DNA content analysis allows discrimination between Trypanosoma cruzi and Trypanosoma rangeli.

PubMed

Naves, Lucila Langoni; da Silva, Marcos Vinícius; Fajardo, Emanuella Francisco; da Silva, Raíssa Bernardes; De Vito, Fernanda Bernadelli; Rodrigues, Virmondes; Lages-Silva, Eliane; Ramírez, Luis Eduardo; Pedrosa, André Luiz

2017-01-01

Trypanosoma cruzi, a human protozoan parasite, is the causative agent of Chagas disease. Currently the species is divided into six taxonomic groups. The genome of the CL Brener clone has been estimated to be 106.4-110.7 Mb, and DNA content analyses revealed that it is a diploid hybrid clone. Trypanosoma rangeli is a hemoflagellate that has the same reservoirs and vectors as T. cruzi; however, it is non-pathogenic to vertebrate hosts. The haploid genome of T. rangeli was previously estimated to be 24 Mb. The parasitic strains of T. rangeli are divided into KP1(+) and KP1(-). Thus, the objective of this study was to investigate the DNA content in different strains of T. cruzi and T. rangeli by flow cytometry. All T. cruzi and T. rangeli strains yielded cell cycle profiles with clearly identifiable G1-0 (2n) and G2-M (4n) peaks. T. cruzi and T. rangeli genome sizes were estimated using the clone CL Brener and the Leishmania major CC1 as reference cell lines because their genome sequences have been previously determined. The DNA content of T. cruzi strains ranged from 87,41 to 108,16 Mb, and the DNA content of T. rangeli strains ranged from 63,25 Mb to 68,66 Mb. No differences in DNA content were observed between KP1(+) and KP1(-) T. rangeli strains. Cultures containing mixtures of the epimastigote forms of T. cruzi and T. rangeli strains resulted in cell cycle profiles with distinct G1 peaks for strains of each species. These results demonstrate that DNA content analysis by flow cytometry is a reliable technique for discrimination between T. cruzi and T. rangeli isolated from different hosts.

Stability of direct band gap under mechanical strains for monolayer MoS2, MoSe2, WS2 and WSe2

NASA Astrophysics Data System (ADS)

Deng, Shuo; Li, Lijie; Li, Min

2018-07-01

Single layer transition-metal dichalcogenides materials (MoS2, MoSe2, WS2 and WSe2) are investigated using the first-principles method with the emphasis on their responses to mechanical strains. All these materials display the direct band gap under a certain range of strains from compressive to tensile (stable range). We have found that this stable range is different for these materials. Through studying on their mechanical properties again using the first-principles approach, it is unveiled that this stable strain range is determined by the Young's modulus. More analysis on strains induced electronic band gap properties have also been conducted.

Genomic Analysis of Phylotype I Strain EP1 Reveals Substantial Divergence from Other Strains in the Ralstonia solanacearum Species Complex

PubMed Central

Li, Peng; Wang, Dechen; Yan, Jinli; Zhou, Jianuan; Deng, Yinyue; Jiang, Zide; Cao, Bihao; He, Zifu; Zhang, Lianhui

2016-01-01

Ralstonia solanacearum species complex is a devastating group of phytopathogens with an unusually wide host range and broad geographical distribution. R. solanacearum isolates may differ considerably in various properties including host range and pathogenicity, but the underlying genetic bases remain vague. Here, we conducted the genome sequencing of strain EP1 isolated from Guangdong Province of China, which belongs to phylotype I and is highly virulent to a range of solanaceous crops. Its complete genome contains a 3.95-Mb chromosome and a 2.05-Mb mega-plasmid, which is considerably bigger than reported genomes of other R. solanacearum strains. Both the chromosome and the mega-plasmid have essential house-keeping genes and many virulence genes. Comparative analysis of strain EP1 with other 3 phylotype I and 3 phylotype II, III, IV strains unveiled substantial genome rearrangements, insertions and deletions. Genome sequences are relatively conserved among the 4 phylotype I strains, but more divergent among strains of different phylotypes. Moreover, the strains exhibited considerable variations in their key virulence genes, including those encoding secretion systems and type III effectors. Our results provide valuable information for further elucidation of the genetic basis of diversified virulences and host range of R. solanacearum species. PMID:27833603

Insecticide Resistance in Eggs and First Instars of the Bed Bug, Cimex lectularius (Hemiptera: Cimicidae).

PubMed

Campbell, Brittany E; Miller, Dini M

2015-01-15

Two strains of the common bed bug, Cimex lectularius L., eggs and first instars collected from pyrethroid-resistant adults were evaluated for insecticide resistance and compared to a susceptible strain. Dose-response bioassays were conducted using two insecticide formulations (Temprid: imidacloprid/β-cyfluthrin, and Transport: acetamiprid/ bifenthrin). The lethal concentration (LC50) for the two resistant egg strains exposed to imidacloprid/β-cyfluthrin ranged from 3 to 5-fold higher than susceptible strain eggs. Resistant strain eggs dipped into formulations of acetamiprid/bifenthrin had LC50 values which were significantly greater (39 to 1,080-fold) than susceptible strain eggs. Similar to eggs, resistant strain first instars exposed to residual applications of imidacloprid/β-cyfluthrin had LC50 values ranging from 121 to 493-fold greater than susceptible strain first instars. When resistant strain first instars were treated with acetamiprid/bifenthrin, they had LC50 values that were 99 to >1,900-fold greater than susceptible strain first instars. To determine differences between egg and first instar resistance, stage resistance ratios (SRR) were compared between the two stages. There was little difference between the egg and first instar stages, indicated by small SRR values ranging from 1.1 to 10.0. This study suggests that insecticide resistance is expressed early during bed bug development.

Insecticide Resistance in Eggs and First Instars of the Bed Bug, Cimex lectularius (Hemiptera: Cimicidae)

PubMed Central

Campbell, Brittany E.; Miller, Dini M.

2015-01-01

Two strains of the common bed bug, Cimex lectularius L., eggs and first instars collected from pyrethroid-resistant adults were evaluated for insecticide resistance and compared to a susceptible strain. Dose-response bioassays were conducted using two insecticide formulations (Temprid: imidacloprid/β-cyfluthrin, and Transport: acetamiprid/bifenthrin). The lethal concentration (LC50) for the two resistant egg strains exposed to imidacloprid/β-cyfluthrin ranged from 3 to 5-fold higher than susceptible strain eggs. Resistant strain eggs dipped into formulations of acetamiprid/bifenthrin had LC50 values which were significantly greater (39 to 1,080-fold) than susceptible strain eggs. Similar to eggs, resistant strain first instars exposed to residual applications of imidacloprid/β-cyfluthrin had LC50 values ranging from 121 to 493-fold greater than susceptible strain first instars. When resistant strain first instars were treated with acetamiprid/bifenthrin, they had LC50 values that were 99 to >1,900-fold greater than susceptible strain first instars. To determine differences between egg and first instar resistance, stage resistance ratios (SRR) were compared between the two stages. There was little difference between the egg and first instar stages, indicated by small SRR values ranging from 1.1 to 10.0. This study suggests that insecticide resistance is expressed early during bed bug development. PMID:26463070

Sensitivity Enhancement of FBG-Based Strain Sensor.

PubMed

Li, Ruiya; Chen, Yiyang; Tan, Yuegang; Zhou, Zude; Li, Tianliang; Mao, Jian

2018-05-17

A novel fiber Bragg grating (FBG)-based strain sensor with a high-sensitivity is presented in this paper. The proposed FBG-based strain sensor enhances sensitivity by pasting the FBG on a substrate with a lever structure. This typical mechanical configuration mechanically amplifies the strain of the FBG to enhance overall sensitivity. As this mechanical configuration has a high stiffness, the proposed sensor can achieve a high resonant frequency and a wide dynamic working range. The sensing principle is presented, and the corresponding theoretical model is derived and validated. Experimental results demonstrate that the developed FBG-based strain sensor achieves an enhanced strain sensitivity of 6.2 pm/με, which is consistent with the theoretical analysis result. The strain sensitivity of the developed sensor is 5.2 times of the strain sensitivity of a bare fiber Bragg grating strain sensor. The dynamic characteristics of this sensor are investigated through the finite element method (FEM) and experimental tests. The developed sensor exhibits an excellent strain-sensitivity-enhancing property in a wide frequency range. The proposed high-sensitivity FBG-based strain sensor can be used for small-amplitude micro-strain measurement in harsh industrial environments.

Sensitivity Enhancement of FBG-Based Strain Sensor

PubMed Central

Chen, Yiyang; Tan, Yuegang; Zhou, Zude; Mao, Jian

2018-01-01

A novel fiber Bragg grating (FBG)-based strain sensor with a high-sensitivity is presented in this paper. The proposed FBG-based strain sensor enhances sensitivity by pasting the FBG on a substrate with a lever structure. This typical mechanical configuration mechanically amplifies the strain of the FBG to enhance overall sensitivity. As this mechanical configuration has a high stiffness, the proposed sensor can achieve a high resonant frequency and a wide dynamic working range. The sensing principle is presented, and the corresponding theoretical model is derived and validated. Experimental results demonstrate that the developed FBG-based strain sensor achieves an enhanced strain sensitivity of 6.2 pm/με, which is consistent with the theoretical analysis result. The strain sensitivity of the developed sensor is 5.2 times of the strain sensitivity of a bare fiber Bragg grating strain sensor. The dynamic characteristics of this sensor are investigated through the finite element method (FEM) and experimental tests. The developed sensor exhibits an excellent strain-sensitivity-enhancing property in a wide frequency range. The proposed high-sensitivity FBG-based strain sensor can be used for small-amplitude micro-strain measurement in harsh industrial environments. PMID:29772826

Patterned, highly stretchable and conductive nanofibrous PANI/PVDF strain sensors based on electrospinning and in situ polymerization

NASA Astrophysics Data System (ADS)

Yu, Gui-Feng; Yan, Xu; Yu, Miao; Jia, Meng-Yang; Pan, Wei; He, Xiao-Xiao; Han, Wen-Peng; Zhang, Zhi-Ming; Yu, Liang-Min; Long, Yun-Ze

2016-01-01

A facile fabrication strategy via electrospinning and followed by in situ polymerization to fabricate a patterned, highly stretchable, and conductive polyaniline/poly(vinylidene fluoride) (PANI/PVDF) nanofibrous membrane is reported. Owing to the patterned structure, the nanofibrous PANI/PVDF strain sensor can detect a strain up to 110%, for comparison, which is 2.6 times higher than the common nonwoven PANI/PVDF mat and much larger than the previously reported values (usually less than 15%). Meanwhile, the conductivity of the patterned strain sensor shows a linear response to the applied strain in a wide range from 0% to about 85%. Additionally, the patterned PANI/PVDF strain sensor can completely recover to its original electrical and mechanical values within a strain range of more than 22%, and exhibits good durability over 10 000 folding-unfolding tests. Furthermore, the strain sensor also can be used to detect finger motion. The results demonstrate promising application of the patterned nanofibrous membrane in flexible electronic fields.A facile fabrication strategy via electrospinning and followed by in situ polymerization to fabricate a patterned, highly stretchable, and conductive polyaniline/poly(vinylidene fluoride) (PANI/PVDF) nanofibrous membrane is reported. Owing to the patterned structure, the nanofibrous PANI/PVDF strain sensor can detect a strain up to 110%, for comparison, which is 2.6 times higher than the common nonwoven PANI/PVDF mat and much larger than the previously reported values (usually less than 15%). Meanwhile, the conductivity of the patterned strain sensor shows a linear response to the applied strain in a wide range from 0% to about 85%. Additionally, the patterned PANI/PVDF strain sensor can completely recover to its original electrical and mechanical values within a strain range of more than 22%, and exhibits good durability over 10 000 folding-unfolding tests. Furthermore, the strain sensor also can be used to detect finger motion. The results demonstrate promising application of the patterned nanofibrous membrane in flexible electronic fields. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08618c

Elevated temperature axial and torsional fatigue behavior of Haynes 188

NASA Technical Reports Server (NTRS)

Bonacuse, Peter J.; Kalluri, Sreeramesh

1995-01-01

The results are reported for high-temperature axial and torsional low-cycle fatigue experiments performed at 760 C in air on thin-walled tubular specimens of Haynes 188, a wrought cobalt-based superalloy. Data are also presented for mean coefficient of thermal expansion, elastic modulus, and shear modulus at various temperatures from room to 1000 C, and monotonic and cyclic stress-strain curves in tension and in shear at 760 C. This data set is used to evaluate several multiaxial fatigue life models (most were originally developed for room temperature multiaxial life prediction) including von Mises equivalent strain range (ASME Boiler and Pressure Code), Manson-Halford, modified multiaxiality factor (proposed in this paper), modified Smith-Watson-Topper, and Fatemi-Socie-Kurath. At von Mises equivalent strain ranges (the torsional strain range divided by the square root of 3, taking the Poisson's ratio to be 0.5), torsionally strained specimens lasted, on average, factors of 2 to 3 times longer than axially strained specimens. The modified multiaxiality factor approach shows promise as a useful method of estimating torsional fatigue life from axial fatigue data at high temperatures. Several difficulties arose with the specimen geometry and extensometry used in these experiments. Cracking at extensometer probe indentations was a problem at smaller strain ranges. Also, as the largest axial and torsional strain range fatigue tests neared completion, a small amount of specimen buckling was observed.

Dynamical properties of the brain tissue under oscillatory shear stresses at large strain range

NASA Astrophysics Data System (ADS)

Boudjema, F.; Khelidj, B.; Lounis, M.

2017-01-01

In this experimental work, we study the viscoelastic behaviour of in vitro brain tissue, particularly the white matter, under oscillatory shear strain. The selective vulnerability of this tissue is the anisotropic mechanical properties of theirs different regions lead to a sensitivity to the angular shear rate and magnitude of strain. For this aim, shear storage modulus (G‧) and loss modulus (G″) were measured over a range of frequencies (1 to 100 Hz), for different levels of strain (1 %, to 50 %). The mechanical responses of the brain matter samples showed a viscoelastic behaviour that depend on the correlated strain level and frequency range and old age sample. The samples have been showed evolution behaviour by increasing then decreasing the strain level. Also, the stiffness anisotropy of brain matter was showed between regions and species.

Fatigue History and in-situ Loading Studies of the overload Effect Using High Resolution X-ray Strain Profiling

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

Croft,M.; Jisrawi, N.; Zhong, Z.

High-energy synchrotron X-ray diffraction experiments are used to perform local crack plane strain profiling of 4140 steel compact tension specimens fatigued at constant amplitude, subjected to a single overload cycle, then fatigued some more at constant amplitude. X-ray strain profiling results on a series of samples employing in-situ load cycling are correlated with the crack growth rate (da/dN) providing insight into the da/dN retardation known as the 'overload effect'. Immediately after the overload, the strain under maximum load is greatly reduced but the range of strain, between zero and maximum load, remains unchanged compared to the pre-overload values. At themore » point of maximum retardation, it is the strain range that is greatly reduced while the maximum-load strain has begun to recover to the pre-overload value. For a sample that has recovered to approximately half of the original da/dN value following the overload, the strain at maximum load is fully recovered while the strain range, though partially recovered, is still substantially reduced. The dominance of the strain range in the overload effect is clearly indicated. Subject to some assumptions, strong quantitative support for a crack growth rate driving force of the suggested form [(K{sub max}){sup -p}({Delta}K){sup p}]{sup {gamma}} is found. A dramatic nonlinear load dependence in the spatial distribution of the strain at maximum retardation is also demonstrated: at low load the response is dominantly at the overload position; whereas at high loads it is dominantly at the crack tip position. This transfer of load response away from the crack tip to the overload position appears fundamental to the overload effect for high R-ratio fatigue as studied here.« less

Survivial Strategies in Bacterial Range Expansions

NASA Astrophysics Data System (ADS)

Frey, Erwin

2014-03-01

Bacterial communities represent complex and dynamic ecological systems. Different environmental conditions as well as bacterial interactions determine the establishment and sustainability of bacterial diversity. In this talk we discuss the competition of three Escherichia coli strains during range expansions on agar plates. In this bacterial model system, a colicin E2 producing strain C competes with a colicin resistant strain R and with a colicin sensitive strain S for new territory. Genetic engineering allows us to tune the growth rates of the strains and to study distinct ecological scenarios. These scenarios may lead to either single-strain dominance, pairwise coexistence, or to the coexistence of all three strains. In order to elucidate the survival mechanisms of the individual strains, we also developed a stochastic agent-based model to capture the ecological scenarios in silico. In a combined theoretical and experimental approach we are able to show that the level of biodiversity depends crucially on the composition of the inoculum, on the relative growth rates of the three strains, and on the effective reach of colicin toxicity.

Functional properties of Lactobacillus plantarum strains isolated from Maasai traditional fermented milk products in Kenya.

PubMed

Mathara, Julius Maina; Schillinger, Ulrich; Kutima, Phillip M; Mbugua, Samuel K; Guigas, Claudia; Franz, Charles; Holzapfel, Wilhelm H

2008-04-01

Lactobacillus plantarum was the major species among the lactic acid bacterial strains isolated from traditional fermented milk of the Maasai in Kenya. Selected strains were characterized for their functional properties using in vitro standard procedures. All strains expressed acid tolerance at pH 2.0 after 2-h exposure of values that ranged from 1% to 100%, while bile tolerance of acid-stressed cells at 0.3% oxgal varied from 30% to 80%. In vitro adhesion to the mucus-secreting cell line HT 29 MTX and binding capacity to extracellular protein matrices was demonstrated for several strains. The four strains tested in a simulated stomach duodenum passage survived with recovery rates ranging from 17% to 100%. Strains were intrinsically resistant to several antibiotics tested. From these in vitro studies, a number of Lb. plantarum strains isolated from the Maasai traditional fermented milk showed probiotic potential. The strains are good candidates for multifunctional starter culture development.

Calibration and evaluation tests of strain gages for use on structure exposed to cryogenic and reentry temperatures

NASA Astrophysics Data System (ADS)

Mueller, Richard N.; Howard, J. Lawrence; Sikorra, Charles F.; Swegle, Allan R.

Commercial strain gages were evaluated for proposed strain measurement on a Rene 41 honeycomb test panel to be subjected to temperatures from -423 F to +1600 F. Foil strain gages of three different temperature compensations, a weldable strain gage, and a capacitive strain gage, were tested to determine characteristics of apparent strain, strain sensitivity, and temperature operational limits under stabilized temperature and several heating and cooling temperature rates. Test results show that strain measurement over the total temperature range can be made using a combination of gages.

Optical fiber strain sensor with improved linearity range

NASA Technical Reports Server (NTRS)

Egalon, Claudio Oliveira (Inventor); Rogowski, Robert S. (Inventor)

1995-01-01

A strain sensor is constructed from a two mode optical fiber. When the optical fiber is surface mounted in a straight line and the object to which the optical fiber is mounted is subjected to strain within a predetermined range, the light intensity of any point at the output of the optical fiber will have a linear relationship to strain, provided the intermodal phase difference is less than 0.17 radians.

Colony Dimorphism in Bradyrhizobium Strains

PubMed Central

Sylvester-Bradley, Rosemary; Thornton, Philip; Jones, Peter

1988-01-01

Ten isolates of Bradyrhizobium spp. which form two colony types were studied; the isolates originated from a range of legume species. The two colony types differed in the amount of gum formed or size or both, depending on the strain. Whole 7-day-old colonies of each type were subcultured to determine the proportion of cells which had changed to the other type. An iterative computerized procedure was used to determine the rate of switching per generation between the two types and to predict proportions reached at equilibrium for each strain. The predicted proportions of the wetter (more gummy) or larger colony type at equilibrium differed significantly between strains, ranging from 0.9999 (strain CIAT 2383) to 0.0216 (strain CIAT 2469), because some strains switched faster from dry to wet (or small to large) and others switched faster from wet to dry (or large to small). Predicted equilibrium was reached after about 140 generations in strain USDA 76. In all but one strain (CIAT 3030) the growth rate of the wetter colony type was greater than or similar to that of the drier type. The mean difference in generation time between the two colony types was 0.37 h. Doubling times calculated for either colony type after 7 days of growth on the agar surface ranged from 6.0 to 7.3 h. The formation of two persistent colony types by one strain (clonal or colony dimorphism) may be a common phenomenon among Bradyrhizobium strains. Images PMID:16347599

Biological removal of arsenic pollution by soil fungi.

PubMed

Srivastava, Pankaj Kumar; Vaish, Aradhana; Dwivedi, Sanjay; Chakrabarty, Debasis; Singh, Nandita; Tripathi, Rudra Deo

2011-05-15

Fifteen fungal strains were isolated from arsenic contaminated (range 9.45-15.63 mg kg(-1)) agricultural soils from the state of West Bengal, India. Five fungal strains were belonged to the Aspergillus and Trichoderma group each, however, remaining five were identified as the Neocosmospora, Sordaria, Rhizopus, Penicillium and sterile mycelial strain. All these fungal strains were cultivated on medium supplemented with 100, 500, 1000, 5000 and 10,000 mg l(-1) of sodium arsenate. After 30-day cultivation under laboratory conditions, radial growth of these strains was determined and compared with control. Toxicity and tolerance of these strains to arsenate were evaluated on the basis of tolerance index. Out of fifteen, only five fungal strains were found resistant and survived with tolerance index pattern as 0.956 (sterile mycelial strain)>0.311 (Rhizopus sp.)>0.306 (Neocosmospora sp.)>0.212 (Penicillium sp.)>0.189 (Aspergillus sp.) at 10,000 mg l(-1) of arsenate. The arsenic removal efficacy of ten fungal strains, tolerant to 5000 mg l(-1) arsenate, was also assayed under laboratory conditions for 21 days. All these strains were cultivated individually on mycological broth enriched with 10 mg l(-1) of arsenic. The initial and final pH of cultivating medium, fungal biomass and removal of arsenic by each fungal strain were evaluated. Fungal biomass of ten strains removed arsenic biologically from the medium which were ranged from 10.92 to 65.81% depending on fungal species. The flux of biovolatilized arsenic was determined indirectly by estimating the sum of arsenic content in fungal biomass and medium. The mean percent removal as flux of biovolatilized arsenic ranged from 3.71 to 29.86%. The most effective removal of arsenic was observed in the Trichoderma sp., sterile mycelial strain, Neocosmospora sp. and Rhizopus sp. fungal strains. These fungal strains can be effectively used for the bioremediation of arsenic-contaminated agricultural soils. Copyright © 2011 Elsevier B.V. All rights reserved.

Phylogenetic Relationship in Different Commercial Strains of Pleurotus nebrodensis Based on ITS Sequence and RAPD.

PubMed

Alam, Nuhu; Shim, Mi Ja; Lee, Min Woong; Shin, Pyeong Gyun; Yoo, Young Bok; Lee, Tae Soo

2009-09-01

The molecular phylogeny in nine different commercial cultivated strains of Pleurotus nebrodensis was studied based on their internal transcribed spacer (ITS) region and RAPD. In the sequence of ITS region of selected strains, it was revealed that the total length ranged from 592 to 614 bp. The size of ITS1 and ITS2 regions varied among the strains from 219 to 228 bp and 211 to 229 bp, respectively. The sequence of ITS2 was more variable than ITS1 and the region of 5.8S sequences were identical. Phylogenetic tree of the ITS region sequences indicated that selected strains were classified into five clusters. The reciprocal homologies of the ITS region sequences ranged from 99 to 100%. The strains were also analyzed by RAPD with 20 arbitrary primers. Twelve primers were efficient to applying amplification of the genomic DNA. The sizes of the polymorphic fragments obtained were in the range of 200 to 2000 bp. RAPD and ITS analysis techniques were able to detect genetic variation among the tested strains. Experimental results suggested that IUM-1381, IUM-3914, IUM-1495 and AY-581431 strains were genetically very similar. Therefore, all IUM and NCBI gene bank strains of P. nebrodensis were genetically same with some variations.

Fabric strain sensor integrated with CNPECs for repeated large deformation

NASA Astrophysics Data System (ADS)

Yi, Weijing

Flexible and soft strain sensors that can be used in smart textiles for wearable applications are much desired. They should meet the requirements of low modulus, large working range and good fatigue resistance as well as good sensing performances. However, there were no commercial products available and the objective of the thesis is to investigate fabric strain sensors based on carbon nanoparticle (CNP) filled elastomer composites (CNPECs) for potential wearing applications. Conductive CNPECs were fabricated and investigated. The introduction of silicone oil (SO) significantly decreased modulus of the composites to less than 1 MPa without affecting their deformability and they showed good stability after heat treatment. With increase of CNP concentration, a percolation appeared in electrical resistivity and the composites can be divided into three ranges. I-V curves and impedance spectra together with electro-mechanical studies demonstrated a balance between sensitivity and working range for the composites with CNP concentrations in post percolation range, and were preferred for sensing applications only if the fatigue life was improved. Due to the good elasticity and failure resist property of knitted fabric under repeated extension, it was adopted as substrate to increase the fatigue life of the conductive composites. After optimization of processing parameters, the conductive fabric with CNP concentration of 9.0CNP showed linear I-V curves when voltage is in the range of -1 V/mm and 1 V/mm and negligible capacitive behavior when frequency below 103 Hz even with strain of 60%. It showed higher sensitivity due to the combination of nonlinear resistance-strain behavior of the CNPECs and non-even strain distribution of knitted fabric under extension. The fatigue life of the conductive fabric was greatly improved. Extended on the studies of CNPECs and the coated conductive fabrics, a fabric strain sensor was designed, fabricated and packaged. The Young's modulus of the packaged fabric strain sensor was less than 1 MPa; the strain gauge factor was 4.76 within the strain range of 0-40% and the hysteresis was 5.5%; the resistance relaxation was 5.56% with a constant strain of 40%; the fatigue life of the sensor was more than 100,000 cycles.

Genetic engineering of industrial strains of Saccharomyces cerevisiae.

PubMed

Le Borgne, Sylvie

2012-01-01

Genetic engineering has been successfully applied to Saccharomyces cerevisiae laboratory strains for different purposes: extension of substrate range, improvement of productivity and yield, elimination of by-products, improvement of process performance and cellular properties, and extension of product range. The potential of genetically engineered yeasts for the massive production of biofuels as bioethanol and other nonfuel products from renewable resources as lignocellulosic biomass hydrolysates has been recognized. For such applications, robust industrial strains of S. cerevisiae have to be used. Here, some relevant genetic and genomic characteristics of industrial strains are discussed in relation to the problematic of the genetic engineering of such strains. General molecular tools applicable to the manipulation of S. cerevisiae industrial strains are presented and examples of genetically engineered industrial strains developed for the production of bioethanol from lignocellulosic biomass are given.

Highly Sensitive Multifilament Fiber Strain Sensors with Ultrabroad Sensing Range for Textile Electronics.

PubMed

Lee, Jaehong; Shin, Sera; Lee, Sanggeun; Song, Jaekang; Kang, Subin; Han, Heetak; Kim, SeulGee; Kim, Seunghoe; Seo, Jungmok; Kim, DaeEun; Lee, Taeyoon

2018-05-22

Highly stretchable fiber strain sensors are one of the most important components for various applications in wearable electronics, electronic textiles, and biomedical electronics. Herein, we present a facile approach for fabricating highly stretchable and sensitive fiber strain sensors by embedding Ag nanoparticles into a stretchable fiber with a multifilament structure. The multifilament structure and Ag-rich shells of the fiber strain sensor enable the sensor to simultaneously achieve both a high sensitivity and largely wide sensing range despite its simple fabrication process and components. The fiber strain sensor simultaneously exhibits ultrahigh gauge factors (∼9.3 × 10 5 and ∼659 in the first stretching and subsequent stretching, respectively), a very broad strain-sensing range (450 and 200% for the first and subsequent stretching, respectively), and high durability for more than 10 000 stretching cycles. The fiber strain sensors can also be readily integrated into a glove to control a hand robot and effectively applied to monitor the large volume expansion of a balloon and a pig bladder for an artificial bladder system, thereby demonstrating the potential of the fiber strain sensors as candidates for electronic textiles, wearable electronics, and biomedical engineering.

Measuring systolic ankle and toe pressure using the strain gauge technique--a comparison study between mercury and indium-gallium strain gauges.

PubMed

Broholm, Rikke; Wiinberg, Niels; Simonsen, Lene

2014-09-01

Measurement of the ankle and toe pressures are often performed using a plethysmograph, compression cuffs and a strain gauge. Usually, the strain gauge contains mercury but other alternatives exist. From 2014, the mercury-containing strain gauge will no longer be available in the European Union. The aim of this study was to compare an indium-gallium strain gauge to the established mercury-containing strain gauge. Consecutive patients referred to the Department of Clinical Physiology and Nuclear Medicine at Bispebjerg and Frederiksberg Hospitals for measurements of systolic ankle and toe pressures volunteered for the study. Ankle and toe pressures were measured twice with the mercury and the indium-gallium strain gauge in random order. Comparison of the correlation between the mean pressure using the mercury and the indium-gallium device and the difference between the two devices was performed for both toe and ankle level. A total of 53 patients were included (36 male). Mean age was 69 (range, 45-92 years). Mean pressures at toe and ankle level with the mercury and the indium-gallium strain gauges were 77 (range, 0-180) mm Hg and 113 (range, 15-190) mm Hg, respectively. Comparison between the mercury and the indium-gallium strain gauge showed a difference in toe blood pressure values of - 0.7 mm Hg (SD: 7.0). At the ankle level, a difference of 2.0 mm Hg (SD: 8.6) was found. The two different devices agree sufficiently in the measurements of systolic ankle and toe pressure for the indium-gallium strain gauge to replace the mercury strain gauge.

Health benefits of probiotics: are mixtures more effective than single strains?

PubMed

Chapman, C M C; Gibson, G R; Rowland, I

2011-02-01

Most studies on probiotics utilise single strains, sometimes incorporated into yoghurts. There are fewer studies on efficacy of mixtures of probiotic strains. This review examines the evidence that (a) probiotic mixtures are beneficial for a range of health-related outcomes and (b) mixtures are more or less effective than their component strains administered separately. Mixtures of probiotics had beneficial effects on the end points including irritable bowel syndrome and gut function, diarrhoea, atopic disease, immune function and respiratory tract infections, gut microbiota modulation, inflammatory bowel disease and treatment of Helicobacter pylori infection. However, only 16 studies compared the effect of a mixture with that of its component strains separately, although in 12 cases (75%), the mixture was more effective. Probiotic mixtures appear to be effective against a wide range of end points. Based on a limited number of studies, multi-strain probiotics appear to show greater efficacy than single strains, including strains that are components of the mixtures themselves. However, whether this is due to synergistic interactions between strains or a consequence of the higher probiotic dose used in some studies is at present unclear.

Genetic and Biochemical Characterization of Monokaryotic Progeny Strains of Button Mushroom (Agaricus bisporus)

PubMed Central

Kwon, Hyuk Woo; Choi, Min Ah; Yun, Yeo Hong; Oh, Youn-Lee; Kong, Won-Sik

2015-01-01

To promote the selection of promising monokaryotic strains of button mushroom (Agaricus bisporus) during breeding, 61 progeny strains derived from basidiospores of two different lines of dikaryotic parental strains, ASI1038 and ASI1346, were analyzed by nucleotide sequencing of the intergenic spacer I (IGS I) region in their rDNA and by extracellular enzyme assays. Nineteen different sizes of IGS I, which ranged from 1,301 to 1,348 bp, were present among twenty ASI1346-derived progeny strains, while 15 different sizes of IGS I, which ranged from 700 to 1,347 bp, were present among twenty ASI1038-derived progeny strains. Phylogenetic analysis of the IGS sequences revealed that different clades were present in both the ASI10388- and ASI1346-derived progeny strains. Plating assays of seven kinds of extracellular enzymes (β-glucosidase, avicelase, CM-cellulase, amylase, pectinase, xylanase, and protease) also revealed apparent variation in the ability to produce extracellular enzymes among the 40 tested progeny strains from both parental A. bisporus strains. Overall, this study demonstrates that characterization of IGS I regions and extracellular enzymes is useful for the assessment of the substrate-degrading ability and heterogenicity of A. bisporus monokaryotic strains. PMID:25892920

Patterned, highly stretchable and conductive nanofibrous PANI/PVDF strain sensors based on electrospinning and in situ polymerization.

PubMed

Yu, Gui-Feng; Yan, Xu; Yu, Miao; Jia, Meng-Yang; Pan, Wei; He, Xiao-Xiao; Han, Wen-Peng; Zhang, Zhi-Ming; Yu, Liang-Min; Long, Yun-Ze

2016-02-07

A facile fabrication strategy via electrospinning and followed by in situ polymerization to fabricate a patterned, highly stretchable, and conductive polyaniline/poly(vinylidene fluoride) (PANI/PVDF) nanofibrous membrane is reported. Owing to the patterned structure, the nanofibrous PANI/PVDF strain sensor can detect a strain up to 110%, for comparison, which is 2.6 times higher than the common nonwoven PANI/PVDF mat and much larger than the previously reported values (usually less than 15%). Meanwhile, the conductivity of the patterned strain sensor shows a linear response to the applied strain in a wide range from 0% to about 85%. Additionally, the patterned PANI/PVDF strain sensor can completely recover to its original electrical and mechanical values within a strain range of more than 22%, and exhibits good durability over 10,000 folding-unfolding tests. Furthermore, the strain sensor also can be used to detect finger motion. The results demonstrate promising application of the patterned nanofibrous membrane in flexible electronic fields.

Creep-fatigue of low cobalt superalloys

NASA Technical Reports Server (NTRS)

Halford, G. R.

1982-01-01

Testing for the low cycle fatigue and creep fatigue resistance of superalloys containing reduced amounts of cobalt is described. The test matrix employed involves a single high temperature appropriate for each alloy. A single total strain range, again appropriate to each alloy, is used in conducting strain controlled, low cycle, creep fatigue tests. The total strain range is based upon the level of straining that results in about 10,000 cycles to failure in a high frequency (0.5 Hz) continuous strain-cycling fatigue test. No creep is expected to occur in such a test. To bracket the influence of creep on the cyclic strain resistance, strain hold time tests with ore minute hold periods are introduced. One test per composition is conducted with the hold period in tension only, one in compression only, and one in both tension and compression. The test temperatures, alloys, and their cobalt compositions that are under study are given.

Strain amplitude-dependent anelasticity in Cu-Ni solid solution due to thermally activated and athermal dislocation-point obstacle interactions

NASA Astrophysics Data System (ADS)

Kustov, S.; Gremaud, G.; Benoit, W.; Golyandin, S.; Sapozhnikov, K.; Nishino, Y.; Asano, S.

1999-02-01

Experimental investigations of the internal friction and the Young's modulus defect in single crystals of Cu-(1.3-7.6) at. % Ni have been performed for 7-300 K over a wide range of oscillatory strain amplitudes. Extensive data have been obtained at a frequency of vibrations around 100 kHz and compared with the results obtained for the same crystals at a frequency of ˜1 kHz. The strain amplitude dependence of the anelastic strain amplitude and the average friction stress acting on a dislocation due to solute atoms are also analyzed. Several stages in the strain amplitude dependence of the internal friction and the Young's modulus defect are revealed for all of the alloy compositions, at different temperatures and in different frequency ranges. For the 100 kHz frequency, low temperatures and low strain amplitudes (˜10-7-10-5), the amplitude-dependent internal friction and the Young's modulus defect are essentially temperature independent, and are ascribed to a purely hysteretic internal friction component. At higher strain amplitudes, a transition stage and a steep strain amplitude dependence of the internal friction and the Young's modulus defect are observed, followed by saturation at the highest strain amplitudes employed. These stages are temperature and frequency dependent and are assumed to be due to thermally activated motion of dislocations. We suggest that the observed regularities in the entire strain amplitude, temperature and frequency ranges correspond to a motion of dislocations in a two-component system of obstacles: weak but long-range ones, due to the elastic interaction of dislocations with solute atoms distributed in the bulk of the crystal; and strong short-range ones, due to the interaction of dislocations with solute atoms distributed close to dislocation glide planes. Based on these assumptions, a qualitative explanation is given for the variety of experimental observations.

A Modified Constitutive Model for Tensile Flow Behaviors of BR1500HS Ultra-High-Strength Steel at Medium and Low Temperature Regions

NASA Astrophysics Data System (ADS)

Zhao, Jun; Quan, Guo-Zheng; Pan, Jia; Wang, Xuan; Wu, Dong-Sen; Xia, Yu-Feng

2018-01-01

Constitutive model of materials is one of the most requisite mathematical model in the finite element analysis, which describes the relationships of flow behaviors with strain, strain rate and temperature. In order to construct such constitutive relationships of ultra-high-strength BR1500HS steel at medium and low temperature regions, the true stress-strain data over a wide temperature range of 293-873 K and strain rate range of 0.01-10 s-1 were collected from a series of isothermal uniaxial tensile tests. The experimental results show that stress-strain relationships are highly non-linear and susceptible to three parameters involving temperature, strain and strain rate. By considering the impacts of strain rate and temperature on strain hardening, a modified constitutive model based on Johnson-Cook model was proposed to characterize flow behaviors in medium and low temperature ranges. The predictability of the improved model was also evaluated by the relative error (W(%)), correlation coefficient (R) and average absolute relative error (AARE). The R-value and AARE-value for modified constitutive model at medium and low temperature regions are 0.9915 & 1.56 % and 0.9570 & 5.39 %, respectively, which indicates that the modified constitutive model can precisely estimate the flow behaviors for BR1500HS steel in the medium and low temperature regions.

Isolation of Escherichia coli and Salmonella spp. from free-ranging wild animals.

PubMed

Iovine, Renata de Oliveira; Dejuste, Catia; Miranda, Flávia; Filoni, Claudia; Bueno, Marina Galvão; de Carvalho, Vania Maria

2015-01-01

Increasing interactions between humans, domestic animals and wildlife may result in inter-species transmission of infectious agents. To evaluate the presence of pathogenic E. coli and Salmonella spp. and to test the antimicrobial susceptibility of isolates, rectal swabs from 36 different free-ranging wild mammals were taken from two distinct natural sites in Brazil: Cantareira State Park (CSP, state of São Paulo) and Santa Isabel do Rio Negro Region (SIRNR, state of Amazonas). The swabs were randomly collected and processed for bacterial isolation, identification, characterization and antimicrobial resistance. Eighteen E. coli strains from CSP and 20 from SIRNR were recovered from 14 and 22 individuals, respectively. Strains from animals captured in CSP, the site with the greatest anthropization, exhibited a higher range and percentage of virulence genes, including an eae+/bfpA+ strain. Antimicrobial resistance was verified in strains originating from both sites; however, in strains from SIRNR, aminopenicillins were almost the exclusive antimicrobial class to which strains exhibited resistance, whereas in CSP there were strains resistant to cephalosporins, sulfonamide, aminoglycoside, tetracycline and fluoroquinolone, in addition to strains exhibiting multidrug resistance. Two strains of Salmonella enterica that are known to be associated with reptiles, serotypes Belem and 60:r:e,n,z15, were recovered only from Amazonian animals and showed susceptibility to all classes of antimicrobials that were tested. Although the potential impact of these pathogens on wildlife remains unknown, bacteria isolated from free-ranging wild animals may provide relevant information about environmental health and should therefore be more deeply studied.

Apparent-Strain Correction for Combined Thermal and Mechanical Testing

NASA Technical Reports Server (NTRS)

Johnson, Theodore F.; O'Neil, Teresa L.

2007-01-01

Combined thermal and mechanical testing requires that the total strain be corrected for the coefficient of thermal expansion mismatch between the strain gage and the specimen or apparent strain when the temperature varies while a mechanical load is being applied. Collecting data for an apparent strain test becomes problematic as the specimen size increases. If the test specimen cannot be placed in a variable temperature test chamber to generate apparent strain data with no mechanical loads, coupons can be used to generate the required data. The coupons, however, must have the same strain gage type, coefficient of thermal expansion, and constraints as the specimen to be useful. Obtaining apparent-strain data at temperatures lower than -320 F is challenging due to the difficulty to maintain steady-state and uniform temperatures on a given specimen. Equations to correct for apparent strain in a real-time fashion and data from apparent-strain tests for composite and metallic specimens over a temperature range from -450 F to +250 F are presented in this paper. Three approaches to extrapolate apparent-strain data from -320 F to -430 F are presented and compared to the measured apparent-strain data. The first two approaches use a subset of the apparent-strain curves between -320 F and 100 F to extrapolate to -430 F, while the third approach extrapolates the apparent-strain curve over the temperature range of -320 F to +250 F to -430 F. The first two approaches are superior to the third approach but the use of either of the first two approaches is contingent upon the degree of non-linearity of the apparent-strain curve.

Flexible surface acoustic wave strain sensor based on single crystalline LiNbO3 thin film

NASA Astrophysics Data System (ADS)

Xu, Hongsheng; Dong, Shurong; Xuan, Weipeng; Farooq, Umar; Huang, Shuyi; Li, Menglu; Wu, Ting; Jin, Hao; Wang, Xiaozhi; Luo, Jikui

2018-02-01

A flexible surface acoustic wave (SAW) strain sensor in the frequency range of 162-325 MHz was developed based on a single crystalline LiNbO3 thin film with dual resonance modes, namely, the Rayleigh mode and the thickness shear mode (TSM). This SAW sensor could handle a wide strain range up to ±3500 μɛ owing to its excellent flexibility, which is nearly six times the detecting range of bulk piezoelectric substrate based SAW strain sensors. The sensor exhibited a high sensitivity of 193 Hz/ μɛ with a maximum hysteresis less than 1.5%. The temperature coefficients of frequency, for Rayleigh and TSM modes, were -85 and -59 ppm/ °C , respectively. No visible deterioration was observed after cyclic bending for hundreds of times, showing its desirable stability and reliability. By utilizing the dual modes, the strain sensor with a self-temperature calibrated capability can be achieved. The results demonstrate that the sensor is an excellent candidate for strain sensing.

Thermomicrobium carboxidum sp. nov., and Thermorudis peleae gen. nov., sp. nov., carbon monoxide-oxidizing bacteria isolated from geothermally heated biofilms.

PubMed

King, C E; King, G M

2014-08-01

Two thermophilic, Gram-stain-positive, rod-shaped, non-spore-forming bacteria (strains KI3(T) and KI4(T)) were isolated from geothermally heated biofilms growing on a tumulus in the Kilauea Iki pit crater on the flank of Kilauea Volcano (Hawai'i, USA). Strain KI3(T) grew over an examined temperature range of 50-70 °C (no growth at 80 °C) and a pH range of 6.0-9.0, with optimum growth at 70 °C and pH 7.0. Strain KI4(T) grew at temperatures of 55-70 °C and a pH range of 5.8-8.0, with optimum growth at 65 °C and pH 6.7-7.1. The DNA G+C contents of strains KI3(T) and KI4(T) were 66.0 and 60.7 mol%, respectively. The major fatty acid for both strains was 12-methyl C(18 : 0). Polar lipids in strain KI3(T) were dominated by glycolipids and phosphatidylinositol, while phosphatidylinositol and phosphoglycolipids dominated in strain KI4(T). Strain KI3(T) oxidized carbon monoxide [6.7±0.8 nmol CO h(-1) (mg protein)(-1)], but strain KI4(T) did not. 16S rRNA gene sequence analyses determined that the strains belong to the class Thermomicrobia, and that strains KI3(T) and KI4(T) are related most closely to Thermomicrobium roseum DSM 5159(T) (96.5 and 91.1% similarity, respectively). 16S rRNA gene sequence similarity between strain KI3(T) and strain KI4(T) was 91.4%. Phenotypic features and phylogenetic analyses supported the affiliation of strain KI3(T) to the genus Thermomicrobium, while results of chemotaxonomic, physiological and biochemical assays differentiated strains KI3(T) and KI4(T) from Thermomicrobium roseum. Strain KI3(T) ( = DSM 27067(T) = ATCC BAA-2535(T)) is thus considered to be the type strain of a novel species, for which the name Thermomicrobium carboxidum sp. nov. is proposed. Additionally, the characterization and phylogenetic position of strain KI4(T) showed that it represents a novel species of a new genus, for which the name Thermorudis peleae gen. nov., sp. nov. is proposed. The type strain of Thermorudis peleae is KI4(T) ( = DSM 27169(T) = ATCC BAA-2536(T)). © 2014 IUMS.

Enhanced resistance of the Pamirs high-mountain strain of Cryptococcus albidus to UV radiation of an ecological range

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

Strakhovskaya, M.G.; Lavrukhina, O.G.; Fraikin, G.Y.

The results of a comparative analysis of the resistance of Pamirs high-mountain and lowland strains of the yeast Cryptococcus albidus to UV radiation of an ecological range are presented. A high-mountain strain, adapted to elevated UV radiation in its habitat, was found to be more resistant to UV light of a total ecorange (290-400 nm), including medium-wave (290-320 nm) and long-wave (320-400 nm) UV ranges. The enhanced UV light resistance of the high-mountain strain can be explained by efficient functioning of the excision DNA repair system. 7 refs., 3 tabs.

Variability and Reproducibility of Segmental Longitudinal Strain Measurement: A Report From the EACVI-ASE Strain Standardization Task Force.

PubMed

Mirea, Oana; Pagourelias, Efstathios D; Duchenne, Jurgen; Bogaert, Jan; Thomas, James D; Badano, Luigi P; Voigt, Jens-Uwe

2018-01-01

In this study, we compared left ventricular (LV) segmental strain measurements obtained with different ultrasound machines and post-processing software packages. Global longitudinal strain (GLS) has proven to be a reproducible and valuable tool in clinical practice. Data about the reproducibility and intervendor differences of segmental strain measurements, however, are missing. We included 63 volunteers with cardiac magnetic resonance-proven infarct scar with segmental LV function ranging from normal to severely impaired. Each subject was examined within 2 h by a single expert sonographer with machines from multiple vendors. All 3 apical views were acquired twice to determine the test-retest and the intervendor variability. Segmental longitudinal peak systolic, end-systolic, and post-systolic strain were measured using 7 vendor-specific systems (Hitachi, Tokyo, Japan; Esaote, Florence, Italy; GE Vingmed Ultrasound, Horten, Norway; Philips, Andover, Massachusetts; Samsung, Seoul, South Korea; Siemens, Mountain View, California; and Toshiba, Otawara, Japan) and 2 independent software packages (Epsilon, Ann Arbor, Michigan; and TOMTEC, Unterschleissheim, Germany) and compared among vendors. Image quality and tracking feasibility differed among vendors (analysis of variance, p < 0.05). The absolute test-retest difference ranged from 2.5% to 4.9% for peak systolic, 2.6% to 5.0% for end-systolic, and 2.5% to 5.0% for post-systolic strain. The average segmental strain values varied significantly between vendors (up to 4.5%). Segmental strain parameters from each vendor correlated well with the mean of all vendors (r 2 range 0.58 to 0.81) but showed very different ranges of values. Bias and limits of agreement were up to -4.6 ± 7.5%. In contrast to GLS, LV segmental longitudinal strain measurements have a higher variability on top of the known intervendor bias. The fidelity of different software to follow segmental function varies considerably. We conclude that single segmental strain values should be used with caution in the clinic. Segmental strain pattern analysis might be a more robust alternative. Copyright © 2018 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

[Determination of in vitro synergy by a checkerboard method when 3 core antimicrobial agents of the retreatment new scheme combined against MDR-MTB and XDR-MTB].

PubMed

Zhang, L L; Yang, H; Xiao, H P; Lu, J M; Sha, W; Zhang, Q

2016-06-01

In order to detect the in vitro synergistic effect of 4 drugs-pasiniazid (PA), moxifloxacin, rifabutin and rifapentini on multidrug-resistant mycobacterium tuberculosis (MDR-MTB) and extensively drug-resistant mycobacterium tuberculosis(XDR-MTB), which were core drugs of"The program of retreatment research of tuberculosis". The checkerboard method was used to detect the minimum inhibitory concentration (MIC) of antituberculosis drug combination schemes (moxifloxacin-PA, moxifloxacin-PA-rifabutin and moxifloxacin-PA-rifapentini) to 40 strains of clinical drug resistant MTB(20 strains of MDR-MTB and 20 XDR-MTB) and the standard strain H37Rv, by calculating the fractional inhibitory concentration index of joint action in vitro to judge the combined effect, with fractional inhibitory concentration index(FICI)≤0.5 and FICI≤0.75 as the basis of 2 drugs and 3 drugs showing synergy. The FICI of moxifloxacin-PA scheme for DR-MTB was 0.125 to 1.000, only 5 strains with a FICI ≤0.5, showing synergistic effect. The FICI of moxifloxacin-Pa-rifabutin scheme with 20 strains of MDR-MTB ranged from 0.310 to 1.260, 10 strains with a FICI≤0.75, showing synergistic effect. The FICI of moxifloxacin-PA-rifabutin scheme with 20 strains of XDR-MTB ranged from 0.215 to 1.250, 11 strains with a FICI≤0.75, showing synergistic effect. The FICI of moxifloxacin-PA-rifapentini scheme with 20 strains of MDR-MTB ranged from 0.150 to 0.780, 19 strains with a FICI≤0.75, showing synergistic effect. The FICI of moxifloxacin-PA-rifapentini scheme with 20 strains of XDR-MTB ranged from 0.200 to 1.280, 16 strains with a FICI≤0.75, showing synergistic effect. The synergistic effect of moxifloxacin-PA scheme was poor, but showing better synergy when further combined with rifabutin or rifapentini. Rifabutin showed better effect than rifapentini, but the synergistic effect of moxifloxacin-PA-rifabutin combination scheme was poor than that of moxifloxacin-PA-rifapentini combination scheme.

Normal Ranges of Right Ventricular Systolic and Diastolic Strain Measures in Children: A Systematic Review and Meta-Analysis

PubMed Central

Levy, Philip T.; Sanchez, Aura; Machefsky, Aliza; Fowler, Susan; Holland, Mark R.; Singh, Gautam K.

2014-01-01

Background Establishment of the range of normal values and associated variations of two-dimensional speckle-tracking echocardiography (2DSTE) derived right ventricular (RV) strain is a prerequisite for its routine clinical application in children. The objectives of this study were to perform a meta-analysis of normal ranges of RV longitudinal strain measurements derived by 2DSTE in children and identify confounders that may contribute to differences in reported measures. Methods A systematic review was launched in PubMed, Embase, Scopus, Cochrane, and ClinicTrials.gov. Search hedges were created to cover the concepts of pediatrics, speckle-tracking echocardiography, and right heart ventricle. Two investigators independently identified and included studies if they reported the 2DSTE derived RV strain measures: RV peak global longitudinal strain (pGLS), systolic strain rate (pGLSRs), early diastolic strain rate (pGLSRe), late diastolic strain rate (pGLSRa), or segmental longitudinal strain at the apical, mid, and basal ventricular levels in healthy children. Quality and reporting of the studies were assessed. The weighted mean was estimated by using random-effects with 95% confidence intervals (CI), heterogeneity was assessed by the Cochran's Q statistic and the inconsistency index (I2), and publication bias was evaluated using funnel plots and the Egger test. Effects of demographic, clinical, equipment, and software variables were assessed in a meta-regression. Results The search identified 226 children from 10 studies. The reported normal mean values of pGLS among the studies varied from −20.80% to −34.10% (mean, −29.03%, 95%CI, −31.52% to −26.54%), pGLSRs varied from −1.30 to −2.40 1/sec (mean, −1.88, 95%CI, −2.10 to −1.59), pGLSRe ranged from 1.7 to 2.69 1/sec (mean, 2.34, 95%CI, 2.00 to 2.67) and pGLSRa ranged from 1.00 to 1.30 1/sec (mean, 1.18, 95% CI, 1.04 to 1.33). A significant base-to-apex segmental strain gradient (p <0.05) was observed in the right ventricular free wall. There was significant between-study heterogeneity and inconsistency (I2>88% and p<0.01 for each strain measure), which was not explained by age, gender, body surface area, heart rate, frame rate, tissue tracking methodology, equipment, or software. The meta-regression showed that these effects were not significant determinants of variations among normal ranges of strain values. There was no evidence of publication bias (Egger test, p=0.59). Conclusions This study is the first to define normal values of two-dimensional speckle tracking echocardiographic (2DSTE) derived right ventricle strain in children on the basis of a meta-analysis. The normal mean value in children for RV global strain is −29.03% (95% CI, −31.52% to −26.54%). The normal mean value for RV global systolic strain rate is −1.88 1/sec (95% CI, −2.10 to −1.59). RV segmental strain has a stable base-to-apex gradient that highlights the dominance of deep longitudinal layers of the RV that are aligned base to apex. Variations among different normal ranges do not appear to be dependent on differences in demographic, clinical, or equipment parameters in this meta-analysis. All of the eligible studies used equipment and software from one manufacturer, General Electric (GE). PMID:24582163

Flexible wire-shaped strain sensor from cotton thread for human health and motion detection.

PubMed

Li, Yuan-Qing; Huang, Pei; Zhu, Wei-Bin; Fu, Shao-Yun; Hu, Ning; Liao, Kin

2017-03-21

In this work, a wire-shaped flexible strain sensor was fabricated by encapsulating conductive carbon thread (CT) with polydimethylsiloxane (PDMS) elastomer. The key strain sensitive material, CT, was prepared by pyrolysing cotton thread in N 2 atmosphere. The CT/PDMS composite wire shows a typical piezo-resistive behavior with high strain sensitivity. The gauge factors (GF) calculated at low strain of 0-4% and high strain of 8-10% are 8.7 and 18.5, respectively, which are much higher than that of the traditional metallic strain sensor (GF around 2). The wire-shaped CT/PDMS composite sensor shows excellent response to cyclic tensile loading within the strain range of 0-10%, the frequency range of 0.01-10 Hz, to up to 2000 cycles. The potential of the wire senor as wearable strain sensor is demonstrated by the finger motion and blood pulse monitoring. Featured by the low costs of cotton wire and PDMS resin, the simple structure and fabrication technique, as well as high performance with miniaturized size, the wire-shaped sensor based on CT/PDMS composite is believed to have a great potential for application in wearable electronics for human health and motion monitoring.

Binding of selected extracellular matrix proteins to enterococci and Streptococcus bovis of animal origin.

PubMed

Styriak, I; Lauková, A; Fallgren, C; Wadström, T

1999-12-01

Thirty-three enterococcal strains and 10 Streptococcus bovis strains were investigated for their protein-binding cell surface components. Seven extracellular matrix (ECM) proteins were immobilized on Difco latex beads to detect these components on the surface of all enterococcal strains and eight non-autoaggregating S. bovis strains by a particle agglutination assay (PAA). Twenty-three selected strains were also examined in microtiter plate assays. According to the absorbance readings (A(570nm)), 11 strains were classified as nonadherent (A(570nm) < 0.1), 10 strains as weakly adherent (0.1 < A(570nm) > 0.3), and 2 strains as strongly adherent (A(570nm) > 0.3) in these assays. A direct correlation was found between the values obtained in PAA and A(570nm) readings of microtiter plate assays. Binding of (125)I-labeled bovine lactoferrin to enterococci and streptococci was in the range of 6%-30% and of (125)I-labeled human vitronectin in the range of 9%-33% to streptococci. The binding of(125)I-labeled ECM proteins to selected strains was much more effectively inhibited by sulfated carbohydrates than by non-sulfated hyaluronic acid, indicating the importance of the sulfate groups of these inhibitors. An inhibition effect of heparin on bLf binding to four selected strains was higher in comparison with fucoidan in the microtiter plates. Thirty-five out of 44 strains had agglutinated rabbit erythrocytes. However, these strains showed no ability to agglutinate bovine or sheep erythrocytes.

Using Predictions Based on Geostatistics to Monitor Trends in Aspergillus flavus Strain Composition.

PubMed

Orum, T V; Bigelow, D M; Cotty, P J; Nelson, M R

1999-09-01

ABSTRACT Aspergillus flavus is a soil-inhabiting fungus that frequently produces aflatoxins, potent carcinogens, in cottonseed and other seed crops. A. flavus S strain isolates, characterized on the basis of sclerotial morphology, are highly toxigenic. Spatial and temporal characteristics of the percentage of the A. flavus isolates that are S strain (S strain incidence) were used to predict patterns across areas of more than 30 km(2). Spatial autocorrelation in S strain incidence in Yuma County, AZ, was shown to extend beyond field boundaries to adjacent fields. Variograms revealed both short-range (2 to 6 km) and long-range (20 to 30 km) spatial structure in S strain incidence. S strain incidence at 36 locations sampled in July 1997 was predicted with a high correlation between expected and observed values (R = 0.85, P = 0.0001) by kriging data from July 1995 and July 1996. S strain incidence at locations sampled in October 1997 and March 1998 was markedly less than predicted by kriging data from the same months in prior years. Temporal analysis of four locations repeatedly sampled from April 1995 through July 1998 also indicated a major reduction in S strain incidence in the Texas Hill area after July 1997. Surface maps generated by kriging point data indicated a similarity in the spatial pattern of S strain incidence among all sampling dates despite temporal changes in the overall S strain incidence. Geostatistics provided useful descriptions of variability in S strain incidence over space and time.

Constitutive modeling of the mechanical behavior of high strength ferritic steels for static and dynamic applications

NASA Astrophysics Data System (ADS)

Abed, Farid H.

2010-11-01

A constitutive relation is presented in this paper to describe the plastic behavior of ferritic steel over a broad range of temperatures and strain rates. The thermo-mechanical behavior of high strength low alloy (HSLA-65) and DH-63 naval structural steels is considered in this study at strains over 40%. The temperatures and strain rates are considered in the range where dynamic strain aging is not effective. The concept of thermal activation analysis as well as the dislocation interaction mechanism is used in developing the flow model for both the isothermal and adiabatic viscoplastic deformation. The flow stresses of the two steels are very sensitive to temperature and strain rate, the yield stresses increase with decreasing temperatures and increasing strain rates. That is, the thermal flow stress is mainly captured by the yield stresses while the hardening stresses are totally pertained to the athermal component of the flow stress. The proposed constitutive model predicts results that compare very well with the measured ones at initial temperature range of 77 K to 1000 K and strain rates between 0.001 s-1 and 8500 s-1 for both steels.

Slope-assisted BOTDA based on vector SBS and frequency-agile technique for wide-strain-range dynamic measurements.

PubMed

Zhou, Dengwang; Dong, Yongkang; Wang, Benzhang; Jiang, Taofei; Ba, Dexin; Xu, Pengbai; Zhang, Hongying; Lu, Zhiwei; Li, Hui

2017-02-06

We present a slope-assisted BOTDA system based on the vector stimulated Brillouin scattering (SBS) and frequency-agile technique (FAT) for the wide-strain-range dynamic measurement. A dimensionless coefficient K defined as the ratio of Brillouin phase-shift to gain is employed to demodulate the strain of the fiber, and it is immune to the power fluctuation of pump pulse and has a linear relation of the frequency detuning for the continuous pump and Stokes waves. For a 30ns-square pump pulse, the available frequency span of the K spectrum can reach up to 200MHz, which is larger than fourfold of 48MHz-linewidth of Brillouin gain spectrum. For a single-slope assisted BOTDA, dynamic strain measurement with the maximum strain of 2467.4με and the vibration frequency components of 10.44Hz and 20.94Hz is obtained. For a multi-slope-assisted BOTDA, dynamic measurement with the strain variation up to 5372.9με and the vibration frequency components of 5.58Hz and 11.14Hz is achieved by using FAT to extend the strain range.

Flexible and transparent strain sensors based on super-aligned carbon nanotube films.

PubMed

Yu, Yang; Luo, Yufeng; Guo, Alexander; Yan, Lingjia; Wu, Yang; Jiang, Kaili; Li, Qunqing; Fan, Shoushan; Wang, Jiaping

2017-05-25

Highly flexible and transparent strain sensors are fabricated by directly coating super-aligned carbon nanotube (SACNT) films on polydimethylsiloxane (PDMS) substrates. The fabrication process is simple, low cost, and favorable for industrial scalability. The SACNT/PDMS strain sensors present a high sensing range of 400%, a fast response of less than 98 ms, and a low creep of 4% at 400% strain. The SACNT/PDMS strain sensors can withstand 5000 stretching-releasing cycles at 400% strain. Moreover, the SACNT/PDMS strain sensors are transparent with 80% transmittance at 550 nm. In situ microscopic observation clarifies that the surface morphology of the SACNT film exhibits a reversible change during the stretching and releasing processes and thus its electrical conductance is able to fully recover to the original value after the loading-unloading cycles. The SACNT/PDMS strain sensors have the advantages of a wide sensing range, fast response, low creep, transparency, and excellent durability, and thus show great potential in wearable devices to monitor fast and large-scale movements without affecting the appearance of the devices.

An extensometer for global measurement of bone strain suitable for use in vivo in humans

NASA Technical Reports Server (NTRS)

Perusek, G. P.; Davis, B. L.; Sferra, J. J.; Courtney, A. C.; D'Andrea, S. E.

2001-01-01

An axial extensometer able to measure global bone strain magnitudes and rates encountered during physiological activity, and suitable for use in vivo in human subjects, is described. The extensometer uses paired capacitive sensors mounted to intraosseus pins and allows measurement of strain due to bending in the plane of the extensometer as well as uniaxial compression or tension. Data are presented for validation of the device against a surface-mounted strain gage in an acrylic specimen under dynamic four-point bending, with square wave and sinusoidal loading inputs up to 1500 mu epsilon and 20 Hz, representative of physiological strain magnitudes and frequencies. Pearson's correlation coefficient (r) between extensometer and strain gage ranged from 0.960 to 0.999. Mean differences between extensometer and strain gage ranged up to 15.3 mu epsilon. Errors in the extensometer output were directly proportional to the degree of bending that occurs in the specimen, however, these errors were predictable and less than 1 mu epsilon for the loading regime studied. The device is capable of tracking strain rates in excess of 90,000 mu epsilon/s.

Polymerization shrinkage kinetics and shrinkage-stress in dental resin-composites.

PubMed

Al Sunbul, Hanan; Silikas, Nick; Watts, David C

2016-08-01

To investigate a set of resin-composites and the effect of their composition on polymerization shrinkage strain and strain kinetics, shrinkage stress and the apparent elastic modulus. Eighteen commercially available resin-composites were investigated. Three specimens (n=3) were made per material and light-cured with an LED unit (1200mW/cm(2)) for 20s. The bonded-disk method was used to measure the shrinkage strain and Bioman shrinkage stress instrument was used to measure shrinkage stress. The shrinkage strain kinetics at 23°C was monitored for 60min. Maximum strain and stress was evaluated at 60min. The shrinkage strain rate was calculated using numerical differentiation. The shrinkage strain values ranged from 1.83 (0.09) % for Tetric Evoceram (TEC) to 4.68 (0.04) % for Beautifil flow plus (BFP). The shrinkage strain rate ranged from 0.11 (0.01%s(-1)) for Gaenial posterior (GA-P) to 0.59 (0.07) %s(-1) for BFP. Shrinkage stress values ranged from 3.94 (0.40)MPa for TET to 10.45 (0.41)MPa for BFP. The apparent elastic modulus ranged from 153.56 (18.7)MPa for Ever X posterior (EVX) to 277.34 (25.5) MPa for Grandio SO heavy flow (GSO). The nature of the monomer system determines the amount of the bulk contraction that occurs during polymerization and the resultant stress. Higher values of shrinkage strain and stress were demonstrated by the investigated flowable materials. The bulk-fill materials showed comparable result when compared to the traditional resin-composites. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Constitutive Modeling of the High-Temperature Flow Behavior of α-Ti Alloy Tube

NASA Astrophysics Data System (ADS)

Lin, Yanli; Zhang, Kun; He, Zhubin; Fan, Xiaobo; Yan, Yongda; Yuan, Shijian

2018-04-01

In the hot metal gas forming process, the deformation conditions, such as temperature, strain rate and deformation degree, are often prominently changed. The understanding of the flow behavior of α-Ti seamless tubes over a relatively wide range of temperatures and strain rates is important. In this study, the stress-strain curves in the temperature range of 973-1123 K and the initial strain rate range of 0.0004-0.4 s-1 were measured by isothermal tensile tests to conduct a constitutive analysis and a deformation behavior analysis. The results show that the flow stress decreases with the decrease in the strain rate and the increase of the deformation temperature. The Fields-Backofen model and Fields-Backofen-Zhang model were used to describe the stress-strain curves. The Fields-Backofen-Zhang model shows better predictability on the flow stress than the Fields-Backofen model, but there exists a large deviation in the deformation condition of 0.4 s-1. A modified Fields-Backofen-Zhang model is proposed, in which a strain rate term is introduced. This modified Fields-Backofen-Zhang model gives a more accurate description of the flow stress variation under hot forming conditions with a higher strain rate up to 0.4 s-1. Accordingly, it is reasonable to adopt the modified Fields-Backofen-Zhang model for the hot forming process which is likely to reach a higher strain rate, such as 0.4 s-1.

Constitutive Modeling of the High-Temperature Flow Behavior of α-Ti Alloy Tube

NASA Astrophysics Data System (ADS)

Lin, Yanli; Zhang, Kun; He, Zhubin; Fan, Xiaobo; Yan, Yongda; Yuan, Shijian

2018-05-01

In the hot metal gas forming process, the deformation conditions, such as temperature, strain rate and deformation degree, are often prominently changed. The understanding of the flow behavior of α-Ti seamless tubes over a relatively wide range of temperatures and strain rates is important. In this study, the stress-strain curves in the temperature range of 973-1123 K and the initial strain rate range of 0.0004-0.4 s-1 were measured by isothermal tensile tests to conduct a constitutive analysis and a deformation behavior analysis. The results show that the flow stress decreases with the decrease in the strain rate and the increase of the deformation temperature. The Fields-Backofen model and Fields-Backofen-Zhang model were used to describe the stress-strain curves. The Fields-Backofen-Zhang model shows better predictability on the flow stress than the Fields-Backofen model, but there exists a large deviation in the deformation condition of 0.4 s-1. A modified Fields-Backofen-Zhang model is proposed, in which a strain rate term is introduced. This modified Fields-Backofen-Zhang model gives a more accurate description of the flow stress variation under hot forming conditions with a higher strain rate up to 0.4 s-1. Accordingly, it is reasonable to adopt the modified Fields-Backofen-Zhang model for the hot forming process which is likely to reach a higher strain rate, such as 0.4 s-1.

An improved Armstrong-Frederick-Type Plasticity Model for Stable Cyclic Stress-Strain Responses Considering Nonproportional Hardening

NASA Astrophysics Data System (ADS)

Li, Jing; Zhang, Zhong-ping; Li, Chun-wang

2018-03-01

This paper modified an Armstrong-Frederick-type plasticity model for investigating the stable cyclic deformation behavior of metallic materials with different sensitivity to nonproportional loadings. In the modified model, the nonproportionality factor and nonproportional cyclic hardening coefficient coupled with the Jiang-Sehitoglu incremental plasticity model were used to estimate the stable stress-strain responses of the two materials (1045HR steel and 304 stainless steel) under various tension-torsion strain paths. A new equation was proposed to calculate the nonproportionality factor on the basis of the minimum normal strain range. Procedures to determine the minimum normal strain range were presented for general multiaxial loadings. Then, the modified model requires only the cyclic strain hardening exponent and cyclic strength coefficient to determine the material constants. It is convenient for predicting the stable stress-strain responses of materials in engineering application. Comparisons showed that the modified model can reflect the effect of nonproportional cyclic hardening well.

Peri-Implant Strain in an In Vitro Model.

PubMed

Hussaini, Souheil; Vaidyanathan, Tritala K; Wadkar, Abhinav P; Quran, Firas A Al; Ehrenberg, David; Weiner, Saul

2015-10-01

An in vitro experimental model was designed and tested to determine the influence that peri-implant strain may have on the overall crestal bone. Strain gages were attached to polymethylmethacrylate (PMMA) models containing a screw-type root form implant at sites 1 mm from the resin-implant interface. Three different types of crown superstructures (cemented, 1-screw [UCLA] and 2-screw abutment types) were tested. Loading (1 Hz, 200 N load) was performed using a MTS Mechanical Test System. The strain gage data were stored and organized in a computer for statistical treatment. Strains for all abutment types did not exceed the physiological range for modeling and remodeling of cancellous bone, 200-2500 με (microstrain). For approximately one-quarter of the trials, the strain values were less than 200 με the zone for bone atrophy. The mean microstrain obtained was 517.7 με. In conclusion, the peri-implant strain in this in vitro model did not exceed the physiologic range of bone remodeling under axial occlusal loading.

Intracellular survival of virulence and low-virulence strains of Vibrio parahaemolyticus in Epinephelus awoara macrophages and peripheral leukocytes.

PubMed

Xu, X J; Sang, B H; Chen, W B; Yan, Q P; Xiong, Z Y; Su, J B; Zou, W Z

2015-01-30

In this study, we examined the virulence factors and pathogenesis of Vibrio parahaemolyticus in Epinephelus awoara. The chemotactic motility of V. parahaemolyticus for phagocytosis and intracellular survival in fish macrophages was determined using virulence strains and low-virulence strains of V. parahaemolyticus. We found that the intracellular mean number of virulence strains of V. parahaemolyticus ranged from 0-180 min after co-incubation with macrophages and peripheral leukocytes, was relatively low, and decreased steadily over the observation period. Low-virulence strains of V. parahaemolyticus were unable to survive in peripheral leukocytes and macrophages. Cell viability in response to V. parahaemolyticus was assessed using the MTT assay. Low-virulence V. parahaemolyticus strains exhibited lower cytotoxicity compared to virulent strains. The average percent of live macrophages and peripheral leukocytes infected by V. parahaemolyticus ranged from 13.50-79.20%. These results indicate that V. parahaemolyticus in E. awoara is a facultative intracellular bacterium that may be involved in virulence.

DETERMINATION OF THE CREEP–FATIGUE INTERACTION DIAGRAM FOR ALLOY 617

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

Wright, J. K.; Carroll, L. J.; Sham, T. -L.

Alloy 617 is the leading candidate material for an intermediate heat exchanger for the very high temperature reactor. To evaluate the behavior of this material in the expected service conditions, creep-fatigue testing was performed. Testing has been performed primarily on a single heat of material at 850 and 950°C for total strain ranges of 0.3 to 1% and tensile hold times as long as 240 minutes. At 850°C, increases in the tensile hold duration degraded the creep fatigue resistance, at least to the investigated strain-controlled hold time of up to 60 minutes at the 0.3% strain range and 240 minutesmore » at the 1.0% strain range. At 950°C, the creep-fatigue cycles to failure becomes constant with increasing hold times, indicating saturation occurs at relatively short hold times. The creep and fatigue damage fractions have been calculated and plotted on a creep-fatigue interaction D-diagram. Results from earlier creep-fatigue tests at 800 and 1000°C on an additional heat of Alloy 617 are also plotted on the D-diagram. The methodology for calculating the damage fractions will be presented, and the effects of strain rate, strain range, temperature, hold time, and strain profile (i.e. holds in tension, compression or both) on the creep-fatigue damage will be explored.« less

Left ventricular hypertrophy with strain and aortic stenosis.

PubMed

Shah, Anoop S V; Chin, Calvin W L; Vassiliou, Vassilis; Cowell, S Joanna; Doris, Mhairi; Kwok, T'ng Choong; Semple, Scott; Zamvar, Vipin; White, Audrey C; McKillop, Graham; Boon, Nicholas A; Prasad, Sanjay K; Mills, Nicholas L; Newby, David E; Dweck, Marc R

2014-10-28

ECG left ventricular hypertrophy with strain is associated with an adverse prognosis in aortic stenosis. We investigated the mechanisms and outcomes associated with ECG strain. One hundred and two patients (age, 70 years [range, 63-75 years]; male, 66%; aortic valve area, 0.9 cm(2) [range, 0.7-1.2 cm(2)]) underwent ECG, echocardiography, and cardiovascular magnetic resonance. They made up the mechanism cohort. Myocardial fibrosis was determined with late gadolinium enhancement (replacement fibrosis) and T1 mapping (diffuse fibrosis). The relationship between ECG strain and cardiovascular magnetic resonance was then assessed in an external validation cohort (n=64). The outcome cohort was made up of 140 patients from the Scottish Aortic Stenosis and Lipid Lowering Trial Impact on Regression (SALTIRE) study and was followed up for 10.6 years (1254 patient-years). Compared with those without left ventricular hypertrophy (n=51) and left ventricular hypertrophy without ECG strain (n=30), patients with ECG strain (n=21) had more severe aortic stenosis, increased left ventricular mass index, more myocardial injury (high-sensitivity plasma cardiac troponin I concentration, 4.3 ng/L [interquartile range, 2.5-7.3 ng/L] versus 7.3 ng/L [interquartile range, 3.2-20.8 ng/L] versus 18.6 ng/L [interquartile range, 9.0-45.2 ng/L], respectively; P<0.001) and increased diffuse fibrosis (extracellular volume fraction, 27.4±2.2% versus 27.2±2.9% versus 30.9±1.9%, respectively; P<0.001). All patients with ECG strain had midwall late gadolinium enhancement (positive and negative predictive values of 100% and 86%, respectively). Indeed, late gadolinium enhancement was independently associated with ECG strain (odds ratio, 1.73; 95% confidence interval, 1.08-2.77; P=0.02), a finding confirmed in the validation cohort. In the outcome cohort, ECG strain was an independent predictor of aortic valve replacement or cardiovascular death (hazard ratio, 2.67; 95% confidence interval, 1.35-5.27; P<0.01). ECG strain is a specific marker of midwall myocardial fibrosis and predicts adverse clinical outcomes in aortic stenosis. © 2014 American Heart Association, Inc.

The mechanical behavior of metal alloys with grain size distribution in a wide range of strain rates

NASA Astrophysics Data System (ADS)

Skripnyak, V. A.; Skripnyak, V. V.; Skripnyak, E. G.

2017-12-01

The paper discusses a multiscale simulation approach for the construction of grain structure of metals and alloys, providing high tensile strength with ductility. This work compares the mechanical behavior of light alloys and the influence of the grain size distribution in a wide range of strain rates. The influence of the grain size distribution on the inelastic deformation and fracture of aluminium and magnesium alloys is investigated by computer simulations in a wide range of strain rates. It is shown that the yield stress depends on the logarithm of the normalized strain rate for light alloys with a bimodal grain distribution and coarse-grained structure.

A Constitutive Relationship between Crack Propagation and Specific Damping Capacity in Steel

DTIC Science & Technology

1990-10-01

diagnostic tool for detecting crack growth in structures. The model must be simple to act as a tool, but it must be comprehensive to provide accuracy...strain for static fracture u ECritical strain above which plastic strain occursP EAverage value of the cyclic plastic-strain rangeP E t ln(Ao/AI), true

Micrococcus flavus sp. nov., isolated from activated sludge in a bioreactor.

PubMed

Liu, Xing-Yu; Wang, Bao-Jun; Jiang, Cheng-Ying; Liu, Shuang-Jiang

2007-01-01

Bacterial strain LW4(T) was isolated from activated sludge of a wastewater-treatment bioreactor. Cells of strain LW4(T) were Gram-positive cocci, with a diameter of 0.7-1.0 microm. Colonies produced on LB agar plates were yellow, smooth, circular and 0.5-1.5 mm in diameter. Strain LW4(T) was aerobic and grew over the temperature range 26-34 degrees C and pH range 5-9, with optimal growth at 30.5-31.5 degrees C and pH 6.0-6.2. The cell-wall peptidoglycan of strain LW4(T) contained amino acid residues of lysine, glutamic acid, alanine, glycine and aspartic acid. The most abundant cellular fatty acids of strain LW4(T) were anteiso-C(15 : 0) (32.15 %) and iso-C(15 : 0) (31.65 %). Major respiratory quinones were MK-8(H(2)) (57.3 %) and MK-7(H(2)) (32.9 %). The DNA G+C content was 71.4 mol% (T(m)). 16S rRNA gene sequence analysis indicated that strain LW4(T) was phylogenetically related to members of the genus Micrococcus, with similarities ranging from 96.5 to 97.3 %. Levels of DNA-DNA relatedness of strain LW4(T) to Micrococcus luteus DSM 20030(T), Micrococcus lylae DSM 20315(T) and Micrococcus antarcticus AS 1.2372(T) were 55, 48 and 36 %, respectively. Based on these results, it is concluded that strain LW4(T) represents a novel species of the genus Micrococcus, for which the name Micrococcus flavus sp. nov. is proposed. The type strain is strain LW4(T) (=CGMCC 1.5361(T)=JCM 14000(T)).

Highly sensitive strain sensors based on fragmentized carbon nanotube/polydimethylsiloxane composites

NASA Astrophysics Data System (ADS)

Gao, Yang; Fang, Xiaoliang; Tan, Jianping; Lu, Ting; Pan, Likun; Xuan, Fuzhen

2018-06-01

Wearable strain sensors based on nanomaterial/elastomer composites have potential applications in flexible electronic skin, human motion detection, human–machine interfaces, etc. In this research, a type of high performance strain sensors has been developed using fragmentized carbon nanotube/polydimethylsiloxane (CNT/PDMS) composites. The CNT/PDMS composites were ground into fragments, and a liquid-induced densification method was used to fabricate the strain sensors. The strain sensors showed high sensitivity with gauge factors (GFs) larger than 200 and a broad strain detection range up to 80%, much higher than those strain sensors based on unfragmentized CNT/PDMS composites (GF < 1). The enhanced sensitivity of the strain sensors is ascribed to the sliding of individual fragmentized-CNT/PDMS-composite particles during mechanical deformation, which causes significant resistance change in the strain sensors. The strain sensors can differentiate mechanical stimuli and monitor various human body motions, such as bending of the fingers, human breathing, and blood pulsing.

Highly sensitive strain sensors based on fragmentized carbon nanotube/polydimethylsiloxane composites.

PubMed

Gao, Yang; Fang, Xiaoliang; Tan, Jianping; Lu, Ting; Pan, Likun; Xuan, Fuzhen

2018-06-08

Wearable strain sensors based on nanomaterial/elastomer composites have potential applications in flexible electronic skin, human motion detection, human-machine interfaces, etc. In this research, a type of high performance strain sensors has been developed using fragmentized carbon nanotube/polydimethylsiloxane (CNT/PDMS) composites. The CNT/PDMS composites were ground into fragments, and a liquid-induced densification method was used to fabricate the strain sensors. The strain sensors showed high sensitivity with gauge factors (GFs) larger than 200 and a broad strain detection range up to 80%, much higher than those strain sensors based on unfragmentized CNT/PDMS composites (GF < 1). The enhanced sensitivity of the strain sensors is ascribed to the sliding of individual fragmentized-CNT/PDMS-composite particles during mechanical deformation, which causes significant resistance change in the strain sensors. The strain sensors can differentiate mechanical stimuli and monitor various human body motions, such as bending of the fingers, human breathing, and blood pulsing.

Comparative analysis of antibiotic resistance and phylogenetic group patterns in human and porcine urinary tract infectious Escherichia coli.

PubMed

Hancock, Viktoria; Nielsen, Eva Møller; Krag, Louise; Engberg, Jørgen; Klemm, Per

2009-11-01

Urinary tract infections (UTIs) are one of the most common infectious diseases in humans and domestic animals such as pigs. The most frequent infectious agent in such infections is Escherichia coli. Virulence characteristics of E. coli UTI strains range from highly virulent pyelonephritis strains to relatively benign asymptomatic bacteriuria strains. Here we analyse a spectrum of porcine and human UTI E. coli strains with respect to their antibiotic resistance patterns and their phylogenetic groups, determined by multiplex PCR. The clonal profiles of the strains differed profoundly; whereas human strains predominantly belonged to clonal types B2 and D, these were not seen among the porcine strains, which all belonged to the E. coli clonal groups A and B1. Contrary to the human strains, the majority of the porcine strains were multidrug resistant. The distinct profiles of the porcine strains suggest selective pressure due to extensive antibiotic use.

Thick film wireless and powerless strain sensor

NASA Astrophysics Data System (ADS)

Jia, Yi; Sun, Ke

2006-03-01

The development of an innovative wireless strain sensing technology has a great potential to extend its applications in manufacturing, civil engineering and aerospace industry. This paper presents a novel wireless and powerless strain sensor with a multi-layer thick film structure. The sensor employs a planar inductor (L) and capacitive transducer (C) resonant tank sensing circuit, and a strain sensitive material of a polarized polyvinylidene fluoride (PVDF) piezoelectric thick film to realize the wireless strain sensing by strain to frequency conversion and to receive radio frequency electromagnetic energy for powering the sensor. The prototype sensor was designed and fabricated. The results of calibration on a strain constant cantilever beam show a great linearity and sensitivity about 0.0013 in a strain range of 0-0.018.

Fiber-Optic Strain Gauge With High Resolution And Update Rate

NASA Technical Reports Server (NTRS)

Figueroa, Fernando; Mahajan, Ajay; Sayeh, Mohammad; Regez, Bradley

2007-01-01

An improved fiber-optic strain gauge is capable of measuring strains in the approximate range of 0 to 50 microstrains with a resolution of 0.1 microstrain. (To some extent, the resolution of the strain gauge can be tailored and may be extensible to 0.01 microstrain.) The total cost of the hardware components of this strain gauge is less than $100 at 2006 prices. In comparison with prior strain gauges capable of measurement of such low strains, this strain gauge is more accurate, more economical, and more robust, and it operates at a higher update rate. Strain gauges like this one are useful mainly for measuring small strains (including those associated with vibrations) in such structures as rocket test stands, buildings, oilrigs, bridges, and dams. The technology was inspired by the need to measure very small strains on structures supporting liquid oxygen tanks, as a way to measure accurately mass of liquid oxygen during rocket engine testing. This improved fiber-optic strain gauge was developed to overcome some of the deficiencies of both traditional foil strain gauges and prior fiber-optic strain gauges. Traditional foil strain gages do not have adequate signal-to-noise ratios at such small strains. Fiber-optic strain gauges have been shown to be potentially useful for measuring such small strains, but heretofore, the use of fiberoptic strain gauges has been inhibited, variously, by complexity, cost, or low update rate.

Genomic analyses of Clostridium perfringens isolates from five toxinotypes.

PubMed

Hassan, Karl A; Elbourne, Liam D H; Tetu, Sasha G; Melville, Stephen B; Rood, Julian I; Paulsen, Ian T

2015-05-01

Clostridium perfringens can be isolated from a range of environments, including soil, marine and fresh water sediments, and the gastrointestinal tracts of animals and humans. Some C. perfringens strains have attractive industrial applications, e.g., in the degradation of waste products or the production of useful chemicals. However, C. perfringens has been most studied as the causative agent of a range of enteric and soft tissue infections of varying severities in humans and animals. Host preference and disease type in C. perfringens are intimately linked to the production of key extracellular toxins and on this basis toxigenic C. perfringens strains have been classified into five toxinotypes (A-E). To date, twelve genome sequences have been generated for a diverse collection of C. perfringens isolates, including strains associated with human and animal infections, a human commensal strain, and a strain with potential industrial utility. Most of the sequenced strains are classified as toxinotype A. However, genome sequences of representative strains from each of the other four toxinotypes have also been determined. Analysis of this collection of sequences has highlighted a lack of features differentiating toxinotype A strains from the other isolates, indicating that the primary defining characteristic of toxinotype A strains is their lack of key plasmid-encoded extracellular toxin genes associated with toxinotype B to E strains. The representative B-E strains sequenced to date each harbour many unique genes. Additional genome sequences are needed to determine if these genes are characteristic of their respective toxinotypes. Copyright © 2014. Published by Elsevier Masson SAS.

Two complementary approaches to quantify variability in heat resistance of spores of Bacillus subtilis.

PubMed

den Besten, Heidy M W; Berendsen, Erwin M; Wells-Bennik, Marjon H J; Straatsma, Han; Zwietering, Marcel H

2017-07-17

Realistic prediction of microbial inactivation in food requires quantitative information on variability introduced by the microorganisms. Bacillus subtilis forms heat resistant spores and in this study the impact of strain variability on spore heat resistance was quantified using 20 strains. In addition, experimental variability was quantified by using technical replicates per heat treatment experiment, and reproduction variability was quantified by using two biologically independent spore crops for each strain that were heat treated on different days. The fourth-decimal reduction times and z-values were estimated by a one-step and two-step model fitting procedure. Grouping of the 20 B. subtilis strains into two statistically distinguishable groups could be confirmed based on their spore heat resistance. The reproduction variability was higher than experimental variability, but both variabilities were much lower than strain variability. The model fitting approach did not significantly affect the quantification of variability. Remarkably, when strain variability in spore heat resistance was quantified using only the strains producing low-level heat resistant spores, then this strain variability was comparable with the previously reported strain variability in heat resistance of vegetative cells of Listeria monocytogenes, although in a totally other temperature range. Strains that produced spores with high-level heat resistance showed similar temperature range for growth as strains that produced low-level heat resistance. Strain variability affected heat resistance of spores most, and therefore integration of this variability factor in modelling of spore heat resistance will make predictions more realistic. Copyright © 2017. Published by Elsevier B.V.

The Shigella human challenge model.

PubMed

Porter, C K; Thura, N; Ranallo, R T; Riddle, M S

2013-02-01

Shigella is an important bacterial cause of infectious diarrhoea globally. The Shigella human challenge model has been used since 1946 for a variety of objectives including understanding disease pathogenesis, human immune responses and allowing for an early assessment of vaccine efficacy. A systematic review of the literature regarding experimental shigellosis in human subjects was conducted. Summative estimates were calculated by strain and dose. While a total of 19 studies evaluating nine strains at doses ranging from 10 to 1 × 1010 colony-forming units were identified, most studies utilized the S. sonnei strain 53G and the S. flexneri strain 2457T. Inoculum solution and pre-inoculation buffering has varied over time although diarrhoea attack rates do not appear to increase above 75-80%, and dysentery rates remain fairly constant, highlighting the need for additional dose-ranging studies. Expansion of the model to include additional strains from different serotypes will elucidate serotype and strain-specific outcome variability.

Low cycle fatigue properties of type 316 stainless steel in vacuum

NASA Astrophysics Data System (ADS)

Furuya, Kazuo; Nagata, Norio; Watanabe, Ryoji

1980-04-01

Low cycle fatigue tests in vacuum were carried out on Type 316 stainless steel under the push-pull type, strain-controlled, continuous cycling mode in the temperature range from room temperature to 1073 K and strain rate from 5 × 10 -3 to 5 × 10 -5/s . Little temperature dependence of the fatigue life at a given plastic strain range is observed. The fatigue life decreases with decreasing strain rate at room temperature and 823 K, but shows little change at 973 and 1073 K. The fracture mode is transgranular in most cases, but an indication of intergranular cracking is observed in the specimens tested at 1073 K and at the lowest strain rate. The results are treated by the general adsorption model.

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.

High-resolution three-dimensional 19F-magnetic resonance imaging of rat lung in situ: evaluation of airway strain in the perfluorocarbon-filled lung.

PubMed

Weigel, Julia K; Steinmann, Daniel; Emerich, Philipp; Stahl, Claudius A; v Elverfeldt, Dominik; Guttmann, Josef

2011-02-01

Perfluorocarbons (PFC) are biologically and chemically inert fluids with high oxygen and CO(2) carrying capacities. Their use as liquid intrapulmonary gas carriers during liquid ventilation has been investigated. We established a method of high resolution 3D-(19)F-MRI of the totally PFC-filled lung. The goal of this study was to investigate longitudinal and circumferential airway strain in the setting of increasing airway pressures on 3D-(19)F-MR images of the PFC-filled lung. Sixteen female Wistar rats were euthanized and the liquid perfluorocarbon FC-84 instilled into their lungs. 3D-(19)F-MRI was performed at various intrapulmonary pressures. Measurements of bronchial length and cross-sectional area were obtained from transversal 2D images for each pressure range. Changes in bronchial area were used to determine circumferential strain, while longitudinal strain was calculated from changes in bronchial length. Our method of 3D-(19)F-MRI allowed clear visualization of the great bronchi. Longitudinal strain increased significantly up to 31.1 cmH(2)O. The greatest strain could be found in the range of low airway pressures. Circumferential strain increased strongly with the initial pressure rise, but showed no significant changes above 10.4 cmH(2)O. Longitudinal strain was generally higher in distal airways, while circumferential strain showed no difference. Analysis of mechanical characteristics showed that longitudinal and circumferential airway expansion occurred in an anisotropic fashion. Whereas longitudinal strain still increased with higher pressures, circumferential strain quickly reached a 'strain limit'. Longitudinal strain was higher in distal bronchi, as dense PFCs gravitate to dependent, in this case to dorso-basal parts of the lung, acting as liquid positive end expiratory pressure.

Effect of strain on the electronic structure and optical properties of germanium

NASA Astrophysics Data System (ADS)

Wen, Shumin; Zhao, Chunwang; Li, Jijun; Hou, Qingyu

2018-05-01

The effects of biaxial strain parallel to the (001) plane on the electronic structures and optical properties of Ge are calculated using the first-principles plane-wave pseudopotential method based on density functional theory. The screened-exchange local-density approximation function was used to obtain more reliable band structures, while strain was changed from ‑4% to +4%. The results show that the bandgap of Ge decreases with the increase of strain. Ge becomes a direct-bandgap semiconductor when the tensile strain reaches to 2%, which is in good agreement with the experimental results. The density of electron states of strained Ge becomes more localized. The tensile strain can increase the static dielectric constant distinctly, whereas the compressive strain can decrease the static dielectric constant slightly. The strain makes the absorption band edge move toward low energy. Both the tensile strain and compressive strain can significantly increase the reflectivity in the range from 7 eV to 14 eV. The tensile strain can decrease the optical conductivity, but the compressive strain can increase the optical conductivity significantly.

Strain localization and elastic-plastic coupling during deformation of porous sandstone

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

Dewers, Thomas A.; Issen, Kathleen A.; Holcomb, David J.

Results of axisymmetric compression tests on weak, porous Castlegate Sandstone (Cretaceous, Utah, USA), covering a range of dilational and compactional behaviors, are examined for localization behavior. Assuming isotropy, bulk and shear moduli evolve as increasing functions of mean stress and Mises equivalent shear stress respectively, and as decreasing functions of work-conjugate plastic strains. Acoustic emissions events located during testing show onset of localization and permit calculation of observed shear and low-angle compaction localization zones, or bands, as localization commences. Total strain measured experimentally partitions into: A) elastic strain with constant moduli, B) elastic strain due to stress dependence of moduli,more » C) elastic strain due to moduli degradation with increasing plastic strain, and D) plastic strain. The third term is the elastic-plastic coupling strain, and though often ignored, contributes significantly to pre-failure total strain for brittle and transitional tests. Constitutive parameters and localization predictions derived from experiments are compared to theoretical predictions. In the brittle regime, predictions of band angles (angle between band normal and maximum compression) demonstrate good agreement with observed shear band angles. Compaction localization was observed in the transitional regime in between shear localization and spatially pervasive compaction, over a small range of mean stresses. In contrast with predictions however, detailed acoustic emissions analyses in this regime show low angle, compaction-dominated but shear-enhanced, localization.« less

The dynamic compressive behavior and constitutive modeling of D1 railway wheel steel over a wide range of strain rates and temperatures

NASA Astrophysics Data System (ADS)

Jing, Lin; Su, Xingya; Zhao, Longmao

The dynamic compressive behavior of D1 railway wheel steel at high strain rates was investigated using a split Hopkinson pressure bar (SHPB) apparatus. Three types of specimens, which were derived from the different positions (i.e., the rim, web and hub) of a railway wheel, were tested over a wide range of strain rates from 10-3 s-1 to 2.4 × 103 s-1 and temperatures from 213 K to 973 K. Influences of the strain rate and temperature on flow stress were discussed, and rate- and temperature-dependent constitutive relationships were assessed by the Cowper-Symonds model, Johnson-Cook model and a physically-based model, respectively. The experimental results show that the compressive true stress versus true strain response of D1 wheel steel is strain rate-dependent, and the strain hardening rate during the plastic flow stage decreases with the elevation of strain rate. Besides, the D1 wheel steel displays obvious temperature-dependence, and the third-type strain aging (3rd SA) is occurred at the temperature region of 673-973 K at a strain rate of ∼1500 s-1. Comparisons of experimental results with theoretical predictions indicate that the physically-based model has a better prediction capability for the 3rd SA characteristic of the tested D1 wheel steel.

Genetic variation within and between strains of outbred Swiss mice.

PubMed

Cui, S; Chesson, C; Hope, R

1993-04-01

The aim of this survey was to measure levels of genetic variation within and between 5 different strains of outbred Swiss mice. Ten to 15 animals from each strain (NIH, Q(S), ARC, IMVS and STUD) were typed, using allozyme electrophoresis, at 10 gene loci: Mod-1, Idh-1, Gpi-I, Es-1, Es-3, Hbb, Pep-3, Gr-1, Got-2 and Pgm-1. Polymorphic variation in at least one of the 5 strains was detected at all 10 loci. The proportion of polymorphic loci ranged from 0.3 (NIH) to 0.8 (IMVS) with a mean of 0.52. Average expected heterozygosities ranged from 0.08 (NIH) to 0.37 (IMVS) with a mean of 0.21. The inbred strain SWR was, as expected, homozygous at all 10 loci. The amount of allelic substitution between pairs of strains was quantified using Nei's genetic distance, and a dendrogram based on these genetic distances showed a close overall similarity in its branching pattern to the known genealogy of the strains. This survey showed that a considerable degree of genetic variation persists in the 5 strains examined, a level of variation similar to that previously detected by Rice and O'Brien (1980) in 3 other outbred Swiss strains.

Genetic Structure of Natural Populations of Escherichia coli in Wild Hosts on Different Continents

PubMed Central

Souza, Valeria; Rocha, Martha; Valera, Aldo; Eguiarte, Luis E.

1999-01-01

Current knowledge of genotypic and phenotypic diversity in the species Escherichia coli is based almost entirely on strains recovered from humans or zoo animals. In this study, we analyzed a collection of 202 strains obtained from 81 mammalian species representing 39 families and 14 orders in Australia and the Americas, as well as several reference strains; we also included a strain from a reptile and 10 from different families of birds collected in Mexico. The strains were characterized genotypically by multilocus enzyme electrophoresis (MLEE) and phenotypically by patterns of sugar utilization, antibiotic resistance, and plasmid profile. MLEE analysis yielded an estimated genetic diversity (H) of 0.682 for 11 loci. The observed genetic diversity in this sample is the greatest yet reported for E. coli. However, this genetic diversity is not randomly distributed; geographic effects and host taxonomic group accounted for most of the genetic differentiation. The genetic relationship among the strains showed that they are more associated by origin and host order than is expected by chance. In a dendrogram, the ancestral cluster includes primarily strains from Australia and ECOR strains from groups B and C. The most differentiated E. coli in our analysis are strains from Mexican carnivores and strains from humans, including those in the ECOR group A. The kinds and numbers of sugars utilized by the strains varied by host taxonomic group and country of origin. Strains isolated from bats were found to exploit the greatest range of sugars, while those from primates utilized the fewest. Toxins are more frequent in strains from rodents from both continents than in any other taxonomic group. Strains from Mexican wild mammals were, on average, as resistant to antibiotics as strains from humans in cities. On average, the Australian strains presented a lower antibiotic resistance than the Mexican strains. However, strains recovered from hosts in cities carried significantly more plasmids than did strains isolated from wild mammals. Previous studies have shown that natural populations of E. coli harbor an extensive genetic diversity that is organized in a limited number of clones. However, knowledge of this worldwide bacterium has been limited. Here, we suggest that the strains from a wide range of wild hosts from different regions of the world are organized in an ecotypic structure where adaptation to the host plays an important role in the population structure. PMID:10427022

Sheath-Core Graphite/Silk Fiber Made by Dry-Meyer-Rod-Coating for Wearable Strain Sensors.

PubMed

Zhang, Mingchao; Wang, Chunya; Wang, Qi; Jian, Muqiang; Zhang, Yingying

2016-08-17

Recent years have witnessed the explosive development of flexible strain sensors. Nanomaterials have been widely utilized to fabricate flexible strain sensors, because of their high flexibility and electrical conductivity. However, the fabrication processes for nanomaterials and the subsequent strain sensors are generally complicated and are manufactured at high cost. In this work, we developed a facile dry-Meyer-rod-coating process to fabricate sheath-core-structured single-fiber strain sensors using ultrafine graphite flakes as the sheath and silk fibers as the core by virtue of their flexibility, high production, and low cost. The fabricated strain sensor exhibits a high sensitivity with a gauge factor of 14.5 within wide workable strain range up to 15%, and outstanding stability (up to 3000 cycles). The single-fiber-based strain sensors could be attached to a human body to detect joint motions or easily integrated into the multidirectional strain sensor for monitoring multiaxial strain, showing great potential applications as wearable strain sensors.

Ultra High Strain Rate Nanoindentation Testing.

PubMed

Sudharshan Phani, Pardhasaradhi; Oliver, Warren Carl

2017-06-17

Strain rate dependence of indentation hardness has been widely used to study time-dependent plasticity. However, the currently available techniques limit the range of strain rates that can be achieved during indentation testing. Recent advances in electronics have enabled nanomechanical measurements with very low noise levels (sub nanometer) at fast time constants (20 µs) and high data acquisition rates (100 KHz). These capabilities open the doors for a wide range of ultra-fast nanomechanical testing, for instance, indentation testing at very high strain rates. With an accurate dynamic model and an instrument with fast time constants, step load tests can be performed which enable access to indentation strain rates approaching ballistic levels (i.e., 4000 1/s). A novel indentation based testing technique involving a combination of step load and constant load and hold tests that enables measurement of strain rate dependence of hardness spanning over seven orders of magnitude in strain rate is presented. A simple analysis is used to calculate the equivalent uniaxial response from indentation data and compared to the conventional uniaxial data for commercial purity aluminum. Excellent agreement is found between the indentation and uniaxial data over several orders of magnitude of strain rate.

Strain-rate dependence of ramp-wave evolution and strength in tantalum

DOE PAGES

Lane, J. Matthew D.; Foiles, Stephen M.; Lim, Hojun; ...

2016-08-25

We have conducted molecular dynamics (MD) simulations of quasi-isentropic ramp-wave compression to very high pressures over a range of strain rates from 10 11 down to 10 8 1/s. Using scaling methods, we collapse wave profiles from various strain rates to a master profile curve, which shows deviations when material response is strain-rate dependent. Thus, we can show with precision where, and how, strain-rate dependence affects the ramp wave. We find that strain rate affects the stress-strain material response most dramatically at strains below 20%, and that above 30% strain the material response is largely independent of strain rate. Wemore » show good overall agreement with experimental stress-strain curves up to approximately 30% strain, above which simulated response is somewhat too stiff. We postulate that this could be due to our interatomic potential or to differences in grain structure and/or size between simulation and experiment. Strength is directly measured from per-atom stress tensor and shows significantly enhanced elastic response at the highest strain rates. As a result, this enhanced elastic response is less pronounced at higher pressures and at lower strain rates.« less

Strain Pattern in Supercooled Liquids

NASA Astrophysics Data System (ADS)

Illing, Bernd; Fritschi, Sebastian; Hajnal, David; Klix, Christian; Keim, Peter; Fuchs, Matthias

2016-11-01

Investigations of strain correlations at the glass transition reveal unexpected phenomena. The shear strain fluctuations show an Eshelby-strain pattern [˜cos (4 θ ) /r2 ], characteristic of elastic response, even in liquids, at long times. We address this using a mode-coupling theory for the strain fluctuations in supercooled liquids and data from both video microscopy of a two-dimensional colloidal glass former and simulations of Brownian hard disks. We show that the long-ranged and long-lived strain signatures follow a scaling law valid close to the glass transition. For large enough viscosities, the Eshelby-strain pattern is visible even on time scales longer than the structural relaxation time τ and after the shear modulus has relaxed to zero.

Strain engineering of the silicon-vacancy center in diamond

NASA Astrophysics Data System (ADS)

Meesala, Srujan; Sohn, Young-Ik; Pingault, Benjamin; Shao, Linbo; Atikian, Haig A.; Holzgrafe, Jeffrey; Gündoǧan, Mustafa; Stavrakas, Camille; Sipahigil, Alp; Chia, Cleaven; Evans, Ruffin; Burek, Michael J.; Zhang, Mian; Wu, Lue; Pacheco, Jose L.; Abraham, John; Bielejec, Edward; Lukin, Mikhail D.; Atatüre, Mete; Lončar, Marko

2018-05-01

We control the electronic structure of the silicon-vacancy (SiV) color-center in diamond by changing its static strain environment with a nano-electro-mechanical system. This allows deterministic and local tuning of SiV optical and spin transition frequencies over a wide range, an essential step towards multiqubit networks. In the process, we infer the strain Hamiltonian of the SiV revealing large strain susceptibilities of order 1 PHz/strain for the electronic orbital states. We identify regimes where the spin-orbit interaction results in a large strain susceptibility of order 100 THz/strain for spin transitions, and propose an experiment where the SiV spin is strongly coupled to a nanomechanical resonator.

Shear Strength of Square Graphene Nanoribbons beyond Wrinkling

NASA Astrophysics Data System (ADS)

Ragab, Tarek; Basaran, Cemal

2018-04-01

Atomistic modeling of armchair and zigzag graphene nanoribbons (GNRs) has been performed to investigate the post-wrinkling behavior under in-plane (x-y) shear deformation. Simulations were performed at 300 K for square GNRs with size ranging from 2.5 nm to 20 nm. Shear stresses led only to diagonal tension, and wrinkling was not accompanied by any diagonal compressive force. Once the diagonal tension reached its ultimate elastic level, three major stress-relaxing phenomena were observed. The type of stress-relaxing phenomenon involved greatly affected the mechanical behavior in terms of the slope of the stress-strain diagram beyond the elastic range. The results showed that the average slope of the stress-strain relation beyond the ultimate elastic stress decreased with the increase of the GNR size. Moreover, the slope of the shear stress-strain curve beyond the ultimate elastic stress was always greater for armchair than for zigzag GNRs. GNRs can sustain very high plastic shear strains beyond 100% before failure. The ultimate elastic stress can range from 20 GPa to 50 GPa, occurring at shear strain ranging from 52% to 19%. The ultimate elastic stress and strain were inversely proportional to the size of the GNR with a power factor ranging from 0.261 for armchair GNRs to 0.354 for zigzag GNRs due to the decrease in the effective width for diagonal tension.

Shear Strength of Square Graphene Nanoribbons beyond Wrinkling

NASA Astrophysics Data System (ADS)

Ragab, Tarek; Basaran, Cemal

2018-07-01

Atomistic modeling of armchair and zigzag graphene nanoribbons (GNRs) has been performed to investigate the post-wrinkling behavior under in-plane ( x- y) shear deformation. Simulations were performed at 300 K for square GNRs with size ranging from 2.5 nm to 20 nm. Shear stresses led only to diagonal tension, and wrinkling was not accompanied by any diagonal compressive force. Once the diagonal tension reached its ultimate elastic level, three major stress-relaxing phenomena were observed. The type of stress-relaxing phenomenon involved greatly affected the mechanical behavior in terms of the slope of the stress-strain diagram beyond the elastic range. The results showed that the average slope of the stress-strain relation beyond the ultimate elastic stress decreased with the increase of the GNR size. Moreover, the slope of the shear stress-strain curve beyond the ultimate elastic stress was always greater for armchair than for zigzag GNRs. GNRs can sustain very high plastic shear strains beyond 100% before failure. The ultimate elastic stress can range from 20 GPa to 50 GPa, occurring at shear strain ranging from 52% to 19%. The ultimate elastic stress and strain were inversely proportional to the size of the GNR with a power factor ranging from 0.261 for armchair GNRs to 0.354 for zigzag GNRs due to the decrease in the effective width for diagonal tension.

Genome analysis and physiological comparison of Alicycliphilus denitrificans strains BC and K601T

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

Oosterkamp, Margreet J.; Veuskens, Teun; Saia, Flavia Talarico

2013-01-01

The genomes of the Betaproteobacteria Alicycliphilus denitrificans strains BC and K601T have been sequenced to get insight into the physiology of the two strains. Strain BC degrades benzene with chlorate as electron acceptor. The cyclohexanol-degrading denitrifying strain K601T is not able to use chlorate as electron acceptor, while strain BC cannot degrade cyclohexanol. The 16S rRNA sequences of strains BC and K601T are identical and the fatty acid methyl ester patterns of the strains are similar. Basic Local Alignment Search Tool (BLAST) analysis of predicted open reading frames of both strains showed most hits with Acidovorax sp. JS42, a bacteriummore » that degrades nitro-aromatics. The genomes include strain-specific plasmids (pAlide201 in strain K601T and pAlide01 and pAlide02 in strain BC). Key genes of chlorate reduction in strain BC were located on a 120 kb megaplasmid (pAlide01), which was absent in strain K601T. Genes involved in cyclohexanol degradation were only found in strain K601T. Benzene and toluene are degraded via oxygenase-mediated pathways in both strains. Genes involved in the meta-cleavage pathway of catechol are present in the genomes of both strains. Strain BC also contains all genes of the ortho-cleavage pathway. The large number of mono- and dioxygenase genes in the genomes suggests that the two strains have a broader substrate range than known thus far.« less

Genome Analysis and Physiological Comparison of Alicycliphilus denitrificans Strains BC and K601T

PubMed Central

Talarico Saia, Flávia; Weelink, Sander A. B.; Goodwin, Lynne A.; Daligault, Hajnalka E.; Bruce, David C.; Detter, John C.; Tapia, Roxanne; Han, Cliff S.; Land, Miriam L.; Hauser, Loren J.; Langenhoff, Alette A. M.; Gerritse, Jan; van Berkel, Willem J. H.; Pieper, Dietmar H.; Junca, Howard; Smidt, Hauke; Schraa, Gosse; Davids, Mark; Schaap, Peter J.; Plugge, Caroline M.; Stams, Alfons J. M.

2013-01-01

The genomes of the Betaproteobacteria Alicycliphilus denitrificans strains BC and K601T have been sequenced to get insight into the physiology of the two strains. Strain BC degrades benzene with chlorate as electron acceptor. The cyclohexanol-degrading denitrifying strain K601T is not able to use chlorate as electron acceptor, while strain BC cannot degrade cyclohexanol. The 16S rRNA sequences of strains BC and K601T are identical and the fatty acid methyl ester patterns of the strains are similar. Basic Local Alignment Search Tool (BLAST) analysis of predicted open reading frames of both strains showed most hits with Acidovorax sp. JS42, a bacterium that degrades nitro-aromatics. The genomes include strain-specific plasmids (pAlide201 in strain K601T and pAlide01 and pAlide02 in strain BC). Key genes of chlorate reduction in strain BC were located on a 120 kb megaplasmid (pAlide01), which was absent in strain K601T. Genes involved in cyclohexanol degradation were only found in strain K601T. Benzene and toluene are degraded via oxygenase-mediated pathways in both strains. Genes involved in the meta-cleavage pathway of catechol are present in the genomes of both strains. Strain BC also contains all genes of the ortho-cleavage pathway. The large number of mono- and dioxygenase genes in the genomes suggests that the two strains have a broader substrate range than known thus far. PMID:23825601

Spall response of single-crystal copper

NASA Astrophysics Data System (ADS)

Turley, W. D.; Fensin, S. J.; Hixson, R. S.; Jones, D. R.; La Lone, B. M.; Stevens, G. D.; Thomas, S. A.; Veeser, L. R.

2018-02-01

We performed a series of systematic spall experiments on single-crystal copper in an effort to determine and isolate the effects of crystal orientation, peak stress, and unloading strain rate on the tensile spall strength. Strain rates ranging from 0.62 to 2.2 × 106 s-1 and peak shock stresses in the 5-14 GPa range, with one additional experiment near 50 GPa, were explored as part of this work. Gun-driven impactors, called flyer plates, generated flat top shocks followed by spall. This work highlights the effect of crystal anisotropy on the spall strength by showing that the spall strength decreases in the following order: [100], [110], and [111]. Over the range of stresses and strain rates explored, the spall strength of [100] copper depends strongly on both the strain rate and shock stress. Except at the very highest shock stress, the results for the [100] orientation show linear relationships between the spall strength and both the applied compressive stress and the strain rate. In addition, hydrodynamic computer code simulations of the spall experiments were performed to calculate the relationship between the strain rate near the spall plane in the target and the rate of free surface velocity release during the pullback. As expected, strain rates at the spall plane are much higher than the strain rates estimated from the free surface velocity release rate. We have begun soft recovery experiments and molecular dynamics calculations to understand the unusual recompression observed in the spall signature for [100] crystals.

A promising strain of Streptomyces sp. with agricultural traits for growth promotion and disease management.

PubMed

Alam, Mansoor; Dharni, Seema; Abdul-Khaliq; Srivastava, Santosh Kumar; Samad, Abdul; Gupta, Mahesh Kumar

2012-08-01

A bacterial strain, Streptomyces sp. CIMAP- A1 was isolated from Geranium rhizosphere and identified by morphological, physiological, biochemical and molecular characters (16S rDNA gene sequence). Phylogenetically, it was found most closely related to S. vinacendrappus, strain NRRL-2363 with 99% sequence similarity. The strain had potential antagonistic activity (in vitro) against wide range of phytopathogenic fungi like Stemphylium sp., Botrytis cinerea, Sclerotinia sclerotiorum, Colletotrichum spp., Curvularia spp., Corynespora cassicola and Thielavia basicola. The extracellular secondary metabolites produced by the strain in the culture filtrates significantly inhibited the spore germination, growth of germ tube of the germinated spores and radial growth of Alternaria alternata, Colletotrichum acutatum, Curvularia andropogonis and Fusarium moniliforme. The extraction of culture filtrate with solvents and purification by following VLC and PTLC methods always yielded a 10th fraction antifungal compound showing activity against wide range of phytopathogenic fungi. The strain was able to produce siderophores and indole-3-acetic acid. The strain was found to enhance the growth and biomass production of Geranium. It increased 11.3% fresh shoot biomass of Geranium and 21.7% essential oil yield.

The CasKR Two-Component System Is Required for the Growth of Mesophilic and Psychrotolerant Bacillus cereus Strains at Low Temperatures

PubMed Central

Diomandé, Sara Esther; Chamot, Stéphanie; Antolinos, Vera; Vasai, Florian; Guinebretière, Marie-Hélène; Bornard, Isabelle; Nguyen-the, Christophe; Broussolle, Véronique

2014-01-01

The different strains of Bacillus cereus can grow at temperatures covering a very diverse range. Some B. cereus strains can grow in chilled food and consequently cause food poisoning. We have identified a new sensor/regulator mechanism involved in low-temperature B. cereus growth. Construction of a mutant of this two-component system enabled us to show that this system, called CasKR, is required for growth at the minimal temperature (Tmin). CasKR was also involved in optimal cold growth above Tmin and in cell survival below Tmin. Microscopic observation showed that CasKR plays a key role in cell shape during cold growth. Introducing the casKR genes in a ΔcasKR mutant restored its ability to grow at Tmin. Although it was first identified in the ATCC 14579 model strain, this mechanism has been conserved in most strains of the B. cereus group. We show that the role of CasKR in cold growth is similar in other B. cereus sensu lato strains with different growth temperature ranges, including psychrotolerant strains. PMID:24509924

Effect of strain rate and dislocation density on the twinning behavior in Tantalum

DOE PAGES

Florando, Jeffrey N.; El-Dasher, Bassem S.; Chen, Changqiang; ...

2016-04-28

The conditions which affect twinning in tantalum have been investigated across a range of strain rates and initial dislocation densities. Tantalum samples were subjected to a range of strain rates, from 10 –4/s to 10 3/s under uniaxial stress conditions, and under laser-induced shock-loading conditions. In this study, twinning was observed at 77K at strain rates from 1/s to 103/s, and during laser-induced shock experiments. The effect of the initial dislocation density, which was imparted by deforming the material to different amounts of pre-strain, was also studied, and it was shown that twinning is suppressed after a given amount ofmore » pre-strain, even as the global stress continues to increase. These results indicate that the conditions for twinning cannot be represented solely by a critical global stress value, but are also dependent on the evolution of the dislocation density. Additionally, the analysis shows that if twinning is initiated, the nucleated twins may continue to grow as a function of strain, even as the dislocation density continues to increase.« less

Use of layer strains in strained-layer superlattices to make devices for operation in new wavelength ranges, E. G. , InAsSb at 8 to 12. mu. m. [InAs/sub 1-x/Sb/sub x/

DOEpatents

Osbourn, G.C.

1983-10-06

An intrinsic semiconductor electro-optical device comprises a p-n junction intrinsically responsive, when cooled, to electromagnetic radiation in the wavelength range of 8 to 12 ..mu..m. This radiation responsive p-n junction comprises a strained-layer superlattice (SLS) of alternating layers of two different III-V semiconductors. The lattice constants of the two semiconductors are mismatched, whereby a total strain is imposed on each pair of alternating semiconductor layers in the SLS structure, the proportion of the total strain which acts on each layer of the pair being proportional to the ratio of the layer thicknesses of each layer in the pair.

Reference Ranges of Left Ventricular Strain Measures by Two-Dimensional Speckle-Tracking Echocardiography in Children: A Systematic Review and Meta-Analysis.

PubMed

Levy, Philip T; Machefsky, Aliza; Sanchez, Aura A; Patel, Meghna D; Rogal, Sarah; Fowler, Susan; Yaeger, Lauren; Hardi, Angela; Holland, Mark R; Hamvas, Aaron; Singh, Gautam K

2016-03-01

Establishment of the range of reference values and associated variations of two-dimensional speckle-tracking echocardiography (2DSTE)-derived left ventricular (LV) strain is a prerequisite for its routine clinical adoption in pediatrics. The aims of this study were to perform a meta-analysis of normal ranges of LV global longitudinal strain (GLS), global circumferential strain (GCS), and global radial strain (GRS) measurements derived by 2DSTE in children and to identify confounding factors that may contribute to variance in reported measures. A systematic review was launched in MEDLINE, Embase, Scopus, the Cumulative Index to Nursing and Allied Health Literature, and the Cochrane Library. Search hedges were created to cover the concepts of pediatrics, STE, and left-heart ventricle. Two investigators independently identified and included studies if they reported 2DSTE-derived LV GLS, GCS, or GRS. The weighted mean was estimated by using random effects models with 95% CIs, heterogeneity was assessed using the Cochran Q statistic and the inconsistency index (I(2)), and publication bias was evaluated using the Egger test. Effects of demographic (age), clinical, and vendor variables were assessed in a metaregression. The search identified 2,325 children from 43 data sets. The reported normal mean values of GLS among the studies varied from -16.7% to -23.6% (mean, -20.2%; 95% CI, -19.5% to -20.8%), GCS varied from -12.9% to -31.4% (mean, -22.3%; 95% CI, -19.9% to -24.6%), and GRS varied from 33.9% to 54.5% (mean, 45.2%; 95% CI, 38.3% to 51.7%). Twenty-six studies reported longitudinal strain only from the apical four-chamber view, with a mean of -20.4% (95% CI, -19.8% to -21.7%). Twenty-three studies reported circumferential strain (mean, -20.3%; 95% CI, -19.4% to -21.2%) and radial strain (mean, 46.7%; 95% CI, 42.3% to 51.1%) from the short-axis view at the midventricular level. A significant apex-to-base segmental longitudinal strain gradient (P < .01) was observed in the LV free wall. There was significant between-study heterogeneity and inconsistency (I(2) > 94% and P < .001 for each strain measure), which was not explained by age, gender, body surface area, blood pressure, heart rate, frame rate, frame rate/heart rate ratio, tissue-tracking methodology, location of reported strain value along the strain curve, ultrasound equipment, or software. The metaregression showed that these effects were not significant determinants of variations among normal ranges of strain values. There was no evidence of publication bias (P = .40). This study defines reference values of 2DSTE-derived LV strain in children on the basis of a meta-analysis. In healthy children, mean LV GLS was -20.2% (95% CI, -19.5% to -20.8%), mean GCS was -22.3% (95% CI, -19.9% to -24.6%), and mean GRS was 45.2% (95% CI, 38.3% to 51.7%). LV segmental longitudinal strain has a stable apex-to-base gradient that is preserved throughout maturation. Although variations among different reference ranges in this meta-analysis were not dependent on differences in demographic, clinical, or vendor parameters, age- and vendor-specific referenced ranges were established as well. Copyright © 2016 American Society of Echocardiography. Published by Elsevier Inc. All rights reserved.

Photoacclimation of Prochlorococcus sp. (Prochlorophyta) Strains Isolated from the North Atlantic and the Mediterranean Sea.

PubMed Central

Partensky, F.; Hoepffner, N.; Li, WKW.; Ulloa, O.; Vaulot, D.

1993-01-01

Two Atlantic (SARG and NATL1) strains and one Mediterranean (MED) strain of Prochlorococcus sp., a recently discovered marine, free-living prochlorophyte, were grown over a range of "white" irradiances (lg) and under low blue light to examine their photoacclimation capacity. All three strains contained divinyl (DV) chlorophylls (Chl) a and b, both distinguishable from "normal" Chls by their red-shifted blue absorption maximum, a Chl c-like pigment at low concentration, zeaxanthin, and [alpha]-carotene. The presence of two phaeophytin b peaks in acidified extracts from both Atlantic strains grown at high lg suggests that these strains also had a normal Chl b-like pigment. In these strains, the total Chl b to DV-Chl a molar ratio decreased from about 1 at 7.5 [mu]mol quanta m-2 s-1 to 0.4 to 0.5 at 133 [mu]mol quanta m-2 s-1. In contrast, the MED strain always had a low DV-Chl b to DV-Chl a molar ratio, ranging between 0.13 at low lg and 0.08 at high lg. The discrepancies between the Atlantic and MED strains could result from differences either in the number of light-harvesting complexes (LHC) II per photosystem II or in the Chl b-binding capacity of the apoproteins constituting LHC II. Photosynthesis was saturated at approximately 5 fg C(fg Chl)-1 h-1 or 6 fg C cell-1 h-1, and growth was saturated at approximately 0.45 d-1 for both MED and SARG strains at 18[deg]C, but saturating irradiances differed between strains. Atlantic strains exhibited increased light-saturated rates and quantum yield for carbon fixation under blue light. PMID:12231684

Atomistic simulations to characterize the influence of applied strain and PKA energy on radiation damage evolution in pure aluminum

NASA Astrophysics Data System (ADS)

Sahi, Qurat-ul-ain; Kim, Yong-Soo

2018-05-01

Knowledge of defects generation, their mobility, growth rate, and spatial distribution is the cornerstone for understanding the surface and structural evolution of a material used under irradiation conditions. In this study, molecular dynamics simulations were used to investigate the coupled effect of primary knock-on atom (PKA) energy and applied strain (uniaxial and hydrostatic) fields on primary radiation damage evolution in pure aluminum. Cascade damage simulations were carried out for PKA energy ranging between 1 and 20 keV and for applied strain values ranging between -2% and 2% at the fixed temperature of 300 K. Simulation results showed that as the atomic displacement cascade proceeds under uniaxial and hydrostatic strains, the peak and surviving number of Frenkel point defects increases with increasing tension; however, these increments were more prominent under larger volume changing deformations (hydrostatic strain). The percentage fraction of point defects that aggregate into clusters increases under tension conditions; compared to the reference conditions with no strain, these increases are around 13% and 7% for interstitials and vacancies, respectively (under 2% uniaxial strain), and 19% and 11% for interstitials and vacancies, respectively (under 2% hydrostatic strain). Clusters formed of vacancies and interstitials were both larger under tensile strain conditions, with increases in both the average and maximum cluster sizes. The rate of increase/decrease in the number of Frenkel pairs, their clustering, and their size distributions under expansion/compression strain conditions were higher for higher PKA energies. Overall, the present results suggest that strain effects should be considered carefully in radiation damage environments, specifically for conditions of low temperature and high radiation energy. Compressive strain conditions could be beneficial for materials used in nuclear reactor power systems.

Genomic landscapes of endogenous retroviruses unveil intricate genetics of conventional and genetically-engineered laboratory mouse strains.

PubMed

Lee, Kang-Hoon; Lim, Debora; Chiu, Sophia; Greenhalgh, David; Cho, Kiho

2016-04-01

Laboratory strains of mice, both conventional and genetically engineered, have been introduced as critical components of a broad range of studies investigating normal and disease biology. Currently, the genetic identity of laboratory mice is primarily confirmed by surveying polymorphisms in selected sets of "conventional" genes and/or microsatellites in the absence of a single completely sequenced mouse genome. First, we examined variations in the genomic landscapes of transposable repetitive elements, named the TREome, in conventional and genetically engineered mouse strains using murine leukemia virus-type endogenous retroviruses (MLV-ERVs) as a probe. A survey of the genomes from 56 conventional strains revealed strain-specific TREome landscapes, and certain families (e.g., C57BL) of strains were discernible with defined patterns. Interestingly, the TREome landscapes of C3H/HeJ (toll-like receptor-4 [TLR4] mutant) inbred mice were different from its control C3H/HeOuJ (TLR4 wild-type) strain. In addition, a CD14 knock-out strain had a distinct TREome landscape compared to its control/backcross C57BL/6J strain. Second, an examination of superantigen (SAg, a "TREome gene") coding sequences of mouse mammary tumor virus-type ERVs in the genomes of the 46 conventional strains revealed a high diversity, suggesting a potential role of SAgs in strain-specific immune phenotypes. The findings from this study indicate that unexplored and intricate genomic variations exist in laboratory mouse strains, both conventional and genetically engineered. The TREome-based high-resolution genetics surveillance system for laboratory mice would contribute to efficient study design with quality control and accurate data interpretation. This genetics system can be easily adapted to other species ranging from plants to humans. Copyright © 2016 Elsevier Inc. All rights reserved.

Strain effects on oxygen migration in perovskites.

PubMed

Mayeshiba, Tam; Morgan, Dane

2015-01-28

Fast oxygen transport materials are necessary for a range of technologies, including efficient and cost-effective solid oxide fuel cells, gas separation membranes, oxygen sensors, chemical looping devices, and memristors. Strain is often proposed as a method to enhance the performance of oxygen transport materials, but the magnitude of its effect and its underlying mechanisms are not well-understood, particularly in the widely-used perovskite-structured oxygen conductors. This work reports on an ab initio prediction of strain effects on migration energetics for nine perovskite systems of the form LaBO3, where B = [Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Ga]. Biaxial strain, as might be easily produced in epitaxial systems, is predicted to lead to approximately linear changes in migration energy. We find that tensile biaxial strain reduces the oxygen vacancy migration barrier across the systems studied by an average of 66 meV per percent strain for a single selected hop, with a low of 36 and a high of 89 meV decrease in migration barrier per percent strain across all systems. The estimated range for the change in migration barrier within each system is ±25 meV per percent strain when considering all hops. These results suggest that strain can significantly impact transport in these materials, e.g., a 2% tensile strain can increase the diffusion coefficient by about three orders of magnitude at 300 K (one order of magnitude at 500 °C or 773 K) for one of the most strain-responsive materials calculated here (LaCrO3). We show that a simple elasticity model, which assumes only dilative or compressive strain in a cubic environment and a fixed migration volume, can qualitatively but not quantitatively model the strain dependence of the migration energy, suggesting that factors not captured by continuum elasticity play a significant role in the strain response.

Cyclic deformation and phase transformation of 6Mo superaustenitic stainless steel

NASA Astrophysics Data System (ADS)

Wang, Shing-Hoa; Wu, Chia-Chang; Chen, Chih-Yuan; Yang, Jer-Ren; Chiu, Po-Kay; Fang, Jason

2007-08-01

A fatigue behavior analysis was performed on superaustenitic stainless steel UNS S31254 (Avesta Sheffield 254 SMO), which contains about 6wt.% molybdenum, to examine the cyclic hardening/softening trend, hysteresis loops, the degree of hardening, and fatigue life during cyclic straining in the total strain amplitude range from 0.2 to 1.5%. Independent of strain rate, hardening occurs first, followed by softening. The degree of hardening is dependent on the magnitude of strain amplitude. The cyclic stress-strain curve shows material softening. The lower slope of the degree of hardening versus the strain amplitude curve at a high strain rate is attributed to the fast development of dislocation structures and quick saturation. The ɛ martensite formation, either in band or sheath form, depending on the strain rate, leads to secondary hardening at the high strain amplitude of 1.5%.

Fiber-Optic Strain Sensors With Linear Characteristics

NASA Technical Reports Server (NTRS)

Egalon, Claudio O.; Rogowski, Robert S.

1993-01-01

Fiber-optic modal domain strain sensors having linear characteristics over wide range of strains proposed. Conceived in effort to improve older fiber-optic strain sensors. Linearity obtained by appropriate choice of design parameters. Pattern of light and dark areas at output end of optical fiber produced by interference between electromagnetic modes in which laser beam propagates in fiber. Photodetector monitors intensity at one point in pattern.

Characterization of Hot Deformation Behavior of a Fe-Cr-Ni-Mo-N Superaustenitic Stainless Steel Using Dynamic Materials Modeling

NASA Astrophysics Data System (ADS)

Pu, Enxiang; Zheng, Wenjie; Song, Zhigang; Feng, Han; Zhu, Yuliang

2017-03-01

Hot deformation behavior of a Fe-24Cr-22Ni-7Mo-0.5N superaustenitic stainless steel was investigated by hot compression tests in a wide temperature range of 950-1250 °C and strain rate range of 0.001-10 s-1. The flow curves show that the flow stress decreases as the deformation temperature increases or the strain rate decreases. The processing maps developed on the basis of the dynamic materials model and flow stress data were adopted to optimize the parameters of hot working. It was found that the strain higher than 0.2 has no significant effect on the processing maps. The optimum processing conditions were in the temperature range of 1125-1220 °C and strain rate range of 0.1-3 s-1. Comparing to other stable domains, microstructural observations in this domain revealed the complete dynamic recrystallization (DRX) with finer and more uniform grain size. Flow instability occurred in the domain of temperature lower than 1100 °C and strain rate higher than 0.1 s-1.

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.

Altering thermal transport by strained-layer epitaxy

NASA Astrophysics Data System (ADS)

Majdi, Tahereh; Pal, Souvik; Hafreager, Anders; Murad, Sohail; Sahu, Rakesh P.; Puri, Ishwar K.

2018-05-01

Since strain changes the interatomic spacing of matter and alters electron and phonon dispersion, an applied strain can modify the thermal conductivity k of a material. We show how the strain induced by heteroepitaxy is a passive mechanism to change k in a thin film. Molecular dynamics simulations of the deposition and epitaxial growth of ZnTe thin films provide insights into the role of interfacial strain in the conductivity of a deposited film. ZnTe films grow strain-free on lattice-matched ZnTe substrates, but similar thin films grown on a lattice-mismatched CdTe substrate exhibit ˜6% biaxial in-plane tensile strain and ˜7% uniaxial out-of-plane compressive strain. In the T = 700 K-1100 K temperature range, the conductivities of strained ZnTe layers decrease to ˜60% of their unstrained values. The resulting understanding of dk/dT shows that strain engineering can be used to alter the performance of a thermal rectifier and also provides a framework for enhancing thermoelectric devices.

Free range and deep litter poultry production systems: effect on performance, carcass yield and meat composition of cockerel chickens.

PubMed

Sogunle, Olajide Mark; Olaniyi, Olagoke Ayobami; Egbeyale, Lawrence Tokunbo; Akinola, Olufemi Sunday; Shittu, Taofeek A; Abiola, Samuel Soladoye; Ladokun, Abimbola O; Sobayo, Richard Abayomi

2013-01-01

This study was carried out on 150 cockerel chickens each of Harco Black and Novogen strains to determine their performance, carcass yield and meat composition on free range and deep litter production systems. The birds were brooded for 4 weeks and thereafter allotted to the different production systems for a period of 12 weeks. Each production system was allotted 150 chicks (75 chicks per strain) with three replicates of 25 chicks. The birds on deep litter production system were fed ad libitum while each bird on free range was fed 50 % of its daily feed requirement. On the 84 th day, a total of 36 birds were randomly selected for analysis of the carcass yield and meat composition. The data generated were subjected to a two-way analysis of variance in a 2 × 2 factorial experimental arrangement. Novogen strain consumed less feed (P < 0.05) on free range and had the best feed/gain (2.72). A higher (P < 0.05) shear force value (3.74 N) was obtained in the thigh muscle for birds on free range. The tibia proximal length and breadth, and tibia distal length and breadth were significantly (P < 0.05) affected by the production systems and strains. On free range, Harco black had more meat (85.69 g) than bone (18.07 g) in the breast while Novogen had the lowest meat/bone (2.38). Conclusively, Novogen strain should be raised on free range for a better performance in terms of feed/gain, but for higher meat composition, Harco black is a better strain.

Brain strain uncertainty due to shape variation in and simplification of head angular velocity profiles.

PubMed

Zhao, Wei; Ji, Songbai

2017-04-01

Head angular velocity, instead of acceleration, is more predictive of brain strains. Surprisingly, no study exists that investigates how shape variation in angular velocity profiles affects brain strains, beyond characteristics such as peak magnitude and impulse duration. In this study, we evaluated brain strain uncertainty due to variation in angular velocity profiles and further compared with that resulting from simplifying the profiles into idealized shapes. To do so, we used reconstructed head impacts from American National Football League for shape extraction and simulated head uniaxial coronal rotations from onset to full stop. The velocity profiles were scaled to maintain an identical peak velocity magnitude and duration in order to isolate the shape for investigation. Element-wise peak maximum principal strains from 44 selected impacts were obtained. We found that the shape of angular velocity profile could significantly affect brain strain magnitude (e.g., percentage difference of 4.29-17.89 % in the whole brain relative to the group average, with cumulative strain damage measure (CSDM) uncertainty range of 23.9 %) but not pattern (correlation coefficient of 0.94-0.99). Strain differences resulting from simplifying angular velocity profiles into idealized shapes were largely within the range due to shape variation, in both percentage difference and CSDM (signed difference of 3.91 % on average, with a typical range of 0-6 %). These findings provide important insight into the uncertainty or confidence in the performance of kinematics-based injury metrics. More importantly, they suggest the feasibility to simplify head angular velocity profiles into idealized shapes, at least within the confinements of the profiles evaluated, to enable real-time strain estimation via pre-computation in the future.

Brain strain uncertainty due to shape variation in and simplification of head angular velocity profiles

PubMed Central

Zhao, Wei; Ji, Songbai

2016-01-01

Head angular velocity, instead of acceleration, is more predictive of brain strains. Surprisingly, no study exists that investigates how shape variation in angular velocity profiles affects brain strains, beyond characteristics such as peak magnitude and impulse duration. In this study, we evaluated brain strain uncertainty due to variation in angular velocity profiles, and further compared with that resulting from simplifying the profiles into idealized shapes. To do so, we used reconstructed head impacts from American National Football League for shape extraction, and simulated head uniaxial coronal rotations from onset to full stop. The velocity profiles were scaled to maintain an identical peak velocity magnitude and duration in order to isolate the shape for investigation. Element-wise peak maximum principal strains from 44 selected impacts were obtained. We found that the shape of angular velocity profile could significantly affect brain strain magnitude (e.g., percentage difference of 4.29–17.89% in the whole-brain relative to the group average, with cumulative strain damage measure (CSDM) uncertainty range of 23.9%) but not pattern (correlation coefficient of 0.94–0.99). Strain differences resulting from simplifying angular velocity profiles into idealized shapes were largely within the range due to shape variation, in both percentage difference and CSDM (signed difference of 3.91% on average, with a typical range of 0–6%). These findings provide important insight into the uncertainty or confidence in the performance of kinematics-based injury metrics. More importantly, they suggest the feasibility to simplify head angular velocity profiles into idealized shapes, at least within the confinements of the profiles evaluated, to enable real-time strain estimation via pre-computation in the future. PMID:27644441

Desulfosporosinus acididurans sp. nov.: an acidophilic sulfate-reducing bacterium isolated from acidic sediments.

PubMed

Sánchez-Andrea, Irene; Stams, Alfons J M; Hedrich, Sabrina; Ňancucheo, Ivan; Johnson, D Barrie

2015-01-01

Three strains of sulfate-reducing bacteria (M1(T), D, and E) were isolated from acidic sediments (White river and Tinto river) and characterized phylogenetically and physiologically. All three strains were obligately anaerobic, mesophilic, spore-forming straight rods, stained Gram-negative and displayed variable motility during active growth. The pH range for growth was 3.8-7.0, with an optimum at pH 5.5. The temperature range for growth was 15-40 °C, with an optimum at 30 °C. Strains M1(T), D, and E used a wide range of electron donors and acceptors, with certain variability within the different strains. The nominated type strain (M1(T)) used ferric iron, nitrate, sulfate, elemental sulfur, and thiosulfate (but not arsenate, sulfite, or fumarate) as electron acceptors, and organic acids (formate, lactate, butyrate, fumarate, malate, and pyruvate), alcohols (glycerol, methanol, and ethanol), yeast extract, and sugars (xylose, glucose, and fructose) as electron donors. It also fermented some substrates such as pyruvate and formate. Strain M1(T) tolerated up to 50 mM ferrous iron and 10 mM aluminum, but was inhibited by 1 mM copper. On the basis of phenotypic, phylogenetic, and genetic characteristics, strains M1(T), D, and E represent a novel species within the genus Desulfosporosinus, for which the name Desulfosporosinus acididurans sp. nov. is proposed. The type strain is M1(T) (=DSM 27692(T) = JCM 19471(T)). Strain M1(T) was the first acidophilic SRB isolated, and it is the third described species of acidophilic SRB besides Desulfosporosinus acidiphilus and Thermodesulfobium narugense.

Tensile Lattice Strain Accelerates Oxygen Surface Exchange and Diffusion in La1–xSrxCoO3−δ Thin Films

PubMed Central

2013-01-01

The influence of lattice strain on the oxygen exchange kinetics and diffusion in oxides was investigated on (100) epitaxial La1–xSrxCoO3−δ (LSC) thin films grown by pulsed laser deposition. Planar tensile and compressively strained LSC films were obtained on single-crystalline SrTiO3 and LaAlO3. 18O isotope exchange depth profiling with ToF-SIMS was employed to simultaneously measure the tracer surface exchange coefficient k* and the tracer diffusion coefficient D* in the temperature range 280–475 °C. In accordance with recent theoretical findings, much faster surface exchange (∼4 times) and diffusion (∼10 times) were observed for the tensile strained films compared to the compressively strained films in the entire temperature range. The same strain effect—tensile strain leading to higher k* and D*—was found for different LSC compositions (x = 0.2 and x = 0.4) and for surface-etched films. The temperature dependence of k* and D* is discussed with respect to the contributions of strain states, formation enthalpy of oxygen vacancies, and vacancy mobility at different temperatures. Our findings point toward the control of oxygen surface exchange and diffusion kinetics by means of lattice strain in existing mixed conducting oxides for energy conversion applications. PMID:23527691

Residual Strain in PCBs with Cu-Plated Holes

NASA Astrophysics Data System (ADS)

Rudajevova, A.; Dušek, K.

2017-12-01

The residual strain in pure printed circuit boards (PCBs) and PCBs with Cu-plated holes has been obtained by measurement of the temperature dependence of their dilatational characteristics in the x, y, and z directions up to 240°C. Shrinkage in all directions was observed for all samples of both materials in the first thermal cycle. No permanent length changes were observed in the second or subsequent thermal cycles. The residual strain was determined from the difference in relative elongation between the first and second thermal cycles. Relaxation of residual strain occurred only in the first thermal cycle, as a thermally activated process. The highest value of relaxed residual strain was found in the z direction for both materials. Relaxation of residual strain in the z direction of the pure PCB occurred only in the negative strain range, whereas relaxation of the PCB with Cu-plated holes occurred in both the positive and negative strain ranges. The relaxation of the positive strain in the PCB with Cu-plated holes in the z direction implies that this part of the PCB was under pressure during its preparation. This relaxation is a consequence of the high coefficient of thermal expansion of PCB laminate in this direction, which can also lead to cracks in Cu holes when the material is heated above the glass-transition temperature.

Macroscopic strain controlled ion current in an elastomeric microchannel

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

Kuo, Chin-Chang; Nguyen, Du; Buchsbaum, Steven

We report on the fabrication of an ultra-high aspect ratio ionically conductive single microchannel with tunable diameter from ≈ 20 μm to fully closed. The 4 mm-long channel is fabricated in a Polydimethylsiloxane (PDMS) mold and its cross-sectional area is controlled by applying macroscopic compressive strain to the mold in a direction perpendicular to the channel length. We investigated the ionic conduction properties of the channel. For a wide range of compressive strain up to ≈ 0.27, the strain dependence of the resistance is monotonic and fully reversible. For strain > 0.27, ionic conduction suddenly shuts off and the system becomes hystereticmore » (whereby a finite strain reduction is required to reopen the channel). Upon unloading, the original behavior is retrieved. This reversible behavior is observed over 200 compression cycles. The cross-sectional area of the channel can be inferred from the ion current measurement, as confirmed by a Nano-Computed Tomography investigation. We show that the cross-sectional area decreases monotonically with the applied compressive strain in the reversible range, in qualitative agreement with linear elasticity theory. We find that the shut-off strain is affected by the spatial extent of the applied strain, which provides additional tunability. Our tunable channel is well-suited for multiple applications in micro/nano-fluidic devices.« less

Strain and ferroelectric soft-mode induced superconductivity in strontium titanate

NASA Astrophysics Data System (ADS)

Dunnett, K.; Narayan, Awadhesh; Spaldin, N. A.; Balatsky, A. V.

2018-04-01

We investigate the effects of strain on superconductivity with particular reference to SrTiO3. Assuming that a ferroelectric mode that softens under tensile strain is responsible for the coupling, an increase in the critical temperature and range of carrier densities for superconductivity is predicted, while the peak of the superconducting dome shifts towards lower carrier densities. Using a Ginzburg-Landau approach in 2D, we find a linear dependence of the critical temperature on strain: if the couplings between the order parameter and strains in different directions differ while their sum is fixed, different behaviors under uniaxial and biaxial strain can be understood.

Strain-relaxation and critical thickness of epitaxial La 1.85Sr 0.15CuO 4 films

DOE PAGES

Meyer, Tricia L; Jiang, Lu; Park, Sungkyun; ...

2015-12-08

We report the thickness-dependent strain-relaxation behavior and the associated impacts upon the superconductivity in epitaxial La 1.85Sr 0.15CuO 4 films grown on different substrates, which provide a range of strain. We have found that the critical thickness for the onset of superconductivity in La 1.85Sr 0.15CuO 4 films is associated with the finite thickness effect and epitaxial strain. In particular, thin films with tensile strain greater than ~0.25% revealed no superconductivity. We attribute this phenomenon to the inherent formation of oxygen vacancies that can be minimized via strain relaxation.

Microstructural Characterization of Alloy 617 Crept into the Tertiary Regime

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

Lillo, Thomas Martin; Wright, Richard Neil

2015-07-01

The microstructure of Alloy 617 was characterized following creep tests interrupted at total creep strains ranging from 2-20%. A range of creep temperatures (750-1000oC) and initial creep stresses (10-145 MPa) produced creep test durations ranging from 1 to 5800 hours. Image analysis of optical photomicrographs on longitudinal sections of the gage length was used to document the fraction of creep porosity as a function of creep parameters. Creep porosity was negligible below tertiary creep strains of 10% and increased with tertiary creep strain, thereafter. For a given temperature and total creep strain, creep porosity increased with decreasing creep stress. Creepmore » porosity increased linearly with duration of the creep experiment. TEM performed on the gage sections did not reveal significant creep cavity formation on grain boundaries at the sub-micron level. It was concluded that the onset of tertiary creep did not result from creep cavitation and more likely arose due to the formation of low energy dislocation substructures with increasing tertiary strain.« less

All five host-range variants of Xanthomonas citri carry one pthA homolog with 17.5 repeats that determines pathogenicity on citrus, but none determine host-range variation.

PubMed

Al-Saadi, Abdulwahid; Reddy, Joseph D; Duan, Yong P; Brunings, Asha M; Yuan, Qiaoping; Gabriel, Dean W

2007-08-01

Citrus canker disease is caused by five groups of Xanthomonas citri strains that are distinguished primarily by host range: three from Asia (A, A*, and A(w)) and two that form a phylogenetically distinct clade and originated in South America (B and C). Every X. citri strain carries multiple DNA fragments that hybridize with pthA, which is essential for the pathogenicity of wide-host-range X. citri group A strain 3213. DNA fragments that hybridized with pthA were cloned from a representative strain from all five groups. Each strain carried one and only one pthA homolog that functionally complemented a knockout mutation of pthA in 3213. Every complementing homolog was of identical size to pthA and carried 17.5 nearly identical, direct tandem repeats, including three new genes from narrow-host-range groups C (pthC), A(w) (pthAW), and A* (pthA*). Every noncomplementing paralog was of a different size; one of these was sequenced from group A* (pthA*-2) and was found to have an intact promoter and full-length reading frame but with 15.5 repeats. None of the complementing homologs nor any of the noncomplementing paralogs conferred avirulence to 3213 on grapefruit or suppressed avirulence of a group A* strain on grapefruit. A knockout mutation of pthC in a group C strain resulted in loss of pathogenicity on lime, but the strain was unaffected in ability to elicit an HR on grapefruit. This pthC- mutant was fully complemented by pthA, pthB, or pthC. Analysis of the predicted amino-acid sequences of all functional pthA homologs and nonfunctional paralogs indicated that the specific sequence of the 17th repeat may be essential for pathogenicity of X. citri on citrus.

Flexible Polydimethylsiloxane Foams Decorated with Multiwalled Carbon Nanotubes Enable Unprecedented Detection of Ultralow Strain and Pressure Coupled with a Large Working Range.

PubMed

Iglio, Rossella; Mariani, Stefano; Robbiano, Valentina; Strambini, Lucanos; Barillaro, Giuseppe

2018-04-25

Low-cost piezoresistive strain/pressure sensors with large working range, at the same time able to reliably detect ultralow strain (≤0.1%) and pressure (≤1 Pa), are one of the challenges that have still to be overcome for flexible piezoresistive materials toward personalized health-monitoring applications. In this work, we report on unprecedented, simultaneous detection of ultrasmall strain (0.1%, i.e., 10 μm displacement over 10 mm) and subtle pressure (20 Pa, i.e., a force of only 2 mN over an area of 1 cm 2 ) in compression mode, coupled with a large working range (i.e., up to 60% for strain-6 mm in displacement-and 50 kPa for pressure) using piezoresistive, flexible three-dimensional (3D) macroporous polydimethylsiloxane (pPDMS) foams decorated with pristine multiwalled carbon nanotubes (CNTs). pPDMS/CNT foams with pore size up to 500 μm (i.e., twice the size of those of commonly used foams, at least) and porosity of 77%, decorated with a nanostructured surface network of CNTs at densities ranging from 7.5 to 37 mg/cm 3 are prepared using a low-cost and scalable process, through replica molding of sacrificial sugar templates and subsequent drop-casting of CNT ink. A thorough characterization shows that piezoresistive properties of the foams can be finely tuned by controlling the CNT density and reach an optimum at a CNT density of 25 mg/cm 3 , for which a maximum change of the material resistivity (e.g., ρ 0 /ρ 50 = 4 at 50% strain) is achieved under compression. Further static and dynamic characterization of the pPDMS/CNT foams with 25 mg/cm 3 of CNTs highlights that detection limits for strain and pressure are 0.03% (3 μm displacement over 10 mm) and 6 Pa (0.6 mN over an area of 1 cm 2 ), respectively; moreover, good stability and limited hysteresis are apparent by cycling the foams with 255 compression-release cycles over the strain range of 0-60%, at different strain rates up to 10 mm/min. Our results on piezoresistive, flexible pPDMS/CNT foams pave the way toward breakthrough applications for personalized health care, though not limited to these, which have not been fully addressed to date with flexible strain/stress sensors.

Impact resistance of fiber composites

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Sinclair, J. H.

1982-01-01

Stress-strain curves are obtained for a variety of glass fiber and carbon fiber reinforced plastics in dynamic tension, over the stress-strain range of 0.00087-2070/sec. The test method is of the one-bar block-to-bar type, using a rotating disk or a pendulum as the loading apparatus and yielding accurate stress-strain curves up to the breaking strain. In the case of glass fiber reinforced plastic, the tensile strength, strain to peak impact stress, total strain and total absorbed energy all increase significantly as the strain rate increases. By contrast, carbon fiber reinforced plastics show lower rates of increase with strain rate. It is recommended that hybrid composites incorporating the high strength and rigidity of carbon fiber reinforced plastic with the high impact absorption of glass fiber reinforced plastics be developed for use in structures subjected to impact loading.

Stress Corrosion Cracking Behavior of Interstitial Free Steel Via Slow Strain Rate Technique

NASA Astrophysics Data System (ADS)

Murkute, Pratik; Ramkumar, J.; Mondal, K.

2016-07-01

An interstitial free steel is subjected to slow strain rate tests to investigate the stress corrosion cracking (SCC) behavior at strain rates ranging from 10-4 to 10-6s-1 in air and 3.5 wt.% NaCl solution. The ratios of time to failure, failure strain, and ultimate tensile stress at different strain rates in air to that in corrosive were considered as SCC susceptibility. Serrated stress-strain curve observed at lowest strain rate is explained by the Portevin-Le Chatelier effect. Maximum susceptibility to SCC at lowest strain rate is attributed to the soluble γ-FeOOH in the rust analyzed by Fourier Transformed Infrared spectroscopy. Mechanism for SCC relates to the anodic dissolution forming the groove, where hydrogen embrittlement can set in and finally fracture happens due to triaxiality.

Intraspecific variability of Steinernema feltiae strains from Cemoro Lawang, eastern Java, Indonesia.

PubMed

Addis, T; Mulawarman, M; Waeyenberge, L; Moens, M; Viaene, N; Ehlers, R U

2010-01-01

Four strains of Steinernema feltiae from Eastern Java, Indonesia were characterized based on morphometric, morphological and molecular data. In addition, their virulence against last instar Tenebrio molitor and heat tolerance was tested. Infective juvenile have a mean body length ranging from 749 to 792 microm. The maximum sequence difference among the four strains was 7 bp (8.8%) in the ITS and 2 bp (0.3%) in D2D3 regions of the rDNA. All the strains are not reproductively isolated and can reproduce with European strain S. feltiae Owiplant. The lowest LC50 was observed for strain SCM (373) and the highest for S. feltiae strain Owiplant (458) IJs/40 T. molitor. All four strains showed relatively better mean heat tolerance when compared with S. feltiae Owiplant, both in adapted and non-adapted heat tolerance experiments.

Analysis of indentation creep

Treesearch

Don S. Stone; Joseph E. Jakes; Jonathan Puthoff; Abdelmageed A. Elmustafa

2010-01-01

Finite element analysis is used to simulate cone indentation creep in materials across a wide range of hardness, strain rate sensitivity, and work-hardening exponent. Modeling reveals that the commonly held assumption of the hardness strain rate sensitivity (mΗ) equaling the flow stress strain rate sensitivity (mσ...

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.

Anisotropic chemical strain in cubic ceria due to oxygen-vacancy-induced elastic dipoles.

PubMed

Das, Tridip; Nicholas, Jason D; Sheldon, Brian W; Qi, Yue

2018-06-06

Accurate characterization of chemical strain is required to study a broad range of chemical-mechanical coupling phenomena. One of the most studied mechano-chemically active oxides, nonstoichiometric ceria (CeO2-δ), has only been described by a scalar chemical strain assuming isotropic deformation. However, combined density functional theory (DFT) calculations and elastic dipole tensor theory reveal that both the short-range bond distortions surrounding an oxygen-vacancy and the long-range chemical strain are anisotropic in cubic CeO2-δ. The origin of this anisotropy is the charge disproportionation between the four cerium atoms around each oxygen-vacancy (two become Ce3+ and two become Ce4+) when a neutral oxygen-vacancy is formed. Around the oxygen-vacancy, six of the Ce3+-O bonds elongate, one of the Ce3+-O bond shorten, and all seven of the Ce4+-O bonds shorten. Further, the average and maximum chemical strain values obtained through tensor analysis successfully bound the various experimental data. Lastly, the anisotropic, oxygen-vacancy-elastic-dipole induced chemical strain is polarizable, which provides a physical model for the giant electrostriction recently discovered in doped and non-doped CeO2-δ. Together, this work highlights the need to consider anisotropic tensors when calculating the chemical strain induced by dilute point defects in all materials, regardless of their symmetry.

Characterisation of a detergent-stable alkaline protease from a novel thermophilic strain Paenibacillus tezpurensis sp. nov. AS-S24-II.

PubMed

Rai, Sudhir K; Roy, Jetendra K; Mukherjee, Ashis K

2010-02-01

An alkaline-protease-producing bacterial strain (AS-S24-II) isolated from a soil sample in Assam is a Gram-stain-positive, catalase-positive, endospore-forming rod and grows at temperatures ranging from 30 degrees C to 60 degrees C and salinity ranging from 0% to 7% (w/v) NaCl. Phenotypic characterisation, chemotaxonomic properties, presence of Paenibacillus-specific signature sequences, and ribotyping data suggested that the strain AS-S24-II represents a novel species of the genus Paenibacillus, for which the name Paenibacillus tezpurensis sp. nov. (MTCC 8959) is proposed. Phylogenetic analysis revealed that P. lentimorbus strain DNG-14 and P. lentimorbus strain DNG-16 represent the closest phylogenetic neighbour of this novel strain. Alkaline protease production (598 x 10(3) U l(-1)) by P. tezpurensis sp. nov. in SmF was optimised by response surface method. A laundry-detergent-stable, Ca(2+)-independent, 43-kDa molecular weight alkaline serine protease from this strain was purified with a 1.7-fold increase in specific activity. The purified protease displayed optimum activity at pH 9.5 and 45-50 degrees C temperature range and exhibited a significant stability and compatibility with surfactants and most of the tested commercial laundry detergents at room temperature. Further, the protease improved the wash performance of detergents, thus demonstrating its feasibility for inclusion in laundry detergent formulations.

Prediction of Flow Stress in Cadmium Using Constitutive Equation and Artificial Neural Network Approach

NASA Astrophysics Data System (ADS)

Sarkar, A.; Chakravartty, J. K.

2013-10-01

A model is developed to predict the constitutive flow behavior of cadmium during compression test using artificial neural network (ANN). The inputs of the neural network are strain, strain rate, and temperature, whereas flow stress is the output. Experimental data obtained from compression tests in the temperature range -30 to 70 °C, strain range 0.1 to 0.6, and strain rate range 10-3 to 1 s-1 are employed to develop the model. A three-layer feed-forward ANN is trained with Levenberg-Marquardt training algorithm. It has been shown that the developed ANN model can efficiently and accurately predict the deformation behavior of cadmium. This trained network could predict the flow stress better than a constitutive equation of the type.

High temperature static strain measurement with an electrical resistance strain gage

NASA Technical Reports Server (NTRS)

Lei, Jih-Fen

1992-01-01

An electrical resistance strain gage that can supply accurate static strain measurement for NASP application is being developed both in thin film and fine wire forms. This gage is designed to compensate for temperature effects on substrate materials with a wide range of thermal expansion coefficients. Some experimental results of the wire gage tested on one of the NASP structure materials, i.e., titanium matrix composites, are presented.

High temperature monotonic and cyclic deformation in a directionally solidified nickel-base superalloy

NASA Technical Reports Server (NTRS)

Huron, Eric S.

1986-01-01

Directionally solidified (DS) MAR-M246+Hf was tested in tension and fatigue, at temperatures from 20 C to 1093 C. Tests were performed on (001) oriented specimens at strain rates of 50 % and 0.5 % per minute. In tension, the yield strength was constant up to 704 C, above which the strength dropped off rapidly. A strong dependence of strength on strain rate was seen at the higher temperatures. The deformation mode was observed to change from heterogeneous to homogeneous with increasing temperature. Low Cycle Fatigue tests were done using a fully reversed waveform and total strain control. For a given plastic strain range, lives increased with increasing temperature. For a given temperature strain rate had a strong effect on life. At 704 C, decreasing strain rates decreased life, while at the higher temperatures, decreasing strain rates increased life, for a given plastic strain range. These results could be explained through considerations of the deformation modes and stress levels. At the higher temperatures, marked coarsening caused beneficial stress reductions, but oxidation limited the life. The longitudinal grain boundaries were found to influence slip behavior. The degree of secondary slip adjacent to the boundaries was found to be related to the degree of misorientation between the grains.

Single nucleotide polymorphism analysis of the enterocin P structural gene of Enterococcus faecium strains isolated from nonfermented animal foods.

PubMed

Arlindo, Samuel; Calo, Pilar; Franco, Carlos; Prado, Marta; Cepeda, Alberto; Barros-Velázquez, Jorge

2006-12-01

The bacteriocins produced by two lactic acid bacteria isolated from nonfermented fresh meat and fish, respectively, and exhibiting a remarkable antilisterial activity, were characterized. Bacteriocinogenic strains were identified as Enterococcus faecium and the maximum bacteriocin production by both strains was detected in the stationary phase of growth. The activity against Listeria monocytogenes was maintained in pH range of 3-7 and was stable in both strains after heating at 100 or 121 degrees C. The genes coding for enterocin P were detected, isolated, and sequenced in both E. faecium strains. They exhibited DNA/DNA homology in the 87.1-97.2% range with respect to the other four enterocin P genes reported so far. Three single nucleotide polymorphism events, silent at the amino acid level, were detected at nucleotide positions 45 (G/A), 75 (A/G), and 90 (T/C) in E. faecium LHICA 28-4 and may explain the differences reported for those loci in other enterocin P-producing E. faecium strains. This work provides the first description of enterocin P-producing E. faecium strains in nonfermented foodstuffs and, in the case of E. faecium LHICA 51, the first report of an enterocin P-producing strain isolated from fish so far.

Persistently Auxetic Materials: Engineering the Poisson Ratio of 2D Self-Avoiding Membranes under Conditions of Non-Zero Anisotropic Strain.

PubMed

Ulissi, Zachary W; Govind Rajan, Ananth; Strano, Michael S

2016-08-23

Entropic surfaces represented by fluctuating two-dimensional (2D) membranes are predicted to have desirable mechanical properties when unstressed, including a negative Poisson's ratio ("auxetic" behavior). Herein, we present calculations of the strain-dependent Poisson ratio of self-avoiding 2D membranes demonstrating desirable auxetic properties over a range of mechanical strain. Finite-size membranes with unclamped boundary conditions have positive Poisson's ratio due to spontaneous non-zero mean curvature, which can be suppressed with an explicit bending rigidity in agreement with prior findings. Applying longitudinal strain along a singular axis to this system suppresses this mean curvature and the entropic out-of-plane fluctuations, resulting in a molecular-scale mechanism for realizing a negative Poisson's ratio above a critical strain, with values significantly more negative than the previously observed zero-strain limit for infinite sheets. We find that auxetic behavior persists over surprisingly high strains of more than 20% for the smallest surfaces, with desirable finite-size scaling producing surfaces with negative Poisson's ratio over a wide range of strains. These results promise the design of surfaces and composite materials with tunable Poisson's ratio by prestressing platelet inclusions or controlling the surface rigidity of a matrix of 2D materials.

In vitro sensitivity of Hungarian Actinobaculum suis strains to selected antimicrobials.

PubMed

Biksi, I; Major, Andrea; Fodor, L; Szenci, O; Vetési, F

2003-01-01

In vitro antimicrobial sensitivity of 12 Hungarian isolates and the type strain ATCC 33144 of Actinobaculum suis to different antimicrobial compounds was determined both by the agar dilution and by the disc diffusion method. By agar dilution, MIC50 values in the range of 0.05-3.125 micrograms/ml were determined for penicillin, ampicillin, ceftiofur, doxycycline, tylosin, pleuromutilins, chloramphenicol, florfenicol, enrofloxacin and lincomycin. The MIC50 value of oxytetracycline and spectinomycin was 6.25 and 12.5 micrograms/ml, respectively. For ofloxacin, flumequine, neomycin, streptomycin, gentamicin, nalidixic acid, nitrofurantoin and sulphamethoxazole + trimethoprim MIC50 values were in the range of 25-100 micrograms/ml. With the disc diffusion method, all strains were sensitive to penicillin, cephalosporins examined, chloramphenicol and florfenicol, tetracyclines examined, pleuromutilins, lincomycin and tylosin. Variable sensitivity was observed for fluoroquinolones (flumequine, enrofloxacin, ofloxacin), most of the strains were susceptible to marbofloxacin. Almost all strains were resistant to aminoglycosides but most of them were sensitive to spectinomycin. A strong correlation was determined for disc diffusion and MIC results (Spearman's rho 0.789, p < 0001). MIC values of the type strain and MIC50 values of other tested strains did not differ significantly. Few strains showed a partially distinct resistance pattern for erythromycin, lincomycin and ampicillin in both methods.

[Vitamin B12-independent strains of Methylophaga marina isolated from Red Sea algae].

PubMed

Li, Ts D; Doronina, N V; Ivanova, E G; Trotsenko, Iu A

2007-01-01

Two strains (KM3 and KM5) of halophilic methylobacteria isolated from Red Sea algae do not require vitamin B12 for growth and can use methanol, methylamine, dimethylamine, trimethylamine, dimethyl sulfide, and fructose as sources of carbon and energy. The cells of these strains are gram-negative motile monotrichous (strain KM3) or peritrichous (strain KM5) rods. The strains are strictly aerobic and require Na+ ions but not growth factors for growth. They are oxidase- and catalase-positive and reduce nitrates to nitrites. Both strains can grow in a temperature range of 4 to 37 degrees C (with optimal growth at 29-34 degrees C), at pH between 5.5 and 8.5 (with optimal growth at pH 7.5-8.0), and in a range of salt concentrations between 0.5 and 15% NaCl (with optimal growth at 5-9% NaCl). The phospholipids of these strains are dominated by phosphatidylethanolamine and phosphatidylglycerol and also include phosphatidylcholine, phosphatidylserine, and cardiolipin. The dominant fatty acids are C(16:1omega7c) and C(16:0). The major ubiquinone is Q8. The cells accumulate ectoin, glutamate, and sucrose as intracellular osmoprotectants. The strains implement the 2-keto-3-deoxy-6-phosphogluconate-dependent variant of the ribulose monophosphate pathway. The G+C content of the DNA is 44.4-44.7 mol %. Analysis of the 16S rRNA genes showed that both strains belong to Gammaproteobacteria and have a high degree of homology (99.4%) to Methylophaga marina ATCC 35842T . Based on the data of polyphasic taxonomy, strains KM3 and KM5 are identified as new strains M. marina KM3 (VKM B-2386) and M. marina KM5 (VKM B-2387). The ability of these strains to produce auxins (indole-3-acetic acid) suggests their metabolic association with marine algae.

Heavy Oils Produced by Aureobasidium pullulans

USDA-ARS?s Scientific Manuscript database

From a survey of more than 50 diverse strains of Aureobasidium pullulans, 21 strains were observed to produce extracellular heavy oils. These strains represented at least 6 phylogenetic clades, although more than half fell into clades 9 and 11. Oil colors ranged from bright yellow to malachite. M...

The change of macrolide resistance rates in group A Streptococcus isolates from children between 2002 and 2013 in Asahikawa city.

PubMed

Sakata, Hiroshi

2015-05-01

This study targeted patients in the Department of Pediatrics, Asahikawa Kosei Hospital, between January 2002 and December 2013. In patients suspected of having hemolytic streptococcal infection, Group A Streptococcus (GAS) strains isolated from a throat swab were examined for antimicrobial susceptibility testing. The MICs were measured by the broth microdilution method. The annual number of GAS strains examined for antimicrobial susceptibility testing ranged from 28 to 65 strains, for a total of 574 strains. Some of the isolates obtained from 2006 to 2009 and from 2011 to 2013 were analyzed to determine their emm types. An erythromycin (EM) resistant strain was not detected until 2004, but one EM-resistant strain appeared in 2005. Subsequently, EM-resistant strains rapidly increased, and 48 of 65 strains (73.8%) examined in 2009 were resistant. In 2010, the number of EM-resistant strains decreased to 12 of 36 strains (33.3%). However, it gradually increased afterwards, and 37 of 60 strains (61.7%) were resistant in 2013. Out of 574 strains examined, 184 exhibited EM-resistance, and the overall resistance rate was 31.9%. Partitioning the 124 strains examined between 2006 and 2008 according to emm types, only emm28 strains, which exhibited a high resistance rate, and emm12 strains demonstrated resistance. For the 142 strains examined between 2011 and 2013, the resistance rate of emm28 strains was similarly high; the resistance of emm12 strains significantly increased, and emm1 strains exhibited a high resistance rate. The number of emm types associated with the resistant strains increased. Copyright © 2015 Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

Dethiosulfovibrio salsuginis sp. nov., an anaerobic, slightly halophilic bacterium isolated from a saline spring.

PubMed

Díaz-Cárdenas, C; López, G; Patel, B K C; Baena, S

2010-04-01

A mesophilic, strictly anaerobic, slightly halophilic bacterium, designated strain USBA 82(T), was isolated from a terrestrial saline spring in the Colombian Andes. The non-spore-forming curved rods (5-7 x 1.3 microm) with pointed or rounded ends, stained Gram-negative and were motile by means of laterally inserted flagella. The strain grew optimally at 30 degrees C (growth range 20-40 degrees C), pH 7.3 (growth range pH 5.5-8.5) and 2 % (w/v) NaCl (growth range 0.1-7 % NaCl). The strain fermented peptides, amino acids and a few organic acids, but growth was not observed on carbohydrates, alcohols or fatty acids. The strain reduced thiosulfate and sulfur to sulfide. Sulfate, sulfite, nitrate and nitrite were not used as electron acceptors. On peptone alone, acetate, succinate, propionate and traces of ethanol were formed, but in the presence of thiosulfate, acetate and succinate were formed. The G+C content of the chromosomal DNA was 52 mol% (T(m)). 16S rRNA gene sequence analysis indicated that strain USBA 82(T) was affiliated to Dethiosulfovibrio peptidovorans within the phylum Synergistetes with a similarity value of approximately 93 %. Based on the differences between the new strain and the type species of the genus Dethiosulfovibrio, we suggest that strain USBA 82(T) represents a novel species of the genus for which the name Dethiosulfovibrio salsuginis sp. nov. is proposed. The type strain is USBA 82(T) (=DSM 21565(T)=KCTC 5659(T)).

Quantitative assessment of viable cells of Lactobacillus plantarum strains in single, dual and multi-strain biofilms.

PubMed

Fernández Ramírez, Mónica D; Kostopoulos, Ioannis; Smid, Eddy J; Nierop Groot, Masja N; Abee, Tjakko

2017-03-06

Biofilms of Lactobacillus plantarum are a potential source for contamination and recontamination of food products. Although biofilms have been mostly studied using single species or even single strains, it is conceivable that in a range of environmental settings including food processing areas, biofilms are composed of multiple species with each species represented by multiple strains. In this study six spoilage related L. plantarum strains FBR1-FBR6 and the model strain L. plantarum WCFS1 were characterised in single, dual and multiple strain competition models. A quantitative PCR approach was used with added propidium monoazide (PMA) enabling quantification of intact cells in the biofilm, representing the viable cell fraction that determines the food spoilage risk. Our results show that the performance of individual strains in multi-strain cultures generally correlates with their performance in pure culture, and relative strain abundance in multi-strain biofilms positively correlated with the relative strain abundance in suspended (planktonic) cultures. Performance of individual strains in dual-strain biofilms was highly influenced by the presence of the secondary strain, and in most cases no correlation between the relative contributions of viable planktonic cells and viable cells in the biofilm was noted. The total biofilm quantified by CV staining of the dual and multi-strain biofilms formed was mainly correlated to CV values of the dominant strain obtained in single strain studies. However, the combination of strain FBR5 and strain WCFS1 showed significantly higher CV values compared to the individual performances of both strains indicating that total biofilm formation was higher in this specific condition. Notably, L. plantarum FBR5 was able to outgrow all other strains and showed the highest relative abundance in dual and multi-strain biofilms. All the dual and multi-strain biofilms contained a considerable number of viable cells, representing a potential source of contamination. Copyright © 2016 Elsevier B.V. All rights reserved.

Isolation of sulfate-reducing bacteria from the terrestrial deep subsurface and description of Desulfovibrio cavernae sp. nov.

PubMed

Sass, Henrik; Cypionka, Heribert

2004-09-01

Deep subsurface sandstones in the area of Berlin (Germany) located 600 to 1060 m below the surface were examined for the presence of viable microorganisms. The in situ temperatures at the sampling sites ranged from 37 to 45 degrees C. Investigations focussed on sulfate-reducing bacteria able to grow on methanol and triethylene glycol, which are added as chemicals to facilitate the long-term underground storage of natural gas. Seven strains were isolated from porewater brines in the porous sandstone. Three of them were obtained with methanol (strains H1M, H3M, and B1M), three strains with triethylene glycol (strains H1T, B1T, and B2T) and one strain with a mixture of lactate, acetate and butyrate (strain H1-13). Due to phenotypic properties six isolates could be identified as members of the genus Desulfovibrio, and strain B2T as a Desulfotomaculum. The salt tolerance and temperature range for growth indicated that the isolates originated from the indigenous deep subsurface sandstones. They grew in mineral media reflecting the in situ ionic composition of the different brines, which contained 1.5 to 190 g NaCl x l(-1) and high calcium and magnesium concentrations. The Desulfovibrio strains grew at temperatures between 20 and 50 degrees C, while the Desulfotomaculum strain was thermophilic and grew between 30 and 65 degrees C. The strains utilized a broad spectrum of electron donors and acceptors. They grew with carbon compounds like lactate, pyruvate, formate, n-alcohols (C1-C5), glycerol, ethylene glycol, malate, succinate, and fumarate. Some strains even utilized glucose as electron donor and carbon source. All strains were able to use sulfate, sulfite and nitrate as electron acceptors. Additionally, three Desulfovibrio strains reduced manganese oxide, the Desulfotomaculum strain reduced manganese oxide, iron oxide, and elemental sulfur. The 16S rRNA analysis revealed that the isolates belong to three different species. The strains H1T, H3M and B1M could be identified as Desulfovibrio indonesiensis, and strain B2T as Desulfotomaculum geothermicum. The other Desulfovibrio strains (H1M, H1-13, and B1T) showed identical 16S rDNA sequences and similarities as low as 93% to their closest relative, Desulfovibrio aminophilusT. Therefore, these isolates were assigned to a new species, Desulfovibrio cavernae sp. nov., with strain H1M as the type strain.

Thermal Mechanical Fatigue Cracks Growth from Laser Drilled Holes in Single Crystal Material (Preprint)

DTIC Science & Technology

2012-03-01

temperature ranges, as well as with and without hot dwell periods. Table 4. Specimens chosen for SEM fractography . Samples ID Temperature variation...intersecting with crystallographic facet. Comparison with the fractography of the specimen (19776A) tested to %25.0 mechanical strain at the 800 F Figure... fractography of the specimen (19777B) tested to %4.0 mechanical strain (see Table 2). Large mechanical strain range generates large stresses around the hole

Detection and genetic characterization of porcine group A rotaviruses in asymptomatic pigs in smallholder farms in East Africa: predominance of P[8] genotype resembling human strains.

PubMed

Amimo, J O; Junga, J O; Ogara, W O; Vlasova, A N; Njahira, M N; Maina, S; Okoth, E A; Bishop, R P; Saif, L J; Djikeng, A

2015-02-25

Viral enteritis is a serious problem accounting for deaths in neonatal animals and humans worldwide. The absence of surveillance programs and diagnostic laboratory facilities have resulted in a lack of data on rotavirus associated diarrheas in pigs in East Africa. Here we describe the incidence of group A rotavirus (RVA) infections in asymptomatic young pigs in East Africa. Of the 446 samples examined, 26.2% (117/446) were positive for RVA. More nursing piglets (78.7%) shed RVA than weaned (32.9%) and grower (5.8%) pigs. RVA incidence was higher in pigs that were either housed_free-range (77.8%) or tethered_free-range (29.0%) than those that were free-range or housed or housed-tethered pigs. The farms with larger herd size (>10 pigs) had higher RVA prevalence (56.5%) than farms with smaller herd size (24.1-29.7%). This study revealed that age, management system and pig density significantly (p<0.01) influenced the incidence of RVA infections, with housed_free-range management system and larger herd size showing higher risks for RVA infection. Partial (811-1604nt region) sequence of the VP4 gene of selected positive samples revealed that different genotypes (P[6], P[8] and P[13]) are circulating in the study area with P[8] being predominant. The P[6] strain shared nucleotide (nt) and amino acid (aa) sequence identity of 84.4-91.3% and 95.1-96.9%, respectively, with known porcine and human P[6] strains. The P[8] strains shared high nt and aa sequence identity with known human P[8] strains ranging from 95.6-100% to 92-100%, respectively. The P[13] strains shared nt and aa sequence identity of 83.6-91.7% and 89.3-96.4%, respectively, only with known porcine P[13] strains. No P[8] strains yielded RNA of sufficient quality/quantity for full genome sequencing. However analysis of the full genome constellation of the P[6], two P[13] and one untypeable strains revealed that the P[6] strain (Ke-003-5) genome constellation was G26-P[6]-I5-R1-C1-M1-A8-N1-T1-E1-H1, P[13] strains (Ug-049 and Ug-453) had G5-P[13]-I5-R1-C1-M1-A8-N1-T7-E1-H1 while the untypeable strain (Ug-218) had G5-P[?]-I5-R1-C1-M1-A8-N1-T1-E1-H? In conclusion, P[6] and P[8] genotypes detected were genetically closely related to human strains suggesting the possibility of interspecies transmission. Further studies are required to determine the role of RVA in swine enteric disease burden and to determine the genetic/antigenic heterogeneity of the circulating strains for development of accurate diagnostic tools and to implement appropriate prophylaxis programs. Copyright © 2014 Elsevier B.V. All rights reserved.

Connecting thermal physiology and latitudinal niche partitioning in marine Synechococcus

PubMed Central

Pittera, Justine; Humily, Florian; Thorel, Maxine; Grulois, Daphné; Garczarek, Laurence; Six, Christophe

2014-01-01

Marine Synechococcus cyanobacteria constitute a monophyletic group that displays a wide latitudinal distribution, ranging from the equator to the polar fronts. Whether these organisms are all physiologically adapted to stand a large temperature gradient or stenotherms with narrow growth temperature ranges has so far remained unexplored. We submitted a panel of six strains, isolated along a gradient of latitude in the North Atlantic Ocean, to long- and short-term variations of temperature. Upon a downward shift of temperature, the strains showed strikingly distinct resistance, seemingly related to their latitude of isolation, with tropical strains collapsing while northern strains were capable of growing. This behaviour was associated to differential photosynthetic performances. In the tropical strains, the rapid photosystem II inactivation and the decrease of the antioxydant β-carotene relative to chl a suggested a strong induction of oxidative stress. These different responses were related to the thermal preferenda of the strains. The northern strains could grow at 10 °C while the other strains preferred higher temperatures. In addition, we pointed out a correspondence between strain isolation temperature and phylogeny. In particular, clades I and IV laboratory strains were all collected in the coldest waters of the distribution area of marine Synechococus. We, however, show that clade I Synechococcus exhibit different levels of adaptation, which apparently reflect their location on the latitudinal temperature gradient. This study reveals the existence of lineages of marine Synechococcus physiologically specialised in different thermal niches, therefore suggesting the existence of temperature ecotypes within the marine Synechococcus radiation. PMID:24401861

Strain measurement on stiff structures: experimental evaluation of three integrated measurement principles

NASA Astrophysics Data System (ADS)

Rausch, J.; Hatzfeld, C.; Karsten, R.; Kraus, R.; Millitzer, J.; Werthschützky, R.

2012-06-01

This paper presents an experimental evaluation of three different strain measuring principles. Mounted on a steel beam resembling a car engine mount, metal foil strain gauges, piezoresistive silicon strain gauges and piezoelectric patches are investigated to measure structure-borne forces to control an active mounting structure. FEA simulation determines strains to be measured in the range of 10-8 up to 10-5 m × m-1. These low strains cannot be measured with conventional metal foil strain gauges, as shown in the experiment conducted. Both piezoresistive and piezoelectric gauges show good results compared to a conventional piezoelectric force sensor. Depending on bandwidth, overload capacity and primary electronic costs, these principles seem to be worth considering in an adaptronic system design. These parameters are described in detail for the principles investigated.

Role of scaffold network in controlling strain and functionalities of nanocomposite films

DOE PAGES

Chen, Aiping; Hu, Jia -Mian; Lu, Ping; ...

2016-06-10

One novel approach to manipulating functionalities in correlated complex oxides is strain. However, significant epitaxial strain can only be achieved in ultrathin layers. We show that, under direct lattice matching framework, large and uniform vertical strain up to 2% can be achieved to significantly modify the magnetic anisotropy, magnetism, and magnetotransport properties in heteroepitaxial nanoscaffold films, over a few hundred nanometers in thickness. Comprehensive designing principles of large vertical strain have been proposed. Phase-field simulations not only reveal the strain distribution but also suggest that the ultimate strain is related to the vertical interfacial area and interfacial dislocation density. Moreover,more » by changing the nanoscaffold density and dimension, the strain and the magnetic properties can be tuned. The established correlation among the vertical interface—strain—properties in nanoscaffold films can consequently be used to tune other functionalities in a broad range of complex oxide films far beyond critical thickness.« less

Mechanical Properties of Transgenic Silkworm Silk Under High Strain Rate Tensile Loading

NASA Astrophysics Data System (ADS)

Chu, J.-M.; Claus, B.; Chen, W.

2017-12-01

Studies have shown that transgenic silkworm silk may be capable of having similar properties of spider silk while being mass-producible. In this research, the tensile stress-strain response of transgenic silkworm silk fiber is systematically characterized using a quasi-static load frame and a tension Kolsky bar over a range of strain-rates between 10^{-3} and 700/s. The results show that transgenic silkworm silk tends to have higher overall ultimate stress and failure strain at high strain rate (700/s) compared to quasi-static strain rates, indicating rate sensitivity of the material. The failure strain at the high strain rate is higher than that of spider silk. However, the stress levels are significantly below that of spider silk, and far below that of high-performance fiber. Failure surfaces are examined via scanning electron microscopy and reveal that the failure modes are similar to those of spider silk.

Role of scaffold network in controlling strain and functionalities of nanocomposite films

PubMed Central

Chen, Aiping; Hu, Jia-Mian; Lu, Ping; Yang, Tiannan; Zhang, Wenrui; Li, Leigang; Ahmed, Towfiq; Enriquez, Erik; Weigand, Marcus; Su, Qing; Wang, Haiyan; Zhu, Jian-Xin; MacManus-Driscoll, Judith L.; Chen, Long-Qing; Yarotski, Dmitry; Jia, Quanxi

2016-01-01

Strain is a novel approach to manipulating functionalities in correlated complex oxides. However, significant epitaxial strain can only be achieved in ultrathin layers. We show that, under direct lattice matching framework, large and uniform vertical strain up to 2% can be achieved to significantly modify the magnetic anisotropy, magnetism, and magnetotransport properties in heteroepitaxial nanoscaffold films, over a few hundred nanometers in thickness. Comprehensive designing principles of large vertical strain have been proposed. Phase-field simulations not only reveal the strain distribution but also suggest that the ultimate strain is related to the vertical interfacial area and interfacial dislocation density. By changing the nanoscaffold density and dimension, the strain and the magnetic properties can be tuned. The established correlation among the vertical interface—strain—properties in nanoscaffold films can consequently be used to tune other functionalities in a broad range of complex oxide films far beyond critical thickness. PMID:27386578

Mechanical Behavior of a Low-Cost Ti-6Al-4V Alloy

NASA Astrophysics Data System (ADS)

Casem, D. T.; Weerasooriya, T.; Walter, T. R.

2018-01-01

Mechanical compression tests were performed on an economical Ti-6Al-4V alloy over a range of strain-rates and temperatures. Low rate experiments (0.001-0.1/s) were performed with a servo-hydraulic load frame and high rate experiments (1000-80,000/s) were performed with the Kolsky bar (Split Hopkinson pressure bar). Emphasis is placed on the large strain, high-rate, and high temperature behavior of the material in an effort to develop a predictive capability for adiabatic shear bands. Quasi-isothermal experiments were performed with the Kolsky bar to determine the large strain response at elevated rates, and bars with small diameters (1.59 mm and 794 µm, instrumented optically) were used to study the response at the higher strain-rates. Experiments were also conducted at temperatures ranging from 81 to 673 K. Two constitutive models are used to represent the data. The first is the Zerilli-Armstrong recovery strain model and the second is a modified Johnson-Cook model which uses the recovery strain term from the Zerilli-Armstrong model. In both cases, the recovery strain feature is critical for capturing the instability that precedes localization.

Effect of strain rate and dislocation density on the twinning behavior in tantalum

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

Florando, Jeffrey N., E-mail: florando1@llnl.gov; Swift, Damian C.; Barton, Nathan R.

2016-04-15

The conditions which affect twinning in tantalum have been investigated across a range of strain rates and initial dislocation densities. Tantalum samples were subjected to a range of strain rates, from 10{sup −4}/s to 10{sup 3}/s under uniaxial stress conditions, and under laser-induced shock-loading conditions. In this study, twinning was observed at 77 K at strain rates from 1/s to 10{sup 3}/s, and during laser-induced shock experiments. The effect of the initial dislocation density, which was imparted by deforming the material to different amounts of pre-strain, was also studied, and it was shown that twinning is suppressed after a givenmore » amount of pre-strain, even as the global stress continues to increase. These results indicate that the conditions for twinning cannot be represented solely by a critical global stress value, but are also dependent on the evolution of the dislocation density. In addition, the analysis shows that if twinning is initiated, the nucleated twins may continue to grow as a function of strain, even as the dislocation density continues to increase.« less

Constitutive Equation and Hot Compression Deformation Behavior of Homogenized Al–7.5Zn–1.5Mg–0.2Cu–0.2Zr Alloy

PubMed Central

He, Jianliang; Zhang, Datong; Zhang, Weiweng; Qiu, Cheng; Zhang, Wen

2017-01-01

The deformation behavior of homogenized Al–7.5Zn–1.5Mg–0.2Cu–0.2Zr alloy has been studied by a set of isothermal hot compression tests, which were carried out over the temperature ranging from 350 °C to 450 °C and the strain rate ranging from 0.001 s−1 to 10 s−1 on Gleeble-3500 thermal simulation machine. The associated microstructure was studied using electron back scattered diffraction (EBSD) and transmission electron microscopy (TEM). The results showed that the flow stress is sensitive to strain rate and deformation temperature. The shape of true stress-strain curves obtained at a low strain rate (≤0.1 s−1) conditions shows the characteristic of dynamic recrystallization (DRX). Two Arrhenius-typed constitutive equation without and with strain compensation were established based on the true stress-strain curves. Constitutive equation with strain compensation has more precise predictability. The main softening mechanism of the studied alloy is dynamic recovery (DRV) accompanied with DRX, particularly at deformation conditions, with low Zener-Holloman parameters. PMID:29057825

Finite Strain Behavior of Polyurea for a Wide Range of Strain Rates

DTIC Science & Technology

2010-02-01

dimensional dynamic compressive behavior of EPDM rubber ," Journal of Engineering Materials and Technology, Transaction of the ASME, 125:294-301. [97] Song, B...and Chen, W. (2004) "Dynamic compressive behavior of EPDM rubber un- der nearly uniaxial strain conditions," Journal of Engineering Materials and... rubber elastic springs to describe the steep initial stiffness of virgin butadiene rubber under tensile and compressive loading at intermediate strain

Direct observation of local magnetic properties in strain engineered lanthanum cobaltate thin films

NASA Astrophysics Data System (ADS)

Park, S.; Wu, Weida; Freeland, J. W.; Ma, J. X.; Shi, J.

2009-03-01

Strain engineered thin film devices with emergent properties have significant impacts on both technical application and material science. We studied strain-induced modification of magnetic properties (Co spin state) in epitaxially grown lanthanum cobaltate (LaCoO3) thin films with a variable temperature magnetic force microscopy (VT-MFM). The real space observation confirms long range magnetic ordering on a tensile-strained film and non-magnetic low-spin configuration on a low-strained film at low temperature. Detailed study of local magnetic properties of these films under various external magnetic fields will be discussed. Our results also demonstrate that VT-MFM is a very sensitive tool to detect the nanoscale strain induced magnetic defects.

Micromachined silicon cantilevers with integrated high-frequency magnetoimpedance sensors for simultaneous strain and magnetic field detection

NASA Astrophysics Data System (ADS)

Buettel, G.; Joppich, J.; Hartmann, U.

2017-12-01

Giant magnetoimpedance (GMI) measurements in the high-frequency regime utilizing a coplanar waveguide with an integrated Permalloy multilayer and micromachined on a silicon cantilever are reported. The fabrication process is described in detail. The aspect ratio of the magnetic multilayer in the magnetoresistive and magnetostrictive device was varied. Tensile strain and compressive strain were applied. Vector network analyzer measurements in the range from the skin effect to ferromagnetic resonance confirm the technological potential of GMI-based micro-electro-mechanical devices for strain and magnetic field sensing applications. The strain-impedance gauge factor was quantified by finite element strain calculations and reaches a maximum value of almost 200.

Engineering industrial Saccharomyces cerevisiae strains for xylose fermentation and comparison for switchgrass conversion.

PubMed

Hector, Ronald E; Dien, Bruce S; Cotta, Michael A; Qureshi, Nasib

2011-09-01

Saccharomyces' physiology and fermentation-related properties vary broadly among industrial strains used to ferment glucose. How genetic background affects xylose metabolism in recombinant Saccharomyces strains has not been adequately explored. In this study, six industrial strains of varied genetic background were engineered to ferment xylose by stable integration of the xylose reductase, xylitol dehydrogenase, and xylulokinase genes. Aerobic growth rates on xylose were 0.04-0.17 h(-1). Fermentation of xylose and glucose/xylose mixtures also showed a wide range of performance between strains. During xylose fermentation, xylose consumption rates were 0.17-0.31 g/l/h, with ethanol yields 0.18-0.27 g/g. Yields of ethanol and the metabolite xylitol were positively correlated, indicating that all of the strains had downstream limitations to xylose metabolism. The better-performing engineered and parental strains were compared for conversion of alkaline pretreated switchgrass to ethanol. The engineered strains produced 13-17% more ethanol than the parental control strains because of their ability to ferment xylose.

Lactobacillus brevis strains from fermented aloe vera survive gastroduodenal environment and suppress common food borne enteropathogens.

PubMed

Kim, Young-Wook; Jeong, Young-Ju; Kim, Ah-Young; Son, Hyun-Hee; Lee, Jong-Am; Jung, Cheong-Hwan; Kim, Chae-Hyun; Kim, Jaeman

2014-01-01

Five novel Lactobacillus brevis strains were isolated from naturally fermented Aloe vera leaf flesh. Each strain was identified by Random Amplified Polymorphic DNA (RAPD) analysis and 16S rRNA sequence comparison. These strains were highly tolerant to acid, surviving in pH2.5 for up to 4 hours, and resistant to 5% bile salts at 37°C for 18 hours. Due to its tolerance to acid and bile salts, one strain passed through the gastric barrier and colonised the intestine after oral administration. All five strains inhibited the growth of many harmful enteropathogens without restraining most of normal commensals in the gut and hence named POAL (Probiotics Originating from Aloe Leaf) strains. Additionally, each strain exhibited discriminative resistance to a wide range of antibiotics. The L. brevis POAL strains, moreover, expressed high levels of the glutamate decarboxylase (GAD) gene which produces a beneficial neurotransmitter, γ-aminobutyric acid (GABA). These characteristics in all suggest that the novel L. brevis strains should be considered as potential food additives and resources for pharmaceutical research.

Measurement of high temperature strain by the laser-speckle strain gauge

NASA Technical Reports Server (NTRS)

Yamaguchi, I.

1984-01-01

By using the laser-speckle strain gauge, the strain of metal at the temperature lower than 250 C is measured. The principle of the gauge is to measure the expansion or contraction of the fine structures of surface by detecting the resultant speckle displacement in an optoelectronic way, whereby the effect of rigid-body motion is automatically cancelled out with the aid of a differential detection system. A transportable apparatus was built and a comparison experiment performed with a resistance strain gauge at room temperature. It has a strain sensitivity of .00002, a gauge length smaller than 1 mm, and no upper limit in a range of strain measurement. In the measurement of high-temperature strain it is free from the need for a dummy gauge and insensitive to an electric drift effect. As examples of strain measurement at high-temperature, thermal expansion and contraction of a top of a soldering iron are measured. The interval of the measurement can be made at shortest 1.6 sec. and the change in the strain is clearly followed until the ultimate stationary temperature is reached.

Lactobacillus brevis Strains from Fermented Aloe vera Survive Gastroduodenal Environment and Suppress Common Food Borne Enteropathogens

PubMed Central

Kim, Young-Wook; Jeong, Young-Ju; Kim, Ah-Young; Son, Hyun-Hee; Lee, Jong-Am; Jung, Cheong-Hwan; Kim, Chae-Hyun; Kim, Jaeman

2014-01-01

Five novel Lactobacillus brevis strains were isolated from naturally fermented Aloe vera leaf flesh. Each strain was identified by Random Amplified Polymorphic DNA (RAPD) analysis and 16S rRNA sequence comparison. These strains were highly tolerant to acid, surviving in pH2.5 for up to 4 hours, and resistant to 5% bile salts at 37°C for 18 hours. Due to its tolerance to acid and bile salts, one strain passed through the gastric barrier and colonised the intestine after oral administration. All five strains inhibited the growth of many harmful enteropathogens without restraining most of normal commensals in the gut and hence named POAL (Probiotics Originating from Aloe Leaf) strains. Additionally, each strain exhibited discriminative resistance to a wide range of antibiotics. The L. brevis POAL strains, moreover, expressed high levels of the glutamate decarboxylase (GAD) gene which produces a beneficial neurotransmitter, γ-aminobutyric acid (GABA). These characteristics in all suggest that the novel L. brevis strains should be considered as potential food additives and resources for pharmaceutical research. PMID:24598940

Antifungal activities of diphenyl diselenide and ebselen against echinocandin-susceptible and -resistant strains of Candida parapsilosis.

PubMed

Chassot, Francieli; Pozzebon Venturini, Tarcieli; Baldissera Piasentin, Fernanda; Morais Santurio, Janio; Estivalet Svidzinski, Terezinha Inez; Hartz Alves, Sydney

2016-10-01

We evaluated the in vitro antifungal activity of diphenyl diselenide and ebselen against echinocandin-susceptible and -resistant strains of Candida parapsilosis using the broth microdilution method. Diphenyl diselenide (MIC range =1-8 µg/mL) and ebselen (MIC range =0.25-4 µg/mL) showed in vitro activity against echinocandin-susceptible isolates. However, ebselen also showed the highest antifungal activity against echinocandin-resistant strains (MIC range =0.06-4 µg/mL). This study demonstrated that the antifungal potential of diphenyl diselenide and ebselen deserves further investigation using in vivo experimental protocols.

Influence of Strain Rate on Heat Release under Quasi-Static Stretching of Metals. Experiment

NASA Astrophysics Data System (ADS)

Zimin, B. A.; Sventitskaya, V. E.; Smirnov, I. V.; Sud'enkov, Yu. V.

2018-04-01

The paper presents the results of experimental studies of energy dissipation during a quasi-static stretching of metals and alloys at room temperature. The strain rates varied in the range of 10-3-10-2 s-1. Samples of M1 copper, AZ31B magnesium alloy, BT6 titanium, 12Cr18Ni10Ti steel, and D16AM aluminum alloy were analyzed. The experimental results demonstrated a significant dependence of the heat release on the strain rate in the absence of its influence on stress-strain diagrams for all the metals studied in this range of strain rates. The correlation of the changes in the character of heat release with the processes of structural transformations at various stages of plastic flow is shown on the qualitative level. A difference in the nature of the processes of heat release in materials with different ratios of the plasticity and strength is noted.

Strain dependence of perfluorinated polymer optical fiber Bragg grating measured at different wavelengths

NASA Astrophysics Data System (ADS)

Ishikawa, Ryo; Lee, Heeyoung; Lacraz, Amédée; Theodosiou, Antreas; Kalli, Kyriacos; Mizuno, Yosuke; Nakamura, Kentaro

2018-03-01

We measure the strain dependence of multiple Bragg wavelengths (corresponding to different diffraction orders) of a fiber Bragg grating (FBG) inscribed in a perfluorinated graded-index polymer optical fiber (PFGI-POF) in the wavelength range up to 1550 nm. On the basis of this result, we show that the fractional sensitivity, which has been conventionally used as a wavelength-independent index for fair comparison of the FBG performance measured at different wavelengths, is dependent on wavelength in this range. The reason for this behavior seems to originate from the non-negligible wavelength dependence of refractive index and its strain-dependence coefficient. Using the wavelength dependence of the refractive index already reported for bulk, we deduce the wavelength dependence of the strain coefficient of the refractive index. This information will be a useful archive in implementing PFGI-POF-based strain sensors based on not only FBGs but also Brillouin scattering in the future.

Four-point bending protocols to study the effects of dynamic strain in osteoblastic cells in vitro.

PubMed

Galea, Gabriel L; Price, Joanna S

2015-01-01

Strain engendered within bone tissue by mechanical loading of the skeleton is a major influence on the processes of bone modeling and remodeling and so a critical determinant of bone mass and architecture. The cells best placed to respond to strain in bone tissue are the resident osteocytes and osteoblasts. To address the mechanisms of strain-related responses in osteoblast-like cells, our group uses both in vivo and in vitro approaches, including a system of four-point bending of the substrate on which cells are cultured. A range of cell lines can be studied using this system but we routinely compare their responses to those in primary cultures of osteoblast-like cells derived from explants of mouse long bones. These cells show a range of well-characterized responses to physiological levels of strain, including increased proliferation, which in vivo is a feature of the osteogenic response.

Effect of strain rate on bake hardening response of BH220 steel

NASA Astrophysics Data System (ADS)

Das, Anindya; Tarafder, Soumitro; Sivaprasad, S.; Chakrabarti, Debalay

2015-09-01

This study aims at understanding the bake hardening ability of ultra low carbon BH220 steel at different strain rates. The as-received material has been pre-strained to four different levels and then deformed in tension under (a) as pre-strained state and (b) after baking at 170 ∘C for 20 minutes, at three different strain rates of 0.001, 0.1 and 100/s. In both the conditions, yield stress increased with pre-strain and strain rate, but bake hardening ability was found to decrease when strain rate was increased. The strain rate sensitivity of the material was also found to decrease with bake hardening. Generation of dislocation forests and their subsequent immobility during baking treatment enables them to act as long range obstacles during further deformation. At higher strain rates, less amount of dislocations are produced which can interact with themselves and produce hardening, because of which bake hardening ability and the strain rate drops. A dislocation based strengthening model, as proposed by Larour et al. 2011 [7], was used to predict the yield stress values obtained at different conditions. The equation produced excellent co-relation with the experimental data.

Structural and luminescent Properties of Bulk InAsSb

DTIC Science & Technology

2011-12-21

have used compositionally graded metamorphic buffer layers to accommodate the misfit strain between InAsxSb1-x alloys and GaSb and InSb substrates in...wavelength range. The authors have used compositionally graded metamorphic buffer layers to accommodate the misfit strain between InAsxSb1x alloys...long wave IR range. We used compositionally graded GaInSb, AlGaInSb, and InAsxSb1x metamorphic buffer layers to accommodate the misfit strain between

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

Occurrence and parameters of frequency of Legionella in warm water systems of hospitals and hotels in Lower Saxony.

PubMed

Habicht, W; Müller, H E

1988-03-01

A total of 1241 water samples was investigated from 103 hospitals and 62 hotels in Lower Saxony 1985-87. 331 of 949 samples from hospitals and 26 of 292 samples from hotels were Legionella positive. All together 70% of the hospitals and 18% of the hotels investigated were Legionella positive, and 836 strains of Legionella were isolated (Table 1). As they could be diagnosed they belong to L. pneumophila SG1 306 strains, SG2 36 strains, SG3 127 strains, SG4 45 strain, SG5 29 strain, SG6 106 strains, SG9 13 strains and SG10 13 strains. Further 134 strains belonging to L. pneumophila but not to SG1-SG12 show cross reactions with serogroups 5, 8, and 10. Finally, 16 strains belong to L. dumoffii and 1 strain to L. anisa (Table 2). The following parameters of water samples were studied, too: temperature, pH value, conductivity, concentration of iron, of organic matter, of other bacteria, occurrence of amoebas, and the materials of water plumbing systems. Most samples contained concentrations of Legionella in the range of 10(1)-10(3) CFU/ml, highest concentrations were 10(5) CFU/ml (Fig. 1). Most frequently, Legionella were isolated within the range of temperature of 35-45 degrees C. However, a few of the water samples were positive for Legionella even up to 66 degrees C (Fig. 3). The conductivity has no and the pH value (Fig. 2) has only little influence on the occurrence of Legionella. There is a positive correlation between concentration of iron and frequency of Legionella (Fig. 4). Also organic matter (Fig. 6) and amoebas (Table 3) seem to enhance the occurrence of Legionella. Plumbing systems consisting of copper showed an inhibitory effect on Legionella during the first five years, whereas no effect could be detected in older systems (Fig. 5).

Assessment of potential probiotic properties of Lactobacillus spp., Lactococcus spp., and Pediococcus spp. strains isolated from kefir.

PubMed

Sabir, Firat; Beyatli, Yavuz; Cokmus, Cumhur; Onal-Darilmaz, Derya

2010-01-01

In this study, the metabolic activities (in terms of quantities of the produced lactic acid, hydrogen peroxide, and exopolysaccharides) of 8 strains of Lactobacillus spp., Lactococcus spp., and Pediococcus spp., were determined. Lactic acid levels produced by strains were 8.1 to 17.4 mg/L. The L. acidophilus Z1L strain produced the maximum amount (3.18 μg/mL) of hydrogen peroxide. The exopolysaccharides (EPS) production by the strains was ranged between 173 and 378 mg/L. The susceptibility of 7 different antibiotics against these strains was also tested. All strains were found to be sensitive to ampicillin. The tolerance of the strains to low pH, their resistance to bile salts of strains, and their abilities to autoaggregate and coaggregate with Escherichia coli ATCC 11229 were also evaluated. High EPS-producing strains showed significant autoaggregation and coaggregation ability with test bacteria (P < 0.01). A correlation also was determined between EPS production and acid-bile tolerance (P < 0.05). EPS production possibly affects or is involved in acid-bile tolerance and aggregation of Lactobacillus spp., Lactococcus spp., and Pediococcus spp. strains and supports the potential of L. acidophilus Z1L strain as new probiotic. © 2010 Institute of Food Technologists®

Comparative Genomics of 12 Strains of Erwinia amylovora Identifies a Pan-Genome with a Large Conserved Core

PubMed Central

Mann, Rachel A.; Smits, Theo H. M.; Bühlmann, Andreas; Blom, Jochen; Goesmann, Alexander; Frey, Jürg E.; Plummer, Kim M.; Beer, Steven V.; Luck, Joanne; Duffy, Brion; Rodoni, Brendan

2013-01-01

The plant pathogen Erwinia amylovora can be divided into two host-specific groupings; strains infecting a broad range of hosts within the Rosaceae subfamily Spiraeoideae (e.g., Malus, Pyrus, Crataegus, Sorbus) and strains infecting Rubus (raspberries and blackberries). Comparative genomic analysis of 12 strains representing distinct populations (e.g., geographic, temporal, host origin) of E. amylovora was used to describe the pan-genome of this major pathogen. The pan-genome contains 5751 coding sequences and is highly conserved relative to other phytopathogenic bacteria comprising on average 89% conserved, core genes. The chromosomes of Spiraeoideae-infecting strains were highly homogeneous, while greater genetic diversity was observed between Spiraeoideae- and Rubus-infecting strains (and among individual Rubus-infecting strains), the majority of which was attributed to variable genomic islands. Based on genomic distance scores and phylogenetic analysis, the Rubus-infecting strain ATCC BAA-2158 was genetically more closely related to the Spiraeoideae-infecting strains of E. amylovora than it was to the other Rubus-infecting strains. Analysis of the accessory genomes of Spiraeoideae- and Rubus-infecting strains has identified putative host-specific determinants including variation in the effector protein HopX1Ea and a putative secondary metabolite pathway only present in Rubus-infecting strains. PMID:23409014

Comparative genomics of 12 strains of Erwinia amylovora identifies a pan-genome with a large conserved core.

PubMed

Mann, Rachel A; Smits, Theo H M; Bühlmann, Andreas; Blom, Jochen; Goesmann, Alexander; Frey, Jürg E; Plummer, Kim M; Beer, Steven V; Luck, Joanne; Duffy, Brion; Rodoni, Brendan

2013-01-01

The plant pathogen Erwinia amylovora can be divided into two host-specific groupings; strains infecting a broad range of hosts within the Rosaceae subfamily Spiraeoideae (e.g., Malus, Pyrus, Crataegus, Sorbus) and strains infecting Rubus (raspberries and blackberries). Comparative genomic analysis of 12 strains representing distinct populations (e.g., geographic, temporal, host origin) of E. amylovora was used to describe the pan-genome of this major pathogen. The pan-genome contains 5751 coding sequences and is highly conserved relative to other phytopathogenic bacteria comprising on average 89% conserved, core genes. The chromosomes of Spiraeoideae-infecting strains were highly homogeneous, while greater genetic diversity was observed between Spiraeoideae- and Rubus-infecting strains (and among individual Rubus-infecting strains), the majority of which was attributed to variable genomic islands. Based on genomic distance scores and phylogenetic analysis, the Rubus-infecting strain ATCC BAA-2158 was genetically more closely related to the Spiraeoideae-infecting strains of E. amylovora than it was to the other Rubus-infecting strains. Analysis of the accessory genomes of Spiraeoideae- and Rubus-infecting strains has identified putative host-specific determinants including variation in the effector protein HopX1(Ea) and a putative secondary metabolite pathway only present in Rubus-infecting strains.

Force-Measuring Clamp

NASA Technical Reports Server (NTRS)

Nunnelee, Mark (Inventor)

2004-01-01

A precision clamp that accurately measures force over a wide range of conditions is described. Using a full bridge or other strain gage configuration. the elastic deformation of the clamp is measured or detected by the strain gages. Thc strain gages transmit a signal that corresponds to the degree of stress upon the clamp. Thc strain gage signal is converted to a numeric display. Calibration is achieved by ero and span potentiometers which enable accurate measurements by the force-measuring clamp.

Mechanical and functional behavior of high-temperature Ni-Ti-Pt shape memory alloys

DOE PAGES

Buchheit, Thomas E.; Susan, Donald F.; Massad, Jordan E.; ...

2016-01-22

A series of Ti-rich Ni-Ti-Pt ternary alloys with 13 to 18 at. pct Pt were processed by vacuum arc melting and characterized for their transformation behavior to identify shape memory alloys (SMA) that undergo transformation between 448 K and 498 K (175 °C and 225 °C) and achieve recoverable strain exceeding 2 pct. From this broader set of compositions, three alloys containing 15.5 to 16.5 at. pct Pt exhibited transformation temperatures in the vicinity of 473 K (200 °C), thus were targeted for more detailed characterization. Preliminary microstructural evaluation of these three compositions revealed a martensitic microstructure with small amountsmore » of Ti 2(Ni,Pt) particles. Room temperature mechanical testing gave a response characteristic of martensitic de-twinning followed by a typical work-hardening behavior to failure. Elevated mechanical testing, performed while the materials were in the austenitic state, revealed yield stresses of approximately 500 MPa and 3.5 pct elongation to failure. Thermal strain recovery characteristics were more carefully investigated with unbiased incremental strain-temperature tests across the 1 to 5 pct strain range, as well as cyclic strain-temperature tests at 3 pct strain. As a result, the unbiased shape recovery results indicated a complicated strain recovery path, dependent on prestrain level, but overall acceptable SMA behavior within the targeted temperature and recoverable strain range.« less

Extending the spectral range of CdSe/ZnSe quantum wells by strain engineering

NASA Astrophysics Data System (ADS)

Finke, A.; Ruth, M.; Scholz, S.; Ludwig, A.; Wieck, A. D.; Reuter, D.; Pawlis, A.

2015-01-01

We demonstrate efficient room-temperature photoluminescence and spectral tuning of epitaxially grown ZnSe/CdSe quantum well structures almost over the whole visible spectrum (470-600 nm wavelength). The key element to achieve the observed high quantum efficiency and enormous tuning range was the implementation of a special strain engineering technique, which allows us to suppress substantial lattice relaxation of CdSe on ZnSe. Previous studies indicated that a CdSe coverage exceeding 3 ML on ZnSe results in the formation of extensive lattice defects and complete quenching of the photoluminescence at low and room temperature. In contrast, our approach of strain engineering enables the deposition of planar CdSe quantum wells with a thickness ranging from 1 to 6 ML with excellent optical properties. We attribute the observed experimental features to a controllable strain compensation effect that is present in an alternating system of tensile and compressively strained epitaxial layers and supported this model by calculations of the transition energies of the ZnSe/CdSe quantum wells.

Comparison of mechanical and microstructural properties of conventional and severe plastic deformation processes

NASA Astrophysics Data System (ADS)

Szombathelyi, V.; Krallics, Gy

2014-08-01

The effect of the deformation processes on yield stress, Vickers microhardness and dislocation density were investigated using commercial purity (A1050) and alloyed aluminum (Al 6082). For the evolution of the dislocation density X-ray line profile analysis was used. In the large plastic strain range the variation of mechanical and microstructure evolution of A1050 and of Al 6082 processed by equal channel angular pressing are investigated using route BC and route C. In the plastic strain range up to 3 plane strain compression test was used to evaluate mechanical properties. The hardness and the yield stress showed a sharp increase after the first pass. In the case of A1050 it was found that the two examined routes has not resulted difference in the flow stress. In the case of Al 6082 the effect of the routes on the yield stress is significant. The present results showed that in the comparable plastic strain range higher yield stress values can be achieved by plane strain compression test than by ECAP.

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.

Yessotoxins profile in strains of Protoceratium reticulatum from Spain and USA.

PubMed

Paz, Beatriz; Riobó, Pilar; Ramilo, Isabel; Franco, José M

2007-07-01

Seven strains of Protoceratium reticulatum isolated from Spain and the USA were cultured in the laboratory. Yessotoxins (YTXs) quantification and toxin profile determination were performed by LC-FLD and LC-MS/MS. The four Spanish strains were found to produce YTX and known YTX analogs, however, YTX was not detected in any of the three USA strains. Among the strains that produced YTXs, toxin production ranged between 2.9 and 28.6pg/cell. The YTX profile was substantially different between strains, in three out of the four Spanish strains YTX was the main toxin and in the fourth homoYTX was the prominent toxin. This work demonstrates that YTX is not always the main toxin in P. reticulatum and a high variability in YTX amounts and profile found in other locations is confirmed.

Isolation and characterization of Lactobacillus helveticus DSM 20075 variants with improved autolytic capacity.

PubMed

Spus, Maciej; Liu, Hua; Wels, Michiel; Abee, Tjakko; Smid, Eddy J

2017-01-16

Lactobacillus helveticus is widely used in dairy fermentations and produces a range of enzymes, which upon cell lysis can be released into the cheese matrix and impact degradation of proteins, peptides and lipids. In our study we set out to explore the potential of Lb. helveticus DSM 20075 for increased autolytic capacity triggered by conditions such as low pH and high salt concentrations encountered in cheese environments. Lb. helveticus DSM 20075 was subjected to varied incubation temperatures (ranging from 37 to 50°C). High-temperature incubation (in the range of 45 to 50°C) allowed us to obtain a collection of six variant strains (V45-V50), which in comparison to the wild-type strain, showed higher growth rates at elevated temperatures (42°C-45°C). Moreover, variant strain V50 showed a 4-fold higher, in comparison to wild type, autolytic capacity in cheese-like conditions. Next, strain V50 was used as an adjunct in lab-scale cheese making trials to measure its impact on aroma formation during ripening. Specifically, in cheeses made with strain V50, the relative abundance of benzaldehyde increased 3-fold compared to cheeses made with the wild-type strain. Analysis of the genome sequence of strain V50 revealed multiple mutations in comparison to the wild-type strain DSM 20075 including a mutation found in a gene coding for a metal ion transporter, which can potentially be linked to intracellular accumulation of Mn 2+ and benzaldehyde formation. The approach of high-temperature incubation can be applied in dairy industry for the selection of (adjunct) cultures targeted at accelerated cheese ripening and aroma formation. Copyright © 2016 Elsevier B.V. All rights reserved.

Desulfomicrobium thermophilum sp. nov., a novel thermophilic sulphate-reducing bacterium isolated from a terrestrial hot spring in Colombia.

PubMed

Thevenieau, France; Fardeau, Marie-Laure; Ollivier, Bernard; Joulian, Catherine; Baena, Sandra

2007-03-01

A moderately thermophilic, sulphate-reducing bacterium, designated strain P6-2(T), was isolated from a terrestrial hot spring located at a height of 2,500 m in the Andean region, Colombia (5 degrees 43'69''N, 73 degrees 6'10''W). Cells of strain P6-2(T) were rod-shaped, stained Gram-negative and were motile by means of a single polar flagellum. The strain grew lithotrophically with H(2) as the electron donor and organotrophically on lactate, pyruvate, ethanol, malate, fumarate, n-propanol and succinate in the presence of sulphate as the terminal electron acceptor. Fumarate and pyruvate was fermented. Strain P6-2(T) grew optimally at 55 degrees C (range 37-60 degrees C), pH 6.6 (range 5.8-8.8) in the presence of 0.5% NaCl (range 0-4.5%) with lactate and sulphate and produced acetate, CO(2) and H(2)S as the major end-products. Sulphate, sulphite and thiosulphate could be used as electron acceptors but not elemental sulphur or nitrate. The G + C content of the genomic DNA was 58.7 mol%. The 16S rRNA sequence analysis indicated that strain P6-2(T) was a member of the class Deltaproteobacteria, domain Bacteria with Desulfomicrobium baculatum being the closest relative (similarity value of 94%). Phylogeny of genes encoding alpha- and beta-subunits of the dissimilatory sulphite reductase (dsrAB genes) supported its affiliation to members of the genus Desulfomicrobium. On the basis of this evidence, we propose to assign strain P6-2(T) as new species of the genus Desulfomicrobium, D. thermophilum sp. nov., with strain P6-2(T) as the type strain (= DSM 16697(T) = CCUG 49732(T)).

Decomposition of Alternative Chirality Amino Acids by Alkaliphilic Anaerobe from Owens Lake, California

NASA Technical Reports Server (NTRS)

Townsend, Alisa; Pikuta, Elena V.; Guisler, Melissa; Hoover, Richard B.

2009-01-01

The study of alkaliphilic microbial communities from anaerobic sediments of Owens and Mono Lakes in California led to the isolation of a bacterial strain capable of metabolizing amino acids with alternative chirality. According to the phylogenetic analysis, the anaerobic strain BK1 belongs to the genus Tindallia; however, despite the characteristics of other described species of this genus, the strain BK1 was able to grow on D-arginine and Dlysine. Cell morphology of this strain showed straight, motile, non-spore-forming rods with sizes 0.45 x 1.2-3 microns. Physiological characteristics of the strain showed that it is catalase negative, obligately anaerobic, mesophilic, and obligately alkaliphilic. This isolate is unable to grow at pH 7 and requires CO3 (2-) ions for growth. The strain has chemo-heterotrophic metabolism and is able to ferment various proteolysis products and some sugars. It plays the role of a primary anaerobe within the trophic chain of an anaerobic microbial community by the degradation of complex protein molecules to smaller and less energetic molecules. The new isolate requires NaCl for growth, and can grow within the range of 0.5-13 %, with the optimum at 1 % NaCl (w/v). The temperature range for the growth of the new isolate is 12-40 C with optimum at 35 C. The pH range for the growth of strain BK1 occurs between 7.8 and 11.0 with optimum at 9.5. This paper presents detailed physiological characteristics of the novel isolate from Owens Lake, a unique relic ecosystem of Astrobiological significance, and makes an accent on the ability of this strain to utilize L-amino acids.

Serrated Flow Behavior of Aisi 316l Austenitic Stainless Steel for Nuclear Reactors

NASA Astrophysics Data System (ADS)

Li, Qingshan; Shen, Yinzhong; Han, Pengcheng

2017-10-01

AISI 316L austenitic stainless steel is a candidate material for Generation IV reactors. In order to investigate the influence of temperature on serrated flow behavior, tensile tests were performed at temperatures ranging from 300 to 700 °C at an initial strain rate of 2×10-4 s-1. Another group of tensile tests were carried out at strain rates ranging from 1×10-4 to 1×10-2 s-1 at 600 °C to examine the influence of strain rates on serrated flow behavior. The steel exhibited serrated flow, suggesting the occurrence of dynamic strain ageing at 450-650°C. No plateau of yield stresses of the steel was observed at an initial strain rate of 2×10-4 s-1. The effective activation energy for serrated flow occurrence was calculated to be about 254.72 kJ/mol-1. Cr, Mn, Ni and Mo solute atoms are expected to be responsible for dynamic strain ageing at high temperatures of 450-650 °C in the steel.

Differences in multiplication of virulent and vaccine strains of poliovirus type I, II, and III in laboratory animals.

PubMed

Koroleva, G A; Lashkevich, V A; Voroshilova, M K

1977-01-01

Multiplication of virulent and vaccine strains of poliovirus type I, II and III in laboratory animals of different species was studied comparatively. The main criterion of virus reproduction was the production of the photoresistant virus progeny after inoculation of the animals with proflavin-photosensitized virus strains. On the whole, virulent poliovirus strains were characterized by replication in a wide range of hosts (monkeys, cotton rats, white mice, guinea pigs, rabbits, chickens, chick embryos), a low infective dose, production of the photoresistant progeny to a high titre, clinically overt disease in some animal species. The vaccine strains multiplied in a norrower range of hosts, had a high infective dose, a low titre of virus progeny, and caused no clinical symptoms of infection. These differences may serve as a marker for differentiation between virulent and attenuated strains in vivo. Administration of guanidine before inoculation of newborn cotton rats completely prevented or delayed by several days the production of photoresistant virus progeny. This fact confirms the stability of the proflavin-poliovirus complex under conditions ruling out virus replication.

Progress Report on Long Hold Time Creep Fatigue of Alloy 617 at 850°C

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

Carroll, Laura Jill

Alloy 617 is the leading candidate material for an intermediate heat exchanger for the very high temperature reactor. To evaluate the behavior of this material in the expected service conditions, strain-controlled cyclic tests that include long hold times up to 240 minutes at maximum tensile strain were conducted at 850°C. In terms of the total number of cycles to failure, the fatigue resistance decreased when a hold time was added at peak tensile strain. Increases in the tensile hold duration degraded the creep-fatigue resistance, at least to the investigated strain controlled hold time of up to 60 minutes at themore » 0.3% strain range and 240 minutes at the 1.0% strain range. The creep-fatigue deformation mode is considered relative to the lack of saturation, or continually decreasing number of cycles to failure with increasing hold times. Additionally, preliminary values from the 850°C creep-fatigue data are calculated for the creep-fatigue damage diagram and have higher values of creep damage than those from tests at 950°C.« less

Strain-engineered growth of two-dimensional materials

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

Ahn, Geun Ho; Amani, Matin; Rasool, Haider

The application of strain to semiconductors allows for controlled modification of their band structure. This principle is employed for the manufacturing of devices ranging from high-performance transistors to solid-state lasers. Traditionally, strain is typically achieved via growth on lattice-mismatched substrates. For two-dimensional (2D) semiconductors, this is not feasible as they typically do not interact epitaxially with the substrate. Here in this paper, we demonstrate controlled strain engineering of 2D semiconductors during synthesis by utilizing the thermal coefficient of expansion mismatch between the substrate and semiconductor. Using WSe 2 as a model system, we demonstrate stable built-in strains ranging from 1%more » tensile to 0.2% compressive on substrates with different thermal coefficient of expansion. Consequently, we observe a dramatic modulation of the band structure, manifested by a strain-driven indirect-to-direct bandgap transition and brightening of the dark exciton in bilayer and monolayer WSe 2, respectively. The growth method developed here should enable flexibility in design of more sophisticated devices based on 2D materials.« less

Effect of strain wave shape on low-cycle fatigue crack propagation of SUS 304 stainless steel at elevated temperatures

NASA Astrophysics Data System (ADS)

Okazaki, Masakazu; Hattori, Ichiro; Shiraiwa, Fujio; Koizumi, Takashi

1983-08-01

Effect of strain wave shape on strain-controlled low-cycle fatigue crack propagation of SUS 304 stainless steel was investigated at 600 and 700 °C. It was found that the rate of crack propagation in a cycle-dependent region was successfully correlated with the range of cyclic J-integral, Δ Jf, regardless of the strain wave shape, frequency, and test temperature. It was also shown that the rate of crack propagation gradually increased from cycle-dependent curve to time-dependent one with decreasing frequency and slow-fast strain wave shape, and that one of the factors governing the rate of crack propagation in such a region was the ratio of the range of creep J-integral to that of total J-integral, Δ J c/Δ JT. Based on the results thus obtained, an interaction damage rule proposed semi-empirically was interpreted, with regard to crack propagation. Furthermore, fatigue crack initiation mechanism in slow-fast strain wave shape was studied, and it was shown that grain boundary sliding took an important role in it.

Strain-engineered growth of two-dimensional materials

DOE PAGES

Ahn, Geun Ho; Amani, Matin; Rasool, Haider; ...

2017-09-20

The application of strain to semiconductors allows for controlled modification of their band structure. This principle is employed for the manufacturing of devices ranging from high-performance transistors to solid-state lasers. Traditionally, strain is typically achieved via growth on lattice-mismatched substrates. For two-dimensional (2D) semiconductors, this is not feasible as they typically do not interact epitaxially with the substrate. Here in this paper, we demonstrate controlled strain engineering of 2D semiconductors during synthesis by utilizing the thermal coefficient of expansion mismatch between the substrate and semiconductor. Using WSe 2 as a model system, we demonstrate stable built-in strains ranging from 1%more » tensile to 0.2% compressive on substrates with different thermal coefficient of expansion. Consequently, we observe a dramatic modulation of the band structure, manifested by a strain-driven indirect-to-direct bandgap transition and brightening of the dark exciton in bilayer and monolayer WSe 2, respectively. The growth method developed here should enable flexibility in design of more sophisticated devices based on 2D materials.« less

[Characterization of a thermophilic Geobacillus strain DM-2 degrading hydrocarbons].

PubMed

Liu, Qing-kun; Wang, Jun; Li, Guo-qiang; Ma, Ting; Liang, Feng-lai; Liu, Ru-lin

2008-12-01

A thermophilic Geobacillus strain DM-2 from a deep-subsurface oil reservoir was investigated on its capability of degrading crude oil under various conditions as well as its characters on degrading hydrocarbons in optimal conditions. The results showed that Geobacillus strain DM-2 was able to degrade crude oil under anoxic wide-range conditions with pH ranging from 4.0 to 10.0, high temperature in the range of 45-70 degrees C and saline concentration ranging from 0.2% to 3.0%. Furthermore, the optimal temperature and pH value for utilizing hydrocarbons by the strain were 60 degrees C and 7.0, respectively. Under such optimal conditions, the strain utilized liquid paraffine emulsified by itself as its carbon source for growth; further analysis by gas chromatography (GC) and infrared absorption spectroscopy demonstrated that it was able to degrade n-alkanes (C14-C30), branched-chain alkanes and aromatic hydrocarbons in crude oil and could also utilize long-chain n-alkanes from C16 to C36, among of which the degradation efficiency of C28 was the highest, up to 88.95%. One metabolite of the strain oxidizing alkanes is fatty acid.While utilizing C16 as carbon source for 5 d, only one fatty acid-acetic acid was detected by HPLC and MS as the product, with the amount of 0.312 g/L, which indicated that it degraded n-alkanes with pathway of inferior terminal oxidation,and then followed by a beta-oxidation pathway. Due to its characters of efficient emulsification, high-performance degradation of hydrocarbons and fatty-acid production under high temperature and anoxic condition, the strain DM-2 may be potentially applied to oil-waste treatment and microbial enhanced heavy oil recovery in extreme conditions.

Analysis of Host Range Restriction Determinants in the Rabbit Model: Comparison of Homologous and Heterologous Rotavirus Infections

PubMed Central

Ciarlet, Max; Estes, Mary K.; Barone, Christopher; Ramig, Robert F.; Conner, Margaret E.

1998-01-01

The main limitation of both the rabbit and mouse models of rotavirus infection is that human rotavirus (HRV) strains do not replicate efficiently in either animal. The identification of individual genes necessary for conferring replication competence in a heterologous host is important to an understanding of the host range restriction of rotavirus infections. We recently reported the identification of the P type of the spike protein VP4 of four lapine rotavirus strains as being P[14]. To determine whether VP4 is involved in host range restriction in rabbits, we evaluated infection in rotavirus antibody-free rabbits inoculated orally with two P[14] HRVs, PA169 (G6) and HAL1166 (G8), and with several other HRV strains and animal rotavirus strains of different P and G types. We also evaluated whether the parental rhesus rotavirus (RRV) (P5B[3], G3) and the derived RRV-HRV reassortant candidate vaccine strains RRV × D (G1), RRV × DS-1 (G2), and RRV × ST3 (G4) would productively infect rabbits. Based on virus shedding, limited replication was observed with the P[14] HRV strains and with the SA11 Cl3 (P[2], G3) and SA11 4F (P6[1], G3) animal rotavirus strains, compared to the homologous ALA strain (P[14], G3). However, even limited infection provided complete protection from rotavirus infection when rabbits were challenged orally 28 days postinoculation (DPI) with 103 50% infective doses of ALA rabbit rotavirus. Other HRVs did not productively infect rabbits and provided no significant protection from challenge, in spite of occasional seroconversion. Simian RRV replicated as efficiently as lapine ALA rotavirus in rabbits and provided complete protection from ALA challenge. Live attenuated RRV reassortant vaccine strains resulted in no, limited, or productive infection of rabbits, but all rabbits were completely protected from heterotypic ALA challenge. The altered replication efficiency of the reassortants in rabbits suggests a role for VP7 in host range restriction. Also, our results suggest that VP4 may be involved in, but is not exclusively responsible for, host range restriction in the rabbit model. The replication efficiency of rotavirus in rabbits also is not controlled by the product of gene 5 (NSP1) alone, since a reassortant rotavirus with ALA gene 5 and all other genes from SA11 was more severely replication restricted than either parental rotavirus strain. PMID:9499095

From the Macro to the Micro: Gel Mapping to Differentiate between Sporozoites of Two Immunologically Distinct Strains of Eimeria maxima (Strains M6 and Guelph)

PubMed Central

Liu, Hongbin; Al Nasr, Ibrahim; Liu, Xianyong; Suo, Xun; Barta, John

2015-01-01

Two immunologically distinct strains of E. maxima were examined in this study: the M6 strain and the Guelph strain. The differential expression between the sporozoites of the two strains of E. maxima was determined by image analysis of 100 μg of protein from each strain separated by standard one- and conventional two-dimensional polyacrylamide gel electrophoresis. In addition to differences in both molecular weight and the electrophoretic mobility, differences in the intensity of polypeptide bands for example, GS 136.4 and M6 169 were explored. Pooled gels were prepared from each strain. A representative 2D-PAGE gel spanning a non-linear pH range of 3–10 of E. maxima strain M6 consisted of approximately 694 polypeptide spots with about 67 (9.6%) of the polypeptide spots being unique relative to the other strain. E. maxima strain GS had about 696 discernable polypeptide spots with 69 spots (9.9%) that differed from those of the M6 strain. In-depth characterization of the variable polypeptide spots; unique polypeptide spots (absence or presence) and shared polypeptide spots with modifications may lead to novel vaccine target in the form of multi-component, multi-stage, multi-immunovariant strains, multi-species subunit vaccine, and diagnostic probe for E. maxima. PMID:26641262

From the Macro to the Micro: Gel Mapping to Differentiate between Sporozoites of Two Immunologically Distinct Strains of Eimeria maxima (Strains M6 and Guelph).

PubMed

El-Ashram, Saeed; Yin, Qing; Liu, Hongbin; Al Nasr, Ibrahim; Liu, Xianyong; Suo, Xun; Barta, John

2015-01-01

Two immunologically distinct strains of E. maxima were examined in this study: the M6 strain and the Guelph strain. The differential expression between the sporozoites of the two strains of E. maxima was determined by image analysis of 100 μg of protein from each strain separated by standard one- and conventional two-dimensional polyacrylamide gel electrophoresis. In addition to differences in both molecular weight and the electrophoretic mobility, differences in the intensity of polypeptide bands for example, GS 136.4 and M6 169 were explored. Pooled gels were prepared from each strain. A representative 2D-PAGE gel spanning a non-linear pH range of 3-10 of E. maxima strain M6 consisted of approximately 694 polypeptide spots with about 67 (9.6%) of the polypeptide spots being unique relative to the other strain. E. maxima strain GS had about 696 discernable polypeptide spots with 69 spots (9.9%) that differed from those of the M6 strain. In-depth characterization of the variable polypeptide spots; unique polypeptide spots (absence or presence) and shared polypeptide spots with modifications may lead to novel vaccine target in the form of multi-component, multi-stage, multi-immunovariant strains, multi-species subunit vaccine, and diagnostic probe for E. maxima.

Microstructure and Texture Evolution in Double-Cone Samples of Ti-6Al-4V Alloy with Colony Preform Microstructure

NASA Astrophysics Data System (ADS)

Yang, Kun Vanna; Lim, Chao Voon Samuel; Zhang, Kai; Sun, Jifeng; Yang, Xiaoguang; Huang, Aijun; Wu, Xinhua; Davies, Christopher H.

2015-12-01

Heat-treated Ti-6Al-4V forged bar with colony microstructure was machined into double-cone-shaped samples for a series of isothermal uniaxial compression test at 1223 K (950 °C) with varying constant crosshead speeds of 12.5, 1.25, and 0.125 mms-1 to a height reduction of 70 pct. Another set of samples deformed under the same conditions were heat treated at 1173 K (900 °C) for an hour followed by water quench. Finite element modeling was used to provide the strains, strain rates, and temperature profiles of the hot compression samples, and the microstructure and texture evolution was examined at four positions on each sample, representative of different strain ranges. Lamellae fragmentation and kinking are the dominant microstructural features at lower strain range up to a maximum of 2.0, whereas globularization dominates at strains above 2.0 for the as-deformed samples. The globularization fraction generally increases with strain, or by post-deformation heat treatment, but fluctuates at lower strain. The grain size of the globular α is almost constant with strain and maximizes for samples with the lowest crosshead speed due to the longer deformation time. The globular α grain also coarsens because of post-deformation heat treatment, with its size increasing with strain level. With respect to texture evolution, a basal transverse ring and another component 30 deg from ND is determined for samples deformed at 12.5 mms-1, which is consistent with the temperature increase to close to β-transus from simulation results. The texture type remains unchanged with its intensity increased and spreads with increasing strain.

Soleus aponeurosis strain distribution following chronic unloading in humans: an in vivo MR phase-contrast study.

PubMed

Lee, Hae-Dong; Finni, Taija; Hodgson, John A; Lai, Alex M; Edgerton, V Reggie; Sinha, Shantanu

2006-06-01

The in vivo strain properties of human skeletal muscle-tendon complexes are poorly understood, particularly following chronic periods of reduced load bearing. We studied eight healthy volunteers who underwent 4 wk of unilateral lower limb suspension (ULLS) to induce chronic unloading. Before and after the ULLS, maximum isometric ankle plantar flexion torque was determined by using a magnetic resonance (MR)-compatible dynamometry. Volumes of the triceps surae muscles and strain distribution of the soleus aponeurosis and the Achilles tendon at a constant submaximal plantar flexion (20% pre-maximal voluntary contraction) were measured by using MRI and velocity-encoded, phase-contrast MRI techniques. Following ULLS, volumes of the soleus and the medial gastrocnemius and the maximum isometric ankle plantar flexion (maximum voluntary contraction) decreased by 5.5+/-1.9, 7.5+/-2.7, and 48.1+/-6.1%, respectively. The strain of the aponeurosis along the length of the muscle before the ULLS was 0.3+/-0.3%, ranging from -1.5 to 2.7% in different locations of the aponeurosis. Following ULLS, the mean strain was -6.4+/-0.3%, ranging from -1.6 to 1.3%. The strain distribution of the midregion of the aponeurosis was significantly influenced by the ULLS, whereas the more distal component showed no consistent changes. Achilles tendon strain was not affected by the ULLS. These results raise the issue as to whether these changes in strain distribution affect the functional properties of the triceps surae and whether the probability of strain injuries within the triceps surae increases following chronic unloading in those regions of this muscle complex in which unusual strains occur.

Stressor-layer-induced elastic strain sharing in SrTiO 3 complex oxide sheets

DOE PAGES

Tilka, J. A.; Park, J.; Ahn, Y.; ...

2018-02-26

A precisely selected elastic strain can be introduced in submicron-thick single-crystal SrTiO 3 sheets using a silicon nitride stressor layer. A conformal stressor layer deposited using plasma-enhanced chemical vapor deposition produces an elastic strain in the sheet consistent with the magnitude of the nitride residual stress. Synchrotron x-ray nanodiffraction reveals that the strain introduced in the SrTiO 3 sheets is on the order of 10 -4, matching the predictions of an elastic model. Using this approach to elastic strain sharing in complex oxides allows the strain to be selected within a wide and continuous range of values, an effect notmore » achievable in heteroepitaxy on rigid substrates.« less

Stressor-layer-induced elastic strain sharing in SrTiO 3 complex oxide sheets

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

Tilka, J. A.; Park, J.; Ahn, Y.

A precisely selected elastic strain can be introduced in submicron-thick single-crystal SrTiO 3 sheets using a silicon nitride stressor layer. A conformal stressor layer deposited using plasma-enhanced chemical vapor deposition produces an elastic strain in the sheet consistent with the magnitude of the nitride residual stress. Synchrotron x-ray nanodiffraction reveals that the strain introduced in the SrTiO 3 sheets is on the order of 10 -4, matching the predictions of an elastic model. Using this approach to elastic strain sharing in complex oxides allows the strain to be selected within a wide and continuous range of values, an effect notmore » achievable in heteroepitaxy on rigid substrates.« less

Characterization of strain and its effects on ferromagnetic nickel nanocubes

NASA Astrophysics Data System (ADS)

Manna, Sohini; Kim, Jong Woo; Lubarda, Marko V.; Wingert, James; Harder, Ross; Spada, Fred; Lomakin, Vitaliy; Shpyrko, Oleg; Fullerton, Eric E.

2017-12-01

We report on the interplay of magnetic properties and intrinsic strain in ferromagnetic nickel nanocubes with cubic anisotropy. Via coherent x-ray diffraction imaging we observed compressive stress at the bottom surface of these cubes. The nanocubes with {100} facets described and imaged in this study were synthesized using a single-step CVD process. Micromagnetic simulations predict the presence of vortices at remanence in the absence of strain. The effects of strain resulting from the compressive stress on the magnetic response of the ferromagnetic cubes is investigated. We observe that measured intrinsic strain is too low to change the magnetic anisotropy of ferromagnetic cubes but topological behavior of magnetic vortices is sensitive to even this low range of strain.

Revisiting borehole strain, typhoons, and slow earthquakes using quantitative estimates of precipitation-induced strain changes

NASA Astrophysics Data System (ADS)

Hsu, Ya-Ju; Chang, Yuan-Shu; Liu, Chi-Ching; Lee, Hsin-Ming; Linde, Alan T.; Sacks, Selwyn I.; Kitagawa, Genshio; Chen, Yue-Gau

2015-06-01

Taiwan experiences high deformation rates, particularly along its eastern margin where a shortening rate of about 30 mm/yr is experienced in the Longitudinal Valley and the Coastal Range. Four Sacks-Evertson borehole strainmeters have been installed in this area since 2003. Liu et al. (2009) proposed that a number of strain transient events, primarily coincident with low-barometric pressure during passages of typhoons, were due to deep-triggered slow slip. Here we extend that investigation with a quantitative analysis of the strain responses to precipitation as well as barometric pressure and the Earth tides in order to isolate tectonic source effects. Estimates of the strain responses to barometric pressure and groundwater level changes for the different stations vary over the ranges -1 to -3 nanostrain/millibar(hPa) and -0.3 to -1.0 nanostrain/hPa, respectively, consistent with theoretical values derived using Hooke's law. Liu et al. (2009) noted that during some typhoons, including at least one with very heavy rainfall, the observed strain changes were consistent with only barometric forcing. By considering a more extensive data set, we now find that the strain response to rainfall is about -5.1 nanostrain/hPa. A larger strain response to rainfall compared to that to air pressure and water level may be associated with an additional strain from fluid pressure changes that take place due to infiltration of precipitation. Using a state-space model, we remove the strain response to rainfall, in addition to those due to air pressure changes and the Earth tides, and investigate whether corrected strain changes are related to environmental disturbances or tectonic-original motions. The majority of strain changes attributed to slow earthquakes seem rather to be associated with environmental factors. However, some events show remaining strain changes after all corrections. These events include strain polarity changes during passages of typhoons (a characteristic that is not anticipated from our estimates of the precipitation transfer function) that are more readily explained in terms of tectonic-origin motions, but clearly the triggering argument is now weaker than that presented in Liu et al. (2009). Additional on-site water level sensors and rain gauges will provide data critical for a more complete understanding, including the currently unresolved issue of why, for some typhoons, there appears to be a much smaller transfer function for precipitation-induced strain changes.

Genetic Variability of Myxoma Virus Genomes

PubMed Central

Braun, Christoph; Thürmer, Andrea; Daniel, Rolf; Schultz, Anne-Kathrin; Bulla, Ingo; Schirrmeier, Horst; Mayer, Dietmar; Neubert, Andreas

2016-01-01

ABSTRACT Myxomatosis is a recurrent problem on rabbit farms throughout Europe despite the success of vaccines. To identify gene variations of field and vaccine strains that may be responsible for changes in virulence, immunomodulation, and immunoprotection, the genomes of 6 myxoma virus (MYXV) strains were sequenced: German field isolates Munich-1, FLI-H, 2604, and 3207; vaccine strain MAV; and challenge strain ZA. The analyzed genomes ranged from 147.6 kb (strain MAV) to 161.8 kb (strain 3207). All sequences were affected by several mutations, covering 24 to 93 open reading frames (ORFs) and resulted in amino acid substitutions, insertions, or deletions. Only strains Munich-1 and MAV revealed the deletion of 10 ORFs (M007L to M015L) and 11 ORFs (M007L to M008.1L and M149R to M008.1R), respectively. Major differences were observed in the 27 immunomodulatory proteins encoded by MYXV. Compared to the reference strain Lausanne, strains FLI-H, 2604, 3207, and ZA showed the highest amino acid identity (>98.4%). In strains Munich-1 and MAV, deletion of 5 and 10 ORFs, respectively, was observed, encoding immunomodulatory proteins with ankyrin repeats or members of the family of serine protease inhibitors. Furthermore, putative immunodominant surface proteins with homology to vaccinia virus (VACV) were investigated in the sequenced strains. Only strain MAV revealed above-average frequencies of amino acid substitutions and frameshift mutations. Finally, we performed recombination analysis and found signs of recombination in vaccine strain MAV. Phylogenetic analysis showed a close relationship of strain MAV and the MSW strain of Californian MYXV. However, in a challenge model, strain MAV provided full protection against lethal challenges with strain ZA. IMPORTANCE Myxoma virus (MYXV) is pathogenic for European rabbits and two North American species. Due to sophisticated strategies in immune evasion and oncolysis, MYXV is an important model virus for immunological and pathological research. In its natural hosts, MYXV causes a benign infection, whereas in European rabbits, it causes the lethal disease myxomatosis. Since the introduction of MYXV into Australia and Europe for the biological control of European rabbits in the 1950s, a coevolution of host and pathogen has started, selecting for attenuated virus strains and increased resistance in rabbits. Evolution of viruses is a continuous process and influences the protective potential of vaccines. In our analyses, we sequenced 6 MYXV field, challenge, and vaccine strains. We focused on genes encoding proteins involved in virulence, host range, immunomodulation, and envelope composition. Genes affected most by mutations play a role in immunomodulation. However, attenuation cannot be linked to individual mutations or gene disruptions. PMID:27903800

[Comparative evaluation of Leningrad-3 mumps vaccine virus neurovirulence in a neonatal rat model].

PubMed

Ignat'ev, G M; Otrashevskaia, E V; Rubin, S A

2011-01-01

The neurovirulence and replication potential of several mumps virus strains, including Leningrad-3 mumps vaccine virus (FSUE SIC "Microgen", Russia) and wild type strains isolated in the Novosibirsk Region (Russia), were assessed in rat tests. The mean neurovirulence scores of the Leningrad-3 virus (< 4.0) were significantly lower than those of wild type strains (ranging from 6.1 to 15.2) and were in accordance with the scores determined for other attenuated mumps vaccine strains (usually ranging from 0 to 5). In general, the relative ability of the viruses to replicate in the rat brain tracked with their neurovirulence scores. These results indicate a low neurovirulence potential of the Leningrad-3 mumps vaccine virus for humans.

A cost-effective edge-filter-based FBG strain interrogator using catastrophic fuse effect microcavity interferometers

NASA Astrophysics Data System (ADS)

Díaz, Camilo A. R.; Marques, Carlos A. F.; Domingues, M. Fátima F.; Ribeiro, Moisés. R. N.; Neto, Anselmo F.; Pontes, Maria J.; André, Paulo S.; Antunes, Paulo F. C.

2018-02-01

This paper presents a simple, compact, stable and inexpensive in-line solution based on catastrophic fuse effect micro-cavity interferometers for edge-filter strain interrogation of a fiber Bragg grating sensor. By using a commercial spliced machine and recycling damage fiber for the catastrophic fuse effect it is possible to construct a micro-cavity with high contrast of more than 20dB, and acceptable half free spectra range (FSR) around 13nm of interrogation range. The strain from 0 to 1440μStrain of the FBG sensor is measured with evidences of high repeatability and stability. Future work will investigate the use of the proposed method for applications requiring higher interrogation rates.

Structure-property relations of calcium-sulfur-hydrogen: An investigation of the electromechanical properties

NASA Astrophysics Data System (ADS)

Yuan, Lijian

This thesis investigates the structure-property relations for the calcium silicate hydrate (C-S-H) gel phase in hardened cement pastes (HCP). Studies were performed with the purpose of gaining insight into the origin of the electromechanical behavior and exploring the dynamic nature of the pore structures of HCP during water transport by using an electrically induced strain method. Emphasis was placed on the fundamental characteristics of the electrically induced strains, the role that electrically stimulated water transport through the interconnecting pore structures in HCP plays, as well as the mechanism underlying the induced strains. Reversible and irreversible components of the induced strains were distinguished under ac electric field. Evidence showed that the reversible strains were due to redistribution of water along the structure of the pore network of specimens, whereas the irreversible strains were related to long-range water transport toward the surface of specimens. In contrast, the contractive strains were found following the water loss during measurements. Investigations as a function of measurement frequency revealed a strong relaxation of the induced strains in the frequency range from 6.7 × 10sp{-3} to 1 Hz. The strong relaxation in the induced strains with electric field was found to be due to space charge polarization and a creep-like deformation. The induced strains were shown to be strongly affected by changes in the gel pore structures. The magnitude of the induced strains was found to be significantly dependent on the moisture content adsorbed. Evidence of a critical percolation of pore solution was also observed. A strong decrease in the induced strains was observed with decreasing temperature due to the influence of ice formation. This decrease was interpreted in terms of a decrease in the electroosmotic volumetric flux and hydraulic permeability with decreasing temperature. The strong non-linearity in the induced strains was found with respect to the electric field strength. The presence of non-linear electric streaming current vs. electric field characteristics was examined, which was modeled by using an electrokinetic equation of state. Evidence of an anomalous temperature dependence in both electrical conductivity and dielectric permitivity was observed, indicating the presence of anomalies associated with a percolation-like transition.

Flow Stress and Processing Map of a PM 8009Al/SiC Particle Reinforced Composite During Hot Compression

NASA Astrophysics Data System (ADS)

Luo, Haibo; Teng, Jie; Chen, Shuang; Wang, Yu; Zhang, Hui

2017-10-01

Hot compression tests of 8009Al alloy reinforced with 15% SiC particles (8009Al/15%SiCp composites) prepared by powder metallurgy (direct hot extrusion methods) were performed on Gleeble-3500 system in the temperature range of 400-550 °C and strain rate range of 0.001-1 s-1. The processing map based on the dynamic material model was established to evaluate the flow instability regime and optimize processing parameters; the associated microstructural changes were studied by the observations of optical metallographic and scanning electron microscopy. The results showed that the flow stress increased initially and reached a plateau after peak stress value with increasing strain. The peak stress increased as the strain rate increased and deformation temperature decreased. The optimum parameters were identified to be deformation temperature range of 500-550 °C and strain rate range of 0.001-0.02 s-1 by combining the processing map with microstructural observation.

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

Fiber-optic extrinsic Fabry-Perot interferometer strain sensor with <50 pm displacement resolution using three-wavelength digital phase demodulation.

PubMed

Schmidt, M; Werther, B; Fuerstenau, N; Matthias, M; Melz, T

2001-04-09

A fiber-optic extrinsic Fabry-Perot interferometer strain sensor (EFPI-S) of ls = 2.5 cm sensor length using three-wavelength digital phase demodulation is demonstrated to exhibit <50 pm displacement resolution (<2nm/m strain resolution) when measuring the cross expansion of a PZT-ceramic plate. The sensing (single-mode downlead-) and reflecting fibers are fused into a 150/360 microm capillary fiber where the fusion points define the sensor length. Readout is performed using an improved version of the previously described three-wavelength digital phase demodulation method employing an arctan-phase stepping algorithm. In the resent experiments the strain sensitivity was varied via the mapping of the arctan - lookup table to the 16-Bit DA-converter range from 188.25 k /V (6 Volt range 1130 k ) to 11.7 k /Volt (range 70 k ).

Effect of various fixation parameters on strain development of screw- and cement-retained implant-supported restorations.

PubMed

Schittenhelm, Birgit; Karl, Matthias; Graef, Friedrich; Heckmann, Siegfried; Taylor, Thomas

2013-01-01

The objective of this study was to quantify the potential effects of screw- and cement-retention on strain development of implant-supported fixed dental prostheses (FDPs). A total of 20 single crowns and 70 three-unit FDPs were fabricated to fit an in vitro model situation with two implants. Using strain gauges attached to the model material adjacent to the implants, strain development of the restorations during fixation was recorded while the parameters cement type (provisional and definitive cement), cementation force (10 N and 100 N), and tightening torque (5 Ncm, 10 Ncm, and 15 Ncm) were varied. MANOVA with Pillai's trace was used for pairwise comparisons between groups (α = .05). Mean absolute strain development ranged from 5.11 µm/m for to 27.26 µm/m for single crowns and from 16.46 µm/m to 689.04 µm/m for multi-unit restorations. Screw-retained single crowns exhibited significantly smaller strain development as compared to cement-retained single crowns (P = .009). The type of cement used seemed to have no effect on strain development of an FDP regardless of the cementation force applied (P = .064 and P = .605). An increase in tightening torque for screw-retained FDPs also had no effect on resulting strain development (P values ranging from .692 to .807). Nonuniform results were found when comparing screw- and cementretention as the retention mechanism for FDPs. Strain development seems to depend predominantly on the accuracy achieved during the fabrication process whereas the retention mechanisms themselves as well as their potential parameters only have a minor effect.

Atlantic salmon, Salmo salar L. are broadly susceptible to isolates representing the North American genogroups of infectious hematopoietic necrosis virus

USGS Publications Warehouse

Kurath, Gael; Winton, James R.; Dale, Ole B.; Purcell, Maureen K.; Falk, Knut; Busch, Robert D.

2016-01-01

Beginning in 1992, three epidemic waves of infectious hematopoietic necrosis, often with high mortality, occurred in farmed Atlantic salmon Salmo salar L. on the west coast of North America. We compared the virulence of eleven strains of infectious hematopoietic necrosis virus (IHNV), representing the U, M and L genogroups, in experimental challenges of juvenile Atlantic salmon in freshwater. All strains caused mortality and there was wide variation within genogroups: cumulative mortality for five U-group strains ranged from 20 to 100%, four M-group strains ranged 30-63% and two L-group strains varied from 41 to 81%. Thus, unlike Pacific salmonids, there was no apparent correlation of virulence in a particular host species with virus genogroup. The mortality patterns indicated two different phenotypes in terms of kinetics of disease progression and final per cent mortality, with nine strains having moderate virulence and two strains (from the U and L genogroups) having high virulence. These phenotypes were investigated by histopathology and immunohistochemistry to describe the variation in the course of IHNV disease in Atlantic salmon. The results from this study demonstrate that IHNV may become a major threat to farmed Atlantic salmon in other regions of the world where the virus has been, or may be, introduced.

Are luminescent bacteria suitable for online detection and monitoring of toxic compounds in drinking water and its sources?

PubMed

Woutersen, Marjolijn; Belkin, Shimshon; Brouwer, Bram; van Wezel, Annemarie P; Heringa, Minne B

2011-05-01

Biosensors based on luminescent bacteria may be valuable tools to monitor the chemical quality and safety of surface and drinking water. In this review, an overview is presented of the recombinant strains available that harbour the bacterial luciferase genes luxCDABE, and which may be used in an online biosensor for water quality monitoring. Many bacterial strains have been described for the detection of a broad range of toxicity parameters, including DNA damage, protein damage, membrane damage, oxidative stress, organic pollutants, and heavy metals. Most lux strains have sensitivities with detection limits ranging from milligrams per litre to micrograms per litre, usually with higher sensitivities in compound-specific strains. Although the sensitivity of lux strains can be enhanced by various molecular manipulations, most reported detection thresholds are still too high to detect levels of individual contaminants as they occur nowadays in European drinking waters. However, lux strains sensing specific toxic effects have the advantage of being able to respond to mixtures of contaminants inducing the same effect, and thus could be used as a sensor for the sum effect, including the effect of compounds that are as yet not identified by chemical analysis. An evaluation of the suitability of lux strains for monitoring surface and drinking water is therefore provided.

Modeling the Hot Tensile Flow Behaviors at Ultra-High-Strength Steel and Construction of Three-Dimensional Continuous Interaction Space for Forming Parameters

NASA Astrophysics Data System (ADS)

Quan, Guo-zheng; Zhan, Zong-yang; Wang, Tong; Xia, Yu-feng

2017-01-01

The response of true stress to strain rate, temperature and strain is a complex three-dimensional (3D) issue, and the accurate description of such constitutive relationships significantly contributes to the optimum process design. To obtain the true stress-strain data of ultra-high-strength steel, BR1500HS, a series of isothermal hot tensile tests were conducted in a wide temperature range of 973-1,123 K and a strain rate range of 0.01-10 s-1 on a Gleeble 3800 testing machine. Then the constitutive relationships were modeled by an optimally constructed and well-trained backpropagation artificial neural network (BP-ANN). The evaluation of BP-ANN model revealed that it has admirable performance in characterizing and predicting the flow behaviors of BR1500HS. A comparison on improved Arrhenius-type constitutive equation and BP-ANN model shows that the latter has higher accuracy. Consequently, the developed BP-ANN model was used to predict abundant stress-strain data beyond the limited experimental conditions. Then a 3D continuous interaction space for temperature, strain rate, strain and stress was constructed based on these predicted data. The developed 3D continuous interaction space for hot working parameters contributes to fully revealing the intrinsic relationships of BR1500HS steel.

High-rate tensile properties of Si-reduced TRIP sheet steels

NASA Astrophysics Data System (ADS)

Choi, Ildong; Park, Yeongdo; Son, Dongmin; Kim, Sung-Joon; Moon, Manbeen

2010-02-01

There have been efforts to develop Si-reduced TRIP steels to improve the wettability of Zn coatings, since the conventional CMnSi-TRIP steels suffer from poor galvanizability. In addition, for the development of potential applications of Si-reduced TRIP steels in vehicle crash management, a better understanding of high strain rate properties is required. In the present study, the effects of alloying elements, such as Cu, Al, Si, and P, on the high-rate tensile properties of Si-reduced TRIP sheet steels were investigated. Tensile tests were performed with a servo-hydraulic tensile testing machine at strain rates ranging from 10-2 to 6 × 102 s-1, and the ultimate tensile strength, elongation, strain rate sensitivity, and absorbed energy were evaluated. The retained austenite volume fractions and carbon content of the specimens were measured using neutron diffraction. The UTS was increased with Cu, Al, Si, and P alloying throughout the strain rate range, and the alloying effect on UTS was considerable with Cu and P. The effects of alloying on the microstructure were not significant. All the steels tested in this study exhibited positive strain rate sensitivity, and the m value at strain rates higher than 10 s-1 was at least two times higher than that at lower strain rates.

Comparison of pulsed-field gel electrophoresis and enterobacterial repetitive intergenic consensus PCR and biochemical tests to characterize Lactococcus garvieae.

PubMed

Ture, M; Altinok, I; Capkin, E

2015-01-01

Biochemical test, pulsed-field gel electrophoresis (PFGE) and enterobacterial repetitive intergenic consensus sequence PCR (ERIC-PCR) were used to compare 42 strains of Lactococcus garvieae isolated from different regions of Turkey, Italy, France and Spain. Twenty biotypes of L. garvieae were formed based on 54 biochemical tests. ERIC-PCR of genomic DNA from different L. garvieae strains resulted in amplification of multiple fragments of DNA in sizes ranging between 200 and 5000 bp with various band intensities. After cutting DNA with ApaI restriction enzyme and running on the PFGE, 11–22 resolvable bands ranging from 2 to 194 kb were observed. Turkish isolates were grouped into two clusters, and only A58 (Italy) strain was connected with Turkish isolates. Similarities between Turkish, Spanish, Italian and French isolates were <50% except 216-6 Rize strain. In Turkey, first lactococcosis occurred in Mugla, and then, it has been spread all over the country. Based on ERIC-PCR, Spanish and Italian strains of L. garvieae were related to Mugla strains. Therefore, after comparing PFGE profiles, ERIC-PCR profiles and phenotypic characteristics of 42 strains of L. garvieae, there were no relationships found between these three typing methods. PFGE method was more discriminative than the other methods. © 2014 John Wiley & Sons Ltd.

Starter culture development for improving safety and quality of Domiati cheese.

PubMed

Ayad, Eman H E

2009-08-01

Eleven lactococci strains (sp. lactis and cremoris) were collected according to specific or selected characteristics for development of defined strain starter (DSS) to improve safety and nutritional quality of traditional and low salt Domiati cheese. Thirteen DSS; nisin-producing system or/and folate-producing strains were prepared. The behaviour of the strains in DSS was studied in milk and in two series of Domiati cheese; the first one made with 5% NaCl and salt tolerant strains, the second made with 3% NaCl and the control cheeses were made without starters. The population dynamics of strains and sensory evaluation of cheese corroborated the results in milk. All strains can grow well together and appeared to produce pleasant flavours, normal (typical) body and texture Domiati cheese. There was no apparent difference in cheese composition between cheeses in each series; the levels were within margins for composition of Domiati cheese. The levels of nisin (IU g(-1)) ranged from 204 to 324 IU g(-1) in 3-months' cheeses. Folate concentration increased in cheeses made with DSS cultures than control and the level ranged from 5.5 to 11.1 microg 100 g(-1) in cheeses after 3 months. All results revealed that selected DSS can be used for improving Domiati cheese.

Microbiological Quality Assessment by PCR and Its Antibiotic Susceptibility in Mangrove Crabs (Ucides cordatus) from Guanabara Bay, Rio de Janeiro, Brazil.

PubMed

Carvalho, M C N; Jayme, M M; Arenazio, G S; Araújo, F V; Leite, S G F; Del Aguila, E M

2016-01-01

The bacteriological quality of crabs from three different mangroves (Itaóca, Suruí, and Piedade) from Rio de Janeiro state, Brazil, was investigated using conventional and molecular methods. The results revealed high counts for total coliforms in meat and hepatopancreas samples. PCR analyses identified 25 Escherichia coli colonies in the Itaóca, Piedade, and Suruí samples, detecting 13 enterotoxigenic colonies and 9 enteroaggregative colonies. Respectively, 12, 11, and 21 Vibrio parahaemolyticus strains were detected in the Itaóca, Piedade, and Suruí samples. Two V. cholerae strains were detected in the Piedade samples. The E. coli strains isolated in the present study showed resistance to gentamicin. E. coli strains from the Piedade samples showed 33% resistance to chloramphenicol and the strains also showed multiresistance to several antimicrobial agents with a MAR index ranging from 0.12 to 0.31. Vibrio strains from Piedade, Itaóca, and Suruí showed 86%, 78%, and 85% resistance, respectively, to ampicillin. The isolated Vibrio strains showed multiresistance to several antimicrobial agents, with a MAR index ranging from 0.12 to 0.25. The presence of these organisms in crab meat is an indication of microbial contamination, which may pose health risks to consumers when improperly cooked.

Microbiological Quality Assessment by PCR and Its Antibiotic Susceptibility in Mangrove Crabs (Ucides cordatus) from Guanabara Bay, Rio de Janeiro, Brazil

PubMed Central

Carvalho, M. C. N.; Jayme, M. M.; Arenazio, G. S.; Araújo, F. V.; Leite, S. G. F.; Del Aguila, E. M.

2016-01-01

The bacteriological quality of crabs from three different mangroves (Itaóca, Suruí, and Piedade) from Rio de Janeiro state, Brazil, was investigated using conventional and molecular methods. The results revealed high counts for total coliforms in meat and hepatopancreas samples. PCR analyses identified 25 Escherichia coli colonies in the Itaóca, Piedade, and Suruí samples, detecting 13 enterotoxigenic colonies and 9 enteroaggregative colonies. Respectively, 12, 11, and 21 Vibrio parahaemolyticus strains were detected in the Itaóca, Piedade, and Suruí samples. Two V. cholerae strains were detected in the Piedade samples. The E. coli strains isolated in the present study showed resistance to gentamicin. E. coli strains from the Piedade samples showed 33% resistance to chloramphenicol and the strains also showed multiresistance to several antimicrobial agents with a MAR index ranging from 0.12 to 0.31. Vibrio strains from Piedade, Itaóca, and Suruí showed 86%, 78%, and 85% resistance, respectively, to ampicillin. The isolated Vibrio strains showed multiresistance to several antimicrobial agents, with a MAR index ranging from 0.12 to 0.25. The presence of these organisms in crab meat is an indication of microbial contamination, which may pose health risks to consumers when improperly cooked. PMID:27065187

Constitutive Model for Hot Deformation of the Cu-Zr-Ce Alloy

NASA Astrophysics Data System (ADS)

Zhang, Yi; Sun, Huili; Volinsky, Alex A.; Wang, Bingjie; Tian, Baohong; Liu, Yong; Song, Kexing

2018-02-01

Hot compressive deformation behavior of the Cu-Zr-Ce alloy has been investigated according to the hot deformation tests in the 550-900 °C temperature range and 0.001-10 s-1 strain rate range. Based on the true stress-true strain curves, the flow stress behavior of the Cu-Zr-Ce alloy was investigated. Microstructure evolution was observed by optical microscopy. Based on the experimental results, a constitutive equation, which reflects the relationships between the stress, strain, strain rate and temperature, has been established. Material constants n, α, Q and ln A were calculated as functions of strain. The equation predicting the flow stress combined with these materials constants has been proposed. The predicted stress is consistent with experimental stress, indicating that developed constitutive equation can adequately predict the flow stress of the Cu-Zr-Ce alloy. Dynamic recrystallization critical strain was determined using the work hardening rate method. According to the dynamic material model, the processing maps for the Cu-Zr and Cu-Zr-Ce alloy were obtained at 0.4 and 0.5 strain. Based on the processing maps and microstructure observations, the optimal processing parameters for the two alloys were determined, and it was found that the addition of Ce can promote the hot workability of the Cu-Zr alloy.

Host specific glycans are correlated with susceptibility to infection by lagoviruses, but not with their virulence.

PubMed

Lopes, Ana M; Breiman, Adrien; Lora, Mónica; Le Moullac-Vaidye, Béatrice; Galanina, Oxana; Nyström, Kristina; Marchandeau, Stephane; Le Gall-Reculé, Ghislaine; Strive, Tanja; Neimanis, Aleksija; Bovin, Nicolai V; Ruvoën-Clouet, Nathalie; Esteves, Pedro J; Abrantes, Joana; Le Pendu, Jacques

2017-11-29

The rabbit hemorrhagic disease virus (RHDV) and the European brown hare syndrome virus (EBHSV) are two lagoviruses from the family Caliciviridae that cause fatal diseases in two leporid genera, Oryctolagus and Lepus , respectively. In the last few years, several examples of host jumps of lagoviruses among leporids were recorded. In addition, a new pathogenic genotype of RHDV emerged and many non-pathogenic strains of lagoviruses have been described. The molecular mechanisms behind host shifts and the emergence of virulence are unknown. Since RHDV uses glycans of the histo-blood group antigen type as attachment factors to initiate infection, we studied if glycan specificities of the new pathogenic RHDV genotype, non-pathogenic lagoviruses and EBHSV potentially play a role in determining host range and virulence of lagoviruses. We observed binding to A, B or H antigens of the histo-blood group family for all strains known to primarily infect European rabbits ( Oryctolagus cuniculus ), that have recently been classified as GI strains. Yet, we could not explain the emergence of virulence since similar glycan specificities were found between several pathogenic and non-pathogenic strains. By contrast, EBHSV, recently classified as GII.1, bound to terminal β-linked N-acetylglucosamine residues of O-glycans. Expression of these attachment factors in the upper respiratory and digestive tracts in three lagomorph species ( Oryctolagus cuniculus, Lepus europaeus and Sylvilagus floridanus ) showed species-specific patterns regarding the susceptibility to infection by these viruses, indicating that species-specific glycan expression is likely a major contributor to lagoviruses host specificity and range. IMPORTANCE Lagoviruses constitute a genus of the Caliciviridae family, comprising highly pathogenic viruses, RHDV and EBHSV, which infect rabbits and hares, respectively. Recently, non-pathogenic strains were discovered and new pathogenic strains have emerged. In addition, host jumps between lagomorphs are observed. The mechanisms responsible for the emergence of pathogenicity and host-species range are unknown. Previous studies showed that RHDV strains attach to glycans expressed in the upper respiratory and digestive tracts of rabbits, the likely doors of virus entry. Here we studied the glycan-binding properties of novel pathogenic and non-pathogenic strains looking for a link between glycan-binding and virulence or between glycan specificity and host range. We found that glycan binding did not correlate with virulence. However, expression of glycan motifs in the upper respiratory and digestive tracts of lagomorphs revealed species-specific patterns associated with the host range of the virus strains, suggesting that glycan diversity contributes to lagoviruses' host range. Copyright © 2017 American Society for Microbiology.

Novel Human Intervertebral Disc Strain Template to Quantify Regional Three-Dimensional Strains in a Population and Compare to Internal Strains Predicted by a Finite Element Model

PubMed Central

Showalter, Brent L.; DeLucca, John F.; Peloquin, John M.; Cortes, Daniel H.; Yoder, Jonathon H.; Jacobs, Nathan T.; Wright, Alexander C.; Gee, James C.; Vresilovic, Edward J.; Elliott, Dawn M.

2017-01-01

Tissue strain is an important indicator of mechanical function, but is difficult to noninvasively measure in the intervertebral disc. The objective of this study was to generate a disc strain template, a 3D average of disc strain, of a group of human L4–L5 discs loaded in axial compression. To do so, magnetic resonance images of uncompressed discs were used to create an average disc shape. Next, the strain tensors were calculated pixel-wise by using a previously developed registration algorithm. Individual disc strain tensor components were then transformed to the template space and averaged to create the disc strain template. The strain template reduced individual variability while highlighting group trends. For example, higher axial and circumferential strains were present in the lateral and posterolateral regions of the disc, which may lead to annular tears. This quantification of group-level trends in local 3D strain is a significant step forward in the study of disc biomechanics. These trends were compared to a finite element model that had been previously validated against the disc-level mechanical response. Depending on the strain component, 81–99% of the regions within the finite element model had calculated strains within one standard deviation of the template strain results. The template creation technique provides a new measurement technique useful for a wide range of studies, including more complex loading conditions, the effect of disc pathologies and degeneration, damage mechanisms, and design and evaluation of treatments. PMID:26694516

Fatigue tests of YBCO coated conductors

NASA Astrophysics Data System (ADS)

Bamba, S.; Tanaka, Y.; Ando, T.; Ueda, H.; Ishiyama, A.; Yamada, Y.; Shiohara, Y.

2008-02-01

In this paper, we report the fatigue characteristics of IBAD/PLD YBCO coated conductors. A YBCO coated conductor used in the superconducting coil of a SMES system is repeatedly subjected to mechanical tensile or compressive strain due to the Lorentz force during electrical charging or discharging. The superconducting characteristic of this conductor may deteriorate because of this cyclic strain. Therefore, it is necessary to investigate the effect of cyclic strain on the superconducting characteristics of YBCO coated conductors that have a laminated structure. We developed an experimental apparatus with a U-shaped sample holder in order to apply cyclic strain to the sample tape. This apparatus was used to perform the fatigue tests on YBCO coated conductors in liquid nitrogen in the absence of an external magnetic field. The strain cycles with the maximum strain epsilonmax (zero external strain → epsilonmax → zero external strain) were applied and repeated up to 5000 times, and the Ic measurements were performed at epsilonmax. Therefore, the application of cyclic strain with epsilonmax ranging from 0.3% to 0.5% did not result in any significant deterioration of the superconducting characteristics of the conductor.

Biosynthesis of gold nanoparticles by actinomycete Streptomyces viridogens strain HM10.

PubMed

Balagurunathan, R; Radhakrishnan, M; Rajendran, R Babu; Velmurugan, D

2011-10-01

Biosynthesis of gold nanoparticles by Streptomycetes from Himalayan Mountain was undertaken for the first time. Out of 10 actinomycete strains tested, four strains (D10, HM10, ANS2 and MSU) showed evidence for the intracellular biosynthesis of gold nanoparticles, among which the strain HM10 showed high potency. Presence of spherical and rod shaped gold nanoparticles in mycelium of the strain HM10 was determined by transmission electron microscopy (TEM) and X-ray diffraction analysis. The average particle size ranged from 18-20 nm. UV spectral analysis indicated that the reduction of chloroauric acid (HAuCl4) occurred within 24 h of reaction period. Further, the strain HM10 showed enhanced growth at 1 and 10 mM concentration of HAuCl4. The gold nanoparticles synthesized by the strain HM10 showed good antibacterial activity against S. aureus and E. coli in well-diffusion method. The potential actinomycete HM10 strain was phenotypically characterized and identified as Streptomyces viridogens (HM10). Thus, actinomycete strain HM10 reported in this study is a newly added source for the biosynthesis of gold nanoparticles.

Highly Stretchable and Transparent Microfluidic Strain Sensors for Monitoring Human Body Motions.

PubMed

Yoon, Sun Geun; Koo, Hyung-Jun; Chang, Suk Tai

2015-12-16

We report a new class of simple microfluidic strain sensors with high stretchability, transparency, sensitivity, and long-term stability with no considerable hysteresis and a fast response to various deformations by combining the merits of microfluidic techniques and ionic liquids. The high optical transparency of the strain sensors was achieved by introducing refractive-index matched ionic liquids into microfluidic networks or channels embedded in an elastomeric matrix. The microfluidic strain sensors offer the outstanding sensor performance under a variety of deformations induced by stretching, bending, pressing, and twisting of the microfluidic strain sensors. The principle of our microfluidic strain sensor is explained by a theoretical model based on the elastic channel deformation. In order to demonstrate its capability of practical usage, the simple-structured microfluidic strain sensors were performed onto a finger, wrist, and arm. The highly stretchable and transparent microfluidic strain sensors were successfully applied as potential platforms for distinctively monitoring a wide range of human body motions in real time. Our novel microfluidic strain sensors show great promise for making future stretchable electronic devices.

Strain evaluation of strengthened concrete structures using FBG sensors

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

Lau Kintak; Zhou Limin; Ye Lin

1999-12-02

Fibre-optic Bragg Grating (FBG) sensor presents a great deal of potential in monitoring the internal status of the concrete structures after repairing or strengthening by an external adhered reinforcement. It can be used in a variety of configurations ranging from pointwise to multi-point strain measurement in order to investigate the strain distribution of the structures. In this paper, an experimental investigation on the rectangular notched-concrete beam, which was strengthened by glass fibre composites with the embedment of multiplexing FBG sensors is presented. Three point bending test was performed to investigate the strain profile of the specimen. Frequency modulated continuous wavemore » (FMCW) technique was used to measure the strain variation of the fibre-grating regions. The results give a good agreement with the electrical resistance strain gauge in early loading condition. The difference of the strain-measuring results between the strain-gauge and FBG sensor was increased when further increasing the applied load. It was suspected that the micro/marco cracks occurred on the concrete surface and that the externally bonded strain-measuring device cannot be detected.« less

In vitro evaluation of the probiotic and functional potential of Lactobacillus strains isolated from fermented food and human intestine.

PubMed

Ren, Dayong; Li, Chang; Qin, Yanqing; Yin, Ronglan; Du, Shouwen; Ye, Fei; Liu, Cunxia; Liu, Hongfeng; Wang, Maopeng; Li, Yi; Sun, Yang; Li, Xiao; Tian, Mingyao; Jin, Ningyi

2014-12-01

This study aims to evaluate the functional and probiotic characteristics of eight indigenous Lactobacillus strains in vitro. The selected lactobacilli include strains of Lactobacillus casei subsp. casei, Lactobacillus salivarius subsp. salicinius, Lactobacillus fermentum, Lactobacillus plantarum, Lactobacillus delbrueckii subsp. lactis, Lactobacillus delbrueckii subsp. bulgaricus, and Lactobacillus rhamnosus. All strains tolerated both pH 2 for 3 h and 1% bile salt for 24 h. The strains CICC 23174 and CGMCC 1.557 were the most adhesive strains producing the highest quantity of EPS. Although a wide variation in the ability of the eight strains to deplete cholesterol and nitrite, antagonize pathogens, scavenge free radical, and stimulate innate immune response were observed, the strains CICC 23174 and CGMCC 1.557 showed the widest range of these useful traits. Taken together, the strains CICC 23174 and CGMCC 1.557 exhibited the best probiotic properties with the potential for use in the production of probiotic fermented foods. Copyright © 2014 Elsevier Ltd. All rights reserved.

Bacillus Strains Most Closely Related to Bacillus nealsonii Are Not Effectively Circumscribed within the Taxonomic Species Definition

PubMed Central

Peak, K. Kealy; Duncan, Kathleen E.; Luna, Vicki A.; King, Debra S.; McCarthy, Peter J.; Cannons, Andrew C.

2011-01-01

Bacillus strains with >99.7% 16S rRNA gene sequence similarity were characterized with DNA:DNA hybridization, cellular fatty acid (CFA) analysis, and testing of 100 phenotypic traits. When paired with the most closely related type strain, percent DNA:DNA similarities (% S) for six Bacillus strains were all far below the recommended 70% threshold value for species circumscription with Bacillus nealsonii. An apparent genomic group of four Bacillus strain pairings with 94%–70% S was contradicted by the failure of the strains to cluster in CFA- and phenotype-based dendrograms as well as by their differentiation with 9–13 species level discriminators such as nitrate reduction, temperature range, and acid production from carbohydrates. The novel Bacillus strains were monophyletic and very closely related based on 16S rRNA gene sequence. Coherent genomic groups were not however supported by similarly organized phenotypic clusters. Therefore, the strains were not effectively circumscribed within the taxonomic species definition. PMID:22046187

Nanowires Bending over Backward from Strain Partitioning in Asymmetric Core-Shell Heterostructures.

PubMed

Lewis, Ryan B; Corfdir, Pierre; Küpers, Hanno; Flissikowski, Timur; Brandt, Oliver; Geelhaar, Lutz

2018-04-11

The flexibility and quasi-one-dimensional nature of nanowires offer wide-ranging possibilities for novel heterostructure design and strain engineering. In this work, we realize arrays of extremely and controllably bent nanowires comprising lattice-mismatched and highly asymmetric core-shell heterostructures. Strain sharing across the nanowire heterostructures is sufficient to bend vertical nanowires over backward to contact either neighboring nanowires or the substrate itself, presenting new possibilities for designing nanowire networks and interconnects. Photoluminescence spectroscopy on bent-nanowire heterostructures reveals that spatially varying strain fields induce charge carrier drift toward the tensile-strained outside of the nanowires, and that the polarization response of absorbed and emitted light is controlled by the bending direction. This unconventional strain field is employed for light emission by placing an active region of quantum dots at the outer side of a bent nanowire to exploit the carrier drift and tensile strain. These results demonstrate how bending in nanoheterostructures opens up new degrees of freedom for strain and device engineering.

Strain engineering on electronic structure and carrier mobility in monolayer GeP3

NASA Astrophysics Data System (ADS)

Zeng, Bowen; Long, Mengqiu; Zhang, Xiaojiao; Dong, Yulan; Li, Mingjun; Yi, Yougen; Duan, Haiming

2018-06-01

Using density functional theory coupled with the Boltzmann transport equation with relaxation time approximation, we have studied the strain effect on the electronic structure and carrier mobility of two-dimensional monolayer GeP3. We find that the energies of valence band maximum and conduction band minimum are nearly linearly shifted with a biaxial strain in the range of  ‑4% to 6%, and the band structure experiences a remarkable transition from semiconductor to metal with the appropriate compression (‑5% strain). Under biaxial strain, the mobility of the electron and hole in monolayer GeP3 reduces and increases by more than one order of magnitude, respectively. It is suggested that it is possible to perform successive transitions from an n-type semiconductor (‑4% strain) to a good performance p-semiconductor (+6% strain) by applying strain in monolayer GeP3, which is potentially useful for flexible electronics and nanosized mechanical sensors.

Aspects of three-dimensional strain at the margin of the extensional orogen, Virgin River depression area, Nevada, Utah, and Arizona

USGS Publications Warehouse

Anderson, R.E.; Barnhard, T.P.

1993-01-01

The Virgin River depression and surrounding mountains are Neogene features that are partly contiguous with the little-strained rocks of the structural transition to the Colorado Plateau province. This contiguity makes the area ideally suited for evaluating the sense, magnitude, and kinematics of Neogene deformation. Analysis along the strain boundary shows that, compared to the adjacent little-strained area, large-magnitude vertical deformation greatly exceeds extensional deformation and that significant amounts of lateral displacement approximately parallel the province boundary. Isostatic rebound following tectonic denudation is an unlikely direct cause of the strong vertical structural relief adjacent to the strain boundary. Instead, the observed structures are first-order features defining a three-dimensional strain field produced by approximately east-west extension, vertical structural attenuation, and extension-normal shortening. All major structural elements of the strain-boundary strain field are also found in the adjacent Basin and Range. -from Authors

Influence of strain rate and temperature on tensile properties and flow behaviour of a reduced activation ferritic-martensitic steel

NASA Astrophysics Data System (ADS)

Vanaja, J.; Laha, K.; Sam, Shiju; Nandagopal, M.; Panneer Selvi, S.; Mathew, M. D.; Jayakumar, T.; Rajendra Kumar, E.

2012-05-01

Tensile strength and flow behaviour of a Reduced Activation Ferritic-Martensitic (RAFM) steel (9Cr-1W-0.06Ta-0.22V-0.08C) have been investigated over a temperature range of 300-873 K at different strain rates. Tensile strength of the steel decreased with temperature and increased with strain rate except at intermediate temperatures. Negative strain rate sensitivity of flow stress of the steel at intermediate temperatures revealed the occurrence of dynamic strain ageing in the steel, even though no serrated flow was observed. The tensile flow behaviour of the material was well represented by the Voce strain hardening equation for all the test conditions. Temperature and strain rate dependence of the various parameters of Voce equation were interpreted with the possible deformation mechanisms. The equivalence between the saturation stress at a given strain rate in tensile test and steady state deformation rate at a given stress in creep test was found to be satisfied by the RAFM steel.

Formability analysis of sheet metals by cruciform testing

NASA Astrophysics Data System (ADS)

Güler, B.; Alkan, K.; Efe, M.

2017-09-01

Cruciform biaxial tests are increasingly becoming popular for testing the formability of sheet metals as they achieve frictionless, in-plane, multi-axial stress states with a single sample geometry. However, premature fracture of the samples during testing prevents large strain deformation necessary for the formability analysis. In this work, we introduce a miniature cruciform sample design (few mm test region) and a test setup to achieve centre fracture and large uniform strains. With its excellent surface finish and optimized geometry, the sample deforms with diagonal strain bands intersecting at the test region. These bands prevent local necking and concentrate the strains at the sample centre. Imaging and strain analysis during testing confirm the uniform strain distributions and the centre fracture are possible for various strain paths ranging from plane-strain to equibiaxial tension. Moreover, the sample deforms without deviating from the predetermined strain ratio at all test conditions, allowing formability analysis under large strains. We demonstrate these features of the cruciform test for three sample materials: Aluminium 6061-T6 alloy, DC-04 steel and Magnesium AZ31 alloy, and investigate their formability at both the millimetre scale and the microstructure scale.

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.

Anti-Candida activity of fluoxetine alone and combined with fluconazole: a synergistic action against fluconazole-resistant strains.

PubMed

Oliveira, Ana S; Gaspar, Carlos A; Palmeira-de-Oliveira, Rita; Martinez-de-Oliveira, José; Palmeira-de-Oliveira, Ana

2014-07-01

The purpose of this work was to determine the antimicrobial activity of fluoxetine, alone and combined with fluconazole, against 29 Candida strains isolated from patients with vulvovaginal candidiasis. MIC and minimum lethal concentration values ranged from 9.8 to 625 μg/ml for all strains tested. The combination of fluconazole with fluoxetine resulted in synergistic activity against six Candida strains, with fractional inhibitory index (FIX) values between 0.15 and 0.31. An indifferent effect was found for the remaining strains, with FIX values between 0.63 and 1. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

Abnormal Strain Rate Sensitivity Driven by a Unit Dislocation-Obstacle Interaction in bcc Fe

NASA Astrophysics Data System (ADS)

Bai, Zhitong; Fan, Yue

2018-03-01

The interaction between an edge dislocation and a sessile vacancy cluster in bcc Fe is investigated over a wide range of strain rates from 108 down to 103 s-1 , which is enabled by employing an energy landscape-based atomistic modeling algorithm. It is observed that, at low strain rates regime less than 105 s-1 , such interaction leads to a surprising negative strain rate sensitivity behavior because of the different intermediate microstructures emerged under the complex interplays between thermal activation and applied strain rate. Implications of our findings regarding the previously established global diffusion model are also discussed.

A Dual-Range Strain Gage Weighing Transducer Employing Automatic Switching

Treesearch

Rodger A. Arola

1968-01-01

Describes a dual-range strain gage transducer which has proven to be an excellent weight-sensing device for weighing trees and tree-length logs; discusses basic principals of the design and operation; and shows that a single transducer having two sensitivity ranges with automatic internal switching can sense weight with good repeatability and that one calibration curve...

Prediction of Mechanical Behaviour of Low Carbon Steel at High Strain Rate Using Thermal Activation Theory and Static Data

NASA Astrophysics Data System (ADS)

Ogawa, Kinya; Kobayashi, Hidetoshi; Sugiyama, Fumiko; Horikawa, Keitaro

Thermal activation theory is well-known to be a useful theory to explain the mechanical behaviour of various metals in the wide range of temperature and strain-rate. In this study, a number of trials to obtain the lower yield stress or flow stress at high strain rates from quasi-static data were carried out using the data shown in the report titled “The final report of research group on high-speed deformation of steels for automotive use”. A relation between the thermal component of stress and the strain rate obtained from experiments for αFe and the temperature-strain rate parameter were used with thermal activation theory. The predictions were successfully performed and they showed that the stress-strain behaviour at high strain rates can be evaluated from quasi-static data with good accuracy.

High strain rate properties of off-axis composite laminates, part 2

NASA Technical Reports Server (NTRS)

Daniel, I. M.

1991-01-01

Unidirectional off-axis graphite/epoxy and graphite/S-glass/epoxy laminates were characterized in uniaxial tension at strain rates ranging from quasi-static to over 500 s(sup -1). Laminate ring specimens were loaded by internal pressure with the tensile stress at 22.5, 30, and 45 degrees relative to the fiber direction. Results were presented in the form of stress-strain curves to failure. Properties determined included moduli, Poisson's ratios, strength, and ultimate strain. In all three laminates of both materials the modulus and strength increase sharply with strain rate, reaching values roughly 100, 150, and 200 percent higher than corresponding static values for the 22.5(sub 8), 30(sub 8), and 45(sub 8) degree laminates, respectively. In the case of ultimate strain no definite trends could be established, but the maximum deviation from the average of any value for any strain rate was less than 18 percent.

Phylogenetic analysis of canine distemper virus in domestic dogs in Nanjing, China.

PubMed

Bi, Zhenwei; Wang, Yongshan; Wang, Xiaoli; Xia, Xingxia

2015-02-01

Canine distemper virus (CDV) infects a broad range of carnivores, including wild and domestic Canidae. The hemagglutinin gene, which encodes the attachment protein that determines viral tropism, has been widely used to determine the relationship between CDV strains of different lineages circulating worldwide. We determined the full-length H gene sequences of seven CDV field strains detected in domestic dogs in Nanjing, China. A phylogenetic analysis of the H gene sequences of CDV strains from different geographic regions and vaccine strains was performed. Four of the seven CDV strains were grouped in the same cluster of the Asia-1 lineage to which the vast majority of Chinese CDV strains belong, whereas the other three were clustered within the Asia-4 lineage, which has never been detected in China. This represents the first record of detection of strains of the Asia-4 lineage in China since this lineage was reported in Thailand in 2013.

Temperature and Strain-Rate Effects on Low-Cycle Fatigue Behavior of Alloy 800H

NASA Technical Reports Server (NTRS)

Rao, K. Bhanu Sankara; Schiffers, H.; Schuster, H.; Halford, G. R.

1996-01-01

The effects of strain rate (4 x 10(exp -6) to 4 x 10(exp -3)/s) and temperature on the Low-Cycle Fatigue (LCF) behavior of alloy 800H have been evaluated in the range 750 C to 950 C. Total axial strain controlled LCF tests were conducted in air at a strain amplitude of +/- 0.30 pct. LCF life decreased with decreasing strain rate and increasing temperature. The cyclic stress response behavior showed a marked variation with temperature and strain rate. The time- and temperature- dependent processes which influence the cyclic stress response and life have been identified and their relative importance assessed. Dynamic strain aging, time-dependent deformation, precipitation of parallel platelets of M(23)C6 on grain boundaries and incoherent ledges of twins, and oxidation were found to operate depending on the test conditions. The largest effect on life was shown by oxidation processes.

Effect of Elastic Strain Fluctuation on Atomic Layer Growth of Epitaxial Silicide in Si Nanowires by Point Contact Reactions.

PubMed

Chou, Yi-Chia; Tang, Wei; Chiou, Chien-Jyun; Chen, Kai; Minor, Andrew M; Tu, K N

2015-06-10

Effects of strain impact a range of applications involving mobility change in field-effect-transistors. We report the effect of strain fluctuation on epitaxial growth of NiSi2 in a Si nanowire via point contact and atomic layer reactions, and we discuss the thermodynamic, kinetic, and mechanical implications. The generation and relaxation of strain shown by in situ TEM is periodic and in synchronization with the atomic layer reaction. The Si lattice at the epitaxial interface is under tensile strain, which enables a high solubility of supersaturated interstitial Ni atoms for homogeneous nucleation of an epitaxial atomic layer of the disilicide phase. The tensile strain is reduced locally during the incubation period of nucleation by the dissolution of supersaturated Ni atoms in the Si lattice but the strained-Si state returns once the atomic layer epitaxial growth of NiSi2 occurs by consuming the supersaturated Ni.

Virulent strain of African swine fever virus eclipses its attenuated derivative after challenge.

PubMed

Titov, Ilya; Burmakina, Galina; Morgunov, Yuriy; Morgunov, Sergey; Koltsov, Andrey; Malogolovkin, Alexander; Kolbasov, Denis

2017-10-01

African swine fever (ASF) is one of the most devastating diseases affecting the swine industry worldwide. No effective vaccine is currently available for disease prevention and control. Although live attenuated vaccines (LAV) have demonstrated great potential for immunizing against homologous strains of African swine fever virus (ASFV), adverse reactions from LAV remain a concern. Here, by using a homologous ASFV Congo strain system, we show passage-attenuated Congo LAV to induce an efficient protective immune response against challenge with the virulent parental Congo strain. Notably, only the parental challenge Congo strain was identified in blood and organs of recovered pigs through B602L gene PCR, long-range PCR, nucleotide sequencing and virus isolation. Thus, despite the great protective potential of homologous attenuated ASFV strain, the challenge Congo strain can persist for weeks in recovered pigs and a recrudescence of virulent virus at late time post-challenge may occur.

Structure of the circumsporozoite protein gene in 18 strains of Plasmodium falciparum.

PubMed

Weber, J L; Hockmeyer, W T

1985-06-01

Using the cloned circumsporozoite (CS) protein gene of a Brazilian strain of Plasmodium falciparum as probe, we have analyzed the structure of the CS protein gene from 17 other Asian, African, Central and South American parasite strains by nucleic acid hybridization. Each strain appears to have one CS protein gene which hybridizes readily to the Brazilian strain probe. The 5' and 3' thirds of the genes are invariant in size in all 18 strains whereas the central third containing the 12 base pair tandem repeats varies in size over a range of about 100 base pairs. Several differences were found in the locations of Sau3A sites in the genes. The Sau3A sites are significant because each of the minority Asn-Val-Asp-Pro repeats in the cloned gene has a Sau3A site. DNA melting of hybrids revealed a high degree of homology between the sequences of the cloned gene and genes from an Asian strain and an African strain. A 14 base oligodeoxynucleotide with a sequence from the central repeat region hybridized to all strains tested. We conclude that the CS protein gene is highly conserved among strains of P. falciparum and that malaria vaccine development with the CS protein is unlikely to be complicated by strain variation.

Adhesive properties of environmental Vibrio alginolyticus strains to biotic and abiotic surfaces.

PubMed

Snoussi, Mejdi; Noumi, Emira; Cheriaa, Jihane; Usai, Donatella; Sechi, Leonardo Antonio; Zanetti, Stefania; Bakhrouf, Amina

2008-10-01

The ability of Vibrio alginolyticus strains isolated from a bathing and fishing area (Khenis, Centre of Tunisia) to adhere to both biotic and abiotic surfaces was evaluated in the present work. The biochemical, physiological and enzymatic activities of all strains was also investigated. Three morphotypes of V. alginolyticus were obtained on Congo red agar and only 14 strains produced black colonies. The majority of strains were able to degrade the skin mucus of both Sparus aurata and Dicentrarchus labrax fishes while the fish mucus preparation of these two specimens exhibits a high level of anti-V. alginolyticus strains. Adhesive properties were observed in 37.5% of the analyzed V. alginolyticus strains to Hep-2 cells and 50% to Caco-2 cells. All strains were able to form a purple pellicule on glass tube when they were stained with Crystal violet. Fifteen percent of V. alginolyticus strains (16/32) were strongly adhesive to polystyrene with a values ranging from 3.04 to 18.25 at 595 nm and only four strains were weak biofilm forming. V. alginolyticus bacterium possess a strong adhesive power to both biotic and inertes surfaces. These proprieties may allow to these strains to persist in this biotope in planctonic state or attached to both biotic and abiotic surfaces.

Morphological characterization and molecular fingerprinting of Nostoc strains by multiplex RAPD.

PubMed

Hillol, Chakdar; Pabbi, Sunil

2012-01-01

Morphological parameters studied for the twenty selected Nostoc strains were mostly found to be consistent with the earlier reports. But the shape of akinetes observed in this study was a little deviation from the existing descriptions and heterocyst frequency was also found to be different in different strains in spite of growing in the same nitrogen free media. Multiplex RAPD produced reproducible and completely polymorphic amplification profiles for all the strains including some strain specific unique bands which are intended to be useful for identification of those strains. At least one to a maximum of two unique bands was produced by different dual primer combinations. For ten strains out of twenty, strain specific bands were found to be generated. Cluster analysis revealed a vast heterogeneity among these Nostoc strains and no specific clustering based on geographical origin was found except a few strains. It was also observed that morphological data may not necessarily correspond to the genetic data in most of the cases. CCC92 (Nostoc muscorum) and CCC48 (Nostoc punctiforme) showed a high degree of similarity which was well supported by high bootstrap value. The level of similarity of the strains ranged from 0.15 to 0.94. Cluster analysis based on multiplex RAPD showed a good fit revealing the discriminatory power of this technique.

Strain Hardening Behaviour and Its Effect on Properties of ZrB2 Reinforced Al Composite Prepared by Powder Metallurgy Technique

NASA Astrophysics Data System (ADS)

Kaku, Sai Mahesh Yadav; Khanra, Asit Kumar; Davidson, M. J.

2018-04-01

Strain hardening behaviour has significant effect on altering the properties of materials. In the present study, Al-ZrB2 metal matrix composites are made through powder metallurgy route. Incremental weight percentage (wt%) of ZrB2 (0, 2, 4 and 6 wt%) are added to Aluminium matrix to produce different composites. The homogenous powder mixture is compacted and pressurelessly sintered. Sintering of composites is performed over a range of 450-575 °C. The optimized sintered condition is observed at 550 °C for 1 h in controlled atmosphere (argon gas flow). The sintered compacts are strained in incremental steps in different levels up to failure. A visible crack on the bulge of the powder preform is considered as the failure. Composites are strain hardened up to failure. To evaluate the effect of temperature on strain hardening, strain hardening is carried out at different temperatures. Composites are densified with the extent of straining and hardness increases with the increase of strain. Hardness increase with the increase in temperature is maintained during strain hardening. To evaluate the corrosion behaviour of Al-ZrB2 composite, potentiodynamic polarization study are performed on the strained composites. Corrosion rate decrease with the extent of straining.

Dynamic tuning of chemiresistor sensitivity using mechanical strain

DOEpatents

Martin, James E; Read, Douglas H

2014-09-30

The sensitivity of a chemiresistor sensor can be dynamically tuned using mechanical strain. The increase in sensitivity is a smooth, continuous function of the applied strain, and the effect can be reversible. Sensitivity tuning enables the response curve of the sensor to be dynamically optimized for sensing analytes, such as volatile organic compounds, over a wide concentration range.

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.

Bathythermal distribution, maturity, and growth of lake trout strains stocked in U.S. waters of Lake Ontario, 1978-1993

USGS Publications Warehouse

Elrod, Joseph H.; O'Gorman, Robert; Schneider, Clifford P.

1996-01-01

Bathythermal distributions, sexual maturity, and growth of lake trout (Salvelinus namaycush) strains stocked in Lake Ontario were determined for fish collected with trawls and gill nets in 1978-93. The purpose was to augment the basis for deciding which strains to continue stocking in an effort to reestablish a self-sustaining population. The Clearwater Lake (CWL) strain was found in shallower, warmer water than all other strains; the Seneca Lake (SEN) strain was usually shallower than the Jenny Lake (JEN) and Lake Superior (SUP) strains at ages 1 and 2 but was usually deeper at age 3 and older. Depth distribution of the 'Ontario strain'--from gametes of several strains that survived to maturity in Lake Ontario-- was similar to that of the SEN and SUP strains. About half the males matured at age 4 and half the females at age 5; males < 500 mm and females < 600 mm long were rarely mature. Least-sqaures mean lengths and weights of the CWL strain were greater than those of all other strains through age 4. At age 7 and older, CWL and JEN fish were generally smaller than all other strains. Means lengths and weights of males and females of the same age and strain frequently differed at age 4 and older. Growth in weight at age 4 and older was not associated with biomass indices of prey fishes. Differences in growth rates among strains were associated with bathythermal distribution which is a heritable trait. Weight-length regressions differed by year, sex, and stage of maturity but were rarely different among strains. Competition for space appeared to affect condition of large lake trout. Growth rates and maturity schedules provide little basis for recommending stocking one strain in preference to another. Depth ranges of strains overlapped widely, but lake trout occupied only about one-fourth of available bottom habitat. Stocking several strains should be continued to maximize use of sustainable habitat.

Strain rate sensitivity of a TRIP-assisted dual-phase high-entropy alloy

NASA Astrophysics Data System (ADS)

Basu, Silva; Li, Zhiming; Pradeep, K. G.; Raabe, Dierk

2018-05-01

Dual-phase high-entropy alloys (DP-HEAs) with transformation induced plasticity (TRIP) have an excellent strength-ductility combination. To reveal their strain-rate sensitivity and hence further understand the corresponding deformation mechanisms, we investigated the tensile behavior and microstructural evolution of a typical TRIP-DP-HEA (Fe50Mn30Co10Cr10, at. %) under different strain rates (i.e., 5 × 10-3 s-1, 1 × 10-3 s-1, 5 × 10-4 s-1 and 1 × 10-4 s-1) at room temperature. The strain rate range was confined to this regime in order to apply the digital image correlation technique for probing the local strain evolution during tensile deformation at high resolution and to correlate it to the microstructure evolution. Grain size effects of the face-centered cubic (FCC) matrix and the volume fractions of the hexagonal-close packed (HCP) phase prior to deformation were also considered. The results show that within the explored strain rate regime the TRIP-DP-HEA has a fairly low strain rate sensitivity parameter within the range from 0.004 to 0.04, which is significantly lower than that of DP and TRIP steels. Samples with varying grain sizes (e.g., 2.8 μm and 38 μm) and starting HCP phase fractions (e.g., 25% and 72%) at different strain rates show similar deformation mechanisms, i.e., dislocation plasticity and strain-induced transformation from the FCC matrix to the HCP phase. The low strain rate sensitivity is attributed to the observed dominant displacive transformation mechanism. Also, the coarse-grained alloy samples with a very high starting HCP phase fraction ( 72%) prior to deformation show very good ductility with a total elongation of 60%, suggesting that both, the initial and the transformed HCP phase in the TRIP-DP-HEA are ductile and deform further via dislocation slip at the different strain rates which were probed.

Microbial control of hydrogen sulfide production

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

Montgomery, A.D.; Bhupathiraju, V.K.; Wofford, N.

1995-12-31

A sulfide-resistant strain of Thiobacillus denitrificans, strain F, prevented the accumulation of sulfide by Desulfovibrio desulfuricans when both organisms were grown in liquid medium. The wild-type strain of T. denitrificans did not prevent the accumulation of sulfide produced by D. desulfuricans. Strain F also prevented the accumulation of sulfide by a mixed population of sulfate-reducing bacteria enriched from an oil field brine. Fermentation balances showed that strain F stoichiometrically oxidized the sulfide produced by D. desulfuricans and the oil field brine enrichment to sulfate. The ability of a strain F to control sulfide production in an experimental system of coresmore » and formation water from the Redfield, Iowa, natural gas storage facility was also investigated. A stable, sulfide-producing biofilm was established in two separate core systems, one of which was inoculated with strain F while the other core system (control) was treated in an identical manner, but was not inoculated with strain F. When formation water with 10 mM acetate and 5 mM nitrate was injected into both core systems, the effluent sulfide concentrations in the control core system ranged from 200 to 460 {mu}M. In the test core system inoculated with strain F, the effluent sulfide concentrations were lower, ranging from 70 to 110 {mu}M. In order to determine whether strain F could control sulfide production under optimal conditions for sulfate-reducing bacteria, the electron donor was changed to lactate and inorganic nutrients (nitrogen and phosphate sources) were added to the formation water. When nutrient-supplemented formation water with 3.1 mM lactate and 10 mM nitrate was used, the effluent sulfide concentrations of the control core system initially increased to about 3,800 {mu}M, and then decreased to about 1,100 {mu}M after 5 weeks. However, in the test core system inoculated with strain F, the effluent sulfide concentrations were much lower, 160 to 330 {mu}M.« less

Simultaneous Presence of PrtH and PrtH2 Proteinases in Lactobacillus helveticus Strains Improves Breakdown of the Pure αs1-Casein▿ †

PubMed Central

Sadat-Mekmene, L.; Jardin, J.; Corre, C.; Mollé, D.; Richoux, R.; Delage, M.-M.; Lortal, S.; Gagnaire, V.

2011-01-01

Lactobacillus helveticus can possess one or two cell envelope proteinases (CEPs), called PrtH2 and PrtH. The aim of this work was to explore the diversity of 15 strains of L. helveticus, isolated from various origins, in terms of their proteolytic activities and specificities on pure caseins or on milk casein micelles. CEP activity differed 14-fold when the strains were assayed on a synthetic substrate, but no significant differences were detected between strains possessing one or two CEPs. No correlation was observed between the proteolytic activities of the strains and their rates of acidification in milk. The kinetics of hydrolysis of purified αs1- and β-casein by L. helveticus whole cells was monitored using Tris-Tricine sodium dodecyl sulfate (SDS) electrophoresis, and for four strains, the peptides released were identified using mass spectrometry. While rapid hydrolysis of pure β-casein was observed for all strains, the hydrolysis kinetics of αs1-casein was the only criterion capable of distinguishing between the strains based on the number of CEPs. Fifty-four to 74 peptides were identified for each strain. When only PrtH2 was present, 22 to 30% of the peptides originated from αs1-casein. The percentage increased to 41 to 49% for strains in which both CEPs were expressed. The peptide size ranged from 6 to 33 amino acids, revealing a broad range of cleavage specificities, involving all classes of amino acids (Leu, Val, Ala, Ile, Glu, Gln, Lys, Arg, Met, and Pro). Regions resistant to proteolysis were identified in both caseins. When strains were grown in milk, a drastic reduction in the number of peptides was observed, reflecting changes in accessibility and/or peptide assimilation during growth. PMID:21037305

Dynamic Behavior of AA2519-T8 Aluminum Alloy Under High Strain Rate Loading in Compression

NASA Astrophysics Data System (ADS)

Olasumboye, A. T.; Owolabi, G. M.; Odeshi, A. G.; Yilmaz, N.; Zeytinci, A.

2018-06-01

In this study, the effects of strain rate on the dynamic behavior, microstructure evolution and hence, failure of the AA2519-T8 aluminum alloy were investigated under compression at strain rates ranging from 1000 to 3500 s-1. Cylindrical specimens of dimensions 3.3 mm × 3.3 mm (L/D = 1) were tested using the split-Hopkinson pressure bar integrated with a digital image correlation system. The microstructure of the alloy was assessed using optical and scanning electron microscopes. Results showed that the dynamic yield strength of the alloy is strain rate dependent, with the maximum yield strength attained by the material being 500 MPa. The peak flow stress of 562 MPa was attained by the material at 3500 s-1. The alloy also showed a significant rate of strain hardening that is typical of other Al-Cu alloys; the rate of strain hardening, however, decreased with increase in strain rate. It was determined that the strain rate sensitivity coefficient of the alloy within the range of high strain rates used in this study is approximately 0.05 at 0.12 plastic strain; a more significant value than what was reported in literature under quasi-static loading. Micrographs obtained showed potential sites for the evolution of adiabatic shear band at 3500 s-1, with a characteristic circular-shaped surface profile comprising partially dissolved second phase particles in the continuous phase across the incident plane of the deformed specimen. The regions surrounding the site showed little or no change in the size of particles. However, the constituent coarse particles were observed as agglomerations of fractured pieces, thus having a shape factor different from those contained in the as-received alloy. Since the investigated alloy is a choice material for military application where it can be exposed to massive deformation at high strain rates, this study provides information on its microstructural and mechanical responses to such extreme loading condition.

Dynamic Behavior of AA2519-T8 Aluminum Alloy Under High Strain Rate Loading in Compression

NASA Astrophysics Data System (ADS)

Olasumboye, A. T.; Owolabi, G. M.; Odeshi, A. G.; Yilmaz, N.; Zeytinci, A.

2018-02-01

In this study, the effects of strain rate on the dynamic behavior, microstructure evolution and hence, failure of the AA2519-T8 aluminum alloy were investigated under compression at strain rates ranging from 1000 to 3500 s-1. Cylindrical specimens of dimensions 3.3 mm × 3.3 mm (L/D = 1) were tested using the split-Hopkinson pressure bar integrated with a digital image correlation system. The microstructure of the alloy was assessed using optical and scanning electron microscopes. Results showed that the dynamic yield strength of the alloy is strain rate dependent, with the maximum yield strength attained by the material being 500 MPa. The peak flow stress of 562 MPa was attained by the material at 3500 s-1. The alloy also showed a significant rate of strain hardening that is typical of other Al-Cu alloys; the rate of strain hardening, however, decreased with increase in strain rate. It was determined that the strain rate sensitivity coefficient of the alloy within the range of high strain rates used in this study is approximately 0.05 at 0.12 plastic strain; a more significant value than what was reported in literature under quasi-static loading. Micrographs obtained showed potential sites for the evolution of adiabatic shear band at 3500 s-1, with a characteristic circular-shaped surface profile comprising partially dissolved second phase particles in the continuous phase across the incident plane of the deformed specimen. The regions surrounding the site showed little or no change in the size of particles. However, the constituent coarse particles were observed as agglomerations of fractured pieces, thus having a shape factor different from those contained in the as-received alloy. Since the investigated alloy is a choice material for military application where it can be exposed to massive deformation at high strain rates, this study provides information on its microstructural and mechanical responses to such extreme loading condition.

Characterization and probiotic potential of Lactobacillus plantarum strains isolated from cheeses.

PubMed

Zago, Miriam; Fornasari, Maria Emanuela; Carminati, Domenico; Burns, Patricia; Suàrez, Viviana; Vinderola, Gabriel; Reinheimer, Jorge; Giraffa, Giorgio

2011-08-01

Ninety-eight Lactobacillus plantarum strains isolated from Italian and Argentinean cheeses were evaluated for probiotic potential. After a preliminary subtractive screening based on the presence of msa and bsh genes, 27 strains were characterized. In general, the selected strains showed high resistance to lysozyme, good adaptation to simulated gastric juice, and a moderate to low bile tolerance. The capacity to agglutinate yeast cells in a mannose-specific manner, as well as the cell surface hydrophobicity was found to be variable among strains. Very high β-galactosidase activity was shown by a considerable number of the tested strains, whereas variable prebiotic utilization ability was observed. Only tetracycline resistance was observed in two highly resistant strains which harbored the tetM gene, whereas none of the strains showed β-glucuronidase activity or was capable of inhibiting pathogens. Three strains (Lp790, Lp813, and Lp998) were tested by in vivo trials. A considerable heterogeneity was found among a number of L. plantarum strains screened in this study, leading to the design of multiple cultures to cooperatively link strains showing the widest range of useful traits. Among the selected strains, Lp790, Lp813, and Lp998 showed the best probiotic potential and would be promising candidates for inclusion as starter cultures for the manufacture of probiotic fermented foods. Copyright © 2011 Elsevier Ltd. All rights reserved.

Genetic variation of viral protein 1 genes of field strains of waterfowl parvoviruses and their attenuated derivatives.

PubMed

Tsai, Hsiang-Jung; Tseng, Chun-hsien; Chang, Poa-chun; Mei, Kai; Wang, Shih-Chi

2004-09-01

To understand the genetic variations between the field strains of waterfowl parvoviruses and their attenuated derivatives, we analyzed the complete nucleotide sequences of the viral protein 1 (VP1) genes of nine field strains and two vaccine strains of waterfowl parvoviruses. Sequence comparison of the VP1 proteins showed that these viruses could be divided into goose parvovirus (GPV) related and Muscovy duck parvovirus (MDPV) related groups. The amino acid difference between GPV- and MDPV-related groups ranged from 13.1% to 15.8%, and the most variable region resided in the N terminus of VP2. The vaccine strains of GPV and MDPV exhibited only 1.2% and 0.3% difference in amino acid when compared with their parental field strains, and most of these differences resided in residues 497-575 of VP1, suggesting that these residues might be important for the attenuation of GPV and MDPV. When the GPV strains isolated in 1982 (the strain 82-0308) and in 2001 (the strain 01-1001) were compared, only 0.3% difference in amino acid was found, while MDPV strains isolated in 1990 (the strain 90-0219) and 1997 (the strain 97-0104) showed only 0.4% difference in amino acid. The result indicates that the genome of waterfowl parvovirus had remained highly stable in the field.

High Temperature - Thin Film Strain Gages Based on Alloys of Indium Tin Oxide

NASA Technical Reports Server (NTRS)

Gregory, Otto J.; Cooke, James D.; Bienkiewicz, Joseph M.

1998-01-01

A stable, high temperature strain gage based on reactively sputtered indium tin oxide (ITO) was demonstrated at temperatures up to 1050 C. These strain sensors exhibited relatively large, negative gage factors at room temperature and their piezoresistive response was both linear and reproducible when strained up to 700 micro-in/in. When cycled between compression and tension, these sensors also showed very little hysteresis, indicating excellent mechanical stability. Thin film strain gages based on selected ITO alloys withstood more than 50,000 strain cycles of +/- 500 micro-in/in during 180 hours of testing in air at 1000 C, with minimal drift at temperature. Drift rates as low as 0.0009%/hr at 1000 C were observed for ITO films that were annealed in nitrogen at 700 C prior to strain testing. These results compare favorably with state of the art 10 micro-m thick PdCr films deposited by NASA, where drift rates of 0.047%/hr at 1050 C were observed. Nitrogen annealing not only produced the lowest drift rates to date, but also produce the largest dynamic gage factors (G = 23.5). These wide bandgap, semiconductor strain sensors also exhibited moderately low temperature coefficients of resistance (TCR) at temperatures up to 1100 C, when tested in a nitrogen ambient. A TCR of +230 ppm/C over the temperature range 200 C < T < 500 C and a TCR of -469 ppm/C over the temperature range 600 C < T < 1100 C was observed for the films tested in nitrogen. However, the resistivity behavior changed considerably when the same films were tested in oxygen ambients. A TCR of -1560 ppm/C was obtained over the temperature range of 200 C < T < 1100 C. When similar films were protected with an overcoat or when ITO films were prepared with higher oxygen contents in the plasma, two distinct TCR's were observed. At T < 800 C, a linear TCR of -210 ppm/C was observed and at T > 800 C, a linear TCR of -2170 DDm/C was observed. The combination of a moderately low TCR and a relatively large gage factor make these semiconducting oxide films promising candidates for the active strain elements in high temperature thin film strain gages, particularly in applications where static strain measurement is desired.

The Features of Fracture Behavior of an Aluminum-Magnesium Alloy AMg6 Under High-Rate Straining

NASA Astrophysics Data System (ADS)

Skripnyak, N. V.

2015-09-01

The results of investigation of fracture dynamics of rolled sheet specimens of an AMg6 alloy are presented for the range of strain rates from 10-3 to 103 s-1. It is found out that the presence of nanostructured surface layers on the thin AMg6 rolled sheets results in improved strength characteristics within the above range of strain rates. A modified model of a deforming medium is proposed to describe the plastic flow and fracture of the AMg6 alloy.

Swept optical SSB-SC modulation technique for high-resolution large-dynamic-range static strain measurement using FBG-FP sensors.

PubMed

Huang, Wenzhu; Zhang, Wentao; Li, Fang

2015-04-01

This Letter presents a static strain demodulation technique for FBG-FP sensors using a suppressed carrier LiNbO(3) (LN) optical single sideband (SSB-SC) modulator. A narrow-linewidth tunable laser source is generated by driving the modulator using a linear chirp signal. Then this tunable single-frequency laser is used to interrogate the FBG-FP sensors with the Pound-Drever-Hall (PDH) technique, which is beneficial to eliminate the influence of light intensity fluctuation of the modulator at different tuning frequencies. The static strain is demodulated by calculating the wavelength difference of the PDH signals between the sensing FBG-FP sensor and the reference FBG-FP sensor. As an experimental result using the modulator, the linearity (R²) of the time-frequency response increases from 0.989 to 0.997, and the frequency-swept range (dynamic range) increases from hundreds of MHz to several GHz compared with commercial PZT-tunable lasers. The high-linearity time-wavelength relationship of the modulator is beneficial for improving the strain measurement resolution, as it can solve the problem of the frequency-swept nonlinearity effectively. In the laboratory test, a 0.67 nanostrain static strain resolution, with a 6 GHz dynamic range, is demonstrated.

Soft network materials with isotropic negative Poisson's ratios over large strains.

PubMed

Liu, Jianxing; Zhang, Yihui

2018-01-31

Auxetic materials with negative Poisson's ratios have important applications across a broad range of engineering areas, such as biomedical devices, aerospace engineering and automotive engineering. A variety of design strategies have been developed to achieve artificial auxetic materials with controllable responses in the Poisson's ratio. The development of designs that can offer isotropic negative Poisson's ratios over large strains can open up new opportunities in emerging biomedical applications, which, however, remains a challenge. Here, we introduce deterministic routes to soft architected materials that can be tailored precisely to yield the values of Poisson's ratio in the range from -1 to 1, in an isotropic manner, with a tunable strain range from 0% to ∼90%. The designs rely on a network construction in a periodic lattice topology, which incorporates zigzag microstructures as building blocks to connect lattice nodes. Combined experimental and theoretical studies on broad classes of network topologies illustrate the wide-ranging utility of these concepts. Quantitative mechanics modeling under both infinitesimal and finite deformations allows the development of a rigorous design algorithm that determines the necessary network geometries to yield target Poisson ratios over desired strain ranges. Demonstrative examples in artificial skin with both the negative Poisson's ratio and the nonlinear stress-strain curve precisely matching those of the cat's skin and in unusual cylindrical structures with engineered Poisson effect and shape memory effect suggest potential applications of these network materials.

Trichomonas vaginalis Contact-Dependent Cytolysis of Epithelial Cells

PubMed Central

Lustig, Gila; Ryan, Christopher M.; Secor, W. Evan

2013-01-01

Trichomonas vaginalis is an extracellular protozoan parasite that binds to the epithelium of the human urogenital tract during infection. In this study, we examined the propensities of 26 T. vaginalis strains to bind to and lyse prostate (BPH-1) and ectocervical (Ect1) epithelium and to lyse red blood cells (RBCs). We found that only three of the strains had a statistically significant preference for either BPH-1 (MSA1103) or Ect1 (LA1 and MSA1123). Overall, we observed that levels of adherence are highly variable among strains, with a 12-fold range of adherence on Ect1 cells and a 45-fold range on BPH-1 cells. Cytolysis levels displayed even greater variability, from no detectable cytolysis to 80% or 90% cytolysis of Ect1 and BPH-1, respectively. Levels of adherence and cytolysis correlate for weakly adherent/cytolytic strains, and a threshold of attachment was found to be necessary to trigger cytolysis; however, this threshold can be reached without inducing cytolysis. Furthermore, cytolysis was completely blocked when we prevented attachment of the parasites to host cells while allowing soluble factors complete access. We demonstrate that hemolysis was a rare trait, with only 4 of the 26 strains capable of lysing >20% RBCs with a 1:30 parasite/RBC ratio. Hemolysis also did not correlate with adherence to or cytolysis of either male (BPH-1)- or female (Ect1)-derived epithelial cell lines. Our results reveal that despite a broad range of pathogenic properties among different T. vaginalis strains, all strains show strict contact-dependent cytolysis. PMID:23429535

Geodetic Measurement of Deformation East of the San Andreas Fault in Central California

NASA Technical Reports Server (NTRS)

Sauber, Jeanne M.; Lisowski, Michael; Solomon, Sean C.

1988-01-01

Triangulation and trilateration data from two geodetic networks located between the western edge of the Great Valley and the San Andreas fault have been used to calculate shear strain rates in the Diablo Range and to estimate the slip rate along the Calaveras and Paicines faults in Central California. Within the Diablo Range the average shear strain rate was determined for the time period between 1962 and 1982 to be 0.15 + or - 0.08 microrad/yr, with the orientation of the most compressive strain at N 16 deg E + or - 14 deg. The orientation of the principal compressive strain predicted from the azimuth of the major structures in the region is N 25 deg E. It is inferred that the measured strain is due to compression across the folds of this area: the average shear straining corresponds to a relative shortening rate of 4.5 + or - 2.4 mm/yr. From an examination of wellbore breakout orientations and the azimuths of P-axes from earthquake focal mechanisms the inferred orientation of maximum compressive stress was found to be similar to the direction of maximum compressive strain implied by the trend of local fold structures. Results do not support the hypothesis of uniform fault-normal compression within the Coast Ranges. From trilateration measurements made between 1972 and 1987 on lines that are within 10 km of the San Andreas fault, a slip rate of 10 to 12 mm/yr was calculated for the Calaveras-Paicines fault south of Hollister. The slip rate of the Paicines fault decreases to 4 mm/yr near Bitter.

Variation in host specificity and gene content in strains from genetically isolated lineages of the ectomycorrhizal fungus Paxillus involutus s. lat.

PubMed

Hedh, Jenny; Johansson, Tomas; Tunlid, Anders

2009-10-01

Ectomycorrhizal fungi are known to vary in host range. Some fungi can enter into symbiosis with multiple plant species, while others have restricted host ranges. The aim of this study was to examine variation in host specificity among strains from the basidiomycete Paxillus involutus s. lat. Recent studies have shown that this fungus consists of at least four genetically isolated lineages, phylogenetic species (PS) I (which corresponds to the morphological species Paxillus obscurosporus), PS II (P. involutus s. str.), PS III (Paxillus validus), and PS IV (not yet supported by any reference material). Thirty-five Paxillus strains of PS I to IV were examined in microcosms for their capacity to infect birch (Betula pendula) and spruce (Picea abies). Seventeen strains were compatible and formed mycorrhizae with both tree species. Seven strains were incompatible with both birch and spruce. The gene content in three pairs of incompatible and compatible strains PS I, II, and III were compared using microarray-based comparative genomic hybridizations. Of 4,113 P. involutus gene representatives analyzed, 390 varied in copy numbers in at least one of the three pairwise comparisons. Only three reporters showed significant changes in all three pairwise comparisons, and none of these were changed in a similar way in three comparisons. Our data indicate that changes in host range have occurred frequently and independently among strains in P. obscurosporus, P. involutus s. str., and P. validus. No evidence was obtained demonstrating that these changes have been associated with the gain or loss of similar genes in these three species.

Isolation of Bdellovibrio sp. from soil samples in Mexico and their potential applications in control of pathogens.

PubMed

Oyedara, Omotayo Opemipo; De Luna-Santillana, Erick de Jesus; Olguin-Rodriguez, Omar; Guo, Xianwu; Mendoza-Villa, Marco Antonio; Menchaca-Arredondo, Jorge Luis; Elufisan, Temidayo Oluyomi; Garza-Hernandez, Javier Alfonso; Garcia Leon, Israel; Rodriguez-Perez, Mario Alberto

2016-12-01

In this study, two strains of Bdellovibrio were isolated from soil samples using the culture-dependent technique and two members of the family Enterobacteriaceae (Klebsiella sp. and Salmonella sp.) as prey. The Bdellovibrio strains were bacteriolytic, plaque-forming, and highly motile gram-negative bacteria. We identified and confirmed the Bdellovibrio strains using microscopy, PCR amplification, and sequencing of the 16S rRNA gene. They were observed to be different strains based on hit locus and prey range analyses. Here, the first report on Bdellovibrio strains isolated from soil in Mexico corroborates earlier report indicating that populations of Bdellovibrio found in soil are heterogeneous thereby the need to identify the various strains. © 2016 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.

Pyrethroid resistance in Australian field populations of the sheep body louse, Bovicola (Damalinia) ovis.

PubMed

Levot, G W; Johnson, P W; Hughes, P B; Powis, K J; Boray, J C; Dawson, K L

1995-01-01

Synthetic pyrethroid (SP) resistance has developed in Australian field populations of the sheep body louse, Bovicola (Damalinia) ovis. Laboratory bioassays were used to measure the susceptibility of lice to cypermethrin and the other registered SPs. Results of these bioassays indicated resistance to cypermethrin, deltamethrin, cyhalothrin and alphacypermethrin. So far, high-level resistance has been diagnosed in only a few strains. The toxicological responses of these strains were clearly separated from those of the majority of louse strains tested. Furthermore, these strains had survived immersion in commercial SP dips. The level of resistance described in some strains was sufficient to cause pour-on products to fail despite the fact that the LC50s of these strains fell within the normal range of field responses.

Pilot-scale cultivation of wall-deficient transgenic Chlamydomonas reinhardtii strains expressing recombinant proteins in the chloroplast.

PubMed

Zedler, Julie A Z; Gangl, Doris; Guerra, Tiago; Santos, Edgar; Verdelho, Vitor V; Robinson, Colin

2016-08-01

Microalgae have emerged as potentially powerful platforms for the production of recombinant proteins and high-value products. Chlamydomonas reinhardtii is a potentially important host species due to the range of genetic tools that have been developed for this unicellular green alga. Transformation of the chloroplast genome offers important advantages over nuclear transformation, and a wide range of recombinant proteins have now been expressed in the chloroplasts of C. reinhardtii strains. This is often done in cell wall-deficient mutants that are easier to transform. However, only a single study has reported growth data for C. reinhardtii grown at pilot scale, and the growth of cell wall-deficient strains has not been reported at all. Here, we report the first pilot-scale growth study for transgenic, cell wall-deficient C. reinhardtii strains. Strains expressing a cytochrome P450 (CYP79A1) or bifunctional diterpene synthase (cis-abienol synthase, TPS4) were grown for 7 days under mixotrophic conditions in a Tris-acetate-phosphate medium. The strains reached dry cell weights of 0.3 g/L within 3-4 days with stable expression levels of the recombinant proteins during the whole upscaling process. The strains proved to be generally robust, despite the cell wall-deficient phenotype, but grew poorly under phototrophic conditions. The data indicate that cell wall-deficient strains may be highly amenable for transformation and suitable for commercial-scale operations under mixotrophic growth regimes.

Lutibacter litoralis gen. nov., sp. nov., a marine bacterium of the family Flavobacteriaceae isolated from tidal flat sediment.

PubMed

Choi, Dong H; Cho, Byung C

2006-04-01

A rod-shaped marine bacterium, designated strain CL-TF09T, isolated from a tidal flat in Ganghwa, Korea, was characterized based on its physiological and biochemical features, fatty acid profile and phylogenetic position. 16S rRNA gene sequence analysis revealed a clear affiliation with the family Flavobacteriaceae. Strain CL-TF09T showed the closest phylogenetic relationship with the genera Tenacibaculum and Polaribacter; sequence similarities between CL-TF09T and the type strains of Tenacibaculum and Polaribacter species ranged from 90.7 to 91.8 %. Cells of strain CL-TF09T were non-motile and grew on solid media as yellow colonies. The strain grew in the presence of 1-5 % sea salts, within a temperature range of 5-30 degrees C and at pH 7-8. The strain had iso-C(15 : 0) 3-OH (17.4 %), iso-C(15 : 0) (16.7 %), anteiso-C(15 : 0) (15.1 %) and iso-C(16 : 0) 3-OH (13.4 %) as predominant fatty acids. The DNA G+C content was 33.9 mol%. Based on the physiological, fatty acid composition and phylogenetic data presented, strain CL-TF09T is considered to represent a novel genus and species of the family Flavobacteriaceae, for which the name Lutibacter litoralis gen. nov., sp. nov. is proposed. The type strain is CL-TF09T (=KCCM 42118T = JCM 13034T).

Characterization of human passive muscles for impact loads using genetic algorithm and inverse finite element methods.

PubMed

Chawla, A; Mukherjee, S; Karthikeyan, B

2009-02-01

The objective of this study is to identify the dynamic material properties of human passive muscle tissues for the strain rates relevant to automobile crashes. A novel methodology involving genetic algorithm (GA) and finite element method is implemented to estimate the material parameters by inverse mapping the impact test data. Isolated unconfined impact tests for average strain rates ranging from 136 s(-1) to 262 s(-1) are performed on muscle tissues. Passive muscle tissues are modelled as isotropic, linear and viscoelastic material using three-element Zener model available in PAMCRASH(TM) explicit finite element software. In the GA based identification process, fitness values are calculated by comparing the estimated finite element forces with the measured experimental forces. Linear viscoelastic material parameters (bulk modulus, short term shear modulus and long term shear modulus) are thus identified at strain rates 136 s(-1), 183 s(-1) and 262 s(-1) for modelling muscles. Extracted optimal parameters from this study are comparable with reported parameters in literature. Bulk modulus and short term shear modulus are found to be more influential in predicting the stress-strain response than long term shear modulus for the considered strain rates. Variations within the set of parameters identified at different strain rates indicate the need for new or improved material model, which is capable of capturing the strain rate dependency of passive muscle response with single set of material parameters for wide range of strain rates.

Patterns of feline immunodeficiency virus multiple infection and genome divergence in a free-ranging population of African lions.

PubMed

Troyer, Jennifer L; Pecon-Slattery, Jill; Roelke, Melody E; Black, Lori; Packer, Craig; O'Brien, Stephen J

2004-04-01

Feline immunodeficiency virus (FIV) is a lentivirus that causes AIDS-like immunodeficiency disease in domestic cats. Free-ranging lions, Panthera leo, carry a chronic species-specific strain of FIV, FIV-Ple, which so far has not been convincingly connected with immune pathology or mortality. FIV-Ple, harboring the three distinct strains A, B, and C defined by pol gene sequence divergences, is endemic in the large outbred population of lions in the Serengeti ecosystem in Tanzania. Here we describe the pattern of variation in the three FIV genes gag, pol-RT, and pol-RNase among lions within 13 prides to assess the occurrence of FIV infection and coinfection. Genome diversity within and among FIV-Ple strains is shown to be large, with strain divergence for each gene approaching genetic distances observed for FIV between different species of cats. Multiple in fections with two or three strains were found in 43% of the FIV-positive individuals based on pol-RT sequence analysis, which may suggest that antiviral immunity or interference evoked by one strain is not consistently protective against infection by a second. This comprehensive study of FIV-Ple in a free-ranging population of lions reveals a dynamic transmission of virus in a social species that has historically adapted to render the virus benign.

Patterns of Feline Immunodeficiency Virus Multiple Infection and Genome Divergence in a Free-Ranging Population of African Lions

PubMed Central

Troyer, Jennifer L.; Pecon-Slattery, Jill; Roelke, Melody E.; Black, Lori; Packer, Craig; O'Brien, Stephen J.

2004-01-01

Feline immunodeficiency virus (FIV) is a lentivirus that causes AIDS-like immunodeficiency disease in domestic cats. Free-ranging lions, Panthera leo, carry a chronic species-specific strain of FIV, FIV-Ple, which so far has not been convincingly connected with immune pathology or mortality. FIV-Ple, harboring the three distinct strains A, B, and C defined by pol gene sequence divergences, is endemic in the large outbred population of lions in the Serengeti ecosystem in Tanzania. Here we describe the pattern of variation in the three FIV genes gag, pol-RT, and pol-RNase among lions within 13 prides to assess the occurrence of FIV infection and coinfection. Genome diversity within and among FIV-Ple strains is shown to be large, with strain divergence for each gene approaching genetic distances observed for FIV between different species of cats. Multiple in fections with two or three strains were found in 43% of the FIV-positive individuals based on pol-RT sequence analysis, which may suggest that antiviral immunity or interference evoked by one strain is not consistently protective against infection by a second. This comprehensive study of FIV-Ple in a free-ranging population of lions reveals a dynamic transmission of virus in a social species that has historically adapted to render the virus benign. PMID:15016897

A microdot multilayer oxide device: let us tune the strain-ionic transport interaction.

PubMed

Schweiger, Sebastian; Kubicek, Markus; Messerschmitt, Felix; Murer, Christoph; Rupp, Jennifer L M

2014-05-27

In this paper, we present a strategy to use interfacial strain in multilayer heterostructures to tune their resistive response and ionic transport as active component in an oxide-based multilayer microdot device on chip. For this, fabrication of strained multilayer microdot devices with sideways attached electrodes is reported with the material system Gd0.1Ce0.9O(2-δ)/Er2O3. The fast ionic conducting Gd0.1Ce0.9O(2-δ) single layers are altered in lattice strain by the electrically insulating erbia phases of a microdot. The strain activated volume of the Gd0.1Ce0.9O(2-δ) is investigated by changing the number of individual layers from 1 to 60 while keeping the microdot at a constant thickness; i.e., the proportion of strained volume was systematically varied. Electrical measurements showed that the activation energy of the devices could be altered by Δ0.31 eV by changing the compressive strain of a microdot ceria-based phase by more than 1.16%. The electrical conductivity data is analyzed and interpreted with a strain volume model and defect thermodynamics. Additionally, an equivalent circuit model is presented for sideways contacted multilayer microdots. We give a proof-of-concept for microdot contacting to capture real strain-ionic transport effects and reveal that for classic top-electrode contacting the effect is nil, highlighting the need for sideways electric contacting on a nanoscopic scale. The near order ionic transport interaction is supported by Raman spectroscopy measurements. These were conducted and analyzed together with fully relaxed single thin film samples. Strain states are described relative to the strain activated volumes of Gd0.1Ce0.9O(2-δ) in the microdot multilayer. These findings reveal that strain engineering in microfabricated devices allows altering the ionic conduction over a wide range beyond classic doping strategies for single films. The reported fabrication route and concept of strained multilayer microdots is a promising path for applying strained multilayer oxides as active new building blocks relevant for a broad range of microelectrochemical devices, e.g., resistive switching memory prototypes, resistive or electrochemical sensors, or as active catalytic solid state surface components for microfuel cells or all-solid-state batteries.

Job strain and changes in the body mass index among working women: A prospective study

PubMed Central

Fujishiro, Kaori; Lawson, Christina C.; Hibert, Eileen Lividoti; Chavarro, Jorge E.; Rich-Edwards, Janet W.

2015-01-01

Objectives The relationship between job strain and weight gain has been unclear, especially for women. Using data from over 52 000 working women, we compare the association between change in job strain and change in BMI across different levels of baseline BMI. Subjects/Methods We used data from participants in the Nurses’ Health Study II (n=52 656, mean age = 38.4), an ongoing prospective cohort study. Using linear regression, we modeled the change in BMI over 4 years as a function of the change in job strain, baseline BMI, and the interaction between the two. Change in job strain was characterized in four categories combining baseline and follow-up levels: consistently low strain [low at both points], decreased strain [high strain at baseline only], increased strain [high strain at follow-up only], and consistently high strain [high at both points]. Age, race/ethnicity, pregnancy history, job types, and health behaviors at baseline were controlled for in the model. Results In adjusted models, women who reported high job strain at least once during the four-year period had a greater increase in BMI (ΔBMI=0.06–0.12, p<0.05) than those who never reported high job strain. The association between the change in job strain exposure and the change in BMI depended on the baseline BMI level (p=0.015 for the interaction): the greater the baseline BMI, the greater the BMI gain associated with consistently high job strain. The BMI gain associated with increased or decreased job strain was uniform across the range of baseline BMI. Conclusions Women with higher BMI may be more vulnerable to BMI gain when exposed to constant work stress. Future research focusing on mediating mechanisms between job strain and BMI change should explore the possibility of differential responses to job strain by initial BMI. PMID:25986779

Constitutive Modeling of the Flow Stress of GCr15 Continuous Casting Bloom in the Heavy Reduction Process

NASA Astrophysics Data System (ADS)

Ji, Cheng; Wang, Zilin; Wu, Chenhui; Zhu, Miaoyong

2018-04-01

According to the calculation results of a 3D thermomechanical-coupled finite-element (FE) model of GCr15 bearing steel bloom during a heavy reduction (HR) process, the variation ranges in the strain rate and strain under HR were described. In addition, the hot deformation behavior of the GCr15 bearing steel was studied over the temperature range from 1023 K to 1573 K (750 °C to 1300 °C) with strain rates of 0.001, 0.01, and 0.1 s-1 in single-pass thermosimulation compression experiments. To ensure the accuracy of the constitutive model, the temperature range was divided into two temperature intervals according to the fully austenitic temperature of GCr15 steel [1173 K (900 °C)]. Two sets of material parameters for the constitutive model were derived based on the true stress-strain curves of the two temperature intervals. A flow stress constitutive model was established using a revised Arrhenius-type constitutive equation, which considers the relationships among the material parameters and true strain. This equation describes dynamic softening during hot compression processes. Considering the effect of glide and climb on the deformation mechanism, the Arrhenius-type constitutive equation was modified by a physically based approach. This model is the most accurate over the temperatures ranging from 1173 K to 1573 K (900 °C to 1300 °C) under HR deformation conditions (ignoring the range from 1273 K to 1573 K (1000 °C to 1300 °C) with a strain rate of 0.1 s-1). To ensure the convergence of the FE calculation, an approximated method was used to estimate the flow stress at temperatures greater than 1573 K (1300 °C).

The mechanical properties of fluoride salts at elevated temperatures. [candidate thermal energy storage materials for solar dynamic systems

NASA Technical Reports Server (NTRS)

Raj, S. V.; Whittenberger, J. D.

1989-01-01

The deformation behavior of CaF2 and LiF single crystals compressed in the 111 and the 100 line directions, respectively, are compared with the mechanical properties of polycrystalline LiF-22 (mol pct) CaF2 eutectic mixture in the temperature range 300 to 1275 K for strain rates varying between 7 x 10 to the -7th and 0.2/s. The true stress-strain curves for the single crystals were found to exhibit three stages in an intermediate range of temperatures and strain rates, whereas those for the eutectic showed negative work-hardening rates after a maximum stress. The true stress-strain rate data for CaF2 and LiF-22 CaF2 could be represented by a power-law relation with the strain rate sensitivities lying between 0.05 and 0.2 for both materials. A similar relation was found to be unsatisfactory in the case of LiF.

Forest farming of shiitake mushrooms: an integrated evaluation of management practices.

PubMed

Bruhn, J N; Mihail, J D; Pickens, J B

2009-12-01

Two outdoor shiitake (Lentinula edodes) cultivation experiments, established in Missouri USA in 1999 and 2000, produced mushrooms in 2000-2005. We examined shiitake production in response to substrate species, inoculum form, inoculum strain, and inoculation timing, using total mushroom weight per log as the primary response variable with log characteristics as covariates. The significantly greater mushroom weight produced by sugar maple logs compared with white or northern red oak was attributable to the higher proportion of undiscolored wood volume in the maple logs, rather than to bark thickness or log diameter. The "wide temperature range" shiitake strain produced significantly greater yield compared with the "warm" or "cold" weather strains. Both the wide-range and warm-weather strains were stimulated to fruit by significant rain events, while the cold-weather strain was responsive to temperature. Inoculation with sawdust spawn gave significantly greater yield than colonized wooden dowels or pre-packaged "thimble" plug inoculum. The second and third full years following inoculation were the most productive.

Effect of Strain Field on Threshold Displacement Energy of Tungsten Studied by Molecular Dynamics Simulation

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

Wang, Dong; Gao, Ning; Setyawan, W.

The influence of strain field on defect formation energy and threshold displacement energy (Ed) in body-centered cubic (BCC) tungsten (W) has been studied with molecular dynamics simulations. Two different W potentials (Fikar and Juslin) were compared and the results indicate that the connection distance and selected function linking the short-range and long-range portions of the potentials affects the threshold displacement energy and its direction-specific values. The minimum Ed direction calculated with the Fikar-potential is <100> and with the Juslin-potential is <111>. Nevertheless, the most stable self-interstitial configuration is found to be a <111>-crowdion for both potentials. This stable configuration doesmore » not change with applied strain. Varying the strain from compression to tension increases the vacancy formation energy but decreases the self-interstitial formation energy. The formation energy of a self-interstitial changes more significantly than a vacancy such that Ed decreases with applied hydrostatic strain from compression to tension.« less

A Modified Double Multiple Nonlinear Regression Constitutive Equation for Modeling and Prediction of High Temperature Flow Behavior of BFe10-1-2 Alloy

NASA Astrophysics Data System (ADS)

Cai, Jun; Wang, Kuaishe; Shi, Jiamin; Wang, Wen; Liu, Yingying

2018-01-01

Constitutive analysis for hot working of BFe10-1-2 alloy was carried out by using experimental stress-strain data from isothermal hot compression tests, in a wide range of temperature of 1,023 1,273 K, and strain rate range of 0.001 10 s-1. A constitutive equation based on modified double multiple nonlinear regression was proposed considering the independent effects of strain, strain rate, temperature and their interrelation. The predicted flow stress data calculated from the developed equation was compared with the experimental data. Correlation coefficient (R), average absolute relative error (AARE) and relative errors were introduced to verify the validity of the developed constitutive equation. Subsequently, a comparative study was made on the capability of strain-compensated Arrhenius-type constitutive model. The results showed that the developed constitutive equation based on modified double multiple nonlinear regression could predict flow stress of BFe10-1-2 alloy with good correlation and generalization.

Deformation Characteristics and Recrystallization Response of a 9310 Steel Alloy

NASA Astrophysics Data System (ADS)

Snyder, David; Chen, Edward Y.; Chen, Charlie C.; Tin, Sammy

2013-01-01

The flow behavior and recrystallization response of a 9310 steel alloy deformed in the ferrite temperature range were studied in this work. Samples were compressed under various conditions of strain (0.6, 0.8 and multi-axial), strain rate (10-4 seconds-1 to 10-1 seconds-1) and temperature [811 K to 1033 K (538 °C to 760 °C)] using a Gleeble thermo-mechanical simulator. Deformation was characterized by both qualitative and quantitative means, using standard microscopy, electron backscatter diffraction (EBSD) analysis and flow stress modeling. The results indicate that deformation is primarily accommodated through dynamic recovery in sub-grain formation. EBSD analysis shows a continuous increase in sub-grain boundary misorientation with increasing strain, ultimately producing recrystallized grains from the sub-grains at high strains. This suggests that a sub-grain rotation recrystallization mechanism predominates in this temperature range. Analyses of the results reveal a decreasing mean dynamically recrystallized grain size with increasing Zener-Hollomon parameter, and an increasing recrystallized fraction with increasing strain.

High temperature tensile and creep behaviour of low pressure plasma-sprayed Ni-Co-Cr-Al-Y coating alloy

NASA Technical Reports Server (NTRS)

Hebsur, M. G.; Miner, R. V.

1986-01-01

The high temperature tensile and creep behavior of low pressure plasma-sprayed plates of a typical Ni-Co-Cr-Al-Y alloy has been studied. From room temperature to 800 K, the Ni-Co-Cr-Al-Y alloy studied has nearly a constant low ductility and a high strength. At higher temperatures, it becomes weak and highly ductile. At and above 1123 K, the behavior is highly dependent on strain rate and exhibits classic superplastic characteristics with a high ductility at intermediate strain rates and a strain rate sensitivity of about 0.5. At either higher or lower strain rates, the ductility decreases and the strain rate sensitivities are about 0.2. In the superplastic deformation range, the activation energy for creep is 120 + or - 20 kJ/mol, suggesting a diffusion-aided grain boundary sliding mechanism. Outside the superplastic range, the activation energy for creep is calculated to be 290 + or - 20 kJ/mol.

Phenotypic Variability in the Coccolithophore Emiliania huxleyi.

PubMed

Blanco-Ameijeiras, Sonia; Lebrato, Mario; Stoll, Heather M; Iglesias-Rodriguez, Debora; Müller, Marius N; Méndez-Vicente, Ana; Oschlies, Andreas

2016-01-01

Coccolithophores are a vital part of oceanic phytoplankton assemblages that produce organic matter and calcium carbonate (CaCO3) containing traces of other elements (i.e. Sr and Mg). Their associated carbon export from the euphotic zone to the oceans' interior plays a crucial role in CO2 feedback mechanisms and biogeochemical cycles. The coccolithophore Emiliania huxleyi has been widely studied as a model organism to understand physiological, biogeochemical, and ecological processes in marine sciences. Here, we show the inter-strain variability in physiological and biogeochemical traits in 13 strains of E. huxleyi from various biogeographical provinces obtained from culture collections commonly used in the literature. Our results demonstrate that inter-strain genetic variability has greater potential to induce larger phenotypic differences than the phenotypic plasticity of single strains cultured under a broad range of variable environmental conditions. The range of variation found in physiological parameters and calcite Sr:Ca highlights the need to reconsider phenotypic variability in paleoproxy calibrations and model parameterizations to adequately translate findings from single strain laboratory experiments to the real ocean.

Strain-rate behavior in tension of the tempered martensitic reduced activation steel Eurofer97

NASA Astrophysics Data System (ADS)

Cadoni, Ezio; Dotta, Matteo; Forni, Daniele; Spätig, Philippe

2011-07-01

The tensile properties of the high-chromium tempered martensitic reduced activation steel Eurofer97 were determined from tests carried out over a wide range of strain-rates on cylindrical specimens. The quasi-static tests were performed with a universal electro-mechanical machine, whereas a hydro-pneumatic machine and a JRC-split Hopkinson tensile bar apparatus were used for medium and high strain-rates respectively. This tempered martensitic stainless steel showed significant strain-rate sensitivity. The constitutive behavior was investigated within a framework of dislocations dynamics model using Kock's approach. The parameters of the model were determined and then used to predict the deformation range of the tensile deformation stability. A very good agreement between the experimental results and predictions of the model was found.

Study of microstructure and fracture properties of blunt notched and sharp cracked high density polyethylene specimens.

PubMed

Pan, Huanyu; Devasahayam, Sheila; Bandyopadhyay, Sri

2017-07-21

This paper examines the effect of a broad range of crosshead speed (0.05 to 100 mm/min) and a small range of temperature (25 °C and 45 °C) on the failure behaviour of high density polyethylene (HDPE) specimens containing a) standard size blunt notch and b) standard size blunt notch plus small sharp crack - all tested in air. It was observed that the yield stress properties showed linear increase with the natural logarithm of strain rate. The stress intensity factors under blunt notch and sharp crack conditions also increased linearly with natural logarithm of the crosshead speed. The results indicate that in the practical temperature range of 25 °C and 45 °C under normal atmosphere and increasing strain rates, HDPE specimens with both blunt notches and sharp cracks possess superior fracture properties. SEM microstructure studies of fracture surfaces showed craze initiation mechanisms at lower strain rate, whilst at higher strain rates there is evidence of dimple patterns absorbing the strain energy and creating plastic deformation. The stress intensity factor and the yield strength were higher at 25 °C compared to those at 45 °C.

Correlation of microstructure and low cycle fatigue properties for 13.5Cr1.1W0.3Ti ODS steel

NASA Astrophysics Data System (ADS)

He, P.; Klimenkov, M.; Möslang, A.; Lindau, R.; Seifert, H. J.

2014-12-01

Reduced activation oxide dispersion strengthened (ODS) steels are prospective structural materials for the blanket system and first wall components in Tokamak-type fusion reactors. Under the pulsed operation, these components will be predominantly subjected to cyclic thermal-mechanical loading which leads to inevitable fatigue damage. In this work, strain controlled isothermal fatigue tests were conducted for 13.5Cr1.1W0.3Ti ODS steel at 550 °C. The total strain range varied from 0.54% to 0.9%. After thermomechanical processing, 13.5CrWTi-ODS steel exhibits a remarkable lifetime extension with a factor of 10-20 for strain ranges Δε ⩽ 0.7%. 13.5Cr ODS steel shows no cyclic softening at all during the whole testing process irrespective of the strain range. TEM observations reveal ultrastable grain structure and constant dislocation densities around 1014 m-2, independent of the number of cycles or the applied strain amplitude. The presence of the stabilized ultrafine Y-Ti-O dispersoids enhances the microstructural stability and therefore leads to outstanding fatigue resistance for 13.5Cr1.1W0.3Ti-ODS steel.

Isolation and Characterization of Mycoplasma sphenisci sp. nov. from the Choana of an Aquarium-Reared Jackass Penguin (Spheniscus demersus)

PubMed Central

Frasca, Salvatore; Weber, E. Scott; Urquhart, Heather; Liao, Xiaofen; Gladd, Martha; Cecchini, Katharine; Hudson, Paul; May, Meghan; Gast, Rebecca J.; Gorton, Timothy S.; Geary, Steven J.

2005-01-01

Strain UCMJ was isolated from the choana of a jackass penguin (Spheniscus demersus) with recurrent mucocaseous choanal discharge. Isolation of this mycoplasma expands the known range of species hosting mycoplasmas. The name Mycoplasma sphenisci sp. nov. is proposed for this new species, for which strain UCMJ is the type strain. PMID:15956436

A wearable strain sensor based on a carbonized nano-sponge/silicone composite for human motion detection.

PubMed

Yu, Xiao-Guang; Li, Yuan-Qing; Zhu, Wei-Bin; Huang, Pei; Wang, Tong-Tong; Hu, Ning; Fu, Shao-Yun

2017-05-25

Melamine sponge, also known as nano-sponge, is widely used as an abrasive cleaner in our daily life. In this work, the fabrication of a wearable strain sensor for human motion detection is first demonstrated with a commercially available nano-sponge as a starting material. The key resistance sensitive material in the wearable strain sensor is obtained by the encapsulation of a carbonized nano-sponge (CNS) with silicone resin. The as-fabricated CNS/silicone sensor is highly sensitive to strain with a maximum gauge factor of 18.42. In addition, the CNS/silicone sensor exhibits a fast and reliable response to various cyclic loading within a strain range of 0-15% and a loading frequency range of 0.01-1 Hz. Finally, the CNS/silicone sensor as a wearable device for human motion detection including joint motion, eye blinking, blood pulse and breathing is demonstrated by attaching the sensor to the corresponding parts of the human body. In consideration of the simple fabrication technique, low material cost and excellent strain sensing performance, the CNS/silicone sensor is believed to have great potential in the next-generation of wearable devices for human motion detection.

Draft ASME Boiler and Pressure Vessel Code Section III, Division 5, Section HB, Subsection B, Code Case for Alloy 617 and Background Documentation

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

Wright, Julie Knibloe

2015-08-01

Alloy 617 is the leading candidate material for an intermediate heat exchanger for the very high temperature reactor. To evaluate the behavior of this material in the expected service conditions, strain controlled cyclic tests that include long hold times up to 240 minutes at maximum tensile strain were conducted at 850°C. In terms of the total number of cycles to failure, the fatigue resistance decreased when a hold time was added at peak tensile strain. Increases in the tensile hold duration degraded the creep fatigue resistance, at least to the investigated strain controlled hold time of up to 60 minutesmore » at the 0.3% strain range and 240 minutes at the 1.0% strain range. The creep fatigue deformation mode is considered relative to the lack of saturation, or continually decreasing number of cycles to failure with increasing hold times. Additionally, preliminary values from the 850°C creep fatigue data are calculated for the creep fatigue damage diagram and have higher values of creep damage than those from tests at 950°C.« less

Strain analysis and microstructural evolution characteristic of neoproterozoic rocks associations of Wadi El Falek, centre Eastern Desert, Egypt

NASA Astrophysics Data System (ADS)

Kassem, Osama M. K.; Rahim, Said H. Abd El; Nashar, El Said R. El

2012-09-01

The estimation of finite strain in rocks is fundamental to a meaningful understanding of deformational processes and products on all scales from microscopic fabric development to regional structural analyses. The Rf/φ and Fry methods on feldspar porphyroclasts and mafic grains from 5 granite, 1 metavolcanic, 3 metasedimentary and 1 granodiorite samples were used in Wadi El Falek region. Finite-strain data shows that a high to moderate range of deformation of the granitic to metavolcano-sedimentary samples and axial ratios in the XZ section range from 1.60 to 4.10 for the Rf/φ method and from 2.80 to 4.90 for the Fry method. Furthermore, the short axes are subvertical associated with a subhorizontal foliation. We conclude that finite strain in the deformed granite rocks is of the same order of magnitude as that from metavolcano-sedimentary rocks. Furthermore, contacts formed during intrusion of plutons with some faults in the Wadi El Falek area under brittle to semi-ductile deformation conditions. In this case, finite strain accumulated during superimposed deformation on the already assembled nappe structure. It indicates that the nappe contacts formed during the accumulation of finite strain.

Strain and Temperature Sensing Properties of Multiwalled Carbon Nanotube Yarn Composites

NASA Technical Reports Server (NTRS)

Kahng, Seun K.; Gates, Thomas S.; Jefferson, Gail D.

2008-01-01

Strain and temperature response of Multiwalled Carbon Nanotube (MWCNT/CNT) yarns on a stainless steel test beam has been studied. The carbon nanotube yarns are spun from a multiwalled carbon nanotube forest grown on a silicon substrate to a 4-ply yarn with a diameter of about 15-20 microns. Four of the 4-ply CNT yarns are arranged in a Wheatstone bridge configuration on the stainless steel test beam using a thin layer of polyurethane resin that insulates and protects the yarns from the test beam. Strain sensitivities of the CNT yarn sensors range from 1.39 to 1.75 mV/V/1000 microstrain at room temperature, and temperature sensitivity of the CNT yarn bridge is 91 microA/degC. Resistance of the yarns range from 215 to 270 ohms for CNT yarn length of approximately 5 mm. Processes used in attaching the CNT yarns on the test beam and experimental procedures used for the measurements are described. Conventional metallic foil strain gages are attached to the test beam to compare with the CNT sensors. The study demonstrates multifunctional capability of the sensor for strain and temperature measurements and shows its applicability where engineering strain is less than 3%.

Isolation of As-tolerant bacteria and their potentials of reducing As and Cd accumulation of edible tissues of vegetables in metal(loid)-contaminated soils.

PubMed

Wang, Xiaohan; Nie, Zongwei; He, Linyan; Wang, Qi; Sheng, Xiafang

2017-02-01

In this study, three As-tolerant bacteria Ralstonia eutropha Q2-8, Rhizobium tropici Q2-13, and Exiguobacterium aurantiacum Q3-11 were isolated from the rhizosphere and bulk soils of Chinese cabbage. The strains were characterized for their production of indole-3-acetic acid (IAA) and siderophores, their effects on soil metal(loid) bioavailability and organic matter content, and their effects on the edible tissue growth and metal(loid) accumulation of Chinese cabbage and radish in the metal(loid)-contaminated soil. The strains produced IAA and siderophores and increased the edible tissue biomass (ranging from 74% to 124%) of the vegetables compared to the controls. Furthermore, strain Q2-8 reduced As contents (ranging from 22% to 50%), while strains Q2-13 and Q3-11 decreased Cd contents (ranging from 21% to 53%) of the edible tissues of the vegetables compared to the controls. Strains Q2-8, Q2-13, and Q3-11 decreased the DTPA-extractable Cd contents (ranging from 16% to 41%) and increased the organic matter contents of the rhizosphere soils compared to the controls. The results showed the effects of the strains on the increased edible tissue growth and reduced As and Cd uptake of the edible tissues and highlighted the possibility to develop a new bacterial-assisted technique for reduced metal(loid) uptake of vegetables in the metal(loid)-contaminated soils. Copyright © 2016 Elsevier B.V. All rights reserved.

Genomic diversity and adaptation of Salmonella enterica serovar Typhimurium from analysis of six genomes of different phage types

PubMed Central

2013-01-01

Background Salmonella enterica serovar Typhimurium (or simply Typhimurium) is the most common serovar in both human infections and farm animals in Australia and many other countries. Typhimurium is a broad host range serovar but has also evolved into host-adapted variants (i.e. isolated from a particular host such as pigeons). Six Typhimurium strains of different phage types (defined by patterns of susceptibility to lysis by a set of bacteriophages) were analysed using Illumina high-throughput genome sequencing. Results Variations between strains were mainly due to single nucleotide polymorphisms (SNPs) with an average of 611 SNPs per strain, ranging from 391 SNPs to 922 SNPs. There were seven insertions/deletions (indels) involving whole or partial gene deletions, four inactivation events due to IS200 insertion and 15 pseudogenes due to early termination. Four of these inactivated or deleted genes may be virulence related. Nine prophage or prophage remnants were identified in the six strains. Gifsy-1, Gifsy-2 and the sopE2 and sspH2 phage remnants were present in all six genomes while Fels-1, Fels-2, ST64B, ST104 and CP4-57 were variably present. Four strains carried the 90-kb plasmid pSLT which contains several known virulence genes. However, two strains were found to lack the plasmid. In addition, one strain had a novel plasmid similar to Typhi strain CT18 plasmid pHCM2. Conclusion The genome data suggest that variations between strains were mainly due to accumulation of SNPs, some of which resulted in gene inactivation. Unique genetic elements that were common between host-adapted phage types were not found. This study advanced our understanding on the evolution and adaptation of Typhimurium at genomic level. PMID:24138507

Repeatability of strain magnitude and strain rate measurements in the periodontal ligament using fibre Bragg gratings: An ex vivo study in a swine model.

PubMed

Romanyk, Dan L; Guan, Raymond; Major, Paul W; Dennison, Christopher R

2017-03-21

Measurement of periodontal ligament (PDL) strain in an ex vivo or in vivo setting of a complete tooth-PDL-bone complex (TPBC) has yet to be achieved in the literature. The objective of this study was to investigate inter- and intra-TPBC PDL strain measurement using fibre Bragg grating (FBG) strain sensors. Second and third premolars from the left and the right side of four swine mandibles were removed to yield sixteen TPBC samples. Samples were secured in a miniature load-frame equipped with a digital actuator used to apply apical-directed displacement to the tooth. The same tooth on left and right sides of the mouth were exposed to the same loading condition over ten trials allowing for comparisons in a split-mouth study. Displacements of 0.2 and 0.3mm were considered along with displacement rates of 0.025, 0.05, and 0.1mm/s, yielding six loading combinations. Hypothesis testing between left and right teeth revealed FBGs did not always measure the same strain between left and right TPBCs. For all strain measures, the average coefficient of variation (CV) (all data collected) was 2.16 (range: 0.274-10.71). For repeated measures in single TPBCs, the minimum CV ranged from 0.037 to 0.449, and generally coincided with the time of maximum strain measured over the test duration. Based on the findings of this study, it is suggested that FBGs can provide repeatable ex vivo strain measures in the PDL of complete TPBCs. Copyright © 2017 Elsevier Ltd. All rights reserved.

Built for speed: strain in the cartilaginous vertebral columns of sharks.

PubMed

Porter, M E; Diaz, Candido; Sturm, Joshua J; Grotmol, Sindre; Summers, A P; Long, John H

2014-02-01

In most bony fishes vertebral column strain during locomotion is almost exclusively in the intervertebral joints, and when these joints move there is the potential to store and release strain energy. Since cartilaginous fishes have poorly mineralized vertebral centra, we tested whether the vertebral bodies undergo substantial strain and thus may be sites of energy storage during locomotion. We measured axial strains of the intervertebral joints and vertebrae in vivo and ex vivo to characterize the dynamic behavior of the vertebral column. We used sonomicrometry to directly measure in vivo and in situ strains of intervertebral joints and vertebrae of Squalus acanthias swimming in a flume. For ex vivo measurements, we used a materials testing system to dynamically bend segments of vertebral column at frequencies ranging from 0.25 to 1.00 Hz and a range of physiologically relevant curvatures, which were determined using a kinematic analysis. The vertebral centra of S. acanthias undergo strain during in vivo volitional movements as well as in situ passive movements. Moreover, when isolated segments of vertebral column were tested during mechanical bending, we measured the same magnitudes of strain. These data support our hypothesis that vertebral column strain in lateral bending is not limited to the intervertebral joints. In histological sections, we found that the vertebral column of S. acanthias has an intracentral canal that is open and covered with a velum layer. An open intracentral canal may indicate that the centra are acting as tunics around some sections of a hydrostat, effectively stiffening the vertebral column. These data suggest that the entire vertebral column of sharks, both joints and centra, is mechanically engaged as a dynamic spring during locomotion. Copyright © 2013 Elsevier GmbH. All rights reserved.

White matter tract-oriented deformation predicts traumatic axonal brain injury and reveals rotational direction-specific vulnerabilities.

PubMed

Sullivan, Sarah; Eucker, Stephanie A; Gabrieli, David; Bradfield, Connor; Coats, Brittany; Maltese, Matthew R; Lee, Jongho; Smith, Colin; Margulies, Susan S

2015-08-01

A systematic correlation between finite element models (FEMs) and histopathology is needed to define deformation thresholds associated with traumatic brain injury (TBI). In this study, a FEM of a transected piglet brain was used to reverse engineer the range of optimal shear moduli for infant (5 days old, 553-658 Pa) and 4-week-old toddler piglet brain (692-811 Pa) from comparisons with measured in situ tissue strains. The more mature brain modulus was found to have significant strain and strain rate dependencies not observed with the infant brain. Age-appropriate FEMs were then used to simulate experimental TBI in infant (n=36) and preadolescent (n=17) piglets undergoing a range of rotational head loads. The experimental animals were evaluated for the presence of clinically significant traumatic axonal injury (TAI), which was then correlated with FEM-calculated measures of overall and white matter tract-oriented tissue deformations, and used to identify the metric with the highest sensitivity and specificity for detecting TAI. The best predictors of TAI were the tract-oriented strain (6-7%), strain rate (38-40 s(-1), and strain times strain rate (1.3-1.8 s(-1) values exceeded by 90% of the brain. These tract-oriented strain and strain rate thresholds for TAI were comparable to those found in isolated axonal stretch studies. Furthermore, we proposed that the higher degree of agreement between tissue distortion aligned with white matter tracts and TAI may be the underlying mechanism responsible for more severe TAI after horizontal and sagittal head rotations in our porcine model of nonimpact TAI than coronal plane rotations.

Minimum inhibitory (MIC) and minimum microbicidal concentration (MMC) of polihexanide and triclosan against antibiotic sensitive and resistant Staphylococcus aureus and Escherichia coli strains

PubMed Central

Assadian, Ojan; Wehse, Katrin; Hübner, Nils-Olaf; Koburger, Torsten; Bagel, Simone; Jethon, Frank; Kramer, Axel

2011-01-01

Background: An in-vitro study was conducted investigating the antimicrobial efficacy of polihexanide and triclosan against clinical isolates and reference laboratory strains of Staphylococcus aureus and Escherichia coli. Methods: The minimal inhibitory concentration (MIC) and the minimal microbicidal concentration (MMC) were determined following DIN 58940-81 using a micro-dilution assay and a quantitative suspension test following EN 1040. Polihexanide was tested in polyethylene glycol 4000, triclosan in aqueous solutions. Results: Against all tested strains the MIC of polihexanide ranged between 1–2 µg/mL. For triclosan the MICs varied depending on strains ranging between 0.5 µg/mL for the reference strains and 64 µg/mL for two clinical isolates. A logRF >5 without and logRF >3 with 0.2% albumin burden was achieved at 0.6 µg/mL triclosan. One exception was S. aureus strain H-5-24, where a triclosan concentration of 0.6 µg/mL required 1 minute without and 10 minutes with albumin burden to achieve the same logRFs. Polihexanide achieved a logRF >5 without and logRF >3 with albumin burden at a concentration of 0.6 µg/mL within 30 sec. The exception was the North-German epidemic MRSA strain, were an application time of 5 minutes was required. Conclusion: The clinical isolates of E. coli generally showed higher MICs against triclosan, both in the micro-dilution assay as well in the quantitative suspension test than comparable reference laboratory strains. For polihexanide and triclosan strain dependant susceptibility was shown. However, both antimicrobial compounds are effective when used in concentrations common in practice. PMID:22242087

From progressive to finite deformation, and back: the universal deformation matrix

NASA Astrophysics Data System (ADS)

Provost, A.; Buisson, C.; Merle, O.

2003-04-01

It is widely accepted that any finite strain recorded in the field may be interpreted in terms of the simultaneous combination of a pure shear component with one or several simple shear components. To predict strain in geological structures, approximate solutions may be obtained by multiplying successive small increments of each elementary strain component. A more rigorous method consists in achieving the simultaneous combination in the velocity gradient tensor but solutions already proposed in the literature are valid for special cases only and cannot be used, e.g., for the general combination of a pure shear component and six elementary simple shear components. In this paper, we show that the combination of any strain components is as simple as a mouse click, both analytically and numerically. The finite deformation matrix is given by L=exp(L.Δt) where L.Δt is the time-integrated velocity gradient tensor. This method makes it possible to predict finite strain for any combination of strain components. Reciprocally, L.Δt=ln(D) , which allows to unravel the simplest deformation history that might be liable for a given finite deformation. Given the strain ellipsoid only, it is still possible to constrain the range of compatible deformation matrices and thus the range of strain component combinations. Interestingly, certain deformation matrices, though geologically sensible, have no real logarithm so cannot be explained by a deformation history implying strain rate components with constant proportions, what implies significant changes of the stress field during the history of deformation. The study as a whole opens the possibility for further investigations on deformation analysis in general, the method could be used wathever the configuration is.

Streptomyces colonosanans sp. nov., A Novel Actinobacterium Isolated from Malaysia Mangrove Soil Exhibiting Antioxidative Activity and Cytotoxic Potential against Human Colon Cancer Cell Lines

PubMed Central

Law, Jodi Woan-Fei; Ser, Hooi-Leng; Duangjai, Acharaporn; Saokaew, Surasak; Bukhari, Sarah I.; Khan, Tahir M.; Ab Mutalib, Nurul-Syakima; Chan, Kok-Gan; Goh, Bey-Hing; Lee, Learn-Han

2017-01-01

Streptomyces colonosanans MUSC 93JT, a novel strain isolated from mangrove forest soil located at Sarawak, Malaysia. The bacterium was noted to be Gram-positive and to form light yellow aerial and vivid yellow substrate mycelium on ISP 2 agar. The polyphasic approach was used to determine the taxonomy of strain MUSC 93JT and the strain showed a range of phylogenetic and chemotaxonomic properties consistent with those of the members of the genus Streptomyces. Phylogenetic and 16S rRNA gene sequence analysis indicated that closely related strains include Streptomyces malachitofuscus NBRC 13059T (99.2% sequence similarity), Streptomyces misionensis NBRC 13063T (99.1%), and Streptomyces phaeoluteichromatogenes NRRL 5799T (99.1%). The DNA–DNA relatedness values between MUSC 93JT and closely related type strains ranged from 14.4 ± 0.1 to 46.2 ± 0.4%. The comparison of BOX-PCR fingerprints indicated MUSC 93JT exhibits a unique DNA profile. The genome of MUSC 93JT consists of 7,015,076 bp. The DNA G + C content was determined to be 69.90 mol%. The extract of strain MUSC 93JT was demonstrated to exhibit potent antioxidant activity via ABTS, metal chelating, and SOD assays. This extract also exhibited anticancer activity against human colon cancer cell lines without significant cytotoxic effect against human normal colon cells. Furthermore, the chemical analysis of the extract further emphasizes the strain is producing chemo-preventive related metabolites. Based on this polyphasic study of MUSC 93JT, it is concluded that this strain represents a novel species, for which the name Streptomyces colonosanans sp. nov. is proposed. The type strain is MUSC 93JT (= DSM 102042T = MCCC 1K02298T). PMID:28559892

Effect of electron beam and gamma radiation on drug-susceptible and drug-resitant listeria monocytogenes strains in salmon under different temperature.

PubMed

Skowron, Krzysztof; Grudlewska, Katarzyna; Gryń, Grzegorz; Skowron, Karolina Jadwiga; Świeca, Agnieszka; Paluszak, Zbigniew; Zimek, Zbigniew; Rafalski, Andrzej; Gospodarek-Komkowska, Eugenia

2018-05-04

To investigate the effect of gamma radiation and high energy electron beam doses on the inactivation of antibiotic-susceptible and antibiotic-resistant Listeria monocytogenes strains inoculated on the surface of raw salmon fillets stored at different temperature (-20°C, 4°C and 25°C). The population of bacteria strains resistance to penicillin, ampicillin, meropenem, erythromycin and trimethoprim-sulfamethoxazole was generated. When using gamma irradiation, the theoretical lethal dose ranged from 1.44 to 5.68 kGy and for electron beam the values ranged from 2.99 to 6.83 kGy. The theoretical lethal dose for both radiation methods was higher for antibiotic-resistant strains. Gamma radiation proved to be a more effective method for extending salmon fillet shelf-life. The evaluation of PFGE electrophoregram revealed that the repair of radiation-caused DNA damage occurred faster in antibiotic-resistant L. monocytogenes strains. The number of live L. monocytogenes cells, 40 hours after irradiation, also was higher in antibiotic-resistant strain suspension. The present study showed that gamma radiation was more effective in the elimination of the tested microorganisms and food preservation, than a high energy electron beam. The antibiotic-resistant L. monocytogenes strains were more resistant to both radiation methods. There are a lot of research on the effect of radiation on the number of bacteria in food products. However, there is almost no information about the effect of strain properties, such as drug susceptibility, virulence, etc., on their resistance to ionizing radiation. An increasing number of drug resistant bacterial strains isolated from food, encourages to take up this research subject. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Prevotella maculosa sp. nov., isolated from the human oral cavity.

PubMed

Downes, Julia; Sutcliffe, Iain C; Booth, Veronica; Wade, William G

2007-12-01

Three strains of anaerobic Gram-negative bacilli isolated from human oral sites were subjected to a comprehensive range of phenotypic and genotypic tests and were found to comprise a homogeneous group. 16S rRNA gene sequence analysis revealed the strains to constitute a novel group within the genus Prevotella, most closely related to Prevotella oris and Prevotella salivae. A novel species, Prevotella maculosa sp. nov., is proposed to accommodate these strains. Prevotella maculosa is saccharolytic and produces acetic and succinic acids as end products of fermentation. The G+C content of the DNA of the type strain is 48 mol%. The type strain of Prevotella maculosa is W1609(T) (=DSM 19339(T) =CCUG 54766(T)).

Biodegradation of propargite by Pseudomonas putida, isolated from tea rhizosphere.

PubMed

Sarkar, Soumik; Seenivasan, Subbiah; Asir, Robert Premkumar Samuel

2010-02-15

Biodegradation of miticide propargite was carried out in vitro by selected Pseudomonas strains isolated from tea rhizosphere. A total number of 13 strains were isolated and further screened based on their tolerance level to different concentrations of propargite. Five best strains were selected and further tested for their nutritional requirements. Among the different carbon sources tested glucose exhibited the highest growth promoting capacity and among nitrogen sources ammonium nitrate supported the growth to the maximum. The five selected Pseudomonas strain exhibited a range of degradation capabilities. Mineral salts medium (MSM) amended with glucose provided better environment for degradation with the highest degradation potential in strain SPR 13 followed by SPR 8 (71.9% and 69.0% respectively).

Stochastic precision analysis of 2D cardiac strain estimation in vivo

NASA Astrophysics Data System (ADS)

Bunting, E. A.; Provost, J.; Konofagou, E. E.

2014-11-01

Ultrasonic strain imaging has been applied to echocardiography and carries great potential to be used as a tool in the clinical setting. Two-dimensional (2D) strain estimation may be useful when studying the heart due to the complex, 3D deformation of the cardiac tissue. Increasing the framerate used for motion estimation, i.e. motion estimation rate (MER), has been shown to improve the precision of the strain estimation, although maintaining the spatial resolution necessary to view the entire heart structure in a single heartbeat remains challenging at high MERs. Two previously developed methods, the temporally unequispaced acquisition sequence (TUAS) and the diverging beam sequence (DBS), have been used in the past to successfully estimate in vivo axial strain at high MERs without compromising spatial resolution. In this study, a stochastic assessment of 2D strain estimation precision is performed in vivo for both sequences at varying MERs (65, 272, 544, 815 Hz for TUAS; 250, 500, 1000, 2000 Hz for DBS). 2D incremental strains were estimated during left ventricular contraction in five healthy volunteers using a normalized cross-correlation function and a least-squares strain estimator. Both sequences were shown capable of estimating 2D incremental strains in vivo. The conditional expected value of the elastographic signal-to-noise ratio (E(SNRe|ɛ)) was used to compare strain estimation precision of both sequences at multiple MERs over a wide range of clinical strain values. The results here indicate that axial strain estimation precision is much more dependent on MER than lateral strain estimation, while lateral estimation is more affected by strain magnitude. MER should be increased at least above 544 Hz to avoid suboptimal axial strain estimation. Radial and circumferential strain estimations were influenced by the axial and lateral strain in different ways. Furthermore, the TUAS and DBS were found to be of comparable precision at similar MERs.

Systemic neonatal candidosis: the karyotyping of Candida albicans strains isolated from neonates and health-workers.

PubMed

Ben Abdeljelil, J; Ben Saida, N; Saghrouni, F; Fathallah, A; Boukadida, J; Sboui, H; Ben Said, M

2010-01-01

Candida albicans has become an important cause of nosocomial infections in neonatal intensive care units (NICUs). The aim of the present study was to compare C. albicans strains isolated from neonates (NN) suffering from systemic candidosis and from nurses in order to determine the relatedness between NN and health workers' strains. Thirty-one C. albicans strains were isolated from 18 NN admitted to the NICU of the neonatology service of Farhat Hached Hospital of Sousse, Tunisia and suffering from systemic candidosis, together with five strains recovered from nurses suffering from C. albicans onychomycosis. Two additional strains were tested, one from an adult patient who developed a systemic candidosis and the second from an adult with inguinal intertrigo. All strains were karyotyped by pulsed-field gel electrophoresis (PFGE) with a CHEF-DR II system. Analysis of PFGE patterns yielded by the 38 strains tested led to the identification of three pulsotypes that were designated I, II and III, and consisted of six chromosomal bands with a size ranging from 700 to >2500 kbp. The most widespread was the pulsotype I, which was shared by 17 NN and the five nurses' strains. The identity between NN and nurses' strains is very suggestive of a nosocomial acquisition from health-workers.

Effect of Strain Rate on Hot Ductility Behavior of a High Nitrogen Cr-Mn Austenitic Steel

NASA Astrophysics Data System (ADS)

Wang, Zhenhua; Meng, Qing; Qu, Minggui; Zhou, Zean; Wang, Bo; Fu, Wantang

2016-03-01

18Mn18Cr0.6N steel specimens were tensile tested between 1173 K and 1473 K (900 °C and 1200 °C) at 9 strain rates ranging from 0.001 to 10 s-1. The tensile strained microstructures were analyzed through electron backscatter diffraction analysis. The strain rate was found to affect hot ductility by influencing the strain distribution, the extent of dynamic recrystallization and the resulting grain size, and dynamic recovery. The crack nucleation sites were primarily located at grain boundaries and were not influenced by the strain rate. At 1473 K (1200 °C), a higher strain rate was beneficial for grain refinement and preventing hot cracking; however, dynamic recovery appreciably occurred at 0.001 s-1 and induced transgranular crack propagation. At 1373 K (1100 °C), a high extent of dynamic recrystallization and fine new grains at medium strain rates led to good hot ductility. The strain gradient from the interior of the grain to the grain boundary increased with decreasing strain rate at 1173 K and 1273 K (900 °C and 1000 °C), which promoted hot cracking. Grain boundary sliding accompanied grain rotation and did not contribute to hot cracking.

Thermal Output of WK-Type Strain Gauges on Various Materials at Cryogenic and Elevated Temperatures

NASA Technical Reports Server (NTRS)

Kowalkowski, Matthew K.; Rivers, H. Kevin; Smith, Russell W.

1998-01-01

Strain gage apparent strain (thermal output) is one of the largest sources of error associated with the measurement of strain when temperatures and mechanical loads are varied. In this paper, experimentally determined apparent strains of WK-type strain gages, installed on both metallic and composite-laminate materials of various lay-ups and resin systems for temperatures ranging from -450 F to 230 F are presented. For the composite materials apparent strain in both the 0 ply orientation angle and the 90 ply orientation angle were measured. Metal specimens tested included: aluminum-lithium alloy (Al-LI 2195-T87), aluminum alloy (Al 2219-T87), and titanium alloy. Composite materials tested include: graphite-toughened-epoxy (IM7/997- 2), graphite-bismaleimide (IM7/5260), and graphite-K3 (IM7/K3B). The experimentally determined apparent strain data are curve fit with a fourth-order polynomial for each of the materials studied. The apparent strain data and the polynomials that are fit to the data are compared with those produced by the strain gage manufacturer, and the results and comparisons are presented. Unacceptably high errors between the manufacture's data and the experimentally determined data were observed (especially at temperatures below - 270-F).

Origin of the Strain Sensitivity for an Organic Heptazole Thin-Film and Its Strain Gauge Application

NASA Astrophysics Data System (ADS)

Bae, Heesun; Jeon, Pyo Jin; Park, Ji Hoon; Lee, Kimoon

2018-04-01

The authors report on the origin of the strain sensitivity for an organic C26H16N2 (heptazole) thinfilm and its application for the detection of tensile strain. From the electrical characterization on the thin-film transistor adopting a heptazole channel, heptazole film exhibits p-channel conduction with a relatively low value of field-effect mobility (0.05 cm2/Vs), suggesting a hopping conduction behavior via hole carriers. By analyzing the strain and temperature dependences of the electrical conductivity, we reveal that the electrical conduction for a heptazole thin-film is dominated by the variable range hopping process with quite a large energy separation (224.9 meV) between the localized states under a relatively long attenuation length (10.46 Å). This indicates that a change in the inter-grain spacing that is much larger than the attenuation length is responsible for the reversible modification of electrical conductivity depending on strain for the heptazole film. By utilizing our heptazole thin-film both as a strain sensitive passive resistor and an active semiconducting channel layer, we can achieve a strain gauge device exhibiting reversible endurance for tensile strains up to 2.12%. Consequently, this study advances the understanding of the fundamental strain sensing mechanism in a heptazole thin-film toward finding a promise material with a strain gauge for applications as potential flexible devices and/or wearable electronics.

The nonstationary strain filter in elastography: Part I. Frequency dependent attenuation.

PubMed

Varghese, T; Ophir, J

1997-01-01

The accuracy and precision of the strain estimates in elastography depend on a myriad number of factors. A clear understanding of the various factors (noise sources) that plague strain estimation is essential to obtain quality elastograms. The nonstationary variation in the performance of the strain filter due to frequency-dependent attenuation and lateral and elevational signal decorrelation are analyzed in this and the companion paper for the cross-correlation-based strain estimator. In this paper, we focus on the role of frequency-dependent attenuation in the performance of the strain estimator. The reduction in the signal-to-noise ratio (SNRs) in the RF signal, and the center frequency and bandwidth downshift with frequency-dependent attenuation are incorporated into the strain filter formulation. Both linear and nonlinear frequency dependence of attenuation are theoretically analyzed. Monte-Carlo simulations are used to corroborate the theoretically predicted results. Experimental results illustrate the deterioration in the precision of the strain estimates with depth in a uniformly elastic phantom. Theoretical, simulation and experimental results indicate the importance of high SNRs values in the RF signals, because the strain estimation sensitivity, elastographic SNRe and dynamic range deteriorate rapidly with a decrease in the SNRs. In addition, a shift in the strain filter toward higher strains is observed at large depths in tissue due to the center frequency downshift.

Fatigue damage mechanisms in boron-aluminium composite laminates

NASA Technical Reports Server (NTRS)

Dvorak, G. J.; Johnson, W. S.

1980-01-01

The relationship between fatigue and shakedown in metal matrix composites is investigated theoretically and experimentally for unidirectional and laminated 6061 Al-B materials. It is shown that no fatigue damage takes place if the applied stress range is such that the material remains elastic, or shakes down, i.e., resumes elastic cyclic straining after a small number of plastic strain cycles. Fatigue damage occurs only in specimens subjected to stress ranges which cause sustained cyclic plastic straining in the aluminum matrix. If the applied stress range is smaller than that required for fatigue failure, after about 10 to the 6th cycles a saturation damage state is reached which remains essentially unchanged with increasing number of cycles.

Characterization of lactococci isolated from milk produced in the Camembert region of Normandy.

PubMed

Desmasures, N; Mangin, I; Corroler, D; Guéguen, M

1998-12-01

Thirty-eight Lactococcus strains, isolated from raw milk produced in two dairy areas in Normandy, were identified at the phenotypic level. Only Lactococcus lactis strains with the lactis phenotype were found in the milk samples. Most strains fermented lactose (97%) and showed proteinase activity (76%). Isolates were characterized by RAPD technique and rRNA gene restriction analysis. More L. lactis strains with the lactis genotype were found in the first area, while L. lactis strains with the cremoris genotype predominated in the second area. RAPD was more efficient than rRNA gene restriction analysis in differentiating between strains with the subsp. lactis genotype. For L. lactis with the subsp. cremoris genotype, the second method gave a better result but there was poor discrimination between strains. Plasmid profiles were determined. Patterns ranged in size from 1.3 to 16.5 kbp, and 29 different profiles were found. Six groups of strains were determined, five of which were specific for the area of origin. It is suggested that the region of manufacture could influence organoleptic properties of cheeses because of different Lactococcus strains in the raw milk used for cheese making.

Isolation of Toxigenic Nocardiopsis Strains from Indoor Environments and Description of Two New Nocardiopsis Species, N. exhalans sp. nov. and N. umidischolae sp. nov.

PubMed Central

Peltola, Joanna S. P.; Andersson, Maria A.; Kämpfer, Peter; Auling, Georg; Kroppenstedt, Reiner M.; Busse, Hans-Jürgen; Salkinoja-Salonen, Mirja S.; Rainey, Frederick A.

2001-01-01

Nocardiopsis strains were isolated from water-damaged indoor environments. Two strains (N. alba subsp. alba 704a and a strain representing a novel species, ES10.1) as well as strains of N. prasina, N. lucentensis, and N. tropica produced methanol-soluble toxins that paralyzed the motility of boar spermatozoa at <30 μg of crude extract (dry weight) ml−1. N. prasina, N. lucentensis, N. tropica, and strain ES10.1 caused cessation of motility by dissipating the mitochondrial membrane potential, Δψ, of the boar spermatozoa. Indoor strain 704a produced a substance that destroyed cell membrane barrier function and depleted the sperm cells of ATP. Indoor strain 64/93 was antagonistic towards Corynebacterium renale. Two indoor Nocardiopsis strains were xerotolerant, and all five utilized a wide range of substrates. This combined with the production of toxic substances suggests good survival and potential hazard to human health in water-damaged indoor environments. Two new species, Nocardiopsis exhalans sp. nov. (ES10.1T) and Nocardiopsis umidischolae sp. nov. (66/93T), are proposed based on morphology, chemotaxonomic and physiological characters, phylogenetic analysis, and DNA-DNA reassociations. PMID:11526036

Influence of volatile organic compounds emitted by Pseudomonas and Serratia strains on Agrobacterium tumefaciens biofilms.

PubMed

Plyuta, Vladimir; Lipasova, Valentina; Popova, Alexandra; Koksharova, Olga; Kuznetsov, Alexander; Szegedi, Erno; Chernin, Leonid; Khmel, Inessa

2016-07-01

The ability to form biofilms plays an important role in bacteria-host interactions, including plant pathogenicity. In this work, we investigated the action of volatile organic compounds (VOCs) produced by rhizospheric strains of Pseudomonas chlororaphis 449, Pseudomonas fluorescens B-4117, Serratia plymuthica IC1270, as well as Serratia proteamaculans strain 94, isolated from spoiled meat, on biofilms formation by three strains of Agrobacterium tumefaciens which are causative agents of crown-gall disease in a wide range of plants. In dual culture assays, the pool of volatiles emitted by the tested Pseudomonas and Serratia strains suppressed the formation of biofilms of A. tumefaciens strains grown on polycarbonate membrane filters and killed Agrobacterium cells in mature biofilms. The individual VOCs produced by the tested Pseudomonas strains, that is, ketones (2-nonanone, 2-heptanone, 2-undecanone), and dimethyl disulfide (DMDS) produced by Serratia strains, were shown to kill A. tumefaciens cells in mature biofilms and suppress their formation. The data obtained in this study suggest an additional potential of some ketones and DMDS as protectors of plants against A. tumefaciens strains, whose virulence is associated with the formation of biofilms on the infected plants. © 2016 APMIS. Published by John Wiley & Sons Ltd.

Dynamic Mechanical Response of Biomedical 316L Stainless Steel as Function of Strain Rate and Temperature

PubMed Central

Lee, Woei-Shyan; Chen, Tao-Hsing; Lin, Chi-Feng; Luo, Wen-Zhen

2011-01-01

A split Hopkinson pressure bar is used to investigate the dynamic mechanical properties of biomedical 316L stainless steel under strain rates ranging from 1 × 103 s−1 to 5 × 103 s−1 and temperatures between 25°C and 800°C. The results indicate that the flow stress, work-hardening rate, strain rate sensitivity, and thermal activation energy are all significantly dependent on the strain, strain rate, and temperature. For a constant temperature, the flow stress, work-hardening rate, and strain rate sensitivity increase with increasing strain rate, while the thermal activation energy decreases. Catastrophic failure occurs only for the specimens deformed at a strain rate of 5 × 103 s−1 and temperatures of 25°C or 200°C. Scanning electron microscopy observations show that the specimens fracture in a ductile shear mode. Optical microscopy analyses reveal that the number of slip bands within the grains increases with an increasing strain rate. Moreover, a dynamic recrystallisation of the deformed microstructure is observed in the specimens tested at the highest temperature of 800°C. PMID:22216015

Biocontrol of Burkholderia cepacia complex bacteria and bacterial phytopathogens by Bdellovibrio bacteriovorus.

PubMed

McNeely, Damian; Chanyi, Ryan M; Dooley, James S; Moore, John E; Koval, Susan F

2017-04-01

Bdellovibrio and like organisms are predatory bacteria that have the unusual property of using the cytoplasmic constituents of other Gram-negative bacteria as nutrients. These predators may thus provide an alternative approach to the biocontrol of human and plant pathogens. Predators were isolated on Burkholderia cenocepacia K56-2 and J2315 as prey cells, in enrichment cultures with soil and sewage. Three isolates (DM7C, DM8A, and DM11A) were identified as Bdellovibrio bacteriovorus on the basis of morphology, a periplasmic life cycle, and 16S rRNA gene sequencing. The prey range of these isolates was tested on Burkholderia cepacia complex bacteria and several phytopathogenic bacteria of agricultural importance. Of 31 strains of the Burkholderia cepacia complex tested, only 4 were resistant to predation by strain DM7C. A subset of 9 of the prey tested were also susceptible to strains DM8A and DM11A. Of 12 phytopathogens tested, 4 were resistant to strains DM7C and DM8A, and only 2 were resistant to strain DM11A. Thus, Bdellovibrio bacteriovorus strains retrieved from environmental samples on 2 Burkholderia cenocepacia isolates from cystic fibrosis patients did not distinguish in their prey range between other isolates of that pathogen or phytopathogens. Such strains hold promise as potential wide-spectrum biocontrol agents.

Growth and photosynthesis of Chlorella strains from polar, temperate and tropical freshwater environments under temperature stress

NASA Astrophysics Data System (ADS)

Lee, Kok-Keong; Lim, Phaik-Eem; Poong, Sze-Wan; Wong, Chiew-Yen; Phang, Siew-Moi; Beardall, John

2017-09-01

Elevated temperatures as a consequence of global warming have significant impacts on the adaptation and survival of microalgae which are important primary producers in many ecosystems. The impact of temperature on the photosynthesis of microalgae is of great interest as the primary production of algal biomass is strongly dependent on the photosynthetic rates in a dynamic environment. Here, we examine the effects of elevated temperature on Chlorella strains originating from different latitudes, namely Antarctic, Arctic, temperate and tropical regions. Chlorophyll fluorescence was used to assess the photosynthetic responses of the microalgae. Rapid light curves (RLCs) and maximum quantum yield (F v/F m) were recorded. The results showed that Chlorella originating from different latitudes portrayed different growth trends and photosynthetic performance. The Chlorella genus is eurythermal, with a broad temperature tolerance range, but with strain-specific characteristics. However, there was a large overlap between the tolerance range of the four strains due to their "eurythermal adaptivity". Changes in the photosynthetic parameters indicated temperature stress. The ability of the four strains to reactivate photosynthesis after inhibition of photosynthesis under high temperatures was also studied. The Chlorella strains were shown to recover in terms of photosynthesis and growth (measured as Chl a) when they were returned to their ambient temperatures. Polar strains showed faster recovery in their optimal temperature compared to that under the ambient temperature from which they were isolated.

TRIP effect in austenitic-martensitic VNS9-Sh steel at various strain rates

NASA Astrophysics Data System (ADS)

Terent'ev, V. F.; Slizov, A. K.; Prosvirnin, D. V.

2016-10-01

The mechanical properties of austenitic-martensitic VNS9-Sh (23Kh15N5AM3-Sh) steel are studied at a static strain rate from 4.1 × 10-5 to 17 × 10-3 s-1 (0.05-20 mm/min). It is found that, as the strain rate increases, the ultimate tensile strength decreases and the physical yield strength remains unchanged (≈1400 MPa). As the strain rate increases, the yield plateau remains almost unchanged and the relative elongation decreases continuously. Because of high microplastic deformation, the conventional yield strength is lower than the physical yield strength over the entire strain rate range under study. The influence of the TRIP effect on the changes in the mechanical properties of VNS9-Sh steel at various strain rates is discussed.

'Candidatus pasteuria usgae' sp. nov., an obligate endoparasite of the phytoparasitic nematode Belonolaimus longicaudatus.

PubMed

Giblin-Davis, R M; Williams, D S; Bekal, S; Dickson, D W; Brito, J A; Becker, J O; Preston, J F

2003-01-01

Taxonomically relevant characteristics of a fastidiously Gram-positive, obligately endoparasitic prokaryote (strain S-1) that uses the phytoparasitic sting nematode Belonolaimus longicaudatus as its host are reviewed. 16S rDNA sequence similarity (> or = 93%) confirms its congeneric ranking with other Pasteuria species and strains from nematodes and cladocerans and corroborates morphological, morphometric and host range evidence suggesting a novel taxon. The 16S rDNA sequence of strain S-1 has greatest similarity (96%) to the 16S rDNA sequences of both Pasteuria penetrans from root-knot nematodes (Meloidogyne species) and the recently reported strain of Pasteuria isolated from the soybean cyst nematode Heterodera glycines. Because the obligately endoparasitic nature of prokaryotes in the genus Pasteuria prevents isolation of definitive type strains, strain S-1 is proposed as 'Candidatus Pasteuria usgae' sp. nov.

Shear modulus of porcine coronary artery in reference to a new strain measure.

PubMed

Zhang, Wei; Lu, Xiao; Kassab, Ghassan S

2007-11-01

To simplify the stress-strain relationship of blood vessels, we define a logarithmic-exponential (log-exp) strain measure to absorb the nonlinearity. As a result, the constitutive relation between the second Piola-Kirchhoff stress and the log-exp strain can be written as a generalized Hooke's law. In this work, the shear modulus of porcine coronary arteries is determined from the experimental data in inflation-stretch-torsion tests. It is found that the shear modulus with respect to the log-exp strain can be viewed as a material constant in the full range of elasticity, and the incremental shear modulus for Cauchy shear stress and small shear strain at various loading levels can be predicted by the proposed Hooke's law. This result further validates the linear constitutive relation for blood vessels when shear deformation is involved.

Microstructure and Strain Rate-Dependent Tensile Deformation Behavior of Fiber Laser-Welded Butt Joints of Dual-Phase Steels

NASA Astrophysics Data System (ADS)

Liu, Yang; Dong, Danyang; Han, Zhiqiang; Yang, Zhibin; Wang, Lu; Dong, Qingwei

2018-05-01

The microstructure and tensile deformation behavior of the fiber laser-welded similar and dissimilar dual-phase (DP) steel joints over a wide range of strain rates from 10-3 to 103 s-1 were investigated for the further applications on the lightweight design of vehicles. The high strain rate dynamic tensile deformation process and full-field strain distribution of the base metals and welded joints were examined using the digital image correlation method and high-speed photography. The strain rate effects on the stress-strain responses, tensile properties, deformation, and fracture behavior of the investigated materials were analyzed. The yield stress (YS) and ultimate tensile strength (UTS) of the dissimilar DP780/DP980 welded joints were lying in-between those of the DP780 and DP980 base metals, and all materials exhibited positive strain rate dependence on the YS and UTS. Owing to the microstructure heterogeneity, the welded joints showed relatively lower ductility in terms of total elongation (TE) than those of the corresponding base metals. The strain localization started before the maximum load was reached, and the strain localization occurred earlier during the whole deformation process with increasing strain rate. As for the dissimilar welded joint, the strain localization tended to occur in the vicinity of the lowest hardness value across the welded joint, which was in the subcritical HAZ at the DP780 side. As the strain rate increased, the typical ductile failure characteristic of the investigated materials did not change.

Microstructure and Strain Rate-Dependent Tensile Deformation Behavior of Fiber Laser-Welded Butt Joints of Dual-Phase Steels

NASA Astrophysics Data System (ADS)

Liu, Yang; Dong, Danyang; Han, Zhiqiang; Yang, Zhibin; Wang, Lu; Dong, Qingwei

2018-04-01

The microstructure and tensile deformation behavior of the fiber laser-welded similar and dissimilar dual-phase (DP) steel joints over a wide range of strain rates from 10-3 to 103 s-1 were investigated for the further applications on the lightweight design of vehicles. The high strain rate dynamic tensile deformation process and full-field strain distribution of the base metals and welded joints were examined using the digital image correlation method and high-speed photography. The strain rate effects on the stress-strain responses, tensile properties, deformation, and fracture behavior of the investigated materials were analyzed. The yield stress (YS) and ultimate tensile strength (UTS) of the dissimilar DP780/DP980 welded joints were lying in-between those of the DP780 and DP980 base metals, and all materials exhibited positive strain rate dependence on the YS and UTS. Owing to the microstructure heterogeneity, the welded joints showed relatively lower ductility in terms of total elongation (TE) than those of the corresponding base metals. The strain localization started before the maximum load was reached, and the strain localization occurred earlier during the whole deformation process with increasing strain rate. As for the dissimilar welded joint, the strain localization tended to occur in the vicinity of the lowest hardness value across the welded joint, which was in the subcritical HAZ at the DP780 side. As the strain rate increased, the typical ductile failure characteristic of the investigated materials did not change.

Effect of rider and riding style on deformation of the front hoof wall in warmblood horses.

PubMed

Summerley, H L; Thomason, J J; Bignell, W W

1998-09-01

A rider modifies the weight distribution and dynamic balance of the horse. But what effect does a rider have on the mechanical behaviour of the hoof during each stance phase? Does riding style have any effect on this behaviour? We attempted to answer these questions using strains recorded from 5 rosette strain gauges glued to the surface of the front hooves of 4 Warmblood horses. Comparisons were made between strains with and without a rider, and when the rider was sitting, rising at a trot, or in a forward seated position. The change in strains from trot to lead or nonlead at a canter, and the effect of turning were also studied. Changing lead at a canter had as least as much effect on strain magnitudes as did turning; strains were up to 43% higher for the nonlead foot, but with little redistribution. Perhaps surprisingly, strains were significantly lower on the quarters by up to 30% with a rider than without, with a 10% increase or decrease at the toe, depending on the individual. Riding style changed strain magnitudes by up to 20% and also caused strain redistribution: strains were higher medially for sitting, and laterally for forward seat, with strains for a rising trot being more evenly distributed and intermediate in magnitude. Studying the range of, and causes of variation in hoof wall strain gives baseline data aimed, in the long term, at providing a biomechanical definition of hoof balance.

Haloanaerobium kushneri sp. nov., an obligately halophilic, anaerobic bacterium from an oil brine

NASA Technical Reports Server (NTRS)

Bhupathiraju, V. K.; McInerney, M. J.; Woese, C. R.; Tanner, R. S.

1999-01-01

Three strains, designated VS-751T, VS-511 and VS-732, of a strictly anaerobic, moderately halophilic, Gram-negative, rod-shaped bacterium were isolated from a highly saline (15-20%) brine from an oil reservoir in central Oklahoma, USA. The optimal concentration of NaCl for growth of these three strains was 2 M (12%), and the strains also grew in the presence of an additional 1 M MgCl2. The strains were mesophilic and grew at a pH range of 6-8. Carbohydrates used by all three strains included glucose, fructose, arabinose, galactose, maltose, mannose, cellobiose, sucrose and inulin. Glucose fermentation products included ethanol, acetate, H2 and CO2, with formate produced by two of the three strains. Differences were noted among strains in the optimal temperature and pH for growth, the maximum and minimum NaCl concentration that supported growth, substrate utilization and cellular fatty acid composition. Despite the phenotypic differences among the three strains, analysis of the 16S rRNA gene sequences and DNA-DNA hybridizations showed that these three strains were members of the same genospecies which belonged to the genus Haloanaerobium. The phenotypic and genotypic characteristics of strains VS-751T, VS-511 and VS-732 are different from those of previously described species of Haloanaerobium. It is proposed that strain VS-751T (ATCC 700103T) be established as the type strain of a new species, Haloanaerobium kushneri.

Haladaptatus pallidirubidus sp. nov., a halophilic archaeon isolated from saline soil samples in Yunnan and Xinjiang, China.

PubMed

Liu, Bing-Bing; Zhao, Wan-Yu; Chu, Xiao; Hozzein, Wael N; Prabhu, Deene Manik; Wadaan, Mohammed A M; Tang, Shu-Kun; Zhang, Li-Li; Li, Wen-Jun

2014-11-01

Two extremely halophilic archaea, designated YIM 90917 and YIM 93656(T), were isolated from saline soils in Yunnan province and Lup nur region in Xinjiang province, western China, respectively. Colonies of the two strains were observed to be pink-pigmented. The cells were found to be Gram-stain negative, coccoid and non-motile. The organisms were found to be aerobic and could grow in an NaCl range of 6-35 % (optimum 18 %), temperatures ranging from 25 to 50 °C (optimum 37-42 °C), pH range from 6.0-8.5 (optimum pH 7.0-7.5) and Mg(2+) range from 0 to 1.5 M (optimum 0.5-1.0 M); Mg(2+) was not necessary for growth. Cells were not observed to lyse in distilled water. Strains YIM 90917 and YIM 93656(T) showed the highest 16S rRNA gene sequence similarities to Haladaptatus cibarius JCM 15962(T) (97.6 and 97.9 %, respectively). In addition, the DNA-DNA hybridizations of strains YIM 90917 and YIM 93656(T) with type strains H. cibarius JCM 15962(T), Haladaptatus litoreus JCM 15771(T) and Haladaptatus paucihalophilus JCM 13897(T) were 37.2 and 38.2 %, 36.6 and 39.0 % and 27.9 and 27.7 %, respectively. The DNA G+C contents of strains YIM 90917 and YIM 93656(T) were determined to be 56.0 and 57.4 mol%. The major polar lipids of the two strains were identified as phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate, sulfated mannosyl glucosyl diether and other four unidentified glycolipids. On the basis of physiological, chemotaxonomic data and phylogenetic analysis, the strains YIM 90917 and YIM 93656(T) can be classified as a novel species of the genus Haladaptatus, for which the name Haladaptatus pallidirubidus sp. nov. is proposed. The type strain is YIM 93656(T) (=JCM 17504(T) = CCTCC AB2010454(T)).

Influence of Cyclic Straining on Fatigue, Deformation, and Fracture Behavior of High-Strength Alloy Steel

NASA Astrophysics Data System (ADS)

Manigandan, K.; Srivatsan, T. S.; Vasudevan, V. K.; Tammana, D.; Poorganji, B.

2016-01-01

In this paper, the results of a study on microstructural influences on mechanical behavior of the high-strength alloy steel Tenax™ 310 are presented and discussed. Under the influence of fully reversed strain cycling, the stress response of this alloy steel revealed softening from the onset of deformation. Cyclic strain resistance exhibited a linear trend for the variation of both elastic strain amplitude with reversals-to-failure, and plastic strain amplitude with reversals-to-failure. Fracture morphology was essentially the same at the macroscopic level over the entire range of cyclic strain amplitudes examined. However, at the fine microscopic level, this high-strength alloy steel revealed fracture to be mixed-mode with features reminiscent of "locally" ductile and brittle mechanisms. The macroscopic mechanisms governing stress response at the fine microscopic level, resultant fatigue life, and final fracture behavior are presented and discussed in light of the mutually interactive influences of intrinsic microstructural effects, deformation characteristics of the microstructural constituents during fully reversed strain cycling, cyclic strain amplitude, and resultant response stress.

Interactions between creep, fatigue and strain aging in two refractory alloys

NASA Technical Reports Server (NTRS)

Sheffler, K. D.

1972-01-01

The application of low-amplitude, high-frequency fatigue vibrations during creep testing of two strain-aging refractory alloys (molybdenum-base TZC and tantalum-base T-111) significantly reduced the creep strength of these materials. This strength reduction caused dramatic increases in both the first stage creep strain and the second stage creep rate. The magnitude of the creep rate acceleration varied directly with both frequency and A ratio (ratio of alternating to mean stress), and also varied with temperature, being greatest in the range where the strain-aging phenomenon was most prominent. It was concluded that the creep rate acceleration resulted from a negative strain rate sensitivity which is associated with the strain aging phenomenon in these materials. (A negative rate sensitivity causes flow stress to decrease with increasing strain rate, instead of increasing as in normal materials). By combining two analytical expressions which are normally used to describe creep and strain aging behavior, an expression was developed which correctly described the influence of temperature, frequency, and A ratio on the TZC creep rate acceleration.

Constitutive relations for determining the critical conditions for dynamic recrystallization behavior

NASA Astrophysics Data System (ADS)

Choe, J. I.

2016-04-01

A series mathematical model has been developed for the prediction of flow stress and microstructure evolution during the hot deformation of metals such as copper or austenitic steels with low stacking fault energies, involving features of both diffusional flow and dislocation motion. As the strain rate increases, multiple peaks on the stress-strain curve decrease. At a high strain rate, the stress rises to a single peak, while dynamic recrystallization causes an oscillatory behavior. At a low strain rate (when there is sufficient time for the recrystallizing grains to grow before they become saturated with high dislocation density with an increase in strain rate), the difference in stored stress between recrystallizing and old grains diminishes, resulting in reduced driving force for grain growth and rendering smaller grains in the alloy. The final average grain size at the steady stage (large strain) increases with a decrease in the strain rate. During large strain deformation, grain size reduction accompanying dislocation creep might be balanced by the grain growth at the border delimiting the ranges of realization (field boundary) of the dislocation-creep and diffusion-creep mechanisms.

The response of equine cortical bone to loading at strain rates experienced in vivo by the galloping horse.

PubMed

Evans, G P; Behiri, J C; Vaughan, L C; Bonfield, W

1992-03-01

The behaviour of cortical bone under load is strain rate-dependent, i.e. it is dependent on the rate at which the load is applied. This is particularly relevant in the galloping horse since the strain rates experienced by the bone are far in excess of those recorded for any other species. In this study the effect of strain rates between 0.0001 and 1 sec-1 on the mechanical properties of equine cortical bone were assessed. Initially, increasing strain rates resulted in increased mechanical properties. Beyond a critical value, however, further increases in strain rate resulted in lower strain to failure and energy absorbing capacity. This critical rate occurred around 0.1 sec-1 which is within the in vivo range for a galloping racehorse. Analysis of the stress-strain curves revealed a transition in the type of deformation at this point from pseudo-ductile to brittle. Bones undergoing brittle deformation are more likely to fail under load, leading to catastrophic fracture and destruction of the animal.

Plasmid profile in oral Fusobacterium nucleatum from humans and Cebus apella monkeys.

PubMed

Paula, Marcia O; Gaetti-Jardim Júnior, Elerson; Avila-Campos, Mario J

2003-01-01

Fusobacterium nucleatum is a strict anaerobe and is indigenous of the human oral cavity. This organism is commonly recovered from different monomicrobial and mixed infections in humans and animals. In this study, the plasmid profile, the plasmid stability and the penicillin-resistance association in oral F. nucleatum isolated from periodontal patients, healthy subjects and Cebus apella monkeys were evaluated. Forty-five F. nucleatum strains from patients, 38 from healthy subjects and seven from C. apella were identified and analyzed. Plasmid extraction was performed in all the isolated strains. These elements were found in 26.7% strains from patients and one strain from C. apella. Strains from healthy subjects did not show any plasmid. Most of strains showed two plasmid bands ranging from 4 to 16 Kb, but digestions with endonucleases showed that they belonged to a single plasmid. The plasmid profile was similar and stable in human and monkey strains. Also, plasmids were classified into three groups according to size. Two strains were positive to beta-lactamase production and no plasmid DNA-hybridization with a beta-lactamase gene probe was observed, suggesting a chromosomal resistance.

Genetic Diversity of G3 Rotavirus Strains Circulating in Argentina during 1998–2012 Assessed by Full Genome Analyses

PubMed Central

Degiuseppe, Juan Ignacio; Parra, Gabriel Ignacio; Stupka, Juan Andrés

2014-01-01

Seasonal shifts in the predominant strains and the periodic emergence of new strains are epidemiological features of human rotaviruses. After the sporadic detection in two samples in 1998, G3P[8] strains reemerged as the predominant rotavirus during 2008–2009 in Argentina. Notably, in 2011 6.3% (37/587) of samples presented the G3P[6] genotypes, which coincided with the recent detection of G3P[6] and G2P[6] strains in South America and Europe. Analyses of the 11 gene segments of four G3P[8] and two G3P[6] strains revealed that G3P[8] strains detected a decade apart (1998 and 2009) presented minor differences, while the G3P[6] strains presented a complete different genomic constellation albeit showing a similar VP7 gene. This study provides insights in the dynamics and evolution of one of the genotypes with the wider range of hosts and inter-species transmission potential. PMID:25337915

Controlling and prevention of surface wrinkling via size-dependent critical wrinkling strain.

PubMed

Han, Xue; Zhao, Yan; Cao, Yanping; Lu, Conghua

2015-06-14

Surface wrinkling may occur in a film-substrate system when the applied strain exceeds the critical value. However, the practically required strain for the onset of surface wrinkling can be different from the theoretically predicted value. Here we investigate the film size effect-dependent critical strain for the mechanical strain-induced surface wrinkling via a combination of experiments and theoretical analysis. In the poly(dimethylsiloxane)-based system fabricated by the smart combination of mechanical straining and selective O2 plasma (OP) exposure through Cu grids, the film size effect on the critical wrinkling strain is systematically studied by considering OP exposure duration, the mesh number and geometry of Cu grids. Meanwhile, a simple analytical solution revealing the film size effect is well established, which shows good consistency with the experimental results. This study provides an experimental and theoretical basis for finely tuning the critical wrinkling strain in a simple and quantitative manner, which can find a wide range of applications in such fields as microelectronic circuits and optical devices, where controlling and/or prevention of surface wrinkling are of great importance.

Screening high oleaginous Chlorella strains from different climate zones.

PubMed

Xu, Jin; Hu, Hanhua

2013-09-01

In outdoor cultivation, screening strains adapted to a wide temperature range or suitable strains for different environmental temperatures is of great importance. In this study, triacylglycerol (TAG) content of 23 oil-producing Chlorella strains from different climate zones were analyzed by thin layer chromatography. Four selected Chlorella strains (NJ-18, NJ-7, NMX35N and NMX139N) with rather high TAG content had higher total lipid content compared with Chlorella vulgaris SAG 211-11b. In particular, NJ-18 displayed the highest TAG productivity among the four high oil-producing Chlorella strains. Accumulation of TAGs in strain NMX35N changed a little from 30 to 40°C, showing a desirable characteristic of accumulating TAGs at high temperatures. Our results demonstrated that NJ-18 and NMX35N had suitable fatty acid profiles and good adaption to low and high temperatures respectively. Therefore, cultivation of the two Chlorella strains together might be a good option for economic biodiesel production during the whole seasons of the year. Copyright © 2013 Elsevier Ltd. All rights reserved.

Microstructure characterization of 316L deformed at high strain rates using EBSD

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

Yvell, K., E-mail: kyv@du.se

2016-12-15

Specimens from split Hopkinson pressure bar experiments, at strain rates between ~ 1000–9000 s{sup −1} at room temperature and 500 °C, have been studied using electron backscatter diffraction. No significant differences in the microstructures were observed at different strain rates, but were observed for different strains and temperatures. Size distribution for subgrains with boundary misorientations > 2° can be described as a bimodal lognormal area distribution. The distributions were found to change due to deformation. Part of the distribution describing the large subgrains decreased while the distribution for the small subgrains increased. This is in accordance with deformation being heterogeneousmore » and successively spreading into the undeformed part of individual grains. The variation of the average size for the small subgrain distribution varies with strain but not with strain rate in the tested interval. The mean free distance for dislocation slip, interpreted here as the average size of the distribution of small subgrains, displays a variation with plastic strain which is in accordance with the different stages in the stress-strain curves. The rate of deformation hardening in the linear hardening range is accurately calculated using the variation of the small subgrain size with strain. - Highlights: •Only changes in strain, not strain rate, gave differences in the microstructure. •A bimodal lognormal size distribution was found to describe the size distribution. •Variation of the subgrain fraction sizes agrees with models for heterogeneous slip. •Variation of subgrain size with strain describes part of the stress strain curve.« less

AN ORGANOTYPIC UNIAXIAL STRAIN MODEL USING MICROFLUIDICS

PubMed Central

Dollé, Jean-Pierre; Morrison, Barclay; Schloss, Rene R.; Yarmush, Martin L.

2012-01-01

Traumatic brain injuries are the leading cause of disability each year in the US. The most common and devastating consequence is the stretching of axons caused by shear deformation that occurs during rotational acceleration of the brain during injury. The injury effects on axonal molecular and functional events are not fully characterized. We have developed a strain injury model that maintains the three dimensional cell architecture and neuronal networks found in vivo with the ability to visualize individual axons and their response to a mechanical injury. The advantage of this model is that it can apply uniaxial strains to axons that make functional connections between two organotypic slices and injury responses can be observed in real-time and over long term. This uniaxial strain model was designed to be capable of applying an array of mechanical strains at various rates of strain, thus replicating a range of modes of axonal injury. Long term culture, preservation of slice and cell orientation, and slice-slice connection on the device was demonstrated. The device has the ability to strain either individual axons or bundles of axons through the control of microchannel dimensions. The fidelity of the model was verified by observing characteristic responses to various strain injuries which included axonal beading, delayed elastic effects and breakdown in microtubules. Microtubule breakdown was shown to be dependent on the degree of the applied strain field, where maximal breakdown was observed at peak strain and minimal breakdown is observed at low strain. This strain injury model could be a powerful tool in assessing strain injury effects on functional axonal connections. PMID:23233120

Hatchery Contributions to Emerging Naturally Produced Lake Huron Lake Trout.

PubMed

Scribner, Kim; Tsehaye, Iyob; Brenden, Travis; Stott, Wendylee; Kanefsky, Jeannette; Bence, James

2018-06-19

Recent assessments indicate the emergence of naturally produced lake trout (Salvelinus namaycush) recruitment throughout Lake Huron in the North American Laurentian Great Lakes (>50% of fish <7 yrs). Because naturally produced fish derived from different stocked hatchery strains are unmarked, managers cannot distinguish strains contributing to natural recruitment. We used 15 microsatellite loci to identify strains of naturally produced lake trout (N=1567) collected in assessment fisheries during early (2002-2004) and late (2009-2012) sampling periods. Individuals from 13 American and Canadian hatchery strains (N=1143) were genotyped to develop standardized baseline information. Strain contributions were estimated using a Bayesian inferential approach. Deviance information criteria was used to compare models evaluating strain contributions at different spatial and temporal scales. The best performing models were the most complex models, suggesting that hatchery strain contributions to naturally produced lake trout varied spatially among management districts and temporally between time periods. Contributions of Seneca strain lake trout were consistently high across most management districts, with contributions increasing from early to late time periods (estimates ranged from 52-94% for the late period across eight of nine districts). Strain contributions deviated from expectations based on historical stocking levels, indicating strains differed with respect to survival, reproductive success, and/or dispersal. Knowledge of recruitment levels of strains stocked in different management districts, and how strain-specific recruitment varies temporally, spatially, and as a function of local or regional stocking is important to prioritize strains for future stocking and management of the transition process from primarily hatchery to naturally produced stocks.

Proteomic analysis reveals different composition of extracellular vesicles released by two Trypanosoma cruzi strains associated with their distinct interaction with host cells.

PubMed

Ribeiro, Kleber Silva; Vasconcellos, Camilla Ioshida; Soares, Rodrigo Pedro; Mendes, Maria Tays; Ellis, Cameron C; Aguilera-Flores, Marcela; de Almeida, Igor Correia; Schenkman, Sergio; Iwai, Leo Kei; Torrecilhas, Ana Claudia

2018-01-01

Trypanosoma cruzi , the aetiologic agent of Chagas disease, releases vesicles containing a wide range of surface molecules known to affect the host immunological responses and the cellular infectivity. Here, we compared the secretome of two distinct strains (Y and YuYu) of T. cruzi , which were previously shown to differentially modulate host innate and acquired immune responses. Tissue culture-derived trypomastigotes of both strains secreted extracellular vesicles (EVs), as demonstrated by electron scanning microscopy. EVs were purified by exclusion chromatography or ultracentrifugation and quantitated using nanoparticle tracking analysis. Trypomastigotes from YuYu strain released higher number of EVs than those from Y strain, enriched with virulence factors trans -sialidase (TS) and cruzipain. Proteomic analysis confirmed the increased abundance of proteins coded by the TS gene family, mucin-like glycoproteins, and some typical exosomal proteins in the YuYu strain, which also showed considerable differences between purified EVs and vesicle-free fraction as compared to the Y strain. To evaluate whether such differences were related to parasite infectivity, J774 macrophages and LLC-MK2 kidney cells were preincubated with purified EVs from both strains and then infected with Y strain trypomastigotes. EVs released by YuYu strain caused a lower infection but higher intracellular proliferation in J774 macrophages than EVs from Y strain. In contrast, YuYu strain-derived EVs caused higher infection of LLC-MK2 cells than Y strain-derived EVs. In conclusion, quantitative and qualitative differences in EVs and secreted proteins from different T. cruzi strains may correlate with infectivity/virulence during the host-parasite interaction.

Proteomic analysis reveals different composition of extracellular vesicles released by two Trypanosoma cruzi strains associated with their distinct interaction with host cells

PubMed Central

Ribeiro, Kleber Silva; Vasconcellos, Camilla Ioshida; Soares, Rodrigo Pedro; Ellis, Cameron C.; Aguilera-Flores, Marcela; de Almeida, Igor Correia

2018-01-01

ABSTRACT Trypanosoma cruzi, the aetiologic agent of Chagas disease, releases vesicles containing a wide range of surface molecules known to affect the host immunological responses and the cellular infectivity. Here, we compared the secretome of two distinct strains (Y and YuYu) of T. cruzi, which were previously shown to differentially modulate host innate and acquired immune responses. Tissue culture-derived trypomastigotes of both strains secreted extracellular vesicles (EVs), as demonstrated by electron scanning microscopy. EVs were purified by exclusion chromatography or ultracentrifugation and quantitated using nanoparticle tracking analysis. Trypomastigotes from YuYu strain released higher number of EVs than those from Y strain, enriched with virulence factors trans-sialidase (TS) and cruzipain. Proteomic analysis confirmed the increased abundance of proteins coded by the TS gene family, mucin-like glycoproteins, and some typical exosomal proteins in the YuYu strain, which also showed considerable differences between purified EVs and vesicle-free fraction as compared to the Y strain. To evaluate whether such differences were related to parasite infectivity, J774 macrophages and LLC-MK2 kidney cells were preincubated with purified EVs from both strains and then infected with Y strain trypomastigotes. EVs released by YuYu strain caused a lower infection but higher intracellular proliferation in J774 macrophages than EVs from Y strain. In contrast, YuYu strain-derived EVs caused higher infection of LLC-MK2 cells than Y strain-derived EVs. In conclusion, quantitative and qualitative differences in EVs and secreted proteins from different T. cruzi strains may correlate with infectivity/virulence during the host–parasite interaction. PMID:29696081

Complete Genome Sequence of a Yersinia enterocolitica “Old World” (3/O:9) Strain and Comparison with the “New World” (1B/O:8) Strain▿†

PubMed Central

Wang, Xin; Li, Yang; Jing, Huaiqi; Ren, Yan; Zhou, Zhemin; Wang, Shaojing; Kan, Biao; Xu, Jianguo; Wang, Lei

2011-01-01

Yersinia enterocolitica is a heterogeneous bacterial species with a wide range of animal reservoirs through which human intestinal illness can be facilitated. In contrast to the epidemiological pattern observed in the United States, infections in China present a pattern similar to those in European countries and Japan, wherein “Old World” strains (biotypes 2 to 5) are prevalent. To gain insights into the evolution of Y. enterocolitica and pathogenic properties toward human hosts, we sequenced the genome of a biotype 3 strain, 105.5R(r) (O:9), obtained from a Chinese patient. Comparative genome sequence analysis with strain 8081 (1B/O:8) revealed new insights into Y. enterocolitica. Both strains have more than 14% specific genes. In strain 105.5R(r), putative virulence factors were found in strain-specific genomic pathogenicity islands that comprised a novel type III secretion system and rtx-like genes. Many of the loci representing ancestral clusters, which are believed to contribute to enteric survival and pathogenesis, are present in strain 105.5R(r) but lost in strain 8081. Insertion elements in 105.5R(r) have a pattern distinct from those in strain 8081 and were exclusively located in a strain-specific region. In summary, our comparative genome analysis indicates that these two strains may have attained their pathogenicity by completely separate evolutionary events, and the 105.5R(r) strain, a representative of the Old World biogroup, lies in a branch of Y. enterocolitica that is distinct from the “New World” 8081 strain. PMID:21325549

Molecular typing of Brucella melitensis endemic strains and differentiation from the vaccine strain Rev-1.

PubMed

Noutsios, Georgios T; Papi, Rigini M; Ekateriniadou, Loukia V; Minas, Anastasios; Kyriakidis, Dimitrios A

2012-03-01

In the present study forty-four Greek endemic strains of Br. melitensis and three reference strains were genotyped by Multi locus Variable Number Tandem Repeat (ML-VNTR) analysis based on an eight-base pair tandem repeat sequence that was revealed in eight loci of Br. melitensis genome. The forty-four strains were discriminated from the vaccine strain Rev-1 by Restriction Fragment Length Polymorphism (RFLP) and Denaturant Gradient Gel Electrophoresis (DGGE). The ML-VNTR analysis revealed that endemic, reference and vaccine strains are genetically closely related, while most of the loci tested (1, 2, 4, 5 and 7) are highly polymorphic with Hunter-Gaston Genetic Diversity Index (HGDI) values in the range of 0.939 to 0.775. Analysis of ML-VNTRs loci stability through in vitro passages proved that loci 1 and 5 are non stable. Therefore, vaccine strain can be discriminated from endemic strains by allele's clusters of loci 2, 4, 6 and 7. RFLP and DGGE were also employed to analyse omp2 gene and reveled different patterns among Rev-1 and endemic strains. In RFLP, Rev-1 revealed three fragments (282, 238 and 44 bp), while endemic strains two fragments (238 and 44 bp). As for DGGE, the electrophoretic mobility of Rev-1 is different from the endemic strains due to heterologous binding of DNA chains of omp2a and omp2b gene. Overall, our data show clearly that it is feasible to genotype endemic strains of Br. melitensis and differentiate them from vaccine strain Rev-1 with ML-VNTR, RFLP and DGGE techniques. These tools can be used for conventional investigations in brucellosis outbreaks.

Computational Models Predict Larger Muscle Tissue Strains at Faster Sprinting Speeds

PubMed Central

Fiorentino, Niccolo M; Rehorn, Michael R; Chumanov, Elizabeth S; Thelen, Darryl G; Blemker, Silvia S

2014-01-01

Introduction: Proximal biceps femoris musculotendon strain injury has been well established as a common injury among athletes participating in sports that require sprinting near or at maximum speed; however, little is known about the mechanisms that make this muscle tissue more susceptible to injury at faster speeds. Purpose: Quantify localized tissue strain during sprinting at a range of speeds. Methods: Biceps femoris long head (BFlh) musculotendon dimensions of 14 athletes were measured on magnetic resonance (MR) images and used to generate a finite element computational model. The model was first validated through comparison with previous dynamic MR experiments. After validation, muscle activation and muscle-tendon unit length change were derived from forward dynamic simulations of sprinting at 70%, 85% and 100% maximum speed and used as input to the computational model simulations. Simulations ran from mid-swing to foot contact. Results: The model predictions of local muscle tissue strain magnitude compared favorably with in vivo tissue strain measurements determined from dynamic MR experiments of the BFlh. For simulations of sprinting, local fiber strain was non-uniform at all speeds, with the highest muscle tissue strain where injury is often observed (proximal myotendinous junction). At faster sprinting speeds, increases were observed in fiber strain non-uniformity and peak local fiber strain (0.56, 0.67 and 0.72, for sprinting at 70%, 85% and 100% maximum speed). A histogram of local fiber strains showed that more of the BFlh reached larger local fiber strains at faster speeds. Conclusions: At faster sprinting speeds, peak local fiber strain, fiber strain non-uniformity and the amount of muscle undergoing larger strains are predicted to increase, likely contributing to the BFlh muscle’s higher injury susceptibility at faster speeds. PMID:24145724

Influence of surrounding media refractive index on the thermal and strain sensitivities of long-period gratings

NASA Astrophysics Data System (ADS)

Canute Kamikawachi, Ricardo; Rafael Collere Possetti, Gustavo; Falate, Rosane; Muller, Marcia; Luís Fabris, José

2007-05-01

A detailed study of the thermal and strain sensitivities of a long-period grating when the device is immersed in different external media is presented. The range of refractive indices analyzed are within 1.000 to 1.447, corresponding to samples of air, water, ethanol, naphtha, thinner, turpentine, and kerosene. Within the same range of refractive indices, the strain sensitivity is between (-0.24 ± 0.03) and (-0.94 ± 0.11) pm/μɛ. For the grating immersed in these fluids, the refractive index sensitivity ranges from -3 to -1035.6 nm per refractive index units. The coupling thermo-optic coefficients and the strain-optic coefficients are also measured, resulting in the range from (2.45 ± 0.04)×10-5 to (15.89 ± 0.82)×10-5 deg C-1 and (-1.15 ± 0.04) to (-1.61 ± 0.04) μɛ-1, respectively. A noticeable nonlinear behavior of the thermal sensitivity is found for external media with refractive indices higher than 1.430.

A Combined Precipitation, Yield Stress, and Work Hardening Model for Al-Mg-Si Alloys Incorporating the Effects of Strain Rate and Temperature

NASA Astrophysics Data System (ADS)

Myhr, Ole Runar; Hopperstad, Odd Sture; Børvik, Tore

2018-05-01

In this study, a combined precipitation, yield strength, and work hardening model for Al-Mg-Si alloys known as NaMo has been further developed to include the effects of strain rate and temperature on the resulting stress-strain behavior. The extension of the model is based on a comprehensive experimental database, where thermomechanical data for three different Al-Mg-Si alloys are available. In the tests, the temperature was varied between 20 °C and 350 °C with strain rates ranging from 10-6 to 750 s-1 using ordinary tension tests for low strain rates and a split-Hopkinson tension bar system for high strain rates, respectively. This large span in temperatures and strain rates covers a broad range of industrial relevant problems from creep to impact loading. Based on the experimental data, a procedure for calibrating the different physical parameters of the model has been developed, starting with the simplest case of a stable precipitate structure and small plastic strains, from which basic kinetic data for obstacle limited dislocation glide were extracted. For larger strains, when work hardening becomes significant, the dynamic recovery was linked to the Zener-Hollomon parameter, again using a stable precipitate structure as a basis for calibration. Finally, the complex situation of concurrent work hardening and dynamic evolution of the precipitate structure was analyzed using a stepwise numerical solution algorithm where parameters representing the instantaneous state of the structure were used to calculate the corresponding instantaneous yield strength and work hardening rate. The model was demonstrated to exhibit a high degree of predictive power as documented by a good agreement between predictions and measurements, and it is deemed well suited for simulations of thermomechanical processing of Al-Mg-Si alloys where plastic deformation is carried out at various strain rates and temperatures.

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

[Isolation and phylogenetic analysis of one actinomycete strain YIM 90022 exhibiting anticancer activity].

PubMed

Chen, Yi-Guang; Li, Wen-Jun; Cui, Xiao-Long; Jiang, Cheng-Lin; Xu, Li-Hua

2006-10-01

One facultative alkaliphilic actinomycete strain YIM 90022 was isolated from hypersaline alkaline soil in Qinghai province, China. An almost-complete 16S rRNA gene sequence (1500 bp) for strain YIM 90022 was obtained. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain YIM 90022 was closely related to four members of the genus Nocardiopsis with 16S rRNA gene sequence similarity values of 98.8% (N. exhalans DSM 44407T), 98.5% (N. prasina DSM 43845T), 98.4% (N. metallicus DSM 44598T) and 97.8% (N. listeri DSM 40297T), but represented a distinct phylogenetic lineage. Repetitive element sequence-based PCR (rep-PCR) genomic fingerprinting was evaluated on strain YIM 90022 and its closest relatives to investigate their genetic relatedness. The analysis of the rep-PCR genomic fingerprints showed that strain YIM 90022 was distinguishable from its closest relatives. The polyphasic taxonomic data presented in this study, including its morphology, physiological and biochemical characteristics, chemotaxonomy, 16S rRNA gene sequence-based phylogenetic analysis and rep-PCR genomic fingerprinting, supported the view that strain YIM 90022 represented a potential new species of the genus Nocardiopsis. The fermentation broth of strain YIM 90022 strongly inhibited growth of cell series of gastric cancer, lung cancer, mammary cancer, melanoma cancer, renal cancer and uterus cancer. Strain YIM 90022 grew well on most tested media, producing exuberant vegetative hyphae and aerial hyphae. The vegetative hyphae are long and fragmented. Light yellow to deep brown diffusible pigments were produced on ISP 2, ISP 3 and ISP 6. Growth of the strain occurred in the pH range 6.0-12.0, with optimal pH8.5. The NaCl tolerate range was 0-15% (W/V). Cell walls contain meso-diaminopimelic acid and have no diagnostic sugars. Polar lipids are phosphatidylcholine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylmethylethanolamine. Major menaquinones are MK-10 (H4, H6). The DNA G + C content is 71.5 mol %.

In vivo bone strain in the mandibular corpus of Sapajus during a range of oral food processing behaviors.

PubMed

Ross, Callum F; Iriarte-Diaz, Jose; Reed, David A; Stewart, Thomas A; Taylor, Andrea B

2016-09-01

It has been hypothesized that mandibular corpus morphology of primates is related to the material properties of the foods that they chew. However, chewing foods with different material properties is accompanied by low levels of variation in mandibular strain patterns in macaques. We hypothesized that if variation in primate mandible form reflects adaptations to feeding on foods with different material and geometric properties, then this variation will be driven primarily by differences in oral food processing behavior rather than differences in chewing per se. To test this hypothesis, we recorded in vivo bone strain data from the lateral and medial surfaces of the mandibular corpus during complete feeding sequences in three adult male Sapajus as they fed on foods with a range of sizes and material properties. We assessed whether variation in mandibular corpus strain regimes is associated with variation in feeding behaviors and/or chewing on different foods, and we quantified the relative variation in mandibular corpus strain regimes associated with chewing on foods of different material properties versus a range of oral food processing behaviors (incisor, premolar, and molar biting; pulling on incisors; mastication). Feeding behavior had a significant effect on mandibular corpus strain regimes, as did chewing side and the cycle number in a feeding sequence. However, food type had weaker effects and usually only through interaction effects with chewing side and/or cycle type. Strain regimes varied most across different chew sides, then across different behaviors, and lastly between mastication cycles on different foods. Strain magnitudes associated with premolar, molar, and incisor biting were larger than those recorded during mastication. These data suggest that intra- and inter-specific variation in mandible morphology is a trade-off between performance requirements of different oral food processing behaviors and of variation in chewing side, with direct effects of food type being less important. Copyright © 2016 Elsevier Ltd. All rights reserved.

Desulfosoma caldarium gen. nov., sp. nov., a thermophilic sulfate-reducing bacterium from a terrestrial hot spring.

PubMed

Baena, Sandra; Perdomo, Natalia; Carvajal, Catalina; Díaz, Carolina; Patel, Bharat K C

2011-04-01

A thermophilic, sulfate-reducing bacterium, designated strain USBA-053(T), was isolated from a terrestrial hot spring located at a height of 2500 m in the Colombian Andes (5° 45' 33.29″ N 73° 6' 49.89″ W), Colombia. Cells of strain USBA-053(T) were oval- to rod-shaped, Gram-negative and motile by means of a single polar flagellum. The strain grew autotrophically with H(2) as the electron donor and heterotrophically on formate, propionate, butyrate, valerate, isovalerate, lactate, pyruvate, ethanol, glycerol, serine and hexadecanoic acid in the presence of sulfate as the terminal electron acceptor. The main end products from lactate degradation, in the presence of sulfate, were acetate, CO(2) and H(2)S. Strain USBA-053(T) fermented pyruvate in the absence of sulfate and grew optimally at 57 °C (growth temperature ranged from 50 °C to 62 °C) and pH 6.8 (growth pH ranged from 5.7 to 7.7). The novel strain was slightly halophilic and grew in NaCl concentrations ranging from 5 to 30 g l(-1), with an optimum at 25 g l(-1) NaCl. Sulfate, thiosulfate and sulfite were used as electron acceptors, but not elemental sulfur, nitrate or nitrite. The G+C content of the genomic DNA was 56±1 mol%. 16S rRNA gene sequence analysis indicated that strain USBA-053(T) was a member of the class Deltaproteobacteria, with Desulfacinum hydrothermale MT-96(T) as the closest relative (93 % gene sequence similarity). On the basis of physiological characteristics and phylogenetic analysis, it is suggested that strain USBA-053(T) represents a new genus and novel species for which the name Desulfosoma caldarium gen. nov., sp. nov. is proposed. The type strain of the type species is USBA-053(T) ( = KCTC 5670(T) = DSM 22027(T)).

Conjugative Plasmid Transfer in Xylella fastidiosa Is Dependent on tra and trb Operon Functions

PubMed Central

Van Horn, Christopher R.

2017-01-01

ABSTRACT The insect-transmitted plant pathogen Xylella fastidiosa is capable of efficient horizontal gene transfer (HGT) and recombination. Natural transformation occurs at high rates in X. fastidiosa, but there also is evidence that certain strains of X. fastidiosa carry native plasmids equipped with transfer and mobilization genes, suggesting conjugation as an additional mechanism of HGT in some instances. Two operons, tra and trb, putatively encoding a conjugative type IV secretion system, are found in some but not all X. fastidiosa isolates, often on native plasmids. X. fastidiosa strains that carry the conjugative transfer genes can belong to different subspecies and frequently differ in host ranges. Using X. fastidiosa strain M23 (X. fastidiosa subsp. fastidiosa) or Dixon (X. fastidiosa subsp. multiplex) as the donor strain and Temecula (X. fastidiosa subsp. fastidiosa) as the recipient strain, plasmid transfer was characterized using the mobilizable broad-host-range vector pBBR5pemIK. Transfer of plasmid pBBR5pemIK was observed under in vitro conditions with both donor strains and was dependent on both tra and trb operon functions. A conjugative mechanism likely contributes to gene transfer between diverse strains of X. fastidiosa, possibly facilitating adaptation to new environments or different hosts. IMPORTANCE Xylella fastidiosa is an important plant pathogen worldwide, infecting a wide range of different plant species. The emergence of new diseases caused by X. fastidiosa, or host switching of existing strains, is thought to be primarily due to the high frequency of HGT and recombination in this pathogen. Transfer of plasmids by a conjugative mechanism enables movement of larger amounts of genetic material at one time, compared with other routes of gene transfer such as natural transformation. Establishing the prevalence and functionality of this mechanism in X. fastidiosa contributes to a better understanding of HGT, adaptation, and disease emergence in this diverse pathogen. PMID:28808128

Conjugative Plasmid Transfer in Xylella fastidiosa Is Dependent on tra and trb Operon Functions.

PubMed

Burbank, Lindsey P; Van Horn, Christopher R

2017-11-01

The insect-transmitted plant pathogen Xylella fastidiosa is capable of efficient horizontal gene transfer (HGT) and recombination. Natural transformation occurs at high rates in X. fastidiosa , but there also is evidence that certain strains of X. fastidiosa carry native plasmids equipped with transfer and mobilization genes, suggesting conjugation as an additional mechanism of HGT in some instances. Two operons, tra and trb , putatively encoding a conjugative type IV secretion system, are found in some but not all X. fastidiosa isolates, often on native plasmids. X. fastidiosa strains that carry the conjugative transfer genes can belong to different subspecies and frequently differ in host ranges. Using X. fastidiosa strain M23 ( X. fastidiosa subsp. fastidiosa ) or Dixon ( X. fastidiosa subsp. multiplex ) as the donor strain and Temecula ( X. fastidiosa subsp. fastidiosa ) as the recipient strain, plasmid transfer was characterized using the mobilizable broad-host-range vector pBBR5pemIK. Transfer of plasmid pBBR5pemIK was observed under in vitro conditions with both donor strains and was dependent on both tra and trb operon functions. A conjugative mechanism likely contributes to gene transfer between diverse strains of X. fastidiosa , possibly facilitating adaptation to new environments or different hosts. IMPORTANCE Xylella fastidiosa is an important plant pathogen worldwide, infecting a wide range of different plant species. The emergence of new diseases caused by X. fastidiosa , or host switching of existing strains, is thought to be primarily due to the high frequency of HGT and recombination in this pathogen. Transfer of plasmids by a conjugative mechanism enables movement of larger amounts of genetic material at one time, compared with other routes of gene transfer such as natural transformation. Establishing the prevalence and functionality of this mechanism in X. fastidiosa contributes to a better understanding of HGT, adaptation, and disease emergence in this diverse pathogen.

Influence of oxygen concentration, fuel composition, and strain rate on synthesis of carbon nanomaterials

NASA Astrophysics Data System (ADS)

Hou, Shuhn-Shyurng; Huang, Wei-Cheng

2015-02-01

This paper investigates the influence of flame parameters including oxygen concentration, fuel composition, and strain rate on the synthesis of carbon nanomaterials in opposed-jet ethylene diffusion flames with or without rigid-body rotation. In the experiments, a mixture of ethylene and nitrogen was introduced from the upper burner; meanwhile, a mixture of oxygen and nitrogen was supplied from the lower burner. A nascent nickel mesh was used as the catalytic metal substrate to collect deposited materials. With non-rotating opposed-jet diffusion flames, carbon nanotubes (CNTs) were successfully produced for oxygen concentrations in the range of 21-50 % at a fixed ethylene concentration of 20 %, and for ethylene concentrations ranging from 14 to 24 % at a constant oxygen concentration of 40 %. With rotating opposed-jet diffusion flames, the strain rate was varied by adjusting the angular velocities of the upper and lower burners. The strain rate governed by flow rotation greatly affects the synthesis of carbon nanomaterials [i.e., CNTs and carbon nano-onions (CNOs)] either through the residence time or carbon sources available. An increase in the angular velocity lengthened the residence time of the flow and thus caused the diffusion flame to experience a decreased strain rate, which in turn produced more carbon sources. The growth of multi-walled CNTs was achieved for the stretched flames experiencing a higher strain rate [i.e., angular velocity was equal to 0 or 1 rotations per second (rps)]. CNOs were synthesized at a lower strain rate (i.e., angular velocity was in the range of 2-5 rps). It is noteworthy that the strain rate controlled by flow rotation greatly influences the fabrication of carbon nanostructures owing to the residence time as well as carbon source. Additionally, more carbon sources and higher temperature are required for the synthesis of CNOs compared with those required for CNTs (i.e., about 605-625 °C for CNTs and 700-800 °C for CNOs).

Low-cycle fatigue analysis of a cooled copper combustion chamber

NASA Technical Reports Server (NTRS)

Miller, R. W.

1974-01-01

A three-dimensional finite element elastoplastic strain analysis was performed for the throat section of regeneratively cooled rocket engine combustion chamber. The analysis included thermal and pressure loads, and the effects of temperature dependent material properties, to determine the strain range corresponding to the engine operating cycle. The strain range was used in conjunction with OFHC copper isothermal fatigue test data to predict engine low-cycle fatigue life. The analysis was performed for chamber configuration and operating conditions corresponding to a hydrogen-oxygen chamber which was fatigue tested to failure at the NASA Lewis Research Center.

Constitutive response of Rene 80 under thermal mechanical loads

NASA Technical Reports Server (NTRS)

Kim, K. S.; Cook, T. S.; Mcknight, R. L.

1988-01-01

The applicability of a classical constitutive model for stress-strain analysis of a nickel base superalloy, Rene' 80, in the gas turbine thermomechanical fatigue (TMF) environment is examined. A variety of tests were conducted to generate basic material data and to investigate the material response under cyclic thermomechanical loading. Isothermal stress-strain data were acquired at a variety of strain rates over the TMF temperature range. Creep curves were examined at 2 temperature ranges, 871 to 982 C and 760 to 871 C. The results provide optimism on the ability of the classical constitutive model for high temperature applications.

In vitro synergy of pseudolaric acid B and fluconazole against clinical isolates of Candida albicans.

PubMed

Guo, Na; Ling, Guanghui; Liang, Xiaoying; Jin, Jing; Fan, Junwen; Qiu, Jiazhang; Song, Yu; Huang, Ning; Wu, Xiuping; Wang, Xuelin; Deng, Xuming; Deng, Xuliang; Yu, Lu

2011-09-01

Candida albicans is the most common fungal pathogen in humans. The emergence of resistance to azole antifungals has raised the issue of using such antifungals in combination to optimise therapeutic outcome. The objective of this study was to evaluate in vitro synergy of pseudolaric acid B (PAB) and fluconazole (FLC) against clinical isolates of C. albicans. The in vitro antifungal activity of PAB, a diterpene acid from Pseudolarix kaempferi Gordon, was evaluated alone and in combination with FLC against 22 FLC-resistant (FLC-R) and 12 FLC-susceptible (FLC-S) C. albicans using the chequerboard microdilution method and time-killing test assays. Synergism was observed in all 22 (100%) FLC-R strains tested as determined by both fractional inhibitory concentration index (FICI) with values ranging from 0.02 to 0.13 and bliss independence (BI) models. Synergism was observed in two of 12 (17%) FLC-S strains as determined by FICI model with values ranging from 0.25 to 0.5 and in three of 12 (18%) FLC-S strains as determined by BI model. For FLC-R strains, the drug concentrations of FLC and PAB, where synergistic interactions were found, ranged from 0.06 to 4 μg ml(-1) and 0.5 to 4 μg ml(-1) respectively. For FLC-S strains, the drug concentrations of FLC and PAB were 1-8 μg ml(-1) and 0.5-4 μg ml(-1) respectively. The BI model gave results consistent with FICI, but no antagonistic activity was observed in any of the strains tested. These interactions between PAB and FLC were confirmed using the time-killing test for the selected strains. Fluconazole and PAB exhibited a good synergism against azole-R isolates of C. albicans. © 2010 Blackwell Verlag GmbH.

Tindallia californiensis sp. nov., a new anaerobic, haloalkaliphilic, spore-forming acetogen isolated from Mono Lake in California

NASA Technical Reports Server (NTRS)

Pikuta, E. V.; Hoover, R. B.; Bej, A. K.; Marsic, D.; Detkova, E. N.; Whitman, W. B.; Krader, P.

2003-01-01

A novel extremely haloalkaliphilic, strictly anaerobic, acetogenic bacterium strain APO was isolated from sediments of the athalassic, meromictic, alkaline Mono Lake in California. The Gram-positive, spore-forming, slightly curved rods with sizes 0.55- 0.7x1.7-3.0 microns were motile by a single laterally attached flagellum. Strain APO was mesophilic (range 10-48 C, optimum of 37 C); halophilic (NaCl range 1-20% (w/v) with optimum of 3-5% (w/v), and alkaliphilic (pH range 8.0-10.5, optimum 9.5). The novel isolate required sodium ions in the medium. Strain APO was an organotroph with a fermentative type of metabolism and used the substrates peptone, bacto-tryptone, casamino acid, yeast extract, L-serine, L-lysine, L-histidine, L-arginine, and pyruvate. The new isolate performed the Stickland reaction with the following amino acid pairs: proline + alanine, glycine + alanine, and tryptophan + valine. The main end product of growth was acetate. High activity of CO dehydrogenase and hydrogenase indicated the presence of a homoacetogenic, non-cycling acetyl-coA pathway. Strain APO was resistant to kanamycin but sensitive to chloramphenicol, tetracycline, and gentamycin. The G+C content of the genomic DNA was 44.4 mol% (by HPLC method). The sequence of the 16s rRNA gene of strain APO possessed 98.2% similarity with the sequence from Tindullia magadiensis Z-7934, but the DNA-DNA hybridization value between these organisms was only 55%. On the basis of these physiological and molecular properties, strain APO is proposed to be a novel species of the genus Tindallia with the name Tindallia californiensis sp. nov., (type strain APO = ATCC BAA-393 - DSM 14871).

Quantitative echocardiographic measures in the assessment of single ventricle function post-Fontan: Incorporation into routine clinical practice.

PubMed

Rios, Rodrigo; Ginde, Salil; Saudek, David; Loomba, Rohit S; Stelter, Jessica; Frommelt, Peter

2017-01-01

Quantitative echocardiographic measurements of single ventricular (SV) function have not been incorporated into routine clinical practice. A clinical protocol, which included quantitative measurements of SV deformation (global circumferential and longitudinal strain and strain rate), standard deviation of time to peak systolic strain, myocardial performance index (MPI), dP/dT from an atrioventricular valve regurgitant jet, and superior mesenteric artery resistance index, was instituted for all patients with a history of Fontan procedure undergoing echocardiography. All measures were performed real time during clinically indicated studies and were included in clinical reports. A total of 100 consecutive patients (mean age = 11.95±6.8 years, range 17 months-31.3 years) completed the protocol between September 1, 2014 to April 29, 2015. Deformation measures were completed in 100% of the studies, MPI in 93%, dP/dT in 55%, and superior mesenteric artery Doppler in 82%. The studies were reviewed to assess for efficiency in completing the protocol. The average time for image acquisition was 27.4±8.8 (range 10-62 minutes). The average time to perform deformation measures was 10.8±5.5 minutes (range 5-35 minutes) and time from beginning of imaging to report completion was 53.4±13.7 minutes (range 27-107 minutes). There was excellent inter-observer reliability when deformation indices were blindly repeated. Patients with a single left ventricle had significantly higher circumferential strain and strain rate, longitudinal strain and strain rate, and dP/dT compared to a single right ventricle. There were no differences in quantitative indices of ventricular function between patients <10 vs. >10 years post-Fontan. Advanced quantitative assessment of SV function post-Fontan can be consistently and efficiently performed real time during clinically indicated echocardiograms with excellent reliability. © 2016, Wiley Periodicals, Inc.

[Retrospective seroprevalence study of bovine leptospirosis in Mexico considering the ecological regions].

PubMed

Alvarez, Miguel Angel Luna; Moles y Cervantes, Luis Pedro; Rosas, Dolores Gavaldón; Vasquez, Carmen Nava; García, Félix Salazar

2005-01-01

The newly published information about the different ecological regions of Mexico was analyzed aimed at knowing the situation of bovine leptospirosis. A bibliographical search was made and the articles were chosen according to the following inclusion criteria: a) diagnosis technique: microscopic agglutination, b) positive criterion titres of 1:100 or higher, c) time period: 1991-2003, d) publications such as thesis, memoirs of congresses, non-scientific journals and journals with arbitrage, e) location by states. The duplicated information was considered as the exclusion criteria. The results of frequency and of serovarieties of leptospirosis were reported by state, considering the different ecological regions. Reference to 17 states is made. The arid and semi-arid region had a frequency of 37.8 % with a range from 31% to 59%, the prevalent serovars were H-89 strain (hardjo genotype hardjoprajitno), hardjo, wolffi and tarassovi. In the dry tropical region, there was a frequency of 45.9 % with a range from 27 to 72 %. The prevailing serovarieties were wolffi, hardjo and tarassovi. In the humid tropical region , the frequency was 63.8 % with a range between 31.7 and 84.6 %. The predominating serovarieties were H-89 strain (hardjo genotype hardjoprajitno), hardjo, wolffi and tarassovi. In the mild climate, the average frequency of leptospirosis was 39.4 % with a range from 22.1 to 54.3 %. The prevailing serovarieties were Palo Alto strain (icterohaemorrhagiae), Sinaloa ACR strain (portlandvere), bratislava, pyrogenes, pomona, and H-89 strain (hardjoprajitno), hardjo, wolffi and tarassovi. It was concluded that the presence of antobodies against L. interrogans is endemic in the different ecological regions of Mexico and that there is an elevated prevalence of serovarieties hardjo, wolffi y tarassovi; although in the temperate region, the Palo Alto strain (icterohaemorrhagiae), the Sinaloa ACR strain (portland vere) and Bratislava are present, too. Apparently, the climate influences on the frequency of presentation of the serovarieties. This is the first analysis of bovine leptospirosis by regions made in Mexico.

Genomic Changes Associated with the Evolutionary Transitions of Nostoc to a Plant Symbiont.

PubMed

Warshan, Denis; Liaimer, Anton; Pederson, Eric; Kim, Sea-Yong; Shapiro, Nicole; Woyke, Tanja; Altermark, Bjørn; Pawlowski, Katharina; Weyman, Philip D; Dupont, Christopher L; Rasmussen, Ulla

2018-05-01

Cyanobacteria belonging to the genus Nostoc comprise free-living strains and also facultative plant symbionts. Symbiotic strains can enter into symbiosis with taxonomically diverse range of host plants. Little is known about genomic changes associated with evolutionary transition of Nostoc from free-living to plant symbiont. Here, we compared the genomes derived from 11 symbiotic Nostoc strains isolated from different host plants and infer phylogenetic relationships between strains. Phylogenetic reconstructions of 89 Nostocales showed that symbiotic Nostoc strains with a broad host range, entering epiphytic and intracellular or extracellular endophytic interactions, form a monophyletic clade indicating a common evolutionary history. A polyphyletic origin was found for Nostoc strains which enter only extracellular symbioses, and inference of transfer events implied that this trait was likely acquired several times in the evolution of the Nostocales. Symbiotic Nostoc strains showed enriched functions in transport and metabolism of organic sulfur, chemotaxis and motility, as well as the uptake of phosphate, branched-chain amino acids, and ammonium. The genomes of the intracellular clade differ from that of other Nostoc strains, with a gain/enrichment of genes encoding proteins to generate l-methionine from sulfite and pathways for the degradation of the plant metabolites vanillin and vanillate, and of the macromolecule xylan present in plant cell walls. These compounds could function as C-sources for members of the intracellular clade. Molecular clock analysis indicated that the intracellular clade emerged ca. 600 Ma, suggesting that intracellular Nostoc symbioses predate the origin of land plants and the emergence of their extant hosts.

On the formation of adiabatic shear bands in titanium alloy Ti17 under severe loading conditions

NASA Astrophysics Data System (ADS)

Boubaker, H. Ben; Ayed, Y.; Mareau, C.; Germain, G.

2018-05-01

For metallic materials, fabrication processes (e.g. machining and forging) may involve important strain rates and high temperatures. For such severe loading conditions, the development of damage is often associated with the formation of Adiabatic Shear Bands (ASB). In this work, the impact of loading conditions (strain rate, temperature) on the formation of ASB in a beta rich titanium alloy (Ti17) is investigated. In this perspective, uniaxial compression tests have been conducted on cylindrical samples with a Gleeble-3500 thermo-mechanical simulator at temperatures ranging from 25°C to 800°C and strain rates ranging from 0.1 to 50 s-1 with axial strains of approximately 50 %. According to the experimental results, the flow curves exhibit hardening from 25°C to 550°C and softening from 600°C to 800°C. When looking at the evolution of flow stress, the strain rate sensitivity is found to increase significantly with increasing temperatures. Also, adiabatic shear bands are preferably observed for high strain rates and low temperatures. The formation of ASB thus seems to be quite dependent on the evolution of the strain rate sensitivity of Ti17. Finally, metallographic observations have been carried out to better understand the process leading to the formation of ASB. Such observations demonstrate that the average width of ASB increases with increasing temperatures and decreasing strain rates. However, such observations do not allow for identifying whether some specific microstructural transformations (e.g recrystallization or phase transformation) could explain the formation of ASB or not.

Hot Deformation Behavior and Flow Stress Prediction of TC4-DT Alloy in Single-Phase Region and Dual-Phase Regions

NASA Astrophysics Data System (ADS)

Liu, Jianglin; Zeng, Weidong; Zhu, Yanchun; Yu, Hanqing; Zhao, Yongqing

2015-05-01

Isothermal compression tests of TC4-DT titanium alloy at the deformation temperature ranging from 1181 to 1341 K covering α + β phase field and β-phase field, the strain rate ranging from 0.01 to 10.0 s-1 and the height reduction of 70% were conducted on a Gleeble-3500 thermo-mechanical simulator. The experimental true stress-true strain data were employed to develop the strain-compensated Arrhenius-type flow stress model and artificial neural network (ANN) model; the predictability of two models was quantified in terms of correlation coefficient ( R) and average absolute relative error (AARE). The R and AARE for the Arrhenius-type flow stress model were 0.9952 and 5.78%, which were poorer linear relation and more deviation than 0.9997 and 1.04% for the feed-forward back-propagation ANN model, respectively. The results indicated that the trained ANN model was more efficient and accurate in predicting the flow behavior for TC4-DT titanium alloy at elevated temperature deformation than the strain-compensated Arrhenius-type constitutive equations. The constitutive relationship compensating strain could track the experimental data across the whole hot working domain other than that at high strain rates (≥1 s-1). The microstructure analysis illustrated that the deformation mechanisms existed at low strain rates (≤0.1 s-1), where dynamic recrystallization occurred, were far different from that at high strain rates (≥1 s-1) that presented bands of flow localization and cracking along grain boundary.

Genomic Changes Associated with the Evolutionary Transitions of Nostoc to a Plant Symbiont

PubMed Central

Liaimer, Anton; Pederson, Eric; Kim, Sea-Yong; Shapiro, Nicole; Woyke, Tanja; Altermark, Bjørn; Pawlowski, Katharina; Weyman, Philip D; Dupont, Christopher L

2018-01-01

Abstract Cyanobacteria belonging to the genus Nostoc comprise free-living strains and also facultative plant symbionts. Symbiotic strains can enter into symbiosis with taxonomically diverse range of host plants. Little is known about genomic changes associated with evolutionary transition of Nostoc from free-living to plant symbiont. Here, we compared the genomes derived from 11 symbiotic Nostoc strains isolated from different host plants and infer phylogenetic relationships between strains. Phylogenetic reconstructions of 89 Nostocales showed that symbiotic Nostoc strains with a broad host range, entering epiphytic and intracellular or extracellular endophytic interactions, form a monophyletic clade indicating a common evolutionary history. A polyphyletic origin was found for Nostoc strains which enter only extracellular symbioses, and inference of transfer events implied that this trait was likely acquired several times in the evolution of the Nostocales. Symbiotic Nostoc strains showed enriched functions in transport and metabolism of organic sulfur, chemotaxis and motility, as well as the uptake of phosphate, branched-chain amino acids, and ammonium. The genomes of the intracellular clade differ from that of other Nostoc strains, with a gain/enrichment of genes encoding proteins to generate l-methionine from sulfite and pathways for the degradation of the plant metabolites vanillin and vanillate, and of the macromolecule xylan present in plant cell walls. These compounds could function as C-sources for members of the intracellular clade. Molecular clock analysis indicated that the intracellular clade emerged ca. 600 Ma, suggesting that intracellular Nostoc symbioses predate the origin of land plants and the emergence of their extant hosts. PMID:29554291

A closer look at prion strains

PubMed Central

Solforosi, Laura; Milani, Michela; Mancini, Nicasio; Clementi, Massimo; Burioni, Roberto

2013-01-01

Prions are infectious proteins that are responsible for transmissible spongiform encephalopathies (TSEs) and consist primarily of scrapie prion protein (PrPSc), a pathogenic isoform of the host-encoded cellular prion protein (PrPC). The absence of nucleic acids as essential components of the infectious prions is the most striking feature associated to these diseases. Additionally, different prion strains have been isolated from animal diseases despite the lack of DNA or RNA molecules. Mounting evidence suggests that prion-strain-specific features segregate with different PrPSc conformational and aggregation states. Strains are of practical relevance in prion diseases as they can drastically differ in many aspects, such as incubation period, PrPSc biochemical profile (e.g., electrophoretic mobility and glycoform ratio) and distribution of brain lesions. Importantly, such different features are maintained after inoculation of a prion strain into genetically identical hosts and are relatively stable across serial passages. This review focuses on the characterization of prion strains and on the wide range of important implications that the study of prion strains involves. PMID:23357828

Study of a high-precision SAW-MOEMS strain sensor with laser optics

NASA Astrophysics Data System (ADS)

Liu, Xinwei; Chen, Shufen; Li, Honglang; Zou, Zhengfeng; Fu, Lei; Meng, Yanbin

2015-02-01

A novel structure design of a surface acoustic wave (SAW) micro-optic-electro-mechanical-system (MOEMS) strain sensor with a light readout unit is presented in this paper. By measuring the polarization intensity ratio of the TE/TM mode outputted from the waveguide, the strain produced from an object can be measured precisely. The basic working principle of the SAW MOEMS strain sensor is introduced and the mathematical model of the strain sensor system is established. The SAW characteristics effected by the strain sensor are mathematically deduced. The coupling coefficient between the SAW modes and light modes can be calculated based on the theory of coupling modes. The conversion coefficient of polarized light modes is obtained. Due to the restrictions of the specific parameters of the device, the level of technology and the material characteristics, the sensitivity of the strain sensor system is calculated through simulation as 0.1 μɛ, with a dynamic range of 0 ~ ±50 μɛ.

Biocontrol of Fusarium Crown and Root Rot and Promotion of Growth of Tomato by Paenibacillus Strains Isolated from Soil

PubMed Central

Xu, Sheng Jun

2014-01-01

In this study, bacterial strains were isolated from soils from 30 locations of Samcheok, Gangwon province. Of the isolated strains, seven showed potential plant growth promoting and antagonistic activities. Based on cultural and morphological characterization, and 16S rRNA gene sequencing, these strains were identified as Paenibacillus species. All seven strains produced ammonia, cellulase, hydrocyanic acid, indole-3-acetic acid, protease, phosphatase, and siderophores. They also inhibited the mycelial growth of Fusarium oxysporum f. sp. radicis-lycopersici in vitro. The seven Paenibacillus strains enhanced a range of growth parameters in tomato plants under greenhouse conditions, in comparison with non-inoculated control plants. Notably, treatment of tomato plants with one identified strain, P. polymyxa SC09-21, resulted in 80.0% suppression of fusarium crown and root rot under greenhouse conditions. The plant growth promoting and antifungal activity of P. polymyxa SC09-21 identified in this study highlight its potential suitability as a bioinoculant. PMID:25071385

Clinical feasibility and validation of 3D principal strain analysis from cine MRI: comparison to 2D strain by MRI and 3D speckle tracking echocardiography.

PubMed

Satriano, Alessandro; Heydari, Bobak; Narous, Mariam; Exner, Derek V; Mikami, Yoko; Attwood, Monica M; Tyberg, John V; Lydell, Carmen P; Howarth, Andrew G; Fine, Nowell M; White, James A

2017-12-01

Two-dimensional (2D) strain analysis is constrained by geometry-dependent reference directions of deformation (i.e. radial, circumferential, and longitudinal) following the assumption of cylindrical chamber architecture. Three-dimensional (3D) principal strain analysis may overcome such limitations by referencing intrinsic (i.e. principal) directions of deformation. This study aimed to demonstrate clinical feasibility of 3D principal strain analysis from routine 2D cine MRI with validation to strain from 2D tagged cine analysis and 3D speckle tracking echocardiography. Thirty-one patients undergoing cardiac MRI were studied. 3D strain was measured from routine, multi-planar 2D cine SSFP images using custom software designed to apply 4D deformation fields to 3D cardiac models to derive principal strain. Comparisons of strain estimates versus those by 2D tagged cine, 2D non-tagged cine (feature tracking), and 3D speckle tracking echocardiography (STE) were performed. Mean age was 51 ± 14 (36% female). Mean LV ejection fraction was 66 ± 10% (range 37-80%). 3D principal strain analysis was feasible in all subjects and showed high inter- and intra-observer reproducibility (ICC range 0.83-0.97 and 0.83-0.98, respectively-p < 0.001 for all directions). Strong correlations of minimum and maximum principal strain were respectively observed versus the following: 3D STE estimates of longitudinal (r = 0.81 and r = -0.64), circumferential (r = 0.76 and r = -0.58) and radial (r = -0.80 and r = 0.63) strain (p < 0.001 for all); 2D tagged cine estimates of longitudinal (r = 0.81 and r = -0.81), circumferential (r = 0.87 and r = -0.85), and radial (r = -0.76 and r = 0.81) strain (p < 0.0001 for all); and 2D cine (feature tracking) estimates of longitudinal (r = 0.85 and -0.83), circumferential (r = 0.88 and r = -0.87), and radial strain (r = -0.79 and r = 0.84, p < 0.0001 for all). 3D principal strain analysis is feasible using routine, multi-planar 2D cine MRI and shows high reproducibility with strong correlations to 2D conventional strain analysis and 3D STE-based analysis. Given its independence from geometry-related directions of deformation this technique may offer unique benefit for the detection and prognostication of myocardial disease, and warrants expanded investigation.

Thermal tolerance characteristics of non-O157 Shiga toxigenic strains of Escherichia coli (STEC) in a beef broth model system are similar to those of O157:H7 STEC.

PubMed

Vasan, Akhila; Leong, Wan Mei; Ingham, Steve C; Ingham, Barbara H

2013-07-01

The non-O157 Shiga toxigenic Escherichia coli (STEC) serogroups most commonly associated with illness are O26, O45, O103, O111, O121, and O145. In the United States, these serogroups are considered adulterants in raw nonintact beef. To begin to understand the behavior of these pathogens in meat systems, we compared the thermal tolerance of acid-adapted cells of non-O157 STEC and O157:H7 STEC in a beef-derived broth. D58°C-values were determined for at least three strains per serogroup, and D54.6°C-values and D63.6°C-values were determined for one strain per serogroup. Each strain was grown to stationary phase in brain heart infusion broth (BHIB; pH 7.0) and inoculated into prewarmed BHIB in a shaking water bath for thermotolerance experiments at 54.6, 58.0, or 63.6°C (three trials per strain). Samples were heated for up to 160 min at 54.6°C, 3 min at 58.0°C, or 45 s at 63.6°C, with periodic sampling followed by rapid cooling and plating on modified Levine's eosin methylene blue agar. For each strain and temperature, the log CFU per milliliter was plotted versus time, and D-values were determined. Across all strains, the least and most heat tolerant STEC serogroups at 58°C were O145 and O157, respectively. D58°C-values in BHIB ranged from 0.44 min for an O145 strain to 1.42 min for an O157:H7 strain. D58°C-values for O157 STEC strains were significantly higher than those for at least one strain in each of the non-O157 STEC serogroups (P < 0.05) except for serogroup O103. At 54.6°C, the most heat-resistant STEC strain belonged to serogroup O103 and was significantly more heat tolerant than the O157:H7 strains (P < 0.05). Grouping the strains, there were no significant differences in heat tolerance between O157 and non-O157 STEC at 63.6°C (P ≥ 0.05). The z-values for non-O157 STEC strains were comparable to those for O157:H7 STEC strains (P ≥ 0.05), ranging from 4.10 to 5.21°C. These results suggest that thermal processing interventions that target destruction of E. coli O157:H7 may have adequate lethality against non-O157 STEC.

Wearable Wide-Range Strain Sensors Based on Ionic Liquids and Monitoring of Human Activities

PubMed Central

Zhang, Shao-Hui; Wang, Feng-Xia; Li, Jia-Jia; Peng, Hong-Dan; Yan, Jing-Hui; Pan, Ge-Bo

2017-01-01

Wearable sensors for detection of human activities have encouraged the development of highly elastic sensors. In particular, to capture subtle and large-scale body motion, stretchable and wide-range strain sensors are highly desired, but still a challenge. Herein, a highly stretchable and transparent stain sensor based on ionic liquids and elastic polymer has been developed. The as-obtained sensor exhibits impressive stretchability with wide-range strain (from 0.1% to 400%), good bending properties and high sensitivity, whose gauge factor can reach 7.9. Importantly, the sensors show excellent biological compatibility and succeed in monitoring the diverse human activities ranging from the complex large-scale multidimensional motions to subtle signals, including wrist, finger and elbow joint bending, finger touch, breath, speech, swallow behavior and pulse wave. PMID:29135928

Differentiation and Monitoring of Cells Using a Biochip for Regenerative Medicine

NASA Astrophysics Data System (ADS)

Uchida, Tomoyuki; Arai, Fumihito; Suzuki, Osamu; Ichikawa, Akihiko; Fukuda, Toshio; Katagiri, Takenobu; Kamijo, Ryutaro; Nakamura, Masanori; Numata, Mamoru; Watanabe, Naruaki

A novel biochip is developed for culturing stem cells. Biochip is made of Polymer (PDMS), and cells can be loaded by gradient strains in one chip. They grow well on a hydrophilic membrane and differentiation is promoted by cyclic strains. In this paper, we propose the method for culturing and monitoring of stem cells such as bone marrow stromal cells (ST2 cells) and myoblasts (C2C12 cells), and the results of culture. First we analyzed strains on a membrane when an air hole is decompressed, and clarified their range. From experiment, bone marrow stromal cells grew well in a narrow range, and we quantified their ALP activity as a measure of differentiation. As myoblasts, the direction of their differentiation was perpendicular to a groove, that is, the same direction of uniaxial strains.

Low-Field-Triggered Large Magnetostriction in Iron-Palladium Strain Glass Alloys.

PubMed

Ren, Shuai; Xue, Dezhen; Ji, Yuanchao; Liu, Xiaolian; Yang, Sen; Ren, Xiaobing

2017-09-22

Development of miniaturized magnetostriction-associated devices requires low-field-triggered large magnetostriction. In this study, we acquired a large magnetostriction (800 ppm) triggered by a low saturation field (0.8 kOe) in iron-palladium (Fe-Pd) alloys. Magnetostriction enhancement jumping from 340 to 800 ppm was obtained with a slight increase in Pd concentration from 31.3 to 32.3 at. %. Further analysis showed that such a slight increase led to suppression of the long-range ordered martensitic phase and resulted in a frozen short-range ordered strain glass state. This strain glass state possessed a two-phase nanostructure with nanosized frozen strain domains embedded in the austenite matrix, which was responsible for the unique magnetostriction behavior. Our study provides a way to design novel magnetostrictive materials with low-field-triggered large magnetostriction.

Dynamic tensile fracture of mortar at ultra-high strain-rates

NASA Astrophysics Data System (ADS)

Erzar, B.; Buzaud, E.; Chanal, P.-Y.

2013-12-01

During the lifetime of a structure, concrete and mortar may be exposed to highly dynamic loadings, such as impact or explosion. The dynamic fracture at high loading rates needs to be well understood to allow an accurate modeling of this kind of event. In this work, a pulsed-power generator has been employed to conduct spalling tests on mortar samples at strain-rates ranging from 2 × 104 to 4 × 104 s-1. The ramp loading allowed identifying the strain-rate anytime during the test. A power law has been proposed to fit properly the rate-sensitivity of tensile strength of this cementitious material over a wide range of strain-rate. Moreover, a specimen has been recovered damaged but unbroken. Micro-computed tomography has been employed to study the characteristics of the damage pattern provoked by the dynamic tensile loading.

Geodetic measurement of deformation east of the San Andreas Fault in Central California

NASA Technical Reports Server (NTRS)

Sauber, Jeanne; Solomon, Sean C.; Lisowski, Michael

1988-01-01

The shear strain rates in the Diablo Range of California have been calculated, and the slip rate along the Calaveras and Paicines faults in Central California have been estimated, on the basis of triangulation and trilateration data from two geodetic networks located between the western edge of the Great Valley and the San Andreas Fault. The orientation of the principal compressive strain predicted from the azimuth of the major structures in the region is N 25 deg E, leading to an average shear strain value that corresponds to a relative shortening rate of 4.5 + or - 2.4 mm/yr. It is inferred that the measured strain is due to compression across the fold of this area. The hypothesized uniform, fault-normal compression within the Coast Ranges is not supported by these results.

Elevated temperature mechanical properties of line pipe steels

NASA Astrophysics Data System (ADS)

Jacobs, Taylor Roth

The effects of test temperature on the tensile properties of four line pipe steels were evaluated. The four materials include a ferrite-pearlite line pipe steel with a yield strength specification of 359 MPa (52 ksi) and three 485 MPa (70 ksi) yield strength acicular ferrite line pipe steels. Deformation behavior, ductility, strength, strain hardening rate, strain rate sensitivity, and fracture behavior were characterized at room temperature and in the temperature range of 200--350 °C, the potential operating range for steels used in oil production by the steam assisted gravity drainage process. Elevated temperature tensile testing was conducted on commercially produced as-received plates at engineering strain rates of 1.67 x 10 -4, 8.33 x 10-4, and 1.67 x 10-3 s-1. The acicular ferrite (X70) line pipe steels were also tested at elevated temperatures after aging at 200, 275, and 350 °C for 100 h under a tensile load of 419 MPa. The presence of serrated yielding depended on temperature and strain rate, and the upper bound of the temperature range where serrated yielding was observed was independent of microstructure between the ferrite-pearlite (X52) steel and the X70 steels. Serrated yielding was observed at intermediate temperatures and continuous plastic deformation was observed at room temperature and high temperatures. All steels exhibited a minimum in ductility as a function of temperature at testing conditions where serrated yielding was observed. At the higher temperatures (>275 °C) the X52 steel exhibited an increase in ductility with an increase in temperature and the X70 steels exhibited a maximum in ductility as a function of temperature. All steels exhibited a maximum in flow strength and average strain hardening rate as a function of temperature. The X52 steel exhibited maxima in flow strength and average strain hardening rate at lower temperatures than observed for the X70 steels. For all steels, the temperature where the maximum in both flow strength and strain hardening occurred increased with increasing strain rate. Strain rate sensitivities were measured using flow stress data from multiple tensile tests and strain rate jump tests on single tensile samples. In flow stress strain rate sensitivity measurements, a transition from negative to positive strain rate sensitivity was observed in the X52 steel at approximately 275--300 °C, and negative strain rate sensitivity was observed at all elevated temperature testing conditions in the X70 steels. In jump test strain rate sensitivity measurements, all four steels exhibited a transition from negative to positive strain rate sensitivity at approximately 250--275 °C. Anisotropic deformation in the X70 steels was observed by measuring the geometry of the fracture surfaces of the tensile samples. The degree of anisotropy changed as a function of temperature and minima in the degree of anisotropy was observed at approximately 300 °C for all three X70 steels. DSA was verified as an active strengthening mechanism at elevated temperatures for all line pipe steels tested resulting in serrated yielding, a minimum in ductility as a function of temperature, a maximum in flow strength as a function of temperature, a maximum in average strain hardening rate as a function of temperature, and negative strain rate sensitivities. Mechanical properties of the X70 steels exhibited different functionality with respect to temperature compared to the X52 steels at temperatures greater than 250 ºC. Changes in the acicular ferrite microstructure during deformation such as precipitate coarsening, dynamic precipitation, tempering of martensite in martensite-austenite islands, or transformation of retained austenite could account for differences in tensile property functionality between the X52 and X70 steels. Long term aging under load (LTA) testing of the X70 steels resulted in increased yield strength compared to standard elevated temperature tensile tests at all temperatures as a result of static strain aging. LTA specimen ultimate tensile strengths (UTS) increased slightly at 200 °C, were comparable at 275 °C, and decreased significantly at 350 °C when compared to as-received (standard) tests at 350 °C. Observed reductions in UTS were a result of decreased strain hardening in the LTA specimens compared to standard tensile specimens. Ideal elevated temperature operating conditions (based on tensile properties) for the X70 line pipe steels in the temperature range relevant to the steam assisted gravity drainage process are around 275--325 °C at the strain rates tested. In the temperature range of 275--325 °C the X70 steels exhibited continuous plastic deformation, a maximum in ductility, a maximum in flow stress, improved strain hardening compared to intermediate temperatures, reduced anisotropic deformation, and after extended use at elevated temperatures, yield strength increases with little change in UTS.

Unusual strain glassy phase in Fe doped Ni2Mn1.5In0.5

NASA Astrophysics Data System (ADS)

Nevgi, R.; Priolkar, K. R.

2018-01-01

Fe doped Ni2Mn1.5In0.5, particularly, Ni2Mn1.4Fe0.1In0.5, despite having an incommensurate, modulated 7M martensitic structure at room temperature exhibits frequency dependent behavior of storage modulus and loss which obeys the Vogel-Fulcher law as well as shows ergodicity breaking between zero field cooled and field cooled strain measurements just above the transition temperature. Both frequency dependence and ergodicity breaking are characteristics of a strain glassy phase and occur due to the presence of strain domains which are large enough to present signatures of long range martensitic order in diffraction but are non-interacting with other strain domains due to the presence of Fe impurities.

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

Compere, A.L.; Griffith, W.L.

The production was evaluated of ethanol, acetone, and butanol from several different carbohydrate materials by five strains of Clostridia and two mixed cultures. The substrates, which were tested at concn ranging between 2.5 and 10% w/v, included pentoses, hexoses, disaccharides, and polysaccharides. The organisms used were Clostridium acetobutylicum strains NRRL B527 and NRRL B3179; Clostridium butylicum strains NRRL B592 and NRRL B593; and Clostridium pasteurianum strain NRRL B598. The mixed cultures contained all of these organisms. Mixed culture 1 contained in addition to the Clostridia, Klebsiella pneumoniae strain NRRL B427. Mixed culture 2 contained mixed culture 1 plus a yeastmore » isolated from kefir culture. Where possible, maxima were found for the conversion of different substrates. 7 tables.« less

Myocardial strain in healthy adults across a broad age range as revealed by cardiac magnetic resonance imaging at 1.5 and 3.0T: Associations of myocardial strain with myocardial region, age, and sex.

PubMed

Mangion, Kenneth; Clerfond, Guillaume; McComb, Christie; Carrick, David; Rauhalammi, Samuli M; McClure, John; Corcoran, David S; Woodward, Rosemary; Orchard, Vanessa; Radjenovic, Aleksandra; Zhong, Xiaodong; Berry, Colin

2016-11-01

To assess myocardial strain using cine displacement encoding with stimulated echoes (DENSE) using 1.5T and 3.0T MRI in healthy adults. Healthy adults without any history of cardiovascular disease underwent magnetic resonance imaging (MRI) at 1.5T and 3.0T within 2 days. The MRI protocol included balanced steady-state free-precession (b-SSFP), 2D cine-echo planar imaging (EPI)-DENSE, and late gadolinium enhancement in subjects >45 years. Acquisitions were divided into six segments; global and segmental peak longitudinal and circumferential strain were derived and analyzed by field strength, age, and gender. In all, 89 volunteers (mean age 44.8 ± 18.0 years, range: 18-87 years) underwent MRI at 1.5T, and 88 of these subjects underwent MRI at 3.0T (1.4 ± 1.4 days between the scans). Compared with 3.0T, the magnitudes of global circumferential (-19.5 ± 2.6% vs. -18.47 ± 2.6%; P = 0.001) and longitudinal (-12.47 ± 3.2% vs. -10.53 ± 3.1%; P = 0.004) strain were greater at 1.5T. At 1.5T, longitudinal strain was greater in females than in males: -10.17 ± 3.4% vs. -13.67 ± 2.4%; P = 0.001. Similar observations occurred for circumferential strain at 1.5T (-18.72 ± 2.2% vs. -20.10 ± 2.7%; P = 0.014) and at 3.0T (-17.92 ± 1.8% vs. -19.1 ± 3.1%; P = 0.047). At 1.5T, longitudinal and circumferential strain were not associated with age after accounting for sex (longitudinal strain P = 0.178, circumferential strain P = 0.733). At 3.0T, longitudinal and circumferential strain were associated with age (P < 0.05). Longitudinal strain values were greater in the apico-septal, basal-lateral, and mid-lateral segments and circumferential strain in the inferior, infero-lateral, and antero-lateral LV segments. Myocardial strain parameters as revealed by cine-DENSE at different MRI field strengths were associated with myocardial region, age, and sex. J. Magn. Reson. Imaging 2016;44:1197-1205. © 2016 The Authors Journal of Magnetic Resonance Imaging published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

Osmotic stress in Arctic and Antarctic strains of the green alga Zygnema (Zygnematales, Streptophyta): effects on photosynthesis and ultrastructure.

PubMed

Kaplan, Franziska; Lewis, Louise A; Herburger, Klaus; Holzinger, Andreas

2013-01-01

The osmotic potential and effects of plasmolysis on photosynthetic oxygen evolution and chlorophyll fluorescence were studied in two Arctic Zygnema sp. (strain B, strain G) and two Antarctic Zygnema sp. (strain E, strain D). Antarctic strain D was newly characterized by rbcL sequence analysis in the present study. The two Antarctic strains, D and E, are most closely related and may represent different isolates of the same species, in contrast, strain B and G are separate lineages. Incipient plasmolysis in the cells was determined by light microscopy after incubating cells in sorbitol solutions ranging between 200 mM and 1000 mM sorbitol for 3, 6 and 24h. In Zygnema strain B and G incipient plasmolysis occurred at ~600 mM sorbitol solution (720 mOsmol kg(-1), ψ=-1.67 MPa) and in strains D and E at ~300 mM (318 mOsmol kg(-1), ψ=-0.8 MPa) sorbitol solution. Hechtian strands were visualized in all plasmolysed cells, which is particularly interesting, as these cells lack pores or plasmodesmata. Ultrastructural changes upon osmotic stress were a retraction of the condensed cytoplasm from the cell walls, damages to chloroplast and mitochondrial membranes, increasing numbers of plastoglobules in the chloroplasts and membrane enclosed particles in the extraplasmatic space. Maximum photosynthetic rates (P(max)) in light saturated range were between 145.5 μmol O(2) h(-1)mg(-1)Chl a in Zygnema G and 752.9 μmol O(2) h(-1)mg(-1)Chl a in Zygnema E. After incubation in 800 mM sorbitol for 3h P(max) decreased to the following percentage of the initial values: B: 16.3%, D: 16.8%, E: 26.1% and G: 35.0%. Osmotic stress (800 mM sorbitol) decreased maximum photochemical quantum yield of photosystem II (F(v)/F(m)) when compared to controls. Maximum values of relative electron transport rates of photosystem II (rETR(max)) decreased after incubation in 400 mM sorbitol in Zygnema D and E, while they decreased in Zygnema B and G only after incubation in 800 mM sorbitol. The kinetics of the rETR curves were similar for the Arctic strains Zygnema B and G, but distinct from the Antarctic strains Zygnema D and E, which were similar when compared with each other. This suggests that the investigated Arctic Zygnema sp. strains might be better adapted to tolerate osmotic water stress than the investigated strains from the Antarctic. Copyright © 2012 Elsevier Ltd. All rights reserved.

Dynamic Uniaxial Compression of HSLA-65 Steel at Elevated Temperatures

NASA Astrophysics Data System (ADS)

Dike, Shweta; Wang, Tianxue; Zuanetti, Bryan; Prakash, Vikas

2017-12-01

In the present study, the dynamic response of a high-strength, low alloy Grade 65 (HSLA-65) steel, used by the United States Navy for ship hull construction, is investigated under dynamic uniaxial compression at temperatures ranging from room temperature to 1000 °C using a novel elevated temperature split-Hopkinson pressure bar. These experiments are designed to probe the dynamic response of HSLA-65 steel in its single α-ferrite phase, mixed α + γ-austenite phase, and the single γ-austenite phase, as a function of temperature. The investigation is conducted at two different average strain rates—1450 and 2100/s. The experimental results indicate that at test temperatures in the range from room temperature to lower than 600 °C, i.e. prior to the development of the mixed α + γ phase, a net softening in flow strength is observed at all levels of plastic strain with increase in test temperatures. As the test temperatures are increased, the rate of this strain softening with temperature is observed to decrease, and at 600 °C the trend reverses itself resulting in an increase in flow stress at all strains tested. This increase in flow stress is understood be due to dynamic strain aging, where solute atoms play a distinctive role in hindering dislocation motion. At 800 °C, a (sharp) drop in the flow stress, equivalent to one-half of its value at room temperature, is observed. As the test temperature are increased to 900 and 1000 °C, further drop in flow stress are observed at all plastic strain levels. In addition, strain hardening in flow stress is observed at all test temperatures up to 600 °C; beyond 800 °C the rate of strain hardening is observed to decrease, with strain softening becoming dominant at temperatures of 900 °C and higher. Moreover, comparing the high strain rate stress versus strain data gathered on HSLA 65 in the current investigation with those available in the literature at quasi-static strain rates, strain-rate hardening can be inferred. The flow stress increases from 700 MPa at 8 × 10-4/s to 950 MPa at 1450/s and then to 1000 MPa at 2100/s at a strain of 0.1. Optical microscopy is used to understand evolution of microstructure in the post-test samples at the various test temperatures employed in the present study.

Streptococcus pyogenes strains in Sao Paulo, Brazil: molecular characterization as a basis for StreptInCor coverage capacity analysis.

PubMed

Freschi de Barros, Samar; De Amicis, Karine Marafigo; Alencar, Raquel; Smeesters, Pierre Robert; Trunkel, Ariel; Postól, Edilberto; Almeida Junior, João Nóbrega; Rossi, Flavia; Pignatari, Antonio Carlos Campos; Kalil, Jorge; Guilherme, Luiza

2015-08-05

Several human diseases are caused by Streptococcus pyogenes, ranging from common infections to autoimmunity. Characterization of the most prevalent strains worldwide is a useful tool for evaluating the coverage capacity of vaccines under development. In this study, a collection of S. pyogenes strains from Sao Paulo, Brazil, was analyzed to describe the diversity of strains and assess the vaccine coverage capacity of StreptInCor. Molecular epidemiology of S. pyogenes strains was performed by emm-genotyping the 229 isolates from different clinical sites, and PCR was used for superantigen profile analysis. The emm-pattern and tissue tropism for these M types were also predicted and compared based on the emm-cluster classification. The strains were fit into 12 different emm-clusters, revealing a diverse phylogenetic origin and, consequently, different mechanisms of infection and escape of the host immune system. Forty-eight emm-types were distinguished in 229 samples, and the 10 most frequently observed types accounted for 69 % of all isolates, indicating a diverse profile of circulating strains comparable to other countries under development. A similar proportion of E and A-C emm-patterns were observed, whereas pattern D was less frequent, indicating that the strains of this collection primarily had a tissue tropism for the throat. In silico analysis of the coverage capacity of StreptInCor, an M protein-conserved regionally based vaccine candidate developed by our group, had a range of 94.5 % to 59.7 %, with a mean of 71.0 % identity between the vaccine antigen and the predicted amino acid sequence of the emm-types included here. This is the first report of S. pyogenes strain characterization in Sao Paulo, one of the largest cities in the world; thus, the strain panel described here is a representative sample for vaccine coverage capacity analysis. Our results enabled evaluation of StreptInCor candidate vaccine coverage capacity against diverse M-types, indicating that the vaccine candidate likely would induce protection against the diverse strains worldwide.

Isolation and Selection of Microalgal Strains from Natural Water Sources in Viet Nam with Potential for Edible Oil Production.

PubMed

Thao, Tran Yen; Linh, Dinh Thi Nhat; Si, Vo Chi; Carter, Taylor W; Hill, Russell T

2017-06-23

Industrial vegetable oil production in Viet Nam depends on oil seeds and crude plant oils that are currently more than 90% imported. As the first step in investigating the feasibility of using microalgae to provide Viet Nam with a domestic source of oil for food and edible oil industries, fifty lipid-producing microalgae were isolated and characterized. The microalgae were isolated from water sources ranging from freshwater to brackish and marine waters from a wide geographic distribution in Viet Nam. Initial analyses showed that 20 of the 50 strains had good growth rates, produced high biomass and had high lipid content, ranging up to 50% of dry weight biomass. 18S rRNA gene sequence analyses of the 50 strains showed a great diversity in this assemblage of microalgae, comprising at least 38 species and representatives of 25 genera : Chlamydomonas , Poterioochromonas , Scenedesmus , Desmodesmus , Chlorella , Bracteacoccus , Monoraphidium , Selenastrum , Acutodesmus , Mychonastes , Ankistrodesmus , Kirchneriella , Raphidocelis , Dictyosphaerium , Coelastrella , Schizochlamydella , Oocystidium , Nannochloris , Auxenochlorella , Chlorosarcinopsis , Stichococcus , Picochlorum , Prasinoderma , Chlorococcum , and Marvania. Some of the species are closely related to well-known lipid producers such as Chlorella sorokiniana , but some other strains are not closely related to the strains found in public sequence databases and likely represent new species. Analysis of oil quality showed that fatty acid profiles of the microalgal strains were very diverse and strain-dependent. Fatty acids in the microalgal oils comprised saturated fatty acids (SFAs), poly-unsaturated fatty acids (PUFAs), and mono-unsaturated fatty acids (MUFAs). The main SFA was palmitic acid. MUFAs and PUFAs were dominated by oleic acid, and linoleic and linolenic acids, respectively. Some strains were especially rich in the essential fatty acid α-linolenic acid (ALA), which comprised more than 20% of the fatty acids in these strains. Other strains had fatty acid compositions similar to that of palm oil. Several strains have been selected on the basis of their suitable fatty acid profiles and high lipid content for further chemical and physical characterization, toxicity and organoleptic tests of their oils, and for scale-up.

Isolation and Selection of Microalgal Strains from Natural Water Sources in Viet Nam with Potential for Edible Oil Production

PubMed Central

Thao, Tran Yen; Linh, Dinh Thi Nhat; Si, Vo Chi; Carter, Taylor W.; Hill, Russell T.

2017-01-01

Industrial vegetable oil production in Viet Nam depends on oil seeds and crude plant oils that are currently more than 90% imported. As the first step in investigating the feasibility of using microalgae to provide Viet Nam with a domestic source of oil for food and edible oil industries, fifty lipid-producing microalgae were isolated and characterized. The microalgae were isolated from water sources ranging from freshwater to brackish and marine waters from a wide geographic distribution in Viet Nam. Initial analyses showed that 20 of the 50 strains had good growth rates, produced high biomass and had high lipid content, ranging up to 50% of dry weight biomass. 18S rRNA gene sequence analyses of the 50 strains showed a great diversity in this assemblage of microalgae, comprising at least 38 species and representatives of 25 genera: Chlamydomonas, Poterioochromonas, Scenedesmus, Desmodesmus, Chlorella, Bracteacoccus, Monoraphidium, Selenastrum, Acutodesmus, Mychonastes, Ankistrodesmus, Kirchneriella, Raphidocelis, Dictyosphaerium, Coelastrella, Schizochlamydella, Oocystidium, Nannochloris, Auxenochlorella, Chlorosarcinopsis, Stichococcus, Picochlorum, Prasinoderma, Chlorococcum, and Marvania. Some of the species are closely related to well-known lipid producers such as Chlorella sorokiniana, but some other strains are not closely related to the strains found in public sequence databases and likely represent new species. Analysis of oil quality showed that fatty acid profiles of the microalgal strains were very diverse and strain-dependent. Fatty acids in the microalgal oils comprised saturated fatty acids (SFAs), poly-unsaturated fatty acids (PUFAs), and mono-unsaturated fatty acids (MUFAs). The main SFA was palmitic acid. MUFAs and PUFAs were dominated by oleic acid, and linoleic and linolenic acids, respectively. Some strains were especially rich in the essential fatty acid α-linolenic acid (ALA), which comprised more than 20% of the fatty acids in these strains. Other strains had fatty acid compositions similar to that of palm oil. Several strains have been selected on the basis of their suitable fatty acid profiles and high lipid content for further chemical and physical characterization, toxicity and organoleptic tests of their oils, and for scale-up. PMID:28644408

Highly stretchable and ultrathin nanopaper composites for epidermal strain sensors.

PubMed

Sun, Jingyao; Zhao, Yanan; Yang, Zhaogang; Shen, Jingjing; Cabrera, Eusebio; Lertola, Matthew J; Yang, Willie; Zhang, Dan; Benatar, Avi; Castro, Jose M; Wu, Daming; Lee, L James

2018-08-31

Multifunctional electronics are attracting great interest with the increasing demand and fast development of wearable electronic devices. Here, we describe an epidermal strain sensor based on an all-carbon conductive network made from multi-walled carbon nanotubes (MWCNTs) impregnated with poly(dimethyl siloxane) (PDMS) matrix through a vacuum filtration process. An ultrasonication treatment was performed to complete the penetration of PDMS resin in seconds. The entangled and overlapped MWCNT network largely enhances the electrical conductivity (1430 S m -1 ), uniformity (remaining stable on different layers), reliable sensing range (up to 80% strain), and cyclic stability of the strain sensor. The homogeneous dispersion of MWCNTs within the PDMS matrix leads to a strong interaction between the two phases and greatly improves the mechanical stability (ca. 160% strain at fracture). The flexible, reversible and ultrathin (<100 μm) film can be directly attached on human skin as epidermal strain sensors for high accuracy and real-time human motion detection.

Origin of the low-frequency internal friction background of gold

NASA Astrophysics Data System (ADS)

Baur, J.; Benoit, W.

1986-11-01

The internal friction (IF) background of gold is studied in the kHz frequency range. Systematic measurements of IF as a function of frequency, strain amplitude, and temperature show that the IF is due to the superposition of two contributions: the thermoelastic effect and a dislocation effect. The thermoelastic effect is responsible for the IF background observed when the strain amplitude tends to zero. It is the only contribution to the IF background which is strain amplitude independent. On the contrary, the dislocation effect contributes only to the strain amplitude-dependent IF background. This effect is proportional to the strain amplitude. In particular, it is zero when the strain amplitude tends to zero. Furthermore, the dislocation contribution is frequency independent. The experimental results show that the dislocation effect cannot be explained by a viscous damping of dislocation motion, but must be related to an hysteretic and athermal motion of dislocations.

Isolation and characterization of ethanol tolerant yeast strains

PubMed Central

Tikka, Chiranjeevi; Osuru, Hari Prasad; Atluri, Navya; Raghavulu, Praveen Chakravarthi Veera; yellapu, Nanda Kumar; Mannur, Ismail Shaik; Prasad, Uppu Venkateswara; Aluru, Sudheer; K, Narasimha Varma; Bhaskar, Matcha

2013-01-01

Yeast strains are commonly associated with sugar rich environments. Various fruit samples were selected as source for isolating yeast cells. The isolated cultures were identified at Genus level by colony morphology, biochemical characteristics and cell morphological characters. An attempt has been made to check the viability of yeast cells under different concentrations of ethanol. Ethanol tolerance of each strain was studied by allowing the yeast to grow in liquid YEPD (Yeast Extract Peptone Dextrose) medium having different concentrations of ethanol. A total of fifteen yeast strains isolated from different samples were used for the study. Seven strains of Saccharomyces cerevisiae obtained from different fruit sources were screened for ethanol tolerance. The results obtained in this study show a range of tolerance levels between 7%-12% in all the stains. Further, the cluster analysis based on 22 RAPD (Random Amplified polymorphic DNA) bands revealed polymorphisms in these seven Saccharomyces strains. PMID:23750092

Substantiating the concept of work strain: its implication for the assessment of work stressors.

PubMed

Szerencsi, Karolina; van Amelsvoort, Ludovic; Kant, Ijmert

2012-03-01

To assess which work stressors are substantially contributing to work strain and examine their relative contribution. We prospectively examined the association between work stressors and work strain, which was defined as employees reporting ill due to work stress. Relevant work stressors were combined into a stressor score with each stressor having its own relevance. Standardized odds ratios (SORs) were calculated using logistic regression analysis and used to compare the associations obtained between already existing scales and the stressor score with work strain. The stressor score yielded an SOR of 1.89 (95% confidence interval: 1.49 to 2.41) for work strain, while psychological demands (JCQ) yielded an SOR of 1.46 (95% confidence interval: 1.09 to 1.88) for work strain. We were able to extend and substantiate the range of relevant work stressors into a more comprehensive measure, which should be used to optimize prevention strategies.

An investigation on high temperature fatigue properties of tempered nuclear-grade deposited weld metals

NASA Astrophysics Data System (ADS)

Cao, X. Y.; Zhu, P.; Yong, Q.; Liu, T. G.; Lu, Y. H.; Zhao, J. C.; Jiang, Y.; Shoji, T.

2018-02-01

Effect of tempering on low cycle fatigue (LCF) behaviors of nuclear-grade deposited weld metal was investigated, and The LCF tests were performed at 350 °C with strain amplitudes ranging from 0.2% to 0.6%. The results showed that at a low strain amplitude, deposited weld metal tempered for 1 h had a high fatigue resistance due to high yield strength, while at a high strain amplitude, the one tempered for 24 h had a superior fatigue resistance due to high ductility. Deposited weld metal tempered for 1 h exhibited cyclic hardening at the tested strain amplitudes. Deposited weld metal tempered for 24 h exhibited cyclic hardening at a low strain amplitude but cyclic softening at a high strain amplitude. Existence and decomposition of martensite-austenite (M-A) islands as well as dislocations activities contributed to fatigue property discrepancy among the two tempered deposited weld metal.

High-Quality draft genome sequence of the Lotus spp. microsymbiont Mesorhizobium loti strain CJ3Sym

DOE PAGES

Reeve, Wayne; Sullivan, John; Ronson, Clive; ...

2015-08-14

Mesorhizobium loti strain CJ3Sym was isolated in 1998 following transfer of the integrative and conjugative element ICE Ml Sym R7A , also known as the R7A symbiosis island, in a laboratory mating from the donor M. loti strain R7A to a nonsymbiotic recipient Mesorhizobium strain CJ3. Strain CJ3 was originally isolated from a field site in the Rocklands range in New Zealand in 1994. CJ3Sym is an aerobic, Gram-negative, non-spore-forming rod. This report reveals the genome of M. loti strain CJ3Sym currently comprises 70 scaffolds totaling 7,563,725 bp. In conclusion, the high-quality draft genome is arranged in 70 scaffolds ofmore » 71 contigs, contains 7,331 protein-coding genes and 70 RNA-only encoding genes, and is part of the GEBA-RNB project proposal.« less

High-Quality draft genome sequence of the Lotus spp. microsymbiont Mesorhizobium loti strain CJ3Sym

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

Reeve, Wayne; Sullivan, John; Ronson, Clive

Mesorhizobium loti strain CJ3Sym was isolated in 1998 following transfer of the integrative and conjugative element ICE Ml Sym R7A , also known as the R7A symbiosis island, in a laboratory mating from the donor M. loti strain R7A to a nonsymbiotic recipient Mesorhizobium strain CJ3. Strain CJ3 was originally isolated from a field site in the Rocklands range in New Zealand in 1994. CJ3Sym is an aerobic, Gram-negative, non-spore-forming rod. This report reveals the genome of M. loti strain CJ3Sym currently comprises 70 scaffolds totaling 7,563,725 bp. In conclusion, the high-quality draft genome is arranged in 70 scaffolds ofmore » 71 contigs, contains 7,331 protein-coding genes and 70 RNA-only encoding genes, and is part of the GEBA-RNB project proposal.« less

Microtubules soften due to cross-sectional flattening

DOE PAGES

Memet, Edvin; Hilitsk, Feodor; Morris, Margaret A.; ...

2018-06-01

We use optical trapping to continuously bend an isolated microtubule while simultaneously measuring the applied force and the resulting filament strain, thus allowing us to determine its elastic properties over a wide range of applied strains. We find that, while in the low-strain regime, microtubules may be quantitatively described in terms of the classical Euler-Bernoulli elastic filament, above a critical strain they deviate from this simple elastic model, showing a softening response with increasing deformations. A three-dimensional thin-shell model, in which the increased mechanical compliance is caused by flattening and eventual buckling of the filament cross-section, captures this softening effectmore » in the high strain regime and yields quantitative values of the effective mechanical properties of microtubules. Our results demonstrate that properties of microtubules are highly dependent on the magnitude of the applied strain and offer a new interpretation for the large variety in microtubule mechanical data measured by different methods.« less

Microtubules soften due to cross-sectional flattening

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

Memet, Edvin; Hilitsk, Feodor; Morris, Margaret A.

We use optical trapping to continuously bend an isolated microtubule while simultaneously measuring the applied force and the resulting filament strain, thus allowing us to determine its elastic properties over a wide range of applied strains. We find that, while in the low-strain regime, microtubules may be quantitatively described in terms of the classical Euler-Bernoulli elastic filament, above a critical strain they deviate from this simple elastic model, showing a softening response with increasing deformations. A three-dimensional thin-shell model, in which the increased mechanical compliance is caused by flattening and eventual buckling of the filament cross-section, captures this softening effectmore » in the high strain regime and yields quantitative values of the effective mechanical properties of microtubules. Our results demonstrate that properties of microtubules are highly dependent on the magnitude of the applied strain and offer a new interpretation for the large variety in microtubule mechanical data measured by different methods.« less

[New antibiotics produced by Bacillus subtilis strains].

PubMed

Malanicheva, I A; Kozlov, D G; Efimenko, T A; Zenkova, V A; Kastrukha, G S; Reznikova, M I; Korolev, A M; Borshchevskaia, L N; Tarasova, O D; Sineokiĭ, S P; Efremenkova, O V

2014-01-01

Two Bacillus subtilis strains isolated from the fruiting body of a basidiomycete fungus Pholiota squarrosa exhibited a broad range of antibacterial activity, including those against methicillin-resistant Staphylococcus aureus INA 00761 (MRSA) and Leuconostoc mes6nteroides VKPM B-4177 resistant to glycopep-> tide antibiotics, as well as antifungal activity. The strains were identified as belonging to the "B. subtilis" com- plex based on their morphological and physiological characteristics, as well as by sequencing of the 16S rRNA gene fragments. Both strains (INA 01085 and INA 01086) produced insignificant amounts of polyene antibiotics (hexaen and pentaen, respectively). Strain INA 01086 produced also a cyclic polypeptide antibiotic containing Asp, Gly, Leu, Pro, Tyr, Thr, Trp, and Phe, while the antibiotic of strain INA 01085 contained, apart from these, two unidentified nonproteinaceous amino acids. Both polypeptide antibiotics were new compounds efficient against gram-positive bacteria and able to override the natural bacterial antibiotic resistance.

Simultaneous measurement of temperature and strain using a phase-shifted fiber Bragg grating inscribed by femtosecond laser

NASA Astrophysics Data System (ADS)

Jiang, Yajun; Liu, Chi; Li, Dong; Yang, Dexing; Zhao, Jianlin

2018-04-01

A novel method for simultaneous measurement of temperature and strain using a single phase-shifted fiber Bragg grating (PS-FBG) is proposed. The PS-FBG is produced by exposing the fusion-spliced fiber with a femtosecond laser and uniform phase mask. Due to the non-uniform structure and strain distribution in the fusion-spliced region, the phase-shift changes with different responses during increases to the temperature and strain; by measuring the central wavelengths and the loss difference of two transmission dips, temperature and strain can be determined simultaneously. The resolutions of this particular sensor in measuring temperature and strain are estimated to be  ±1.5 °C and  ±12.2 µɛ in a range from  -50 °C to 150 °C and from 0 µɛ to 2070 µɛ.

Brucella abortus Strain 2308 Wisconsin Genome: Importance of the Definition of Reference Strains

PubMed Central

Suárez-Esquivel, Marcela; Ruiz-Villalobos, Nazareth; Castillo-Zeledón, Amanda; Jiménez-Rojas, César; Roop II, R. Martin; Comerci, Diego J.; Barquero-Calvo, Elías; Chacón-Díaz, Carlos; Caswell, Clayton C.; Baker, Kate S.; Chaves-Olarte, Esteban; Thomson, Nicholas R.; Moreno, Edgardo; Letesson, Jean J.; De Bolle, Xavier; Guzmán-Verri, Caterina

2016-01-01

Brucellosis is a bacterial infectious disease affecting a wide range of mammals and a neglected zoonosis caused by species of the genetically homogenous genus Brucella. As in most studies on bacterial diseases, research in brucellosis is carried out by using reference strains as canonical models to understand the mechanisms underlying host pathogen interactions. We performed whole genome sequencing analysis of the reference strain B. abortus 2308 routinely used in our laboratory, including manual curated annotation accessible as an editable version through a link at https://en.wikipedia.org/wiki/Brucella#Genomics. Comparison of this genome with two publically available 2308 genomes showed significant differences, particularly indels related to insertional elements, suggesting variability related to the transposition of these elements within the same strain. Considering the outcome of high resolution genomic techniques in the bacteriology field, the conventional concept of strain definition needs to be revised. PMID:27746773

Characterization of electronic structure of periodically strained graphene

DOE PAGES

Aslani, Marjan; Garner, C. Michael; Kumar, Suhas; ...

2015-11-03

We induced periodic biaxial tensile strain in polycrystalline graphene by wrapping it over a substrate with repeating pillar-like structures with a periodicity of 600 nm. Using Raman spectroscopy, we determined to have introduced biaxial strains in graphene in the range of 0.4% to 0.7%. Its band structure was characterized using photoemission from valance bands, shifts in the secondary electron emission, and x-ray absorption from the carbon 1s levels to the unoccupied graphene conduction bands. It was observed that relative to unstrained graphene, strained graphene had a higher work function and higher density of states in the valence and conduction bands.more » Furthermore, we measured the conductivity of the strained and unstrained graphene in response to a gate voltage and correlated the changes in their behavior to the changes in the electronic structure. From these sets of data, we propose a simple band diagram representing graphene with periodic biaxial strain.« less

Computational Simulation of the High Strain Rate Tensile Response of Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.

2002-01-01

A research program is underway to develop strain rate dependent deformation and failure models for the analysis of polymer matrix composites subject to high strain rate impact loads. Under these types of loading conditions, the material response can be highly strain rate dependent and nonlinear. State variable constitutive equations based on a viscoplasticity approach have been developed to model the deformation of the polymer matrix. The constitutive equations are then combined with a mechanics of materials based micromechanics model which utilizes fiber substructuring to predict the effective mechanical and thermal response of the composite. To verify the analytical model, tensile stress-strain curves are predicted for a representative composite over strain rates ranging from around 1 x 10(exp -5)/sec to approximately 400/sec. The analytical predictions compare favorably to experimentally obtained values both qualitatively and quantitatively. Effective elastic and thermal constants are predicted for another composite, and compared to finite element results.

Micropatterned stretchable circuit and strain sensor fabricated by lithography on an electrospun nanofiber mat.

PubMed

Park, Minwoo; Im, Jungkyun; Park, Jongjin; Jeong, Unyong

2013-09-11

This paper describes a novel approach for composite nanofiber mats and its application to fabricate a strain sensor. Electrospun poly(4-vinylpyridine) (P4VP) nanofiber mats are micropatterned by a lithographic approach that includes selective oxidation of the nanofibers and removal of unreacted fibers. The P4VP/HAuCl4 complex is converted to P4VP/Au composites by chemical reduction. We investigate the electrical resistivity of the composite mats according to the number of complexation-and-reduction cycles, the thickness of the fiber mats, and the annealing temperatures which control the percolation of the Au nanoparticles in the fiber mats. Nozzle printing of a polymeric solution on the patterned nanofiber mats simply produces an array of strain-sensitive and strain-invariant units. The patterns demonstrate high strain-sensing performance without any mechanical and electrical failure over 200 bending cycles in the strain range of ε<0.17.

Medicinal Value and Taxonomy of the Tinder Polypore, Fomes fomentarius (Agaricomycetes): A Review.

PubMed

Gáper, Ján; Gáperová, Svetlana; Pristas, Peter; Naplavova, Katerina

2016-01-01

The tinder polypore, Fomes fomentarius, is a wood-decaying macrofungus well known for its potential use in a wide range of biotechnological applications. The existence of 3 distinct internal transcribed spacer lineages/sublineages among its strains has been clearly established. Sublineage A1 consists of strains isolated from North America, whereas sublineage A2 consists of strains only from Europe. Lineage B comprises strains from Europe and Asia. A better understanding of the biological features of F. fomentarius lineages/sublineages could lead to improved characterization, leading to better biotechnological applications. The medicinal value of F. fomentarius is discussed.

[Antigenic determination of human anti-rabies vaccine against viral street strains common in the wild animal population in Poland].

PubMed

Seroka, D

1994-01-01

The aim of the study was to compare the antigen properties of a vaccine strain with street strains isolated from various animal hosts throughout the country. Investigation was carried out using monoclonal antibodies against NC protein. Also, two tests were carried out: the modified NIH test for potency and the neutralization test using the sera of people vaccinated against rabies (PM vaccine strain). The investigated street strains were used in both tests as the challenge viruses. A suspension of these strains diluted five times made it possible to avoid extreme values of animal survival (0% or 100%) what, consequently, made calculation of the LD50 value easier. A different rabies virus serotype (EBLI virus) in the population of insectivore bats Eptesicus serotinus and antigen variants within the first serotype, having common epitopes with strains of the vaccine virus SAD B19 and the polar rabies virus, were found to be present throughout the country. The concentrated and purified vaccine containing the PM virus did not protect mice against infection with strains of viruses isolated from bats (protection index 10 and lower). For the remaining strains, depending on the animal source of their isolation, the protection index ranged from 10 to 1000 and higher. The properties neutralizing a dose of 5 i.u./ml of serum from the subject inoculated with the vaccine containing the PM strain were similar for all the investigated strains; 0,5 i.u./ml did not neutralize the strain isolated from a racoon dog.

Phenotypic characterization and adhesive properties of vaginal Candida spp. strains provided by the CHU Farhat Hached (Sousse, Tunisia).

PubMed

Noumi, Emira; Snoussi, Mejdi; Noumi, Inès; Saghrouni, Fatma; Aouni, Mahjoub; Valentin, Eulogio

2015-01-01

Vulvovaginal candidiasis is a common infection among women worldwide, being Candida albicans the most commonly isolated species. Therefore, controlling this opportunistic yeast is one of the key factors for reducing nosocomial infection. We investigated several virulence properties of 28 vaginal strains of Candida isolated from Tunisian women suffering from vulvovaginitis. We also analyzed the virulence properties of a clinical Candida krusei strain and five Candida reference strains. Candida strains were subjected to microscopic analysis and culture in Candida ID2 chromogenic medium. The adhesive properties of these strains were estimated by the microtiter plate - the safranin-staining - and the Congo red agar (CRA) methods, for determining yeast ability to form biofilms on biomaterials used in urinary catheter manufacturing. Their potency to produce hydrolytic enzymes was also studied. Our results showed that nine out of the total studied strains produced phospholipase. In addition, very high protease activity was detected in 23 Candida strains. All Candida strains were beta-hemolytic and adhered to polystyrene microtiter plates in varying degrees. Two vaginal C. albicans strains were strongly adhesive to polystyrene and glass slides. Also, our results showed that vaginal Candida strains were more adhesive to the three tested materials than the reference strains. This study shows the presence of a range of virulence and adhesion factors in clinical isolates of vaginal Candida. Consequently, control and treatment of vaginal candidiasis as a means to prevent biofilm formation on urinary catheters is of crucial importance. Copyright © 2013 Revista Iberoamericana de Micología. Published by Elsevier Espana. All rights reserved.

An exponential scaling law for the strain dependence of the Nb3Sn critical current density

NASA Astrophysics Data System (ADS)

Bordini, B.; Alknes, P.; Bottura, L.; Rossi, L.; Valentinis, D.

2013-07-01

The critical current density of the Nb3Sn superconductor is strongly dependent on the strain applied to the material. In order to investigate this dependence, it is a common practice to measure the critical current of Nb3Sn strands for different values of applied axial strain. In the literature, several models have been proposed to describe these experimental data in the reversible strain region. All these models are capable of fitting the measurement results in the strain region where data are collected, but tend to predict unphysical trends outside the range of data, and especially for large strain values. In this paper we present a model of a new strain function, together with the results obtained by applying the new scaling law on relevant datasets. The data analyzed consisted of the critical current measurements at 4.2 K that were carried out under applied axial strain at Durham University and the University of Geneva on different strand types. With respect to the previous models proposed, the new scaling function does not present problems at large strain values, has a lower number of fitting parameters (only two instead of three or four), and is very stable, so that, starting from few experimental points, it can estimate quite accurately the strand behavior in a strain region where there are no data. A relationship is shown between the proposed strain function and the elastic strain energy, and an analogy is drawn with the exponential form of the McMillan equation for the critical temperature.

Chromosomal Diversity in Lactococcus lactis and the Origin of Dairy Starter Cultures

PubMed Central

Kelly, William J.; Ward, Lawrence J. H.; Leahy, Sinead C.

2010-01-01

A large collection of Lactococcus lactis strains, including wild-type isolates and dairy starter cultures, were screened on the basis of their phenotype and the macrorestriction patterns produced from pulsed-field gel electrophoresis (PFGE) analysis of SmaI digests of genomic DNA. Three groups of dairy starter cultures, used for different purposes in the dairy industry, and a fourth group made up of strains isolated from the environment were selected for analysis of their chromosomal diversity using the endonuclease I-CeuI. Chromosome architecture was largely conserved with each strain having six copies of the rRNA genes, and the chromosome size of individual strains ranged between 2,240 and 2,688 kb. The origin of L. lactis strains showed the greatest correlation with chromosome size, and dairy strains, particularly those with the cremoris phenotype, had smaller chromosomes than wild-type strains. Overall, this study, coupled with analysis of the sequenced L. lactis genomes, provides evidence that defined strain dairy starter cultures have arisen from plant L. lactis strains. Adaptation of these strains to the dairy environment has involved loss of functions resulting in smaller chromosomes and acquisition of genes (usually plasmid associated) that facilitate growth in milk. We conclude that dairy starter cultures generally and the industrially used cremoris and diacetylactis phenotype strains in particular comprise a specialized group of L. lactis strains that have been selected to become an essential component of industrial processes and have evolved accordingly, so that they are no longer fit to survive outside the dairy environment. PMID:20847124

Halorubrum chaoviator sp. nov., a haloarchaeon isolated from sea salt in Baja California, Mexico, Western Australia and Naxos, Greece

PubMed Central

Mancinelli, Rocco L.; Landheim, Ragnhild; Sanchez-Porro, Cristina; Dornmayr-Pfaffenhuemer, Marion; Gruber, Claudia; Legat, Andrea; Ventosa, Antonio; Radax, Christian; Ihara, Kunio; White, Melisa R.; Stan-Lotter, Helga

2011-01-01

Three halophilic isolates, strains Halo-G*T, AUS-1 and Naxos II, were compared. Halo-G* was isolated from an evaporitic salt crystal from Baja California, Mexico, whereas AUS-1 and Naxos II were isolated from salt pools in Western Australia and the Greek island of Naxos, respectively. Halo-G*T had been exposed previously to conditions of outer space and survived 2 weeks on the Biopan facility. Chemotaxonomic and molecular comparisons suggested high similarity between the three strains. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that the strains clustered with Halorubrum species, showing sequence similarities of 99.2–97.1 %. The DNA–DNA hybridization values of strain Halo-G*T and strains AUS-1 and Naxos II are 73 and 75 %, respectively, indicating that they constitute a single species. The DNA relatedness between strain Halo-G*T and the type strains of 13 closely related species of the genus Halorubrum ranged from 39 to 2 %, suggesting that the three isolates constitute a different genospecies. The G+C content of the DNA of the three strains was 65.5–66.5 mol%. All three strains contained C20C20 derivatives of diethers of phosphatidylglycerol, phosphatidylglyceromethylphosphate and phosphatidylglycerolsulfate, together with a sulfated glycolipid. On the basis of these results, a novel species that includes the three strains is proposed, with the name Halorubrum chaoviator sp. nov. The type strain is strain Halo-G*T (=DSM 19316T =NCIMB 14426T =ATCC BAA-1602T). PMID:19567575

Differentiation of Lactobacillus brevis strains using Matrix-Assisted-Laser-Desorption-Ionization-Time-of-Flight Mass Spectrometry with respect to their beer spoilage potential.

PubMed

Kern, Carola C; Vogel, Rudi F; Behr, Jürgen

2014-06-01

Lactobacillus (L.) brevis is one of the most frequently encountered bacteria in beer-spoilage incidents. As the species Lactobacillus brevis comprises strains showing varying ability to grow in beer, ranging from growth in low hopped wheat to highly hopped pilsner beer, differentiation and classification of L. brevis with regard to their beer-spoiling ability is of vital interest for the brewing industry. Matrix-Assisted-Laser-Desorption-Ionization-Time-Of-Flight Mass Spectrometry (MALDI-TOF MS) has been shown as a powerful tool for species and sub-species differentiation of bacterial isolates and is increasingly used for strain-level differentiation. Seventeen L. brevis strains, representative of different spoilage types, were characterized according to their tolerance to iso-alpha-acids and their growth in wheat-, lager- and pilsner beer. MALDI-TOF MS spectra were acquired to perform strain-level identification, cluster analysis and biomarker detection. Strain-level identification was achieved in 90% out of 204 spectra. Misidentification occurred nearly exclusively among strains belonging to the same spoilage type. Though spectra of strongly beer-spoiling strains showed remarkable similarity, no decisive single markers were detected to be present in all strains of one group. However, MALDI-TOF MS spectra can be reliably assigned to the corresponding strain and thus allow to track single strains and connect them to their physiological properties. Copyright © 2013 Elsevier Ltd. All rights reserved.

Dehalogenation of chlorobenzenes, dichlorotoluenes, and tetrachloroethene by three Dehalobacter spp.

PubMed

Nelson, Jennifer L; Jiang, Jiandong; Zinder, Stephen H

2014-04-01

Three enrichment cultures containing Dehalobacter spp. were developed that dehalogenate each of the dichlorobenzene (DCB) isomers to monochlorobenzene (MCB), and the strains using 1,2-DCB (12DCB1) or 1,3-DCB (13DCB1) are now considered isolated, whereas the strain using 1,4-DCB (14DCB1) is considered highly enriched. In this study, we examined the dehalogenation capability of each strain to use chlorobenzenes with three or more chlorines, tetrachloroethene (PCE), or dichlorotoluene (DCT) isomers. Strain 12DCB1 preferentially dehalogenated singly flanked chlorines, but not doubly flanked or unflanked chlorines. It dehalogenated pentachlorobenzene to MCB with little buildup of intermediates. Strain 13DCB1, which could use either 1,3-DCB or 1,2-DCB, demonstrated the widest dehalogenation spectrum of electron acceptors tested, and dehalogenated every chlorobenzene isomer except 1,4-DCB. Notably, strain 13DCB1 dehalogenated the recalcitrant 1,3,5-trichlorobenzene isomer to MCB, and qPCR of 16S rRNA genes indicated that strain 13DCB1 grew. Strain 14DCB1 exhibited the narrowest range of substrate utilization, but was the only strain to dehalogenate para-substituted chlorines. Strains 12DCB1 and 13DCB1 dehalogenated PCE to cis-dichloroethene, and all strains dehalogenated 3,4-DCT to monochlorotoluene. These findings show that Dehalobacter spp., like Dehalococcoides spp., are versatile dehalogenators and should be considered when determining the fate of chlorinated organics at contaminated sites.

The Impact of Strain Reversal on Microstructure Evolution and Orientation Relationships in Ti-6Al-4V with an Initial Alpha Colony Microstructure

NASA Astrophysics Data System (ADS)

Muszka, K.; Lopez-Pedrosa, M.; Raszka, K.; Thomas, M.; Rainforth, W. M.; Wynne, B. P.

2014-12-01

The effect of forward and reverse torsion on flow behavior and microstructure evolution, particularly dynamic and static spheroidization, on Ti-6Al-4V with an alpha lamella colony microstructure was studied. Testing was undertaken sub beta transus [1088 K (815 °C)] at strain rates of either 0.05 or 0.5 s-1. Quantitative metallography and electron back scatter diffraction has identified that a critical monotonic strain ( ɛ c) in the range of 0.3 to 0.6 is required to initiate rapid dynamic spheroidization of the alpha lamella. For material deformed to strains below ɛ c and then reversed to a zero net strain the orientation relationships between alpha colonies are close to ideal Burgers, enabling prior beta grains to be fully reconstructed. Material deformed to strains greater than ɛ c and reversed lose Burgers and no beta reconstruction is possible, suggesting ɛ c is the strain required to generate break-up of lamella. Static spheroidization is, however, sensitive to strain path around ɛ c. Annealing at 1088 K (815 °C) for 4 hours for material subjected to 0.25 forward + 0.25 forward strain produces 48 pct spheroidized grains while material with 0.25 forward + 0.25 reverse strain has 10 pct spheroidization. This is believed to be a direct consequence of different levels of the stored energy between these two strain paths.

Ultrasensitive tunability of the direct bandgap of 2D InSe flakes via strain engineering

NASA Astrophysics Data System (ADS)

Li, Yang; Wang, Tianmeng; Wu, Meng; Cao, Ting; Chen, Yanwen; Sankar, Raman; Ulaganathan, Rajesh K.; Chou, Fangcheng; Wetzel, Christian; Xu, Cheng-Yan; Louie, Steven G.; Shi, Su-Fei

2018-04-01

InSe, a member of the layered materials family, is a superior electronic and optical material which retains a direct bandgap feature from the bulk to atomically thin few-layers and high electronic mobility down to a single layer limit. We, for the first time, exploit strain to drastically modify the bandgap of two-dimensional (2D) InSe nanoflakes. We demonstrated that we could decrease the bandgap of a few-layer InSe flake by 160 meV through applying an in-plane uniaxial tensile strain to 1.06% and increase the bandgap by 79 meV through applying an in-plane uniaxial compressive strain to 0.62%, as evidenced by photoluminescence (PL) spectroscopy. The large reversible bandgap change of ~239 meV arises from a large bandgap change rate (bandgap strain coefficient) of few-layer InSe in response to strain, ~154 meV/% for uniaxial tensile strain and ~140 meV/% for uniaxial compressive strain, representing the most pronounced uniaxial strain-induced bandgap strain coefficient experimentally reported in 2D materials. We developed a theoretical understanding of the strain-induced bandgap change through first-principles DFT and GW calculations. We also confirmed the bandgap change by photoconductivity measurements using excitation light with different photon energies. The highly tunable bandgap of InSe in the infrared regime should enable a wide range of applications, including electro-mechanical, piezoelectric and optoelectronic devices.

Silage Collected from Dairy Farms Harbors an Abundance of Listeriaphages with Considerable Host Range and Genome Size Diversity

PubMed Central

Vongkamjan, Kitiya; Switt, Andrea Moreno; den Bakker, Henk C.; Fortes, Esther D.

2012-01-01

Since the food-borne pathogen Listeria monocytogenes is common in dairy farm environments, it is likely that phages infecting this bacterium (“listeriaphages”) are abundant on dairy farms. To better understand the ecology and diversity of listeriaphages on dairy farms and to develop a diverse phage collection for further studies, silage samples collected on two dairy farms were screened for L. monocytogenes and listeriaphages. While only 4.5% of silage samples tested positive for L. monocytogenes, 47.8% of samples were positive for listeriaphages, containing up to >1.5 × 104 PFU/g. Host range characterization of the 114 phage isolates obtained, with a reference set of 13 L. monocytogenes strains representing the nine major serotypes and four lineages, revealed considerable host range diversity; phage isolates were classified into nine lysis groups. While one serotype 3c strain was not lysed by any phage isolates, serotype 4 strains were highly susceptible to phages and were lysed by 63.2 to 88.6% of phages tested. Overall, 12.3% of phage isolates showed a narrow host range (lysing 1 to 5 strains), while 28.9% of phages represented broad host range (lysing ≥11 strains). Genome sizes of the phage isolates were estimated to range from approximately 26 to 140 kb. The extensive host range and genomic diversity of phages observed here suggest an important role of phages in the ecology of L. monocytogenes on dairy farms. In addition, the phage collection developed here has the potential to facilitate further development of phage-based biocontrol strategies (e.g., in silage) and other phage-based tools. PMID:23042180

Prediction of stress- and strain-based forming limits of automotive thin sheets by numerical, theoretical and experimental methods

NASA Astrophysics Data System (ADS)

Béres, Gábor; Weltsch, Zoltán; Lukács, Zsolt; Tisza, Miklós

2018-05-01

Forming limit is a complex concept of limit values related to the onset of local necking in the sheet metal. In cold sheet metal forming, major and minor limit strains are influenced by the sheet thickness, strain path (deformation history) as well as material parameters and microstructure. Forming Limit Curves are plotted in ɛ1 - ɛ2 coordinate system providing the classic strain-based Forming Limit Diagram (FLD). Using the appropriate constitutive model, the limit strains can be changed into the stress-based Forming Limit Diagram (SFLD), irrespective of the strain path. This study is about the effect of the hardening model parameters on defining of limit stress values during Nakazima tests for automotive dual phase (DP) steels. Five limit strain pairs were specified experimentally with the loading of five different sheet geometries, which performed different strain-paths from pure shear (-2ɛ2=ɛ1) up to biaxial stretching (ɛ2=ɛ1). The former works of Hill, Levy-Tyne and Keeler-Brazier made possible some kind of theoretical strain determination, too. This was followed by the stress calculation based on the experimental and theoretical strain data. Since the n exponent in the Nádai expression is varying with the strain at some DP steels, we applied the least-squares method to fit other hardening model parameters (Ludwik, Voce, Hockett-Sherby) to calculate the stress fields belonging to each limit strains. The results showed that each model parameters could produce some discrepancies between the limit stress states in the range of higher equivalent strains than uniaxial stretching. The calculated hardening models were imported to FE code to extend and validate the results by numerical simulations.

Effects of Bacterial Host and Dichloromethane Dehalogenase on the Competitiveness of Methylotrophic Bacteria Growing with Dichloromethane

PubMed Central

Gisi, Daniel; Willi, Laurent; Traber, Hubert; Leisinger, Thomas; Vuilleumier, Stéphane

1998-01-01

Methylobacterium sp. strain DM4 and Methylophilus sp. strain DM11 can grow with dichloromethane (DCM) as the sole source of carbon and energy by virtue of homologous glutathione-dependent DCM dehalogenases with markedly different kinetic properties (the kcat values of the enzymes of these strains are 0.6 and 3.3 s−1, respectively, and the Km values are 9 and 59 μM, respectively). These strains, as well as transconjugant bacteria expressing the DCM dehalogenase gene (dcmA) from DM11 or DM4 on a broad-host-range plasmid in the background of dcmA mutant DM4-2cr, were investigated by growing them under growth-limiting conditions and in the presence of an excess of DCM. The maximal growth rates and maximal levels of dehalogenase for chemostat-adapted bacteria were higher than the maximal growth rates and maximal levels of dehalogenase for batch-grown bacteria. The substrate saturation constant of strain DM4 was much lower than the Km of its associated dehalogenase, suggesting that this strain is adapted to scavenge low concentrations of DCM. Strains and transconjugants expressing the DCM dehalogenase from strain DM11, on the other hand, had higher growth rates than bacteria expressing the homologous dehalogenase from strain DM4. Competition experiments performed with pairs of DCM-degrading strains revealed that a strain expressing the dehalogenase from DM4 had a selective advantage in continuous culture under substrate-limiting conditions, while strains expressing the DM11 dehalogenase were superior in batch culture when there was an excess of substrate. Only DCM-degrading bacteria with a dcmA gene similar to that from strain DM4, however, were obtained in batch enrichment cultures prepared with activated sludge from sewage treatment plants. PMID:9546153

Impact of homogeneous strain on uranium vacancy diffusion in uranium dioxide

DOE PAGES

Goyal, Anuj; Phillpot, Simon R.; Subramanian, Gopinath; ...

2015-03-03

We present a detailed mechanism of, and the effect of homogeneous strains on, the migration of uranium vacancies in UO 2. Vacancy migration pathways and barriers are identified using density functional theory and the effect of uniform strain fields are accounted for using the dipole tensor approach. We report complex migration pathways and noncubic symmetry associated with the uranium vacancy in UO 2 and show that these complexities need to be carefully accounted for to predict the correct diffusion behavior of uranium vacancies. We show that under homogeneous strain fields, only the dipole tensor of the saddle with respect tomore » the minimum is required to correctly predict the change in the energy barrier between the strained and the unstrained case. Diffusivities are computed using kinetic Monte Carlo simulations for both neutral and fully charged state of uranium single and divacancies. We calculate the effect of strain on migration barriers in the temperature range 800–1800 K for both vacancy types. Homogeneous strains as small as 2% have a considerable effect on diffusivity of both single and divacancies of uranium, with the effect of strain being more pronounced for single vacancies than divacancies. In contrast, the response of a given defect to strain is less sensitive to changes in the charge state of the defect. Further, strain leads to anisotropies in the mobility of the vacancy and the degree of anisotropy is very sensitive to the nature of the applied strain field for strain of equal magnitude. Our results indicate that the influence of strain on vacancy diffusivity will be significantly greater when single vacancies dominate the defect structure, such as sintering, while the effects will be much less substantial under irradiation conditions where divacancies dominate.« less

First report of the epiphytic dinoflagellate Gambierdiscus caribaeus in the temperate waters off Jeju Island, Korea: morphology and molecular characterization.

PubMed

Jeong, Hae Jin; Lim, An Suk; Jang, Se Hyeon; Yih, Won Ho; Kang, Nam Seon; Lee, Sung Yeon; Yoo, Yeong Du; Kim, Hyung Seop

2012-01-01

Gambierdiscus spp. are epiphytic, benthic dinoflagellates. Some species have been shown to be toxic and cause ciguatera fish poisoning. We report, for the first time, the occurrence of Gambierdiscus caribaeus isolated from the waters off Jeju Island in Korea. Its morphology was similar to that of the original Belize strains of G. caribaeus. Gambierdiscus caribaeus has been reported in the tropical and subtropical waters of the Pacific, Gulf of Mexico, Caribbean Sea, and Floridian coast. Our report extends its range to the North Pacific Ocean. The plates of the Korean strain were arranged in a Kofoidian series of Po, 3', 7'', 6c, 6s, 5''', 1p, and 2'''', morphologically closer to other strains of G. caribaeus than to G. carpenteri. When properly aligned, its small subunit (SSU) rDNA was 0.5% different from those of Gambierdiscus sp. C-1, a strain that was isolated from the waters off eastern Japan, but was 2.4-4.0% different from those of the NOAA strains of G. caribaeus and 3.1-3.4% different from those of the NOAA strains of G. carpenteri. Additionally, the D1-D3 large subunit (LSU) rDNA sequence of the Korean strain of G. caribaeus was 4.7-5.3% different from those of the NOAA strains of G. caribaeus and 7.1-7.5% different from those of all reported G. carpenteri strains, including the NOAA strains. In phylogenetic trees based on SSU and LSU rDNA sequences, our Korean strain was basal to the clade consisting of the NOAA strains of G. caribaeus, which in turn was sister clade to all reported G. carpenteri strains. © 2012 The Author(s) Journal of Eukaryotic Microbiology © 2012 International Society of Protistologists.

Effects of Recovery Behavior and Strain-Rate Dependence of Stress-Strain Curve on Prediction Accuracy of Thermal Stress Analysis During Casting

NASA Astrophysics Data System (ADS)

Motoyama, Yuichi; Shiga, Hidetoshi; Sato, Takeshi; Kambe, Hiroshi; Yoshida, Makoto

2017-06-01

Recovery behavior (recovery) and strain-rate dependence of the stress-strain curve (strain-rate dependence) are incorporated into constitutive equations of alloys to predict residual stress and thermal stress during casting. Nevertheless, few studies have systematically investigated the effects of these metallurgical phenomena on the prediction accuracy of thermal stress in a casting. This study compares the thermal stress analysis results with in situ thermal stress measurement results of an Al-Si-Cu specimen during casting. The results underscore the importance for the alloy constitutive equation of incorporating strain-rate dependence to predict thermal stress that develops at high temperatures where the alloy shows strong strain-rate dependence of the stress-strain curve. However, the prediction accuracy of the thermal stress developed at low temperatures did not improve by considering the strain-rate dependence. Incorporating recovery into the constitutive equation improved the accuracy of the simulated thermal stress at low temperatures. Results of comparison implied that the constitutive equation should include strain-rate dependence to simulate defects that develop from thermal stress at high temperatures, such as hot tearing and hot cracking. Recovery should be incorporated into the alloy constitutive equation to predict the casting residual stress and deformation caused by the thermal stress developed mainly in the low temperature range.

Isolation, identification and characterization of an algicidal bacterium from Lake Taihu and preliminary studies on its algicidal compounds.

PubMed

Tian, Chuan; Liu, Xianglong; Tan, Jing; Lin, Shengqin; Li, Daotang; Yang, Hong

2012-01-01

In an effort to identify a bio-agent capable of controlling cyanobacterial blooms, we isolated a bacterial strain, A27, which exhibited strong algicidal activity against the dominant bloom-forming species of Microcystis aeruginosa in Lake Taihu. Based on 16S rRNA gene sequence analysis, this strain belongs to the genus Exiguobacterium. This is the first report of an algicidal bacterial strain belonging to the genus Exiguobacterium. Strain A27 exhibited algicidal activity against a broad range of cyanobacteria, but elicited little or no algicidal activity against the two green algal strains tested. The algicidal activity of strain A27 was shown to be dependent on the density of the bacteria and to have a threshold density of 1.5x10(6) CFU/mL. Our data also showed that the algicidal activity of strain A27 depended on different growth stages of Microcystis aeruginosa (exponential approximately lag phase > early stationary) rather than that of the bacterium itself. Our results also suggested the algicidal activity of strain A27 occurred via the production of extracellular algicidal compounds. Investigation of the algicidal compounds revealed that there were at least two different algicidal compounds produced by strain A27. These results indicated that strain A27 has great potential for use in the control of outbreaks of cyanobacterial blooms in Lake Taihu.

Skeletal muscle tensile strain dependence: hyperviscoelastic nonlinearity

PubMed Central

Wheatley, Benjamin B; Morrow, Duane A; Odegard, Gregory M; Kaufman, Kenton R; Donahue, Tammy L Haut

2015-01-01

Introduction Computational modeling of skeletal muscle requires characterization at the tissue level. While most skeletal muscle studies focus on hyperelasticity, the goal of this study was to examine and model the nonlinear behavior of both time-independent and time-dependent properties of skeletal muscle as a function of strain. Materials and Methods Nine tibialis anterior muscles from New Zealand White rabbits were subject to five consecutive stress relaxation cycles of roughly 3% strain. Individual relaxation steps were fit with a three-term linear Prony series. Prony series coefficients and relaxation ratio were assessed for strain dependence using a general linear statistical model. A fully nonlinear constitutive model was employed to capture the strain dependence of both the viscoelastic and instantaneous components. Results Instantaneous modulus (p<0.0005) and mid-range relaxation (p<0.0005) increased significantly with strain level, while relaxation at longer time periods decreased with strain (p<0.0005). Time constants and overall relaxation ratio did not change with strain level (p>0.1). Additionally, the fully nonlinear hyperviscoelastic constitutive model provided an excellent fit to experimental data, while other models which included linear components failed to capture muscle function as accurately. Conclusions Material properties of skeletal muscle are strain-dependent at the tissue level. This strain dependence can be included in computational models of skeletal muscle performance with a fully nonlinear hyperviscoelastic model. PMID:26409235

Final Report Auto/Steel Partnership Phase II

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

Cady, C.M.; Chen, S.R.; Gray, G.T. III

1999-06-09

This is the final report in which effects of strain-rate, temperature, and stress-state on the yield stress and the strain hardening behavior of many common steels used in automobile construction were investigated. The yield and flow stresses were found to exhibit very high rate sensitivities for most of the steels while the hardening rates were found to be insensitive to strain rate and temperature at lower temperatures or at higher strain rates. This behavior is consistent with the observation that overcoming the intrinsic Peierls stress is shown to be the rate-controlling mechanism in these materials at low temperatures. The dependencemore » of the yield stress on temperature and strain rate was found to decrease while the strain hardening rate increased. The Mechanical Threshold Stress (MTS) model was adopted to model the stress-strain behavior of the steels. Parameters for the constitutive relations were derived for the MTS model and also for the Johnson-Cook (JC) and the Zerilli-Armstrong (ZA) models. The results of this study substantiate the applicability of these models for describing the high strain-rate deformation of these materials. The JC and ZA models, however, due to their use of a power strain hardening law were found to yield constitutive relations for the materials which are strongly dependent on the range of strains for which the models were optimized.« less

Virulence variation among epidemic and non-epidemic strains of Saint Louis encephalitis virus circulating in Argentina

PubMed Central

Rivarola, María Elisa; Tauro, Laura Beatriz; Llinás, Guillermo Albrieu; Contigiani, Marta Silvia

2014-01-01

Saint Louis encephalitis virus caused an outbreak of febrile illness and encephalitis cases in Córdoba, Argentina, in 2005. During this outbreak, the strain CbaAr-4005 was isolated from Culex quinquefasciatus mosquitoes. We hypothesised that this epidemic variant would be more virulent in a mouse model than two other non-epidemic strains (78V-6507 and CorAn-9275) isolated under different epidemiological conditions. To test this hypothesis, we performed a biological characterisation in a murine model, including mortality, morbidity and infection percentages and lethal infection indices using the three strains. Mice were separated into age groups (7, 10 and 21-day-old mice) and analysed after infection. The strain CbaAr-4005 was the most infective and lethal of the three variants, whereas the other two strains exhibited a decreasing mortality percentage with increasing animal age. The strain CbaAr-4005 produced the highest morbidity percentages and no significant differences among age groups were observed. The epidemic strain caused signs of illness in all inoculated animals and showed narrower ranges from the onset of symptoms than the other strains. CbaAr-4005 was the most virulent for Swiss albino mice. Our results highlight the importance of performing biological characterisations of arbovirus strains likely to be responsible for emerging or reemerging human diseases. PMID:24810175

Quality Factor Effect on the Wireless Range of Microstrip Patch Antenna Strain Sensors

PubMed Central

Daliri, Ali; Galehdar, Amir; Rowe, Wayne S. T.; John, Sabu; Wang, Chun H.; Ghorbani, Kamran

2014-01-01

Recently introduced passive wireless strain sensors based on microstrip patch antennas have shown great potential for reliable health and usage monitoring in aerospace and civil industries. However, the wireless interrogation range of these sensors is limited to few centimeters, which restricts their practical application. This paper presents an investigation on the effect of circular microstrip patch antenna (CMPA) design on the quality factor and the maximum practical wireless reading range of the sensor. The results reveal that by using appropriate substrate materials the interrogation distance of the CMPA sensor can be increased four-fold, from the previously reported 5 to 20 cm, thus improving considerably the viability of this type of wireless sensors for strain measurement and damage detection. PMID:24451457

Quality factor effect on the wireless range of microstrip patch antenna strain sensors.

PubMed

Daliri, Ali; Galehdar, Amir; Rowe, Wayne S T; John, Sabu; Wang, Chun H; Ghorbani, Kamran

2014-01-02

Recently introduced passive wireless strain sensors based on microstrip patch antennas have shown great potential for reliable health and usage monitoring in aerospace and civil industries. However, the wireless interrogation range of these sensors is limited to few centimeters, which restricts their practical application. This paper presents an investigation on the effect of circular microstrip patch antenna (CMPA) design on the quality factor and the maximum practical wireless reading range of the sensor. The results reveal that by using appropriate substrate materials the interrogation distance of the CMPA sensor can be increased four-fold, from the previously reported 5 to 20 cm, thus improving considerably the viability of this type of wireless sensors for strain measurement and damage detection.

Complete and Draft Genome Sequences of Nine Lactobacillus sakei Strains Selected from the Three Known Phylogenetic Lineages and Their Main Clonal Complexes.

PubMed

Loux, Valentin; Coeuret, Gwendoline; Zagorec, Monique; Champomier Vergès, Marie-Christine; Chaillou, Stéphane

2018-04-19

We present here the complete and draft genome sequences of nine Lactobacillus sakei strains, selected from the entire range of clonal complexes from the three known lineages of the species. The strains were chosen to provide a wide view of pangenomic and plasmidic diversity for this important foodborne species. Copyright © 2018 Loux et al.

Activity of OPT-80, a novel macrocycle, compared with those of eight other agents against selected anaerobic species.

PubMed

Credito, Kim L; Appelbaum, Peter C

2004-11-01

Agar dilution MIC was used to compare activities of OPT-80, linezolid, vancomycin, teicoplanin, quinupristin/dalfopristin, amoxicillin/clavulanate, imipenem, clindamycin, and metronidazole against 350 gram-positive and -negative anaerobes. OPT-80 was active against gram-positive strains only, especially Clostridium spp. (85 strains tested, including 21 strains of C. difficile), with MICs ranging between

Transparent Stretchable Self-Powered Patchable Sensor Platform with Ultrasensitive Recognition of Human Activities.

PubMed

Hwang, Byeong-Ung; Lee, Ju-Hyuck; Trung, Tran Quang; Roh, Eun; Kim, Do-Il; Kim, Sang-Woo; Lee, Nae-Eung

2015-09-22

Monitoring of human activities can provide clinically relevant information pertaining to disease diagnostics, preventive medicine, care for patients with chronic diseases, rehabilitation, and prosthetics. The recognition of strains on human skin, induced by subtle movements of muscles in the internal organs, such as the esophagus and trachea, and the motion of joints, was demonstrated using a self-powered patchable strain sensor platform, composed on multifunctional nanocomposites of low-density silver nanowires with a conductive elastomer of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate/polyurethane, with high sensitivity, stretchability, and optical transparency. The ultra-low-power consumption of the sensor, integrated with both a supercapacitor and a triboelectric nanogenerator into a single transparent stretchable platform based on the same nanocomposites, results in a self-powered monitoring system for skin strain. The capability of the sensor to recognize a wide range of strain on skin has the potential for use in new areas of invisible stretchable electronics for human monitoring. A new type of transparent, stretchable, and ultrasensitive strain sensor based on a AgNW/PEDOT:PSS/PU nanocomposite was developed. The concept of a self-powered patchable sensor system integrated with a supercapacitor and a triboelectric nanogenerator that can be used universally as an autonomous invisible sensor system was used to detect the wide range of strain on human skin.

Biochemical characterisation of the esterase activities of wine lactic acid bacteria.

PubMed

Matthews, Angela; Grbin, Paul R; Jiranek, Vladimir

2007-11-01

Esters are an important group of volatile compounds that can contribute to wine flavour. Wine lactic acid bacteria (LAB) have been shown to produce esterases capable of hydrolysing ester substrates. This study aims to characterise the esterase activities of nine LAB strains under important wine conditions, namely, acidic conditions, low temperature (to 10 degrees C) and in the presence of ethanol (2-18% v/v). Esterase substrate specificity was also examined using seven different ester substrates. The bacteria were generally found to have a broad pH activity range, with the majority of strains showing maximum activity close to pH 6.0. Exceptions included an Oenococcus oeni strain that retained most activity even down to a pH of 4.0. Most strains exhibited highest activity across the range 30-40 degrees C. Increasing ethanol concentration stimulated activity in some of the strains. In particular, O. oeni showed an increase in activity up to a maximum ethanol concentration of around 16%. Generally, strains were found to have greater activity towards short-chained esters (C2-C8) compared to long-chained esters (C10-C18). Even though the optimal physicochemical conditions for enzyme activity differed from those found in wine, these findings are of potential importance to oenology because significant activities remained under wine-like conditions.

Tensile stress-strain and work hardening behaviour of P9 steel for wrapper application in sodium cooled fast reactors

NASA Astrophysics Data System (ADS)

Christopher, J.; Choudhary, B. K.; Isaac Samuel, E.; Mathew, M. D.; Jayakumar, T.

2012-01-01

Tensile flow behaviour of P9 steel with different silicon content has been examined in the framework of Hollomon, Ludwik, Swift, Ludwigson and Voce relationships for a wide temperature range (300-873 K) at a strain rate of 1.3 × 10 -3 s -1. Ludwigson equation described true stress ( σ)-true plastic strain ( ɛ) data most accurately in the range 300-723 K. At high temperatures (773-873 K), Ludwigson equation reduces to Hollomon equation. The variations of instantaneous work hardening rate ( θ = dσ/ dɛ) and θσ with stress indicated two-stage work hardening behaviour. True stress-true plastic strain, flow parameters, θ vs. σ and θσ vs. σ with respect to temperature exhibited three distinct temperature regimes and displayed anomalous behaviour due to dynamic strain ageing at intermediate temperatures. Rapid decrease in flow stress and flow parameters, and rapid shift in θ- σ and θσ- σ towards lower stresses with increase in temperature indicated dominance of dynamic recovery at high temperatures.

Characterization of the Mechanical Stress-Strain Performance of Aerospace Alloy Materials Using Frequency-Domain Photoacoustic Ultrasound and Photothermal Methods: An FEM Approach

NASA Astrophysics Data System (ADS)

Huan, Huiting; Mandelis, Andreas; Liu, Lixian

2018-04-01

Determining and keeping track of a material's mechanical performance is very important for safety in the aerospace industry. The mechanical strength of alloy materials is precisely quantified in terms of its stress-strain relation. It has been proven that frequency-domain photothermoacoustic (FD-PTA) techniques are effective methods for characterizing the stress-strain relation of metallic alloys. PTA methodologies include photothermal (PT) diffusion and laser thermoelastic photoacoustic ultrasound (PAUS) generation which must be separately discussed because the relevant frequency ranges and signal detection principles are widely different. In this paper, a detailed theoretical analysis of the connection between thermoelastic parameters and stress/strain tensor is presented with respect to FD-PTA nondestructive testing. Based on the theoretical model, a finite element method (FEM) was further implemented to simulate the PT and PAUS signals at very different frequency ranges as an important analysis tool of experimental data. The change in the stress-strain relation has an impact on both thermal and elastic properties, verified by FEM and results/signals from both PT and PAUS experiments.

The effects of orthotic intervention on multisegment foot kinematics and plantar fascia strain in recreational runners.

PubMed

Sinclair, Jonathan; Isherwood, Josh; Taylor, Paul J

2015-02-01

Chronic injuries are a common complaint in recreational runners. Foot orthoses have been shown to be effective for the treatment of running injuries but their mechanical effects are still not well understood. This study aims to examine the influence of orthotic intervention on multisegment foot kinematics and plantar fascia strain during running. Fifteen male participants ran at 4.0 m · s(-1) with and without orthotics. Multisegment foot kinematics and plantar fascia strain were obtained during the stance phase and contrasted using paired t tests. Relative coronal plane range of motion of the midfoot relative to the rearfoot was significantly reduced with orthotics (1.0°) compared to without (2.2°). Similarly, relative transverse plane range of motion was significantly lower with orthotics (1.1°) compared to without (1.8°). Plantar fascia strain did not differ significantly between orthotic (7.1) and nonorthotic (7.1) conditions. This study shows that although orthotics did not serve to reduce plantar fascia strain, they are able to mediate reductions in coronal and transverse plane rotations of the midfoot.

Tensile and compressive stress-strain behavior of heat treated boron-aluminum

NASA Technical Reports Server (NTRS)

Kennedy, J. M.; Tenney, D. R.; Herakovich, C. T.

1978-01-01

An experimental study was conducted to assess the effects of heat treatment and cyclic mechanical loading on the tensile and compressive stress-strain behavior of six boron-aluminum composites having different laminate orientations and being subjected to different heat treatments. The heat treatments were as-fabricated, T6, and T6N consisting of T6 treatment followed by cryogenic quench in liquid nitrogen prior to testing. All laminates were tested in monotonic and cyclic compression, while the tensile-test data are taken from the literature for comparison purposes. It is shown that the linear elastic range of the T6- and T6N-condition specimens is larger than that of the as-fabricated specimens, and that cyclic loading in tension or compression strain hardens the specimens and extends the linear elastic range. For laminates containing 0-deg plies, the stress-strain behavior upon unloading is found to be nonlinear, whereas the other laminates exhibit a linear behavior upon unloading. Specimens in the T6 and T6N conditions show higher strain hardening than the as-fabricated specimens.

Phenotypic Variability in the Coccolithophore Emiliania huxleyi

PubMed Central

Lebrato, Mario; Stoll, Heather M.; Iglesias-Rodriguez, Debora; Müller, Marius N.; Méndez-Vicente, Ana; Oschlies, Andreas

2016-01-01

Coccolithophores are a vital part of oceanic phytoplankton assemblages that produce organic matter and calcium carbonate (CaCO3) containing traces of other elements (i.e. Sr and Mg). Their associated carbon export from the euphotic zone to the oceans' interior plays a crucial role in CO2 feedback mechanisms and biogeochemical cycles. The coccolithophore Emiliania huxleyi has been widely studied as a model organism to understand physiological, biogeochemical, and ecological processes in marine sciences. Here, we show the inter-strain variability in physiological and biogeochemical traits in 13 strains of E. huxleyi from various biogeographical provinces obtained from culture collections commonly used in the literature. Our results demonstrate that inter-strain genetic variability has greater potential to induce larger phenotypic differences than the phenotypic plasticity of single strains cultured under a broad range of variable environmental conditions. The range of variation found in physiological parameters and calcite Sr:Ca highlights the need to reconsider phenotypic variability in paleoproxy calibrations and model parameterizations to adequately translate findings from single strain laboratory experiments to the real ocean. PMID:27348427

Highly Sensitive and Very Stretchable Strain Sensor Based on a Rubbery Semiconductor.

PubMed

Kim, Hae-Jin; Thukral, Anish; Yu, Cunjiang

2018-02-07

There is a growing interest in developing stretchable strain sensors to quantify the large mechanical deformation and strain associated with the activities for a wide range of species, such as humans, machines, and robots. Here, we report a novel stretchable strain sensor entirely in a rubber format by using a solution-processed rubbery semiconductor as the sensing material to achieve high sensitivity, large mechanical strain tolerance, and hysteresis-less and highly linear responses. Specifically, the rubbery semiconductor exploits π-π stacked poly(3-hexylthiophene-2,5-diyl) nanofibrils (P3HT-NFs) percolated in silicone elastomer of poly(dimethylsiloxane) to yield semiconducting nanocomposite with a large mechanical stretchability, although P3HT is a well-known nonstretchable semiconductor. The fabricated strain sensors exhibit reliable and reversible sensing capability, high gauge factor (gauge factor = 32), high linearity (R 2 > 0.996), and low hysteresis (degree of hysteresis <12%) responses at the mechanical strain of up to 100%. A strain sensor in this format can be scalably manufactured and implemented as wearable smart gloves. Systematic investigations in the materials design and synthesis, sensor fabrication and characterization, and mechanical analysis reveal the key fundamental and application aspects of the highly sensitive and very stretchable strain sensors entirely from rubbers.

Deformation behavior of open-cell dry natural rubber foam: Effect of different concentration of blowing agent and compression strain rate

NASA Astrophysics Data System (ADS)

Samsudin, M. S. F.; Ariff, Z. M.; Ariffin, A.

2017-04-01

Compression and deformation behavior of partially open cell natural rubber (NR) foam produced from dry natural rubber (DNR), were investigated by performing compressive deformation at different strains and strain rates. Different concentrations of sodium bicarbonate as a blowing agent (BA) were utilized, from 4 to 16 phr in order to produce foams with range of cell size and morphology. Overall, increasing of blowing agent concentration had significantly changed relative foam density. Compression stress-strain curves of the foams exhibited that the compression behavior was directly correlated to the foam cells morphology and physical density. Pronounced changes were noticed for foams with bigger cells particularly at 4 phr concentration of BA where the compression stress at plateau region was greater compared to those with higher concentration of BA. Cell deformation progressive images confirmed that the foams demonstrated small degree of struts bending at 15% of strain and followed by continuous severe struts bending and elastic buckling up to 50% of strain. Compression test at different strain rates revealed that the strain rate factor only affected the foams with 4 phr of BA by causing immediate increment in the compression stress value when higher strain rate was applied.

An embeddable optical strain gauge based on a buckled beam.

PubMed

Du, Yang; Chen, Yizheng; Zhu, Chen; Zhuang, Yiyang; Huang, Jie

2017-11-01

We report, for the first time, a low cost, compact, and novel mechanically designed extrinsic Fabry-Perot interferometer (EFPI)-based optical fiber sensor with a strain amplification mechanism for strain measurement. The fundamental design principle includes a buckled beam with a coated gold layer, mounted on two grips. A Fabry-Perot cavity is produced between the buckled beam and the endface of a single mode fiber (SMF). A ceramic ferrule is applied for supporting and orienting the SMF. The principal sensor elements are packaged and protected by two designed metal shells. The midpoint of the buckled beam will experience a deflection vertically when the beam is subjected to a horizontally/axially compressive displacement. It has been found that the vertical deflection of the beam at midpoint can be 6-17 times larger than the horizontal/axial displacement, which forms the basis of a strain amplification mechanism. The user-configurable buckling beam geometry-based strain amplification mechanism enables the strain sensor to achieve a wide range of strain measurement sensitivities. The designed EFPI was used to monitor shrinkage of a square brick of mortar. The strain was measured during the drying/curing stage. We envision that it could be a good strain sensor to be embedded in civil materials/structures under a harsh environment for a prolonged period of time.

An embeddable optical strain gauge based on a buckled beam

NASA Astrophysics Data System (ADS)

Du, Yang; Chen, Yizheng; Zhu, Chen; Zhuang, Yiyang; Huang, Jie

2017-11-01

We report, for the first time, a low cost, compact, and novel mechanically designed extrinsic Fabry-Perot interferometer (EFPI)-based optical fiber sensor with a strain amplification mechanism for strain measurement. The fundamental design principle includes a buckled beam with a coated gold layer, mounted on two grips. A Fabry-Perot cavity is produced between the buckled beam and the endface of a single mode fiber (SMF). A ceramic ferrule is applied for supporting and orienting the SMF. The principal sensor elements are packaged and protected by two designed metal shells. The midpoint of the buckled beam will experience a deflection vertically when the beam is subjected to a horizontally/axially compressive displacement. It has been found that the vertical deflection of the beam at midpoint can be 6-17 times larger than the horizontal/axial displacement, which forms the basis of a strain amplification mechanism. The user-configurable buckling beam geometry-based strain amplification mechanism enables the strain sensor to achieve a wide range of strain measurement sensitivities. The designed EFPI was used to monitor shrinkage of a square brick of mortar. The strain was measured during the drying/curing stage. We envision that it could be a good strain sensor to be embedded in civil materials/structures under a harsh environment for a prolonged period of time.

Localized strain measurements of the intervertebral disc annulus during biaxial tensile testing.

PubMed

Karakolis, Thomas; Callaghan, Jack P

2015-01-01

Both inter-lamellar and intra-lamellar failures of the annulus have been described as potential modes of disc herniation. Attempts to characterize initial lamellar failure of the annulus have involved tensile testing of small tissue samples. The purpose of this study was to evaluate a method of measuring local surface strains through image analysis of a tensile test conducted on an isolated sample of annular tissue in order to enhance future studies of intervertebral disc failure. An annulus tissue sample was biaxial strained to 10%. High-resolution images captured the tissue surface throughout testing. Three test conditions were evaluated: submerged, non-submerged and marker. Surface strains were calculated for the two non-marker conditions based on motion of virtual tracking points. Tracking algorithm parameters (grid resolution and template size) were varied to determine the effect on estimated strains. Accuracy of point tracking was assessed through a comparison of the non-marker conditions to a condition involving markers placed on tissue surface. Grid resolution had a larger effect on local strain than template size. Average local strain error ranged from 3% to 9.25% and 0.1% to 2.0%, for the non-submerged and submerged conditions, respectively. Local strain estimation has a relatively high potential for error. Submerging the tissue provided superior strain estimates.

High strain rate properties of angle-ply composite laminates, part 3

NASA Technical Reports Server (NTRS)

Daniel, I. M.

1991-01-01

Angle-ply graphite/epoxy and graphite/S-glass/epoxy laminates were characterized in uniaxial tension at strain rates ranging from quasi-static to over 500 s(sup -1). Laminate ring specimens of +/-15(sub 2s), +/-22.5(sub 2s), +/-30(sub 2s), +/-45(sub 2s), +/-60(sub 2s), +/-67.5(sub 2s), and +/-75(sub 2s) degree layups were loaded under internal pressure. Results were presented in the form of stress-strain curves to failure. Properties determined included moduli, Poisson's ratios, strength, and ultimate strain. In all seven laminates for the two materials tested the modulus and strength increase with strain rate. The effect of strain rate varies with layup, being lowest for the fiber dominated +/-15(sub 2s) degree laminates and highest for the matrix dominated +/-75(sub 2s) degree laminates. The highest increments over the static values are 10 to 25 percent for the +/-15(sub 2s) degree layup and 200 to 275 percent for the +/-75(sub 2s) degree layup. Ultimate strains do not show any significant trends with strain rate. In almost all cases the ultimate strain values are within +/-20 percent of the mean value and in half of the cases the deviation from the mean are less than 10 percent.

Selection of cyanobacteria isolated from mosquito breeding sites as a potential food source for mosquito larvae.

PubMed Central

Thiery, I; Nicolas, L; Rippka, R; Tandeau de Marsac, N

1991-01-01

One way to increase the persistence of larvicidal toxins in mosquito breeding sites is to clone the corresponding genes in microorganisms, such as cyanobacteria, which could serve as a source of food for the larvae. We isolated and cultured 10 strains of cyanobacteria from three mosquito breeding sites along the French Mediterranean coast. Most of the strains were tolerant to a relatively wide range of salt concentrations, and all of them were totally or partially resistant to at least four of the five biological or chemical larvicides used in the local mosquito control program. Six unicellular strains from these habitats and Synechococcus strain PCC 7942, a strain maintained for more than 10 years under laboratory conditions, were assessed for ingestion and digestion by larvae Culex pipiens and Anopheles gambiae mosquitoes. The numbers of cells ingested and digested were dependent on the cyanobacterial strain and varied with the mosquito species. Three of the new isolates, Synechococcus strain PCC 8905 and Synechocystis strains PCC 8906 and PCC 8912, were ingested and digested rapidly by larvae of both mosquito species. Since these strains are also tolerant to larvicides and relatively resistant to elevated salt concentrations, they meet the basic requirements for potential recipients of bacterial genes that encode endotoxins. PMID:1677241

An Elevated-Temperature Tension-Compression Test and Its Application to Magnesium AZ31B

NASA Astrophysics Data System (ADS)

Piao, Kun

Many metals, particularly ones with HCP crystal structures, undergo deformation by combinations of twinning and slip, the proportion of which depends on variables such as temperature and strain rate. Typical techniques to reveal such mechanisms rely on metallography, x-ray diffraction, or electron optics. Simpler, faster, less expensive mechanical tests were developed in the current work and applied to Mg AZ31B. An apparatus was designed, simulated, optimized, and constructed to enable the large-strain, continuous tension/compression testing of sheet materials at elevated temperature. Thermal and mechanical FE analyses were used to locate cartridge heaters, thus enabling the attainment of temperatures up to 350°C within 15 minutes of start-up, and ensuring temperature uniformity throughout the gage length within 8°C. The low-cost device also makes isothermal testing possible at strain rates higher than corresponding tests in air. Analysis was carried out to predict the attainable compressive strains using novel finite element (FE) modeling and a single parameter characteristic of the machine and fixtures. The limits of compressive strain vary primarily with the material thickness and the applied-side-force-to-material-strength ratio. Predictions for a range of sheet alloys with measured buckling strains from -0.04 to -0.17 agreed within a standard deviation of 0.025 (0.015 excluding one material that was not initially flat). In order to demonstrate the utility of the new method, several sheet materials were tested over a range of temperatures. Some of the data obtained is the first of its kind. Magnesium AZ31B sheets were tested at temperatures up to 250°C with strain rate of 0.001/s. The inflected stress-strain curve observed in compression at room temperature disappeared between 125°C and 150°C, corresponding to the suppression of twinning, and suggesting a simple method for identifying the deformation mechanism transition temperature. The temperature-dependent behavior of selected advanced high strength steels (TWIP and DP) was revealed by preliminary tests at room temperature, 150°C and 250°C. For Mg AZ31B alloy sheets, the curvature of compressive stress-strain plots over a fixed strain range was found to be a consistent indicator of twinning magnitude, independent of temperature and strain rate. The relationship between curvature and areal fraction of twins is presented. Transition temperatures determined based on stress-strain curvature were consistent with ones determined by metallographic analysis and flow stresses, and depended on strain rate by the Zener-Hollomon parameter, a critical value for which was measured. The transition temperature was found to depend significantly on grain size, a relationship for which was established. Finally, it was shown that the transition temperature can be determined consistently, and much faster, using a single novel "Step-Temperature" test.

Desulfohalophilus alkaliarsenatis gen. nov., sp. nov., an extremely halophilic sulfate- and arsenate-respiring bacterium from Searles Lake, California

USGS Publications Warehouse

Blum, Jodi Switzer; Kulp, Thomas R.; Han, Sukkyun; Lanoil, Brian; Saltikov, Chad W.; Stolz, John F.; Miller, Laurence G.; Oremland, Ronald S.

2012-01-01

A haloalkaliphilic sulfate-respiring bacterium, strain SLSR-1, was isolated from a lactate-fed stable enrichment culture originally obtained from the extreme environment of Searles Lake, California. The isolate proved capable of growth via sulfate-reduction over a broad range of salinities (125–330 g/L), although growth was slowest at salt-saturation. Strain SLSR-1 was also capable of growth via dissimilatory arsenate-reduction and displayed an even broader range of salinity tolerance (50–330 g/L) when grown under these conditions. Strain SLSR-1 could also grow via dissimilatory nitrate reduction to ammonia. Growth experiments in the presence of high borate concentrations indicated a greater sensitivity of sulfate-reduction than arsenate-respiration to this naturally abundant anion in Searles Lake. Strain SLSR-1 contained genes involved in both sulfate-reduction (dsrAB) and arsenate respiration (arrA). Amplicons of 16S rRNA gene sequences obtained from DNA extracted from Searles Lake sediment revealed the presence of close relatives of strain SLSR-1 as part of the flora of this ecosystem despite the fact that sulfate-reduction activity could not be detected in situ. We conclude that strain SLSR-1 can only achieve growth via arsenate-reduction under the current chemical conditions prevalent at Searles Lake. Strain SLSR-1 is a deltaproteobacterium in the family Desulfohalobiacea of anaerobic, haloalkaliphilic bacteria, for which we propose the name Desulfohalophilus alkaliarsenatis gen. nov., sp. nov.

Experimental Characterization of Stress- and Strain-Dependent Stiffness in Grouted Rock Masses.

PubMed

Kim, Ji-Won; Chong, Song-Hun; Cho, Gye-Chun

2018-03-29

Grouting of fractured rock mass prior to excavation results in grout-filled discontinuities that govern the deformation characteristics of a site. The influence of joint characteristics on the properties of grouted rocks is important in assessing the effects of grouting on jointed rock mass. However, grouting remains a predominantly empirical practice and the effects of grouting on rock joint behavior and material properties have yet to be accurately assessed. Granular materials, including jointed rocks, typically display nonlinear strain-dependent responses that can be characterized by the shear modulus degradation curve. In this study, the effects of grouting on the strain-dependent shear stiffness of jointed rock mass were investigated at the small-strain (below 10 -5 ) and mid-strain (10 -5 to 10 -3 ) ranges using the quasi-static resonant column test and rock mass dynamic test devices. The effects of curing time, axial stress, initial joint roughness, and grouted joint thickness were examined. The results show that (1) grouting of rock joints leads to decreased stress sensitivity and increased small-strain shear stiffness for all tested samples; (2) the grouted rock samples display similar modulus degradation characteristics as the applied grout material; (3) the initial joint roughness determines the stress-dependent behaviors and general stiffness range of the jointed and grouted rocks, but the strain-dependent behaviors are dependent on the properties of the grout material; (4) increased grouted joint thickness results in larger contribution of the grout properties in the overall grouted rock mass.

Experimental Characterization of Stress- and Strain-Dependent Stiffness in Grouted Rock Masses

PubMed Central

Cho, Gye-Chun

2018-01-01

Grouting of fractured rock mass prior to excavation results in grout-filled discontinuities that govern the deformation characteristics of a site. The influence of joint characteristics on the properties of grouted rocks is important in assessing the effects of grouting on jointed rock mass. However, grouting remains a predominantly empirical practice and the effects of grouting on rock joint behavior and material properties have yet to be accurately assessed. Granular materials, including jointed rocks, typically display nonlinear strain-dependent responses that can be characterized by the shear modulus degradation curve. In this study, the effects of grouting on the strain-dependent shear stiffness of jointed rock mass were investigated at the small-strain (below 10−5) and mid-strain (10−5 to 10−3) ranges using the quasi-static resonant column test and rock mass dynamic test devices. The effects of curing time, axial stress, initial joint roughness, and grouted joint thickness were examined. The results show that (1) grouting of rock joints leads to decreased stress sensitivity and increased small-strain shear stiffness for all tested samples; (2) the grouted rock samples display similar modulus degradation characteristics as the applied grout material; (3) the initial joint roughness determines the stress-dependent behaviors and general stiffness range of the jointed and grouted rocks, but the strain-dependent behaviors are dependent on the properties of the grout material; (4) increased grouted joint thickness results in larger contribution of the grout properties in the overall grouted rock mass. PMID:29596371

Flow and fracture behavior of aluminum alloy 6082-T6 at different tensile strain rates and triaxialities.

PubMed

Chen, Xuanzhen; Peng, Yong; Peng, Shan; Yao, Song; Chen, Chao; Xu, Ping

2017-01-01

This study aims to investigate the flow and fracture behavior of aluminum alloy 6082-T6 (AA6082-T6) at different strain rates and triaxialities. Two groups of Charpy impact tests were carried out to further investigate its dynamic impact fracture property. A series of tensile tests and numerical simulations based on finite element analysis (FEA) were performed. Experimental data on smooth specimens under various strain rates ranging from 0.0001~3400 s-1 shows that AA6082-T6 is rather insensitive to strain rates in general. However, clear rate sensitivity was observed in the range of 0.001~1 s-1 while such a characteristic is counteracted by the adiabatic heating of specimens under high strain rates. A Johnson-Cook constitutive model was proposed based on tensile tests at different strain rates. In this study, the average stress triaxiality and equivalent plastic strain at facture obtained from numerical simulations were used for the calibration of J-C fracture model. Both of the J-C constitutive model and fracture model were employed in numerical simulations and the results was compared with experimental results. The calibrated J-C fracture model exhibits higher accuracy than the J-C fracture model obtained by the common method in predicting the fracture behavior of AA6082-T6. Finally, the Scanning Electron Microscope (SEM) of fractured specimens with different initial stress triaxialities were analyzed. The magnified fractographs indicate that high initial stress triaxiality likely results in dimple fracture.

Ginger (Zingiber officinale Roscoe) and the Gingerols Inhibit the Growth of Cag A+ Strains of Helicobacter pylori

PubMed Central

Mahady, Gail B.; Pendland, Susan L.; Yun, Gina S.; Lu, Zhi-Zhen; Stoia, Adina

2013-01-01

Background Ginger root (Zingiber officinale) has been used traditionally for the treatment of gastrointestinal ailments such as motion sickness, dyspepsia and hyperemesis gravidarum, and is also reported to have chemopreventative activity in animal models. The gingerols are a group of structurally related polyphenolic compounds isolated from ginger and known to be the active constituents. Since Helicobacter pylori (HP) is the primary etiological agent associated with dyspepsia, peptic ulcer disease and the development of gastric and colon cancer, the anti-HP effects of ginger and its constituents were tested in vitro. Materials and Methods A methanol extract of the dried powdered ginger rhizome, fractions of the extract and the isolated constituents, 6-,8-, 10-gingerol and 6-shogoal, were tested against 19 strains of HP, including 5 CagA+ strains. Results The methanol extract of ginger rhizome inhibited the growth of all 19 strains in vitro with a minimum inhibitory concentration range of 6.25–50 µg/ml. One fraction of the crude extract, containing the gingerols, was active and inhibited the growth of all HP strains with an MIC range of 0.78 to 12.5 µg/ml and with significant activity against the CagA+ strains. Conclusion These data demonstrate that ginger root extracts containing the gingerols inhibit the growth of H. pylori CagA+ strains in vitro and this activity may contribute to its chemopreventative effects. PMID:14666666

Bacillus vanillea sp. nov., Isolated from the Cured Vanilla Bean.

PubMed

Chen, Yong-gan; Gu, Feng-lin; Li, Ji-hua; Xu, Fei; He, Shu-zhen; Fang, Yi-ming

2015-02-01

A Gram-positive bacterium, designated strain XY18(T), was isolated from a cured vanilla bean in Hainan province, China. Cells were rod-shaped, endospore producing, and peritrichous flagella. Strain XY18(T) grew at salinities of 0-8 % (w/v) NaCl (optimally 1-4 %), pH 4.0-8.0 (optimally 5.0-7.0 %) and temperature range 20-45 °C (optimally 28-35 °C). The predominant menaquinone was MK-7. The major cellular fatty acids were anteiso-C15:0, iso-C15:0, anteiso-C17:0, and iso-C17:0. Phylogenetic analysis based on 16S rRNA gene sequence indicated that strain XY18(T) was a member of the genus Bacillus, and closely related to B. amyloliquefaciens NBRC 15535(T) and B. siamensis PD-A10(T), with 99.1 and 99.2 % sequence similarity, respectively. However, the DNA-DNA hybridization value between strain XY18(T) and B. amyloliquefaciens NBRC 15535(T) was 35.7 %. The genomic DNA G+C content of strain XY18(T) was 46.4 mol%, significantly differed from B. siamensis PD-A10(T) (41.4 %), which was higher than the range of 4 % indicative of species. On the basis of polyphasic taxonomic study, including phenotypic features, chemotaxonomy, and phylogenetic analyses, strain XY18(T) represents a novel species within the genus Bacillus, for which the name Bacillus vanillea sp. nov. is proposed. The type strain is XY18(T) (=CGMCC 8629 = NCCB 100507).

Strain effects on thermal conductivity of nanostructured silicon by Raman piezothermography

NASA Astrophysics Data System (ADS)

Murphy, Kathryn Fay

A fundamental problem facing the rational design of materials is the independent control of electrical and thermal properties, with implications for a wide range of applications including thermoelectrics, solar thermal power generation, and thermal logic. One strategy for controlling transport involves manipulating the length scales which affect it. For instance, Si thermal conductivity may be reduced with relatively little change in electrical properties when the confining dimension (e.g., nanowire diameter) is small enough that heat carriers are preferentially scattered at free surfaces. However, tailoring properties by geometry or chemistry alone does not allow for on-demand modification, precluding applications which require responsive behavior such as thermal transistors, thermoelectric modules which adapt to their environmental temperature, or switchable thermal barriers. One means of tuning transport is elastic strain, which has long been exploited to improve carrier mobility in electronic devices. Uniform strain is predicted to affect thermal conductivity primarily via changes in heat capacity and phonon velocity, and crystalline defects such as vacancies or dislocations---which induce large strain gradients---should lower thermal conductivity by decreasing the phonon mean free path. Nanowires are ideal for the study of strain and defect effects due to the availability of a range of elastic strain an order of magnitude larger than in bulk and due to their small volumes. However, experimental measurements of strain-mediated thermal conductivity in nanowires have been limited due to the complexity of simultaneously applying and measuring stress or strain, heating, and measuring temperature. In this dissertation, we measure strain effects on thermal conductivity using a novel non-contact approach which we name Raman piezothermography. We apply a uniaxial load to individual Si nanowires, Si thin films, and Si micromeshes under a confocal mu-Raman microscope and, using the Raman laser as a heat source and the Raman spectrum as a measure of temperature, determine thermal transport properties. We show that uniaxial strain up to ˜1% has a weak effect on Si nanowire or thin film thermal conductivity, but irradiation-induced defects in nanowires yield dramatic reductions due to increased phonon scattering. Such defects are accompanied by large strain gradients, but decoupling the effect of these gradients from local changes in mass and interatomic potential is experimentally untenable. To isolate the effect of strain gradients, we extend our method to Si micromeshes, which exhibit nonuniform strains upon loading. The complex strain states achieved cause more drastic reductions of thermal conductivity due to enhanced phonon-phonon scattering in the presence of a strain gradient. The directions suggested by our experiments, as well as the development of the method, will allow for more robust understanding and control of thermal transport in nanostructures.

The airborne laser ranging system, its capabilities and applications

NASA Technical Reports Server (NTRS)

Kahn, W. D.; Degnan, J. J.; Englar, T. S., Jr.

1982-01-01

The airborne laser ranging system is a multibeam short pulse laser ranging system on board an aircraft. It simultaneously measures the distances between the aircraft and six laser retroreflectors (targets) deployed on the Earth's surface. The system can interrogate over 100 targets distributed over an area of 25,000 sq, kilometers in a matter of hours. Potentially, a total of 1.3 million individual range measurements can be made in a six hour flight. The precision of these range measurements is approximately + or - 1 cm. These measurements are used in procedure which is basically an extension of trilateration techniques to derive the intersite vector between the laser ground targets. By repeating the estimation of the intersite vector, strain and strain rate errors can be estimated. These quantities are essential for crustal dynamic studies which include determination and monitoring of regional strain in the vicinity of active fault zones, land subsidence, and edifice building preceding volcanic eruptions.

Diversity of metabolic capacities among strains degrading polycyclic aromatic hydrocarbons

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

Bouchez, M.; Besnaienou, B.; Blanchet, D.

1995-12-31

Strains of Pseudomonas and Rhodococcus genera were isolated for their capacity to use, as a sole carbon and energy source, one of the following polycyclic aromatic hydrocarbons (PAHs): naphthalene (NAP), fluorene (FLU), phenanthrene (PHE), anthracene (ANT), fluoranthene (FLT), and pyrene (PYR). The range of PAHs supporting growth of these pure strains was usually restricted, but several other hydrocarbons were used by Rhodococcus sp. All strains could grow on simple organic acids. Maximal specific growth rates ({mu}{sub max}) of all strains on their PAH growth substrates were determined by respirometry. No clear relationships between {mu}{sub max} values and the molecular weightmore » or water solubility of PAHs were apparent, but Pseudomonas sp. exhibited the highest {mu}{sub max} values. Carbon balances for PAH biodegradation were established. Differences between strains were observed, but high mineralization rates and low production of soluble metabolites were obtained for all PAHs. Bacterial biomass represented 16% to 35% of the carbon consumed. Strain diversity was also apparent in the interactions observed in the degradation of a mixture of two PAHs by individual strains, which often involved inhibition of PAH substrate degradation, with or without cometabolization of the second PAH.« less

Genetic diversity analysis of Leuconostoc mesenteroides from Korean vegetables and food products by multilocus sequence typing.

PubMed

Sharma, Anshul; Kaur, Jasmine; Lee, Sulhee; Park, Young-Seo

2018-06-01

In the present study, 35 Leuconostoc mesenteroides strains isolated from vegetables and food products from South Korea were studied by multilocus sequence typing (MLST) of seven housekeeping genes (atpA, groEL, gyrB, pheS, pyrG, rpoA, and uvrC). The fragment sizes of the seven amplified housekeeping genes ranged in length from 366 to 1414 bp. Sequence analysis indicated 27 different sequence types (STs) with 25 of them being represented by a single strain indicating high genetic diversity, whereas the remaining 2 were characterized by five strains each. In total, 220 polymorphic nucleotide sites were detected among seven housekeeping genes. The phylogenetic analysis based on the STs of the seven loci indicated that the 35 strains belonged to two major groups, A (28 strains) and B (7 strains). Split decomposition analysis showed that intraspecies recombination played a role in generating diversity among strains. The minimum spanning tree showed that the evolution of the STs was not correlated with food source. This study signifies that the multilocus sequence typing is a valuable tool to access the genetic diversity among L. mesenteroides strains from South Korea and can be used further to monitor the evolutionary changes.

Flexible Carbon Nanotube Films for High Performance Strain Sensors

PubMed Central

Kanoun, Olfa; Müller, Christian; Benchirouf, Abderahmane; Sanli, Abdulkadir; Dinh, Trong Nghia; Al-Hamry, Ammar; Bu, Lei; Gerlach, Carina; Bouhamed, Ayda

2014-01-01

Compared with traditional conductive fillers, carbon nanotubes (CNTs) have unique advantages, i.e., excellent mechanical properties, high electrical conductivity and thermal stability. Nanocomposites as piezoresistive films provide an interesting approach for the realization of large area strain sensors with high sensitivity and low manufacturing costs. A polymer-based nanocomposite with carbon nanomaterials as conductive filler can be deposited on a flexible substrate of choice and this leads to mechanically flexible layers. Such sensors allow the strain measurement for both integral measurement on a certain surface and local measurement at a certain position depending on the sensor geometry. Strain sensors based on carbon nanostructures can overcome several limitations of conventional strain sensors, e.g., sensitivity, adjustable measurement range and integral measurement on big surfaces. The novel technology allows realizing strain sensors which can be easily integrated even as buried layers in material systems. In this review paper, we discuss the dependence of strain sensitivity on different experimental parameters such as composition of the carbon nanomaterial/polymer layer, type of polymer, fabrication process and processing parameters. The insights about the relationship between film parameters and electromechanical properties can be used to improve the design and fabrication of CNT strain sensors. PMID:24915183

Creep Strain and Strain Rate Response of 2219 Al Alloy at High Stress Levels

NASA Technical Reports Server (NTRS)

Taminger, Karen M. B.; Wagner, John A.; Lisagor, W. Barry

1998-01-01

As a result of high localized plastic deformation experienced during proof testing in an International Space Station connecting module, a study was undertaken to determine the deformation response of a 2219-T851 roll forging. After prestraining 2219-T851 Al specimens to simulate strains observed during the proof testing, creep tests were conducted in the temperature range from ambient temperature to 107 C (225 F) at stress levels approaching the ultimate tensile strength of 2219-T851 Al. Strain-time histories and strain rate responses were examined. The strain rate response was extremely high initially, but decayed rapidly, spanning as much as five orders of magnitude during primary creep. Select specimens were subjected to incremental step loading and exhibited initial creep rates of similar magnitude for each load step. Although the creep rates decreased quickly at all loads, the creep rates dropped faster and reached lower strain rate levels for lower applied loads. The initial creep rate and creep rate decay associated with primary creep were similar for specimens with and without prestrain; however, prestraining (strain hardening) the specimens, as in the aforementioned proof test, resulted in significantly longer creep life.

Effects of pH and temperature on growth and glycerol production kinetics of two indigenous wine strains of Saccharomyces cerevisiae from Turkey

PubMed Central

Yalcin, Seda Karasu; Yesim Ozbas, Z.

2008-01-01

The study was performed in a batch system in order to determine the effects of pH and temperature on growth and glycerol production kinetics of two indigenous wine yeast strains Saccharomyces cerevisiae Kalecik 1 and Narince 3. The highest values of dry mass and specific growth rate were obtained at pH 4.00 for both of the strains. Maximum specific glycerol production rates were obtained at pH 5.92 and 6.27 for the strains Kalecik 1 and Narince 3, respectively. Kalecik 1 strain produced maximum 8.8 gL−1 of glycerol at pH 6.46. Maximum glycerol concentration obtained by the strain Narince 3 was 9.1 gL−1 at pH 6.48. Both yeasts reached maximum specific growth rate at 30°C. Optimum temperature range for glycerol production was determined as 25-30°C for the strain Kalecik 1. The strain Narince 3 reached maximum specific glycerol production rate at 30°C. Maximum glycerol concentrations at 30°C were obtained as 8.5 and 7.6 gL−1 for Kalecik 1 and Narince 3, respectively. PMID:24031225

High Precision Temperature Insensitive Strain Sensor Based on Fiber-Optic Delay

PubMed Central

Yang, Ning; Su, Jun; Fan, Zhiqiang; Qiu, Qi

2017-01-01

A fiber-optic delay based strain sensor with high precision and temperature insensitivity was reported, which works on detecting the delay induced by strain instead of spectrum. In order to analyze the working principle of this sensor, the elastic property of fiber-optic delay was theoretically researched and the elastic coefficient was measured as 3.78 ps/km·με. In this sensor, an extra reference path was introduced to simplify the measurement of delay and resist the cross-effect of environmental temperature. Utilizing an optical fiber stretcher driven by piezoelectric ceramics, the performance of this strain sensor was tested. The experimental results demonstrate that temperature fluctuations contribute little to the strain error and that the calculated strain sensitivity is as high as 4.75 με in the range of 350 με. As a result, this strain sensor is proved to be feasible and practical, which is appropriate for strain measurement in a simple and economical way. Furthermore, on basis of this sensor, the quasi-distributed measurement could be also easily realized by wavelength division multiplexing and wavelength addressing for long-distance structure health and security monitoring. PMID:28468323

The effect of temperature on the low cycle fatigue of type 316L stainless steel over the range 20-200°C

NASA Astrophysics Data System (ADS)

Chung, T. E.; Kalantary, M. R.; Faulkner, R. G.; Boutard, J.-L.

1992-09-01

Strain-controlled low cycle fatigue tests (with and without tensile hold) were performed on type 316L stainless steel over the temperature range 20-200°C. The results indicate that for strain ranges of less than 1%, the fatigue life was temperature independent. By contrast, for strain ranges of 1% or more, fatigue life decreased significantly as temperature was increased from 20 to approximately 50°C. It then increased with further increases in temperature until approximately 100°C and beyond when it became relatively temperature insensitive. Fatigue life at all temperatures was reduced with the superimposition of a speak tension hold of 50 s. A model based on the temperature-assisted diffusion of interstitial carbon atoms is proposed to explain the phenomenon.

Dynamic tensile fracture of mortar at ultra-high strain-rates

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

Erzar, B., E-mail: benjamin.erzar@cea.fr; Buzaud, E.; Chanal, P.-Y.

2013-12-28

During the lifetime of a structure, concrete and mortar may be exposed to highly dynamic loadings, such as impact or explosion. The dynamic fracture at high loading rates needs to be well understood to allow an accurate modeling of this kind of event. In this work, a pulsed-power generator has been employed to conduct spalling tests on mortar samples at strain-rates ranging from 2 × 10{sup 4} to 4 × 10{sup 4} s{sup −1}. The ramp loading allowed identifying the strain-rate anytime during the test. A power law has been proposed to fit properly the rate-sensitivity of tensile strength of thismore » cementitious material over a wide range of strain-rate. Moreover, a specimen has been recovered damaged but unbroken. Micro-computed tomography has been employed to study the characteristics of the damage pattern provoked by the dynamic tensile loading.« less

Proteiniclasticum ruminis gen. nov., sp. nov., a strictly anaerobic proteolytic bacterium isolated from yak rumen.

PubMed

Zhang, Kegui; Song, Lei; Dong, Xiuzhu

2010-09-01

Two strictly anaerobic, proteolytic bacterial strains, designated strain D3RC-2(T) and D3RC-3r, were isolated from a cellulose-degrading mixed culture enriched from yak rumen content. The strains were Gram-stain negative and non-spore-forming with cell sizes of 0.5-0.8 x 0.6-2.0 mum. The temperature range for growth was 24-46 degrees C (optimum 38-39 degrees C) and the pH range was between 5.6 and 8.7 (optimum 7.0-7.3). Both strains used soya peptone, tryptone, l-phenylalanine, l-leucine, l-methionine, l-serine, l-valine, l-threonine and l-histidine as carbon and nitrogen sources, but did not use any of the saccharides tested. The major fermentation products from PY medium were acetate, propionate and iso-butyrate. The DNA G+C contents of strains D3RC-2(T) and D3RC-3r were 41.0+/-0.1 mol% and 41.3+/-0.1 mol% (HPLC), respectively. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the two strains represented a new phyletic sublineage within the family Clostridiaceae, with <93.8 % 16S rRNA gene sequence similarity to recognized species. On the basis of the phenotypic, genotypic and physiological evidence, strains D3RC-2(T) and D3RC-3r are proposed as representing a novel species of a new genus, for which the name Proteiniclasticum ruminis gen. nov., sp. nov. is proposed. The type strain of the type species is D3RC-2(T) (=AS 1.5057(T)=JCM 14817(T)).

Accuracy of speckle tracking in the context of stress echocardiography in short axis view: An in vitro validation study.

PubMed

Hodzic, Amir; Chayer, Boris; Wang, Diya; Porée, Jonathan; Cloutier, Guy; Milliez, Paul; Normand, Hervé; Garcia, Damien; Saloux, Eric; Tournoux, Francois

2018-01-01

This study aimed to test the accuracy of a speckle tracking algorithm to assess myocardial deformation in a large range of heart rates and strain magnitudes compared to sonomicrometry. Using a tissue-mimicking phantom with cyclic radial deformation, radial strain derived from speckle tracking (RS-SpT) of the upper segment was assessed in short axis view by conventional echocardiography (Vivid q, GE) and post-processed with clinical software (EchoPAC, GE). RS-SpT was compared with radial strain measured simultaneously by sonomicrometers (RS-SN). Radial strain was assessed with increasing deformation rates (60 to 160 beats/min) and increasing pulsed volumes (50 to 100 ml/beat) to simulate physiological changes occurring during stress echocardiography. There was a significant correlation (R2 = 0.978, P <0.001) and a close agreement (bias ± 2SD, 0.39 ± 1.5%) between RS-SpT and RS-SN. For low strain values (<15%), speckle tracking showed a small but significant overestimation of radial strain compared to sonomicrometers. Two-way analysis of variance did not show any significant effect of the deformation rate. For RS-SpT, the feasibility was excellent and the intra- and inter-observer variability were low (the intraclass correlation coefficients were 0.96 and 0.97, respectively). Speckle tracking demonstrated a good correlation with sonomicrometry for the assessment of radial strain independently of the heart rate and strain magnitude in a physiological range of values. Though speckle tracking seems to be a reliable and reproducible technique to assess myocardial deformation variations during stress echocardiography, further studies are mandated to analyze the impact of angulated and artefactual out-of-plane motions and inter-vendor variability.

Accuracy of speckle tracking in the context of stress echocardiography in short axis view: An in vitro validation study

PubMed Central

Chayer, Boris; Wang, Diya; Porée, Jonathan; Cloutier, Guy; Milliez, Paul; Normand, Hervé; Garcia, Damien; Saloux, Eric; Tournoux, Francois

2018-01-01

Aim This study aimed to test the accuracy of a speckle tracking algorithm to assess myocardial deformation in a large range of heart rates and strain magnitudes compared to sonomicrometry. Methods and results Using a tissue-mimicking phantom with cyclic radial deformation, radial strain derived from speckle tracking (RS-SpT) of the upper segment was assessed in short axis view by conventional echocardiography (Vivid q, GE) and post-processed with clinical software (EchoPAC, GE). RS-SpT was compared with radial strain measured simultaneously by sonomicrometers (RS-SN). Radial strain was assessed with increasing deformation rates (60 to 160 beats/min) and increasing pulsed volumes (50 to 100 ml/beat) to simulate physiological changes occurring during stress echocardiography. There was a significant correlation (R2 = 0.978, P <0.001) and a close agreement (bias ± 2SD, 0.39 ± 1.5%) between RS-SpT and RS-SN. For low strain values (<15%), speckle tracking showed a small but significant overestimation of radial strain compared to sonomicrometers. Two-way analysis of variance did not show any significant effect of the deformation rate. For RS-SpT, the feasibility was excellent and the intra- and inter-observer variability were low (the intraclass correlation coefficients were 0.96 and 0.97, respectively). Conclusions Speckle tracking demonstrated a good correlation with sonomicrometry for the assessment of radial strain independently of the heart rate and strain magnitude in a physiological range of values. Though speckle tracking seems to be a reliable and reproducible technique to assess myocardial deformation variations during stress echocardiography, further studies are mandated to analyze the impact of angulated and artefactual out-of-plane motions and inter-vendor variability. PMID:29584751

Protective Effect of Immunization with Heat-Labile Enterotoxin in Gnotobiotic Rats Monocontaminated with Enterotoxigenic Escherichia coli

PubMed Central

Klipstein, Frederick A.; Engert, Richard F.; Short, Helen B.

1980-01-01

The protective effect of active immunization with a purified preparation of the polymyxin-release form of Escherichia coli heat-labile enterotoxin (LT), administered using a parenteral prime and peroral boosts given after ablation of gastric secretion by means of cimetidine, was assessed in gnotobiotic rats which were challenged by monocontamination with enterotoxigenic strains of E. coli. Water transport was evaluated by the in vivo marker perfusion technique at weekly intervals over a 3-week period after contamination. Water transport in unimmunized control rats was consistently in absorption in those contaminated by a nontoxigenic strain, in secretion during only week 2 in those contaminated by an LT+/− strain, in secretion during weeks 2 and 3 in those contaminated by an LT+/ST+ (heat-stable enterotoxin) strain, and consistently in absorption in those contaminated by an −/ST+ strain. Rats immunized with a booster dosage of 250 μg had a significant increase (P < 0.001) in net water absorption as compared to unimmunized rats, with values in the borderline range of absorption, when challenged with either the LT+/− or LT+/ST+ strains. Rats immunized with a 10-fold-higher boosting dosage had a significant increase (P < 0.001) in net water absorption as compared to those boosted at the lower dosage; water absorption was within the normal range. There was no difference between the ileal bacterial counts of unimmunized and immunized rats challenged by the various strains. These observations indicate that this immunization program provides complete protection in an animal model against challenge by intestinal contamination with enterotoxigenic strains of E. coli which produce LT, either alone or in combination with ST. PMID:6991436

In vitro synergism of trifluorothymidine and ganciclovir against HSV-1.

PubMed

Hobden, Jeffery A; Kumar, Manish; Kaufman, Herbert E; Clement, Christian; Varnell, Emily D; Bhattacharjee, Partha S; Hill, James M

2011-02-01

To determine whether trifluorothymidine (TFT) and ganciclovir (GCV) are synergistic against herpes simplex virus type 1 (HSV-1). TFT and GCV activity against 12 strains of HSV-1 (including an acyclovir-resistant strain) was measured by plaque-forming unit (PFU) inhibition. Cellular toxicity was assessed with an MTT dye reduction assay. Synergism was determined by calculating fractional inhibitory concentration (FIC indices) based on PFU reduction. Concentrations of TFT resulting in 50% inhibition of PFUs (IC(50)) of acyclovir-susceptible HSV-1 strains ranged from 3.07 ± 0.36 to 12.52 ± 0.61 μM. GCV IC(50) values ranged from 0.40 ± 0.02 to 1.59 ± 0.14 μM. IC(50) values of TFT and GCV against the acyclovir-resistant strain were 15.40 ± 3.17 and 93.00 ± 9.64 μM, respectively. Concentrations of TFT or GCV resulting in 50% cell cytotoxicity (CC(50)) were 0.99 ± 0.01 and 92.91 ± 8.92 μM, respectively. TFT and GCV combined (10:1) were 10 times more potent against all acyclovir-susceptible HSV-1 strains. For 8 of 12 HSV-1 strains, the IC(50) of TFT and GCV combined was lower than the CC(50) of either drug. For acyclovir-susceptible HSV-1 strains, TFT and GCV combined generated a FIC index of <0.5, suggesting strong synergism between the two drugs. The FIC value for TFT and GCV combined against the acyclovir-resistant HSV-1 strain was 0.84, indicating nonantagonism. TFT and GCV are synergistic against acyclovir-susceptible HSV-1 at concentrations significantly less toxic than if each antiviral were used as a sole agent.

In Vitro Synergism of Trifluorothymidine and Ganciclovir against HSV-1

PubMed Central

Hobden, Jeffery A.; Kumar, Manish; Kaufman, Herbert E.; Clement, Christian; Varnell, Emily D.; Bhattacharjee, Partha S.

2011-01-01

Purpose. To determine whether trifluorothymidine (TFT) and ganciclovir (GCV) are synergistic against herpes simplex virus type 1 (HSV-1). Methods. TFT and GCV activity against 12 strains of HSV-1 (including an acyclovir-resistant strain) was measured by plaque-forming unit (PFU) inhibition. Cellular toxicity was assessed with an MTT dye reduction assay. Synergism was determined by calculating fractional inhibitory concentration (FIC indices) based on PFU reduction. Results. Concentrations of TFT resulting in 50% inhibition of PFUs (IC50) of acyclovir-susceptible HSV-1 strains ranged from 3.07 ± 0.36 to 12.52 ± 0.61 μM. GCV IC50 values ranged from 0.40 ± 0.02 to 1.59 ± 0.14 μM. IC50 values of TFT and GCV against the acyclovir-resistant strain were 15.40 ± 3.17 and 93.00 ± 9.64 μM, respectively. Concentrations of TFT or GCV resulting in 50% cell cytotoxicity (CC50) were 0.99 ± 0.01 and 92.91 ± 8.92 μM, respectively. TFT and GCV combined (10:1) were 10 times more potent against all acyclovir-susceptible HSV-1 strains. For 8 of 12 HSV-1 strains, the IC50 of TFT and GCV combined was lower than the CC50 of either drug. For acyclovir-susceptible HSV-1 strains, TFT and GCV combined generated a FIC index of <0.5, suggesting strong synergism between the two drugs. The FIC value for TFT and GCV combined against the acyclovir-resistant HSV-1 strain was 0.84, indicating nonantagonism. Conclusions. TFT and GCV are synergistic against acyclovir-susceptible HSV-1 at concentrations significantly less toxic than if each antiviral were used as a sole agent. PMID:20861476

Mobilisporobacter senegalensis gen. nov., sp. nov., an anaerobic bacterium isolated from tropical shea cake.

PubMed

Mbengue, Malick; Thioye, Abdoulaye; Labat, Marc; Casalot, Laurence; Joseph, Manon; Samb, Abdoulaye; Ben Ali Gam, Zouhaier

2016-03-01

A Gram-stain positive, endospore-forming, strictly anaerobic bacterium, designated strain Gal1 T , was isolated from shea cake, a waste material from the production of shea butter, originating from Saraya, Senegal. The cells were rod-shaped, slightly curved, and motile with peritrichous flagella. The strain was oxidase-negative and catalase-negative. Growth was observed at temperatures ranging from 15 to 45 °C (optimum 30 °C) and at pH 6.5-9.3 (optimum pH 7.8). The salinity range for growth was 0-3.5 % NaCl (optimum 1 %). Yeast extract was required for growth. Strain Gal1 T fermented various carbohydrates such as mannose, mannitol, arabinose, cellobiose, fructose, glucose, maltose, sucrose, trehalose and lactose and the major end-products were ethanol and acetate. The only major cellular fatty acid was C16 : 0 (19.6 %). The DNA base G+C content of strain Gal1 T was 33.8 mol%. Analysis of the 16S rRNA gene sequence of the isolate indicated that this strain was related to Mobilitalea sibirica DSM 26468 T with 94.27 % similarity, Clostridium populeti ATTC 35295 T with 93.94 % similarity, and Clostridium aminovalericum DSM 1283 T and Anaerosporobacter mobilis DSM 15930 T with 93.63 % similarity. On the basis of phenotypic characteristics, phylogenetic analysis and the results of biochemical and physiological tests, strain Gal1 T was clearly distinguished from closely related genera, and strain Gal1 T can be assigned to a novel species of a new genus for which the name Mobilisporobacter senegalensis gen. nov., sp. nov. is proposed. The type strain is Gal1 T ( = DSM 26537 T  = JCM 18753 T ).

Genome characterization of a novel binary toxin-positive strain of Clostridium difficile and comparison with the epidemic 027 and 078 strains.

PubMed

Peng, Zhong; Liu, Sidi; Meng, Xiujuan; Liang, Wan; Xu, Zhuofei; Tang, Biao; Wang, Yuanguo; Duan, Juping; Fu, Chenchao; Wu, Bin; Wu, Anhua; Li, Chunhui

2017-01-01

Clostridium difficile is an anaerobic Gram-positive spore-forming gut pathogen that causes antibiotic-associated diarrhea worldwide. A small number of C. difficile strains express the binary toxin (CDT), which is generally found in C. difficile 027 (ST1) and/or 078 (ST11) in clinic. However, we isolated a binary toxin-positive non-027, non-078 C. difficile LC693 that is associated with severe diarrhea in China. The genotype of this strain was determined as ST201. To understand the pathogenesis-basis of C. difficile ST201, the strain LC693 was chosen for whole genome sequencing, and its genome sequence was analyzed together with the other two ST201 strains VL-0104 and VL-0391 and compared to the epidemic 027/ST1 and 078/ST11 strains. The project finally generated an estimated genome size of approximately 4.07 Mbp for strain LC693. Genome size of the three ST201 strains ranged from 4.07 to 4.16 Mb, with an average GC content between 28.5 and 28.9%. Phylogenetic analysis demonstrated that the ST201 strains belonged to clade 3. The ST201 genomes contained more than 40 antibiotic resistance genes and 15 of them were predicted to be associated with vancomycin-resistance. The ST201 strains contained a larger PaLoc with a Tn6218 element inserted than the 027/ST1 and 078/ST11 strains, and encoded a truncated TcdC. In addition, the ST201 strains contained intact binary toxin coding and regulation genes which are highly homologous to the 027/ST1 strain. Genome comparison of the ST201 strains with the epidemic 027 and 078 strain identified 641 genes specific for C. difficile ST201, and a number of them were predicted as fitness and virulence associated genes. The presence of those genes also contributes to the pathogenesis of the ST201 strains. In this study, the genomic characterization of three binary toxin-positive C. difficile ST201 strains in clade 3 was discussed and compared to the genomes of the epidemic 027 and the 078 strains. Our analysis identified a number fitness and virulence associated genes/loci in the ST201 genomes that contribute to the pathogenesis of C. difficile ST201.

Production of high titer attenuated poliovirus strains on the serum-free PER.C6(®) cell culture platform for the generation of safe and affordable next generation IPV.

PubMed

Sanders, Barbara P; Oakes, Isabel de los Rios; van Hoek, Vladimir; Liu, Ying; Marissen, Wilfred; Minor, Philip D; Wimmer, Eckard; Schuitemaker, Hanneke; Custers, Jerome H H V; Macadam, Andrew; Cello, Jeronimo; Edo-Matas, Diana

2015-11-27

As poliovirus eradication draws closer, alternative Inactivated Poliovirus Vaccines (IPV) are needed to overcome the risks associated with continued use of the Oral Poliovirus Vaccine and of neurovirulent strains used during manufacture of conventional (c) IPV. We have previously demonstrated the susceptibility of the PER.C6(®) cell line to cIPV strains; here we investigated the suspension cell culture platform for growth of attenuated poliovirus strains. We examined attenuated Sabin strain productivity on the PER.C6(®) cell platform compared to the conventional Vero cell platform. The suitability of the suspension cell platform for propagation of rationally-attenuated poliovirus strains (stabilized Sabin type 3 S19 derivatives and genetically attenuated and stabilized MonoCre(X) strains), was also assessed. Yields were quantified by infectious titer determination and D-antigen ELISA using either serotype-specific polyclonal rabbit sera for Sabin strains or monoclonal cIPV-strain-specific antibodies for cIPV, S19 and MonoCre(X) strains. PER.C6(®) cells supported the replication of Sabin strains to yields of infectious titers that were in the range of cIPV strains at 32.5°C. Sabin strains achieved 30-fold higher yields (p<0.0001) on the PER.C6(®) cell platform as compared to the Vero cell platform in infectious titer and D-antigen content. Furthermore, Sabin strain productivity on the PER.C6(®) cell platform was maintained at 10l scale. Yields of infectious titers of S19 and MonoCre(X) strains were 0.5-1 log10 lower than seen for cIPV strains, whereas D-antigen yield and productivities in doses/ml using rationally-attenuated strains were in line with yields reported for cIPV strains. Sabin and rationally-attenuated polioviruses can be grown to high infectious titers and D-antigen yields. Sabin strain infection shows increased productivity on the PER.C6(®) cell platform as compared to the conventional Vero cell platform. Novel cell platforms with the potential for higher yields could contribute to increased affordability of a next generation of IPV vaccines needed for achieving and maintaining poliovirus eradication. Copyright © 2015 Elsevier Ltd. All rights reserved.

[Sensitivity of fungi in the genus Candida to antimicrobial preparations].

PubMed

Paliĭ, G K; Ivanova, S A

1986-03-01

Sensitivity of 50 Candida fungus strains isolated from patients with chronic intestine diseases was studied with respect to amphotericin B, levorin, enteroseptol, intestopan and decamethoxin. The rate of forming resistant variants of the strains with respect to decamethoxin and development of their cross resistance to levorin was estimated. It was shown that decamethoxin was the most active antifungal drug among the drugs tested. Estimation of sensitivity of the Candida strains to enteroseptol and intestopan revealed that the fungicidal concentration of enteroseptol for 78 per cent of the strains ranged within 3.9-7.8 micrograms/ml. It was demonstrated that development of resistance to decamethoxin in the strains of Candida albicans was slow and did not reach high levels. No cross resistance between decamethoxin and levorin was detected.

Experimental Investigation of a Piezo-Optical Transducer for Highly Sensitive Strain Gauges

NASA Astrophysics Data System (ADS)

Paulish, A. G.; Zagubisalo, P. S.; Barakov, V. N.; Pavlov, M. A.

2018-03-01

The characteristics of a piezo-optical transducer of a new design with high strain sensitivity at compact size have been studied.The original form of the photoelastic element provides a considerable increase in the stress in its working area at a given external force, resulting in an increase in the sensitivity of the transducer. The main characteristics of the transducer were measured using a specially designed device. The strain at a given applied force was calculated using a developed mathematical model of the transducer. As a result, the sensitivity to the relative strain was Δ x/ x=3 · 10-10, the dynamic range was at least four orders of magnitude higher and the gauge factor three orders of magnitude higher than those of strain-resistive gauges.

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.

Distributed temperature and strain discrimination with stimulated brillouin scattering and rayleigh backscatter in an optical fiber.

PubMed

Zhou, Da-Peng; Li, Wenhai; Chen, Liang; Bao, Xiaoyi

2013-01-31

A distributed optical fiber sensor with the capability of simultaneously measuring temperature and strain is proposed using a large effective area non-zero dispersion shifted fiber (LEAF) with sub-meter spatial resolution. The Brillouin frequency shift is measured using Brillouin optical time-domain analysis (BOTDA) with differential pulse-width pair technique, while the spectrum shift of the Rayleigh backscatter is measured using optical frequency-domain reflectometry (OFDR). These shifts are the functions of both temperature and strain, and can be used as two independent parameters for the discrimination of temperature and strain. A 92 m measurable range with the spatial resolution of 50 cm is demonstrated experimentally, and accuracies of ±1.2 °C in temperature and ±15 με in strain could be achieved.

Polycrystalline Ba0.6Sr0.4TiO3 thin films on r-plane sapphire: Effect of film thickness on strain and dielectric properties

NASA Astrophysics Data System (ADS)

Fardin, E. A.; Holland, A. S.; Ghorbani, K.; Akdogan, E. K.; Simon, W. K.; Safari, A.; Wang, J. Y.

2006-10-01

Polycrystalline Ba0.6Sr0.4TiO3 (BST) films grown on r-plane sapphire exhibit strong variation of in-plane strain over the thickness range of 25-400nm. At a critical thickness of ˜200nm, the films are strain relieved; in thinner films, the strain is tensile, while compressive strain was observed in the 400nm film. Microwave properties of the films were measured from 1to20GHz by the interdigital capacitor method. A capacitance tunability of 64% was observed in the 200nm film, while thinner films showed improved Q factor. These results demonstrate the possibility of incorporating frequency agile BST-based devices into the silicon on sapphire process.

Chimera states in multi-strain epidemic models with temporary immunity

NASA Astrophysics Data System (ADS)

Bauer, Larissa; Bassett, Jason; Hövel, Philipp; Kyrychko, Yuliya N.; Blyuss, Konstantin B.

2017-11-01

We investigate a time-delayed epidemic model for multi-strain diseases with temporary immunity. In the absence of cross-immunity between strains, dynamics of each individual strain exhibit emergence and annihilation of limit cycles due to a Hopf bifurcation of the endemic equilibrium, and a saddle-node bifurcation of limit cycles depending on the time delay associated with duration of temporary immunity. Effects of all-to-all and non-local coupling topologies are systematically investigated by means of numerical simulations, and they suggest that cross-immunity is able to induce a diverse range of complex dynamical behaviors and synchronization patterns, including discrete traveling waves, solitary states, and amplitude chimeras. Interestingly, chimera states are observed for narrower cross-immunity kernels, which can have profound implications for understanding the dynamics of multi-strain diseases.

Preliminary assessment of the safety and immunogenicity of a new CTXPhi-negative, hemagglutinin/protease-defective El Tor strain as a cholera vaccine candidate.

PubMed

Benítez, J A; García, L; Silva, A; García, H; Fando, R; Cedré, B; Pérez, A; Campos, J; Rodríguez, B L; Pérez, J L; Valmaseda, T; Pérez, O; Pérez, A; Ramírez, M; Ledón, T; Jidy, M D; Lastre, M; Bravo, L; Sierra, G

1999-02-01

Vibrio cholerae 638 (El Tor, Ogawa), a new CTXPhi-negative hemagglutinin/protease-defective strain that is a cholera vaccine candidate, was examined for safety and immunogenicity in healthy adult volunteers. In a double-blind placebo-controlled study, no significant adverse reactions were observed in volunteers ingesting strain 638. Four volunteers of 42 who ingested strain 638 and 1 of 14 who received placebo experienced loose stools. The strain strongly colonized the human small bowel, as evidenced by its isolation from the stools of 37 of 42 volunteers. V. cholerae 638, at doses ranging from 4 x 10(7) to 2 x 10(9) vibrios, elicited significant serum vibriocidal antibody and anti-Ogawa immunoglobulin A antibody secreting cell responses.

Preliminary Assessment of the Safety and Immunogenicity of a New CTXΦ-Negative, Hemagglutinin/Protease-Defective El Tor Strain as a Cholera Vaccine Candidate

PubMed Central

Benítez, Jorge A.; García, Luis; Silva, Anisia; García, Hilda; Fando, Rafael; Cedré, Barbara; Pérez, Antonio; Campos, Javier; Rodríguez, Boris L.; Pérez, José L.; Valmaseda, Tania; Pérez, Oliver; Pérez, Alberto; Ramírez, Margarita; Ledón, Talena; Jidy, Manuel Díaz; Lastre, Miriam; Bravo, Laura; Sierra, Gustavo

1999-01-01

Vibrio cholerae 638 (El Tor, Ogawa), a new CTXΦ-negative hemagglutinin/protease-defective strain that is a cholera vaccine candidate, was examined for safety and immunogenicity in healthy adult volunteers. In a double-blind placebo-controlled study, no significant adverse reactions were observed in volunteers ingesting strain 638. Four volunteers of 42 who ingested strain 638 and 1 of 14 who received placebo experienced loose stools. The strain strongly colonized the human small bowel, as evidenced by its isolation from the stools of 37 of 42 volunteers. V. cholerae 638, at doses ranging from 4 × 107 to 2 × 109 vibrios, elicited significant serum vibriocidal antibody and anti-Ogawa immunoglobulin A antibody secreting cell responses. PMID:9916056

Effect of misalignment on mechanical behavior of metals in creep. [computer programs

NASA Technical Reports Server (NTRS)

Wu, H. C.

1979-01-01

Application of the endochronic theory of viscoplasticity to creep, creep recovery, and stress relaxation at the small strain and short time range produced the following results: (1) The governing constitutive equations for constant-strain-rate stress-strain behavior, creep, creep recovery, and stress relaxation were derived by imposing appropriate constraints on the general constitutive equation of the endochronic theory. (2) A set of material constants was found which correlate strain-hardening, creep, creep recovery, and stress relaxation. (3) The theory predicts with reasonable accuracy the creep and creep recovery behaviors at short time. (4) The initial strain history prior to the creep stage affects the subsequent creep significantly. (5) A critical stress was established for creep recovery. A computer program, written for the misalignment problem is reported.

Activities of two novel macrolides, GW 773546 and GW 708408, compared with those of telithromycin, erythromycin, azithromycin, and clarithromycin against Haemophilus influenzae.

PubMed

Kosowska, Klaudia; Credito, Kim; Pankuch, Glenn A; Hoellman, Dianne; Lin, Gengrong; Clark, Catherine; Dewasse, Bonifacio; McGhee, Pamela; Jacobs, Michael R; Appelbaum, Peter C

2004-11-01

The MIC at which 50% of strains are inhibited (MIC(50)) and the MIC(90) of GW 773546, a novel macrolide, were 1.0 and 2.0 microg/ml, respectively, for 223 beta-lactamase-positive, beta-lactamase-negative, and beta-lactamase-negative ampicillin-resistant Haemophilus influenzae strains. The MIC(50)s and MIC(90)s of GW 708408, a second novel macrolide, and telithromycin, an established ketolide, were 2.0 and 4.0 microg/ml, respectively, while the MIC(50) and MIC(90) of azithromycin were 1.0 and 2.0 microg/ml, respectively. The MIC(50) and MIC(90) of erythromycin were 4.0 and 8.0 microg/ml, respectively; and those of clarithromycin were 4.0 and 16.0 microg/ml, respectively. All compounds except telithromycin were bactericidal (99.9% killing) against nine strains at two times the MIC after 24 h. Telithromycin was bactericidal against eight of the nine strains. In addition, both novel macrolides and telithromycin at two times the MIC showed 99% killing of all nine strains after 12 h and 90% killing of all strains after 6 h. After 24 h, all drugs were bactericidal against four to seven strains when they were tested at the MIC. Ten of 11 strains tested by multistep selection analysis yielded resistant clones after 14 to 43 passages with erythromycin. Azithromycin gave resistant clones of all strains after 20 to 50 passages, and clarithromycin gave resistant clones of 9 of 11 strains after 14 to 41 passages. By comparison, GW 708408 gave resistant clones of 9 of 11 strains after 14 to 44 passages, and GW 773546 gave resistant clones of 10 of 11 strains after 14 to 45 passages. Telithromycin gave resistant clones of 7 of 11 strains after 18 to 45 passages. Mutations mostly in the L22 and L4 ribosomal proteins and 23S rRNA were detected in resistant strains selected with all compounds, with alterations in the L22 protein predominating. Single-step resistance selection studies at the MIC yielded spontaneous resistant mutants at frequencies of 1.5 x 10(-9) to 2.2 x 10(-6) with GW 773546, 1.5 x 10(-9) to 6.0 x 10(-4) with GW 708408, and 7.1 x 10(-9) to 3.8 x 10(-4) with telithromycin, whereas the frequencies were 1.3 x 10(-9) to 6.0 x 10(-4) with erythromycin and azithromycin and 2.0 x 10(-9) to 2.0 x 10(-3) with clarithromycin. Alterations in the L22 protein (which were predominant) and the L4 protein were present in mutants selected by the single-step selection process. The postantibiotic effects of GW 773546, GW 708408, and telithromycin for seven H. influenzae strains were 6.6 h (range, 5.2 to 8.8 h), 4.7 h (range, 2.6 to 6.9 h), and 6.4 h (range, 3.8 to 9.7 h), respectively. The results of in vitro studies obtained with both novel macrolides were similar to those obtained with telithromycin and better than those obtained with older macrolides.

Activities of Two Novel Macrolides, GW 773546 and GW 708408, Compared with Those of Telithromycin, Erythromycin, Azithromycin, and Clarithromycin against Haemophilus influenzae

PubMed Central

Kosowska, Klaudia; Credito, Kim; Pankuch, Glenn A.; Hoellman, Dianne; Lin, Gengrong; Clark, Catherine; Dewasse, Bonifacio; McGhee, Pamela; Jacobs, Michael R.; Appelbaum, Peter C.

2004-01-01

The MIC at which 50% of strains are inhibited (MIC50) and the MIC90 of GW 773546, a novel macrolide, were 1.0 and 2.0 μg/ml, respectively, for 223 β-lactamase-positive, β-lactamase-negative, and β-lactamase-negative ampicillin-resistant Haemophilus influenzae strains. The MIC50s and MIC90s of GW 708408, a second novel macrolide, and telithromycin, an established ketolide, were 2.0 and 4.0 μg/ml, respectively, while the MIC50 and MIC90 of azithromycin were 1.0 and 2.0 μg/ml, respectively. The MIC50 and MIC90 of erythromycin were 4.0 and 8.0 μg/ml, respectively; and those of clarithromycin were 4.0 and 16.0 μg/ml, respectively. All compounds except telithromycin were bactericidal (99.9% killing) against nine strains at two times the MIC after 24 h. Telithromycin was bactericidal against eight of the nine strains. In addition, both novel macrolides and telithromycin at two times the MIC showed 99% killing of all nine strains after 12 h and 90% killing of all strains after 6 h. After 24 h, all drugs were bactericidal against four to seven strains when they were tested at the MIC. Ten of 11 strains tested by multistep selection analysis yielded resistant clones after 14 to 43 passages with erythromycin. Azithromycin gave resistant clones of all strains after 20 to 50 passages, and clarithromycin gave resistant clones of 9 of 11 strains after 14 to 41 passages. By comparison, GW 708408 gave resistant clones of 9 of 11 strains after 14 to 44 passages, and GW 773546 gave resistant clones of 10 of 11 strains after 14 to 45 passages. Telithromycin gave resistant clones of 7 of 11 strains after 18 to 45 passages. Mutations mostly in the L22 and L4 ribosomal proteins and 23S rRNA were detected in resistant strains selected with all compounds, with alterations in the L22 protein predominating. Single-step resistance selection studies at the MIC yielded spontaneous resistant mutants at frequencies of 1.5 × 10−9 to 2.2 × 10−6 with GW 773546, 1.5 × 10−9 to 6.0 × 10−4 with GW 708408, and 7.1 × 10−9 to 3.8 × 10−4 with telithromycin, whereas the frequencies were 1.3 × 10−9 to 6.0 × 10−4 with erythromycin and azithromycin and 2.0 × 10−9 to 2.0 × 10−3 with clarithromycin. Alterations in the L22 protein (which were predominant) and the L4 protein were present in mutants selected by the single-step selection process. The postantibiotic effects of GW 773546, GW 708408, and telithromycin for seven H. influenzae strains were 6.6 h (range, 5.2 to 8.8 h), 4.7 h (range, 2.6 to 6.9 h), and 6.4 h (range, 3.8 to 9.7 h), respectively. The results of in vitro studies obtained with both novel macrolides were similar to those obtained with telithromycin and better than those obtained with older macrolides. PMID:15504829

Activity of OPT-80, a Novel Macrocycle, Compared with Those of Eight Other Agents against Selected Anaerobic Species

PubMed Central

Credito, Kim L.; Appelbaum, Peter C.

2004-01-01

Agar dilution MIC was used to compare activities of OPT-80, linezolid, vancomycin, teicoplanin, quinupristin/dalfopristin, amoxicillin/clavulanate, imipenem, clindamycin, and metronidazole against 350 gram-positive and -negative anaerobes. OPT-80 was active against gram-positive strains only, especially Clostridium spp. (85 strains tested, including 21 strains of C. difficile), with MICs ranging between ≤0.016 and 0.25 μg/ml. PMID:15504874

Experimental Aerodynamic Facilities of the Aerodynamics Research and Concepts Assistance Section

DTIC Science & Technology

1983-02-01

experimental data desired. Internal strain gage balances covering a range of sizes and load capabilities are available for static force and moment tests...tunnel. Both sting and side wall model mounts are available which can be adapted to a variety of internal strain gage balance systems for force and...model components or liquids in the test section. A selection of internal and external strain gage balances and associated mounting fixtures are

Optimization of Nickel Nanocomposite for Large Strain Sensing Applications

DTIC Science & Technology

2011-01-01

piezoresistive response of the material. As part of this study the effect of the addition of a second conductive filler particle of a distinct length scale...corresponding increase in the overall conductivity of the composite. The composite conductivity is increased about an order of magnitude for each additional ...strain at which the mean resis - Fig. 10. Schematic representation of how εerr was calculated from the range of the volume resistivity for a given strain

Investigation of a ceramic matrix composite under strain controlled fatigue condition

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

Gudaitis, J.J.; Mall, S.

The fatigue behavior along with damage mechanisms and failure modes of a fiber reinforced ceramic matrix composite with a cross-ply lay-up was investigated under strain controlled mode. Two fatigue conditions involving tension-tension and tension-compression cycling were employed. The strain range versus fatigue life curves for both fatigue conditions were in agreement with each other. However, damage mechanisms and failure modes were different for both cases.

Microstructure and crystallographic preferred orientation of polycrystalline microgarnet aggregates developed during progressive creep, recovery, and grain boundary sliding

USGS Publications Warehouse

Massey, M.A.; Prior, D.J.; Moecher, D.P.

2011-01-01

Optical microscopy, electron probe microanalysis, and electron backscatter diffraction methods have been used to examine a broad range of garnet microstructures within a high strain zone that marks the western margin of a major transpression zone in the southern New England Appalachians. Garnet accommodated variable states of finite strain, expressed as low strain porphyroclasts (Type 1), high strain polycrystalline aggregates (Type 2), and transitional morphologies (Type 3) that range between these end members. Type 1 behaved as rigid porphyroclasts and is characterized by four concentric Ca growth zones. Type 2 help define foliation and lineation, are characterized by three Ca zones, and possess a consistent bulk crystallographic preferred orientation of (100) symmetrical to the tectonic fabric. Type 3 show variable degrees of porphyroclast associated with aggregate, where porphyroclasts display complex compositional zoning that corresponds to lattice distortion, low-angle boundaries, and subgrains, and aggregate CPO mimics porphyroclast orientation. All aggregates accommodated a significant proportion of greenschist facies deformation through grain boundary sliding, grain rotation and impingement, and pressure solution, which lead to a cohesive behavior and overall strain hardening of the aggregates. The characteristic CPO could not have been developed in this manner, and was the result of an older phase of partitioned amphibolite facies dislocation creep, recovery including chemical segregation, and recrystallization of porphyroclasts. This study demonstrates the significance of strain accommodation within garnet and its affect on composition under a range of PT conditions, and emphasizes the importance of utilizing EBSD methods with studies that rely upon a sound understanding of garnet. ?? 2010 Elsevier Ltd.

Thermococcus sulfurophilus sp. nov., a New Hyperthermophilic, Sulfur-Reducing Archaeon Isolated from Deep-Sea Hydrothermal Vent

NASA Technical Reports Server (NTRS)

Pikuta, Elena V.; Hoover, Richard B.; Whitman, William B.; Marsic, Damien; Garriott, Owen; Six, N. Frank (Technical Monitor)

2002-01-01

A new hyperthermophilic, anaerobic, sulfur-reducing, organo-heterotrophic archaeon, strain OGL-20P, was isolated from "black smoker" chimney material at the Rainbow hydrothermal vent site in the Atlantic Ocean (36.2 N; 33.9 W). The cells of strain OGL-20P have irregular coccoid shape and are motile with a single flagellum. Growth occurs within pH range of 5.5-8.2 (optimal at pH 7.0-7.2), salinity range of 1-5% NaCl (optimal concentration 3% NaCl wt/vol), and temperature range of +55 C to +94 C (optimal growth at +83 C to +85 C). Strain OGL-20P is resistant to freezing (at -20 C). New isolate is strictly anaerobic with sulfur-type of respiration. A limited number of compounds are utilized as electron donors, including peptone, becto-tryptone, casamino-acids, and yeast extract but does not grow with separate amino acids. Sulfur and Iron can be used as electron acceptors; but not sulfate, sulfite, thiosulfate or nitrate. Strain OGL-20P is resistant to chloramphenicol, kanamycin, and gentamycin. Growth of str. OGL20P is inhibited by tetracyclin but not by Na2MoO4. The G+C content of DNA is 57.2 mol%. The 16S ribosomal RNA sequence analysis allows one to classify strain OGL-20P as a representative of a now species of Thermococcus genus. The name Thermococcus sulfurophilus op. nov., was suggested for the new isolate, type strain OGL-20P (sup T) (= ATCC BAA_394 (sup T) = DSM...(supT)).

Reclassification of Paenibacillus riograndensis as a Genomovar of Paenibacillus sonchi: Genome-Based Metrics Improve Bacterial Taxonomic Classification

PubMed Central

Sant’Anna, Fernando H.; Ambrosini, Adriana; de Souza, Rocheli; de Carvalho Fernandes, Gabriela; Bach, Evelise; Balsanelli, Eduardo; Baura, Valter; Brito, Luciana F.; Wendisch, Volker F.; de Oliveira Pedrosa, Fábio; de Souza, Emanuel M.; Passaglia, Luciane M. P.

2017-01-01

Species from the genus Paenibacillus are widely studied due to their biotechnological relevance. Dozens of novel species descriptions of this genus were published in the last couple of years, but few utilized genomic data as classification criteria. Here, we demonstrate the importance of using genome-based metrics and phylogenetic analyses to identify and classify Paenibacillus strains. For this purpose, Paenibacillus riograndensis SBR5T, Paenibacillus sonchi X19-5T, and their close relatives were compared through phenotypic, genotypic, and genomic approaches. With respect to P. sonchi X19-5T, P. riograndensis SBR5T, Paenibacillus sp. CAR114, and Paenibacillus sp. CAS34 presented ANI (average nucleotide identity) values ranging from 95.61 to 96.32%, gANI (whole-genome average nucleotide identity) values ranging from 96.78 to 97.31%, and dDDH (digital DNA–DNA hybridization) values ranging from 68.2 to 73.2%. Phylogenetic analyses of 16S rRNA, gyrB, recA, recN, and rpoB genes and concatenated proteins supported the monophyletic origin of these Paenibacillus strains. Therefore, we propose to assign Paenibacillus sp. CAR114 and Paenibacillus sp. CAS34 to P. sonchi species, and reclassify P. riograndensis SBR5T as a later heterotypic synonym of P. sonchi (type strain X19-5T), with the creation of three novel genomovars, P. sonchi genomovar Sonchi (type strain X19-5T), P. sonchi genomovar Riograndensis (type strain SBR5T), P. sonchi genomovar Oryzarum (type strain CAS34T = DSM 102041T; = BR10511T). PMID:29046663

Direct comparison of cardiac magnetic resonance feature tracking and 2D/3D echocardiography speckle tracking for evaluation of global left ventricular strain.

PubMed

Obokata, Masaru; Nagata, Yasufumi; Wu, Victor Chien-Chia; Kado, Yuichiro; Kurabayashi, Masahiko; Otsuji, Yutaka; Takeuchi, Masaaki

2016-05-01

Cardiac magnetic resonance (CMR) feature tracking (FT) with steady-state free precession (SSFP) has advantages over traditional myocardial tagging to analyse left ventricular (LV) strain. However, direct comparisons of CMRFT and 2D/3D echocardiography speckle tracking (2/3DEST) for measurement of LV strain are limited. The aim of this study was to investigate the feasibility and reliability of CMRFT and 2D/3DEST for measurement of global LV strain. We enrolled 106 patients who agreed to undergo both CMR and 2D/3DE on the same day. SSFP images at multiple short-axis and three apical views were acquired. 2DE images from three levels of short-axis, three apical views, and 3D full-volume datasets were also acquired. Strain data were expressed as absolute values. Feasibility was highest in CMRFT, followed by 2DEST and 3DEST. Analysis time was shortest in 3DEST, followed by CMRFT and 2DEST. There was good global longitudinal strain (GLS) correlation between CMRFT and 2D/3DEST (r = 0.83 and 0.87, respectively) with the limit of agreement (LOA) ranged from ±3.6 to ±4.9%. Excellent global circumferential strain (GCS) correlation between CMRFT and 2D/3DEST was observed (r = 0.90 and 0.88) with LOA of ±6.8-8.5%. Global radial strain showed fair correlations (r = 0.69 and 0.82, respectively) with LOA ranged from ±12.4 to ±16.3%. CMRFT GCS showed least observer variability with highest intra-class correlation. Although not interchangeable, the high GLS and GCS correlation between CMRFT and 2D/3DEST makes CMRFT a useful modality for quantification of global LV strain in patients, especially those with suboptimal echo image quality. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2015. For permissions please email: journals.permissions@oup.com.

Through-Layer Buckle Wavelength-Gradient Design for the Coupling of High Sensitivity and Stretchability in a Single Strain Sensor.

PubMed

He, Tengyu; Lin, Chucheng; Shi, Liangjing; Wang, Ranran; Sun, Jing

2018-03-21

Recent years have witnessed a breathtaking development of wearable strain sensors. Coupling high sensitivity and stretchability in a strain sensor is greatly desired by emerging wearable applications but remains a big challenge. To tackle this issue, a through-layer buckle wavelength-gradient design is proposed and a facile and universal fabrication strategy is demonstrated to introduce such a gradient into the sensing film with multilayered sensing units. Following this strategy, strain sensors are fabricated using graphene woven fabrics (GWFs) as sensing units, which exhibit highly tunable electromechanical performances. Specifically, the sensor with 10-layer GWFs has a gauge factor (GF) of 2996 at a maximum strain of 242.74% and an average GF of 327. It also exhibits an extremely low minimum detection limit of 0.02% strain, a fast signal response of less than 90 ms, and a high cyclic durability through more than 10 000 cycling test. Such excellent performances qualify it in accurately monitoring full-range human activities, ranging from subtle stimuli (e.g., pulse, respiration, and voice recognition) to vigorous motions (finger bending, walking, jogging, and jumping). The combination of experimental observations and modeling study shows that the predesigned through-layer buckle wavelength gradient leads to a layer-by-layer crack propagation process, which accounts for the underlying working mechanism. Modeling study shows a great potential for further improvement of sensing performances by adjusting fabrication parameters such as layers of sensing units ( n) and step pre-strain (ε sp ). For one thing, when ε sp is fixed, the maximum sensing strain could be adjusted from >240% ( n = 10) to >450% ( n = 15) and >1200% ( n = 20). For the other, when n is fixed, the maximum sensing strain could be adjusted from >240% (ε sp = 13.2%) to >400% (ε sp = 18%) and >800% (ε sp = 25%).

A quantitative survey of gravity receptor function in mutant mouse strains.

PubMed

Jones, Sherri M; Johnson, Kenneth R; Yu, Heping; Erway, Lawrence C; Alagramam, Kumar N; Pollak, Natasha; Jones, Timothy A

2005-12-01

The purpose of this research was to identify vestibular deficits in mice using linear vestibular evoked potentials (VsEPs). VsEP thresholds, peak latencies, and peak amplitudes from 24 strains with known genetic mutations and 6 inbred background strains were analyzed and descriptive statistics generated for each strain. Response parameters from mutant homozygotes were compared with heterozygote and/or background controls and all strain averages were contrasted to normative ranges. Homozygotes of the following recessive mutations had absent VsEPs at the ages tested: Espn(je), Atp2b2dfw-2J, Spnb4qv-lnd2J, Spnb4qv-3J, Myo7ash1, Tmie(sr), Myo6sv, jc, Pcdh15av-J, Pcdh15av-2J, Pcdh15av-3J, Cdh23v-2J, Sans(js), hr, Kcne1pkr and Pou3f4del. These results suggest profound gravity receptor deficits for these homozygotes, which is consistent with the structural deficits that have been documented for many of these strains. Homozygotes of Catna2cdf, Grid2ho4J, Wnt1sw, qk, and Mbpshi strains and heterozygotes of Grid2lc had measurable VsEPs but one or more response parameters differed from the respective control group (heterozygote or background strain) or were outside normal ranges. For example, qk and Mbpshi homozygotes showed significantly prolonged latencies consistent with the abnormal myelin that has been described for these strains. Prolonged latencies may suggest deficits in neural conduction; elevated thresholds suggest reduced sensitivity, and reduced amplitudes may be suggestive for reduced neural synchrony. One mutation, Otx1jv, had all VsEP response parameters within normal limits--an expected finding because the abnormality in Otxljv is presumably restricted to the lateral semicircular canal. Interestingly, some heterozygote groups also showed abnormalities in one or more VsEP response parameters, suggesting that vestibular dysfunction, although less severe, may be present in some heterozygous animals.

Halosiccatus urmianus gen. nov., sp. nov., a haloarchaeon from a salt lake.

PubMed

Mehrshad, Maliheh; Amoozegar, Mohammad Ali; Makhdoumi, Ali; Fazeli, Seyed Abolhassan Shahzadeh; Farahani, Homa; Asadi, Basaer; Schumann, Peter; Ventosa, Antonio

2016-02-01

A novel, orange-pigmented, halophilic archaeon, strain DC8 T , was isolated from Urmia salt lake in north-west Iran. The cells of strain DC8 T were non-motile and pleomorphic, from small rods to triangular or disc shaped. The novel strain needed at least 2.5 M NaCl and 0.02 M MgCl 2 for growth. Optimal growth was achieved at 4.0 M NaCl and 0.1 M MgCl 2 . The optimum pH and temperature for growth were pH 7.5 and 45 °C, respectively, and it was able to grow over a pH range of 7.0 to 8.5 and a temperature range of 25 to 55 °C. Analysis of the 16S rRNA gene sequence showed that strain DC8 T was a member of the family Halobacteriaceae ; however, its similarity was as low as 90.1 %, 89.3 % and 89.1 % to the most closely related haloarchaeal taxa, including type species of members of the genera Halosimplex , Halobaculum and Halomicrobium , respectively. The G+C content of its DNA was 68.1 mol%. Polar lipid analyses revealed that strain DC8 T contained phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate and phosphatidic acid. One unknown phospholipid, two major glycolipids and one minor glycolipid were also detected. The only quinone present was MK-8 (II-H 2 ). The physiological, biochemical and phylogenetic differences between strain DC8 T and other extremely halophilic archaeal genera with validly published names supported that this strain represents a novel species of a new genus within the family Halobacteriaceae , for which the name Halosiccatus urmianus gen. nov., sp. nov. is proposed. The type strain is strain DC8 T ( = IBRC-M 10911 T  = CECT 8793 T ).

Plastic behavior of polycrystalline copper at optical scales of deformation

NASA Astrophysics Data System (ADS)

Domber, Jeanette Leah

Microplasticity is permanent deformation that occurs below the proportional limit of a material. For precision deployable optical spacecraft, it is unknown how microplasticity will affect the performance of the precision structure. An examination of the rolling of thin film optical reflectors indicates a strong dependence of the post-deployed shape on the strain hardening exponent of the material. However, confirmation of the valid extension of the constitutive model used to predict the deployed shape to microscopic strain regimes is necessary. The primary objective of this thesis is threefold: determine the relationship between stress and strain at nano to microstrain levels for representative materials; determine if the relationship between microscopic and macroscopic plastic behavior can be accurately characterized by the Ramberg-Osgood strain hardening constitutive model with a single set of material parameters; and determine if dislocation motion is the root cause of microplastic behavior at room temperature. The test apparatus, with a dynamic force range of 40,000 to 1, measures strains from 0.01 to 1000 parts per million (ppm) of cylindrical amorphous quartz and cold-worked and annealed tempered polycrystalline copper specimen. Elastic behavior in all three materials was consistent with typical values. However, plastic responses were larger than expected. Stresses on the order of 10 to 10,000 kPa (1.45 to 1450 psi) produced permanent strain in all three types of materials ranging from 0.01 to 1 ppm, some of which was attributable to a systematic error in the measurement. Extrapolating macroplastic behavior to lower stress and strain values underestimates the amount of microplasticity observed in the material. Therefore, material property characterization is required at all strain levels that are of concern for a particular application. The similarity in the levels of measured permanent strain for a given stress level between the as-drawn and annealed copper is consistent with the observed dislocation substructure of the two materials, which is also similar. This uniformity indicates that microplastic behavior at room temperature is driven by dislocation glide.

Streptomyces colonosanans sp. nov., A Novel Actinobacterium Isolated from Malaysia Mangrove Soil Exhibiting Antioxidative Activity and Cytotoxic Potential against Human Colon Cancer Cell Lines.

PubMed

Law, Jodi Woan-Fei; Ser, Hooi-Leng; Duangjai, Acharaporn; Saokaew, Surasak; Bukhari, Sarah I; Khan, Tahir M; Ab Mutalib, Nurul-Syakima; Chan, Kok-Gan; Goh, Bey-Hing; Lee, Learn-Han

2017-01-01

Streptomyces colonosanans MUSC 93J T , a novel strain isolated from mangrove forest soil located at Sarawak, Malaysia. The bacterium was noted to be Gram-positive and to form light yellow aerial and vivid yellow substrate mycelium on ISP 2 agar. The polyphasic approach was used to determine the taxonomy of strain MUSC 93J T and the strain showed a range of phylogenetic and chemotaxonomic properties consistent with those of the members of the genus Streptomyces . Phylogenetic and 16S rRNA gene sequence analysis indicated that closely related strains include Streptomyces malachitofuscus NBRC 13059 T (99.2% sequence similarity), Streptomyces misionensis NBRC 13063 T (99.1%), and Streptomyces phaeoluteichromatogenes NRRL 5799 T (99.1%). The DNA-DNA relatedness values between MUSC 93J T and closely related type strains ranged from 14.4 ± 0.1 to 46.2 ± 0.4%. The comparison of BOX-PCR fingerprints indicated MUSC 93J T exhibits a unique DNA profile. The genome of MUSC 93J T consists of 7,015,076 bp. The DNA G + C content was determined to be 69.90 mol%. The extract of strain MUSC 93J T was demonstrated to exhibit potent antioxidant activity via ABTS, metal chelating, and SOD assays. This extract also exhibited anticancer activity against human colon cancer cell lines without significant cytotoxic effect against human normal colon cells. Furthermore, the chemical analysis of the extract further emphasizes the strain is producing chemo-preventive related metabolites. Based on this polyphasic study of MUSC 93J T , it is concluded that this strain represents a novel species, for which the name Streptomyces colonosanans sp. nov. is proposed. The type strain is MUSC 93J T (= DSM 102042 T = MCCC 1K02298 T ).

Phonon dispersion evolution in uniaxially strained aluminum crystal

NASA Astrophysics Data System (ADS)

Parthasarathy, Ranganathan; Misra, Anil; Aryal, Sitaram; Ouyang, Lizhi

2018-04-01

The influence of loading upon the phonon dispersion of crystalline materials could be highly nonlinear with certain particular trends that depend upon the loading path. In this paper, we have calculated the influence of [100] uniaxial strain on the phonon dispersion and group velocities in fcc aluminum using second moments of position obtained from molecular dynamics (MD) simulation at 300 K. In contrast to nonlinear monotonic variation of both longitudinal and transverse phonon frequencies along the Δ , Λ and Σ lines of the first Brillouin zone under tension, transverse phonon branches along the Λ line show inflection at specific wavevectors when the compressive strain exceeds 5%. Further, the longitudinal group velocities along the high-symmetry Δ line vary non-monotonically with strain, reaching a minimum at 5% compressive strain. Throughout the strain range studied, the equilibrium positions of atoms displace in an affine manner preserving certain static structural symmetry. We attribute the anomalies in the phonon dispersion to the non-affine evolution of second moments of atomic position, and the associated plateauing of force constants under the applied strain path.

A closer look at prion strains: characterization and important implications.

PubMed

Solforosi, Laura; Milani, Michela; Mancini, Nicasio; Clementi, Massimo; Burioni, Roberto

2013-01-01

Prions are infectious proteins that are responsible for transmissible spongiform encephalopathies (TSEs) and consist primarily of scrapie prion protein (PrP (Sc) ), a pathogenic isoform of the host-encoded cellular prion protein (PrP (C) ). The absence of nucleic acids as essential components of the infectious prions is the most striking feature associated to these diseases. Additionally, different prion strains have been isolated from animal diseases despite the lack of DNA or RNA molecules. Mounting evidence suggests that prion-strain-specific features segregate with different PrP (Sc) conformational and aggregation states. Strains are of practical relevance in prion diseases as they can drastically differ in many aspects, such as incubation period, PrP (Sc) biochemical profile (e.g., electrophoretic mobility and glycoform ratio) and distribution of brain lesions. Importantly, such different features are maintained after inoculation of a prion strain into genetically identical hosts and are relatively stable across serial passages. This review focuses on the characterization of prion strains and on the wide range of important implications that the study of prion strains involves.

Constitutive behavior and processing maps of low-expansion GH909 superalloy

NASA Astrophysics Data System (ADS)

Yao, Zhi-hao; Wu, Shao-cong; Dong, Jian-xin; Yu, Qiu-ying; Zhang, Mai-cang; Han, Guang-wei

2017-04-01

The hot deformation behavior of GH909 superalloy was studied systematically using isothermal hot compression tests in a temperature range of 960 to 1040°C and at strain rates from 0.02 to 10 s-1 with a height reduction as large as 70%. The relations considering flow stress, temperature, and strain rate were evaluated via power-law, hyperbolic sine, and exponential constitutive equations under different strain conditions. An exponential equation was found to be the most appropriate for process modeling. The processing maps for the superalloy were constructed for strains of 0.2, 0.4, 0.6, and 0.8 on the basis of the dynamic material model, and a total processing map that includes all the investigated strains was proposed. Metallurgical instabilities in the instability domain mainly located at higher strain rates manifested as adiabatic shear bands and cracking. The stability domain occurred at 960-1040°C and at strain rates less than 0.2 s-1; these conditions are recommended for optimum hot working of GH909 superalloy.

Rational selection of Leuconostoc strains for mixed starters based on the physiological biodiversity found in raw milk fermentations.

PubMed

Sánchez, Jorge Ignacio; Martínez, Beatriz; Rodríguez, Ana

2005-12-15

The technological abilities of eleven wild Leuconostoc strains isolated from artisanal Afuega'l Pitu cheese, a homemade acid-coagulated cheese from raw milk from Asturias (northern Spain), were studied in order to test their potential application as components of dairy starters. Metabolic activity, production of flavour compounds, resistance to NaCl, acid, nisin and freezing, as well as genetic biodiversity were investigated. Marked differences among all tested strains reflected the existing biodiversity in naturally fermented products. After evaluation of their performance, strains IPLA567 and IPLA979 revealed the best properties to be used use in mixed dairy starter cultures. These two strains were able to ferment lactose and galactose and produced larger amounts of lactic acid than the others. Moreover, they showed high tolerance levels to NaCl, acid and nisin, although their resistance to freezing was slightly lower than the other strains. This study evidences the fact that natural environments can be considered as a proper source of new strains, which may help the dairy industry to widen their fermented products range.

Physiologically Based Pharmacokinetic (PBPK) Modeling of ...

EPA Pesticide Factsheets

Background: Quantitative estimation of toxicokinetic variability in the human population is a persistent challenge in risk assessment of environmental chemicals. Traditionally, inter-individual differences in the population are accounted for by default assumptions or, in rare cases, are based on human toxicokinetic data.Objectives: To evaluate the utility of genetically diverse mouse strains for estimating toxicokinetic population variability for risk assessment, using trichloroethylene (TCE) metabolism as a case study. Methods: We used data on oxidative and glutathione conjugation metabolism of TCE in 16 inbred and one hybrid mouse strains to calibrate and extend existing physiologically-based pharmacokinetic (PBPK) models. We added one-compartment models for glutathione metabolites and a two-compartment model for dichloroacetic acid (DCA). A Bayesian population analysis of inter-strain variability was used to quantify variability in TCE metabolism. Results: Concentration-time profiles for TCE metabolism to oxidative and glutathione conjugation metabolites varied across strains. Median predictions for the metabolic flux through oxidation was less variable (5-fold range) than that through glutathione conjugation (10-fold range). For oxidative metabolites, median predictions of trichloroacetic acid production was less variable (2-fold range) than DCA production (5-fold range), although uncertainty bounds for DCA exceeded the predicted variability. Conclusions:

Hot deformation characteristics of as-cast high-Cr ultra-super-critical rotor steel with columnar grains

NASA Astrophysics Data System (ADS)

Ding, Zong-ye; Hu, Qiao-dan; Zeng, Long; Li, Jian-guo

2016-11-01

Isothermal hot compression tests of as-cast high-Cr ultra-super-critical (USC) rotor steel with columnar grains perpendicular to the compression direction were carried out in the temperature range from 950 to 1250°C at strain rates ranging from 0.001 to 1 s-1. The softening mechanism was dynamic recovery (DRV) at 950°C and the strain rate of 1 s-1, whereas it was dynamic recrystallization (DRX) under the other conditions. A modified constitutive equation based on the Arrhenius model with strain compensation reasonably predicted the flow stress under various deformation conditions, and the activation energy was calculated to be 643.92 kJ•mol-1. The critical stresses of dynamic recrystallization under different conditions were determined from the work-hardening rate ( θ)-flow stress ( σ) and -∂ θ/∂ σ-σ curves. The optimum processing parameters via analysis of the processing map and the softening mechanism were determined to be a deformation temperature range from 1100 to 1200°C and a strain-rate range from 0.001 to 0.08 s-1, with a power dissipation efficiency η greater than 31%.

Erwinia amylovora CRISPR Elements Provide New Tools for Evaluating Strain Diversity and for Microbial Source Tracking

PubMed Central

McGhee, Gayle C.; Sundin, George W.

2012-01-01

Clustered regularly interspaced short palindromic repeats (CRISPRs) comprise a family of short DNA repeat sequences that are separated by non repetitive spacer sequences and, in combination with a suite of Cas proteins, are thought to function as an adaptive immune system against invading DNA. The number of CRISPR arrays in a bacterial chromosome is variable, and the content of each array can differ in both repeat number and in the presence or absence of specific spacers. We utilized a comparative sequence analysis of CRISPR arrays of the plant pathogen Erwinia amylovora to uncover previously unknown genetic diversity in this species. A total of 85 E. amylovora strains varying in geographic isolation (North America, Europe, New Zealand, and the Middle East), host range, plasmid content, and streptomycin sensitivity/resistance were evaluated for CRISPR array number and spacer variability. From these strains, 588 unique spacers were identified in the three CRISPR arrays present in E. amylovora, and these arrays could be categorized into 20, 17, and 2 patterns types, respectively. Analysis of the relatedness of spacer content differentiated most apple and pear strains isolated in the eastern U.S. from western U.S. strains. In addition, we identified North American strains that shared CRISPR genotypes with strains isolated on other continents. E. amylovora strains from Rubus and Indian hawthorn contained mostly unique spacers compared to apple and pear strains, while strains from loquat shared 79% of spacers with apple and pear strains. Approximately 23% of the spacers matched known sequences, with 16% targeting plasmids and 5% targeting bacteriophage. The plasmid pEU30, isolated in E. amylovora strains from the western U.S., was targeted by 55 spacers. Lastly, we used spacer patterns and content to determine that streptomycin-resistant strains of E. amylovora from Michigan were low in diversity and matched corresponding streptomycin-sensitive strains from the background population. PMID:22860008

Erwinia amylovora CRISPR elements provide new tools for evaluating strain diversity and for microbial source tracking.

PubMed

McGhee, Gayle C; Sundin, George W

2012-01-01

Clustered regularly interspaced short palindromic repeats (CRISPRs) comprise a family of short DNA repeat sequences that are separated by non repetitive spacer sequences and, in combination with a suite of Cas proteins, are thought to function as an adaptive immune system against invading DNA. The number of CRISPR arrays in a bacterial chromosome is variable, and the content of each array can differ in both repeat number and in the presence or absence of specific spacers. We utilized a comparative sequence analysis of CRISPR arrays of the plant pathogen Erwinia amylovora to uncover previously unknown genetic diversity in this species. A total of 85 E. amylovora strains varying in geographic isolation (North America, Europe, New Zealand, and the Middle East), host range, plasmid content, and streptomycin sensitivity/resistance were evaluated for CRISPR array number and spacer variability. From these strains, 588 unique spacers were identified in the three CRISPR arrays present in E. amylovora, and these arrays could be categorized into 20, 17, and 2 patterns types, respectively. Analysis of the relatedness of spacer content differentiated most apple and pear strains isolated in the eastern U.S. from western U.S. strains. In addition, we identified North American strains that shared CRISPR genotypes with strains isolated on other continents. E. amylovora strains from Rubus and Indian hawthorn contained mostly unique spacers compared to apple and pear strains, while strains from loquat shared 79% of spacers with apple and pear strains. Approximately 23% of the spacers matched known sequences, with 16% targeting plasmids and 5% targeting bacteriophage. The plasmid pEU30, isolated in E. amylovora strains from the western U.S., was targeted by 55 spacers. Lastly, we used spacer patterns and content to determine that streptomycin-resistant strains of E. amylovora from Michigan were low in diversity and matched corresponding streptomycin-sensitive strains from the background population.

Broiler genetic strain and sex effects on meat characteristics.

PubMed

López, K P; Schilling, M W; Corzo, A

2011-05-01

A randomized complete block design within a factorial arrangement of treatments was used to evaluate the effect of strain and sex on carcass characteristics, meat quality, and sensory acceptability. Two broiler strains were reared: a commercially available strain (strain A) and a strain currently in the test phase (strain B) that has been genetically selected to maximize breast yield. Broilers were harvested in a pilot scale processing plant using commercial prototype equipment at 42 d of age. Carcasses were deboned at 4 h postmortem. The left half of each breast was evaluated for pH, color, cooking loss, shear force, and proximate analysis. The right side of each breast was used for consumer acceptability testing. Thigh meat was evaluated for proximate composition. No interactions were observed throughout the study. Male broilers had a higher (P < 0.05) live BW, carcass weight, and breast weight and lower (P < 0.05) dressing percentage and breast meat yield when compared with females. Broilers from strain B presented a higher (P < 0.05) breast yield and dressing percentage than those broilers corresponding to the commercially available broiler strain. At 24 h postmortem, female broilers presented a lower ultimate pH and higher Commission internationale de l'éclairage yellowness values (ventral side of the pectoralis major) when compared with male broilers. On average, no differences existed (P > 0.05) among treatments with respect to pH decline, cooking loss, shear values, and proximate composition. In addition, no differences (P > 0.05) existed among breast meat from the different strains with respect to consumer acceptability of appearance, texture, flavor, and overall acceptability, but breast meat from strain B was slightly preferred (P < 0.05) over that of strain A with respect to aroma. However, breast meat from both strains received scores in the range of "like slightly to like moderately." Overall data suggest that all treatments yielded high quality breast and thigh meat and strain cross did not present variability in terms of consumer acceptability.

The Contribution of Experimental in vivo Models to Understanding the Mechanisms of Adaptation to Mechanical Loading in Bone

PubMed Central

Meakin, Lee B.; Price, Joanna S.; Lanyon, Lance E.

2014-01-01

Changing loading regimens by natural means such as exercise, with or without interference such as osteotomy, has provided useful information on the structure:function relationship in bone tissue. However, the greatest precision in defining those aspects of the overall strain environment that influence modeling and remodeling behavior has been achieved by relating quantified changes in bone architecture to quantified changes in bones’ strain environment produced by direct, controlled artificial bone loading. Jiri Hert introduced the technique of artificial loading of bones in vivo with external devices in the 1960s using an electromechanical device to load rabbit tibiae through transfixing stainless steel pins. Quantifying natural bone strains during locomotion by attaching electrical resistance strain gages to bone surfaces was introduced by Lanyon, also in the 1960s. These studies in a variety of bones in a number of species demonstrated remarkable uniformity in the peak strains and maximum strain rates experienced. Experiments combining strain gage instrumentation with artificial loading in sheep, pigs, roosters, turkeys, rats, and mice has yielded significant insight into the control of strain-related adaptive (re)modeling. This diversity of approach has been largely superseded by non-invasive transcutaneous loading in rats and mice, which is now the model of choice for many studies. Together such studies have demonstrated that over the physiological strain range, bone’s mechanically adaptive processes are responsive to dynamic but not static strains; the size and nature of the adaptive response controlling bone mass is linearly related to the peak loads encountered; the strain-related response is preferentially sensitive to high strain rates and unresponsive to static ones; is most responsive to unusual strain distributions; is maximized by remarkably few strain cycles, and that these are most effective when interrupted by short periods of rest between them. PMID:25324829

Comparison and Combination of Strain and Shear Wave Elastography of Breast Masses for Differentiation of Benign and Malignant Lesions by Quantitative Assessment: Preliminary Study.

PubMed

Seo, Mirinae; Ahn, Hye Shin; Park, Sung Hee; Lee, Jong Beum; Choi, Byung Ihn; Sohn, Yu-Mee; Shin, So Youn

2018-01-01

To compare the diagnostic performance of strain and shear wave elastography of breast masses for quantitative assessment in differentiating benign and malignant lesions and to evaluate the diagnostic accuracy of combined strain and shear wave elastography. Between January and February 2016, 37 women with 45 breast masses underwent both strain and shear wave ultrasound (US) elastographic examinations. The American College of Radiology Breast Imaging Reporting and Data System (BI-RADS) final assessment on B-mode US imaging was assessed. We calculated strain ratios for strain elastography and the mean elasticity value and elasticity ratio of the lesion to fat for shear wave elastography. Diagnostic performances were compared by using the area under the receiver operating characteristic curve (AUC). The 37 women had a mean age of 47.4 years (range, 20-79 years). Of the 45 lesions, 20 were malignant, and 25 were benign. The AUCs for elasticity values on strain and shear wave elastography showed no significant differences (strain ratio, 0.929; mean elasticity, 0.898; and elasticity ratio, 0.868; P > .05). After selectively downgrading BI-RADS category 4a lesions based on strain and shear wave elastographic cutoffs, the AUCs for the combined sets of B-mode US and elastography were improved (B-mode + strain, 0.940; B-mode + shear wave; 0.964; and B-mode, 0.724; P < .001). Combined strain and shear wave elastography showed significantly higher diagnostic accuracy than each individual elastographic modality (P = .031). These preliminary results showed that strain and shear wave elastography had similar diagnostic performance. The addition of strain and shear wave elastography to B-mode US improved diagnostic performance. The combination of strain and shear wave elastography results in a higher diagnostic yield than each individual elastographic modality. © 2017 by the American Institute of Ultrasound in Medicine.

Reduction of the Mg acceptor activation energy in GaN, AlN, Al0.83Ga0.17N and MgGa δ-doping (AlN)5/(GaN)1: the strain effect

NASA Astrophysics Data System (ADS)

Jiang, Xin-He; Shi, Jun-Jie; Zhang, Min; Zhong, Hong-Xia; Huang, Pu; Ding, Yi-Min; He, Ying-Ping; Cao, Xiong

2015-12-01

To resolve the p-type doping problem of Al-rich AlGaN alloys, we investigate the influence of biaxial and hydrostatic strains on the activation energy, formation energy and band gap of Mg-doped GaN, AlN, Al0.83Ga0.17N disorder alloy and (AlN)5/(GaN)1 superlattice based on first-principles calculations by combining the standard DFT and hybrid functional. We find that the Mg acceptor activation energy {{E}\\text{A}} , the formation energy {{E}\\text{f}} and the band gap {{E}\\text{g}} decrease with increasing the strain ɛ. The hydrostatic strain has a more remarkable impact on {{E}\\text{g}} and {{E}\\text{A}} than the biaxial strain. Both {{E}\\text{A}} and {{E}\\text{g}} have a linear dependence on the hydrostatic strain. For the biaxial strain, {{E}\\text{g}} shows a parabolic dependence on ɛ if \\varepsilon ≤slant 0 while it becomes linear if \\varepsilon ≥slant 0 . In GaN and (AlN)5/(GaN)1, {{E}\\text{A}} parabolically depends on the biaxial compressive strain and linearly depends on the biaxial tensible strain. However, the dependence is approximately linear over the whole biaxial strain range in AlN and Al0.83Ga0.17N. The Mg acceptor activation energy in (AlN)5/(GaN)1 can be reduced from 0.26 eV without strain to 0.16 (0.22) eV with the hydrostatic (biaxial) tensible strain 3%.

Detection of wide genetic diversity and several novel strains among non-avium nontuberculous mycobacteria isolated from farmed and wild animals in Hungary.

PubMed

Rónai, Z; Eszterbauer, E; Csivincsik, Á; Guti, C F; Dencső, L; Jánosi, S; Dán, Á

2016-07-01

Besides Mycobacterium avium numerous nontuberculous Mycobacterium (NTM) species exist, which pose constant health risk to both humans and animals. The aim of our study was to identify non-avium NTM isolates from veterinary origin in Hungary, and to detect the occurrence of rifampicin resistance among them. Two hundred and twenty-five strains isolated between 2006 and 2013 from domestic and wild animals and veterinary important samples were identified on the basis of partial DNA sequences of different structural or coding genes, besides commercial kits and multiplex PCR. From 14 different sources, 28 NTM strains and 8 hitherto unidentified strain types were detected. Mycobacterium nonchromogenicum was the most frequently occurring strain (25·78%). Besides, new hosts and mycobacteria-related pathological symptoms were detected. Noticeable rifampicin resistance (42·76%) was found among 159 strains from six different host species. Furthermore, we described the problematics of strain-misidentifications using commercial kits. Our study identified the most common non-avium NTM strains in Hungary, and provided account of their occurrence, host range, and pathogenicity. The detected high rifampicin resistance among the strains isolated mainly from fallow and red deer clearly shows that more attention should be paid to the examination of wild animals especially to those ones which may have contact or shared territory with farmed animals. In domestic animal husbandry the maintenance of tuberculosis free status is of primary importance. As immunological cross-reactions due to NTM hamper the diagnosis of bovine tuberculosis, the precise identification of NTM strains would be essential in the veterinary diagnostics, especially for potentially zoonotic strains. This is the first study investigating the strain diversity of non-avium NTM in Hungary. © 2016 The Society for Applied Microbiology.

New insight into the epidemiology of rabbit hemorrhagic disease viruses in Portugal: retrospective study reveals the circulation of genogroup 5 (G5) in Azores and discloses the circulation of G1 and G6 strains in mainland until 2008.

PubMed

Duarte, Margarida Dias; Henriques, Ana Margarida; Barros, Sílvia; Luís, Tiago; Fagulha, Teresa; Ramos, Fernanda; Fevereiro, Miguel

2014-10-01

The genetic relationships between 10 rabbit hemorrhagic disease strains collected in Portugal between 2006 and 2013, originated in the mainland and Azorean islands, were investigated based on the vp60 gene variability. A genetic diversity ranging from 2% to 13% was determined among the 10-vp60 complete sequences revealing a significant level of genetic heterogeneity between same strains. Phylogenetic Bayesian analysis showed that the Portuguese RHDV strains fell within different genogroups, namely G1, G5 and G6. Interestingly, all strains obtained from Azores, where RHDV was first detected in 1988, belong to G5 genogroup. G5 strains, that were not identified in the continent so far, seem to be the dominant group in these Atlantic islands. G1-related strains belonging to the Iberian group 3 (n=3) and G6 (RHDVa) strains (n=2) were identified among the samples originated in mainland which were collected between 2006 and 2008. Although the presence of G1 and G6 in Portugal had been shown before, our data refines the time of circulation of these strains until at least 2008. In summary, this study revises the epidemiological information of RHDV in Portugal since it reports for the first time the presence of G5 strains in Azores and demonstrates the circulation of G1 and G6 strains in mainland Portugal until the late 2000s. Copyright © 2014 Elsevier B.V. All rights reserved.

A Retrospective Study on Genetic Heterogeneity within Treponema Strains: Subpopulations Are Genetically Distinct in a Limited Number of Positions.

PubMed

Čejková, Darina; Strouhal, Michal; Norris, Steven J; Weinstock, George M; Šmajs, David

2015-01-01

Pathogenic uncultivable treponemes comprise human and animal pathogens including agents of syphilis, yaws, bejel, pinta, and venereal spirochetosis in rabbits and hares. A set of 10 treponemal genome sequences including those of 4 Treponema pallidum ssp. pallidum (TPA) strains (Nichols, DAL-1, Mexico A, SS14), 4 T. p. ssp. pertenue (TPE) strains (CDC-2, Gauthier, Samoa D, Fribourg-Blanc), 1 T. p. ssp. endemicum (TEN) strain (Bosnia A) and one strain (Cuniculi A) of Treponema paraluisleporidarum ecovar Cuniculus (TPLC) were examined with respect to the presence of nucleotide intrastrain heterogeneous sites. The number of identified intrastrain heterogeneous sites in individual genomes ranged between 0 and 7. Altogether, 23 intrastrain heterogeneous sites (in 17 genes) were found in 5 out of 10 investigated treponemal genomes including TPA strains Nichols (n = 5), DAL-1 (n = 4), and SS14 (n = 7), TPE strain Samoa D (n = 1), and TEN strain Bosnia A (n = 5). Although only one heterogeneous site was identified among 4 tested TPE strains, 16 such sites were identified among 4 TPA strains. Heterogeneous sites were mostly strain-specific and were identified in four tpr genes (tprC, GI, I, K), in genes involved in bacterial motility and chemotaxis (fliI, cheC-fliY), in genes involved in cell structure (murC), translation (prfA), general and DNA metabolism (putative SAM dependent methyltransferase, topA), and in seven hypothetical genes. Heterogeneous sites likely represent both the selection of adaptive changes during infection of the host as well as an ongoing diversifying evolutionary process.

Finite-strain analysis of Metavolcano-sedimentary rocks at Gabel El Mayet area, Central Eastern Desert, Egypt

NASA Astrophysics Data System (ADS)

Kassem, Osama M. K.; Abd El Rahim, Said H.

2010-09-01

Finite strain was estimated in the metavolcano-sedimentary rocks, which surround by serpentinites of Gabel El Mayet area. Finite strain shows a relationship to nappe contacts between the metavolcano-sedimentary rocks and serpentinite and sheds light on the nature of the subhorizontal foliation typical for the Gable Mayet shear zone. We used the Rf/ ϕ and Fry methods on feldspar porphyroclasts and mafic grains from 10 metasedimentary and six metavolcanic samples in Gabel El Mayet region. Our finite-strain data show that the metavolcano-sedimentary rocks were moderately deformed and axial ratios in the XZ section range from 1.9 to 3.9. The long axes of the finite-strain ellipsoids trend W/WNW in the north and W/WSW in the south of the Gabel El Mayet shear zone. Furthermore, the short axes are subvertical to a subhorizontal foliation. The strain magnitudes increase towards the tectonic contacts between the metavolcano-sedimentary rocks and serpentinite. The data indicate oblate strain symmetry in the metavolcano-sedimentary rocks. Hence, our strain data also indicate flattening strain. We assume that the metasedimentary and metavolcanics rocks have similar deformation behaviour. The fact that finite strain accumulated during the metamorphism indicates that the nappe contacts formed during the accumulation of finite strain and thus during thrusting. We conclude that the nappe contacts formed during progressive thrusting under brittle to semi-brittle deformation conditions by simple shear and involved a component of vertical shortening, which caused the subhorizontal foliation in the Gabel El Mayet shear zone.

Dynamic Strain Aging of Nickel-Base Alloys 800H and 690

NASA Astrophysics Data System (ADS)

Moss, Tyler E.; Was, Gary S.

2012-10-01

The objective of the current investigation is to characterize the dynamic strain aging (DSA) behavior in alloys 800H and 690. Constant extension rate tests were conducted at strain rates in the range of 10-4 s-1 to 10-7 s-1and temperatures between 295 K and 673 K (22 °C and 400 °C), in an argon atmosphere. Maps for the occurrence of serrated flow as a function of strain rate and temperature were built for both alloys. The enthalpy of serrated flow appearance of alloy 800H was found to be 1.07 ± 0.30 eV.

Non-linear properties of metallic cellular materials with a negative Poisson's ratio

NASA Technical Reports Server (NTRS)

Choi, J. B.; Lakes, R. S.

1992-01-01

Negative Poisson's ratio copper foam was prepared and characterized experimentally. The transformation into re-entrant foam was accomplished by applying sequential permanent compressions above the yield point to achieve a triaxial compression. The Poisson's ratio of the re-entrant foam depended on strain and attained a relative minimum at strains near zero. Poisson's ratio as small as -0.8 was achieved. The strain dependence of properties occurred over a narrower range of strain than in the polymer foams studied earlier. Annealing of the foam resulted in a slightly greater magnitude of negative Poisson's ratio and greater toughness at the expense of a decrease in the Young's modulus.

Cellular fatty acid composition of Erysipelothrix rhusiopathiae and Erysipelothrix tonsillarum.

PubMed

Takahashi, T; Tamura, Y; Endoh, Y S; Hara, N

1994-04-01

The cellular fatty acid compositions in 6 strains of Erysipelothrix rhusiopathiae and 7 strains of Erysipelothrix tonsillarum were determined by gas chromatography. Fatty acids, ranging from C10 to C18, were detected in the test strains. The fatty acid profile was characterized by very high percentages of 18:1 (cis-9) (cis-9-octadecenoic acid; 72.4 to 82.1%) and 16:1 (hexadecenoic acid; 8.7 to 13.7%). The profiles of the E. rhusiopathiae and E. tonsillarum strains resembled each other, indicating that discrimination between E. rhusiopathiae and E. tonsillarum from qualitative or quantitative fatty acid differences is difficult.

Wide distribution range of rhizobial symbionts associated with pantropical sea-dispersed legumes.

PubMed

Bamba, Masaru; Nakata, Sayuri; Aoki, Seishiro; Takayama, Koji; Núñez-Farfán, Juan; Ito, Motomi; Miya, Masaki; Kajita, Tadashi

2016-12-01

To understand the geographic distributions of rhizobia that associated with widely distributed wild legumes, 66 nodules obtained from 41 individuals including three sea-dispersed legumes (Vigna marina, Vigna luteola, and Canavalia rosea) distributed across the tropical and subtropical coastal regions of the world were studied. Partial sequences of 16S rRNA and nodC genes extracted from the nodules showed that only Bradyrhizobium and Sinorhizobium were associated with the pantropical legumes, and some of the symbiont strains were widely distributed over the Pacific. Horizontal gene transfer of nodulation genes were observed within the Bradyrhizobium and Sinorhizobium lineages. BLAST searches in GenBank also identified records of these strains from various legumes across the world, including crop species. However, one of the rhizobial strains was not found in GenBank, which implies the strain may have adapted to the littoral environment. Our results suggested that some rhizobia, which associate with the widespread sea-dispersed legume, distribute across a broad geographic range. By establishing symbiotic relationships with widely distributed rhizobia, the pantropical legumes may also be able to extend their range much further than other legume species.

Genetic diversity among silkworm (Bombyx mori L., Lep., Bombycidae) germplasms revealed by microsatellites.

PubMed

Li, Muwang; Shen, Li; Xu, Anying; Miao, Xuexia; Hou, Chengxiang; Sun, Pingjiang; Zhang, Yuehua; Huang, Yongping

2005-10-01

To determine genetic relationships among strains of silkworm, Bombyx mori L., 31 strains with different origins, number of generations per year, number of molts per generation, and morphological characters were studied using simple sequence repeat (SSR) markers. Twenty-six primer pairs flanking microsatellite sequences in the silkworm genome were assayed. All were polymorphic and unambiguously separated silkworm strains from each other. A total of 188 alleles were detected with a mean value of 7.2 alleles/locus (range 2-17). The average heterozygosity value for each SSR locus ranged from 0 to 0.60, and the highest one was 0.96 (Fl0516 in 4013). The mean polymorphism index content (PIC) was 0.66 (range 0.12-0.89). Unweighted pair group method with arithmetic means (UPGMA) cluster analysis of Nei's genetic distance grouped silkworm strains based on their origin. Seven major ecotypic silkworm groups were analyzed. Principal components analysis (PCA) for SSR data support their UPGMA clustering. The results indicated that SSR markers are an efficient tool for fingerprinting cultivars and conducting genetic-diversity studies in the silkworm.

Undrained behavior and shear strength of clean sand containing low-plastic fines

NASA Astrophysics Data System (ADS)

To-Anh Phan, Vu; Hsiao, Darn-Horng

2018-04-01

This study presents experimental tests to understand the undrained behavior of sand containing various fines contents. The specimens were prepared by the wet tamping method. The consolidated undrained triaxial shear tests were carried out by sands mixed with amounts of fines in ranging from 0 to 60%. The results showed that the deviator stress quickly reaches the peak value with an axial strain in a range of 0.5 to 2%, and then, the value drops significantly with further increases in the axial strain, the pore water pressure of all the sand-fines mixtures rapidly increases as the axial strain reaches a value in a range from 1 to 2% and then slowly increases and reaches a stable state when strain is greater than 8%. Peak deviator stress gradually decreases with an increasing fines content from 0 to 40%, thereafter, the peak deviator significantly increases with further increases in the fines content up to 60%, irrespective of confining pressure values using in these tests. Finally, the effective internal friction angles are remarkably greater than the total friction angles for various sand-fines mixtures.

Hot Deformation Behavior and Intrinsic Workability of Carbon Nanotube-Aluminum Reinforced ZA27 Composites

NASA Astrophysics Data System (ADS)

Liu, Yang; Geng, Cong; Zhu, Yunke; Peng, Jinfeng; Xu, Junrui

2017-04-01

Using a controlled thermal simulator system, hybrid carbon nanotube-aluminum reinforced ZA27 composites were subjected to hot compression testing in the temperature range of 473-523 K with strain rates of 0.01-10 s-1. Based on experimental results, a developed-flow stress model was established using a constitutive equation coupled with strain to describe strain softening arising from dynamic recrystallization. The intrinsic workability was further investigated by constructing three-dimensional (3D) processing maps aided by optical observations of microstructures. The 3D processing maps were constructed based on a dynamic model of materials to delineate variations in the efficiency of power dissipation and flow instability domains. The instability domains exhibited adiabatic shear band and flow localization, which need to be prevented during hot processing. The recommended domain is predicated to be within the temperature range 550-590 K and strain rate range 0.01-0.35 s-1. In this state, the main softening mechanism is dynamic recrystallization. The results from processing maps agree well with the microstructure observations.

Voltage-impulse-induced dual-range nonvolatile magnetization modulation in metglas/PZT heterostructure

NASA Astrophysics Data System (ADS)

Tang, Xiaoli; Su, Hua; Zhang, Huaiwu; Sun, Nian X.

2016-11-01

Dual-range, nonvolatile magnetization modulation induced by voltage impulses was investigated in the metglas/lead zirconate titanate (PZT) heterostructure at room temperature. The heterostructure was obtained by bonding a square metglas ribbon on the top electrode of the PZT substrate, which contained defect dipoles resulting from acceptor doping. The PZT substrate achieved two strain hysteretic loops with the application of specific voltage impulse excitation modes. Through strain-mediated magnetoelectric coupling between the metglas ribbon and the PZT substrate, two strain hysteretic loops led to a dual-range nonvolatile magnetization modulation in the heterostructure. Reversible and stable voltage-impulse-induced nonvolatile modulation in the ferromagnetic resonance field and magnetic hysteresis characteristics were also realized. This method provides a promising approach in reducing energy consumption in magnetization modulation and other related devices.

A comparative study of P450 gene expression in field and laboratory Musca domestica L. strains.

PubMed

Højland, Dorte H; Vagn Jensen, Karl-Martin; Kristensen, Michael

2014-08-01

The housefly is a global pest that has developed resistance to most insecticides applied for its control. Resistance has been associated with cytochrome P450 monooxygenases (P450s). The authors compare the expression of six genes possibly associated with insecticide resistance in three unselected strains: a multiresistant strain (791a), a neonicotinoid-resistant strain (766b) and a new field strain (845b). CYP4G2 was highly expressed throughout the range of strains and proved to be the one of the most interesting expression profiles of all P450s analysed. CYP6G4 was expressed up to 11-fold higher in 766b than in WHO-SRS. Significant differences between expression of P450 genes between F1 flies from 845b and established laboratory strains were shown. In general, P450 gene expression in 845b was 2-14-fold higher than in the reference strain (P < 0.0101) and 2-23-fold higher than in the multiresistant strain (P < 0.0110). The newly collected field strain 845b had significantly higher constitutive gene expression than both WHO-SRS and 791a. High constitutive expression of CYP4G2 in houseflies indicates a possible role of this gene in metabolic resistance. There is a strong indication that CYP6G4 is a major insecticide resistance gene involved in neonicotinoid resistance. © 2013 Society of Chemical Industry.

Isolation and in vitro selection of actinomycetes strains as potential probiotics for aquaculture

PubMed Central

Bernal, Milagro García; Campa-Córdova, Ángel Isidro; Saucedo, Pedro Enrique; González, Marlen Casanova; Marrero, Ricardo Medina; Mazón-Suástegui, José Manuel

2015-01-01

Aim: This study was designed to describe a series of in vitro tests that may aid the discovery of probiotic strains from actinomycetes. Materials and Methods: Actinomycetes were isolated from marine sediments using four different isolation media, followed by antimicrobial activity and toxicity assessment by the agar diffusion method and the hemolysis of human blood cells, respectively. Extracellular enzymatic production was monitored by the hydrolysis of proteins, lipids and carbohydrates. Tolerance to different pH values and salt concentrations was also determined, followed by hydrophobicity analysis and genetic identification of the most promising strains. Results: Five out of 31 isolated strains showed antimicrobial activity against three Vibrio species. Three non-hemolytic strains (N7, RL8 and V4) among these active isolates yielded positive results in hydrophobicity tests and exhibited good growth at salt concentrations ranging from 0% to 10%, except strain RL8, which required a salt concentration >0.6%. Although these strains did not grow at pH<3, they showed different enzymatic activities. Phylogenetic analysis revealed that strains N7 and V4 have more than 99% identity with several Streptomyces species, whereas the closest matches to strain RL8 are Streptomyces panacagri and Streptomyces flocculus, with 98% and 98.2% similarity, respectively. Conclusion: Three actinomycetes strains showing probiotic-like properties were discovered using several in vitro tests that can be easily implemented in different institutions around the world. PMID:27047067

Practical on-site measurement of heat strain with the use of a perceptual strain index.

PubMed

Chan, Albert P C; Yang, Y

2016-02-01

There have been increased interests in research on quantifying heat strain of construction workers and formulating corresponding guidelines for working in hot weather. The aim of this study was to validate a subjective measurement tool, the perceptual strain index (PeSI), for measuring heat strain in real-work settings. A total of sixteen construction workers were invited to participate in the field surveys. Empiric-based human monitoring was carried out with simultaneous micrometeorological (wet-bulb globe temperature, WBGT), physiological (heart rate, HR), and perceptual (perceived exertion, RPE; thermal sensation, TS) measurements throughout the test. The relative heart rate (RHR), the physiological strain index (PSIHR), and the PeSI were then calculated accordingly. The PeSI exhibited moderate correlations with WBGT and RHR (r = 0.42 and 0.40, respectively), which indicated the PeSI was sensitive to the variants of WBGT and RHR. The results of regression analysis indicated that the PeSI changed in the same general manner as the PSIHR, with a relatively large determination coefficient (R(2) = 0.67). The established perceptual strain zone illustrated that the PeSI ranging from 7 to 8 would be the exposure limit of construction workers in hot weather. The PeSI is a simple, robust, reliable, and user-friendly tool for heat strain assessment in occupational settings. The perceptual strain zone will provide practical guidelines for on-site heat strain monitoring for construction workers.