Reducing Undue Conservatism in "Higher Frequency" Structural Design Loads in Aerospace Components

NASA Technical Reports Server (NTRS)

Knight, J. Brent

2012-01-01

This study is intended to investigate the frequency dependency of significant strain due to vibratory loads in aerospace vehicle components. The notion that "higher frequency" dynamic loads applied as static loads is inherently conservative is perceived as widely accepted. This effort is focused on demonstrating that principle and attempting to evolve methods to capitalize on it to mitigate undue conservatism. It has been suggested that observations of higher frequency modes that resulted in very low corresponding strain did so due to those modes not being significant. Two avionics boxes, one with its first significant mode at 341 Hz and the other at 857 Hz, were attached to a flat panel installed on a curved orthogrid panel which was driven acoustically in tests performed at NASA/MSFC. Strain and acceleration were measured at select locations on each of the boxes. When possible, strain gage rosettes and accelerometers were installed on either side of a given structural member so that measured strain and acceleration data would directly correspond to one another. Ultimately, a frequency above which vibratory loads can be disregarded for purposes of static structural analyses and sizing of typical robust aerospace components is sought.

Characterization of Elastic-plastic Material Properties for IMC Layer of ENEPIG by Using Reverse Algorithm

NASA Astrophysics Data System (ADS)

Kim, Jong-Min; Lee, Hyun-Boo; Chang, Yoon-Suk; Choi, Jae-Boong; Kim, Young-Jin; Ji, Kum-Young

2010-05-01

Recently, the reliability assurance of lead-free solder to prevent environmental contamination is quite important issue for chip-scale packaging. Although lots of efforts have been devoted to the solder undergone drop, shear and creep loads, there was a little research on IMC due primarily to its thickness restriction and geometric irregularity. However, the IMC is known as the weakest layer governing failures of the solder joint. The present work is to characterize realistic material properties of the IMC for ENEPIG process. Lee's modified reverse algorithm was adopted to determine elastic-plastic stress-strain curve and so forth, after examining several methods, which requires inherently elastic data. In this context, a series of nano-indentation tests as well as corresponding simulations were carried out by changing indentation depths from 200 to 400 nm and strain rates from 0.05 to 0.10 1/s. It would be conclude that effect of strain rate is relatively small and IMC layer should be more than 5 times of indentation depth when using the recommended method, which are applicable to generate realistic material properties for further diverse structural integrity simulations.

Investigating the Strain, Temperature and Humidity Sensitivity of a Multimode Graded-Index Perfluorinated Polymer Optical Fiber with Bragg Grating

PubMed Central

Zheng, Yulong; Bremer, Kort

2018-01-01

In this work we investigate the strain, temperature and humidity sensitivity of a Fiber Bragg Grating (FBG) inscribed in a near infrared low-loss multimode perfluorinated polymer optical fiber based on cyclic transparent optical polymer (CYTOP). For this purpose, FBGs were inscribed into the multimode CYTOP fiber with a core diameter of 50 µm by using a krypton fluoride (KrF) excimer laser and the phase mask method. The evolution of the reflection spectrum of the FBG detected with a multimode interrogation technique revealed a single reflection peak with a full width at half maximum (FHWM) bandwidth of about 9 nm. Furthermore, the spectral envelope of the single FBG reflection peak can be optimized depending on the KrF excimer laser irradiation time. A linear shift of the Bragg wavelength due to applied strain, temperature and humidity was measured. Furthermore, depending on irradiation time of the KrF excimer laser, both the failure strain and strain sensitivity of the multimode fiber with FBG can be controlled. The inherent low light attenuation in the near infrared wavelength range (telecommunication window) of the multimode CYTOP fiber and the single FBG reflection peak when applying the multimode interrogation set-up will allow for new applications in the area of telecommunication and optical sensing. PMID:29734734

Investigating the Strain, Temperature and Humidity Sensitivity of a Multimode Graded-Index Perfluorinated Polymer Optical Fiber with Bragg Grating.

PubMed

Zheng, Yulong; Bremer, Kort; Roth, Bernhard

2018-05-05

In this work we investigate the strain, temperature and humidity sensitivity of a Fiber Bragg Grating (FBG) inscribed in a near infrared low-loss multimode perfluorinated polymer optical fiber based on cyclic transparent optical polymer (CYTOP). For this purpose, FBGs were inscribed into the multimode CYTOP fiber with a core diameter of 50 µm by using a krypton fluoride (KrF) excimer laser and the phase mask method. The evolution of the reflection spectrum of the FBG detected with a multimode interrogation technique revealed a single reflection peak with a full width at half maximum (FHWM) bandwidth of about 9 nm. Furthermore, the spectral envelope of the single FBG reflection peak can be optimized depending on the KrF excimer laser irradiation time. A linear shift of the Bragg wavelength due to applied strain, temperature and humidity was measured. Furthermore, depending on irradiation time of the KrF excimer laser, both the failure strain and strain sensitivity of the multimode fiber with FBG can be controlled. The inherent low light attenuation in the near infrared wavelength range (telecommunication window) of the multimode CYTOP fiber and the single FBG reflection peak when applying the multimode interrogation set-up will allow for new applications in the area of telecommunication and optical sensing.

Plant-Based Assessment of Inherent Soil Productivity and Contributions to China’s Cereal Crop Yield Increase since 1980

PubMed Central

Fan, Mingsheng; Lal, Rattan; Cao, Jian; Qiao, Lei; Su, Yansen; Jiang, Rongfeng; Zhang, Fusuo

2013-01-01

Objective China’s food production has increased 6-fold during the past half-century, thanks to increased yields resulting from the management intensification, accomplished through greater inputs of fertilizer, water, new crop strains, and other Green Revolution’s technologies. Yet, changes in underlying quality of soils and their effects on yield increase remain to be determined. Here, we provide a first attempt to quantify historical changes in inherent soil productivity and their contributions to the increase in yield. Methods The assessment was conducted based on data-set derived from 7410 on-farm trials, 8 long-term experiments and an inventory of soil organic matter concentrations of arable land. Results Results show that even without organic and inorganic fertilizer addition crop yield from on-farm trials conducted in the 2000s was significantly higher compared with those in the 1980s — the increase ranged from 0.73 to 1.76 Mg/ha for China’s major irrigated cereal-based cropping systems. The increase in on-farm yield in control plot since 1980s was due primarily to the enhancement of soil-related factors, and reflected inherent soil productivity improvement. The latter led to higher and stable yield with adoption of improved management practices, and contributed 43% to the increase in yield for wheat and 22% for maize in the north China, and, 31%, 35% and 22% for early and late rice in south China and for single rice crop in the Yangtze River Basin since 1980. Conclusions Thus, without an improvement in inherent soil productivity, the ‘Agricultural Miracle in China’ would not have happened. A comprehensive strategy of inherent soil productivity improvement in China, accomplished through combining engineering-based measures with biological-approaches, may be an important lesson for the developing world. We propose that advancing food security in 21st century for both China and other parts of world will depend on continuously improving inherent soil productivity. PMID:24058605

Essential features of residual stress determination in thin-walled plane structures in a base of whole field interferometric measurements

NASA Astrophysics Data System (ADS)

Pisarev, Vladimir S.; Odintsev, I.; Balalov, V.; Apalkov, A.

2003-05-01

Sophisticated technique for reliable quantitative deriving residual stress values from initial experimental data, which are inherent in combined implementing the hole drilling method with both holographic and speckle interferometry, is described in detail. The approach developed includes both possible ways of obtaining initial experimental information. The first of them consists of recording a set of required interference fringe patterns, which are resulted from residual stress energy release after through hole drilling, in two orthogonal directions that coincide with principal strain directions. The second way is obtaining a series of interrelated fringe patterns when a direction of either observation in reflection hologram interferometry or dual-beam illumination in speckle interferometry lies arbitrary with respect to definite principal strain direction. A set of the most typical both actual and analogous reference fringe patterns, which are related to both reflection hologram and dual-beam speckle interferometry, are presented.

Effects of Annealing Process on the Formability of Friction Stir Welded Al-Li Alloy 2195 Plates

NASA Technical Reports Server (NTRS)

Chen, Po-Shou; Bradford, Vann; Russell, Carolyn

2011-01-01

Large rocket cryogenic tank domes have typically been fabricated using Al-Cu based alloys like Al-Cu alloy 2219. The use of aluminum-lithium based alloys for rocket fuel tank domes can reduce weight because aluminum-lithium alloys have lower density and higher strength than Al-Cu alloy 2219. However, Al-Li alloys have rarely been used to fabricate rocket fuel tank domes because of the inherent low formability characteristic that make them susceptible to cracking during the forming operations. The ability to form metal by stretch forming or spin forming without excessive thinning or necking depends on the strain hardening exponent "n". The stain hardening exponent is a measure of how rapidly a metal becomes stronger and harder. A high strain hardening exponent is beneficial to a material's ability to uniformly distribute the imposed strain. Marshall Space Flight Center has developed a novel annealing process that can achieve a work hardening exponent on the order of 0.27 to 0.29, which is approximately 50% higher than what is typically obtained for Al-Li alloys using the conventional method. The strain hardening exponent of the Al-Li alloy plates or blanks heat treated using the conventional method is typically on the order of 0.17 to 0.19. The effects of this novel annealing process on the formability of friction stir welded Al-Li alloy blanks are being studied at Marshall Space Flight Center. The formability ratings will be generated using the strain hardening exponent, strain rate sensitivity and forming range. The effects of forming temperature on the formability will also be studied. The objective of this work is to study the deformation behavior of the friction stir welded Al-Li alloy 2195 blank and determine the formability enhancement by the new annealing process.

Analysis of residual transverse stresses in a thick UD glass/polyester pultruded profile using hole drilling with strain gage and digital image correlation

NASA Astrophysics Data System (ADS)

Yuksel, Onur; Baran, Ismet; Ersoy, Nuri; Akkerman, Remko

2018-05-01

Process induced stresses inherently exist in fiber reinforced polymer composites particularly in thick parts due to the presence of non-uniform cure, shrinkage and thermal expansion/contraction during manufacturing. In order to increase the reliability and the performance of the composite materials, process models are developed to predict the residual stress formation. The accuracy of the process models is dependent on the geometrical (micro to macro), material and process parameters as well as the numerical implementation. Therefore, in order to have reliable process modelling framework, there is a need for validation and if necessary calibration of the developed models. This study focuses on measurement of the transverse residual stresses in a relatively thick pultruded profile (20×20 mm) made of glass/polyester. Process-induced residual stresses in the middle of the profile are examined with different techniques which have never been applied for transverse residual stresses in thick unidirectional composites. Hole drilling method with strain gage and digital image correlation are employed. Strain values measured from measurements are used in a finite element model (FEM) to simulate the hole drilling process and predict the residual stress level. The measured released strain is found to be approximately 180 μm/m from the strain gage. The tensile residual stress at the core of the profile is estimated approximately as 7-10 MPa. Proposed methods and measured values in this study will enable validation and calibration of the process models based on the residual stresses.

High-temperature Strain Sensor and Mounting Development

NASA Technical Reports Server (NTRS)

Williams, W. Dan; Lei, Jih-Fen; Reardon, Lawrence F.; Krake, Keith; Lemcoe, M. M.; Holmes, Harlan K.; Moore, Thomas C., Sr.

1996-01-01

This report describes Government Work Package Task 29 (GWP29), whose purpose was to develop advanced strain gage technology in support of the National Aerospace Plane (NASP) Program. The focus was on advanced resistance strain gages with a temperature range from room temperature to 2000 F (1095 C) and on methods for reliably attaching these gages to the various materials anticipated for use in the NASP program. Because the NASP program required first-cycle data, the installed gages were not prestabilized or heat treated on the test coupons before first-cycle data were recorded. NASA Lewis Research Center, the lead center for GWP29, continued its development of the palladium-chromium gage; NASA Langley Research Center investigated a new concept gage using Kanthal A1; and the NASA Dryden Flight Research Center chose the well-known BCL-3 iron-chromium-aluminum gage. Each center then tested all three gages. The parameters investigated were apparent strain, drift strain, and gage factor as a function of temperature, plus gage size and survival rate over the test period. Although a significant effort was made to minimize the differences in test equipment between the three test sites (e.g., the same hardware and software were used for final data processing), the center employed different data acquisition systems and furnace configurations so that some inherent differences may be evident in the final results.

The gravitational wave strain in the characteristic formalism of numerical relativity

NASA Astrophysics Data System (ADS)

Bishop, Nigel T.; Reisswig, Christian

2014-01-01

The extraction of the gravitational wave signal, within the context of a characteristic numerical evolution is revisited. A formula for the gravitational wave strain is developed and tested, and is made publicly available as part of the PITT code within the Einstein Toolkit. Using the new strain formula, we show that artificial non-linear drifts inherent in time integrated waveforms can be reduced for the case of a binary black hole merger configuration. For the test case of a rapidly spinning stellar core collapse model, however, we find that the drift must have different roots.

Discerning strain effects in microbial dose-response data.

PubMed

Coleman, Margaret E; Marks, Harry M; Golden, Neal J; Latimer, Heejeong K

In order to estimate the risk or probability of adverse events in risk assessment, it is necessary to identify the important variables that contribute to the risk and provide descriptions of distributions of these variables for well-defined populations. One component of modeling dose response that can create uncertainty is the inherent genetic variability among pathogenic bacteria. For many microbial risk assessments, the "default" assumption used for dose response does not account for strain or serotype variability in pathogenicity and virulence, other than perhaps, recognizing the existence of avirulent strains. However, an examination of data sets from human clinical trials in which Salmonella spp. and Campylobacter jejuni strains were administered reveals significant strain differences. This article discusses the evidence for strain variability and concludes that more biologically based alternatives are necessary to replace the default assumptions commonly used in microbial risk assessment, specifically regarding strain variability.

Discrete-element modeling of nacre-like materials: Effects of random microstructures on strain localization and mechanical performance

NASA Astrophysics Data System (ADS)

Abid, Najmul; Mirkhalaf, Mohammad; Barthelat, Francois

2018-03-01

Natural materials such as nacre, collagen, and spider silk are composed of staggered stiff and strong inclusions in a softer matrix. This type of hybrid microstructure results in remarkable combinations of stiffness, strength, and toughness and it now inspires novel classes of high-performance composites. However, the analytical and numerical approaches used to predict and optimize the mechanics of staggered composites often neglect statistical variations and inhomogeneities, which may have significant impacts on modulus, strength, and toughness. Here we present an analysis of localization using small representative volume elements (RVEs) and large scale statistical volume elements (SVEs) based on the discrete element method (DEM). DEM is an efficient numerical method which enabled the evaluation of more than 10,000 microstructures in this study, each including about 5,000 inclusions. The models explore the combined effects of statistics, inclusion arrangement, and interface properties. We find that statistical variations have a negative effect on all properties, in particular on the ductility and energy absorption because randomness precipitates the localization of deformations. However, the results also show that the negative effects of random microstructures can be offset by interfaces with large strain at failure accompanied by strain hardening. More specifically, this quantitative study reveals an optimal range of interface properties where the interfaces are the most effective at delaying localization. These findings show how carefully designed interfaces in bioinspired staggered composites can offset the negative effects of microstructural randomness, which is inherent to most current fabrication methods.

Full-scale investigation of wind-induced vibrations of mast-arm traffic signal structures.

DOT National Transportation Integrated Search

2014-08-01

Because of their inherent : fl : exibility and low damping ratios, cantilevered mast : - : arm : tra : ffi : c signal structures are suscepti : b : le to : wind : - : induced vibrations. : These vibrations : cause stru : ctural stresses and strains t...

In vitro selection of miltefosine resistance in promastigotes of Leishmania donovani from Nepal: genomic and metabolomic characterization.

PubMed

Shaw, C D; Lonchamp, J; Downing, T; Imamura, H; Freeman, T M; Cotton, J A; Sanders, M; Blackburn, G; Dujardin, J C; Rijal, S; Khanal, B; Illingworth, C J R; Coombs, G H; Carter, K C

2016-03-01

In this study, we followed the genomic, lipidomic and metabolomic changes associated with the selection of miltefosine (MIL) resistance in two clinically derived Leishmania donovani strains with different inherent resistance to antimonial drugs (antimony sensitive strain Sb-S; and antimony resistant Sb-R). MIL-R was easily induced in both strains using the promastigote-stage, but a significant increase in MIL-R in the intracellular amastigote compared to the corresponding wild-type did not occur until promastigotes had adapted to 12.2 μM MIL. A variety of common and strain-specific genetic changes were discovered in MIL-adapted parasites, including deletions at the LdMT transporter gene, single-base mutations and changes in somy. The most obvious lipid changes in MIL-R promastigotes occurred to phosphatidylcholines and lysophosphatidylcholines and results indicate that the Kennedy pathway is involved in MIL resistance. The inherent Sb resistance of the parasite had an impact on the changes that occurred in MIL-R parasites, with more genetic changes occurring in Sb-R compared with Sb-S parasites. Initial interpretation of the changes identified in this study does not support synergies with Sb-R in the mechanisms of MIL resistance, though this requires an enhanced understanding of the parasite's biochemical pathways and how they are genetically regulated to be verified fully. © 2015 The Authors. Molecular Microbiology published by John Wiley & Sons Ltd.

Resistance of Pseudomonas aeruginosa isolates to hydrogel contact lens disinfection correlates with cytotoxic activity.

PubMed

Lakkis, C; Fleiszig, S M

2001-04-01

One of the most common pathogens in infection of hydrogel contact lens wearers is Pseudomonas aeruginosa, which can gain access to the eye via contamination of the lens, lens case, and lens care solutions. Only one strain per species is used in current regulatory testing for the marketing of chemical contact lens disinfectants. The aim of this study was to determine whether P. aeruginosa strains vary in their susceptibility to hydrogel contact lens disinfectants. A method for rapidly screening bacterial susceptibility to contact lens disinfectants was developed, based on measurement of the MIC. The susceptibility of 35 P. aeruginosa isolates to two chemical disinfectants was found to vary among strains. MICs ranged from 6.25 to 100% for both disinfectants at 37 degrees C, and a number of strains were not inhibited by a 100% disinfectant concentration in the lens case environment at room temperature (22 degrees C). Resistance to disinfection appeared to be an inherent rather than acquired trait, since some resistant strains had been isolated prior to the introduction of the disinfectants and some susceptible P. aeruginosa strains could not be made more resistant by repeated disinfectant exposure. A number of P. aeruginosa strains which were comparatively more resistant to short-term disinfectant exposure also demonstrated the ability to grow to levels above the initial inoculum in one chemical disinfectant after long-term (24 to 48 h) disinfectant exposure. Resistance was correlated with acute cytotoxic activity toward corneal epithelial cells and with exsA, which encodes a protein that regulates cytotoxicity via a complex type III secretion system. These results suggest that chemical disinfection solutions may select for contamination with cytotoxic strains. Further investigation of the mechanisms and factors responsible for resistance may also lead to strategies for reducing adverse responses to contact lens wear.

Analysis, compensation, and correction of temperature effects on FBG strain sensors

NASA Astrophysics Data System (ADS)

Haber, T. C.; Ferguson, S.; Guthrie, D.; Graver, T. W.; Soller, B. J.; Mendez, Alexis

2013-05-01

One of the most common fiber optic sensor (FOS) types used are fiber Bragg gratings (FBG), and the most frequently measured parameter is strain. Hence, FBG strain sensors are one of the most prevalent FOS devices in use today in structural sensing and monitoring in civil engineering, aerospace, marine, oil and gas, composites and smart structure applications. However, since FBGs are simultaneously sensitive to both temperature and strain, it becomes essential to utilize sensors that are either fully temperature insensitive or, alternatively, properly temperature compensated to avoid erroneous measurements. In this paper, we introduce the concept of measured "total strain", which is inherent and unique to optical strain sensors. We review and analyze the temperature and strain sensitivities of FBG strain sensors and decompose the total measured strain into thermal and non-thermal components. We explore the differences between substrate CTE and System Thermal Response Coefficients, which govern the type and quality of thermal strain decomposition analysis. Finally, we present specific guidelines to achieve proper temperature-insensitive strain measurements by combining adequate installation, sensor packaging and data correction techniques.

Characterization of the biology and infectivity of Leishmania infantum viscerotropic and dermotropic strains isolated from HIV+ and HIV- patients in the murine model of visceral leishmaniasis

PubMed Central

2013-01-01

Background Leishmaniasis is a group of diseases with a variety of clinical manifestations. The form of the disease is highly dependent on the infective Leishmania species and the immunological status of the host. The infectivity of the parasite strain also plays an important role in the progression of the infection. The aim of this work is to understand the influence of the natural infectivity of Leishmania strains in the outcome of visceral leishmaniasis. Methods In this study we have characterized four strains of L. infantum in terms of molecular typing, in vitro cultivation and differentiation. Two strains were isolated from HIV+ patients with visceral leishmaniasis (Bibiano and E390M), one strain was isolated from a cutaneous lesion in an immunocompetent patient (HL) and another internal reference strain causative of visceral leishmaniasis (ST) also from an immunocompetent patient was used for comparison. For this objective, we have compared their virulence by in vitro and in vivo infectivity in a murine model of visceral leishmaniasis. Results Molecular typing unraveled a new k26 sequence attributed to MON-284 zymodeme and allowed the generation of a molecular signature for the identification of each strain. In vitro cultivation enabled the production of promastigotes with comparable growth curves and metacyclogenesis development. The HL strain was the most infective, showing the highest parasite loads in vitro that were corroborated with the in vivo assays, 6 weeks post-infection in BALB/c mice. The two strains isolated from HIV+ patients, both belonging to two different zymodemes, revealed different kinetics of infection. Conclusion Differences in in vitro and in vivo infectivity found in the murine model were then attributed to intrinsic characteristics of each strain. This work is supported by other studies that present the parasite’s inherent features as factors for the multiplicity of clinical manifestations and severity of leishmaniasis. PMID:23622683

Visualizing period fluctuations in strained-layer superlattices with scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Kanedy, K.; Lopez, F.; Wood, M. R.; Gmachl, C. F.; Weimer, M.; Klem, J. F.; Hawkins, S. D.; Shaner, E. A.; Kim, J. K.

2018-01-01

We show how cross-sectional scanning tunneling microscopy (STM) may be used to accurately map the period fluctuations throughout epitaxial, strained-layer superlattices based on the InAs/InAsSb and InGaAs/InAlAs material systems. The concept, analogous to Bragg's law in high-resolution x-ray diffraction, relies on an analysis of the [001]-convolved reciprocal-space satellite peaks obtained from discrete Fourier transforms of individual STM images. Properly implemented, the technique enables local period measurements that reliably discriminate vertical fluctuations localized to within ˜5 superlattice repeats along the [001] growth direction and orthogonal, lateral fluctuations localized to within ˜40 nm along <110> directions in the growth plane. While not as accurate as x-ray, the inherent, single-image measurement error associated with the method may be made as small as 0.1%, allowing the vertical or lateral period fluctuations contributing to inhomogeneous energy broadening and carrier localization in these structures to be pinpointed and quantified. The direct visualization of unexpectedly large, lateral period fluctuations on nanometer length scales in both strain-balanced systems supports a common understanding in terms of correlated interface roughness.

The Ins and Outs of DNA Fingerprinting the Infectious Fungi

PubMed Central

Soll, David R.

2000-01-01

DNA fingerprinting methods have evolved as major tools in fungal epidemiology. However, no single method has emerged as the method of choice, and some methods perform better than others at different levels of resolution. In this review, requirements for an effective DNA fingerprinting method are proposed and procedures are described for testing the efficacy of a method. In light of the proposed requirements, the most common methods now being used to DNA fingerprint the infectious fungi are described and assessed. These methods include restriction fragment length polymorphisms (RFLP), RFLP with hybridization probes, randomly amplified polymorphic DNA and other PCR-based methods, electrophoretic karyotyping, and sequencing-based methods. Procedures for computing similarity coefficients, generating phylogenetic trees, and testing the stability of clusters are then described. To facilitate the analysis of DNA fingerprinting data, computer-assisted methods are described. Finally, the problems inherent in the collection of test and control isolates are considered, and DNA fingerprinting studies of strain maintenance during persistent or recurrent infections, microevolution in infecting strains, and the origin of nosocomial infections are assessed in light of the preceding discussion of the ins and outs of DNA fingerprinting. The intent of this review is to generate an awareness of the need to verify the efficacy of each DNA fingerprinting method for the level of genetic relatedness necessary to answer the epidemiological question posed, to use quantitative methods to analyze DNA fingerprint data, to use computer-assisted DNA fingerprint analysis systems to analyze data, and to file data in a form that can be used in the future for retrospective and comparative studies. PMID:10756003

A review on prevalence, control measure, and tolerance of Tanzania Shorthorn Zebu cattle to East Coast fever in Tanzania.

PubMed

Laisser, E L K; Chenyambuga, S W; Karimuribo, E D; Msalya, G; Kipanyula, M J; Mwilawa, A J; Mdegela, R H; Kusiluka, L J M

2017-04-01

In Tanzania, control of East Coast fever (ECF) has predominantly relied on tick control using acaricides and chemotherapy, little on ECF vaccination, and very little on dissemination regarding animal immunization. In this paper, the prevalence, control measure, and tolerance of Tanzania Shorthorn Zebu (TSHZ) cattle to ECF are reviewed. In addition, the opportunities available for reducing the use of acaricides for the benefit of the farmers in terms of reduction of costs of purchasing acaricides and environmental pollution are described. The tick distribution and epidemiological factors for ECF such as the agro-ecological zones (AEZ), livestock production systems (LPS), strain, and age of the animals are also described. These factors influence the epidemiology of ECF and the distribution of TSHZ strains in different geographic locations of Tanzania. We have further showed that there is a tendency of farmers to select among the strains of TSHZ for animals which can tolerate ticks and ECF and crossbreed them with their local strains with the aim of benefiting from the inherent characteristics of the most tolerant strains. Generally, many strains of TSHZ cattle are tolerant to tick infestation and ECF infection and can be bred to respond to the needs of the people. In this review paper, we recommend that in future, ECF epidemiological studies should account for factors such as livestock production system, agro-climate, breed of animal, tick control strategy, and the dynamic interactions between them. In conclusion, we have demonstrated that an integrated control method involving use of acaricides, immunization, and ECF-tolerant/-resistant animals is required.

Quantifying Patterns of Smooth Muscle Motility in the Gut and Other Organs With New Techniques of Video Spatiotemporal Mapping

PubMed Central

Lentle, Roger G.; Hulls, Corrin M.

2018-01-01

The uses and limitations of the various techniques of video spatiotemporal mapping based on change in diameter (D-type ST maps), change in longitudinal strain rate (L-type ST maps), change in area strain rate (A-type ST maps), and change in luminous intensity of reflected light (I-maps) are described, along with their use in quantifying motility of the wall of hollow structures of smooth muscle such as the gut. Hence ST-methods for determining the size, speed of propagation and frequency of contraction in the wall of gut compartments of differing geometric configurations are discussed. We also discuss the shortcomings and problems that are inherent in the various methods and the use of techniques to avoid or minimize them. This discussion includes, the inability of D-type ST maps to indicate the site of a contraction that does not reduce the diameter of a gut segment, the manipulation of axis [the line of interest (LOI)] of L-maps to determine the true axis of propagation of a contraction, problems with anterior curvature of gut segments and the use of adjunct image analysis techniques that enhance particular features of the maps. PMID:29686624

Divorcing Strain Classification from Species Names.

PubMed

Baltrus, David A

2016-06-01

Confusion about strain classification and nomenclature permeates modern microbiology. Although taxonomists have traditionally acted as gatekeepers of order, the numbers of, and speed at which, new strains are identified has outpaced the opportunity for professional classification for many lineages. Furthermore, the growth of bioinformatics and database-fueled investigations have placed metadata curation in the hands of researchers with little taxonomic experience. Here I describe practical challenges facing modern microbial taxonomy, provide an overview of complexities of classification for environmentally ubiquitous taxa like Pseudomonas syringae, and emphasize that classification can be independent of nomenclature. A move toward implementation of relational classification schemes based on inherent properties of whole genomes could provide sorely needed continuity in how strains are referenced across manuscripts and data sets. Copyright © 2016 Elsevier Ltd. All rights reserved.

Tensile strain effect in ferroelectric perovskite oxide thin films on spinel magnesium aluminum oxide substrate

NASA Astrophysics Data System (ADS)

Zhou, Xiaolan

Ferroelectrics are used in FeRAM (Ferroelectric random-access memory). Currently (Pb,Zr)TiO3 is the most common ferroelectric material. To get lead-free and high performance ferroelectric material, we investigated perovskite ferroelectric oxides (Ba,Sr)TiO3 and BiFeO3 films with strain. Compressive strain has been investigated intensively, but the effects of tensile strain on the perovskite films have yet to be explored. We have deposited (Ba,Sr)TiO3, BiFeO3 and related films by pulsed laser deposition (PLD) and analyzed the films by X-ray diffractometry (XRD), atomic force microscopy (AFM), etc. To obtain inherently fully strained films, the selection of the appropriate substrates is crucial. MgAl2O4 matches best with good quality and size, yet the spinel structure has an intrinsic incompatibility to that of perovskite. We introduced a rock-salt structure material (Ni 1-xAlxO1+delta) as a buffer layer to mediate the structural mismatch for (Ba,Sr)TiO3 films. With buffer layer Ni1-xAlxO1+delta, we show that the BST films have high quality crystallization and are coherently epitaxial. AFM images show that the films have smoother surfaces when including the buffer layer, indicating an inherent compatibility between BST-NAO and NAO-MAO. In-plane Ferroelectricity measurement shows double hysteresis loops, indicating an antiferroelectric-like behavior: pinned ferroelectric domains with antiparallel alignments of polarization. The Curie temperatures of the coherent fully strained BST films are also measured. It is higher than 900°C, at least 800°C higher than that of bulk. The improved Curie temperature makes the use of BST as FeRAM feasible. We found that the special behaviors of ferroelectricity including hysteresis loop and Curie temperature are due to inherent fully tensile strain. This might be a clue of physics inside ferroelectric stain engineering. An out-of-plane ferroelectricity measurement would provide a full whole story of the tensile strain. However, a well suited electrode material that is both conducting, and full strained on the MgAl2O4 substrate is quite rare. We will supply some answers to this unique problem. XRD results show that Ni1-xAlxO1+delta (x=0.3, 0.4 & 0.5) film, although highly mixed with Al2O3, still takes rock-salt structure and is grown very well on the spinel MgAl 2O4 substrate, with perfect crystallization and a smooth surface. Ni0.7Al0.3O1+ delta and Ni 0.6Al0.4O1+ delta are good buffer layers for perovskite film on spinel MgAl2O4 substrate. Ni 0.5Al0.5O1+ delta could also be a good buffer layer. The structural transition from rock-salt to spinel was found at x=0.67. Tensile strain effects from thermal expansion difference of BiFeO3 films were found. Thermal expansion difference caused strain does not change the ferroelectric property greatly, due to film relaxation. BiFeO3 film with NAO buffer exhibit much larger strain.

Origin of embrittlement in metallic glasses

PubMed Central

Garrett, Glenn R.; Demetriou, Marios D.; Launey, Maximilien E.; Johnson, William L.

2016-01-01

Owing to their glassy nature, metallic glasses demonstrate a toughness that is extremely sensitive to the frozen-in configurational state. This sensitivity gives rise to “annealing embrittlement,” which is often severe and in many respects limits the technological advancement of these materials. Here, equilibrium configurations (i.e., “inherent states”) of a metallic glass are established around the glass transition, and the configurational properties along with the plane-strain fracture toughness are evaluated to associate the intrinsic glass toughness with the inherent state properties and identify the fundamental origin of embrittlement. The established correlations reveal a one-to-one correspondence between toughness and shear modulus continuous over a broad range of inherent states, suggesting that annealing embrittlement is controlled almost solely by an increasing resistance to shear flow. This annealing embrittlement sensitivity is shown to vary substantially between metallic glass compositions, and appears to correlate well with the fragility of the metallic glass. PMID:27573817

The Assessment of Cement Mortars after Thermal Degradation by Acoustic Non-destructive Methods

NASA Astrophysics Data System (ADS)

Topolář, L.; Štefková, D.; Hoduláková, M.

2017-10-01

Thanks, the terrorist attacks on the worldwide interest in the design of structures for fire greatly increased. One of the advantages of concrete over other building materials is its inherent fire-resistive properties. The concrete structural components still must be able to withstand dead and live loads without collapse even though the rise in temperature causes a decrease in the strength and modulus of elasticity for concrete and steel reinforcement. In addition, fully developed fires cause expansion of structural components and the resulting stresses and strains must be resisted. This paper reports the results of measurements by Impact-echo method and measurement by ultrasound. Both methods are based on the acoustic properties of the material which are dependent on its condition. These acoustic methods allow identifying defects and are thus suitable for monitoring the building structure condition. The results are obtained in the laboratory during the degradation of composite materials based on cement by high-temperature.

Identification of Isopentenol Biosynthetic Genes from Bacillus subtilis by a Screening Method Based on Isoprenoid Precursor Toxicity▿

PubMed Central

Withers, Sydnor T.; Gottlieb, Shayin S.; Lieu, Bonny; Newman, Jack D.; Keasling, Jay D.

2007-01-01

We have developed a novel method to clone terpene synthase genes. This method relies on the inherent toxicity of the prenyl diphosphate precursors to terpenes, which resulted in a reduced-growth phenotype. When these precursors were consumed by a terpene synthase, normal growth was restored. We have demonstrated that this method is capable of enriching a population of engineered Escherichia coli for those clones that express the sesquiterpene-producing amorphadiene synthase. In addition, we enriched a library of genomic DNA from the isoprene-producing bacterium Bacillus subtilis strain 6051 in E. coli engineered to produce elevated levels of isopentenyl diphosphate and dimethylallyl diphosphate. The selection resulted in the discovery of two genes (yhfR and nudF) whose protein products acted directly on the prenyl diphosphate precursors and produced isopentenol. Expression of nudF in E. coli engineered with the mevalonate-based isopentenyl pyrophosphate biosynthetic pathway resulted in the production of isopentenol. PMID:17693564

Photobactericidal activity of methylene blue derivatives against vancomycin-resistant Enterococcus spp.

PubMed

Wainwright, M; Phoenix, D A; Gaskell, M; Marshall, B

1999-12-01

The toxicities and phototoxicities of methylene blue and its two methylated derivatives were measured against one standard and three vancomycin-resistant pathogenic strains of Enterococcus spp. Each of the compounds was bactericidal and the derivatives exhibited photobactericidal activity on illumination at a 'light' dose of 6.3 J/cm(2) against one or more of the strains. Increased bactericidal and photobactericidal activity in the methylated derivatives is thought to be due to their higher hydrophobicities allowing greater interaction with the bacterial cell wall. In addition, the derivatives exhibited higher inherent photosensitizing efficacies.

Speeding up 3D speckle tracking using PatchMatch

NASA Astrophysics Data System (ADS)

Zontak, Maria; O'Donnell, Matthew

2016-03-01

Echocardiography provides valuable information to diagnose heart dysfunction. A typical exam records several minutes of real-time cardiac images. To enable complete analysis of 3D cardiac strains, 4-D (3-D+t) echocardiography is used. This results in a huge dataset and requires effective automated analysis. Ultrasound speckle tracking is an effective method for tissue motion analysis. It involves correlation of a 3D kernel (block) around a voxel with kernels in later frames. The search region is usually confined to a local neighborhood, due to biomechanical and computational constraints. For high strains and moderate frame-rates, however, this search region will remain large, leading to a considerable computational burden. Moreover, speckle decorrelation (due to high strains) leads to errors in tracking. To solve this, spatial motion coherency between adjacent voxels should be imposed, e.g., by averaging their correlation functions.1 This requires storing correlation functions for neighboring voxels, thus increasing memory demands. In this work, we propose an efficient search using PatchMatch, 2 a powerful method to find correspondences between images. Here we adopt PatchMatch for 3D volumes and radio-frequency signals. As opposed to an exact search, PatchMatch performs random sampling of the search region and propagates successive matches among neighboring voxels. We show that: 1) Inherently smooth offset propagation in PatchMatch contributes to spatial motion coherence without any additional processing or memory demand. 2) For typical scenarios, PatchMatch is at least 20 times faster than the exact search, while maintaining comparable tracking accuracy.

Safety assessment in plant layout design using indexing approach: implementing inherent safety perspective. Part 1 - guideword applicability and method description.

PubMed

Tugnoli, Alessandro; Khan, Faisal; Amyotte, Paul; Cozzani, Valerio

2008-12-15

Layout planning plays a key role in the inherent safety performance of process plants since this design feature controls the possibility of accidental chain-events and the magnitude of possible consequences. A lack of suitable methods to promote the effective implementation of inherent safety in layout design calls for the development of new techniques and methods. In the present paper, a safety assessment approach suitable for layout design in the critical early phase is proposed. The concept of inherent safety is implemented within this safety assessment; the approach is based on an integrated assessment of inherent safety guideword applicability within the constraints typically present in layout design. Application of these guidewords is evaluated along with unit hazards and control devices to quantitatively map the safety performance of different layout options. Moreover, the economic aspects related to safety and inherent safety are evaluated by the method. Specific sub-indices are developed within the integrated safety assessment system to analyze and quantify the hazard related to domino effects. The proposed approach is quick in application, auditable and shares a common framework applicable in other phases of the design lifecycle (e.g. process design). The present work is divided in two parts: Part 1 (current paper) presents the application of inherent safety guidelines in layout design and the index method for safety assessment; Part 2 (accompanying paper) describes the domino hazard sub-index and demonstrates the proposed approach with a case study, thus evidencing the introduction of inherent safety features in layout design.

Tension and Compression Creep Apparatus for wood-Plastic Composites

Treesearch

Scott E. Hamel; John C. Hermanson; Steven M. Cramer

2011-01-01

Design of structural members made of wood-plastic composites (WPC) is not possible without accurate test data for tension and compression. The viscoelastic behavior of these materials means that these data are required for both the quasi-static stress-strain response, and the long-term creep response. Their relative incompressibility causes inherent difficulties in...

Resilience and Impact of Children's Intellectual Disability on Indian Parents

ERIC Educational Resources Information Center

Rajan, Anugraha Merin; John, Romate

2017-01-01

Resilience of parents in the context of raising a child with intellectual disability is gaining attention as a mechanism that addresses their inherent strengths to withstand the potential associated strain. Understanding its underlying factors has applications in fostering their resilience. The present study explored the resilience of parents and…

Inclusive Pedagogy and Knowledge in Special Education: Addressing the Tension

ERIC Educational Resources Information Center

Mintz, Joseph; Wyse, Dominic

2015-01-01

There has been an increasing focus in policy and practice on adopting inclusive pedagogy as a way of reconceptualising how schools work with children with special educational needs (SEN). The paper considers the split between knowledge and pedagogy inherent in some dominant strains of "inclusive pedagogy". Drawing on the "knowledge…

Electromechanical properties of Na0.5Bi0.5TiO3-SrTiO3-PbTiO3 solid solutions

NASA Astrophysics Data System (ADS)

Svirskas, Šarūnas; Dunce, Marija; Birks, Eriks; Sternberg, Andris; Banys, Jūras

2018-03-01

Thorough studies of electric field-induced strain are presented in 0.4Na1/2Bi1/2TiO3-(0.6-x)SrTiO3-xPbTiO3 (NBT-ST-PT) ternary solid solutions. The increase of concentration of lead x induces crossover from relaxor to ferroelectric. Strain in a relaxor state can be described by electrostrictive behavior. The electrostrictive coefficients correspond to other well-known relaxor ferroelectrics. The concentration region with a stable ferroelectric phase revealed that the polarization dependence of strain does not exhibit nonlinearity, although they are inherent to the electric field dependence of strain. In this case, electric field dependence of strain is described in terms of the Rayleigh law and the role of domain wall contribution is extracted. Finally, the character of strain at the electric field-induced phase transition between the nonpolar and the ferroelectric states is studied. The data shows that in the vicinity of the electric field induced phase transition the strain vs. electric field displays electrostrictive character.

Resistance of Pseudomonas aeruginosa Isolates to Hydrogel Contact Lens Disinfection Correlates with Cytotoxic Activity

PubMed Central

Lakkis, Carol; Fleiszig, Suzanne M. J.

2001-01-01

One of the most common pathogens in infection of hydrogel contact lens wearers is Pseudomonas aeruginosa, which can gain access to the eye via contamination of the lens, lens case, and lens care solutions. Only one strain per species is used in current regulatory testing for the marketing of chemical contact lens disinfectants. The aim of this study was to determine whether P. aeruginosa strains vary in their susceptibility to hydrogel contact lens disinfectants. A method for rapidly screening bacterial susceptibility to contact lens disinfectants was developed, based on measurement of the MIC. The susceptibility of 35 P. aeruginosa isolates to two chemical disinfectants was found to vary among strains. MICs ranged from 6.25 to 100% for both disinfectants at 37°C, and a number of strains were not inhibited by a 100% disinfectant concentration in the lens case environment at room temperature (22°C). Resistance to disinfection appeared to be an inherent rather than acquired trait, since some resistant strains had been isolated prior to the introduction of the disinfectants and some susceptible P. aeruginosa strains could not be made more resistant by repeated disinfectant exposure. A number of P. aeruginosa strains which were comparatively more resistant to short-term disinfectant exposure also demonstrated the ability to grow to levels above the initial inoculum in one chemical disinfectant after long-term (24 to 48 h) disinfectant exposure. Resistance was correlated with acute cytotoxic activity toward corneal epithelial cells and with exsA, which encodes a protein that regulates cytotoxicity via a complex type III secretion system. These results suggest that chemical disinfection solutions may select for contamination with cytotoxic strains. Further investigation of the mechanisms and factors responsible for resistance may also lead to strategies for reducing adverse responses to contact lens wear. PMID:11283074

Efficient estimation of the maximum metabolic productivity of batch systems

DOE PAGES

St. John, Peter C.; Crowley, Michael F.; Bomble, Yannick J.

2017-01-31

Production of chemicals from engineered organisms in a batch culture involves an inherent trade-off between productivity, yield, and titer. Existing strategies for strain design typically focus on designing mutations that achieve the highest yield possible while maintaining growth viability. While these methods are computationally tractable, an optimum productivity could be achieved by a dynamic strategy in which the intracellular division of resources is permitted to change with time. New methods for the design and implementation of dynamic microbial processes, both computational and experimental, have therefore been explored to maximize productivity. However, solving for the optimal metabolic behavior under the assumptionmore » that all fluxes in the cell are free to vary is a challenging numerical task. Here, previous studies have therefore typically focused on simpler strategies that are more feasible to implement in practice, such as the time-dependent control of a single flux or control variable.« less

RNA circularization reveals terminal sequence heterogeneity in a double-stranded RNA virus.

PubMed

Widmer, G

1993-03-01

Double-stranded RNA viruses (dsRNA), termed LRV1, have been found in several strains of the protozoan parasite Leishmania. With the aim of constructing a full-length cDNA copy of the viral genome, including its terminal sequences, a protocol based on PCR amplification across the 3'-5' junction of circularized RNA was developed. This method proved to be applicable to dsRNA. It provided a relatively simple alternative to one-sided PCR, without loss of specificity inherent in the use of generic primers. LRV1 terminal nucleotide sequences obtained by this method showed a considerable variation in length, particularly at the 5' end of the positive strand, as well as the potential for forming 3' overhangs. The opposite genomic end terminates in 0, 1, or 2 TCA trinucleotide repeats. These results are compared with terminal sequences derived from one-sided PCR experiments.

Multiphase-field model of small strain elasto-plasticity according to the mechanical jump conditions

NASA Astrophysics Data System (ADS)

Herrmann, Christoph; Schoof, Ephraim; Schneider, Daniel; Schwab, Felix; Reiter, Andreas; Selzer, Michael; Nestler, Britta

2018-04-01

We introduce a small strain elasto-plastic multiphase-field model according to the mechanical jump conditions. A rate-independent J_2 -plasticity model with linear isotropic hardening and without kinematic hardening is applied exemplary. Generally, any physically nonlinear mechanical model is compatible with the subsequently presented procedure. In contrast to models with interpolated material parameters, the proposed model is able to apply different nonlinear mechanical constitutive equations for each phase separately. The Hadamard compatibility condition and the static force balance are employed as homogenization approaches to calculate the phase-inherent stresses and strains. Several verification cases are discussed. The applicability of the proposed model is demonstrated by simulations of the martensitic transformation and quantitative parameters.

Inherently-Forced Tensile Strain in Nanodiamond-Derived Onion-like Carbon: Consequences in Defect-Induced Electrochemical Activation

PubMed Central

Ko, Young-Jin; Cho, Jung-Min; Kim, Inho; Jeong, Doo Seok; Lee, Kyeong-Seok; Park, Jong-Keuk; Baik, Young-Joon; Choi, Heon-Jin; Lee, Seung-Cheol; Lee, Wook-Seong

2016-01-01

We analyzed the nanodiamond-derived onion-like carbon (OLC) as function of synthesis temperature (1000~1400 °C), by high-resolution electron microscopy, electron energy loss spectroscopy, visible-Raman spectroscopy, ultraviolet photoemission spectroscopy, impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry. The temperature dependences of the obtained properties (averaged particle size, tensile strain, defect density, density of states, electron transfer kinetics, and electrochemical oxidation current) unanimously coincided: they initially increased and saturated at 1200 °C. It was attributed to the inherent tensile strains arising from (1) the volume expansion associated with the layer-wise diamond-to-graphite transformation of the core, which caused forced dilation of the outer shells during their thermal synthesis; (2) the extreme curvature of the shells. The former origin was dominant over the latter at the outermost shell, of which the relevant evolution in defect density, DOS and electron transfer kinetics determined the electrochemical performances. In detection of dopamine (DA), uric acid (UA) and ascorbic acid (AA) using the OLC as electrode, their oxidation peak currents were enhanced by factors of 15~60 with annealing temperature. Their limit of detection and the linear range of detection, in the post-treatment-free condition, were as excellent as those of the nano-carbon electrodes post-treated by Pt-decoration, N-doping, plasma, or polymer. PMID:27032957

Fabrication of elastomeric silk fibers.

PubMed

Bradner, Sarah A; Partlow, Benjamin P; Cebe, Peggy; Omenetto, Fiorenzo G; Kaplan, David L

2017-09-01

Methods to generate fibers from hydrogels, with control over mechanical properties, fiber diameter, and crystallinity, while retaining cytocompatibility and degradability, would expand options for biomaterials. Here, we exploited features of silk fibroin protein for the formation of tunable silk hydrogel fibers. The biological, chemical, and morphological features inherent to silk were combined with elastomeric properties gained through enzymatic crosslinking of the protein. Postprocessing via methanol and autoclaving provided tunable control of fiber features. Mechanical, optical, and chemical analyses demonstrated control of fiber properties by exploiting the physical cross-links, and generating double network hydrogels consisting of chemical and physical cross-links. Structure and chemical analyses revealed crystallinity from 30 to 50%, modulus from 0.5 to 4 MPa, and ultimate strength 1-5 MPa depending on the processing method. Fabrication and postprocessing combined provided fibers with extensibility from 100 to 400% ultimate strain. Fibers strained to 100% exhibited fourth order birefringence, revealing macroscopic orientation driven by chain mobility. The physical cross-links were influenced in part by the drying rate of fabricated materials, where bound water, packing density, and microstructural homogeneity influenced cross-linking efficiency. The ability to generate robust and versatile hydrogel microfibers is desirable for bottom-up assembly of biological tissues and for broader biomaterial applications. © 2017 Wiley Periodicals, Inc.

New Germplasms of the Culinary-Medicinal Button Mushroom, Agaricus bisporus (Agaricomycetes): Two Wild Strains from the Tibetan Plateau (China).

PubMed

Li, Bin-Bin; Jiang, Si-Ping; Xu, Ai-Guo; Dorji, Phurbu; Wang, Wen-Jing; Wang, Xiao-Liang; Wei, Tie-Zheng; Zhang, Zu-Tang; Yao, Yi-Jian

2017-01-01

Agaricus bisporus is one of the most important commercially cultivated culinary-medicinal mushrooms worldwide. In China, most of the cultivated strains of the fungus were introduced from other countries and cultivated in the eastern provinces. In this study, 2 wild strains of A. bisporus, 2091 and 2094, isolated from fresh specimens collected from the Tibetan Plateau, were domesticated and cultivated alongside a commercial hybrid strain, As2796, in Lhasa, China, for comparison in order to provide new germplasms for cultivation. Basic characteristics, mushroom yield, dry weight, polysaccharide contents, and antioxidant activities of the tested strains were analyzed. Compared with strain As2796, the 2 wild strains displayed good values for mycelial growth, time to fruiting, mushroom yield, dry weight, and polysaccharide contents, and their basidiomata had distinct morphological characteristics (e.g., brown or pale brown caps with some white scales). In addition, the antioxidant activities (reducing power and DPPH radical scavenging effect) of strain 2094 were significantly higher than those of the other 2 strains. Domestication of the 2 wild strains would add more genetic variation into the germplasm of A. bisporus for cultivation, especially in China, and might help to address the problem inherent to the nearly monoculture crop lacking genetic diversity in China.

Substrate-Limited Saccharomyces cerevisiae Yeast Strains Allow Control of Fermentation during Bread Making.

PubMed

Struyf, Nore; Laurent, Jitka; Verspreet, Joran; Verstrepen, Kevin J; Courtin, Christophe M

2017-04-26

Identification and use of yeast strains that are unable to consume one or more otherwise fermentable substrate types could allow a more controlled fermentation process with more flexibility regarding fermentation times. In this study, Saccharomyces cerevisiae strains with different capacities to consume substrates present in wheat were selected to investigate the impact of substrate limitation on dough fermentation and final bread volume. Results show that fermentation of dough with maltose-negative strains relies on the presence of fructan and sucrose as fermentable substrates and can be used for regular bread making. Levels of fructan and sucrose, endogenously present or added, hence determine the extent of fermentation and timing at the proofing stage. Whole meal is inherently more suitable for substrate-limited fermentation than white flour due to the presence of higher native levels of these substrates. Bread making protocols with long fermentation times are accommodated by addition of substrates such as sucrose.

The Portevin–Le Chatelier effect: a review of experimental findings

PubMed Central

Yilmaz, Ahmet

2011-01-01

The Portevin–Le Chatelier (PLC) effect manifests itself as an unstable plastic flow during tensile tests of some dilute alloys under certain regimes of strain rate and temperature. The plastic strain becomes localized in the form of bands which move along a specimen gauge in various ways as the PLC effect occurs. Because the localization of strain causes degradation of the inherent structural properties and surface quality of materials, understanding the effect is crucial for the effective use of alloys. The characteristic behaviors of localized strain bands and techniques commonly used to study the PLC effect are summarized in this review. A brief overview of experimental findings, the effect of material properties and test parameters on the PLC effect, and some discussion on the mechanisms of the effect are included. Tests for predicting the early failure of structural materials due to embrittlement induced by the PLC effect are also discussed. PMID:27877450

Identification of strained black phosphorous by Raman spectroscopy

NASA Astrophysics Data System (ADS)

Wan, Jiawei; Guo, Junhong; Hu, Fangren

2017-04-01

Phosphorene has a very high hole mobility and can be a tuned band structure, and has become an ideal material for electronic devices. For this new type of two-dimensional material, in the applied strain, black phosphorus (BP) can be changed into an indirect band gap and metallic materials from the direct band gap semiconductor material, which greatly affect its inherent physical characteristics. How to identify strained microstructure changes becomes an important problem. The calculated Raman spectra disclose that the A{}{{g}}2 mode and B{}2{{g}} mode will split and the Raman spectra appear, while the A{}{{g}}1 mode is shifted to low-frequency region. The deformation induced by strain will effectively change the Raman mode position and intensity, this can be used to identify phosphorus changes. Project supported by the National Science Foundation of China (Nos. 61505085, 61574080, 61274127) and the Innovation Project of Jiangsu Graduate Student, China (No. SJLX15_0379).

Chemical and Stress Resistances of Clostridium difficile Spores and Vegetative Cells

PubMed Central

Edwards, Adrianne N.; Karim, Samiha T.; Pascual, Ricardo A.; Jowhar, Lina M.; Anderson, Sarah E.; McBride, Shonna M.

2016-01-01

Clostridium difficile is a Gram-positive, sporogenic and anaerobic bacterium that causes a potentially fatal colitis. C. difficile enters the body as dormant spores that germinate in the colon to form vegetative cells that secrete toxins and cause the symptoms of infection. During transit through the intestine, some vegetative cells transform into spores, which are more resistant to killing by environmental insults than the vegetative cells. Understanding the inherent resistance properties of the vegetative and spore forms of C. difficile is imperative for the development of methods to target and destroy the bacterium. The objective of this study was to define the chemical and environmental resistance properties of C. difficile vegetative cells and spores. We examined vegetative cell and spore tolerances of three C. difficile strains, including 630Δerm, a 012 ribotype and a derivative of a past epidemic strain; R20291, a 027 ribotype and current epidemic strain; and 5325, a clinical isolate that is a 078 ribotype. All isolates were tested for tolerance to ethanol, oxygen, hydrogen peroxide, butanol, chloroform, heat and sodium hypochlorite (household bleach). Our results indicate that 630Δerm vegetative cells (630 spo0A) are more resistant to oxidative stress than those of R20291 (R20291 spo0A) and 5325 (5325 spo0A). In addition, 5325 spo0A vegetative cells exhibited greater resistance to organic solvents. In contrast, 630Δerm spores were more sensitive than R20291 or 5325 spores to butanol. Spores from all three strains exhibited high levels of resistance to ethanol, hydrogen peroxide, chloroform and heat, although R20291 spores were more resistant to temperatures in the range of 60–75°C. Finally, household bleach served as the only chemical reagent tested that consistently reduced C. difficile vegetative cells and spores of all tested strains. These findings establish conditions that result in vegetative cell and spore elimination and illustrate the resistance of C. difficile to common decontamination methods. These results further demonstrate that the vegetative cells and spores of various C. difficile strains have different resistance properties that may impact decontamination of surfaces and hands. PMID:27833595

Measurement of Strain Distributions in Mouse Femora with 3D-Digital Speckle Pattern Interferometry

PubMed Central

Yang, Lianxiang; Zhang, Ping; Liu, Sheng; Samala, Praveen R; Su, Min; Yokota, Hiroki

2007-01-01

Bone is a mechanosensitive tissue that adapts its mass, architecture and mechanical properties to external loading. Appropriate mechanical loads offer an effective means to stimulate bone remodeling and prevent bone loss. A role of in situ strain in bone is considered essential in enhancement of bone formation, and establishing a quantitative relationship between 3D strain distributions and a rate of local bone formation is important. Digital speckle pattern interferometry (DSPI) can achieve whole-field, non-contacting measurements of microscopic deformation for high-resolution determination of 3D strain distributions. However, the current system does not allow us to derive accurate strain distributions because of complex surface contours inherent to biological samples. Through development of a custom-made piezoelectric loading device as well as a new DSPI-based force calibration system, we built an advanced DSPI system and integrated local contour information to deformation data. Using a mouse femur in response to a knee loading modality as a model system, we determined 3D strain distributions and discussed effectiveness and limitations of the described system. PMID:18670581

Evaluation of the MicroScan ESBL plus confirmation panel for detection of extended-spectrum beta-lactamases in clinical isolates of oxyimino-cephalosporin-resistant Gram-negative bacteria.

PubMed

Stürenburg, Enno; Lang, Melanie; Horstkotte, Matthias A; Laufs, Rainer; Mack, Dietrich

2004-11-01

We aimed to assess the performance of the MicroScan ESBL plus confirmation panel using a series of 87 oxyimino-cephalosporin-resistant Gram-negative bacilli of various species. Organisms tested included 57 extended-spectrum beta-lactamase (ESBL) strains comprising Enterobacter aerogenes (3), Enterobacter cloacae (10), Escherichia coli (11), Klebsiella pneumoniae (26), Klebsiella oxytoca (3) and Proteus mirabilis (4). Also included were 30 strains resistant to oxyimino cephalosporins but lacking ESBLs, which were characterized with other resistance mechanisms, such as inherent clavulanate susceptibility in Acinetobacter spp. (4), hyperproduction of AmpC enzyme in Citrobacter freundii (2), E. aerogenes (3), E. cloacae (3), E. coli (4), Hafnia alvei (1) and Morganella morganii (1), production of plasmid-mediated AmpC beta-lactamase in K. pneumoniae (3) and E. coli (3) or hyperproduction of K1 enzyme in K. oxytoca (6). The MicroScan MIC-based clavulanate synergy correctly classified 50 of 57 ESBL strains as ESBL-positive and 23 of 30 non-ESBL strains as ESBL-negative (yielding a sensitivity of 88% and a specificity of 76.7%, respectively). False negatives among ESBL producers were highest with Enterobacter spp. due to masking interactions between ESBL and AmpC beta-lactamases. False-positive classifications occurred in two Acinetobacter spp., one E. coli producing plasmid-mediated AmpC beta-lactamase and two K. oxytoca hyperproducing their chromosomal K1 beta-lactamase. The MicroScan clavulanate synergy test proved to be a valuable tool for ESBL confirmation. However, this test has limitations in detecting ESBLs in Enterobacter spp. and in discriminating ESBL-related resistance from the K1 enzyme and from inherent clavulanate susceptibility in Acinetobacter spp.

Effects of local field and inherent strain in reflectance anisotropy spectra of A{sup III}B{sup V} semiconductors with naturally oxidized surfaces

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

Berkovits, V. L.; Kosobukin, V. A.; Gordeeva, A. B.

2015-12-28

Reflectance anisotropy (RA) spectra of naturally oxidized (001) surfaces of GaAs and InAs crystals are measured for photon energies from 1.5 up to 5.5 eV. The differential high-accuracy RA spectra reveal features substantially different from those caused by either a reconstruction of clean surface or a built-in near-surface electric field. Models of atomic structure with anisotropic transition layers of excess arsenic atoms specific for GaAs(001)/oxide and InAs(001)/oxide interfaces are proposed. In conformity with these models, a general theory of reflectance anisotropy is developed for semiconductor/oxide interfaces within the Green's function technique. The theory takes into account the combined effect of localmore » field due to interface dipoles and of intrinsic near-surface strain of the crystal. Measured RA spectra are analyzed in the model of valence-bond dipoles occupying a rectangular lattice in a multilayer medium. Comparing the measured and calculated spectra, we conclude that RA spectra of oxidized GaAs(001) and InAs(001) surfaces are simultaneously influenced by interface and near-surface anisotropies. The former is responsible for the broad-band spectral features which are associated with polarizability of the valence bonds attached to As atoms at the crystal/oxide interface. The near-surface anisotropy is due to inherent uniaxial straining the near-surface region of crystal. The effect of strain on RA spectra is experimentally and theoretically substantiated for GaAs crystal wafers undergone a uniaxial applied stress. Basically, this work results in the following. It establishes the physical nature of different levels of RA spectra observed in a majority of papers, but never analyzed. It demonstrates how the studied features of RA spectra could be applied for optical characterization of strained interfaces and atomic layers.« less

Effects of local field and inherent strain in reflectance anisotropy spectra of AIIIBV semiconductors with naturally oxidized surfaces

NASA Astrophysics Data System (ADS)

Berkovits, V. L.; Kosobukin, V. A.; Gordeeva, A. B.

2015-12-01

Reflectance anisotropy (RA) spectra of naturally oxidized (001) surfaces of GaAs and InAs crystals are measured for photon energies from 1.5 up to 5.5 eV. The differential high-accuracy RA spectra reveal features substantially different from those caused by either a reconstruction of clean surface or a built-in near-surface electric field. Models of atomic structure with anisotropic transition layers of excess arsenic atoms specific for GaAs(001)/oxide and InAs(001)/oxide interfaces are proposed. In conformity with these models, a general theory of reflectance anisotropy is developed for semiconductor/oxide interfaces within the Green's function technique. The theory takes into account the combined effect of local field due to interface dipoles and of intrinsic near-surface strain of the crystal. Measured RA spectra are analyzed in the model of valence-bond dipoles occupying a rectangular lattice in a multilayer medium. Comparing the measured and calculated spectra, we conclude that RA spectra of oxidized GaAs(001) and InAs(001) surfaces are simultaneously influenced by interface and near-surface anisotropies. The former is responsible for the broad-band spectral features which are associated with polarizability of the valence bonds attached to As atoms at the crystal/oxide interface. The near-surface anisotropy is due to inherent uniaxial straining the near-surface region of crystal. The effect of strain on RA spectra is experimentally and theoretically substantiated for GaAs crystal wafers undergone a uniaxial applied stress. Basically, this work results in the following. It establishes the physical nature of different levels of RA spectra observed in a majority of papers, but never analyzed. It demonstrates how the studied features of RA spectra could be applied for optical characterization of strained interfaces and atomic layers.

Nature and nurture: environmental influences on a genetic rat model of depression.

PubMed

Mehta-Raghavan, N S; Wert, S L; Morley, C; Graf, E N; Redei, E E

2016-03-29

In this study, we sought to learn whether adverse events such as chronic restraint stress (CRS), or 'nurture' in the form of environmental enrichment (EE), could modify depression-like behavior and blood biomarker transcript levels in a genetic rat model of depression. The Wistar Kyoto More Immobile (WMI) is a genetic model of depression that aided in the identification of blood transcriptomic markers, which successfully distinguished adolescent and adult subjects with major depressive disorders from their matched no-disorder controls. Here, we followed the effects of CRS and EE in adult male WMIs and their genetically similar control strain, the Wistar Kyoto Less Immobile (WLI), that does not show depression-like behavior, by measuring the levels of these transcripts in the blood and hippocampus. In WLIs, increased depression-like behavior and transcriptomic changes were present in response to CRS, but in WMIs no behavioral or additive transcriptomic changes occurred. Environmental enrichment decreased both the inherent depression-like behavior in the WMIs and the behavioral difference between WMIs and WLIs, but did not reverse basal transcript level differences between the strains. The inverse behavioral change induced by CRS and EE in the WLIs did not result in parallel inverse expression changes of the transcriptomic markers, suggesting that these behavioral responses to the environment work via separate molecular pathways. In contrast, 'trait' transcriptomic markers with expression differences inherent and unchanging between the strains regardless of the environment suggest that in our model, environmental and genetic etiologies of depression work through independent molecular mechanisms.

Nanoscale Electronic Conditioning for Improvement of Nanowire Light-Emitting-Diode Efficiency.

PubMed

May, Brelon J; Belz, Matthew R; Ahamed, Arshad; Sarwar, A T M G; Selcu, Camelia M; Myers, Roberto C

2018-04-24

Commercial III-Nitride LEDs and lasers spanning visible and ultraviolet wavelengths are based on epitaxial films. Alternatively, nanowire-based III-Nitride optoelectronics offer the advantage of strain compliance and high crystalline quality growth on a variety of inexpensive substrates. However, nanowire LEDs exhibit an inherent property distribution, resulting in uneven current spreading through macroscopic devices that consist of millions of individual nanowire diodes connected in parallel. Despite being electrically connected, only a small fraction of nanowires, sometimes <1%, contribute to the electroluminescence (EL). Here, we show that a population of electrical shorts exists in the devices, consisting of a subset of low-resistance nanowires that pass a large portion of the total current in the ensemble devices. Burn-in electronic conditioning is performed by applying a short-term overload voltage; the nanoshorts experience very high current density, sufficient to render them open circuits, thereby forcing a new current path through more nanowire LEDs in an ensemble device. Current-voltage measurements of individual nanowires are acquired using conductive atomic force microscopy to observe the removal of nanoshorts using burn-in. In macroscopic devices, this results in a 33× increase in peak EL and reduced leakage current. Burn-in conditioning of nanowire ensembles therefore provides a straightforward method to mitigate nonuniformities inherent to nanowire devices.

Trajectory Control for Very Flexible Aircraft

DTIC Science & Technology

2006-10-30

aircraft are coupled with the aeroelastic equations that govern the geometrically nonlinear structural response of the vehicle. A low -order strain...nonlinear structural formulation, the finite state aerodynamic model, and the nonlinear rigid body equations together provide a low -order complete...nonlinear aircraft analysis tool. Due to the inherent flexibility of the aircraft modeling, the low order structural fre- quencies are of the same order

Newcastle Disease Virus Vectored Bivalent Vaccine against Virulent Infectious Bursal Disease and Newcastle Disease of Chickens

PubMed Central

Chellappa, Madhan Mohan; Pathak, Dinesh C.; Vakharia, Vikram N.

2017-01-01

Newcastle disease virus (NDV) strain F is a lentogenic vaccine strain used for primary vaccination in day-old chickens against Newcastle disease (ND) in India and Southeast Asian countries. Recombinant NDV-F virus and another recombinant NDV harboring the major capsid protein VP2 gene of a very virulent infectious bursal disease virus (IBDV); namely rNDV-F and rNDV-F/VP2, respectively, were generated using the NDV F strain. The rNDV-F/VP2 virus was slightly attenuated, as compared to the rNDV-F virus, as evidenced from the mean death time and intracerebral pathogenicity index analysis. This result indicates that rNDV-F/VP2 behaves as a lentogenic virus and it is stable even after 10 serial passages in embryonated chicken eggs. When chickens were vaccinated with the rNDV F/VP2, it induced both humoral and cell mediated immunity, and was able to confer complete protection against very virulent IBDV challenge and 80% protection against virulent NDV challenge. These results suggest that rNDV-F could be an effective and inherently safe vaccine vector. Here, we demonstrate that a bivalent NDV-IBDV vaccine candidate generated by reverse genetics method is safe, efficacious and cost-effective, which will greatly aid the poultry industry in developing countries. PMID:28954433

Genetic differences in NMDA and D1 receptor levels, and operant responding for food and morphine in Lewis and Fischer 344 rats.

PubMed

Martín, Sonsoles; Lyupina, Yulia; Crespo, José Antonio; González, Begoña; García-Lecumberri, Carmen; Ambrosio, Emilio

2003-05-30

Previously, we have shown that Lewis (LEW) rats acquire faster than Fischer 344 (F344) rats operant food- and morphine-reinforced tasks under fixed-ratio schedules of reinforcement. The first purpose of the present work has been to study if differences in operant responding behavior may participate in the reported differences in morphine self-administration behavior between both inbred rat strains. To this end, we have analyzed the microstructure of responding obtained under a variable-interval (VI) of food reinforcement by calculating the inter-response time (IRT) for each rat strain. LEW rats exhibited shorter IRTs than F344 rats, suggesting that LEW rats may have an inherent high or compulsive operant responding activity. When subjects of both inbred rat strains were submitted to a schedule of morphine reinforcement of high responding requirements such as progressive ratio schedules, LEW rats also reached significantly higher breaking points and final response ratio than F344 rats for i.v. morphine self-administration. Given that there are neurochemical differences between both rat strains and that glutamatergic N-methyl-D-aspartate (NMDA) and dopaminergic D(1) receptors have been involved in operant responding behavior, a second purpose of this work has been to measure basal NMDA and D(1) receptor levels in these rat strains by quantitative receptor autoradiography. Compared to F344 rats, LEW rats showed higher basal NMDA receptor levels in frontal and cingulate cortex, caudate putamen, central amygdaloid nuclei, and intermediate white layer of superior colliculus, and higher basal D(1) receptor levels in several areas of hippocampus and thalamus, and substantia nigra pars reticulata. Taken together, these results suggest that an inherent high operant responding activity of LEW rats may have a role in the previous reported faster acquisition of opiate-reinforced behavior in operant self-administration paradigms under fixed-ratio schedules of reinforcement. In addition, a basal higher NMDA and D(1) receptor levels of LEW rats compared to F344 rats may participate in the neurochemical background that mediates the behavioral differences between both inbred rat strains.

Automatic EEG artifact removal: a weighted support vector machine approach with error correction.

PubMed

Shao, Shi-Yun; Shen, Kai-Quan; Ong, Chong Jin; Wilder-Smith, Einar P V; Li, Xiao-Ping

2009-02-01

An automatic electroencephalogram (EEG) artifact removal method is presented in this paper. Compared to past methods, it has two unique features: 1) a weighted version of support vector machine formulation that handles the inherent unbalanced nature of component classification and 2) the ability to accommodate structural information typically found in component classification. The advantages of the proposed method are demonstrated on real-life EEG recordings with comparisons made to several benchmark methods. Results show that the proposed method is preferable to the other methods in the context of artifact removal by achieving a better tradeoff between removing artifacts and preserving inherent brain activities. Qualitative evaluation of the reconstructed EEG epochs also demonstrates that after artifact removal inherent brain activities are largely preserved.

[Improvement of laboratory diagnostics of cholera due to genetically altered (hybrid) variants of cholera Vibrio biovar El Tor].

PubMed

Savel'eva, I V; Khatsukov, K X; Savel'eva, E I; Moskvitina, S I; Kovalev, D A; Savel'ev, V N; Kulichenko, A N; Antonenko, A D; Babenyshev, B V

2015-01-01

Improvement of laboratory diagnostics of cholera taking into the account appearance of hybrid variants of cholera vibrio El Tor biovar in the 1990s. Phenotypic and molecular-genetic properties of typical toxigenic (151 strains) and hybrid (102 strains) variants of El Tor biovar cholera vibrios, isolated in the Caucuses in 1970-1990 and 1993-1998, respectively, were studied. Toxigenicity gene DNA fragments, inherent to El Tor biovars or classic, were detected by using a reagent kit "Genes of Vibrio cholerae variant ctxB-rstR-rstC, REF" developed by us. Reagent kit "Genes of V. cholerae variant ctxB-rstR-rstC, REF" is proposed to be used for laboratory diagnostics of cholera during study of material from humans or environmental objects and for identification of V. cholerae 01 on genome level in PCR-analysis as a necessary addition to the classic scheme of bacteriological analysis. Laboratory diagnostics of cholera due to genetically altered (hybrid) variants of cholera vibrio El Tor biovar is based on a complex study of material from humans and environmental objects by routine bacteriologic and PCR-analysis methods with the aim of detection of gene DNA fragments in the studied material, that determine biovar (classic or El Tor), identification of V. cholerae O1 strains with differentiation of El Tor vibrios into typical and altered, as well as determination of enterotoxin, produced by the specific cholera vibrio strain (by the presence ctxB(El) or ctxB(Cl) gene DNA fragment, coding biosynthesis of CT-2 or CT-1, respectively).

Mesoscopic Metal-Insulator Transition at Ferroelastic Domain Walls in VO2

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

Jones, Keith M; Kalinin, Sergei V; Kolmakov, Andrei

2010-01-01

The novel phenomena induced by symmetry breaking at homointerfaces between ferroic variants in ferroelectric and ferroelastic materials have attracted recently much attention. Using variable temperature scanning microwave microscopy, we demonstrate the mesoscopic strain-induced metal-insulator phase transitions in the vicinity of ferroelastic domain walls in the semiconductive VO2 that nucleated at temperatures as much as 10-12 C below bulk transition, resulting in the formation of conductive channels in the material. Density functional theory is used to rationalize the process low activation energy. This behavior, linked to the strain inhomogeneity inherent in ferroelastic materials, can strongly affect interpretation of phase-transition studies inmore » VO2 and similar materials with symmetry-lowering transitions, and can also be used to enable new generations of electronic devices though strain engineering of conductive and semiconductive regions.« less

Strain-mediated electronic properties of pristine and Mn-doped GaN monolayers

NASA Astrophysics Data System (ADS)

Sharma, Venus; Srivastava, Sunita

2018-04-01

Graphene-like two-dimensional (2D) monolayer structures GaN has gained enormous amount of interest due to high thermal stability and inherent energy band gap for practical applications. First principles calculations are performed to investigate the electronic structure and strain-mediated electronic properties of pristine and Mn-doped GaN monolayer. Binding energy of Mn dopant at various adsorption site is found to be nearly same indicating these sites to be equally favorable for adsorption of foreign atom. Depending on the adsorption site, GaN monolayer can act as p-type or n-type magnetic semiconductor. The tensile strength of both pristine and doped GaN monolayer (∼24 GPa) at ultimate tensile strain of 34% is comparable with the tensile strength of graphene. The in-plane biaxial strain modulate the energy band gap of both pristine and doped-monolayer from direct to indirect gap semiconductor and finally retendered theme into metal at critical value of applied strain. These characteristics make GaN monolayer to be potential candidate for the future applications in tunable optoelectronics.

Salmonella Strains Isolated from Galápagos Iguanas Show Spatial Structuring of Serovar and Genomic Diversity

PubMed Central

Lankau, Emily W.; Cruz Bedon, Lenin; Mackie, Roderick I.

2012-01-01

It is thought that dispersal limitation primarily structures host-associated bacterial populations because host distributions inherently limit transmission opportunities. However, enteric bacteria may disperse great distances during food-borne outbreaks. It is unclear if such rapid long-distance dispersal events happen regularly in natural systems or if these events represent an anthropogenic exception. We characterized Salmonella enterica isolates from the feces of free-living Galápagos land and marine iguanas from five sites on four islands using serotyping and genomic fingerprinting. Each site hosted unique and nearly exclusive serovar assemblages. Genomic fingerprint analysis offered a more complex model of S. enterica biogeography, with evidence of both unique strain pools and of spatial population structuring along a geographic gradient. These findings suggest that even relatively generalist enteric bacteria may be strongly dispersal limited in a natural system with strong barriers, such as oceanic divides. Yet, these differing results seen on two typing methods also suggests that genomic variation is less dispersal limited, allowing for different ecological processes to shape biogeographical patterns of the core and flexible portions of this bacterial species' genome. PMID:22615968

Effects of partitioned enthalpy of mixing on glass-forming ability

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

Song, Wen-Xiong; Zhao, Shi-Jin, E-mail: shijin.zhao@shu.edu.cn

2015-04-14

We explore the inherent reason at atomic level for the glass-forming ability of alloys by molecular simulation, in which the effect of partitioned enthalpy of mixing is studied. Based on Morse potential, we divide the enthalpy of mixing into three parts: the chemical part (Δ E{sub nn}), strain part (Δ E{sub strain}), and non-bond part (Δ E{sub nnn}). We find that a large negative Δ E{sub nn} value represents strong AB chemical bonding in AB alloy and is the driving force to form a local ordered structure, meanwhile the transformed local ordered structure needs to satisfy the condition (Δ E{submore » nn}/2 + Δ E{sub strain}) < 0 to be stabilized. Understanding the chemical and strain parts of enthalpy of mixing is helpful to design a new metallic glass with a good glass forming ability. Moreover, two types of metallic glasses (i.e., “strain dominant” and “chemical dominant”) are classified according to the relative importance between chemical effect and strain effect, which enriches our knowledge of the forming mechanism of metallic glass. Finally, a soft sphere model is established, different from the common hard sphere model.« less

Large Area Active Brazing of Multi-tile Ceramic-Metal Structures

DTIC Science & Technology

2012-05-01

metallurgical bonds. The major disadvantage of using active brazing for metals and ceramics is the high processing temperature required that results in...steels) and form strong, metallurgical bonds. However, the high processing temperatures result in large strain (stress) build-up from the inherent...metals such as titanium alloys and stainless steels) and form strong, metallurgical bonds. However, the high processing temperatures result in large

Utilisation of ISA Reverse Genetics and Large-Scale Random Codon Re-Encoding to Produce Attenuated Strains of Tick-Borne Encephalitis Virus within Days.

PubMed

de Fabritus, Lauriane; Nougairède, Antoine; Aubry, Fabien; Gould, Ernest A; de Lamballerie, Xavier

2016-01-01

Large-scale codon re-encoding is a new method of attenuating RNA viruses. However, the use of infectious clones to generate attenuated viruses has inherent technical problems. We previously developed a bacterium-free reverse genetics protocol, designated ISA, and now combined it with large-scale random codon-re-encoding method to produce attenuated tick-borne encephalitis virus (TBEV), a pathogenic flavivirus which causes febrile illness and encephalitis in humans. We produced wild-type (WT) and two re-encoded TBEVs, containing 273 or 273+284 synonymous mutations in the NS5 and NS5+NS3 coding regions respectively. Both re-encoded viruses were attenuated when compared with WT virus using a laboratory mouse model and the relative level of attenuation increased with the degree of re-encoding. Moreover, all infected animals produced neutralizing antibodies. This novel, rapid and efficient approach to engineering attenuated viruses could potentially expedite the development of safe and effective new-generation live attenuated vaccines.

Mycobacteriocins produced by rapidly growing mycobacteria are Tween-hydrolyzing esterases.

PubMed Central

Saito, H; Tomioka, H; Watanabe, T; Yoneyama, T

1983-01-01

Smegmatocin, a protein produced by Mycobacterium smegmatis ATCC 14468, was found to have an esterase activity, hydrolyzing Tween 80, polyoxyethylene sorbitan monooleate, added to the assay medium for various "bacteriocins" from mycobacteria. Because M. diernhoferi ATCC 19340 (indicator strain for smegmatocin) is highly susceptible to oleic acid and smegmatocin requires Tween 80 for manifestation of its anti-M. diernhoferi activity, it is likely that smegmatocin-mediated antimicrobial action is caused by oleic acid generated by hydrolysis of Tween 80 by the inherent esterase action of smegmatocin. Other mycobacteriocins from rapidly growing mycobacteria also have inherent esterase activity against Tween 80 and require Tween 80 for expression of antimycobacterial action. Smegmatocin was found to hydrolyze various polyoxyethylene (sorbitan) fatty acyl esters but not sorbitan monooleate and glyceryl esters. Images PMID:6826523

Computer algorithm for analyzing and processing borehole strainmeter data

USGS Publications Warehouse

Langbein, John O.

2010-01-01

The newly installed Plate Boundary Observatory (PBO) strainmeters record signals from tectonic activity, Earth tides, and atmospheric pressure. Important information about tectonic processes may occur at amplitudes at and below tidal strains and pressure loading. If incorrect assumptions are made regarding the background noise in the strain data, then the estimates of tectonic signal amplitudes may be incorrect. Furthermore, the use of simplifying assumptions that data are uncorrelated can lead to incorrect results and pressure loading and tides may not be completely removed from the raw data. Instead, any algorithm used to process strainmeter data must incorporate the strong temporal correlations that are inherent with these data. The technique described here uses least squares but employs data covariance that describes the temporal correlation of strainmeter data. There are several advantages to this method since many parameters are estimated simultaneously. These parameters include: (1) functional terms that describe the underlying error model, (2) the tidal terms, (3) the pressure loading term(s), (4) amplitudes of offsets, either those from earthquakes or from the instrument, (5) rate and changes in rate, and (6) the amplitudes and time constants of either logarithmic or exponential curves that can characterize postseismic deformation or diffusion of fluids near the strainmeter. With the proper error model, realistic estimates of the standard errors of the various parameters are obtained; this is especially critical in determining the statistical significance of a suspected, tectonic strain signal. The program also provides a method of tracking the various adjustments required to process strainmeter data. In addition, the program provides several plots to assist with identifying either tectonic signals or other signals that may need to be removed before any geophysical signal can be identified.

Subscale Test Methods for Combustion Devices

NASA Technical Reports Server (NTRS)

Anderson, W. E.; Sisco, J. C.; Long, M. R.; Sung, I.-K.

2005-01-01

Stated goals for long-life LRE s have been between 100 and 500 cycles: 1) Inherent technical difficulty of accurately defining the transient and steady state thermochemical environments and structural response (strain); 2) Limited statistical basis on failure mechanisms and effects of design and operational variability; and 3) Very high test costs and budget-driven need to protect test hardware (aversion to test-to-failure). Ambitious goals will require development of new databases: a) Advanced materials, e.g., tailored composites with virtually unlimited property variations; b) Innovative functional designs to exploit full capabilities of advanced materials; and c) Different cycles/operations. Subscale testing is one way to address technical and budget challenges: 1) Prototype subscale combustors exposed to controlled simulated conditions; 2) Complementary to conventional laboratory specimen database development; 3) Instrumented with sensors to measure thermostructural response; and 4) Coupled with analysis

Stepping stones towards a new prokaryotic taxonomy.

PubMed

Gevers, Dirk; Dawyndt, Peter; Vandamme, Peter; Willems, Anne; Vancanneyt, Marc; Swings, Jean; De Vos, Paul

2006-11-29

Technological developments provide new insights into prokaryotic evolution and diversity and provoke a continuous need to update taxonomy and revise classification schemes. Our present species concept and definition are being challenged by the growing amount of whole genomic information, which should allow improvements in the natural species definition. The continuous quest for an objective and stable method for sorting strains into coherent homogeneous groups is inherent to prokaryotic systematics and nomenclature. Morphological, biochemical, physiological, phenotypic and chemotaxonomic criteria have been complemented by molecular data and pragmatic, purpose built, species definitions are being replaced by more natural ones based on evolutionary insights. It is imperative to give due consideration to both fundamental and applied aspects of future species concepts and definitions. The present paper discusses the present practice in prokaryotic taxonomy of how this system developed and how it may evolve in the future.

Whole genome sequencing in the prevention and control of Staphylococcus aureus infection.

PubMed

Price, J R; Didelot, X; Crook, D W; Llewelyn, M J; Paul, J

2013-01-01

Staphylococcus aureus remains a leading cause of hospital-acquired infection but weaknesses inherent in currently available typing methods impede effective infection prevention and control. The high resolution offered by whole genome sequencing has the potential to revolutionise our understanding and management of S. aureus infection. To outline the practicalities of whole genome sequencing and discuss how it might shape future infection control practice. We review conventional typing methods and compare these with the potential offered by whole genome sequencing. In contrast with conventional methods, whole genome sequencing discriminates down to single nucleotide differences and allows accurate characterisation of transmission events and outbreaks and additionally provides information about the genetic basis of phenotypic characteristics, including antibiotic susceptibility and virulence. However, translating its potential into routine practice will depend on affordability, acceptable turnaround times and on creating a reliable standardised bioinformatic infrastructure. Whole genome sequencing has the potential to provide a universal test that facilitates outbreak investigation, enables the detection of emerging strains and predicts their clinical importance. Copyright © 2012 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.

Ultrasound Elastography: Review of Techniques and Clinical Applications

PubMed Central

Sigrist, Rosa M.S.; Liau, Joy; Kaffas, Ahmed El; Chammas, Maria Cristina; Willmann, Juergen K.

2017-01-01

Elastography-based imaging techniques have received substantial attention in recent years for non-invasive assessment of tissue mechanical properties. These techniques take advantage of changed soft tissue elasticity in various pathologies to yield qualitative and quantitative information that can be used for diagnostic purposes. Measurements are acquired in specialized imaging modes that can detect tissue stiffness in response to an applied mechanical force (compression or shear wave). Ultrasound-based methods are of particular interest due to its many inherent advantages, such as wide availability including at the bedside and relatively low cost. Several ultrasound elastography techniques using different excitation methods have been developed. In general, these can be classified into strain imaging methods that use internal or external compression stimuli, and shear wave imaging that use ultrasound-generated traveling shear wave stimuli. While ultrasound elastography has shown promising results for non-invasive assessment of liver fibrosis, new applications in breast, thyroid, prostate, kidney and lymph node imaging are emerging. Here, we review the basic principles, foundation physics, and limitations of ultrasound elastography and summarize its current clinical use and ongoing developments in various clinical applications. PMID:28435467

Correction of the post -- necking true stress -- strain data using instrumented nanoindentation

NASA Astrophysics Data System (ADS)

Romero Fonseca, Ivan Dario

The study of large plastic deformations has been the focus of numerous studies particularly in the metal forming processes and fracture mechanics fields. A good understanding of the plastic flow properties of metallic alloys and the true stresses and true strains induced during plastic deformation is crucial to optimize the aforementioned processes, and to predict ductile failure in fracture mechanics analyzes. Knowledge of stresses and strains is extracted from the true stress-strain curve of the material from the uniaxial tensile test. In addition, stress triaxiality is manifested by the neck developed during the last stage of a tensile test performed on a ductile material. This necking phenomenon is the factor responsible for deviating from uniaxial state into a triaxial one, then, providing an inaccurate description of the material's behavior after the onset of necking. The research of this dissertation is aimed at the development of a correction method for the nonuniform plastic deformation (post-necking) portion of the true stress-strain curve. The correction proposed is based on the well-known relationship between hardness and flow (yield) stress, except that instrumented nanoindentation hardness is utilized rather than conventional macro or micro hardness. Three metals with different combinations of strain hardening behavior and crystal structure were subjected to quasi-static tensile tests: power-law strain hardening low carbon G10180 steel (BCC) and electrolytic tough pitch copper C11000 (FCC), and linear strain hardening austenitic stainless steel S30400 (FCC). Nanoindentation hardness values, measured on the broken tensile specimen, were converted into flow stress values by means of the constraint factor C from Tabor's, the representative plastic strainepsilonr and the post-test true plastic strains measured. Micro Vickers hardness testing was carried out on the sample as well. The constraint factors were 5.5, 4.5 and 4.5 and the representative plastic strains were 0.028, 0.062 and 0.061 for G101800, C11000 and S30400 respectively. The established corrected curves relating post-necking flow stress to true plastic strain turned out to be well represented by a power-law function. Experimental results dictated that a unique single value for C and for epsilonr is not appropriate to describe materials with different plastic behaviors. Therefore, Tabor's equation, along with the representative plastic strain concept, has been misused in the past. The studied materials exhibited different nanohardness and plastic strain distributions due to their inherently distinct elasto-plastic response. The proposed post-necking correction separates out the effect of triaxiality on the uniaxial true stress-strain curve provided that the nanohardness-flow stress relationship is based on uniaxial values of stress. Some type of size effect, due to the microvoids at the tip of the neck, influenced nanohardness measurements. The instrumented nanoindentation technique proved to be a very suitable method to probe elasto-plastic properties of materials such as nanohardness, elastic modulus, and quasi-static strain rate sensitivity among others. Care should be taken when converting nanohardness to Vickers and vice versa due to their different area definition used. Nanohardness to Vickers ratio oscillated between 1.01 and 1.17.

Rapid mycobacteria drug susceptibility testing using Gel Microdrop (GMD) Growth Assay and flow cytometry.

PubMed

Akselband, Y; Cabral, C; Shapiro, D S; McGrath, P

2005-08-01

Control of multi-drug-resistant tuberculosis has been hampered by the lack of simple, rapid and sensitive methods for assessing bacterial growth and antimicrobial susceptibility. Due to the increasing incidence and high frequency of mutations, it is unlikely that culture methods will disappear in the foreseeable future. Therefore, the need to modernize methods for rapid detection of viable clinical isolates, at a minimum as a gold standard, will persist. Previously, we confirmed the feasibility of using the Gel Microdrop (GMD) Growth Assay for identifying sub-populations of resistant Mycobacteria by testing different laboratory strains. Briefly, this assay format relies on encapsulating single bacterium in agarose microspheres and identifying clonogenic growth using flow cytometry and fluorescent staining. In this study, we modified the GMD Growth Assay to make it suitable for clinical applications. We demonstrated the effectiveness and safety of this novel approach for detecting drug susceptibility in clinically relevant laboratory strains as well as clinical isolates of Mycobacterium tuberculosis. Correlation between results using the GMD Growth Assay format and results using two well characterized methods (Broth Microdilution MIC and BACTEC 460TB) was 87.5% and 90%, respectively. However, due to the inherent sensitivity of flow cytometry and the ability to detect small (<1%) sub-populations of resistant mycobacteria, the GMD Growth Assay identified more cases of drug resistance. Using 4 clinically relevant mycobacterial strains, we assessed susceptibility to primary anti-tuberculosis drugs using both the Broth Microdilution MIC method and the GMD Growth Assay. We performed 24 tests on isoniazid-resistant BCG, Mycobacterium tuberculosis H37Ra and Mycobacterium avium strains. The Broth Microdilution MIC method identified 7 cases (29.1%) of resistance to INH and EMB compared to the GMD Growth Assay which identified resistance in 10 cases (41.6%); in 3 cases (12.5%), resistance to INH and EMB was detected only with the GMD Growth Assay. In addition, using 20 Mycobacterium tuberculosis clinical isolates, we compared results using BACTEC 460TB method performed by collaborators and the GMD Growth Assay. Eight of 20 (40%) clinical isolates, which were not identified as drug-resistant using the conventional BACTEC 460TB method, were resistant to 1, 2, or 3 different concentrations of drugs using the GMD Growth Assay (13 cases of 140 experiments). In one case (isolate 1879), resistance to 10.0 microg/ml of STR detected using BACTEC 460TB method was not confirmed by the GMD Growth Assay. Thus, the overall agreement between these methods was 90% (14 discrepant results of 140 experiments). These data demonstrate that the GMD Growth Assay is an accurate and sensitive method for rapid susceptibility testing of Mycobacterium tuberculosis for use in clinical reference laboratory settings.

Nature and nurture: environmental influences on a genetic rat model of depression

PubMed Central

Mehta-Raghavan, N S; Wert, S L; Morley, C; Graf, E N; Redei, E E

2016-01-01

In this study, we sought to learn whether adverse events such as chronic restraint stress (CRS), or ‘nurture' in the form of environmental enrichment (EE), could modify depression-like behavior and blood biomarker transcript levels in a genetic rat model of depression. The Wistar Kyoto More Immobile (WMI) is a genetic model of depression that aided in the identification of blood transcriptomic markers, which successfully distinguished adolescent and adult subjects with major depressive disorders from their matched no-disorder controls. Here, we followed the effects of CRS and EE in adult male WMIs and their genetically similar control strain, the Wistar Kyoto Less Immobile (WLI), that does not show depression-like behavior, by measuring the levels of these transcripts in the blood and hippocampus. In WLIs, increased depression-like behavior and transcriptomic changes were present in response to CRS, but in WMIs no behavioral or additive transcriptomic changes occurred. Environmental enrichment decreased both the inherent depression-like behavior in the WMIs and the behavioral difference between WMIs and WLIs, but did not reverse basal transcript level differences between the strains. The inverse behavioral change induced by CRS and EE in the WLIs did not result in parallel inverse expression changes of the transcriptomic markers, suggesting that these behavioral responses to the environment work via separate molecular pathways. In contrast, ‘trait' transcriptomic markers with expression differences inherent and unchanging between the strains regardless of the environment suggest that in our model, environmental and genetic etiologies of depression work through independent molecular mechanisms. PMID:27023176

Agricultural use of Burkholderia (Pseudomonas) cepacia: a threat to human health?

PubMed Central

Holmes, A.; Govan, J.; Goldstein, R.

1998-01-01

In the past 2 decades, Burkholderia cepacia has emerged as a human pathogen causing numerous outbreaks, particularly among cystic fibrosis (CF) patients. One highly transmissible strain has spread across North America and Britain, and another between hospitalized CF and non-CF patients. Meanwhile, the organism has been developed as a biopesticide for protecting crops against fungal diseases and has potential as a bioremediation agent for breaking down recalcitrant herbicides and pesticides. However, B. cepacia is inherently resistant to multiple antibiotics; selection of strains "safe" for environmental application is not at present possible phenotypically or genotypically; molecular epidemiology and phylogenetic studies demonstrate that highly transmissible strains emerge randomly; and the organism has a capacity for rapid mutation and adaptation (facilitated by numerous insertion sequences), and a large, complex genome divided into separate chromosomes. Therefore, the widespread agricultural use of B. cepacia should be approached with caution. PMID:9621192

Substrate stiffness-modulated registry phase correlations in cardiomyocytes map structural order to coherent beating

NASA Astrophysics Data System (ADS)

Dasbiswas, K.; Majkut, S.; Discher, D. E.; Safran, Samuel A.

2015-01-01

Recent experiments show that both striation, an indication of the structural registry in muscle fibres, as well as the contractile strains produced by beating cardiac muscle cells can be optimized by substrate stiffness. Here we show theoretically how the substrate rigidity dependence of the registry data can be mapped onto that of the strain measurements. We express the elasticity-mediated structural registry as a phase-order parameter using a statistical physics approach that takes the noise and disorder inherent in biological systems into account. By assuming that structurally registered myofibrils also tend to beat in phase, we explain the observed dependence of both striation and strain measurements of cardiomyocytes on substrate stiffness in a unified manner. The agreement of our ideas with experiment suggests that the correlated beating of heart cells may be limited by the structural order of the myofibrils, which in turn is regulated by their elastic environment.

Strain energy release rates of composite interlaminar end-notch and mixed-mode fracture: A sublaminate/ply level analysis and a computer code

NASA Technical Reports Server (NTRS)

Valisetty, R. R.; Chamis, C. C.

1987-01-01

A computer code is presented for the sublaminate/ply level analysis of composite structures. This code is useful for obtaining stresses in regions affected by delaminations, transverse cracks, and discontinuities related to inherent fabrication anomalies, geometric configurations, and loading conditions. Particular attention is focussed on those layers or groups of layers (sublaminates) which are immediately affected by the inherent flaws. These layers are analyzed as homogeneous bodies in equilibrium and in isolation from the rest of the laminate. The theoretical model used to analyze the individual layers allows the relevant stresses and displacements near discontinuities to be represented in the form of pure exponential-decay-type functions which are selected to eliminate the exponential-precision-related difficulties in sublaminate/ply level analysis. Thus, sublaminate analysis can be conducted without any restriction on the maximum number of layers, delaminations, transverse cracks, or other types of discontinuities. In conjunction with the strain energy release rate (SERR) concept and composite micromechanics, this computational procedure is used to model select cases of end-notch and mixed-mode fracture specimens. The computed stresses are in good agreement with those from a three-dimensional finite element analysis. Also, SERRs compare well with limited available experimental data.

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

Moritake, Takashi; Proton Medical Research Center, University of Tsukuba, Tsukuba; Fujita, Hidetoshi

Purpose: To examine whether inherent factors produce differences in lung morbidity in response to carbon ion (C-ion) irradiation, and to identify the molecules that have a key role in strain-dependent adverse effects in the lung. Methods and Materials: Three strains of female mice (C3H/He Slc, C57BL/6J Jms Slc, and A/J Jms Slc) were locally irradiated in the thorax with either C-ion beams (290 MeV/n, in 6 cm spread-out Bragg peak) or with {sup 137}Cs {gamma}-rays as a reference beam. We performed survival assays and histologic examination of the lung with hematoxylin-eosin and Masson's trichrome staining. In addition, we performed immunohistochemicalmore » staining for hyaluronic acid (HA), CD44, and Mac3 and assayed for gene expression. Results: The survival data in mice showed a between-strain variance after C-ion irradiation with 10 Gy. The median survival time of C3H/He was significantly shortened after C-ion irradiation at the higher dose of 12.5 Gy. Histologic examination revealed early-phase hemorrhagic pneumonitis in C3H/He and late-phase focal fibrotic lesions in C57BL/6J after C-ion irradiation with 10 Gy. Pleural effusion was apparent in C57BL/6J and A/J mice, 168 days after C-ion irradiation with 10 Gy. Microarray analysis of irradiated lung tissue in the three mouse strains identified differential expression changes in growth differentiation factor 15 (Gdf15), which regulates macrophage function, and hyaluronan synthase 1 (Has1), which plays a role in HA metabolism. Immunohistochemistry showed that the number of CD44-positive cells, a surrogate marker for HA accumulation, and Mac3-positive cells, a marker for macrophage infiltration in irradiated lung, varied significantly among the three mouse strains during the early phase. Conclusions: This study demonstrated a strain-dependent differential response in mice to C-ion thoracic irradiation. Our findings identified candidate molecules that could be implicated in the between-strain variance to early hemorrhagic pneumonitis after C-ion irradiation.« less

Antibacterial properties of Chinese herbal medicines against nosocomial antibiotic resistant strains of Pseudomonas aeruginosa in Taiwan.

PubMed

Liu, Ching-Shen; Cham, Thau-Ming; Yang, Cheng-Hong; Chang, Hsueh-Wei; Chen, Chia-Hong; Chuang, Li-Yeh

2007-01-01

Pseudomonas aeruginosa is well-recognized as a nosocomial pathogen, which exhibits inherent drug resistance. In this study, the antibacterial activity of ethanol extracts of 58 Chinese herbal medicines used in Taiwan were tested against 89 nosocomial antibiotic resistant strains of Pseudomonas aeruginosa. The results gathered by the disc diffusion method showed that 26 out of the 58 herbal extracts exhibited antibacterial activity. Among the 26 herbal extracts, 10 extracts showed broad-spectrum antibacterial activities and were selected for further antibacterial property assay. The minimum inhibitory concentrations (MIC) of the active partition fractions ranged from 0.25 to 11.0 mg/L. The presence of flavonoid compounds in the active fractions of test herbal extracts was observed by the TLC-bioautography. The results from the time-kill assay revealed that most of the herbal extracts completely killed the test organisms within 4 hours. Exposure of the test strains to a sub-MIC level of the herbal extracts for 10 consecutive subcultures did not induce resistance to the active components. A combination of the active herbal fractions with antibiotics showed that one of the herbal medicines, the hexane fraction of Ramulus Cinnamomi, possessed a synergistic effect with tetracycline, gentamycin, and streptomycin. In conclusion, the tested Chinese medical herbs have the potential to be developed into natural antibiotics. This is the first evaluation for screening large amounts of medical plants against nosocomial antibiotic resistant bacteria in Taiwan.

Disruption of methicillin-resistant Staphylococcus aureus protein synthesis by tannins

PubMed Central

Adnan, Siti-Noor-Adnalizawati; Ibrahim, Nazlina; Yaacob, Wan Ahmad

2017-01-01

Introduction Methicillin-resistant Staphylococcus aureus (MRSA) is a worldwide public health threat, displaying multiple antibiotic resistance that causes morbidity and mortality. Management of multidrug-resistant (MDR) MRSA infections is extremely difficult due to their inherent resistance to currently used antibiotics. New antibiotics are needed to combat the emergence of antimicrobial resistance. Methods The in vitro effect of tannins was studied against MRSA reference strain (ATCC 43300) and MRSA clinical strains utilizing antimicrobial assays in conjunction with both scanning and transmission electron microscopy. To reveal the influence of tannins in MRSA protein synthesis disruption, we utilized next-generation sequencing (NGS) to provide further insight into the novel protein synthesis transcriptional response of MRSA exposed to these compounds. Results Tannins possessed both bacteriostatic and bactericidal activity with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 0.78 and 1.56 mg/mL, respectively, against all tested MRSA. Scanning and transmission electron microscopy of MRSA treated with tannins showed decrease in cellular volume, indicating disruption of protein synthesis. Conclusion Analysis of a genome-wide transcriptional profile of the reference strain ATCC 43300 MRSA in response to tannins has led to the finding that tannins induced significant modulation in essential ribosome pathways, which caused a reduction in the translation processes that lead to inhibition of protein synthesis and obviation of bacterial growth. These findings highlight the potential of tannins as new promising anti-MRSA agents in clinical application such as body wash and topical cream or ointments. PMID:29264356

Giant strain control of magnetoelectric effect in Ta|Fe|MgO

PubMed Central

Odkhuu, Dorj

2016-01-01

The exploration of electric field controlled magnetism has come under scrutiny for its intriguing magnetoelectric phenomenon as well as technological advances in spintronics. Herein, the tremendous effect of an epitaxial strain on voltage-controlled perpendicular magnetic anisotropy (VPMA) is demonstrated in a transition-metal|ferromagnet|MgO (TM|FM|MgO) heterostructure from first-principles electronic structure computation. By tuning the epitaxial strain in Ta|Fe|MgO as a model system of TM|FM|MgO, we find distinctly different behaviours of VPMA from V- to Λ-shape trends with a substantially large magnetoelectric coefficient, up to an order of 103 fJV−1m−1. We further reveal that the VPMA modulation under strain is mainly governed by the inherently large spin-orbit coupling of Ta 5d–Fe 3d hybridized orbitals at the TM|FM interface, although the Fe 3d–O 2p hybridization at the FM|MgO interface is partly responsible in determining the PMA of Ta|Fe|MgO. These results suggest that the control of epitaxial strain enables the engineering of VPMA, and provides physical insights for the divergent behaviors of VPMA and magnetoelectric coefficients found in TM|FM|MgO experiments. PMID:27597448

Research and application of microbial enzymes--India's contribution.

PubMed

Chand, Subhash; Mishra, Prashant

2003-01-01

Enzymes have attracted the attention of scientists world over due to their wide range of physiological, analytical and industrial applications. Although enzymes have been isolated, purified and studied from microbial, animal and plant sources, microorganisms represent the most common source of enzymes due to their broad biochemical diversity, feasibility of mass culture and ease of genetic manipulation. With the advent of molecular biology techniques, a number of genes of industrially important enzymes has been cloned and expressed in order to improve the production of enzymes, substrate utilization and other commercially useful properties. Special attention has been focused on enzymes isolated from thermophiles due to their inherent stability and industrial applications. In addition, a variety of methods have been employed to modify enzymes for their industrial usage including strain improvement, chemical modifications, modification of reaction environment, immobilization and protein engineering. A wide range of applications of enzymes in different bioprocess industries is discussed.

Structural characterization of high temperature composites

NASA Technical Reports Server (NTRS)

Mandell, J. F.; Grande, D. H.

1991-01-01

Glass, ceramic, and carbon matrix composite materials have emerged in recent years with potential properties and temperature resistance which make them attractive for high temperature applications such as gas turbine engines. At the outset of this study, only flexural tests were available to evaluate brittle matrix composites at temperatures in the 600 to 1000 C range. The results are described of an ongoing effort to develop appropriate tensile, compression, and shear test methods for high temperature use. A tensile test for unidirectional composites was developed and used to evaluate the properties and behavior of ceramic fiber reinforced glass and glass-ceramic matrix composites in air at temperatures up to 1000 C. The results indicate generally efficient fiber reinforcement and tolerance to matrix cracking similar to polymer matrix composites. Limiting properties in these materials may be an inherently very low transverse strain to failure, and high temperature embrittlement due to fiber/matrix interface oxidation.

Optical signal processing of spatially distributed sensor data in smart structures

NASA Technical Reports Server (NTRS)

Bennett, K. D.; Claus, R. O.; Murphy, K. A.; Goette, A. M.

1989-01-01

Smart structures which contain dense two- or three-dimensional arrays of attached or embedded sensor elements inherently require signal multiplexing and processing capabilities to permit good spatial data resolution as well as the adequately short calculation times demanded by real time active feedback actuator drive circuitry. This paper reports the implementation of an in-line optical signal processor and its application in a structural sensing system which incorporates multiple discrete optical fiber sensor elements. The signal processor consists of an array of optical fiber couplers having tailored s-parameters and arranged to allow gray code amplitude scaling of sensor inputs. The use of this signal processor in systems designed to indicate the location of distributed strain and damage in composite materials, as well as to quantitatively characterize that damage, is described. Extension of similar signal processing methods to more complicated smart materials and structures applications are discussed.

Complex systems in metabolic engineering.

PubMed

Winkler, James D; Erickson, Keesha; Choudhury, Alaksh; Halweg-Edwards, Andrea L; Gill, Ryan T

2015-12-01

Metabolic engineers manipulate intricate biological networks to build efficient biological machines. The inherent complexity of this task, derived from the extensive and often unknown interconnectivity between and within these networks, often prevents researchers from achieving desired performance. Other fields have developed methods to tackle the issue of complexity for their unique subset of engineering problems, but to date, there has not been extensive and comprehensive examination of how metabolic engineers use existing tools to ameliorate this effect on their own research projects. In this review, we examine how complexity affects engineering at the protein, pathway, and genome levels within an organism, and the tools for handling these issues to achieve high-performing strain designs. Quantitative complexity metrics and their applications to metabolic engineering versus traditional engineering fields are also discussed. We conclude by predicting how metabolic engineering practices may advance in light of an explicit consideration of design complexity. Copyright © 2015 Elsevier Ltd. All rights reserved.

Probiotic Ferulic Acid Esterase Active Lactobacillus fermentum NCIMB 5221 APA Microcapsules for Oral Delivery: Preparation and in Vitro Characterization.

PubMed

Tomaro-Duchesneau, Catherine; Saha, Shyamali; Malhotra, Meenakshi; Coussa-Charley, Michael; Kahouli, Imen; Jones, Mitchell L; Labbé, Alain; Prakash, Satya

2012-02-16

Probiotics possess potential therapeutic and preventative effects for various diseases and metabolic disorders. One important limitation for the oral delivery of probiotics is the harsh conditions of the upper gastrointestinal tract (GIT) which challenge bacterial viability and activity. One proposed method to surpass this obstacle is the use of microencapsulation to improve the delivery of bacterial cells to the lower GIT. The aim of this study is to use alginate-poly-L-lysine-alginate (APA) microcapsules to encapsulate Lactobacillus fermentum NCIMB 5221 and characterize its enzymatic activity and viability through a simulated GIT. This specific strain, in previous research, was characterized for its inherent ferulic acid esterase (FAE) activity which could prove beneficial in the development of a therapeutic for the treatment and prevention of cancers and metabolic disorders. Our findings demonstrate that the APA microcapsule does not slow the mass transfer of substrate into and that of the FA product out of the microcapsule, while also not impairing bacterial cell viability. The use of simulated gastrointestinal conditions led to a significant 2.5 log difference in viability between the free (1.10 × 104 ± 1.00 × 103 cfu/mL) and the microencapsulated (5.50 × 106 ± 1.00 × 105 cfu/mL) L. fermentum NCIMB 5221 following exposure. The work presented here suggests that APA microencapsulation can be used as an effective oral delivery method for L. fermentum NCIMB 5221, a FAE-active probiotic strain.

Computer based experimental studies of the Fry method of strain analysis on 2- and 3- dimensional grain populations

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

Longiaru, S.; Bhattacharyya, T.

1985-01-01

Inherent in Fry's (1979) all-object separation method of strain analysis are the subtle conditions that 1) the grains or phenocrysts being counted are of equal diameter and 2) that the true centers of such grains lie within the plane of measurement. When such conditions are met, the technique yields accurate, easily interpreted voids within all-object separation (AOS) plots for both deformed and non-deformed populations. Natural grain or phenocryst populations generally do not conform to these limitation and practical application of the technique from either a cut rock surface or thin section often yields diffuse patterns that are not easily interpreted.more » The authors examine the effect of grain size variation and grain/matrix ratio on AOS diagrams developed from computer generated spherical grain populations constructed in both two and three dimensions. They employ a random number generator and simple fitting algorithm to develop grain populations with known statistical parameters. Such control allows for the modeling of many types of natural grain size populations such as fluvial sandstones, porphyritic ash flow tuffs, augen gneisses, etc. They show that significant grain size variation in a two dimensional population contributes substantial noise in to the AOS diagram and that an additional level of noise is encountered when dealing with slices through populations modeled in three dimensions. Some of this noise can be eliminated by rigorous sampling of only subsets of the total grain population.« less

Probiotic Ferulic Acid Esterase Active Lactobacillus fermentum NCIMB 5221 APA Microcapsules for Oral Delivery: Preparation and in Vitro Characterization

PubMed Central

Tomaro-Duchesneau, Catherine; Saha, Shyamali; Malhotra, Meenakshi; Coussa-Charley, Michael; Kahouli, Imen; Jones, Mitchell L.; Labbé, Alain; Prakash, Satya

2012-01-01

Probiotics possess potential therapeutic and preventative effects for various diseases and metabolic disorders. One important limitation for the oral delivery of probiotics is the harsh conditions of the upper gastrointestinal tract (GIT) which challenge bacterial viability and activity. One proposed method to surpass this obstacle is the use of microencapsulation to improve the delivery of bacterial cells to the lower GIT. The aim of this study is to use alginate-poly-L-lysine-alginate (APA) microcapsules to encapsulate Lactobacillus fermentum NCIMB 5221 and characterize its enzymatic activity and viability through a simulated GIT. This specific strain, in previous research, was characterized for its inherent ferulic acid esterase (FAE) activity which could prove beneficial in the development of a therapeutic for the treatment and prevention of cancers and metabolic disorders. Our findings demonstrate that the APA microcapsule does not slow the mass transfer of substrate into and that of the FA product out of the microcapsule, while also not impairing bacterial cell viability. The use of simulated gastrointestinal conditions led to a significant 2.5 log difference in viability between the free (1.10 × 104 ± 1.00 × 103 cfu/mL) and the microencapsulated (5.50 × 106 ± 1.00 × 105 cfu/mL) L. fermentum NCIMB 5221 following exposure. The work presented here suggests that APA microencapsulation can be used as an effective oral delivery method for L. fermentum NCIMB 5221, a FAE-active probiotic strain. PMID:24288090

Plant-based assessment of inherent soil productivity and contributions to China's cereal crop yield increase since 1980.

PubMed

Fan, Mingsheng; Lal, Rattan; Cao, Jian; Qiao, Lei; Su, Yansen; Jiang, Rongfeng; Zhang, Fusuo

2013-01-01

China's food production has increased 6-fold during the past half-century, thanks to increased yields resulting from the management intensification, accomplished through greater inputs of fertilizer, water, new crop strains, and other Green Revolution's technologies. Yet, changes in underlying quality of soils and their effects on yield increase remain to be determined. Here, we provide a first attempt to quantify historical changes in inherent soil productivity and their contributions to the increase in yield. The assessment was conducted based on data-set derived from 7410 on-farm trials, 8 long-term experiments and an inventory of soil organic matter concentrations of arable land. Results show that even without organic and inorganic fertilizer addition crop yield from on-farm trials conducted in the 2000s was significantly higher compared with those in the 1980s - the increase ranged from 0.73 to 1.76 Mg/ha for China's major irrigated cereal-based cropping systems. The increase in on-farm yield in control plot since 1980s was due primarily to the enhancement of soil-related factors, and reflected inherent soil productivity improvement. The latter led to higher and stable yield with adoption of improved management practices, and contributed 43% to the increase in yield for wheat and 22% for maize in the north China, and, 31%, 35% and 22% for early and late rice in south China and for single rice crop in the Yangtze River Basin since 1980. Thus, without an improvement in inherent soil productivity, the 'Agricultural Miracle in China' would not have happened. A comprehensive strategy of inherent soil productivity improvement in China, accomplished through combining engineering-based measures with biological-approaches, may be an important lesson for the developing world. We propose that advancing food security in 21st century for both China and other parts of world will depend on continuously improving inherent soil productivity.

The Antimicrobial Properties of Zinc-Releasing Bioceramics

NASA Astrophysics Data System (ADS)

He, Xin

Up to 80% of nosocomial infections are caused by biofilm-producing bacteria such as Staphylococci and Pseudomonas aeruginosa. These types of microorganisms can become resistant to antibiotics and are difficult to eliminate. As such, there is tremendous interest in developing bioactive implant materials that can help to minimize these post- operative infections. Using water-based chemistry, we developed an economical, biodegradable and biocompatible orthopedic implant material consisting of zinc- doped hydroxyapatite (HA), which mimics the main inorganic component of the bone. Because the crystallinity of HA is typically too compact for efficient drug release, we substituted calcium ions in HA with zinc during the synthesis step to perturb the crystal structure. An added benefit is that zinc itself is a microelement of the human body with anti-inflammatory property, and we hypothesized that Zn-doped HA is an inherently antibacterial material. All HA samples were synthesized by a co-precipitation method using aqueous solutions of Zinc nitrate, Calcium Nitrate, and Ammonium Phosphate. XRD data showed that Zn was successfully incorporated into the HA. The effectiveness of Zn-doped HA against a model biofilm-forming bacterium is currently being evaluated using a wild-type strain and a streptomycin- resistant strain of Pseudomonas syringae pv. papulans (Psp) which is a plant pathogen isolated from diseased apples. Key words: Hydroxyapatite, Zinc, Citrate, Pseudomonas, Antibacterial.

High-Strain-Rate Material Behavior and Adiabatic Material Instability in Impact of Micron-Scale Al-6061 Particles

NASA Astrophysics Data System (ADS)

Chen, Qiyong; Alizadeh, Arash; Xie, Wanting; Wang, Xuemei; Champagne, Victor; Gouldstone, Andrew; Lee, Jae-Hwang; Müftü, Sinan

2018-04-01

Impact of spherical particles onto a flat sapphire surface was investigated in 50-950 m/s impact speed range experimentally and theoretically. Material parameters of the bilinear Johnson-Cook model were determined based on comparison of deformed particle shapes from experiment and simulation. Effects of high-strain-rate plastic flow, heat generation due to plasticity, material damage, interfacial friction and heat transfer were modeled. Four distinct regions were identified inside the particle by analyzing temporal variation of material flow. A relatively small volume of material near the impact zone becomes unstable due to plasticity-induced heating, accompanied by severe drop in the flow stress for impact velocity that exceeds 500 m/s. Outside of this region, flow stress is reduced due to temperature effects without the instability. Load carrying capacity of the material degrades and the material expands horizontally leading to jetting. The increase in overall plastic and frictional dissipation with impact velocity was found to be inherently lower than the increase in the kinetic energy at high speeds, leading to the instability. This work introduces a novel method to characterize HSR (109 s-1) material properties and also explains coupling between HSR material behavior and mechanics that lead to extreme deformation.

Near Real-Time Probabilistic Damage Diagnosis Using Surrogate Modeling and High Performance Computing

NASA Technical Reports Server (NTRS)

Warner, James E.; Zubair, Mohammad; Ranjan, Desh

2017-01-01

This work investigates novel approaches to probabilistic damage diagnosis that utilize surrogate modeling and high performance computing (HPC) to achieve substantial computational speedup. Motivated by Digital Twin, a structural health management (SHM) paradigm that integrates vehicle-specific characteristics with continual in-situ damage diagnosis and prognosis, the methods studied herein yield near real-time damage assessments that could enable monitoring of a vehicle's health while it is operating (i.e. online SHM). High-fidelity modeling and uncertainty quantification (UQ), both critical to Digital Twin, are incorporated using finite element method simulations and Bayesian inference, respectively. The crux of the proposed Bayesian diagnosis methods, however, is the reformulation of the numerical sampling algorithms (e.g. Markov chain Monte Carlo) used to generate the resulting probabilistic damage estimates. To this end, three distinct methods are demonstrated for rapid sampling that utilize surrogate modeling and exploit various degrees of parallelism for leveraging HPC. The accuracy and computational efficiency of the methods are compared on the problem of strain-based crack identification in thin plates. While each approach has inherent problem-specific strengths and weaknesses, all approaches are shown to provide accurate probabilistic damage diagnoses and several orders of magnitude computational speedup relative to a baseline Bayesian diagnosis implementation.

Inherent Anticipation in the Pharmaceutical and Biotechnology Industries.

PubMed

Goldman, Michael; Evans, Georgia; Zappia, Andrew

2015-04-15

Pharmaceutical and biotech research often involves discovering new properties of, or new methods to use, existing compositions. The doctrine of inherent anticipation, however, prevents the issuance and/or validity of a patent for discoveries deemed to have been implicitly disclosed in the prior art. This can be a barrier to patent rights in these technologies. Inherent anticipation therefore creates uncertainty for patent protection in the pharmaceutical and biotech sciences. Despite this uncertainty, Federal Circuit jurisprudence provides guidance on the boundaries of the inherent anticipation doctrine. In view of the case law, certain strategies may be employed to protect inventions that may potentially be viewed as inherent in the prior art. Copyright © 2015 Cold Spring Harbor Laboratory Press; all rights reserved.

The research of distributed interactive simulation based on HLA in coal mine industry inherent safety

NASA Astrophysics Data System (ADS)

Dou, Zhi-Wu

2010-08-01

To solve the inherent safety problem puzzling the coal mining industry, analyzing the characteristic and the application of distributed interactive simulation based on high level architecture (DIS/HLA), a new method is proposed for developing coal mining industry inherent safety distributed interactive simulation adopting HLA technology. Researching the function and structure of the system, a simple coal mining industry inherent safety is modeled with HLA, the FOM and SOM are developed, and the math models are suggested. The results of the instance research show that HLA plays an important role in developing distributed interactive simulation of complicated distributed system and the method is valid to solve the problem puzzling coal mining industry. To the coal mining industry, the conclusions show that the simulation system with HLA plays an important role to identify the source of hazard, to make the measure for accident, and to improve the level of management.

Dictionary learning-based spatiotemporal regularization for 3D dense speckle tracking

NASA Astrophysics Data System (ADS)

Lu, Allen; Zontak, Maria; Parajuli, Nripesh; Stendahl, John C.; Boutagy, Nabil; Eberle, Melissa; O'Donnell, Matthew; Sinusas, Albert J.; Duncan, James S.

2017-03-01

Speckle tracking is a common method for non-rigid tissue motion analysis in 3D echocardiography, where unique texture patterns are tracked through the cardiac cycle. However, poor tracking often occurs due to inherent ultrasound issues, such as image artifacts and speckle decorrelation; thus regularization is required. Various methods, such as optical flow, elastic registration, and block matching techniques have been proposed to track speckle motion. Such methods typically apply spatial and temporal regularization in a separate manner. In this paper, we propose a joint spatiotemporal regularization method based on an adaptive dictionary representation of the dense 3D+time Lagrangian motion field. Sparse dictionaries have good signal adaptive and noise-reduction properties; however, they are prone to quantization errors. Our method takes advantage of the desirable noise suppression, while avoiding the undesirable quantization error. The idea is to enforce regularization only on the poorly tracked trajectories. Specifically, our method 1.) builds data-driven 4-dimensional dictionary of Lagrangian displacements using sparse learning, 2.) automatically identifies poorly tracked trajectories (outliers) based on sparse reconstruction errors, and 3.) performs sparse reconstruction of the outliers only. Our approach can be applied on dense Lagrangian motion fields calculated by any method. We demonstrate the effectiveness of our approach on a baseline block matching speckle tracking and evaluate performance of the proposed algorithm using tracking and strain accuracy analysis.

Comparison of Virulence of Legionella longbeachae Strains in Guinea Pigs and U937 Macrophage-Like Cells

PubMed Central

Doyle, Robyn M.; Cianciotto, Nicholas P.; Banvi, Shaila; Manning, Paul A.; Heuzenroeder, Michael W.

2001-01-01

A guinea pig model of experimental legionellosis was established for assessment of virulence of isolates of Legionella longbeachae. The results showed that there were distinct virulence groupings of L. longbeachae serogroup 1 strains based on the severity of disease produced in this model. Statistical analysis of the animal model data suggests that Australian isolates of L. longbeachae may be inherently more virulent than non-Australian strains. Infection studies performed with U937 cells were consistent with the animal model studies and showed that isolates of this species were capable of multiplying within these phagocytic cells. Electron microscopy studies of infected lung tissue were also undertaken to determine the intracellular nature of L. longbeachae serogroup 1 infection. The data showed that phagosomes containing virulent L. longbeachae serogroup 1 appeared bloated, contained cellular debris and had an apparent rim of ribosomes while those containing avirulent L. longbeachae serogroup 1 were compact, clear and smooth. PMID:11500403

Single Targeted Exon Mutation Creates a True Congenic Mouse for Competitive Hematopoietic Stem Cell Transplantation: The C57BL/6-CD45.1(STEM) Mouse.

PubMed

Mercier, Francois E; Sykes, David B; Scadden, David T

2016-06-14

Defining the molecular regulators of hematopoietic stem and progenitor cells (HSPCs) requires in vivo functional analyses. Competitive bone marrow transplants (BMTs) compare control and test HSPCs to demonstrate the functional role of a genetic change or chemical perturbation. Competitive BMT is enabled by antibodies that specifically recognize hematopoietic cells from congenic mouse strains due to variants of the cell surface protein CD45, designated CD45.1 and CD45.2. The current congenic competitor strain, B6.SJL-Ptprc(a) Pepc(b)/BoyJ (CD45.1), has a substantial inherent disadvantage in competition against the C57BL/6 (CD45.2) strain, confounding experimental interpretation. Despite backcrossing, the congenic interval over which the B6.SJL-Ptprc(a) Pepc(b)/BoyJ strain differs is almost 40 Mb encoding ∼300 genes. Here, we demonstrate that a single amino acid change determines the CD45.1 epitope. Further, we report on the single targeted exon mutant (STEM) mouse strain, CD45.1(STEM), which is functionally equivalent to CD45.2 cells in competitive BMT. This strain will permit the precise definition of functional roles for candidate genes using in vivo HSPC assays. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Unusual Enhancement in Intrinsic Thermal Conductivity of Multilayer Graphene by Tensile Strains

DOE PAGES

Kuang, Youdi; Lindsay, Lucas R.; Huang, Baoling

2015-01-01

High basal plane thermal conductivity k of multi-layer graphene makes it promising for thermal management applications. Here we examine the effects of tensile strain on thermal transport in this system. Using a first principles Boltzmann-Peierls equation for phonon transport approach, we calculate the room-temperature in-plane lattice k of multi-layer graphene (up to four layers) and graphite under different isotropic tensile strains. The calculated in-plane k of graphite, finite mono-layer graphene and 3-layer graphene agree well with previous experiments. The dimensional transitions of the intrinsic k and the extent of the diffusive transport regime from mono-layer graphene to graphite are presented.more » We find a peak enhancement of intrinsic k for multi-layer graphene and graphite with increasing strain and the largest enhancement amplitude is about 40%. In contrast the calculated intrinsic k with tensile strain decreases for diamond and diverges for graphene, we show that the competition between the decreased mode heat capacities and the increased lifetimes of flexural phonons with increasing strain contribute to this k behavior. Similar k behavior is observed for 2-layer hexagonal boron nitride systems, suggesting that it is an inherent thermal transport property in multi-layer systems assembled of purely two dimensional atomic layers. This study provides insights into engineering k of multi-layer graphene and boron nitride by strain and into the nature of thermal transport in quasi-two-dimensional and highly anisotropic systems.« less

A visco-hyperelastic constitutive model for human spine ligaments.

PubMed

Jiang, Yugang; Wang, Yu; Peng, Xiongqi

2015-03-01

Human spine ligaments show a highly non-linear, strain rate dependent biomechanical behavior under tensile tests. A visco-hyperelastic fiber-reinforced constitutive model was accordingly developed for human ligaments, in which the energy density function is decomposed into two parts. The first part represents the elastic strain energy stored in the soft tissue, and the second part denotes the energy dissipated due to its inherent viscous characteristics. The model is applied to various human spinal ligaments including the anterior and posterior longitudinal ligaments, ligamentum flavum, capsular ligament, and interspinous ligament. Material parameters for each type of ligament were obtained by curve-fitting with corresponding experimental data available in the literature. The results indicate that the model presented here can properly characterize the visco-hyperelastic biomechanical behavior of human spine ligaments.

The Shock and Vibration Bulletin. Part 1. Welcome, Keynote Address, Invited Papers.

DTIC Science & Technology

1980-09-01

modes. Turning and pointing such a structure is a bit like aiming a wet noodle floating in a bowl of water. If you do it very slowly, it can be done...effective plastic strain 7P can be computed at each finite difference mesh point for each instant of time. Furthermore, the plastic work effected...attempted at any instant . In somewhat similar vein, digital control systems have the inherent capability to improve the performance of re- sponse

Effect of x-ray treatments on pathogenic bacteria, inherent microbiota, color, and texture on parsley leaves.

PubMed

Mahmoud, Barakat S M

2012-10-01

This work is a part of systematic studies of the effect of X-ray treatments on fresh produce. The main objective of this investigation was to study the effects of X-ray treatments in reducing the concentration of artificially inoculated Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica, and Shigella flexneri, and inherent microbiota on parsley leaves. The secondary objective was to study the effects of X-ray treatments on color and texture parameters on treated parsley leaves. The Dip-inoculated method was used to inoculate parsley leaves with a mixture of two or three strains of each tested organism at 10(8) to 10(9) colony-forming unit (CFU)/mL; the inoculated parsley leaves were then air-dried and followed by treatment with different doses of X-ray (0, 0.1, 0.5, 1.0, and 1.5 kGy) at 22°C and 55-60% relative humidity. Surviving bacterial populations on parsley leaves were evaluated using a nonselective medium (tryptic soy agar) with a selective medium overlay for each bacterium: E. coli O157:H7 (CT-SMAC agar), L. monocytogenes (MOA), and S. enterica and S. flexneri (XLD). Approximately 5.8, 3.1, 5.7, and 5.2 log CFU reductions of E. coli O157:H7, L. monocytogenes, S. enterica, and Shigella flexneri were achieved by treatment with 1.0 kGy X-ray, respectively. Furthermore, the populations of E. coli O157:H7, L. monocytogenes, S. enterica, and Shigella flexneri were reduced to less than the detectable limit (1.0 log CFU/g) by treatment with 1.5 kGy X-ray. Treatment with 1.5 kGy X-ray significantly reduced the initial inherent microbiota on parsley leaves, and inherent levels were significantly (p < 0.05) lower than the control sample throughout refrigerated storage for 30 days. No significant differences (p > 0.05) in color or texture of control and treated samples with 0.1-1.5 X-ray were observed. The results of investigation indicated that X-ray is an effective technology to eliminate E. coli O157:H7, L. monocytogenes, S. enterica, and Shigella flexneri, and to extend the shelf life of parsley leaves.

Geographic Origin and Host Cultivar Influence on Digestive Physiology of Spodoptera exigua (Lepidoptera: Noctuidae) Larvae

PubMed Central

Golikhajeh, Neshat; Razmjou, Jabraeil

2017-01-01

Digestive enzymatic activity in three geographic strains (Miandiab, Kalposh and Moghan regions) of Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) reared on different sugar beet cultivars (Dorothea, Rozier, Persia and Perimer) was studied under laboratory conditions (25 ± 1 °C, 65 ± 5% RH, and a photo period of 16:8 (L:D) h photoperiod). The results of this study demonstrated that digestive protease and amylase activity of S. exigua larvae was affected by both geographic origin of the pest and host plant cultivar. Three strains reared on the same sugar beet cultivars demonstrated different levels of proteolytic and amylolytic activities in fourth and fifth instars. The highest proteolytic and amylolytic activity, in most cases, was observed in larvae collected from Kalposh region. Among different sugar beet cultivars, the highest protease activity in three strains was observed on cultivars Rozier and Perimer. Nevertheless, the highest amylase activity was seen on cultivar Dorothea, and the lowest activity was seen on cultivar Rozier. This study suggested that variations in digestive enzymatic activity of three geographic strains of S. exigua might be attributed to local adaptation with their local host plant and environmental conditions inherent by larvae. PMID:28069730

Stability of surface plastic flow in large strain deformation of metals

NASA Astrophysics Data System (ADS)

Viswanathan, Koushik; Udapa, Anirduh; Sagapuram, Dinakar; Mann, James; Chandrasekar, Srinivasan

We examine large-strain unconstrained simple shear deformation in metals using a model two-dimensional cutting system and high-speed in situ imaging. The nature of the deformation mode is shown to be a function of the initial microstructure state of the metal and the deformation geometry. For annealed metals, which exhibit large ductility and strain hardening capacity, the commonly assumed laminar flow mode is inherently unstable. Instead, the imposed shear is accommodated by a highly rotational flow-sinuous flow-with vortex-like components and large-amplitude folding on the mesoscale. Sinuous flow is triggered by a plastic instability on the material surface ahead of the primary region of shear. On the other hand, when the material is extensively strain-hardened prior to shear, laminar flow again becomes unstable giving way to shear banding. The existence of these flow modes is established by stability analysis of laminar flow. The role of the initial microstructure state in determining the change in stability from laminar to sinuous / shear-banded flows in metals is elucidated. The implications for cutting, forming and wear processes for metals, and to surface plasticity phenomena such as mechanochemical Rehbinder effects are discussed.

The genomic proliferation of transposable elements in colonizing populations: Schistosoma mansoni in the new world.

PubMed

Wijayawardena, Bhagya K; DeWoody, J Andrew; Minchella, Dennis J

2015-06-01

Transposable elements (TEs) are mobile genes with an inherent ability to move within and among genomes. Theory predicts that TEs proliferate extensively during physiological stress due to the breakdown of TE repression systems. We tested this hypothesis in Schistosoma mansoni, a widespread trematode parasite that causes the human disease schistosomiasis. According to phylogenetic analysis, S. mansoni invaded the new world during the last 500 years. We hypothesized that new world strains of S. mansoni would have more copies of TEs than old world strains due to the physiological stress associated with invasion of the new world. We quantified the copy number of six TEs (Saci-1, Saci-2 and Saci-3, Perere-1, Merlin-sm1, and SmTRC1) in the genome and the transcriptome of old world and new world strains of S. mansoni, using qPCR relative quantification. As predicted, the genomes of new world parasites contain significantly more copies of class I and class II TEs in both laboratory and field strains. However, such differences are not observed in the transcriptome suggesting that either TE silencing mechanisms have reactivated to control the expression of these elements or the presence of inactive truncated copies of TEs.

A Probability Analysis of Historical Pregnancy and Fetal Data from Dutch Belted and New Zealand White Rabbit Strains from Embryo-Fetal Development Studies.

PubMed

Posobiec, Lorraine M; Cox, Estella M; Solomon, Howard M; Lewis, Elise M; Wang, Kai-fen; Stanislaus, Dinesh

2016-04-01

Embryo-fetal development (EFD) studies, typically in pregnant rats and rabbits, are conducted prior to enrolling females of reproductive age in clinical trials. Common rabbit strains used are the New Zealand White (NZW) and Dutch Belted (DB). As fetal abnormalities can occur in all groups, including controls, Historical Control Data (HCD) is compiled using data from control groups of EFD studies, and is used along with each study's concurrent control group to help determine whether fetal abnormalities are caused by the test article or are part of background incidences. A probability analysis was conducted on 2014 HCD collected at Charles River Inc., Horsham PA on Covance NZW, Covance DB, and Charles River (CR) NZW rabbits. The analysis was designed to determine the probability of 2 or 3 out of a group of 22 does aborting their litter or of having a fetal abnormality by chance. Results demonstrate that pregnancy parameters and fetal observations differ not only between strains, but between sources of rabbits of the same strain. As a result the probability of these observations occurring by chance in two or three litters was drastically different. Although no one single strain is perfect, this analysis highlights the need to appreciate the inherent differences in pregnancy and fetal abnormalities between strains, and points out that an apparent isolated increased incidence of an observation in one strain will not necessarily be test-article related in another strain. A robust HCD is critical for interpretation of EFD rabbit studies, regardless of the rabbit strain used. © 2016 Wiley Periodicals, Inc.

An Energy-Based Hysteresis Model for Magnetostrictive Transducers

NASA Technical Reports Server (NTRS)

Calkins, F. T.; Smith, R. C.; Flatau, A. B.

1997-01-01

This paper addresses the modeling of hysteresis in magnetostrictive transducers. This is considered in the context of control applications which require an accurate characterization of the relation between input currents and strains output by the transducer. This relation typically exhibits significant nonlinearities and hysteresis due to inherent properties of magnetostrictive materials. The characterization considered here is based upon the Jiles-Atherton mean field model for ferromagnetic hysteresis in combination with a quadratic moment rotation model for magnetostriction. As demonstrated through comparison with experimental data, the magnetization model very adequately quantifies both major and minor loops under various operating conditions. The combined model can then be used to accurately characterize output strains at moderate drive levels. The advantages to this model lie in the small number (six) of required parameters and the flexibility it exhibits in a variety of operating conditions.

Note: Modified anvil design for improved reliability in DT-Cup experiments.

PubMed

Hunt, Simon A; Dobson, David P

2017-12-01

The Deformation T-Cup (DT-Cup) is a modified 6-8 multi-anvil apparatus capable of controlled strain-rate deformation experiments at pressures greater than 18 GPa. Controlled strain-rate deformation was enabled by replacing two of the eight cubic "second-stage" anvils with hexagonal cross section deformation anvils and modifying the "first-stage" wedges. However, with these modifications approximately two-thirds of experiments end with rupture of the hexagonal anvils. By replacing the hexagonal anvils with cubic anvils and, split, deformation wedge extensions, we restore the massive support to the deformation anvils that were inherent in the original multi-anvil design and prevent deformation anvil failure. With the modified parts, the DT-Cup has an experimental success rate that is similar to that of a standard hydrostatic 6-8 multi-anvil apparatus.

[ABILITY OF STAPHYLOCOCCUS OF VARIOUS STRAINS TO CREATE BIOFILMS AND THEIR EFFECT ON HUMAN BODY CELLS].

PubMed

Kornienko, M A; Kopyltsov, V N; Shevlyagina, N V; Didenko, L V; Lyubasovskaya, L A; Priputnevich, T V; Ilina, E N

2016-01-01

The urgency of the staphylococcus research is due to its ability to cause severe infections: softtissue infections, endocarditis, sepsis, toxic shock syndrome, and food poisoning. Coagulase-positive Staphylococcus aureus is the main infection agent of intrahospital infections. This agent has many factors of pathogenicity, which are well known. Among the coagulase-negative staphylococcus (CNS) strains, S. haemolyticus and S. epidermidis are clinically important, because they cause infections in patients with weak immune system. The mechanisms of the CNS pathogenicity are insufficiently understood. The goal of this work was to evaluate the potential pathogenicity of clinical strains of CNS from their capacity to create biofilms and the character of their interaction with human body cells by the example of the HT-29 cell culture. The research was carried out in laboratory strain S. aureus ATCC 29213 and clinical strains S. haemolyticus SH39, S. epidermidis SE36-1 isolated from the neonatal autopsy materials. The visual tests of biofilm formation by each strain and testing of the impact of the strains on the cell culture HT-29 was carried out in this work. The two species of CNS form biofilms at a higher rate than S. aureus. Upon incubation for 2 h of HT-29 cells with staphylococcus strains tested in this work, adhesion of bacteria on cell surface was observed. The adhesion was most pronounced in case of S. aureus ATCC 29213 and S. haemolyticus SH39. Upon 3 h of incubation with S. aureus ATCC 29213 and S. haemolyticus SH39, destruction of cell HT-29 monolayer was observed. The incubation for 24 h with the 3 strains tested in this work caused complete destruction of cell HT-29 monolayer. The maximal toxic effect on HT-29 cells was inherent in the strain S. haemolyticus SH39. The aggregate of the results obtained in this work indicates the presence of the pathogenicity factors in the strains S. haemolyticus SH39, which require additional research.

Progress in Metabolic Engineering of Saccharomyces cerevisiae

PubMed Central

Nevoigt, Elke

2008-01-01

Summary: The traditional use of the yeast Saccharomyces cerevisiae in alcoholic fermentation has, over time, resulted in substantial accumulated knowledge concerning genetics, physiology, and biochemistry as well as genetic engineering and fermentation technologies. S. cerevisiae has become a platform organism for developing metabolic engineering strategies, methods, and tools. The current review discusses the relevance of several engineering strategies, such as rational and inverse metabolic engineering, evolutionary engineering, and global transcription machinery engineering, in yeast strain improvement. It also summarizes existing tools for fine-tuning and regulating enzyme activities and thus metabolic pathways. Recent examples of yeast metabolic engineering for food, beverage, and industrial biotechnology (bioethanol and bulk and fine chemicals) follow. S. cerevisiae currently enjoys increasing popularity as a production organism in industrial (“white”) biotechnology due to its inherent tolerance of low pH values and high ethanol and inhibitor concentrations and its ability to grow anaerobically. Attention is paid to utilizing lignocellulosic biomass as a potential substrate. PMID:18772282

Constitutive modeling of jugular vein-derived venous valve leaflet tissues.

PubMed

Kaul, Nayyan; Huang, Hsiao-Ying Shadow

2017-11-01

Venous valve tissues, though used in vein reconstruction surgeries and bioprosthetic valves with moderate success, have not been extensively studied with respect to their structure. Their inherent anisotropic, non-linear behavior combined with severe diseases which affect veins, such as chronic venous insufficiency, warrant understanding the structure and material behavior of these tissues. Hence, before any bioprosthetic grafts may be used in place of tissues, it is of the utmost importance to understand the mechanical and structural properties of these tissues as this may lead to higher success rates for valve replacement surgeries. The longevity of the bioprosthetics may also increase if the manufactured grafts behave the same as native valves. Building on the scant information about the uniaxial and biaxial mechanical properties of jugular venous valves and wall tissues from previous studies, the current focus of our investigation lies in understanding the material behavior by establishing a phenomenological strain energy-based constitutive relation for the tissues. We used bovine veins to study the behavior of valve leaflet tissue and adjoining wall tissue (from the proximal and distal ends of the veins) under different biaxial testing protocols. We looked at the behavior of numerical partial derivatives of the strain energy to select a suitable functional form for the strain energy for wall and valve tissues. Using this strain energy descriptor, we determined the Cauchy stress and compared it with experimental results under additional sets of displacement-controlled biaxial testing protocols to find material specific model parameters by the Powell's method algorithm. Results show that whereas wall tissue strain energy can be explained using a polynomial non-linear function, the valve tissue, due to higher non-linearities, requires an exponential function. This study may provide useful information for the primary stages of bioprosthetic designs and replacement surgeries and may support future studies investigating structural models. It may also support the study of valvular diseases by providing a way to understand material properties and behavior and to form a continuum model when required for numerical analyses and computational simulations. Copyright © 2017 Elsevier Ltd. All rights reserved.

A comparative analysis of single cell and droplet-based FACS for improving production phenotypes: Riboflavin overproduction in Yarrowia lipolytica.

PubMed

Wagner, James M; Liu, Leqian; Yuan, Shuo-Fu; Venkataraman, Maya V; Abate, Adam R; Alper, Hal S

2018-04-23

Evolutionary approaches to strain engineering inherently require the identification of suitable selection techniques for the product and phenotype of interest. In this work, we undertake a comparative analysis of two related but functionally distinct methods of high-throughput screening: traditional single cell fluorescence activated cell sorting (single cell FACS) and microdroplet-enabled FACS (droplet FACS) using water/oil/water (w/o/w) emulsions. To do so, we first engineer and evolve the non-conventional yeast Yarrowia lipolytica for high extracellular production of riboflavin (vitamin B2), an innately fluorescent product. Following mutagenesis and adaptive evolution, a direct parity-matched comparison of these two selection strategies was conducted. Both single cell FACS and droplet FACS led to significant increases in total riboflavin titer (32 and 54 fold relative to the parental PO1f strain, respectively). However, single cell FACS favored intracellular riboflavin accumulation (with only 70% of total riboflavin secreted) compared with droplet FACS that favored extracellular product accumulation (with 90% of total riboflavin secreted). We find that for the test case of riboflavin, the extent of secretion and total production were highly correlated. The resulting differences in production modes and levels clearly demonstrate the significant impact that selection approaches can exert on final evolutionary outcomes in strain engineering. Moreover, we note that these results provide a cautionary tale when intracellular read-outs of product concentration (including signals from biosensors) are used as surrogates for total production of potentially secreted products. In this regard, these results demonstrate that extracellular production is best assayed through an encapsulation technique when performing high throughput screening. Copyright © 2018 International Metabolic Engineering Society. Published by Elsevier Inc. All rights reserved.

Fabrication and implantation of miniature dual-element strain gages for measuring in vivo gastrointestinal contractions in rodents.

PubMed

Holmes, Gregory M; Swartz, Emily M; McLean, Margaret S

2014-09-18

Gastrointestinal dysfunction remains a major cause of morbidity and mortality. Indeed, gastrointestinal (GI) motility in health and disease remains an area of productive research with over 1,400 published animal studies in just the last 5 years. Numerous techniques have been developed for quantifying smooth muscle activity of the stomach, small intestine, and colon. In vitro and ex vivo techniques offer powerful tools for mechanistic studies of GI function, but outside the context of the integrated systems inherent to an intact organism. Typically, measuring in vivo smooth muscle contractions of the stomach has involved an anesthetized preparation coupled with the introduction of a surgically placed pressure sensor, a static pressure load such as a mildly inflated balloon or by distending the stomach with fluid under barostatically-controlled feedback. Yet many of these approaches present unique disadvantages regarding both the interpretation of results as well as applicability for in vivo use in conscious experimental animal models. The use of dual element strain gages that have been affixed to the serosal surface of the GI tract has offered numerous experimental advantages, which may continue to outweigh the disadvantages. Since these gages are not commercially available, this video presentation provides a detailed, step-by-step guide to the fabrication of the current design of these gages. The strain gage described in this protocol is a design for recording gastric motility in rats. This design has been modified for recording smooth muscle activity along the entire GI tract and requires only subtle variation in the overall fabrication. Representative data from the entire GI tract are included as well as discussion of analysis methods, data interpretation and presentation.

Optical fiber sensors for the non-destructive evaluation of materials

NASA Technical Reports Server (NTRS)

1986-01-01

The operation of the modal domain vibration sensor was demonstrated in several simple vibrational systems. Two apparent advantages are the sensors bandwidth and sensitivity. An inherent drawback of standard vibration detection devices is their rapid cost increase with high frequency bandwidth. This sensor showed consistent response in the freqency range of 1.5 to 400 Hz. By imparting very small but measurable excitations in the structures, the sensors ability to respond to very low order vibration induced strain was established. Dynamic ranges on the order of 18 to 22 dB for the CF beam and string systems respectively were observed. The sensor itself represents a very simple system: a coherent source, a single fiber and a low bandwidth detector. The inherent advantages of ruggedness and immunity to external radiation can also be added. Finally, the sensor minimally impairs structural motion through loading, an advantage in monitoring small vibrations or lightweight structures. Some drawbacks of the sensor are also noted.

Effect of shape and size of lung and chest wall on stresses in the lung

NASA Technical Reports Server (NTRS)

Vawter, D. L.; Matthews, F. L.; West, J. B.

1975-01-01

To understand better the effect of shape and size of lung and chest wall on the distribution of stresses, strains, and surface pressures, we analyzed a theoretical model using the technique of finite elements. First we investigated the effects of changing the chest wall shape during expansion, and second we studied lungs of a variety of inherent shapes and sizes. We found that, in general, the distributions of alveolar size, mechanical stresses, and surface pressures in the lungs were dominated by the weight of the lung and that changing the shape of the lung or chest wall had relatively little effect. Only at high states of expansion where the lung was very stiff did changing the shape of the chest wall cause substantial changes. Altering the inherent shape of the lung generally had little effect but the topographical differences in stresses and surface pressures were approximately proportional to lung height. The results are generally consistent with those found in the dog by Hoppin et al (1969).

Efficient estimation of the maximum metabolic productivity of batch systems.

PubMed

St John, Peter C; Crowley, Michael F; Bomble, Yannick J

2017-01-01

Production of chemicals from engineered organisms in a batch culture involves an inherent trade-off between productivity, yield, and titer. Existing strategies for strain design typically focus on designing mutations that achieve the highest yield possible while maintaining growth viability. While these methods are computationally tractable, an optimum productivity could be achieved by a dynamic strategy in which the intracellular division of resources is permitted to change with time. New methods for the design and implementation of dynamic microbial processes, both computational and experimental, have therefore been explored to maximize productivity. However, solving for the optimal metabolic behavior under the assumption that all fluxes in the cell are free to vary is a challenging numerical task. Previous studies have therefore typically focused on simpler strategies that are more feasible to implement in practice, such as the time-dependent control of a single flux or control variable. This work presents an efficient method for the calculation of a maximum theoretical productivity of a batch culture system using a dynamic optimization framework. The proposed method follows traditional assumptions of dynamic flux balance analysis: first, that internal metabolite fluxes are governed by a pseudo-steady state, and secondly that external metabolite fluxes are dynamically bounded. The optimization is achieved via collocation on finite elements, and accounts explicitly for an arbitrary number of flux changes. The method can be further extended to calculate the complete Pareto surface of productivity as a function of yield. We apply this method to succinate production in two engineered microbial hosts, Escherichia coli and Actinobacillus succinogenes , and demonstrate that maximum productivities can be more than doubled under dynamic control regimes. The maximum theoretical yield is a measure that is well established in the metabolic engineering literature and whose use helps guide strain and pathway selection. We present a robust, efficient method to calculate the maximum theoretical productivity: a metric that will similarly help guide and evaluate the development of dynamic microbial bioconversions. Our results demonstrate that nearly optimal yields and productivities can be achieved with only two discrete flux stages, indicating that near-theoretical productivities might be achievable in practice.

Strain rate sensitivity of the tensile strength of two silicon carbides: experimental evidence and micromechanical modelling

NASA Astrophysics Data System (ADS)

Zinszner, Jean-Luc; Erzar, Benjamin; Forquin, Pascal

2017-01-01

Ceramic materials are commonly used to design multi-layer armour systems thanks to their favourable physical and mechanical properties. However, during an impact event, fragmentation of the ceramic plate inevitably occurs due to its inherent brittleness under tensile loading. Consequently, an accurate model of the fragmentation process is necessary in order to achieve an optimum design for a desired armour configuration. In this work, shockless spalling tests have been performed on two silicon carbide grades at strain rates ranging from 103 to 104 s-1 using a high-pulsed power generator. These spalling tests characterize the tensile strength strain rate sensitivity of each ceramic grade. The microstructural properties of the ceramics appear to play an important role on the strain rate sensitivity and on the dynamic tensile strength. Moreover, this experimental configuration allows for recovering damaged, but unbroken specimens, giving unique insight on the fragmentation process initiated in the ceramics. All the collected data have been compared with corresponding results of numerical simulations performed using the Denoual-Forquin-Hild anisotropic damage model. Good agreement is observed between numerical simulations and experimental data in terms of free surface velocity, size and location of the damaged zones along with crack density in these damaged zones. This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'.

3D mechanical stratigraphy of a deformed multi-layer: Linking sedimentary architecture and strain partitioning

NASA Astrophysics Data System (ADS)

Cawood, Adam J.; Bond, Clare E.

2018-01-01

Stratigraphic influence on structural style and strain distribution in deformed sedimentary sequences is well established, in models of 2D mechanical stratigraphy. In this study we attempt to refine existing models of stratigraphic-structure interaction by examining outcrop scale 3D variations in sedimentary architecture and the effects on subsequent deformation. At Monkstone Point, Pembrokeshire, SW Wales, digital mapping and virtual scanline data from a high resolution virtual outcrop have been combined with field observations, sedimentary logs and thin section analysis. Results show that significant variation in strain partitioning is controlled by changes, at a scale of tens of metres, in sedimentary architecture within Upper Carboniferous fluvio-deltaic deposits. Coupled vs uncoupled deformation of the sequence is defined by the composition and lateral continuity of mechanical units and unit interfaces. Where the sedimentary sequence is characterized by gradational changes in composition and grain size, we find that deformation structures are best characterized by patterns of distributed strain. In contrast, distinct compositional changes vertically and in laterally equivalent deposits results in highly partitioned deformation and strain. The mechanical stratigraphy of the study area is inherently 3D in nature, due to lateral and vertical compositional variability. Consideration should be given to 3D variations in mechanical stratigraphy, such as those outlined here, when predicting subsurface deformation in multi-layers.

Strain rate sensitivity of the tensile strength of two silicon carbides: experimental evidence and micromechanical modelling.

PubMed

Zinszner, Jean-Luc; Erzar, Benjamin; Forquin, Pascal

2017-01-28

Ceramic materials are commonly used to design multi-layer armour systems thanks to their favourable physical and mechanical properties. However, during an impact event, fragmentation of the ceramic plate inevitably occurs due to its inherent brittleness under tensile loading. Consequently, an accurate model of the fragmentation process is necessary in order to achieve an optimum design for a desired armour configuration. In this work, shockless spalling tests have been performed on two silicon carbide grades at strain rates ranging from 10 3 to 10 4  s -1 using a high-pulsed power generator. These spalling tests characterize the tensile strength strain rate sensitivity of each ceramic grade. The microstructural properties of the ceramics appear to play an important role on the strain rate sensitivity and on the dynamic tensile strength. Moreover, this experimental configuration allows for recovering damaged, but unbroken specimens, giving unique insight on the fragmentation process initiated in the ceramics. All the collected data have been compared with corresponding results of numerical simulations performed using the Denoual-Forquin-Hild anisotropic damage model. Good agreement is observed between numerical simulations and experimental data in terms of free surface velocity, size and location of the damaged zones along with crack density in these damaged zones.This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'. © 2016 The Author(s).

Strain rate sensitivity of the tensile strength of two silicon carbides: experimental evidence and micromechanical modelling

PubMed Central

Erzar, Benjamin

2017-01-01

Ceramic materials are commonly used to design multi-layer armour systems thanks to their favourable physical and mechanical properties. However, during an impact event, fragmentation of the ceramic plate inevitably occurs due to its inherent brittleness under tensile loading. Consequently, an accurate model of the fragmentation process is necessary in order to achieve an optimum design for a desired armour configuration. In this work, shockless spalling tests have been performed on two silicon carbide grades at strain rates ranging from 103 to 104 s−1 using a high-pulsed power generator. These spalling tests characterize the tensile strength strain rate sensitivity of each ceramic grade. The microstructural properties of the ceramics appear to play an important role on the strain rate sensitivity and on the dynamic tensile strength. Moreover, this experimental configuration allows for recovering damaged, but unbroken specimens, giving unique insight on the fragmentation process initiated in the ceramics. All the collected data have been compared with corresponding results of numerical simulations performed using the Denoual–Forquin–Hild anisotropic damage model. Good agreement is observed between numerical simulations and experimental data in terms of free surface velocity, size and location of the damaged zones along with crack density in these damaged zones. This article is part of the themed issue ‘Experimental testing and modelling of brittle materials at high strain rates’. PMID:27956504

Dynamic and Inherent B0 Correction for DTI Using Stimulated Echo Spiral Imaging

PubMed Central

Avram, Alexandru V.; Guidon, Arnaud; Truong, Trong-Kha; Liu, Chunlei; Song, Allen W.

2013-01-01

Purpose To present a novel technique for high-resolution stimulated echo (STE) diffusion tensor imaging (DTI) with self-navigated interleaved spirals (SNAILS) readout trajectories that can inherently and dynamically correct for image artifacts due to spatial and temporal variations in the static magnetic field (B0) resulting from eddy currents, tissue susceptibilities, subject/physiological motion, and hardware instabilities. Methods The Hahn spin echo formed by the first two 90° radio-frequency pulses is balanced to consecutively acquire two additional images with different echo times (TE) and generate an inherent field map, while the diffusion-prepared STE signal remains unaffected. For every diffusion-encoding direction, an intrinsically registered field map is estimated dynamically and used to effectively and inherently correct for off-resonance artifacts in the reconstruction of the corresponding diffusion-weighted image (DWI). Results After correction with the dynamically acquired field maps, local blurring artifacts are specifically removed from individual STE DWIs and the estimated diffusion tensors have significantly improved spatial accuracy and larger fractional anisotropy. Conclusion Combined with the SNAILS acquisition scheme, our new method provides an integrated high-resolution short-TE DTI solution with inherent and dynamic correction for both motion-induced phase errors and off-resonance effects. PMID:23630029

Probabilistic homogenization of random composite with ellipsoidal particle reinforcement by the iterative stochastic finite element method

NASA Astrophysics Data System (ADS)

Sokołowski, Damian; Kamiński, Marcin

2018-01-01

This study proposes a framework for determination of basic probabilistic characteristics of the orthotropic homogenized elastic properties of the periodic composite reinforced with ellipsoidal particles and a high stiffness contrast between the reinforcement and the matrix. Homogenization problem, solved by the Iterative Stochastic Finite Element Method (ISFEM) is implemented according to the stochastic perturbation, Monte Carlo simulation and semi-analytical techniques with the use of cubic Representative Volume Element (RVE) of this composite containing single particle. The given input Gaussian random variable is Young modulus of the matrix, while 3D homogenization scheme is based on numerical determination of the strain energy of the RVE under uniform unit stretches carried out in the FEM system ABAQUS. The entire series of several deterministic solutions with varying Young modulus of the matrix serves for the Weighted Least Squares Method (WLSM) recovery of polynomial response functions finally used in stochastic Taylor expansions inherent for the ISFEM. A numerical example consists of the High Density Polyurethane (HDPU) reinforced with the Carbon Black particle. It is numerically investigated (1) if the resulting homogenized characteristics are also Gaussian and (2) how the uncertainty in matrix Young modulus affects the effective stiffness tensor components and their PDF (Probability Density Function).

Consolidated bioprocessing of transgenic switchgrass by an engineered and evolved Clostridium thermocellum strain

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

Yee, Kelsey L; Rodriguez Jr, Miguel; Thompson, Olivia A

Background: Switchgrass is an abundant and dedicated bioenergy feedstock however its inherent recalcitrance is one of the economic hurdles for producing biofuels. The down-regulation of the caffeic acid O-methyl transferase (COMT) gene in the lignin pathway of switchgrass reduced lignin content and S/G ratio, and the transgenic lines showed improved fermentation yield with S. cerevisiae and C. thermocellum (ATCC 27405) in comparison to the wild-type switchgrass. Results: Here we examine the fermentation potential of the COMT transgenic switchgrass and its wild-type line, with an engineered and evolved Clostridium thermocellum (M1570) strain. The fermentation of the transgenic switchgrass had superior conversionmore » relative to the control line with an increase of 20% and ethanol was the primary metabolite accounting for 90% of the total metabolites measured by HPLC. Conclusions: The down-regulation of the COMT gene in switchgrass reduced recalcitrance and improved microbial bioconversion yield. Moreover, these results showed ethanol as the main fermentation metabolite produced by an engineered and evolved C. thermocellum strain grown on a transgenic switchgrass.« less

A Shape Memory Alloy Based Cryogenic Thermal Conduction Switch

NASA Technical Reports Server (NTRS)

Notardonato, W. U.; Krishnan, V. B.; Singh, J. D.; Woodruff, T. R.; Vaidyanathan, R.

2005-01-01

Shape memory alloys (SMAs) can produce large strains when deformed (e.g., up to 8%). Heating results in a phase transformation and associated recovery of all the accumulated strain. This strain recovery can occur against large forces, resulting in their use as actuators. Thus an SMA element can integrate both sensory and actuation functions, by inherently sensing a change in temperature and actuating by undergoing a shape change as a result of a temperature-induced phase transformation. Two aspects of our work on cryogenic SMAs are addressed here. First - a shape memory alloy based cryogenic thermal conduction switch for operation between dewars of liquid methane and liquid oxygen in a common bulkhead arrangement is discussed. Such a switch integrates the sensor element and the actuator element and can be used to create a variable thermal sink to other cryogenic tanks for liquefaction, densification, and zero boil-off systems for advanced spaceport applications. Second - fabrication via arc-melting and subsequent materials testing of SMAs with cryogenic transformation temperatures for use in the aforementioned switch is discussed.

High-Resolution Multi-Shot Spiral Diffusion Tensor Imaging with Inherent Correction of Motion-Induced Phase Errors

PubMed Central

Truong, Trong-Kha; Guidon, Arnaud

2014-01-01

Purpose To develop and compare three novel reconstruction methods designed to inherently correct for motion-induced phase errors in multi-shot spiral diffusion tensor imaging (DTI) without requiring a variable-density spiral trajectory or a navigator echo. Theory and Methods The first method simply averages magnitude images reconstructed with sensitivity encoding (SENSE) from each shot, whereas the second and third methods rely on SENSE to estimate the motion-induced phase error for each shot, and subsequently use either a direct phase subtraction or an iterative conjugate gradient (CG) algorithm, respectively, to correct for the resulting artifacts. Numerical simulations and in vivo experiments on healthy volunteers were performed to assess the performance of these methods. Results The first two methods suffer from a low signal-to-noise ratio (SNR) or from residual artifacts in the reconstructed diffusion-weighted images and fractional anisotropy maps. In contrast, the third method provides high-quality, high-resolution DTI results, revealing fine anatomical details such as a radial diffusion anisotropy in cortical gray matter. Conclusion The proposed SENSE+CG method can inherently and effectively correct for phase errors, signal loss, and aliasing artifacts caused by both rigid and nonrigid motion in multi-shot spiral DTI, without increasing the scan time or reducing the SNR. PMID:23450457

Strain Gauges Based on CVD Graphene Layers and Exfoliated Graphene Nanoplatelets with Enhanced Reproducibility and Scalability for Large Quantities

PubMed Central

Yokaribas, Volkan; Schneider, Daniel S.; Friebertshäuser, Philipp; Lemme, Max C.; Fritzen, Claus-Peter

2017-01-01

The two-dimensional material graphene promises a broad variety of sensing activities. Based on its low weight and high versatility, the sensor density can significantly be increased on a structure, which can improve reliability and reduce fluctuation in damage detection strategies such as structural health monitoring (SHM). Moreover; it initializes the basis of structure–sensor fusion towards self-sensing structures. Strain gauges are extensively used sensors in scientific and industrial applications. In this work, sensing in small strain fields (from −0.1% up to 0.1%) with regard to structural dynamics of a mechanical structure is presented with sensitivities comparable to bulk materials by measuring the inherent piezoresistive effect of graphene grown by chemical vapor deposition (CVD) with a very high aspect ratio of approximately 4.86 × 108. It is demonstrated that the increasing number of graphene layers with CVD graphene plays a key role in reproducible strain gauge application since defects of individual layers may become less important in the current path. This may lead to a more stable response and, thus, resulting in a lower scattering.. Further results demonstrate the piezoresistive effect in a network consisting of liquid exfoliated graphene nanoplatelets (GNP), which result in even higher strain sensitivity and reproducibility. A model-assisted approach provides the main parameters to find an optimum of sensitivity and reproducibility of GNP films. The fabricated GNP strain gauges show a minimal deviation in PRE effect with a GF of approximately 5.6 and predict a linear electromechanical behaviour up to 1% strain. Spray deposition is used to develop a low-cost and scalable manufacturing process for GNP strain gauges. In this context, the challenge of reproducible and reliable manufacturing and operating must be overcome. The developed sensors exhibit strain gauges by considering the significant importance of reproducible sensor performances and open the path for graphene strain gauges for potential usages in science and industry. PMID:29258260

Psychiatric illness in physicians.

PubMed Central

Shortt, S E

1979-01-01

Psychiatric illness and behavioural problems among physicians are reviewed in this paper. Some studies suggest that the medical profession has a high rate of alcoholism, drug abuse and marital discord. As well, physicians appear to commit suicide and to seek admission to psychiatric institutions more frequently than comparable populations. Considered as etiologic factors in psychiatric illness among physicians are the role strain inherent in the profession and the personality development of individual practitioners prior to their entering medical school. The review concludes with suggestions for an improved approach to treatment and prevention. PMID:380794

Overcoming inherent magnetic instability, preventing spin canting and magnetic coding in an assembly of ferrimagnetic nanoparticles

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

Dey, S.; Kumar, S., E-mail: kumars@phys.jdvu.ac.in; Dey, S. K.

2014-08-11

The authors find that for mechanically milled Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} (∼10 nm), the mechanical strain induced enhancement of anisotropy energy helps to retain stable magnetic order. The reduction of magnetization can be prevented by keeping the cation distribution of nanometric ferrites at its equilibrium ratio. Moreover, the sample can be used in coding, storing, and retrieving of binary bit (“0” and “1”) through magnetic field change.

Global sensitivity analysis in stochastic simulators of uncertain reaction networks.

PubMed

Navarro Jimenez, M; Le Maître, O P; Knio, O M

2016-12-28

Stochastic models of chemical systems are often subjected to uncertainties in kinetic parameters in addition to the inherent random nature of their dynamics. Uncertainty quantification in such systems is generally achieved by means of sensitivity analyses in which one characterizes the variability with the uncertain kinetic parameters of the first statistical moments of model predictions. In this work, we propose an original global sensitivity analysis method where the parametric and inherent variability sources are both treated through Sobol's decomposition of the variance into contributions from arbitrary subset of uncertain parameters and stochastic reaction channels. The conceptual development only assumes that the inherent and parametric sources are independent, and considers the Poisson processes in the random-time-change representation of the state dynamics as the fundamental objects governing the inherent stochasticity. A sampling algorithm is proposed to perform the global sensitivity analysis, and to estimate the partial variances and sensitivity indices characterizing the importance of the various sources of variability and their interactions. The birth-death and Schlögl models are used to illustrate both the implementation of the algorithm and the richness of the proposed analysis method. The output of the proposed sensitivity analysis is also contrasted with a local derivative-based sensitivity analysis method classically used for this type of systems.

Global sensitivity analysis in stochastic simulators of uncertain reaction networks

DOE PAGES

Navarro Jimenez, M.; Le Maître, O. P.; Knio, O. M.

2016-12-23

Stochastic models of chemical systems are often subjected to uncertainties in kinetic parameters in addition to the inherent random nature of their dynamics. Uncertainty quantification in such systems is generally achieved by means of sensitivity analyses in which one characterizes the variability with the uncertain kinetic parameters of the first statistical moments of model predictions. In this work, we propose an original global sensitivity analysis method where the parametric and inherent variability sources are both treated through Sobol’s decomposition of the variance into contributions from arbitrary subset of uncertain parameters and stochastic reaction channels. The conceptual development only assumes thatmore » the inherent and parametric sources are independent, and considers the Poisson processes in the random-time-change representation of the state dynamics as the fundamental objects governing the inherent stochasticity. Here, a sampling algorithm is proposed to perform the global sensitivity analysis, and to estimate the partial variances and sensitivity indices characterizing the importance of the various sources of variability and their interactions. The birth-death and Schlögl models are used to illustrate both the implementation of the algorithm and the richness of the proposed analysis method. The output of the proposed sensitivity analysis is also contrasted with a local derivative-based sensitivity analysis method classically used for this type of systems.« less

Global sensitivity analysis in stochastic simulators of uncertain reaction networks

NASA Astrophysics Data System (ADS)

Navarro Jimenez, M.; Le Maître, O. P.; Knio, O. M.

2016-12-01

Stochastic models of chemical systems are often subjected to uncertainties in kinetic parameters in addition to the inherent random nature of their dynamics. Uncertainty quantification in such systems is generally achieved by means of sensitivity analyses in which one characterizes the variability with the uncertain kinetic parameters of the first statistical moments of model predictions. In this work, we propose an original global sensitivity analysis method where the parametric and inherent variability sources are both treated through Sobol's decomposition of the variance into contributions from arbitrary subset of uncertain parameters and stochastic reaction channels. The conceptual development only assumes that the inherent and parametric sources are independent, and considers the Poisson processes in the random-time-change representation of the state dynamics as the fundamental objects governing the inherent stochasticity. A sampling algorithm is proposed to perform the global sensitivity analysis, and to estimate the partial variances and sensitivity indices characterizing the importance of the various sources of variability and their interactions. The birth-death and Schlögl models are used to illustrate both the implementation of the algorithm and the richness of the proposed analysis method. The output of the proposed sensitivity analysis is also contrasted with a local derivative-based sensitivity analysis method classically used for this type of systems.

Comparison of full 3-D, thin-film 3-D, and thin-film plate analyses of a postbuckled embedded delamination

NASA Technical Reports Server (NTRS)

Whitcomb, John D.

1989-01-01

Strain-energy release rates are often used to predict when delamination growth will occur in laminates under compression. Because of the inherently high computational cost of performing such analyses, less rigorous analyses such as thin-film plate analysis were used. The assumptions imposed by plate theory restrict the analysis to the calculation of total strain energy, G(sub t). The objective is to determine the accuracy of thin-film plate analysis by comparing the distribution of G(sub t) calculated using fully three dimensional (3D), thin-film 3D, and thin-film plate analyses. Thin-film 3D analysis is the same as thin-film plate analysis, except 3D analysis is used to model the sublaminate. The 3D stress analyses were performed using the finite element program NONLIN3D. The plate analysis results were obtained from published data, which used STAGS. Strain-energy release rates were calculated using variations of the virtual crack closure technique. The results demonstrate that thin-film plate analysis can predict the distribution of G(sub t) quite well, at least for the configurations considered. Also, these results verify the accuracy of the strain-energy release rate procedure for plate analysis.

Strain sensors for high field pulse magnets

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

Martinez, Christian; Zheng, Yan; Easton, Daniel

2009-01-01

In this paper we present an investigation into several strain sensing technologies that are being considered to monitor mechanical deformation within the steel reinforcement shells used in high field pulsed magnets. Such systems generally operate at cryogenic temperatures to mitigate heating issues that are inherent in the coils of nondestructive, high field pulsed magnets. The objective of this preliminary study is to characterize the performance of various strain sensing technologies at liquid nitrogen temperatures (-196 C). Four sensor types are considered in this investigation: fiber Bragg gratings (FBG), resistive foil strain gauges (RFSG), piezoelectric polymers (PVDF), and piezoceramics (PZT). Threemore » operational conditions are considered for each sensor: bond integrity, sensitivity as a function of temperature, and thermal cycling effects. Several experiments were conducted as part of this study, investigating adhesion with various substrate materials (stainless steel, aluminum, and carbon fiber), sensitivity to static (FBG and RFSG) and dynamic (RFSG, PVDF and PZT) load conditions, and sensor diagnostics using PZT sensors. This work has been conducted in collaboration with the National High Magnetic Field Laboratory (NHMFL), and the results of this study will be used to identify the set of sensing technologies that would be best suited for integration within high field pulsed magnets at the NHMFL facility.« less

Linking Microstructural Changes to Bulk Behavior in Shear Disordered Matter

NASA Astrophysics Data System (ADS)

Blair, Daniel

Soft and biological materials often exhibit disordered and heterogeneous microstructure. In most cases, the transmission and distribution of stresses through these complex materials reflects their inherent heterogeneity. Through the combination of rheology and 4D imaging we can directly alter and quantify the connection between microstructure and local stresses. We subject soft and biological materials to precise shear deformations while measuring real space information about the distribution and redistribution of the applied stress.In this talk, I will focus on the flow behavior of two distinct but related disordered materials; a flowing compressed emulsion above its yield stress and a strained collagen network. In the emulsion system, I will present experimental and computational results on the dynamical response, at the level of individual droplets, that directly links the particle motion and deformation to the rheology. I will also present results that utilize boundary stress microscopy to quantify the spatial distribution of surface stresses that arise from sheared in-vitro collagen networks. I will outline our main conclusions which is that the strain stiffening behavior observed in collagen networks can be parameterized by a single characteristic strain and associated stress. This characteristic rheological signature seems to describe both the strain stiffening regime and network yielding. NSF DMR: 0847490.

Predicting km-scale shear zone formation

NASA Astrophysics Data System (ADS)

Gerbi, Christopher; Culshaw, Nicholas; Shulman, Deborah; Foley, Maura; Marsh, Jeffrey

2015-04-01

Because km-scale shear zones play a first-order role in lithospheric kinematics, accurate conceptual and numerical models of orogenic development require predicting when and where they form. Although a strain-based algorithm in the upper crust for weakening due to faulting appears to succeed (e.g., Koons et al., 2010, doi:10.1029/2009TC002463), a comparable general rule for the viscous crust remains unestablished. Here we consider two aspects of the geological argument for a similar algorithm in the viscous regime, namely (1) whether predicting km-scale shear zone development based on a single parameter (such as strain or shear heating) is reasonable; and (2) whether lithologic variability inherent in most orogenic systems precludes a simple predictive rule. A review of tectonically significant shear zones worldwide and more detailed investigations in the Central Gneiss belt of the Ontario segment of the Grenville Province reveals that most km-scale shear zones occur at lithological boundaries and involve mass transfer, but have fairly little else in common. As examples, the relatively flat-lying Twelve Mile Bay shear zone in the western Central Gneiss belt bounds the Parry Sound domain and is likely the product of both localized anatexis and later retrograde hydration with attendant metamorphism. Moderately dipping shear zones in granitoids of the Grenville Front Tectonic Zone apparently resulted from cooperation among several complementary microstructural processes, such as grain size reduction, enhanced diffusion, and a small degree of metamorphic reaction. Localization into shear zones requires the operation of some spatially restricted processes such as stress concentration, metamorphism/fluid access, textural evolution, and thermal perturbation. All of these could be due in part to strain, but not necessarily linearly related to strain. Stress concentrations, such as those that form at rheological boundaries, may be sufficient to nucleate high strain gradients but are insufficient to maintain them because the stress perturbations will dissipate with deformation. Metamorphism can unquestionably cause sufficient rheological change, but only in certain rock types: for example, granitoids have much less capacity for metamorphically induced rheologic change than do mafic rocks. The magnitude of phase geometry variation observed in natural systems suggests that morphological change (e.g., interconnection of weak phases) likely has little direct affect on strength changes, although other textural factors related to diffusion paths and crystallographic orientation could play a significant role. Thermal perturbation, mainly in the form of shear heating, remains potentially powerful but inconclusive. Taken together, these observations indicate that a simple algorithm predicting shear zone formation will not succeed in many geologically relevant instances. One significant reason may be that the inherent lithologic variation at the km scale, such as observed in the Central Gneiss belt, prevents the development of self-organized strain patterns that would form in more rheologically uniform systems.

Graphene-based smart materials

NASA Astrophysics Data System (ADS)

Yu, Xiaowen; Cheng, Huhu; Zhang, Miao; Zhao, Yang; Qu, Liangti; Shi, Gaoquan

2017-09-01

The high specific surface area and the excellent mechanical, electrical, optical and thermal properties of graphene make it an attractive component for high-performance stimuli-responsive or 'smart' materials. Complementary to these inherent properties, functionalization or hybridization can substantially improve the performance of these materials. Typical graphene-based smart materials include mechanically exfoliated perfect graphene, chemical vapour deposited high-quality graphene, chemically modified graphene (for example, graphene oxide and reduced graphene oxide) and their macroscopic assemblies or composites. These materials are sensitive to a range of stimuli, including gas molecules or biomolecules, pH value, mechanical strain, electrical field, and thermal or optical excitation. In this Review, we outline different graphene-based smart materials and their potential applications in actuators, chemical or strain sensors, self-healing materials, photothermal therapy and controlled drug delivery. We also introduce the working mechanisms of graphene-based smart materials and discuss the challenges facing the realization of their practical applications.

Controlled cobalt doping of magnetosomes in vivo.

PubMed

Staniland, Sarah; Williams, Wyn; Telling, Neil; Van Der Laan, Gerrit; Harrison, Andrew; Ward, Bruce

2008-03-01

Magnetotactic bacteria biomineralize iron into magnetite (Fe3O4) nanoparticles that are surrounded by lipid vesicles. These 'magnetosomes' have considerable potential for use in bio- and nanotechnological applications because of their narrow size and shape distribution and inherent biocompatibility. The ability to tailor the magnetic properties of magnetosomes by chemical doping would greatly expand these applications; however, the controlled doping of magnetosomes has so far not been achieved. Here, we report controlled in vivo cobalt doping of magnetosomes in three strains of the bacterium Magnetospirillum. The presence of cobalt increases the coercive field of the magnetosomes--that is, the field necessary to reverse their magnetization--by 36-45%, depending on the strain and the cobalt content. With elemental analysis, X-ray absorption and magnetic circular dichroism, we estimate the cobalt content to be between 0.2 and 1.4%. These findings provide an important advance in designing biologically synthesized nanoparticles with useful highly tuned magnetic properties.

Lactic Fermentation as an Efficient Tool to Enhance the Antioxidant Activity of Tropical Fruit Juices and Teas

PubMed Central

Fessard, Amandine; Kapoor, Ashish; Patche, Jessica; Assemat, Sophie; Hoarau, Mathilde; Bourdon, Emmanuel; Bahorun, Theeshan; Remize, Fabienne

2017-01-01

Tropical fruits like pineapple, papaya, mango, and beverages such as green or black teas, represent an underestimated source of antioxidants that could exert health-promoting properties. Most food processing technologies applied to fruit beverages or teas result in an impairment of inherent nutritional properties. Conversely, we hypothesise that lactic acid fermentation may constitute a promising route to maintain and even improve the nutritional qualities of processed fruits. Using specific growth media, lactic acid bacteria were selected from the fruit phyllosphere diversity and fruit juice, with the latter undergoing acidification kinetics analyses and characterised for exopolysaccharide production. Strains able to ferment tropical fruit juices or teas into pleasant beverages, within a short time, were of particular interest. Strains Weissella cibaria 64 and Leuconostoc mesenteroides 12b, able to increase antioxidant activity, were specifically studied as potential starters for lactic fermented pineapple juice. PMID:28489022

A novel method for correcting scanline-observational bias of discontinuity orientation

PubMed Central

Huang, Lei; Tang, Huiming; Tan, Qinwen; Wang, Dingjian; Wang, Liangqing; Ez Eldin, Mutasim A. M.; Li, Changdong; Wu, Qiong

2016-01-01

Scanline observation is known to introduce an angular bias into the probability distribution of orientation in three-dimensional space. In this paper, numerical solutions expressing the functional relationship between the scanline-observational distribution (in one-dimensional space) and the inherent distribution (in three-dimensional space) are derived using probability theory and calculus under the independence hypothesis of dip direction and dip angle. Based on these solutions, a novel method for obtaining the inherent distribution (also for correcting the bias) is proposed, an approach which includes two procedures: 1) Correcting the cumulative probabilities of orientation according to the solutions, and 2) Determining the distribution of the corrected orientations using approximation methods such as the one-sample Kolmogorov-Smirnov test. The inherent distribution corrected by the proposed method can be used for discrete fracture network (DFN) modelling, which is applied to such areas as rockmass stability evaluation, rockmass permeability analysis, rockmass quality calculation and other related fields. To maximize the correction capacity of the proposed method, the observed sample size is suggested through effectiveness tests for different distribution types, dispersions and sample sizes. The performance of the proposed method and the comparison of its correction capacity with existing methods are illustrated with two case studies. PMID:26961249

Geobacteraceae strains and methods

DOEpatents

Lovley, Derek R.; Nevin, Kelly P.; Yi, Hana

2015-07-07

Embodiments of the present invention provide a method of producing genetically modified strains of electricigenic microbes that are specifically adapted for the production of electrical current in microbial fuel cells, as well as strains produced by such methods and fuel cells using such strains. In preferred embodiments, the present invention provides genetically modified strains of Geobacter sulfurreducens and methods of using such strains.

Procedures for characterizing an alloy and predicting cyclic life with the total strain version of Strainrange Partitioning

NASA Technical Reports Server (NTRS)

Saltsman, James F.; Halford, Gary R.

1989-01-01

Procedures are presented for characterizing an alloy and predicting cyclic life for isothermal and thermomechanical fatigue conditions by using the total strain version of strainrange partitioning (TS-SRP). Numerical examples are given. Two independent alloy characteristics are deemed important: failure behavior, as reflected by the inelastic strainrange versus cyclic life relations; and flow behavior, as indicated by the cyclic stress-strain-time response (i.e., the constitutive behavior). Failure behavior is characterized by conducting creep-fatigue tests in the strain regime, wherein the testing times are reasonably short and the inelastic strains are large enough to be determined accurately. At large strainranges, stress-hold, strain-limited tests are preferred because a high rate of creep damage per cycle is inherent in this type of test. At small strainranges, strain-hold cycles are more appropriate. Flow behavior is characterized by conducting tests wherein the specimen is usually cycled far short of failure and the wave shape is appropriate for the duty cycle of interest. In characterizing an alloy pure fatigue, or PP, failure tests are conducted first. Then depending on the needs of the analyst a series of creep-fatigue tests are conducted. As many of the three generic SRP cycles are featured as are required to characterize the influence of creep on fatigue life (i.e., CP, PC, and CC cycles, respectively, for tensile creep only, compressive creep only, and both tensile and compressive creep). Any mean stress effects on life also must be determined and accounted for when determining the SRP inelastic strainrange versus life relations for cycles featuring creep. This is particularly true for small strainranges. The life relations thus are established for a theoretical zero mean stress condition.

Part II: Strain- and sex-specific effects of adolescent exposure to THC on adult brain and behaviour: Variants of learning, anxiety and volumetric estimates.

PubMed

Keeley, R J; Trow, J; Bye, C; McDonald, R J

2015-07-15

Marijuana is one of the most highly used psychoactive substances in the world, and its use typically begins during adolescence, a period of substantial brain development. Females across species appear to be more susceptible to the long-term consequences of marijuana use. Despite the identification of inherent differences between rat strains including measures of anatomy, genetics and behaviour, no studies to our knowledge have examined the long-term consequences of adolescent exposure to marijuana or its main psychoactive component, Δ(9)-tetrahydrocannabinol (THC), in males and females of two widely used rat strains: Long-Evans hooded (LER) and Wistar (WR) rats. THC was administered for 14 consecutive days following puberty onset, and once they reached adulthood, changes in behaviour and in the volume of associated brain areas were quantified. Rats were assessed in behavioural tests of motor, spatial and contextual learning, and anxiety. Some tasks showed effects of injection, since handled and vehicle groups were included as controls. Performance on all tasks, except motor learning, and the volume of associated brain areas were altered with injection or THC administration, although these effects varied by strain and sex group. Finally, analysis revealed treatment-specific correlations between performance and brain volumes. This study is the first of its kind to directly compare males and females of two rat strains for the long-term consequences of adolescent THC exposure. It highlights the importance of considering strain and identifies certain rat strains as susceptible or resilient to the effects of THC. Copyright © 2015 Elsevier B.V. All rights reserved.

Harnessing genetic diversity in Saccharomyces cerevisiae for fermentation of xylose in hydrolysates of alkaline hydrogen peroxide-pretreated biomass.

PubMed

Sato, Trey K; Liu, Tongjun; Parreiras, Lucas S; Williams, Daniel L; Wohlbach, Dana J; Bice, Benjamin D; Ong, Irene M; Breuer, Rebecca J; Qin, Li; Busalacchi, Donald; Deshpande, Shweta; Daum, Chris; Gasch, Audrey P; Hodge, David B

2014-01-01

The fermentation of lignocellulose-derived sugars, particularly xylose, into ethanol by the yeast Saccharomyces cerevisiae is known to be inhibited by compounds produced during feedstock pretreatment. We devised a strategy that combined chemical profiling of pretreated feedstocks, high-throughput phenotyping of genetically diverse S. cerevisiae strains isolated from a range of ecological niches, and directed engineering and evolution against identified inhibitors to produce strains with improved fermentation properties. We identified and quantified for the first time the major inhibitory compounds in alkaline hydrogen peroxide (AHP)-pretreated lignocellulosic hydrolysates, including Na(+), acetate, and p-coumaric (pCA) and ferulic (FA) acids. By phenotyping these yeast strains for their abilities to grow in the presence of these AHP inhibitors, one heterozygous diploid strain tolerant to all four inhibitors was selected, engineered for xylose metabolism, and then allowed to evolve on xylose with increasing amounts of pCA and FA. After only 149 generations, one evolved isolate, GLBRCY87, exhibited faster xylose uptake rates in both laboratory media and AHP switchgrass hydrolysate than its ancestral GLBRCY73 strain and completely converted 115 g/liter of total sugars in undetoxified AHP hydrolysate into more than 40 g/liter ethanol. Strikingly, genome sequencing revealed that during the evolution from GLBRCY73, the GLBRCY87 strain acquired the conversion of heterozygous to homozygous alleles in chromosome VII and amplification of chromosome XIV. Our approach highlights that simultaneous selection on xylose and pCA or FA with a wild S. cerevisiae strain containing inherent tolerance to AHP pretreatment inhibitors has potential for rapid evolution of robust properties in lignocellulosic biofuel production.

The experimental basis for interpreting particle and magnetic fabrics of sheared till

USGS Publications Warehouse

Iverson, N.R.; Hooyer, T.S.; Thomason, J.F.; Graesch, M.; Shumway, J.R.

2008-01-01

Particle fabrics of basal tills may allow testing of the bed-deformation model of glacier flow, which requires high bed shear strains (>100). Field studies, however, have not yielded a systematic relationship between shear-strain magnitude and fabric development. To isolate this relationship four basal tills and viscous putty were sheared in a ring-shear device to strains as high as 714. Fabric was characterized within a zone of shear deformation using the long-axis orientations of fine-gravel and sand particles and the anisotropy of magnetic susceptibility (AMS) of small (???5-8 cm3) intact samples. Results indicate that till particles rotate toward the plane of shearing with long-axis orientations that become tightly clustered in the direction of shear (0??78 < S1 < 0??94 for three-dimensional data). These strong, steady-state fabrics are attained at shear strains of 7-30, with no evidence of fabric weakening with further strain, regardless of the specific till or particle-size fraction under consideration. These results do not support the Jeffery model of particle rotation, which correctly describes particle rotation in the viscous putty but not in the tills, owing to fluid-mechanical assumptions of the model that are violated in till. The sensitivity of fabric development to shear-strain magnitude indicates that, for most till units where shear-strain magnitude is poorly known, attributing fabric variations to spatial differences in other variables, such as till thickness or water content, will be inherently speculative. Attributing fabric characteristics to particular basal till facies is uncertain because shear-strain magnitude is unlikely to be closely correlated to till facies. Weak or spatially variable fabrics, in the absence of post-depositional disturbance or major deviations from unidirectional simple shear, indicate that till has not been pervasively sheared to the high strains required by the bed-deformation model. Strong flow-parallel fabrics are a necessary but insufficient criterion for confirming the model. Copyright ?? 2008 John Wiley & Sons, Ltd.

GeneGuard: A modular plasmid system designed for biosafety.

PubMed

Wright, Oliver; Delmans, Mihails; Stan, Guy-Bart; Ellis, Tom

2015-03-20

Synthetic biology applications in biosensing, bioremediation, and biomining envision the use of engineered microbes beyond a contained laboratory. Deployment of such microbes in the environment raises concerns of unchecked cellular proliferation or unwanted spread of synthetic genes. While antibiotic-resistant plasmids are the most utilized vectors for introducing synthetic genes into bacteria, they are also inherently insecure, acting naturally to propagate DNA from one cell to another. To introduce security into bacterial synthetic biology, we here took on the task of completely reformatting plasmids to be dependent on their intended host strain and inherently disadvantageous for others. Using conditional origins of replication, rich-media compatible auxotrophies, and toxin-antitoxin pairs we constructed a mutually dependent host-plasmid platform, called GeneGuard. In this, replication initiators for the R6K or ColE2-P9 origins are provided in trans by a specified host, whose essential thyA or dapA gene is translocated from a genomic to a plasmid location. This reciprocal arrangement is stable for at least 100 generations without antibiotic selection and is compatible for use in LB medium and soil. Toxin genes ζ or Kid are also employed in an auxiliary manner to make the vector disadvantageous for strains not expressing their antitoxins. These devices, in isolation and in concert, severely reduce unintentional plasmid propagation in E. coli and B. subtilis and do not disrupt the intended E. coli host's growth dynamics. Our GeneGuard system comprises several versions of modular cargo-ready vectors, along with their requisite genomic integration cassettes, and is demonstrated here as an efficient vector for heavy-metal biosensors.

Genetic potential of common bean progenies selected for crude fiber content obtained through different breeding methods.

PubMed

Júnior, V A P; Melo, P G S; Pereira, H S; Bassinello, P Z; Melo, L C

2015-05-29

Gastrointestinal health is of great importance due to the increasing consumption of functional foods, especially those concern-ing diets rich in fiber content. The common bean has been valorized as a nutritious food due to its appreciable fiber content and the fact that it is consumed in many countries. The current study aimed to evaluate and compare the genetic potential of common bean progenies of the carioca group, developed through different breeding methods, for crude fiber content. The progenies originated through hybridization of two advanced strains, CNFC 7812 and CNFC 7829, up to the F7 generation using three breeding methods: bulk-population, bulk within F2 families, and single seed descent. Fifteen F8 progenies were evaluated in each method, as well as two check cultivars and both parents, us-ing a 7 x 7 simple lattice design, with experimental plots comprised of two 4-m long rows. Field trials were conducted in eleven environments encompassing four Brazilian states and three different sowing times during 2009 and 2010. Estimates of genetic parameters indicate differences among the breeding methods, which seem to be related to the different processes for sampling the advanced progenies inherent to each method, given that the trait in question is not subject to natural selection. Variability amongst progenies occurred within the three breeding methods and there was also a significant effect of environment on the progeny for all methods. Progenies developed by bulk-population attained the highest estimates of genetic parameters, had less interaction with the environment, and greater variability.

Comparison of three methods of calculating strain in the mouse ulna in exogenous loading studies.

PubMed

Norman, Stephanie C; Wagner, David W; Beaupre, Gary S; Castillo, Alesha B

2015-01-02

Axial compression of mouse limbs is commonly used to induce bone formation in a controlled, non-invasive manner. Determination of peak strains caused by loading is central to interpreting results. Load-strain calibration is typically performed using uniaxial strain gauges attached to the diaphyseal, periosteal surface of a small number of sacrificed animals. Strain is measured as the limb is loaded to a range of physiological loads known to be anabolic to bone. The load-strain relationship determined by this subgroup is then extrapolated to a larger group of experimental mice. This method of strain calculation requires the challenging process of strain gauging very small bones which is subject to variability in placement of the strain gauge. We previously developed a method to estimate animal-specific periosteal strain during axial ulnar loading using an image-based computational approach that does not require strain gauges. The purpose of this study was to compare the relationship between load-induced bone formation rates and periosteal strain at ulnar midshaft using three different methods to estimate strain: (A) Nominal strain values based solely on load-strain calibration; (B) Strains calculated from load-strain calibration, but scaled for differences in mid-shaft cross-sectional geometry among animals; and (C) An alternative image-based computational method for calculating strains based on beam theory and animal-specific bone geometry. Our results show that the alternative method (C) provides comparable correlation between strain and bone formation rates in the mouse ulna relative to the strain gauge-dependent methods (A and B), while avoiding the need to use strain gauges. Published by Elsevier Ltd.

Antioxidant defense parameters as predictive biomarkers for fermentative capacity of active dried wine yeast.

PubMed

Gamero-Sandemetrio, Esther; Gómez-Pastor, Rocío; Matallana, Emilia

2014-08-01

The production of active dried yeast (ADY) is a common practice in industry for the maintenance of yeast starters and as a means of long term storage. The process, however, causes multiple cell injuries, with oxidative damage being one of the most important stresses. Consequentially, dehydration tolerance is a highly appreciated property in yeast for ADY production. In this study we analyzed the cellular redox environment in three Saccharomyces cerevisiae wine strains, which show markedly different fermentative capacities after dehydration. To measure/quantify the effect of dehydration on the S. cerevisiae strains, we used: (i) fluorescent probes; (ii) antioxidant enzyme activities; (ii) intracellular damage; (iii) antioxidant metabolites; and (iv) gene expression, to select a minimal set of biochemical parameters capable of predicting desiccation tolerance in wine yeasts. Our results show that naturally enhanced antioxidant defenses prevent oxidative damage after wine yeast biomass dehydration and improve fermentative capacity. Based on these results we chose four easily assayable parameters/biomarkers for the selection of industrial yeast strains of interest for ADY production: trehalose and glutathione levels, and glutathione reductase and catalase enzymatic activities. Yeast strains selected in accordance with this process display high levels of trehalose, low levels of oxidized glutathione, a high induction of glutathione reductase activity, as well as a high basal level and sufficient induction of catalase activity, which are properties inherent in superior ADY strains. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Design Optimization Toolkit: Users' Manual

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

Aguilo Valentin, Miguel Alejandro

The Design Optimization Toolkit (DOTk) is a stand-alone C++ software package intended to solve complex design optimization problems. DOTk software package provides a range of solution methods that are suited for gradient/nongradient-based optimization, large scale constrained optimization, and topology optimization. DOTk was design to have a flexible user interface to allow easy access to DOTk solution methods from external engineering software packages. This inherent flexibility makes DOTk barely intrusive to other engineering software packages. As part of this inherent flexibility, DOTk software package provides an easy-to-use MATLAB interface that enables users to call DOTk solution methods directly from the MATLABmore » command window.« less

Measurement with verification of stationary signals and noise in extremely quiet environments: Measuring below the noise floor

PubMed Central

Ellingson, Roger M.; Gallun, Frederick J.; Bock, Guillaume

2015-01-01

It can be problematic to measure stationary acoustic sound pressure level in any environment when the target level approaches or lies below the minimum measureable sound pressure level of the measurement system itself. This minimum measureable level, referred to as the inherent measurement system noise floor, is generally established by noise emission characteristics of measurement system components such as microphones, preamplifiers, and other system circuitry. In this paper, methods are presented and shown accurate measuring stationary levels within 20 dB above and below this system noise floor. Methodology includes (1) measuring inherent measurement system noise, (2) subtractive energy based, inherent noise adjustment of levels affected by system noise floor, and (3) verifying accuracy of inherent noise adjustment technique. While generalizable to other purposes, the techniques presented here were specifically developed to quantify ambient noise levels in very quiet rooms used to evaluate free-field human hearing thresholds. Results obtained applying the methods to objectively measure and verify the ambient noise level in an extremely quiet room, using various measurement system noise floors and analysis bandwidths, are presented and discussed. The verified results demonstrate the adjustment method can accurately extend measurement range to 20 dB below the measurement system noise floor, and how measurement system frequency bandwidth can affect accuracy of reported noise levels. PMID:25786932

Towards developing a compact model for magnetization switching in straintronics magnetic random access memory devices

NASA Astrophysics Data System (ADS)

Barangi, Mahmood; Erementchouk, Mikhail; Mazumder, Pinaki

2016-08-01

Strain-mediated magnetization switching in a magnetic tunneling junction (MTJ) by exploiting a combination of piezoelectricity and magnetostriction has been proposed as an energy efficient alternative to spin transfer torque (STT) and field induced magnetization switching methods in MTJ-based magnetic random access memories (MRAM). Theoretical studies have shown the inherent advantages of strain-assisted switching, and the dynamic response of the magnetization has been modeled using the Landau-Lifshitz-Gilbert (LLG) equation. However, an attempt to use LLG for simulating dynamics of individual elements in large-scale simulations of multi-megabyte straintronics MRAM leads to extremely time-consuming calculations. Hence, a compact analytical solution, predicting the flipping delay of the magnetization vector in the nanomagnet under stress, combined with a liberal approximation of the LLG dynamics in the straintronics MTJ, can lead to a simplified model of the device suited for fast large-scale simulations of multi-megabyte straintronics MRAMs. In this work, a tensor-based approach is developed to study the dynamic behavior of the stressed nanomagnet. First, using the developed method, the effect of stress on the switching behavior of the magnetization is investigated to realize the margins between the underdamped and overdamped regimes. The latter helps the designer realize the oscillatory behavior of the magnetization when settling along the minor axis, and the dependency of oscillations on the stress level and the damping factor. Next, a theoretical model to predict the flipping delay of the magnetization vector is developed and tested against LLG-based numerical simulations to confirm the accuracy of findings. Lastly, the obtained delay is incorporated into the approximate solutions of the LLG dynamics, in order to create a compact model to liberally and quickly simulate the magnetization dynamics of the MTJ under stress. Using the developed delay equation, the efficiency of the straintronics switching over the STT method is highlighted by analytically investigating the energy-delay trade-off of both methodologies.

Towards developing a compact model for magnetization switching in straintronics magnetic random access memory devices

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

Barangi, Mahmood, E-mail: barangi@umich.edu; Erementchouk, Mikhail; Mazumder, Pinaki

Strain-mediated magnetization switching in a magnetic tunneling junction (MTJ) by exploiting a combination of piezoelectricity and magnetostriction has been proposed as an energy efficient alternative to spin transfer torque (STT) and field induced magnetization switching methods in MTJ-based magnetic random access memories (MRAM). Theoretical studies have shown the inherent advantages of strain-assisted switching, and the dynamic response of the magnetization has been modeled using the Landau-Lifshitz-Gilbert (LLG) equation. However, an attempt to use LLG for simulating dynamics of individual elements in large-scale simulations of multi-megabyte straintronics MRAM leads to extremely time-consuming calculations. Hence, a compact analytical solution, predicting the flippingmore » delay of the magnetization vector in the nanomagnet under stress, combined with a liberal approximation of the LLG dynamics in the straintronics MTJ, can lead to a simplified model of the device suited for fast large-scale simulations of multi-megabyte straintronics MRAMs. In this work, a tensor-based approach is developed to study the dynamic behavior of the stressed nanomagnet. First, using the developed method, the effect of stress on the switching behavior of the magnetization is investigated to realize the margins between the underdamped and overdamped regimes. The latter helps the designer realize the oscillatory behavior of the magnetization when settling along the minor axis, and the dependency of oscillations on the stress level and the damping factor. Next, a theoretical model to predict the flipping delay of the magnetization vector is developed and tested against LLG-based numerical simulations to confirm the accuracy of findings. Lastly, the obtained delay is incorporated into the approximate solutions of the LLG dynamics, in order to create a compact model to liberally and quickly simulate the magnetization dynamics of the MTJ under stress. Using the developed delay equation, the efficiency of the straintronics switching over the STT method is highlighted by analytically investigating the energy-delay trade-off of both methodologies.« less

Monte Carlo method for computing density of states and quench probability of potential energy and enthalpy landscapes.

PubMed

Mauro, John C; Loucks, Roger J; Balakrishnan, Jitendra; Raghavan, Srikanth

2007-05-21

The thermodynamics and kinetics of a many-body system can be described in terms of a potential energy landscape in multidimensional configuration space. The partition function of such a landscape can be written in terms of a density of states, which can be computed using a variety of Monte Carlo techniques. In this paper, a new self-consistent Monte Carlo method for computing density of states is described that uses importance sampling and a multiplicative update factor to achieve rapid convergence. The technique is then applied to compute the equilibrium quench probability of the various inherent structures (minima) in the landscape. The quench probability depends on both the potential energy of the inherent structure and the volume of its corresponding basin in configuration space. Finally, the methodology is extended to the isothermal-isobaric ensemble in order to compute inherent structure quench probabilities in an enthalpy landscape.

[Ultrasound duplex scanning of head and neck vessels with the aim of preoperational preparation of the patients with inherent microtia of the III degree].

PubMed

Chkadua, T Z; Kuz'mina, I V; Ramazanova, Iu I

2010-01-01

For surgical treatment of patients with inherent microtia of the III degree we use one stage method of otoplasty with silicone implant and parietotemporal fascial flap. In order to receive most full picture of the status of superficial temporal artery and its branches the additional diagnostic study is necessary. Method of ultrasound duplex scanning let to study any vessel in real time regimen under monitor screen control. Received by us results of ultrasound duplex scanning of superficial temporal artery branches in patients with inherent microtia of the III degree let us to conclude about the status of the vessel wall, to determine diameter and vessel occlusion, to evaluate and measure blood flow parameters. It is diagnostically necessary criteria for answering the question about flap vitality and in such a way let to avoid possible complications.

21 CFR 177.1637 - Poly(oxy-1,2-ethanediyloxycarbonyl-2,6-naphthalenediylcarbonyl) resins.

Code of Federal Regulations, 2013 CFR

2013-04-01

... between 1.33 and 1.40 grams per cubic centimeter. (2) Inherent viscosity. The finished food-contact article shall have a minimum inherent viscosity of 0.55 deciliter per gram in a solution of 0.1 gram of.../tetrachloroethane/phenol. The viscosity is determined by Eastman Chemical Co.'s method ECD-A-AC-G-V-1-5...

21 CFR 177.1637 - Poly(oxy-1,2-ethanediyloxycarbonyl-2,6-naphthalenediylcarbonyl) resins.

Code of Federal Regulations, 2012 CFR

2012-04-01

... between 1.33 and 1.40 grams per cubic centimeter. (2) Inherent viscosity. The finished food-contact article shall have a minimum inherent viscosity of 0.55 deciliter per gram in a solution of 0.1 gram of.../tetrachloroethane/phenol. The viscosity is determined by Eastman Chemical Co.'s method ECD-A-AC-G-V-1-5...

21 CFR 177.1637 - Poly(oxy-1,2-ethanediyloxycarbonyl-2,6-naphthalenediylcarbonyl) resins.

Code of Federal Regulations, 2011 CFR

2011-04-01

... between 1.33 and 1.40 grams per cubic centimeter. (2) Inherent viscosity. The finished food-contact article shall have a minimum inherent viscosity of 0.55 deciliter per gram in a solution of 0.1 gram of.../tetrachloroethane/phenol. The viscosity is determined by Eastman Chemical Co.'s method ECD-A-AC-G-V-1-5...

Inheritance of brewing-relevant phenotypes in constructed Saccharomyces cerevisiae × Saccharomyces eubayanus hybrids.

PubMed

Krogerus, Kristoffer; Seppänen-Laakso, Tuulikki; Castillo, Sandra; Gibson, Brian

2017-04-21

Interspecific hybridization has proven to be a potentially valuable technique for generating de novo lager yeast strains that possess diverse and improved traits compared to their parent strains. To further enhance the value of hybridization for strain development, it would be desirable to combine phenotypic traits from more than two parent strains, as well as remove unwanted traits from hybrids. One such trait, that has limited the industrial use of de novo lager yeast hybrids, is their inherent tendency to produce phenolic off-flavours; an undesirable trait inherited from the Saccharomyces eubayanus parent. Trait removal and the addition of traits from a third strain could be achieved through sporulation and meiotic recombination or further mating. However, interspecies hybrids tend to be sterile, which impedes this opportunity. Here we generated a set of five hybrids from three different parent strains, two of which contained DNA from all three parent strains. These hybrids were constructed with fertile allotetraploid intermediates, which were capable of efficient sporulation. We used these eight brewing strains to examine two brewing-relevant phenotypes: stress tolerance and phenolic off-flavour formation. Lipidomics and multivariate analysis revealed links between several lipid species and the ability to ferment in low temperatures and high ethanol concentrations. Unsaturated fatty acids, such as oleic acid, and ergosterol were shown to positively influence growth at high ethanol concentrations. The ability to produce phenolic off-flavours was also successfully removed from one of the hybrids, Hybrid T2, through meiotic segregation. The potential application of these strains in industrial fermentations was demonstrated in wort fermentations, which revealed that the meiotic segregant Hybrid T2 not only didn't produce any phenolic off-flavours, but also reached the highest ethanol concentration and consumed the most maltotriose. Our study demonstrates the possibility of constructing complex yeast hybrids that possess traits that are relevant to industrial lager beer fermentation and that are derived from several parent strains. Yeast lipid composition was also shown to have a central role in determining ethanol and cold tolerance in brewing strains.

Physical well-being of oncology caregivers: an important quality-of-life domain.

PubMed

Glajchen, Myra

2012-11-01

To provide an overview of research and practice related to the physical well-being of oncology caregivers. Literature retrieved through the PubMed and CINAHL databases. Caregivers play an important role in supporting people with cancer at every stage of the illness trajectory. Because caregiving is inherently stressful, caregivers should be routinely included in the assessment and treatment of patients with cancer. Oncology nurses are uniquely positioned to play a vital role in recognizing caregiver strain and intervening to break the cycle of unremitting physical and psychosocial burden. Copyright © 2012 Elsevier Inc. All rights reserved.

Differential patterns of acquired virulence genes distinguish Salmonella strains

PubMed Central

Conner, Christopher P.; Heithoff, Douglas M.; Julio, Steven M.; Sinsheimer, Robert L.; Mahan, Michael J.

1998-01-01

Analysis of several Salmonella typhimurium in vivo-induced genes located in regions of atypical base composition has uncovered acquired genetic elements that cumulatively engender pathogenicity. Many of these regions are associated with mobile elements, encode predicted adhesin and invasin-like functions, and are required for full virulence. Some of these regions distinguish broad host range from host-adapted Salmonella serovars and may contribute to inherent differences in host specificity, tissue tropism, and disease manifestation. Maintenance of this archipelago of acquired sequence by selection in specific hosts reveals a fossil record of the evolution of pathogenic species. PMID:9539791

In-Situ Printing of Conductive Polylactic Acid (cPLA) Strain Sensors Embedded into Additively Manufactured Parts using Fused Deposition Modeling

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

Ouellette, Brittany Joy

Additive Manufacturing (AM) technology has been around for decades, but until recently, machines have been expensive, relatively large, and not available to most institutions. Increased technological advances in 3D printing and awareness throughout industry, universities, and even hobbyists has increased demand to substitute AM parts in place of traditionally manufactured (subtractive) designs; however, there is a large variability of part quality and mechanical behavior due to the inherent printing process, which must be understood before AM parts are used for load bearing and structural design.

Multiple effects of genetic background on variegated transgene expression in mice.

PubMed Central

Opsahl, Margaret L; McClenaghan, Margaret; Springbett, Anthea; Reid, Sarah; Lathe, Richard; Colman, Alan; Whitelaw, C Bruce A

2002-01-01

BLG/7 transgenic mice express an ovine beta-lactoglobulin transgene during lactation. Unusually, transgene expression levels in milk differ between siblings. This variable expression is due to variegated transgene expression in the mammary gland and is reminiscent of position-effect variegation. The BLG/7 line was created and maintained on a mixed CBA x C57BL/6 background. We have investigated the effect on transgene expression of backcrossing for 13 generations into these backgrounds. Variable transgene expression was observed in all populations examined, confirming that it is an inherent property of the transgene array at its site of integration. There were also strain-specific effects on transgene expression that appear to be independent of the inherent variegation. The transgene, compared to endogenous milk protein genes, is specifically susceptible to inbreeding depression. Outcrossing restored transgene expression levels to that of the parental population; thus suppression was not inherited. Finally, no generation-dependent decrease in mean expression levels was observed in the parental population. Thus, although the BLG/7 transgene is expressed in a variegated manner, there was no generation-associated accumulated silencing of transgene expression. PMID:11901126

Multiple effects of genetic background on variegated transgene expression in mice.

PubMed

Opsahl, Margaret L; McClenaghan, Margaret; Springbett, Anthea; Reid, Sarah; Lathe, Richard; Colman, Alan; Whitelaw, C Bruce A

2002-03-01

BLG/7 transgenic mice express an ovine beta-lactoglobulin transgene during lactation. Unusually, transgene expression levels in milk differ between siblings. This variable expression is due to variegated transgene expression in the mammary gland and is reminiscent of position-effect variegation. The BLG/7 line was created and maintained on a mixed CBA x C57BL/6 background. We have investigated the effect on transgene expression of backcrossing for 13 generations into these backgrounds. Variable transgene expression was observed in all populations examined, confirming that it is an inherent property of the transgene array at its site of integration. There were also strain-specific effects on transgene expression that appear to be independent of the inherent variegation. The transgene, compared to endogenous milk protein genes, is specifically susceptible to inbreeding depression. Outcrossing restored transgene expression levels to that of the parental population; thus suppression was not inherited. Finally, no generation-dependent decrease in mean expression levels was observed in the parental population. Thus, although the BLG/7 transgene is expressed in a variegated manner, there was no generation-associated accumulated silencing of transgene expression.

Effectiveness of Shot Peening in Suppressing Fatigue Cracking at Non-Metallic Inclusions in Udimet(trademark) 720

NASA Technical Reports Server (NTRS)

Barrie, Robert L.; Gabb, Timothy P.; Telesman, Jack; Kantzos, Peter T.; Prescenzi, Anthony; Biles, Tiffany; Bonacuse, Peter J.

2005-01-01

The fatigue lives of modern powder metallurgy disk alloys can be reduced by over an order of magnitude by surface cracking at inherent non-metallic inclusions. The objective of this work was to study the effectiveness of shot peening in suppressing LCF crack initiation and growth at surface nonmetallic inclusions. Inclusions were carefully introduced at elevated levels during powder metallurgy processing of the nickel-base disk superalloy Udimet 720. Multiple strain-controlled fatigue tests were then performed on machined specimens at 427 and 650 C in peened and unpeened conditions. Analyses were performed to compare the low cycle fatigue lives and failure initiation sites as a function of inclusion content, shot peening, and fatigue conditions. A large majority of the failures in as-machined specimens with introduced inclusions occurred at cracks initiating from inclusions intersecting the specimen surface. The inclusions could reduce fatigue life by up to 100X. Large inclusions had the greatest effect on life in tests at low strain ranges and high strain ratios. Shot peening can be used to improve life in these conditions by reducing the most severe effects of inclusions.

Effectiveness of Shot Peening In Suppressing Fatigue Cracking At Non-Metallic Inclusions In Udimet(Registered Trademark)720

NASA Technical Reports Server (NTRS)

Barrie, Robert L.; Gabb, Timothy P.; Telesman, Jack; Kantzos, Peter T.; Prescenzi, Anthony; Biles, T.; Bonacuse, P. J.

2006-01-01

The fatigue lives of modern powder metallurgy disk alloys can be reduced over an order of magnitude by cracking at inherent non-metallic inclusions. The objective of this work was to study the effectiveness of shot peening in suppressing LCF crack initiation and growth at surface nonmetallic inclusions. Inclusions were carefully introduced at elevated levels during powder metallurgy processing of the nickel-base disk superalloy Udimet 720. Multiple strain-controlled fatigue tests were then performed on machined specimens with and without shot peened test sections at 427 C and 650 C. The low cycle fatigue lives and failure initiation sites varied as functions of inclusion content, shot peening, and fatigue conditions. A large majority of the failures in as-machined specimens with the introduced inclusions occurred at cracks initiating from inclusions intersecting the specimen surface. These inclusions reduced fatigue life by up to 100X, when compared to lives of material without inclusions residing at specimen surface. Large inclusions produced the greatest reductions in life for tests at low strain ranges and high strain ratios. Shot peening improved life in many cases by reducing the most severe effects of inclusions.

The Use of Linear Instrumental Variables Methods in Health Services Research and Health Economics: A Cautionary Note

PubMed Central

Terza, Joseph V; Bradford, W David; Dismuke, Clara E

2008-01-01

Objective To investigate potential bias in the use of the conventional linear instrumental variables (IV) method for the estimation of causal effects in inherently nonlinear regression settings. Data Sources Smoking Supplement to the 1979 National Health Interview Survey, National Longitudinal Alcohol Epidemiologic Survey, and simulated data. Study Design Potential bias from the use of the linear IV method in nonlinear models is assessed via simulation studies and real world data analyses in two commonly encountered regression setting: (1) models with a nonnegative outcome (e.g., a count) and a continuous endogenous regressor; and (2) models with a binary outcome and a binary endogenous regressor. Principle Findings The simulation analyses show that substantial bias in the estimation of causal effects can result from applying the conventional IV method in inherently nonlinear regression settings. Moreover, the bias is not attenuated as the sample size increases. This point is further illustrated in the survey data analyses in which IV-based estimates of the relevant causal effects diverge substantially from those obtained with appropriate nonlinear estimation methods. Conclusions We offer this research as a cautionary note to those who would opt for the use of linear specifications in inherently nonlinear settings involving endogeneity. PMID:18546544

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

Ice, G.E.; Barbee, T.; Bionta, R.

The increasing availability of synchrotron x-ray sources has stimulated the development of advanced hard x-ray (E{>=}5 keV) microprobes. New x-ray optics have been demonstrated which show promise for achieving intense submicron hard x-ray probes. These probes will be used for extraordinary elemental detection by x-ray fluorescence/absorption and for microdiffraction to identify phase and strain. The inherent elemental and crystallographic sensitivity of an x-ray microprobe and its inherently nondestructive and penetrating nature makes the development of an advanced hard x-ray microprobe an important national goal. In this workshop state-of-the-art hard x-ray microprobe optics were described and future directions were discussed. Genemore » Ice, Oak Ridge National Laboratory (ORNL), presented an overview of the current status of hard x-ray microprobe optics and described the use of crystal spectrometers to improve minimum detectable limits in fluorescent microprobe experiments. Al Thompson, Lawrence Berkeley Laboratory (LBL), described work at the Center for X-ray Optics to develop a hard x-ray microprobe based on Kirkpatrick-Baez (KB) optics. Al Thompson also showed the results of some experimental measurements with their KB optics. Malcolm Howells presented a method for bending elliptical mirrors and Troy Barbee commented on the use of graded d spacings to achieve highest efficiency in KB multilayer microfocusing. Richard Bionta, Lawrence Livermore National Laboratory (LLNL), described the development of the first hard x-ray zone plates and future promise of so called {open_quotes}jelly roll{close_quotes} or sputter slice zone plates. Wenbing Yun, Argonne National Laboratory (ANL), described characterization of jelly roll and lithographically produced zone plates and described the application of zone plates to focus extremely narrow bandwidths by nuclear resonance. This report summarizes the presentations of the workshop subgroup on hard x-ray microprobes.« less

Inherent variations in CO-H2S-mediated carotid body O2 sensing mediate hypertension and pulmonary edema

PubMed Central

Peng, Ying-Jie; Makarenko, Vladislav V.; Nanduri, Jayasri; Vasavda, Chirag; Raghuraman, Gayatri; Yuan, Guoxiang; Gadalla, Moataz M.; Kumar, Ganesh K.; Snyder, Solomon H.; Prabhakar, Nanduri R.

2014-01-01

Oxygen (O2) sensing by the carotid body and its chemosensory reflex is critical for homeostatic regulation of breathing and blood pressure. Humans and animals exhibit substantial interindividual variation in this chemosensory reflex response, with profound effects on cardiorespiratory functions. However, the underlying mechanisms are not known. Here, we report that inherent variations in carotid body O2 sensing by carbon monoxide (CO)-sensitive hydrogen sulfide (H2S) signaling contribute to reflex variation in three genetically distinct rat strains. Compared with Sprague-Dawley (SD) rats, Brown-Norway (BN) rats exhibit impaired carotid body O2 sensing and develop pulmonary edema as a consequence of poor ventilatory adaptation to hypobaric hypoxia. Spontaneous Hypertensive (SH) rat carotid bodies display inherent hypersensitivity to hypoxia and develop hypertension. BN rat carotid bodies have naturally higher CO and lower H2S levels than SD rat, whereas SH carotid bodies have reduced CO and greater H2S generation. Higher CO levels in BN rats were associated with higher substrate affinity of the enzyme heme oxygenase 2, whereas SH rats present lower substrate affinity and, thus, reduced CO generation. Reducing CO levels in BN rat carotid bodies increased H2S generation, restoring O2 sensing and preventing hypoxia-induced pulmonary edema. Increasing CO levels in SH carotid bodies reduced H2S generation, preventing hypersensitivity to hypoxia and controlling hypertension in SH rats. PMID:24395806

BXD recombinant inbred strains participate in social preference, anxiety and depression behaviors along sex-differences in cytokines and tactile allodynia.

PubMed

López-Granero, Caridad; Antunes Dos Santos, Alessandra; Ferrer, Beatriz; Culbreth, Megan; Chakraborty, Sudipta; Barrasa, Angel; Gulinello, Maria; Bowman, Aaron B; Aschner, Michael

2017-06-01

Depression and anxiety are the most common psychiatric disorders, representing a major public health concern. Dysregulation of oxidative and inflammatory systems may be associated with psychiatric disorders, such as depression and anxiety. Due to the need to find appropriate animal models to the understanding of such disorders, we queried whether 2 BXD recombinant inbred (RI) mice strains (BXD21/TyJ RI and BXD84/RwwJ RI mice) and C57BL/6 wild-type mice show differential performance in depression and anxiety related behaviors and biomarkers. Specifically, we assessed social preference, elevated plus maze, forced swim, and Von Frey tests at 3-4 months-of-age, as well as activation of cytokines and antioxidant mRNA levels in the cortex at 7 months-of-age. We report that (1) the BXD84/RwwJ RI strain exhibits anxiety disorder and social avoidance-like behavior (2) BXD21/TyJ RI strain shows a resistance to depression illness, and (3) sex-dependent cytokine profiles and allodynia with elevated inflammatory activity were inherent to male BXD21/TyJ RI mice. In conclusion, we provide novel data in favor of the use of BXD recombinant inbred mice to further understand anxiety and depression disorders. Copyright © 2017 Elsevier Ltd. All rights reserved.

Mechanical Behavior of AZ31B Mg Alloy Sheets under Monotonic and Cyclic Loadings at Room and Moderately Elevated Temperatures

PubMed Central

Nguyen, Ngoc-Trung; Seo, Oh Suk; Lee, Chung An; Lee, Myoung-Gyu; Kim, Ji-hoon; Kim, Heon Young

2014-01-01

Large-strain monotonic and cyclic loading tests of AZ31B magnesium alloy sheets were performed with a newly developed testing system, at different temperatures, ranging from room temperature to 250 °C. Behaviors showing significant twinning during initial in-plane compression and untwinning in subsequent tension at and slightly above room temperature were recorded. Strong yielding asymmetry and nonlinear hardening behavior were also revealed. Considerable Bauschinger effects, transient behavior, and variable permanent softening responses were observed near room temperature, but these were reduced and almost disappeared as the temperature increased. Different stress–strain responses were inherent to the activation of twinning at lower temperatures and non-basal slip systems at elevated temperatures. A critical temperature was identified to account for the transition between the twinning-dominant and slip-dominant deformation mechanisms. Accordingly, below the transition point, stress–strain curves of cyclic loading tests exhibited concave-up shapes for compression or compression following tension, and an unusual S-shape for tension following compression. This unusual shape disappeared when the temperature was above the transition point. Shrinkage of the elastic range and variation in Young’s modulus due to plastic strain deformation during stress reversals were also observed. The texture-induced anisotropy of both the elastic and plastic behaviors was characterized experimentally. PMID:28788514

Analysis of Feedback in after Action Reviews

DTIC Science & Technology

1987-06-01

CONNTSM Page INTRODUCTIUN . . . . . . . . . . . . . . . . . . . A Perspective on Feedback. . ....... • • ..... • 1 Overviev of %,•urrent Research...part of their training program . The AAR is in marked contrast to the critique method of feedback which is often used in military training. The AAR...feedback is task-inherent feedback. Task-inherent feedback refers to human-machine interacting systems, e.g., computers , where in a visual tracking task

Experimental investigation of dynamic fragmentation of laser shock-loaded by soft recovery and X-ray radiography

NASA Astrophysics Data System (ADS)

Xin, Jianting; He, Weihua; Chu, Genbai; Gu, Yuqiu

2017-06-01

Dynamic fragmentation of metal under shock pressure is an important issue for both fundamental science and practical applications. And in recent decades, laser provides a promising shock loading technique for investigating the process of dynamic fragmentation under extreme condition application of high strain rate. Our group has performed experimental investigation of dynamic fragmentation under laser shock loading by soft recovery and X-ray radiography at SGC / ó prototype laser facility. The fragments under different loading pressures were recovered by PMP foam and analyzed by X-ray micro-tomography and the improved watershed method. The experiment result showed that the bilinear exponential distribution is more appropriate for representing the fragment size distribution. We also developed X-ray radiography technique. Owing to its inherent advantage over shadowgraph technique, X-ray radiography can potentially determine quantitatively material densities by measuring the X-ray transmission. Our group investigated dynamic process of microjetting by X-ray radiography technique, the recorded radiographic images show clear microjetting from the triangular grooves in the free surface of tin sample.

Laser Metrology In Biomechanics

NASA Astrophysics Data System (ADS)

Pryputniewicz, Ryszard J.

1983-12-01

Modern treatment of sceletal disharmonies and malocclusions utilizes application of external forces. In order to effectively use these therapeutic forces, knowledge of three-dimensional displacements of bones with correlation to biological changes is required. In the past, this problem has been studied in a number of ways using, for example, strain gauges, brittle coatings, photoelasticity, as well as clinical observations and mathematical modeling. Becouse of their inherent limitations, these techniques did not always provide all the information necessary for development of meaningful relationships between the applied force system and the resulting biological remodeling. However, recent advances in the field of la-ser metrology allowed to overcome some of the dificulties found in the earlier methods and permitted development of new techniques for non-invasive measurements of bone motions in three-dimensional space. These laser techniques are particularly useful in biomechanics because they provide for rapid and accurate determination of displacements over the entire surface of the investigate object. In this paper, application of laser techniques for quantitative in-vivo and in-vitro measurements in biomechanics will be discussed and illustrated with representative examples.

Asymptotic stability of spectral-based PDF modeling for homogeneous turbulent flows

NASA Astrophysics Data System (ADS)

Campos, Alejandro; Duraisamy, Karthik; Iaccarino, Gianluca

2015-11-01

Engineering models of turbulence, based on one-point statistics, neglect spectral information inherent in a turbulence field. It is well known, however, that the evolution of turbulence is dictated by a complex interplay between the spectral modes of velocity. For example, for homogeneous turbulence, the pressure-rate-of-strain depends on the integrated energy spectrum weighted by components of the wave vectors. The Interacting Particle Representation Model (IPRM) (Kassinos & Reynolds, 1996) and the Velocity/Wave-Vector PDF model (Van Slooten & Pope, 1997) emulate spectral information in an attempt to improve the modeling of turbulence. We investigate the evolution and asymptotic stability of the IPRM using three different approaches. The first approach considers the Lagrangian evolution of individual realizations (idealized as particles) of the stochastic process defined by the IPRM. The second solves Lagrangian evolution equations for clusters of realizations conditional on a given wave vector. The third evolves the solution of the Eulerian conditional PDF corresponding to the aforementioned clusters. This last method avoids issues related to discrete particle noise and slow convergence associated with Lagrangian particle-based simulations.

Application of genotypic and phenotypic analyses to commercial probiotic strain identity and relatedness.

PubMed

Yeung, P S M; Kitts, C L; Cano, R; Tong, P S; Sanders, M E

2004-01-01

The objective of this study was to generate strain-specific genomic patterns of a bank of 67 commercial and reference probiotic strains, with a focus on probiotic lactobacilli. Pulsed-field gel electrophoresis (PFGE) was used as the primary method for strain differentiation. This method was compared with carbohydrate fermentation analysis. To supplement visual comparison, PFGE patterns were analysed quantitatively by cluster analysis using unweighted pair group method with arithmetic averages. SmaI, NotI and XbaI were found to effectively generate clear and easy-to-interpret PFGE patterns of a range of probiotic strains. Some probiotic strains from different sources shared highly similar PFGE patterns. Results document the value of genotypic strain identification methods, combined with phenotypic methods, for determining probiotic strain identity and relatedness. No correlation was found between relatedness determined by carbohydrate fermentation profiles alone compared with PFGE analysis alone. Some commercial strains are probably derived from similar sources. This approach is valuable to the probiotic industry to develop commercial strain identification patterns, to provide quality control of strain manufacturing production runs, to track use of protected strains and to determine the relatedness among different research and commercial probiotic strains.

Two-Dimensional Wavelike Spinel Lithium Titanate for Fast Lithium Storage

PubMed Central

Liu, Jiehua; Wei, Xiangfeng; Liu, Xue-Wei

2015-01-01

Safe fast-charging lithium-ion batteries (LIBs) have huge potential market size on demand according to their shortened charging time for high-power devices. Zero-strain spinel Li4Ti5O12 is one of ideal candidates for safe high-power batteries owing to its good cycling performance, low cost and safety. However, the inherent insulating characteristic of LTO seriously limits its high-rate capability. In this work, we successfully synthesize novel wavelike spinel LTO nanosheets using a facile ‘co-hydrolysis’ method, which is superior to molten-salt approach and traditional solvothermal method in some respects. The unique 2D structures have single-crystal framework with shortened path for Li ion transport. As a result, the N-doped 2D wavelike LTO with 0.6 wt.% of ‘carbon joint’ not only exhibits exciting capacity of ~180 and ~150 mA h g−1 for fast lithium storage at high discharge/charge rates of 1.7 and 8.5 A g−1 (10C and 50C) respectively, but also shows excellent low-temperature performance at −20°C. In addition, the cost may be further decreased due to recycled functional reagents. This novel nanostructured 2D LTO anode material makes it possible to develop safe fast-charging high-power lithium ion batteries. PMID:25985465

Fixing methods for the use of optical fibers in interferometric arrangements

NASA Astrophysics Data System (ADS)

Cubik, Jakub; Kepak, Stanislav; Fajkus, Marcel; Zboril, Ondrej; Nedoma, Jan; Davidson, Alan; Vasinek, Vladimir

2016-12-01

Today interferometric sensors are among the most accurate available thanks to their inherent high sensitivity. These highly versatile sensors may be used to measure phenomena such as temperature, strain, fluid level, flow, vibration, stress, etc. This article concentrates on the composition of fiber-optic interferometers, in particular the Mach-Zehnder type. The Mach-Zehnder type is composed of two arms, one for measurement and a second serving as a reference. When light enters the interferometer, ideally the phase of the light is shifted only in the measurement arm while the phase in the second arm remains unchanged. Interference occurs when the light recombining at the output and the resulting light intensity is proportional to the measurand. A major issue in the application of fiber based sensors is laying and fixing the fibers effectively in real life environments. Different approaches are necessary for both arms. The reference arm should as far as possible be isolated from the measurand. In this paper, various isolating materials are considered, however there are almost unlimited materials that may be used for isolation purposes. Conventional construction methods and materials were used such as aluminum tubing, flexible PVC tubing, double sided tape, steel clinches, superglue, PVC strips and PVC strips filled by silicon.

Dynamics and control of twisting bi-stable structures

NASA Astrophysics Data System (ADS)

Arrieta, Andres F.; van Gemmeren, Valentin; Anderson, Aaron J.; Weaver, Paul M.

2018-02-01

Compliance-based morphing structures have the potential to offer large shape adaptation, high stiffness and low weight, while reducing complexity, friction, and scalability problems of mechanism based systems. A promising class of structure that enables these characteristics are multi-stable structures given their ability to exhibit large deflections and rotations without the expensive need for continuous actuation, with the latter only required intermittently. Furthermore, multi-stable structures exhibit inherently fast response due to the snap-through instability governing changes between stable states, enabling rapid configuration switching between the discrete number of programmed shapes of the structure. In this paper, the design and utilisation of the inherent nonlinear dynamics of bi-stable twisting I-beam structures for actuation with low strain piezoelectric materials is presented. The I-beam structure consists of three compliant components assembled into a monolithic single element, free of moving parts, and showing large deflections between two stable states. Finite element analysis is utilised to uncover the distribution of strain across the width of the flange, guiding the choice of positioning for piezoelectric actuators. In addition, the actuation authority is maximised by calculating the generalised coupling coefficient for different positions of the piezoelectric actuators. The results obtained are employed to tailor and test I-beam designs exhibiting desired large deflection between stable states, while still enabling the activation of snap-through with the low strain piezoelectric actuators. To this end, the dynamic response of the I-beams to piezoelectric excitation is investigated, revealing that resonant excitations are insufficient to dynamically trigger snap-through. A novel bang-bang control strategy, which exploits the nonlinear dynamics of the structure successfully triggers both single and constant snap-through between the stable states of the bi-stable twisting I-beam structures. The obtained optimal piezoelectric actuator positioning is not necessarily intuitive and when used with the proposed dynamic actuation strategy serve as a blueprint for the actuation of such multi-stable compliant structures to produce fast and large deflections with highly embeddable actuators. This class of structures has potential applications in aerospace systems and soft/compliant robotics.

A novel one-stage cultivation/fermentation strategy for improved biogas production with microalgal biomass.

PubMed

Klassen, Viktor; Blifernez-Klassen, Olga; Hoekzema, Yoep; Mussgnug, Jan H; Kruse, Olaf

2015-12-10

The use of alga biomass for biogas generation has been studied for over fifty years but until today, several distinct features, like inefficient degradation and low C/N ratios, limit the applicability of algal biomass for biogas production in larger scale. In this work we investigated a novel, one-stage combined cultivation/fermentation strategy including inherently progressing nitrogen starvation conditions to generate improved microalgal biomass substrates. For this strategy, comparable low amounts of nitrogen fertilizers were applied during cultivation and no additional enzymatic, chemical or physical pretreatments had to be performed. The results of this study demonstrate that progressing nitrogen limitation leads to continuously increasing C/N ratios of the biomass up to levels of 24-26 for all three tested alga strains (Chlamydomonas reinhardtii, Parachlorella kessleri and Scenedesmus obliquus). Importantly, the degradation efficiency of the algal cells increased with progressing starvation, leading to strain-specific cell disintegration efficiencies of 35%-100% during the fermentation process. Nitrogen limitation treatment resulted in a 65% increase of biogas yields for C. reinhardtii biomass (max. 698±23mL biogas g(-1) VS) when compared to replete conditions. For P. kessleri and S. obliquus, yields increased by 94% and 106% (max. 706±39mL and 586±36mL biogas g(-1) VS, respectively). From these results we conclude that this novel one-stage cultivation strategy with inherent nitrogen limitation can be used as a pretreatment for microalgal biomass generation, in order to produce accessible substrates with optimized C/N ratios for the subsequent anaerobic fermentation process, thus increasing methane production and avoiding the risk of ammonia inhibition effects within the fermenter. Copyright © 2015 Elsevier B.V. All rights reserved.

A vanadium-doped ZnO nanosheets-polymer composite for flexible piezoelectric nanogenerators

NASA Astrophysics Data System (ADS)

Shin, Sung-Ho; Kwon, Yang Hyeog; Lee, Min Hyung; Jung, Joo-Yun; Seol, Jae Hun; Nah, Junghyo

2016-01-01

We report high performance flexible piezoelectric nanogenerators (PENGs) by employing vanadium (V)-doped ZnO nanosheets (NSs) and the polydimethylsiloxane (PDMS) composite structure. The V-doped ZnO NSs were synthesized to overcome the inherently low piezoelectric properties of intrinsic ZnO. Ferroelectric phase transition induced in the V-doped ZnO NSs contributed to significantly improve the performance of the PENGs after the poling process. Consequently, the PENGs exhibited high output voltage and current up to ~32 V and ~6.2 μA, respectively, under the applied strain, which are sufficient to directly turn on a number of light emitting diodes (LEDs). The composite approach for PENG fabrication is scalable, robust, and reproducible during periodic bending/releasing over extended cycles. The approach introduced here extends the performance limits of ZnO-based PENGs and demonstrates their potential as energy harvesting devices.We report high performance flexible piezoelectric nanogenerators (PENGs) by employing vanadium (V)-doped ZnO nanosheets (NSs) and the polydimethylsiloxane (PDMS) composite structure. The V-doped ZnO NSs were synthesized to overcome the inherently low piezoelectric properties of intrinsic ZnO. Ferroelectric phase transition induced in the V-doped ZnO NSs contributed to significantly improve the performance of the PENGs after the poling process. Consequently, the PENGs exhibited high output voltage and current up to ~32 V and ~6.2 μA, respectively, under the applied strain, which are sufficient to directly turn on a number of light emitting diodes (LEDs). The composite approach for PENG fabrication is scalable, robust, and reproducible during periodic bending/releasing over extended cycles. The approach introduced here extends the performance limits of ZnO-based PENGs and demonstrates their potential as energy harvesting devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07185b

Gap Detection in School-Age Children and Adults: Effects of Inherent Envelope Modulation and the Availability of Cues across Frequency

ERIC Educational Resources Information Center

Buss, Emily; Hall, Joseph W., III; Porter, Heather; Grose, John H.

2014-01-01

Purpose: The present study evaluated the effects of inherent envelope modulation and the availability of cues across frequency on behavioral gap detection with noise-band stimuli in school-age children. Method: Listeners were 34 normal-hearing children (ages 5.2-15.6 years) and 12 normal-hearing adults (ages 18.5-28.8 years). Stimuli were…

Regeneration methods

Treesearch

James P. Barnett; James B. Baker

1991-01-01

Southern pines can be regenerated naturally, by clearcutting, seedtree, shelterwood, or selection reproduction culling methods, or artificially, by direct seeding or by planting either container or bareroot seedlings. All regeneration methods have inherent advantages: and disadvantages; thus, land managers must consider many factors before deciding on a specific method...

Atomic force microscopy study of the structure function relationships of the biofilm-forming bacterium Streptococcus mutans

NASA Astrophysics Data System (ADS)

Cross, Sarah E.; Kreth, Jens; Zhu, Lin; Qi, Fengxia; Pelling, Andrew E.; Shi, Wenyuan; Gimzewski, James K.

2006-02-01

Atomic force microscopy (AFM) has garnered much interest in recent years for its ability to probe the structure, function and cellular nanomechanics inherent to specific biological cells. In particular, we have used AFM to probe the important structure-function relationships of the bacterium Streptococcus mutans. S. mutans is the primary aetiological agent in human dental caries (tooth decay), and is of medical importance due to the virulence properties of these cells in biofilm initiation and formation, leading to increased tolerance to antibiotics. We have used AFM to characterize the unique surface structures of distinct mutants of S. mutans. These mutations are located in specific genes that encode surface proteins, thus using AFM we have resolved characteristic surface features for mutant strains compared to the wild type. Ultimately, our characterization of surface morphology has shown distinct differences in the local properties displayed by various S. mutans strains on the nanoscale, which is imperative for understanding the collective properties of these cells in biofilm formation.

Quantification of flexoelectricity in PbTiO3/SrTiO3 superlattice polar vortices using machine learning and phase-field modeling.

PubMed

Li, Q; Nelson, C T; Hsu, S-L; Damodaran, A R; Li, L-L; Yadav, A K; McCarter, M; Martin, L W; Ramesh, R; Kalinin, S V

2017-11-13

Flexoelectricity refers to electric polarization generated by heterogeneous mechanical strains, namely strain gradients, in materials of arbitrary crystal symmetries. Despite more than 50 years of work on this effect, an accurate identification of its coupling strength remains an experimental challenge for most materials, which impedes its wide recognition. Here, we show the presence of flexoelectricity in the recently discovered polar vortices in PbTiO 3 /SrTiO 3 superlattices based on a combination of machine-learning analysis of the atomic-scale electron microscopy imaging data and phenomenological phase-field modeling. By scrutinizing the influence of flexocoupling on the global vortex structure, we match theory and experiment using computer vision methodologies to determine the flexoelectric coefficients for PbTiO 3 and SrTiO 3 . Our findings highlight the inherent, nontrivial role of flexoelectricity in the generation of emergent complex polarization morphologies and demonstrate a viable approach to delineating this effect, conducive to the deeper exploration of both topics.

Few-mode optical fiber based simultaneously distributed curvature and temperature sensing.

PubMed

Wu, Hao; Tang, Ming; Wang, Meng; Zhao, Can; Zhao, Zhiyong; Wang, Ruoxu; Liao, Ruolin; Fu, Songnian; Yang, Chen; Tong, Weijun; Shum, Perry Ping; Liu, Deming

2017-05-29

The few-mode fiber (FMF) based Brillouin sensing operated in quasi-single mode (QSM) has been reported to achieve the distributed curvature measurement by monitoring the bend-induced strain variation. However, its practicality is limited by the inherent temperature-strain cross-sensitivity of Brillouin sensors. Here we proposed and experimentally demonstrated an approach for simultaneously distributed curvature and temperature sensing, which exploits a hybrid QSM operated Raman-Brillouin system in FMFs. Thanks to the larger spot size of the fundamental mode in the FMF, the Brillouin frequency shift change of the FMF is used for curvature estimation while the temperature variation is alleviated through Raman signals with the enhanced signal-to-noise ratio (SNR). Within 2 minutes measuring time, a 1.5 m spatial resolution is achieved along a 2 km FMF. The worst resolution of the square of fiber curvature is 0.333 cm -2 while the temperature resolution is 1.301 °C at the end of fiber.

Nonlinear Acoustic Propagation into the Seafloor

NASA Astrophysics Data System (ADS)

McDonald, B. Edward

2006-05-01

Explosions near the seafloor result in shock waves entering a much more complicated medium than water or air. Nonlinearities may be increased by two processes inherent to granular media: (1) a poroelastic nonlinearity comparable to the addition of bubbles to water, and (2) the Hertz force resulting from elastic deformation of grains, proportional to the Youngs modulus of the grains times the strain rate to the power 3/2. These two types of nonlinearity for shock propagation into the seafloor are investigated using a variant of the NPE model. The traditional Taylor series expansion of the equation of state (pressure as a function of density) is not appropriate to the Hertz force in the limit of small strain. We present a simple nonlinear wave equation model for compressional waves in marine sediments that retains the Hertz force explicitly with overdensity to the power 3/2. Numerical results for shock propagation are compared with similarity solutions for quadratic nonlinearity and for the fractional nonlinearity of the Hertz force.

InAs/GaInSb strained layer superlattice as an infrared detector material: an overview

NASA Astrophysics Data System (ADS)

Johnson, Jeffrey L.

2000-04-01

The investigation of the InAs/Ga1-xInxSb strained layer superlattice (SLS) has been largely motivated by the promise of overcoming limitations of current mature high-performance IR detectors, such as those using HgCdTe and extrinsic silicon. It also offers fundamentally superior performance over other newly emerging III-V bandgap- engineered materials such as QWIPs. The inherent properties of the InAs/GaInSb SLS have identified it as an attractive alternative for niche VLWIR applications requiring high performance under low backgrounds at operating temperatures > 40K. If this material system proves to meet the stringent demands of VLWIR applications, it will most certainly play a significant role as an alternative materials for photovoltaic focal pane arrays operating in the LWIR and MWIR regimes as well. This paper is an overview of SLS technology development, and focuses on critical development needs as seen from the perspective of the IR detector industry.

N-Glycan Modification in Aspergillus Species▿

PubMed Central

Kainz, Elke; Gallmetzer, Andreas; Hatzl, Christian; Nett, Juergen H.; Li, Huijuan; Schinko, Thorsten; Pachlinger, Robert; Berger, Harald; Reyes-Dominguez, Yazmid; Bernreiter, Andreas; Gerngross, Tillmann; Wildt, Stefan; Strauss, Joseph

2008-01-01

The production by filamentous fungi of therapeutic glycoproteins intended for use in mammals is held back by the inherent difference in protein N-glycosylation and by the inability of the fungal cell to modify proteins with mammalian glycosylation structures. Here, we report protein N-glycan engineering in two Aspergillus species. We functionally expressed in the fungal hosts heterologous chimeric fusion proteins containing different localization peptides and catalytic domains. This strategy allowed the isolation of a strain with a functional α-1,2-mannosidase producing increased amounts of N-glycans of the Man5GlcNAc2 type. This strain was further engineered by the introduction of a functional GlcNAc transferase I construct yielding GlcNAcMan5GlcNac2 N-glycans. Additionally, we deleted algC genes coding for an enzyme involved in an early step of the fungal glycosylation pathway yielding Man3GlcNAc2 N-glycans. This modification of fungal glycosylation is a step toward the ability to produce humanized complex N-glycans on therapeutic proteins in filamentous fungi. PMID:18083888

Tailoring of the thermomechanical performance of VO2 nanowire bimorph actuators by ion implantation

NASA Astrophysics Data System (ADS)

Karl, H.; Peyinghaus, S. C.

2015-12-01

Vanadium dioxide VO2 nanowire bimorph actuators work on the basis of the large abrupt length change at the metal-insulator phase transition (MIT). A key parameter for the bimorph performance and efficiency is the bending curvature and the width of the temperature hysteresis of the MIT which is inherently large for single domain VO2 metal side coated nanowires. In this work we present single-clamped Ir side coated VO2 bimorphs which show unprecedented high bending curvatures of up to 105 m-1 and new type of side ion-implanted VO2 nanowire bimorph actuators with a nearly completely suppressed temperature hysteresis. It is assumed that ion-beam induced radiation defects in the VO2 crystal structure act as nucleation sites for the MIT. Moreover it will be shown that mechanical strain intentionally built-in during VO2 nanowire bimorph fabrication allows to direct phase transformation via a strain stabilized metastable phase and thus allows to control bending response on temperature change.

Reversible control of magnetic interactions by electric field in a single-phase material.

PubMed

Ryan, P J; Kim, J-W; Birol, T; Thompson, P; Lee, J-H; Ke, X; Normile, P S; Karapetrova, E; Schiffer, P; Brown, S D; Fennie, C J; Schlom, D G

2013-01-01

Intrinsic magnetoelectric coupling describes the interaction between magnetic and electric polarization through an inherent microscopic mechanism in a single-phase material. This phenomenon has the potential to control the magnetic state of a material with an electric field, an enticing prospect for device engineering. Here, we demonstrate 'giant' magnetoelectric cross-field control in a tetravalent titanate film. In bulk form, EuTiO(3), is antiferromagnetic. However, both anti and ferromagnetic interactions coexist between different nearest europium neighbours. In thin epitaxial films, strain was used to alter the relative strength of the magnetic exchange constants. We not only show that moderate biaxial compression precipitates local magnetic competition, but also demonstrate that the application of an electric field at this strain condition switches the magnetic ground state. Using first-principles density functional theory, we resolve the underlying microscopic mechanism resulting in G-type magnetic order and illustrate how it is responsible for the 'giant' magnetoelectric effect.

Structural and electronic transformation in low-angle twisted bilayer graphene

NASA Astrophysics Data System (ADS)

Gargiulo, Fernando; Yazyev, Oleg V.

2018-01-01

Experiments on bilayer graphene unveiled a fascinating realization of stacking disorder where triangular domains with well-defined Bernal stacking are delimited by a hexagonal network of strain solitons. Here we show by means of numerical simulations that this is a consequence of a structural transformation of the moiré pattern inherent to twisted bilayer graphene taking place at twist angles θ below a crossover angle θ\\star=1.2\\circ . The transformation is governed by the interplay between the interlayer van der Waals interaction and the in-plane strain field, and is revealed by a change in the functional form of the twist energy density. This transformation unveils an electronic regime characteristic of vanishing twist angles in which the charge density converges, though not uniformly, to that of ideal bilayer graphene with Bernal stacking. On the other hand, the stacking domain boundaries form a distinct charge density pattern that provides the STM signature of the hexagonal solitonic network.

Precise calibration of spatial phase response nonuniformity arising in liquid crystal on silicon.

PubMed

Xu, Jingquan; Qin, SiYi; Liu, Chen; Fu, Songnian; Liu, Deming

2018-06-15

In order to calibrate the spatial phase response nonuniformity of liquid crystal on silicon (LCoS), we propose to use a Twyman-Green interferometer to characterize the wavefront distortion, due to the inherent curvature of the device. During the characterization, both the residual carrier frequency introduced by the Fourier transform evaluation method and the lens aberration are error sources. For the tilted phase error introduced by residual carrier frequency, the least mean square fitting method is used to obtain the tilted phase error. Meanwhile, we use Zernike polynomials fitting based on plane mirror calibration to mitigate the lens aberration. For a typical LCoS with 1×12,288 pixels after calibration, the peak-to-valley value of the inherent wavefront distortion is approximately 0.25λ at 1550 nm, leading to a half-suppression of wavefront distortion. All efforts can suppress the root mean squares value of the inherent wavefront distortion to approximately λ/34.

X-ray Topographic Methods and Application to Analysis of Electronic Materials

NASA Technical Reports Server (NTRS)

Mayo, W. E.; Liu, H. Y.; Chaudhuri, J.

1984-01-01

Three supplementary X-ray techniques new to semiconductor applications are discussed. These are the Computer Aided Rocking Curve Analyzer, the Divergent Beam Method and a new method based on enhanced X-ray flourescence. The first method is used for quantitative mapping of an elastic or plastic strain field while the other two methods are used only to measure elastic strains. The divergent beam method is used for measuring the full strain tensor while the microfluorescence method is useful for monitoring strain uniformity. These methods are discussed in detail and examples of their application is presented. Among these are determination of the full strain ellipsoid in state-of-the-art liquid phase epitaxy deposited III-V epitaxial films; mapping of the plastic strain concentrations in tensile deformed Si; and quantitative determination of damage in V3Si due to ion implantation.

Strain typing of acetic acid bacteria responsible for vinegar production by the submerged elaboration method.

PubMed

Fernández-Pérez, Rocío; Torres, Carmen; Sanz, Susana; Ruiz-Larrea, Fernanda

2010-12-01

Strain typing of 103 acetic acid bacteria isolates from vinegars elaborated by the submerged method from ciders, wines and spirit ethanol, was carried on in this study. Two different molecular methods were utilised: pulsed field gel electrophoresis (PFGE) of total DNA digests with a number of restriction enzymes, and enterobacterial repetitive intergenic consensus (ERIC) - PCR analysis. The comparative study of both methods showed that restriction fragment PFGE of SpeI digests of total DNA was a suitable method for strain typing and for determining which strains were present in vinegar fermentations. Results showed that strains of the species Gluconacetobacter europaeus were the most frequent leader strains of fermentations by the submerged method in the studied vinegars, and among them strain R1 was the predominant one. Results showed as well that mixed populations (at least two different strains) occurred in vinegars from cider and wine, whereas unique strains were found in spirit vinegars, which offered the most stressing conditions for bacterial growth. Copyright © 2010 Elsevier Ltd. All rights reserved.

Whole metagenome profiles of particulates collected from the International Space Station

DOE PAGES

Be, Nicholas A.; Avila-Herrera, Aram; Allen, Jonathan E.; ...

2017-07-17

Background The built environment of the International Space Station (ISS) is a highly specialized space in terms of both physical characteristics and habitation requirements. It is unique with respect to conditions of microgravity, exposure to space radiation, and increased carbon dioxide concentrations. Additionally, astronauts inhabit a large proportion of this environment. The microbial composition of ISS particulates has been reported; however, its functional genomics, which are pertinent due to potential impact of its constituents on human health and operational mission success, are not yet characterized. Methods This study examined the whole metagenome of ISS microbes at both species- and gene-levelmore » resolution. Air filter and dust samples from the ISS were analyzed and compared to samples collected in a terrestrial cleanroom environment. Furthermore, metagenome mining was carried out to characterize dominant, virulent, and novel microorganisms. The whole genome sequences of select cultivable strains isolated from these samples were extracted from the metagenome and compared. Results Species-level composition in the ISS was found to be largely dominated by Corynebacterium ihumii GD7, with overall microbial diversity being lower in the ISS relative to the cleanroom samples. When examining detection of microbial genes relevant to human health such as antimicrobial resistance and virulence genes, it was found that a larger number of relevant gene categories were observed in the ISS relative to the cleanroom. Strain-level cross-sample comparisons were made for Corynebacterium, Bacillus, and Aspergillus showing possible distinctions in the dominant strain between samples. Conclusion Species-level analyses demonstrated distinct differences between the ISS and cleanroom samples, indicating that the cleanroom population is not necessarily reflective of space habitation environments. Lastly, the overall population of viable microorganisms and the functional diversity inherent to this unique closed environment are of critical interest with respect to future space habitation. Observations and studies such as these will be important to evaluating the conditions required for long-term health of human occupants in such environments.« less

Whole metagenome profiles of particulates collected from the International Space Station

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

Be, Nicholas A.; Avila-Herrera, Aram; Allen, Jonathan E.

Background The built environment of the International Space Station (ISS) is a highly specialized space in terms of both physical characteristics and habitation requirements. It is unique with respect to conditions of microgravity, exposure to space radiation, and increased carbon dioxide concentrations. Additionally, astronauts inhabit a large proportion of this environment. The microbial composition of ISS particulates has been reported; however, its functional genomics, which are pertinent due to potential impact of its constituents on human health and operational mission success, are not yet characterized. Methods This study examined the whole metagenome of ISS microbes at both species- and gene-levelmore » resolution. Air filter and dust samples from the ISS were analyzed and compared to samples collected in a terrestrial cleanroom environment. Furthermore, metagenome mining was carried out to characterize dominant, virulent, and novel microorganisms. The whole genome sequences of select cultivable strains isolated from these samples were extracted from the metagenome and compared. Results Species-level composition in the ISS was found to be largely dominated by Corynebacterium ihumii GD7, with overall microbial diversity being lower in the ISS relative to the cleanroom samples. When examining detection of microbial genes relevant to human health such as antimicrobial resistance and virulence genes, it was found that a larger number of relevant gene categories were observed in the ISS relative to the cleanroom. Strain-level cross-sample comparisons were made for Corynebacterium, Bacillus, and Aspergillus showing possible distinctions in the dominant strain between samples. Conclusion Species-level analyses demonstrated distinct differences between the ISS and cleanroom samples, indicating that the cleanroom population is not necessarily reflective of space habitation environments. Lastly, the overall population of viable microorganisms and the functional diversity inherent to this unique closed environment are of critical interest with respect to future space habitation. Observations and studies such as these will be important to evaluating the conditions required for long-term health of human occupants in such environments.« less

Infective Endocarditis: Identification of Catalase-Negative, Gram-Positive Cocci from Blood Cultures by Partial 16S rRNA Gene Analysis and by Vitek 2 Examination.

PubMed

Abdul-Redha, Rawaa Jalil; Kemp, Michael; Bangsborg, Jette M; Arpi, Magnus; Christensen, Jens Jørgen

2010-01-01

Streptococci, enterococci and Streptococcus-like bacteria are frequent etiologic agents of infective endocarditis and correct species identification can be a laboratory challenge. Viridans streptococci (VS) not seldomly cause contamination of blood cultures. Vitek 2 and partial sequencing of the 16S rRNA gene were applied in order to compare the results of both methods. STRAINS ORIGINATED FROM TWO GROUPS OF PATIENTS: 149 strains from patients with infective endocarditis and 181 strains assessed as blood culture contaminants. Of the 330 strains, based on partial 16S rRNA gene sequencing results, 251 (76%) were VS strains, 10 (3%) were pyogenic streptococcal strains, 54 (16%) were E. faecalis strains and 15 (5%) strains belonged to a group of miscellaneous catalase-negative, Gram-positive cocci. Among VS strains, respectively, 220 (87,6%) and 31 (12,3%) obtained agreeing and non-agreeing identifications with the two methods with respect to allocation to the same VS group. Non-agreeing species identification mostly occurred among strains in the contaminant group, while for endocarditis strains notably fewer disagreeing results were observed.Only 67 of 150 strains in the mitis group strains obtained identical species identifications by the two methods. Most VS strains belonging to the groups of salivarius, anginosus, and mutans obtained agreeing species identifications with the two methods, while this only was the case for 13 of the 21 bovis strains. Pyogenic strains (n=10), Enterococcus faecalis strains (n=54) and a miscellaneous group of catalase-negative, Gram-positive cocci (n=15) seemed well identified by both methods, except that disagreements in identifications in the miscellaneous group of strains occurred for 6 of 15 strains.

Analysis of the variation in the determination of the shear modulus of the erythrocyte membrane: Effects of the constitutive law and membrane modeling

PubMed Central

Dimitrakopoulos, P.

2013-01-01

Despite research spanning several decades, the exact value of the shear modulus Gs of the erythrocyte membrane is still ambiguous, and a wealth of studies, using measurements based on micropipette aspirations, ektacytometry systems and other flow chambers, and optical tweezers as well as application of several models have found different average values in the range 2–10 µN/m. Our study shows that different methodologies have predicted the correct shear modulus for the specific membrane modeling employed, i.e. the variation in the shear modulus determination results from the specific membrane modeling. Available experimental findings from ektacytometry systems and optical tweezers suggest that the dynamics of the erythrocyte membrane is strain-hardening at both moderate and large deformations. Thus the erythrocyte shear modulus cannot be determined accurately using strain-softening models (such as the neo-Hookean and Evans laws) or strain-softening/strain-hardening models (such as the Yeoh law) which overestimate the erythrocyte shear modulus. According to our analysis, the only available strain-hardening constitutive law, the Skalak et al. law, is able to match well both deformation-shear rate data from ektacytometry and force-extension data from optical tweezers at moderate and large strains, using an average value of the shear modulus of Gs = 2.4–2.75 µN/m, i.e. very close to that found in the linear regime of deformations via force-extension data from optical tweezers, Gs = 2.5±0.4 µN/m. In addition, our analysis suggests that a standard deviation in Gs of 0.4–0.5 µN/m (owing to the inherent differences between erythrocytes within a large population) describes well the findings from optical tweezers at small and large strains as well as from micro-pipette aspirations. PMID:22680508

Strain Differences in Fitness of Escherichia coli O157:H7 to Resist Protozoan Predation and Survival in Soil

PubMed Central

Ravva, Subbarao V.; Sarreal, Chester Z.; Mandrell, Robert E.

2014-01-01

Escherichia coli O157:H7 (EcO157) associated with the 2006 spinach outbreak appears to have persisted as the organism was isolated, three months after the outbreak, from environmental samples in the produce production areas of the central coast of California. Survival in harsh environments may be linked to the inherent fitness characteristics of EcO157. This study evaluated the comparative fitness of outbreak-related clinical and environmental strains to resist protozoan predation and survive in soil from a spinach field in the general vicinity of isolation of strains genetically indistinguishable from the 2006 outbreak strains. Environmental strains from soil and feral pig feces survived longer (11 to 35 days for 90% decreases, D-value) with Vorticella microstoma and Colpoda aspera, isolated previously from dairy wastewater; these D-values correlated (P<0.05) negatively with protozoan growth. Similarly, strains from cow feces, feral pig feces, and bagged spinach survived significantly longer in soil compared to clinical isolates indistinguishable by 11-loci multi-locus variable-number tandem-repeat analysis. The curli-positive (C+) phenotype, a fitness trait linked with attachment in ruminant and human gut, decreased after exposure to protozoa, and in soils only C− cells remained after 7 days. The C+ phenotype correlated negatively with D-values of EcO157 exposed to soil (r s = −0.683; P = 0.036), Vorticella (r s = −0.465; P = 0.05) or Colpoda (r s = −0.750; P = 0.0001). In contrast, protozoan growth correlated positively with C+ phenotype (Vorticella, r s = 0.730, P = 0.0004; Colpoda, r s = 0.625, P = 0.006) suggesting a preference for consumption of C+ cells, although they grew on C− strains also. We speculate that the C− phenotype is a selective trait for survival and possibly transport of the pathogen in soil and water environments. PMID:25019377

Strain differences in fitness of Escherichia coli O157:H7 to resist protozoan predation and survival in soil.

PubMed

Ravva, Subbarao V; Sarreal, Chester Z; Mandrell, Robert E

2014-01-01

Escherichia coli O157:H7 (EcO157) associated with the 2006 spinach outbreak appears to have persisted as the organism was isolated, three months after the outbreak, from environmental samples in the produce production areas of the central coast of California. Survival in harsh environments may be linked to the inherent fitness characteristics of EcO157. This study evaluated the comparative fitness of outbreak-related clinical and environmental strains to resist protozoan predation and survive in soil from a spinach field in the general vicinity of isolation of strains genetically indistinguishable from the 2006 outbreak strains. Environmental strains from soil and feral pig feces survived longer (11 to 35 days for 90% decreases, D-value) with Vorticella microstoma and Colpoda aspera, isolated previously from dairy wastewater; these D-values correlated (P<0.05) negatively with protozoan growth. Similarly, strains from cow feces, feral pig feces, and bagged spinach survived significantly longer in soil compared to clinical isolates indistinguishable by 11-loci multi-locus variable-number tandem-repeat analysis. The curli-positive (C+) phenotype, a fitness trait linked with attachment in ruminant and human gut, decreased after exposure to protozoa, and in soils only C- cells remained after 7 days. The C+ phenotype correlated negatively with D-values of EcO157 exposed to soil (rs = -0.683; P = 0.036), Vorticella (rs = -0.465; P = 0.05) or Colpoda (rs = -0.750; P = 0.0001). In contrast, protozoan growth correlated positively with C+ phenotype (Vorticella, rs = 0.730, P = 0.0004; Colpoda, rs = 0.625, P = 0.006) suggesting a preference for consumption of C+ cells, although they grew on C- strains also. We speculate that the C- phenotype is a selective trait for survival and possibly transport of the pathogen in soil and water environments.

Fatigue properties of JIS H3300 C1220 copper for strain life prediction

NASA Astrophysics Data System (ADS)

Harun, Muhammad Faiz; Mohammad, Roslina

2018-05-01

The existing methods for estimating strain life parameters are dependent on the material's monotonic tensile properties. However, a few of these methods yield quite complicated expressions for calculating fatigue parameters, and are specific to certain groups of materials only. The Universal Slopes method, Modified Universal Slopes method, Uniform Material Law, the Hardness method, and Medians method are a few existing methods for predicting strain-life fatigue based on monotonic tensile material properties and hardness of material. In the present study, nine methods for estimating fatigue life and properties are applied on JIS H3300 C1220 copper to determine the best methods for strain life estimation of this ductile material. Experimental strain-life curves are compared to estimations obtained using each method. Muralidharan-Manson's Modified Universal Slopes method and Bäumel-Seeger's method for unalloyed and low-alloy steels are found to yield batter accuracy in estimating fatigue life with a deviation of less than 25%. However, the prediction of both methods only yield much better accuracy for a cycle of less than 1000 or for strain amplitudes of more than 1% and less than 6%. Manson's Original Universal Slopes method and Ong's Modified Four-Point Correlation method are found to predict the strain-life fatigue of copper with better accuracy for a high number of cycles of strain amplitudes of less than 1%. The differences between mechanical behavior during monotonic and cyclic loading and the complexity in deciding the coefficient in an equation are probably the reason for the lack of a reliable method for estimating fatigue behavior using the monotonic properties of a group of materials. It is therefore suggested that a differential approach and new expressions be developed to estimate the strain-life fatigue parameters for ductile materials such as copper.

Effective Stress Law in Unconventional Reservoirs under Different Boundary Conditions

NASA Astrophysics Data System (ADS)

Saurabh, S.; Harpalani, S.

2017-12-01

Unconventional reservoirs have attracted a great deal of research interest worldwide during the past two decades. Low permeability and specialized techniques required to exploit these resources present opportunities for improvement in both production rates and ultimate recovery. Understanding subsurface stress modifications and permeability evolution are valuable when evaluating the prospects of unconventional reservoirs. These reservoir properties are functions of effective stress. As a part of this study, effective stress law, specifically the variation of anisotropic Biot's coefficient under various boundary conditions believed to exist in gas reservoirs by different researchers, has been established. Pressure-dependent-permeability (PdK) experiments were carried out on San Juan coal under different boundary conditions, that is, uniaxial strain condition and constant volume condition. Stress and strain in the vertical and horizontal directions were monitored throughout the experiment. Data collected during the experiments was used to determine the Biot's coefficient in vertical and horizontal directions under these two boundary conditions, treating coal as transversely isotropic. The variation of Biot's coefficient was found to be well correlated with the variation in coal permeability. Based on the estimated values of Biot's coefficients, a theory of variation in its value is presented for other boundary conditions. The findings of the study shed light on the inherent behavior of Biot's coefficient under different reservoir boundary conditions. This knowledge can improve the modeling work requiring estimation of effective stress in reservoirs, such as, pressure-/stress- dependent permeability. At the same time, if the effective stresses are known with more certainty by other methods, it enables assessment of the unknown reservoir boundary conditions.

Characterization of craniofacial sutures using the finite element method.

PubMed

Maloul, Asmaa; Fialkov, Jeffrey; Wagner, Diane; Whyne, Cari M

2014-01-03

Characterizing the biomechanical behavior of sutures in the human craniofacial skeleton (CFS) is essential to understand the global impact of these articulations on load transmission, but is challenging due to the complexity of their interdigitated morphology, the multidirectional loading they are exposed to and the lack of well-defined suture material properties. This study aimed to quantify the impact of morphological features, direction of loading and suture material properties on the mechanical behavior of sutures and surrounding bone in the CFS. Thirty-six idealized finite element (FE) models were developed. One additional specimen-specific FE model was developed based on the morphology obtained from a µCT scan to represent the morphological complexity inherent in CFS sutures. Outcome variables of strain energy (SE) and von Mises stress (σvm) were evaluated to characterize the sutures' biomechanical behavior. Loading direction was found to impact the relationship between SE and interdigitation index and yielded varied patterns of σvm in both the suture and surrounding bone. Adding bone connectivity reduced suture strain energy and altered the σvm distribution. Incorporating transversely isotropic material properties was found to reduce SE, but had little impact on stress patterns. High-resolution µCT scanning of the suture revealed a complex morphology with areas of high and low interdigitations. The specimen specific suture model results were reflective of SE absorption and σvm distribution patterns consistent with the simplified FE results. Suture mechanical behavior is impacted by morphologic factors (interdigitation and connectivity), which may be optimized for regional loading within the CFS. © 2013 Elsevier Ltd. All rights reserved.

Simplified Life-Cycle Cost Estimation

NASA Technical Reports Server (NTRS)

Remer, D. S.; Lorden, G.; Eisenberger, I.

1983-01-01

Simple method for life-cycle cost (LCC) estimation avoids pitfalls inherent in formulations requiring separate estimates of inflation and interest rates. Method depends for validity observation that interest and inflation rates closely track each other.

Effective material parameter retrieval of anisotropic elastic metamaterials with inherent nonlocality

NASA Astrophysics Data System (ADS)

Lee, Hyung Jin; Lee, Heung Son; Ma, Pyung Sik; Kim, Yoon Young

2016-09-01

In this paper, the scattering (S-) parameter retrieval method is presented specifically for anisotropic elastic metamaterials; so far, no retrieval has been accomplished when elastic metamaterials exhibit fully anisotropic behavior. Complex constitutive property and intrinsic scattering behavior of elastic metamaterials make their characterization far more complicated than that for acoustic and electromagnetic metamaterials. In particular, elastic metamaterials generally exhibit anisotropic scattering behavior due to higher scattering modes associated with shear deformation. They also exhibit nonlocal responses to some degrees, which originate from strong multiple scattering interactions even in the long wavelength limit. Accordingly, the conventional S-parameter retrieval methods cannot be directly used for elastic metamaterials, because they determine only the diagonal components in effective tensor property. Also, the conventional methods simply use the analytic inversion formulae for the material characterization so that inherent nonlocality cannot be taken into account. To establish a retrieval method applicable to anisotropic elastic metamaterials, we propose an alternative S-parameter method to deal with full anisotropy of elastic metamaterials. To retrieve the whole effective anisotropic parameter, we utilize not only normal but also oblique wave incidences. For the retrieval, we first retrieve the ratio of the effective stiffness tensor to effective density and then determine the effective density. The proposed retrieval method is validated by characterizing the effective material parameters of various types of non-resonant anisotropic metamaterials. It is found that the whole effective parameters are retrieved consistently regardless of used retrieval conditions in spite of inherent nonlocality.

Oleaginous yeasts for biodiesel: current and future trends in biology and production.

PubMed

Sitepu, Irnayuli R; Garay, Luis A; Sestric, Ryan; Levin, David; Block, David E; German, J Bruce; Boundy-Mills, Kyria L

2014-11-15

Production of biodiesel from edible plant oils is quickly expanding worldwide to fill a need for renewable, environmentally-friendly liquid transportation fuels. Due to concerns over use of edible commodities for fuels, production of biodiesel from non-edible oils including microbial oils is being developed. Microalgae biodiesel is approaching commercial viability, but has some inherent limitations such as requirements for sunlight. While yeast oils have been studied for decades, recent years have seen significant developments including discovery of new oleaginous yeast species and strains, greater understanding of the metabolic pathways that determine oleaginicity, optimization of cultivation processes for conversion of various types of waste plant biomass to oil using oleaginous yeasts, and development of strains with enhanced oil production. This review examines aspects of oleaginous yeasts not covered in depth in other recent reviews. Topics include the history of oleaginous yeast research, especially advances in the early 20th century; the phylogenetic diversity of oleaginous species, beyond the few species commonly studied; and physiological characteristics that should be considered when choosing yeast species and strains to be utilized for conversion of a given type of plant biomass to oleochemicals. Standardized terms are proposed for units that describe yeast cell mass and lipid production. Copyright © 2014. Published by Elsevier Inc.

Feature tracking CMR reveals abnormal strain in preclinical arrhythmogenic right ventricular dysplasia/ cardiomyopathy: a multisoftware feasibility and clinical implementation study.

PubMed

Bourfiss, Mimount; Vigneault, Davis M; Aliyari Ghasebeh, Mounes; Murray, Brittney; James, Cynthia A; Tichnell, Crystal; Mohamed Hoesein, Firdaus A; Zimmerman, Stefan L; Kamel, Ihab R; Calkins, Hugh; Tandri, Harikrishna; Velthuis, Birgitta K; Bluemke, David A; Te Riele, Anneline S J M

2017-09-01

Regional right ventricular (RV) dysfunction is the hallmark of Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy (ARVD/C), but is currently only qualitatively evaluated in the clinical setting. Feature Tracking Cardiovascular Magnetic Resonance (FT-CMR) is a novel quantitative method that uses cine CMR to calculate strain values. However, most prior FT-CMR studies in ARVD/C have focused on global RV strain using different software methods, complicating implementation of FT-CMR in clinical practice. We aimed to assess the clinical value of global and regional strain using FT-CMR in ARVD/C and to determine differences between commercially available FT-CMR software packages. We analyzed cine CMR images of 110 subjects (39 overt ARVD/C [mutation+/phenotype+], 40 preclinical ARVD/C [mutation+/phenotype-] and 31 control) for global and regional (subtricuspid, anterior, apical) RV strain in the horizontal longitudinal axis using four FT-CMR software methods (Multimodality Tissue Tracking, TomTec, Medis and Circle Cardiovascular Imaging). Intersoftware agreement was assessed using Bland Altman plots. For global strain, all methods showed reduced strain in overt ARVD/C patients compared to control subjects (p < 0.041), whereas none distinguished preclinical from control subjects (p > 0.275). For regional strain, overt ARVD/C patients showed reduced strain compared to control subjects in all segments which reached statistical significance in the subtricuspid region for all software methods (p < 0.037), in the anterior wall for two methods (p < 0.005) and in the apex for one method (p = 0.012). Preclinical subjects showed abnormal subtricuspid strain compared to control subjects using one of the software methods (p = 0.009). Agreement between software methods for absolute strain values was low (Intraclass Correlation Coefficient = 0.373). Despite large intersoftware variability of FT-CMR derived strain values, all four software methods distinguished overt ARVD/C patients from control subjects by both global and subtricuspid strain values. In the subtricuspid region, one software package distinguished preclinical from control subjects, suggesting the potential to identify early ARVD/C prior to overt disease expression.

REPRESENTATIVE SAMPLING AND ANALYSIS OF HETEROGENEOUS SOILS

EPA Science Inventory

Standard sampling and analysis methods for hazardous substances in contaminated soils currently are available and routinely employed. Standard methods inherently assume a homogeneous soil matrix and contaminant distribution; therefore only small sample quantities typically are p...

A new radial strain and strain rate estimation method using autocorrelation for carotid artery

NASA Astrophysics Data System (ADS)

Ye, Jihui; Kim, Hoonmin; Park, Jongho; Yeo, Sunmi; Shim, Hwan; Lim, Hyungjoon; Yoo, Yangmo

2014-03-01

Atherosclerosis is a leading cause of cardiovascular disease. The early diagnosis of atherosclerosis is of clinical interest since it can prevent any adverse effects of atherosclerotic vascular diseases. In this paper, a new carotid artery radial strain estimation method based on autocorrelation is presented. In the proposed method, the strain is first estimated by the autocorrelation of two complex signals from the consecutive frames. Then, the angular phase from autocorrelation is converted to strain and strain rate and they are analyzed over time. In addition, a 2D strain image over region of interest in a carotid artery can be displayed. To evaluate the feasibility of the proposed radial strain estimation method, radiofrequency (RF) data of 408 frames in the carotid artery of a volunteer were acquired by a commercial ultrasound system equipped with a research package (V10, Samsung Medison, Korea) by using a L5-13IS linear array transducer. From in vivo carotid artery data, the mean strain estimate was -0.1372 while its minimum and maximum values were -2.961 and 0.909, respectively. Moreover, the overall strain estimates are highly correlated with the reconstructed M-mode trace. Similar results were obtained from the estimation of the strain rate change over time. These results indicate that the proposed carotid artery radial strain estimation method is useful for assessing the arterial wall's stiffness noninvasively without increasing the computational complexity.

Hydroxyapatite Fibers: A Review of Synthesis Methods

NASA Astrophysics Data System (ADS)

Qi, Mei-Li; He, Kun; Huang, Zhen-Nan; Shahbazian-Yassar, Reza; Xiao, Gui-Yong; Lu, Yu-Peng; Shokuhfar, Tolou

2017-08-01

Hydroxyapatite (HA) exhibits excellent biocompatibility, bioactivity, osteoconductivity, non-toxicity and so on, making it a perfect candidate for biomedical applications. However, HA is not qualified to be used in load-bearing sites due to its poor flexural strength and fracture toughness. Design, synthesis and application of fibrous HA is a promising strategy to overcome the inherent brittleness. This review provides a brief description of HA and hydroxyapatite fiber (HAF), then introduces different synthesis methods of HAF and highlights the inherent merits and drawbacks involved in each method. Finally, the future perspectives in this active research area are given. The purpose of this review is to acquaint the reader with this promising new field of biomaterials research and with emphasis on recent techniques to obtain continuous, uniform and long HAF.

Strain Characterization and Microstructure Evolution Under Deformation in 2060 Alloy

NASA Astrophysics Data System (ADS)

Jin, X.; Zhang, G. D.; Zhao, Y. F.; Xue, F.

2018-05-01

A new method of DIC combined with EBSD is developed for the characterization of strain and microstructure evolution during bending. The traditional microhardness point and DIC methods are used to study the microstructure evolution in 2060 alloy during bending; the interested area suffers under tensile stress, the microstructure evolution is collected by SEM, EBSD, digital image correlation (DIC) method during bending. The results shows that the DIC method can both realize the strain tensor characterization of the interested area, and can also express the local strain tensor in the micro-area even more. The degree of grain division in the process of deformation is related to the strain in this region; the grains have larger strain of small angle grain boundary (SLGBs), which results in a new micro-organizational structure. The misorientation is smaller with larger strain degree while the misorientation is larger with smaller strain.

Initial Assessment of the Effects of Nonmetallic Inclusions on Fatigue Life of Powder-Metallurgy-Processed Udimet(TM) 720

NASA Technical Reports Server (NTRS)

Gabb, T. P.; Telesman, J.; Kantzos, P. T.; Bonacuse, P. J.; Barrie, R. L.

2002-01-01

The fatigue lives of modern powder metallurgy (PM) disk alloys are influenced by variabilities in alloy microstructure and mechanical properties. These properties can vary due to the different steps of materials/component processing and machining. One of these variables, the presence of nonmetallic inclusions, has been shown to significantly degrade low-cycle fatigue (LCF) life. Nonmetallic inclusions are inherent defects in powder alloys that are a by-product of powder-processing techniques. Contamination of the powder can occur in the melt, during powder atomization, or during any of the various handling processes through consolidation. In modern nickel disk powder processing facilities, the levels of inclusion contamination have been reduced to less than 1 part per million by weight. Despite the efforts of manufacturers to ensure the cleanliness of their powder production processes, the presence of inclusions remains a source of great concern for the designer. the objective of this study was to investigate the effects on fatigue life of these inclusions. Since natural inclusions occur so infrequently, elevated levels of inclusions were carefully introduced in a nickel-based disk superalloy, Udimet 720 (registered trademark of Special Metals Corporation), produced using PM processing. Multiple strain-controlled fatigue tests were then performed on this material at 650 C. Analyses were performed to compare the LCF lives and failure initiation sites as functions of inclusion content and fatigue conditions. A large majority of the failures in specimens with introduced inclusions occurred at cracks initiating from inclusions at the specimen surface. The inclusions could reduce fatigue life by up to 100 times. These effects were found to be dependent on strain range and strain ratio. Tests at lower strain ranges and higher strain ratios produced larger effects of inclusions on life.

Shear, principal, and equivalent strains in equal-channel angular deformation

NASA Astrophysics Data System (ADS)

Xia, K.; Wang, J.

2001-10-01

The shear and principal strains involved in equal channel angular deformation (ECAD) were analyzed using a variety of methods. A general expression for the total shear strain calculated by integrating infinitesimal strain increments gave the same result as that from simple geometric considerations. The magnitude and direction of the accumulated principal strains were calculated based on a geometric and a matrix algebra method, respectively. For an intersecting angle of π/2, the maximum normal strain is 0.881 in the direction at π/8 (22.5 deg) from the longitudinal direction of the material in the exit channel. The direction of the maximum principal strain should be used as the direction of grain elongation. Since the principal direction of strain rotates during ECAD, the total shear strain and principal strains so calculated do not have the same meaning as those in a strain tensor. Consequently, the “equivalent” strain based on the second invariant of a strain tensor is no longer an invariant. Indeed, the equivalent strains calculated using the total shear strain and that using the total principal strains differed as the intensity of deformation increased. The method based on matrix algebra is potentially useful in mathematical analysis and computer calculation of ECAD.

RobOKoD: microbial strain design for (over)production of target compounds.

PubMed

Stanford, Natalie J; Millard, Pierre; Swainston, Neil

2015-01-01

Sustainable production of target compounds such as biofuels and high-value chemicals for pharmaceutical, agrochemical, and chemical industries is becoming an increasing priority given their current dependency upon diminishing petrochemical resources. Designing these strains is difficult, with current methods focusing primarily on knocking-out genes, dismissing other vital steps of strain design including the overexpression and dampening of genes. The design predictions from current methods also do not translate well-into successful strains in the laboratory. Here, we introduce RobOKoD (Robust, Overexpression, Knockout and Dampening), a method for predicting strain designs for overproduction of targets. The method uses flux variability analysis to profile each reaction within the system under differing production percentages of target-compound and biomass. Using these profiles, reactions are identified as potential knockout, overexpression, or dampening targets. The identified reactions are ranked according to their suitability, providing flexibility in strain design for users. The software was tested by designing a butanol-producing Escherichia coli strain, and was compared against the popular OptKnock and RobustKnock methods. RobOKoD shows favorable design predictions, when predictions from these methods are compared to a successful butanol-producing experimentally-validated strain. Overall RobOKoD provides users with rankings of predicted beneficial genetic interventions with which to support optimized strain design.

RobOKoD: microbial strain design for (over)production of target compounds

PubMed Central

Stanford, Natalie J.; Millard, Pierre; Swainston, Neil

2015-01-01

Sustainable production of target compounds such as biofuels and high-value chemicals for pharmaceutical, agrochemical, and chemical industries is becoming an increasing priority given their current dependency upon diminishing petrochemical resources. Designing these strains is difficult, with current methods focusing primarily on knocking-out genes, dismissing other vital steps of strain design including the overexpression and dampening of genes. The design predictions from current methods also do not translate well-into successful strains in the laboratory. Here, we introduce RobOKoD (Robust, Overexpression, Knockout and Dampening), a method for predicting strain designs for overproduction of targets. The method uses flux variability analysis to profile each reaction within the system under differing production percentages of target-compound and biomass. Using these profiles, reactions are identified as potential knockout, overexpression, or dampening targets. The identified reactions are ranked according to their suitability, providing flexibility in strain design for users. The software was tested by designing a butanol-producing Escherichia coli strain, and was compared against the popular OptKnock and RobustKnock methods. RobOKoD shows favorable design predictions, when predictions from these methods are compared to a successful butanol-producing experimentally-validated strain. Overall RobOKoD provides users with rankings of predicted beneficial genetic interventions with which to support optimized strain design. PMID:25853130

The Application of Strain Range Partitioning Method to Torsional Creep-Fatigue Interaction

NASA Technical Reports Server (NTRS)

Zamrik, S. Y.

1975-01-01

The method of strain range partitioning was applied to a series of torsional fatigue tests conducted on tubular 304 stainless steel specimens at 1200 F. Creep strain was superimposed on cycling strain, and the resulting strain range was partitioned into four components; completely reversed plastic shear strain, plastic shear strain followed by creep strain, creep strain followed by plastic strain and completely reversed creep strain. Each strain component was related to the cyclic life of the material. The damaging effects of the individual strain components were expressed by a linear life fraction rule. The plastic shear strain component showed the least detrimental factor when compared to creep strain reversed by plastic strain. In the latter case, a reduction of torsional fatigue life in the order of magnitude of 1.5 was observed.

Deriving depths of deep chlorophyll maximum and water inherent optical properties: A regional model

NASA Astrophysics Data System (ADS)

Xiu, Peng; Liu, Yuguang; Li, Gang; Xu, Qing; Zong, Haibo; Rong, Zengrui; Yin, Xiaobin; Chai, Fei

2009-10-01

The Bohai Sea is a semi-enclosed inland sea with case-2 waters near the coast. A comprehensive set of optical data was collected during three cruises in June, August, and September 2005 in the Bohai Sea. The vertical profile measurements, such as chlorophyll concentration, water turbidity, downwelling irradiance, and diffuse attenuation coefficient, showed that the Bohai Sea was vertically stratified with a relative clear upper layer superimposed on a turbid lower layer. The upper layer was found to correspond to the euphotic zone and the deep chlorophyll maximum (DCM) occurs at the base of this layer. By tuning a semi-analytical model (Lee et al., 1998, 1999) for the Bohai Sea, we developed a method to derive water inherent optical properties and the depth of DCM from above-surface measurements. Assuming a 'fake' bottom in the stratified water, this new method retrieves the 'fake' bottom depth, which is highly correlated with the DCM depth. The average relative error between derived and measured values is 33.9% for phytoplankton absorption at 440 nm, 25.6% for colored detrital matter (detritus plus gelbstoff) absorption at 440 nm, and 24.2% for the DCM depth. This modified method can retrieve water inherent optical properties and monitor the depth of DCM in the Bohai Sea, and the method is also applicable to other stratified waters.

The inherent limits of predicting school violence.

PubMed

Mulvey, E P; Cauffman, E

2001-10-01

The recent media hype over school shootings has led to demands for methods of identifying school shooters before they act. Despite the fact that schools remain one of the safest places for youths to be, schools are beginning to adopt identification systems to determine which students could be future killers. The methods used to accomplish this not only are unproven but are inherently limited in usefulness and often do more harm than good for both the children and the school setting. The authors' goals in the present article are to place school shootings in perspective relative to other risks of violence that children face and to provide a reasonable and scientifically defensible approach to improving the safety of schools.

Truncated Sum Rules and Their Use in Calculating Fundamental Limits of Nonlinear Susceptibilities

NASA Astrophysics Data System (ADS)

Kuzyk, Mark G.

Truncated sum rules have been used to calculate the fundamental limits of the nonlinear susceptibilities and the results have been consistent with all measured molecules. However, given that finite-state models appear to result in inconsistencies in the sum rules, it may seem unclear why the method works. In this paper, the assumptions inherent in the truncation process are discussed and arguments based on physical grounds are presented in support of using truncated sum rules in calculating fundamental limits. The clipped harmonic oscillator is used as an illustration of how the validity of truncation can be tested and several limiting cases are discussed as examples of the nuances inherent in the method.

A novel method of strain - bending moment calibration for blade testing

NASA Astrophysics Data System (ADS)

Greaves, P.; Prieto, R.; Gaffing, J.; van Beveren, C.; Dominy, R.; Ingram, G.

2016-09-01

A new method of interpreting strain data in full scale static and fatigue tests has been implemented as part of the Offshore Renewable Energy Catapult's ongoing development of biaxial fatigue testing of wind turbine blades. During bi-axial fatigue tests, it is necessary to be able to distinguish strains arising from the flapwise motion of the blade from strains arising from the edgewise motion. The method exploits the beam-like structure of blades and is derived using the equations of beam theory. It offers several advantages over the current state of the art method of calibrating strain gauges.

Topology optimization of hyperelastic structures using a level set method

NASA Astrophysics Data System (ADS)

Chen, Feifei; Wang, Yiqiang; Wang, Michael Yu; Zhang, Y. F.

2017-12-01

Soft rubberlike materials, due to their inherent compliance, are finding widespread implementation in a variety of applications ranging from assistive wearable technologies to soft material robots. Structural design of such soft and rubbery materials necessitates the consideration of large nonlinear deformations and hyperelastic material models to accurately predict their mechanical behaviour. In this paper, we present an effective level set-based topology optimization method for the design of hyperelastic structures that undergo large deformations. The method incorporates both geometric and material nonlinearities where the strain and stress measures are defined within the total Lagrange framework and the hyperelasticity is characterized by the widely-adopted Mooney-Rivlin material model. A shape sensitivity analysis is carried out, in the strict sense of the material derivative, where the high-order terms involving the displacement gradient are retained to ensure the descent direction. As the design velocity enters into the shape derivative in terms of its gradient and divergence terms, we develop a discrete velocity selection strategy. The whole optimization implementation undergoes a two-step process, where the linear optimization is first performed and its optimized solution serves as the initial design for the subsequent nonlinear optimization. It turns out that this operation could efficiently alleviate the numerical instability and facilitate the optimization process. To demonstrate the validity and effectiveness of the proposed method, three compliance minimization problems are studied and their optimized solutions present significant mechanical benefits of incorporating the nonlinearities, in terms of remarkable enhancement in not only the structural stiffness but also the critical buckling load.

Passive wireless strain monitoring of tire using capacitance change

NASA Astrophysics Data System (ADS)

Matsuzaki, Ryosuke; Todoroki, Akira

2004-07-01

In-service strain monitoring of tires of automobile is quite effective for improving the reliability of tires and Anti-lock Braking System (ABS). Since conventional strain gages have high stiffness and require lead wires, the conventional strain gages are cumbersome for the strain measurements of the tires. In a previous study, the authors proposed a new wireless strain monitoring method that adopts the tire itself as a sensor, with an oscillating circuit. This method is very simple and useful, but it requires a battery to activate the oscillating circuit. In the present study, the previous method for wireless tire monitoring is improved to produce a passive wireless sensor. A specimen made from a commercially available tire is connected to a tuning circuit comprising an inductance and a capacitance as a condenser. The capacitance change of tire causes change of the tuning frequency. This change of the tuned radio wave enables us to measure the applied strain of the specimen wirelessly, without any power supply from outside. This new passive wireless method is applied to a specimen and the static applied strain is measured. As a result, the method is experimentally shown to be effective as a passive wireless strain monitoring of tires.

Right ventricular strain analysis from three-dimensional echocardiography by using temporally diffeomorphic motion estimation.

PubMed

Zhang, Zhijun; Zhu, Meihua; Ashraf, Muhammad; Broberg, Craig S; Sahn, David J; Song, Xubo

2014-12-01

Quantitative analysis of right ventricle (RV) motion is important for study of the mechanism of congenital and acquired diseases. Unlike left ventricle (LV), motion estimation of RV is more difficult because of its complex shape and thin myocardium. Although attempts of finite element models on MR images and speckle tracking on echocardiography have shown promising results on RV strain analysis, these methods can be improved since the temporal smoothness of the motion is not considered. The authors have proposed a temporally diffeomorphic motion estimation method in which a spatiotemporal transformation is estimated by optimization of a registration energy functional of the velocity field in their earlier work. The proposed motion estimation method is a fully automatic process for general image sequences. The authors apply the method by combining with a semiautomatic myocardium segmentation method to the RV strain analysis of three-dimensional (3D) echocardiographic sequences of five open-chest pigs under different steady states. The authors compare the peak two-point strains derived by their method with those estimated from the sonomicrometry, the results show that they have high correlation. The motion of the right ventricular free wall is studied by using segmental strains. The baseline sequence results show that the segmental strains in their methods are consistent with results obtained by other image modalities such as MRI. The image sequences of pacing steady states show that segments with the largest strain variation coincide with the pacing sites. The high correlation of the peak two-point strains of their method and sonomicrometry under different steady states demonstrates that their RV motion estimation has high accuracy. The closeness of the segmental strain of their method to those from MRI shows the feasibility of their method in the study of RV function by using 3D echocardiography. The strain analysis of the pacing steady states shows the potential utility of their method in study on RV diseases.

Effect of manmade pixels on the inherent dimension of natural material distributions

NASA Astrophysics Data System (ADS)

Schlamm, Ariel; Messinger, David; Basener, William

2009-05-01

The inherent dimension of hyperspectral data may be a useful metric for discriminating between the presence of manmade and natural materials in a scene without reliance on spectral signatures take from libraries. Previously, a simple geometric method for approximating the inherent dimension was introduced along with results from application to single material clusters. This method uses an estimate of the slope from a graph based on the point density estimation in the spectral space. Other information can be gathered from the plot which may aid in the discrimination between manmade and natural materials. In order to use these measures to differentiate between the two material types, the effect of the inclusion of manmade pixels on the phenomenology of the background distribution must be evaluated. Here, a procedure for injecting manmade pixels into a natural region of a scene is discussed. The results of dimension estimation on natural scenes with varying amounts of manmade pixels injected are presented here, indicating that these metrics can be sensitive to the presence of manmade phenomenology in an image.

Passive wireless strain monitoring of tyres using capacitance and tuning frequency changes

NASA Astrophysics Data System (ADS)

Matsuzaki, Ryosuke; Todoroki, Akira

2005-08-01

In-service strain monitoring of tyres of automobiles is quite effective for improving the reliability of tyres and anti-lock braking systems (ABS). Conventional strain gauges have high stiffness and require lead wires. Therefore, they are cumbersome for tyre strain measurements. In a previous study, the authors proposed a new wireless strain monitoring method that adopts the tyre itself as a sensor, with an oscillating circuit. This method is very simple and useful, but it requires a battery to activate the oscillating circuit. In the present study, the previous method for wireless tyre monitoring is improved to produce a passive wireless sensor. A specimen made from a commercially available tyre is connected to a tuning circuit comprising an inductance and a capacitance as a condenser. The capacitance change of the tyre alters the tuning frequency. This change of the tuned radio wave facilitates wireless measurement of the applied strain of the specimen without any power supply. This passive wireless method is applied to a specimen and the static applied strain is measured. Experiments demonstrate that the method is effective for passive wireless strain monitoring of tyres.

A Subband Coding Method for HDTV

NASA Technical Reports Server (NTRS)

Chung, Wilson; Kossentini, Faouzi; Smith, Mark J. T.

1995-01-01

This paper introduces a new HDTV coder based on motion compensation, subband coding, and high order conditional entropy coding. The proposed coder exploits the temporal and spatial statistical dependencies inherent in the HDTV signal by using intra- and inter-subband conditioning for coding both the motion coordinates and the residual signal. The new framework provides an easy way to control the system complexity and performance, and inherently supports multiresolution transmission. Experimental results show that the coder outperforms MPEG-2, while still maintaining relatively low complexity.

Embracing the Fog of War: Assessment and Metrics in Counterinsurgency

DTIC Science & Technology

2012-01-01

There are no inher- ently “good” or “bad” metrics in COIN. No single metric is necessarily good or bad. For example, it would not be correct to say , “A...Intelligence, says , “We must con- tinually remember that intelligence can reduce but never eliminate the uncertainty that is an inherent feature of...in the method or measure been assessed, and are they apparent to outsiders (transparent)? 18 Bernard, 2006, p. 53. Bernard goes on to say , Ultimately

Every silver lining has a cloud: the scientific and animal welfare issues surrounding a new approach to the production of transgenic animals.

PubMed

Combes, Robert D; Balls, Michael

2014-05-01

The scientific basis and advantages of using recently developed CRISPR/Cas-9 technology for transgenesis have been assessed with respect to other production methods, laboratory animal welfare, and the scientific relevance of transgenic models of human diseases in general. As the new technology is straightforward, causes targeted DNA double strand breaks and can result in homozygous changes in a single step, it is more accurate and more efficient than other production methods and speeds up transgenesis. CRISPR/Cas-9 also obviates the use of embryonic stem cells, and is being used to generate transgenic non-human primates (NHPs). While the use of this method reduces the level of animal wastage resulting from the production of each new strain, any long-term contribution to reduction will be offset by the overall increase in the numbers of transgenic animals likely to result from its widespread usage. Likewise, the contribution to refinement of using a more-precise technique, thereby minimising the occurrence of unwanted genetic effects, will be countered by a probable substantial increase in the production of transgenic strains of increasingly sentient species. For ethical and welfare reasons, we believe that the generation of transgenic NHPs should be allowed only in extremely exceptional circumstances. In addition, we present information, which, on both welfare and scientific grounds, leads us to question the current policy of generating ever-more new transgenic models in light of the general failure of many of them, after over two decades of ubiquitous use, to result in significant advances in the understanding and treatment of many key human diseases. Because this unsatisfactory situation is likely to be due to inherent, as well as possibly avoidable, limitations in the transgenic approach to studying disease, which are briefly reviewed, it is concluded that a thorough reappraisal of the rationale for using genetically-altered animals in fundamental research and by the pharmaceutical industry, and for its support by funding bodies, should be undertaken. In the meantime, the use of CRISPR/Cas-9 to generate new transgenic cells in culture is to be guardedly encouraged. 2014 FRAME.

A new and efficient approach for construction of uridine/uracil auxotrophic mutants in the filamentous fungus Aspergillus oryzae using Agrobacterium tumefaciens-mediated transformation.

PubMed

Nguyen, Khuyen Thi; Ho, Quynh Ngoc; Do, Loc Thi Binh Xuan; Mai, Linh Thi Dam; Pham, Duc-Ngoc; Tran, Huyen Thi Thanh; Le, Diep Hong; Nguyen, Huy Quang; Tran, Van-Tuan

2017-06-01

Aspergillus oryzae is a filamentous fungus widely used in food industry and as a microbial cell factory for recombinant protein production. Due to the inherent resistance of A. oryzae to common antifungal compounds, genetic transformation of this mold usually requires auxotrophic mutants. In this study, we show that Agrobacterium tumefaciens-mediated transformation (ATMT) method is very efficient for deletion of the pyrG gene in different Aspergillus oryzae wild-type strains to generate uridine/uracil auxotrophic mutants. Our data indicated that all the obtained uridine/uracil auxotrophic transformants, which are 5- fluoroorotic acid (5-FOA) resistant, exist as the pyrG deletion mutants. Using these auxotrophic mutants and the pyrG selectable marker for genetic transformation via A. tumefaciens, we could get about 1060 transformants per 10 6 fungal spores. In addition, these A. oryzae mutants were also used successfully for expression of the DsRed fluorescent reporter gene under control of the A. oryzae amyB promoter by the ATMT method, which resulted in obvious red transformants on agar plates. Our work provides a new and effective approach for constructing the uridine/uracil auxotrophic mutants in the importantly industrial fungus A. oryzae. This strategy appears to be applicable to other filamentous fungi to develop similar genetic transformation systems based on auxotrophic/nutritional markers for food-grade recombinant applications.

JTHERGAS: Thermodynamic Estimation from 2D Graphical Representations of Molecules

PubMed Central

Blurock, Edward; Warth, V.; Grandmougin, X.; Bounaceur, R.; Glaude, P.A.; Battin-Leclerc, F.

2013-01-01

JTHERGAS is a versatile calculator (implemented in JAVA) to estimate thermodynamic information from two dimensional graphical representations of molecules and radicals involving covalent bonds based on the Benson additivity method. The versatility of JTHERGAS stems from its inherent philosophy that all the fundamental data used in the calculation should be visible, to see exactly where the final values came from, and modifiable, to account for new data that can appear in the literature. The main use of this method is within automatic combustion mechanism generation systems where fast estimation of a large number and variety of chemical species is needed. The implementation strategy is based on meta-atom definitions and substructure analysis allowing a highly extensible database without modification of the core algorithms. Several interfaces for the database and the calculations are provided from terminal line commands, to graphical interfaces to web-services. The first order estimation of thermodynamics is based summing up the contributions of each heavy atom bonding description. Second order corrections due to steric hindrance and ring strain are made. Automatic estimate of contributions due to internal, external and optical symmetries are also made. The thermodynamical data for radicals is calculated by taking the difference due to the lost of a hydrogen radical taking into account changes in symmetry, spin, rotations, vibrations and steric hindrances. The software is public domain and is based on standard libraries such as CDK and CML. PMID:23761949

Antibiotic Resistance among Clinical Ureaplasma Isolates Recovered from Neonates in England and Wales between 2007 and 2013

PubMed Central

Chalker, Victoria J.; Jones, Lucy C.; Maxwell, Nicola C.; Spiller, O. Brad

2015-01-01

Ureaplasma spp. are associated with numerous clinical sequelae with treatment options being limited due to patient and pathogen factors. This report examines the prevalence and mechanisms of antibiotic resistance among clinical strains isolated from 95 neonates, 32 women attending a sexual health clinic, and 3 patients under investigation for immunological disorders, between 2007 and 2013 in England and Wales. MICs were determined by using broth microdilution assays, and a subset of isolates were compared using the broth microdilution method and the Mycoplasma IST2 assay. The underlying molecular mechanisms for resistance were determined for all resistant isolates. Three isolates carried the tet(M) tetracycline resistance gene (2.3%; confidence interval [CI], 0.49 to 6.86%); two isolates were ciprofloxacin resistant (1.5%; CI, 0.07 to 5.79%) but sensitive to levofloxacin and moxifloxacin, while no resistance was seen to any macrolides tested. The MIC values for chloramphenicol were universally low (2 μg/ml), while inherently high-level MIC values for gentamicin were seen (44 to 66 μg/ml). The Mycoplasma IST2 assay identified a number of false positives for ciprofloxacin resistance, as the method does not conform to international testing guidelines. While antibiotic resistance among Ureaplasma isolates remains low, continued surveillance is essential to monitor trends and threats from importation of resistant clones. PMID:26459899

Antibiotic Resistance among Clinical Ureaplasma Isolates Recovered from Neonates in England and Wales between 2007 and 2013.

PubMed

Beeton, Michael L; Chalker, Victoria J; Jones, Lucy C; Maxwell, Nicola C; Spiller, O Brad

2016-01-01

Ureaplasma spp. are associated with numerous clinical sequelae with treatment options being limited due to patient and pathogen factors. This report examines the prevalence and mechanisms of antibiotic resistance among clinical strains isolated from 95 neonates, 32 women attending a sexual health clinic, and 3 patients under investigation for immunological disorders, between 2007 and 2013 in England and Wales. MICs were determined by using broth microdilution assays, and a subset of isolates were compared using the broth microdilution method and the Mycoplasma IST2 assay. The underlying molecular mechanisms for resistance were determined for all resistant isolates. Three isolates carried the tet(M) tetracycline resistance gene (2.3%; confidence interval [CI], 0.49 to 6.86%); two isolates were ciprofloxacin resistant (1.5%; CI, 0.07 to 5.79%) but sensitive to levofloxacin and moxifloxacin, while no resistance was seen to any macrolides tested. The MIC values for chloramphenicol were universally low (2 μg/ml), while inherently high-level MIC values for gentamicin were seen (44 to 66 μg/ml). The Mycoplasma IST2 assay identified a number of false positives for ciprofloxacin resistance, as the method does not conform to international testing guidelines. While antibiotic resistance among Ureaplasma isolates remains low, continued surveillance is essential to monitor trends and threats from importation of resistant clones. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Transformation-invariant and nonparametric monotone smooth estimation of ROC curves.

PubMed

Du, Pang; Tang, Liansheng

2009-01-30

When a new diagnostic test is developed, it is of interest to evaluate its accuracy in distinguishing diseased subjects from non-diseased subjects. The accuracy of the test is often evaluated by receiver operating characteristic (ROC) curves. Smooth ROC estimates are often preferable for continuous test results when the underlying ROC curves are in fact continuous. Nonparametric and parametric methods have been proposed by various authors to obtain smooth ROC curve estimates. However, there are certain drawbacks with the existing methods. Parametric methods need specific model assumptions. Nonparametric methods do not always satisfy the inherent properties of the ROC curves, such as monotonicity and transformation invariance. In this paper we propose a monotone spline approach to obtain smooth monotone ROC curves. Our method ensures important inherent properties of the underlying ROC curves, which include monotonicity, transformation invariance, and boundary constraints. We compare the finite sample performance of the newly proposed ROC method with other ROC smoothing methods in large-scale simulation studies. We illustrate our method through a real life example. Copyright (c) 2008 John Wiley & Sons, Ltd.

21 CFR 177.1960 - Vinyl chloride-hexene-1 copolymers.

Code of Federal Regulations, 2013 CFR

2013-04-01

... accepted applicability. (ii) Inherent viscosity in cyclohexanone at 30 °C is not less than 0.59 deciliters per gram as determined by ASTM method D1243-79, “Standard Test Method for Dilute Solution Viscosity of...

21 CFR 177.1960 - Vinyl chloride-hexene-1 copolymers.

Code of Federal Regulations, 2012 CFR

2012-04-01

... accepted applicability. (ii) Inherent viscosity in cyclohexanone at 30 °C is not less than 0.59 deciliters per gram as determined by ASTM method D1243-79, “Standard Test Method for Dilute Solution Viscosity of...

21 CFR 177.1960 - Vinyl chloride-hexene-1 copolymers.

Code of Federal Regulations, 2011 CFR

2011-04-01

... accepted applicability. (ii) Inherent viscosity in cyclohexanone at 30 °C is not less than 0.59 deciliters per gram as determined by ASTM method D1243-79, “Standard Test Method for Dilute Solution Viscosity of...

Development of Self-Powered Wireless Structural Health Monitoring (SHM) for Wind Turbine Blades

NASA Astrophysics Data System (ADS)

Lim, Dong-Won

Wind turbine blade failure can lead to unexpected power interruptions. Monitoring wind turbine blades is important to ensure seamless electricity delivery from power generation to consumers. Structural health monitoring (SHM) enables early recognition of structural problems so that the safety and reliability of operation can be enhanced. This dissertation focuses on the development of a wireless SHM system for wind turbine blades. The sensor is comprised of a piezoelectric energy harvester (EH) and a telemetry unit. The sensor node is mounted on the blade surface. As the blade rotates, the blade flexes, and the energy harvester captures the strain energy on the blade surface. Once sufficient electricity is captured, a pulse is sent from the sensing node to a gateway. Then, a central monitoring algorithm processes a series of pulses received from all three blades. This wireless SHM, which uses commercially available components, can be retrofitted to existing turbines. The harvested energy for sensing can be estimated in terms of two factors: the available strain energy and conversion efficiency. The available strain energy was evaluated using the FAST (Fatigue, Aerodynamics, Structures, and Turbulence) simulator. The conversion efficiency was studied analytically and experimentally. An experimental set-up was designed to mimic the expected strain frequency and amplitude for rotor blades. From a series of experiments, the efficiency of a piezoelectric EH at a typical rotor speed (0.2 Hz) was approximately 0.5%. The power requirement for sending one measurement (280 muJ) can be achieved in 10 minutes. Designing a detection algorithm is challenging due to this low sampling rate. A new sensing approach-the timing of pulses from the transmitter-was introduced. This pulse timing, which is tied to the charging time, is indicative of the structural health. The SHM system exploits the inherent triple redundancy of the three blades. The timing data of the three blades are compared to discern an outlier, corresponding to a damaged blade. Two types of post-processing of pulses were investigated: (1) comparing the ratios of signal timings (i.e. transmission ratio); and (2) comparing the difference between signal timings (i.e. residuals). For either method, damage is indicated when the energy ratio or residual exceeds a threshold level. When residuals are used to detect damage, performance measures such as the false alarm rate and detection probability can also be imposed. The SHM algorithms were evaluated using strain energy data from a 2.5 MW wind turbine.

Staphylococcus aureus but not Listeria monocytogenes adapt to triclosan and adaptation correlates with increased fabI expression and agr deficiency

PubMed Central

2013-01-01

Background The ability of pathogens to adapt to the widely used biocide, triclosan, varies substantially. The purpose of the study was to examine bacterial adaptation over an extended period of time to low increments of triclosan concentrations. Focus was two human pathogens, S. aureus and L. monocytogenes that previously have displayed inherent high and low adaptability, respectively. Results Three strains of L. monocytogenes and two strains of S. aureus including the community-acquired USA300 were exposed to increasing, sub-lethal concentrations of triclosan in triclosan-containing agar gradients. Following 25 days of exposure on agar plates to sub-lethal concentrations of triclosan with a twofold concentration increase every second day, minimum inhibitory concentration (MIC) for S. aureus increased from 0.125 (8325–4) and 0.0625 (USA 300) mg/L to 4 mg/L. The MIC of all three L. monocytogenes strains was initially 4 mg/L and remained unaltered by the exposure. The adapted S. aureus isolates retained normal colony size but displayed increased expression of fabI encoding an essential enzyme in bacterial fatty acid synthesis. Also, they displayed decreased or no expression of the virulence associated agrC of the agr quorum sensing system. While most adapted strains of USA300 carried mutations in fabI, none of the adapted strains of 8325–4 did. Conclusions Adaptability to triclosan varies substantially between Gram positive human pathogens. S. aureus displayed an intrinsically lower MIC for triclosan compared to L. monocytogenes but was easily adapted leading to the same MIC as L. monocytogenes. Even though all adapted S. aureus strains over-expressed fabI and eliminated expression of the agr quorum sensing system, adaptation in USA300 involved fabI mutations whereas this was not the case for 8325–4. Thus, adaptation to triclosan by S. aureus appears to involve multiple genetic pathways. PMID:23898801

Energy evolution mechanism in process of Sandstone failure and energy strength criterion

NASA Astrophysics Data System (ADS)

Wang, Yunfei; Cui, Fang

2018-07-01

To reveal the inherent relation between energy change and confining pressure during the process of sandstone damage, and its characteristics of energy storage and energy dissipation in different deformation stage. Obtaining the mechanical parameters by testing the Sandstone of two1 coal seam roof under uniaxial compression in Zhaogu coalmine, using Particle Flow Code (PFC) and fish program to get the meso-mechanical parameters, studying Sandstone energy evolution mechanism under different confining pressures, and deducing energy strength criterion based on energy principle of rock failure, some main researching results are reached as follows: with the increasing of confining pressure, the Sandstone yield stage and ductility increases, but brittleness decreases; Under higher confining pressure, the elastic strain energy of Sandstone before peak approximately keeps constant in a certain strain range, and rock absorbs all the energy which converts into surface energy required for internal damage development; Under lower confining pressure, Sandstone no longer absorbs energy with increasing strain after peak under lower confining pressure, while it sequentially absorbs energy under higher confining pressure; Under lower confining pressure, the energy Sandstone before peak absorbed mainly converts into elastic strain energy, while under higher confining pressure, dissipation energy significantly increases before peak, which indicates that the degree rock strength loss is higher under higher confining pressure; with the increasing of confining pressure, the limit of elastic strain energy increases and there exists a favourable linear variation relationship; At the peak point, the ratio of elastic strain energy to total energy of Sandstone nonlinearly decreases, while the ratio of dissipation energy to total energy nonlinearly increases with the increasing of confining pressure; According to energy evolution mechanism of rock failure, an energy strength criterion is derived. The criterion equation includes lithology constants and three principal stresses, and its physical meaning is clear. This criterion has an evident advantage than Hoek-Brown and Drucker-Prager criterion in calculation accuracy and can commendably describe rock failure characteristics.

Alternative methods of reproduction. Effects on the child.

PubMed

Sokoloff, B Z

1987-01-01

Artificial donor insemination (DI), surrogate parenting, in vitro fertilization, and embryo transfer are alternative methods of reproduction being utilized with increasing frequency. Technological developments are being studied in detail. Because of the secrecy inherent in the families involved, there has been little written describing the emotional and psychological well-being of the participants. Significant factors, such as unlimited pregnancies per donor, lack of recordkeeping of the genetic background of each insemination, need for psychological counseling of the parents, the impact of the "family secret" of the pregnancy, and the well-being of the offspring, have not been adequately addressed. There has been little effort to make use of our experience in adoption in relation to many of these same areas. No medical guidelines or legislation exist. The inherent problems associated with these parenting methods and practices are discussed along with recommendations for improvement.

A Unified Development of Basis Reduction Methods for Rotor Blade Analysis

NASA Technical Reports Server (NTRS)

Ruzicka, Gene C.; Hodges, Dewey H.; Rutkowski, Michael (Technical Monitor)

2001-01-01

The axial foreshortening effect plays a key role in rotor blade dynamics, but approximating it accurately in reduced basis models has long posed a difficult problem for analysts. Recently, though, several methods have been shown to be effective in obtaining accurate,reduced basis models for rotor blades. These methods are the axial elongation method,the mixed finite element method, and the nonlinear normal mode method. The main objective of this paper is to demonstrate the close relationships among these methods, which are seemingly disparate at first glance. First, the difficulties inherent in obtaining reduced basis models of rotor blades are illustrated by examining the modal reduction accuracy of several blade analysis formulations. It is shown that classical, displacement-based finite elements are ill-suited for rotor blade analysis because they can't accurately represent the axial strain in modal space, and that this problem may be solved by employing the axial force as a variable in the analysis. It is shown that the mixed finite element method is a convenient means for accomplishing this, and the derivation of a mixed finite element for rotor blade analysis is outlined. A shortcoming of the mixed finite element method is that is that it increases the number of variables in the analysis. It is demonstrated that this problem may be rectified by solving for the axial displacements in terms of the axial forces and the bending displacements. Effectively, this procedure constitutes a generalization of the widely used axial elongation method to blades of arbitrary topology. The procedure is developed first for a single element, and then extended to an arbitrary assemblage of elements of arbitrary type. Finally, it is shown that the generalized axial elongation method is essentially an approximate solution for an invariant manifold that can be used as the basis for a nonlinear normal mode.

Designing Hyperchaotic Cat Maps With Any Desired Number of Positive Lyapunov Exponents.

PubMed

Hua, Zhongyun; Yi, Shuang; Zhou, Yicong; Li, Chengqing; Wu, Yue

2018-02-01

Generating chaotic maps with expected dynamics of users is a challenging topic. Utilizing the inherent relation between the Lyapunov exponents (LEs) of the Cat map and its associated Cat matrix, this paper proposes a simple but efficient method to construct an -dimensional ( -D) hyperchaotic Cat map (HCM) with any desired number of positive LEs. The method first generates two basic -D Cat matrices iteratively and then constructs the final -D Cat matrix by performing similarity transformation on one basic -D Cat matrix by the other. Given any number of positive LEs, it can generate an -D HCM with desired hyperchaotic complexity. Two illustrative examples of -D HCMs were constructed to show the effectiveness of the proposed method, and to verify the inherent relation between the LEs and Cat matrix. Theoretical analysis proves that the parameter space of the generated HCM is very large. Performance evaluations show that, compared with existing methods, the proposed method can construct -D HCMs with lower computation complexity and their outputs demonstrate strong randomness and complex ergodicity.

Synthesis and characterization of metal oxide semiconductors by a facile co-electroplating-annealing method and formation of ZnO/CuO pn heterojunctions with rectifying behavior

NASA Astrophysics Data System (ADS)

Turkdogan, Sunay; Kilic, Bayram

2018-01-01

We have developed a unique growth method and demonstrated the growth of CuO and ZnO semiconductor materials and the fabrication of their pn heterojunctions in ambient atmosphere. The pn heterojunctions were constructed using inherently p-type CuO and inherently n-type ZnO materials. Both p- and n-type semiconductors and pn heterojunctions were prepared using a simple but versatile growth method that relies on the transformation of electroplated Cu and Zn metals into CuO and ZnO semiconductors, respectively and is capable of a large-scale production desired in most of the applications. The structural, chemical, optical and electrical properties of the materials and junctions were investigated using various characterization methods and the results show that our growth method, materials and devices are quite promising to be utilized for various applications including but not limited to solar cells, gas/humidity sensors and photodetectors.

Deep learning architecture for air quality predictions.

PubMed

Li, Xiang; Peng, Ling; Hu, Yuan; Shao, Jing; Chi, Tianhe

2016-11-01

With the rapid development of urbanization and industrialization, many developing countries are suffering from heavy air pollution. Governments and citizens have expressed increasing concern regarding air pollution because it affects human health and sustainable development worldwide. Current air quality prediction methods mainly use shallow models; however, these methods produce unsatisfactory results, which inspired us to investigate methods of predicting air quality based on deep architecture models. In this paper, a novel spatiotemporal deep learning (STDL)-based air quality prediction method that inherently considers spatial and temporal correlations is proposed. A stacked autoencoder (SAE) model is used to extract inherent air quality features, and it is trained in a greedy layer-wise manner. Compared with traditional time series prediction models, our model can predict the air quality of all stations simultaneously and shows the temporal stability in all seasons. Moreover, a comparison with the spatiotemporal artificial neural network (STANN), auto regression moving average (ARMA), and support vector regression (SVR) models demonstrates that the proposed method of performing air quality predictions has a superior performance.

Health issues for surfers.

PubMed

Zoltan, Todd B; Taylor, Kenneth S; Achar, Suraj A

2005-06-15

Surfers are prone to acute injuries as well as conditions resulting from chronic environmental exposure. Sprains, lacerations, strains, and fractures are the most common types of trauma. Injury from the rider's own surfboard may be the prevailing mechanism. Minor wound infections can be treated on an outpatient basis with ciprofloxacin or trimethoprim-sulfamethoxazole. Jellyfish stings are common and may be treated with heat application. Other treatment regimens have had mixed results. Seabather's eruption is a pruritic skin reaction caused by exposure to nematocyst-containing coelenterate larvae. Additional surfing hazards include stingrays, coral reefs, and, occasionally, sharks. Otologic sequelae of surfing include auditory exostoses, tympanic membrane rupture, and otitis externa. Sun exposure and skin cancer risk are inherent dangers of this sport.

Treatment of low strains and long hold times in high temperature metal fatigue by strainrange partitioning

NASA Technical Reports Server (NTRS)

Manson, S. S.; Zab, R.

1977-01-01

A procedure for treating creep-fatigue for low strainranges and long hold times is outlined. A semi-experimental approach, wherein several cycles of the imposed loading is actually applied to a specimen in order to determine the stable hysteresis loop, can be very useful in the analysis. Because such tests require only a small fraction of the total failure time, they are not inherently prohibitive if experimental equipment is available. The need for accurate constitutive equations is bypassed because the material itself acts to translate the imposed loading into the responsive hysteresis loops. When strainrange partitioning has been applied in such cases very good results have been obtained.

Technical note: development of a quantitative PCR method for monitoring strain dynamics during yogurt manufacture.

PubMed

Miller, D M; Dudley, E G; Roberts, R F

2012-09-01

Yogurt starter cultures may consist of multiple strains of Lactobacillus delbrueckii ssp. bulgaricus (LB) and Streptococcus thermophilus (ST). Conventional plating methods for monitoring LB and ST levels during yogurt manufacture do not allow for quantification of individual strains. The objective of the present work was to develop a quantitative PCR method for quantification of individual strains in a commercial yogurt starter culture. Strain-specific primers were designed for 2 ST strains (ST DGCC7796 and ST DGCC7710), 1 LB strain (DGCC4078), and 1 Lactobacillus delbrueckii ssp. lactis strain (LL; DGCC4550). Primers for the individual ST and LB strains were designed to target unique DNA sequences in clustered regularly interspersed short palindromic repeats. Primers for LL were designed to target a putative mannitol-specific IIbC component of the phosphotransferase system. Following evaluation of primer specificity, standard curves relating cell number to cycle threshold were prepared for each strain individually and in combination in yogurt mix, and no significant differences in the slopes were observed. Strain balance data was collected for yogurt prepared at 41 and 43°C to demonstrate the potential application of this method. Copyright © 2012 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Comparison and Evaluation of the Molecular Typing Methods for Toxigenic Vibrio cholerae in Southwest China.

PubMed

Liao, Feng; Mo, Zhishuo; Chen, Meiling; Pang, Bo; Fu, Xiaoqing; Xu, Wen; Jing, Huaiqi; Kan, Biao; Gu, Wenpeng

2018-01-01

Vibrio cholerae O1 strains taken from the repository of Yunnan province, southwest China, were abundant and special. We selected 70 typical toxigenic V. cholerae (69 O1 and one O139 serogroup strains) isolated from Yunnan province, performed the pulsed field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and MLST of virulence gene (V-MLST) methods, and evaluated the resolution abilities for typing methods. The ctxB subunit sequence analysis for all strains have shown that cholera between 1986 and 1995 was associated with mixed infections with El Tor and El Tor variants, while infections after 1996 were all caused by El Tor variant strains. Seventy V. cholerae obtained 50 PFGE patterns, with a high resolution. The strains could be divided into three groups with predominance of strains isolated during 1980s, 1990s, and 2000s, respectively, showing a good consistency with the epidemiological investigation. We also evaluated two MLST method for V. cholerae , one was used seven housekeeping genes ( adk , gyrB , metE , pntA , mdh , purM , and pyrC ), and all the isolates belonged to ST69; another was used nine housekeeping genes ( cat , chi , dnaE , gyrB , lap , pgm , recA , rstA , and gmd ). A total of seven sequence types (STs) were found by using this method for all the strains; among them, rstA gene had five alleles, recA and gmd have two alleles, and others had only one allele. The virulence gene sequence typing method ( ctxAB , tcpA , and toxR ) showed that 70 strains were divided into nine STs; among them, tcpA gene had six alleles, toxR had five alleles, while ctxAB was identical for all the strains. The latter two sequences based typing methods also had consistency with epidemiology of the strains. PFGE had a higher resolution ability compared with the sequence based typing method, and MLST used seven housekeeping genes showed the lower resolution power than nine housekeeping genes and virulence genes methods. These two sequence typing methods could distinguish some epidemiological special strains in local area.

Profiling the robustness, efficiency and limits of the forward-adjoint method for 3-D mantle convection modelling

NASA Astrophysics Data System (ADS)

Price, M. G.; Davies, J. H.

2018-02-01

Knowledge of Earth's past mantle structure is inherently unknown. This lack of knowledge presents problems in many areas of Earth science, including in mantle circulation modelling (MCM). As a mathematical model of mantle convection, MCMs require boundary and initial conditions. While boundary conditions are readily available from sources such as plate reconstructions for the upper surface, and as free slip at the core-mantle boundary, the initial condition is not known. MCMs have historically `created' an initial condition using long `spin up' processes using the oldest available plate reconstruction period available. While these do yield good results when models are run to present day, it is difficult to infer with confidence results from early in a model's history. Techniques to overcome this problem are now being studied in geodynamics, such as by assimilating the known internal structure (e.g. from seismic tomography) of Earth at present day backwards in time. One such method is to use an iterative process known as the forward-adjoint method. While this is an efficient means of solving this inverse problem, it still strains all but the most cutting edge computational systems. In this study we endeavour to profile the effectiveness of this method using synthetic test cases as our known data source. We conclude that savings in terms of computational expense for forward-adjoint models can be achieved by streamlining the time-stepping of the calculation, as well as determining the most efficient method of updating initial conditions in the iterative scheme. Furthermore, we observe that in the models presented, there exists an upper limit on the time interval over which solutions will practically converge, although this limit is likely to be linked to Rayleigh number.

[Isolation and identification of Cronobacter (Enterobacter sakazakii) strains from food].

PubMed

Dong, Xiaohui; Li, Chengsi; Wu, Qingping; Zhang, Jumei; Mo, Shuping; Guo, Weipeng; Yang, Xiaojuan; Xu, Xiaoke

2013-05-04

This study aimed to detect and quantify Cronobacter in 300 powdered milk samples and 50 non-powdered milk samples. Totally, 24 Cronobacter (formerly Enterobacter sakazakii) strains isolated from powdered milk and other foods were identified and confirmed. Cronobacter strains were detected quantitatively using most probable number (MPN) method and molecular detection method. We identified 24 Cronobacter strains using biochemical patterns, including indole production and dulcitol, malonate, melezitose, turanose, and myo-Inositol utilization. Of the 24 strains, their 16S rRNA genes were sequenced, and constructed phylogenetic tree by N-J (Neighbour-Joining) with the 16S rRNA gene sequences of 17 identified Cronobacter strains and 10 non-Cronobacter strains. Quantitative detection showed that Cronobacter strains were detected in 23 out of 350 samples yielding 6.6% detection rate. Twenty-four Cronobacter strains were isolated from 23 samples and the Cronobacter was more than 100 MPN/100g in 4 samples out of 23 samples. The 24 Cronobacter spp. isolates strains were identified and confirmed, including 19 Cronobacter sakazakii strains, 2 C. malonaticus strains, 2 C. dubliensis subsp. lactaridi strains, and 1 C. muytjensii strain. The combination of molecular detection method and most probable number (MPN) method could be suitable for the detection of Cronobacter in powdered milk, with low rate of contamination and high demand of quantitative detection. 24 isolated strains were confirmed and identified by biochemical patterns and molecular technology, and C. sakazakii could be the dominant species. The problem of Cronobacter in powdered milk should be a hidden danger to nurseling, and should catch the government and consumer's attention.

Method for Estimating Operational Loads on Aerospace Structures Using Span-Wisely Distributed Surface Strains

NASA Technical Reports Server (NTRS)

Ko, William L.; Fleischer, Van Tran

2013-01-01

This report presents a new method for estimating operational loads (bending moments, shear loads, and torques) acting on slender aerospace structures using distributed surface strains (unidirectional strains). The surface strain-sensing stations are to be evenly distributed along each span-wise strain-sensing line. A depth-wise cross section of the structure along each strain-sensing line can then be considered as an imaginary embedded beam. The embedded beam was first evenly divided into multiple small domains with domain junctures matching the strain-sensing stations. The new method is comprised of two steps. The first step is to determine the structure stiffness (bending or torsion) using surface strains obtained from a simple bending (or torsion) loading case, for which the applied bending moment (or torque) is known. The second step is to use the strain-determined structural stiffness (bending or torsion), and a new set of surface strains induced by any other loading case to calculate the associated operational loads (bending moments, shear loads, or torques). Performance of the new method for estimating operational loads was studied in light of finite-element analyses of several example structures subjected to different loading conditions. The new method for estimating operational loads was found to be fairly accurate, and is very promising for applications to the flight load monitoring of flying vehicles with slender wings.

Hydrogen production from microbial strains

DOEpatents

Harwood, Caroline S; Rey, Federico E

2012-09-18

The present invention is directed to a method of screening microbe strains capable of generating hydrogen. This method involves inoculating one or more microbes in a sample containing cell culture medium to form an inoculated culture medium. The inoculated culture medium is then incubated under hydrogen producing conditions. Once incubating causes the inoculated culture medium to produce hydrogen, microbes in the culture medium are identified as candidate microbe strains capable of generating hydrogen. Methods of producing hydrogen using one or more of the microbial strains identified as well as the hydrogen producing strains themselves are also disclosed.

Comparison of two methods for detection of strain localization in sheet forming

NASA Astrophysics Data System (ADS)

Lumelskyj, Dmytro; Lazarescu, Lucian; Banabic, Dorel; Rojek, Jerzy

2018-05-01

This paper presents a comparison of two criteria of strain localization in experimental research and numerical simulation of sheet metal forming. The first criterion is based on the analysis of the through-thickness thinning (through-thickness strain) and its first time derivative in the most strained zone. The limit strain in the second method is determined by the maximum of the strain acceleration. Experimental and numerical investigation have been carried out for the Nakajima test performed for different specimens of the DC04 grade steel sheet. The strain localization has been identified by analysis of experimental and numerical curves showing the evolution of strains and their derivatives in failure zones. The numerical and experimental limit strains calculated from both criteria have been compared with the experimental FLC evaluated according to the ISO 12004-2 norm. It has been shown that the first method predicts formability limits closer to the experimental FLC. The second criterion predicts values of strains higher than FLC determined according to ISO norm. These values are closer to the strains corresponding to the fracture limit. The results show that analysis of strain evolution allows us to determine strain localization in numerical simulation and experimental studies.

Two-dimensional surface strain measurement based on a variation of Yamaguchi's laser-speckle strain gauge

NASA Technical Reports Server (NTRS)

Barranger, John P.

1990-01-01

A novel optical method of measuring 2-D surface strain is proposed. Two linear strains along orthogonal axes and the shear strain between those axes is determined by a variation of Yamaguchi's laser-speckle strain gage technique. It offers the advantages of shorter data acquisition times, less stringent alignment requirements, and reduced decorrelation effects when compared to a previously implemented optical strain rosette technique. The method automatically cancels the translational and rotational components of rigid body motion while simplifying the optical system and improving the speed of response.

Sub-inhibitory concentrations of oxacillin modify the expression of agr locus in Staphylococcus aureus clinical strains belonging to different clonal complexes.

PubMed

Viedma, Esther; Pérez-Montarelo, Dafne; Villa, Jennifer; Muñoz-Gallego, Irene; Larrosa, Nieves; Fernández-Hidalgo, Nuria; Gavaldà, Joan; Almirante, Benito; Chaves, Fernando

2018-04-16

The ability of Staphylococcus aureus to invade tissues and cause an infectious disease is the result of a multi-factorial process supported by the huge number of virulence factors inherent to this microorganism tightly regulated by the accessory gene regulator (agr). During antimicrobial therapy bacteria may be exposed to sub-inhibitory concentrations (subMICs) of antibiotics that may trigger transcriptional changes that may have an impact on the pathogenesis of infection. The objective of this study was to investigate the effect of oxacillin sub-MICs on agr system expression as the key component in the regulation of virulence in methicillin-susceptible (MSSA) and -resistant S. aureus (MRSA) strains. Furthermore, we studied the genetic basis of the agr locus and their potential association with the expression levels. We have examined the expression of RNAIII and agrA mRNA as biomarkers for agr expression in the presence and absence of oxacillin subMICs in 10 MSSA and 4 MRSA clinical strains belonging to 5 clonal complexes (CC45-agrI, CC8-agrI, CC5-agrII, CC15-agrII and CC30-agrIII) causing endovascular complications. The DNA sequences of agr locus were obtained by whole genome sequencing. Our results revealed that exposure to subMICs of oxacillin had an impact on agr locus expression modifying the relative levels of expression with increases in 11 strains and with decreases in 3 strains. Thereby, the exposure to subMICs of oxacillin resulted in higher levels of expression of agr in CC15 and CC45 and lower levels in CC30. We also observed the presence of mutations in agrC and agrA in 13/14 strains with similar mutation profiles among strains within individual CCs except for strains of CC5. Although, agr expression levels differed among strains within CCs, the presence of these mutations was associated with differences in agr expression levels in most cases. Changes in agr expression induced by exposure to oxacillin subMICs should be considered because they could lead to changes in the virulence modulation and have an adverse effect on the course of infection, especially in certain clonal complexes.

Quantification of flexoelectricity in PbTiO 3/SrTiO 3 superlattice polar vortices using machine learning and phase-field modeling

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

Li, Q.; Nelson, C. T.; Hsu, S. -L.

Flexoelectricity refers to electric polarization generated by heterogeneous mechanical strains, namely strain gradients, in materials of arbitrary crystal symmetries. Despite more than 50 years of work on this effect, an accurate identification of its coupling strength remains an experimental challenge for most materials, which impedes its wide recognition. Here, we show the presence of flexoelectricity in the recently discovered polar vortices in PbTiO 3 /SrTiO 3 superlattices based on a combination of machine-learning analysis of the atomic-scale electron microscopy imaging data and phenomenological phase-field modeling. By scrutinizing the influence of flexocoupling on the global vortex structure, we match theory andmore » experiment using computer vision methodologies to determine the flexoelectric coefficients for PbTiO 3 and SrTiO 3. Here, our findings highlight the inherent, nontrivial role of flexoelectricity in the generation of emergent complex polarization morphologies and demonstrate a viable approach to delineating this effect, conducive to the deeper exploration of both topics.« less

Alcoholytic Cleavage of Polyhydroxyalkanoate Chains by Class IV Synthases Induced by Endogenous and Exogenous Ethanol

PubMed Central

Hyakutake, Manami; Tomizawa, Satoshi; Mizuno, Kouhei; Abe, Hideki

2014-01-01

Polyhydroxyalkanoate (PHA)-producing Bacillus strains express class IV PHA synthase, which is composed of the subunits PhaR and PhaC. Recombinant Escherichia coli expressing PHA synthase from Bacillus cereus strain YB-4 (PhaRCYB-4) showed an unusual reduction of the molecular weight of PHA produced during the stationary phase of growth. Nuclear magnetic resonance analysis of the low-molecular-weight PHA revealed that its carboxy end structure was capped by ethanol, suggesting that the molecular weight reduction was the result of alcoholytic cleavage of PHA chains by PhaRCYB-4 induced by endogenous ethanol. This scission reaction was also induced by exogenous ethanol in both in vivo and in vitro assays. In addition, PhaRCYB-4 was observed to have alcoholysis activity for PHA chains synthesized by other synthases. The PHA synthase from Bacillus megaterium (PhaRCBm) from another subgroup of class IV synthases was also assayed and was shown to have weak alcoholysis activity for PHA chains. These results suggest that class IV synthases may commonly share alcoholysis activity as an inherent feature. PMID:24334666

Quantification of flexoelectricity in PbTiO 3/SrTiO 3 superlattice polar vortices using machine learning and phase-field modeling

DOE PAGES

Li, Q.; Nelson, C. T.; Hsu, S. -L.; ...

2017-11-13

Flexoelectricity refers to electric polarization generated by heterogeneous mechanical strains, namely strain gradients, in materials of arbitrary crystal symmetries. Despite more than 50 years of work on this effect, an accurate identification of its coupling strength remains an experimental challenge for most materials, which impedes its wide recognition. Here, we show the presence of flexoelectricity in the recently discovered polar vortices in PbTiO 3 /SrTiO 3 superlattices based on a combination of machine-learning analysis of the atomic-scale electron microscopy imaging data and phenomenological phase-field modeling. By scrutinizing the influence of flexocoupling on the global vortex structure, we match theory andmore » experiment using computer vision methodologies to determine the flexoelectric coefficients for PbTiO 3 and SrTiO 3. Here, our findings highlight the inherent, nontrivial role of flexoelectricity in the generation of emergent complex polarization morphologies and demonstrate a viable approach to delineating this effect, conducive to the deeper exploration of both topics.« less

Shockwave dynamics: a comparison between stochastic and periodic porous architectures

NASA Astrophysics Data System (ADS)

Branch, Brittany; Ionite, Axinte; Clements, Bradford; Montgomery, David; Schmalzer, Andrew; Patterson, Brian; Mueller, Alexander; Jensen, Brian; Dattelbaum, Dana

Polymeric foams are used extensively as structural supports and load mitigating materials in which they are subjected to compressive loading at a range of strain rates, up to the high strain rates encountered in blast and shockwave loading. To date, there have been few insights into compaction phenomena in porous structures at the mesoscale, and the influence of structure on shockwave localization. Of particular interest is when the properties of the inherent mesoscopic, periodic structure begin to emerge, versus the discrete behavior of the individual cell. Here, we illustrate, for the first time, modulation of shockwave dynamics controlled at micron-length scales in additively manufactured periodic porous structures measured using in situ, time-resolved x-ray phase contrast imaging at the Advanced Photon Source. Further, we demonstrate how the shockwave dynamics in periodic structures differ from stochastic foams of similar density and we conclude that microstructural control in elastomer foams has a dramatic effect on shockwave dynamics and can be tailored towards a variety of applications. Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory (project# 20160103DR) and DOE/NNSA Campaign 2.

a Thermal Conduction Switch Based on Low Hysteresis Nitife Shape Memory Alloy Helical Springs

NASA Astrophysics Data System (ADS)

Krishnan, V. B.; Bewerse, C.; Notardonato, W. U.; Vaidyanathan, R.

2008-03-01

Shape memory alloy (SMA) actuators possess an inherent property of sensing a change in temperature and delivering significant force against external loads through a shape change resulting from a temperature-induced phase transformation. The utilization of a reversible trigonal (R-phase) to cubic phase transformation in NiTiFe SMAs allows for this strain recovery to occur with reduced hysteresis between the forward and reverse transformations. However, the magnitude of the strain recovery associated with the R-phase transformation is lower than that of the monoclinic to cubic phase transformation. The use of helical springs can compensate for this design constraint as they produce significant stroke when compared to straight elements such as thin strips and wires. This work reports on the development and implementation of NiTiFe helical springs in a low-hysteresis thermal conduction switch for advanced spaceport applications associated with NASA's requirements for future lunar and Mars missions. Such a low-hysteresis thermal conduction switch can provide on-demand heat transfer between two reservoirs at different temperatures.

A Combinatorial Kin Discrimination System in Bacillus subtilis.

PubMed

Lyons, Nicholas A; Kraigher, Barbara; Stefanic, Polonca; Mandic-Mulec, Ines; Kolter, Roberto

2016-03-21

Multicellularity inherently involves a number of cooperative behaviors that are potentially susceptible to exploitation but can be protected by mechanisms such as kin discrimination. Discrimination of kin from non-kin has been observed in swarms of the bacterium Bacillus subtilis, but the underlying molecular mechanism has been unknown. We used genetic, transcriptomic, and bioinformatic analyses to uncover kin recognition factors in this organism. Our results identified many molecules involved in cell-surface modification and antimicrobial production and response. These genes varied significantly in expression level and mutation phenotype among B. subtilis strains, suggesting interstrain variation in the exact kin discrimination mechanism used. Genome analyses revealed a substantial diversity of antimicrobial genes present in unique combinations in different strains, with many likely acquired by horizontal gene transfer. The dynamic combinatorial effect derived from this plethora of kin discrimination genes creates a tight relatedness cutoff for cooperation that has likely led to rapid diversification within the species. Our data suggest that genes likely originally selected for competitive purposes also generate preferential interactions among kin, thus stabilizing multicellular lifestyles. Copyright © 2016 Elsevier Ltd. All rights reserved.

Clostridium perfringens Type E Virulence Traits Involved in Gut Colonization

PubMed Central

Redondo, Leandro M.; Carrasco, Juan M. Díaz; Redondo, Enzo A.; Delgado, Fernando; Miyakawa, Mariano E. Fernández

2015-01-01

Clostridium perfringens type E disease in ruminants has been characterized by hemorrhagic enteritis or sudden death. Although type E isolates are defined by the production of alpha and iota toxin, little is known about the pathogenesis of C. perfringens type E infections. Thus far, the role of iota toxin as a virulence factor is unknown. In this report, iota toxin showed positive effects on adherence and colonization of C. perfringens type E while having negative effect on the adherence of type A cells. In-vitro and in-vivo models suggest that toxinotype E would be particularly adapted to exploit the changes induced by iota toxin in the surface of epithelial cells. In addition, type E strains produce metabolites that affected the growth of potential intra-specific competitors. These results suggest that the alteration of the enterocyte morphology induced by iota toxin concomitantly with the specific increase of type E cell adhesion and the strong intra-specific growth inhibition of other strains could be competitive traits inherent to type E isolates that improve its fitness within the bovine gut environment. PMID:25799452

Wireless magnetoelastic transducers for biomedical applications

NASA Astrophysics Data System (ADS)

Green, S. R.; Gianchandani, Y. B.

2017-05-01

This paper highlights emerging medical applications for magnetoelastic sensing and actuation, each taking advantage of the wireless capabilities and small form factor enabled by the magnetoelastic transduction technique. Magnetoelastic transduction leverages the strong coupling between stress, strain, and magnetization intrinsic to some materials - notably amorphous metals and rare earth crystalline alloys. This coupling provides inherently wireless transduction that does not require any onboard power; these traits are especially advantageous in diagnostic and therapeutic medical implant applications. This paper first describes the basic transduction technique, and considerations for design and fabrication of medical systems which utilize the technique. These considerations include material selection, magnetic biasing, packaging, and interrogation approaches. The first application highlighted is stent monitoring, in which the masssensitive magnetoelastic resonator is integrated along the inner sidewall of the stent to provide early detection of stent occlusion. Prototype tests indicate clinical feasibility and a full scale range from zero stent occlusion to full stent occlusion. Wireless ranges of up to 15 cm in situ have been achieved using 25 mm long resonators. The second application is wireless strain sensing, which can be useful for orthopedic implants and orthodontia. A differential strain sensor is described, with a dynamic range of 0-1.85 mstrain - accommodating typical palatal expander strain - and a sensitivity of 12.5x103 ppm/mstrain. Finally, a wireless actuator intended to agitate fluid for mitigation of encapsulation of glaucoma drainage devices is shown. Peak actuator vibration amplitudes of 1.5 μm - sufficient to affect cell adhesion in other studies - are recorded at a wireless range of 25-30 mm.

Comparative Analysis of Drosophila melanogaster Gut Microbiota with Respect to Host Strain, Sex, and Age.

PubMed

Han, Gangsik; Lee, Hyo Jung; Jeong, Sang Eun; Jeon, Che Ok; Hyun, Seogang

2017-07-01

Microbiota has a significant impact on the health of the host individual. The complexity of the interactions between mammalian hosts and their microbiota highlights the value of using Drosophila melanogaster as a model organism, because of its relatively simple microbial community and ease of physiological and genetic manipulation. However, highly variable and sometimes inconsistent results regarding the microbiota of D. melanogaster have been reported for host samples collected from different geographical locations; discrepancies that may be because of the inherent physiological conditions of the D. melanogaster host. Here, we conducted a comparative analysis of the gut microbiota of two D. melanogaster laboratory strains, w 1118 and Canton S, with respect to the sex and age of the host, by pyrosequencing of the 16S rRNA gene. In addition to the widespread and abundant commensal bacterial genera Lactobacillus and Acetobacter, we identified Enterococcus and Leuconostoc as major host-strain-specific bacterial genera. The relative proportions of these bacterial genera, and those of the species within each, were found to differ markedly with respect to strain, sex, and age of the host, even though host individuals were reared under the same nutritional conditions. By using various bioinformatic tools, we uncovered several characteristic features of microbiota corresponding to specific categories of the flies: host-sex-bias association of specific bacteria, age-dependent alteration of microbiota across host species and sex, and uniqueness of the microbiota of female w 1118 flies. Our results, thus, help to further our understanding of host-microbe interactions in the D. melanogaster model.

Genotoxicity studies on DNA-interactive telomerase inhibitors with application as anti-cancer agents.

PubMed

Harrington, Dean J; Cemeli, Eduardo; Carder, Joanna; Fearnley, Jamie; Estdale, Sian; Perry, Philip J; Jenkins, Terence C; Anderson, Diana

2003-01-01

Telomerase-targeted strategies have aroused recent interest in anti-cancer chemotherapy, because DNA-binding drugs can interact with high-order tetraplex rather than double-stranded (duplex) DNA targets in tumour cells. However, the protracted cell-drug exposure times necessary for clinical application require that telomerase inhibitory efficacy must be accompanied by both low inherent cytotoxicity and the absence of mutagenicity/genotoxicity. For the first time, the genotoxicity of a number of structurally diverse DNA-interactive telomerase inhibitors is examined in the Ames test using six Salmonella typhimurium bacterial strains (TA1535, TA1537, TA1538, TA98, TA100, and TA102). DNA damage induced by each agent was also assessed using the Comet assay with human lymphocytes. The two assay procedures revealed markedly different genotoxicity profiles that are likely to reflect differences in metabolism and/or DNA repair between bacterial and mammalian cells. The mutational spectrum for a biologically active fluorenone derivative, shown to be mutagenic in the TA100 strain, was characterised using a novel and rapid assay method based upon PCR amplification of a fragment of the hisG46 allele, followed by RFLP analysis. Preliminary analysis indicates that the majority (84%) of mutations induced by this compound are C --> A transversions at position 2 of the missense proline codon of the hisG46 allele. However, despite its genotoxic bacterial profile, this fluorenone agent gave a negative response in the Comet assay, and demonstrates how unwanted systemic effects (e.g., cytotoxicity and genotoxicity) can be prevented or ameliorated through suitable molecular fine-tuning of a candidate drug in targeted human tumour cells. Copyright 2003 Wiley-Liss, Inc.

Reliable Detection of Herpes Simplex Virus Sequence Variation by High-Throughput Resequencing.

PubMed

Morse, Alison M; Calabro, Kaitlyn R; Fear, Justin M; Bloom, David C; McIntyre, Lauren M

2017-08-16

High-throughput sequencing (HTS) has resulted in data for a number of herpes simplex virus (HSV) laboratory strains and clinical isolates. The knowledge of these sequences has been critical for investigating viral pathogenicity. However, the assembly of complete herpesviral genomes, including HSV, is complicated due to the existence of large repeat regions and arrays of smaller reiterated sequences that are commonly found in these genomes. In addition, the inherent genetic variation in populations of isolates for viruses and other microorganisms presents an additional challenge to many existing HTS sequence assembly pipelines. Here, we evaluate two approaches for the identification of genetic variants in HSV1 strains using Illumina short read sequencing data. The first, a reference-based approach, identifies variants from reads aligned to a reference sequence and the second, a de novo assembly approach, identifies variants from reads aligned to de novo assembled consensus sequences. Of critical importance for both approaches is the reduction in the number of low complexity regions through the construction of a non-redundant reference genome. We compared variants identified in the two methods. Our results indicate that approximately 85% of variants are identified regardless of the approach. The reference-based approach to variant discovery captures an additional 15% representing variants divergent from the HSV1 reference possibly due to viral passage. Reference-based approaches are significantly less labor-intensive and identify variants across the genome where de novo assembly-based approaches are limited to regions where contigs have been successfully assembled. In addition, regions of poor quality assembly can lead to false variant identification in de novo consensus sequences. For viruses with a well-assembled reference genome, a reference-based approach is recommended.

Size effects in olivine control strength in low-temperature plasticity regime

NASA Astrophysics Data System (ADS)

Kumamoto, K. M.; Thom, C.; Wallis, D.; Hansen, L. N.; Armstrong, D. E. J.; Goldsby, D. L.; Warren, J. M.; Wilkinson, A. J.

2017-12-01

The strength of the lithospheric mantle during deformation by low-temperature plasticity controls a range of geological phenomena, including lithospheric-scale strain localization, the evolution of friction on deep seismogenic faults, and the flexure of tectonic plates. However, constraints on the strength of olivine in this deformation regime are difficult to obtain from conventional rock-deformation experiments, and previous results vary considerably. We demonstrate via nanoindentation that the strength of olivine in the low-temperature plasticity regime is dependent on the length-scale of the test, with experiments on smaller volumes of material exhibiting larger yield stresses. This "size effect" has previously been explained in engineering materials as a result of the role of strain gradients and associated geometrically necessary dislocations in modifying plastic behavior. The Hall-Petch effect, in which a material with a small grain size exhibits a higher strength than one with a large grain size, is thought to arise from the same mechanism. The presence of a size effect resolves discrepancies among previous experimental measurements of olivine, which were either conducted using indentation methods or were conducted on polycrystalline samples with small grain sizes. An analysis of different low-temperature plasticity flow laws extrapolated to room temperature reveals a power-law relationship between length-scale (grain size for polycrystalline deformation and contact radius for indentation tests) and yield strength. This suggests that data from samples with large inherent length scales best represent the plastic strength of the coarse-grained lithospheric mantle. Additionally, the plastic deformation of nanometer- to micrometer-sized asperities on fault surfaces may control the evolution of fault roughness due to their size-dependent strength.

A novel method for the synergistic remediation of oil-water mixtures using nanoparticles and oil-degrading bacteria.

PubMed

Alabresm, Amjed; Chen, Yung Pin; Decho, Alan W; Lead, Jamie

2018-07-15

Releases of crude oil and other types of oil from numerous sources can impose catastrophic physical, chemical, and biological effects on aquatic ecosystems. While currently-used oil removal techniques possess many advantages, they have inherent limitations, including low removal efficiencies and waste disposal challenges. The present study quantified the synergistic interactions of polyvinylpyrrolidone (PVP) coated magnetite nanoparticles (NP) and oil-degrading bacteria for enhanced oil removal at the laboratory scale. The results showed that at relatively high oil concentrations (375 mg L -1 ), NP alone could remove approximately 70% of lower-chain alkanes (C9-C22) and 65% of higher-chain (C23-C26), after only 1 h, when magnetic separation of NP was used. Removal efficiency did not increase significantly after that, which was likely due to saturation of the NP with oil. Microbial bioremediation, using strains of oil-degrading bacteria, removed almost zero oil immediately but 80-90% removal after 24-48 h. The combination of NPs and oil-degrading bacterial strains worked effectively to remove essentially 100% of oil within 48 h or less. This was likely due to the sorption of oil components to NPs and their subsequent utilization by bacteria as a joint Fe and C source, although the mechanisms of removal require further testing. Furthermore, results showed that the emission of selected volatile organic compounds (VOCs) and semi volatile organic compounds (SVOCs) were reduced after addition of NPs and bacteria separately. When combined, VOC and SVOC emissions were reduced by up to 80%. Copyright © 2018 Elsevier B.V. All rights reserved.

Normalized Rotational Multiple Yield Surface Framework (NRMYSF) stress-strain curve prediction method based on small strain triaxial test data on undisturbed Auckland residual clay soils

NASA Astrophysics Data System (ADS)

Noor, M. J. Md; Ibrahim, A.; Rahman, A. S. A.

2018-04-01

Small strain triaxial test measurement is considered to be significantly accurate compared to the external strain measurement using conventional method due to systematic errors normally associated with the test. Three submersible miniature linear variable differential transducer (LVDT) mounted on yokes which clamped directly onto the soil sample at equally 120° from the others. The device setup using 0.4 N resolution load cell and 16 bit AD converter was capable of consistently resolving displacement of less than 1µm and measuring axial strains ranging from less than 0.001% to 2.5%. Further analysis of small strain local measurement data was performed using new Normalized Multiple Yield Surface Framework (NRMYSF) method and compared with existing Rotational Multiple Yield Surface Framework (RMYSF) prediction method. The prediction of shear strength based on combined intrinsic curvilinear shear strength envelope using small strain triaxial test data confirmed the significant improvement and reliability of the measurement and analysis methods. Moreover, the NRMYSF method shows an excellent data prediction and significant improvement toward more reliable prediction of soil strength that can reduce the cost and time of experimental laboratory test.

Vectorial strain gauge method using single flexible orthogonal polydimethylsiloxane gratings

NASA Astrophysics Data System (ADS)

Guo, Hao; Tang, Jun; Qian, Kun; Tsoukalas, Dimitris; Zhao, Miaomiao; Yang, Jiangtao; Zhang, Binzhen; Chou, Xiujian; Liu, Jun; Xue, Chenyang; Zhang, Wendong

2016-03-01

A vectorial strain gauge method using a single sensing element is reported based on the double-sided polydimethylsiloxane (PDMS) Fraunhofer diffraction gratings structures. Using O2 plasma treatment steps, orthogonal wrinkled gratings were fabricated on both sides of a pre-strained PDMS film. Diffracted laser spots from this structure have been used to experimentally demonstrate, that any applied strain can be quantitatively characterized in both the x and y directions with an error of less than 0.6% and with a gauge factor of approximately 10. This simple and low cost technology which is completely different from the traditional vectorial strain gauge method, can be applied to surface vectorial strain measurement and multi-axis integrated mechanical sensors.

Dynamic strain distribution of FRP plate under blast loading

NASA Astrophysics Data System (ADS)

Saburi, T.; Yoshida, M.; Kubota, S.

2017-02-01

The dynamic strain distribution of a fiber re-enforced plastic (FRP) plate under blast loading was investigated using a Digital Image Correlation (DIC) image analysis method. The testing FRP plates were mounted in parallel to each other on a steel frame. 50 g of composition C4 explosive was used as a blast loading source and set in the center of the FRP plates. The dynamic behavior of the FRP plate under blast loading were observed by two high-speed video cameras. The set of two high-speed video image sequences were used to analyze the FRP three-dimensional strain distribution by means of DIC method. A point strain profile extracted from the analyzed strain distribution data was compared with a directly observed strain profile using a strain gauge and it was shown that the strain profile under the blast loading by DIC method is quantitatively accurate.

Method for hygromechanical characterization of graphite/epoxy composite

NASA Technical Reports Server (NTRS)

Yaniv, Gershon; Peimanidis, Gus; Daniel, Isaac M.

1987-01-01

An experimental method is described for measuring hygroscopic swelling strains and mechanical strains of moisture-conditioned composite specimens. The method consists of embedding encapsulated strain gages in the midplane of the composite laminate; thus it does not interfere with normal moisture diffusion. It is particularly suited for measuring moisture swelling coefficients and for mechanical testing of moisture-conditioned specimens at high strain rates. Results obtained by the embedded gage method were shown to be more reliable and reproducible than those obtained by surface gages, dial gages, or extensometers.

Inversion of the strain-life and strain-stress relationships for use in metal fatigue analysis

NASA Technical Reports Server (NTRS)

Manson, S. S.

1979-01-01

The paper presents closed-form solutions (collocation method and spline-function method) for the constants of the cyclic fatigue life equation so that they can be easily incorporated into cumulative damage analysis. The collocation method involves conformity with the experimental curve at specific life values. The spline-function method is such that the basic life relation is expressed as a two-part function, one applicable at strains above the transition strain (strain at intersection of elastic and plastic lines), the other below. An illustrative example is treated by both methods. It is shown that while the collocation representation has the advantage of simplicity of form, the spline-function representation can be made more accurate over a wider life range, and is simpler to use.

BIOMOLECULAR SENSING FOR BIOLOGICAL PROCESSES AND ENVIRONMENTAL MONITORING APPLICATIONS

EPA Science Inventory

Biomolecular recognition is being increasingly employed as the basis for a variety of analytical methods such as biosensors. he sensitivity, selectivity, and format versatility inherent in these methods may allow them to be adapted to solving a number of analytical problems. ltho...

Comparison of methods for in vitro testing of susceptibility of porcine Mycoplasma species to antimicrobial agents.

PubMed

Ter Laak, E A; Pijpers, A; Noordergraaf, J H; Schoevers, E C; Verheijden, J H

1991-02-01

The MICs of 18 antimicrobial agents used against strains of three porcine Mycoplasma species were determined by a serial broth dilution method. Twenty field strains of M. hyorhinis, ten field strains of M. hyopneumoniae, six field strains of M. flocculare, and the type strains of these species were tested. Twelve field strains and the type strain of M. hyorhinis were also tested by an agar dilution method. Tests were read at various time points. When the broth dilution method was used, the final MIC had to be read 2 days after color changes had stopped. MICs of tetracycline, oxytetracycline, doxycycline, and minocycline were low for the three Mycoplasma species tested. MICs of chlortetracycline were 8 to 16 times higher than MICs of the other tetracyclines. Spiramycin, tylosin, kitasamycin, spectinomycin, tiamulin, lincomycin, and clindamycin were effective against all strains of M. hyorhinis and M. hyopneumoniae. The quinolones were highly effective against M. hyopneumoniae but less effective against M. hyorhinis. The susceptibility patterns for M. hyopneumoniae and M. flocculare were similar.

Comparison of methods for in vitro testing of susceptibility of porcine Mycoplasma species to antimicrobial agents.

PubMed Central

Ter Laak, E A; Pijpers, A; Noordergraaf, J H; Schoevers, E C; Verheijden, J H

1991-01-01

The MICs of 18 antimicrobial agents used against strains of three porcine Mycoplasma species were determined by a serial broth dilution method. Twenty field strains of M. hyorhinis, ten field strains of M. hyopneumoniae, six field strains of M. flocculare, and the type strains of these species were tested. Twelve field strains and the type strain of M. hyorhinis were also tested by an agar dilution method. Tests were read at various time points. When the broth dilution method was used, the final MIC had to be read 2 days after color changes had stopped. MICs of tetracycline, oxytetracycline, doxycycline, and minocycline were low for the three Mycoplasma species tested. MICs of chlortetracycline were 8 to 16 times higher than MICs of the other tetracyclines. Spiramycin, tylosin, kitasamycin, spectinomycin, tiamulin, lincomycin, and clindamycin were effective against all strains of M. hyorhinis and M. hyopneumoniae. The quinolones were highly effective against M. hyopneumoniae but less effective against M. hyorhinis. The susceptibility patterns for M. hyopneumoniae and M. flocculare were similar. PMID:2024954

Effects of juvenile hormone analog formulations on development and reproduction in the bed bug Cimex lectularius (Hemiptera: Cimicidae).

PubMed

Goodman, Mark H; Potter, Michael F; Haynes, Kenneth F

2013-02-01

Bed bugs (Cimex lectularius L.) have become a common insect pest in urban areas and are often difficult to manage. Eradication is made more problematic by widespread insecticide resistance, raising interest in alternative control products. Juvenile hormone analogs (JHAs) such as methoprene and hydroprene are relatively harmless to non-arthropods and have proved to be effective against other urban insect pests. Two JHA products (Gentrol(®) and Precor(®), Central Life Sciences, Schaumburg, IL) were tested for efficacy against various bed bug stages as direct spray and as dry residue using three bed bug strains. At 1× and 2× the label rate, Precor(®) [active ingredient (S)-methoprene] had no significant effect on the development or fecundity of bed bugs. At 2× the label rate, confinement to residues of Gentrol(®) [active ingredient (S)-hydroprene] had no significant effect, but residues at 3× and 10× the label rate caused a reduction in fecundity and impaired development. Field strains were more susceptible to the reproductive effects of (S)-hydroprene than a long-maintained laboratory strain. While JHAs are attractive alternatives for pest management because of their inherent safety and distinct mode of action, these JHA formulations would have little impact on bed bug populations without relabeling to allow for higher application rates. Copyright © 2012 Society of Chemical Industry.

Strain-specific outcomes of repeated social defeat and chronic fluoxetine treatment in the mouse.

PubMed

Razzoli, Maria; Carboni, Lucia; Andreoli, Michela; Michielin, Francesca; Ballottari, Alice; Arban, Roberto

2011-01-01

Social stress is a risk factor for affective disorders in vulnerable individuals. Although the biological nature of stress susceptibility/resilience remains to be elucidated, genetic variation is considered amongst the principal contributors to brain disorders. Furthermore, genetic predisposition may be determinant for the therapeutic outcome, as proposed for antidepressant treatments. In the present studies we compared the inherently diverse genetic backgrounds of 2 mouse strains by assessing the efficacy of a chronic antidepressant treatment in a repeated social stress procedure. C57BL/6J and BalbC mice underwent 10-day social defeats followed by 28-day fluoxetine treatment (10 mg/kg/mL, p.o.). In C57BL/6J, most of the social defeat-induced changes were of metabolic nature including persistently altered feed efficiency and decreased abdominal fat stores that were ameliorated by fluoxetine. BalbC mouse behavior was persistently affected by social defeat both in the social avoidance and the forced swim tests, and in either procedure it was restored by chronic fluoxetine, whereas their endocrine parameters were mostly unaffected. The highlighted strain-specific responsivity to the metabolic and behavioral consequences of social defeat and to the chronic antidepressant treatment offers a promising research tool to further explore the underlying neural mechanisms and genetic basis of stress susceptibility and treatment response. Copyright © 2010 Elsevier Inc. All rights reserved.

The Analysis of Discourse as Evaluation of Productive Thinking.

ERIC Educational Resources Information Center

Tripp, D. H.

This paper provides a thorough description of a method of analyzing and scoring group discussions from a particular point of view. After discussing shortcomings of traditional methods of reporting data from group discussions and problems inherent in the use of paper-and-pencil creativity tests, the author describes a method which was developed as…

Interpreting Significant Discrete-Time Periods in Survival Analysis.

ERIC Educational Resources Information Center

Schumacker, Randall E.; Denson, Kathleen B.

Discrete-time survival analysis is a new method for educational researchers to employ when looking at the timing of certain educational events. Previous continuous-time methods do not allow for the flexibility inherent in a discrete-time method. Because both time-invariant and time-varying predictor variables can now be used, the interaction of…

Deep learning and texture-based semantic label fusion for brain tumor segmentation

NASA Astrophysics Data System (ADS)

Vidyaratne, L.; Alam, M.; Shboul, Z.; Iftekharuddin, K. M.

2018-02-01

Brain tumor segmentation is a fundamental step in surgical treatment and therapy. Many hand-crafted and learning based methods have been proposed for automatic brain tumor segmentation from MRI. Studies have shown that these approaches have their inherent advantages and limitations. This work proposes a semantic label fusion algorithm by combining two representative state-of-the-art segmentation algorithms: texture based hand-crafted, and deep learning based methods to obtain robust tumor segmentation. We evaluate the proposed method using publicly available BRATS 2017 brain tumor segmentation challenge dataset. The results show that the proposed method offers improved segmentation by alleviating inherent weaknesses: extensive false positives in texture based method, and the false tumor tissue classification problem in deep learning method, respectively. Furthermore, we investigate the effect of patient's gender on the segmentation performance using a subset of validation dataset. Note the substantial improvement in brain tumor segmentation performance proposed in this work has recently enabled us to secure the first place by our group in overall patient survival prediction task at the BRATS 2017 challenge.

Deep Learning and Texture-Based Semantic Label Fusion for Brain Tumor Segmentation.

PubMed

Vidyaratne, L; Alam, M; Shboul, Z; Iftekharuddin, K M

2018-01-01

Brain tumor segmentation is a fundamental step in surgical treatment and therapy. Many hand-crafted and learning based methods have been proposed for automatic brain tumor segmentation from MRI. Studies have shown that these approaches have their inherent advantages and limitations. This work proposes a semantic label fusion algorithm by combining two representative state-of-the-art segmentation algorithms: texture based hand-crafted, and deep learning based methods to obtain robust tumor segmentation. We evaluate the proposed method using publicly available BRATS 2017 brain tumor segmentation challenge dataset. The results show that the proposed method offers improved segmentation by alleviating inherent weaknesses: extensive false positives in texture based method, and the false tumor tissue classification problem in deep learning method, respectively. Furthermore, we investigate the effect of patient's gender on the segmentation performance using a subset of validation dataset. Note the substantial improvement in brain tumor segmentation performance proposed in this work has recently enabled us to secure the first place by our group in overall patient survival prediction task at the BRATS 2017 challenge.

Rapid label-free identification of Klebsiella pneumoniae antibiotic resistant strains by the drop-coating deposition surface-enhanced Raman scattering method

NASA Astrophysics Data System (ADS)

Cheong, Youjin; Kim, Young Jin; Kang, Heeyoon; Choi, Samjin; Lee, Hee Joo

2017-08-01

Although many methodologies have been developed to identify unknown bacteria, bacterial identification in clinical microbiology remains a complex and time-consuming procedure. To address this problem, we developed a label-free method for rapidly identifying clinically relevant multilocus sequencing typing-verified quinolone-resistant Klebsiella pneumoniae strains. We also applied the method to identify three strains from colony samples, ATCC70063 (control), ST11 and ST15; these are the prevalent quinolone-resistant K. pneumoniae strains in East Asia. The colonies were identified using a drop-coating deposition surface-enhanced Raman scattering (DCD-SERS) procedure coupled with a multivariate statistical method. Our workflow exhibited an enhancement factor of 11.3 × 106 to Raman intensities, high reproducibility (relative standard deviation of 7.4%), and a sensitive limit of detection (100 pM rhodamine 6G), with a correlation coefficient of 0.98. All quinolone-resistant K. pneumoniae strains showed similar spectral Raman shifts (high correlations) regardless of bacterial type, as well as different Raman vibrational modes compared to Escherichia coli strains. Our proposed DCD-SERS procedure coupled with the multivariate statistics-based identification method achieved excellent performance in discriminating similar microbes from one another and also in subtyping of K. pneumoniae strains. Therefore, our label-free DCD-SERS procedure coupled with the computational decision supporting method is a potentially useful method for the rapid identification of clinically relevant K. pneumoniae strains.

Validity test of the IPD-Work consortium approach for creating comparable job strain groups between Job Content Questionnaire and Demand-Control Questionnaire.

PubMed

Choi, Bongkyoo; Ko, Sangbaek; Ostergren, Per-Olof

2015-01-01

This study aims to test the validity of the IPD-Work Consortium approach for creating comparable job strain groups between the Job Content Questionnaire (JCQ) and the Demand-Control Questionnaire (DCQ). A random population sample (N = 682) of all middle-aged Malmö males and females was given a questionnaire with the 14-item JCQ and 11-item DCQ for the job control and job demands. The JCQ job control and job demands scores were calculated in 3 different ways: using the 14-item JCQ standard scale formulas (method 1); dropping 3 job control items and using the 11-item JCQ standard scale formulas with additional scale weights (method 2); and the approach of the IPD Group (method 3), dropping 3 job control items, but using the simple 11-item summation-based scale formulas. The high job strain was defined as a combination of high demands and low control. Between the 2 questionnaires, false negatives for the high job strain were much greater than false positives (37-49% vs. 7-13%). When the method 3 was applied, the sensitivity of the JCQ for the high job strain against the DCQ was lowest (0.51 vs. 0.60-0.63 when the methods 1 and 2 were applied), although the specificity was highest (0.93 vs. 0.87-0.89 when the methods 1 and 2 were applied). The prevalence of the high job strain with the JCQ (the method 3 was applied) was considerably lower (4-7%) than with the JCQ (the methods 1 and 2 were applied) and the DCQ. The number of congruent cases for the high job strain between the 2 questionnaires was smallest when the method 3 was applied. The IPD-Work Consortium approach showed 2 major weaknesses to be used for epidemiological studies on the high job strain and health outcomes as compared to the standard JCQ methods: the greater misclassification of the high job strain and lower prevalence of the high job strain. This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.

Probabilistic structural mechanics research for parallel processing computers

NASA Technical Reports Server (NTRS)

Sues, Robert H.; Chen, Heh-Chyun; Twisdale, Lawrence A.; Martin, William R.

1991-01-01

Aerospace structures and spacecraft are a complex assemblage of structural components that are subjected to a variety of complex, cyclic, and transient loading conditions. Significant modeling uncertainties are present in these structures, in addition to the inherent randomness of material properties and loads. To properly account for these uncertainties in evaluating and assessing the reliability of these components and structures, probabilistic structural mechanics (PSM) procedures must be used. Much research has focused on basic theory development and the development of approximate analytic solution methods in random vibrations and structural reliability. Practical application of PSM methods was hampered by their computationally intense nature. Solution of PSM problems requires repeated analyses of structures that are often large, and exhibit nonlinear and/or dynamic response behavior. These methods are all inherently parallel and ideally suited to implementation on parallel processing computers. New hardware architectures and innovative control software and solution methodologies are needed to make solution of large scale PSM problems practical.

Topical Review: Unique Contributions of Magnetic Resonance Imaging to Pediatric Psychology Research

PubMed Central

Duraccio, Kara M.; Carbine, Kaylie M.; Kirwan, C. Brock

2016-01-01

Objective This review aims to provide a brief introduction of the utility of magnetic resonance imaging (MRI) methods in pediatric psychology research, describe several exemplar studies that highlight the unique benefits of MRI techniques for pediatric psychology research, and detail methods for addressing several challenges inherent to pediatric MRI research. Methods Literature review. Results Numerous useful applications of MRI research in pediatric psychology have been illustrated in published research. MRI methods yield information that cannot be obtained using neuropsychological or behavioral measures. Conclusions Using MRI in pediatric psychology research may facilitate examination of neural structures and processes that underlie health behaviors. Challenges inherent to conducting MRI research with pediatric research participants (e.g., head movement) may be addressed using evidence-based strategies. We encourage pediatric psychology researchers to consider adopting MRI techniques to answer research questions relevant to pediatric health and illness. PMID:26141118

Factors affecting finite strain estimation in low-grade, low-strain clastic rocks

NASA Astrophysics Data System (ADS)

Pastor-Galán, Daniel; Gutiérrez-Alonso, Gabriel; Meere, Patrick A.; Mulchrone, Kieran F.

2009-12-01

The computer strain analysis methods SAPE, MRL and DTNNM have permitted the characterization of finite strain in two different regions with contrasting geodynamic scenarios; (1) the Talas Ala Tau (Tien Shan, Kyrgyzs Republic) and (2) the Somiedo Nappe and Narcea Antiform (Cantabrian to West Asturian-Leonese Zone boundary, Variscan Belt, NW of Iberia). The performed analyses have revealed low-strain values and the regional strain trend in both studied areas. This study also investigates the relationship between lithology (grain size and percentage of matrix) and strain estimates the two methodologies used. The results show that these methods are comparable and the absence of significant finite strain lithological control in rocks deformed under low metamorphic and low-strain conditions.

Efficiency of PCR-based methods in discriminating Bifidobacterium longum ssp. longum and Bifidobacterium longum ssp. infantis strains of human origin.

PubMed

Srůtková, Dagmar; Spanova, Alena; Spano, Miroslav; Dráb, Vladimír; Schwarzer, Martin; Kozaková, Hana; Rittich, Bohuslav

2011-10-01

Bifidobacterium longum is considered to play an important role in health maintenance of the human gastrointestinal tract. Probiotic properties of bifidobacterial isolates are strictly strain-dependent and reliable methods for the identification and discrimination of this species at both subspecies and strain levels are thus required. Differentiation between B. longum ssp. longum and B. longum ssp. infantis is difficult due to high genomic similarities. In this study, four molecular-biological methods (species- and subspecies-specific PCRs, random amplified polymorphic DNA (RAPD) method using 5 primers, repetitive sequence-based (rep)-PCR with BOXA1R and (GTG)(5) primers and amplified ribosomal DNA restriction analysis (ARDRA)) and biochemical analysis, were compared for the classification of 30 B. longum strains (28 isolates and 2 collection strains) on subspecies level. Strains originally isolated from the faeces of breast-fed healthy infants (25) and healthy adults (3) showed a high degree of genetic homogeneity by PCR with subspecies-specific primers and rep-PCR. When analysed by RAPD, the strains formed many separate clusters without any potential for subspecies discrimination. These methods together with arabionose/melezitose fermentation analysis clearly differentiated only the collection strains into B. longum ssp. longum and B. longum ssp. infantis at the subspecies level. On the other hand, ARDRA analysis differentiated the strains into the B. longum/infantis subspecies using the cleavage analysis of genus-specific amplicon with just one enzyme, Sau3AI. According to our results the majority of the strains belong to the B. longum ssp. infantis (75%). Therefore we suggest ARDRA using Sau3AI restriction enzyme as the first method of choice for distinguishing between B. longum ssp. longum and B. longum ssp. infantis. Copyright © 2011 Elsevier B.V. All rights reserved.

Predictions and Experimental Microstructural Characterization of High Strain Rate Failure Modes in Layered Aluminum Composites

NASA Astrophysics Data System (ADS)

Khanikar, Prasenjit

Different aluminum alloys can be combined, as composites, for tailored dynamic applications. Most investigations pertaining to metallic alloy layered composites, however, have been based on quasi-static approaches. The dynamic failure of layered metallic composites, therefore, needs to be characterized in terms of strength, toughness, and fracture response. A dislocation-density based crystalline plasticity formulation, finite-element techniques, rational crystallographic orientation relations and a new fracture methodology were used to predict the failure modes associated with the high strain rate behavior of aluminum layered composites. Two alloy layers, a high strength alloy, aluminum 2195, and an aluminum alloy 2139, with high toughness, were modeled with representative microstructures that included precipitates, dispersed particles, and different grain boundary (GB) distributions. The new fracture methodology, based on an overlap method and phantom nodes, is used with a fracture criteria specialized for fracture on different cleavage planes. One of the objectives of this investigation, therefore, was to determine the optimal arrangements of the 2139 and 2195 aluminum alloys for a metallic layered composite that would combine strength, toughness and fracture resistance for high strain-rate applications. Different layer arrangements were investigated for high strain-rate applications, and the optimal arrangement was with the high toughness 2139 layer on the bottom, which provided extensive shear strain localization, and the high strength 2195 layer on the top for high strength resistance. The layer thickness of the bottom high toughness layer also affected the bending behavior of the roll-boned interface and the potential delamination of the layers. Shear strain localization, dynamic cracking and delamination were the mutually competing failure mechanisms for the layered metallic composite, and control of these failure modes can be optimized for high strain-rate applications. The second major objective of this investigation was the use of recently developed dynamic fracture formulations to model and analyze the crack nucleation and propagation of aluminum layered composites subjected to high strain rate loading conditions and how microstructural effects, such as precipitates, dispersed particles, and GB orientations affect failure evolution. This dynamic fracture approach is used to investigate crack nucleation and crack growth as a function of the different microstructural characteristics of each alloy in layered composites with and without pre-existing cracks. The zigzag nature of the crack paths were mainly due to the microstructural features, such as precipitates and dispersed particles distributions and orientations ahead of the crack front, and it underscored the capabilities of the fracture methodology. The evolution of dislocation density and the formation of localized shear slip contributed to the blunting of the propagating crack. Extensive geometrical and thermal softening due to the localized plastic slip also affected crack path orientations and directions. These softening mechanisms resulted in the switching of cleavage planes, which affected crack path orientations. Interface delamination can also have an important role in the failure and toughening of the layered composites. Different scenarios of delamination were investigated, such as planar crack growth and crack penetration into the layers. The presence of brittle surface oxide platelets in the interface region also significantly influenced the interface delamination process. Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Optical Microscopy (OM) characterization provided further physical insights and validation of the predictive capabilities. The inherent microstructural features of each alloy play a significant role in the dynamic fracture, shear strain localization, and interface delamination of the layered metallic composite. These microstructural features, such as precipitates, dispersed particles, and GB orientations and distributions can be optimized for desired behavior of metallic composites.

Performance Analysis and Experimental Validation of the Direct Strain Imaging Method

Treesearch

Athanasios Iliopoulos; John G. Michopoulos; John C. Hermanson

2013-01-01

Direct Strain Imaging accomplishes full field measurement of the strain tensor on the surface of a deforming body, by utilizing arbitrarily oriented engineering strain measurements originating from digital imaging. In this paper an evaluation of the method’s performance with respect to its operating parameter space is presented along with a preliminary...

APPLICATION OF A FINITE-DIFFERENCE TECHNIQUE TO THE HUMAN RADIOFREQUENCY DOSIMETRY PROBLEM

EPA Science Inventory

A powerful finite difference numerical technique has been applied to the human radiofrequency dosimetry problem. The method possesses inherent advantages over the method of moments approach in that its implementation requires much less computer memory. Consequently, it has the ca...

High-speed engine/component performance assessment using exergy and thrust-based methods

NASA Technical Reports Server (NTRS)

Riggins, D. W.

1996-01-01

This investigation summarizes a comparative study of two high-speed engine performance assessment techniques based on energy (available work) and thrust-potential (thrust availability). Simple flow-fields utilizing Rayleigh heat addition and one-dimensional flow with friction are used to demonstrate the fundamental inability of conventional energy techniques to predict engine component performance, aid in component design, or accurately assess flow losses. The use of the thrust-based method on these same examples demonstrates its ability to yield useful information in all these categories. Energy and thrust are related and discussed from the stand-point of their fundamental thermodynamic and fluid dynamic definitions in order to explain the differences in information obtained using the two methods. The conventional definition of energy is shown to include work which is inherently unavailable to an aerospace Brayton engine. An engine-based energy is then developed which accurately accounts for this inherently unavailable work; performance parameters based on this quantity are then shown to yield design and loss information equivalent to the thrust-based method.

Fault Detection for Nonlinear Process With Deterministic Disturbances: A Just-In-Time Learning Based Data Driven Method.

PubMed

Yin, Shen; Gao, Huijun; Qiu, Jianbin; Kaynak, Okyay

2017-11-01

Data-driven fault detection plays an important role in industrial systems due to its applicability in case of unknown physical models. In fault detection, disturbances must be taken into account as an inherent characteristic of processes. Nevertheless, fault detection for nonlinear processes with deterministic disturbances still receive little attention, especially in data-driven field. To solve this problem, a just-in-time learning-based data-driven (JITL-DD) fault detection method for nonlinear processes with deterministic disturbances is proposed in this paper. JITL-DD employs JITL scheme for process description with local model structures to cope with processes dynamics and nonlinearity. The proposed method provides a data-driven fault detection solution for nonlinear processes with deterministic disturbances, and owns inherent online adaptation and high accuracy of fault detection. Two nonlinear systems, i.e., a numerical example and a sewage treatment process benchmark, are employed to show the effectiveness of the proposed method.

Effects of forcefield and sampling method in all-atom simulations of inherently disordered proteins: Application to conformational preferences of human amylin

PubMed Central

Peng, Enxi; Todorova, Nevena

2017-01-01

Although several computational modelling studies have investigated the conformational behaviour of inherently disordered protein (IDP) amylin, discrepancies in identifying its preferred solution conformations still exist between various forcefields and sampling methods used. Human islet amyloid polypeptide has long been a subject of research, both experimentally and theoretically, as the aggregation of this protein is believed to be the lead cause of type-II diabetes. In this work, we present a systematic forcefield assessment using one of the most advanced non-biased sampling techniques, Replica Exchange with Solute Tempering (REST2), by comparing the secondary structure preferences of monomeric amylin in solution. This study also aims to determine the ability of common forcefields to sample a transition of the protein from a helical membrane bound conformation into the disordered solution state of amylin. Our results demonstrated that the CHARMM22* forcefield showed the best ability to sample multiple conformational states inherent for amylin. It is revealed that REST2 yielded results qualitatively consistent with experiments and in quantitative agreement with other sampling methods, however far more computationally efficiently and without any bias. Therefore, combining an unbiased sampling technique such as REST2 with a vigorous forcefield testing could be suggested as an important step in developing an efficient and robust strategy for simulating IDPs. PMID:29023509

Effects of forcefield and sampling method in all-atom simulations of inherently disordered proteins: Application to conformational preferences of human amylin.

PubMed

Peng, Enxi; Todorova, Nevena; Yarovsky, Irene

2017-01-01

Although several computational modelling studies have investigated the conformational behaviour of inherently disordered protein (IDP) amylin, discrepancies in identifying its preferred solution conformations still exist between various forcefields and sampling methods used. Human islet amyloid polypeptide has long been a subject of research, both experimentally and theoretically, as the aggregation of this protein is believed to be the lead cause of type-II diabetes. In this work, we present a systematic forcefield assessment using one of the most advanced non-biased sampling techniques, Replica Exchange with Solute Tempering (REST2), by comparing the secondary structure preferences of monomeric amylin in solution. This study also aims to determine the ability of common forcefields to sample a transition of the protein from a helical membrane bound conformation into the disordered solution state of amylin. Our results demonstrated that the CHARMM22* forcefield showed the best ability to sample multiple conformational states inherent for amylin. It is revealed that REST2 yielded results qualitatively consistent with experiments and in quantitative agreement with other sampling methods, however far more computationally efficiently and without any bias. Therefore, combining an unbiased sampling technique such as REST2 with a vigorous forcefield testing could be suggested as an important step in developing an efficient and robust strategy for simulating IDPs.

Method for analyzing microbial communities

DOEpatents

Zhou, Jizhong [Oak Ridge, TN; Wu, Liyou [Oak Ridge, TN

2010-07-20

The present invention provides a method for quantitatively analyzing microbial genes, species, or strains in a sample that contains at least two species or strains of microorganisms. The method involves using an isothermal DNA polymerase to randomly and representatively amplify genomic DNA of the microorganisms in the sample, hybridizing the resultant polynucleotide amplification product to a polynucleotide microarray that can differentiate different genes, species, or strains of microorganisms of interest, and measuring hybridization signals on the microarray to quantify the genes, species, or strains of interest.

FY17 Status Report on the Initial EPP Finite Element Analysis of Grade 91 Steel

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

Messner, M. C.; Sham, T. -L.

This report describes a modification to the elastic-perfectly plastic (EPP) strain limits design method to account for cyclic softening in Gr. 91 steel. The report demonstrates that the unmodified EPP strain limits method described in current ASME code case is not conservative for materials with substantial cyclic softening behavior like Gr. 91 steel. However, the EPP strain limits method can be modified to be conservative for softening materials by using softened isochronous stress-strain curves in place of the standard curves developed from unsoftened creep experiments. The report provides softened curves derived from inelastic material simulations and factors describing the transformationmore » of unsoftened curves to a softened state. Furthermore, the report outlines a method for deriving these factors directly from creep/fatigue tests. If the material softening saturates the proposed EPP strain limits method can be further simplified, providing a methodology based on temperature-dependent softening factors that could be implemented in an ASME code case allowing the use of the EPP strain limits method with Gr. 91. Finally, the report demonstrates the conservatism of the modified method when applied to inelastic simulation results and two bar experiments.« less

Design of biobased and biodegradable - compostable engineered plastics based on poly(lactide)

NASA Astrophysics Data System (ADS)

Schneider, Jeffrey Samuelson

Poly(lactide) (PLA) is a biobased and biodegradable - compostable plastic that is derived from renewable resources such as corn and sugar cane. It possesses excellent strength and stiffness properties and is recognized as safe for biomedical and food packaging applications. Commercially, it costs $1/lb and is now competitive with petroleum based polymers that have dominated the industry for decades. However, the material has some inherently weak properties that prevent it from certain applications - most notably, its rheological properties, brittleness, and poor high temperature performance. Cost effective modifications of the polymer to enhance these deficiencies could allow for increased applications and further its commercial growth. Multiple synthetic strategies have been developed to address PLA's performance property deficiencies. PLA typically exhibits poor melt strength and does not have the ability to strain harden, partially a result of its highly linear nature. Strain hardening and high melt strength are crucial elements of a material when producing blown films, a large untapped market for PLA. By increasing molecular weight and introducing long-chain branching into the material, these properties can be improved. Epoxy-functionalized PLA (EF-PLA) was synthesized by reacting PLA with a multifunctional epoxy polymer (MEP) using reactive extrusion processing (REX). These modified PLA polymers can function as a rheology modifier for PLA and a compatibilizer for blends with other biopolyesters. The modified PLA showed an increased melt strength and exhibited significant strain hardening, thus making it more suited for blown film applications. Blown films comprised of PLA and poly(butylene adipate-co-terephthalate) (PBAT) were produced using EF-PLA as a reactive modifier for rheological enhancement and compatibilization. This resulted in films with better processability (as seen by increased bubble stability) and improved mechanical properties, compared to a common rheology modifier used in industry. These modifiers have been successfully scaled up to a 400 kg/hr process and are currently used to make high quality biodegradable blown films for multiple commercial applications. PLA is an extremely brittle material, typically experiencing only 3-4% elongation prior to fracture. This hinders some of its applications and therefore toughening is needed for future commercial growth. Two different methods of modifying PLA with polysiloxanes are studied and discussed. Polysiloxanes serve as a highly attractive material for toughening PLA due to their inherent properties. Because of the longer bond and higher bond angle of the -Si-O-Si- (siloxane) backbone compared to a carbon based backbone, there is a reduced energy barrier for rotation leading to substantial flexibility. Polysiloxanes also possess good thermal and oxidative stability, biocompatibility, and very low surface tension values, all which could benefit PLA greatly. Lastly, most injection molded PLA products lose their rigidity above Tg (˜55°C) due to a rubbery amorphous phase and low crystallinity. This prevents products like PLA cutlery from being used effectively at elevated temperatures, like those of hot foods. The high temperature mechanical properties of injection molded PLA are enhanced using a combination of nucleating agents and processing improvements to impart high levels of crystallinity, resulting in a substantial increase in the mechanical performance at these temperatures.

A new analytical method for estimating lumped parameter constants of linear viscoelastic models from strain rate tests

NASA Astrophysics Data System (ADS)

Mattei, G.; Ahluwalia, A.

2018-04-01

We introduce a new function, the apparent elastic modulus strain-rate spectrum, E_{app} ( \\dot{ɛ} ), for the derivation of lumped parameter constants for Generalized Maxwell (GM) linear viscoelastic models from stress-strain data obtained at various compressive strain rates ( \\dot{ɛ}). The E_{app} ( \\dot{ɛ} ) function was derived using the tangent modulus function obtained from the GM model stress-strain response to a constant \\dot{ɛ} input. Material viscoelastic parameters can be rapidly derived by fitting experimental E_{app} data obtained at different strain rates to the E_{app} ( \\dot{ɛ} ) function. This single-curve fitting returns similar viscoelastic constants as the original epsilon dot method based on a multi-curve global fitting procedure with shared parameters. Its low computational cost permits quick and robust identification of viscoelastic constants even when a large number of strain rates or replicates per strain rate are considered. This method is particularly suited for the analysis of bulk compression and nano-indentation data of soft (bio)materials.

Study on Finite Element Model Updating in Highway Bridge Static Loading Test Using Spatially-Distributed Optical Fiber Sensors

PubMed Central

Wu, Bitao; Lu, Huaxi; Chen, Bo; Gao, Zhicheng

2017-01-01

A finite model updating method that combines dynamic-static long-gauge strain responses is proposed for highway bridge static loading tests. For this method, the objective function consisting of static long-gauge stains and the first order modal macro-strain parameter (frequency) is established, wherein the local bending stiffness, density and boundary conditions of the structures are selected as the design variables. The relationship between the macro-strain and local element stiffness was studied first. It is revealed that the macro-strain is inversely proportional to the local stiffness covered by the long-gauge strain sensor. This corresponding relation is important for the modification of the local stiffness based on the macro-strain. The local and global parameters can be simultaneously updated. Then, a series of numerical simulation and experiments were conducted to verify the effectiveness of the proposed method. The results show that the static deformation, macro-strain and macro-strain modal can be predicted well by using the proposed updating model. PMID:28753912

Study on Finite Element Model Updating in Highway Bridge Static Loading Test Using Spatially-Distributed Optical Fiber Sensors.

PubMed

Wu, Bitao; Lu, Huaxi; Chen, Bo; Gao, Zhicheng

2017-07-19

A finite model updating method that combines dynamic-static long-gauge strain responses is proposed for highway bridge static loading tests. For this method, the objective function consisting of static long-gauge stains and the first order modal macro-strain parameter (frequency) is established, wherein the local bending stiffness, density and boundary conditions of the structures are selected as the design variables. The relationship between the macro-strain and local element stiffness was studied first. It is revealed that the macro-strain is inversely proportional to the local stiffness covered by the long-gauge strain sensor. This corresponding relation is important for the modification of the local stiffness based on the macro-strain. The local and global parameters can be simultaneously updated. Then, a series of numerical simulation and experiments were conducted to verify the effectiveness of the proposed method. The results show that the static deformation, macro-strain and macro-strain modal can be predicted well by using the proposed updating model.

Strain intensity factor approach for predicting the strength of continuously reinforced metal matrix composites

NASA Technical Reports Server (NTRS)

Poe, Clarence C., Jr.

1989-01-01

A method was previously developed to predict the fracture toughness (stress intensity factor at failure) of composites in terms of the elastic constants and the tensile failing strain of the fibers. The method was applied to boron/aluminum composites made with various proportions of 0 deg and +/- 45 deg plies. Predicted values of fracture toughness were in gross error because widespread yielding of the aluminum matrix made the compliance very nonlinear. An alternate method was develolped to predict the strain intensity factor at failure rather than the stress intensity factor because the singular strain field was not affected by yielding as much as the stress field. Far-field strains at failure were calculated from the strain intensity factor, and then strengths were calculated from the far-field strains using uniaxial stress-strain curves. The predicted strengths were in good agreement with experimental values, even for the very nonlinear laminates that contained only +/- 45 deg plies. This approach should be valid for other metal matrix composites that have continuous fibers.

Development of a Trypanosoma cruzi strain typing assay using MS2 peptide spectral libraries (Tc-STAMS2)

PubMed Central

de Oliveira, Gilberto Santos; Kawahara, Rebeca; Rosa-Fernandes, Livia; Avila, Carla Cristi; Teixeira, Marta M. G.; Larsen, Martin R.

2018-01-01

Background Chagas disease also known as American trypanosomiasis is caused by the protozoan Trypanosoma cruzi. Over the last 30 years, Chagas disease has expanded from a neglected parasitic infection of the rural population to an urbanized chronic disease, becoming a potentially emergent global health problem. T. cruzi strains were assigned to seven genetic groups (TcI-TcVI and TcBat), named discrete typing units (DTUs), which represent a set of isolates that differ in virulence, pathogenicity and immunological features. Indeed, diverse clinical manifestations (from asymptomatic to highly severe disease) have been attempted to be related to T.cruzi genetic variability. Due to that, several DTU typing methods have been introduced. Each method has its own advantages and drawbacks such as high complexity and analysis time and all of them are based on genetic signatures. Recently, a novel method discriminated bacterial strains using a peptide identification-free, genome sequence-independent shotgun proteomics workflow. Here, we aimed to develop a Trypanosoma cruzi Strain Typing Assay using MS/MS peptide spectral libraries, named Tc-STAMS2. Methods/Principal findings The Tc-STAMS2 method uses shotgun proteomics combined with spectral library search to assign and discriminate T. cruzi strains independently on the genome knowledge. The method is based on the construction of a library of MS/MS peptide spectra built using genotyped T. cruzi reference strains. For identification, the MS/MS peptide spectra of unknown T. cruzi cells are identified using the spectral matching algorithm SpectraST. The Tc-STAMS2 method allowed correct identification of all DTUs with high confidence. The method was robust towards different sample preparations, length of chromatographic gradients and fragmentation techniques. Moreover, a pilot inter-laboratory study showed the applicability to different MS platforms. Conclusions and significance This is the first study that develops a MS-based platform for T. cruzi strain typing. Indeed, the Tc-STAMS2 method allows T. cruzi strain typing using MS/MS spectra as discriminatory features and allows the differentiation of TcI-TcVI DTUs. Similar to genomic-based strategies, the Tc-STAMS2 method allows identification of strains within DTUs. Its robustness towards different experimental and biological variables makes it a valuable complementary strategy to the current T. cruzi genotyping assays. Moreover, this method can be used to identify DTU-specific features correlated with the strain phenotype. PMID:29608573

INFLUENCE OF EXPOSURE ASSESSMENT METHOD IN AN EPIDEMIOLOGIC STUDY OF TRIHALOMETHANE EXPOSURE AND SPONTANEOUS ABORTION

EPA Science Inventory

Trihalomethanes are common contaminants of chlorinated drinking water. Studies of their health effects have been hampered by exposure misclassification, due in part to limitations inherent in using utility sampling records. We used two exposure assessment methods, one based on ut...

Human Movement Potential: Its Ideokinetic Facilitation.

ERIC Educational Resources Information Center

Sweigard, Lulu E.

This book focuses on the interdependence of postural alignment and the performance of movement. It provides an educational method (ideokinesis), which stresses the inherent capacity of the nervous system to determine the most efficient neuromuscular coordination for each movement. This method of teaching body balance and efficient movement has…

Phylogenetic Analysis of Shewanella Strains by DNA Relatedness Derived from Whole Genome Microarray DNA-DNA Hybridization and Comparison with Other Methods

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

Wu, Liyou; Yi, T. Y.; Van Nostrand, Joy

Phylogenetic analyses were done for the Shewanella strains isolated from Baltic Sea (38 strains), US DOE Hanford Uranium bioremediation site [Hanford Reach of the Columbia River (HRCR), 11 strains], Pacific Ocean and Hawaiian sediments (8 strains), and strains from other resources (16 strains) with three out group strains, Rhodopseudomonas palustris, Clostridium cellulolyticum, and Thermoanaerobacter ethanolicus X514, using DNA relatedness derived from WCGA-based DNA-DNA hybridizations, sequence similarities of 16S rRNA gene and gyrB gene, and sequence similarities of 6 loci of Shewanella genome selected from a shared gene list of the Shewanella strains with whole genome sequenced based on the averagemore » nucleotide identity of them (ANI). The phylogenetic trees based on 16S rRNA and gyrB gene sequences, and DNA relatedness derived from WCGA hybridizations of the tested Shewanella strains share exactly the same sub-clusters with very few exceptions, in which the strains were basically grouped by species. However, the phylogenetic analysis based on DNA relatedness derived from WCGA hybridizations dramatically increased the differentiation resolution at species and strains level within Shewanella genus. When the tree based on DNA relatedness derived from WCGA hybridizations was compared to the tree based on the combined sequences of the selected functional genes (6 loci), we found that the resolutions of both methods are similar, but the clustering of the tree based on DNA relatedness derived from WMGA hybridizations was clearer. These results indicate that WCGA-based DNA-DNA hybridization is an idea alternative of conventional DNA-DNA hybridization methods and it is superior to the phylogenetics methods based on sequence similarities of single genes. Detailed analysis is being performed for the re-classification of the strains examined.« less

Novel image analysis methods for quantification of in situ 3-D tendon cell and matrix strain.

PubMed

Fung, Ashley K; Paredes, J J; Andarawis-Puri, Nelly

2018-01-23

Macroscopic tendon loads modulate the cellular microenvironment leading to biological outcomes such as degeneration or repair. Previous studies have shown that damage accumulation and the phases of tendon healing are marked by significant changes in the extracellular matrix, but it remains unknown how mechanical forces of the extracellular matrix are translated to mechanotransduction pathways that ultimately drive the biological response. Our overarching hypothesis is that the unique relationship between extracellular matrix strain and cell deformation will dictate biological outcomes, prompting the need for quantitative methods to characterize the local strain environment. While 2-D methods have successfully calculated matrix strain and cell deformation, 3-D methods are necessary to capture the increased complexity that can arise due to high levels of anisotropy and out-of-plane motion, particularly in the disorganized, highly cellular, injured state. In this study, we validated the use of digital volume correlation methods to quantify 3-D matrix strain using images of naïve tendon cells, the collagen fiber matrix, and injured tendon cells. Additionally, naïve tendon cell images were used to develop novel methods for 3-D cell deformation and 3-D cell-matrix strain, which is defined as a quantitative measure of the relationship between matrix strain and cell deformation. The results support that these methods can be used to detect strains with high accuracy and can be further extended to an in vivo setting for observing temporal changes in cell and matrix mechanics during degeneration and healing. Copyright © 2017. Published by Elsevier Ltd.

Myocardial strains from 3D displacement encoded magnetic resonance imaging

PubMed Central

2012-01-01

Background The ability to measure and quantify myocardial motion and deformation provides a useful tool to assist in the diagnosis, prognosis and management of heart disease. The recent development of magnetic resonance imaging methods, such as harmonic phase analysis of tagging and displacement encoding with stimulated echoes (DENSE), make detailed non-invasive 3D kinematic analyses of human myocardium possible in the clinic and for research purposes. A robust analysis method is required, however. Methods We propose to estimate strain using a polynomial function which produces local models of the displacement field obtained with DENSE. Given a specific polynomial order, the model is obtained as the least squares fit of the acquired displacement field. These local models are subsequently used to produce estimates of the full strain tensor. Results The proposed method is evaluated on a numerical phantom as well as in vivo on a healthy human heart. The evaluation showed that the proposed method produced accurate results and showed low sensitivity to noise in the numerical phantom. The method was also demonstrated in vivo by assessment of the full strain tensor and to resolve transmural strain variations. Conclusions Strain estimation within a 3D myocardial volume based on polynomial functions yields accurate and robust results when validated on an analytical model. The polynomial field is capable of resolving the measured material positions from the in vivo data, and the obtained in vivo strains values agree with previously reported myocardial strains in normal human hearts. PMID:22533791

Section Height Determination Methods of the Isotopographic Surface in a Complex Terrain Relief

ERIC Educational Resources Information Center

Syzdykova, Guldana D.; Kurmankozhaev, Azimhan K.

2016-01-01

A new method for determining the vertical interval of isotopographic surfaces on rugged terrain was developed. The method is based on the concept of determining the differentiated size of the vertical interval using spatial-statistical properties inherent in the modal characteristic, the degree of variability of apical heights and the chosen map…

Nano-fabricated superconducting radio-frequency composites, method for producing nano-fabricated superconducting rf composites

DOEpatents

Norem, James H.; Pellin, Michael J.

2013-06-11

Superconducting rf is limited by a wide range of failure mechanisms inherent in the typical manufacture methods. This invention provides a method for fabricating superconducting rf structures comprising coating the structures with single atomic-layer thick films of alternating chemical composition. Also provided is a cavity defining the invented laminate structure.

Grounded Theory in Practice: Is It Inherently a Mixed Method?

ERIC Educational Resources Information Center

Johnson, R. B.; McGowan, M. W.; Turner, L. A.

2010-01-01

We address 2 key points of contention in this article. First, we engage the debate concerning whether particular methods are necessarily linked to particular research paradigms. Second, we briefly describe a mixed methods version of grounded theory (MM-GT). Grounded theory can be tailored to work well in any of the 3 major forms of mixed methods…

Teacher stress research: problems and progress.

PubMed

Pithers, R T

1995-12-01

There is a reasonably large body of published research evidence available which indicates that teaching is a 'highly' or 'extremely highly' stressful occupation for up to one-third of its professionals. Generalisations such as this one, however, are wrought with problems. These problems, for instance, range from confusion about the definition of stress through to how it is to be measured. They include methodological problems inherent in some of the research used to examine the area of teacher stress and as well include, for example, confusion about the effect of mediating variables in the production of stress and strain. This paper examines some of the more important pervasive research problems in current research on teacher stress and makes some suggestions for research progress.

Antibody immunoprophylaxis and immunotherapy for influenza virus infection: Utilization of monoclonal or polyclonal antibodies?

PubMed

Berry, Cassandra M

2018-03-04

Control programs for emerging influenza are in urgent need of novel therapeutic strategies to mitigate potentially devastating threats from pathogenic strains with pandemic potential. Current vaccines and antivirals have inherent limitations in efficacy, especially with rapid evolutionary changes of influenza viruses. Antibody-based antiviral protection harnesses the natural power of the immune system. Antibodies present prophylactic and therapeutic intervention options for prevention and control of influenza, especially for at-risk populations. Specific monoclonal antibodies are well defined in purity and initial efficacy but polyclonal antibodies are easier to scale-up and cost-effective with long-term efficacy, using batches with broadly neutralizing properties against influenza variants. This review presents the pros and cons of monoclonal versus polyclonal antibody therapy for influenza.

Simulation and Analysis of Converging Shock Wave Test Problems

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

Ramsey, Scott D.; Shashkov, Mikhail J.

2012-06-21

Results and analysis pertaining to the simulation of the Guderley converging shock wave test problem (and associated code verification hydrodynamics test problems involving converging shock waves) in the LANL ASC radiation-hydrodynamics code xRAGE are presented. One-dimensional (1D) spherical and two-dimensional (2D) axi-symmetric geometric setups are utilized and evaluated in this study, as is an instantiation of the xRAGE adaptive mesh refinement capability. For the 2D simulations, a 'Surrogate Guderley' test problem is developed and used to obviate subtleties inherent to the true Guderley solution's initialization on a square grid, while still maintaining a high degree of fidelity to the originalmore » problem, and minimally straining the general credibility of associated analysis and conclusions.« less

Giant self-biased magnetoelectric coupling in co-fired textured layered composites

NASA Astrophysics Data System (ADS)

Yan, Yongke; Zhou, Yuan; Priya, Shashank

2013-02-01

Co-fired magnetostrictive/piezoelectric/magnetostrictive laminate structure with silver inner electrode was synthesized and characterized. We demonstrate integration of textured piezoelectric microstructure with the cost-effective low-temperature co-fired layered structure to achieve strong magnetoelectric coupling. Using the co-fired composite, a strategy was developed based upon the hysteretic response of nickel-copper-zinc ferrite magnetostrictive materials to achieve peak magnetoelectric response at zero DC bias, referred as self-biased magnetoelectric response. Fundamental understanding of self-bias phenomenon in composites with single phase magnetic material was investigated by quantifying the magnetization and piezomagnetic changes with applied DC field. We delineate the contribution arising from the interfacial strain and inherent magnetic hysteretic behavior of copper modified nickel-zinc ferrite towards self-bias response.

A New Correction Technique for Strain-Gage Measurements Acquired in Transient-Temperature Environments

NASA Technical Reports Server (NTRS)

Richards, W. Lance

1996-01-01

Significant strain-gage errors may exist in measurements acquired in transient-temperature environments if conventional correction methods are applied. As heating or cooling rates increase, temperature gradients between the strain-gage sensor and substrate surface increase proportionally. These temperature gradients introduce strain-measurement errors that are currently neglected in both conventional strain-correction theory and practice. Therefore, the conventional correction theory has been modified to account for these errors. A new experimental method has been developed to correct strain-gage measurements acquired in environments experiencing significant temperature transients. The new correction technique has been demonstrated through a series of tests in which strain measurements were acquired for temperature-rise rates ranging from 1 to greater than 100 degrees F/sec. Strain-gage data from these tests have been corrected with both the new and conventional methods and then compared with an analysis. Results show that, for temperature-rise rates greater than 10 degrees F/sec, the strain measurements corrected with the conventional technique produced strain errors that deviated from analysis by as much as 45 percent, whereas results corrected with the new technique were in good agreement with analytical results.

A method of batch-purifying microalgae with multiple antibiotics at extremely high concentrations

NASA Astrophysics Data System (ADS)

Han, Jichang; Wang, Song; Zhang, Lin; Yang, Guanpin; Zhao, Lu; Pan, Kehou

2016-01-01

Axenic microalgal strains are highly valued in diverse microalgal studies and applications. Antibiotics, alone or in combination, are often used to avoid bacterial contamination during microalgal isolation and culture. In our preliminary trials, we found that many microalgae ceased growing in antibiotics at extremely high concentrations but could resume growth quickly when returned to an antibiotics-free liquid medium and formed colonies when spread on a solid medium. We developed a simple and highly efficient method of obtaining axenic microalgal cultures based on this observation. First, microalgal strains of different species or strains were treated with a mixture of ampicillin, gentamycin sulfate, kanamycin, neomycin and streptomycin (each at a concentration of 600 mg/L) for 3 days; they were then transferred to antibiotics-free medium for 5 days; and finally they were spread on solid f/2 media to allow algal colonies to form. With this method, five strains of Nannochloropsis sp. (Eustigmatophyceae), two strains of Cylindrotheca sp. (Bacillariophyceae), two strains of Tetraselmis sp. (Chlorodendrophyceae) and one strain of Amphikrikos sp. (Trebouxiophyceae) were purified successfully. The method shows promise for batch-purifying microalgal cultures.

Laser speckle strain and deformation sensor using linear array image cross-correlation method for specifically arranged triple-beam triple-camera configuration

NASA Technical Reports Server (NTRS)

Sarrafzadeh-Khoee, Adel K. (Inventor)

2000-01-01

The invention provides a method of triple-beam and triple-sensor in a laser speckle strain/deformation measurement system. The triple-beam/triple-camera configuration combined with sequential timing of laser beam shutters is capable of providing indications of surface strain and structure deformations. The strain and deformation quantities, the four variables of surface strain, in-plane displacement, out-of-plane displacement and tilt, are determined in closed form solutions.

Discriminatory Indices of Typing Methods for Epidemiologic Analysis of Contemporary Staphylococcus aureus Strains.

PubMed

Rodriguez, Marcela; Hogan, Patrick G; Satola, Sarah W; Crispell, Emily; Wylie, Todd; Gao, Hongyu; Sodergren, Erica; Weinstock, George M; Burnham, Carey-Ann D; Fritz, Stephanie A

2015-09-01

Historically, a number of typing methods have been evaluated for Staphylococcus aureus strain characterization. The emergence of contemporary strains of community-associated S. aureus, and the ensuing epidemic with a predominant strain type (USA300), necessitates re-evaluation of the discriminatory power of these typing methods for discerning molecular epidemiology and transmission dynamics, essential to investigations of hospital and community outbreaks. We compared the discriminatory index of 5 typing methods for contemporary S. aureus strain characterization. Children presenting to St. Louis Children's Hospital and community pediatric practices in St. Louis, Missouri (MO), with community-associated S. aureus infections were enrolled. Repetitive sequence-based PCR (repPCR), pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), staphylococcal protein A (spa), and staphylococcal cassette chromosome (SCC) mec typing were performed on 200 S. aureus isolates. The discriminatory index of each method was calculated using the standard formula for this metric, where a value of 1 is highly discriminatory and a value of 0 is not discriminatory. Overall, we identified 26 distinct strain types by repPCR, 17 strain types by PFGE, 30 strain types by MLST, 68 strain types by spa typing, and 5 strain types by SCCmec typing. RepPCR had the highest discriminatory index (D) of all methods (D = 0.88), followed by spa typing (D = 0.87), MLST (D = 0.84), PFGE (D = 0.76), and SCCmec typing (D = 0.60). The method with the highest D among MRSA isolates was repPCR (D = 0.64) followed by spa typing (D = 0.45) and MLST (D = 0.44). The method with the highest D among MSSA isolates was spa typing (D = 0.98), followed by MLST (D = 0.93), repPCR (D = 0.92), and PFGE (D = 0.89). Among isolates designated USA300 by PFGE, repPCR was most discriminatory, with 10 distinct strain types identified (D = 0.63). We identified 45 MRSA isolates which were classified as identical by PFGE, MLST, spa typing, and SCCmec typing (USA300, ST8, t008, SCCmec IV, respectively); within this collection, there were 5 distinct strain types identified by repPCR. The typing methods yielded comparable discriminatory power for S. aureus characterization overall; when discriminating among USA300 isolates, repPCR retained the highest discriminatory power. This property is advantageous for investigations conducted in the era of contemporary S. aureus infections.

Discriminatory Indices of Typing Methods for Epidemiologic Analysis of Contemporary Staphylococcus aureus Strains

PubMed Central

Rodriguez, Marcela; Hogan, Patrick G.; Satola, Sarah W.; Crispell, Emily; Wylie, Todd; Gao, Hongyu; Sodergren, Erica; Weinstock, George M.; Burnham, Carey-Ann D.; Fritz, Stephanie A.

2015-01-01

Abstract Historically, a number of typing methods have been evaluated for Staphylococcus aureus strain characterization. The emergence of contemporary strains of community-associated S. aureus, and the ensuing epidemic with a predominant strain type (USA300), necessitates re-evaluation of the discriminatory power of these typing methods for discerning molecular epidemiology and transmission dynamics, essential to investigations of hospital and community outbreaks. We compared the discriminatory index of 5 typing methods for contemporary S. aureus strain characterization. Children presenting to St. Louis Children's Hospital and community pediatric practices in St. Louis, Missouri (MO), with community-associated S. aureus infections were enrolled. Repetitive sequence-based PCR (repPCR), pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), staphylococcal protein A (spa), and staphylococcal cassette chromosome (SCC) mec typing were performed on 200 S. aureus isolates. The discriminatory index of each method was calculated using the standard formula for this metric, where a value of 1 is highly discriminatory and a value of 0 is not discriminatory. Overall, we identified 26 distinct strain types by repPCR, 17 strain types by PFGE, 30 strain types by MLST, 68 strain types by spa typing, and 5 strain types by SCCmec typing. RepPCR had the highest discriminatory index (D) of all methods (D = 0.88), followed by spa typing (D = 0.87), MLST (D = 0.84), PFGE (D = 0.76), and SCCmec typing (D = 0.60). The method with the highest D among MRSA isolates was repPCR (D = 0.64) followed by spa typing (D = 0.45) and MLST (D = 0.44). The method with the highest D among MSSA isolates was spa typing (D = 0.98), followed by MLST (D = 0.93), repPCR (D = 0.92), and PFGE (D = 0.89). Among isolates designated USA300 by PFGE, repPCR was most discriminatory, with 10 distinct strain types identified (D = 0.63). We identified 45 MRSA isolates which were classified as identical by PFGE, MLST, spa typing, and SCCmec typing (USA300, ST8, t008, SCCmec IV, respectively); within this collection, there were 5 distinct strain types identified by repPCR. The typing methods yielded comparable discriminatory power for S. aureus characterization overall; when discriminating among USA300 isolates, repPCR retained the highest discriminatory power. This property is advantageous for investigations conducted in the era of contemporary S. aureus infections. PMID:26376402

Method for construction of bacterial strains with increased succinic acid production

DOEpatents

Donnelly, Mark I.; Sanville-Millard, Cynthia; Chatterjee, Ranjini

2000-01-01

A fermentation process for producing succinic acid is provided comprising selecting a bacterial strain that does not produce succinic acid in high yield, disrupting the normal regulation of sugar metabolism of said bacterial strain, and combining the mutant bacterial strain and selected sugar in anaerobic conditions to facilitate production of succinic acid. Also provided is a method for changing low yield succinic acid producing bacteria to high yield succinic acid producing bacteria comprising selecting a bacterial strain having a phosphotransferase system and altering the phosphotransferase system so as to allow the bacterial strain to simultaneously metabolize different sugars.

Methodology optimization and diversification for the investigation of virulence potential in Haemophilus influenzae clinical strains.

PubMed

Giucă, Mihaela Cristina; Străuţ, Monica; Surdeanu, Maria; Nica, Maria; Ungureanu, Vasilica; Mihăescu, Grigore

2011-01-01

Ten Haemophilus influenzae strains were isolated from patients aged between 1.6 - 24 years, with various diagnoses (acute meningitis, acute upper respiratory infection, otitis media and acute sinusitis). Identification was based on phenotypic and molecular characteristics; antibiotic susceptibility testing was performed by diffusion method according to CLSI standards 2011 for seven antibiotics. The results of molecular testing showed that all the studied strains produced an amplicon of 1000 bp with ompP2 primers indicating that all strains were H. influenzae. For six strains, the PCR amplicon obtained with bexA specific primers, proving that the strains were capsulated. The results of phenotypic testing showed that four strains were ampicillin nonsusceptible and (beta-lactamase-positive. The virulence potential of H. influenzae clinical strains was investigated by phenotypic methods, including the assessment of the soluble virulence factors on specific media containing the biochemical substratum for the investigated enzymatic factor, as well as the adherence and invasion capacity to HeLa cells monolayer using Cravioto modified method. The studied strains exhibited mainly a diffuse adherence pattern and different adherence indexes. Interestingly, two strains isolated from the same pacient (blood and CSF) showed a different degree of invasiveness, the strain isolated from blood being 20 times more invasive than the one isolated from CSF.

A method for determination of equine hoof strain patterns using photoelasticity: an in vitro study.

PubMed

Dejardin, L M; Arnoczky, S P; Cloud, G L

1999-05-01

During impact, equine hooves undergo viscoelastic deformations which may result in potentially harmful strains. Previous hoof strain studies using strain gauges have been inconclusive due to arbitrary gauge placement. Photoelastic stress analysis (PSA) is a full-field technique which visually displays strains over entire loaded surfaces. This in vitro study identifies normal hoof strain patterns using PSA. Custom-made photoelastic plastic sheets were applied to the hoof surface. The hooves were axially loaded (225 kg) under level and varus/valgus conditions. Strain patterns were video-recorded through a polariscope. Strains were concentrated between middle and distal thirds of the hoof wall regardless of the loading conditions. This strain distribution appears to result from the differential expansion of the hoof wall under load. Increasing load resulted in higher strains and asymmetric loading resulted in an ipsilateral increase in strain magnitudes without altering strain locations. This study shows that PSA is a reliable method with which to evaluate hoof strains in vitro and is sensitive enough to reflect subtle load-related strain alterations.

Error decomposition and estimation of inherent optical properties.

PubMed

Salama, Mhd Suhyb; Stein, Alfred

2009-09-10

We describe a methodology to quantify and separate the errors of inherent optical properties (IOPs) derived from ocean-color model inversion. Their total error is decomposed into three different sources, namely, model approximations and inversion, sensor noise, and atmospheric correction. Prior information on plausible ranges of observation, sensor noise, and inversion goodness-of-fit are employed to derive the posterior probability distribution of the IOPs. The relative contribution of each error component to the total error budget of the IOPs, all being of stochastic nature, is then quantified. The method is validated with the International Ocean Colour Coordinating Group (IOCCG) data set and the NASA bio-Optical Marine Algorithm Data set (NOMAD). The derived errors are close to the known values with correlation coefficients of 60-90% and 67-90% for IOCCG and NOMAD data sets, respectively. Model-induced errors inherent to the derived IOPs are between 10% and 57% of the total error, whereas atmospheric-induced errors are in general above 43% and up to 90% for both data sets. The proposed method is applied to synthesized and in situ measured populations of IOPs. The mean relative errors of the derived values are between 2% and 20%. A specific error table to the Medium Resolution Imaging Spectrometer (MERIS) sensor is constructed. It serves as a benchmark to evaluate the performance of the atmospheric correction method and to compute atmospheric-induced errors. Our method has a better performance and is more appropriate to estimate actual errors of ocean-color derived products than the previously suggested methods. Moreover, it is generic and can be applied to quantify the error of any derived biogeophysical parameter regardless of the used derivation.

Single-step scanner-based digital image correlation (SB-DIC) method for large deformation mapping in rubber

NASA Astrophysics Data System (ADS)

Goh, C. P.; Ismail, H.; Yen, K. S.; Ratnam, M. M.

2017-01-01

The incremental digital image correlation (DIC) method has been applied in the past to determine strain in large deformation materials like rubber. This method is, however, prone to cumulative errors since the total displacement is determined by combining the displacements in numerous stages of the deformation. In this work, a method of mapping large strains in rubber using DIC in a single-step without the need for a series of deformation images is proposed. The reference subsets were deformed using deformation factors obtained from the fitted mean stress-axial stretch ratio curve obtained experimentally and the theoretical Poisson function. The deformed reference subsets were then correlated with the deformed image after loading. The recently developed scanner-based digital image correlation (SB-DIC) method was applied on dumbbell rubber specimens to obtain the in-plane displacement fields up to 350% axial strain. Comparison of the mean axial strains determined from the single-step SB-DIC method with those from the incremental SB-DIC method showed an average difference of 4.7%. Two rectangular rubber specimens containing circular and square holes were deformed and analysed using the proposed method. The resultant strain maps from the single-step SB-DIC method were compared with the results of finite element modeling (FEM). The comparison shows that the proposed single-step SB-DIC method can be used to map the strain distribution accurately in large deformation materials like rubber at much shorter time compared to the incremental DIC method.

[Use of multiple locus variable number tandem repeats analysis for the Brucella systematization].

PubMed

Kulakov, Iu K; Kovalev, D A; Misetova, E N; Golovneva, S I; Liapustina, L V; Zheludkov, M M

2012-01-01

The methods of molecular-genetic differentiation to strain level acquire increasing significance in the current system of struggle with brucellosis. MLVA (multiple locus variable number tandem repeats analysis) was selected for molecular-genetic differentiation to strain level and simultaneous establishment of the genetic relationship of investigated Brucella strains. The goal of this work was MLVA typing of three pathogenic Brucella species strains with the analysis of stability of chosen loci, discrimination power and concordance to conventional phenotypic methods of the Brucella differentiation for use in systematization of brucellosis causing agents. Twenty six Brucella strains representing reference (n = 15), vaccine (n = 2) and field strains of three pathogenic Brucella species were tested: B. melitensis (n = 3), B. abortus (n = 2), B. suis (n = 2), and isolates (n = 2) with unidentified taxonomic position using MLVA with 9 pairs primers on known variable loci of Brucella genome. The analysis of the stability of chosen loci, discrimination power on Hunter-Gaston discrimination index (HGDI) and consistency to phenotypic methods of identification was performed. MLVA was confirmed for the results of phenotypic methods of identification, stability of the chosen loci in majority reference, and vaccine strains with a high index of variability HGDI 0.9969 for all loci. A dendrogram was plotted on the basis of MLVA data on distributed Brucella strains in related clusters according to its taxonomic species and biovar positions and construction of 25 genotypes. B. melitensis strains formed cluster related to the reference strain of B. melitensis 63/9 biovar 2. Australian isolates of Brucella 83-4 and Brucella 83-6 isolated from rodents formed a cluster distant from other strains of Brucella. MLVA is a promising method for differentiation of Brucella strains with known and unresolved taxonomic status for their systematization and creation of MLVA genotype catalogue that will promote qualitative improvement of brucellosis surveillance system in Russia.

High resolution identity testing of inactivated poliovirus vaccines

PubMed Central

Mee, Edward T.; Minor, Philip D.; Martin, Javier

2015-01-01

Background Definitive identification of poliovirus strains in vaccines is essential for quality control, particularly where multiple wild-type and Sabin strains are produced in the same facility. Sequence-based identification provides the ultimate in identity testing and would offer several advantages over serological methods. Methods We employed random RT-PCR and high throughput sequencing to recover full-length genome sequences from monovalent and trivalent poliovirus vaccine products at various stages of the manufacturing process. Results All expected strains were detected in previously characterised products and the method permitted identification of strains comprising as little as 0.1% of sequence reads. Highly similar Mahoney and Sabin 1 strains were readily discriminated on the basis of specific variant positions. Analysis of a product known to contain incorrect strains demonstrated that the method correctly identified the contaminants. Conclusion Random RT-PCR and shotgun sequencing provided high resolution identification of vaccine components. In addition to the recovery of full-length genome sequences, the method could also be easily adapted to the characterisation of minor variant frequencies and distinction of closely related products on the basis of distinguishing consensus and low frequency polymorphisms. PMID:26049003

Efficient screening of environmental isolates for Saccharomyces cerevisiae strains that are suitable for brewing.

PubMed

Fujihara, Hidehiko; Hino, Mika; Takashita, Hideharu; Kajiwara, Yasuhiro; Okamoto, Keiko; Furukawa, Kensuke

2014-01-01

We developed an efficient screening method for Saccharomyces cerevisiae strains from environmental isolates. MultiPlex PCR was performed targeting four brewing S. cerevisiae genes (SSU1, AWA1, BIO6, and FLO1). At least three genes among the four were amplified from all S. cerevisiae strains. The use of this method allowed us to successfully obtain S. cerevisiae strains.

Development of a Trypanosoma cruzi strain typing assay using MS2 peptide spectral libraries (Tc-STAMS2).

PubMed

de Oliveira, Gilberto Santos; Kawahara, Rebeca; Rosa-Fernandes, Livia; Mule, Simon Ngao; Avila, Carla Cristi; Teixeira, Marta M G; Larsen, Martin R; Palmisano, Giuseppe

2018-04-01

Chagas disease also known as American trypanosomiasis is caused by the protozoan Trypanosoma cruzi. Over the last 30 years, Chagas disease has expanded from a neglected parasitic infection of the rural population to an urbanized chronic disease, becoming a potentially emergent global health problem. T. cruzi strains were assigned to seven genetic groups (TcI-TcVI and TcBat), named discrete typing units (DTUs), which represent a set of isolates that differ in virulence, pathogenicity and immunological features. Indeed, diverse clinical manifestations (from asymptomatic to highly severe disease) have been attempted to be related to T.cruzi genetic variability. Due to that, several DTU typing methods have been introduced. Each method has its own advantages and drawbacks such as high complexity and analysis time and all of them are based on genetic signatures. Recently, a novel method discriminated bacterial strains using a peptide identification-free, genome sequence-independent shotgun proteomics workflow. Here, we aimed to develop a Trypanosoma cruzi Strain Typing Assay using MS/MS peptide spectral libraries, named Tc-STAMS2. The Tc-STAMS2 method uses shotgun proteomics combined with spectral library search to assign and discriminate T. cruzi strains independently on the genome knowledge. The method is based on the construction of a library of MS/MS peptide spectra built using genotyped T. cruzi reference strains. For identification, the MS/MS peptide spectra of unknown T. cruzi cells are identified using the spectral matching algorithm SpectraST. The Tc-STAMS2 method allowed correct identification of all DTUs with high confidence. The method was robust towards different sample preparations, length of chromatographic gradients and fragmentation techniques. Moreover, a pilot inter-laboratory study showed the applicability to different MS platforms. This is the first study that develops a MS-based platform for T. cruzi strain typing. Indeed, the Tc-STAMS2 method allows T. cruzi strain typing using MS/MS spectra as discriminatory features and allows the differentiation of TcI-TcVI DTUs. Similar to genomic-based strategies, the Tc-STAMS2 method allows identification of strains within DTUs. Its robustness towards different experimental and biological variables makes it a valuable complementary strategy to the current T. cruzi genotyping assays. Moreover, this method can be used to identify DTU-specific features correlated with the strain phenotype.

Deformation microstructures and magnetite texture development in synthetic shear zones

NASA Astrophysics Data System (ADS)

Till, Jessica L.; Moskowitz, Bruce M.

2014-08-01

We present observations of deformation features in magnetite from synthetic magnetite-bearing silicate aggregates deformed between 1000 °C and 1200 °C in transpressional shear experiments with strains of up to 300%. Anisotropy of magnetic susceptibility and shape preferred orientation (SPO) analysis were combined with electron backscatter diffraction (EBSD) to characterize the magnetite deformation fabrics and intragrain microstructures. Crystallographic preferred orientation (CPO) in magnetite is very weak in all deformed samples and does not vary as a function of either temperature or shear strain. Magnetic anisotropy and SPO increase strongly with both strain and deformation temperature and indicate that strain partitioning between magnetite and the plagioclase matrix decreases at higher temperatures. EBSD orientation mapping of individual magnetite particles revealed substantial dispersions in intragrain orientation, analogous to undulose extinction, after deformation at 1000 and 1100 °C, indicating that dislocation creep processes were active in magnetite despite the lack of a well-developed CPO. Geometrical analysis of crystallographic orientation dispersions from grain map data indicates that low-angle grain boundary formation in magnetite could have been accommodated by slip on {110} or {100} planes, but no evidence for dominant slip on the expected {111} planes was found. Evidence for activation of multiple slip systems was seen in some magnetite grains and could be partially responsible for the lack of CPO in magnetite. These results suggest that, at least in polyphase rocks, crystallographic textures in magnetite may be inherently weak or slow to develop and CPO alone is not an adequate indicator of magnetite deformation mechanisms. These results may aid in the interpretation of deformation textures in other spinel-structured phases such as chromite and ringwoodite.

Biocontrol agents promote growth of potato pathogens, depending on environmental conditions.

PubMed

Cray, Jonathan A; Connor, Mairéad C; Stevenson, Andrew; Houghton, Jonathan D R; Rangel, Drauzio E N; Cooke, Louise R; Hallsworth, John E

2016-05-01

There is a pressing need to understand and optimize biological control so as to avoid over-reliance on the synthetic chemical pesticides that can damage environmental and human health. This study focused on interactions between a novel biocontrol-strain, Bacillus sp. JC12GB43, and potato-pathogenic Phytophthora and Fusarium species. In assays carried out in vitro and on the potato tuber, the bacterium was capable of near-complete inhibition of pathogens. This Bacillus was sufficiently xerotolerant (water activity limit for growth = 0.928) to out-perform Phytophthora infestans (~0.960) and challenge Fusarium coeruleum (~0.847) and Fusarium sambucinum (~0.860) towards the lower limits of their growth windows. Under some conditions, however, strain JC12GB43 stimulated proliferation of the pathogens: for instance, Fusarium coeruleum growth-rate was increased under chaotropic conditions in vitro (132 mM urea) by >100% and on tubers (2-M glycerol) by up to 570%. Culture-based assays involving macromolecule-stabilizing (kosmotropic) compatible solutes provided proof-of-principle that the Bacillus may provide kosmotropic metabolites to the plant pathogen under conditions that destabilize macromolecular systems of the fungal cell. Whilst unprecedented, this finding is consistent with earlier reports that fungi can utilize metabolites derived from bacterial cells. Unless the antimicrobial activities of candidate biocontrol strains are assayed over a full range of field-relevant parameters, biocontrol agents may promote plant pathogen infections and thereby reduce crop yields. These findings indicate that biocontrol activity, therefore, ought to be regarded as a mode-of-behaviour (dependent on prevailing conditions) rather than an inherent property of a bacterial strain. © 2016 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.

Gyroscopic sensing in the wings of the hawkmoth Manduca sexta: the role of sensor location and directional sensitivity.

PubMed

Hinson, Brian T; Morgansen, Kristi A

2015-10-06

The wings of the hawkmoth Manduca sexta are lined with mechanoreceptors called campaniform sensilla that encode wing deformations. During flight, the wings deform in response to a variety of stimuli, including inertial-elastic loads due to the wing flapping motion, aerodynamic loads, and exogenous inertial loads transmitted by disturbances. Because the wings are actuated, flexible structures, the strain-sensitive campaniform sensilla are capable of detecting inertial rotations and accelerations, allowing the wings to serve not only as a primary actuator, but also as a gyroscopic sensor for flight control. We study the gyroscopic sensing of the hawkmoth wings from a control theoretic perspective. Through the development of a low-order model of flexible wing flapping dynamics, and the use of nonlinear observability analysis, we show that the rotational acceleration inherent in wing flapping enables the wings to serve as gyroscopic sensors. We compute a measure of sensor fitness as a function of sensor location and directional sensitivity by using the simulation-based empirical observability Gramian. Our results indicate that gyroscopic information is encoded primarily through shear strain due to wing twisting, where inertial rotations cause detectable changes in pronation and supination timing and magnitude. We solve an observability-based optimal sensor placement problem to find the optimal configuration of strain sensor locations and directional sensitivities for detecting inertial rotations. The optimal sensor configuration shows parallels to the campaniform sensilla found on hawkmoth wings, with clusters of sensors near the wing root and wing tip. The optimal spatial distribution of strain directional sensitivity provides a hypothesis for how heterogeneity of campaniform sensilla may be distributed.

Are Teacher Course Evaluations Biased against Faculty That Teach Quantitative Methods Courses?

ERIC Educational Resources Information Center

Royal, Kenneth D.; Stockdale, Myrah R.

2015-01-01

The present study investigated graduate students' responses to teacher/course evaluations (TCE) to determine if students' responses were inherently biased against faculty who teach quantitative methods courses. Item response theory (IRT) and Differential Item Functioning (DIF) techniques were utilized for data analysis. Results indicate students…

Signification des temps grammaticaux (Significance of Grammatical Tenses).

ERIC Educational Resources Information Center

Cintas, Pierre F.; Descles, Jean-Pierre

1988-01-01

A method for teaching concepts of time (state, event, and process) inherent in grammatical tenses is outlined. The technique uses diagrams to illustrate the concepts and their semantic implications. (MSE)

Evaluation of repetitive-PCR and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) for rapid strain typing of Bacillus coagulans

PubMed Central

Nakayama, Motokazu; Tomita, Ayumi; Sonoda, Takumi; Hasumi, Motomitsu; Miyamoto, Takahisa

2017-01-01

In order to establish rapid and accurate typing method for Bacillus coagulans strains which is important for controlling in some canned foods and tea-based beverages manufacturing because of the high-heat resistance of the spores and high tolerance of the vegetative cells to catechins and chemicals, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and repetitive-PCR (rep-PCR) were evaluated. For this purpose, 28 strains of B. coagulans obtained from various culture collections were tested. DNA sequence analyses of the genes encoding 16S rRNA and DNA gyrase classified the test strains into two and three groups, respectively, regardless of their phenotypes. Both MALDI-TOF MS and rep-PCR methods classified the test strains in great detail. Strains classified in each group showed similar phenotypes, such as carbohydrate utilization determined using API 50CH. In particular, the respective two pairs of strains which showed the same metabolic characteristic were classified into the same group by both MALDI-TOF MS and rep-PCR methods separating from the other strains. On the other hand, the other strains which have the different profiles of carbohydrate utilization were separated into different groups by these methods. These results suggested that the combination of MALDI-TOF MS and rep-PCR analyses was advantageous for the rapid and detailed typing of bacterial strains in respect to both phenotype and genotype. PMID:29020109

Evaluation of repetitive-PCR and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) for rapid strain typing of Bacillus coagulans.

PubMed

Sato, Jun; Nakayama, Motokazu; Tomita, Ayumi; Sonoda, Takumi; Hasumi, Motomitsu; Miyamoto, Takahisa

2017-01-01

In order to establish rapid and accurate typing method for Bacillus coagulans strains which is important for controlling in some canned foods and tea-based beverages manufacturing because of the high-heat resistance of the spores and high tolerance of the vegetative cells to catechins and chemicals, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and repetitive-PCR (rep-PCR) were evaluated. For this purpose, 28 strains of B. coagulans obtained from various culture collections were tested. DNA sequence analyses of the genes encoding 16S rRNA and DNA gyrase classified the test strains into two and three groups, respectively, regardless of their phenotypes. Both MALDI-TOF MS and rep-PCR methods classified the test strains in great detail. Strains classified in each group showed similar phenotypes, such as carbohydrate utilization determined using API 50CH. In particular, the respective two pairs of strains which showed the same metabolic characteristic were classified into the same group by both MALDI-TOF MS and rep-PCR methods separating from the other strains. On the other hand, the other strains which have the different profiles of carbohydrate utilization were separated into different groups by these methods. These results suggested that the combination of MALDI-TOF MS and rep-PCR analyses was advantageous for the rapid and detailed typing of bacterial strains in respect to both phenotype and genotype.

Development of strain-specific PCR primers for quantitative detection of Bacillus mesentericus strain TO-A in human feces.

PubMed

Sato, Naoki; Seo, Genichiro; Benno, Yoshimi

2014-01-01

Strain-specific polymerase chain reaction (PCR) primers for detection of Bacillus mesentericus strain TO-A (BM TO-A) were developed. The randomly amplified polymorphic DNA (RAPD) technique was used to produce potential strain-specific markers. A 991-bp RAPD marker found to be strain-specific was sequenced, and two primer pairs specific to BM TO-A were constructed based on this sequence. In addition, we explored a more specific DNA region using inverse PCR, and designed a strain-specific primer set for use in real-time quantitative PCR (qPCR). These primer pairs were tested against 25 Bacillus subtilis strains and were found to be strain-specific. After examination of the detection limit and linearity of detection of BM TO-A in feces, the qPCR method and strain-specific primers were used to quantify BM TO-A in the feces of healthy volunteers who had ingested 3×10(8) colony forming unit (CFU) of BM TO-A per day in tablets. During the administration period, BM TO-A was detected in the feces of all 24 subjects, and the average number of BM TO-A detected using the culture method and qPCR was about 10(4.8) and 10(5.8) cells per gram of feces, respectively. Using the qPCR method, BM TO-A was detected in the feces of half of the subjects 3 d after withdrawal, and was detected in the feces of only one subject 1 week after withdrawal. These results suggest that the qPCR method using BM TO-A strain-specific primers is useful for the quantitative detection of this strain in feces.

Estimation of lattice strain in nanocrystalline RuO2 by Williamson-Hall and size-strain plot methods

NASA Astrophysics Data System (ADS)

Sivakami, R.; Dhanuskodi, S.; Karvembu, R.

2016-01-01

RuO2 nanoparticles (RuO2 NPs) have been successfully synthesized by the hydrothermal method. Structure and the particle size have been determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM). UV-Vis spectra reveal that the optical band gap of RuO2 nanoparticles is red shifted from 3.95 to 3.55 eV. BET measurements show a high specific surface area (SSA) of 118-133 m2/g and pore diameter (10-25 nm) has been estimated by Barret-Joyner-Halenda (BJH) method. The crystallite size and lattice strain in the samples have been investigated by Williamson-Hall (W-H) analysis assuming uniform deformation, deformation stress and deformation energy density, and the size-strain plot method. All other relevant physical parameters including stress, strain and energy density have been calculated. The average crystallite size and the lattice strain evaluated from XRD measurements are in good agreement with the results of TEM.

Metagenomic assembly through the lens of validation: recent advances in assessing and improving the quality of genomes assembled from metagenomes.

PubMed

Olson, Nathan D; Treangen, Todd J; Hill, Christopher M; Cepeda-Espinoza, Victoria; Ghurye, Jay; Koren, Sergey; Pop, Mihai

2017-08-07

Metagenomic samples are snapshots of complex ecosystems at work. They comprise hundreds of known and unknown species, contain multiple strain variants and vary greatly within and across environments. Many microbes found in microbial communities are not easily grown in culture making their DNA sequence our only clue into their evolutionary history and biological function. Metagenomic assembly is a computational process aimed at reconstructing genes and genomes from metagenomic mixtures. Current methods have made significant strides in reconstructing DNA segments comprising operons, tandem gene arrays and syntenic blocks. Shorter, higher-throughput sequencing technologies have become the de facto standard in the field. Sequencers are now able to generate billions of short reads in only a few days. Multiple metagenomic assembly strategies, pipelines and assemblers have appeared in recent years. Owing to the inherent complexity of metagenome assembly, regardless of the assembly algorithm and sequencing method, metagenome assemblies contain errors. Recent developments in assembly validation tools have played a pivotal role in improving metagenomics assemblers. Here, we survey recent progress in the field of metagenomic assembly, provide an overview of key approaches for genomic and metagenomic assembly validation and demonstrate the insights that can be derived from assemblies through the use of assembly validation strategies. We also discuss the potential for impact of long-read technologies in metagenomics. We conclude with a discussion of future challenges and opportunities in the field of metagenomic assembly and validation. © The Author 2017. Published by Oxford University Press.

Macro-architectured cellular materials: Properties, characteristic modes, and prediction methods

NASA Astrophysics Data System (ADS)

Ma, Zheng-Dong

2017-12-01

Macro-architectured cellular (MAC) material is defined as a class of engineered materials having configurable cells of relatively large (i.e., visible) size that can be architecturally designed to achieve various desired material properties. Two types of novel MAC materials, negative Poisson's ratio material and biomimetic tendon reinforced material, were introduced in this study. To estimate the effective material properties for structural analyses and to optimally design such materials, a set of suitable homogenization methods was developed that provided an effective means for the multiscale modeling of MAC materials. First, a strain-based homogenization method was developed using an approach that separated the strain field into a homogenized strain field and a strain variation field in the local cellular domain superposed on the homogenized strain field. The principle of virtual displacements for the relationship between the strain variation field and the homogenized strain field was then used to condense the strain variation field onto the homogenized strain field. The new method was then extended to a stress-based homogenization process based on the principle of virtual forces and further applied to address the discrete systems represented by the beam or frame structures of the aforementioned MAC materials. The characteristic modes and the stress recovery process used to predict the stress distribution inside the cellular domain and thus determine the material strengths and failures at the local level are also discussed.

Cross-reactions between alpha-streptococci and Omniserum, a polyvalent pneumococcal serum, demonstrated by direct immunofluorescence, immunoelectroosmophoresis, and latex agglutination.

PubMed Central

Holmberg, H; Danielsson, D; Hardie, J; Krook, A; Whiley, R

1985-01-01

In recent years several groups have used serological methods to demonstrate pneumococcal capsular antigens in sputum. In the present study 123 strains of alpha-hemolytic streptococci (including 97 strains from sputum or pharyngeal specimens) were tested for cross-reactions with a polyvalent antipneumococcal serum (Omniserum). Representatives of the following species were included: Streptococcus bovis, S. equinus, S. intermedius, S. lactis, S. milleri, S. mitis, S. mutans, S. sobrinus, S. salivarius, S. sanguis, S. suis, and Aerococcus viridans. Serological reactions were detected by direct immunofluorescence, immunoelectroosmophoresis, and latex agglutination. Fifteen (12%) of the strains gave positive reactions by all three methods. Positive reactions were also observed with another 32 strains (26%) with two of the methods, whereas 37 strains (30%) gave positive reactions by just one technique. Altogether 84 (68%) strains gave positive reactions with one or more of the methods. Latex agglutination gave positive reactions with 26 (21%) strains compared with 57 (46%) in immunofluorescence and 63 (51%) in immunoelectroosmophoresis. Absorption of the antiserum with one alpha-hemolytic strain reduced but did not entirely eliminate the cross-reactions with five tested strains. These findings indicate a potential risk of cross-reactions with polyvalent antipneumococcal serum in tests carried out on sputa or other specimens which may be contaminated with alpha-hemolytic streptococci. PMID:3889046

Smart materials: strain sensing and stress determination by means of nanotube sensing systems, composites, and devices

NASA Technical Reports Server (NTRS)

Kim, Jong Dae (Inventor); Nagarajaiah, Satish (Inventor); Barrera, Enrique V. (Inventor); Dharap, Prasad (Inventor); Zhiling, Li (Inventor)

2010-01-01

The present invention is directed toward devices comprising carbon nanotubes that are capable of detecting displacement, impact, stress, and/or strain in materials, methods of making such devices, methods for sensing/detecting/monitoring displacement, impact, stress, and/or strain via carbon nanotubes, and various applications for such methods and devices. The devices and methods of the present invention all rely on mechanically-induced electronic perturbations within the carbon nanotubes to detect and quantify such stress/strain. Such detection and quantification can rely on techniques which include, but are not limited to, electrical conductivity/conductance and/or resistivity/resistance detection/measurements, thermal conductivity detection/measurements, electroluminescence detection/measurements, photoluminescence detection/measurements, and combinations thereof. All such techniques rely on an understanding of how such properties change in response to mechanical stress and/or strain.

Identification, Classification, and Phylogeny of the Pathogenic Species Exophiala jeanselmei and Related Species by Mitochondrial Cytochrome b Gene Analysis

PubMed Central

Wang, Li; Yokoyama, Koji; Miyaji, Makoto; Nishimura, Kazuko

2001-01-01

We analyzed a 402-bp sequence of the mitochondrial cytochrome b gene of 34 strains of Exophiala jeanselmei and 16 strains representing 12 related species. The strains of E. jeanselmei were classified into 20 DNA types and 17 amino acid types. The differences between these strains were found in 1 to 60 nucleotides and 1 to 17 amino acids. On the basis of the identities and similarities of nucleotide and amino acid sequences, some strains were reidentified: i.e., two strains of E. jeanselmei var. hetermorpha and one strain of E. castellanii as E. dermatitidis (including the type strain), three strains of E. jeanselmei as E. jeanselmei var. lecanii-corni (including the type strain), three strains of E. jeanselmei as E. bergeri (including the type strain), seven strains of E. jeanselmei as E. pisciphila (including the type strain), seven strains of E. jeanselmei as E. jeanselmei var. jeanselmei (including the type strain), one strain of E. jeanselmei as Fonsecaea pedrosoi (including the type strain), and one strain of E. jeanselmei as E. spinifera (including the type strain). Some E. jeanselmei strains showed distinct nucleotide and amino acid sequences. The amino-acid-based UPGMA (unweighted pair group method with the arithmetic mean) tree exhibited nearly the same topology as those of the DNA-based trees obtained by neighbor joining, maximum parsimony, and maximum likelihood methods. PMID:11724862

[Isolation and antimicrobial activities of actinomycetes from vermicompost].

PubMed

Wang, Xue-jun; Yan, Shuang-lin; Min, Chang-li; Yang, Yan

2015-02-01

In this paper, actinomycetes were isolated from vermicompost by tablet coating method. Antimicrobial activities of actinomycetes were measured by the agar block method. Strains with high activity were identified based on morphology and biochemical characteristics, as well as 16S rDNA gene sequence analysis. The results showed that 26 strains of actinomycetes were isolated, 16 of them had antimicrobial activities to the test strains which accounts for 61.54% of all strains. Among the 16 strains, the strain QYF12 and QYF22 had higher antimicrobial activity to Micrococcus luteus, with a formed inhibition zone of 27 mm and 31 mm, respectively. While the strain QYF26 had higher antimicrobial activity to Bacillus subtilis, and the inhibition zone diameter was 21 mm. Based on the identification of strains with high activity, the strain QYF12 was identified as Streptomyces chartreusis, the strain QYF22 was S. ossamyceticus and the strain QYF26 was S. gancidicus. This study provided a theoretical basis for further separate antibacterial product used for biological control.

Does fingerprinting truly represent the diversity of wine yeasts? A case study with interdelta genotyping of Saccharomyces cerevisiae strains.

PubMed

Pfliegler, W P; Sipiczki, M

2016-12-01

Simple and efficient genotyping methods are widely used to assess the diversity of a large number of microbial strains, e.g. wine yeasts isolated from a specific geographical area or a vintage. Such methods are often also the first to be applied, to decrease the number of strains deemed interesting for a more time-consuming physiological characterization. Here, we aimed to use a physiologically characterized strain collection of 69 Saccharomyces cerevisiae strains from Hungarian wine regions to determine whether geographical origin or physiological similarity can be recovered by clustering the strains with one or two simultaneously used variations of interdelta genotyping. Our results indicate that although a detailed clustering with high resolution can be achieved with this method, the clustering of strains is largely contrasting when different primer sets are used and it does not recover geographical or physiological groups. Genotyping is routinely used for assessing the diversity of a large number of isolates/strains of a single species, e.g. a collection of wine yeasts. We tested the efficiency of interdelta genotyping on a collection of Saccharomyces wine yeasts from four wine regions of Hungary that was previously characterized physiologically. Interdelta fingerprinting recovered neither physiological nor geographical similarities, and in addition, the two different primer pairs widely used for this method showed conflicting and barely comparable results. Thus, this method does not necessarily represent the true diversity of a strain collection, but detailed clustering may be achieved by the combined use of primer sets. © 2016 The Society for Applied Microbiology.

Experiments With Magnetic Vector Potential

ERIC Educational Resources Information Center

Skinner, J. W.

1975-01-01

Describes the experimental apparatus and method for the study of magnetic vector potential (MVP). Includes a discussion of inherent errors in the calculations involved, precision of the results, and further applications of MVP. (GS)

Estimation of Staphylococcus aureus growth parameters from turbidity data: characterization of strain variation and comparison of methods.

PubMed

Lindqvist, R

2006-07-01

Turbidity methods offer possibilities for generating data required for addressing microorganism variability in risk modeling given that the results of these methods correspond to those of viable count methods. The objectives of this study were to identify the best approach for determining growth parameters based on turbidity data and use of a Bioscreen instrument and to characterize variability in growth parameters of 34 Staphylococcus aureus strains of different biotypes isolated from broiler carcasses. Growth parameters were estimated by fitting primary growth models to turbidity growth curves or to detection times of serially diluted cultures either directly or by using an analysis of variance (ANOVA) approach. The maximum specific growth rates in chicken broth at 17 degrees C estimated by time to detection methods were in good agreement with viable count estimates, whereas growth models (exponential and Richards) underestimated growth rates. Time to detection methods were selected for strain characterization. The variation of growth parameters among strains was best described by either the logistic or lognormal distribution, but definitive conclusions require a larger data set. The distribution of the physiological state parameter ranged from 0.01 to 0.92 and was not significantly different from a normal distribution. Strain variability was important, and the coefficient of variation of growth parameters was up to six times larger among strains than within strains. It is suggested to apply a time to detection (ANOVA) approach using turbidity measurements for convenient and accurate estimation of growth parameters. The results emphasize the need to consider implications of strain variability for predictive modeling and risk assessment.

Characterization of oral Helicobacter pylori strain by 4 methods.

PubMed

Boyanova, Lyudmila; Panov, Vladimir; Yordanov, Daniel; Gergova, Galina; Mitov, Ivan

2013-12-01

The aim of the study was to describe oral Helicobacter pylori strain from a child by 4 methods. The strain was positive by immunofluorescence, ureA- and cagA positive, vacA s1 m2 genotype and resistant to metronidazole and clarithromycin. In conclusion, virulent and antibiotic resistant H. pylori strains can be present in oral cavity from patients with chronic dental and gastroduodenal diseases. © 2013.

Variation of strain rate sensitivity index of a superplastic aluminum alloy in different testing methods

NASA Astrophysics Data System (ADS)

Majidi, Omid; Jahazi, Mohammad; Bombardier, Nicolas; Samuel, Ehab

2017-10-01

The strain rate sensitivity index, m-value, is being applied as a common tool to evaluate the impact of the strain rate on the viscoplastic behaviour of materials. The m-value, as a constant number, has been frequently taken into consideration for modeling material behaviour in the numerical simulation of superplastic forming processes. However, the impact of the testing variables on the measured m-values has not been investigated comprehensively. In this study, the m-value for a superplastic grade of an aluminum alloy (i.e., AA5083) has been investigated. The conditions and the parameters that influence the strain rate sensitivity for the material are compared with three different testing methods, i.e., monotonic uniaxial tension test, strain rate jump test and stress relaxation test. All tests were conducted at elevated temperature (470°C) and at strain rates up to 0.1 s-1. The results show that the m-value is not constant and is highly dependent on the applied strain rate, strain level and testing method.

Temperature and strain registration by fibre-optic strain sensor in the polymer composite materials manufacturing

NASA Astrophysics Data System (ADS)

Matveenko, V. P.; Kosheleva, N. A.; Shardakov, I. N.; Voronkov, A. A.

2018-04-01

The presence of process-induced strains induced by various manufacturing and operational factors is one of the characteristics of polymer composite materials (PCM). Conventional methods of registration and evaluation of process-induced strains can be laborious, time-consuming and demanding in terms of technical applications. The employment of embedded fibre-optic strain sensors (FOSS) offers a real prospect of measuring residual strains. This paper demonstrates the potential for using embedded FOSS for recording technological strains in a PCM plate. The PCM plate is manufactured from prepreg, using the direct compression-moulding method. In this method, the prepared reinforcing package is placed inside a mould, heated, and then exposed to compaction pressure. The examined technology can be used for positioning FOSS between the layers of the composite material. Fibre-optic sensors, interacting with the material of the examined object, make it possible to register the evolution of the strain process during all stages of polymer-composite formation. FOSS data were recorded with interrogator ASTRO X 327. The obtained data were processed using specially developed algorithms.

The multilocus sequence typing network: mlst.net.

PubMed

Aanensen, David M; Spratt, Brian G

2005-07-01

The unambiguous characterization of strains of a pathogen is crucial for addressing questions relating to its epidemiology, population and evolutionary biology. Multilocus sequence typing (MLST), which defines strains from the sequences at seven house-keeping loci, has become the method of choice for molecular typing of many bacterial and fungal pathogens (and non-pathogens), and MLST schemes and strain databases are available for a growing number of prokaryotic and eukaryotic organisms. Sequence data are ideal for strain characterization as they are unambiguous, meaning strains can readily be compared between laboratories via the Internet. Laboratories undertaking MLST can quickly progress from sequencing the seven gene fragments to characterizing their strains and relating them to those submitted by others and to the population as a whole. We provide the gateway to a number of MLST schemes, each of which contain a set of tools for the initial characterization of strains, and methods for relating query strains to other strains of the species, including clustering based on differences in allelic profiles, phylogenetic trees based on concatenated sequences, and a recently developed method (eBURST) for identifying clonal complexes within a species and displaying the overall structure of the population. This network of MLST websites is available at http://www.mlst.net.

Acid-Catalyzed Preparation of Biodiesel from Waste Vegetable Oil: An Experiment for the Undergraduate Organic Chemistry Laboratory

ERIC Educational Resources Information Center

Bladt, Don; Murray, Steve; Gitch, Brittany; Trout, Haylee; Liberko, Charles

2011-01-01

This undergraduate organic laboratory exercise involves the sulfuric acid-catalyzed conversion of waste vegetable oil into biodiesel. The acid-catalyzed method, although inherently slower than the base-catalyzed methods, does not suffer from the loss of product or the creation of emulsion producing soap that plagues the base-catalyzed methods when…

Inflatable device for installing strain gage bridges

NASA Technical Reports Server (NTRS)

Cook, C. E.; Smith, G. E.; Monaghan, R. C. (Inventor)

1983-01-01

Methods and devices for installing in a tubular shaft multiple strain gages are disclosed with focus on a method and a device for pneumatically forcing strain gages into seated engagement with the internal surfaces of a tubular shaft in an installation of multiple strain gages in a tubular shaft. The strain gages or other electron devices are seated in a template-like component which is wrapped about a pneumatically expansible body. The component is inserted into a shaft and the body is pneumatically expanded after a suitable adhesive was applied to the surfaces.

Non-destructive and three-dimensional measurement of local strain development during tensile deformation in an aluminium alloy

NASA Astrophysics Data System (ADS)

Kobayashi, M.; Miura, H.; Toda, H.

2015-08-01

Anisotropy of mechanical responses depending on crystallographic orientation causes inhomogeneous deformation on the mesoscopic scale (grain size scale). Investigation of the local plastic strain development is important for discussing recrystallization mechanisms, because the sites with higher local plastic strain may act as potential nucleation sites for recrystallization. Recently, high-resolution X-ray tomography, which is non-destructive inspection method, has been utilized for observation of the materials structure. In synchrotron radiation X-ray tomography, more than 10,000 microstructural features, like precipitates, dispersions, compounds and hydrogen pores, can be observed in aluminium alloys. We have proposed employing these microstructural features as marker gauges to measure local strains, and then have developed a method to calculate the three-dimensional strain distribution by tracking the microstructural features. In this study, we report the development of local plastic strain as a function of the grain microstructure in an aluminium alloy by means of this three-dimensional strain measurement technique. Strongly heterogeneous strain development was observed during tensile loading to 30%. In other words, some parts of the sample deform little whereas another deforms a lot. However, strain in the whole specimen was keeping harmony. Comparing the microstructure with the strain concentration that is obtained by this method has a potential to reveal potential nucleation sites of recrystallization.

Isolation of Novel Bacteria Including Rarely Cultivated Phyla, Acidobacteria and Verrucomicrobia, from the Roots of Emergent Plants by Simple Culturing Method

PubMed Central

Tanaka, Yasuhiro; Matsuzawa, Hiroaki; Tamaki, Hideyuki; Tagawa, Masahiro; Toyama, Tadashi; Kamagata, Yoichi; Mori, Kazuhiro

2017-01-01

A number of novel bacteria including members of rarely cultivated phyla, Acidobacteria and Verrucomicrobia, were successfully isolated from the roots of two emergent plants, Iris pseudacorus and Scirpus juncoides, by a simple culturing method. A total of 47.1% (66 strains) for I. pseudacorus and 42.1% (59 strains) for S. juncoides of all isolates (140 strains from each sample) were phylogenetically novel. Furthermore, Acidobacteria and Verrucomicrobia occupied 10.7% (15 strains) and 2.9% (4 strains) of I. pseudacorus isolates, and 2.1% (3 strains) and 3.6% (5 strains) of S. juncoides isolates, respectively, indicating that plant roots are attractive sources for isolating rarely cultivated microbes. PMID:28740039

Simultaneous measurement of absolute strain and differential strain based on fiber Bragg grating Fabry-Perot sensor

NASA Astrophysics Data System (ADS)

Wang, Kuiru; Wang, Bo; Yan, Binbin; Sang, Xinzhu; Yuan, Jinhui; Peng, Gang-Ding

2013-10-01

We present a fiber Bragg grating Fabry-Perot (FBG-FP) sensor using the fast Fourier transform (FFT) demodulation for measuring the absolute strain and differential strain simultaneously. The amplitude and phase characteristics of Fourier transform spectrum have been studied. The relation between the amplitude of Fourier spectrum and the differential strain has been presented. We fabricate the fiber grating FP cavity sensor, and carry out the experiment on the measurement of absolute strain and differential strain. Experimental results verify the demodulation method, and show that this sensor has a good accuracy in the scope of measurement. The demodulating method can expand the number of multiplexed sensors combining with wavelength division multiplexing and time division multiplexing.

21 CFR 177.1960 - Vinyl chloride-hexene-1 copolymers.

Code of Federal Regulations, 2014 CFR

2014-04-01

... determined by any suitable analytical procedure of generally accepted applicability. (ii) Inherent viscosity... D1243-79, “Standard Test Method for Dilute Solution Viscosity of Vinyl Chloride Polymers,” which is...

Decentralized Orchestration of Composite Ogc Web Processing Services in the Cloud

NASA Astrophysics Data System (ADS)

Xiao, F.; Shea, G. Y. K.; Cao, J.

2016-09-01

Current web-based GIS or RS applications generally rely on centralized structure, which has inherent drawbacks such as single points of failure, network congestion, and data inconsistency, etc. The inherent disadvantages of traditional GISs need to be solved for new applications on Internet or Web. Decentralized orchestration offers performance improvements in terms of increased throughput and scalability and lower response time. This paper investigates build time and runtime issues related to decentralized orchestration of composite geospatial processing services based on OGC WPS standard specification. A case study of dust storm detection was demonstrated to evaluate the proposed method and the experimental results indicate that the method proposed in this study is effective for its ability to produce the high quality solution at a low cost of communications for geospatial processing service composition problem.

Comparison of DNA-based techniques for differentiation of production strains of ale and lager brewing yeast.

PubMed

Kopecká, J; Němec, M; Matoulková, D

2016-06-01

Brewing yeasts are classified into two species-Saccharomyces pastorianus and Saccharomyces cerevisiae. Most of the brewing yeast strains are natural interspecies hybrids typically polyploids and their identification is thus often difficult giving heterogenous results according to the method used. We performed genetic characterization of a set of the brewing yeast strains coming from several yeast culture collections by combination of various DNA-based techniques. The aim of this study was to select a method for species-specific identification of yeast and discrimination of yeast strains according to their technological classification. A group of 40 yeast strains were characterized using PCR-RFLP analysis of ITS-5·8S, NTS, HIS4 and COX2 genes, multiplex PCR, RAPD-PCR of genomic DNA, mtDNA-RFLP and electrophoretic karyotyping. Reliable differentiation of yeast to the species level was achieved by PCR-RFLP of HIS4 gene. Numerical analysis of the obtained RAPD-fingerprints and karyotype revealed species-specific clustering corresponding with the technological classification of the strains. Taxonomic position and partial hybrid nature of strains were verified by multiplex PCR. Differentiation among species using the PCR-RFLP of ITS-5·8S and NTS region was shown to be unreliable. Karyotyping and RFLP of mitochondrial DNA evinced small inaccuracies in strain categorization. PCR-RFLP of HIS4 gene and RAPD-PCR of genomic DNA are reliable and suitable methods for fast identification of yeast strains. RAPD-PCR with primer 21 is a fast and reliable method applicable for differentiation of brewing yeasts with only 35% similarity of fingerprint profile between the two main technological groups (ale and lager) of brewing strains. It was proved that PCR-RFLP method of HIS4 gene enables precise discrimination among three technologically important Saccharomyces species. Differentiation of brewing yeast to the strain level can be achieved using the RAPD-PCR technique. © 2016 The Society for Applied Microbiology.

Method of producing purified carotenoid compounds

NASA Technical Reports Server (NTRS)

Eggink, Laura (Inventor)

2007-01-01

A method of producing a carotenoid in solid form includes culturing a strain of Chlorophyta algae cells in a minimal inorganic medium and separating the algae comprising a solid form of carotenoid. In one embodiment f the invention, the strain of Chlorophyta algae cells includes a strain f Chlamydomonas algae cells.

Effect of various Portland cement paste compositions on early-age strain

NASA Astrophysics Data System (ADS)

Guzzetta, Alana G.

Early-age strain in paste, mortar, and concrete mixtures was investigated using a new method where the specimen shape was a cone frustum. Strain of the specimen from both the horizontal and vertical directions was captured by height change measurement. The volumetric strain was then calculated as a function of the height change and was plotted versus time. A correlation was found between the slopes of the volumetric strain curve resulting from this test method and the initial setting time of the tested material. An initial evaluation of the repeatability of this innovative test method was conducted. The early-age strain effects of aggregate volume, shrinkage reducing admixture, water-cementitious ratio (w/cm), and partial cement replacement with supplementary cementitious materials were tested and individually compared. From these comparisons, it was observed that ambient temperature, bleed water development, and rheological properties had a significant impact on the volumetric strain results. Data showed increased strain as aggregate volume was reduced and as the w/cm was changed from 0.25 up to 0.50. The addition of shrinkage reducing admixture generally caused an increase in the 36-hour volumetric strain value. In most of the mixtures, cement replacement with 20% fly ash or 10% metakaolin reduced the measured volumetric strain when the w/cm was 0.30. Replacement of cement with 10% silica fume caused an insignificant change in volumetric strain results.

Piezoelectric Composites by Solid Freeform Fabrication: A Nature-Inspired Approach

NASA Astrophysics Data System (ADS)

Safari, A.; Akdoğan, E. K.

Piezoelectrics and electrostrictors are indispensable materials for use in transducer technology, as they inherently possess both direct (sensing) and converse (actuation) effects. A piezoelectric/electrostrictive sensor converts a mechanical input (displacement or force) into a measurable electrical output through piezoelectric/electrostrictive energy conversion. In the case of a piezoelectric, an applied mechanical force (stress) induces a voltage across the terminals of the transducer. On the other hand, an applied mechanical force induces a change in the capacitance of an electrostrictive transducer that could be electrically detected. Hence, the mechanical to electrical energy conversion is accomplished directly when a piezoelectric is used, while the same is obtained indirectly if the electroactive material of choice is an electrostrictor. Conversely, both piezoelectric and electrostrictive materials develop an elastic strain under an applied electric field. The said elastic strain is linearly proportional to the applied field in a piezoelectric, whereas electrostrictive coupling involves the second-order (quadratic) coupling of electric field with elastic strain. While piezoelectricity is possible only in noncentrosymetric point groups, electrostriction is observed in all solids, which make it a much more general solid-state phenomenon. Sensing and actuation functions can coexist in a given transducer by the intelligent use of such materials. Piezoelectrics and electrostrictors, therefore, constitute the backbone of modern transducer technology, as mechanical to electric energy (and vice versa) conversion can be accomplished with great efficiency in a way that is second to none among all phenomena known to date [1,2].

Biotypes analysis of Corynebacterium glutamicum growing in dicarboxylic acids demonstrates the existence of industrially-relevant intra-species variations.

PubMed

Pérez-García, Fernando; Vasco-Cárdenas, María F; Barreiro, Carlos

2016-09-02

Production enhancement of industrial microbial products or strains has been traditionally tackled by mutagenesis with chemical methods, irradiation or genetic manipulation. However, the final yield increase must go hand in hand with the resistance increasing against the usual inherent toxicity of the final products. Few studies have been carried out on resistance improvement and even fewer on the initial selection of naturally-generated biotypes, which could decrease the artificial mutagenesis. This fact is vital in the case of GRAS microorganisms as Corynebacterium glutamicum involved in food, feed and cosmetics production. The characteristic wide diversity and plasticity in terms of their genetic material of Actinobacteria eases the biotypes generation. Thus, differences in morphology, glutamate and lysine production and growth in media supplemented with dicarboxylic acids were analysed in four biotypes of C. glutamicum ATCC 13032. A 2D-DIGE analysis of these biotypes growing with itaconic acid allowed us to define their differences. Thus, an optimized central metabolism and better protection against the generated stress conditions present the CgL biotype as a suitable platform for production of itaconic acid, which is used as a building block (e.g.: acrylic plastic). This analysis highlights the preliminary biotypes screening as a way to reach optimal industrial productions.

Drawbacks of the use of cotrimoxazole in foreign-body infections.

PubMed

El Haj, Cristina; Ribera, Alba; Lloberas, Nuria; Tubau, Fe; Ariza, Javier; Murillo, Oscar

The anti-staphylococcal efficacy of cotrimoxazole in the setting of difficult-to-treat infections seems to be compromised by large amounts of pus and devitalized tissue, and, therefore, high levels of thymidine. Our objective was to evaluate the activity of cotrimoxazole against a staphylococcal foreign-body infection experimental model, which also yields significant quantities of thymidine. We used a rat tissue-cage model of infection (with high inherent thymidine levels) caused by a strain of methicillin-susceptible Staphylococcus aureus (MSSA; ATCC 29213). MIC values were determined (microdilution method) and compared in the presence or absence of tissue-cage fluid samples. The inefficacy of cotrimoxazole was found to be similar to that of the control group. The MIC of cotrimoxazole was 4-8 fold higher in the presence of rat tissue-cage fluid. The inefficacy of cotrimoxazole in our foreign-body infection model by MSSA, and the probable negative impact of the presence of thymidine on its efficacy, challenge the use of this drug in acute phases of foreign-body infections. It should be reserved as an alternative treatment when the infection is more controlled. Copyright © 2017 Elsevier España, S.L.U. and Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica. All rights reserved.

Draft sequencing and comparative genomics of Xylella fastidiosa strains reveal novel biological insights.

PubMed

Bhattacharyya, Anamitra; Stilwagen, Stephanie; Reznik, Gary; Feil, Helene; Feil, William S; Anderson, Iain; Bernal, Axel; D'Souza, Mark; Ivanova, Natalia; Kapatral, Vinayak; Larsen, Niels; Los, Tamara; Lykidis, Athanasios; Selkov, Eugene; Walunas, Theresa L; Purcell, Alexander; Edwards, Rob A; Hawkins, Trevor; Haselkorn, Robert; Overbeek, Ross; Kyrpides, Nikos C; Predki, Paul F

2002-10-01

Draft sequencing is a rapid and efficient method for determining the near-complete sequence of microbial genomes. Here we report a comparative analysis of one complete and two draft genome sequences of the phytopathogenic bacterium, Xylella fastidiosa, which causes serious disease in plants, including citrus, almond, and oleander. We present highlights of an in silico analysis based on a comparison of reconstructions of core biological subsystems. Cellular pathway reconstructions have been used to identify a small number of genes, which are likely to reside within the draft genomes but are not captured in the draft assembly. These represented only a small fraction of all genes and were predominantly large and small ribosomal subunit protein components. By using this approach, some of the inherent limitations of draft sequence can be significantly reduced. Despite the incomplete nature of the draft genomes, it is possible to identify several phage-related genes, which appear to be absent from the draft genomes and not the result of insufficient sequence sampling. This region may therefore identify potential host-specific functions. Based on this first functional reconstruction of a phytopathogenic microbe, we spotlight an unusual respiration machinery as a potential target for biological control. We also predicted and developed a new defined growth medium for Xylella.

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

Winstead, Cherese; Katagumpola, Pushpika

The degrees of substitution of chitosan derivatives were varied and the viscoelastic behavior of these biopolymer solutions was studied using rheology. Chitosan is a cationic copolymer of glucosamine and N-acetylglucosamine obtained by alkaline deacetylation of chitin. Due to its inherent non-toxicity, biocompatibility, and biodegradability, chitosan has gained much interest. However, the poor solubility of the biopolymer in water and most common organic solvents limits its applications. Therefore, the focus of this work is the chemical modification of chitosan via carboxymethylation as well as studying the viscoelastic behavior of these polymer solutions. Varying degrees of substitution (DS) of carboxymethyl chitosan derivativesmore » were synthesized by treating chitosan with monochloroacetic acid under alkylated medium varying the reaction time and temperature. The effect of degree of substitution on the rheology of these polymer solutions was studied as a function of concentration. The viscosity of chitosan derivatives sharply increased with increase in degree of substitution. G' and G' dependence on strain and angular frequency were studied and were found to exhibit predominantly viscous behavior. Additional characterization of the derivatized products were further studied using Fourier transform infrared (FT-IR), {sup 1}H Nuclear Magnetic Resonance ({sup 1}H NMR) spectroscopy, X-ray diffraction (XRD), and thermal gravimetric analysis as well as differential scanning calorimetry (DSC). Degree of substitution (DS) was calculated by titrimetric method.« less

Mesoscale Effective Property Simulations Incorporating Conductive Binder

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

Trembacki, Bradley L.; Noble, David R.; Brunini, Victor E.

Lithium-ion battery electrodes are composed of active material particles, binder, and conductive additives that form an electrolyte-filled porous particle composite. The mesoscale (particle-scale) interplay of electrochemistry, mechanical deformation, and transport through this tortuous multi-component network dictates the performance of a battery at the cell-level. Effective electrode properties connect mesoscale phenomena with computationally feasible battery-scale simulations. We utilize published tomography data to reconstruct a large subsection (1000+ particles) of an NMC333 cathode into a computational mesh and extract electrode-scale effective properties from finite element continuum-scale simulations. We present a novel method to preferentially place a composite binder phase throughout the mesostructure,more » a necessary approach due difficulty distinguishing between non-active phases in tomographic data. We compare stress generation and effective thermal, electrical, and ionic conductivities across several binder placement approaches. Isotropic lithiation-dependent mechanical swelling of the NMC particles and the consideration of strain-dependent composite binder conductivity significantly impact the resulting effective property trends and stresses generated. Lastly, our results suggest that composite binder location significantly affects mesoscale behavior, indicating that a binder coating on active particles is not sufficient and that more accurate approaches should be used when calculating effective properties that will inform battery-scale models in this inherently multi-scale battery simulation challenge.« less

New Generation Live Vaccines against Human Respiratory Syncytial Virus Designed by Reverse Genetics

PubMed Central

Collins, Peter L.; Murphy, Brian R.

2005-01-01

Development of a live pediatric vaccine against human respiratory syncytial virus (RSV) is complicated by the need to immunize young infants and the difficulty in balancing attenuation and immunogenicity. The ability to introduce desired mutations into infectious virus by reverse genetics provides a method for identifying and designing highly defined attenuating mutations. These can be introduced in combinations as desired to achieve gradations of attenuation. Attenuation is based on several strategies: multiple independent temperature-sensitive point mutations in the polymerase, a temperature-sensitive point mutation in a transcription signal, a set of non–temperature-sensitive mutations involving several genes, deletion of a viral RNA synthesis regulatory protein, and deletion of viral IFN α/β antagonists. The genetic stability of the live vaccine can be increased by judicious choice of mutations. The virus also can be engineered to increase the level of expression of the protective antigens. Protective antigens from antigenically distinct RSV strains can be added or swapped to increase the breadth of coverage. Alternatively, the major RSV protective antigens can be expressed from transcription units added to an attenuated parainfluenza vaccine virus, making a bivalent vaccine. This would obviate the difficulties inherent in the fragility and inefficient in vitro growth of RSV, simplifying vaccine design and use. PMID:16113487

Mesoscale Effective Property Simulations Incorporating Conductive Binder

DOE PAGES

Trembacki, Bradley L.; Noble, David R.; Brunini, Victor E.; ...

2017-07-26

Lithium-ion battery electrodes are composed of active material particles, binder, and conductive additives that form an electrolyte-filled porous particle composite. The mesoscale (particle-scale) interplay of electrochemistry, mechanical deformation, and transport through this tortuous multi-component network dictates the performance of a battery at the cell-level. Effective electrode properties connect mesoscale phenomena with computationally feasible battery-scale simulations. We utilize published tomography data to reconstruct a large subsection (1000+ particles) of an NMC333 cathode into a computational mesh and extract electrode-scale effective properties from finite element continuum-scale simulations. We present a novel method to preferentially place a composite binder phase throughout the mesostructure,more » a necessary approach due difficulty distinguishing between non-active phases in tomographic data. We compare stress generation and effective thermal, electrical, and ionic conductivities across several binder placement approaches. Isotropic lithiation-dependent mechanical swelling of the NMC particles and the consideration of strain-dependent composite binder conductivity significantly impact the resulting effective property trends and stresses generated. Lastly, our results suggest that composite binder location significantly affects mesoscale behavior, indicating that a binder coating on active particles is not sufficient and that more accurate approaches should be used when calculating effective properties that will inform battery-scale models in this inherently multi-scale battery simulation challenge.« less

A realistic appraisal of methods to enhance desiccation tolerance of entomopathogenic nematodes.

PubMed

Perry, Roland N; Ehlers, Ralf-Udo; Glazer, Itamar

2012-06-01

Understanding the desiccation survival attributes of infective juveniles of entomopathogenic nematodes (EPN) of the genera Steinernema and Heterorhabditis, is central to evaluating the reality of enhancing the shelf-life and field persistence of commercial formulations. Early work on the structural and physiological aspects of desiccation survival focused on the role of the molted cuticle in controlling the rate of water loss and the importance of energy reserves, particularly neutral lipids. The accumulation of trehalose was also found to enhance desiccation survival. Isolation of natural populations that can survive harsh environments, such as deserts, indicated that some populations have enhanced abilities to survive desiccation. However, survival abilities of EPN are limited compared with those of some species of plant-parasitic nematodes inhabiting aerial parts of plants. Research on EPN stress tolerance has expanded on two main lines: i) to select strains of species, currently in use commercially, which have increased tolerance to environmental extremes; and ii) to utilize molecular information, including expressed sequence tags and genome sequence data, to determine the underlying genetic factors that control longevity and stress tolerance of EPN. However, given the inherent limitations of EPN survival ability, it is likely that improved formulation will be the major factor to enhance EPN longevity and, perhaps, increase the range of applications.

Electrostatic transfer of epitaxial graphene to glass.

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

Ohta, Taisuke; Pan, Wei; Howell, Stephen Wayne

2010-12-01

We report on a scalable electrostatic process to transfer epitaxial graphene to arbitrary glass substrates, including Pyrex and Zerodur. This transfer process could enable wafer-level integration of graphene with structured and electronically-active substrates such as MEMS and CMOS. We will describe the electrostatic transfer method and will compare the properties of the transferred graphene with nominally-equivalent 'as-grown' epitaxial graphene on SiC. The electronic properties of the graphene will be measured using magnetoresistive, four-probe, and graphene field effect transistor geometries [1]. To begin, high-quality epitaxial graphene (mobility 14,000 cm2/Vs and domains >100 {micro}m2) is grown on SiC in an argon-mediated environmentmore » [2,3]. The electrostatic transfer then takes place through the application of a large electric field between the donor graphene sample (anode) and the heated acceptor glass substrate (cathode). Using this electrostatic technique, both patterned few-layer graphene from SiC(000-1) and chip-scale monolayer graphene from SiC(0001) are transferred to Pyrex and Zerodur substrates. Subsequent examination of the transferred graphene by Raman spectroscopy confirms that the graphene can be transferred without inducing defects. Furthermore, the strain inherent in epitaxial graphene on SiC(0001) is found to be partially relaxed after the transfer to the glass substrates.« less

A direct correlation of x-ray diffraction orientation distributions to the in-plane stiffness of semi-crystalline organic semiconducting films

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

Zhao, Bingxiao; Awartani, Omar; O'Connor, Brendan

2016-05-02

Large charge mobilities of semi-crystalline organic semiconducting films could be obtained by mechanically aligning the material phases of the film with the loading axis. A key element is to utilize the inherent stiffness of the material for optimal or desired alignment. However, experimentally determining the moduli of semi-crystalline organic thin films for different loading directions is difficult, if not impossible, due to film thickness and material anisotropy. In this paper, we address these challenges by presenting an approach based on combining a composite mechanics stiffness orientation formulation with a Gaussian statistical distribution to directly estimate the in-plane stiffness (transverse isotropy)more » of aligned semi-crystalline polymer films based on crystalline orientation distributions obtained by X-ray diffraction experimentally at different applied strains. Our predicted results indicate that the in-plane stiffness of an annealing film was initially isotropic, and then it evolved to transverse isotropy with increasing mechanical strains. This study underscores the significance of accounting for the crystalline orientation distributions of the film to obtain an accurate understanding and prediction of the elastic anisotropy of semi-crystalline polymer films.« less

Toward Systems Metabolic Engineering of Streptomycetes for Secondary Metabolites Production.

PubMed

Robertsen, Helene Lunde; Weber, Tilmann; Kim, Hyun Uk; Lee, Sang Yup

2018-01-01

Streptomycetes are known for their inherent ability to produce pharmaceutically relevant secondary metabolites. Discovery of medically useful, yet novel compounds has become a great challenge due to frequent rediscovery of known compounds and a consequent decline in the number of relevant clinical trials in the last decades. A paradigm shift took place when the first whole genome sequences of streptomycetes became available, from which silent or "cryptic" biosynthetic gene clusters (BGCs) were discovered. Cryptic BGCs reveal a so far untapped potential of the microorganisms for the production of novel compounds, which has spurred new efforts in understanding the complex regulation between primary and secondary metabolism. This new trend has been accompanied with development of new computational resources (genome and compound mining tools), generation of various high-quality omics data, establishment of molecular tools, and other strain engineering strategies. They all come together to enable systems metabolic engineering of streptomycetes, allowing more systematic and efficient strain development. In this review, the authors present recent progresses within systems metabolic engineering of streptomycetes for uncovering their hidden potential to produce novel compounds and for the improved production of secondary metabolites. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Antibacterial activity of local herbs collected from Murree (Pakistan) against multi-drug resistant Klebsiella pneumonae, E. coli and methyciline resistant Staphylococcus aureus.

PubMed

Mansoor, Qaisar; Shaheen, Saira; Javed, Uzma; Shaheen, Uzma; Iqrar, Irum; Ismail, Muhammad

2013-07-01

Exploring healing power in plants emerged in prehistory of human civilization. Sustaining good health has been achieved over the millions of years by use of plant products in various traditional sockets. A major contribution of medicinal plants to health care systems is their limitless possession of bioactive components that stimulate explicit physiological actions. Luckily Pakistan is blessed with huge reservoir of plants with medicinal potential and some of them; we focused in this study for their medicinal importance.In this study we checked the antibacterial activity inherent in Ricinus communis, Solanum nigrum, Dodonaea viscose and Berberis lyceum extracts for multidrug resistance bacterial strains Klebsiella pneumonae, E. coli and methyciline resistant Staphylococcus aureus. MRSA showed sensitivity for Ricinus communis. Multidrug resistant Klebsiella pneumonae was sensitive with Pine roxburgii and Ricinus communis but weakly susceptible for Solanum nigrum. Multidrug resistant E. coli was resistant to all plant extracts. Treatment of severe infections caused by the bacterial strains used in this study with Ricinus communis, Pine roxburgii and Solanum nigrum can lower the undesired side effects of synthetic medicine and also reduce the economic burden.

Systematic Phenotyping of a Large-Scale Candida glabrata Deletion Collection Reveals Novel Antifungal Tolerance Genes

PubMed Central

Hiller, Ekkehard; Istel, Fabian; Tscherner, Michael; Brunke, Sascha; Ames, Lauren; Firon, Arnaud; Green, Brian; Cabral, Vitor; Marcet-Houben, Marina; Jacobsen, Ilse D.; Quintin, Jessica; Seider, Katja; Frohner, Ingrid; Glaser, Walter; Jungwirth, Helmut; Bachellier-Bassi, Sophie; Chauvel, Murielle; Zeidler, Ute; Ferrandon, Dominique; Gabaldón, Toni; Hube, Bernhard; d'Enfert, Christophe; Rupp, Steffen; Cormack, Brendan; Haynes, Ken; Kuchler, Karl

2014-01-01

The opportunistic fungal pathogen Candida glabrata is a frequent cause of candidiasis, causing infections ranging from superficial to life-threatening disseminated disease. The inherent tolerance of C. glabrata to azole drugs makes this pathogen a serious clinical threat. To identify novel genes implicated in antifungal drug tolerance, we have constructed a large-scale C. glabrata deletion library consisting of 619 unique, individually bar-coded mutant strains, each lacking one specific gene, all together representing almost 12% of the genome. Functional analysis of this library in a series of phenotypic and fitness assays identified numerous genes required for growth of C. glabrata under normal or specific stress conditions, as well as a number of novel genes involved in tolerance to clinically important antifungal drugs such as azoles and echinocandins. We identified 38 deletion strains displaying strongly increased susceptibility to caspofungin, 28 of which encoding proteins that have not previously been linked to echinocandin tolerance. Our results demonstrate the potential of the C. glabrata mutant collection as a valuable resource in functional genomics studies of this important fungal pathogen of humans, and to facilitate the identification of putative novel antifungal drug target and virulence genes. PMID:24945925

A force compliant surgical robotic tool with IPMC actuator and integrated sensing

NASA Astrophysics Data System (ADS)

Fu, Lixue; McDaid, Andrew J.; Aw, Kean C.

2013-08-01

A robotic surgical device, actuated by Ionic Polymer-metal Composite (IPMC), integrated with a strain gauge to achieve force control is proposed. Test results have proved the capabilities of this device to conduct surgical procedures. The recent growth of patient acceptance and demand for robotic aided surgery has stimulated the progress of research where in many applications the performance has been proven to surpass human surgeons. A new area which uses the inherently force compliant and back-drivable properties of polymers, IPMC in this case, has shown its potential to undertake precise surgical procedures in delicate environments of medical practice. This is because IPMCs have similar actuation characteristics to real biological systems ensuring the safety of the practice. Nevertheless, little has been done in developing IPMCs as a rotary joint actuators used as functional surgical devices. This research demonstrates the design of a single degree of freedom (1DOF) robotic surgical instrument with one joint mechanism actuated by IPMC with an embedded strain gauge as a feedback unit, and controlled by a scheduled gain PI controller. With the simplicity of the system it was proven to be able to cut to the desired controlled force and hence depth.

Two-Fold Anisotropy Governs Morphological Evolution and Stress Generation in Sodiated Black Phosphorus for Sodium Ion Batteries.

PubMed

Chen, Tianwu; Zhao, Peng; Guo, Xu; Zhang, Sulin

2017-04-12

Phosphorus represents a promising anode material for sodium ion batteries owing to its extremely high theoretical capacity. Recent in situ transmission electron microscopy studies evidenced anisotropic swelling in sodiated black phosphorus, which may find an origin from the two intrinsic anisotropic properties inherent to the layered structure of black phosphorus: sodium diffusional directionality and insertion strain anisotropy. To understand the morphological evolution and stress generation in sodiated black phosphorus, we develop a chemo-mechanical model by incorporating the intrinsic anisotropic properties into the large elasto-plastic deformation. Our modeling results reveal that the apparent morphological evolution in sodiated black phosphorus is critically controlled by the coupled effect of the two intrinsic anisotropic properties. In particular, sodium diffusional directionality generates sharp interphases along the [010] and [001] directions, which constrain anisotropic development of the insertion strain. The coupled effect renders distinctive stress-generation and fracture mechanisms when sodiation starts from different crystal facets. In addition to providing a powerful modeling framework for sodiation and lithiation of layered structures, our findings shed significant light on the sodiation-induced chemo-mechanical degradation of black phosphorus as a promising anode for the next-generation sodium ion batteries.

Sublethal detergent concentrations increase metabolization of recalcitrant polyphosphonates by the cyanobacterium Spirulina platensis.

PubMed

Forlani, Giuseppe; Bertazzini, Michele; Giberti, Samuele; Wieczorek, Dorota; Kafarski, Paweł; Lipok, Jacek

2013-05-01

As a consequence of increasing industrial applications, thousand tons of polyphosphonates are introduced every year into the environment. The inherent stability of the C-P bond results in a prolonged half-life. Moreover, low uptake rates limit further their microbial metabolization. To assess whether low detergent concentrations were able to increase polyphosphonate utilization by the cyanobacterium Spirulina platensis, tolerance limits to the exposure to various detergents were determined by measuring the growth rate in the presence of graded levels below the critical micellar concentration. Then, the amount of hexamethylenediamine-N,N,N',N'-tetrakis(methylphosphonic acid) that is metabolized in the absence or in the presence of sublethal detergent concentrations was quantified by (31)P NMR analysis on either P-starved or P-fed cyanobacterial cultures. The strain tolerated the presence of detergents in the order: nonionic > anionic > cationic. When added to the culture medium at the highest concentrations showing no detrimental effects upon cell viability, detergents either improved or decreased polyphosphonate utilization, the anionic sodium dodecyl sulfate being the most beneficial. Metabolization was not lower in P-fed cells--a result that strengthens the possibility of using, in the future, this strain for bioremediation purposes.

A comparison of the fatigue behavior of cast Ti-7.5Mo with c.p. titanium, Ti-6Al-4V and Ti-13Nb-13Zr alloys.

PubMed

Lin, Chia-Wei; Ju, Chien-Ping; Chern Lin, Jiin-Huey

2005-06-01

The purpose of the present study is to compare the high-cycle fatigue behavior of newly developed Ti-7.5Mo alloy with that of c.p. Ti, Ti-13Nb-13Zr and Ti-6Al-4V alloys in their as-cast state. Experimental results indicate that Ti-6Al-4V and c.p. Ti have higher stress-controlled fatigue resistance but lower strain-controlled fatigue resistance than Ti-7.5Mo and Ti-13Nb-13Zr. Among four materials Ti-7.5Mo demonstrates the best strain-controlled fatigue performance. The fracture surfaces of the present materials are comprised of three morphologically distinct zones: crack initiation zone, crack propagation zone, and the final-stage overload zone. The fatigue cracks almost always initiate from casting-induced surface/subsurface pores. A river pattern is observed in the propagation zone. In the overload zone dimples are typically observed. Three factors most significantly affecting the fatigue performance of the present materials are the presence of the casting-induced surface/subsurface pores; the location of the pores; and the inherent mechanical properties of the materials.

Reversed structures and bounce structures: are they recognizable? Are they real?

NASA Astrophysics Data System (ADS)

Means, W. D.

1999-08-01

This note poses two related questions about structural evolution in rocks. How easy is it to recognize structural features that have reversed their sense of development over time? Are there circumstances in rock deformation where early intensification of structure sows the seeds for a later, more or less inevitable, diminution of intensity? It is suggested, as a partial answer to the first question, that there is an irreversibility principle inherent to most structural development, such that even if bulk strain is reversed, the structural changes that accompanied `forward' structural development will not be completely reversed when the strain is reversed. Where this principle applies, it should always be possible to recognize structural reversals, by sufficiently close observation of the final state. It is suggested, as a partial answer to the second question, that where energy is stored by forward structural changes, this energy can often be expected to drive further structural changes, and these further changes may sometimes cause the original structure to `bounce' back to a less intense state. These questions may have some bearing on developing a firmer basis for kinematic analysis, and for understanding overprinting structures in orogens.

Method of producing strained-layer semiconductor devices via subsurface-patterning

DOEpatents

Dodson, Brian W.

1993-01-01

A method is described for patterning subsurface features in a semiconductor device, wherein the semiconductor device includes an internal strained layer. The method comprises creating a pattern of semiconductor material over the semiconductor device, the semiconductor material having a predetermined thickness which stabilizes areas of the strained semiconductor layer that lie beneath the pattern. Subsequently, a heating step is applied to the semiconductor device to cause a relaxation in areas of the strained layer which do not lie beneath the semiconductor material pattern, whereby dislocations result in the relaxed areas and impair electrical transport therethrough.

[Molecular-genetic characteristics of Mycobacterium tuberculosis strains isolated from patients with tuberculous spondylitis].

PubMed

Viazovaia, A A; Solov'eva, N S; Zhuravlev, V Iu; Mokrousov, I V; Manicheva, O A; Vishnevskiĭ, B I; Narvskaia, O V

2013-01-01

Molecular-genetic characteristic of M. tuberculosis strains isolated from operation material of patients with tuberculous spondylitis. 107 strains of M. tuberculosis isolated in 2007 - 2011 from patients with spine tuberculosis were studied by methods of spoligotyping and MIRU-VNTR by 12 and 24 loci. Strains of genetic family Beijing dominated (n = 80), 78% of those had multiple drug resistance (MDR). Strains of genetic families T, H3 (Ural), LAM, Manu, H4 and S were also detected. Differentiating of 80 strains of Beijing genotype by MIRU-VNTR method by 24 loci revealed 24 variants (HGI = 0.83) including 7 clusters, the largest of those (100-32) included 23 strains (87% MDR). The leading role of Beijing genotype M. tuberculosis strains in development of tuberculous spondylitis with multiple drug resistance of the causative agent is shown.

Direct measurement of intrinsic critical strain and internal strain in barrier films

NASA Astrophysics Data System (ADS)

Vellinga, W. P.; De Hosson, J. Th. M.; Bouten, P. C. P.

2011-08-01

Resistance measurements during uniaxial tensile deformation of very thin (10 nm) conducting oxide films deposited on 150 nm SiN films on polyethylene naphthalate are discussed. It is first shown that certain characteristics of resistance versus strain curves are representative for the fracture behavior of the SiN film and not for that of the thin conducting oxide film. Subsequently, it is shown that the hysteresis in curves of resistance as a function of strain offers a way to directly measure the intrinsic critical strain of the SiN film without the need to determine internal strains from independent (curvature) measurements that rely on knowledge of moduli and geometry. The method should be applicable, in general, to measure intrinsic critical strain and residual strains of thin brittle films on polymers. Advantages and limitations of the method are discussed.

Current Taxonomical Situation of Streptococcus suis.

PubMed

Okura, Masatoshi; Osaki, Makoto; Nomoto, Ryohei; Arai, Sakura; Osawa, Ro; Sekizaki, Tsutomu; Takamatsu, Daisuke

2016-06-24

Streptococcus suis, a major porcine pathogen and an important zoonotic agent, is considered to be composed of phenotypically and genetically diverse strains. However, recent studies reported several "S. suis-like strains" that were identified as S. suis by commonly used methods for the identification of this bacterium, but were regarded as distinct species from S. suis according to the standards of several taxonomic analyses. Furthermore, it has been suggested that some S. suis-like strains can be assigned to several novel species. In this review, we discuss the current taxonomical situation of S. suis with a focus on (1) the classification history of the taxon of S. suis; (2) S. suis-like strains revealed by taxonomic analyses; (3) methods for detecting and identifying this species, including a novel method that can distinguish S. suis isolates from S. suis-like strains; and (4) current topics on the reclassification of S. suis-like strains.

Investigation of the interpolation method to improve the distributed strain measurement accuracy in optical frequency domain reflectometry systems.

PubMed

Cui, Jiwen; Zhao, Shiyuan; Yang, Di; Ding, Zhenyang

2018-02-20

We use a spectrum interpolation technique to improve the distributed strain measurement accuracy in a Rayleigh-scatter-based optical frequency domain reflectometry sensing system. We demonstrate that strain accuracy is not limited by the "uncertainty principle" that exists in the time-frequency analysis. Different interpolation methods are investigated and used to improve the accuracy of peak position of the cross-correlation and, therefore, improve the accuracy of the strain. Interpolation implemented by padding zeros on one side of the windowed data in the spatial domain, before the inverse fast Fourier transform, is found to have the best accuracy. Using this method, the strain accuracy and resolution are both improved without decreasing the spatial resolution. The strain of 3 μϵ within the spatial resolution of 1 cm at the position of 21.4 m is distinguished, and the measurement uncertainty is 3.3 μϵ.

A novel and rapid method for obtaining high titre intact prion strains from mammalian brain.

PubMed

Wenborn, Adam; Terry, Cassandra; Gros, Nathalie; Joiner, Susan; D'Castro, Laura; Panico, Silvia; Sells, Jessica; Cronier, Sabrina; Linehan, Jacqueline M; Brandner, Sebastian; Saibil, Helen R; Collinge, John; Wadsworth, Jonathan D F

2015-05-07

Mammalian prions exist as multiple strains which produce characteristic and highly reproducible phenotypes in defined hosts. How this strain diversity is encoded by a protein-only agent remains one of the most interesting and challenging questions in biology with wide relevance to understanding other diseases involving the aggregation or polymerisation of misfolded host proteins. Progress in understanding mammalian prion strains has however been severely limited by the complexity and variability of the methods used for their isolation from infected tissue and no high resolution structures have yet been reported. Using high-throughput cell-based prion bioassay to re-examine prion purification from first principles we now report the isolation of prion strains to exceptional levels of purity from small quantities of infected brain and demonstrate faithful retention of biological and biochemical strain properties. The method's effectiveness and simplicity should facilitate its wide application and expedite structural studies of prions.

Methods of manipulating stressed epistructures

DOEpatents

Wanlass, Mark W

2014-04-08

A method of processing an epistructure or processing a semiconductor device including associating a conformal and flexible handle with the epistructure and removing the epistructure and handle as a unit from the parent substrate. The method further includes causing the epistructure and handle unit to conform to a shape that differs from the shape the epistructure otherwise inherently assumes upon removal from the parent substrate. A device prepared according to the disclosed methods.

Methods for Maintaining Insect Cell Cultures

PubMed Central

Lynn, Dwight E.

2002-01-01

Insect cell cultures are now commonly used in insect physiology, developmental biology, pathology, and molecular biology. As the field has advanced from methods development to a standard procedure, so has the diversity of scientists using the technique. This paper describes methods that are effective for maintaining various insect cell lines. The procedures are differentiated between loosely or non-attached cell strains, attached cell strains, and strongly adherent cell strains. PMID:15455043

Development of a multiplex PCR-based rapid typing method for enterohemorrhagic Escherichia coli O157 strains.

PubMed

Ooka, Tadasuke; Terajima, Jun; Kusumoto, Masahiro; Iguchi, Atsushi; Kurokawa, Ken; Ogura, Yoshitoshi; Asadulghani, Md; Nakayama, Keisuke; Murase, Kazunori; Ohnishi, Makoto; Iyoda, Sunao; Watanabe, Haruo; Hayashi, Tetsuya

2009-09-01

Enterohemorrhagic Escherichia coli O157 (EHEC O157) is a food-borne pathogen that has raised worldwide public health concern. The development of simple and rapid strain-typing methods is crucial for the rapid detection and surveillance of EHEC O157 outbreaks. In the present study, we developed a multiplex PCR-based strain-typing method for EHEC O157, which is based on the variability in genomic location of IS629 among EHEC O157 strains. This method is very simple, in that the procedures are completed within 2 h, the analysis can be performed without the need for special equipment or techniques (requiring only conventional PCR and agarose gel electrophoresis systems), the results can easily be transformed into digital data, and the genes for the major virulence markers of EHEC O157 (the stx(1), stx(2), and eae genes) can be detected simultaneously. Using this method, 201 EHEC O157 strains showing different XbaI digestion patterns in pulsed-field gel electrophoresis (PFGE) analysis were classified into 127 types, and outbreak-related strains showed identical or highly similar banding patterns. Although this method is less discriminatory than PFGE, it may be useful as a primary screening tool for EHEC O157 outbreaks.

A permutation testing framework to compare groups of brain networks.

PubMed

Simpson, Sean L; Lyday, Robert G; Hayasaka, Satoru; Marsh, Anthony P; Laurienti, Paul J

2013-01-01

Brain network analyses have moved to the forefront of neuroimaging research over the last decade. However, methods for statistically comparing groups of networks have lagged behind. These comparisons have great appeal for researchers interested in gaining further insight into complex brain function and how it changes across different mental states and disease conditions. Current comparison approaches generally either rely on a summary metric or on mass-univariate nodal or edge-based comparisons that ignore the inherent topological properties of the network, yielding little power and failing to make network level comparisons. Gleaning deeper insights into normal and abnormal changes in complex brain function demands methods that take advantage of the wealth of data present in an entire brain network. Here we propose a permutation testing framework that allows comparing groups of networks while incorporating topological features inherent in each individual network. We validate our approach using simulated data with known group differences. We then apply the method to functional brain networks derived from fMRI data.

Improved Accuracy of the Inherent Shrinkage Method for Fast and More Reliable Welding Distortion Calculations

NASA Astrophysics Data System (ADS)

Mendizabal, A.; González-Díaz, J. B.; San Sebastián, M.; Echeverría, A.

2016-07-01

This paper describes the implementation of a simple strategy adopted for the inherent shrinkage method (ISM) to predict welding-induced distortion. This strategy not only makes it possible for the ISM to reach accuracy levels similar to the detailed transient analysis method (considered the most reliable technique for calculating welding distortion) but also significantly reduces the time required for these types of calculations. This strategy is based on the sequential activation of welding blocks to account for welding direction and transient movement of the heat source. As a result, a significant improvement in distortion prediction is achieved. This is demonstrated by experimentally measuring and numerically analyzing distortions in two case studies: a vane segment subassembly of an aero-engine, represented with 3D-solid elements, and a car body component, represented with 3D-shell elements. The proposed strategy proves to be a good alternative for quickly estimating the correct behaviors of large welded components and may have important practical applications in the manufacturing industry.

Evaluation of New Repair Methods for Seal Surface Defects on Reusable Solid Rocket Motor (RSRM) Hardware

NASA Technical Reports Server (NTRS)

Stanley, Stephanie; Selvidge, Shawn

2003-01-01

The focus of the evaluation was to develop a back-up method to cell plating for the improvement or repair of seal surface defects within D6-AC steel and 7075-T73 aluminum used in the RSRM program. Several techniques were investigated including thermal and non-thermal based techniques. Ideally the repair would maintain the inherent properties of the substrate without losing integrity at the repair site. The repaired sites were tested for adhesion, corrosion, hardness, microhardness, surface toughness, thermal stability, ability to withstand bending of the repair site, and the ability to endure a high-pressure water blast without compromising the repaired site. The repaired material could not change the inherent properties of the substrate throughout each of the test in order to remain a possible technique to repair the RSRM substrate materials. One repair method, Electro-Spark Alloying, passed all the testing and is considered a candidate for further evaluation.

Evaluation of New Repair Methods for Seal Surface Defects on Reusable Solid Rocket Motor (RSRM) Hardware

NASA Technical Reports Server (NTRS)

Stanley, Stephanie D.; Selvidge, Shawn A.; Cash, Steve (Technical Monitor)

2002-01-01

The focus of the evaluation was to develop a back-up method to cell plating for the improvement or repair of seal surface defects within D6-AC steel and 7075-T73 aluminum used in the RSRM program. Several techniques were investigated including thermal and non-thermal based techniques. Ideally the repair would maintain the inherent properties of the substrate without losing integrity at the repair site. The repaired sites were tested for adhesion, corrosion, hardness, microhardness, surface toughness, thermal stability, ability to withstand bending of the repair site, and the ability to endure a high-pressure water blast without compromising the repaired site. The repaired material could not change the inherent properties of the substrate throughout each of the test in order to remain a possible technique to repair the RSRM substrate materials. One repair method, Electro-Spark Alloying, passed all the testing and is considered a candidate for further evaluation.

Preserving Simplecticity in the Numerical Integration of Linear Beam Optics

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

Allen, Christopher K.

2017-07-01

Presented are mathematical tools and methods for the development of numerical integration techniques that preserve the symplectic condition inherent to mechanics. The intended audience is for beam physicists with backgrounds in numerical modeling and simulation with particular attention to beam optics applications. The paper focuses on Lie methods that are inherently symplectic regardless of the integration accuracy order. Section 2 provides the mathematically tools used in the sequel and necessary for the reader to extend the covered techniques. Section 3 places those tools in the context of charged-particle beam optics; in particular linear beam optics is presented in terms ofmore » a Lie algebraic matrix representation. Section 4 presents numerical stepping techniques with particular emphasis on a third-order leapfrog method. Section 5 discusses the modeling of field imperfections with particular attention to the fringe fields of quadrupole focusing magnets. The direct computation of a third order transfer matrix for a fringe field is shown.« less

Topical Review: Unique Contributions of Magnetic Resonance Imaging to Pediatric Psychology Research.

PubMed

Jensen, Chad D; Duraccio, Kara M; Carbine, Kaylie M; Kirwan, C Brock

2016-03-01

This review aims to provide a brief introduction of the utility of magnetic resonance imaging (MRI) methods in pediatric psychology research, describe several exemplar studies that highlight the unique benefits of MRI techniques for pediatric psychology research, and detail methods for addressing several challenges inherent to pediatric MRI research. Literature review. Numerous useful applications of MRI research in pediatric psychology have been illustrated in published research. MRI methods yield information that cannot be obtained using neuropsychological or behavioral measures. Using MRI in pediatric psychology research may facilitate examination of neural structures and processes that underlie health behaviors. Challenges inherent to conducting MRI research with pediatric research participants (e.g., head movement) may be addressed using evidence-based strategies. We encourage pediatric psychology researchers to consider adopting MRI techniques to answer research questions relevant to pediatric health and illness. © The Author 2015. Published by Oxford University Press on behalf of the Society of Pediatric Psychology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Strain Prioritization for Natural Product Discovery by a High-Throughput Real-Time PCR Method

PubMed Central

2015-01-01

Natural products offer unmatched chemical and structural diversity compared to other small-molecule libraries, but traditional natural product discovery programs are not sustainable, demanding too much time, effort, and resources. Here we report a strain prioritization method for natural product discovery. Central to the method is the application of real-time PCR, targeting genes characteristic to the biosynthetic machinery of natural products with distinct scaffolds in a high-throughput format. The practicality and effectiveness of the method were showcased by prioritizing 1911 actinomycete strains for diterpenoid discovery. A total of 488 potential diterpenoid producers were identified, among which six were confirmed as platensimycin and platencin dual producers and one as a viguiepinol and oxaloterpin producer. While the method as described is most appropriate to prioritize strains for discovering specific natural products, variations of this method should be applicable to the discovery of other classes of natural products. Applications of genome sequencing and genome mining to the high-priority strains could essentially eliminate the chance elements from traditional discovery programs and fundamentally change how natural products are discovered. PMID:25238028

Using Blogs in Qualitative Educational Research: An Exploration of Method

ERIC Educational Resources Information Center

Harricharan, Michelle; Bhopal, Kalwant

2014-01-01

When compared with wider social research, qualitative educational research has been relatively slow to take up online research methods (ORMs). There is some very notable research in the area but, in general, ORMs have not achieved wide applicability in qualitative educational contexts apart from research that is inherently linked to the Internet,…

A new method for fingerprinting sediments source contributions using distances from discriminant function analysis

USDA-ARS?s Scientific Manuscript database

Mixing models have been used to predict sediment source contributions. The inherent problem of the mixing models limited the number of sediment sources. The objective of this study is to develop and evaluate a new method using Discriminant Function Analysis (DFA) to fingerprint sediment source contr...

Tools for the Classroom? an Examination of Existing Sociometric Methods for Teacher Use

ERIC Educational Resources Information Center

McMullen, Jake A.; Veermans, Koen; Laine, Kaarina

2014-01-01

Despite the recent technical and theoretical advances in the investigation of children's social relations, the inherent complexity of these methods may prevent their easy integration into the classroom. A simple and effective tool can be valuable for teachers who wish to investigate students' social realities in the classroom. Therefore, the…

Characterizing source-sink dynamics with genetic parentage assignments

Treesearch

M. Zachariah Peery; Steven R. Beissinger; Roger F. House; Martine Berube; Laurie A. Hall; Anna Sellas; Per J. Palsboll

2008-01-01

Source-sink dynamics have been suggested to characterize the population structure of many species, but the prevalence of source-sink systems in nature is uncertain because of inherent challenges in estimating migration rates among populations. Migration rates are often difficult to estimate directly with demographic methods, and indirect genetic methods are subject to...

Evaluating Special Educator Effectiveness: Addressing Issues Inherent to Value-Added Modeling

ERIC Educational Resources Information Center

Steinbrecher, Trisha D.; Selig, James P.; Cosbey, Joanna; Thorstensen, Beata I.

2014-01-01

States are increasingly using value-added approaches to evaluate teacher effectiveness. There is much debate regarding whether these methods should be employed and, if employed, what role such methods should play in comprehensive teacher evaluation systems. In this article, we consider the use of value-added modeling (VAM) to evaluate special…

Situating Qualitative Modes of Inquiry within the Discipline of Statistics Education Research

ERIC Educational Resources Information Center

Groth, Randall E.

2010-01-01

Qualitative methods have become common in statistics education research, but questions linger about their role in scholarship. Currently, influential policy documents lend credence to the notion that qualitative methods are inherently inferior to quantitative ones. In this paper, several of the questions about qualitative research raised in recent…

Is Aggression the Same for Boys and Girls? Assessing Measurement Invariance with Confirmatory Factor Analysis and Item Response Theory

ERIC Educational Resources Information Center

Kim, Sangwon; Kim, Seock-Ho; Kamphaus, Randy W.

2010-01-01

Gender differences in aggression have typically been based on studies utilizing a mean difference method. From a measurement perspective, this method is inherently problematic unless an aggression measure possesses comparable validity across gender. Stated differently, establishing measurement invariance on the measure of aggression is…

Multiscale Reactive Molecular Dynamics

DTIC Science & Technology

2012-08-15

biology cannot be described without considering electronic and nuclear-level dynamics and their coupling to slower, cooperative motions of the system ...coupling to slower, cooperative motions of the system . These inherently multiscale problems require computationally efficient and accurate methods to...condensed phase systems with computational efficiency orders of magnitudes greater than currently possible with ab initio simulation methods, thus

Evaluation of a Multi-Case Participatory Action Research Project: The Case of SOLINSA

ERIC Educational Resources Information Center

Home, Robert; Rump, Niels

2015-01-01

Purpose: Scholars agree that evaluation of participatory action research is inherently valuable; however there have been few attempts at evaluating across methods and across interventions because the perceived success of a method is affected by context, researcher skills and the aims of the participants. This paper describes the systematic…

A maximum likelihood approach to diffeomorphic speckle tracking for 3D strain estimation in echocardiography.

PubMed

Curiale, Ariel H; Vegas-Sánchez-Ferrero, Gonzalo; Bosch, Johan G; Aja-Fernández, Santiago

2015-08-01

The strain and strain-rate measures are commonly used for the analysis and assessment of regional myocardial function. In echocardiography (EC), the strain analysis became possible using Tissue Doppler Imaging (TDI). Unfortunately, this modality shows an important limitation: the angle between the myocardial movement and the ultrasound beam should be small to provide reliable measures. This constraint makes it difficult to provide strain measures of the entire myocardium. Alternative non-Doppler techniques such as Speckle Tracking (ST) can provide strain measures without angle constraints. However, the spatial resolution and the noisy appearance of speckle still make the strain estimation a challenging task in EC. Several maximum likelihood approaches have been proposed to statistically characterize the behavior of speckle, which results in a better performance of speckle tracking. However, those models do not consider common transformations to achieve the final B-mode image (e.g. interpolation). This paper proposes a new maximum likelihood approach for speckle tracking which effectively characterizes speckle of the final B-mode image. Its formulation provides a diffeomorphic scheme than can be efficiently optimized with a second-order method. The novelty of the method is threefold: First, the statistical characterization of speckle generalizes conventional speckle models (Rayleigh, Nakagami and Gamma) to a more versatile model for real data. Second, the formulation includes local correlation to increase the efficiency of frame-to-frame speckle tracking. Third, a probabilistic myocardial tissue characterization is used to automatically identify more reliable myocardial motions. The accuracy and agreement assessment was evaluated on a set of 16 synthetic image sequences for three different scenarios: normal, acute ischemia and acute dyssynchrony. The proposed method was compared to six speckle tracking methods. Results revealed that the proposed method is the most accurate method to measure the motion and strain with an average median motion error of 0.42 mm and a median strain error of 2.0 ± 0.9%, 2.1 ± 1.3% and 7.1 ± 4.9% for circumferential, longitudinal and radial strain respectively. It also showed its capability to identify abnormal segments with reduced cardiac function and timing differences for the dyssynchrony cases. These results indicate that the proposed diffeomorphic speckle tracking method provides robust and accurate motion and strain estimation. Copyright © 2015. Published by Elsevier B.V.

Improved method to fully compensate the spatial phase nonuniformity of LCoS devices with a Fizeau interferometer.

PubMed

Lu, Qiang; Sheng, Lei; Zeng, Fei; Gao, Shijie; Qiao, Yanfeng

2016-10-01

Liquid crystal on silicon (LCoS) devices usually show spatial phase nonuniformity (SPNU) in applications of phase modulation, which comprises the phase retardance nonuniformity (PRNU) as a function of the applied voltage and inherent wavefront distortion (WFD) introduced by the device itself. We propose a multipoint calibration method utilizing a Fizeau interferometer to compensate SPNU of the device. Calibration of PRNU is realized by defining a grid of 3×6 cells onto the aperture and then calculating phase retardance of each cell versus a gradient gray pattern. With designing an adjusted gray pattern calculated by the calibrated multipoint phase retardance function, compensation of inherent WFD is achieved. The peak-to-valley (PV) value of the residual WFD compensated by the multipoint calibration method is significantly reduced from 2.5λ to 0.140λ, while the PV value of the residual WFD after global calibration is reduced to 0.364λ. Experimental results of the generated finite-energy 2D Airy beams in Fourier space demonstrate the effectiveness of this multipoint calibration method.

True orbit simulation of piecewise linear and linear fractional maps of arbitrary dimension using algebraic numbers

NASA Astrophysics Data System (ADS)

Saito, Asaki; Yasutomi, Shin-ichi; Tamura, Jun-ichi; Ito, Shunji

2015-06-01

We introduce a true orbit generation method enabling exact simulations of dynamical systems defined by arbitrary-dimensional piecewise linear fractional maps, including piecewise linear maps, with rational coefficients. This method can generate sufficiently long true orbits which reproduce typical behaviors (inherent behaviors) of these systems, by properly selecting algebraic numbers in accordance with the dimension of the target system, and involving only integer arithmetic. By applying our method to three dynamical systems—that is, the baker's transformation, the map associated with a modified Jacobi-Perron algorithm, and an open flow system—we demonstrate that it can reproduce their typical behaviors that have been very difficult to reproduce with conventional simulation methods. In particular, for the first two maps, we show that we can generate true orbits displaying the same statistical properties as typical orbits, by estimating the marginal densities of their invariant measures. For the open flow system, we show that an obtained true orbit correctly converges to the stable period-1 orbit, which is inherently possessed by the system.

A Tensor-Based Subspace Approach for Bistatic MIMO Radar in Spatial Colored Noise

PubMed Central

Wang, Xianpeng; Wang, Wei; Li, Xin; Wang, Junxiang

2014-01-01

In this paper, a new tensor-based subspace approach is proposed to estimate the direction of departure (DOD) and the direction of arrival (DOA) for bistatic multiple-input multiple-output (MIMO) radar in the presence of spatial colored noise. Firstly, the received signals can be packed into a third-order measurement tensor by exploiting the inherent structure of the matched filter. Then, the measurement tensor can be divided into two sub-tensors, and a cross-covariance tensor is formulated to eliminate the spatial colored noise. Finally, the signal subspace is constructed by utilizing the higher-order singular value decomposition (HOSVD) of the cross-covariance tensor, and the DOD and DOA can be obtained through the estimation of signal parameters via rotational invariance technique (ESPRIT) algorithm, which are paired automatically. Since the multidimensional inherent structure and the cross-covariance tensor technique are used, the proposed method provides better angle estimation performance than Chen's method, the ESPRIT algorithm and the multi-SVD method. Simulation results confirm the effectiveness and the advantage of the proposed method. PMID:24573313

A tensor-based subspace approach for bistatic MIMO radar in spatial colored noise.

PubMed

Wang, Xianpeng; Wang, Wei; Li, Xin; Wang, Junxiang

2014-02-25

In this paper, a new tensor-based subspace approach is proposed to estimate the direction of departure (DOD) and the direction of arrival (DOA) for bistatic multiple-input multiple-output (MIMO) radar in the presence of spatial colored noise. Firstly, the received signals can be packed into a third-order measurement tensor by exploiting the inherent structure of the matched filter. Then, the measurement tensor can be divided into two sub-tensors, and a cross-covariance tensor is formulated to eliminate the spatial colored noise. Finally, the signal subspace is constructed by utilizing the higher-order singular value decomposition (HOSVD) of the cross-covariance tensor, and the DOD and DOA can be obtained through the estimation of signal parameters via rotational invariance technique (ESPRIT) algorithm, which are paired automatically. Since the multidimensional inherent structure and the cross-covariance tensor technique are used, the proposed method provides better angle estimation performance than Chen's method, the ESPRIT algorithm and the multi-SVD method. Simulation results confirm the effectiveness and the advantage of the proposed method.

Inherent Structure versus Geometric Metric for State Space Discretization

PubMed Central

Liu, Hanzhong; Li, Minghai; Fan, Jue; Huo, Shuanghong

2016-01-01

Inherent structure (IS) and geometry-based clustering methods are commonly used for analyzing molecular dynamics trajectories. ISs are obtained by minimizing the sampled conformations into local minima on potential/effective energy surface. The conformations that are minimized into the same energy basin belong to one cluster. We investigate the influence of the applications of these two methods of trajectory decomposition on our understanding of the thermodynamics and kinetics of alanine tetrapeptide. We find that at the micro cluster level, the IS approach and root-mean-square deviation (RMSD) based clustering method give totally different results. Depending on the local features of energy landscape, the conformations with close RMSDs can be minimized into different minima, while the conformations with large RMSDs could be minimized into the same basin. However, the relaxation timescales calculated based on the transition matrices built from the micro clusters are similar. The discrepancy at the micro cluster level leads to different macro clusters. Although the dynamic models established through both clustering methods are validated approximately Markovian, the IS approach seems to give a meaningful state space discretization at the macro cluster level. PMID:26915811

The analysis and utilization of cycling training data.

PubMed

Jobson, Simon A; Passfield, Louis; Atkinson, Greg; Barton, Gabor; Scarf, Philip

2009-01-01

Most mathematical models of athletic training require the quantification of training intensity and quantity or 'dose'. We aim to summarize both the methods available for such quantification, particularly in relation to cycle sport, and the mathematical techniques that may be used to model the relationship between training and performance. Endurance athletes have used training volume (kilometres per week and/or hours per week) as an index of training dose with some success. However, such methods usually fail to accommodate the potentially important influence of training intensity. The scientific literature has provided some support for alternative methods such as the session rating of perceived exertion, which provides a subjective quantification of the intensity of exercise; and the heart rate-derived training impulse (TRIMP) method, which quantifies the training stimulus as a composite of external loading and physiological response, multiplying the training load (stress) by the training intensity (strain). Other methods described in the scientific literature include 'ordinal categorization' and a heart rate-based excess post-exercise oxygen consumption method. In cycle sport, mobile cycle ergometers (e.g. SRM and PowerTap) are now widely available. These devices allow the continuous measurement of the cyclists' work rate (power output) when riding their own bicycles during training and competition. However, the inherent variability in power output when cycling poses several challenges in attempting to evaluate the exact nature of a session. Such variability means that average power output is incommensurate with the cyclist's physiological strain. A useful alternative may be the use of an exponentially weighted averaging process to represent the data as a 'normalized power'. Several research groups have applied systems theory to analyse the responses to physical training. Impulse-response models aim to relate training loads to performance, taking into account the dynamic and temporal characteristics of training and, therefore, the effects of load sequences over time. Despite the successes of this approach it has some significant limitations, e.g. an excessive number of performance tests to determine model parameters. Non-linear artificial neural networks may provide a more accurate description of the complex non-linear biological adaptation process. However, such models may also be constrained by the large number of datasets required to 'train' the model. A number of alternative mathematical approaches such as the Performance-Potential-Metamodel (PerPot), mixed linear modelling, cluster analysis and chaos theory display conceptual richness. However, much further research is required before such approaches can be considered as viable alternatives to traditional impulse-response models. Some of these methods may not provide useful information about the relationship between training and performance. However, they may help describe the complex physiological training response phenomenon.

Conservation properties of numerical integration methods for systems of ordinary differential equations

NASA Technical Reports Server (NTRS)

Rosenbaum, J. S.

1976-01-01

If a system of ordinary differential equations represents a property conserving system that can be expressed linearly (e.g., conservation of mass), it is then desirable that the numerical integration method used conserve the same quantity. It is shown that both linear multistep methods and Runge-Kutta methods are 'conservative' and that Newton-type methods used to solve the implicit equations preserve the inherent conservation of the numerical method. It is further shown that a method used by several authors is not conservative.

A three-dimensional strain measurement method in elastic transparent materials using tomographic particle image velocimetry

PubMed Central

Suzuki, Sara; Aoyama, Yusuke; Umezu, Mitsuo

2017-01-01

Background The mechanical interaction between blood vessels and medical devices can induce strains in these vessels. Measuring and understanding these strains is necessary to identify the causes of vascular complications. This study develops a method to measure the three-dimensional (3D) distribution of strain using tomographic particle image velocimetry (Tomo-PIV) and compares the measurement accuracy with the gauge strain in tensile tests. Methods and findings The test system for measuring 3D strain distribution consists of two cameras, a laser, a universal testing machine, an acrylic chamber with a glycerol water solution for adjusting the refractive index with the silicone, and dumbbell-shaped specimens mixed with fluorescent tracer particles. 3D images of the particles were reconstructed from 2D images using a multiplicative algebraic reconstruction technique (MART) and motion tracking enhancement. Distributions of the 3D displacements were calculated using a digital volume correlation. To evaluate the accuracy of the measurement method in terms of particle density and interrogation voxel size, the gauge strain and one of the two cameras for Tomo-PIV were used as a video-extensometer in the tensile test. The results show that the optimal particle density and interrogation voxel size are 0.014 particles per pixel and 40 × 40 × 40 voxels with a 75% overlap. The maximum measurement error was maintained at less than 2.5% in the 4-mm-wide region of the specimen. Conclusions We successfully developed a method to experimentally measure 3D strain distribution in an elastic silicone material using Tomo-PIV and fluorescent particles. To the best of our knowledge, this is the first report that applies Tomo-PIV to investigate 3D strain measurements in elastic materials with large deformation and validates the measurement accuracy. PMID:28910397

Viral hemorrhagic septicemia virus in North America

USGS Publications Warehouse

Meyers, Theodore R.; Winton, James R.

1995-01-01

The first detections of viral hemorrhagic septicemia virus (VHSV) in North America were in Washington State from adult coho (Oncorhynchus kisutch) and chinook (O. tshawytscha) salmon in 1988. Subsequently, VHSV was isolated from adult coho salmon returning to hatcheries in the Pacific Northwest in 1989, 1991 and 1994. These isolates represented a strain of VHSV that was genetically different from European VHSV as determined by DNA sequence analysis and T1 ribonuclease fingerprinting. The North American strain of VHSV was also isolated from skin lesions of Pacific cod (Gadus macrocephalus) taken from Prince William Sound (PWS), Alaska in 1990, 1991 and 1993. In 1993 and 1994, the virus was isolated from Pacific herring (Clupea harengus pallasi) in Alaskan waters of PWS, Kodiak Island, Auke Bay and Port Frederick. During 1993 and 1994 the herring fishery in PWS failed from a probable complex of environmental stressors but VHSV isolates were associated with hemorrhages of the skin and fins in fish that returned to spawn. Also in 1993 and 1994, VHSV was isolated from apparently healthy stocks of herring in British Columbia, Canada and Puget Sound, Washington. Thus, the North American strain of VHSV is enzootic in the Northeastern Pacific Ocean among Pacific herring stocks with Pacific cod serving as a secondary reservoir. Although the North American strain of the virus appears to be moderately pathogenic for herring, causing occasional self-limiting epizootics, it was shown to be relatively avirulent for several species of salmonids. Pacific herring are common prey for cod and salmon and were most probably the source of the VHSV isolates from the adult salmon returning to spawn in rivers or at hatcheries in Washington State. Compelling circumstances involving the European isolates of VHSV suggest that this strain of the virus also is enzootic among marine fish in the Atlantic Oean. The highly pathogenic nature of the European strain of VHSV for salmonid fish may be the result of the exposure of rainbow trout (O. mykiss), an introduced species, in a stressful environment of intensive culture and the high rate of mutation inherent in all rhabdoviruses. Consequently, we recommend that efforts be made to eradicate the North American strain of VHSV when detected in live salmonids to reduce the possibility of its evolution into a more virulent salmonid virus.

Common position of indels that cause deviations from canonical genome organization in different measles virus strains.

PubMed

Ivancic-Jelecki, Jelena; Slovic, Anamarija; Šantak, Maja; Tešović, Goran; Forcic, Dubravko

2016-07-29

The canonical genome organization of measles virus (MV) is characterized by total size of 15 894 nucleotides (nts) and defined length of every genomic region, both coding and non-coding. Only rarely have reports of strains possessing non-canonical genomic properties (possessing indels, with or without the change of total genome length) been published. The observed mutations are mutually compensatory in a sense that the total genome length remains polyhexameric. Although programmed and highly precise pseudo-templated nucleotide additions during transcription are inherent to polymerases of all viruses belonging to family Paramyxoviridae, a similar mechanism that would serve to non-randomly correct genome length, if an indel has occurred during replication, has so far not been described in the context of a complete virus genome. We compiled all complete MV genomic sequences (64 in total) available in open access sequence databases. Multiple sequence comparisons and phylogenetic analyses were performed with the aim of exploring whether non-recombinant and non-evolutionary linked measles strains that show deviations from canonical genome organization possess a common genetic characteristic. In 11 MV sequences we detected deviations from canonical genome organization due to short indels located within homopolymeric stretches or next to them. In nine out of 11 identified non-canonical MV sequences, a common feature was observed: one mutation, either an insertion or a deletion, was located in a 28 nts long region in F gene 5' untranslated region (positions 5051-5078 in genomic cDNA of canonical strains). This segment is composed of five tandemly linked homopolymeric stretches, its consensus sequence is G6-7C7-8A6-7G1-3C5-6. Although none of the mononucleotide repeats within this segment has fixed length, the total number of nts in canonical strains is always 28. These nine non-canonical strains, as well as the tenth (not mutated in 5051-5078 segment), can be grouped in three clusters, based on their passage histories/epidemiological data/genetic similarities. There are no indications that the 3 clusters are evolutionary linked, other than the fact that they all belong to clade D. A common narrow genomic region was found to be mutated in different, non-related, wild type strains suggesting that this region might have a function in non-random genome length corrections occurring during MV replication.

Deep Whole-Genome Sequencing to Detect Mixed Infection of Mycobacterium tuberculosis

PubMed Central

Gan, Mingyu; Liu, Qingyun; Yang, Chongguang; Gao, Qian; Luo, Tao

2016-01-01

Mixed infection by multiple Mycobacterium tuberculosis (MTB) strains is associated with poor treatment outcome of tuberculosis (TB). Traditional genotyping methods have been used to detect mixed infections of MTB, however, their sensitivity and resolution are limited. Deep whole-genome sequencing (WGS) has been proved highly sensitive and discriminative for studying population heterogeneity of MTB. Here, we developed a phylogenetic-based method to detect MTB mixed infections using WGS data. We collected published WGS data of 782 global MTB strains from public database. We called homogeneous and heterogeneous single nucleotide variations (SNVs) of individual strains by mapping short reads to the ancestral MTB reference genome. We constructed a phylogenomic database based on 68,639 homogeneous SNVs of 652 MTB strains. Mixed infections were determined if multiple evolutionary paths were identified by mapping the SNVs of individual samples to the phylogenomic database. By simulation, our method could specifically detect mixed infections when the sequencing depth of minor strains was as low as 1× coverage, and when the genomic distance of two mixed strains was as small as 16 SNVs. By applying our methods to all 782 samples, we detected 47 mixed infections and 45 of them were caused by locally endemic strains. The results indicate that our method is highly sensitive and discriminative for identifying mixed infections from deep WGS data of MTB isolates. PMID:27391214

Sequence-related amplified polymorphism (SRAP) marker as a new method for identification of endophytic fungi from Taxus.

PubMed

Ren, Na; Liu, Jiajia; Yang, Dongliang; Chen, Jianhua; Luan, Mingbao; Hong, Juan

2012-01-01

A total of 20 endophytic fungi stains were classified into four groups using traditional morphological identification method, and were studied for genetic diversity by sequence-related amplified polymorphism (SRAP) technique. Genomic DNA (deoxyribonucleic acid) of these strains was extracted with CTAB method. SRAP analysis was done with 24 pairs of primers. All strains could be uniquely distinguished with 584 bands and 446 polymorphism bands which generated 76.4% of polymorphic ratio. Unweighted pair-group method with arithmetical averages cluster analysis enabled construction of a dendrogram for estimating genetic distances between different strains. All strains, which were just divided into four groups by traditional morphology identification, were clustered into four major groups at GS = 0.603 and further separated into eight sub-groups at GS = 0.921. Dendrogram also revealed a large genetic variation in 20 strains; different primer combinations allowed them distinctly distinguished one from others with relatively low genetic similarity. The results show that the SRAP technology is more efficient than traditional morphology identification. It is found that SRAP markers could more really reflect the genetic diversity of endophytic fungi strains from Taxus, and also could be used as a method for identification of endophytic fungi from Taxus. It also suggests that SRAP can be used to establish foundation for further screening of taxol-producing endophytic fungi strains which can produce high levels of paclitaxel.

Full field study of strain distribution near the crack tip in the fracture of solid propellants via large strain digital image correlation and optical microscopy

NASA Astrophysics Data System (ADS)

Gonzalez, Javier

A full field method for visualizing deformation around the crack tip in a fracture process with large strains is developed. A digital image correlation program (DIC) is used to incrementally compute strains and displacements between two consecutive images of a deformation process. Values of strain and displacements for consecutive deformations are added, this way solving convergence problems in the DIC algorithm when large deformations are investigated. The method developed is used to investigate the strain distribution within 1 mm of the crack tip in a particulate composite solid (propellant) using microscopic visualization of the deformation process.

Total strain version of strainrange partitioning for thermomechanical fatigue at low strains

NASA Technical Reports Server (NTRS)

Halford, G. R.; Saltsman, J. F.

1987-01-01

A new method is proposed for characterizing and predicting the thermal fatigue behavior of materials. The method is based on three innovations in characterizing high temperature material behavior: (1) the bithermal concept of fatigue testing; (2) advanced, nonlinear, cyclic constitutive models; and (3) the total strain version of traditional strainrange partitioning.

Quantifying disbond area

NASA Astrophysics Data System (ADS)

Lowden, D. W.

1992-10-01

Disbonds simulated in a composite helicopter rotor blade were profiled using eddy currents. The method is inherently accurate and reproducible. An algorithm is described for calculating disbond margin. Disbond area is estimated assuming in-service disbondments exhibit circular geometry.

Genetic assessment of strain-specific sources of lake trout recruitment in the Great Lakes

USGS Publications Warehouse

Page, Kevin S.; Scribner, Kim T.; Bennett, Kristine R.; Garzel, Laura M.; Burnham-Curtis, Mary K.

2003-01-01

Populations of wild lake trout Salvelinus namaycush have been extirpated from nearly all their historical habitats across the Great Lakes. Efforts to restore self-sustaining lake trout populations in U.S. waters have emphasized the stocking of coded-wire-tagged juveniles from six hatchery strains (Seneca Lake, Lewis Lake, Green Lake, Apostle Islands, Isle Royale, and Marquette) into vacant habitats. Strain-specific stocking success has historically been based on estimates of the survival and catch rates of coded-wire-tagged adults returning to spawning sites. However, traditional marking methods and estimates of relative strain abundance provide no means of assessing strain fitness (i.e., the realized contributions to natural recruitment) except by assuming that young-of-the-year production is proportional to adult spawner abundance. We used microsatellite genetic data collected from six hatchery strains with likelihood-based individual assignment tests (IA) and mixed-stock analysis (MSA) to identify the strain composition of young of the year recruited each year. We show that strain classifications based on IA and MSA were concordant and that the accuracy of both methods varied based on strain composition. Analyses of young-of-the-year lake trout samples from Little Traverse Bay (Lake Michigan) and Six Fathom Bank (Lake Huron) revealed that strain contributions differed significantly from estimates of the strain composition of adults returning to spawning reefs. The Seneca Lake strain contributed the majority of juveniles produced on Six Fathom Bank and more young of the year than expected within Little Traverse Bay. Microsatellite markers provided a method for accurately classifying the lake trout hatchery strains used for restoration efforts in the Great Lakes and for assessment of strain-specific reproductive success.

Estimation of lattice strain in nanocrystalline RuO2 by Williamson-Hall and size-strain plot methods.

PubMed

Sivakami, R; Dhanuskodi, S; Karvembu, R

2016-01-05

RuO2 nanoparticles (RuO2 NPs) have been successfully synthesized by the hydrothermal method. Structure and the particle size have been determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM). UV-Vis spectra reveal that the optical band gap of RuO2 nanoparticles is red shifted from 3.95 to 3.55eV. BET measurements show a high specific surface area (SSA) of 118-133m(2)/g and pore diameter (10-25nm) has been estimated by Barret-Joyner-Halenda (BJH) method. The crystallite size and lattice strain in the samples have been investigated by Williamson-Hall (W-H) analysis assuming uniform deformation, deformation stress and deformation energy density, and the size-strain plot method. All other relevant physical parameters including stress, strain and energy density have been calculated. The average crystallite size and the lattice strain evaluated from XRD measurements are in good agreement with the results of TEM. Copyright © 2015 Elsevier B.V. All rights reserved.

Novel method for measuring a dense 3D strain map of robotic flapping wings

NASA Astrophysics Data System (ADS)

Li, Beiwen; Zhang, Song

2018-04-01

Measuring dense 3D strain maps of the inextensible membranous flapping wings of robots is of vital importance to the field of bio-inspired engineering. Conventional high-speed 3D videography methods typically reconstruct the wing geometries through measuring sparse points with fiducial markers, and thus cannot obtain the full-field mechanics of the wings in detail. In this research, we propose a novel system to measure a dense strain map of inextensible membranous flapping wings by developing a superfast 3D imaging system and a computational framework for strain analysis. Specifically, first we developed a 5000 Hz 3D imaging system based on the digital fringe projection technique using the defocused binary patterns to precisely measure the dynamic 3D geometries of rapidly flapping wings. Then, we developed a geometry-based algorithm to perform point tracking on the precisely measured 3D surface data. Finally, we developed a dense strain computational method using the Kirchhoff-Love shell theory. Experiments demonstrate that our method can effectively perform point tracking and measure a highly dense strain map of the wings without many fiducial markers.

WE-EF-210-06: Ultrasound 2D Strain Measurement of Radiation-Induced Toxicity: Phantom and Ex Vivo Experiments

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

Liu, T; Torres, M; Rossi, P

Purpose: Radiation-induced fibrosis is a common long-term complication affecting many patients following cancer radiotherapy. Standard clinical assessment of subcutaneous fibrosis is subjective and often limited to visual inspection and palpation. Ultrasound strain imaging describes the compressibility (elasticity) of biological tissues. This study’s purpose is to develop a quantitative ultrasound strain imaging that can consistently and accurately characterize radiation-induce fibrosis. Methods: In this study, we propose a 2D strain imaging method based on deformable image registration. A combined affine and B-spline transformation model is used to calculate the displacement of tissue between pre-stress and post-stress B-mode image sequences. The 2D displacementmore » is estimated through a hybrid image similarity measure metric, which is a combination of the normalized mutual information (NMI) and normalized sum-of-squared-differences (NSSD). And 2D strain is obtained from the gradient of the local displacement. We conducted phantom experiments under various compressions and compared the performance of our proposed method with the standard cross-correlation (CC)- based method using the signal-to-noise (SNR) and contrast-to-noise (CNS) ratios. In addition, we conducted ex-vivo beef muscle experiment to further validate the proposed method. Results: For phantom study, the SNR and CNS values of the proposed method were significantly higher than those calculated from the CC-based method under different strains. The SNR and CNR increased by a factor of 1.9 and 2.7 comparing to the CC-based method. For the ex-vivo experiment, the CC-based method failed to work due to large deformation (6.7%), while our proposed method could accurately detect the stiffness change. Conclusion: We have developed a 2D strain imaging technique based on the deformable image registration, validated its accuracy and feasibility with phantom and ex-vivo data. This 2D ultrasound strain imaging technology may be valuable as physicians try to eliminate radiation-induce fibrosis and improve the therapeutic ratio of cancer radiotherapy. This research is supported in part by DOD PCRP Award W81XWH-13-1-0269, and National Cancer Institute (NCI) Grant CA114313.« less

Longitudinally Jointed Edge-Wise Compression HoneyComb Composite Sandwich Coupon Testing And Fe Analysis: Three Methods of Strain Measurement, And Comparison

NASA Technical Reports Server (NTRS)

Farrokh, Babak; Rahim, Nur Aida Abul; Segal, Ken; Fan, Terry; Jones, Justin; Hodges, Ken; Mashni, Noah; Garg, Naman; Sang, Alex

2013-01-01

Three distinct strain measurement methods (i.e., foil resistance strain gages, fiber optic strain sensors, and a three-dimensional digital image photogrammetry that gives full field strain and displacement measurements) were implemented to measure strains on the back and front surfaces of a longitudinally jointed curved test article subjected to edge-wise compression testing, at NASA Goddard Space Flight Center, according to ASTM C364. The pre-test finite element analysis (FEA) was conducted to assess ultimate failure load and predict strain distribution pattern throughout the test coupon. The predicted strain pattern contours were then utilized as guidelines for installing the strain measurement instrumentations. The foil resistance strain gages and fiber optic strain sensors were bonded on the specimen at locations with nearly the same analytically predicted strain values, and as close as possible to each other, so that, comparisons between the measured strains by strain gages and fiber optic sensors, as well as the three-dimensional digital image photogrammetric system are relevant. The test article was loaded to failure (at 167 kN), at the compressive strain value of 10,000 micro epsilon. As a part of this study, the validity of the measured strains by fiber optic sensors is examined against the foil resistance strain gages and the three-dimensional digital image photogrammetric data, and comprehensive comparisons are made with FEA predictions.

Comparison of Haemophilus parasuis reference strains and field isolates by using random amplified polymorphic DNA and protein profiles

PubMed Central

2012-01-01

Background Haemophilus parasuis is the causative agent of Glässer’s disease and is a pathogen of swine in high-health status herds. Reports on serotyping of field strains from outbreaks describe that approximately 30% of them are nontypeable and therefore cannot be traced. Molecular typing methods have been used as alternatives to serotyping. This study was done to compare random amplified polymorphic DNA (RAPD) profiles and whole cell protein (WCP) lysate profiles as methods for distinguishing H. parasuis reference strains and field isolates. Results The DNA and WCP lysate profiles of 15 reference strains and 31 field isolates of H. parasuis were analyzed using the Dice and neighbor joining algorithms. The results revealed unique and reproducible DNA and protein profiles among the reference strains and field isolates studied. Simpson’s index of diversity showed significant discrimination between isolates when three 10mer primers were combined for the RAPD method and also when both the RAPD and WCP lysate typing methods were combined. Conclusions The RAPD profiles seen among the reference strains and field isolates did not appear to change over time which may reflect a lack of DNA mutations in the genes of the samples. The recent field isolates had different WCP lysate profiles than the reference strains, possibly because the number of passages of the type strains may affect their protein expression. PMID:22703293

Involvement of upper torso stress amplification, tissue compression and distortion in the pathogenesis of keloids.

PubMed

Bux, Shamin; Madaree, Anil

2012-03-01

Keloids are benign tumours composed of fibrous tissue produced during excessive tissue repair triggered by minor injury, trauma or surgical incision. Although it is recognized that keloids have a propensity to form in the upper torso of the body, the predisposing factors responsible for this have not been investigated. It is crucial that the aetiopathoical factors implicated in keloid formation be established to provide guidelines for well-informed more successful treatment. We compared keloid-prone and keloid-protected skin, identified pertinent morphological differences and explored how inherent structural characteristics and intrinsic factors may promote keloid formation. It was determined that keloid prone areas were covered with high tension skin that had low stretch and a low elastic modulus when compared with skin in keloid protected areas where the skin was lax with a high elastic modulus and low pre-stress level. Factors contributing to elevated internal stress in keloid susceptible skin were the protrusion of hard connective tissue such as bony prominences or cartilage into the dermis of skin as well as inherent skin characteristics such as the bundled arrangement of collagen in the reticular dermis, the existent high tension, the low elastic modulus, low stretch ability, contractile forces exerted by wound healing fibroblastic cells and external forces. Stress promotes keloid formation by causing dermal distortion and compression which subsequently stimulate proliferation and enhanced protein synthesis in wound healing fibroblastic cells. The strain caused by stress also compresses and occludes microvessels causing ischaemic effects and reperfusion injury which stimulate growth when blood rich in growth factors returns to the tissue. The growth promoting effects of increased internal stress, primarily, and growth factors released by reperfusing blood, manifest in keloid formation. Other inherent skin characteristics promoting keloid growth during the late stages of wound healing in the upper torso are the thinner epidermis, the presence of vellus hairs, the absence of protective immunoglobulin A (IgA), and the thick fragile quality of upper torso skin. As it is not known why there is a predilection for keloids to form in the upper torso of the body, this hypothesis implicating and associating inherent morphological characteristics and elevated stress in the aetiopathogenesis of keloids is of potential value in terms of prevention, management and treatment of these enigmatic tumours. Copyright © 2011 Elsevier Ltd. All rights reserved.

Microbial reductive dehalogenation of vinyl chloride

DOEpatents

Spormann, Alfred M [Stanford, CA; Muller, Jochen A [Baltimore, MD; Rosner, Bettina M [Berlin, DE; Von Abendroth, Gregory [Nannhein, DE; Meshulam-Simon, Galit [Los Altos, CA; McCarty, Perry L [Stanford, CA

2011-11-22

Compositions and methods are provided that relate to the bioremediation of chlorinated ethenes, particularly the bioremediation of vinyl chloride by Dehalococcoides-like organisms. An isolated strain of bacteria, Dehalococcoides sp. strain VS, that metabolizes vinyl chloride is provided; the genetic sequence of the enzyme responsible for vinyl chloride dehalogenation; methods of assessing the capability of endogenous organisms at an environmental site to metabolize vinyl chloride; and a method of using the strains of the invention for bioremediation.

Microbial reductive dehalogenation of vinyl chloride

DOEpatents

Spormann, Alfred M [Stanford, CA; Muller, Jochen A [Baltimore, MD; Rosner, Bettina M [Berlin, DE; Von Abendroth, Gregory [Mannheim, DE; Meshulam-Simon, Galit [Los Angeles, CA; McCarty, Perry L [Stanford, CA

2014-02-11

Compositions and methods are provided that relate to the bioremediation of chlorinated ethenes, particularly the bioremediation of vinyl chloride by Dehalococcoides-like organisms. An isolated strain of bacteria, Dehalococcoides sp. strain VS, that metabolizes vinyl chloride is provided; the genetic sequence of the enzyme responsible for vinyl chloride dehalogenation; methods of assessing the capability of endogenous organisms at an environmental site to metabolize vinyl chloride; and a method of using the strains of the invention for bioremediation.

Methods of producing protoporphyrin IX and bacterial mutants therefor

DOEpatents

Zhou, Jizhong; Qiu, Dongru; He, Zhili; Xie, Ming

2016-03-01

The presently disclosed inventive concepts are directed in certain embodiments to a method of producing protoporphyrin IX by (1) cultivating a strain of Shewanella bacteria in a culture medium under conditions suitable for growth thereof, and (2) recovering the protoporphyrin IX from the culture medium. The strain of Shewanella bacteria comprises at least one mutant hemH gene which is incapable of normal expression, thereby causing an accumulation of protoporphyrin IX. In certain embodiments of the method, the strain of Shewanella bacteria is a strain of S. loihica, and more specifically may be S. loihica PV-4. In certain embodiments, the mutant hemH gene of the strain of Shewanella bacteria may be a mutant of shew_2229 and/or of shew_1140. In other embodiments, the presently disclosed inventive concepts are directed to mutant strains of Shewanella bacteria having at least one mutant hemH gene which is incapable of normal expression, thereby causing an accumulation of protoporphyrin IX during cultivation of the bacteria. In certain embodiments the strain of Shewanella bacteria is a strain of S. loihica, and more specifically may be S. loihica PV-4. In certain embodiments, the mutant hemH gene of the strain of Shewanella bacteria may be a mutant of shew_2229 and/or shew_1140.

Practical applications of current loop signal conditioning

NASA Astrophysics Data System (ADS)

Anderson, Karl F.

1994-10-01

This paper describes a variety of practical application circuits based on the current loop signal conditioning paradigm. Equations defining the circuit response are also provided. The constant current loop is a fundamental signal conditioning circuit concept that can be implemented in a variety of configurations for resistance-based transducers, such as strain gages and resistance temperature devices. The circuit features signal conditioning outputs which are unaffected by extremely large variations in lead wire resistance, direct current frequency response, and inherent linearity with respect to resistance change. Sensitivity of this circuit is double that of a Wheatstone bridge circuit. Electrical output is zero for resistance change equals zero. The same excitation and output sense wires can serve multiple transducers. More application arrangements are possible with constant current loop signal conditioning than with the Wheatstone bridge.

Actuating materials. Voxelated liquid crystal elastomers.

PubMed

Ware, Taylor H; McConney, Michael E; Wie, Jeong Jae; Tondiglia, Vincent P; White, Timothy J

2015-02-27

Dynamic control of shape can bring multifunctionality to devices. Soft materials capable of programmable shape change require localized control of the magnitude and directionality of a mechanical response. We report the preparation of soft, ordered materials referred to as liquid crystal elastomers. The direction of molecular order, known as the director, is written within local volume elements (voxels) as small as 0.0005 cubic millimeters. Locally, the director controls the inherent mechanical response (55% strain) within the material. In monoliths with spatially patterned director, thermal or chemical stimuli transform flat sheets into three-dimensional objects through controlled bending and stretching. The programmable mechanical response of these materials could yield monolithic multifunctional devices or serve as reconfigurable substrates for flexible devices in aerospace, medicine, or consumer goods. Copyright © 2015, American Association for the Advancement of Science.

Current loop signal conditioning: Practical applications

NASA Technical Reports Server (NTRS)

Anderson, Karl F.

1995-01-01

This paper describes a variety of practical application circuits based on the current loop signal conditioning paradigm. Equations defining the circuit response are also provided. The constant current loop is a fundamental signal conditioning circuit concept that can be implemented in a variety of configurations for resistance-based transducers, such as strain gages and resistance temperature detectors. The circuit features signal conditioning outputs which are unaffected by extremely large variations in lead wire resistance, direct current frequency response, and inherent linearity with respect to resistance change. Sensitivity of this circuit is double that of a Wheatstone bridge circuit. Electrical output is zero for resistance change equals zero. The same excitation and output sense wires can serve multiple transducers. More application arrangements are possible with constant current loop signal conditioning than with the Wheatstone bridge.

Assessment of a hybrid finite element-transfer matrix model for flat structures with homogeneous acoustic treatments.

PubMed

Alimonti, Luca; Atalla, Noureddine; Berry, Alain; Sgard, Franck

2014-05-01

Modeling complex vibroacoustic systems including poroelastic materials using finite element based methods can be unfeasible for practical applications. For this reason, analytical approaches such as the transfer matrix method are often preferred to obtain a quick estimation of the vibroacoustic parameters. However, the strong assumptions inherent within the transfer matrix method lead to a lack of accuracy in the description of the geometry of the system. As a result, the transfer matrix method is inherently limited to the high frequency range. Nowadays, hybrid substructuring procedures have become quite popular. Indeed, different modeling techniques are typically sought to describe complex vibroacoustic systems over the widest possible frequency range. As a result, the flexibility and accuracy of the finite element method and the efficiency of the transfer matrix method could be coupled in a hybrid technique to obtain a reduction of the computational burden. In this work, a hybrid methodology is proposed. The performances of the method in predicting the vibroacoutic indicators of flat structures with attached homogeneous acoustic treatments are assessed. The results prove that, under certain conditions, the hybrid model allows for a reduction of the computational effort while preserving enough accuracy with respect to the full finite element solution.

Interference of alpha-hemolytic streptococci isolated from tonsillar surface on beta-hemolytic streptococci (Streptococcus pyogenes)--a methodological study.

PubMed

Grahn, E; Holm, S E; Ekedahl, C; Roos, K

1983-07-01

The interference between alpha-streptococcal strains obtained from patients with repeated tonsillitis and a collection of group A streptococcal strains were studied. For this purpose three in vitro methods were designed and compared. The results obtained by a simple plating technique suitable for screening purposes were found to correlate well with those using more laborious techniques. In a limited scale some of the alpha- and beta-streptococcal combinations were tested under in vivo conditions using a tissue cage model allowing repeated sampling. In most instances agreement between the results of the in vitro and in vivo methods was registered. Several alpha-strains having inhibitory capacity to the majority of a collection of group A streptococci belonging to different serotypes were found, but also alpha-strains with an inhibitory activity restricted to few group A isolates within a certain serotype. Also beta-streptococcal strains with growth inhibiting activity towards some alpha-strains were found. As the methods were chosen to eliminate many of the unspecific inhibitory factors and the beta-hemolytic test strains showed a pattern of inhibition that varied for each of the reference alpha-strains the activity is most likely attributed to bacteriocin-like substances.

Parallel heuristics for scalable community detection

DOE PAGES

Lu, Hao; Halappanavar, Mahantesh; Kalyanaraman, Ananth

2015-08-14

Community detection has become a fundamental operation in numerous graph-theoretic applications. Despite its potential for application, there is only limited support for community detection on large-scale parallel computers, largely owing to the irregular and inherently sequential nature of the underlying heuristics. In this paper, we present parallelization heuristics for fast community detection using the Louvain method as the serial template. The Louvain method is an iterative heuristic for modularity optimization. Originally developed in 2008, the method has become increasingly popular owing to its ability to detect high modularity community partitions in a fast and memory-efficient manner. However, the method ismore » also inherently sequential, thereby limiting its scalability. Here, we observe certain key properties of this method that present challenges for its parallelization, and consequently propose heuristics that are designed to break the sequential barrier. For evaluation purposes, we implemented our heuristics using OpenMP multithreading, and tested them over real world graphs derived from multiple application domains. Compared to the serial Louvain implementation, our parallel implementation is able to produce community outputs with a higher modularity for most of the inputs tested, in comparable number or fewer iterations, while providing real speedups of up to 16x using 32 threads.« less

Approaches to advancescientific understanding of macrosystems ecology

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

Levy, Ofir; Ball, Becky; Bond-Lamberty, Benjamin

Macrosystem ecological studies inherently investigate processes that interact across multiple spatial and temporal scales, requiring intensive sampling and massive amounts of data from diverse sources to incorporate complex cross-scale and hierarchical interactions. Inherent challenges associated with these characteristics include high computational demands, data standardization and assimilation, identification of important processes and scales without prior knowledge, and the need for large, cross-disciplinary research teams that conduct long-term studies. Therefore, macrosystem ecology studies must utilize a unique set of approaches that are capable of encompassing these methodological characteristics and associated challenges. Several case studies demonstrate innovative methods used in current macrosystem ecologymore » studies.« less

Inherent overload protection for the series resonant converter

NASA Technical Reports Server (NTRS)

King, R. J.; Stuart, T. A.

1983-01-01

The overload characteristics of the full bridge series resonant power converter are considered. This includes analyses of the two most common control methods presently in use. The first of these uses a current zero crossing detector to synchronize the control signals and is referred to as the alpha controller. The second is driven by a voltage controlled oscillator and is referred to as the gamma controller. It is shown that the gamma controller has certain reliability advantages in that it can be designed with inherent short circuit protection. Experimental results are included for an 86 kHz converter using power metal-oxide-semiconductor field-effect transistors (MOSFETs).

Inherent Conservatism in Deterministic Quasi-Static Structural Analysis

NASA Technical Reports Server (NTRS)

Verderaime, V.

1997-01-01

The cause of the long-suspected excessive conservatism in the prevailing structural deterministic safety factor has been identified as an inherent violation of the error propagation laws when reducing statistical data to deterministic values and then combining them algebraically through successive structural computational processes. These errors are restricted to the applied stress computations, and because mean and variations of the tolerance limit format are added, the errors are positive, serially cumulative, and excessively conservative. Reliability methods circumvent these errors and provide more efficient and uniform safe structures. The document is a tutorial on the deficiencies and nature of the current safety factor and of its improvement and transition to absolute reliability.

Comparative Genomics of Oral Isolates of Streptococcus mutans by in silico Genome Subtraction Does Not Reveal Accessory DNA Associated with Severe Early Childhood Caries

PubMed Central

Argimón, Silvia; Konganti, Kranti; Chen, Hao; Alekseyenko, Alexander V.; Brown, Stuart; Caufield, Page W.

2014-01-01

Comparative genomics is a popular method for the identification of microbial virulence determinants, especially since the sequencing of a large number of whole bacterial genomes from pathogenic and non-pathogenic strains has become relatively inexpensive. The bioinformatics pipelines for comparative genomics usually include gene prediction and annotation and can require significant computer power. To circumvent this, we developed a rapid method for genome-scale in silico subtractive hybridization, based on blastn and independent of feature identification and annotation. Whole genome comparisons by in silico genome subtraction were performed to identify genetic loci specific to Streptococcus mutans strains associated with severe early childhood caries (S-ECC), compared to strains isolated from caries-free (CF) children. The genome similarity of the 20 S. mutans strains included in this study, calculated by Simrank k-mer sharing, ranged from 79.5 to 90.9%, confirming this is a genetically heterogeneous group of strains. We identified strain-specific genetic elements in 19 strains, with sizes ranging from 200 bp to 39 kb. These elements contained protein-coding regions with functions mostly associated with mobile DNA. We did not, however, identify any genetic loci consistently associated with dental caries, i.e., shared by all the S-ECC strains and absent in the CF strains. Conversely, we did not identify any genetic loci specific with the healthy group. Comparison of previously published genomes from pathogenic and carriage strains of Neisseria meningitidis with our in silico genome subtraction yielded the same set of genes specific to the pathogenic strains, thus validating our method. Our results suggest that S. mutans strains derived from caries active or caries free dentitions cannot be differentiated based on the presence or absence of specific genetic elements. Our in silico genome subtraction method is available as the Microbial Genome Comparison (MGC) tool, with a user-friendly JAVA graphical interface. PMID:24291226

A Fatigue Life Prediction Method Based on Strain Intensity Factor

PubMed Central

Zhang, Wei; Liu, Huili; Wang, Qiang; He, Jingjing

2017-01-01

In this paper, a strain-intensity-factor-based method is proposed to calculate the fatigue crack growth under the fully reversed loading condition. A theoretical analysis is conducted in detail to demonstrate that the strain intensity factor is likely to be a better driving parameter correlated with the fatigue crack growth rate than the stress intensity factor (SIF), especially for some metallic materials (such as 316 austenitic stainless steel) in the low cycle fatigue region with negative stress ratios R (typically R = −1). For fully reversed cyclic loading, the constitutive relation between stress and strain should follow the cyclic stress-strain curve rather than the monotonic one (it is a nonlinear function even within the elastic region). Based on that, a transformation algorithm between the SIF and the strain intensity factor is developed, and the fatigue crack growth rate testing data of 316 austenitic stainless steel and AZ31 magnesium alloy are employed to validate the proposed model. It is clearly observed that the scatter band width of crack growth rate vs. strain intensity factor is narrower than that vs. the SIF for different load ranges (which indicates that the strain intensity factor is a better parameter than the stress intensity factor under the fully reversed load condition). It is also shown that the crack growth rate is not uniquely determined by the SIF range even under the same R, but is also influenced by the maximum loading. Additionally, the fatigue life data (strain-life curve) of smooth cylindrical specimens are also used for further comparison, where a modified Paris equation and the equivalent initial flaw size (EIFS) are involved. The results of the proposed method have a better agreement with the experimental data compared to the stress intensity factor based method. Overall, the strain intensity factor method shows a fairly good ability in calculating the fatigue crack propagation, especially for the fully reversed cyclic loading condition. PMID:28773049

Fusion of sensor geometry into additive strain fields measured with sensing skin

NASA Astrophysics Data System (ADS)

Downey, Austin; Sadoughi, Mohammadkazem; Laflamme, Simon; Hu, Chao

2018-07-01

Recently, numerous studies have been conducted on flexible skin-like membranes for the cost effective monitoring of large-scale structures. The authors have proposed a large-area electronic consisting of a soft elastomeric capacitor (SEC) that transduces a structure’s strain into a measurable change in capacitance. Arranged in a network configuration, SECs deployed onto the surface of a structure could be used to reconstruct strain maps. Several regression methods have been recently developed with the purpose of reconstructing such maps, but all these algorithms assumed that each SEC-measured strain located at its geometric center. This assumption may not be realistic since an SEC measures the average strain value of the whole area covered by the sensor. One solution is to reduce the size of each SEC, but this would also increase the number of required sensors needed to cover the large-scale structure, therefore increasing the need for the power and data acquisition capabilities. Instead, this study proposes an algorithm that accounts for the sensor’s strain averaging feature by adjusting the strain measurements and constructing a full-field strain map using the kriging interpolation method. The proposed algorithm fuses the geometry of an SEC sensor into the strain map reconstruction in order to adaptively adjust the average kriging-estimated strain of the area monitored by the sensor to the signal. Results show that by considering the sensor geometry, in addition to the sensor signal and location, the proposed strain map adjustment algorithm is capable of producing more accurate full-field strain maps than the traditional spatial interpolation method that considered only signal and location.

Development of Theoretical and Computational Methods for Single-Source Bathymetric Data

DTIC Science & Technology

2016-09-15

Methods for Single-Source N00014-16-1-2035 Bathymetric Data Sb. GRANT NUMBER 11893686 Sc. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Sd. PROJECT NUMBER...A method is outlined for fusing the information inherent in such source documents, at different scales, into a single picture for the marine...algorithm reliability, which reflects the degree of inconsistency of the source documents, is also provided. A conceptual outline of the method , and a

[Surveillance of Antimicrobial Resistant Esherichia coli by Rectal Swab Method--Annual Change of Prevalence of Quinolone-resistant and ESBL Producing Strains from 2009 to 2013].

PubMed

Nasu, Yoshitsugu; Sako, Shinichi; Yano, Tomofumi; Kosaka, Noriko

2015-09-01

Although most of commonly used antimicrobial agents had been susceptible to Esherichia coli, recently there are a lot of reports concerning about community-acquired infection caused by resistant E. coli. The aim of this study is to define the prevalence of resistant E. coli in normal flora colonization by the rectal swab method. From June 2009 to December 2013, 251 male patients (50-85 year-old, median 68) planned to transrectal prostate biopsy participated in this study. Stools stuck on the glove at the digital examination were provided for culture specimen. Identification of E. coli and determination of MIC was performed by MicroScan WalkAway40plus (Siemens). Isolated E. coli were deemed quinolone-resistant strains when their MIC of levofloxacine was 4 μg/mL or above according to the breakpoint MIC by the CLSI criteria. ESBL producing ability was determined by the double disk method used by CVA contained ESBL definition disc (Eikenkagaku). Of the 251 study patients, 224 patients had positive cultures of E. coli. Twenty-four patients had quinolone-resistant strains and 9 patients had ESBL producing strains. The prevalence of quinolone-resistant strains in 2009, 2010, 2011, 2012 and 2013 were 5.9% (2 out of 34 strains), 13.5% (5 out of 37 strains), 12.5% (4 out of 32 strains), 9.0% (6 out of 67) and 13.0% (7 out of 54 strains), respectively. The prevalence of ESBL producing strains in 2009, 2010, 2011, 2012 and 2013 were 0% (0 out of 34 strains), 5.4% (2 out of 37 strains), 3.1% (1 out of 32 strains), 3.0% (2 out of 67 strains) and 7.4% (4 out of 54 strains), respectively. In 2013, the prevalence of antimicrobial resistant E. coli, both quinolone-resistant and ESBL producing strains, were increasing. We have to pay a close attention to the increase of resistant E. coli.

Elastoplastic State of an Elliptical Cylindrical Shell with a Circular Hole

NASA Astrophysics Data System (ADS)

Storozhuk, E. A.; Chernyshenko, I. S.; Pigol', O. V.

2017-11-01

Static problems for an elastoplastic elliptical cylindrical shell with a circular hole are formulated and a numerical method for solving it is developed. The basic equations are derived using the Kirchhoff-Love theory of deep shells and the theory of small elastoplastic strains. The method employs the method of additional stresses and the finite-element method. The influence of plastic strains and geometrical parameters of the shell subject to internal pressure on the distributions of stresses, strains, and displacements in the zone of their concentration is studied.

Thick Acellular Heart Extracellular Matrix with Inherent Vasculature: A Potential Platform for Myocardial Tissue Regeneration

PubMed Central

Sarig, Udi; Au-Yeung, Gigi C.T.; Wang, Yao; Bronshtein, Tomer; Dahan, Nitsan; Boey, Freddy Y.C.; Venkatraman, Subbu S.

2012-01-01

The decellularization of porcine heart tissue offers many opportunities for the production of physiologically relevant myocardial mimetic scaffolds. Earlier, we reported the successful isolation of a thin porcine cardiac extracellular matrix (pcECM) exhibiting relevant bio-mechanical properties for myocardial tissue engineering. Nevertheless, since native cardiac tissue is much thicker, such thin scaffolds may offer limited regeneration capacity. However, generation of thicker myocardial mimetic tissue constructs is hindered by diffusion limitations (∼100 μm), and the lack of a proper vascular-like network within these constructs. In our present work, we focused on optimizing the decellularization procedure for thicker tissue slabs (10–15 mm), while retaining their inherent vasculature, and on characterizing the resulting pcECM. The trypsin/Triton-based perfusion procedure that resulted in a nonimmunogenic and cell-supportive pcECM was found to be more effective in cell removal and in the preservation of fiber morphology and structural characteristics than stirring, sonication, or sodium dodecyl sulfate/Triton-based procedures. Mass spectroscopy revealed that the pcECM is mainly composed of ECM proteins with no apparent cellular protein remains. Mechanical testing indicated that the obtained pcECM is viscoelastic in nature and possesses the typical stress-strain profile of biological materials. It is stiffer than native tissue yet exhibits matched mechanical properties in terms of energy dissipation, toughness, and ultimate stress behavior. Vascular network functionality was maintained to the first three–four branches from the main coronary vessels. Taken together, these results reaffirm the efficiency of the decellularization procedure reported herein for yielding thick nonimmunogenic cell-supportive pcECM scaffolds, preserving both native tissue ultra-structural properties and an inherent vascular network. When reseeded with the appropriate progenitor cells, these scaffolds can potentially serve as ex vivo screening platforms for new therapeutics, as models for human cardiac ECM, or as biomedical constructs for patch or transmural transplantation strategies. PMID:22663095

Elastic and plastic strain measurement in high temperature environment using laser speckle

NASA Technical Reports Server (NTRS)

Chiang, Fu-Pen

1992-01-01

Two laser speckle methods are described to measure strain in high temperature environment and thermal strain caused by high temperature. Both are non-contact, non-destructive and remote sensing techniques that can be automated. The methods have different but overlapping ranges of application with one being more suitable for large plastic deformation.

Strain preservation of experimental animals: vitrification of two-cell stage embryos for multiple mouse strains.

PubMed

Eto, Tomoo; Takahashi, Riichi; Kamisako, Tsutomu

2015-04-01

Strain preservation of experimental animals is crucial for experimental reproducibility. Maintaining complete animal strains, however, is costly and there is a risk for genetic mutations as well as complete loss due to disasters or illness. Therefore, the development of effective vitrification techniques for cryopreservation of multiple experimental animal strains is important. We examined whether a vitrification method using cryoprotectant solutions, P10 and PEPeS, is suitable for preservation of multiple inbred and outbred mouse strains. First, we investigated whether our vitrification method using cryoprotectant solutions was suitable for two-cell stage mouse embryos. In vitro development of embryos exposed to the cryoprotectant solutions was similar to that of fresh controls. Further, the survival rate of the vitrified embryos was extremely high (98.1%). Next, we collected and vitrified two-cell stage embryos of 14 mouse strains. The average number of embryos obtained from one female was 7.3-33.3. The survival rate of vitrified embryos ranged from 92.8% to 99.1%, with no significant differences among mouse strains. In vivo development did not differ significantly between fresh controls and vitrified embryos of each strain. For strain preservation using cryopreserved embryos, two offspring for inbred lines and one offspring for outbred lines must be produced from two-cell stage embryos collected from one female. The expected number of surviving fetuses obtained from embryos collected from one female of either the inbred or outbred strains ranged from 2.9 to 19.5. The findings of the present study indicated that this vitrification method is suitable for strain preservation of multiple mouse strains. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Homogenisation of the strain distribution in stretch formed parts to improve part properties

NASA Astrophysics Data System (ADS)

Schmitz, Roman; Winkelmann, Mike; Bailly, David; Hirt, Gerhard

2018-05-01

Inhomogeneous strain and sheet thickness distributions can be observed in complex sheet metal parts manufactured by stretch forming. In literature, this problem is solved by flexible clampings adapted to the part geometry. In this paper, an approach, which does not rely on extensive tooling, is presented. The strain distribution in the sheet is influenced by means of hole patterns. Holes are introduced into the sheet area between clamping and part next to areas where high strains are expected. When deforming the sheet, high strains are shifted out of the part area. In a local area around the holes, high strains concentrate perpendicular to the drawing direction. Thus, high strains in the part area are reduced and the strain distribution is homogenised. To verify this approach, an FE-model of a stretch forming process of a conical part is implemented in LS-Dyna. The model is validated by corresponding experiments. In the first step, the positioning of the holes is applied manually based on the numerically determined strain distribution and experience. In order to automate the positioning of the holes, an optimisation method is applied in a second step. The presented approach implemented in LS-OPT uses the response surface method to identify the positioning and radius of the holes homogenising the strain in a defined area of the sheet. Due to nonlinear increase of computational complexity with increasing number of holes, the maximum number of holes is set to three. With both, the manual and the automated method, hole patterns were found which allow for a relative reduction of maximum strains and for a homogenisation of the strain distribution. Comparing the manual and automated positioning of holes, the pattern determined by automated optimisation shows better results in terms of homogenising the strain distribution.

Ocean Optics Protocols for Satellite Ocean Color Sensor Validation. Volume 4; Inherent Optical Properties: Instruments, Characterizations, Field Measurements and Data Analysis Protocols; Revised

NASA Technical Reports Server (NTRS)

Mueller, J. L. (Editor); Fargion, Giuletta S. (Editor); McClain, Charles R. (Editor); Pegau, Scott; Zaneveld, J. Ronald V.; Mitchell, B. Gregg; Kahru, Mati; Wieland, John; Stramska, Malgorzat

2003-01-01

This document stipulates protocols for measuring bio-optical and radiometric data for the Sensor Intercomparison and Merger for Biological and Interdisciplinary Oceanic Studies (SIMBIOS) Project activities and algorithm development. The document is organized into 6 separate volumes as Ocean Optics Protocols for Satellite Ocean Color Sensor Validation, Revision 4. Volume I: Introduction, Background and Conventions; Volume II: Instrument Specifications, Characterization and Calibration; Volume III: Radiometric Measurements and Data Analysis Methods; Volume IV: Inherent Optical Properties: Instruments, Characterization, Field Measurements and Data Analysis Protocols; Volume V: Biogeochemical and Bio-Optical Measurements and Data Analysis Methods; Volume VI: Special Topics in Ocean Optics Protocols and Appendices. The earlier version of Ocean Optics Protocols for Satellite Ocean Color Sensor Validation, Revision 3 (Mueller and Fargion 2002, Volumes 1 and 2) is entirely superseded by the six volumes of Revision 4 listed above.

Ocean Optics Protocols for Satellite Ocean Color Sensor Validation, Revision 4, Volume IV: Inherent Optical Properties: Instruments, Characterizations, Field Measurements and Data Analysis Protocols

NASA Technical Reports Server (NTRS)

Mueller, J. L.; Fargion, G. S.; McClain, C. R. (Editor); Pegau, S.; Zanefeld, J. R. V.; Mitchell, B. G.; Kahru, M.; Wieland, J.; Stramska, M.

2003-01-01

This document stipulates protocols for measuring bio-optical and radiometric data for the Sensor Intercomparision and Merger for Biological and Interdisciplinary Oceanic Studies (SIMBIOS) Project activities and algorithm development. The document is organized into 6 separate volumes as Ocean Optics Protocols for Satellite Ocean Color Sensor Validation, Revision 4. Volume I: Introduction, Background, and Conventions; Volume II: Instrument Specifications, Characterization and Calibration; Volume III: Radiometric Measurements and Data Analysis Methods; Volume IV: Inherent Optical Properties: Instruments, Characterization, Field Measurements and Data Analysis Protocols; Volume V: Biogeochemical and Bio-Optical Measurements and Data Analysis Methods; Volume VI: Special Topics in Ocean Optics Protocols and Appendices. The earlier version of Ocean Optics Protocols for Satellite Ocean Color Sensor Validation, Revision 3 is entirely superseded by the six volumes of Revision 4 listed above.

A novel method for the simultaneous measurement of temperature and strain using a three-wire connection

NASA Astrophysics Data System (ADS)

Cappa, Paolo; Marinozzi, Franco; Sciuto, Salvatore Andrea

2001-04-01

A novel methodology to simultaneously measure strain and temperature by means of an electrical resistance strain gauge powered by an ac signal and connected to a strain indicator by means of thermocouple wires is proposed. The experimental validation of the viability of this method is conducted by means of a purely electrical simulation of both strain and temperature signals, respectively from -2000 to 2000 µm m-1 and -250 to 230 °C. The results obtained showed that strain measurement is affected by an error always less than ±2 µm m-1 for the whole range of simulated strains, while the error in temperature evaluation is always less than 0.6 °C. The effect of cross-talk between the two signals was determined to be insignificant.

Rapid lysostaphin test to differentiate Staphylococcus and Micrococcus species.

PubMed Central

Geary, C; Stevens, M

1986-01-01

A rapid, simple lysostaphin lysis susceptibility test to differentiate the genera Staphylococcus and Micrococcus was evaluated. Of 181 strains from culture collections, 95 of 95 Staphylococcus strains were lysed, and 79 of 79 Micrococcus strains were not lysed. The seven Planococcus strains were resistant. Clinical isolates (890) were tested with lysostaphin and for the ability to produce acid from glycerol in the presence of erythromycin. Overall agreement between the methods was 99.2%. All clinical Micrococcus strains (43) were resistant to lysostaphin, and all clinical Staphylococcus strains (847) were susceptible. Seven of the Staphylococcus strains did not produce acid from glycerol in the presence of erythromycin. This lysostaphin test provides results in 2 h. It is easier to perform than previously described lysostaphin lysis methods. It is also more rapid and accurate than the glycerol-erythromycin test. PMID:3519667

[Distribution of anaerobes in periodontal abscess and its resistance to antibiotics].

PubMed

He, Jun-lin; Yu, Li-ying; Chen, Jia-zhen

2012-12-01

To isolate and culture the predominant anaerobes from the periodontal abscesses, and to test the antibiotic susceptibility and drug resistant genes of the strains. The isolated strains were identified by both API20A biochemical method and polymerase chain reaction (PCR) method. The antibiotic susceptibility test was performed by agar dilution method. The resistant genes of the drug-resistant strains obtained were screened by PCR. The anaerobes were detected in 48% (28/58) of the samples and Prevotella melaninogenica (Pm) was mostly identified in 43% (12/28). API20A biochemical method had 82% (23/28) agreement with the 16SrRNA method in identification rate. Anaerobes were resistant to metronidazole, clindamycin and cefmetazole. The erythromycin-resistant methylase genes F (ermF) gene was detected in three of eight clindamycin resistant strains. None of them was found coded on bacterial plasmids. However, no metronidazole resistant gene was detected on drug resistant strains. Pm was the predominant species dectected in the periodontal abscess of the patients. The antibiotic agents should be used based on the genotypes and general condition of the patients.

Damage identification method for continuous girder bridges based on spatially-distributed long-gauge strain sensing under moving loads

NASA Astrophysics Data System (ADS)

Wu, Bitao; Wu, Gang; Yang, Caiqian; He, Yi

2018-05-01

A novel damage identification method for concrete continuous girder bridges based on spatially-distributed long-gauge strain sensing is presented in this paper. First, the variation regularity of the long-gauge strain influence line of continuous girder bridges which changes with the location of vehicles on the bridge is studied. According to this variation regularity, a calculation method for the distribution regularity of the area of long-gauge strain history is investigated. Second, a numerical simulation of damage identification based on the distribution regularity of the area of long-gauge strain history is conducted, and the results indicate that this method is effective for identifying damage and is not affected by the speed, axle number and weight of vehicles. Finally, a real bridge test on a highway is conducted, and the experimental results also show that this method is very effective for identifying damage in continuous girder bridges, and the local element stiffness distribution regularity can be revealed at the same time. This identified information is useful for maintaining of continuous girder bridges on highways.

A Test Method for Monitoring Modulus Changes during Durability Tests on Building Joint Sealants

Treesearch

Christopher C. White; Donald L. Hunston; Kar Tean Tan; Gregory T. Schueneman

2012-01-01

The durability of building joint sealants is generally assessed using a descriptive methodology involving visual inspection of exposed specimens for defects. It is widely known that this methodology has inherent limitations, including that the results are qualitative. A new test method is proposed that provides more fundamental and quantitative information about...

Risk management in fly-by-wire systems

NASA Technical Reports Server (NTRS)

Knoll, Karyn T.

1993-01-01

A general description of various types of fly-by-wire systems is provided. The risks inherent in digital flight control systems, like those used in the Space Shuttle, are identified. The results of a literature survey examining risk management methods in use throughout the aerospace industry are presented. The applicability of these methods to the Space Shuttle program is discussed.

The Q-Sort method: use in landscape assessment research and landscape planning

Treesearch

David G. Pitt; Ervin H. Zube

1979-01-01

The assessment of visual quality inherently involves the measurement of perceptual response to landscape. The Q-Sort Method is a psychometric technique which produces reliable and valid interval measurements of people's perceptions of landscape visual quality as depicted in photographs. It is readily understood by participants across a wide range of age groups and...

Comparison of Ribotyping, Randomly Amplified Polymorphic DNA Analysis, and Pulsed-Field Gel Electrophoresis in Typing of Lactobacillus rhamnosus and L. casei Strains

PubMed Central

Tynkkynen, Soile; Satokari, Reetta; Saarela, Maria; Mattila-Sandholm, Tiina; Saxelin, Maija

1999-01-01

A total of 24 strains, biochemically identified as members of the Lactobacillus casei group, were identified by PCR with species-specific primers. The same set of strains was typed by randomly amplified polymorphic DNA (RAPD) analysis, ribotyping, and pulsed-field gel electrophoresis (PFGE) in order to compare the discriminatory power of the methods. Species-specific primers for L. rhamnosus and L. casei identified the type strain L. rhamnosus ATCC 7469 and the neotype strain L. casei ATCC 334, respectively, but did not give any signal with the recently revived species L. zeae, which contains the type strain ATCC 15820 and the strain ATCC 393, which was previously classified as L. casei. Our results are in accordance with the suggested new classification of the L. casei group. Altogether, 21 of the 24 strains studied were identified with the species-specific primers. In strain typing, PFGE was the most discriminatory method, revealing 17 genotypes for the 24 strains studied. Ribotyping and RAPD analysis yielded 15 and 12 genotypes, respectively. PMID:10473394

Comparison of ribotyping, randomly amplified polymorphic DNA analysis, and pulsed-field gel electrophoresis in typing of Lactobacillus rhamnosus and L. casei strains.

PubMed

Tynkkynen, S; Satokari, R; Saarela, M; Mattila-Sandholm, T; Saxelin, M

1999-09-01

A total of 24 strains, biochemically identified as members of the Lactobacillus casei group, were identified by PCR with species-specific primers. The same set of strains was typed by randomly amplified polymorphic DNA (RAPD) analysis, ribotyping, and pulsed-field gel electrophoresis (PFGE) in order to compare the discriminatory power of the methods. Species-specific primers for L. rhamnosus and L. casei identified the type strain L. rhamnosus ATCC 7469 and the neotype strain L. casei ATCC 334, respectively, but did not give any signal with the recently revived species L. zeae, which contains the type strain ATCC 15820 and the strain ATCC 393, which was previously classified as L. casei. Our results are in accordance with the suggested new classification of the L. casei group. Altogether, 21 of the 24 strains studied were identified with the species-specific primers. In strain typing, PFGE was the most discriminatory method, revealing 17 genotypes for the 24 strains studied. Ribotyping and RAPD analysis yielded 15 and 12 genotypes, respectively.

Uniaxial strain on graphene: Raman spectroscopy study and band-gap opening.

PubMed

Ni, Zhen Hua; Yu, Ting; Lu, Yun Hao; Wang, Ying Ying; Feng, Yuan Ping; Shen, Ze Xiang

2008-11-25

Graphene was deposited on a transparent and flexible substrate, and tensile strain up to approximately 0.8% was loaded by stretching the substrate in one direction. Raman spectra of strained graphene show significant red shifts of 2D and G band (-27.8 and -14.2 cm(-1) per 1% strain, respectively) because of the elongation of the carbon-carbon bonds. This indicates that uniaxial strain has been successfully applied on graphene. We also proposed that, by applying uniaxial strain on graphene, tunable band gap at K point can be realized. First-principle calculations predicted a band-gap opening of approximately 300 meV for graphene under 1% uniaxial tensile strain. The strained graphene provides an alternative way to experimentally tune the band gap of graphene, which would be more efficient and more controllable than other methods that are used to open the band gap in graphene. Moreover, our results suggest that the flexible substrate is ready for such a strain process, and Raman spectroscopy can be used as an ultrasensitive method to determine the strain.

Finite element simulation and comparison of a shear strain and equivalent strain during ECAP and asymmetric rolling

NASA Astrophysics Data System (ADS)

Pesin, A.; Pustovoytov, D.; Shveyova, T.; Vafin, R.

2017-12-01

The level of a shear strain and equivalent strain plays a key role in terms of the possibility of using the asymmetric rolling process as a method of severe plastic deformation. Strain mode (pure shear or simple shear) can affect very strongly on the equivalent strain and the grain refinement of the material. This paper presents the results of FEM simulations and comparison of the equivalent strain in the aluminium alloy 5083 processed by a single-pass equal channel angular pressing (simple shear), symmetric rolling (pure shear) and asymmetric rolling (simultaneous pure and simple shear). The nonlinear effect of rolls speed ratio on the deformation characteristics during asymmetric rolling was found. Extremely high equivalent strain up to e=4.2 was reached during a single-pass asymmetric rolling. The influence of the shear strain on the level of equivalent strain is discussed. Finite element analysis of the deformation characteristics, presented in this study, can be used for optimization of the asymmetric rolling process as a method of severe plastic deformation.

Bacillus "next generation" diagnostics: moving from detection toward subtyping and risk-related strain profiling.

PubMed

Ehling-Schulz, Monika; Messelhäusser, Ute

2013-01-01

The highly heterogeneous genus Bacillus comprises the largest species group of endospore forming bacteria. Because of their ubiquitous nature, Bacillus spores can enter food production at several stages resulting in significant economic losses and posing a potential risk to consumers due the capacity of certain Bacillus strains for toxin production. In the past, food microbiological diagnostics was focused on the determination of species using conventional culture-based methods, which are still widely used. However, due to the extreme intra-species diversity found in the genus Bacillus, DNA-based identification and typing methods are gaining increasing importance in routine diagnostics. Several studies showed that certain characteristics are rather strain-dependent than species-specific. Therefore, the challenge for current and future Bacillus diagnostics is not only the efficient and accurate identification on species level but also the development of rapid methods to identify strains with specific characteristics (such as stress resistance or spoilage potential), trace contamination sources, and last but not least discriminate potential hazardous strains from non-toxic strains.

Strain intensity factor approach for predicting the strength of continuously reinforced metal matrix composites

NASA Technical Reports Server (NTRS)

Poe, C. C., Jr.

1988-01-01

A method was previously developed to predict the fracture toughness (stress intensity factor at failure) of composites in terms of the elastic constants and the tensile failing strain of the fibers. The method was applied to boron/aluminum composites made with various proportions of 0 to + or - 45 deg plies. Predicted values of fracture toughness were in gross error because widespread yielding of the aluminum matrix made the compliance very nonlinear. An alternate method was developed to predict the strain intensity factor at failure rather than the stress intensity factor because the singular strain field was not affected by yielding as much as the stress field. Strengths of specimens containing crack-like slits were calculated from predicted failing strains using uniaxial stress-strain curves. Predicted strengths were in good agreement with experimental values, even for the very nonlinear laminates that contained only + or - 45 deg plies. This approach should be valid for other metal matrix composites that have continuous fibers.

Fatigue crack identification method based on strain amplitude changing

NASA Astrophysics Data System (ADS)

Guo, Tiancai; Gao, Jun; Wang, Yonghong; Xu, Youliang

2017-09-01

Aiming at the difficulties in identifying the location and time of crack initiation in the castings of helicopter transmission system during fatigue tests, by introducing the classification diagnostic criteria of similar failure mode to find out the similarity of fatigue crack initiation among castings, an engineering method and quantitative criterion for detecting fatigue cracks based on strain amplitude changing is proposed. This method is applied on the fatigue test of a gearbox housing, whose results indicates: during the fatigue test, the system alarms when SC strain meter reaches the quantitative criterion. The afterwards check shows that a fatigue crack less than 5mm is found at the corresponding location of SC strain meter. The test result proves that the method can provide accurate test data for strength life analysis.

High-throughput screening of high Monascus pigment-producing strain based on digital image processing.

PubMed

Xia, Meng-lei; Wang, Lan; Yang, Zhi-xia; Chen, Hong-zhang

2016-04-01

This work proposed a new method which applied image processing and support vector machine (SVM) for screening of mold strains. Taking Monascus as example, morphological characteristics of Monascus colony were quantified by image processing. And the association between the characteristics and pigment production capability was determined by SVM. On this basis, a highly automated screening strategy was achieved. The accuracy of the proposed strategy is 80.6 %, which is compatible with the existing methods (81.1 % for microplate and 85.4 % for flask). Meanwhile, the screening of 500 colonies only takes 20-30 min, which is the highest rate among all published results. By applying this automated method, 13 strains with high-predicted production were obtained and the best one produced as 2.8-fold (226 U/mL) of pigment and 1.9-fold (51 mg/L) of lovastatin compared with the parent strain. The current study provides us with an effective and promising method for strain improvement.

Tissue Viscoelasticity Imaging Using Vibration and Ultrasound Coupler Gel

NASA Astrophysics Data System (ADS)

Yamakawa, Makoto; Shiina, Tsuyoshi

2012-07-01

In tissue diagnosis, both elasticity and viscosity are important indexes. Therefore, we propose a method for evaluating tissue viscoelasticity by applying vibration that is usually performed in elastography and using an ultrasound coupler gel with known viscoelasticity. In this method, we use three viscoelasticity parameters based on the coupler strain and tissue strain: the strain ratio as an elasticity parameter, and the phase difference and the normalized hysteresis loop area as viscosity parameters. In the agar phantom experiment, using these viscoelasticity parameters, we were able to estimate the viscoelasticity distribution of the phantom. In particular, the strain ratio and the phase difference were robust to strain estimation error.

Accuracy and Reproducibility of Strain by Speckle Tracking in Pediatric Subjects with Normal Heart and Single Ventricular Physiology: A 2D Speckle Tracking Echocardiography and Magnetic Resonance Imaging Correlative Study

PubMed Central

Singh, Gautam K.; Cupps, Brian; Pasque, Michael; Woodard, Pamela K.; Holland, Mark R.; Ludomirsky, Achiau

2013-01-01

Background Myocardial strain is a sensitive measure of ventricular systolic function. Two-dimensional speckle-tracking echocardiography (2DSE) is an angle-independent method for strain measurement but has not been validated in pediatric subjects. We evaluated the accuracy and reproducibility of 2DSE-measured strain against reference tagged MRI-measured strain in pediatric subjects with normal hearts and those with single ventricle (SV) of left ventricle (LV) morphology s/p Fontan procedure. Methods Peak systolic circumferential (CS) and longitudinal (LS) strains in segments (n = 16) of LVs in age and BSA matched 20 healthy and 12 pediatric subjects with tricuspid atresia s/p Fontan procedure were measured by 2DSE and tagged MRI. Average (global) and regional segmental strains measured by two methods were compared using Spearman and Bland-Altman analyses. Results 2DSE and tagged MRI measured global strains demonstrated close agreements, which were better for LS than CS and in normal LVs than in SVs (95% limits of agreement: +0.0% to +3.12%, −2.48 % to +1.08%, −4.6% to +1.8% and −3.6% to +1.8% respectively). There was variability in agreement between regional strains with wider limits in apical than in basal regions in normal LVs and heterogeneous in SVs. The strain values were significantly (p < 0.05) higher in normal LVs than in SVs except for basal LSs, which were similar in both cohorts. The regional strains in normal LVs demonstrated an apico-basal magnitude gradient whereas SVs showed heterogeneity. The reproducibility was the most robust for images obtained with frame rates between 60 and 90 frame/sec; global LS in both cohorts; and basal strains in normal LVs. Conclusions 2DSE-measured strains agree with MRI-measured strain globally but vary regionally particularly in SVs. Global strain may be more robust tool for the cardiac function evaluation than regional strain in SV physiology. The reliability of 2DSE measured strain is affected by the frame rate, nature of strain, and ventricular geometry. PMID:20850945

Methods of expanding bacteriophage host-range and bacteriophage produced by the methods

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

Crown, Kevin K.; Santarpia, Joshua

A method of producing novel bacteriophages with expanded host-range and bacteriophages with expanded host ranges are disclosed. The method produces mutant phage strains which are infectious to a second host and can be more infectious to their natural host than in their natural state. The method includes repeatedly passaging a selected phage strain into bacterial cultures that contain varied ratios of its natural host bacterial strain with a bacterial strain that the phage of interest is unable to infect; the target-host. After each passage the resulting phage are purified and screened for activity against the target-host via double-overlay assays. Whenmore » mutant phages that are shown to infect the target-host are discovered, they are further propagated in culture that contains only the target-host to produce a stock of the resulting mutant phage.« less

Plane elasto-plastic analysis of v-notched plate under bending by boundary integral equation method. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Rzasnicki, W.

1973-01-01

A method of solution is presented, which, when applied to the elasto-plastic analysis of plates having a v-notch on one edge and subjected to pure bending, will produce stress and strain fields in much greater detail than presently available. Application of the boundary integral equation method results in two coupled Fredholm-type integral equations, subject to prescribed boundary conditions. These equations are replaced by a system of simultaneous algebraic equations and solved by a successive approximation method employing Prandtl-Reuss incremental plasticity relations. The method is first applied to number of elasto-static problems and the results compared with available solutions. Good agreement is obtained in all cases. The elasto-plastic analysis provides detailed stress and strain distributions for several cases of plates with various notch angles and notch depths. A strain hardening material is assumed and both plane strain and plane stress conditions are considered.

Mycobacterium avium restriction fragment length polymorphism-IS IS1245 and the simple double repetitive element polymerase chain reaction typing method to screen genetic diversity in Brazilian strains.

PubMed

Sequeira, Patrícia Carvalho de; Fonseca, Leila de Souza; Silva, Marlei Gomes da; Saad, Maria Helena Féres

2005-11-01

Simple double repetitive element polymerase chain reaction (MaDRE-PCR) and Pvu II-IS1245 restriction fragment length polymorphism (RFLP) typing methods were used to type 41 Mycobacterium avium isolates obtained from 14 AIDS inpatients and 10 environment and animals specimens identified among 53 mycobacteria isolated from 237 food, chicken, and pig. All environmental and animals strains showed orphan patterns by both methods. By MaDRE-PCR four patients, with multiple isolates, showed different patterns, suggesting polyclonal infection that was confirmed by RFLP in two of them. This first evaluation of MaDRE-PCR on Brazilian M. avium strains demonstrated that the method seems to be useful as simple and less expensive typing method for screening genetic diversity in M. avium strains on selected epidemiological studies, although with limitation on analysis identical patterns except for one band.

Optimization of Stability Constrained Geometrically Nonlinear Shallow Trusses Using an Arc Length Sparse Method with a Strain Energy Density Approach

NASA Technical Reports Server (NTRS)

Hrinda, Glenn A.; Nguyen, Duc T.

2008-01-01

A technique for the optimization of stability constrained geometrically nonlinear shallow trusses with snap through behavior is demonstrated using the arc length method and a strain energy density approach within a discrete finite element formulation. The optimization method uses an iterative scheme that evaluates the design variables' performance and then updates them according to a recursive formula controlled by the arc length method. A minimum weight design is achieved when a uniform nonlinear strain energy density is found in all members. This minimal condition places the design load just below the critical limit load causing snap through of the structure. The optimization scheme is programmed into a nonlinear finite element algorithm to find the large strain energy at critical limit loads. Examples of highly nonlinear trusses found in literature are presented to verify the method.

CRISPR Approaches to Small Molecule Target Identification. | Office of Cancer Genomics

Cancer.gov

A long-standing challenge in drug development is the identification of the mechanisms of action of small molecules with therapeutic potential. A number of methods have been developed to address this challenge, each with inherent strengths and limitations. We here provide a brief review of these methods with a focus on chemical-genetic methods that are based on systematically profiling the effects of genetic perturbations on drug sensitivity.

Interim reliability evaluation program, Browns Ferry fault trees

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

Stewart, M.E.

1981-01-01

An abbreviated fault tree method is used to evaluate and model Browns Ferry systems in the Interim Reliability Evaluation programs, simplifying the recording and displaying of events, yet maintaining the system of identifying faults. The level of investigation is not changed. The analytical thought process inherent in the conventional method is not compromised. But the abbreviated method takes less time, and the fault modes are much more visible.

[Isolation of endophytic fungi from medicinal plant Brucea javanica and their microbial inhibition activity].

PubMed

Liang, Zi-Ning; Zhu, Hua; Lai, Kai-Ping; Chen, Long

2014-04-01

To isolate and identify endophytic fungi from Brucea javanica, and to detect the antimicrobial activity of these strains. Endophytic fungi were isolated by tissue inoculation culture and identified by conventional morphological characteristic method. Seven kinds of pathogenic fungi and three kinds of bacteria were used as targeting microbes to test microbial inhibition activities by agar plate antagonistic action and modified agar gel diffusion methods, respectively. A total of 83 endophytic fungi strains were isolated from the root, stem, leaf and fruit of Brucea javanica. 34 strains were obtained from the stem, 32 strains were obtained from the leaf, 15 strains were isolated from the root and 2 strains came from the fruit. These 73 strains which had been identified attribute to 5 orders, 6 families and 12 genera. For the isolated strains, 14 strains had antifungal activities against at least one pathogenic fungi, 9 strains showed antibacterial activities against one or more bacteria. Especially, the strain YJ-17 which belonged to Phomopsis genus showed the best inhibitory effect on the targeting microbes. The endophytic fungi from Brucea javanica show diversity and microbial inhibition activity, and are worthy for further study on plant disease controlling.

Field methods to measure surface displacement and strain with the Video Image Correlation method

NASA Technical Reports Server (NTRS)

Maddux, Gary A.; Horton, Charles M.; Mcneill, Stephen R.; Lansing, Matthew D.

1994-01-01

The objective of this project was to develop methods and application procedures to measure displacement and strain fields during the structural testing of aerospace components using paint speckle in conjunction with the Video Image Correlation (VIC) system.

Detection and differentiation of coxiella burnetii in biological fluids

DOEpatents

Frazier, Marvin E.; Mallavia, Louis P.; Samuel, James E.; Baca, Oswald G.

1993-01-01

Methods for detecting the presence of Coxiella burnetii in biological samples, as well as a method for differentiating strains of C. burnetii that are capable of causing acute disease from those strains capable of causing chronic disease are disclosed. The methods generally comprise treating cells contained within the biological sample to expose cellular DNA, and hybridizing the cellular DNA with a DNA probe containing DNA sequences that specifically hybridize with C. burnetii DNA of strains associated with the capacity to cause acute or chronic disease.

Method for determining the hardness of strain hardening articles of tungsten-nickel-iron alloy

DOEpatents

Wallace, Steven A.

1984-01-01

The present invention is directed to a rapid nondestructive method for determining the extent of strain hardening in an article of tungsten-nickel-iron alloy. The method comprises saturating the article with a magnetic field from a permanent magnet, measuring the magnetic flux emanating from the article, comparing the measurements of the magnetic flux emanating from the article with measured magnetic fluxes from similarly shaped standards of the alloy with known amounts of strain hardening to determine the hardness.

Measuring the triaxial load-deformation response of orthotropic materials subjected to large and small strain regimes

Treesearch

Edmond P. Saliklis; Steven M. Cramer; John C. Hermanson

1998-01-01

A new method for obtaining triaxial stress versus strain data is presented. The method tests cubic specimens and can provide constitutive data along three mutually perpendicular axes. Issues of removing the effects of boundary conditions in the proposed device are discussed. Two devices were constructed and used to obtain triaxial stress versus strain data on...

Digital Image Correlation of 2D X-ray Powder Diffraction Data for Lattice Strain Evaluation

PubMed Central

Zhang, Hongjia; Sui, Tan; Daisenberger, Dominik; Fong, Kai Soon

2018-01-01

High energy 2D X-ray powder diffraction experiments are widely used for lattice strain measurement. The 2D to 1D conversion of diffraction patterns is a necessary step used to prepare the data for full pattern refinement, but is inefficient when only peak centre position information is required for lattice strain evaluation. The multi-step conversion process is likely to lead to increased errors associated with the ‘caking’ (radial binning) or fitting procedures. A new method is proposed here that relies on direct Digital Image Correlation analysis of 2D X-ray powder diffraction patterns (XRD-DIC, for short). As an example of using XRD-DIC, residual strain values along the central line in a Mg AZ31B alloy bar after 3-point bending are calculated by using both XRD-DIC and the conventional ‘caking’ with fitting procedures. Comparison of the results for strain values in different azimuthal angles demonstrates excellent agreement between the two methods. The principal strains and directions are calculated using multiple direction strain data, leading to full in-plane strain evaluation. It is therefore concluded that XRD-DIC provides a reliable and robust method for strain evaluation from 2D powder diffraction data. The XRD-DIC approach simplifies the analysis process by skipping 2D to 1D conversion, and opens new possibilities for robust 2D powder diffraction data analysis for full in-plane strain evaluation. PMID:29543728

Geobacter strains that use alternate organic compounds, methods of making, and methods of use thereof

DOEpatents

Lovley, Derek R; Summers, Zarath Morgan; Haveman, Shelley Annette; Izallalen, Mounir

2013-12-03

In preferred embodiments, the present invention provides new isolated strains of Geobacter species that are capable of using a carbon source that is selected from C.sub.3 to C.sub.12 organic compounds selected from pyruvate or metabolic precursors of pyruvate as an electron donor in metabolism and in subsequent energy production. In other aspects, other preferred embodiments of the present invention include methods of making such strains and methods of using such strains. In general, the wild type strain of the microorganisms has been shown to be unable to use these C.sub.3 to C.sub.12 organic compounds as electron donors in metabolic steps such as the reduction of metallic ions. The inventive strains of microorganisms are useful improving bioremediation applications, including in situ bioremediation (including uranium bioremediation and halogenated solvent bioremediation), microbial fuel cells, power generation from small and large-scale waste facilities (e.g., biomass waste from dairy, agriculture, food processing, brewery, or vintner industries, etc.) using microbial fuel cells, and other applications of microbial fuel cells, including, but not limited to, improved electrical power supplies for environmental sensors, electronic sensors, and electric vehicles.

Molecular typing of uropathogenic E. coli strains by the ERIC-PCR method.

PubMed

Ardakani, Maryam Afkhami; Ranjbar, Reza

2016-04-01

Escherichia coli (E. coli) is the most common cause of urinary infections in hospitals. The aim of this study was to evaluate the ERIC-PCR method for molecular typing of uropathogenic E. coli strains isolated from hospitalized patients. In a cross sectional study, 98 E. coli samples were collected from urine samples taken from patients admitted to Baqiyatallah Hospital from June 2014 to January 2015. The disk agar diffusion method was used to determine antibiotic sensitivity. DNA proliferation based on repetitive intergenic consensus was used to classify the E. coli strains. The products of proliferation were electrophoresed on 1.5% agarose gel, and their dendrograms were drawn. The data were analyzed by online Insillico software. The method used in this research proliferated numerous bands (4-17 bands), ranging from 100 to 3000 base pairs. The detected strains were classified into six clusters (E1-E6) with 70% similarity between them. In this study, uropathogenic E. coli strains belonged to different genotypic clusters. It was found that ERIC-PCR had good differentiation power for molecular typing of uropathogenic E. coli strains isolated from the patients in the study.

High resolution identity testing of inactivated poliovirus vaccines.

PubMed

Mee, Edward T; Minor, Philip D; Martin, Javier

2015-07-09

Definitive identification of poliovirus strains in vaccines is essential for quality control, particularly where multiple wild-type and Sabin strains are produced in the same facility. Sequence-based identification provides the ultimate in identity testing and would offer several advantages over serological methods. We employed random RT-PCR and high throughput sequencing to recover full-length genome sequences from monovalent and trivalent poliovirus vaccine products at various stages of the manufacturing process. All expected strains were detected in previously characterised products and the method permitted identification of strains comprising as little as 0.1% of sequence reads. Highly similar Mahoney and Sabin 1 strains were readily discriminated on the basis of specific variant positions. Analysis of a product known to contain incorrect strains demonstrated that the method correctly identified the contaminants. Random RT-PCR and shotgun sequencing provided high resolution identification of vaccine components. In addition to the recovery of full-length genome sequences, the method could also be easily adapted to the characterisation of minor variant frequencies and distinction of closely related products on the basis of distinguishing consensus and low frequency polymorphisms. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Semiconductor material and method for enhancing solubility of a dopant therein

DOEpatents

Sadigh, Babak; Lenosky, Thomas J.; Rubia, Tomas Diaz; Giles, Martin; Caturla, Maria-Jose; Ozolins, Vidvuds; Asta, Mark; Theiss, Silva; Foad, Majeed; Quong, Andrew

2003-09-09

A method for enhancing the equilibrium solubility of boron and indium in silicon. The method involves first-principles quantum mechanical calculations to determine the temperature dependence of the equilibrium solubility of two important p-type dopants in silicon, namely boron and indium, under various strain conditions. The equilibrium thermodynamic solubility of size-mismatched impurities, such as boron and indium in silicon, can be raised significantly if the silicon substrate is strained appropriately. For example, for boron, a 1% compressive strain raises the equilibrium solubility by 100% at 1100.degree. C.; and for indium, a 1% tensile strain at 1100.degree. C., corresponds to an enhancement of the solubility by 200%.