hazard, exploring a suitable risk threshold for pressure hazards, and reviewing the methods used to determine stored energy. The literature review and technical analysis concludes the use of stored energy as a method for determining a potential risk, the 1000 lbf-ft threshold, and the methods used by PNNL to calculate stored energy are all appropriate. Recommendations for further program improvements are also discussed

  1. Modeling the pressure-dilatation correlation

    NASA Technical Reports Server (NTRS)

    Sarkar, S.

    1991-01-01

    It is generally accepted that pressure dilatation, which is an additional compressibility term in turbulence transport equations, may be important for high speed flows. Recent direct simulations of homogeneous shear turbulence have given concrete evidence that the pressure dilatation is important insofar that it contributes to the reduced growth of turbulent kinetic energy due to compressibility effects. The problem of modeling pressure dilatation is addressed. A component of the pressure dilatation is isolated which exhibits temporal oscillations and, using direct numerical simulations of homogeneous shear turbulence and isotropic turbulence, show that it has a negligible contribution to the evolution of turbulent kinetic energy. Then, an analysis for the case of homogeneous turbulence is performed to obtain a model for the nonoscillatory pressure dilatation. This model algebraically relates the pressure dilatation to quantities traditionally obtained in incompressible turbulence closures. The model is validated by direct comparison with the pressure dilatation data obtained from the simulations.

  2. [Risk assessment for pressure ulcer in critical patients].

    PubMed

    Gomes, Flávia Sampaio Latini; Bastos, Marisa Antonini Ribeiro; Matozinhos, Fernanda Penido; Temponi, Hanrieti Rotelli; Velásquez-Meléndez, Gustavo

    2011-04-01

    Bedridden patients are in risk to developing pressure ulcers and represent a priority group to be studied to identify this condition. To reach this goal, specific instruments are used to assess this problem. The objective of this study was to analyze the risk factors to developing pressure ulcers in adult patients hospitalized in ICUs. This is a sectional analytical study, in which evaluations were performed on 140 patients, hospitalized in 22 ICUs, using the Braden scale. Results showed that patients hospitalized from 15 days or more showed some level of risk. The highest frequencies of pressure ulcers were found in patients in the following categories: sensorial perception (completely limited), moistness (constantly moist), mobility (completely immobilized), activity (bedridden), nutrition (adequate) and friction and shear (problem). In conclusion, the use of this scale is an important strategy when providing care to patients in intensive treatment. PMID:21655778

  3. Hyperhomocysteinemia in preeclampsia is associated to higher risk pressure profiles.

    PubMed

    Noto, R; Neri, S; Noto, Z; Cilio, D; Abate, G; Noto, P; Pepi, F; Leanza, A; Molino, G

    2003-01-01

    Homocysteine levels have been determined with Chromatography on HPLC column, between the 20th and the 24th week of pregnancy, in women with analogous characteristics (a) normotensive, (b) with pregnancy-induced hypertension (PIH), low (LR), medium (MR), high risk (HR). The group they belonged to was confirmed after natural or caesarean delivery. All the patients were submitted to 24 hour blood pressure monitoring for the evaluation of further pressure risk parameters: mean arterial pressure (MAP), non dippers, percentages of pressure peaks. Homocysteine levels in normotensive pregnant women (5.8 +/- 1.7 microM) were low. Significant high levels of homocysteine were present proportionally to the risk degree of PIH. Higher levels of homocysteine statistically significant were present in non dippers of all groups (MR p < 0.05; HR p < 0.01). A direct correlation between plasmatic homocisteine levels and pressure profiles was found out in non dippers (r = 0.56, r = 0.55, r = 0.50 respectively) and in dippers (r = 0.7, r = 0.75, r = 0.60 respectively), and also between levels of homocysteine, MAP value, and pathological percentages of systolic and diastolic nocturnal peaks. In pregnant women presenting preeclampsia afterwards, high levels of homocysteine were not different from mean values present in high risk PIH pregnant women (13.3 +/- 1.9 vs. 16.4 +/- 1.7 microM). High levels of homocysteine early determined in the second trimester of PIH pregnancies seem to be associated to a pregnancy higher risk, coexisting with dangerous pressure profiles. High levels confirm a pregnant woman to belong to a higher or lower risk degree of vascular damage, but in the same group context high levels of homocisteine do not allow to identify those pregnant women who will develop eclampsia. PMID:14650644

  4. More Young Adults at Risk for High Blood Pressure | NIH MedlinePlus the Magazine

    MedlinePlus

    ... Feature: High Blood Pressure More Young Adults at Risk for High Blood Pressure Past Issues / Fall 2011 ... high blood pressure. NIH-funded analysis indicates higher risk for young adults than previously believed. With more ...

  5. New Zealand Seismic Risk Model

    NASA Astrophysics Data System (ADS)

    Molas, G.; Aslani, H.; Bryngelson, J.; Khan, Z.

    2006-12-01

    A seismic risk model for New Zealand has been developed to assisted insurers and reinsurers in assessing their financial risk posed by earthquakes. This presentation summarizes the methodology and data within the model and includes a discussion of the key results from the hazard and risk perspectives. The earthquake, risk-model framework has four components. First, the stochastic event set is determined, as well as its associated event probabilities. A ground-motion model including geotechnical data is added to complete the seismic hazard model. To determine risk, regional building vulnerability curves and a financial model are incorporated. An insurer property exposure database was developed to determine the insured seismic risk in these countries. Using this model, examination of resulting hazard maps (200, 475, 1000 and 2500 years) and of city-level, hazard-curves gives insight to the key drivers of risk across the region. Hazard de-aggregation allow for examination of key drivers of risk in terms of seismic sources, event magnitude and events types. Examination of loss costs for residential and commercial (short and mid-rise) structures gives insight into the risk perspective for these various lines of business. Finally, incorporation of the insurer property exposure allows for an examination of the insured risk across the region and between exposure concentrations including Wellington, Auckland and Christchurch.

  6. Risk Associated with Pulse Pressure on Out-of-Office Blood Pressure Measurement

    PubMed Central

    Gu, Yu-Mei; Aparicio, Lucas S.; Liu, Yan-Ping; Asayama, Kei; Hansen, Tine W.; Niiranen, Teemu J.; Boggia, José; Thijs, Lutgarde; Staessen, Jan A.

    2014-01-01

    Background Longitudinal studies have demonstrated that the risk of cardiovascular disease increases with pulse pressure (PP). However, PP remains an elusive cardiovascular risk factor with findings being inconsistent between studies. The 2013 ESH/ESC guideline proposed that PP is useful in stratification and suggested a threshold of 60 mm Hg, which is 10 mm Hg higher compared to that in the 2007 guideline; however, no justification for this increase was provided. Methodology Published thresholds of PP are based on office blood pressure measurement and often on arbitrary categorical analyses. In the International Database on Ambulatory blood pressure in relation to Cardiovascular Outcomes (IDACO) and the International Database on HOme blood pressure in relation to Cardiovascular Outcome (IDHOCO), we determined outcome-driven thresholds for PP based on ambulatory or home blood pressure measurement, respectively. Results The main findings were that for people aged <60 years, PP did not refine risk stratification, whereas in older people the thresholds were 64 and 76 mm Hg for the ambulatory and home PP, respectively. However, PP provided little added predictive value over and beyond classical risk factors. PMID:26587443

  7. Modeling Scala Media as a Pressure Vessel

    NASA Astrophysics Data System (ADS)

    Lepage, Eric; Olofsson, A.˚Ke

    2011-11-01

    The clinical condition known as endolymphatic hydrops is the swelling of scala media and may result in loss in hearing sensitivity consistent with other forms of low-frequency biasing. Because outer hair cells (OHCs) are displacement-sensitive and hearing levels tend to be preserved despite large changes in blood pressure and CSF pressure, it seems unlikely that the OHC respond passively to changes in static pressures in the chambers. This suggests the operation of a major feedback control loop which jointly regulates homeostasis and hearing sensitivity. Therefore the internal forces affecting the cochlear signal processing amplifier cannot be just motile responses. A complete account of the cochlear amplifier must include static pressures. To this end we have added a third, pressure vessel to our 1-D 140-segment, wave-digital filter active model of cochlear mechanics, incorporating the usual nonlinear forward transduction. In each segment the instantaneous pressure is the sum of acoustic pressure and global static pressure. The object of the model is to maintain stable OHC operating point despite any global rise in pressure in the third chamber. Such accumulated pressure is allowed to dissipate exponentially. In this first 3-chamber implementation we explore the possibility that acoustic pressures are rectified. The behavior of the model is critically dependent upon scaling factors and time-constants, yet by initial assumption, the pressure tends to accumulate in proportion to sound level. We further explore setting of the control parameters so that the accumulated pressure either stays within limits or may rise without bound.

  8. PTA1 Helium Pressurization System Model

    NASA Technical Reports Server (NTRS)

    Steadman, Todd; Majumdar, Alok; Holt, Kimberly

    1999-01-01

    A transient model of the Propulsion Test Article 1 (PTA1) Helium Pressurization System was developed using the Generalized Fluid System Simulation Program (GFSSP). The model included feed lines from the facility interface to the engine purge interface and Liquid Oxygen (LOX) and Rocket Propellant 1 (RP-1) tanks, the propellant tanks themselves including ullage space and propellant feed lines to their respective pump interfaces. GFSSPs capability was extended to model a control valve to maintain ullage pressure within a specified limit and pressurization processes such as heat transfer between ullage gas, propellant and the tank wall. The purpose of the model is to predict the flow system characteristics in the entire pressurization system during 80 seconds of pre-pressurization operation, 420 seconds of pressurization stand-by operation and 150 seconds of engine operation. Subsequent to the work presented here, the PTA1 model has been updated to include the LOX and RP-1 pumps, while the pressurization option itself has been modified to include the effects of mass transfer. This updated model will be compared with PTA1 test data as it becomes available.

  9. Fiber bundle model under fluid pressure

    NASA Astrophysics Data System (ADS)

    Amitrano, David; Girard, Lucas

    2016-03-01

    Internal fluid pressure often plays an important role in the rupture of brittle materials. This is a major concern for many engineering applications and for natural hazards. More specifically, the mechanisms through which fluid pressure, applied at a microscale, can enhance the failure at a macroscale and accelerate damage dynamics leading to failure remains unclear. Here we revisit the fiber bundle model by accounting for the effect of fluid under pressure that contributes to the global load supported by the fiber bundle. Fluid pressure is applied on the broken fibers, following Biot's theory. The statistical properties of damage avalanches and their evolution toward macrofailure are analyzed for a wide range of fluid pressures. The macroscopic strength of the new model appears to be strongly controlled by the action of the fluid, particularly when the fluid pressure becomes comparable with the fiber strength. The behavior remains consistent with continuous transition, i.e., second order, including for large pressure. The main change concerns the damage acceleration toward the failure that is well modeled by the concept of sweeping of an instability. When pressure is increased, the exponent β characterizing the power-law distribution avalanche sizes significantly decreases and the exponent γ characterizing the cutoff divergence when failure is approached significantly increases. This proves that fluid pressure plays a key role in failure process acting as destabilization factor. This indicates that macrofailure occurs more readily under fluid pressure, with a behavior that becomes progressively unstable as fluid pressure increases. This may have considerable consequences on our ability to forecast failure when fluid pressure is acting.

  10. Fiber bundle model under fluid pressure.

    PubMed

    Amitrano, David; Girard, Lucas

    2016-03-01

    Internal fluid pressure often plays an important role in the rupture of brittle materials. This is a major concern for many engineering applications and for natural hazards. More specifically, the mechanisms through which fluid pressure, applied at a microscale, can enhance the failure at a macroscale and accelerate damage dynamics leading to failure remains unclear. Here we revisit the fiber bundle model by accounting for the effect of fluid under pressure that contributes to the global load supported by the fiber bundle. Fluid pressure is applied on the broken fibers, following Biot's theory. The statistical properties of damage avalanches and their evolution toward macrofailure are analyzed for a wide range of fluid pressures. The macroscopic strength of the new model appears to be strongly controlled by the action of the fluid, particularly when the fluid pressure becomes comparable with the fiber strength. The behavior remains consistent with continuous transition, i.e., second order, including for large pressure. The main change concerns the damage acceleration toward the failure that is well modeled by the concept of sweeping of an instability. When pressure is increased, the exponent β characterizing the power-law distribution avalanche sizes significantly decreases and the exponent γ characterizing the cutoff divergence when failure is approached significantly increases. This proves that fluid pressure plays a key role in failure process acting as destabilization factor. This indicates that macrofailure occurs more readily under fluid pressure, with a behavior that becomes progressively unstable as fluid pressure increases. This may have considerable consequences on our ability to forecast failure when fluid pressure is acting. PMID:27078437

  11. RISK 0301 - MOLECULAR MODELING

    EPA Science Inventory

    Risk assessment practices, in general, for a range of diseases now encourages the use of mechanistic data to enhance the ability to predict responses at low, environmental exposures. In particular, the pathway from normal biology to pathologic state can be dcscribed by a set of m...

  12. Developing a pressure ulcer risk factor minimum data set and risk assessment framework

    PubMed Central

    Coleman, Susanne; Nelson, E Andrea; Keen, Justin; Wilson, Lyn; McGinnis, Elizabeth; Dealey, Carol; Stubbs, Nikki; Muir, Delia; Farrin, Amanda; Dowding, Dawn; Schols, Jos MGA; Cuddigan, Janet; Berlowitz, Dan; Jude, Edward; Vowden, Peter; Bader, Dan L; Gefen, Amit; Oomens, Cees WJ; Schoonhoven, Lisette; Nixon, Jane

    2014-01-01

    Aim To agree a draft pressure ulcer risk factor Minimum Data Set to underpin the development of a new evidenced-based Risk Assessment Framework. Background A recent systematic review identified the need for a pressure ulcer risk factor Minimum Data Set and development and validation of an evidenced-based pressure ulcer Risk Assessment Framework. This was undertaken through the Pressure UlceR Programme Of reSEarch (RP-PG-0407-10056), funded by the National Institute for Health Research and incorporates five phases. This article reports phase two, a consensus study. Design Consensus study. Method A modified nominal group technique based on the Research and Development/University of California at Los Angeles appropriateness method. This incorporated an expert group, review of the evidence and the views of a Patient and Public Involvement service user group. Data were collected December 2010–December 2011. Findings The risk factors and assessment items of the Minimum Data Set (including immobility, pressure ulcer and skin status, perfusion, diabetes, skin moisture, sensory perception and nutrition) were agreed. In addition, a draft Risk Assessment Framework incorporating all Minimum Data Set items was developed, comprising a two stage assessment process (screening and detailed full assessment) and decision pathways. Conclusion The draft Risk Assessment Framework will undergo further design and pre-testing with clinical nurses to assess and improve its usability. It will then be evaluated in clinical practice to assess its validity and reliability. The Minimum Data Set could be used in future for large scale risk factor studies informing refinement of the Risk Assessment Framework. PMID:24845398

  13. Cardiac risk factors: new cholesterol and blood pressure management guidelines.

    PubMed

    Anthony, David; George, Paul; Eaton, Charles B

    2014-06-01

    The 2013 American College of Cardiology/American Heart Association cholesterol guidelines depart from low-density lipoprotein (LDL) treatment targets and recommend treating four specific patient groups with statins. Statins are the only cholesterol-lowering drugs with randomized trial evidence of benefit for preventing atherosclerotic cardiovascular disease (ASCVD). The groups are patients with clinical ASCVD; patients ages 40 to 75 years with diabetes and LDL of 70 to 189 mg/dL but no clinical ASCVD; patients 21 years or older with LDL levels of 190 mg/dL or higher; and patients ages 40 to 75 years with LDL of 70 to 189 mg/dL without clinical ASCVD or diabetes but with 10-year ASCVD risk of 7.5% or higher. Ten-year ASCVD risk may be calculated using the Pooled Cohort Equations. The Eighth Joint National Committee (JNC 8) guidelines for blood pressure management recommend a blood pressure goal of less than 140/90 mm Hg for all adults except those 60 years or older. For the latter group, the JNC 8 recommends a systolic blood pressure goal of less than 150 mm Hg. In another notable change from prior guidelines, the JNC 8 recommends relaxing the systolic blood pressure goal for patients with diabetes and chronic kidney disease to less than 140 mm Hg from less than 130 mm Hg. PMID:24936717

  14. Liver Cancer Risk Prediction Models

    Cancer.gov

    Developing statistical models that estimate the probability of developing liver cancer over a defined period of time will help clinicians identify individuals at higher risk of specific cancers, allowing for earlier or more frequent screening and counseling of behavioral changes to decrease risk.

  15. Cervical Cancer Risk Prediction Models

    Cancer.gov

    Developing statistical models that estimate the probability of developing cervical cancer over a defined period of time will help clinicians identify individuals at higher risk of specific cancers, allowing for earlier or more frequent screening and counseling of behavioral changes to decrease risk.

  16. Pancreatic Cancer Risk Prediction Models

    Cancer.gov

    Developing statistical models that estimate the probability of developing pancreatic cancer over a defined period of time will help clinicians identify individuals at higher risk of specific cancers, allowing for earlier or more frequent screening and counseling of behavioral changes to decrease risk.

  17. Prostate Cancer Risk Prediction Models

    Cancer.gov

    Developing statistical models that estimate the probability of developing prostate cancer over a defined period of time will help clinicians identify individuals at higher risk of specific cancers, allowing for earlier or more frequent screening and counseling of behavioral changes to decrease risk.

  18. Ovarian Cancer Risk Prediction Models

    Cancer.gov

    Developing statistical models that estimate the probability of developing ovarian cancer over a defined period of time will help clinicians identify individuals at higher risk of specific cancers, allowing for earlier or more frequent screening and counseling of behavioral changes to decrease risk.

  19. Lung Cancer Risk Prediction Models

    Cancer.gov

    Developing statistical models that estimate the probability of developing lung cancer over a defined period of time will help clinicians identify individuals at higher risk of specific cancers, allowing for earlier or more frequent screening and counseling of behavioral changes to decrease risk.

  20. Bladder Cancer Risk Prediction Models

    Cancer.gov

    Developing statistical models that estimate the probability of developing bladder cancer over a defined period of time will help clinicians identify individuals at higher risk of specific cancers, allowing for earlier or more frequent screening and counseling of behavioral changes to decrease risk.

  1. Testicular Cancer Risk Prediction Models

    Cancer.gov

    Developing statistical models that estimate the probability of testicular cervical cancer over a defined period of time will help clinicians identify individuals at higher risk of specific cancers, allowing for earlier or more frequent screening and counseling of behavioral changes to decrease risk.

  2. Colorectal Cancer Risk Prediction Models

    Cancer.gov

    Developing statistical models that estimate the probability of developing colorectal cancer over a defined period of time will help clinicians identify individuals at higher risk of specific cancers, allowing for earlier or more frequent screening and counseling of behavioral changes to decrease risk.

  3. Breast Cancer Risk Prediction Models

    Cancer.gov

    Developing statistical models that estimate the probability of developing breast cancer over a defined period of time will help clinicians identify individuals at higher risk of specific cancers, allowing for earlier or more frequent screening and counseling of behavioral changes to decrease risk.

  4. Esophageal Cancer Risk Prediction Models

    Cancer.gov

    Developing statistical models that estimate the probability of developing esophageal cancer over a defined period of time will help clinicians identify individuals at higher risk of specific cancers, allowing for earlier or more frequent screening and counseling of behavioral changes to decrease risk.

  5. Modeling of parenteral container headspace pressure.

    PubMed

    Bryant, P L

    1998-01-01

    When containers and related closure systems holding fluids are heated, internal pressures are generated. Depending upon conditions, surprisingly high pressures can be developed. These pressures are often sufficient to break system integrity. Numerous factors combine to determine the pressure generated within the container and closure system. Each of these factors can vary during the manufacture and service life of the product. Prudent pharmaceutical design seeks to set and control all the factors in such a manner that container and related closure integrity are maintained from the time of assembly to the time of use. Answers can be obtained by pure experimentation ("cut, try, recut and retry until it comes out right") or by predicting performance with a good mathematical model and testing once to verify the model. Pure experimentation requires extensive prototype parts and testing thereof. The mathematical model approach is more exact and produces a better product quicker and at lower cost. This paper uses a simple tubing vial to demonstrate the two approaches to controlling internal pressures from assembly to use. A mathematical model with experimental verification produces high confidence that the system integrity will be maintained as desired. The model used to predict the headspace pressure of the tubing vial is of significance in estimating performance of similar containers and related closures. It can rapidly produce product with predictable behavior. As such, the model is an excellent tool for designers of pharmaceutical products. PMID:9691675

  6. Concordance of Shape Risk Scale, a new pressure ulcer risk tool, with Braden Scale.

    PubMed

    Soppi, Esa T; Iivanainen, Ansa K; Korhonen, Pasi A

    2014-12-01

    The occurrence of pressure ulcers was examined in a cross-sectional study in 23 health care facilities and in home care involving 548 patients. The screening of pressure ulcer risk was assessed simultaneously using the Braden Scale and the new Shape Risk Scale (SRS), and the results were compared. The overall prevalence of pressure ulcers in the study population was 15·5% (85/548). The Braden Scale was performed as described in the literature. The direct concordance of the Braden and SRS scales was 46%. In more than 90% of cases, the SRS classified patients as well as or better than the Braden Scale. The SRS allocates patients significantly different from the Braden Scale into the risk categories, especially the difference is significant between the low and medium-risk categories. The greatest advantage of SRS to Braden Scale is that it correctly identifies patients with low risk of pressure ulcers. It is interesting that the two risk scores, taking into consideration the basically different pathophysiological factors, can still give rather similar results. The users considered that both scales are easy to use. PMID:24751183

  7. Risk modelling in portfolio optimization

    NASA Astrophysics Data System (ADS)

    Lam, W. H.; Jaaman, Saiful Hafizah Hj.; Isa, Zaidi

    2013-09-01

    Risk management is very important in portfolio optimization. The mean-variance model has been used in portfolio optimization to minimize the investment risk. The objective of the mean-variance model is to minimize the portfolio risk and achieve the target rate of return. Variance is used as risk measure in the mean-variance model. The purpose of this study is to compare the portfolio composition as well as performance between the optimal portfolio of mean-variance model and equally weighted portfolio. Equally weighted portfolio means the proportions that are invested in each asset are equal. The results show that the portfolio composition of the mean-variance optimal portfolio and equally weighted portfolio are different. Besides that, the mean-variance optimal portfolio gives better performance because it gives higher performance ratio than the equally weighted portfolio.

  8. Comparing visual and objective skin assessment with pressure injury risk.

    PubMed

    Borzdynski, Caroline J; McGuiness, William; Miller, Charne

    2016-08-01

    Contemporary approaches to pressure injury (PI) risk identification rely on the use of risk assessment tools and visual skin assessment. Objective biophysical measures that assess skin hydration, melanin, erythema and lipids have not been traditionally used in PI risk; however, these may prove useful as a risk assessment tool. The relationship between subjective visual assessments of skin condition, biophysical measures and PI risk warrants investigation. This study used a descriptive correlational design to examine the relationship between measures of skin hydration, colour (melanin and erythema) and lipids at PI-prone areas amongst geriatric persons (n = 38), obtained using biophysical skin measures and visual skin assessment. Twice daily measures of epidermal hydration, colour and lipids were assessed using the SD202 Skin Diagnostic (Courage + Khazaka GmBH, Cologne, Germany) over pressure-prone areas of the body of study participants over seven consecutive days. Concurrent visual assessment of skin hydration and colour was performed. Results obtained using the SD202 Skin Diagnostic were compared with results gathered from visual assessment and examined for their association with participants' PI risk based on scores of the Norton Risk Assessment Scale. While epidermal hydration and skin colour reading scores did not vary significantly over the data collection period, lipid readings could not be registered on any occasion. With the exception of skin dryness, skin parameters via both objective and subjective means had significant, positive correlations. Statistically significant correlations emerged between visual assessment of skin wetness at the sacrum (r = -0·441, P < 0·01) and ischia (r = -0·468, P < 0·01) and Norton Risk Assessment Scale scores. It was found that the objective assessment of epidermal hydration (skin wetness) was also significantly associated with PI risk at the sacrum (r = -0·528, P < 0·01), as well as the right ischia (r = -0·410, P

  9. Mid- to Late-Life Trajectories of Blood Pressure and the Risk of Stroke: The Rotterdam Study.

    PubMed

    Portegies, Marileen L P; Mirza, Saira Saeed; Verlinden, Vincentius J A; Hofman, Albert; Koudstaal, Peter J; Swanson, Sonja A; Ikram, M Arfan

    2016-06-01

    Hypertension is a major modifiable risk factor for stroke. Associations of blood pressure with incident stroke are mostly based on single or average blood pressure levels. However, this approach does not take into account long-term trajectories of blood pressure, which can vary considerably in the elderly. Within the population-based Rotterdam Study, we examined trajectories of systolic blood pressure in 6745 participants (60.0% women) over an age-range from 55 to 106 years and jointly modeled their risk of stroke and competing causes of death using joint latent class mixed modeling. Four trajectories were identified. Class 1 was characterized by blood pressure increasing gradually from on average 120 to 160 mm Hg over 5 decades (n=4938). Compared with this class, class 2, characterized by a similar midlife blood pressure, but a steep increase (n=822, increasing from 120 to 200 mm Hg), and class 4, characterized by a high midlife blood pressure (n=115; average 160 mm Hg) and had a higher risk of stroke and death. Class 3, characterized by a moderate midlife blood pressure (n=870; average 140 mm Hg), had a similar risk of death as class 1, but the highest risk of stroke. Assessing trajectories of blood pressure provides a more nuanced understanding of the associations between blood pressure, stroke, and mortality. In particular, high blood pressure and rapidly increasing blood pressure patterns are associated with a high risk of stroke and death, whereas moderately high blood pressure is only related to an increased risk of stroke. Future studies should explore the potential pathogenic significance of these patterns. PMID:27160196

  10. Biomechanical modelling of normal pressure hydrocephalus.

    PubMed

    Dutta-Roy, Tonmoy; Wittek, Adam; Miller, Karol

    2008-07-19

    This study investigates the mechanics of normal pressure hydrocephalus (NPH) growth using a computational approach. We created a generic 3-D brain mesh of a healthy human brain and modelled the brain parenchyma as single phase and biphasic continuum. In our model, hyperelastic constitutive law and finite deformation theory described deformations within the brain parenchyma. We used a value of 155.77Pa for the shear modulus (mu) of the brain parenchyma. Additionally, in our model, contact boundary definitions constrained the brain outer surface inside the skull. We used transmantle pressure difference to load the model. Fully nonlinear, implicit finite element procedures in the time domain were used to obtain the deformations of the ventricles and the brain. To the best of our knowledge, this was the first 3-D, fully nonlinear model investigating NPH growth mechanics. Clinicians generally accept that at most 1mm of Hg transmantle pressure difference (133.416Pa) is associated with the condition of NPH. Our computations showed that transmantle pressure difference of 1mm of Hg (133.416Pa) did not produce NPH for either single phase or biphasic model of the brain parenchyma. A minimum transmantle pressure difference of 1.764mm of Hg (235.44Pa) was required to produce the clinical condition of NPH. This suggested that the hypothesis of a purely mechanical basis for NPH growth needs to be revised. We also showed that under equal transmantle pressure difference load, there were no significant differences between the computed ventricular volumes for biphasic and incompressible/nearly incompressible single phase model of the brain parenchyma. As a result, there was no major advantage gained by using a biphasic model for the brain parenchyma. We propose that for modelling NPH, nearly incompressible single phase model of the brain parenchyma was adequate. Single phase treatment of the brain parenchyma simplified the mathematical description of the NPH model and resulted in

  11. Combined impact of lead, cadmium, polychlorinated biphenyls and non-chemical risk factors on blood pressure in NHANES

    SciTech Connect

    Peters, Junenette L. Patricia Fabian, M. Levy, Jonathan I.

    2014-07-15

    High blood pressure is associated with exposure to multiple chemical and non-chemical risk factors, but epidemiological analyses to date have not assessed the combined effects of both chemical and non-chemical stressors on human populations in the context of cumulative risk assessment. We developed a novel modeling approach to evaluate the combined impact of lead, cadmium, polychlorinated biphenyls (PCBs), and multiple non-chemical risk factors on four blood pressure measures using data for adults aged ≥20 years from the National Health and Nutrition Examination Survey (1999–2008). We developed predictive models for chemical and other stressors. Structural equation models were applied to account for complex associations among predictors of stressors as well as blood pressure. Models showed that blood lead, serum PCBs, and established non-chemical stressors were significantly associated with blood pressure. Lead was the chemical stressor most predictive of diastolic blood pressure and mean arterial pressure, while PCBs had a greater influence on systolic blood pressure and pulse pressure, and blood cadmium was not a significant predictor of blood pressure. The simultaneously fit exposure models explained 34%, 43% and 52% of the variance for lead, cadmium and PCBs, respectively. The structural equation models were developed using predictors available from public data streams (e.g., U.S. Census), which would allow the models to be applied to any U.S. population exposed to these multiple stressors in order to identify high risk subpopulations, direct intervention strategies, and inform public policy. - Highlights: • We evaluated joint impact of chemical and non-chemical stressors on blood pressure. • We built predictive models for lead, cadmium and polychlorinated biphenyls (PCBs). • Our approach allows joint evaluation of predictors from population-specific data. • Lead, PCBs and established non-chemical stressors were related to blood pressure.

  12. Longitudinal Patterns of Change in Systolic Blood Pressure and Incidence of Cardiovascular Disease: The Atherosclerosis Risk in Communities Study.

    PubMed

    Petruski-Ivleva, Natalia; Viera, Anthony J; Shimbo, Daichi; Muntner, Paul; Avery, Christy L; Schneider, Andrea L C; Couper, David; Kucharska-Newton, Anna

    2016-06-01

    Elevated blood pressure in midlife contributes significantly to the risk of cardiovascular disease. However, patterns of blood pressure increase may differ among individuals and may result in differential risk. Our goal was to examine the contribution of longitudinal patterns of blood pressure change to incidence of heart failure, coronary heart disease, stroke, and cardiovascular disease mortality. Latent class growth models were used to identify patterns of change in blood pressure across 4 clinical examinations (1987-1998) among 9845 Atherosclerosis Risk in Communities (ARIC) cohort participants (mean age, 53.7 [SD 5.7] years). Patterns of change in systolic blood pressure included slowly and steeply increasing, a decreasing and a sustained elevated blood pressure. Changes in diastolic and mid-blood pressure (½ systolic+½ diastolic) were less pronounced. The association of blood pressure pattern group membership with incidence of clinical outcomes was examined in follow-up from the fourth clinical examination (1996-1998) to December 31, 2011, using Poisson regression models adjusted for demographic and metabolic characteristics, and hypertension medication use. A gradient of rates of all events was observed across the identified patterns. Associations were attenuated after adjustment for covariates. Cumulative systolic blood pressure load, rather than the temporal pattern of change in systolic blood pressure itself, plays a role in determining the risk of cardiovascular disease, in particular, of heart failure and cardiovascular disease mortality, independent of blood pressure level measured at one point in time. PMID:27045024

  13. Common Carotid Intima-Media Thickness Measurements Do Not Improve Cardiovascular Risk Prediction in Individuals With Elevated Blood Pressure

    PubMed Central

    Bots, Michiel L.; Groenewegen, Karlijn A.; Anderson, Todd J.; Britton, Annie R.; Dekker, Jacqueline M.; Engström, Gunnar; Evans, Greg W.; de Graaf, Jacqueline; Grobbee, Diederick E.; Hedblad, Bo; Hofman, Albert; Holewijn, Suzanne; Ikeda, Ai; Kavousi, Maryam; Kitagawa, Kazuo; Kitamura, Akihiko; Ikram, M. Arfan; Lonn, Eva M.; Lorenz, Matthias W.; Mathiesen, Ellisiv B.; Nijpels, Giel; Okazaki, Shuhei; O’Leary, Daniel H.; Polak, Joseph F.; Price, Jacqueline F.; Robertson, Christine; Rembold, Christopher M.; Rosvall, Maria; Rundek, Tatjana; Salonen, Jukka T.; Sitzer, Matthias; Stehouwer, Coen D.A.; Franco, Oscar H.; Peters, Sanne A.E.; den Ruijter, Hester M.

    2015-01-01

    Carotid intima-media thickness (CIMT) is a marker of cardiovascular risk. It is unclear whether measurement of mean common CIMT improves 10-year risk prediction of first-time myocardial infarction or stroke in individuals with elevated blood pressure. We performed an analysis among individuals with elevated blood pressure (ie, a systolic blood pressure ≥140 mm Hg and a diastolic blood pressure ≥ 90 mm Hg) in USE-IMT, a large ongoing individual participant data meta-analysis. We refitted the risk factors of the Framingham Risk Score on asymptomatic individuals (baseline model) and expanded this model with mean common CIMT (CIMT model) measurements. From both models, 10-year risks to develop a myocardial infarction or stroke were estimated. In individuals with elevated blood pressure, we compared discrimination and calibration of the 2 models and calculated the net reclassification improvement (NRI). We included 17 254 individuals with elevated blood pressure from 16 studies. During a median follow-up of 9.9 years, 2014 first-time myocardial infarctions or strokes occurred. The C-statistics of the baseline and CIMT models were similar (0.73). NRI with the addition of mean common CIMT was small and not significant (1.4%; 95% confidence intervals, −1.1 to 3.7). In those at intermediate risk (n=5008, 10-year absolute risk of 10% to 20%), the NRI was 5.6% (95% confidence intervals, 1.6–10.4). There is no added value of measurement of mean common CIMT in individuals with elevated blood pressure for improving cardiovascular risk prediction. For those at intermediate risk, the addition of mean common CIMT to an existing cardiovascular risk score is small but statistically significant. PMID:24614213

  14. Entropic pressure in lattice models for polymers

    NASA Astrophysics Data System (ADS)

    Hammer, Yosi; Kantor, Yacov

    2014-11-01

    In lattice models, local pressure on a surface is derived from the change in the free energy of the system due to the exclusion of a certain boundary site, while the total force on the surface can be obtained by a similar exclusion of all surface sites. In these definitions, while the total force on the surface of a lattice system matches the force measured in a continuous system, the local pressure does not. Moreover, in a lattice system, the sum of the local pressures is not equal to the total force as is required in a continuous system. The difference is caused by correlation between occupations of surface sites as well as finite displacement of surface elements used in the definition of the pressures and the force. This problem is particularly acute in the studies of entropic pressure of polymers represented by random or self-avoiding walks on a lattice. We propose a modified expression for the local pressure which satisfies the proper relation between the pressure and the total force, and show that for a single ideal polymer in the presence of scale-invariant boundaries it produces quantitatively correct values for continuous systems. The required correction to the pressure is non-local, i.e., it depends on long range correlations between contact points of the polymer and the surface.

  15. Entropic pressure in lattice models for polymers.

    PubMed

    Hammer, Yosi; Kantor, Yacov

    2014-11-28

    In lattice models, local pressure on a surface is derived from the change in the free energy of the system due to the exclusion of a certain boundary site, while the total force on the surface can be obtained by a similar exclusion of all surface sites. In these definitions, while the total force on the surface of a lattice system matches the force measured in a continuous system, the local pressure does not. Moreover, in a lattice system, the sum of the local pressures is not equal to the total force as is required in a continuous system. The difference is caused by correlation between occupations of surface sites as well as finite displacement of surface elements used in the definition of the pressures and the force. This problem is particularly acute in the studies of entropic pressure of polymers represented by random or self-avoiding walks on a lattice. We propose a modified expression for the local pressure which satisfies the proper relation between the pressure and the total force, and show that for a single ideal polymer in the presence of scale-invariant boundaries it produces quantitatively correct values for continuous systems. The required correction to the pressure is non-local, i.e., it depends on long range correlations between contact points of the polymer and the surface. PMID:25429960

  16. Time series modelling of surface pressure data

    NASA Astrophysics Data System (ADS)

    Al-Awadhi, Shafeeqah; Jolliffe, Ian

    1998-03-01

    In this paper we examine time series modelling of surface pressure data, as measured by a barograph, at Herne Bay, England, during the years 1981-1989. Autoregressive moving average (ARMA) models have been popular in many fields over the past 20 years, although applications in climatology have been rather less widespread than in some disciplines. Some recent examples are Milionis and Davies (Int. J. Climatol., 14, 569-579) and Seleshi et al. (Int. J. Climatol., 14, 911-923). We fit standard ARMA models to the pressure data separately for each of six 2-month natural seasons. Differences between the best fitting models for different seasons are discussed. Barograph data are recorded continuously, whereas ARMA models are fitted to discretely recorded data. The effect of different spacings between the fitted data on the models chosen is discussed briefly.Often, ARMA models can give a parsimonious and interpretable representation of a time series, but for many series the assumptions underlying such models are not fully satisfied, and more complex models may be considered. A specific feature of surface pressure data in the UK is that its behaviour is different at high and at low pressures: day-to-day changes are typically larger at low pressure levels than at higher levels. This means that standard assumptions used in fitting ARMA models are not valid, and two ways of overcoming this problem are investigated. Transformation of the data to better satisfy the usual assumptions is considered, as is the use of non-linear, specifically threshold autoregressive (TAR), models.

  17. Multifractal Value at Risk model

    NASA Astrophysics Data System (ADS)

    Lee, Hojin; Song, Jae Wook; Chang, Woojin

    2016-06-01

    In this paper new Value at Risk (VaR) model is proposed and investigated. We consider the multifractal property of financial time series and develop a multifractal Value at Risk (MFVaR). MFVaR introduced in this paper is analytically tractable and not based on simulation. Empirical study showed that MFVaR can provide the more stable and accurate forecasting performance in volatile financial markets where large loss can be incurred. This implies that our multifractal VaR works well for the risk measurement of extreme credit events.

  18. [Using the 'Driving Force - Pressure - State - Exposure - Effects - Action' (DPSEEA) model of the World Health Organization (WHO) for the analysis of risks related to the use of pesticides in agricultural activities in the state of Rio de Janeiro].

    PubMed

    Araújo-Pinto, Mariana de; Peres, Frederico; Moreira, Josino Costa

    2012-06-01

    This paper seeks to apply the DPSEEA model (WHO) to identify major health risks to rural workers and the environment associated with the intensive use of pesticides in the State of Rio de Janeiro, based on an analysis of official public documents and a review of the (national and international) literature. It emphasizes the two main representative branches of agriculture in the state: family farming in the mountain region and the monoculture of sugarcane in the flatlands. Results show that the bulk of the determinants identified in the DPSEEA Matrix are related to deficiencies in actions for monitoring and surveillance of pesticide use, as well as a lack of technical assistance provided by the Public Sector in Rio de Janeiro State. Most of the actions developed in the state address the effects of pesticide exposure and, to a lesser extent, exposure to these chemicals, failing to focus on the higher levels of the matrix (such as driving forces and pressure). These are considered, by several authors, as the most appropriate when tackling the complex and systemic issues, such as the scope of this paper. By means of this study, an attempt was made to enable the application of the DPSEEA Model to assist in environmental and occupational health surveillance initiatives. PMID:22699645

  19. Information risk and security modeling

    NASA Astrophysics Data System (ADS)

    Zivic, Predrag

    2005-03-01

    This research paper presentation will feature current frameworks to addressing risk and security modeling and metrics. The paper will analyze technical level risk and security metrics of Common Criteria/ISO15408, Centre for Internet Security guidelines, NSA configuration guidelines and metrics used at this level. Information IT operational standards view on security metrics such as GMITS/ISO13335, ITIL/ITMS and architectural guidelines such as ISO7498-2 will be explained. Business process level standards such as ISO17799, COSO and CobiT will be presented with their control approach to security metrics. Top level, the maturity standards such as SSE-CMM/ISO21827, NSA Infosec Assessment and CobiT will be explored and reviewed. For each defined level of security metrics the research presentation will explore the appropriate usage of these standards. The paper will discuss standards approaches to conducting the risk and security metrics. The research findings will demonstrate the need for common baseline for both risk and security metrics. This paper will show the relation between the attribute based common baseline and corporate assets and controls for risk and security metrics. IT will be shown that such approach spans over all mentioned standards. The proposed approach 3D visual presentation and development of the Information Security Model will be analyzed and postulated. Presentation will clearly demonstrate the benefits of proposed attributes based approach and defined risk and security space for modeling and measuring.

  20. Cabin Environment Physics Risk Model

    NASA Technical Reports Server (NTRS)

    Mattenberger, Christopher J.; Mathias, Donovan Leigh

    2014-01-01

    This paper presents a Cabin Environment Physics Risk (CEPR) model that predicts the time for an initial failure of Environmental Control and Life Support System (ECLSS) functionality to propagate into a hazardous environment and trigger a loss-of-crew (LOC) event. This physics-of failure model allows a probabilistic risk assessment of a crewed spacecraft to account for the cabin environment, which can serve as a buffer to protect the crew during an abort from orbit and ultimately enable a safe return. The results of the CEPR model replace the assumption that failure of the crew critical ECLSS functionality causes LOC instantly, and provide a more accurate representation of the spacecraft's risk posture. The instant-LOC assumption is shown to be excessively conservative and, moreover, can impact the relative risk drivers identified for the spacecraft. This, in turn, could lead the design team to allocate mass for equipment to reduce overly conservative risk estimates in a suboptimal configuration, which inherently increases the overall risk to the crew. For example, available mass could be poorly used to add redundant ECLSS components that have a negligible benefit but appear to make the vehicle safer due to poor assumptions about the propagation time of ECLSS failures.

  1. Command Process Modeling & Risk Analysis

    NASA Technical Reports Server (NTRS)

    Meshkat, Leila

    2011-01-01

    Commanding Errors may be caused by a variety of root causes. It's important to understand the relative significance of each of these causes for making institutional investment decisions. One of these causes is the lack of standardized processes and procedures for command and control. We mitigate this problem by building periodic tables and models corresponding to key functions within it. These models include simulation analysis and probabilistic risk assessment models.

  2. Lunar Landing Operational Risk Model

    NASA Technical Reports Server (NTRS)

    Mattenberger, Chris; Putney, Blake; Rust, Randy; Derkowski, Brian

    2010-01-01

    Characterizing the risk of spacecraft goes beyond simply modeling equipment reliability. Some portions of the mission require complex interactions between system elements that can lead to failure without an actual hardware fault. Landing risk is currently the least characterized aspect of the Altair lunar lander and appears to result from complex temporal interactions between pilot, sensors, surface characteristics and vehicle capabilities rather than hardware failures. The Lunar Landing Operational Risk Model (LLORM) seeks to provide rapid and flexible quantitative insight into the risks driving the landing event and to gauge sensitivities of the vehicle to changes in system configuration and mission operations. The LLORM takes a Monte Carlo based approach to estimate the operational risk of the Lunar Landing Event and calculates estimates of the risk of Loss of Mission (LOM) - Abort Required and is Successful, Loss of Crew (LOC) - Vehicle Crashes or Cannot Reach Orbit, and Success. The LLORM is meant to be used during the conceptual design phase to inform decision makers transparently of the reliability impacts of design decisions, to identify areas of the design which may require additional robustness, and to aid in the development and flow-down of requirements.

  3. Risk-based inspection of pressurizer surge lines

    NASA Astrophysics Data System (ADS)

    Shah, Nitin J.; Dwivedy, Keshab K.

    1996-11-01

    The Reactor Coolant System (RCS) piping of a pressurized water reactor (PWR) plant is probably the best in terms of resistance to known degradation mechanisms of passive components. However, a failure in the RCS piping is extremely important in terms of safety and economic significance. Therefore, an effective management tool is needed to mitigate the potential effects of degradation due to aging or other effects such that plant reliability and availability are not affected. Currently, the RCS piping of all US PWR plants is being subjected to inservice inspection (ISI) based upon certain deterministics criteria set by the ASME code and the NRC regulatory guide. Even though the history of large RCS piping has not shown any degradation, the ISI continues at many locations at greta expense to the plant owners whereas, there can be only a few locations of relatively high vulnerability. A risk based ISI can provide an alternative and cost-effective solution in this situation. Pressurizer surge line is a unique segment in the RCS which is subjected to significant transient loadings due to stratification and striping during the normal heatup and cooldown processes. Therefore, the surge line is considered for illustration. Examples of structural reliability studies of pressurizer surge lines in four PWR units are presented in this paper to demonstrate possible reduction of ISI and significant cost saving without reduction of plant safety or reliability.

  4. Modeling steam pressure under martian lava flows

    USGS Publications Warehouse

    Dundas, Colin M.; Keszthelyi, Laszlo P.

    2013-01-01

    Rootless cones on Mars are a valuable indicator of past interactions between lava and water. However, the details of the lava–water interactions are not fully understood, limiting the ability to use these features to infer new information about past water on Mars. We have developed a model for the pressurization of a dry layer of porous regolith by melting and boiling ground ice in the shallow subsurface. This model builds on previous models of lava cooling and melting of subsurface ice. We find that for reasonable regolith properties and ice depths of decimeters, explosive pressures can be reached. However, the energy stored within such lags is insufficient to excavate thick flows unless they draw steam from a broader region than the local eruption site. These results indicate that lag pressurization can drive rootless cone formation under favorable circumstances, but in other instances molten fuel–coolant interactions are probably required. We use the model results to consider a range of scenarios for rootless cone formation in Athabasca Valles. Pressure buildup by melting and boiling ice under a desiccated lag is possible in some locations, consistent with the expected distribution of ice implanted from atmospheric water vapor. However, it is uncertain whether such ice has existed in the vicinity of Athabasca Valles in recent history. Plausible alternative sources include surface snow or an aqueous flood shortly before the emplacement of the lava flow.

  5. Layzer type models for pressure driven shells

    SciTech Connect

    Hurricane, O A

    2004-09-16

    Models for the nonlinear instability of finite thickness shells driven by pressure are constructed in the style of Layzer. Equations for both Cartesian and cylindrically convergent/divergent geometries are derived. The resulting equations are appropriate for incompressible shells with unity Atwood number. Predictions from the equations compare well with two-dimensional simulations.

  6. Communicating Health Risks under Pressure: Homeland Security Applications

    SciTech Connect

    Garrahan, K.G.; Collie, S.L.

    2006-07-01

    The U.S. Environmental Protection Agency's (EPA) Office of Research and Development (ORD) Threat and Consequence Assessment Division (TCAD) within the National Homeland Security Research Center (NHSRC) has developed a tool for rapid communication of health risks and likelihood of exposure in preparation for terrorist incidents. The Emergency Consequence Assessment Tool (ECAT) is a secure web-based tool designed to make risk assessment and consequence management faster and easier for high priority terrorist threat scenarios. ECAT has been designed to function as 'defensive play-book' for health advisors, first responders, and decision-makers by presenting a series of evaluation templates for priority scenarios that can be modified for site-specific applications. Perhaps most importantly, the risk communication aspect is considered prior to an actual release event, so that management or legal advisors can concur on general risk communication content in preparation for press releases that can be anticipated in case of an actual emergency. ECAT serves as a one-stop source of information for retrieving toxicological properties for agents of concern, estimating exposure to these agents, characterizing health risks, and determining what actions need to be undertaken to mitigate the risks. ECAT has the capability to be used at a command post where inputs can be checked and communicated while the response continues in real time. This front-end planning is intended to fill the gap most commonly identified during tabletop exercises: a need for concise, timely, and informative risk communication to all parties. Training and customization of existing chemical and biological release scenarios with modeling of exposure to air and water, along with custom risk communication 'messages' intended for public, press, shareholders, and other partners enable more effective communication during times of crisis. For DOE, the ECAT could serve as a prototype that would be amenable to

  7. A Corrosion Risk Assessment Model for Underground Piping

    NASA Technical Reports Server (NTRS)

    Datta, Koushik; Fraser, Douglas R.

    2009-01-01

    The Pressure Systems Manager at NASA Ames Research Center (ARC) has embarked on a project to collect data and develop risk assessment models to support risk-informed decision making regarding future inspections of underground pipes at ARC. This paper shows progress in one area of this project - a corrosion risk assessment model for the underground high-pressure air distribution piping system at ARC. It consists of a Corrosion Model of pipe-segments, a Pipe Wrap Protection Model; and a Pipe Stress Model for a pipe segment. A Monte Carlo simulation of the combined models provides a distribution of the failure probabilities. Sensitivity study results show that the model uncertainty, or lack of knowledge, is the dominant contributor to the calculated unreliability of the underground piping system. As a result, the Pressure Systems Manager may consider investing resources specifically focused on reducing these uncertainties. Future work includes completing the data collection effort for the existing ground based pressure systems and applying the risk models to risk-based inspection strategies of the underground pipes at ARC.

  8. Ecological risk assessment of water environment for Luanhe River Basin based on relative risk model.

    PubMed

    Liu, Jingling; Chen, Qiuying; Li, Yongli

    2010-11-01

    The relative risk model (RRM) was applied in regional ecological risk assessments successfully. In this study, the RRM was developed through increasing the data of risk source and introducing the source-stressor-habitat exposure filter (SSH), the endpoint-habitat exposure filter (EH) and the stressor-endpoint effect filter (SE) to reflect the meaning of exposure and effect more explicit. Water environment which include water quality, water quantity and aquatic ecosystems was selected as the ecological risk assessment endpoints. The Luanhe River Basin located in the North China was selected as model case. The results showed that there were three low risk regions, one medium risk region and two high risk regions in the Luanhe River Basin. The results also indicated habitat destruction was the largest stressor with the risk scores as high as 11.87 for the Luanhe water environment, the second was oxygen consuming organic pollutants (9.28) and the third was nutrients (7.78). So these three stressors were the main influencing factors of the ecological pressure in the study area. Furthermore, animal husbandry was the biggest source with the risk scores as high as 20.38, the second was domestic sewage (14.00), and the third was polluting industry (9.96). For habitats, waters and farmland were enduring the bigger pressure and should be taken considerable attention. Water deterioration and ecological service values damaged were facing the biggest risk pressure, and secondly was biodiversity decreased and landscape fragmentation. PMID:20683654

  9. Low surface pressure models for Titan's atmosphere

    NASA Technical Reports Server (NTRS)

    Caldwell, J.

    1978-01-01

    The inversion model for the atmosphere of Titan is reviewed. The basic features of the model are: a cold surface (80 K), a warm stratosphere (160 K) and a low surface pressure (20 mbar). The model is consistent with all existing thermal infrared spectrophotometry, but it cannot preclude the existence of an opaque, cloud, thick atmosphere. The model excludes other gases than methane as bulk constituents. Radio wavelengths observations, including recent data from the very large array, are discussed. These long wavelength observations may be the only direct means of sampling the surface environment before an entry probe or flyby.

  10. Model dependent behaviour of pressure hypertrophied myocardium.

    PubMed

    Cooper, G; Tomanek, R J

    1987-05-01

    Two animal models with contrasting responses to pressure overloading were used to determine whether cardiac dysfunction is a general property of pressure hypertrophied myocardium or a specific property of a particular model. Chronic progressive cardiac pressure overload was compared in (a) the left ventricle of the adult and aged spontaneously hypertensive rat, in which pressure overloading begins in the pup, and (b) the right ventricle of the adult cat, in which pressure overloading was initiated surgically in the kitten. Nine hypertensive and nine control rats were studied at 1 year of age, when hypertension is stable in this model; five hypertensive and five control rats were then studied at 2 years of age, when both groups of rats are beginning to show appreciable senile mortality. Systolic blood pressure was similarly increased in both hypertensive groups; compared with the normotensive control groups, the ratio of left ventricular to body weight was 36% and 76% higher in the 1 and 2 year old hypertensive groups respectively. During isotonic contractions of left ventricular papillary muscles the extent and velocity of shortening in muscles from the control and hypertensive rats in each group were the same, but shortening and relaxation times were prolonged in muscles from the hypertensive rats in both age groups. During isometric contractions developed tension and the rate of tension rise were the same throughout, but the time integral of active tension was increased in muscles from the hypertensive rats in both age groups. The ratio of oxygen consumption to either external work or developed tension was decreased in muscles from the hypertensive rats. In contrast to these data, previous data from the hypertrophied cat model showed reductions in both the velocity and the extent of isotonic shortening as well as in the rate and amount of isometric tension development, and prolongation of contraction was not observed. A similar but smaller decrease in the oxygen

  11. Modeling atmospheric pressure plasmas for biomedical applications

    NASA Astrophysics Data System (ADS)

    Graves, David

    2007-10-01

    The use of cold, atmospheric pressure plasmas for biomedical treatments is an exciting new application in gaseous electronics. Investigations to date include various tissue treatments and surgery, bacterial destruction, and the promotion of wound healing, among others. In this talk, I will present results from modeling the `plasma needle,' an atmospheric pressure plasma configuration that has been explored by several groups around the world. The biomedical efficacy of the plasma needle has been demonstrated but the mechanisms of cell and tissue modification or bacterial destruction are only just being established. One motivation for developing models is to help interpret experiments and evaluate postulated mechanisms. The model reveals important elements of the plasma needle sustaining mechanisms and operating modes. However, the extraordinary complexity of plasma-tissue interactions represents a long-term challenge for this burgeoning field.

  12. Analytic Modeling of Pressurization and Cryogenic Propellant

    NASA Technical Reports Server (NTRS)

    Corpening, Jeremy H.

    2010-01-01

    An analytic model for pressurization and cryogenic propellant conditions during all mission phases of any liquid rocket based vehicle has been developed and validated. The model assumes the propellant tanks to be divided into five nodes and also implements an empirical correlation for liquid stratification if desired. The five nodes include a tank wall node exposed to ullage gas, an ullage gas node, a saturated propellant vapor node at the liquid-vapor interface, a liquid node, and a tank wall node exposed to liquid. The conservation equations of mass and energy are then applied across all the node boundaries and, with the use of perfect gas assumptions, explicit solutions for ullage and liquid conditions are derived. All fluid properties are updated real time using NIST Refprop.1 Further, mass transfer at the liquid-vapor interface is included in the form of evaporation, bulk boiling of liquid propellant, and condensation given the appropriate conditions for each. Model validation has proven highly successful against previous analytic models and various Saturn era test data and reasonably successful against more recent LH2 tank self pressurization ground test data. Finally, this model has been applied to numerous design iterations for the Altair Lunar Lander, Ares V Core Stage, and Ares V Earth Departure Stage in order to characterize Helium and autogenous pressurant requirements, propellant lost to evaporation and thermodynamic venting to maintain propellant conditions, and non-uniform tank draining in configurations utilizing multiple LH2 or LO2 propellant tanks. In conclusion, this model provides an accurate and efficient means of analyzing multiple design configurations for any cryogenic propellant tank in launch, low-acceleration coast, or in-space maneuvering and supplies the user with pressurization requirements, unusable propellants from evaporation and liquid stratification, and general ullage gas, liquid, and tank wall conditions as functions of time.

  13. Biomechanical modeling to prevent ischial pressure ulcers.

    PubMed

    Luboz, Vincent; Petrizelli, Marion; Bucki, Marek; Diot, Bruno; Vuillerme, Nicolas; Payan, Yohan

    2014-07-18

    With 300,000 paraplegic persons only in France, ischial pressure ulcers represent a major public health issue. They result from the buttocks׳ soft tissues compression by the bony prominences. Unfortunately, the current clinical techniques, with - in the best case - embedded pressure sensor mats, are insufficient to prevent them because most are due to high internal strains which can occur even with low pressures at the skin surface. Therefore, improving prevention requires using a biomechanical model to estimate internal strains from skin surface pressures. However, the buttocks׳ soft tissues׳ stiffness is still unknown. This paper provides a stiffness sensitivity analysis using a finite element model. Different layers with distinct Neo Hookean materials simulate the skin, fat and muscles. With Young moduli in the range [100-500 kPa], [25-35 kPa], and [80-140 kPa] for the skin, fat, and muscles, respectively, maximum internal strains reach realistic 50 to 60% values. The fat and muscle stiffnesses have an important influence on the strain variations, while skin stiffness is less influent. Simulating different sitting postures and changing the muscle thickness also result in a variation in the internal strains. PMID:24873863

  14. Approach for Mitigating Pressure Garment Design Risks in a Mobile Lunar Surface Systems Architecture

    NASA Technical Reports Server (NTRS)

    Aitchison, Lindsay

    2009-01-01

    The stated goals of the 2004 Vision for Space Exploration focus on establishing a human presence throughout the solar system beginning with the establishment of a permanent human presence on the Moon. However, the precise objectives to be accomplished on the lunar surface and the optimal system architecture to achieve those objectives have been a topic of much debate since the inception of the Constellation Program. There are two basic styles of system architectures being traded at the Programmatic level: a traditional large outpost that would focus on techniques for survival off our home planet and a greater depth of exploration within one area, or a mobile approach- akin to a series of nomadic camps- that would allow greater breadth of exploration opportunities. The traditional outpost philosophy is well within the understood pressure garment design space with respect to developing interfaces and operational life cycle models. The mobile outpost, however, combines many unknowns with respect to pressure garment performance and reliability that could dramatically affect the cost and schedule risks associated with the Constellation space suit system. This paper provides an overview of the concepts being traded for a mobile architecture from the operations and hardware implementation perspective, describes the primary risks to the Constellation pressure garment associated with each of the concepts, and summarizes the approach necessary to quantify the pressure garment design risks to enable the Constellation Program to make informed decisions when deciding on an overall lunar surface systems architecture.

  15. Pressurization Risk Assessment of CO2 Reservoirs Utilizing Design of Experiments and Response Surface Methods

    NASA Astrophysics Data System (ADS)

    Guyant, E.; Han, W. S.; Kim, K. Y.; Park, E.; Han, K.

    2015-12-01

    Monitoring of pressure buildup can provide explicit information on reservoir integrity and is an appealing tool, however pressure variation is dependent on a variety of factors causing high uncertainty in pressure predictions. This work evaluated pressurization of a reservoir system in the presence of leakage pathways as well as exploring the effects of compartmentalization of the reservoir utilizing design of experiments (Definitive Screening, Box Behnken, Central Composite, and Latin Hypercube designs) and response surface methods. Two models were developed, 1) an idealized injection scenario in order to evaluate the performance of multiple designs, and 2) a complex injection scenario implementing the best performing design to investigate pressurization of the reservoir system. A holistic evaluation of scenario 1, determined that the Central Composite design would be used for the complex injection scenario. The complex scenario evaluated 5 risk factors: reservoir, seal, leakage pathway and fault permeabilities, and horizontal position of the pathway. A total of 60 response surface models (RSM) were developed for the complex scenario with an average R2 of 0.95 and a NRMSE of 0.067. Sensitivity to the input factors was dynamic through space and time; at the earliest time (0.05 years) the reservoir permeability was dominant, and for later times (>0.5 years) the fault permeability became dominant for all locations. The RSM's were then used to conduct a Monte Carlo Analysis to further analyze pressurization risks, identifying the P10, P50, P90 values. This identified the in zone (lower) P90 values as 2.16, 1.77, and 1.53 MPa and above zone values of 1.35, 1.23, 1.09 MPa for monitoring locations 1, 2, and 3, respectively. In summary, the design of experiments and response surface methods allowed for an efficient sensitivity and uncertainty analysis to be conducted permitting a complete evaluation of the pressurization across the entire parameter space.

  16. Models for computing combat risk

    NASA Astrophysics Data System (ADS)

    Jelinek, Jan

    2002-07-01

    Combat always involves uncertainty and uncertainty entails risk. To ensure that a combat task is prosecuted with the desired probability of success, the task commander has to devise an appropriate task force and then adjust it continuously in the course of battle. In order to do so, he has to evaluate how the probability of task success is related to the structure, capabilities and numerical strengths of combatants. For this purpose, predictive models of combat dynamics for combats in which the combatants fire asynchronously at random instants are developed from the first principles. Combats involving forces with both unlimited and limited ammunition supply are studied and modeled by stochastic Markov processes. In addition to the Markov models, another class of models first proposed by Brown was explored. The models compute directly the probability of win, in which we are primarily interested, without integrating the state probability equations. Experiments confirm that they produce exactly the same results at much lower computational cost.

  17. Blood pressure and risk of cancer incidence and mortality in the Metabolic Syndrome and Cancer Project.

    PubMed

    Stocks, Tanja; Van Hemelrijck, Mieke; Manjer, Jonas; Bjørge, Tone; Ulmer, Hanno; Hallmans, Göran; Lindkvist, Björn; Selmer, Randi; Nagel, Gabriele; Tretli, Steinar; Concin, Hans; Engeland, Anders; Jonsson, Håkan; Stattin, Pär

    2012-04-01

    Observational studies have shown inconsistent results for the association between blood pressure and cancer risk. We investigated the association in 7 cohorts from Norway, Austria, and Sweden. In total, 577799 adults with a mean age of 44 years were followed for, on average, 12 years. Incident cancers were 22184 in men and 14744 in women, and cancer deaths were 8724 and 4525, respectively. Cox regression was used to calculate hazard ratios of cancer per 10-mmHg increments of midblood pressure, which corresponded with 0.7 SDs and, for example, an increment of systolic/diastolic blood pressure of 130/80 to 142/88 mmHg. All of the models used age as the time scale and were adjusted for possible confounders, including body mass index and smoking status. In men, midblood pressure was positively related to total incident cancer (hazard ratio per 10 mmHg increment: 1.07 [95% CI: 1.04-1.09]) and to cancer of the oropharynx, colon, rectum, lung, bladder, kidney, malignant melanoma, and nonmelanoma skin cancer. In women, midblood pressure was not related to total incident cancer but was positively related to cancer of the liver, pancreas, cervix, uterine corpus, and malignant melanoma. A positive association was also found for cancer mortality, with HRs per 10-mmHg increment of 1.12 (95% CI: 1.08-1.15) for men and 1.06 (95% CI: 1.02-1.11) for women. These results suggest a small increased cancer risk overall in men with elevated blood pressure level and a higher risk for cancer death in men and women. PMID:22353615

  18. Intelligent adversary risk analysis: a bioterrorism risk management model.

    PubMed

    Parnell, Gregory S; Smith, Christopher M; Moxley, Frederick I

    2010-01-01

    The tragic events of 9/11 and the concerns about the potential for a terrorist or hostile state attack with weapons of mass destruction have led to an increased emphasis on risk analysis for homeland security. Uncertain hazards (natural and engineering) have been successfully analyzed using probabilistic risk analysis (PRA). Unlike uncertain hazards, terrorists and hostile states are intelligent adversaries who can observe our vulnerabilities and dynamically adapt their plans and actions to achieve their objectives. This article compares uncertain hazard risk analysis with intelligent adversary risk analysis, describes the intelligent adversary risk analysis challenges, and presents a probabilistic defender-attacker-defender model to evaluate the baseline risk and the potential risk reduction provided by defender investments. The model includes defender decisions prior to an attack; attacker decisions during the attack; defender actions after an attack; and the uncertainties of attack implementation, detection, and consequences. The risk management model is demonstrated with an illustrative bioterrorism problem with notional data. PMID:20002893

  19. The Braden Q+P: a pediatric perioperative pressure ulcer risk assessment and intervention tool.

    PubMed

    Galvin, Patricia A; Curley, Martha A Q

    2012-09-01

    Pressure ulcers continue to be a personally and financially expensive complication of surgery and hospitalization. The effects of anesthesia, immobilization during surgery, and use of multiple medical devices all place the surgical patient at high risk for pressure-related skin injury. As part of a comprehensive pressure ulcer prevention initiative, nurses in the cardiac and main ORs at Children's Hospital Boston, Massachusetts, became concerned that current pressure ulcer risk assessment tools did not adequately capture the intense but short-term risk posed in the operating and procedural suites. A team, formed to investigate this matter, developed a tool to guide nursing assessment of patient risk and to plan nursing interventions to prevent pressure ulcers. Results after implementation of the Braden Q+P tool appear to show improvement in preventing pressure ulcers. Increased awareness of pressure ulcer prevention, a hospital focus on skin care, and nursing education about pressure ulcers supported this improvement. PMID:22935255

  20. Impact of Continuous Positive Airway Pressure on Cardiovascular Risk Factors in High-Risk Patients.

    PubMed

    Zhao, Ying Y; Redline, Susan

    2015-11-01

    Cardiovascular disease remains the leading cause of morbidity and mortality in developed countries. Obstructive sleep apnea is a highly prevalent condition characterized by repetitive upper airway collapse during sleep. A large body of evidence suggests that obstructive sleep apnea is associated with the development of cardiovascular disease and increased cardiovascular morbidity and mortality. Continuous positive airway pressure (CPAP) is the current gold standard for the treatment of obstructive sleep apnea. CPAP devices maintain upper airway patency using a pneumatic splint, thereby ameliorating the repetitive deoxygenation and reoxygenation characteristic of sleep in obstructive sleep apnea patients. Accumulating evidence suggests that CPAP treatment may lead to a reduction in blood pressure. Limited evidence also suggests that CPAP therapy may modulate glucose metabolism, serum cholesterol levels, and inflammatory biomarkers. Thus, CPAP treatment may be associated with cardiovascular risk factor modification in patients with obstructive sleep apnea, who are often obese and at an increased risk of developing cardiovascular disease. This review updates the knowledge on the effects of CPAP on cardiovascular risk factors from recently published randomized trials. PMID:26370408

  1. A Quantitative Software Risk Assessment Model

    NASA Technical Reports Server (NTRS)

    Lee, Alice

    2002-01-01

    This slide presentation reviews a risk assessment model as applied to software development. the presentation uses graphs to demonstrate basic concepts of software reliability. It also discusses the application to the risk model to the software development life cycle.

  2. A Study of the Factors Associated with Risk for Development of Pressure Ulcers: A Longitudinal Analysis

    PubMed Central

    Thomas, Elizebeth; Vinodkumar, Sudhaya; Mathew, Silvia; Setia, Maninder Singh

    2015-01-01

    Background: Pressure ulcers (PUs) are prevalent in hospitalized patients; they may cause clinical, psychological, and economic problems in these patients. Previous studies are cross-sectional, have used pooled data, or cox-regression models to assess the risk for developing PU. However, PU risk scores change over time and models that account for time varying variables are useful for cohort analysis of data. Aims and Objectives: The present longitudinal study was conducted to compare the risk of PU between surgical and nonsurgical patients, and to evaluate the factors associated with the development of these ulcers over a period of time. Materials and Methods: We evaluated 290 hospitalized patients over a 4 months period. The main outcomes for our analysis were: (1) Score on the pressure risk assessment scale; and (2) the proportion of individuals who were at severe risk for developing PUs. We used random effects models for longitudinal analysis of the data. Results: The mean PU score was significantly higher in the nonsurgical patients compared with surgical patients at baseline (15.23 [3.86] vs. 9.33 [4.57]; P < 0.01). About 7% of the total patients had a score of >20 at baseline and were considered as being at high-risk for PU; the proportion was significantly higher among the nonsurgical patients compared with the surgical patients (14% vs. 4%, P = 0.003). In the adjusted models, there was no difference for severe risk for PU between surgical and nonsurgical patients (odds ratios [ORs]: 0.37, 95% confidence interval [CI]: 0.01–12.80). An additional day in the ward was associated with a significantly higher likelihood of being at high-risk for PU (OR: 1.47, 95% CI: 1.16–1.86). Conclusion: There were no significant differences between patients who were admitted for surgery compared with those who were not. An additional day in the ward, however, is important for developing a high-risk score for PU on the monitoring scale, and these patients require active

  3. NGNP Risk Management Database: A Model for Managing Risk

    SciTech Connect

    John Collins; John M. Beck

    2011-11-01

    The Next Generation Nuclear Plant (NGNP) Risk Management System (RMS) is a database used to maintain the project risk register. The RMS also maps risk reduction activities to specific identified risks. Further functionality of the RMS includes mapping reactor suppliers Design Data Needs (DDNs) to risk reduction tasks and mapping Phenomena Identification Ranking Table (PIRTs) to associated risks. This document outlines the basic instructions on how to use the RMS. This document constitutes Revision 1 of the NGNP Risk Management Database: A Model for Managing Risk. It incorporates the latest enhancements to the RMS. The enhancements include six new custom views of risk data - Impact/Consequence, Tasks by Project Phase, Tasks by Status, Tasks by Project Phase/Status, Tasks by Impact/WBS, and Tasks by Phase/Impact/WBS.

  4. Pressurized Cadaver Model in Cardiothoracic Surgical Simulation.

    PubMed

    Greene, Christina L; Minneti, Michael; Sullivan, Maura E; Baker, Craig J

    2015-09-01

    Simulation is increasingly recognized as an integral aspect of thoracic surgery education. A number of simulators have been introduced to teach component cardiothoracic skills; however, no good model exists for numerous essential skills including redo sternotomy and internal mammary artery takedown. These procedures are often relegated to thoracic surgery residents but have significant negative implications if performed incorrectly. Fresh tissue dissection is recognized as the gold standard for surgical simulation, but the lack of circulating blood volume limits surgical realism. Our aim is to describe the technique of the pressurized cadaver for use in cardiothoracic surgical procedures, focusing on internal mammary artery takedown. PMID:26354651

  5. Animal Models in Pressure Ulcer Research

    PubMed Central

    Salcido, Richard; Popescu, Adrian; Ahn, Chulhyun

    2007-01-01

    Background/Objective: Research targeting the pathophysiology, prevention, and treatment of pressure ulcers (PrUs) continue to be a significant priority for clinical and basic science research. Spinal cord injury patients particularly benefit from PrU research, because the prevalence of chronic wounds in this category is increasing despite standardized medical care. Because of practical, ethical, and safety considerations, PrUs in the human environment are limited to studies involving patients with pre-existing ulcers. Therefore, we are limited in our basic knowledge pertaining to the development, progression, and healing environment in this devastating disease. Methods: This review provides a synopsis of literature and a discussion of techniques used to induce PrUs in animal models. The question of what animal model best mimics the human PrU environment has been a subject of debate by investigators, peer review panels, and editors. The similarities in wound development and healing in mammalian tissue make murine models a relevant model for understanding the causal factors as well as the wound healing elements. Although we are beginning to understand some of the mechanisms of PrU development, a key dilemma of what makes an apparently healthy tissue develop a PrU waits to be solved. Results and Conclusions: No single method of induction and exploring PrUs in animals can address all the aspects of the pathology of chronic wounds. Each model has its particular strengths and weaknesses. Certain types of models can selectively identify specific aspects of wound development, quantify the extent of lesions, and assess outcomes from interventions. The appropriate interpretation of these methods is significant for proper study design, an understanding of the results, and extrapolation to clinical relevance. PMID:17591222

  6. Drivers of extinction risk in African mammals: the interplay of distribution state, human pressure, conservation response and species biology

    PubMed Central

    Di Marco, Moreno; Buchanan, Graeme M.; Szantoi, Zoltan; Holmgren, Milena; Grottolo Marasini, Gabriele; Gross, Dorit; Tranquilli, Sandra; Boitani, Luigi; Rondinini, Carlo

    2014-01-01

    Although conservation intervention has reversed the decline of some species, our success is outweighed by a much larger number of species moving towards extinction. Extinction risk modelling can identify correlates of risk and species not yet recognized to be threatened. Here, we use machine learning models to identify correlates of extinction risk in African terrestrial mammals using a set of variables belonging to four classes: species distribution state, human pressures, conservation response and species biology. We derived information on distribution state and human pressure from satellite-borne imagery. Variables in all four classes were identified as important predictors of extinction risk, and interactions were observed among variables in different classes (e.g. level of protection, human threats, species distribution ranges). Species biology had a key role in mediating the effect of external variables. The model was 90% accurate in classifying extinction risk status of species, but in a few cases the observed and modelled extinction risk mismatched. Species in this condition might suffer from an incorrect classification of extinction risk (hence require reassessment). An increased availability of satellite imagery combined with improved resolution and classification accuracy of the resulting maps will play a progressively greater role in conservation monitoring. PMID:24733953

  7. Fluid dynamic modelling of renal pelvic pressure during endoscopic stone removal

    NASA Astrophysics Data System (ADS)

    Oratis, Alexandros; Subasic, John; Bird, James; Eisner, Brian

    2015-11-01

    Endoscopic kidney stone removal procedures are known to increase internal pressure in the renal pelvis, the kidney's urinary collecting system. High renal pelvic pressure incites systemic absorption of irrigation fluid, which can increase the risk of postoperative fever and sepsis or the unwanted absorption of electrolytes. Urologists choose the appropriate surgical procedure based on patient history and kidney stone size. However, no study has been conducted to compare the pressure profiles of each procedure, nor is there a precise sense of how the renal pelvic pressure scales with various operational parameters. Here we develop physical models for the flow rates and renal pelvic pressure for various procedures. We show that the results of our models are consistent with existing urological data on each procedure and that the models can predict pressure profiles where data is unavailable.

  8. Predictive capacity of risk assessment scales and clinical judgment for pressure ulcers: a meta-analysis.

    PubMed

    García-Fernández, Francisco Pedro; Pancorbo-Hidalgo, Pedro L; Agreda, J Javier Soldevilla

    2014-01-01

    A systematic review with meta-analysis was completed to determine the capacity of risk assessment scales and nurses' clinical judgment to predict pressure ulcer (PU) development. Electronic databases were searched for prospective studies on the validity and predictive capacity of PUs risk assessment scales published between 1962 and 2010 in English, Spanish, Portuguese, Korean, German, and Greek. We excluded gray literature sources, integrative review articles, and retrospective or cross-sectional studies. The methodological quality of the studies was assessed according to the guidelines of the Critical Appraisal Skills Program. Predictive capacity was measured as relative risk (RR) with 95% confidence intervals. When 2 or more valid original studies were found, a meta-analysis was conducted using a random-effect model and sensitivity analysis. We identified 57 studies, including 31 that included a validation study. We also retrieved 4 studies that tested clinical judgment as a risk prediction factor. Meta-analysis produced the following pooled predictive capacity indicators: Braden (RR = 4.26); Norton (RR = 3.69); Waterlow (RR = 2.66); Cubbin-Jackson (RR = 8.63); EMINA (RR = 6.17); Pressure Sore Predictor Scale (RR = 21.4); and clinical judgment (RR = 1.89). Pooled analysis of 11 studies found adequate risk prediction capacity in various clinical settings; the Braden, Norton, EMINA (mEntal state, Mobility, Incontinence, Nutrition, Activity), Waterlow, and Cubbin-Jackson scales showed the highest predictive capacity. The clinical judgment of nurses was found to achieve inadequate predictive capacity when used alone, and should be used in combination with a validated scale. PMID:24280770

  9. Predictive Validity of Pressure Ulcer Risk Assessment Tools for Elderly: A Meta-Analysis.

    PubMed

    Park, Seong-Hi; Lee, Young-Shin; Kwon, Young-Mi

    2016-04-01

    Preventing pressure ulcers is one of the most challenging goals existing for today's health care provider. Currently used tools which assess risk of pressure ulcer development rarely evaluate the accuracy of predictability, especially in older adults. The current study aimed at providing a systemic review and meta-analysis of 29 studies using three pressure ulcer risk assessment tools: Braden, Norton, and Waterlow Scales. Overall predictive validities of pressure ulcer risks in the pooled sensitivity and specificity indicated a similar range with a moderate accuracy level in all three scales, while heterogeneity showed more than 80% variability among studies. The studies applying the Braden Scale used five different cut-off points representing the primary cause of heterogeneity. Results indicate that commonly used screening tools for pressure ulcer risk have limitations regarding validity and accuracy for use with older adults due to heterogeneity among studies. PMID:26337859

  10. Modeling Research Project Risks with Fuzzy Maps

    ERIC Educational Resources Information Center

    Bodea, Constanta Nicoleta; Dascalu, Mariana Iuliana

    2009-01-01

    The authors propose a risks evaluation model for research projects. The model is based on fuzzy inference. The knowledge base for fuzzy process is built with a causal and cognitive map of risks. The map was especially developed for research projects, taken into account their typical lifecycle. The model was applied to an e-testing research…

  11. Common carotid intima-media thickness measurements do not improve cardiovascular risk prediction in individuals with elevated blood pressure: the USE-IMT collaboration.

    PubMed

    Bots, Michiel L; Groenewegen, Karlijn A; Anderson, Todd J; Britton, Annie R; Dekker, Jacqueline M; Engström, Gunnar; Evans, Greg W; de Graaf, Jacqueline; Grobbee, Diederick E; Hedblad, Bo; Hofman, Albert; Holewijn, Suzanne; Ikeda, Ai; Kavousi, Maryam; Kitagawa, Kazuo; Kitamura, Akihiko; Ikram, M Arfan; Lonn, Eva M; Lorenz, Matthias W; Mathiesen, Ellisiv B; Nijpels, Giel; Okazaki, Shuhei; O'Leary, Daniel H; Polak, Joseph F; Price, Jacqueline F; Robertson, Christine; Rembold, Christopher M; Rosvall, Maria; Rundek, Tatjana; Salonen, Jukka T; Sitzer, Matthias; Stehouwer, Coen D A; Franco, Oscar H; Peters, Sanne A E; den Ruijter, Hester M

    2014-06-01

    Carotid intima-media thickness (CIMT) is a marker of cardiovascular risk. It is unclear whether measurement of mean common CIMT improves 10-year risk prediction of first-time myocardial infarction or stroke in individuals with elevated blood pressure. We performed an analysis among individuals with elevated blood pressure (i.e., a systolic blood pressure ≥140 mm Hg and a diastolic blood pressure ≥ 90 mm Hg) in USE-IMT, a large ongoing individual participant data meta-analysis. We refitted the risk factors of the Framingham Risk Score on asymptomatic individuals (baseline model) and expanded this model with mean common CIMT (CIMT model) measurements. From both models, 10-year risks to develop a myocardial infarction or stroke were estimated. In individuals with elevated blood pressure, we compared discrimination and calibration of the 2 models and calculated the net reclassification improvement (NRI). We included 17 254 individuals with elevated blood pressure from 16 studies. During a median follow-up of 9.9 years, 2014 first-time myocardial infarctions or strokes occurred. The C-statistics of the baseline and CIMT models were similar (0.73). NRI with the addition of mean common CIMT was small and not significant (1.4%; 95% confidence intervals, -1.1 to 3.7). In those at intermediate risk (n=5008, 10-year absolute risk of 10% to 20%), the NRI was 5.6% (95% confidence intervals, 1.6-10.4). There is no added value of measurement of mean common CIMT in individuals with elevated blood pressure for improving cardiovascular risk prediction. For those at intermediate risk, the addition of mean common CIMT to an existing cardiovascular risk score is small but statistically significant. PMID:24614213

  12. Intraglottal velocity and pressure measurements in a hemilarynx model

    PubMed Central

    Oren, Liran; Gutmark, Ephraim; Khosla, Sid

    2015-01-01

    Determining the mechanisms of self-sustained oscillation of the vocal folds requires characterization of the pressures produced by intraglottal aerodynamics. Because most of the intraglottal aerodynamic forces cannot be measured in a tissue model of the larynx, current understanding of vocal fold vibration mechanism is derived from mechanical, analytical, and computational models. Previous studies have computed intraglottal pressures from measured intraglottal velocity fields and intraglottal geometry; however, this technique for determining pressures is not yet validated. In this study, intraglottal pressure measurements taken in a hemilarynx model are compared with pressure values that are computed from simultaneous velocity measurements. The results showed that significant negative pressure formed near the superior aspect of the folds during closing, which agrees with previous measurements in other hemilarynx models. Intraglottal velocity measurements show that the flow near the superior aspect separates from the glottal wall during closing and may develop into a vortex, which further augments the magnitude of negative pressure. Intraglottal pressure distributions, computed by solving the pressure Poisson equation, showed good agreement with pressure measurements. The match between the pressure computations and its measurements validates the current technique, which was previously used to estimate intraglottal pressure distribution in a full larynx model. PMID:25698025

  13. Intraglottal velocity and pressure measurements in a hemilarynx model.

    PubMed

    Oren, Liran; Gutmark, Ephraim; Khosla, Sid

    2015-02-01

    Determining the mechanisms of self-sustained oscillation of the vocal folds requires characterization of the pressures produced by intraglottal aerodynamics. Because most of the intraglottal aerodynamic forces cannot be measured in a tissue model of the larynx, current understanding of vocal fold vibration mechanism is derived from mechanical, analytical, and computational models. Previous studies have computed intraglottal pressures from measured intraglottal velocity fields and intraglottal geometry; however, this technique for determining pressures is not yet validated. In this study, intraglottal pressure measurements taken in a hemilarynx model are compared with pressure values that are computed from simultaneous velocity measurements. The results showed that significant negative pressure formed near the superior aspect of the folds during closing, which agrees with previous measurements in other hemilarynx models. Intraglottal velocity measurements show that the flow near the superior aspect separates from the glottal wall during closing and may develop into a vortex, which further augments the magnitude of negative pressure. Intraglottal pressure distributions, computed by solving the pressure Poisson equation, showed good agreement with pressure measurements. The match between the pressure computations and its measurements validates the current technique, which was previously used to estimate intraglottal pressure distribution in a full larynx model. PMID:25698025

  14. Genetic risks and genetic model specification.

    PubMed

    Zheng, Gang; Zhang, Wei; Xu, Jinfeng; Yuan, Ao; Li, Qizhai; Gastwirth, Joseph L

    2016-08-21

    Genetic risks and genetic models are often used in design and analysis of genetic epidemiology studies. A genetic model is defined in terms of two genetic risk measures: genotype relative risk and odds ratio. The impacts of choosing a risk measure on the resulting genetic models are studied in the power to detect association and deviation from Hardy-Weinberg equilibrium in cases using genetic relative risk. Extensive simulations demonstrate that the power of a study to detect associations using odds ratio is lower than that using relative risk with the same value when other parameters are fixed. When the Hardy-Weinberg equilibrium holds in the general population, the genetic model can be inferred by the deviation from Hardy-Weinberg equilibrium in only cases. Furthermore, it is more efficient than that based on the deviation from Hardy-Weinberg equilibrium in all cases and controls. PMID:27181372

  15. More Young Adults at Risk for High Blood Pressure | NIH MedlinePlus the Magazine

    MedlinePlus

    ... young adults have high blood pressure. NIH-funded analysis indicates higher risk for young adults than previously ... 12 ounces of beer or five ounces of wine.) Finally, quit smoking. Among other things, smoking damages ...

  16. A theoretical model to study melting of metals under pressure

    NASA Astrophysics Data System (ADS)

    Kholiya, Kuldeep; Chandra, Jeewan

    2015-10-01

    On the basis of the thermal equation-of-state a simple theoretical model is developed to study the pressure dependence of melting temperature. The model is then applied to compute the high pressure melting curve of 10 metals (Cu, Mg, Pb, Al, In, Cd, Zn, Au, Ag and Mn). It is found that the melting temperature is not linear with pressure and the slope dTm/dP of the melting curve decreases continuously with the increase in pressure. The results obtained with the present model are also compared with the previous theoretical and experimental data. A good agreement between theoretical and experimental result supports the validity of the present model.

  17. Requirements based system risk modeling

    NASA Technical Reports Server (NTRS)

    Meshkat, Leila; Cornford, Steven; Feather, Martin

    2004-01-01

    The problem that we address in this paper is assessing the expected degree of success of the system or mission based on the degree to which each requirement is satisfied and the relative weight of the requirements. We assume a complete list of the requirements, the relevant risk elements and their probability of occurrence and the quantified effect of the risk elements on the requirements. In order to assess the degree to which each requirement is satisfied, we need to determine the effect of the various risk elements on the requirement.

  18. A new velocity-pressure-compaction model for uncemented sediments

    NASA Astrophysics Data System (ADS)

    Saul, M. J.; Lumley, D. E.

    2013-05-01

    Knowledge of the pressure dependence of rock properties is useful for a wide range of earth science problems, especially related to pore pressure changes caused by fluid injection or withdrawal, as often occurs in groundwater, hydrocarbon and CO2 sequestration reservoirs. A long-standing problem is that theoretical models of velocity-pressure response often do not match laboratory measurements, and alternately, empirical regressions fit to such data do not extrapolate accurately to wider pressure ranges since they have little or no physical basis. Accurate determination of the dry rock frame properties at low effective pressure is a key aspect of the problem, particularly when ultrasonic laboratory measurements are not available in this pressure range. We present a new model to describe the pressure sensitivity of the bulk and shear moduli for uncemented sedimentary rocks. Our model incorporates effects of sedimentary compaction and critical porosity, including a relationship to account for porosity and density change with pressure. The model is tested on laboratory measurements for various rock samples and fits well over a wide range of pressures. The new velocity-pressure model should be useful for improved prediction and interpretation of pressure-dependent rock properties and seismic data.

  19. Modeling extreme risks in ecology.

    PubMed

    Burgman, Mark; Franklin, James; Hayes, Keith R; Hosack, Geoffrey R; Peters, Gareth W; Sisson, Scott A

    2012-11-01

    Extreme risks in ecology are typified by circumstances in which data are sporadic or unavailable, understanding is poor, and decisions are urgently needed. Expert judgments are pervasive and disagreements among experts are commonplace. We outline approaches to evaluating extreme risks in ecology that rely on stochastic simulation, with a particular focus on methods to evaluate the likelihood of extinction and quasi-extinction of threatened species, and the likelihood of establishment and spread of invasive pests. We evaluate the importance of assumptions in these assessments and the potential of some new approaches to account for these uncertainties, including hierarchical estimation procedures and generalized extreme value distributions. We conclude by examining the treatment of consequences in extreme risk analysis in ecology and how expert judgment may better be harnessed to evaluate extreme risks. PMID:22817845

  20. Blood pressure level impacts risk of death among HIV seropositive adults in Kenya: a retrospective analysis of electronic health records

    PubMed Central

    2014-01-01

    Background Mortality among people with human immunodeficiency virus (HIV) infection is increasingly due to non-communicable causes. This has been observed mostly in developed countries and the routine care of HIV infected individuals has now expanded to include attention to cardiovascular risk factors. Cardiovascular risk factors such as high blood pressure are often overlooked among HIV seropositive (+) individuals in sub-Saharan Africa. We aimed to determine the effect of blood pressure on mortality among HIV+ adults in Kenya. Methods We performed a retrospective analysis of electronic medical records of a large HIV treatment program in western Kenya between 2005 and 2010. All included individuals were HIV+. We excluded participants with AIDS, who were <16 or >80 years old, or had data out of acceptable ranges. Missing data for key covariates was addressed by inverse probability weighting. Primary outcome measures were crude mortality rate and mortality hazard ratio (HR) using Cox proportional hazards models adjusted for potential confounders including HIV stage. Results There were 49,475 (74% women) HIV+ individuals who met inclusion and exclusion criteria. Mortality rates for men and women were 3.8 and 1.8/100 person-years, respectively, and highest among those with the lowest blood pressures. Low blood pressure was associated with the highest mortality incidence rate (IR) (systolic <100 mmHg IR 5.2 [4.8-5.7]; diastolic <60 mmHg IR 9.2 [8.3-10.2]). Mortality rate among men with high systolic blood pressure without advanced HIV (3.0, 95% CI: 1.6-5.5) was higher than men with normal systolic blood pressure (1.1, 95% CI: 0.7-1.7). In weighted proportional hazards regression models, men without advanced HIV disease and systolic blood pressure ≥140 mmHg carried a higher mortality risk than normotensive men (HR: 2.39, 95% CI: 0.94-6.08). Conclusions Although there has been little attention paid to high blood pressure among HIV+ Africans, we show that blood

  1. Hypertension syndrome and cardiovascular events. High blood pressure is only one risk factor.

    PubMed

    Glasser, S P

    2001-11-01

    It is becoming increasingly clear that high blood pressure is not the sole cause of the high cardiovascular morbidity and mortality rates associated with hypertension. Reduction of blood pressure is of utmost importance, but many other factors contribute significantly to the risk of adverse cardiovascular events and death. In this article, Dr Glasser reviews hypertension as a syndrome, emphasizing therapy to improve blood pressure control, increase arterial compliance, and inhibit or reverse vascular remodeling. PMID:11727651

  2. High Blood Pressure, Afib and Your Risk of Stroke

    MedlinePlus

    ... is generally considered the most common controllable risk factor for stroke, but atrial fibrillation is the most powerful, said Ralph L. Sacco, M.D., professor and chairman of neurology at the Miller School of Medicine at the University of Miami and past president of the American ...

  3. Pressure Sensitive Paint Applied to Flexible Models Project

    NASA Technical Reports Server (NTRS)

    Schairer, Edward T.; Kushner, Laura Kathryn

    2014-01-01

    One gap in current pressure-measurement technology is a high-spatial-resolution method for accurately measuring pressures on spatially and temporally varying wind-tunnel models such as Inflatable Aerodynamic Decelerators (IADs), parachutes, and sails. Conventional pressure taps only provide sparse measurements at discrete points and are difficult to integrate with the model structure without altering structural properties. Pressure Sensitive Paint (PSP) provides pressure measurements with high spatial resolution, but its use has been limited to rigid or semi-rigid models. Extending the use of PSP from rigid surfaces to flexible surfaces would allow direct, high-spatial-resolution measurements of the unsteady surface pressure distribution. Once developed, this new capability will be combined with existing stereo photogrammetry methods to simultaneously measure the shape of a dynamically deforming model in a wind tunnel. Presented here are the results and methodology for using PSP on flexible surfaces.

  4. Childhood Risk Factors for Thin Body Preoccupation and Social Pressure to Be Thin

    ERIC Educational Resources Information Center

    Agras, W. Stewart; Bryson, Susan; Hammer, Lawrence D.; Kraemer, Helena C.

    2007-01-01

    Objective: Thin body preoccupation and social pressure to be thin (TBPSP) in adolescence are risk factors for the development of full and partial bulimia nervosa and binge eating disorder. This study examined precursors of these potent risk factors. Method: A prospective study followed 134 children from birth to 11.0 years and their parents.…

  5. Giving in to Group Pressure: The Impact of Socialization and Risk on Perceived Outcomes

    ERIC Educational Resources Information Center

    McIntyre, Katharine A.; Platania, Judith

    2009-01-01

    The current study applies the perspective of decision theory to understanding how choices are made in an in-group setting involving social pressure and risk. Two hundred sixty-one undergraduate students provided assessments of consequences associated with illegally consuming alcohol in different environments with differing degrees of risk. In…

  6. Orthostatic Blood Pressure Test for Risk Stratification in Patients with Hypertrophic Cardiomyopathy

    PubMed Central

    Münch, Julia; Aydin, Ali; Suling, Anna; Voigt, Christian; Blankenberg, Stefan; Patten, Monica

    2015-01-01

    Background Hypertrophic cardiomyopathy (HCM) is the most common cause of sudden cardiac death (SCD) in young adults, mainly ascribed to ventricular tachycardia (VT). Assuming that VT is the major cause of (pre-) syncope in HCM patients, its occurrence is essential for SCD risk stratification and primarily preventive ICD-implantation. However, evidence of VT during syncope is often missing. As the differentiation of potential lethal causes for syncope such as VT from more harmless reasons is crucial, HCM patients were screened for orthostatic dysregulation by using a simple orthostatic blood pressure test. Methods Over 15 months (IQR [9;20]) 100 HCM patients (55.8±16.2 yrs, 61% male) were evaluated for (pre-)syncope and VT (24h-ECGs, device-memories) within the last five years. Eighty patients underwent an orthostatic blood pressure test. Logistic regression models were used for statistical analysis. Results In older patients (>40 yrs) a positive orthostatic test result increased the chance of (pre-) syncope by a factor of 63 (95%-CI [8.8; 447.9], p<0.001; 93% sensitivity, 95%-CI [76; 99]; 74% specificity, 95%-CI [58; 86]). No correlation with VT was shown. A prolonged QTc interval also increased the chance of (pre-) syncope by a factor of 6.6 (95%-CI [2.0; 21.7]; p=0.002). Conclusions The orthostatic blood pressure test is highly valuable for evaluation of syncope and presyncope especially in older HCM patients, suggesting that orthostatic syncope might be more relevant than previously assumed. Considering the high complication rates due to ICD therapies, this test may provide useful information for the evaluation of syncope in individual risk stratification and may help to prevent unnecessary device implantations, especially in older HCM patients. PMID:26107635

  7. Risk evaluation on the basis of pressure rate measured by automatic pressure tracking adiabatic calorimeter.

    PubMed

    Iwata, Yusaku; Koseki, Hiroshi

    2008-11-15

    An automatic pressure tracking adiabatic calorimeter (APTAC) had been employed to obtain the thermokinetic and the vapor pressure data during runaway reactions. The APTAC is an adiabatic calorimeter with a large-scale sample mass and low thermal inertia, and is an extremely useful tool for assessing thermal hazards of reactive chemicals. The data obtained by the APTAC are important information for the design of the safe industrial process. The thermodynamics parameters and the gas production were discussed on the basis of the experimental data of various concentrations and weights of di-tert-butyl peroxide (DTBP)/toluene solution for the purpose of investigating the properties of the APTAC data. The thermal decomposition of DTBP was studied on the basis of the temperature data and the pressure data obtained by the APTAC. The activation energy and the frequency factor of DTBP are nearly constant and the same as the literature values in the concentrations between 20 and 60 wt.%. The pressure rise due to gas production is important data for designing the relief vent of a reactor. The time history of the gas production was investigated with various weights and concentrations. The total gas production index, which had the vapor pressure correction, was 1.0 in the decomposition of DTBP. PMID:18313846

  8. A Prediction Model of the Capillary Pressure J-Function.

    PubMed

    Xu, W S; Luo, P Y; Sun, L; Lin, N

    2016-01-01

    The capillary pressure J-function is a dimensionless measure of the capillary pressure of a fluid in a porous medium. The function was derived based on a capillary bundle model. However, the dependence of the J-function on the saturation Sw is not well understood. A prediction model for it is presented based on capillary pressure model, and the J-function prediction model is a power function instead of an exponential or polynomial function. Relative permeability is calculated with the J-function prediction model, resulting in an easier calculation and results that are more representative. PMID:27603701

  9. Canards in a rheodynamic model of cardiac pressure pulsations

    NASA Astrophysics Data System (ADS)

    Xie, Feng; Chen, Xian-Feng

    2007-09-01

    This paper reports on the canard phenomenon occurring in a rheodynamic model of cardiac pressure pulsations. By singular perturbation techniques the corresponding parameter value at which canards exist is obtained. The physiological significance of canards in this model is given.

  10. Casting Stainless-Steel Models Around Pressure Tubes

    NASA Technical Reports Server (NTRS)

    Vasquez, Peter; Micol, John R.

    1992-01-01

    Survivability of thin-wall stainless-steel tubing increased to nearly 100 percent. Improves state of art in pressure-model castings and reduces cost associated with machining complete model from stainless-steel blank.

  11. Is It Daily, Monthly, or Yearly Blood Pressure Variability that Enhances Cardiovascular Risk?

    PubMed

    Dolan, Eamon; O'Brien, Eoin

    2015-11-01

    Variability is a phenomenon common to most biological processes that we can measure and is a particular feature of blood pressure (BP). Variability causes concern for many physicians regarding its clinical meaning and potential impact on cardiovascular risk. In this review, we assess the role of different time periods of blood pressure variability (BPV) in cardiovascular risk stratification. We review the indices of BPV derived from ambulatory blood pressure measurement (ABPM), home blood pressure measurement (HBPM), or at the clinic setting with the intention of providing a clear message for clinical practice. BPV, either derived from ABPM or HBPM, does not consistently augment cardiovascular risk prediction over and beyond that of average BP, particularly in low-risk individuals. That said, it would seem that certain medications such as calcium channel blockers may have a beneficial effect on visit-to-visit BPV and perhaps reduce the associated cardiovascular risk. This highlights the benefits in using combination therapy which might couple a number of therapeutic benefits such as the reductions of mean blood pressure and BPV. Overall, we should remain aware that the average BP level remains the main modifiable risk factor derived from BP measurements and continue to improve the control of hypertension and adverse health outcomes. PMID:26351017

  12. A methodology for modeling regional terrorism risk.

    PubMed

    Chatterjee, Samrat; Abkowitz, Mark D

    2011-07-01

    Over the past decade, terrorism risk has become a prominent consideration in protecting the well-being of individuals and organizations. More recently, there has been interest in not only quantifying terrorism risk, but also placing it in the context of an all-hazards environment in which consideration is given to accidents and natural hazards, as well as intentional acts. This article discusses the development of a regional terrorism risk assessment model designed for this purpose. The approach taken is to model terrorism risk as a dependent variable, expressed in expected annual monetary terms, as a function of attributes of population concentration and critical infrastructure. This allows for an assessment of regional terrorism risk in and of itself, as well as in relation to man-made accident and natural hazard risks, so that mitigation resources can be allocated in an effective manner. The adopted methodology incorporates elements of two terrorism risk modeling approaches (event-based models and risk indicators), producing results that can be utilized at various jurisdictional levels. The validity, strengths, and limitations of the model are discussed in the context of a case study application within the United States. PMID:21232062

  13. Thermodynamic models for bounding pressurant mass requirements of cryogenic tanks

    NASA Technical Reports Server (NTRS)

    Vandresar, Neil T.; Haberbusch, Mark S.

    1994-01-01

    Thermodynamic models have been formulated to predict lower and upper bounds for the mass of pressurant gas required to pressurize a cryogenic tank and then expel liquid from the tank. Limiting conditions are based on either thermal equilibrium or zero energy exchange between the pressurant gas and initial tank contents. The models are independent of gravity level and allow specification of autogenous or non-condensible pressurants. Partial liquid fill levels may be specified for initial and final conditions. Model predictions are shown to successfully bound results from limited normal-gravity tests with condensable and non-condensable pressurant gases. Representative maximum collapse factor maps are presented for liquid hydrogen to show the effects of initial and final fill level on the range of pressurant gas requirements. Maximum collapse factors occur for partial expulsions with large final liquid fill fractions.

  14. Development of Standardized Probabilistic Risk Assessment Models for Shutdown Operations Integrated in SPAR Level 1 Model

    SciTech Connect

    S. T. Khericha; J. Mitman

    2008-05-01

    Nuclear plant operating experience and several studies show that the risk from shutdown operation during Modes 4, 5, and 6 at pressurized water reactors and Modes 4 and 5 at boiling water reactors can be significant. This paper describes using the U.S. Nuclear Regulatory Commission’s full-power Standardized Plant Analysis Risk (SPAR) model as the starting point for development of risk evaluation models for commercial nuclear power plants. The shutdown models are integrated with their respective internal event at-power SPAR model. This is accomplished by combining the modified system fault trees from the SPAR full-power model with shutdown event tree logic. Preliminary human reliability analysis results indicate that risk is dominated by the operator’s ability to correctly diagnose events and initiate systems.

  15. Statistical models for operational risk management

    NASA Astrophysics Data System (ADS)

    Cornalba, Chiara; Giudici, Paolo

    2004-07-01

    The Basel Committee on Banking Supervision has released, in the last few years, recommendations for the correct determination of the risks to which a banking organization is subject. This concerns, in particular, operational risks, which are all those management events that may determine unexpected losses. It is necessary to develop valid statistical models to measure and, consequently, predict, such operational risks. In the paper we present the possible approaches, including our own proposal, which is based on Bayesian networks.

  16. Quantitative risk modeling in aseptic manufacture.

    PubMed

    Tidswell, Edward C; McGarvey, Bernard

    2006-01-01

    Expedient risk assessment of aseptic manufacturing processes offers unique opportunities for improved and sustained assurance of product quality. Contemporary risk assessments applied to aseptic manufacturing processes, however, are commonly handicapped by assumptions and subjectivity, leading to inexactitude. Quantitative risk modeling augmented with Monte Carlo simulations represents a novel, innovative, and more efficient means of risk assessment. This technique relies upon fewer assumptions and removes subjectivity to more swiftly generate an improved, more realistic, quantitative estimate of risk. The fundamental steps and requirements for an assessment of the risk of bioburden ingress into aseptically manufactured products are described. A case study exemplifies how quantitative risk modeling and Monte Carlo simulations achieve a more rapid and improved determination of the risk of bioburden ingress during the aseptic filling of a parenteral product. Although application of quantitative risk modeling is described here purely for the purpose of process improvement, the technique has far wider relevance in the assisted disposition of batches, cleanroom management, and the utilization of real-time data from rapid microbial monitoring technologies. PMID:17089696

  17. Mechanical Modeling of a WIPP Drum Under Pressure

    SciTech Connect

    Smith, Jeffrey A.

    2014-11-25

    Mechanical modeling was undertaken to support the Waste Isolation Pilot Plant (WIPP) technical assessment team (TAT) investigating the February 14th 2014 event where there was a radiological release at the WIPP. The initial goal of the modeling was to examine if a mechanical model could inform the team about the event. The intention was to have a model that could test scenarios with respect to the rate of pressurization. It was expected that the deformation and failure (inability of the drum to contain any pressure) would vary according to the pressurization rate. As the work progressed there was also interest in using the mechanical analysis of the drum to investigate what would happen if a drum pressurized when it was located under a standard waste package. Specifically, would the deformation be detectable from camera views within the room. A finite element model of a WIPP 55-gallon drum was developed that used all hex elements. Analyses were conducted using the explicit transient dynamics module of Sierra/SM to explore potential pressurization scenarios of the drum. Theses analysis show similar deformation patterns to documented pressurization tests of drums in the literature. The calculated failure pressures from previous tests documented in the literature vary from as little as 16 psi to 320 psi. In addition, previous testing documented in the literature shows drums bulging but not failing at pressures ranging from 69 to 138 psi. The analyses performed for this study found the drums failing at pressures ranging from 35 psi to 75 psi. When the drums are pressurized quickly (in 0.01 seconds) there is significant deformation to the lid. At lower pressurization rates the deformation of the lid is considerably less, yet the lids will still open from the pressure. The analyses demonstrate the influence of pressurization rate on deformation and opening pressure of the drums. Analyses conducted with a substantial mass on top of the closed drum demonstrate that the

  18. PRISM: a planned risk information seeking model.

    PubMed

    Kahlor, LeeAnn

    2010-06-01

    Recent attention on health-related information seeking has focused primarily on information seeking within specific health and health risk contexts. This study attempts to shift some of that focus to individual-level variables that may impact health risk information seeking across contexts. To locate these variables, the researcher posits an integrated model, the Planned Risk Information Seeking Model (PRISM). The model, which treats risk information seeking as a deliberate (planned) behavior, maps variables found in the Theory of Planned Behavior (TPB; Ajzen, 1991) and the Risk Information Seeking and Processing Model (RISP; Griffin, Dunwoody, & Neuwirth, 1999), and posits linkages among those variables. This effort is further informed by Kahlor's (2007) Augmented RISP, the Theory of Motivated Information Management (Afifi & Weiner, 2004), the Comprehensive Model of Information Seeking (Johnson & Meischke, 1993), the Health Information Acquisition Model (Freimuth, Stein, & Kean, 1989), and the Extended Parallel Processing Model (Witte, 1998). The resulting integrated model accounted for 59% of the variance in health risk information-seeking intent and performed better than the TPB or the RISP alone. PMID:20512716

  19. The Relationship of Medicaid Payment Rates, Bed Constraint Policies, and Risk-Adjusted Pressure Ulcers

    PubMed Central

    Grabowski, David C; Angelelli, Joseph J

    2004-01-01

    Objective To examine the effect of Medicaid reimbursement rates on nursing home quality in the presence of certificate-of-need (CON) and construction moratorium laws. Data Sources/Study Setting A single cross-section of Medicaid certified nursing homes in 1999 (N=13,736). Study Design A multivariate regression model was used to examine the effect of Medicaid payment rates and other explanatory variables on risk-adjusted pressure ulcer incidence. The model is alternatively considered for all U.S. nursing home markets, those most restrictive markets, and those high-Medicaid homes to isolate potentially resource-poor environments. Data Extraction Methods A merged data file was constructed with resident-level information from the Minimum Data Set, facility-level information from the On-Line, Survey, Certification, and Reporting (OSCAR) system and market- and state-level information from various published sources. Principal Findings In the analysis of all U.S. markets, there was a positive relationship between the Medicaid payment rate and nursing home quality. The results from this analysis imply that a 10 percent increase in Medicaid payment was associated with a 1.5 percent decrease in the incidence of risk-adjusted pressure ulcers. However, there was a limited association between Medicaid payment rates and quality in the most restrictive markets. Finally, there was a strong relationship between Medicaid payment and quality in high-Medicaid homes providing strong evidence that the level of Medicaid payment is especially important within resource poor facilities. Conclusions These findings provide support for the idea that increased Medicaid reimbursement may be an effective means toward improving nursing home quality, although CON and moratorium laws may mitigate this relationship. PMID:15230928

  20. High pressure common rail injection system modeling and control.

    PubMed

    Wang, H P; Zheng, D; Tian, Y

    2016-07-01

    In this paper modeling and common-rail pressure control of high pressure common rail injection system (HPCRIS) is presented. The proposed mathematical model of high pressure common rail injection system which contains three sub-systems: high pressure pump sub-model, common rail sub-model and injector sub-model is a relative complicated nonlinear system. The mathematical model is validated by the software Matlab and a virtual detailed simulation environment. For the considered HPCRIS, an effective model free controller which is called Extended State Observer - based intelligent Proportional Integral (ESO-based iPI) controller is designed. And this proposed method is composed mainly of the referred ESO observer, and a time delay estimation based iPI controller. Finally, to demonstrate the performances of the proposed controller, the proposed ESO-based iPI controller is compared with a conventional PID controller and ADRC. PMID:27012440

  1. Korean Risk Assessment Model for Breast Cancer Risk Prediction

    PubMed Central

    Park, Boyoung; Ma, Seung Hyun; Shin, Aesun; Chang, Myung-Chul; Choi, Ji-Yeob; Kim, Sungwan; Han, Wonshik; Noh, Dong-Young; Ahn, Sei-Hyun; Kang, Daehee; Yoo, Keun-Young; Park, Sue K.

    2013-01-01

    Purpose We evaluated the performance of the Gail model for a Korean population and developed a Korean breast cancer risk assessment tool (KoBCRAT) based upon equations developed for the Gail model for predicting breast cancer risk. Methods Using 3,789 sets of cases and controls, risk factors for breast cancer among Koreans were identified. Individual probabilities were projected using Gail's equations and Korean hazard data. We compared the 5-year and lifetime risk produced using the modified Gail model which applied Korean incidence and mortality data and the parameter estimators from the original Gail model with those produced using the KoBCRAT. We validated the KoBCRAT based on the expected/observed breast cancer incidence and area under the curve (AUC) using two Korean cohorts: the Korean Multicenter Cancer Cohort (KMCC) and National Cancer Center (NCC) cohort. Results The major risk factors under the age of 50 were family history, age at menarche, age at first full-term pregnancy, menopausal status, breastfeeding duration, oral contraceptive usage, and exercise, while those at and over the age of 50 were family history, age at menarche, age at menopause, pregnancy experience, body mass index, oral contraceptive usage, and exercise. The modified Gail model produced lower 5-year risk for the cases than for the controls (p = 0.017), while the KoBCRAT produced higher 5-year and lifetime risk for the cases than for the controls (p<0.001 and <0.001, respectively). The observed incidence of breast cancer in the two cohorts was similar to the expected incidence from the KoBCRAT (KMCC, p = 0.880; NCC, p = 0.878). The AUC using the KoBCRAT was 0.61 for the KMCC and 0.89 for the NCC cohort. Conclusions Our findings suggest that the KoBCRAT is a better tool for predicting the risk of breast cancer in Korean women, especially urban women. PMID:24204664

  2. Genetic variants in novel pathways influence blood pressure and cardiovascular disease risk.

    PubMed

    Ehret, Georg B; Munroe, Patricia B; Rice, Kenneth M; Bochud, Murielle; Johnson, Andrew D; Chasman, Daniel I; Smith, Albert V; Tobin, Martin D; Verwoert, Germaine C; Hwang, Shih-Jen; Pihur, Vasyl; Vollenweider, Peter; O'Reilly, Paul F; Amin, Najaf; Bragg-Gresham, Jennifer L; Teumer, Alexander; Glazer, Nicole L; Launer, Lenore; Zhao, Jing Hua; Aulchenko, Yurii; Heath, Simon; Sõber, Siim; Parsa, Afshin; Luan, Jian'an; Arora, Pankaj; Dehghan, Abbas; Zhang, Feng; Lucas, Gavin; Hicks, Andrew A; Jackson, Anne U; Peden, John F; Tanaka, Toshiko; Wild, Sarah H; Rudan, Igor; Igl, Wilmar; Milaneschi, Yuri; Parker, Alex N; Fava, Cristiano; Chambers, John C; Fox, Ervin R; Kumari, Meena; Go, Min Jin; van der Harst, Pim; Kao, Wen Hong Linda; Sjögren, Marketa; Vinay, D G; Alexander, Myriam; Tabara, Yasuharu; Shaw-Hawkins, Sue; Whincup, Peter H; Liu, Yongmei; Shi, Gang; Kuusisto, Johanna; Tayo, Bamidele; Seielstad, Mark; Sim, Xueling; Nguyen, Khanh-Dung Hoang; Lehtimäki, Terho; Matullo, Giuseppe; Wu, Ying; Gaunt, Tom R; Onland-Moret, N Charlotte; Cooper, Matthew N; Platou, Carl G P; Org, Elin; Hardy, Rebecca; Dahgam, Santosh; Palmen, Jutta; Vitart, Veronique; Braund, Peter S; Kuznetsova, Tatiana; Uiterwaal, Cuno S P M; Adeyemo, Adebowale; Palmas, Walter; Campbell, Harry; Ludwig, Barbara; Tomaszewski, Maciej; Tzoulaki, Ioanna; Palmer, Nicholette D; Aspelund, Thor; Garcia, Melissa; Chang, Yen-Pei C; O'Connell, Jeffrey R; Steinle, Nanette I; Grobbee, Diederick E; Arking, Dan E; Kardia, Sharon L; Morrison, Alanna C; Hernandez, Dena; Najjar, Samer; McArdle, Wendy L; Hadley, David; Brown, Morris J; Connell, John M; Hingorani, Aroon D; Day, Ian N M; Lawlor, Debbie A; Beilby, John P; Lawrence, Robert W; Clarke, Robert; Hopewell, Jemma C; Ongen, Halit; Dreisbach, Albert W; Li, Yali; Young, J Hunter; Bis, Joshua C; Kähönen, Mika; Viikari, Jorma; Adair, Linda S; Lee, Nanette R; Chen, Ming-Huei; Olden, Matthias; Pattaro, Cristian; Bolton, Judith A Hoffman; Köttgen, Anna; Bergmann, Sven; Mooser, Vincent; Chaturvedi, Nish; Frayling, Timothy M; Islam, Muhammad; Jafar, Tazeen H; Erdmann, Jeanette; Kulkarni, Smita R; Bornstein, Stefan R; Grässler, Jürgen; Groop, Leif; Voight, Benjamin F; Kettunen, Johannes; Howard, Philip; Taylor, Andrew; Guarrera, Simonetta; Ricceri, Fulvio; Emilsson, Valur; Plump, Andrew; Barroso, Inês; Khaw, Kay-Tee; Weder, Alan B; Hunt, Steven C; Sun, Yan V; Bergman, Richard N; Collins, Francis S; Bonnycastle, Lori L; Scott, Laura J; Stringham, Heather M; Peltonen, Leena; Perola, Markus; Vartiainen, Erkki; Brand, Stefan-Martin; Staessen, Jan A; Wang, Thomas J; Burton, Paul R; Soler Artigas, Maria; Dong, Yanbin; Snieder, Harold; Wang, Xiaoling; Zhu, Haidong; Lohman, Kurt K; Rudock, Megan E; Heckbert, Susan R; Smith, Nicholas L; Wiggins, Kerri L; Doumatey, Ayo; Shriner, Daniel; Veldre, Gudrun; Viigimaa, Margus; Kinra, Sanjay; Prabhakaran, Dorairaj; Tripathy, Vikal; Langefeld, Carl D; Rosengren, Annika; Thelle, Dag S; Corsi, Anna Maria; Singleton, Andrew; Forrester, Terrence; Hilton, Gina; McKenzie, Colin A; Salako, Tunde; Iwai, Naoharu; Kita, Yoshikuni; Ogihara, Toshio; Ohkubo, Takayoshi; Okamura, Tomonori; Ueshima, Hirotsugu; Umemura, Satoshi; Eyheramendy, Susana; Meitinger, Thomas; Wichmann, H-Erich; Cho, Yoon Shin; Kim, Hyung-Lae; Lee, Jong-Young; Scott, James; Sehmi, Joban S; Zhang, Weihua; Hedblad, Bo; Nilsson, Peter; Smith, George Davey; Wong, Andrew; Narisu, Narisu; Stančáková, Alena; Raffel, Leslie J; Yao, Jie; Kathiresan, Sekar; O'Donnell, Christopher J; Schwartz, Stephen M; Ikram, M Arfan; Longstreth, W T; Mosley, Thomas H; Seshadri, Sudha; Shrine, Nick R G; Wain, Louise V; Morken, Mario A; Swift, Amy J; Laitinen, Jaana; Prokopenko, Inga; Zitting, Paavo; Cooper, Jackie A; Humphries, Steve E; Danesh, John; Rasheed, Asif; Goel, Anuj; Hamsten, Anders; Watkins, Hugh; Bakker, Stephan J L; van Gilst, Wiek H; Janipalli, Charles S; Mani, K Radha; Yajnik, Chittaranjan S; Hofman, Albert; Mattace-Raso, Francesco U S; Oostra, Ben A; Demirkan, Ayse; Isaacs, Aaron; Rivadeneira, Fernando; Lakatta, Edward G; Orru, Marco; Scuteri, Angelo; Ala-Korpela, Mika; Kangas, Antti J; Lyytikäinen, Leo-Pekka; Soininen, Pasi; Tukiainen, Taru; Würtz, Peter; Ong, Rick Twee-Hee; Dörr, Marcus; Kroemer, Heyo K; Völker, Uwe; Völzke, Henry; Galan, Pilar; Hercberg, Serge; Lathrop, Mark; Zelenika, Diana; Deloukas, Panos; Mangino, Massimo; Spector, Tim D; Zhai, Guangju; Meschia, James F; Nalls, Michael A; Sharma, Pankaj; Terzic, Janos; Kumar, M V Kranthi; Denniff, Matthew; Zukowska-Szczechowska, Ewa; Wagenknecht, Lynne E; Fowkes, F Gerald R; Charchar, Fadi J; Schwarz, Peter E H; Hayward, Caroline; Guo, Xiuqing; Rotimi, Charles; Bots, Michiel L; Brand, Eva; Samani, Nilesh J; Polasek, Ozren; Talmud, Philippa J; Nyberg, Fredrik; Kuh, Diana; Laan, Maris; Hveem, Kristian; Palmer, Lyle J; van der Schouw, Yvonne T; Casas, Juan P; Mohlke, Karen L; Vineis, Paolo; Raitakari, Olli; Ganesh, Santhi K; Wong, Tien Y; Tai, E Shyong; Cooper, Richard S; Laakso, Markku; Rao, Dabeeru C; Harris, Tamara B; Morris, Richard W; Dominiczak, Anna F; Kivimaki, Mika; Marmot, Michael G; Miki, Tetsuro; Saleheen, Danish; Chandak, Giriraj R; Coresh, Josef; Navis, Gerjan; Salomaa, Veikko; Han, Bok-Ghee; Zhu, Xiaofeng; Kooner, Jaspal S; Melander, Olle; Ridker, Paul M; Bandinelli, Stefania; Gyllensten, Ulf B; Wright, Alan F; Wilson, James F; Ferrucci, Luigi; Farrall, Martin; Tuomilehto, Jaakko; Pramstaller, Peter P; Elosua, Roberto; Soranzo, Nicole; Sijbrands, Eric J G; Altshuler, David; Loos, Ruth J F; Shuldiner, Alan R; Gieger, Christian; Meneton, Pierre; Uitterlinden, Andre G; Wareham, Nicholas J; Gudnason, Vilmundur; Rotter, Jerome I; Rettig, Rainer; Uda, Manuela; Strachan, David P; Witteman, Jacqueline C M; Hartikainen, Anna-Liisa; Beckmann, Jacques S; Boerwinkle, Eric; Vasan, Ramachandran S; Boehnke, Michael; Larson, Martin G; Järvelin, Marjo-Riitta; Psaty, Bruce M; Abecasis, Gonçalo R; Chakravarti, Aravinda; Elliott, Paul; van Duijn, Cornelia M; Newton-Cheh, Christopher; Levy, Daniel; Caulfield, Mark J; Johnson, Toby

    2011-10-01

    Blood pressure is a heritable trait influenced by several biological pathways and responsive to environmental stimuli. Over one billion people worldwide have hypertension (≥140 mm Hg systolic blood pressure or  ≥90 mm Hg diastolic blood pressure). Even small increments in blood pressure are associated with an increased risk of cardiovascular events. This genome-wide association study of systolic and diastolic blood pressure, which used a multi-stage design in 200,000 individuals of European descent, identified sixteen novel loci: six of these loci contain genes previously known or suspected to regulate blood pressure (GUCY1A3-GUCY1B3, NPR3-C5orf23, ADM, FURIN-FES, GOSR2, GNAS-EDN3); the other ten provide new clues to blood pressure physiology. A genetic risk score based on 29 genome-wide significant variants was associated with hypertension, left ventricular wall thickness, stroke and coronary artery disease, but not kidney disease or kidney function. We also observed associations with blood pressure in East Asian, South Asian and African ancestry individuals. Our findings provide new insights into the genetics and biology of blood pressure, and suggest potential novel therapeutic pathways for cardiovascular disease prevention. PMID:21909115

  3. Modelling suicide risk in later life.

    PubMed

    Lo, C F; Kwok, Cordelia M Y

    2006-08-01

    Affective disorder is generally regarded as the prominent risk factor for suicide in the old age population. Despite the large number of empirical studies available in the literature, there is no attempt in modelling the dynamics of an individual's level of suicide risk theoretically yet. In particular, a dynamic model which can simulate the time evolution of an individual's level of risk for suicide and provide quantitative estimates of the probability of suicide risk is still lacking. In the present study we apply the contingent claims analysis of credit risk modelling in the field of quantitative finance to derive a theoretical stochastic model for estimation of the probability of suicide risk in later life in terms of a signalling index of affective disorder. Our model is based upon the hypothesis that the current state of affective disorder of a patient can be represented by a signalling index and exhibits stochastic movement and that a threshold of affective disorder, which signifies the occurrence of suicide, exists. According to the numerical results, the implications of our model are consistent with the clinical findings. Hence, we believe that such a dynamic model will be essential to the design of effective suicide prevention strategies in the target population of older adults, especially in the primary care setting. PMID:16797044

  4. Integrated Environmental Modeling: Quantitative Microbial Risk Assessment

    EPA Science Inventory

    The presentation discusses the need for microbial assessments and presents a road map associated with quantitative microbial risk assessments, through an integrated environmental modeling approach. A brief introduction and the strengths of the current knowledge are illustrated. W...

  5. Foot Modeling and Smart Plantar Pressure Reconstruction from Three Sensors

    PubMed Central

    Ghaida, Hussein Abou; Mottet, Serge; Goujon, Jean-Marc

    2014-01-01

    In order to monitor pressure under feet, this study presents a biomechanical model of the human foot. The main elements of the foot that induce the plantar pressure distribution are described. Then the link between the forces applied at the ankle and the distribution of the plantar pressure is established. Assumptions are made by defining the concepts of a 3D internal foot shape, which can be extracted from the plantar pressure measurements, and a uniform elastic medium, which describes the soft tissues behaviour. In a second part, we show that just 3 discrete pressure sensors per foot are enough to generate real time plantar pressure cartographies in the standing position or during walking. Finally, the generated cartographies are compared with pressure cartographies issued from the F-SCAN system. The results show 0.01 daN (2% of full scale) average error, in the standing position. PMID:25400713

  6. Visual Impairment/lntracranial Pressure Risk Clinical Care Data Tools

    NASA Technical Reports Server (NTRS)

    Van Baalen, Mary; Mason, Sara S.; Taiym, Wafa; Wear, Mary L.; Moynihan, Shannan; Alexander, David; Hart, Steve; Tarver, William

    2014-01-01

    Prior to 2010, several ISS crewmembers returned from spaceflight with changes to their vision, ranging from a mild hyperopic shift to frank disc edema. As a result, NASA expanded clinical vision testing to include more comprehensive medical imaging, including Optical Coherence Tomography and 3 Tesla Brain and Orbit MRIs. The Space and Clinical Operations (SCO) Division developed a clinical practice guideline that classified individuals based on their symptoms and diagnoses to facilitate clinical care. For the purposes of clinical surveillance, this classification was applied retrospectively to all crewmembers who had sufficient testing for classification. This classification is also a tool that has been leveraged for researchers to identify potential risk factors. In March 2014, driven in part by a more comprehensive understanding of the imaging data and increased imaging capability on orbit, the SCO Division revised their clinical care guidance to outline in-flight care and increase post-flight follow up. The new clinical guidance does not include a classification scheme

  7. Overpaying morbidity adjusters in risk equalization models.

    PubMed

    van Kleef, R C; van Vliet, R C J A; van de Ven, W P M M

    2016-09-01

    Most competitive social health insurance markets include risk equalization to compensate insurers for predictable variation in healthcare expenses. Empirical literature shows that even the most sophisticated risk equalization models-with advanced morbidity adjusters-substantially undercompensate insurers for selected groups of high-risk individuals. In the presence of premium regulation, these undercompensations confront consumers and insurers with incentives for risk selection. An important reason for the undercompensations is that not all information with predictive value regarding healthcare expenses is appropriate for use as a morbidity adjuster. To reduce incentives for selection regarding specific groups we propose overpaying morbidity adjusters that are already included in the risk equalization model. This paper illustrates the idea of overpaying by merging data on morbidity adjusters and healthcare expenses with health survey information, and derives three preconditions for meaningful application. Given these preconditions, we think overpaying may be particularly useful for pharmacy-based cost groups. PMID:26420555

  8. Kinetic modelling of pressure filtration of ceramic powder suspensions

    SciTech Connect

    Correia, L.A.; Salomoni, A.; Hey, A.W.

    1995-09-01

    A kinetic model developed for radial pressure filtration is described and used to study the casting behaviour of an Alumina (Al6SG) and a Zirconia (TZ3Ys) slip stabilized with Dolapix CE64. For the Zirconia slip no influence of pressure and curvature is found. The casting behaviour of the Alumina slip seems to be influenced by both the pressure and the curvature of the filtrating surface.

  9. Risk Management in environmental geotechnical modelling

    NASA Astrophysics Data System (ADS)

    Tammemäe, Olavi; Torn, Hardi

    2008-01-01

    The objective of this article is to provide an overview of the basis of risk analysis, assessment and management, accompanying problems and principles of risk management when drafting an environmental geotechnical model, enabling the analysis of an entire territory or developed region as a whole. The environmental impact will remain within the limits of the criteria specified with the standards and will be acceptable for human health and environment. An essential part of the solution of the problem is the engineering-geological model based on risk analysis and the assessment and forecast of mutual effects of the processes.

  10. Modeling turbulent boundary layers in adverse pressure gradients

    NASA Technical Reports Server (NTRS)

    Belcher, Stephen E.

    1991-01-01

    Many of the turbulent layers encountered in practical flows develop in adverse pressure gradients; hence, the dynamics of the thickening and possible separation of the boundary layer has important implications for design practices. What are the key physical processes that govern how a turbulent boundary layer responds to an adverse pressure gradient, and how should these processes be modeled? Despite the ubiquity of such flows in engineering and nature, these equations remain largely unanswered. The turbulence closure models presently used to describe these flows commonly use 'wall functions' that have ad hoc corrections for the effects of pressure gradients. There is, therefore, a practical and theoretical need to examine the effects of adverse pressure gradients on wall bounded turbulent flows in order to develop models based on sound physical principle. The evolution of a turbulent boundary layer on a flat wall with an externally imposed pressure gradient is studied.

  11. Clustering of cardiovascular behavioral risk factors and blood pressure among people diagnosed with hypertension: a nationally representative survey in China

    PubMed Central

    Li, Yichong; Feng, Xiaoqi; Zhang, Mei; Zhou, Maigeng; Wang, Ning; Wang, Limin

    2016-01-01

    This study aimed to examine association between the number of behavioral risk factors and blood pressure (BP) level among a nationally representative sample of Chinese people diagnosed with hypertension. A total of 31,694 respondents aged 18+ years with diagnosed hypertension were extracted from the 2013–2014 China Chronic Disease and Risk Factor Surveillance. BP of each respondent was classified into six levels according to criteria in 2007 Guidelines for the Management of Arterial Hypertension. Information for smoking, alcohol drinking, fruit and vegetables consumption, physical inactivity, and overweight and obesity were obtained. The average number of risk factors was determined by BP level to explore potential risk factor clustering. Ten generalized proportional odds models were used to examine association between clustering of behavioral risk factors and BP level. A clear gradient between the number of behavioral risk factors and BP level was observed for men and women (P < 0.05 for both genders). BP level for men and women was much likely to upgrade as number of risk factors accumulated (P < 0.01 for 10 models). Behavioral modifications may decrease BP, and combinations of two or more behavioral interventions could potentially result in even better BP management among people diagnosed with hypertension. PMID:27279273

  12. Clustering of cardiovascular behavioral risk factors and blood pressure among people diagnosed with hypertension: a nationally representative survey in China.

    PubMed

    Li, Yichong; Feng, Xiaoqi; Zhang, Mei; Zhou, Maigeng; Wang, Ning; Wang, Limin

    2016-01-01

    This study aimed to examine association between the number of behavioral risk factors and blood pressure (BP) level among a nationally representative sample of Chinese people diagnosed with hypertension. A total of 31,694 respondents aged 18+ years with diagnosed hypertension were extracted from the 2013-2014 China Chronic Disease and Risk Factor Surveillance. BP of each respondent was classified into six levels according to criteria in 2007 Guidelines for the Management of Arterial Hypertension. Information for smoking, alcohol drinking, fruit and vegetables consumption, physical inactivity, and overweight and obesity were obtained. The average number of risk factors was determined by BP level to explore potential risk factor clustering. Ten generalized proportional odds models were used to examine association between clustering of behavioral risk factors and BP level. A clear gradient between the number of behavioral risk factors and BP level was observed for men and women (P < 0.05 for both genders). BP level for men and women was much likely to upgrade as number of risk factors accumulated (P < 0.01 for 10 models). Behavioral modifications may decrease BP, and combinations of two or more behavioral interventions could potentially result in even better BP management among people diagnosed with hypertension. PMID:27279273

  13. Pressurized water reactor fuel crud and corrosion modeling

    NASA Astrophysics Data System (ADS)

    Deshon, Jeff; Hussey, Dennis; Kendrick, Brian; McGurk, John; Secker, Jeff; Short, Michael

    2011-08-01

    Pressurized water reactors circulate high-temperature water that slowly corrodes Inconel and stainless steel system surfaces, and the nickel/iron based corrosion products deposit in regions of the fuel where sub-cooled nucleate boiling occurs. The deposited corrosion products, called `crud', can have an adverse impact on fuel performance. Boron can concentrate within the crud in the boiling regions of the fuel leading to a phenomenon known as axial offset anomaly (AOA). In rare cases, fuel clad integrity can be compromised because of crud-induced localized corrosion (CILC) of the zirconium-based alloy. Westinghouse and the Electric Power Research Institute have committed to understanding the crud transport process and develop a risk assessment software tool called boron-induced offset anomaly (BOA) to avoid AOA and CILC. This paper reviews the history of the BOA model development and new efforts to develop a micro-scale model called MAMBA for use in the Consortium for Advanced Light Water Reactor Simulation (CASL) program.

  14. A turbulence model for nonequilibrium adverse pressure gradient flows

    NASA Technical Reports Server (NTRS)

    Horstman, C. C.

    1976-01-01

    This paper presents a method for calculating compressible adverse pressure gradient boundary layers by using an algebraic eddy viscosity turbulence model that has been modified for variable pressure gradient and turbulence memory effects. The pressure gradient corrections are based on previous incompressible data correlations. Several methods for including the effects of turbulence memory are evaluated. A new lag model, which gives good agreement with available experimental data, is developed. Finally, a correlation is developed for the lag length parameter employed in the model as a function of the known experimental flow variables.

  15. The incidence, risk factors and characteristics of pressure ulcers in hospitalized patients in China

    PubMed Central

    Jiang, Qixia; Li, Xiaohua; Qu, Xiaolong; Liu, Yun; Zhang, Liyan; Su, Chunyin; Guo, Xiujun; Chen, Yuejuan; Zhu, Yajun; Jia, Jing; Bo, Suping; Liu, Li; Zhang, Rui; Xu, Ling; Wu, Leyan; Wang, Hai; Wang, Jiandong

    2014-01-01

    Pressure ulcers are very common in hospital patients. Though many studies have been reported in many countries, the large-scale benchmarking prevalence of pressure ulcers in China is not available. The aim of this study is to quantify the prevalence of pressure ulcers and the incidence of hospital-acquired pressure ulcers and analyze risk factors in hospitalized patients in China. A multi-central cross-sectional survey was conducted in one university hospital and 11 general hospitals in China. The Minimum Data Set (MDS) recommended by European Pressure Ulcer Advisory Panel (EUPAP) was used to collect information of inpatients. All patients stayed in hospital more than 24 hours and older than 18 years signed consent form and were included. Data from 39952 out of 40415 (98.85%) inpatients were analyzed. Of the 39952 patients, 631 patients (including 1024 locations) had pressure ulcers. The prevalence rate of pressure ulcers in 12 hospitals was 1.58% (0.94-2.97%). The incidence of hospital-acquired pressure ulcers (HAPU) was 0.63% (0.20-1.20%). The most common locations developed pressure ulcers were sacrum, heels, and iliac crests. The common stages of pressure ulcers were stage I and II. Patients in Intensive Care Unit, Geriatric and Neurological Department were easier to develop pressure ulcers. The prevalence and incidence of pressure ulcers in China was lower than that reported in European and other countries. The stages of pressure ulcers in China were different than that reported in European countries. Our study provides with a baseline value for intensive research on pressure ulcer in China. PMID:24966973

  16. Minimum risk route model for hazardous materials

    SciTech Connect

    Ashtakala, B.; Eno, L.A.

    1996-09-01

    The objective of this study is to determine the minimum risk route for transporting a specific hazardous material (HM) between a point of origin and a point of destination (O-D pair) in the study area which minimizes risk to population and environment. The southern part of Quebec is chosen as the study area and major cities are identified as points of origin and destination on the highway network. Three classes of HM, namely chlorine gas, liquefied petroleum gas (LPG), and sulfuric acid, are chosen. A minimum risk route model has been developed to determine minimum risk routes between an O-D pair by using population or environment risk units as link impedances. The risk units for each link are computed by taking into consideration the probability of an accident and its consequences on that link. The results show that between the same O-D pair, the minimum risk routes are different for various HM. The concept of risk dissipation from origin to destination on the minimum risk route has been developed and dissipation curves are included.

  17. Characterization of a Murine Pressure Ulcer Model to Assess Efficacy of Adipose-derived Stromal Cells

    PubMed Central

    Strong, Amy L.; Bowles, Annie C.; MacCrimmon, Connor P.; Lee, Stephen J.; Frazier, Trivia P.; Katz, Adam J.; Gawronska-Kozak, Barbara; Bunnell, Bruce A.

    2015-01-01

    Background: As the world’s population lives longer, the number of individuals at risk for pressure ulcers will increase considerably in the coming decades. In developed countries, up to 18% of nursing home residents suffer from pressure ulcers and the resulting hospital costs can account for up to 4% of a nation’s health care budget. Although full-thickness surgical skin wounds have been used as a model, preclinical rodent studies have demonstrated that repeated cycles of ischemia and reperfusion created by exposure to magnets most closely mimic the human pressure ulcer condition. Methods: This study uses in vivo and in vitro quantitative parameters to characterize the temporal kinetics and histology of pressure ulcers in young, female C57BL/6 mice exposed to 2 or 3 ischemia-reperfusion cycles. This pressure ulcer model was validated further in studies examining the efficacy of adipose-derived stromal/stem cell administration. Results: Optimal results were obtained with the 2-cycle model based on the wound size, histology, and gene expression profile of representative angiogenic and reparative messenger RNAs. When treated with adipose-derived stromal/stem cells, pressure ulcer wounds displayed a dose-dependent and significant acceleration in wound closure rates and improved tissue histology. Conclusion: These findings document the utility of this simplified preclinical model for the evaluation of novel tissue engineering and medical approaches to treat pressure ulcers in humans. PMID:25878945

  18. Modeling flow in a pressure-sensitive, heterogeneous medium

    SciTech Connect

    Vasco, Donald W.; Minkoff, Susan E.

    2009-06-01

    Using an asymptotic methodology, including an expansion in inverse powers of {radical}{omega}, where {omega} is the frequency, we derive a solution for flow in a medium with pressure dependent properties. The solution is valid for a heterogeneous medium with smoothly varying properties. That is, the scale length of the heterogeneity must be significantly larger then the scale length over which the pressure increases from it initial value to its peak value. The resulting asymptotic expression is similar in form to the solution for pressure in a medium in which the flow properties are not functions of pressure. Both the expression for pseudo-phase, which is related to the 'travel time' of the transient pressure disturbance, and the expression for pressure amplitude contain modifications due to the pressure dependence of the medium. We apply the method to synthetic and observed pressure variations in a deforming medium. In the synthetic test we model one-dimensional propagation in a pressure-dependent medium. Comparisons with both an analytic self-similar solution and the results of a numerical simulation indicate general agreement. Furthermore, we are able to match pressure variations observed during a pulse test at the Coaraze Laboratory site in France.

  19. Low temperature ablation models made by pressure/vacuum application

    NASA Technical Reports Server (NTRS)

    Fischer, M. C.; Heier, W. C.

    1970-01-01

    Method developed employs high pressure combined with strong vacuum force to compact ablation models into desired conical shape. Technique eliminates vapor hazard and results in high material density providing excellent structural integrity.

  20. Development and validation of instantaneous risk model in nuclear power plant's risk monitor

    SciTech Connect

    Wang, J.; Li, Y.; Wang, F.; Wang, J.; Hu, L.

    2012-07-01

    The instantaneous risk model is the fundament of calculation and analysis in a risk monitor. This study focused on the development and validation of an instantaneous risk model. Therefore the principles converting from the baseline risk model to the instantaneous risk model were studied and separated trains' failure modes modeling method was developed. The development and validation process in an operating nuclear power plant's risk monitor were also introduced. Correctness of instantaneous risk model and rationality of converting method were demonstrated by comparison with the result of baseline risk model. (authors)

  1. Genetic and BMI Risks for Predicting Blood Pressure in Three Generations of West African Dogon Women

    PubMed Central

    Taylor, Jacquelyn Y.; Sampson, Deborah; Taylor, Andre D.; Caldwell, Dennis; Sun, Yan V.

    2011-01-01

    The study of genetic polymorphisms and body mass index (BMI) among African women in Africa and in the United States contributes to our understanding of the genetic and environmental risk factors for hypertension. African American women have the highest prevalence of hypertension and obesity compared to other ethnic groups in the United States. Using a crosssectional research design, we examined the effects of genetic and environmental risks of single nucleotide polymorphisms (SNPs) and BMI on blood pressure (BP) among three generations of West African Dogon women (N = 199). We genotyped six SNPs located in the candidate genes known to be related to hypertension. We tested the associations between these SNPs and systolic BP (SBP) and diastolic BP (DBP) with Fisher’s exact tests, chi-square tests for independence, and multivariable linear mixed models. The SNP rs8179526 (SLC4A5) was significantly associated with SBP adjusted for age, age2, and BMI (p = .02). The “C” allele variant of rs8179526 (allele frequency of 0.445) was associated with higher SBP. This SNP did not deviate from the Hardy-Weinberg equilibrium (HWE) with p value of .772. The SNP × BMI interaction effects associated with SBP and DBP were not significant. rs8179526 is located on the SLC4A5 gene on chromosome 2. SLC4A5 encodes a protein that transports sodium and bicarbonate across cell membranes while regulating cellular pH and contains several SNPs linked to elevated BP. Knowledge of the SNP’s effect on hypertension among West African women can help health practitioners educate their patients about genetic risks of developing hypertension. PMID:21859746

  2. Modelling oxygen self-diffusion in UO2 under pressure

    DOE PAGESBeta

    Cooper, Michael William D.; Grimes, R. W.; Fitzpatrick, M. E.; Chroneos, A.

    2015-10-22

    Access to values for oxygen self-diffusion over a range of temperatures and pressures in UO2 is important to nuclear fuel applications. Here, elastic and expansivity data are used in the framework of a thermodynamic model, the cBΩ model, to derive the oxygen self-diffusion coefficient in UO2 over a range of pressures (0–10 GPa) and temperatures (300–1900 K). Furthermore, the significant reduction in oxygen self-diffusion as a function of increasing hydrostatic pressure, and the associated increase in activation energy, is identified.

  3. Evaluation of simplified analytical models for CO2 plume movement and pressure buildup

    NASA Astrophysics Data System (ADS)

    Oruganti, Y.; Mishra, S.

    2011-12-01

    CO2 injection into the sub-surface is emerging as a viable technology for reducing anthropogenic CO2 emissions into the atmosphere. When large amounts of CO2 are sequestered, pressure buildup is an associated risk, along with plume movement beyond the injected domain. In this context, simple modeling tools become valuable assets in preliminary CO2 injection project screening and implementation phases. This study presents an evaluation of two commonly used simplified analytical models for plume movement and pressure buildup, (1) the sharp interface model of Nordbotten et al. (2005), and the corresponding pressure distribution solution of Mathias et al. (2008), and (2) the 3-region model of Burton et al. (2008) based on fractional flow and steady-state pressure gradient considerations. The three-region model of Burton et al. assumes a constant pressure outer boundary. In this study, we incorporate the radius of investigation of the pressure front as the transient pressure boundary, in order to represent an infinite-acting system. The sharp-interface model also assumes the system to be infinite-acting. Temperature and pressure conditions used in these models correspond to the "warm, shallow" and "cold, deep" aquifer conditions as defined by Nordbotten et al. The saturation and pressure profiles as well as injection-well pressure buildup predicted by the analytical models are compared with those from the numerical simulator STOMP in order to provide a verification of the simplified modeling assumptions. Both the STOMP results and the three-region model show two sharp fronts (the drying and two-phase fronts), and a good match is obtained between the front positions at any time. For the sharp interface model, the vertically averaged gas saturation does not exhibit two sharp fronts as seen in the STOMP simulations, but shows a gradual change in saturation with radial distance over the two-phase region. The pressure profiles from STOMP and the analytical model are

  4. Improved Solar-Radiation-Pressure Models for GPS Satellites

    NASA Technical Reports Server (NTRS)

    Bar-Sever, Yoaz; Kuang, Da

    2006-01-01

    A report describes a series of computational models conceived as an improvement over prior models for determining effects of solar-radiation pressure on orbits of Global Positioning System (GPS) satellites. These models are based on fitting coefficients of Fourier functions of Sun-spacecraft- Earth angles to observed spacecraft orbital motions.

  5. Thresholds for Diagnosing Hypertension Based on Automated Office Blood Pressure Measurements and Cardiovascular Risk.

    PubMed

    Myers, Martin G; Kaczorowski, Janusz; Paterson, J Michael; Dolovich, Lisa; Tu, Karen

    2015-09-01

    The risk of cardiovascular events in relation to blood pressure is largely based on readings taken with a mercury sphygmomanometer in populations which differ from those of today in terms of hypertension severity and drug therapy. Given replacement of the mercury sphygmomanometer with electronic devices, we sought to determine the blood pressure threshold for a significant increase in cardiovascular risk using a fully automated device, which takes multiple readings with the subject resting quietly alone. Participants were 3627 community-dwelling residents aged >65 years untreated for hypertension. Automated office blood pressure readings were obtained in a community pharmacy with subjects seated and undisturbed. This method for recording blood pressure produces similar readings in different settings, including a pharmacy and family doctor's office providing the above procedures are followed. Subjects were followed for a mean (SD) of 4.9 (1.0) years for fatal and nonfatal cardiovascular events. Adjusted hazard ratios (95% confidence intervals) were computed for 10 mm Hg increments in blood pressure (mm Hg) using Cox proportional hazards regression and the blood pressure category with the lowest event rate as the reference category. A total of 271 subjects experienced a cardiovascular event. There was a significant (P=0.02) increase in the hazard ratio of 1.66 (1.09, 2.54) at a systolic blood pressure of 135 to 144 and 1.72 (1.21, 2.45; P=0.003) at a diastolic blood pressure of 80 to 89. A significant (P=0.03) increase in hazard ratio of 1.73 (1.04, 2.86) occurred with a pulse pressure of 80 to 89. These findings are consistent with a threshold of 135/85 for diagnosing hypertension in older subjects using automated office blood pressure. PMID:26269653

  6. Long range Ising model for credit risk modeling

    NASA Astrophysics Data System (ADS)

    Molins, Jordi; Vives, Eduard

    2005-07-01

    Within the framework of maximum entropy principle we show that the finite-size long-range Ising model is the adequate model for the description of homogeneous credit portfolios and the computation of credit risk when default correlations between the borrowers are included. The exact analysis of the model suggest that when the correlation increases a first-order-like transition may occur inducing a sudden risk increase.

  7. An asperity-deformation model for effective pressure

    NASA Astrophysics Data System (ADS)

    Gangi, Anthony F.; Carlson, Richard L.

    1996-05-01

    Variations of the mechanical and transport properties of cracked and/or porous rocks under isotropic stress depend on both the confining pressure ( Pc) and the pore-fluid pressure ( Pp). To a first approximation, these rock properties are functions of the differential pressure, Pd = Pc - Pp; at least for low differential pressures. However, at higher differential pressures, the properties depend in a more complicated way upon the two pressures. The concept of effective pressure, Pe, is used to denote this variation and it is defined as Pe( Pc, Pp) = Pc - n( Pc, Pp) Pp. If n = 1 (and therefore, is independent of Pc and Pp), the effective pressure is just the differential pressure. We have used an asperity-deformation model and a force-balance equation to derive expressions for the effective pressure. We equate the total external force (in one direction), Fc, to the total force on the asperities, Fa, and the force of the fluid, Fp, acting in that same direction. The fluid force, Fp, acts only on the parts of the crack (or pore-volume) faces which are not in contact. Then, the asperity pressure, Pa, is the average force per unit area acting on the crack (or grain) contacts P a = {F a}/{A} = {F c}/{A} - {F p}/{A} = P c - (1 - {A c}/{A})P p, where A is the total area over which Fc acts and Ac is the area of contact of the crack asperities or the grains. Thus, the asperity pressure, Pa, is greater than the differential pressure, Pd, because Pp acts on a smaller area, A- Ac, than the total area, A. For elastic asperities, the area of contact Ac and the strain (e.g., crack and pore openings) remain the same, to a high degree of approximation, at constant asperity pressure. Therefore, transport properties such as permeability, resistivity, thermal conductivity, etc. are constant, to the same degree of approximation, at constant asperity pressure. For these properties, the asperity pressure is, very accurately, the effective pressure, Pc. Using this model, we find that the

  8. Conceptual models for cumulative risk assessment.

    PubMed

    Linder, Stephen H; Sexton, Ken

    2011-12-01

    In the absence of scientific consensus on an appropriate theoretical framework, cumulative risk assessment and related research have relied on speculative conceptual models. We argue for the importance of theoretical backing for such models and discuss 3 relevant theoretical frameworks, each supporting a distinctive "family" of models. Social determinant models postulate that unequal health outcomes are caused by structural inequalities; health disparity models envision social and contextual factors acting through individual behaviors and biological mechanisms; and multiple stressor models incorporate environmental agents, emphasizing the intermediary role of these and other stressors. The conclusion is that more careful reliance on established frameworks will lead directly to improvements in characterizing cumulative risk burdens and accounting for disproportionate adverse health effects. PMID:22021317

  9. Constructing high-pressure thermodynamic models: problems and possible solutions

    NASA Astrophysics Data System (ADS)

    Brosh, E.

    2013-12-01

    Conventional thermodynamic databases (e.g. Fabrichnaya et al. 2004, Holland and Powell 1998, 2011) consist of expressions for the Gibbs energy at ambient pressure, extended to higher pressures through the integration of some EOS (Equation Of State). While this is simple and straight-forward, such thermodynamic models are prone to produce manifestly unphysical predictions of negative thermal expansion and even negative heat capacity at high pressure. It has been shown (Brosh et al. 2007) that these errors arise not only from problems the EOS itself but also from incompatibilities between the EOS and the models used for extrapolations of the heat capacity at ambient pressure. One solution is a radical restructuring of thermodynamic databases. Instead of modelling the Gibbs energy, new databases can be based on modelling the Helmholtz energy using Debye-Mie-Grüneisen EOS. This approach is very successful for modelling solid substances (Jacobs 2009, 2010, Dorogokupets et al. 2007, 2012) but the Debye-Mie-Grüneisen equations of state are not easily applicable to liquids. Other difficulties stem from the treatment of the predicted mechanical instability above the normal melting point. However, the most severe difficulty with the utilization of the Debye-Mie-Grüneisen approach is that it is incompatible with the current ambient-pressure thermodynamic databases and one will not be able to use them as a basis for high pressure modelling. Another approach (Brosh et al. 2007) is based on an interpolation of the thermophysical properties between the ambient pressure models given in conventional databases and the Debye-Mie-Grüneisen model at extreme pressures. This avoids most of the spurious anomalies of conventional models. The limitations of the interpolation scheme are the inclusion of several model parameters whose physical essence is not well-defined and an underestimation of the heat capacity at high pressures. In this presentation, the predictions of the

  10. Modelling and Analysis of High Pressure Peaking Switch

    NASA Astrophysics Data System (ADS)

    S, Bindu; Parekh, Mrunal; Mangalvedekar, H. A.; Sharma, Archana; Chakravarthy, D. P.

    2012-07-01

    This paper presents modelling and analysis of peaking switch used in Marx generator, such that the rise time of the pulse produced by the Marx generator is reduced substantially. Towards this FEMM (Finite Element Methods Magnetics) software is used for the field modelling of the switch and MATLAB for circuit modelling to observe the rise time. The switch has to produce pulse with sub-nanosecond rise time, hence the electrode distance has to be minimum. This switch can withstand high voltage only under high pressure. A mathematical model is simulated in MATLAB to see the performance under high pressure.

  11. Cryogenic Pressure Control Modeling for Ellipsoidal Space Tanks

    NASA Technical Reports Server (NTRS)

    Lopez, Alfredo; Grayson, Gary D.; Chandler, Frank O.; Hastings, Leon J.; Heyadat, Ali

    2007-01-01

    A computational fluid dynamics (CFD) model is developed to simulate pressure control of an ellipsoidal-shaped liquid hydrogen tank under external heating in normal gravity. Pressure control is provided by an axial jet thermodynamic vent system (TVS) centered within the vessel that injects cooler liquid into the tank, mixing the contents and reducing tank pressure. The two-phase cryogenic tank model considers liquid hydrogen in its own vapor with liquid density varying with temperature only and a fully compressible ullage. The axisymmetric model is developed using a custom version of the commercially available FLOW-31) software. Quantitative model validation is ,provided by engineering checkout tests performed at Marshall Space Flight Center in 1999 in support of the Solar Thermal Upper Stage_ Technology Demonstrator (STUSTD) program. The engineering checkout tests provide cryogenic tank self-pressurization test data at various heat leaks and tank fill levels. The predicted self-pressurization rates, ullage and liquid temperatures at discrete locations within the STUSTD tank are in good agreement with test data. The work presented here advances current CFD modeling capabilities for cryogenic pressure control and helps develop a low cost CFD-based design process for space hardware.

  12. Assessing Predictive Validity of Pressure Ulcer Risk Scales- A Systematic Review and Meta-Analysis

    PubMed Central

    PARK, Seong-Hi; LEE, Hea Shoon

    2016-01-01

    Background: The purpose of this study was to present a scientific reason for pressure ulcer risk scales: Cubbin& Jackson modified Braden, Norton, and Waterlow, as a nursing diagnosis tool by utilizing predictive validity of pressure sores. Methods: Articles published between 1966 and 2013 from periodicals indexed in the Ovid Medline, Embase, CINAHL, KoreaMed, NDSL, and other databases were selected using the key word “pressure ulcer”. QUADAS-II was applied for assessment for internal validity of the diagnostic studies. Selected studies were analyzed using meta-analysis with MetaDisc 1.4. Results: Seventeen diagnostic studies with high methodological quality, involving 5,185 patients, were included. In the results of the meta-analysis, sROC AUC of Braden, Norton, and Waterflow scale was over 0.7, showing moderate predictive validity, but they have limited interpretation due to significant differences between studies. In addition, Waterlow scale is insufficient as a screening tool owing to low sensitivity compared with other scales. Conclusion: The contemporary pressure ulcer risk scale is not suitable for uninform practice on patients under standardized criteria. Therefore, in order to provide more effective nursing care for bedsores, a new or modified pressure ulcer risk scale should be developed upon strength and weaknesses of existing tools. PMID:27114977

  13. Awareness and Knowledge of Cardiovascular Risk through Blood Pressure and Cholesterol Testing in College Freshmen

    ERIC Educational Resources Information Center

    Melnyk, J. A.; Panza, G.; Zaleski, A.; Taylor, B.

    2015-01-01

    Background: Cardiovascular disease (CVD) is the leading cause of death in the United States, yet knowledge of CVD risk factors is surprisingly low in college students. Purpose: The purpose of this study was to determine the effectiveness of an individualized blood pressure, cholesterol, and CVD education intervention on college freshmen. Methods:…

  14. Microscopic pressure-cooker model for studying molecules in confinement

    NASA Astrophysics Data System (ADS)

    Santamaria, Ruben; Adamowicz, Ludwik; Rosas-Acevedo, Hortensia

    2015-04-01

    A model for a system of a finite number of molecules in confinement is presented and expressions for determining the temperature, pressure, and volume of the system are derived. The present model is a generalisation of the Zwanzig-Langevin model because it includes pressure effects in the system. It also has general validity, preserves the ergodic hypothesis, and provides a formal framework for previous studies of hydrogen clusters in confinement. The application of the model is illustrated by an investigation of a set of prebiotic compounds exposed to varying pressure and temperature. The simulations performed within the model involve the use of a combination of molecular dynamics and density functional theory methods implemented on a computer system with a mixed CPU-GPU architecture.

  15. Pressure transient modeling of a fractured geothermal reservior

    SciTech Connect

    Robinson, B.A.

    1990-01-01

    A fracture network model has been developed to simulate transient fluid flow behavior in a fractured rock mass. Included is a pressure-dependent aperture submodel to simulate behavior often seen in fractured systems. The model is used to simulate data from the Fenton Hill Hot Dry Rock (HDR) geothermal reservoir. Both low-pressure/low-flow-rate and high-pressure/high-flow-rate transient data are adequately simulated. The model parameters obtained suggest ways in which the model can be refined to achieve even more realistic fits to the data. The model is then used to demonstrate more efficient operating modes than the two-well circulating mode usually proposed for HDR reservoirs. 11 refs., 9 figs., 1 tab.

  16. Optimal Blood Pressure Goals in Patients With Hypertension at High Risk for Cardiovascular Events.

    PubMed

    Aronow, Wilbert S

    2016-01-01

    Existing epidemiologic and clinical trial data suggest that the blood pressure in patients with hypertension at high risk for cardiovascular events because of coronary artery disease, diabetes mellitus, chronic kidney disease, stroke, or heart failure should be reduced to <140/90 mm Hg in patients younger than 80 years and the systolic blood pressure be reduced to 140-145 mm Hg if tolerated in patients aged 80 years and older. Studies from patients with coronary artery disease, diabetes mellitus, chronic kidney disease, stroke, and heart failure will be discussed that support a blood pressure goal of <140/90 mm Hg in patients younger than 80 years at high risk for cardiovascular events. PMID:23591024

  17. Suicide risk assessment and suicide risk formulation: essential components of the therapeutic risk management model.

    PubMed

    Silverman, Morton M

    2014-09-01

    Suicide and other suicidal behaviors are often associated with psychiatric disorders and dysfunctions. Therefore, psychiatrists have significant opportunities to identify at-risk individuals and offer treatment to reduce that risk. Although a suicide risk assessment is a core competency requirement, many clinical psychiatrists lack the requisite training and skills to appropriately assess for suicide risk. Moreover, the standard of care requires psychiatrists to foresee the possibility that a patient might engage in suicidal behavior, hence to conduct a suicide risk formulation sufficient to guide triage and treatment planning. Based on data collected via a suicide risk assessment, a suicide risk formulation is a process whereby the psychiatrist forms a judgment about a patient's foreseeable risk of suicidal behavior in order to inform triage decisions, safety and treatment planning, and interventions to reduce risk. This paper addresses the components of this process in the context of the model for therapeutic risk management of the suicidal patient developed at the Veterans Integrated Service Network (VISN) 19 Mental Illness Research, Education and Clinical Center by Wortzel et al. PMID:25226200

  18. CFD Modeling of Helium Pressurant Effects on Cryogenic Tank Pressure Rise Rates in Normal Gravity

    NASA Technical Reports Server (NTRS)

    Grayson, Gary; Lopez, Alfredo; Chandler, Frank; Hastings, Leon; Hedayat, Ali; Brethour, James

    2007-01-01

    A recently developed computational fluid dynamics modeling capability for cryogenic tanks is used to simulate both self-pressurization from external heating and also depressurization from thermodynamic vent operation. Axisymmetric models using a modified version of the commercially available FLOW-3D software are used to simulate actual physical tests. The models assume an incompressible liquid phase with density that is a function of temperature only. A fully compressible formulation is used for the ullage gas mixture that contains both condensable vapor and a noncondensable gas component. The tests, conducted at the NASA Marshall Space Flight Center, include both liquid hydrogen and nitrogen in tanks with ullage gas mixtures of each liquid's vapor and helium. Pressure and temperature predictions from the model are compared to sensor measurements from the tests and a good agreement is achieved. This further establishes the accuracy of the developed FLOW-3D based modeling approach for cryogenic systems.

  19. The Nursing Diagnosis of risk for pressure ulcer: content validation 1

    PubMed Central

    dos Santos, Cássia Teixeira; Almeida, Miriam de Abreu; Lucena, Amália de Fátima

    2016-01-01

    Abstract Objective: to validate the content of the new nursing diagnosis, termed risk for pressure ulcer. Method: the content validation with a sample made up of 24 nurses who were specialists in skin care from six different hospitals in the South and Southeast of Brazil. Data collection took place electronically, through an instrument constructed using the SurveyMonkey program, containing a title, definition, and 19 risk factors for the nursing diagnosis. The data were analyzed using Fehring's method and descriptive statistics. The project was approved by a Research Ethics Committee. Results: title, definition and seven risk factors were validated as "very important": physical immobilization, pressure, surface friction, shearing forces, skin moisture, alteration in sensation and malnutrition. Among the other risk factors, 11 were validated as "important": dehydration, obesity, anemia, decrease in serum albumin level, prematurity, aging, smoking, edema, impaired circulation, and decrease in oxygenation and in tissue perfusion. The risk factor of hyperthermia was discarded. Conclusion: the content validation of these components of the nursing diagnosis corroborated the importance of the same, being able to facilitate the nurse's clinical reasoning and guiding clinical practice in the preventive care for pressure ulcers. PMID:27305182

  20. Is Pulse Pressure an Independent Risk Factor for Incident Stroke, REasons for Geographic And Racial Differences in Stroke

    PubMed Central

    Halberg, Daniel L.; Sands, Charles D.; Mosher, Aleena; Muntner, Paul M.; Howard, George

    2015-01-01

    BACKGROUND Pulse pressure (PP) is a potential risk factor of stroke. The relationship of incident stroke with systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and PP was examined. METHODS Data were from the REasons for Geographic And Racial Differences in Stroke national cohort study of 30,239 black and white participants aged ≥45 years, enrolled between 2003 and 2007. PP (SBP−DBP) and MAP (MAP = DBP + 1/3*PP) were calculated. Telephone follow-up occurred every six months for self or proxy-reported suspected stroke events, confirmed using expert adjudication. Cox-proportional hazards models examined the association of incident stroke for the different BP measurements with multivariable adjustment for sociodemographic and clinical risk factors including gender and race. RESULTS Men and women without prevalent stroke at baseline were analyzed (n = 25,462). During follow-up (mean 6.3±2.3 years, maximum 10 years), 916 strokes occurred. Unadjusted PP (hazard ratio [HR] = 1.30; 95% confidence interval [CI] 1.24–1.35), SBP (HR = 1.22; 95% CI 1.18–1.32), MAP (HR = 1.24; 95% CI 1.16–1.32), and DBP (HR = 1.09; 95% CI 1.01–1.17) were associated with stroke risk; however, after adjustment for SBP and other risk factors, the association with PP was attenuated (HR = 0.98; 95% CI 0.90–1.07), whereas SBP persisted as a predictor (HR = 1.14; 95% CI 1.06–1.23). These associations were consistent across age (younger vs. older >70 years) and race (black vs. white). CONCLUSIONS PP is positively associated with incident stroke, but not independently from SBP; and, there were no significant gender, racial, or regional differences in that association. PMID:25588699

  1. Modeling and Managing Risk in Billing Infrastructures

    NASA Astrophysics Data System (ADS)

    Baiardi, Fabrizio; Telmon, Claudio; Sgandurra, Daniele

    This paper discusses risk modeling and risk management in information and communications technology (ICT) systems for which the attack impact distribution is heavy tailed (e.g., power law distribution) and the average risk is unbounded. Systems with these properties include billing infrastructures used to charge customers for services they access. Attacks against billing infrastructures can be classified as peripheral attacks and backbone attacks. The goal of a peripheral attack is to tamper with user bills; a backbone attack seeks to seize control of the billing infrastructure. The probability distribution of the overall impact of an attack on a billing infrastructure also has a heavy-tailed curve. This implies that the probability of a massive impact cannot be ignored and that the average impact may be unbounded - thus, even the most expensive countermeasures would be cost effective. Consequently, the only strategy for managing risk is to increase the resilience of the infrastructure by employing redundant components.

  2. Model of a stationary microwave argon discharge at atmospheric pressure

    SciTech Connect

    Zhelyazkov, I.; Pencheva, M.; Benova, E.

    2008-03-19

    The many applications of microwave gas discharges at atmospheric pressure in various fields of science, technology and medicine require an adequate model of these discharges. Such a model is based on the electromagnetic wave's propagation properties and on the elementary processes in the discharge bulk. In contrast to the microwave discharges at low-gas pressures, where many elementary processes might be ignored because of their negligible contribution to the electron and heavy particle's balance equations, for such discharges at atmospheric pressure the consideration of a large number of collisional processes is mandatory. For the build of a successful discharge-column model one needs three important quantities, notably the power {theta} necessary for sustaining an electron - ion pair, electron - neutral collision frequency for momentum transfer v{sub en}, and gas temperature T{sub g}. The first two key parameters are obtained by a collisional-radiative model of the argon at atmospheric pressure, while the microwave frequency {omega}/2{pi} = 2.45 GHz, plasma column radius R, gas pressure p and gas temperature T{sub g} are fixed external parameters determined by the experimental conditions. Here, we present a model of a capillary argon microwave plasma column with a length L {approx_equal} 14 cm, sustained by wave power of 110 W - the model yields the longitudinal distributions of the plasma density, expended wave power, wave electric field magnitude, and complex wave number.

  3. Model of a stationary microwave argon discharge at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Zhelyazkov, I.; Pencheva, M.; Benova, E.

    2008-03-01

    The many applications of microwave gas discharges at atmospheric pressure in various fields of science, technology and medicine require an adequate model of these discharges. Such a model is based on the electromagnetic wave's propagation properties and on the elementary processes in the discharge bulk. In contrast to the microwave discharges at low-gas pressures, where many elementary processes might be ignored because of their negligible contribution to the electron and heavy particle's balance equations, for such discharges at atmospheric pressure the consideration of a large number of collisional processes is mandatory. For the build of a successful discharge-column model one needs three important quantities, notably the power θ necessary for sustaining an electron—ion pair, electron—neutral collision frequency for momentum transfer ven, and gas temperature Tg. The first two key parameters are obtained by a collisional-radiative model of the argon at atmospheric pressure, while the microwave frequency ω/2π = 2.45 GHz, plasma column radius R, gas pressure p and gas temperature Tg are fixed external parameters determined by the experimental conditions. Here, we present a model of a capillary argon microwave plasma column with a length L ≈ 14 cm, sustained by wave power of 110 W—the model yields the longitudinal distributions of the plasma density, expended wave power, wave electric field magnitude, and complex wave number.

  4. An electronic scanner of pressure for wind tunnel models

    NASA Technical Reports Server (NTRS)

    Kauffman, Ronald C.; Coe, Charles F.

    1986-01-01

    An electronic scanner of pressure (ESOP) has been developed by NASA Ames Research Center for installation in wind tunnel models. An ESOP system consists of up to 20 pressure modules (PMs), each with 48 pressure transducers and a heater, an analog-to-digital (A/D) converter module, a microprocessor, a data controller, a monitor unit, a control and processing unit, and a heater controller. The PMs and the A/D converter module are sized to be installed in the models tested in the Ames Aerodynamics Division wind tunnels. A unique feature of the pressure module is the lack of moving parts such as a pneumatic switch used in other systems for in situ calibrations. This paper describes the ESOP system and the results of the initial testing of the system. The initial results indicate the system meets the original design goal of 0.15 percent accuracy.

  5. Unsteady pressure loads in a generic high speed engine model

    NASA Technical Reports Server (NTRS)

    Parrott, Tony L.; Jones, Michael G.; Thurlow, Ernie M.

    1992-01-01

    Unsteady pressure loads were measured along the top interior wall of a generic high-speed engine (GHSE) model undergoing performance tests in the combustion-Heated Scramjet Test Facility at the Langley Research Center. Flow to the model inlet was simulated at 72000 ft and a flight Mach number of 4. The inlet Mach number was 3.5 with a total temperature and pressure of 1640 R and 92 psia. The unsteady pressure loads were measured with 5 piezoresistive gages, recessed into the wall 4 to 12 gage diameters to reduce incident heat flux to the diaphragms, and distributed from the inlet to the combustor. Contributors to the unsteady pressure loads included boundary layer turbulence, combustion noise, and transients generated by unstart loads. Typical turbulent boundary layer rms pressures in the inlet ranged from 133 dB in the inlet to 181 dB in the combustor over the frequency range from 0 to 5 kHz. Downstream of the inlet exist, combustion noise was shown to dominate boundary layer turbulence noise at increased heat release rates. Noise levels in the isolator section increased by 15 dB when the fuel-air ratio was increased from 0.37 to 0.57 of the stoichiometric ratio. Transient pressure disturbances associated with engine unstarts were measured in the inlet and have an upstream propagation speed of about 7 ft/sec and pressure jumps of at least 3 psia.

  6. Assessing the Impact of Agricultural Pressures on N and P Loads and Potential Eutrophication Risk at Regional Scales

    NASA Astrophysics Data System (ADS)

    Dupas, R.; Gascuel-odoux, C.; Delmas, M.; Moatar, F.

    2014-12-01

    Excessive nutrient loading of freshwater bodies results in increased eutrophication risk worldwide. The processes controlling N/P transfer in agricultural landscapes are well documented through scientific studies conducted in intensively monitored catchments. However, managers need tools to assess water quality and evaluate the contribution of agriculture to eutrophication at regional scales, including unmonitored or poorly monitored areas. To this end, we present an assessment framework which includes: i) a mass-balance model to estimate diffuse N/P transfer and retention and ii) indicators based on N:P:Si molar ratios to assess potential eutrophication risk from external loads. The model, called Nutting (Dupas et al., 2013), integrates variables for both detailed description of agricultural pressures (N surplus, soil P content) and characterisation of physical attributes of catchments (including spatial attributes). It was calibrated on 160 catchments, and applied to 2210 unmonitored headwater bodies in France (Dupas et al., under review). N and P retention represented 53% and 95% of soil N and P surplus, respectively, and was mainly controlled by runoff and an index characterising infiltration/runoff properties. According to our estimates, diffuse agricultural sources represented a mean of 97% of N loads and N exceeded Si in 93% of the catchments, whilst they represented 46% of P loads and P exceeded Si in 26-65% of the catchments. Estimated eutrophication risk was highly sensitive to assumptions about P bioavailability, hence the range of headwaters potentially at risk spanned 26-63% of the catchments, depending on assumptions. To reduce this uncertainty, we recommend introducing P bioavailability tests in water monitoring programs, especially in sensitive areas. Dupas R et al. Assessing N emissions in surface water at the national level: comparison of country-wide vs. regionalized models. Sci Total Environ 2013; 443: 152-62. Dupas R et al. Assessing the impact

  7. Modelling Unsteady Wall Pressures Beneath Turbulent Boundary Layers

    NASA Technical Reports Server (NTRS)

    Ahn, B-K.; Graham, W. R.; Rizzi, S. A.

    2004-01-01

    As a structural entity of turbulence, hairpin vortices are believed to play a major role in developing and sustaining the turbulence process in the near wall region of turbulent boundary layers and may be regarded as the simplest conceptual model that can account for the essential features of the wall pressure fluctuations. In this work we focus on fully developed typical hairpin vortices and estimate the associated surface pressure distributions and their corresponding spectra. On the basis of the attached eddy model, we develop a representation of the overall surface pressure spectra in terms of the eddy size distribution. Instantaneous wavenumber spectra and spatial correlations are readily derivable from this representation. The model is validated by comparison of predicted wavenumber spectra and cross-correlations with existing emperical models and experimental data.

  8. Prediction of mean arterial blood pressure with linear stochastic models.

    PubMed

    Genc, Sahika

    2011-01-01

    A model-based approach that integrates known portion of the cardiovascular system and unknown portion through a parameter estimation to predict evolution of the mean arterial pressure is considered. The unknown portion corresponds to the neural portion that acts like a controller that takes corrective actions to regulate the arterial blood pressure at a constant level. The input to the neural part is the arterial pressure and output is the sympathetic nerve activity. In this model, heart rate is considered a proxy for sympathetic nerve activity. The neural portion is modeled as a linear discrete-time system with random coefficients. The performance of the model is tested on a case study of acute hypotensive episodes (AHEs) on PhysioNet data. TPRs and FPRs improve as more data becomes available during estimation period. PMID:22254409

  9. Accurate pressure gradient calculations in hydrostatic atmospheric models

    NASA Technical Reports Server (NTRS)

    Carroll, John J.; Mendez-Nunez, Luis R.; Tanrikulu, Saffet

    1987-01-01

    A method for the accurate calculation of the horizontal pressure gradient acceleration in hydrostatic atmospheric models is presented which is especially useful in situations where the isothermal surfaces are not parallel to the vertical coordinate surfaces. The present method is shown to be exact if the potential temperature lapse rate is constant between the vertical pressure integration limits. The technique is applied to both the integration of the hydrostatic equation and the computation of the slope correction term in the horizontal pressure gradient. A fixed vertical grid and a dynamic grid defined by the significant levels in the vertical temperature distribution are employed.

  10. Risk management model of winter navigation operations.

    PubMed

    Valdez Banda, Osiris A; Goerlandt, Floris; Kuzmin, Vladimir; Kujala, Pentti; Montewka, Jakub

    2016-07-15

    The wintertime maritime traffic operations in the Gulf of Finland are managed through the Finnish-Swedish Winter Navigation System. This establishes the requirements and limitations for the vessels navigating when ice covers this area. During winter navigation in the Gulf of Finland, the largest risk stems from accidental ship collisions which may also trigger oil spills. In this article, a model for managing the risk of winter navigation operations is presented. The model analyses the probability of oil spills derived from collisions involving oil tanker vessels and other vessel types. The model structure is based on the steps provided in the Formal Safety Assessment (FSA) by the International Maritime Organization (IMO) and adapted into a Bayesian Network model. The results indicate that ship independent navigation and convoys are the operations with higher probability of oil spills. Minor spills are most probable, while major oil spills found very unlikely but possible. PMID:27207023

  11. Exaggerated blood pressure response during the exercise treadmill test as a risk factor for hypertension

    PubMed Central

    Lima, S.G.; Albuquerque, M.F.P.M.; Oliveira, J.R.M.; Ayres, C.F.J.; Cunha, J.E.G.; Oliveira, D.F.; Lemos, R.R.; Souza, M.B.R.; Silva, O. Barbosa e

    2013-01-01

    Exaggerated blood pressure response (EBPR) during the exercise treadmill test (ETT) has been considered to be a risk factor for hypertension. The relationship of polymorphisms of the renin-angiotensin system gene with hypertension has not been established. Our objective was to evaluate whether EBPR during exercise is a clinical marker for hypertension. The study concerned a historical cohort of normotensive individuals. The exposed individuals were those who presented EBPR. At the end of the observation period (41.7 months = 3.5 years), the development of hypertension was analyzed within the two groups. Genetic polymorphisms and blood pressure behavior were assessed as independent variables, together with the classical risk factors for hypertension. The I/D gene polymorphism of the angiotensin-converting enzyme and M235T of angiotensinogen were ruled out as risk factors for hypertension. EBPR during ETT is not an independent influence on the chances of developing hypertension. No differences were observed between the hypertensive and normotensive individuals regarding gender (P = 0.655), skin color (P = 0.636), family history of hypertension (P = 0.225), diabetes mellitus (P = 0.285), or hypertriglyceridemia (P = 0.734). The risk of developing hypertension increased with increasing body mass index (BMI) and advancing age. The risk factors, which independently influenced the development of hypertension, were age and BMI. EBPR did not constitute an independent risk factor for hypertension and is probably a preclinical phase in the spectrum of normotension and hypertension. PMID:23598646

  12. Pressure compensated fiber laser hydrophone: modeling and experimentation.

    PubMed

    Chandrika, Unnikrishnan Kuttan; Pallayil, Venugopalan; Lim, Kian Meng; Chew, Chye Heng

    2013-10-01

    A pressure compensated metal diaphragm based fiber laser hydrophone configuration that can provide good sensitivity, large bandwidth, and sea state zero noise floor is proposed in this paper. A simplified theoretical model of the proposed sensor configuration is developed in which the acoustic elements of the sensor configuration are modeled using a four-pole acoustic transfer matrix and the structural elements are modeled as second order single degree of freedom elements. This model is then used to optimize the design parameters of the sensor system to achieve the performance objectives. An axisymmetric finite element analysis of the sensor configuration is also carried out to validate the results from the simplified theoretical model. Prototype sensors were fabricated and hydrostatic testing in a pressure vessel validated the static pressure compensation performance of the sensor. Frequency dependent sensitivity of the sensor system was measured through acoustic testing in a water tank. The prototype sensor gave a flat frequency response up to 5 kHz and experimental results compared well with theoretical predictions. The sensor has an acceleration rejection figure on the order of 0 dB ref 1 m/s(2) Pa and the pressure compensation approach worked reasonably well up to a hydrostatic pressures equivalent to a depth of 50 m. PMID:24116409

  13. On the pressure calculation for polarizable models in computer simulation.

    PubMed

    Kiss, Péter T; Baranyai, András

    2012-03-14

    We present a short overview of pressure calculation in molecular dynamics or Monte Carlo simulations. The emphasis is given to polarizable models in order to resolve the controversy caused by the paper of M. J. Louwerse and E. J. Baerends [Chem. Phys. Lett. 421, 138 (2006)] about pressure calculation in systems with periodic boundaries. We systematically derive expressions for the pressure and show that despite the lack of explicit pairwise additivity, the pressure formula for polarizable models is identical with that of nonpolarizable ones. However, a strict condition for using this formula is that the induced dipole should be in perfect mechanical equilibrium prior to pressure calculation. The perfect convergence of induced dipoles ensures conservation of energy as well. We demonstrate using more cumbersome but exact methods that the derived expressions for the polarizable model of water provide correct numerical results. We also show that the inaccuracy caused by imperfect convergence of the induced dipoles correlates with the inaccuracy of the calculated pressure. PMID:22423830

  14. Clinical Model for Suicide Risk Assessment.

    ERIC Educational Resources Information Center

    Kral, Michael J.; Sakinofsky, Isaac

    1994-01-01

    Presents suicide risk assessment in a two-tiered model comprising background/contextual factors and subjectivity. The subjectivity portion is formulated around Shneidman's concepts of perturbation and lethality. Discusses decision of hospital admission versus ambulatory care. Suggests that theoretically informed approach should serve both…

  15. Exercise Blood Pressure and the Risk for Future Hypertension Among Normotensive Middle‐Aged Adults

    PubMed Central

    Berger, Assaf; Grossman, Ehud; Katz, Moshe; Kivity, Shaye; Klempfner, Robert; Segev, Shlomo; Goldenberg, Ilan; Sidi, Yehezkel; Maor, Elad

    2015-01-01

    Background The aim of the present study was to examine whether exercise blood pressure can be used to predict the development of hypertension in normotensive middle‐aged adults. Methods and Results We investigated 7082 normotensive subjects who were annually screened in a tertiary medical center and completed maximal treadmill exercise tests at each visit. After the initial 3 years, subjects were divided into approximate quartiles according to their average exercise systolic and diastolic blood pressure responses (≤158; 158 to 170; 170 to 183; ≥183 mm Hg for systolic blood pressure and ≤73; 73 to 77; 77 to 82; ≥82 mm Hg for diastolic blood pressure). Mean age of the study population was 48±9 years and 73% were men. Average baseline resting blood pressure was 120/77±12/7 mm Hg. During a follow‐up of 5±3 years, 1036 (14.6%) subjects developed hypertension. The cumulative probability of new‐onset hypertension at 5 years was significantly increased with increasing quartiles of exercise systolic blood pressure (5%, 9%, 17%, and 35%, respectively; P<0.001), with a similar association shown for diastolic blood pressure. After adjustment for baseline resting blood pressure and clinical parameters, each 5‐mm Hg increments in exercise either systolic or diastolic blood pressures were independently associated with respective 11% (P<0.001) and 30% (P<0.001) increased risk for the development of hypertension. Conclusions In normotensive middle‐aged individuals, blood pressure response to exercise is associated with future development of hypertension. PMID:25904593

  16. Significant interarm blood pressure difference predicts cardiovascular risk in hypertensive patients: CoCoNet study.

    PubMed

    Kim, Su-A; Kim, Jang Young; Park, Jeong Bae

    2016-06-01

    There has been a rising interest in interarm blood pressure difference (IAD), due to its relationship with peripheral arterial disease and its possible relationship with cardiovascular disease. This study aimed to characterize hypertensive patients with a significant IAD in relation to cardiovascular risk. A total of 3699 patients (mean age, 61 ± 11 years) were prospectively enrolled in the study. Blood pressure (BP) was measured simultaneously in both arms 3 times using an automated cuff-oscillometric device. IAD was defined as the absolute difference in averaged BPs between the left and right arm, and an IAD ≥ 10 mm Hg was considered to be significant. The Framingham risk score was used to calculate the 10-year cardiovascular risk. The mean systolic IAD (sIAD) was 4.3 ± 4.1 mm Hg, and 285 (7.7%) patients showed significant sIAD. Patients with significant sIAD showed larger body mass index (P < 0.001), greater systolic BP (P = 0.050), more coronary artery disease (relative risk = 1.356, P = 0.034), and more cerebrovascular disease (relative risk = 1.521, P = 0.072). The mean 10-year cardiovascular risk was 9.3 ± 7.7%. By multiple regression, sIAD was significantly but weakly correlated with the 10-year cardiovascular risk (β = 0.135, P = 0.008). Patients with significant sIAD showed a higher prevalence of coronary artery disease, as well as an increase in 10-year cardiovascular risk. Therefore, accurate measurements of sIAD may serve as a simple and cost-effective tool for predicting cardiovascular risk in clinical settings. PMID:27310982

  17. Effects of established blood pressure loci on blood pressure values and hypertension risk in an Algerian population sample.

    PubMed

    Lardjam-Hetraf, S A; Mediene-Benchekor, S; Ouhaibi-Djellouli, H; Meroufel, D N; Boulenouar, H; Hermant, X; Hamani-Medjaoui, I; Saidi-Mehtar, N; Amouyel, P; Houti, L; Goumidi, L; Meirhaeghe, A

    2015-05-01

    Genome-wide association studies and subsequent replication studies have pinpointed 29 genetic variants associated with blood pressure (BP). None of these studies included North African populations. We therefore looked at whether or not these genetic variants modulated BP and hypertension (HTN) risk in an Algerian population sample. Twenty-nine single-nucleotide polymorphisms (SNPs) were genotyped in a representative sample of 787 subjects from the InSulino-résistance à ORan (ISOR) study (378 men and 409 women aged between 30 and 64 years and recruited from within the city of Oran, Algeria). Genetic variants were considered both individually and when combined as genetic predisposition scores (GPSs) for systolic BP (SBP), diastolic BP (DBP) and HTN risk. The SNPs in CYP1A1-ULK3, HFE and SH2B3 were significantly associated with BP and/or HTN. The SBP-GPS, DBP-GPS and HTN-GPS were associated with higher levels of DBP (+0.24 mm Hg P=0.05, +0.23 mm Hg P = 0.05 and +0.26 mm Hg P = 0.03, respectively). Moreover, the three GPSs tended to be associated with a 6% higher risk of HTN. Our study is the first to show that some of the BP loci validated in subjects of European descent were associated (either individually or when combined as GPSs) with BP traits and/or the HTN risk in an Algerian population, but to a lesser extent than in European populations. Although larger studies and meta-analyses of North African populations are needed to confirm the present results, our data contribute to a better understanding of genetic susceptibility to HTN. PMID:25231511

  18. High pressure air jet in the endoscopic preparation room: risk of noise exposure on occupational health.

    PubMed

    Chiu, King-Wah; Lu, Lung-Sheng; Wu, Cheng-Kun

    2015-01-01

    After high-level disinfection of gastrointestinal endoscopes, they are hung to dry in order to prevent residual water droplets impact on patient health. To allow for quick drying and clinical reuse, some endoscopic units use a high pressure air jet (HPAJ) to remove the water droplets on the endoscopes. The purpose of this study was to evaluate the excessive noise exposure with the use of HPAJ in endoscopic preparation room and to investigate the risk to occupational health. Noise assessment was taken during 7 automatic endoscopic reprocessors (AERs) and combined with/without HPAJ use over an 8-hour time-weighted average (TWA). Analytical procedures of the NIOSH and the ISO for noise-induced hearing loss were estimated to develop analytic models. The peak of the noise spectrum of combined HPAJ and 7 AERs was significantly higher than that of the 7 AERs alone (108.3 ± 1.36 versus 69.3 ± 3.93 dBA, P < 0.0001). The risk of hearing loss (HL > 2.5 dB) was 2.15% at 90 dBA, 11.6% at 95 dBA, and 51.3% at 100 dBA. The odds ratio was 49.1 (95% CI: 11.9 to 203.6). The noise generated by the HPAJ to work over TWA seriously affected the occupational health and safety of those working in an endoscopic preparation room. PMID:25710009

  19. Modeling a Transient Pressurization with Active Cooling Sizing Tool

    NASA Technical Reports Server (NTRS)

    Guzik, Monica C.; Plachta, David W.; Elchert, Justin P.

    2011-01-01

    As interest in the area of in-space zero boil-off cryogenic propellant storage develops, the need to visualize and quantify cryogen behavior during ventless tank self-pressurization and subsequent cool-down with active thermal control has become apparent. During the course of a mission, such as the launch ascent phase, there are periods that power to the active cooling system will be unavailable. In addition, because it is not feasible to install vacuum jackets on large propellant tanks, as is typically done for in-space cryogenic applications for science payloads, instances like the launch ascent heating phase are important to study. Numerous efforts have been made to characterize cryogenic tank pressurization during ventless cryogen storage without active cooling, but few tools exist to model this behavior in a user-friendly environment for general use, and none exist that quantify the marginal active cooling system size needed for power down periods to manage tank pressure response once active cooling is resumed. This paper describes the Transient pressurization with Active Cooling Tool (TACT), which is based on a ventless three-lump homogeneous thermodynamic self-pressurization model1 coupled with an active cooling system estimator. TACT has been designed to estimate the pressurization of a heated but unvented cryogenic tank, assuming an unavailable power period followed by a given cryocooler heat removal rate. By receiving input data on the tank material and geometry, propellant initial conditions, and passive and transient heating rates, a pressurization and recovery profile can be found, which establishes the time needed to return to a designated pressure. This provides the ability to understand the effect that launch ascent and unpowered mission segments have on the size of an active cooling system. A sample of the trends found show that an active cooling system sized for twice the steady state heating rate would results in a reasonable time for tank

  20. High Blood Pressure and Related Factors Among Individuals at High Risk for HIV/Sexually Transmitted Infections.

    PubMed

    Nam, Soohyun; Whittemore, Robin; Jeon, Sangchoon; Davey-Rothwell, Melissa A; Latkin, Carl

    2016-06-01

    Data from a social network-based human immunodeficiency virus (HIV)/sexually transmitted infection (STI) prevention study with a total of 330 men and women at high risk for HIV/STIs were used to examine the relationships between substance use, depressive symptoms, general health, cardiovascular disease risk factors, sociodemographic characteristics, and systolic/diastolic blood pressure (SBP/DBP). Approximately 60% of the participants had prehypertension to stage 2 hypertension. In the base model, older patients (P<.0001), men (P=.003), and patients with poorer self-reported health (P=.029) were significantly associated with high SBP, whereas older age (P<.001) and higher body mass index (P<.001) were significantly associated with higher DBP. After adjusting for the base model, high frequency of alcohol drinking and high frequency of binge drinking remained significant for high SBP and DBP. These data suggest that future cardiovascular disease programs should target moderate alcohol consumption to improve blood pressure among individuals at high risk for HIV/STIs. PMID:26514661

  1. Low-pressure hydrogen plasmas explored using a global model

    NASA Astrophysics Data System (ADS)

    Samuell, Cameron M.; Corr, Cormac S.

    2016-02-01

    Low-pressure hydrogen plasmas have found applications in a variety of technology areas including fusion, neutral beam injection and material processing applications. To better understand these discharges, a global model is developed to predict the behaviour of electrons, ground-state atomic and molecular hydrogen, three positive ion species (H+, \\text{H}2+ , and \\text{H}3+ ), a single negative ion species (H-), and fourteen vibrationally excited states of molecular hydrogen ({{\\text{H}}2}≤ft(\\upsilon =1\\right. -14)). The model is validated by comparison with experimental results from a planar inductively coupled GEC reference cell and subsequently applied to the MAGPIE linear helicon reactor. The MAGPIE reactor is investigated for a range of pressures from 1 to 100 mTorr and powers up to 5 kW. With increasing power between 50 W and 5 kW at 10 mTorr the density of all charged species increases as well as the dissociative fraction while the electron temperature remains almost constant at around 3 eV. For gas pressures from 1-100 mTorr at an input power of 1 kW, the electron density remains almost constant, the electron temperature and dissociative fraction decreases, while \\text{H}3+ density increases in density and also dominates amongst ion species. Across these power and pressure scans, electronegativity remains approximately constant at around 2.5%. The power and pressure determines the dominant ion species in the plasma with \\text{H}3+ observed to dominate at high pressures and low powers whereas H+ tends to be dominant at low pressures and high powers. A sensitivity analysis is used to demonstrate how experimental parameters (power, pressure, reactor wall material, geometry etc) influence individual species’ density as well as the electron temperature. Physical reactor changes including the length, radius and wall recombination coefficient are found to have the largest influence on outputs obtained from the model.

  2. Ambulatory monitoring derived blood pressure variability and cardiovascular risk factors in elderly hypertensive patients.

    PubMed

    Magdás, Annamária; Szilágyi, László; Belényi, Boglárka; Incze, Alexandru

    2014-01-01

    Hypertension in the elderly is characterized by isolated systolic hypertension and high variability, but its clinical significance is not yet fully understood. The goal of this paper was to assess circadian blood pressure variability (BPV) in elderly hypertensives, and to determine its relationship to cardiovascular risk factors. To achieve this goal, a number of 75 inefficiently treated hypertensive patients were studied, 45 elderly, aged over 60 years, 30 middle-aged, younger than 60 years. After 24-hour ambulatory blood pressure monitoring (ABPM), blood pressure (BP) values, pulse pressure (PP), morning surge were compared between the groups. BPV was calculated using average real variability (ARV). The relationships between BPV, pulse pressure, left ventricular mass index (LVMI), and cardiovascular risk factors were assessed in both groups. As a result, it was found that left ventricular mass (p=0.01), PP, morning surge, 24-hour systolic ARV were significantly higher in the elderly group (p<0.05). In both groups, higher 24-hour BPV was associated with an increase in LVMI. In the elderly population 24-hour BPV was positively correlated to increased PP, total cholesterol and triglyceride levels (p<0.05). Moreover, it was concluded that ABPM-derived BP variability index could be an early predictive marker of end-organ damage in hypertension. Its reduction might be an important objective of hypertension management in elderly. PMID:25226958

  3. Sex-specific differences in cardiovascular risk factors and blood pressure control in hypertensive patients.

    PubMed

    Tziomalos, Konstantinos; Giampatzis, Vasilios; Baltatzi, Maria; Efthymiou, Elias; Psianou, Konstantia; Papastergiou, Natalia; Magkou, Dimitra; Bougatsa, Vagia; Savopoulos, Christos; Hatzitolios, Apostolos I

    2014-04-01

    Cardiovascular disease (CVD) and cardiovascular risk factors are frequently undertreated in women. However, it is unclear whether the prevalence of additional cardiovascular risk factors and the total cardiovascular risk differ between hypertensive men and women. There are also limited data regarding rates of blood pressure control in the two sexes outside the United States. The authors aimed to compare the cardiovascular risk profile between sexes. A total of 1810 hypertensive patients (40.4% men, age 56.5±13.5 years) attending the hypertension outpatient clinic of our department were studied. Men were more frequently smokers than women and were more heavy smokers than the latter. Serum high-density lipoprotein cholesterol levels were lower and serum triglyceride levels were higher in men. On the other hand, abdominal obesity and chronic kidney disease were more prevalent in women. The estimated cardiovascular risk was higher in men than in women but the prevalence of established CVD did not differ between the sexes. The percentage of patients with controlled hypertension and the number of antihypertensive medications were similar in men and women. In conclusion, hypertensive men have more adverse cardiovascular risk factor profile and greater estimated cardiovascular risk than women. However, the prevalence of established CVD does not differ between sexes. These findings further reinforce current guidelines that recommend that management of hypertension and of other cardiovascular risk factors should be as aggressive in women as in men in order to prevent cardiovascular events. PMID:24621371

  4. Control of Blood Pressure and Risk Attenuation: Post Trial Follow-Up of Randomized Groups

    PubMed Central

    Jafar, Tazeen H.; Jehan, Imtiaz; Liang, Feng; Barbier, Sylvaine; Islam, Muhammad; Bux, Rasool; Khan, Aamir Hameed; Nadkarni, Nivedita; Poulter, Neil; Chaturvedi, Nish; Ebrahim, Shah

    2015-01-01

    Background Evidence on long term effectiveness of public health strategies for lowering blood pressure (BP) is scarce. In the Control of Blood Pressure and Risk Attenuation (COBRA) Trial, a 2 x 2 factorial, cluster randomized controlled trial, the combined home health education (HHE) and trained general practitioner (GP) intervention delivered over 2 years was more effective than no intervention (usual care) in lowering systolic BP among adults with hypertension in urban Pakistan. However, it was not clear whether the effect would be sustained after the cessation of intervention. We conducted 7 years follow-up inclusive of 5 years of post intervention period of COBRA trial participants to assess the effectiveness of the interventions on BP during extended follow-up. Methods A total of 1341 individuals 40 years or older with hypertension (systolic BP 140 mm Hg or greater, diastolic BP 90 mm Hg or greater, or already receiving treatment) were followed by trained research staff masked to randomization status. BP was measured thrice with a calibrated automated device (Omron HEM-737 IntelliSense) in the sitting position after 5 minutes of rest. BP measurements were repeated after two weeks. Generalized estimating equations (GEE) were used to analyze the primary outcome of change in systolic BP from baseline to 7- year follow-up. The multivariable model was adjusted for clustering, age at baseline, sex, baseline systolic and diastolic BP, and presence of diabetes. Findings After 7 years of follow-up, systolic BP levels among those randomised to combined HHE plus trained GP intervention were significantly lower (2.1 [4.1–0.1] mm Hg) compared to those randomised to usual care, (P = 0.04). Participants receiving the combined intervention compared to usual care had a greater reduction in LDL-cholesterol (2.7 [4.8 to 0.6] mg/dl. Conclusions The benefit in systolic BP reduction observed in the original cohort assigned to the combined intervention was attenuated but still

  5. Risk analysis: divergent models and convergent interpretations

    NASA Technical Reports Server (NTRS)

    Carnes, B. A.; Gavrilova, N.

    2001-01-01

    Material presented at a NASA-sponsored workshop on risk models for exposure conditions relevant to prolonged space flight are described in this paper. Analyses used mortality data from experiments conducted at Argonne National Laboratory on the long-term effects of external whole-body irradiation on B6CF1 mice by 60Co gamma rays and fission neutrons delivered as a single exposure or protracted over either 24 or 60 once-weekly exposures. The maximum dose considered was restricted to 1 Gy for neutrons and 10 Gy for gamma rays. Proportional hazard models were used to investigate the shape of the dose response at these lower doses for deaths caused by solid-tissue tumors and tumors of either connective or epithelial tissue origin. For protracted exposures, a significant mortality effect was detected at a neutron dose of 14 cGy and a gamma-ray dose of 3 Gy. For single exposures, radiation-induced mortality for neutrons also occurred within the range of 10-20 cGy, but dropped to 86 cGy for gamma rays. Plots of risk relative to control estimated for each observed dose gave a visual impression of nonlinearity for both neutrons and gamma rays. At least for solid-tissue tumors, male and female mortality was nearly identical for gamma-ray exposures, but mortality risks for females were higher than for males for neutron exposures. As expected, protracting the gamma-ray dose reduced mortality risks. Although curvature consistent with that observed visually could be detected by a model parameterized to detect curvature, a relative risk term containing only a simple term for total dose was usually sufficient to describe the dose response. Although detectable mortality for the three pathology end points considered typically occurred at the same level of dose, the highest risks were almost always associated with deaths caused by tumors of epithelial tissue origin.

  6. Lower blood pressure goals in high-risk cardiovascular patients: are they defensible?

    PubMed

    Hopkins, Keith A; Bakris, George L

    2010-08-01

    This review highlights the paucity of data that support actively decreasing blood pressures (BP) to a level of less than 130/80 mm Hg. Although the data support a lower cardiovascular (CV) event rate with this lower level of pressure in high-risk CV people, early aggressive intervention to prevent levels from going above this mark prevent development of worsening atherosclerosis. Although no trial will ever prove this concept of prevention, common sense and multiple animal experiments support it. Most patients should have their systolic BP reduced to levels well below 140 mm Hg approaching 130 mm Hg, not 140 mm Hg. PMID:20621249

  7. Survivorship models for estimating the risk of decompression sickness.

    PubMed

    Kumar, K V; Powell, M R

    1994-07-01

    Several approaches have been used for modeling the incidence of decompression sickness (DCS) such as Hill's dose-response and logistic regression. Most of these methods do not include the time-to-onset information in the model. Survival analysis (failure time analysis) is appropriate when the time to onset of an event is of interest. The applicability of survival analysis for modeling the risk of DCS is illustrated by using data obtained from hypobaric chamber exposures simulating extravehicular activities (n = 426). Univariate analysis of incidence-free survival proportions were obtained for Doppler-detectable circulating microbubbles (CMB), symptoms of DCS and test aborts. A log-linear failure time regression model with 360-min half-time tissue ratio (TR) as covariate was constructed, and estimated probabilities for various TR values were calculated. Further regression analysis by including CMB status in this model showed significant improvement (p < 0.05) in the estimation of DCS over the previous model. Since DCS is dependent on the exposure pressure as well as the duration of exposure, we recommend the use of survival analysis for modeling the risk of DCS. PMID:7945136

  8. Landslide risk models for decision making.

    PubMed

    Bonachea, Jaime; Remondo, Juan; de Terán, José Ramón Díaz; González-Díez, Alberto; Cendrero, Antonio

    2009-11-01

    This contribution presents a quantitative procedure for landslide risk analysis and zoning considering hazard, exposure (or value of elements at risk), and vulnerability. The method provides the means to obtain landslide risk models (expressing expected damage due to landslides on material elements and economic activities in monetary terms, according to different scenarios and periods) useful to identify areas where mitigation efforts will be most cost effective. It allows identifying priority areas for the implementation of actions to reduce vulnerability (elements) or hazard (processes). The procedure proposed can also be used as a preventive tool, through its application to strategic environmental impact analysis (SEIA) of land-use plans. The underlying hypothesis is that reliable predictions about hazard and risk can be made using models based on a detailed analysis of past landslide occurrences in connection with conditioning factors and data on past damage. The results show that the approach proposed and the hypothesis formulated are essentially correct, providing estimates of the order of magnitude of expected losses for a given time period. Uncertainties, strengths, and shortcomings of the procedure and results obtained are discussed and potential lines of research to improve the models are indicated. Finally, comments and suggestions are provided to generalize this type of analysis. PMID:19732396

  9. Landslide risk mapping and modeling in China

    NASA Astrophysics Data System (ADS)

    Li, W.; Hong, Y.

    2015-12-01

    Under circumstances of global climate change, tectonic stress and human effect, landslides are among the most frequent and severely widespread natural hazards on Earth, as demonstrated in the World Atlas of Natural Hazards (McGuire et al., 2004). Every year, landslide activities cause serious economic loss as well as casualties (Róbert et al., 2005). How landslides can be monitored and predicted is an urgent research topic of the international landslide research community. Particularly, there is a lack of high quality and updated landslide risk maps and guidelines that can be employed to better mitigate and prevent landslide disasters in many emerging regions, including China (Hong, 2007). Since the 1950s, landslide events have been recorded in the statistical yearbooks, newspapers, and monographs in China. As disasters have been increasingly concerned by the government and the public, information about landslide events is becoming available from online news reports (Liu et al., 2012).This study presents multi-scale landslide risk mapping and modeling in China. At the national scale, based on historical data and practical experiences, we carry out landslide susceptibility and risk mapping by adopting a statistical approach and pattern recognition methods to construct empirical models. Over the identified landslide hot-spot areas, we further evaluate the slope-stability for each individual site (Sidle and Hirotaka, 2006), with the ultimate goal to set up a space-time multi-scale coupling system of Landslide risk mapping and modeling for landslide hazard monitoring and early warning.

  10. High-pressure intrapleural chemotherapy: feasibility in the pig model

    PubMed Central

    2012-01-01

    Background The usual treatments for pleural malignancies are mostly palliative. In contrast, peritoneal malignancies are often treated with a curative intent by cytoreductive surgery and intraperitoneal chemotherapy. As pressure has been shown to increase antitumor efficacy, we applied the concept of high-pressure intracavitary chemotherapy to the pleural space in a swine model. Methods Cisplatin and gemcitabine were selected because of their antineoplasic efficacy in vitro in a wide spectrum of cancer cell lines. The pleural cavity of 21 pigs was filled with saline solution; haemodynamic and respiratory parameters were monitored. The pressure was increased to 15-25 cm H2O. This treatment was associated with pneumonectomy in 6 pigs. Five pigs were treated with chemotherapy under pressure. Results The combination of gemcitabine (100 mg/l) and cisplatin (30 mg/l) was highly cytotoxic in vitro. The maximum tolerated pressure was 20 cm H20, due to haemodynamic failure. Pneumonectomy was not tolerated, either before or after pleural infusion. Five pigs survived intrapleural chemotherapy associating gemcitabine and cisplatin with 20 cm H2O pressure for 60 min. Conclusions High-pressure intrapleural chemotherapy is feasible in pigs. Further experiments will establish the pharmacokinetics and determine whether the benefit already shown in the peritoneum is also obtained in the pleura. PMID:22309737

  11. Quantitative risk modelling for new pharmaceutical compounds.

    PubMed

    Tang, Zhengru; Taylor, Mark J; Lisboa, Paulo; Dyas, Mark

    2005-11-15

    The process of discovering and developing new drugs is long, costly and risk-laden. Faced with a wealth of newly discovered compounds, industrial scientists need to target resources carefully to discern the key attributes of a drug candidate and to make informed decisions. Here, we describe a quantitative approach to modelling the risk associated with drug development as a tool for scenario analysis concerning the probability of success of a compound as a potential pharmaceutical agent. We bring together the three strands of manufacture, clinical effectiveness and financial returns. This approach involves the application of a Bayesian Network. A simulation model is demonstrated with an implementation in MS Excel using the modelling engine Crystal Ball. PMID:16257374

  12. Tyre pressure monitoring using a dynamical model-based estimator

    NASA Astrophysics Data System (ADS)

    Reina, Giulio; Gentile, Angelo; Messina, Arcangelo

    2015-04-01

    In the last few years, various control systems have been investigated in the automotive field with the aim of increasing the level of safety and stability, avoid roll-over, and customise handling characteristics. One critical issue connected with their integration is the lack of state and parameter information. As an example, vehicle handling depends to a large extent on tyre inflation pressure. When inflation pressure drops, handling and comfort performance generally deteriorate. In addition, it results in an increase in fuel consumption and in a decrease in lifetime. Therefore, it is important to keep tyres within the normal inflation pressure range. This paper introduces a model-based approach to estimate online tyre inflation pressure. First, basic vertical dynamic modelling of the vehicle is discussed. Then, a parameter estimation framework for dynamic analysis is presented. Several important vehicle parameters including tyre inflation pressure can be estimated using the estimated states. This method aims to work during normal driving using information from standard sensors only. On the one hand, the driver is informed about the inflation pressure and he is warned for sudden changes. On the other hand, accurate estimation of the vehicle states is available as possible input to onboard control systems.

  13. Air pollution, blood pressure, and the risk of hypertensive complications during pregnancy: the generation R study.

    PubMed

    van den Hooven, Edith H; de Kluizenaar, Yvonne; Pierik, Frank H; Hofman, Albert; van Ratingen, Sjoerd W; Zandveld, Peter Y J; Mackenbach, Johan P; Steegers, Eric A P; Miedema, Henk M E; Jaddoe, Vincent W V

    2011-03-01

    Exposure to air pollution is associated with elevated blood pressure and cardiovascular disease. We assessed the associations of exposure to particulate matter (PM(10)) and nitrogen dioxide (NO(2)) levels with blood pressure measured in each trimester of pregnancy and the risks of pregnancy-induced hypertension and preeclampsia in 7006 women participating in a prospective cohort study in the Netherlands. Information on gestational hypertensive disorders was obtained from medical records. PM(10) exposure was not associated with first trimester systolic and diastolic blood pressure, but a 10-μg/m(3) increase in PM(10) levels was associated with a 1.11-mm Hg (95% confidence interval [CI] 0.43 to 1.79) and 2.11-mm Hg (95% CI 1.34 to 2.89) increase in systolic blood pressure in the second and third trimester, respectively. Longitudinal analyses showed that elevated PM(10) exposure levels were associated with a steeper increase in systolic blood pressure throughout pregnancy (P<0.01), but not with diastolic blood pressure patterns. Elevated NO(2) exposure was associated with higher systolic blood pressure levels in the first, second, and third trimester (P<0.05), and with a more gradual increase when analyzed longitudinally (P<0.01). PM(10) exposure, but not NO(2) exposure, was associated with an increased risk of pregnancy-induced hypertension (odds ratio 1.72 [95% CI 1.12 to 2.63] per 10-μg/m(3) increase). In conclusion, our results suggest that air pollution may affect maternal cardiovascular health during pregnancy. The effects might be small but relevant on a population level. PMID:21220700

  14. Design and modeling of a silicon resonant pressure sensor

    NASA Astrophysics Data System (ADS)

    Cui, Zheng; Chen, Deyong; Xia, Shanhong

    2001-04-01

    Modelling of a silicon resonator as a pressure sensor is presented. The resonator is electrothermally excited and the resonance frequency shift is detected by a piezoresistive thin film detector. Computer simulation using commercial MEMS software tool IntelliSuiteTM is compared with analytical model. Various design aspects, such as the pressure sensitivity, electrothermal heating of vibrating beam, influence of detection current and damping effect are investigated. Silicon resonator sensor have been fabricated and measured. The characteristics predicted by computer simulation has been confirmed by experimental results.

  15. Development of relative risk model for regional groundwater risk assessment: a case study in the lower Liaohe River Plain, China.

    PubMed

    Li, Xianbo; Zuo, Rui; Teng, Yanguo; Wang, Jinsheng; Wang, Bin

    2015-01-01

    Increasing pressure on water supply worldwide, especially in arid areas, has resulted in groundwater overexploitation and contamination, and subsequent deterioration of the groundwater quality and threats to public health. Environmental risk assessment of regional groundwater is an important tool for groundwater protection. This study presents a new approach for assessing the environmental risk assessment of regional groundwater. It was carried out with a relative risk model (RRM) coupled with a series of indices, such as a groundwater vulnerability index, which includes receptor analysis, risk source analysis, risk exposure and hazard analysis, risk characterization, and management of groundwater. The risk map is a product of the probability of environmental contamination and impact. The reliability of the RRM was verified using Monte Carlo analysis. This approach was applied to the lower Liaohe River Plain (LLRP), northeastern China, which covers 23604 km2. A spatial analysis tool within GIS which was used to interpolate and manipulate the data to develop environmental risk maps of regional groundwater, divided the level of risk from high to low into five ranks (V, IV, III, II, I). The results indicate that areas of relative risk rank (RRR) V cover 2324 km2, covering 9.8% of the area; RRR IV covers 3986 km2, accounting for 16.9% of the area. It is a new and appropriate method for regional groundwater resource management and land use planning, and is a rapid and effective tool for improving strategic decision making to protect groundwater and reduce environmental risk. PMID:26020518

  16. Development of Relative Risk Model for Regional Groundwater Risk Assessment: A Case Study in the Lower Liaohe River Plain, China

    PubMed Central

    Li, Xianbo; Zuo, Rui; Teng, Yanguo; Wang, Jinsheng; Wang, Bin

    2015-01-01

    Increasing pressure on water supply worldwide, especially in arid areas, has resulted in groundwater overexploitation and contamination, and subsequent deterioration of the groundwater quality and threats to public health. Environmental risk assessment of regional groundwater is an important tool for groundwater protection. This study presents a new approach for assessing the environmental risk assessment of regional groundwater. It was carried out with a relative risk model (RRM) coupled with a series of indices, such as a groundwater vulnerability index, which includes receptor analysis, risk source analysis, risk exposure and hazard analysis, risk characterization, and management of groundwater. The risk map is a product of the probability of environmental contamination and impact. The reliability of the RRM was verified using Monte Carlo analysis. This approach was applied to the lower Liaohe River Plain (LLRP), northeastern China, which covers 23604 km2. A spatial analysis tool within GIS which was used to interpolate and manipulate the data to develop environmental risk maps of regional groundwater, divided the level of risk from high to low into five ranks (V, IV, III, II, I). The results indicate that areas of relative risk rank (RRR) V cover 2324 km2, covering 9.8% of the area; RRR IV covers 3986 km2, accounting for 16.9% of the area. It is a new and appropriate method for regional groundwater resource management and land use planning, and is a rapid and effective tool for improving strategic decision making to protect groundwater and reduce environmental risk. PMID:26020518

  17. Novel methods to evaluate fracture risk models

    PubMed Central

    Donaldson, M.G.; Cawthon, P. M.; Schousboe, J.T.; Ensrud, K.E.; Lui, L.Y.; Cauley, J.A.; Hillier, T.A.; Taylor, B.C.; Hochberg, M.C.; Bauer, D.C.; Cummings, S.R.

    2013-01-01

    Fracture prediction models help identify individuals at high risk who may benefit from treatment. Area Under the Curve (AUC) is used to compare prediction models. However, the AUC has limitations and may miss important differences between models. Novel reclassification methods quantify how accurately models classify patients who benefit from treatment and the proportion of patients above/below treatment thresholds. We applied two reclassification methods, using the NOF treatment thresholds, to compare two risk models: femoral neck BMD and age (“simple model”) and FRAX (”FRAX model”). The Pepe method classifies based on case/non-case status and examines the proportion of each above and below thresholds. The Cook method examines fracture rates above and below thresholds. We applied these to the Study of Osteoporotic Fractures. There were 6036 (1037 fractures) and 6232 (389 fractures) participants with complete data for major osteoporotic and hip fracture respectively. Both models for major osteoporotic fracture (0.68 vs. 0.69) and hip fracture (0.75 vs. 0.76) had similar AUCs. In contrast, using reclassification methods, each model classified a substantial number of women differently. Using the Pepe method, the FRAX model (vs. simple model), missed treating 70 (7%) cases of major osteoporotic fracture but avoided treating 285 (6%) non-cases. For hip fracture, the FRAX model missed treating 31 (8%) cases but avoided treating 1026 (18%) non-cases. The Cook method (both models, both fracture outcomes) had similar fracture rates above/below the treatment thresholds. Compared with the AUC, new methods provide more detailed information about how models classify patients. PMID:21351143

  18. Simulation Assisted Risk Assessment: Blast Overpressure Modeling

    NASA Technical Reports Server (NTRS)

    Lawrence, Scott L.; Gee, Ken; Mathias, Donovan; Olsen, Michael

    2006-01-01

    A probabilistic risk assessment (PRA) approach has been developed and applied to the risk analysis of capsule abort during ascent. The PRA is used to assist in the identification of modeling and simulation applications that can significantly impact the understanding of crew risk during this potentially dangerous maneuver. The PRA approach is also being used to identify the appropriate level of fidelity for the modeling of those critical failure modes. The Apollo launch escape system (LES) was chosen as a test problem for application of this approach. Failure modes that have been modeled and/or simulated to date include explosive overpressure-based failure, explosive fragment-based failure, land landing failures (range limits exceeded either near launch or Mode III trajectories ending on the African continent), capsule-booster re-contact during separation, and failure due to plume-induced instability. These failure modes have been investigated using analysis tools in a variety of technical disciplines at various levels of fidelity. The current paper focuses on the development and application of a blast overpressure model for the prediction of structural failure due to overpressure, including the application of high-fidelity analysis to predict near-field and headwinds effects.

  19. The Pressure Gradient Force in Sigma-Co Ocean Models

    NASA Astrophysics Data System (ADS)

    Slørdal, Leiv Håvard

    1997-05-01

    The error in computing the horizontal pressure gradient force near steep topography is investigated in a primitive equation, -co-ordinate, numerical ocean model (Blumberg and Mellor, in Three -Dimensional Coastal Ocean Models, Vol. 4, American Geophysical Union, Washington D.C., 1987, pp. 1-16). By performing simple test experiments where the density field is allowed to vary in both the vertical and the horizontal direction, severe errors are detected in the areas where the isopycnals hit the sloping bottom. An alternative method of computing the pressure force (Stelling and van Kester, Int. j. numer. methods fluids, 18, 915-935 (1994) is adopted, resulting in substantial reduction of the errors. However, a systematic underestimation of the calculated quantities is revealed, leading to erroneous depth-mean values of the pressure force. In this study a modification of the Stelling and van Kester method is proposed which seems to improve the overall performance of the method.

  20. Quantitative Risk Modeling of Fire on the International Space Station

    NASA Technical Reports Server (NTRS)

    Castillo, Theresa; Haught, Megan

    2014-01-01

    The International Space Station (ISS) Program has worked to prevent fire events and to mitigate their impacts should they occur. Hardware is designed to reduce sources of ignition, oxygen systems are designed to control leaking, flammable materials are prevented from flying to ISS whenever possible, the crew is trained in fire response, and fire response equipment improvements are sought out and funded. Fire prevention and mitigation are a top ISS Program priority - however, programmatic resources are limited; thus, risk trades are made to ensure an adequate level of safety is maintained onboard the ISS. In support of these risk trades, the ISS Probabilistic Risk Assessment (PRA) team has modeled the likelihood of fire occurring in the ISS pressurized cabin, a phenomenological event that has never before been probabilistically modeled in a microgravity environment. This paper will discuss the genesis of the ISS PRA fire model, its enhancement in collaboration with fire experts, and the results which have informed ISS programmatic decisions and will continue to be used throughout the life of the program.

  1. Postural effects on intracranial pressure: modeling and clinical evaluation.

    PubMed

    Qvarlander, Sara; Sundström, Nina; Malm, Jan; Eklund, Anders

    2013-11-01

    The physiological effect of posture on intracranial pressure (ICP) is not well described. This study defined and evaluated three mathematical models describing the postural effects on ICP, designed to predict ICP at different head-up tilt angles from the supine ICP value. Model I was based on a hydrostatic indifference point for the cerebrospinal fluid (CSF) system, i.e., the existence of a point in the system where pressure is independent of body position. Models II and III were based on Davson's equation for CSF absorption, which relates ICP to venous pressure, and postulated that gravitational effects within the venous system are transferred to the CSF system. Model II assumed a fully communicating venous system, and model III assumed that collapse of the jugular veins at higher tilt angles creates two separate hydrostatic compartments. Evaluation of the models was based on ICP measurements at seven tilt angles (0-71°) in 27 normal pressure hydrocephalus patients. ICP decreased with tilt angle (ANOVA: P < 0.01). The reduction was well predicted by model III (ANOVA lack-of-fit: P = 0.65), which showed excellent fit against measured ICP. Neither model I nor II adequately described the reduction in ICP (ANOVA lack-of-fit: P < 0.01). Postural changes in ICP could not be predicted based on the currently accepted theory of a hydrostatic indifference point for the CSF system, but a new model combining Davson's equation for CSF absorption and hydrostatic gradients in a collapsible venous system performed well and can be useful in future research on gravity and CSF physiology. PMID:24052030

  2. Probabilistic Seismic Risk Model for Western Balkans

    NASA Astrophysics Data System (ADS)

    Stejskal, Vladimir; Lorenzo, Francisco; Pousse, Guillaume; Radovanovic, Slavica; Pekevski, Lazo; Dojcinovski, Dragi; Lokin, Petar; Petronijevic, Mira; Sipka, Vesna

    2010-05-01

    A probabilistic seismic risk model for insurance and reinsurance purposes is presented for an area of Western Balkans, covering former Yugoslavia and Albania. This territory experienced many severe earthquakes during past centuries producing significant damage to many population centres in the region. The highest hazard is related to external Dinarides, namely to the collision zone of the Adriatic plate. The model is based on a unified catalogue for the region and a seismic source model consisting of more than 30 zones covering all the three main structural units - Southern Alps, Dinarides and the south-western margin of the Pannonian Basin. A probabilistic methodology using Monte Carlo simulation was applied to generate the hazard component of the model. Unique set of damage functions based on both loss experience and engineering assessments is used to convert the modelled ground motion severity into the monetary loss.

  3. A Boussinesq-scaled, pressure-Poisson water wave model

    NASA Astrophysics Data System (ADS)

    Donahue, Aaron S.; Zhang, Yao; Kennedy, Andrew B.; Westerink, Joannes J.; Panda, Nishant; Dawson, Clint

    2015-02-01

    Through the use of Boussinesq scaling we develop and test a model for resolving non-hydrostatic pressure profiles in nonlinear wave systems over varying bathymetry. A Green-Nagdhi type polynomial expansion is used to resolve the pressure profile along the vertical axis, this is then inserted into the pressure-Poisson equation, retaining terms up to a prescribed order and solved using a weighted residual approach. The model shows rapid convergence properties with increasing order of polynomial expansion which can be greatly improved through the application of asymptotic rearrangement. Models of Boussinesq scaling of the fully nonlinear O (μ2) and weakly nonlinear O (μN) are presented, the analytical and numerical properties of O (μ2) and O (μ4) models are discussed. Optimal basis functions in the Green-Nagdhi expansion are determined through manipulation of the free-parameters which arise due to the Boussinesq scaling. The optimal O (μ2) model has dispersion accuracy equivalent to a Padé [2,2] approximation with one extra free-parameter. The optimal O (μ4) model obtains dispersion accuracy equivalent to a Padé [4,4] approximation with two free-parameters which can be used to optimize shoaling or nonlinear properties. In comparison to experimental results the O (μ4) model shows excellent agreement to experimental data.

  4. Yoga lifestyle intervention reduces blood pressure in HIV-infected adults with cardiovascular disease risk factors

    PubMed Central

    Cade, Todd; Reeds, Dominic N.; Mondy, Kristin E.; Overton, Turner; Grassino, Joseph; Tucker, Shawn; Bopp, Coco; Laciny, Erin; Hubert, Sara; Lassa-Claxton, Sherry; Yarasheski, Kevin E.

    2009-01-01

    People living with human immunodeficiency virus infection (HIV) are at increased risk for developing cardiovascular disease (CVD). Safe and effective interventions for lowering CVD risk in HIV are high priorities. Objective We conducted a prospective, randomized, controlled study to evaluate whether a yoga lifestyle intervention improves CVD risk factors, virologic or immunologic status, or quality of life in HIV-infected adults more than in a matched control group. Methods Sixty HIV-infected adults with mild-moderate CVD risk were assigned to 20 wks of supervised yoga practice or standard of care treatment. Baseline and week 20 measures were; 2hr-oral glucose tolerance test with insulin monitoring, body composition, fasting serum lipid/lipoprotein profile, resting blood pressures, CD4+ T-cell number and plasma HIV RNA, and the Medical Outcomes Study SF-36 health-related quality of life inventory. Results Resting systolic and diastolic blood pressures were reduced more (p=0.04) in the yoga group (−5±2 and −3±1 mmHg) than in the standard of care group (+1±2 and +2±2 mmHg), despite no greater reduction in body weight, fat mass, proatherogenic lipids, or improvements in glucose tolerance or overall quality of life after yoga. Immune and virologic status was not adversely affected. Conclusion Among traditional lifestyle modifications, yoga is a low cost, simple to administer, non-pharmacological, popular behavioral intervention that can lower blood pressure in pre-hypertensive HIV-infected adults with mild-moderate CVD risk factors. PMID:20059570

  5. Local plantar pressure relief in therapeutic footwear: design guidelines from finite element models.

    PubMed

    Erdemir, Ahmet; Saucerman, Jeffrey J; Lemmon, David; Loppnow, Bryan; Turso, Brie; Ulbrecht, Jan S; Cavanagh, Peter Re

    2005-09-01

    A major goal of therapeutic footwear in patients with pain or those at risk for skin injury is to relieve focal loading under prominent metatarsal heads. One frequent approach is to place plugs of compliant material into the midsole of the shoe. This study investigated 36 plug designs, a combination of three materials, six geometries, and two placements using a two-dimensional (2D) finite element model. Realistic loading conditions were obtained from plantar pressures (PP) recorded during walking in five subjects who wore control midsoles manufactured using Microcell Puff. Measured peak pressures underneath the second metatarsal head were similar to the results of the control model. PP obtained from simulations with the plugs built into a firm midsole were compared to the simulation results of the control midsole. Large plugs (e.g. 40 mm width), made out of Microcell Puff Lite or Plastazote Medium, placed at peak pressure sites, resulted in highest reductions in peak pressures (18-28%). Smaller plugs benefited from tapering when placed at high pressure areas. Case studies were completed on a healthy male subject and a diabetic female patient to address the efficacy of a plug design favored by our simulations (pressure based placement, 40 x 20 mm, Plastazote Medium). Successful reductions of second metatarsal head pressures were observed with a mediolateral load redistribution that was not represented by our model. 2D computer simulations allowed systematic investigation of plug properties without the need for high volume experimentation on human subjects and established basic guidelines for plug selection. In particular, plugs that are placed based on plantar pressure measurements were proven to be more effective when compared to those positioned according to the projection of the bony landmark on the foot-shoe plantar contact area. PMID:16023466

  6. Human Plague Risk: Spatial-Temporal Models

    NASA Technical Reports Server (NTRS)

    Pinzon, Jorge E.

    2010-01-01

    This chpater reviews the use of spatial-temporal models in identifying potential risks of plague outbreaks into the human population. Using earth observations by satellites remote sensing there has been a systematic analysis and mapping of the close coupling between the vectors of the disease and climate variability. The overall result is that incidence of plague is correlated to positive El Nino/Southem Oscillation (ENSO).

  7. Use of a Poroelastic Model to Predict Intramuscular Pressure

    PubMed Central

    Morrow, D. A.; Odegard, G. M.; Kaufman, K. R.

    2014-01-01

    Measurement of individual muscle tension in a clinical setting has yet to be achieved. Previous investigators have suggested that the tension in skeletal muscle, comprised of approximately 70% fluid, could be determined using interstitial muscle fluid pressure (IMP). A computational model is needed to aid in understanding IMP distribution in muscles of varying geometry and contractile states without exhaustive testing. The first aim of this study was to determine a set of transversely isotropic material properties (i.e., permeability, relaxed modulus, and drained Poisson’s ratio) for excised skeletal muscle using inverse finite element analysis with a poroelastic constitutive formulation on tension data from either longitudinal or transverse uniaxial load-relaxation tests of skeletal muscle tissue. The second aim was to compare pore pressure estimated from a model to experimental pressure measurements to assess its ability to accurately predict IMP. Results of this study indicated that skeletal muscle was transversely isotropic under load-relaxation as demonstrated by significant differences in the drained Poisson’s ratio. It was also noted that the drained Poisson’s ratios under both longitudinal and transverse loading were negative in these tests of excised muscle tissue. Pore pressure calculated with this model provided a good prediction of the development of IMP. These results point to the benefit of using a poroelastic model of skeletal muscle to predict IMP. PMID:25541627

  8. Technology for pressure-instrumented thin airfoil models

    NASA Technical Reports Server (NTRS)

    Wigley, David A.

    1988-01-01

    A novel method of airfoil model construction was developed. This Laminated Sheet technique uses 0.8 mm thick sheets of A286 containing a network of pre-formed channels which are vacuum brazed together to form the airfoil. A 6.25 percent model of the X29A canard, which has a 5 percent thick section, was built using this technique. The model contained a total of 96 pressure orifices, 56 in three chordwise rows on the upper surface and 37 in three similar rows on the lower surface. It was tested in the NASA Langley 0.3 m Transonic Cryogenic Tunnel. Unique aerodynamic data was obtained over the full range of temperature and pressure. Part of the data was at transonic Mach numbers and flight Reynolds number. A larger two dimensional model of the NACA 64a-105 airfoil section was also fabricated. Scale up presented some problems, but a testable airfoil was fabricated.

  9. Validated Analytical Model of a Pressure Compensation Drip Irrigation Emitter

    NASA Astrophysics Data System (ADS)

    Shamshery, Pulkit; Wang, Ruo-Qian; Taylor, Katherine; Tran, Davis; Winter, Amos

    2015-11-01

    This work is focused on analytically characterizing the behavior of pressure-compensating drip emitters in order to design low-cost, low-power irrigation solutions appropriate for off-grid communities in developing countries. There are 2.5 billion small acreage farmers worldwide who rely solely on their land for sustenance. Drip, compared to flood, irrigation leads to up to 70% reduction in water consumption while increasing yields by 90% - important in countries like India which are quickly running out of water. To design a low-power drip system, there is a need to decrease the pumping pressure requirement at the emitters, as pumping power is the product of pressure and flow rate. To efficiently design such an emitter, the relationship between the fluid-structure interactions that occur in an emitter need to be understood. In this study, a 2D analytical model that captures the behavior of a common drip emitter was developed and validated through experiments. The effects of independently changing the channel depth, channel width, channel length and land height on the performance were studied. The model and the key parametric insights presented have the potential to be optimized in order to guide the design of low-pressure, clog-resistant, pressure-compensating emitters.

  10. A Raster Based Approach To Solar Pressure Modeling

    NASA Technical Reports Server (NTRS)

    Wright, Theodore

    2014-01-01

    The impact of photons upon a spacecraft introduces small forces and moments. The magnitude and direction of the forces depend on the material properties of the spacecraft components being illuminated. Which components are being lit depends on the orientation of the craft with respect to the Sun as well as the gimbal angles for any significant moving external parts (solar arrays, typically). Some components may shield others from the Sun.To determine solar pressure in the presence overlapping components, a 3D model can be used to determine which components are illuminated. A view (image) of the model as seen from the Sun shows the only contributors to solar pressure. This image can be decomposed into pixels, each of which can be treated as a non-overlapping flat plate as far as solar pressure calculations are concerned. The sums of the pressures and moments on these plates approximate the solar pressure and moments on the entire vehicle.The image rasterization technique can also be used to compute other spacecraft attributes that are dependent on attitude and geometry, including solar array power generation capability and free molecular flow drag.

  11. Global model for high pressure electronegative radio-frequency discharges

    SciTech Connect

    Lee, Y.T.; Lieberman, M.A.; Lichtenberg, A.J.; Bose, F.; Baltes, H.; Patrick, R.

    1997-01-01

    We develop a global model for high pressure (0.1{endash}1 Torr) electronegative rf discharges and apply it to model a capacitively driven plasma etcher. The molecular gases considered consist of either pure chlorine species or a mixture of chlorine and helium species. The charged and neutral heavy particle densities together with the electron density and electron temperature are calculated by using the equations of particle balance and power balance for the input discharge parameters rf power or rf current, inlet pressure, gas flow rates, reactor diameter, and gap spacing. The power is deposited in the electrons via ohmic heating and in those ions accelerated across the dc sheath potential. The voltage across the sheath is calculated self-consistently with the densities and the electron temperature by using a collisional Child law sheath model. Analytic scaling laws for the dependence of charged and neutral particle densities, electron temperature, rf voltage and current, sheath width, and plasma impedance on pressure and absorbed rf power are presented and used to explain the numerical results obtained from the global model. The model results are compared to recent experimental measurements in a chlorine discharge over a range of absorbed power P{sub abs}=20{endash}180W at an inlet pressure p{sub in}=0.4 Torr and a range of pressure 0.1{endash}1.6 Torr with a fixed input power of 100 W. We obtain reasonable agreement for P{sub abs}{lt}200W and for 0.2 Torr{lt}p{sub in}{lt}1Torr. {copyright} {ital 1997 American Vacuum Society.}

  12. Explicit Pore Pressure Material Model in Carbon-Cloth Phenolic

    NASA Technical Reports Server (NTRS)

    Gutierrez-Lemini, Danton; Ehle, Curt

    2003-01-01

    An explicit material model that uses predicted pressure in the pores of a carbon-cloth phenolic (CCP) composite has been developed. This model is intended to be used within a finite-element model to predict phenomena specific to CCP components of solid-fuel-rocket nozzles subjected to high operating temperatures and to mechanical stresses that can be great enough to cause structural failures. Phenomena that can be predicted with the help of this model include failures of specimens in restrained-thermal-growth (RTG) tests, pocketing erosion, and ply lifting

  13. NGNP Risk Management Database: A Model for Managing Risk

    SciTech Connect

    John Collins

    2009-09-01

    To facilitate the implementation of the Risk Management Plan, the Next Generation Nuclear Plant (NGNP) Project has developed and employed an analytical software tool called the NGNP Risk Management System (RMS). A relational database developed in Microsoft® Access, the RMS provides conventional database utility including data maintenance, archiving, configuration control, and query ability. Additionally, the tool’s design provides a number of unique capabilities specifically designed to facilitate the development and execution of activities outlined in the Risk Management Plan. Specifically, the RMS provides the capability to establish the risk baseline, document and analyze the risk reduction plan, track the current risk reduction status, organize risks by reference configuration system, subsystem, and component (SSC) and Area, and increase the level of NGNP decision making.

  14. Modeling Opponents in Adversarial Risk Analysis.

    PubMed

    Rios Insua, David; Banks, David; Rios, Jesus

    2016-04-01

    Adversarial risk analysis has been introduced as a framework to deal with risks derived from intentional actions of adversaries. The analysis supports one of the decisionmakers, who must forecast the actions of the other agents. Typically, this forecast must take account of random consequences resulting from the set of selected actions. The solution requires one to model the behavior of the opponents, which entails strategic thinking. The supported agent may face different kinds of opponents, who may use different rationality paradigms, for example, the opponent may behave randomly, or seek a Nash equilibrium, or perform level-k thinking, or use mirroring, or employ prospect theory, among many other possibilities. We describe the appropriate analysis for these situations, and also show how to model the uncertainty about the rationality paradigm used by the opponent through a Bayesian model averaging approach, enabling a fully decision-theoretic solution. We also show how as we observe an opponent's decision behavior, this approach allows learning about the validity of each of the rationality models used to predict his decision by computing the models' (posterior) probabilities, which can be understood as a measure of their validity. We focus on simultaneous decision making by two agents. PMID:26133501

  15. Facial pressure zones of an oronasal interface for noninvasive ventilation: a computer model analysis* **

    PubMed Central

    Barros, Luana Souto; Talaia, Pedro; Drummond, Marta; Natal-Jorge, Renato

    2014-01-01

    OBJECTIVE: To study the effects of an oronasal interface (OI) for noninvasive ventilation, using a three-dimensional (3D) computational model with the ability to simulate and evaluate the main pressure zones (PZs) of the OI on the human face. METHODS: We used a 3D digital model of the human face, based on a pre-established geometric model. The model simulated soft tissues, skull, and nasal cartilage. The geometric model was obtained by 3D laser scanning and post-processed for use in the model created, with the objective of separating the cushion from the frame. A computer simulation was performed to determine the pressure required in order to create the facial PZs. We obtained descriptive graphical images of the PZs and their intensity. RESULTS: For the graphical analyses of each face-OI model pair and their respective evaluations, we ran 21 simulations. The computer model identified several high-impact PZs in the nasal bridge and paranasal regions. The variation in soft tissue depth had a direct impact on the amount of pressure applied (438-724 cmH2O). CONCLUSIONS: The computer simulation results indicate that, in patients submitted to noninvasive ventilation with an OI, the probability of skin lesion is higher in the nasal bridge and paranasal regions. This methodology could increase the applicability of biomechanical research on noninvasive ventilation interfaces, providing the information needed in order to choose the interface that best minimizes the risk of skin lesion. PMID:25610506

  16. Risk assessment of physiological effects of atmospheric composition and pressure in Constellation vehicles

    NASA Astrophysics Data System (ADS)

    Scheuring, Richard; Conkin, Johnny; Jones, Jeffrey A.; Gernhardt, Michael L.

    Introduction: To limit the risk of fire and reduce denitrogenation time to prevent decompression sickness to support frequent extravehicular activities on the Moon, a hypobaric (PB=414mmHg) and mildly hypoxic ( ppO2=132mmHg, 32% O2-68%N2) living environment is considered for the Crew Exploration Vehicle (CEV) and Lunar Surface Access Module (LSAM). With acute change in ppO2 from 145-178mmHg at standard vehicular operating pressure to less than 125mmHg at desired lunar surface vehicular operating pressures, there is the possibility that some crewmembers may develop symptoms of Acute Mountain Sickness (AMS). The signs and symptoms of AMS (headache plus nausea, dizziness, fatigue, or sleeplessness) could impact crew health and performance on lunar surface missions. Methods: We performed a literature review on the topic of the physiological effects of reduced ppO2 and absolute pressure. The results of nine studies were evaluated. Results: There is evidence for an absolute pressure effect per se on AMS, so the higher the altitude for a given hypoxic alveolar oxygen (O2) partial pressure (PAO2), the greater the AMS response is. Between 7% and 25% of adults may experience mild AMS near 2000 m altitude following a rapid ascent from sea level while breathing air (6500 ft, acute PAO2=75mmHg). The operational experience with the Shuttle staged denitrogenation protocol at 528mmHg (3048 m) while breathing 26.5% O2 (acute PAO2=85mmHg) in astronauts adapting to microgravity suggests a similar likely experience in the proposed CEV environment. Conclusions: We believe the risk of mild AMS is greater given a PAO2 of 77mmHg at 4876 m altitude while breathing 32% O2 than at 1828 m altitude while breathing 21% O2. Only susceptible astronauts would develop mild and transient AMS with prolonged exposure to 414 mmHg (4876 m) while breathing 32% O2 (acute PAO2=77mmHg). So the following may be employed for operational risk reduction: (1) develop procedures to increase PB as needed in the

  17. Functional Risk Modeling for Lunar Surface Systems

    NASA Technical Reports Server (NTRS)

    Thomson, Fraser; Mathias, Donovan; Go, Susie; Nejad, Hamed

    2010-01-01

    We introduce an approach to risk modeling that we call functional modeling , which we have developed to estimate the capabilities of a lunar base. The functional model tracks the availability of functions provided by systems, in addition to the operational state of those systems constituent strings. By tracking functions, we are able to identify cases where identical functions are provided by elements (rovers, habitats, etc.) that are connected together on the lunar surface. We credit functional diversity in those cases, and in doing so compute more realistic estimates of operational mode availabilities. The functional modeling approach yields more realistic estimates of the availability of the various operational modes provided to astronauts by the ensemble of surface elements included in a lunar base architecture. By tracking functional availability the effects of diverse backup, which often exists when two or more independent elements are connected together, is properly accounted for.

  18. A Simplified Model for Detonation Based Pressure-Gain Combustors

    NASA Technical Reports Server (NTRS)

    Paxson, Daniel E.

    2010-01-01

    A time-dependent model is presented which simulates the essential physics of a detonative or otherwise constant volume, pressure-gain combustor for gas turbine applications. The model utilizes simple, global thermodynamic relations to determine an assumed instantaneous and uniform post-combustion state in one of many envisioned tubes comprising the device. A simple, second order, non-upwinding computational fluid dynamic algorithm is then used to compute the (continuous) flowfield properties during the blowdown and refill stages of the periodic cycle which each tube undergoes. The exhausted flow is averaged to provide mixed total pressure and enthalpy which may be used as a cycle performance metric for benefits analysis. The simplicity of the model allows for nearly instantaneous results when implemented on a personal computer. The results compare favorably with higher resolution numerical codes which are more difficult to configure, and more time consuming to operate.

  19. Modelling of microwave sustained capillary plasma columns at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Pencheva, M.; Petrova, Ts; Benova, E.; Zhelyazkov, I.

    2006-07-01

    In this work we present a model of argon microwave sustained discharge at high pressure (1 atm), which includes two self-consistently linked parts - electrodynamic and kinetic ones. The model is based on a steady-state Boltzmann equation in an effective field approximation coupled with a collisional-radiative model for high-pressure argon discharge numerically solved together with Maxwell's equation for an azimuthally symmetric TM surface wave and wave energy balance equation. It is applied for the purpose of theoretical description of the discharge in a stationary state. The phase diagram, the electron energy distribution function as well as the dependences of the electron and heavy particles densities and the mean input power per electron on the electron number density and wave number are presented.

  20. Numerical Modeling of Pressurization of a Propellant Tank

    NASA Technical Reports Server (NTRS)

    Majumdar, Alok; Steadman, Todd

    1999-01-01

    An unsteady finite volume procedure has been developed to predict the history o pressure, temperature and mass flow rate of the pressurant and propellant during the expulsion of the propellant from a tan. The time dependent mass, momentum and energy conservation equations are solved at the ullage space. The model accounts for the change in the ullage volume due to expulsion of the propellant. It also accounts for the heat transfer from the tank wall and propellant to the ullage gas. The procedure was incorporated in the Generalized Fluid System Simulation Program (GFSSP). The results of several test cases were then compared with a published correlation of pressurant requirements for a given displacement of propellant. The agreement between the predictions and the correlation was found to be satisfactory.

  1. Numerical Modeling of Pressurization of a Propellant Tank

    NASA Technical Reports Server (NTRS)

    Majumdar, Alok; Steadman, Todd

    1998-01-01

    An unsteady finite volume procedure has been developed to predict the history of pressure, temperature and mass flow rate of the pressurant and propellant during the expulsion of the propellant from a tank. The time dependent mass, momentum and energy conservation equations are solved at the ullage space. The model accounts for the change in the ullage volume due to expulsion of the propellant. It also accounts for the heat transfer from the tank wall and propellant to the ullage gas. The procedure was incorporated in the Generalized Fluid System Simulation Program (GFSSP). The results of several test cases were then compared with a published correlation of pressurant requirements for a given displacement of propellant. The agreement between the predictions and the correlation was found to be satisfactory.

  2. A Spatio-temporal Model of African Animal Trypanosomosis Risk

    PubMed Central

    Dicko, Ahmadou H.; Percoma, Lassane; Sow, Adama; Adam, Yahaya; Mahama, Charles; Sidibé, Issa; Dayo, Guiguigbaza-Kossigan; Thévenon, Sophie; Fonta, William; Sanfo, Safietou; Djiteye, Aligui; Salou, Ernest; Djohan, Vincent; Cecchi, Giuliano; Bouyer, Jérémy

    2015-01-01

    Background African animal trypanosomosis (AAT) is a major constraint to sustainable development of cattle farming in sub-Saharan Africa. The habitat of the tsetse fly vector is increasingly fragmented owing to demographic pressure and shifts in climate, which leads to heterogeneous risk of cyclical transmission both in space and time. In Burkina Faso and Ghana, the most important vectors are riverine species, namely Glossina palpalis gambiensis and G. tachinoides, which are more resilient to human-induced changes than the savannah and forest species. Although many authors studied the distribution of AAT risk both in space and time, spatio-temporal models allowing predictions of it are lacking. Methodology/Principal Findings We used datasets generated by various projects, including two baseline surveys conducted in Burkina Faso and Ghana within PATTEC (Pan African Tsetse and Trypanosomosis Eradication Campaign) national initiatives. We computed the entomological inoculation rate (EIR) or tsetse challenge using a range of environmental data. The tsetse apparent density and their infection rate were separately estimated and subsequently combined to derive the EIR using a “one layer-one model” approach. The estimated EIR was then projected into suitable habitat. This risk index was finally validated against data on bovine trypanosomosis. It allowed a good prediction of the parasitological status (r2 = 67%), showed a positive correlation but less predictive power with serological status (r2 = 22%) aggregated at the village level but was not related to the illness status (r2 = 2%). Conclusions/Significance The presented spatio-temporal model provides a fine-scale picture of the dynamics of AAT risk in sub-humid areas of West Africa. The estimated EIR was high in the proximity of rivers during the dry season and more widespread during the rainy season. The present analysis is a first step in a broader framework for an efficient risk management of climate

  3. Electricity market pricing, risk hedging and modeling

    NASA Astrophysics Data System (ADS)

    Cheng, Xu

    In this dissertation, we investigate the pricing, price risk hedging/arbitrage, and simplified system modeling for a centralized LMP-based electricity market. In an LMP-based market model, the full AC power flow model and the DC power flow model are most widely used to represent the transmission system. We investigate the differences of dispatching results, congestion pattern, and LMPs for the two power flow models. An appropriate LMP decomposition scheme to quantify the marginal costs of the congestion and real power losses is critical for the implementation of financial risk hedging markets. However, the traditional LMP decomposition heavily depends on the slack bus selection. In this dissertation we propose a slack-independent scheme to break LMP down into energy, congestion, and marginal loss components by analyzing the actual marginal cost of each bus at the optimal solution point. The physical and economic meanings of the marginal effect at each bus provide accurate price information for both congestion and losses, and thus the slack-dependency of the traditional scheme is eliminated. With electricity priced at the margin instead of the average value, the market operator typically collects more revenue from power sellers than that paid to power buyers. According to the LMP decomposition results, the revenue surplus is then divided into two parts: congestion charge surplus and marginal loss revenue surplus. We apply the LMP decomposition results to the financial tools, such as financial transmission right (FTR) and loss hedging right (LHR), which have been introduced to hedge against price risks associated to congestion and losses, to construct a full price risk hedging portfolio. The two-settlement market structure and the introduction of financial tools inevitably create market manipulation opportunities. We investigate several possible market manipulation behaviors by virtual bidding and propose a market monitor approach to identify and quantify such

  4. Modeling Flood Risk for South Korea

    NASA Astrophysics Data System (ADS)

    Mei, Y.; Li, S.

    2014-12-01

    Catastrophic flood events have caused significant losses for South Korea each year. It is very important to generate high resolution flood return period map for the government and insurance company to evaluate the flood risk. This research was initiated to achieve this goal. A 2000 year spatial distributed stochastical rainfall was generated by analyzing the historical rainfall of South Korea using principle component analysis. A rainfall-runoff model and a routing model were calibrated by driving the model with historical forcing and calibrated against gauge observations. The calibrated model was used to couple with the stochastical forcing to generate 2000 year discharge and runoff. The flood maps with different return periods were generated by numerically solving the shallow water equations using finite volume method on GPUs. The results of this research showed a reasonable flood map in South Korea, compared with the observed data. Further, this research could be used as an important reference for the government and insurance companies for risk management purpose.

  5. Modeling situation awareness and crash risk.

    PubMed

    Fisher, Donald L; Strayer, David L

    2014-01-01

    In this article we develop a model of the relationship between crash risk and a driver's situation awareness. We consider a driver's situation awareness to reflect the dynamic mental model of the driving environment and to be dependent upon several psychological processes including Scanning the driving environment, Predicting and anticipating hazards, Identifying potential hazards in the driving scene as they occur, Deciding on an action, and Executing an appropriate Response (SPIDER). Together, SPIDER is important for establishing and maintaining good situation awareness of the driving environment and good situation awareness is important for coordinating and scheduling the SPIDER-relevant processes necessary for safe driving. An Order-of-Processing (OP) model makes explicit the SPIDER-relevant processes and how they predict the likelihood of a crash when the driver is or is not distracted by a secondary task. For example, the OP model shows how a small decrease in the likelihood of any particular SPIDER activity being completed successfully (because of a concurrent secondary task performance) would lead to a large increase in the relative risk of a crash. PMID:24776225

  6. Modeling Situation Awareness and Crash Risk

    PubMed Central

    Fisher, Donald L.; Strayer, David. L.

    2014-01-01

    In this article we develop a model of the relationship between crash risk and a driver’s situation awareness. We consider a driver’s situation awareness to reflect the dynamic mental model of the driving environment and to be dependent upon several psychological processes including Scanning the driving environment, Predicting and anticipating hazards, Identifying potential hazards in the driving scene as they occur, Deciding on an action, and Executing an appropriate Response (SPIDER). Together, SPIDER is important for establishing and maintaining good situation awareness of the driving environment and good situation awareness is important for coordinating and scheduling the SPIDER-relevant processes necessary for safe driving. An Order-of-Processing (OP) model makes explicit the SPIDER-relevant processes and how they predict the likelihood of a crash when the driver is or is not distracted by a secondary task. For example, the OP model shows how a small decrease in the likelihood of any particular SPIDER activity being completed successfully (because of a concurrent secondary task performance) would lead to a large increase in the relative risk of a crash. PMID:24776225

  7. Association of vitamin D status with arterial blood pressure and hypertension risk: a mendelian randomisation study

    PubMed Central

    Vimaleswaran, Karani S; Cavadino, Alana; Berry, Diane J; Jorde, Rolf; Dieffenbach, Aida Karina; Lu, Chen; Alves, Alexessander Couto; Heerspink, Hiddo J Lambers; Tikkanen, Emmi; Eriksson, Joel; Wong, Andrew; Mangino, Massimo; Jablonski, Kathleen A; Nolte, Ilja M; Houston, Denise K; Ahluwalia, Tarunveer Singh; van der Most, Peter J; Pasko, Dorota; Zgaga, Lina; Thiering, Elisabeth; Vitart, Veronique; Fraser, Ross M; Huffman, Jennifer E; de Boer, Rudolf A; Schöttker, Ben; Saum, Kai-Uwe; McCarthy, Mark I; Dupuis, Josée; Herzig, Karl-Heinz; Sebert, Sylvain; Pouta, Anneli; Laitinen, Jaana; Kleber, Marcus E; Navis, Gerjan; Lorentzon, Mattias; Jameson, Karen; Arden, Nigel; Cooper, Jackie A; Acharya, Jayshree; Hardy, Rebecca; Raitakari, Olli; Ripatti, Samuli; Billings, Liana K; Lahti, Jari; Osmond, Clive; Penninx, Brenda W; Rejnmark, Lars; Lohman, Kurt K; Paternoster, Lavinia; Stolk, Ronald P; Hernandez, Dena G; Byberg, Liisa; Hagström, Emil; Melhus, Håkan; Ingelsson, Erik; Mellström, Dan; Ljunggren, Östen; Tzoulaki, Ioanna; McLachlan, Stela; Theodoratou, Evropi; Tiesler, Carla M T; Jula, Antti; Navarro, Pau; Wright, Alan F; Polasek, Ozren; Hayward, Caroline; Wilson, James F; Rudan, Igor; Salomaa, Veikko; Heinrich, Joachim; Campbell, Harry; Price, Jacqueline F; Karlsson, Magnus; Lind, Lars; Michaëlsson, Karl; Bandinelli, Stefania; Frayling, Timothy M; Hartman, Catharina A; Sørensen, Thorkild I A; Kritchevsky, Stephen B; Langdahl, Bente Lomholt; Eriksson, Johan G; Florez, Jose C; Spector, Tim D; Lehtimäki, Terho; Kuh, Diana; Humphries, Steve E; Cooper, Cyrus; Ohlsson, Claes; März, Winfried; de Borst, Martin H; Kumari, Meena; Kivimaki, Mika; Wang, Thomas J; Power, Chris; Brenner, Hermann; Grimnes, Guri; van der Harst, Pim; Snieder, Harold; Hingorani, Aroon D; Pilz, Stefan; Whittaker, John C; Järvelin, Marjo-Riitta; Hyppönen, Elina

    2015-01-01

    Summary Background Low plasma 25-hydroxyvitamin D (25[OH]D) concentration is associated with high arterial blood pressure and hypertension risk, but whether this association is causal is unknown. We used a mendelian randomisation approach to test whether 25(OH)D concentration is causally associated with blood pressure and hypertension risk. Methods In this mendelian randomisation study, we generated an allele score (25[OH]D synthesis score) based on variants of genes that affect 25(OH)D synthesis or substrate availability (CYP2R1 and DHCR7), which we used as a proxy for 25(OH)D concentration. We meta-analysed data for up to 108 173 individuals from 35 studies in the D-CarDia collaboration to investigate associations between the allele score and blood pressure measurements. We complemented these analyses with previously published summary statistics from the International Consortium on Blood Pressure (ICBP), the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) consortium, and the Global Blood Pressure Genetics (Global BPGen) consortium. Findings In phenotypic analyses (up to n=49 363), increased 25(OH)D concentration was associated with decreased systolic blood pressure (β per 10% increase, −0·12 mm Hg, 95% CI −0·20 to −0·04; p=0·003) and reduced odds of hypertension (odds ratio [OR] 0·98, 95% CI 0·97−0·99; p=0·0003), but not with decreased diastolic blood pressure (β per 10% increase, −0·02 mm Hg, −0·08 to 0·03; p=0·37). In meta-analyses in which we combined data from D-CarDia and the ICBP (n=146 581, after exclusion of overlapping studies), each 25(OH)D-increasing allele of the synthesis score was associated with a change of −0·10 mm Hg in systolic blood pressure (−0·21 to −0·0001; p=0·0498) and a change of −0·08 mm Hg in diastolic blood pressure (−0·15 to −0·02; p=0·01). When D-CarDia and consortia data for hypertension were meta-analysed together (n=142 255), the synthesis score was associated

  8. The effect of modifiable risk factors on geographic mortality differentials: a modelling study

    PubMed Central

    2012-01-01

    Background Australian mortality rates are higher in regional and remote areas than in major cities. The degree to which this is driven by variation in modifiable risk factors is unknown. Methods We applied a risk prediction equation incorporating smoking, cholesterol and blood pressure to a national, population based survey to project all-causes mortality risk by geographic region. We then modelled life expectancies at different levels of mortality risk by geographic region using a risk percentiles model. Finally we set high values of each risk factor to a target level and modelled the subsequent shift in the population to lower levels of mortality risk and longer life expectancy. Results Survival is poorer in both Inner Regional and Outer Regional/Remote areas compared to Major Cities for men and women at both high and low levels of predicted mortality risk. For men smoking, high cholesterol and high systolic blood pressure were each associated with the mortality difference between Major Cities and Outer Regional/Remote areas--accounting for 21.4%, 20.3% and 7.7% of the difference respectively. For women smoking and high cholesterol accounted for 29.4% and 24.0% of the difference respectively but high blood pressure did not contribute to the observed mortality differences. The three risk factors taken together accounted for 45.4% (men) and 35.6% (women) of the mortality difference. The contribution of risk factors to the corresponding differences for inner regional areas was smaller, with only high cholesterol and smoking contributing to the difference in men-- accounting for 8.8% and 6.3% respectively-- and only smoking contributing to the difference in women--accounting for 12.3%. Conclusions These results suggest that health intervention programs aimed at smoking, blood pressure and total cholesterol could have a substantial impact on mortality inequities for Outer Regional/Remote areas. PMID:22276576

  9. Risk Assessment of Physiological Effects of Atmospheric Composition and Pressure in Constellation Vehicles

    NASA Technical Reports Server (NTRS)

    Scheuring, Richard A.; Conkin, Johnny; Jones, Jeffrey A.; Gernhardt, Michael L.

    2007-01-01

    To reduce denitrogenation time to prevent decompression sickness to support frequent extravehicular activities on the Moon, and to limit the risk of fire, a hypobaric (P(sub B) = 414 mmHg) and mildly hypoxic (ppO2 = 132 mmHg, 32% O2 - 68% N2) living environment is being considered during lunar missions for the Crew Exploration Vehicle (CEV) and Lunar Surface Access Module (LSAM). If the vehicular ppO2 is acutely changed from 145-178 mmHg at standard vehicular operating pressure to less than 125 mmHg at desired lunar surface outpost operating pressures, there is the possibility that some crewmembers may develop symptoms of Acute Mountain Sickness (AMS). The signs and symptoms of AMS (headache plus nausea, dizziness, fatigue, or sleeplessness), could impact crew health and performance on lunar surface missions. Methods: An exhaustive literature review on the topic of the physiological effects of reduced ppO2 and absolute pressure as may contribute to the development of hypoxia and altitude symptoms or AMS. The results of the nine most rigorous studies were collated, analyzed and contents on the physiological concerns associated with hypobaric operations, AMS and hypoxia symptoms summarized. Results: Although space vehicles have operated in hypobaric conditions previously, they have not operated in a mildly hypoxic ppO2. There is evidence for an absolute pressure effect per se on AMS, such that the higher the altitude for a given hypoxic alveolar O2 partial pressure (P(sub A)O2), the greater the likelihood of an AMS response. About 25% of adults are likely to experience mild AMS near 2,000 m (xxx mmHg) altitude following a rapid ascent from sea level while breathing air (6,500 feet, acute (P(sub A)O2) = 75 mmHg). The operational experience with the Shuttle staged denitrogenation protocol at 528 mmHg (3,048 m) while breathing 26.5% O2 (acute (P(sub A)O2) = 85 mmHg) in astronauts adapting to microgravity suggests a similar likely experience in the proposed CEV

  10. Predictive power of the Braden scale for pressure sore risk in adult critical care patients: a comprehensive review.

    PubMed

    Cox, Jill

    2012-01-01

    Critical care is designed for managing the sickest patients within our healthcare system. Multiple factors associated with an increased likelihood of pressure ulcer development have been investigated in the critical care population. Nevertheless, there is a lack of consensus regarding which of these factors poses the greatest risk for pressure ulceration. While the Braden scale for pressure sore risk is the most commonly used tool for measuring pressure ulcer risk in the United States, research focusing on the cumulative Braden Scale score and subscale scores is lacking in the critical care population. This author conducted a literature review on pressure ulcer risk assessment in the critical care population, to include the predictive value of both the total score and the subscale scores. In this review, the subscales sensory perception, mobility, moisture, and friction/shear were found to be associated with an increased likelihood of pressure ulcer development; in contrast, the Activity and Nutrition subscales were not found to predict pressure ulcer development in this population. In order to more precisely quantify risk in the critically ill population, modification of the Braden scale or development of a critical care specific risk assessment tool may be indicated. PMID:22948495

  11. Risk-based inspection priorities for PWR high-pressure injection system components

    SciTech Connect

    Vo, T.V.; Simonen, F.A.; Phan, H.K. )

    1993-01-01

    Under U.S. Nuclear Regulatory Commission sponsorship, Pacific Northwest Laboratory developed a risk-based method that can be used to establish in-service inspection priorities for nuclear power plant components. The overall goal of this effort was to develop technical bases for improvements of inspection plans and to provide recommendations for revisions of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code, Sec. XI. The developed method used results of probabilistic risk assessment in combination with the failure modes and effects analysis (FMEA) technique to establish in-service inspection priorities for systems and components. The Surry nuclear power station, unit 1 (Surry-1) was selected for study. Inspection priorities for several pressure boundary systems at Surry-1 were determined in the early phase of the project. To complete the study, the remaining safety systems, plus balance of plant, have been analyzed; one of these is the high-pressure injection (HPI) system. This paper presents the results of inspection priorities for the HPI system.

  12. Reducing stroke in women with risk factor management: blood pressure and cholesterol.

    PubMed

    Baghshomali, Sanam; Bushnell, Cheryl

    2014-09-01

    Stroke is a major cause of death and disability in adults worldwide. Prevention focused on modifiable risk factors, such as hypertension and hyperlipidemia, has shown them to be of significant importance in decreasing the risk of stroke. Multiple studies have brought to light the differences between men and women with regards to stroke and these risk factors. Women have a higher prevalence of stroke, mortality and disability and it has been shown that preventive and treatment options are not as comprehensive for women. Hence, it is of great necessity to evaluate and summarize the differences in gender and stroke risk factors in order to target disparities and optimize prevention, especially because women have a higher lifetime risk of stroke. The purpose of this review is to summarize sex differences in the prevalence of hypertension and hyperlipidemia. In addition, we will review the sex differences in stroke prevention effectiveness and adherence to blood pressure and cholesterol medications, and suggest future directions for research to reduce the burden of stroke in women. PMID:25335544

  13. Discordance between ambulatory versus clinic blood pressure according to global cardiovascular risk group

    PubMed Central

    Shin, Jinho; Park, Sung Ha; Kim, Ju Han; Ihm, Sang Hyun; Kim, Kwang-il; Kim, Woo Shik; Pyun, Wook Bum; Kim, Yu-Mi; Choi, Sung-il; Kim, Soon Kil

    2015-01-01

    Background/Aims: The detection of white coat hypertension (WCH), treated normalized hypertension, and masked hypertension (MH) is important to improve the effectiveness of hypertension management. However, whether global cardiovascular risk (GCR) profile has any effect on the discordance between ambulatory blood pressure (ABP) and clinic blood pressure (CBP) is unknown. Methods: Data from 1,916 subjects, taken from the Korean Multicenter Registry for ABP monitoring, were grouped according to diagnostic and therapeutic thresholds for CBP and ABP (140/90 and 135/85 mmHg, respectively). GCR was assessed using European Society of Hypertension 2007 guidelines. Results: The mean subject age was 54.1 ± 14.9 years, and 48.9% of patients were female. The discordancy rate between ABP and CBP in the untreated and treated patients was 32.5% and 26.5%, respectively (p = 0.02). The prevalence of WCH or treated normalized hypertension and MH was 14.4% and 16.0%, respectively. Discordance between ABP and CBP was lower in the very high added-risk group compared to the moderate added-risk group (odds ratio [OR], 0.649; 95% confidence interval [CI], 0.487 to 0.863; p = 0.003). The prevalence of WCH or treated normalized hypertension was also lower in the very high added-risk group (OR, 0.451; 95% CI, 0.311 to 0.655). Conclusions: Discordance between ABP and CBP was observed more frequently in untreated subjects than in treated subjects, and less frequently in the very high added-risk group, which was due mainly to the lower prevalence of WCH or treated normalized hypertension. PMID:26354055

  14. Tantalum strength model incorporating temperature, strain rate and pressure

    NASA Astrophysics Data System (ADS)

    Lim, Hojun; Battaile, Corbett; Brown, Justin; Lane, Matt

    Tantalum is a body-centered-cubic (BCC) refractory metal that is widely used in many applications in high temperature, strain rate and pressure environments. In this work, we propose a physically-based strength model for tantalum that incorporates effects of temperature, strain rate and pressure. A constitutive model for single crystal tantalum is developed based on dislocation kink-pair theory, and calibrated to measurements on single crystal specimens. The model is then used to predict deformations of single- and polycrystalline tantalum. In addition, the proposed strength model is implemented into Sandia's ALEGRA solid dynamics code to predict plastic deformations of tantalum in engineering-scale applications at extreme conditions, e.g. Taylor impact tests and Z machine's high pressure ramp compression tests, and the results are compared with available experimental data. Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  15. Central hemodynamics in risk assessment strategies: additive value over and above brachial blood pressure.

    PubMed

    Yannoutsos, Alexandra; Rinaldi, Elisa R; Zhang, Yi; Protogerou, Athanassios D; Safar, Michel E; Blacher, Jacques

    2015-01-01

    Although the clinical relevance of brachial blood pressure (BP) measurement for cardiovascular (CV) risk stratification is nowadays widely accepted, this approach can nevertheless present several limitations. Pulse pressure (PP) amplification accounts for the notable increase in PP from central to peripheral arterial sites. Target organs are more greatly exposed to central hemodynamic changes than peripheral organs. The pathophysiological significance of local BP pulsatility, which has a role in the pathogenesis of target organ damage in both the macro- and the microcirculation, may therefore not be accurately captured by brachial BP as traditionally evaluated with cuff measurements. The predictive value of central systolic BP and PP over brachial BP for major clinical outcomes has been demonstrated in the general population, in elderly adults and in patients at high CV risk, irrespective of the invasive or non-invasive methods used to assess central BP. Aortic stiffness, timing and intensity of wave reflections, and cardiac performance appear as major factors influencing central PP. Great emphasis has been placed on the role of aortic stiffness, disturbed arterial wave reflections and their intercorrelation in the pathophysiological mechanisms of CV diseases as well as on their capacity to predict target organ damage and clinical events. Comorbidities and age-related changes, together with gender-related specificities of arterial and cardiac parameters, are known to affect the predictive ability of central hemodynamics on individual CV risk. PMID:25341861

  16. Identity development as a buffer of adolescent risk behaviors in the context of peer group pressure and control.

    PubMed

    Dumas, Tara M; Ellis, Wendy E; Wolfe, David A

    2012-08-01

    We examined identity development as a moderator of the relation between peer group pressure and control and adolescents' engagement in risk behaviors. Participants (n=1070; M(age)=15.45 years) completed a self-report measure of identity exploration, the degree to which they have explored a variety of self-relevant values, beliefs and goals, and identity commitment, the degree to which they have secured a personal identity. Participants further reported on their frequency of risk behaviors (substance use and general deviancy) and experienced peer group pressure and control. Results confirmed that identity commitment was a buffer of substance use and identity exploration was a buffer of general deviancy in more pressuring peer groups. In more controlling peer groups, teens with greater identity commitment engaged in less risk behavior than teens with low-identity commitment. Thus, identity development may be a suitable target to deter negative effects of peer pressure in high-risk adolescents. PMID:22265669

  17. Vibrational properties of model monatomic crystals under pressure

    NASA Astrophysics Data System (ADS)

    Wolf, George H.; Jeanloz, Raymond

    1985-12-01

    The roles of the attractive and repulsive forces in controlling the vibrational properties of monatomic crystals are systematically evaluated as a function of compression. Face-centered-cubic, hexagonal, and body-centered-cubic structures are considered with Lennard-Jones and Buckingham-type interatomic potentials. At zero pressure, the phonon frequencies and their mode-Grüneisen parameters deviate strongly from those of a reference state where the atoms interact solely through the corresponding purely repulsive potential. In detail, the degree of deviation depends on the structure, relative range of the repulsive and attractive forces, and the vibrational wavelength. With increasing pressure, the phonon frequencies asymptotically approach values of the purely repulsive reference state. Higher-order properties such as the mode-Grüneisen parameters and their logarithmic volume derivatives approach the repulsive limiting values more rapidly than do the frequencies, provided the associated modes do not become unstable. The close-packed lattices are dynamically stable at all positive pressures and display only a small variation among different orders of the frequency spectra Debye moments. However, this variation can be quite large for any structure at strains near that where the lattice is dynamically unstable. We find that the thermal Grüneisen parameter decreases with pressure, but the commonly assumed power-law relation of the thermal Grüneisen parameter with volume is violated. Average anharmonic vibrational properties are well described by a cell model in these monatomic systems at both low and high pressures. In addition, a strong correlation is found between the static-lattice compressional properties and the average vibrational properties; free-volume relations give good estimates of the high-temperature thermal properties, especially at high pressures.

  18. Post-extrasystolic Blood Pressure Potentiation as a Risk Predictor in Cardiac Patients

    PubMed Central

    Steger, Alexander; Sinnecker, Daniel; Barthel, Petra; Müller, Alexander; Gebhardt, Josef; Schmidt, Georg

    2016-01-01

    For more than 100 years physicians have observed that heartbeats following extrasystolic beats are characterised by augmented myocardial contractility. This phenomenon was termed post-extrasystolic potentiation (PESP). In the 1970s it was first noted that PESP measured at the blood pressure level is typically pronounced in heart failure patients. Only recently, it was shown that PESP measured non-invasively as post-extrasystolic blood pressure potentiation was a strong and independent predictor of death in survivors of myocardial infarction and in patients with chronic heart failure. A similar parameter (PESPAfib) can be also assessed in patients with atrial fibrillation. PESP and PESPAfib can be understood as non-invasive parameters that indicate myocardial dysfunction. They have the potential to improve risk stratification strategies for cardiac patients. PMID:27403290

  19. A hybrid likelihood algorithm for risk modelling.

    PubMed

    Kellerer, A M; Kreisheimer, M; Chmelevsky, D; Barclay, D

    1995-03-01

    The risk of radiation-induced cancer is assessed through the follow-up of large cohorts, such as atomic bomb survivors or underground miners who have been occupationally exposed to radon and its decay products. The models relate to the dose, age and time dependence of the excess tumour rates, and they contain parameters that are estimated in terms of maximum likelihood computations. The computations are performed with the software package EPI-CURE, which contains the two main options of person-by person regression or of Poisson regression with grouped data. The Poisson regression is most frequently employed, but there are certain models that require an excessive number of cells when grouped data are used. One example involves computations that account explicitly for the temporal distribution of continuous exposures, as they occur with underground miners. In past work such models had to be approximated, but it is shown here that they can be treated explicitly in a suitably reformulated person-by person computation of the likelihood. The algorithm uses the familiar partitioning of the log-likelihood into two terms, L1 and L0. The first term, L1, represents the contribution of the 'events' (tumours). It needs to be evaluated in the usual way, but constitutes no computational problem. The second term, L0, represents the event-free periods of observation. It is, in its usual form, unmanageable for large cohorts. However, it can be reduced to a simple form, in which the number of computational steps is independent of cohort size. The method requires less computing time and computer memory, but more importantly it leads to more stable numerical results by obviating the need for grouping the data. The algorithm may be most relevant to radiation risk modelling, but it can facilitate the modelling of failure-time data in general. PMID:7604154

  20. Highly physical penumbra solar radiation pressure modeling with atmospheric effects

    NASA Astrophysics Data System (ADS)

    Robertson, Robert; Flury, Jakob; Bandikova, Tamara; Schilling, Manuel

    2015-10-01

    We present a new method for highly physical solar radiation pressure (SRP) modeling in Earth's penumbra. The fundamental geometry and approach mirrors past work, where the solar radiation field is modeled using a number of light rays, rather than treating the Sun as a single point source. However, we aim to clarify this approach, simplify its implementation, and model previously overlooked factors. The complex geometries involved in modeling penumbra solar radiation fields are described in a more intuitive and complete way to simplify implementation. Atmospheric effects are tabulated to significantly reduce computational cost. We present new, more efficient and accurate approaches to modeling atmospheric effects which allow us to consider the high spatial and temporal variability in lower atmospheric conditions. Modeled penumbra SRP accelerations for the Gravity Recovery and Climate Experiment (GRACE) satellites are compared to the sub-nm/s2 precision GRACE accelerometer data. Comparisons to accelerometer data and a traditional penumbra SRP model illustrate the improved accuracy which our methods provide. Sensitivity analyses illustrate the significance of various atmospheric parameters and modeled effects on penumbra SRP. While this model is more complex than a traditional penumbra SRP model, we demonstrate its utility and propose that a highly physical model which considers atmospheric effects should be the basis for any simplified approach to penumbra SRP modeling.

  1. Can Ambulatory Blood Pressure Variability Contribute to Individual Cardiovascular Risk Stratification?

    PubMed

    Magdás, Annamária; Szilágyi, László; Incze, Alexandru

    2016-01-01

    Objective. The aim of this study is to define the normal range for average real variability (ARV) and to establish whether it can be considered as an additional cardiovascular risk factor. Methods. In this observational study, 110 treated hypertensive patients were included and admitted for antihypertensive treatment adjustment. Circadian blood pressure was recorded with validated devices. Blood pressure variability (BPV) was assessed according to the ARV definition. Based on their variability, patients were classified into low, medium, and high variability groups using the fuzzy c-means algorithm. To assess cardiovascular risk, blood samples were collected. Characteristics of the groups were compared by ANOVA tests. Results. Low variability was defined as ARV below 9.8 mmHg (32 patients), medium as 9.8-12.8 mmHg (48 patients), and high variability above 12.8 mmHg (30 patients). Mean systolic blood pressure was 131.2 ± 16.7, 135.0 ± 12.1, and 141.5 ± 11.4 mmHg in the low, medium, and high variability groups, respectively (p = 0.0113). Glomerular filtration rate was 78.6 ± 29.3, 74.8 ± 26.4, and 62.7 ± 23.2 mL/min/1.73 m(2) in the low, medium, and high variability groups, respectively (p = 0.0261). Conclusion. Increased values of average real variability represent an additional cardiovascular risk factor. Therefore, reducing BP variability might be as important as achieving optimal BP levels, but there is need for further studies to define a widely acceptable threshold value. PMID:27247614

  2. Can Ambulatory Blood Pressure Variability Contribute to Individual Cardiovascular Risk Stratification?

    PubMed Central

    Magdás, Annamária; Szilágyi, László; Incze, Alexandru

    2016-01-01

    Objective. The aim of this study is to define the normal range for average real variability (ARV) and to establish whether it can be considered as an additional cardiovascular risk factor. Methods. In this observational study, 110 treated hypertensive patients were included and admitted for antihypertensive treatment adjustment. Circadian blood pressure was recorded with validated devices. Blood pressure variability (BPV) was assessed according to the ARV definition. Based on their variability, patients were classified into low, medium, and high variability groups using the fuzzy c-means algorithm. To assess cardiovascular risk, blood samples were collected. Characteristics of the groups were compared by ANOVA tests. Results. Low variability was defined as ARV below 9.8 mmHg (32 patients), medium as 9.8–12.8 mmHg (48 patients), and high variability above 12.8 mmHg (30 patients). Mean systolic blood pressure was 131.2 ± 16.7, 135.0 ± 12.1, and 141.5 ± 11.4 mmHg in the low, medium, and high variability groups, respectively (p = 0.0113). Glomerular filtration rate was 78.6 ± 29.3, 74.8 ± 26.4, and 62.7 ± 23.2 mL/min/1.73 m2 in the low, medium, and high variability groups, respectively (p = 0.0261). Conclusion. Increased values of average real variability represent an additional cardiovascular risk factor. Therefore, reducing BP variability might be as important as achieving optimal BP levels, but there is need for further studies to define a widely acceptable threshold value. PMID:27247614

  3. Modeling plasma pressure anisotropy's effect on Saturn's global magnetospheric dynamics

    NASA Astrophysics Data System (ADS)

    Tilley, M.; Harnett, E. M.; Winglee, R.

    2014-12-01

    A 3D multi-fluid, multi-scale plasma model with a complete treatment of plasma pressure anisotropy is employed to study global magnetospheric dynamics at Saturn. Cassini has observed anisotropies in the Saturnian magnetosphere, and analyses have showed correlations between anisotropy and plasma convection, ring current structure and intensity, confinement of plasma to the equatorial plane, as well as mass transport to the outer magnetosphere. The energization and transport of plasma within Saturn's magnetosphere is impactful upon the induced magnetic environments and atmospheres of potentially habitable satellites such as Enceladus and Titan. Recent efforts to couple pressure anisotropy with 3D multi-fluid plasma modeling have shown a significant move towards matching observations for simulations of Earth's magnetosphere. Our approach is used to study the effects of plasma pressure anisotropy on global processes of the Saturnian magnetosphere such as identifying the effect of pressure anisotropy on the centrifugal interchange instability. Previous simulation results have not completely replicated all aspects of the structure and formation of the interchange 'fingers' measured by Cassini at Saturn. The related effects of anisotropy, in addition to those mentioned above, include contribution to formation of MHD waves (e.g. reduction of Alfvén wave speed) and formation of firehose and mirror instabilities. An accurate understanding of processes such as the interchange instability is required if a complete picture of mass and energy transport at Saturn is to be realized. The results presented here will detail how the inclusion of a full treatment of pressure anisotropy for idealized solar wind conditions modifies the interchange structure and shape of the tail current sheet. Simulation results are compared to observations made by Cassini.

  4. Modelling of the pressure-velocity correlation in turbulence diffusion

    NASA Astrophysics Data System (ADS)

    Fu, Song

    1993-05-01

    In the context of second-moment closure, the mechanism of turbulence diffusion consists of mainly two parts: a triple velocity correlation and a pressure-velocity correlation. The first correlation is measurable and can be analyzed theoretically through its transport equation. The second correlation cannot, however, be obtained directly from experiments and knowledge about it is comparatively limited. Most current computations of turbulent flows adopt diffusion models which neglect the effect of the pressure-velocity correlation in the diffusion process. The importance of this correlation effect is elucidated; the neglect of this effect constitutes some of the major defects in the application of the second-moment closures. Through the relation between the two correlations, established by Lumley (1978), we propose a new type of turbulence diffusion model which takes into account the pressure effect. Application of this new model in the computation of the turbulence shearless mixing layer and plane- and round-jet flows shows that the spreading rates of these flows can be captured satisfactorily.

  5. Models of pressure compaction and their application for wheat meal

    NASA Astrophysics Data System (ADS)

    Skonecki, Stanisław; Kulig, Ryszard; Łysiak, Grzegorz

    2014-03-01

    Processes of compaction of granular materials were described using selected models. The analysis of their accuracy on the example of wheat was the basis for the discussion on their applicability to the processing of plant-origin materials. Parameters of the model equations for wheat, compressed at 10-18% moisture content were calculated, and the relations between these parameters and wheat moisture were determined. It was found that the analyzed models described the pressure compaction of granular plant material with different accuracy, and were highly dependent on moisture. The study also indicated that the model of Ferrero et al. fits the experimental results well. The parameters of this model reflected very well the physical phenomena which occur during compression.

  6. Galileo's relativity principle, the concept of pressure, and complex characteristics, for the six-equation, one-pressure model

    SciTech Connect

    Makowitz, H.

    1992-10-01

    We have studied various formulations of the concept of pressure, in the context of the usual Six-Equation Model of thermal-hydraulics. A different concept of pressure, than the usual one, has been used. This new pressure concept is Galilean Invariant, and results for the One-Pressure Model with the same complex characteristic roots as the Basic III-Posed Model,'' discussed in the literature for the cases we have investigated. We have also examined several Two-Pressure formulations and shown that two pressures are a necessary but not sufficient condition for obtaining a Well-Posed system. Several counter examples are presented. We have shown that the standard theory is not Galilean Invariant and suggested that the origin of III-Posedness is due to our closure relationships. We also question whether the current theory can satisfy conservation principles for mass, energy, and momentum.

  7. Modeling of formation of extended NH solids under high pressure

    NASA Astrophysics Data System (ADS)

    Batyrev, Iskander G.

    Structure of N-H extended network under high pressure was modelled using the evolutionary algorithm program USPEX based on plane wave DFT calculations (VASP). Concentration ratio of N2 to H2 gases was 3:1, 4:1, and 9:1. Range of the studied pressures was 10 - 50 GPa on compression, and from 50 to 1 GPa on isotropic decompression of the extended network. Formation of an extended network with covalent bonds occurs between 30-50 GPa. Higher concentration of N requires higher pressure to form a covalent bond network. New structure of NH extended solids with covalent bonds are predicted: with P-1(CI-1) symmetry group for 9:1 ratio, with PBAM (D2H +9) symmetry group for 4:1 ratio, and with P-1(CI-1) for 3:1 ratio of N2 to H2 gas. Calculations of the mixtures of N2 and H2 gases at pressures in the range of 10-20 GPa resulted in a variety of structures without a covalent network, but consisting of nitrogen-containing molecules. For example, the lowest energy structure for a 3:1 ratio of N to H atoms consists of tetrazene and N2 molecules. At 10 GPa the lowest energy structure appears to be a combination of protonated ammonia and N2 molecules.

  8. Automating Risk Analysis of Software Design Models

    PubMed Central

    Ruiz, Guifré; Heymann, Elisa; César, Eduardo; Miller, Barton P.

    2014-01-01

    The growth of the internet and networked systems has exposed software to an increased amount of security threats. One of the responses from software developers to these threats is the introduction of security activities in the software development lifecycle. This paper describes an approach to reduce the need for costly human expertise to perform risk analysis in software, which is common in secure development methodologies, by automating threat modeling. Reducing the dependency on security experts aims at reducing the cost of secure development by allowing non-security-aware developers to apply secure development with little to no additional cost, making secure development more accessible. To automate threat modeling two data structures are introduced, identification trees and mitigation trees, to identify threats in software designs and advise mitigation techniques, while taking into account specification requirements and cost concerns. These are the components of our model for automated threat modeling, AutSEC. We validated AutSEC by implementing it in a tool based on data flow diagrams, from the Microsoft security development methodology, and applying it to VOMS, a grid middleware component, to evaluate our model's performance. PMID:25136688

  9. Automating risk analysis of software design models.

    PubMed

    Frydman, Maxime; Ruiz, Guifré; Heymann, Elisa; César, Eduardo; Miller, Barton P

    2014-01-01

    The growth of the internet and networked systems has exposed software to an increased amount of security threats. One of the responses from software developers to these threats is the introduction of security activities in the software development lifecycle. This paper describes an approach to reduce the need for costly human expertise to perform risk analysis in software, which is common in secure development methodologies, by automating threat modeling. Reducing the dependency on security experts aims at reducing the cost of secure development by allowing non-security-aware developers to apply secure development with little to no additional cost, making secure development more accessible. To automate threat modeling two data structures are introduced, identification trees and mitigation trees, to identify threats in software designs and advise mitigation techniques, while taking into account specification requirements and cost concerns. These are the components of our model for automated threat modeling, AutSEC. We validated AutSEC by implementing it in a tool based on data flow diagrams, from the Microsoft security development methodology, and applying it to VOMS, a grid middleware component, to evaluate our model's performance. PMID:25136688

  10. Extreme Earthquake Risk Estimation by Hybrid Modeling

    NASA Astrophysics Data System (ADS)

    Chavez, M.; Cabrera, E.; Ashworth, M.; Garcia, S.; Emerson, D.; Perea, N.; Salazar, A.; Moulinec, C.

    2012-12-01

    The estimation of the hazard and the economical consequences i.e. the risk associated to the occurrence of extreme magnitude earthquakes in the neighborhood of urban or lifeline infrastructure, such as the 11 March 2011 Mw 9, Tohoku, Japan, represents a complex challenge as it involves the propagation of seismic waves in large volumes of the earth crust, from unusually large seismic source ruptures up to the infrastructure location. The large number of casualties and huge economic losses observed for those earthquakes, some of which have a frequency of occurrence of hundreds or thousands of years, calls for the development of new paradigms and methodologies in order to generate better estimates, both of the seismic hazard, as well as of its consequences, and if possible, to estimate the probability distributions of their ground intensities and of their economical impacts (direct and indirect losses), this in order to implement technological and economical policies to mitigate and reduce, as much as possible, the mentioned consequences. Herewith, we propose a hybrid modeling which uses 3D seismic wave propagation (3DWP) and neural network (NN) modeling in order to estimate the seismic risk of extreme earthquakes. The 3DWP modeling is achieved by using a 3D finite difference code run in the ~100 thousands cores Blue Gene Q supercomputer of the STFC Daresbury Laboratory of UK, combined with empirical Green function (EGF) techniques and NN algorithms. In particular the 3DWP is used to generate broadband samples of the 3D wave propagation of extreme earthquakes (plausible) scenarios corresponding to synthetic seismic sources and to enlarge those samples by using feed-forward NN. We present the results of the validation of the proposed hybrid modeling for Mw 8 subduction events, and show examples of its application for the estimation of the hazard and the economical consequences, for extreme Mw 8.5 subduction earthquake scenarios with seismic sources in the Mexican