Sb-induced strain fluctuations in a strained layer superlattice of InAs/InAsSb

DOE PAGES

Kim, Honggyu; Meng, Yifei; Klem, John F.; ...

2018-04-28

Here, we show that Sb substitution for As in a MBE grown InAs/InAsSb strained layer superlattice (SLS) is accompanied by significant strain fluctuations. The SLS was observed using scanning transmission electron microscopy along the [100] zone axis where the cation and anion atomic columns are separately resolved. Strain analysis based on atomic column positions reveals asymmetrical transitions in the strain profile across the SLS interfaces. The averaged strain profile is quantitatively fitted to the segregation model, which yields a distribution of Sb in agreement with our scanning tunneling microscopy result. The subtraction of the calculated strain reveals an increase inmore » strain fluctuations with the Sb concentration, as well as isolated regions with large strain deviations extending spatially over ~1 nm, which suggest the presence of point defects.« less

Sb-induced strain fluctuations in a strained layer superlattice of InAs/InAsSb

NASA Astrophysics Data System (ADS)

Kim, Honggyu; Meng, Yifei; Klem, John F.; Hawkins, Samuel D.; Kim, Jin K.; Zuo, Jian-Min

2018-04-01

We show that Sb substitution for As in a MBE grown InAs/InAsSb strained layer superlattice (SLS) is accompanied by significant strain fluctuations. The SLS was observed using scanning transmission electron microscopy along the [100] zone axis where the cation and anion atomic columns are separately resolved. Strain analysis based on atomic column positions reveals asymmetrical transitions in the strain profile across the SLS interfaces. The averaged strain profile is quantitatively fitted to the segregation model, which yields a distribution of Sb in agreement with the scanning tunneling microscopy result. The subtraction of the calculated strain reveals an increase in strain fluctuations with the Sb concentration, as well as isolated regions with large strain deviations extending spatially over ˜1 nm, which suggest the presence of point defects.

Sb-induced strain fluctuations in a strained layer superlattice of InAs/InAsSb

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

Kim, Honggyu; Meng, Yifei; Klem, John F.

Here, we show that Sb substitution for As in a MBE grown InAs/InAsSb strained layer superlattice (SLS) is accompanied by significant strain fluctuations. The SLS was observed using scanning transmission electron microscopy along the [100] zone axis where the cation and anion atomic columns are separately resolved. Strain analysis based on atomic column positions reveals asymmetrical transitions in the strain profile across the SLS interfaces. The averaged strain profile is quantitatively fitted to the segregation model, which yields a distribution of Sb in agreement with our scanning tunneling microscopy result. The subtraction of the calculated strain reveals an increase inmore » strain fluctuations with the Sb concentration, as well as isolated regions with large strain deviations extending spatially over ~1 nm, which suggest the presence of point defects.« less

Hollow Cylinder Tests on Boom Clay: Modelling of Strain Localization in the Anisotropic Excavation Damaged Zone

NASA Astrophysics Data System (ADS)

François, Bertrand; Labiouse, Vincent; Dizier, Arnaud; Marinelli, Ferdinando; Charlier, Robert; Collin, Frédéric

2014-01-01

Boom Clay is extensively studied as a potential candidate to host underground nuclear waste disposal in Belgium. To guarantee the safety of such a disposal, the mechanical behaviour of the clay during gallery excavation must be properly predicted. In that purpose, a hollow cylinder experiment on Boom Clay has been designed to reproduce, in a small-scale test, the Excavation Damaged Zone (EDZ) as experienced during the excavation of a disposal gallery in the underground. In this article, the focus is made on the hydro-mechanical constitutive interpretation of the displacement (experimentally obtained by medium resolution X-ray tomography scanning). The coupled hydro-mechanical response of Boom Clay in this experiment is addressed through finite element computations with a constitutive model including strain hardening/softening, elastic and plastic cross-anisotropy and a regularization method for the modelling of strain localization processes. The obtained results evidence the directional dependency of the mechanical response of the clay. The softening behaviour induces transient strain localization processes, addressed through a hydro-mechanical second grade model. The shape of the obtained damaged zone is clearly affected by the anisotropy of the materials, evidencing an eye-shaped EDZ. The modelling results agree with experiments not only qualitatively (in terms of the shape of the induced damaged zone), but also quantitatively (for the obtained displacement in three particular radial directions).

Strain mapping in TEM using precession electron diffraction

DOEpatents

Taheri, Mitra Lenore; Leff, Asher Calvin

2017-02-14

A sample material is scanned with a transmission electron microscope (TEM) over multiple steps having a predetermined size at a predetermined angle. Each scan at a predetermined step and angle is compared to a template, wherein the template is generated from parameters of the material and the scanning. The data is then analyzed using local mis-orientation mapping and/or Nye's tensor analysis to provide information about local strain states.

Morphology and formation mechanism in precipitation of calcite induced by Curvibacter lanceolatus strain HJ-1

NASA Astrophysics Data System (ADS)

Zhang, Chonghong; Li, Fuchun; Lv, Jiejie

2017-11-01

Precipitation of calcium carbobate induced by microbial activities is common occurrence in controlled solution, but the formation mechanism and morphology in precipitation of calcite in solution systems is unclear, and the role of microbes is disputed. Here, culture experiment was performed for 50 days using the Curvibacter lanceolatus strain HJ-1 in a M2 culture medium, and the phase composition and morphology of the precipitates were characterized by the X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and scanning electron microscopy (SEM) techniques. We show that the precipitation processes in our experiment lead to unusual morphologies of crystals corresponding to different growth stages, and the morphologies of the precipitated crystal aggregates ranging from the main rod-, cross-, star-, cauliflower-like morphologies to spherulitic structure. The complex and unusual morphologies of the precipitated calcite by strain HJ-1 may provide a reference point for better understanding the biomineralization mechanism of calcite, moreover, morphological transition of minerals revealed that the multi-ply crystals-aggregation mechanism for calcite growth in crystallisation media.

Suppressive Potential of Paenibacillus Strains Isolated from the Tomato Phyllosphere against Fusarium Crown and Root Rot of Tomato

PubMed Central

Sato, Ikuo; Yoshida, Shigenobu; Iwamoto, Yutaka; Aino, Masataka; Hyakumachi, Mitsuro; Shimizu, Masafumi; Takahashi, Hideki; Ando, Sugihiro; Tsushima, Seiya

2014-01-01

The suppressive potentials of Bacillus and Paenibacillus strains isolated from the tomato phyllosphere were investigated to obtain new biocontrol candidates against Fusarium crown and root rot of tomato. The suppressive activities of 20 bacterial strains belonging to these genera were examined using seedlings and potted tomato plants, and two Paenibacillus strains (12HD2 and 42NP7) were selected as biocontrol candidates against the disease. These two strains suppressed the disease in the field experiment. Scanning electron microscopy revealed that the treated bacterial cells colonized the root surface, and when the roots of the seedlings were treated with strain 42NP7 cells, the cell population was maintained on the roots for at least for 4 weeks. Although the bacterial strains had no direct antifungal activity against the causal pathogen in vitro, an increase was observed in the antifungal activities of acetone extracts from tomato roots treated with the cells of both bacterial strains. Furthermore, RT-PCR analysis verified that the expression of defense-related genes was induced in both the roots and leaves of seedlings treated with the bacterial cells. Thus, the root-colonized cells of the two Paenibacillus strains were considered to induce resistance in tomato plants, which resulted in the suppression of the disease. PMID:24920171

Temperature Driven Topological Switch in 1T'-MoTe2 and Strain Induced Nematicity in NaFeAs

NASA Astrophysics Data System (ADS)

Berger, Ayelet Denise Notis

Quasiparticle interference (QPI) is a powerful technique within Scanning Tunneling Microscopy (STM) that is used to probe the electronic bandstructure of materials. This thesis presents two examples using QPI to measure the bandstructure in materials with exotic electronic states that can be tuned via outside parameters (temperature and strain). In Part I of the thesis, we discuss the temperature dependence of Fermi Arcs in 1T'-MoTe 2, and then in Part II, the strain dependent nematic state in NaFeAs. The recent discovery of Weyl semimetals has introduced a new family of materials with topologically protected electronic properties and potential applications due to their anomalous transport effects. Even more useful is a Weyl semimetal that can be turned "on" and "off," switching between a topological and trivial state. One possible material is MoTe2, which undergoes a phase transition at 240K. This thesis consists of experiments using Scanning Tunneling Microscopy (STM) and Spectroscopy (STS) at different temperatures to visualize changes in the electronic bandstructure of MoTe2 across the topological phase transition. We show that a signature of topologically protected Fermi Arcs is present at low temperatures but disappears at room temperature, in the trivial phase. We include an in-depth discussion of how to account for thermal effects when comparing these two types of measurements. In Part II, we discuss strain induced nematicity in NaFeAs, an iron pnictide. Nematic fluctuations and spin correlations play an important role in the phase diagram of the iron pnictides, a family of unconventional superconductors. Illuminating the mechanism behind this symmetry breaking is key to understanding the superconducting state. Previous work has shown that nematicity in the iron pnictides responds strongly to applied strain [1, 2]. In this thesis, I present results from a new experimental technique, elasto-scanning tunneling microscopy (E-STM), which combines in situ strain and atomic resolution STM/STS. For the first time, we are able to observe the effects of strain on nematicity at the local level. We perform E-STM measurements in both the spin density wave phase and the tetragonal phase of NaFeAs and measure a distinct response in each. We successfully use strain to manipulate domain boundaries in the spin density wave state and we find the intensity of nematic fluctuations is coupled to strain in NaFeAs in the tetragonal phase.

Measurement of Strain and Stress Distributions in Structural Materials by Electron Moiré Method

NASA Astrophysics Data System (ADS)

Kishimoto, Satoshi; Xing, Yougming; Tanaka, Yoshihisa; Kagawa, Yutaka

A method for measuring the strain and stress distributions in structural materials has been introduced. Fine model grids were fabricated by electron beam lithography, and an electron beam scan by a scanning electron microscope (SEM) was used as the master grid. Exposure of the electron beam scan onto the model grid in an SEM produced the electron beam moiré fringes of bright and dark parts caused by the different amounts of the secondary electrons per a primary electron. For demonstration, the micro-creep deformation of pure copper was observed. The creep strain distribution and the grain boundary sliding were analyzed. The residual strain and stress at the interface between a fiber and a matrix of a fiber reinforced plastic (FRP) were measured using the pushing-out test and this electron moiré method. Also, a non-uniform deformation around the boundary of 3-point bended laminated steel was observed and the strain distribution analyzed.

The Microstructural Evolution and Mechanical Properties of Zr-Based Metallic Glass under Different Strain Rate Compressions

PubMed Central

Chen, Tao-Hsing; Tsai, Chih-Kai

2015-01-01

In this study, the high strain rate deformation behavior and the microstructure evolution of Zr-Cu-Al-Ni metallic glasses under various strain rates were investigated. The influence of strain and strain rate on the mechanical properties and fracture behavior, as well as microstructural properties was also investigated. Before mechanical testing, the structure and thermal stability of the Zr-Cu-Al-Ni metallic glasses were studied with X-ray diffraction (XRD) and differential scanning calorimeter. The mechanical property experiments and microstructural observations of Zr-Cu-Al-Ni metallic glasses under different strain rates ranging from 10−3 to 5.1 × 103 s−1 and at temperatures of 25 °C were investigated using compressive split-Hopkinson bar (SHPB) and an MTS tester. An in situ transmission electron microscope (TEM) nanoindenter was used to carry out compression tests and investigate the deformation behavior arising at nanopillars of the Zr-based metallic glass. The formation and interaction of shear band during the plastic deformation were investigated. Moreover, it was clearly apparent that the mechanical strength and ductility could be enhanced by impeding the penetration of shear bands with reinforced particles. PMID:28788034

Stability and dynamic of strain mediated adatom superlattices on Cu<111 >

NASA Astrophysics Data System (ADS)

Kappus, Wolfgang

2013-03-01

Substrate strain mediated adatom equilibrium density distributions have been calculated for Cu<111 > surfaces using two complementing methods. A hexagonal adatom superlattice in a coverage range up to 0.045 ML is derived for repulsive short range interactions. For zero short range interactions a hexagonal superstructure of adatom clusters is derived in a coverage range about 0.08 ML. Conditions for the stability of the superlattice against formation of dimers or clusters and degradation are analyzed using simple neighborhood models. Such models are also used to investigate the dynamic of adatoms within their superlattice neighborhood. Collective modes of adatom diffusion are proposed from the analogy with bulk lattice dynamics and methods for measurement are suggested. The recently put forward explanation of surface state mediated interactions for superstructures found in scanning tunneling microscopy experiments is put in question and strain mediated interactions are proposed as an alternative.

Si(111) strained layers on Ge(111): Evidence for c (2 ×4 ) domains

NASA Astrophysics Data System (ADS)

Zhachuk, R.; Coutinho, J.; Dolbak, A.; Cherepanov, V.; Voigtländer, B.

2017-08-01

The tensile-strained Si (111 ) layers grown on top of Ge (111 ) substrates are studied by combining scanning tunneling microscopy, low-energy electron diffraction, and first-principles calculations. It is shown that the layers exhibit c (2 ×4 ) domains, which are separated by domain walls along <1 ¯10 > directions. A model structure for the c (2 ×4 ) domains is proposed, which shows low formation energy and good agreement with the experimental data. The results of our calculations suggest that Ge atoms are likely to replace Si atoms with dangling bonds on the surface (rest-atoms and adatoms), thus significantly lowering the surface energy and inducing the formation of domain walls. The experiments and calculations demonstrate that when surface strain changes from compressive to tensile, the (111) reconstruction converts from dimer-adatom-stacking fault-based to adatom-based structures.

Raise and collapse of pseudo Landau levels in graphene

NASA Astrophysics Data System (ADS)

Castro, Eduardo V.; Cazalilla, Miguel A.; Vozmediano, María A. H.

2017-12-01

Lattice deformations couple to the low-energy electronic excitations of graphene as vector fields similar to the electromagnetic potential. The observation of strain-induced pseudo Landau levels with scanning tunnel microscopy experiments has been one of the most exciting events in the history of graphene. Nevertheless, the experimental observation presents some ambiguities. Similar strain patterns show different images that are sometimes difficult to interpret. In this Rapid Communication, we show that, for some strain configurations, the deformation potential acts as a parallel electric field able to destabilize the Landau level structure via a mechanism identical to that occurring for real electromagnetic fields. This effect also alters the estimations of the value of the pseudomagnetic field, which can be significantly bigger. The mechanism applies equally if the electric field has an external origin, which opens the door to an electric control of giant pseudomagnetic fields in graphene.

Plant growth-promoting rhizobacteria strain Bacillus amyloliquefaciens NJN-6-enriched bio-organic fertilizer suppressed Fusarium wilt and promoted the growth of banana plants.

PubMed

Yuan, Jun; Ruan, Yunze; Wang, Beibei; Zhang, Jian; Waseem, Raza; Huang, Qiwei; Shen, Qirong

2013-04-24

Bacillus amyloliquefaciens strain NJN-6 is an important plant growth-promoting rhizobacteria (PGPR) which can produce secondary metabolites antagonistic to several soil-borne pathogens. In this study, the ability of a bio-organic fertilizer (BIO) containing NJN-6 strain to promote the growth and suppress Fusarium wilt of banana plants was evaluated in a pot experiment. The results showed that the application of BIO significantly decreased the incidence of Fusarium wilt and promoted the growth of banana plants compared to that for the organic fertilizer (OF). To determine the beneficial mechanism of the strain, the colonization of NJN-6 strain on banana roots was evaluated using scanning electron microscopy (SEM). The plant growth-promoting hormones indole-3-acetic acid (IAA) and gibberellin A3 (GA3), along with antifungal lipopeptides iturin A, were detected when the NJN-6 strain was incubated in both Landy medium with additional l-tryptophan and in root exudates of banana plants. In addition, some antifungal volatile organic compounds and iturin A were also detected in BIO. In summary, strain NJN-6 could colonize the roots of banana plants after the application of BIO and produced active compounds which were beneficial for the growth of banana plants.

Verification of finite element analysis of fixed partial denture with in vitro electronic strain measurement.

PubMed

Wang, Gaoqi; Zhang, Song; Bian, Cuirong; Kong, Hui

2016-01-01

The purpose of the study was to verify the finite element analysis model of three-unite fixed partial denture with in vitro electronic strain analysis and analyze clinical situation with the verified model. First, strain gauges were attached to the critical areas of a three-unit fixed partial denture. Strain values were measured under 300 N load perpendicular to the occlusal plane. Secondly, a three-dimensional finite element model in accordance with the electronic strain analysis experiment was constructed from the scanning data. And the strain values obtained by finite element analysis and in vitro measurements were compared. Finally, the clinical destruction of the fixed partial denture was evaluated with the verified finite element analysis model. There was a mutual agreement and consistency between the finite element analysis results and experimental data. The finite element analysis revealed that failure will occur in the veneer layer on buccal surface of the connector under occlusal force of 570 N. The results indicate that the electronic strain analysis is an appropriate and cost saving method to verify the finite element model. The veneer layer on buccal surface of the connector is the weakest area in the fixed partial denture. Copyright © 2015 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

Compaction bands in shale revealed through digital volume correlation of time-resolved X-ray tomography scans

NASA Astrophysics Data System (ADS)

McBeck, J.; Kobchenko, M.; Hall, S.; Tudisco, E.; Cordonnier, B.; Renard, F.

2017-12-01

Previous studies have identified compaction bands primarily within sandstones, and in fewer instances, within other porous rocks and sediments. Using Digital Volume Correlation (DVC) of X-ray microtomography scans, we find evidence of localized zones of high axial contraction that form tabular structures sub-perpendicular to maximum compression, σ1, in Green River shale. To capture in situ strain localization throughout loading, two shale cores were deformed in the HADES triaxial deformation apparatus installed on the X-ray microtomography beamline ID19 at the European Synchrotron Radiation Facility. In these experiments, we increase σ1 in increments of two MPa, with constant confining pressure (20 MPa), until the sample fails in macroscopic shear. After each stress step, a 3D image of the sample inside the rig is acquired at a voxel resolution of 6.5 μm. The evolution of lower density regions within 3D reconstructions of linear attenuation coefficients reveal the development of fractures that fail with some opening. If a fracture produces negligible dilation, it may remain undetected in image segmentation of the reconstructions. We use the DVC software TomoWarp2 to identify undetected fractures and capture the 3D incremental displacement field between each successive pair of microtomography scans acquired in each experiment. The corresponding strain fields reveal localized bands of high axial contraction that host minimal shear strain, and thus match the kinematic definition of compaction bands. The bands develop sub-perpendicular to σ1 in the two samples in which pre-existing bedding laminations were oriented parallel and perpendicular to σ1. As the shales deform plastically toward macroscopic shear failure, the number of bands and axial contraction within the bands increase, while the spacing between the bands decreases. Compaction band development accelerates the rate of overall axial contraction, increasing the mean axial contraction throughout the sample, and strengthens the shale sufficiently to localize shear faults. These results are critical to robust assessment of deformation patterns in shale rocks in contexts such as nuclear waste storage, hydrocarbon recovery and groundwater access.

A Shear Strain Route Dependency of Martensite Formation in 316L Stainless Steel.

PubMed

Kang, Suk Hoon; Kim, Tae Kyu; Jang, Jinsung; Oh, Kyu Hwan

2015-06-01

In this study, the effect of simple shearing on microstructure evolution and mechanical properties of 316L austenitic stainless steel were investigated. Two different shear strain routes were obtained by twisting cylindrical specimens in the forward and backward directions. The strain-induced martensite phase was effectively obtained by alteration of the routes. Formation of the martensite phase clearly resulted in significant hardening of the steel. Grain-size reduction and strain-induced martensitic transformation within the deformed structures of the strained specimens were characterized by scanning electron microscopy - electron back-scattered diffraction, X-ray diffraction, and the TEM-ASTAR (transmission electron microscopy - analytical scanning transmission atomic resolution, automatic crystal orientation/phase mapping for TEM) system. Significant numbers of twin networks were formed by alteration of the shear strain routes, and the martensite phases were nucleated at the twin interfaces.

A virtual laboratory for neutron and synchrotron strain scanning

NASA Astrophysics Data System (ADS)

James, J. A.; Santisteban, J. R.; Edwards, L.; Daymond, M. R.

2004-07-01

The new generation of dedicated Engineering Strain Scanners at neutron and synchrotron facilities offer considerable improvements in both counting time and spatial resolution. In order to make full use of these advances in instrumentation, the routine tasks associated with setting up measurement runs and analysing the data need to be made as efficient as possible. Such tasks include the planning of the experiment, the alignment and positioning of the specimen, the least-squares refinement of diffraction spectra, the definition of strain in the sample coordinate system, and its visualization within a 3D model of the specimen. With this aim in mind, we have written a software providing support for most of these operations. The approach is based on a virtual lab consisting of 3D models of the sample and laboratory equipment. The system has been developed for ENGIN-X, the new engineering strain scanner recently commissioned at ISIS, but it is flexible enough to be ported to other neutron or synchrotron strain scanners. The software has been designed with visiting industrial and academic researchers in mind, users who need to be able to control the instrument after only a short period of training.

Life prediction of l6 steel using strain-life curve and cyclic stress-strain curve by means of low cycle fatigue testing

NASA Astrophysics Data System (ADS)

Inamdar, Sanket; Ukhande, Manoj; Date, Prashant; Lomate, Dattaprasad; Takale, Shyam; Singh, RKP

2017-05-01

L6 Steel is used as die material in closed die hot forging process. This material is having some unique properties. These properties are due to its composition. Strain softening is the noticeable property of this material. Due to this in spite of cracking at high stress this material gets plastically deformed and encounters loss in time as well as money. Studies of these properties are necessary to nurture this material at fullest extent. In this paper, numerous experiments have been carried on L6 material to evaluate cyclic Stress - strain behavior as swell as strain-life behavior of the material. Low cycle fatigue test is carried out on MTS fatigue test machine at fully reverse loading condition R=-1. Also strain softening effect on forging metal forming process is explained in detail. The failed samples during low cycle fatigue test further investigated metallurgically on scanning electron microscopy. Based on this study, life estimation of hot forging die is carried out and it’s correlation with actual shop floor data is found out. This work also concludes about effect of pre-treatments like nitro-carburizing and surface coating on L6 steel material, to enhance its fatigue life to certain extent.

Effect of Tween 80 on formation of the superficial L1 layer of the Mycobacterium avium-Mycobacterium intracellulare complex.

PubMed Central

Masaki, S; Sugimori, G; Okamoto, A; Imose, J; Hayashi, Y

1991-01-01

The effects of Tween 80 supplementation of liquid culture medium on the formation of the superficial L1 layer of the Mycobacterium avium-Mycobacterium intracellulare complex (MAC) were examined by serological and scanning electron microscopic experiments. Specific antiserum to the glycopeptidolipids on the L1 layer of M. avium S-139, made in a rabbit, was used for seroagglutination reactions with antigens prepared from strain S-139 grown in medium supplemented with various levels of Tween 80 (0, 0.05, 0.5, 5, and 50 mg/ml). The agglutination titers gradually decreased as the concentration of Tween 80 rose. Scanning electron microscopy showed that the fibrillar materials consisting mainly of glycopeptidolipids on the L1 layer of strain S-139 also disappeared with increases in the concentration of Tween 80. In addition, there was no obvious correlation between (i) the plasmid DNAs and serotypes of MAC and (ii) formation of the L1 layer of MAC. It is therefore concluded that Tween 80 used to supplement liquid culture medium affects formation of the L1 layer, which has been considered to be one of the pathogenic factors of MAC. Images PMID:1885740

High Strain Rate Tensile Testing of Silver Nanowires: Rate-Dependent Brittle-to-Ductile Transition.

PubMed

Ramachandramoorthy, Rajaprakash; Gao, Wei; Bernal, Rodrigo; Espinosa, Horacio

2016-01-13

The characterization of nanomaterials under high strain rates is critical to understand their suitability for dynamic applications such as nanoresonators and nanoswitches. It is also of great theoretical importance to explore nanomechanics with dynamic and rate effects. Here, we report in situ scanning electron microscope (SEM) tensile testing of bicrystalline silver nanowires at strain rates up to 2/s, which is 2 orders of magnitude higher than previously reported in the literature. The experiments are enabled by a microelectromechanical system (MEMS) with fast response time. It was identified that the nanowire plastic deformation has a small activation volume (<10b(3)), suggesting dislocation nucleation as the rate controlling mechanism. Also, a remarkable brittle-to-ductile failure mode transition was observed at a threshold strain rate of 0.2/s. Transmission electron microscopy (TEM) revealed that along the nanowire, dislocation density and spatial distribution of plastic regions increase with increasing strain rate. Furthermore, molecular dynamic (MD) simulations show that deformation mechanisms such as grain boundary migration and dislocation interactions are responsible for such ductility. Finally, the MD and experimental results were interpreted using dislocation nucleation theory. The predicted yield stress values are in agreement with the experimental results for strain rates above 0.2/s when ductility is pronounced. At low strain rates, random imperfections on the nanowire surface trigger localized plasticity, leading to a brittle-like failure.

Anti-Toxoplasma activity of various molecular weights and concentrations of chitosan nanoparticles on tachyzoites of RH strain.

PubMed

Teimouri, Aref; Azami, Sanaz Jafarpour; Keshavarz, Hossein; Esmaeili, Fariba; Alimi, Rasoul; Mavi, Sara Ayazian; Shojaee, Saeedeh

2018-01-01

Natural polysaccharides such as chitosan (CS) are widely used as antimicrobial agents. In recent years, and considering that CS has a strong antimicrobial potential, interest has been focused on antimicrobial activity of chitosan nanoparticles (CS NPs). The main factors affecting the antibacterial activity of chitosan include molecular weight (MW) and concentration. In this regard, the aim of this study was to produce various MWs and concentrations of CS NPs, through the ionic gelation method, and investigate their potential anti-parasitic activity against tachyzoites of Toxoplasma gondii RH strain. The MWs and degree of deacetylation of the CS were characterized using viscometric and acid-base titration methods, respectively. The efficacy of various MWs and concentrations of NPs was assessed by performing in vitro experiments for tachyzoites of T. gondii RH strain, such as MTT assay, scanning electron microscopy, bioassay in mice and PCR. In vivo experiment was carried out in BALB/c mice which were inoculated with tachyzoites of T. gondii RH strain and treated with various MWs of CS NPs. The results of in vitro and in vivo experiments revealed that anti- Toxoplasma activity strengthened as the CS NPs concentration increased and the MW decreased. In vitro experiment showed 100% mortality of tachyzoites at 500 and 1,000 ppm concentrations of low molecular weight (LMW) CS NPs after 180 min and at 2,000 ppm after 120 min. Furthermore, a 100% mortality of tachyzoites was observed at 1,000 and 2,000 ppm concentrations of medium molecular weight (MMW) CS NPs and at 2,000 ppm concentration of high molecular weight (HMW) CS NPs after 180 min. Growth inhibition rates of tachyzoites in peritoneal exudates of mice receiving low, medium and high MWs of CS NPs were found to be 86%, 84% and 79% respectively, compared to those of mice in sulfadiazine treatment group (positive control). Various MWs of CS NPs exhibited great anti- Toxoplasma efficiency against tachyzoites of RH strain, with the greatest efficacy shown by LMW CS NPs in both experiments. It seems that CS NPs can be used as an alternative natural medicine in the treatment of toxoplasmosis.

Controllable spin-charge transport in strained graphene nanoribbon devices

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

Diniz, Ginetom S., E-mail: ginetom@gmail.com; Guassi, Marcos R.; Qu, Fanyao

2014-09-21

We theoretically investigate the spin-charge transport in two-terminal device of graphene nanoribbons in the presence of a uniform uniaxial strain, spin-orbit coupling, exchange field, and smooth staggered potential. We show that the direction of applied strain can efficiently tune strain-strength induced oscillation of band-gap of armchair graphene nanoribbon (AGNR). It is also found that electronic conductance in both AGNR and zigzag graphene nanoribbon (ZGNR) oscillates with Rashba spin-orbit coupling akin to the Datta-Das field effect transistor. Two distinct strain response regimes of electronic conductance as function of spin-orbit couplings magnitude are found. In the regime of small strain, conductance ofmore » ZGNR presents stronger strain dependence along the longitudinal direction of strain. Whereas for high values of strain shows larger effect for the transversal direction. Furthermore, the local density of states shows that depending on the smoothness of the staggered potential, the edge states of AGNR can either emerge or be suppressed. These emerging states can be determined experimentally by either spatially scanning tunneling microscope or by scanning tunneling spectroscopy. Our findings open up new paradigms of manipulation and control of strained graphene based nanostructure for application on novel topological quantum devices.« less

Investigation of threading dislocation blocking in strained-layer InGaAs/GaAs heterostructures using scanning cathodoluminescence microscopy

NASA Astrophysics Data System (ADS)

Russell, J. J.; Zou, J.; Moon, A. R.; Cockayne, D. J. H.

2000-08-01

Threading dislocation glide relieves strain in strained-layer heterostructures by increasing the total length of interface misfit dislocations. The blocking theory proposed by Freund [J. Appl. Phys. 68, 2073 (1990)] predicts the thickness above which gliding threading dislocations are able to overcome the resistance force produced by existing orthogonal misfit dislocations. A set of wedge-shaped samples of InxGa1-xAs/GaAs (x=0.04) strained-layer heterostructures was grown using molecular-beam epitaxy in order to test the theory of dislocation blocking over a range of thicknesses within one sample. Scanning cathodoluminescence microscopy techniques were used to image the misfit dislocations. The cathodoluminescence results confirm the model proposed by Freund.

Early Adhesion of Candida albicans onto Dental Acrylic Surfaces.

PubMed

Aguayo, S; Marshall, H; Pratten, J; Bradshaw, D; Brown, J S; Porter, S R; Spratt, D; Bozec, L

2017-07-01

Denture-associated stomatitis is a common candidal infection that may give rise to painful oral symptoms, as well as be a reservoir for infection at other sites of the body. As poly (methyl methacrylate) (PMMA) remains the main material employed in the fabrication of dentures, the aim of this research was to evaluate the adhesion of Candida albicans cells onto PMMA surfaces by employing an atomic force microscopy (AFM) single-cell force spectroscopy (SCFS) technique. For experiments, tipless AFM cantilevers were functionalized with PMMA microspheres and probed against C. albicans cells immobilized onto biopolymer-coated substrates. Both a laboratory strain and a clinical isolate of C. albicans were used for SCFS experiments. Scanning electron microscopy (SEM) and AFM imaging of C. albicans confirmed the polymorphic behavior of both strains, which was dependent on growth culture conditions. AFM force-spectroscopy results showed that the adhesion of C. albicans to PMMA is morphology dependent, as hyphal tubes had increased adhesion compared with yeast cells ( P < 0.05). C. albicans budding mother cells were found to be nonadherent, which contrasts with the increased adhesion observed in the tube region. Comparison between strains demonstrated increased adhesion forces for a clinical isolate compared with the lab strain. The clinical isolate also had increased survival in blood and reduced sensitivity to complement opsonization, providing additional evidence of strain-dependent differences in Candida-host interactions that may affect virulence. In conclusion, PMMA-modified AFM probes have shown to be a reliable technique to characterize the adhesion of C. albicans to acrylic surfaces.

Landau level splitting in nitrogen-seeded epitaxial graphene

DOE PAGES

Rothwell, S. L.; Wang, F.; Liu, G.; ...

2016-07-01

We present a new form of semiconducting graphene grown on C-face silicon carbide, SiC(0001), seeded with a sub-monolayer of nitrogen. This graphene exhibits a gap of 0.3-0.7 eV from the Fermi level to the valence band dependent on lm thickness as measured via angle resolved photo-emission spectroscopy (ARPES). Scanning tunneling microscopy (STM) images imply that the bandgap may be the result of strain-induced confinement. STM indicates that much of the graphene consists of wide at hexagonal plateaus, 8-20 nm2 on average, surrounded by both smooth and disordered folds of length scales from 0.5-2 nm tall, 1-4 nm thick, and 1-20more » nm long. The remainder of the surface is covered in smooth or disordered ripples and folds intermixed. Scanning tunneling spectroscopy (STS) measurements on all features show peaks suggestive of Landau levels, and have been analyzed to give pseudo-magnetic field magnitudes. The magnetic lengths associated with these fields are less than the average plateau diameter but comparable to typical fold widths. We consider a growth process whereby the graphene grows pinned to the substrate by the interface nitrogen. The graphene experiences compressive strain as a result of both this pinning as well as competing thermal expansion forces between the substrate and lm. As a result, graphene on nitrogen-seeded SiC has a more concentrated network of strained ripples and folds than seen on C-face SiC graphene without nitrogen.« less

Two-dimensional mapping of triaxial strain fields in a multiferroic BiFeO3 thin film using scanning x-ray microdiffraction

NASA Astrophysics Data System (ADS)

Bark, Chung W.; Cho, Kyung C.; Koo, Yang M.; Tamura, Nobumichi; Ryu, Sangwoo; Jang, Hyun M.

2007-03-01

The dramatically enhanced polarizations and saturation magnetizations observed in the epitaxially constrained BiFeO3 (BFO) thin films with their pronounced grain-orientation dependence have attracted much attention and are attributed largely to the constrained in-plane strain. Thus, it is highly desirable to directly obtain information on the two-dimensional (2D) distribution of the in-plane strain and its correlation with the grain orientation of each corresponding microregion. Here the authors report a 2D quantitative mapping of the grain orientation and the local triaxial strain field in a 250nm thick multiferroic BFO film using a synchrotron x-ray microdiffraction technique. This direct scanning measurement demonstrates that the deviatoric component of the in-plane strain tensor is between 5×10-3 and 6×10-3 and that the local triaxial strain is fairly well correlated with the grain orientation in that particular region.

Evaluation of crystallographic strain, rotation and defects in functional oxides by the moiré effect in scanning transmission electron microscopy.

PubMed

Naden, A B; O'Shea, K J; MacLaren, D A

2018-04-20

Moiré patterns in scanning transmission electron microscopy (STEM) images of epitaxial perovskite oxides are used to assess strain and defect densities over fields of view extending over several hundred nanometers. The patterns arise from the geometric overlap of the rastered STEM electron beam and the samples' crystal periodicities and we explore the emergence and application of these moiré fringes for rapid strain analysis. Using the epitaxial functional oxide perovskites BiFeO 3 and Pr 1-x Ca x MnO 3 , we discuss the impact of large degrees of strain on the quantification of STEM moiré patterns, identify defects in the fringe patterns and quantify strain and lattice rotation. Such a wide-area analysis of crystallographic strain and defects is crucial for developing structure-function relations of functional oxides and we find the STEM moiré technique to be an attractive means of structural assessment that can be readily applied to low dose studies of damage sensitive crystalline materials.

Evaluation of crystallographic strain, rotation and defects in functional oxides by the moiré effect in scanning transmission electron microscopy

NASA Astrophysics Data System (ADS)

Naden, A. B.; O'Shea, K. J.; MacLaren, D. A.

2018-04-01

Moiré patterns in scanning transmission electron microscopy (STEM) images of epitaxial perovskite oxides are used to assess strain and defect densities over fields of view extending over several hundred nanometers. The patterns arise from the geometric overlap of the rastered STEM electron beam and the samples’ crystal periodicities and we explore the emergence and application of these moiré fringes for rapid strain analysis. Using the epitaxial functional oxide perovskites BiFeO3 and Pr1-x Ca x MnO3, we discuss the impact of large degrees of strain on the quantification of STEM moiré patterns, identify defects in the fringe patterns and quantify strain and lattice rotation. Such a wide-area analysis of crystallographic strain and defects is crucial for developing structure-function relations of functional oxides and we find the STEM moiré technique to be an attractive means of structural assessment that can be readily applied to low dose studies of damage sensitive crystalline materials.

Short range smectic order driving long range nematic order: Example of cuprates

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

Markiewicz, R. S.; Lorenzana, J.; Seibold, G.

We present a model for describing the combined presence of nematic and ‘smectic’ or stripe-like orders seen in recent scanning tunneling microscopy (STM) experiments on cuprates. The smectic order is treated as an electronic charge density wave with an associated Peierls distortion or a ‘Pomeranchuk wave’. This primary order is restricted to nanoscale domains by disorder effects, while the secondary coupling to strain generates the nematic order with a considerably longer range. Lastly, a variety of experimental results are shown to be consistent with our theoretical predictions.

Short range smectic order driving long range nematic order: Example of cuprates

DOE PAGES

Markiewicz, R. S.; Lorenzana, J.; Seibold, G.; ...

2016-01-27

We present a model for describing the combined presence of nematic and ‘smectic’ or stripe-like orders seen in recent scanning tunneling microscopy (STM) experiments on cuprates. The smectic order is treated as an electronic charge density wave with an associated Peierls distortion or a ‘Pomeranchuk wave’. This primary order is restricted to nanoscale domains by disorder effects, while the secondary coupling to strain generates the nematic order with a considerably longer range. Lastly, a variety of experimental results are shown to be consistent with our theoretical predictions.

In Vivo Consumption of Cranberry Exerts ex Vivo Antiadhesive Activity against FimH-Dominated Uropathogenic Escherichia coli: A Combined in Vivo, ex Vivo, and in Vitro Study of an Extract from Vaccinium macrocarpon.

PubMed

Rafsanjany, Nasli; Senker, Jandirk; Brandt, Simone; Dobrindt, Ulrich; Hensel, Andreas

2015-10-14

For investigation of the molecular interaction of cranberry extract with adhesins of uropathogenic Escherichia coli (UPEC), urine from four volunteers consuming standardized cranberry extract (proanthocyanidin content = 1.24%) was analyzed within ex vivo experiments, indicating time-dependent significant inhibition of 40-50% of bacterial adhesion of UPEC strain NU14 to human T24 bladder cells. Under in vitro conditions a dose-dependent increase in bacterial adhesion was observed with proanthocyanidin-enriched cranberry Vaccinium macrocarpon extract (proanthocyanidin content = 21%). Confocal laser scanning microscopy and scanning electron microscopy proved that V.m. extract led to the formation of bacterial clusters on the outer plasma membrane of the host cells without subsequent internalization. This agglomerating activity was not observed when a PAC-depleted extract (V.m. extract(≠PAC)) was used, which showed significant inhibition of bacterial adhesion in cases where type 1 fimbriae dominated and mannose-sensitive UPEC strain NU14 was used. V.m. extract(≠PAC) had no inhibitory activity against P- and F1C-fimbriae dominated strain 2980. Quantitative gene expression analysis indicated that PAC-containing as well as PAC-depleted cranberry extracts increased the fimH expression in NU14 as part of a feedback mechanism after blocking FimH. For strain 2980 the PAC-containing extract led to up-regulation of P- and F1C-fimbriae, whereas the PAC-depleted extract had no influence on gene expression. V.m. and V.m. extract(≠PAC) did not influence biofilm and curli formation in UPEC strains NU14 and 2980. These data lead to the conclusion that also proanthocyanidin-free cranberry extracts exert antiadhesive activity by interaction with mannose-sensitive type 1 fimbriae of UPEC.

Structure-property evolution during polymer crystallization

NASA Astrophysics Data System (ADS)

Arora, Deepak

The main theme of this research is to understand the structure-property evolution during crystallization of a semicrystalline thermoplastic polymer. A combination of techniques including rheology, small angle light scattering, differential scanning calorimetry and optical microscopy are applied to follow the mechanical and optical properties along with crystallinity and the morphology. Isothermal crystallization experiments on isotactic poly-1-butene at early stages of spherulite growth provide quantitative information about nucleation density, volume fraction of spherulites and their crystallinity, and the mechanism of connecting into a sample spanning structure. Optical microscopy near the fluid-to-solid transition suggests that the transition, as determined by time-resolved mechanical spectroscopy, is not caused by packing/jamming of spherulites but by the formation of a percolating network structure. The effect of strain, Weissenberg number (We ) and specific mechanical work (w) on rate of crystallization (nucleation followed by growth) and on growth of anisotropy was studied for shear-induced crystallization of isotactic poly-1-butene. The samples were sheared for a finite strain at the beginning of the experiment and then crystallized without further flow (Janeschitz-Kriegl protocol). Strain requirements to attain steady state/leveling off of the rate of crystallization were found to be much larger than the strain needed to achieve steady state of flow. The large strain and We>1 criteria were also observed for morphological transition from spherulitic growth to oriented growth. An apparatus for small angle light scattering (SALS) and light transmission measurements under shear was built and tested at the University of Massachusetts Amherst. As a new development, the polarization direction can be rotated by a liquid crystal polarization rotator (LCPR) with a short response time of 20 ms. The experiments were controlled and analyzed with a LabVIEW(TM) based code (LabVIEW(TM) 7.1) in real time. The SALS apparatus was custom built for ExxonMobil Research in Clinton NJ.

New modes of electron microscopy for materials science enabled by fast direct electron detectors

NASA Astrophysics Data System (ADS)

Minor, Andrew

There is an ongoing revolution in the development of electron detector technology that has enabled modes of electron microscopy imaging that had only before been theorized. The age of electron microscopy as a tool for imaging is quickly giving way to a new frontier of multidimensional datasets to be mined. These improvements in electron detection have enabled cryo-electron microscopy to resolve the three-dimensional structures of non-crystalized proteins, revolutionizing structural biology. In the physical sciences direct electron detectors has enabled four-dimensional reciprocal space maps of materials at atomic resolution, providing all the structural information about nanoscale materials in one experiment. This talk will highlight the impact of direct electron detectors for materials science, including a new method of scanning nanobeam diffraction. With faster detectors we can take a series of 2D diffraction patterns at each position in a 2D STEM raster scan resulting in a four-dimensional data set. For thin film analysis, direct electron detectors hold the potential to enable strain, polarization, composition and electrical field mapping over relatively large fields of view, all from a single experiment.

Modeling damage evolution in a hybrid ceramic matrix composite under static tensile load

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

Bonora, N.; Newaz, G.

In this investigation, damage evolution in a unidirectional hybrid ceramic composite made from Nicalon and SiC fibers in a Lithium Aluminosilicate (LAS) glass matrix was studied. The static stress-strain response of the composite exhibited a linear response followed by load drop in a progressive manner. Careful experiments were conducted stopping the tests at various strain levels and using replication technique, scanning and optical microscopy to monitor the evolution of damage in these composites. It was observed that the constituents of the composite failed in a sequential manner at increasing strain levels. The matrix cracks were followed by SiC fiber failuresmore » near ultimate tensile stress. After that, the load drop was associated with progressive failure of the Nicalon fibers. Identification of these failure modes were critical to the development of a concentric cylinder model representing all three constituent phases to predict the constitutive response of the CMC computationally. The strain-to-failure of the matrix and fibers were used to progressively fail the constituents in the model and the overall experimental constitutive response of the CMC was recovered. A strain based analytical representation was developed relating stiffness loss to applied strain. Based on this formulation, damage evolution and its consequence on tensile stress-strain response was predicted for room temperature behavior of hybrid CMCs. The contribution of the current work is that the proposed strain-damage phenomenological model can capture the damage evolution and the corresponding material response for continuous fiber-reinforced CMCs. The modeling approach shows much promise for the complex damage processes observed in hybrid CMCs.« less

Visualization of microbiological processes underlying stress relaxation in Pseudomonas aeruginosa biofilms.

PubMed

Peterson, Brandon W; Busscher, Henk J; Sharma, Prashant K; van der Mei, Henny C

2014-06-01

Bacterial biofilms relieve themselves from external stresses through internal rearrangement, as mathematically modeled in many studies, but never microscopically visualized for their underlying microbiological processes. The aim of this study was to visualize rearrangement processes occurring in mechanically deformed biofilms using confocal-laser-scanning-microscopy after SYTO9 (green-fluorescent) and calcofluor-white (blue-fluorescent) staining to visualize bacteria and extracellular-polymeric matrix substances, respectively. We apply 20% uniaxial deformation to Pseudomonas aeruginosa biofilms and fix deformed biofilms prior to staining, after allowing different time-periods for relaxation. Two isogenic P. aeruginosa strains with different abilities to produce extracellular polymeric substances (EPS) were used. By confocal-laser-scanning-microscopy all biofilms showed intensity distributions for fluorescence from which rearrangement of EPS and bacteria in deformed biofilms were derived. For the P. aeruginosa strain producing EPS, bacteria could not find new, stable positions within 100 s after deformation, while EPS moved toward deeper layers within 20 s. Bacterial rearrangement was not seen in P. aeruginosa biofilms deficient in production of EPS. Thus, EPS is required to stimulate bacterial rearrangement in mechanically deformed biofilms within the time-scale of our experiments, and the mere presence of water is insufficient to induce bacterial movement, likely due to its looser association with the bacteria.

The analgesic effects of oral paracetamol in two strains of mice undergoing vasectomy.

PubMed

Dickinson, Amy L; Leach, Matthew C; Flecknell, Paul A

2009-10-01

As the production of transgenic mice increases, the need for vasectomized mice also increases. Currently, there is no accurate method of identifying pain in these mice which can be used routinely and therefore no acceptable analgesic regimens can be established. Sixteen male CBA/CaCrl and 16 male DBA/2JCrl mice were randomly allocated to one of four treatment groups (saline, low, medium and high dose oral paracetamol) and then underwent abdominal vasectomy. Their behaviour was videotaped (filmed) preoperatively and at one hour postoperatively and the data were analysed using an automated system - HomeCageScan. HomeCageScan detected significant changes in 16 behaviours following vasectomy. Such behaviours included twitching, rearing and grooming with varying levels of significance between the strains. No significant effects of drug treatment in any of the behaviours analysed by HomeCageScan were detected in the postoperative observation period. Strain-specific changes do occur in behaviour following abdominal vasectomy and HomeCageScan is capable of detecting these changes. The use of orally administered paracetamol was deemed to be an ineffective analgesic for CBA/CaCrl and DBA/2JCrl mice undergoing vasectomy.

2D strain mapping using scanning transmission electron microscopy Moiré interferometry and geometrical phase analysis.

PubMed

Pofelski, A; Woo, S Y; Le, B H; Liu, X; Zhao, S; Mi, Z; Löffler, S; Botton, G A

2018-04-01

A strain characterization technique based on Moiré interferometry in a scanning transmission electron microscope (STEM) and geometrical phase analysis (GPA) method is demonstrated. The deformation field is first captured in a single STEM Moiré hologram composed of multiple sets of periodic fringes (Moiré patterns) generated from the interference between the periodic scanning grating, fixing the positions of the electron probe on the sample, and the crystal structure. Applying basic principles from sampling theory, the Moiré patterns arrangement is then simulated using a STEM electron micrograph reference to convert the experimental STEM Moiré hologram into information related to the crystal lattice periodicities. The GPA method is finally applied to extract the 2D relative strain and rotation fields. The STEM Moiré interferometry enables the local information to be de-magnified to a large length scale, comparable to what can be achieved in dark-field electron holography. The STEM Moiré GPA method thus extends the conventional high-resolution STEM GPA capabilities by providing comparable quantitative 2D strain mapping with a larger field of view (up to a few microns). Copyright © 2017 Elsevier B.V. All rights reserved.

Investigating ultraflexible freestanding graphene by scanning tunneling microscopy and spectroscopy

NASA Astrophysics Data System (ADS)

Breitwieser, R.; Hu, Yu-Cheng; Chao, Yen Cheng; Tzeng, Yi Ren; Liou, Sz-Chian; Lin, Keng Ching; Chen, Chih Wei; Pai, Woei Wu

2017-08-01

A strictly two-dimensional (2D) material such as freestanding graphene (FSG) is rarely investigated at the atomic scale by scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). A basic difficulty in probing FSG by STM and STS is the mechanical instability when a highly compliant 2D atomic layer interacts with a proximal tip. Here we report a detailed method to conduct reliable STM and STS on FSG with atomic precision. We found that FSG is intrinsically rippled and exhibits a nonlinear strain-stress relation under applied normal forces; it shows a very soft region of bending strain and stiffer regions of in-plane tensile strain once the nanoscale ripples of FSG are eliminated. The elimination of the nanoripples can be controlled by tip-induced pulling or pushing force through the so-called closed-loop Z-V STS mode which can monitor the FSG deformation. A key factor for controllable STM and STS measurements is to select tunneling set points to place FSG in metastable configurations, as determined from stress-strain (i.e., Z-V) response. Atomic imaging and electronic states thus measured must be interpreted by considering the dynamical deformation of FSG as tunneling parameters, and therefore tip-FSG forces, are varied.

Effect of pre-strain on precipitation and exfoliation corrosion resistance in an Al-Zn-Mg alloy

NASA Astrophysics Data System (ADS)

Lu, Xianghan; Du, Zhiwei; Han, Xiaolei; Li, Ting; Wang, Guojun; Lu, Liying; Bai, Xiaoxia; Zhou, Tietao

2017-12-01

To investigate the effect of pre-strain on behaviors in a specially developed Al-4.5Zn-1.2Mg alloy, transmission electron microscopy (TEM) bright field (BF) imaging combined with select area electron diffraction (SAED), Vickers-hardness tests and electrical conductivity tests was conducted for insight into precipitation in aluminum (Al) matrix during two step ageing, and standard exfoliation corrosion (EXCO) test combined with high-angle angular dark field scanning transmission electron microscopy (HAADF-STEM) and scanning electron microscopy (SEM) was carried out for corrosion behavior. Results showed that pre-strain accelerated precipitation during two step ageing as the sequence of: (i) supersaturated solid solution (SSS), GPI zones precipitations, GPI dissolution; (ii) SSS, fcc precipitates, η’ phases or η phases. And the precipitation hardening of the fcc precipitates was not effective as GPI zones. Pre-strain also accelerated EXCO developing, which was mainly attributed to the coverage ratio of η phases on high-angle grain boundaries (HAGBs) increasing as pre-strain increase.

Detecting imipenem resistance in Acinetobacter baumannii by automated systems (BD Phoenix, Microscan WalkAway, Vitek 2); high error rates with Microscan WalkAway

PubMed Central

2009-01-01

Background Increasing reports of carbapenem resistant Acinetobacter baumannii infections are of serious concern. Reliable susceptibility testing results remains a critical issue for the clinical outcome. Automated systems are increasingly used for species identification and susceptibility testing. This study was organized to evaluate the accuracies of three widely used automated susceptibility testing methods for testing the imipenem susceptibilities of A. baumannii isolates, by comparing to the validated test methods. Methods Selected 112 clinical isolates of A. baumanii collected between January 2003 and May 2006 were tested to confirm imipenem susceptibility results. Strains were tested against imipenem by the reference broth microdilution (BMD), disk diffusion (DD), Etest, BD Phoenix, MicroScan WalkAway and Vitek 2 automated systems. Data were analysed by comparing the results from each test method to those produced by the reference BMD test. Results MicroScan performed true identification of all A. baumannii strains while Vitek 2 unidentified one strain, Phoenix unidentified two strains and misidentified two strains. Eighty seven of the strains (78%) were resistant to imipenem by BMD. Etest, Vitek 2 and BD Phoenix produced acceptable error rates when tested against imipenem. Etest showed the best performance with only two minor errors (1.8%). Vitek 2 produced eight minor errors(7.2%). BD Phoenix produced three major errors (2.8%). DD produced two very major errors (1.8%) (slightly higher (0.3%) than the acceptable limit) and three major errors (2.7%). MicroScan showed the worst performance in susceptibility testing with unacceptable error rates; 28 very major (25%) and 50 minor errors (44.6%). Conclusion Reporting errors for A. baumannii against imipenem do exist in susceptibility testing systems. We suggest clinical laboratories using MicroScan system for routine use should consider using a second, independent antimicrobial susceptibility testing method to validate imipenem susceptibility. Etest, whereever available, may be used as an easy method to confirm imipenem susceptibility. PMID:19291298

Effects of different culture media on biodegradation of triclosan by Rhodotorula mucilaginosa and Penicillium sp.

PubMed

Ertit Taştan, Burcu; Özdemir, Caner; Tekinay, Turgay

Triclosan is an antimicrobial agent and a persistent pollutant. The biodegradation of triclosan is dependent on many variables including the biodegradation organism and the environmental conditions. Here, we evaluated the triclosan degradation potential of two fungi strains, Rhodotorula mucilaginosa and Penicillium sp., and the rate of its turnover to 2,4-dichlorophenol (2,4-DCP). Both of these strains showed less susceptibility to triclosan when grown in minimal salt medium. In order to further evaluate the effects of environmental conditions on triclosan degradation, three different culture conditions including original thermal power plant wastewater, T6 nutrimedia and ammonium mineral salts medium were used. The maximum triclosan degradation yield was 48% for R. mucilaginosa and 82% for Penicillium sp. at 2.7 mg/L triclosan concentration. Biodegradation experiments revealed that Penicillium sp. was more tolerant to triclosan. Scanning electron microscopy micrographs also showed the morphological changes of fungus when cells were treated with triclosan. Overall, these fungi strains could be used as effective microorganisms in active uptake (degradation) and passive uptake (sorption) of triclosan and their efficiency can be increased by optimizing the culture conditions.

Size effects on elasticity, yielding, and fracture of silver nanowires: In situ experiments

NASA Astrophysics Data System (ADS)

Zhu, Yong; Qin, Qingquan; Xu, Feng; Fan, Fengru; Ding, Yong; Zhang, Tim; Wiley, Benjamin J.; Wang, Zhong Lin

2012-01-01

This paper reports the quantitative measurement of a full spectrum of mechanical properties of fivefold twinned silver (Ag) nanowires (NWs), including Young's modulus, yield strength, and ultimate tensile strength. In-situ tensile testing of Ag NWs with diameters between 34 and 130 nm was carried out inside a scanning electron microscope (SEM). Young's modulus, yield strength, and ultimate tensile strength all increased as the NW diameter decreased. The maximum yield strength in our tests was found to be 2.64 GPa, which is about 50 times the bulk value and close to the theoretical value of Ag in the 110 orientation. The size effect in the yield strength is mainly due to the stiffening size effect in the Young's modulus. Yield strain scales reasonably well with the NW surface area, which reveals that yielding of Ag NWs is due to dislocation nucleation from surface sources. Pronounced strain hardening was observed for most NWs in our study. The strain hardening, which has not previously been reported for NWs, is mainly attributed to the presence of internal twin boundaries.

Optimizing surface defects for atomic-scale electronics: Si dangling bonds

NASA Astrophysics Data System (ADS)

Scherpelz, Peter; Galli, Giulia

2017-07-01

Surface defects created and probed with scanning tunneling microscopes are a promising platform for atomic-scale electronics and quantum information technology applications. Using first-principles calculations we demonstrate how to engineer dangling bond (DB) defects on hydrogenated Si(100) surfaces, which give rise to isolated impurity states that can be used in atomic-scale devices. In particular, we show that sample thickness and biaxial strain can serve as control parameters to design the electronic properties of DB defects. While in thick Si samples the neutral DB state is resonant with bulk valence bands, ultrathin samples (1-2 nm) lead to an isolated impurity state in the gap; similar behavior is seen for DB pairs and DB wires. Strain further isolates the DB from the valence band, with the response to strain heavily dependent on sample thickness. These findings suggest new methods for tuning the properties of defects on surfaces for electronic and quantum information applications. Finally, we present a consistent and unifying interpretation of many results presented in the literature for DB defects on hydrogenated silicon surfaces, rationalizing apparent discrepancies between different experiments and simulations.

Validation and application of HPLC-ESI-MS/MS method for the quantification of RBBR decolorization, a model for highly toxic molecules, using several fungi strains.

PubMed

Perlatti, Bruno; da Silva, Maria Fátima das Graças Fernandes; Fernandes, João Batista; Forim, Moacir Rossi

2012-11-01

A novel analytical method using HPLC-MS/MS operating in selected reaction monitoring (SRM) for evaluation of fungi efficacy to decolorize Remazol Brilliant Blue R (RBBR) dye solution was developed, validated and applied. The method shows high sensibility allowing the detection of 4.6 pM of RBBR. Four fungal strains were tested in liquid medium, three strains of Aspergillus (Aspergillus aculeatus, Aspergillus flavus and Aspergillus fumigatus) and Phanerochaete chrysosporium. All fungi were able to degrade the dye, with efficiencies ranging from 40% for P. chrysosporium up to 99% for A. flavus during a 30-day incubation period. During the experiment, increased accumulation of degradation products was observed in A. flavus cultures containing RBBR. Through the use of full scan HPLC-MS technique it was possible to propose the biogenesis of the microbial metabolic degradation pathway. Screening using microorganisms and RBBR may be hereafter used to investigate microbial biodegradation of high toxicity molecules such as dioxins. Copyright © 2012 Elsevier Ltd. All rights reserved.

An experimental investigation of damage evolution in a ceramic matrix composite

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

Walter, M.E.; Ravichandran, G.

The mechanical behavior of a glass-ceramic matrix composite, SiC/CAS (calcium aluminosilicate reinforced with unidirectional SiC fibers), is studied. Results based on uniaxial tension experiments are presented for specimens with fibers aligned in the loading direction. Axial and transverse strain gages on all four gage section surfaces and in situ acoustic emission and ultrasonic wave speed measurements were used to monitor the evolution of damage. All measurements were made with high-resolution, continuous data acquisition. Post-test optical and scanning electron microscopy was also used to identify the various micromechanisms of damage. The experimental results demonstrate the existence of zones of deformation'' whichmore » are associated with the onset of different damage mechanisms. It is shown that the observed stress-strain behavior can be explained in terms of the material properties of the matrix and the fiber, the material processing, and the postulated zones of deformation.« less

Bioremediation of chromium by novel strains Enterobacter aerogenes T2 and Acinetobacter sp. PD 12 S2.

PubMed

Panda, Jigisha; Sarkar, Priyabrata

2012-06-01

This study had an objective to identify the most potent chromium-resistant bacteria isolated from tannery effluent and apply them for bioremediation of chromium in tannery effluents. Two such strains (previously characterized and identified by us)--Enterobacter aerogenes (NCBI GenBank USA Accession no. GU265554) and Acinetobacter sp. PD 12 (NCBI GenBank USA Accession no. GU084179)--showed powerful chromium resistivity and bioremediation capabilities among many stains isolated from tannery waste. Parameters such as pH, concentration of hexavalent chromium or Cr (VI), and inoculum volume were varied to observe optimum bioconversion and bioaccumulation of Cr (VI) when the said strains were grown in M9 minimal salt media. E. aerogenes was used to remediate chromium from tannery effluents in a laboratory level experiment. Observation by Scanning Electron Microscope and chromium peak in Energy Dispersive X-ray Spectroscopic microanalysis revealed that E. aerogenes helped remediate a moderate amount of Cr (VI) (8-16 mg L(-1)) over a wide range of pH values at 35-37°C (within 26.05 h). High inoculum percentage of Acinetobacter sp. PD 12 also enabled bioremediation of 8-16 mg L(-1) of Cr (VI) over a wide range of temperature (25-37°C), mainly at pH 7 (within 63.28 h). The experiment with real tannery effluent gave very encouraging results. The strain E. aerogenes can be used in bioremediation of Cr (VI) since it could work in actual environmental conditions with extraordinarily high capacity.

Noncontacting-optical-strain device

NASA Technical Reports Server (NTRS)

Silver, R. H.

1970-01-01

Noncontacting-strain-measuring gauge and extensometer remotely measures the mechanical displacement along the entire length of a test specimen. Measurement is accomplished by continuous scanning of a reflected light from reflective bench markings or stripes previously affixed to the specimen.

Statistical evidence of strain induced breaking of metallic point contacts

NASA Astrophysics Data System (ADS)

Alwan, Monzer; Candoni, Nadine; Dumas, Philippe; Klein, Hubert R.

2013-06-01

A scanning tunneling microscopy in break junction regime and a mechanically controllable break junction are used to acquire thousands of conductance-elongation curves by stretching until breaking and re-connecting Au junctions. From a robust statistical analysis performed on large sets of experiments, parameters such as lifetime, elongation and occurrence probabilities are extracted. The analysis of results obtained for different stretching speeds of the electrodes indicates that the breaking mechanism of di- and mono-atomic junction is identical, and that the junctions undergo atomic rearrangement during their stretching and at the moment of breaking.

Correction of image drift and distortion in a scanning electron microscopy.

PubMed

Jin, P; Li, X

2015-12-01

Continuous research on small-scale mechanical structures and systems has attracted strong demand for ultrafine deformation and strain measurements. Conventional optical microscope cannot meet such requirements owing to its lower spatial resolution. Therefore, high-resolution scanning electron microscope has become the preferred system for high spatial resolution imaging and measurements. However, scanning electron microscope usually is contaminated by distortion and drift aberrations which cause serious errors to precise imaging and measurements of tiny structures. This paper develops a new method to correct drift and distortion aberrations of scanning electron microscope images, and evaluates the effect of correction by comparing corrected images with scanning electron microscope image of a standard sample. The drift correction is based on the interpolation scheme, where a series of images are captured at one location of the sample and perform image correlation between the first image and the consequent images to interpolate the drift-time relationship of scanning electron microscope images. The distortion correction employs the axial symmetry model of charged particle imaging theory to two images sharing with the same location of one object under different imaging fields of view. The difference apart from rigid displacement between the mentioned two images will give distortion parameters. Three-order precision is considered in the model and experiment shows that one pixel maximum correction is obtained for the employed high-resolution electron microscopic system. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

Strain-specific colonization pattern of Rhizoctonia antagonists in the root system of sugar beet.

PubMed

Zachow, Christin; Fatehi, Jamshid; Cardinale, Massimiliano; Tilcher, Ralf; Berg, Gabriele

2010-10-01

To develop effective biocontrol strategies, basic knowledge of plant growth promotion (PGP) and root colonization by antagonists is essential. The survival and colonization patterns of five different biocontrol agents against Rhizoctonia solani AG2-2IIIB in the rhizosphere of greenhouse-grown sugar beet plants were analysed in single and combined treatments. The study included bacteria (Pseudomonas fluorescens L13-6-12, Pseudomonas trivialis RE(*) 1-1-14, Serratia plymuthica 3Re4-18) as well as fungi (Trichoderma gamsii AT1-2-4, Trichoderma velutinum G1/8). Microscopic analysis by confocal laser scanning microscopy revealed different colonization patterns for each DsRed2/green fluorescent protein-labelled strain. Bacteria and T. velutinum G1/8 colonized the root surface and the endorhiza in single and co-culture, while for T. gamsii AT1-2-4, only the transfer of spores was observed. Whereas Pseudomonas strains formed large microcolonies consisting of hundreds of cells, S. plymuthica was arranged in small endophytic clusters or clouds around the entire root system. In co-culture, each strain showed its typical pattern and occupied specific niches on the root, without clear evidence of morphological interactions. PGP was only observed for four strains with rhizosphere competence and not for T. gamsii AT1-2-4. The results provide useful information on which combination of strains to test in larger biocontrol experiments directed to applications. © 2010 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Deciphering the factors associated with the colonization of rice plants by cyanobacteria.

PubMed

Bidyarani, Ngangom; Prasanna, Radha; Chawla, Gautam; Babu, Santosh; Singh, Rajendra

2015-04-01

Cyanobacteria-rice plant interactions were analyzed using a hydroponics experiment. The activity of plant defense and pathogenesis-related enzymes, scanning electron microscopy, growth, nitrogen fixation (measured as ARA), and DNA fingerprinting assays proved useful in illustrating the nature of associations of cyanobacteria with rice plants. Microscopic analyses revealed the presence of short filaments and coiled masses of filaments of cyanobacteria near the epidermis and cortex of roots and shoot tissues. Among the six cyanobacterial strains employed, Calothrix sp. (RPC1), Anabaena laxa (RPAN8), and Anabaena azollae (C16) were the best performing strains, in terms of colonization in roots and stem. These strains also enhanced nitrogen fixation and stimulated the activity of plant defense/cell wall-degrading enzymes. A significantly high correlation was also recorded between the elicited plant enzymes, growth, and ARA. DNA fingerprinting using highly iterated palindromic sequences (HIP-TG) further helped in proving the establishment of inoculated organisms in the roots/shoots of rice plants. This study illustrated that the colonization of cyanobacteria in the plant tissues is facilitated by increased elicitation of plant enzymes, leading to improved plant growth, nutrient mobilization, and enhanced plant fitness. Such strains can be promising candidates for developing "cyanobacteria colonized-nitrogen-fixing rice plants" in the future. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanoscale-Barrier Formation Induced by Low-Dose Electron-Beam Exposure in Ultrathin MoS2 Transistors.

PubMed

Matsunaga, Masahiro; Higuchi, Ayaka; He, Guanchen; Yamada, Tetsushi; Krüger, Peter; Ochiai, Yuichi; Gong, Yongji; Vajtai, Robert; Ajayan, Pulickel M; Bird, Jonathan P; Aoki, Nobuyuki

2016-10-05

Utilizing an innovative combination of scanning-probe and spectroscopic techniques, supported by first-principles calculations, we demonstrate how electron-beam exposure of field-effect transistors, implemented from ultrathin molybdenum disulfide (MoS 2 ), may cause nanoscale structural modifications that in turn significantly modify the electrical operation of these devices. Quite surprisingly, these modifications are induced by even the relatively low electron doses used in conventional electron-beam lithography, which are found to induce compressive strain in the atomically thin MoS 2 . Likely arising from sulfur-vacancy formation in the exposed regions, the strain gives rise to a local widening of the MoS 2 bandgap, an idea that is supported both by our experiment and by the results of first-principles calculations. A nanoscale potential barrier develops at the boundary between exposed and unexposed regions and may cause extrinsic variations in the resulting electrical characteristics exhibited by the transistor. The widespread use of electron-beam lithography in nanofabrication implies that the presence of such strain must be carefully considered when seeking to harness the potential of atomically thin transistors. At the same time, this work also promises the possibility of exploiting the strain as a means to achieve "bandstructure engineering" in such devices.

Copper tolerance in Frankia sp. strain EuI1c involves surface binding and copper transport.

PubMed

Rehan, Medhat; Furnholm, Teal; Finethy, Ryan H; Chu, Feixia; El-Fadly, Gomaah; Tisa, Louis S

2014-09-01

Several Frankia strains have been shown to be copper-tolerant. The mechanism of their copper tolerance was investigated for Frankia sp. strain EuI1c. Copper binding was shown by binding studies. Unusual globular structures were observed on the surface of the bacterium. These globular structures were composed of aggregates containing many relatively smaller "leaf-like" structures. Scanning electron microscopy with energy-dispersive X-ray (SEM-EDAX) analysis of these structures indicated elevated copper and phosphate levels compared to the control cells. Fourier transform infrared spectroscopy (FTIR) analysis indicated an increase in extracellular phosphate on the cell surface of copper-stressed cells. Bioinformatics' analysis of the Frankia sp. strain EuI1c genome revealed five potential cop genes: copA, copZ, copC, copCD, and copD. Experiments with Frankia sp. strain EuI1c using qRT-PCR indicated an increase in messenger RNA (mRNA) levels of the five cop genes upon Cu(2+) stress. After 5 days of Cu(2+) stress, the copA, copZ, copC, copCD, and copD mRNA levels increased 25-, 8-, 18-, 18-, and 25-fold, respectively. The protein profile of Cu(2+)-stressed Frankia sp. strain EuI1c cells revealed the upregulation of a 36.7 kDa protein that was identified as FraEuI1c_1092 (sulfate-binding periplasmic transport protein). Homologues of this gene were only present in the genomes of the Cu(2+)-resistant Frankia strains (EuI1c, DC12, and CN3). These data indicate that copper tolerance by Frankia sp. strain EuI1c involved the binding of copper to the cell surface and transport proteins.

Bioassay and Scanning Electron Microscopic Observations Reveal High Virulence of Entomopathogenic Fungus, Beauveria bassiana, on the Onion Maggot (Diptera: Anthomyiidae) Adults.

PubMed

Zhang, Hui; Wu, Shengyong; Xing, Zhenlong; Wang, Xiaoqing; Lei, Zhongren

2016-12-01

When flies were dipped in 1 × 10 8 conidia/ml conidia suspensions and then kept in the incubator (22 ± 1 °C, 70 ± 5% RH), scanning electron microscope observations revealed that, at 2 h, the majority of adhering Beauveria bassiana conidia were attached to either the wing surface or the interstitial area between the macrochaetae on the thorax and abdomen of the onion maggot adults. Germ tubes were being produced and had oriented toward the cuticle by 18 h. Penetration of the insect cuticle had occurred by 36 h, and by 48 h, germ tubes had completely penetrated the cuticle. Fungal mycelia had emerged from the insect body and were proliferating after 72 h. The superficial area and structure of the wings and macrochaetae may facilitate the attachment of conidia and enable effective penetration. The susceptibility of adults to 12 isolates, at a concentration of 1 × 10 7 conidia/ml, was tested in laboratory experiments. Eight of the more potent strains caused in excess of 85% adult mortality 8 d post inoculation, while the median lethal time (LT 50 ) of these strains was <6 d. The virulence of the more effective strains was further tested, and the median lethal concentrations (LC 50 ) were calculated by exposing adults to doses ranging from 10 3 -10 7 conidia/ml. The lowest LC 50 value, found in the isolate XJWLMQ-32, for the adults was 3.87 × 10 3 conidia/ml. These results demonstrate that some B. bassiana strains are highly virulent to onion maggot adults and should be considered as potential biocontrol agents against the adult flies. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

A novel compliance measurement in radial arteries using strain-gauge plethysmography.

PubMed

Liu, Shing-Hong; Tyan, Chu-Chang; Chang, Kang-Ming

2009-09-01

We propose a novel method for assessing the compliance of the radial artery by using a two-axis mechanism and a standard positioning procedure for detecting the optimal measuring site. A modified sensor was designed to simultaneously measure the arterial diameter change waveform (ADCW) and pressure pulse waveform with a strain gauge and piezoresistor. In the x-axis scanning, the sensor could be placed close to the middle of the radial artery when the ADCW reached the maximum amplitude. In the Z-axis scanning, the contact pressure was continuously increased for data measurement. Upon the deformation of the strain gauge following the change in the vascular cross-section, the ADCW was transferred to the change of the vascular radius. The loaded strain compliance of the radial artery (C(strain)) can be determined by dividing the dynamic changed radius by the pulse pressure. Twenty-three untreated, mild or moderate hypertensive patients aged 29-85 were compared with 14 normotensive patients aged 25-62. The maximum strain compliance between the two groups was significantly different (p < 0.005). Of the hypertensive patients, 14 were at risk of developing hyperlipidemia. There was a significant difference between this and the normotension group (p < 0.005).

Virtual Patterson Experiment - A Way to Access the Rheology of Aggregates and Melanges

NASA Astrophysics Data System (ADS)

Delannoy, Thomas; Burov, Evgueni; Wolf, Sylvie

2014-05-01

Understanding the mechanisms of lithospheric deformation requires bridging the gap between human-scale laboratory experiments and the huge geological objects they represent. Those experiments are limited in spatial and time scale as well as in choice of materials (e.g., mono-phase minerals, exaggerated temperatures and strain rates), which means that the resulting constitutive laws may not fully represent real rocks at geological spatial and temporal scales. We use the thermo-mechanical numerical modelling approach as a tool to link both experiments and nature and hence better understand the rheology of the lithosphere, by enabling us to study the behavior of polymineralic aggregates and their impact on the localization of the deformation. We have adapted the large strain visco-elasto-plastic Flamar code to allow it to operate at all spatial and temporal scales, from sub-grain to geodynamic scale, and from seismic time scales to millions of years. Our first goal was to reproduce real rock mechanics experiments on deformation of mono and polymineralic aggregates in Patterson's load machine in order to deepen our understanding of the rheology of polymineralic rocks. In particular, we studied in detail the deformation of a 15x15 mm mica-quartz sample at 750 °C and 300 MPa. This mixture includes a molten phase and a solid phase in which shear bands develop as a result of interactions between ductile and brittle deformation and stress concentration at the boundaries between weak and strong phases. We used digitized x-ray scans of real samples as initial configuration for the numerical models so the model-predicted deformation and stress-strain behavior can match those observed in the laboratory experiment. Analyzing the numerical experiments providing the best match with the press experiments and making other complementary models by changing different parameters in the initial state (strength contrast between the phases, proportions, microstructure, etc.) provides a number of new elements of understanding of the mechanisms governing the localization of the deformation across the aggregates. We next used stress-strain curves derived from the numerical experiments to study in detail the evolution of the rheological behavior of each mineral phase as well as that of the mixtures in order to formulate constitutive relations for mélanges and polymineralic aggregates. The next step of our approach would be to link the constitutive laws obtained at small scale (laws that govern the rheology of a polymineralic aggregate, the effect of the presence of a molten phase, etc.) to the large-scale behavior of the Earth by implementing them in lithosphere-scale models.

Position-based scanning for comparative genomics and identification of genetic islands in Haemophilus influenzae type b.

PubMed

Bergman, Nicholas H; Akerley, Brian J

2003-03-01

Bacteria exhibit extensive genetic heterogeneity within species. In many cases, these differences account for virulence properties unique to specific strains. Several such loci have been discovered in the genome of the type b serotype of Haemophilus influenzae, a human pathogen able to cause meningitis, pneumonia, and septicemia. Here we report application of a PCR-based scanning procedure to compare the genome of a virulent type b (Hib) strain with that of the laboratory-passaged Rd KW20 strain for which a complete genome sequence is available. We have identified seven DNA segments or H. influenzae genetic islands (HiGIs) present in the type b genome and absent from the Rd genome. These segments vary in size and content and show signs of horizontal gene transfer in that their percent G+C content differs from that of the rest of the H. influenzae genome, they contain genes similar to those found on phages or other mobile elements, or they are flanked by DNA repeats. Several of these loci represent potential pathogenicity islands, because they contain genes likely to mediate interactions with the host. These newly identified genetic islands provide areas of investigation into both the evolution and pathogenesis of H. influenzae. In addition, the genome scanning approach developed to identify these islands provides a rapid means to compare the genomes of phenotypically diverse bacterial strains once the genome sequence of one representative strain has been determined.

Direct imaging of defect formation in strained organic flexible electronics by Scanning Kelvin Probe Microscopy

PubMed Central

Cramer, Tobias; Travaglini, Lorenzo; Lai, Stefano; Patruno, Luca; de Miranda, Stefano; Bonfiglio, Annalisa; Cosseddu, Piero; Fraboni, Beatrice

2016-01-01

The development of new materials and devices for flexible electronics depends crucially on the understanding of how strain affects electronic material properties at the nano-scale. Scanning Kelvin-Probe Microscopy (SKPM) is a unique technique for nanoelectronic investigations as it combines non-invasive measurement of surface topography and surface electrical potential. Here we show that SKPM in non-contact mode is feasible on deformed flexible samples and allows to identify strain induced electronic defects. As an example we apply the technique to investigate the strain response of organic thin film transistors containing TIPS-pentacene patterned on polymer foils. Controlled surface strain is induced in the semiconducting layer by bending the transistor substrate. The amount of local strain is quantified by a mathematical model describing the bending mechanics. We find that the step-wise reduction of device performance at critical bending radii is caused by the formation of nano-cracks in the microcrystal morphology of the TIPS-pentacene film. The cracks are easily identified due to the abrupt variation in SKPM surface potential caused by a local increase in resistance. Importantly, the strong surface adhesion of microcrystals to the elastic dielectric allows to maintain a conductive path also after fracture thus providing the opportunity to attenuate strain effects. PMID:27910889

The effect of the pore-fluid factor on strength and failure mechanism of Wilkeson sandstone

NASA Astrophysics Data System (ADS)

Kätker, A. K.; Rempe, M.; Renner, J.

2016-12-01

The effective stress law, σn,eff = σn - αpf, is a central tool in analysing phenomena related to hydromechanical coupling, such as fluid-induced seismicity or aftershock activity. The effective-stress coefficient α assumes different values for specific physical properties and may deviate from 1. The limited number of studies suggest that brittle compressive strength obeys an effective-stress law when effective drainage is achieved. Yet, open questions remain regarding, e.g., the role of the loading path. We performed suites of triaxial compression tests on samples of Wilkeson sandstone at a range of pore-fluid pressures but identical effective confining pressure (60, 100, and 120 MPa) maintaining the pore-fluid factor λ = pf / pc constant (0.05, 0.2, 0.4, 0.55) during the isostatic loading stage to ensure uniform loading paths. Samples were shortened with a strain rate of 4×10-7 s-1 yielding drained conditions. All tests were terminated at a total axial strain of 4.5% for comparability of microstructures. The tests also included continuous permeability determination and ultrasonic p-wave-velocity measurements to monitor microstructural evolution. Results from experiments conducted at peff = 100 MPa show that dry samples exhibit a higher peak strength and brittle failure while water-saturated samples tend to deform at lower stress by cataclastic flow indicating physico-chemical weakening. Regardless of pore-fluid factor, the saturated experiments exhibit similar peak and residual strength. Differences in failure mechanism (degree of macroscopic localization) and volumetric strain evolution are however noticed, albeit without systematic relation to pore-fluid factor. Microstructure analyses by optical and scanning electron microscopy revealed an evolution from localized shear zones in dry experiments and experiments with a low pore-fluid factor to rather distributed cataclastic flow for experiments with high pore fluid factors. Yet, mechanical and structural differences observed so far may result from sample-to-sample variability and the proximity of the experimental conditions to the brittle-ductile transition.

Effects of harmful cyanobacteria on the freshwater pathogenic free-living amoeba Acanthamoeba castellanii.

PubMed

Urrutia-Cordero, Pablo; Agha, Ramsy; Cirés, Samuel; Lezcano, María Ángeles; Sánchez-Contreras, María; Waara, Karl-Otto; Utkilen, Hans; Quesada, Antonio

2013-04-15

Grazing is a major regulating factor in cyanobacterial population dynamics and, subsequently, considerable effort has been spent on investigating the effects of cyanotoxins on major metazoan grazers. However, protozoan grazers such as free-living amoebae can also feed efficiently on cyanobacteria, while simultaneously posing a major threat for public health as parasites of humans and potential reservoirs of opportunistic pathogens. In this study, we conducted several experiments in which the freshwater amoeba Acanthamoeba castellanii was exposed to pure microcystin-LR (MC-LR) and six cyanobacterial strains, three MC-producing strains (MC-LR, MC-RR, MC-YR, MC-WR, [Dha7] MC-RR) and three strains containing other oligopeptides such as anabaenopeptins and cyanopeptolins. Although the exposure to high concentrations of pure MC-LR yielded no effects on amoeba, all MC-producing strains inflicted high mortality rates on amoeba populations, suggesting that toxic effects must be mediated through the ingestion of toxic cells. Interestingly, an anabaenopeptin-producing strain caused the greatest inhibition of amoeba growth, indicating that toxic bioactive compounds other than MCs are of great importance for amoebae grazers. Confocal scanning microscopy revealed different alterations in amoeba cytoskeleton integrity and as such, the observed declines in amoeba densities could have indeed been caused via a cascade of cellular events primarily triggered by oligopeptides with protein-phosphatase inhibition capabilities such as MCs or anabaenopeptins. Moreover, inducible-defense mechanisms such as the egestion of toxic, MC-producing cyanobacterial cells and the increase of resting stages (encystation) in amoebae co-cultivated with all cyanobacterial strains were observed in our experiments. Consequently, cyanobacterial strains showed different susceptibilities to amoeba grazing which were possibly influenced by the potentiality of their toxic secondary metabolites. Hence, this study shows the importance of cyanobacterial toxicity against amoeba grazing and, that cyanobacteria may contain a wide range of chemical compounds capable of negatively affect free-living, herbivorous amoebae. Moreover, this is of high importance for understanding the interactions and population dynamics of such organisms in aquatic ecosystems. Copyright © 2012 Elsevier B.V. All rights reserved.

Data mining graphene: Correlative analysis of structure and electronic degrees of freedom in graphenic monolayers with defects

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

Ziatdinov, Maxim A.; Fujii, Shintaro; Kiguchi, Manabu

The link between changes in the material crystal structure and its mechanical, electronic, magnetic, and optical functionalities known as the structure-property relationship is the cornerstone of the contemporary materials science research. The recent advances in scanning transmission electron and scanning probe microscopies (STEM and SPM) have opened an unprecedented path towards examining the materials structure property relationships on the single-impurity and atomic-configuration levels. Lacking, however, are the statistics-based approaches for cross-correlation of structure and property variables obtained in different information channels of the STEM and SPM experiments. Here we have designed an approach based on a combination of sliding windowmore » Fast Fourier Transform, Pearson correlation matrix, linear and kernel canonical correlation, to study a relationship between lattice distortions and electron scattering from the SPM data on graphene with defects. Our analysis revealed that the strength of coupling to strain is altered between different scattering channels which can explain coexistence of several quasiparticle interference patterns in the nanoscale regions of interest. In addition, the application of the kernel functions allowed us extracting a non-linear component of the relationship between the lattice strain and scattering intensity in graphene. Lastly, the outlined approach can be further utilized to analyzing correlations in various multi-modal imaging techniques where the information of interest is spatially distributed and has usually a complex multidimensional nature.« less

Microstructure and thermomechanical properties relationship of segmented thermoplastic polyurethane (TPU)

NASA Astrophysics Data System (ADS)

Frick, Achim; Borm, Michael; Kaoud, Nouran; Kolodziej, Jan; Neudeck, Jens

2014-05-01

Thermoplastic polyurethanes (TPU) are important polymeric materials for seals. In competition with Acrylonitrile butadiene rubbers (NBR), TPU exhibits higher strength and a considerable better abrasion resistance. The advantage of NBR over TPU is a smaller compression set but however TPU excels in its much shorter processing cycle times. Generally a TPU is a block copolymer composed of hard and soft segments, which plays an important role in determining the material properties. TPU can be processed either to ready moulded parts or can be incorporated by multi component moulding, in both cases it shows decent mechanical properties. In the present work, the relationship between melt-process induced TPU morphology and resultant thermo mechanical properties were examined and determined by means of quasi-static tensile test, creep experiment, tension test and dynamical mechanical analysis (DMA). Scanning electron beam microscope (SEM) and differential scanning calorimeter (DSC) were used to study the morphology of the samples. A significant mathematical description of the stress-strain behaviour of TPU was found using a 3 term approach. Moreover it became evident that processing conditions such as processing temperature have crucial influence on morphology as well as short and long-term performance. To be more precise, samples processed at higher temperatures showed a lack of large hard segment agglomerates, a smaller strength for strains up to 250% and higher creep compliance.

Data mining graphene: Correlative analysis of structure and electronic degrees of freedom in graphenic monolayers with defects

DOE PAGES

Ziatdinov, Maxim A.; Fujii, Shintaro; Kiguchi, Manabu; ...

2016-11-09

The link between changes in the material crystal structure and its mechanical, electronic, magnetic, and optical functionalities known as the structure-property relationship is the cornerstone of the contemporary materials science research. The recent advances in scanning transmission electron and scanning probe microscopies (STEM and SPM) have opened an unprecedented path towards examining the materials structure property relationships on the single-impurity and atomic-configuration levels. Lacking, however, are the statistics-based approaches for cross-correlation of structure and property variables obtained in different information channels of the STEM and SPM experiments. Here we have designed an approach based on a combination of sliding windowmore » Fast Fourier Transform, Pearson correlation matrix, linear and kernel canonical correlation, to study a relationship between lattice distortions and electron scattering from the SPM data on graphene with defects. Our analysis revealed that the strength of coupling to strain is altered between different scattering channels which can explain coexistence of several quasiparticle interference patterns in the nanoscale regions of interest. In addition, the application of the kernel functions allowed us extracting a non-linear component of the relationship between the lattice strain and scattering intensity in graphene. Lastly, the outlined approach can be further utilized to analyzing correlations in various multi-modal imaging techniques where the information of interest is spatially distributed and has usually a complex multidimensional nature.« less

Expression of ESBL-like activity in infrequently encountered members of the family Enterobacteriaceae.

PubMed

Abbott, Sharon L; Lidgard, Janice A; Cheung, Wendy K W; Obeso, Martha N; Berrada, Zenda L; Janda, J Michael

2012-03-01

A collection of 94 unusual members of the Enterobacteriaceae were screened for the presence of extended spectrum β-lactamases (ESBLs) using the MicroScan ESβL plus dried confirmation panel. Presumptively positive strains were then confirmed for the presence of an ESBL by double disk diffusion, E-test strips (AB Biodisk, Solna, Sweden) and PCR for SHV, TEM, and CTX-M2 genes. Of the 18 strains initially positive on the ESβL panel only three strains (Leminorella grimontii, Klebsiella ozaenae, and Kluyvera ascorbata) were positive by confirmation methods. These results suggest laboratories should be cautious regarding the methodology employed in screening for the presence of ESBLs in enteric bacteria. However, it should be noted that of the 94 strains, 29 were found to be resistant to two or more of the antibiotics present in the MicroScan ESβL plus panel indicating that there are potential treatment issues with these organisms despite their lack of ESBLs.

In vitro inhibitory effects of farnesol and interactions between farnesol and antifungals against biofilms of Candida albicans resistant strains.

PubMed

Xia, Jinping; Qian, Fang; Xu, Wenqian; Zhang, Zhenzhen; Wei, Xin

2017-04-01

Antifungal resistance is a serious problem in clinical infections. Farnesol, which is a potential antifungal agent against biofilms formed by Candida albicans resistant strains (a fluconazole-resistant isolate derived from SC5314 and two clinical Candida resistant isolates), was investigated in this study. The inhibitory effects of farnesol on biofilms were examined by XTT assay. The morphological changes and biofilm thicknesses were analyzed by scanning electron microscopy and confocal laser scanning microscopy, respectively. Additionally, the checkerboard microdilution method was used to investigate the interactions between farnesol and antifungals (fluconazole, amphotericin B, caspofungin, itraconazole, terbinafine and 5-flurocytosine) against biofilms. The results showed decreased SMICs of farnesol and thinner biofilms in the farnesol-treated groups, indicating that farnesol inhibited the development of biofilms formed by the resistant strain. Furthermore, there were synergistic effects between farnesol and fluconazole/5-flurocytosine, while there were antagonistic effects between farnesol and terbinafine/itraconazole, respectively, on the biofilms formed by the resistant strains.

A 3D finite element model of an implanted scapula: importance of a multiparametric validation using experimental data.

PubMed

Maurel, N; Diop, A; Grimberg, J

2005-09-01

In order to help to understand the loosening phenomenon around glenoïd prostheses, a 3D finite element model of a previously tested implanted scapula has been developed. The construction of the model was done using CT scans of the tested scapula. Different bone material properties were tested and shell elements or 8 nodes hexaedric elements were used to model the cortical bone. Surface contact elements were introduced on one hand between the bone and the lower part of the plate of the implant, and on the other, between the loading metallic ball and the upper surface of the implant. The results of the model were compared with those issued from in vitro experiments carried out on the same scapula. The evaluation of the model was done for nine cases of loading of 500 N distributed on the implant, in terms of strains (principal strains of six spots around peripheral cortex of the glenoïd) and displacement of four points positioned on the implant. The best configuration of the model presented here, fits with experiments for most of the strains (difference lower than 150microdef) but it seems to be still too stiff (mainly in the lower part). Nevertheless, we want, in this paper, to underline the importance of doing a multiparametric validation for such a model. Indeed, some models can give correct results for one case of loading but bad results for another kind of loading, some others can give good results for one kind of compared parameters (like strains for instance) but bad results for the other one (like displacements).

Noninvasive detection of intimal xanthoma using combined ultrasound, strain rate and photoacoustic imaging.

PubMed

Graf, Iulia M; Kim, Seungsoo; Wang, Bo; Smalling, Richard; Emelianov, Stanislav

2012-03-01

The structure, composition and mechanics of carotid artery are good indicators of early progressive atherosclerotic lesions. The combination of three imaging modalities (ultrasound, strain rate and photoacoustic imaging) which could provide corroborative information about the named arterial properties could enhance the characterization of intimal xanthoma. The experiments were performed using a New Zealand white rabbit model of atherosclerosis. The aorta excised from an atherosclerotic rabbit was scanned ex vivo using the three imaging techniques: (1) ultrasound imaging of the longitudinal section: standard ultrasound B-mode (74Hz frame rate); (2) strain rate imaging: the artery was flushed with blood and a 1.5Hz physiologic pulsation was induced, while the ultrasound data were recorded at higher frame rate (296Hz); (3) photoacoustic imaging: the artery was irradiated with nanosecond pulsed laser light of low fluence in the 1210-1230nm wavelength range and the photoacoustic data was recorded at 10Hz frame rate. Post processing algorithms based on cross-correlation and optical absorption variation were implemented to derive strain rate and spectroscopic photoacoustic images, respectively. Based on the spatio-temporal variation in displacement of different regions within the arterial wall, strain rate imaging reveals differences in tissue mechanical properties. Additionally, spectroscopic photoacoustic imaging can spatially resolve the optical absorption properties of arterial tissue and identify the location of lipid pools. The study demonstrates that ultrasound, strain rate and photoacoustic imaging can be used to simultaneously evaluate the structure, the mechanics and the composition of atherosclerotic lesions to improve the assessment of plaque vulnerability. Copyright © 2011 Elsevier B.V. All rights reserved.

Work Hardening Behavior of 1020 Steel During Cold-Beating Simulation

NASA Astrophysics Data System (ADS)

CUI, Fengkui; LING, Yuanfei; XUE, Jinxue; LIU, Jia; LIU, Yuhui; LI, Yan

2017-03-01

The present research of cold-beating formation mainly focused on roller design and manufacture, kinematics, constitutive relation, metal flow law, thermo-mechanical coupling, surface micro-topography and microstructure evolution. However, the research on surface quality and performance of workpieces in the process of cold-beating is rare. Cold-beating simulation experiment of 1020 steel is conducted at room temperature and strain rates ranging from 2000 to 4000 s-1 base on the law of plastic forming. According to the experimental data, the model of strain hardening of 1020 steel is established, Scanning Electron Microscopy(SEM) is conducted, the mechanism of the work hardening of 1020 steel is clarified by analyzing microstructure variation of 1020 steel. It is found that the strain rate hardening effect of 1020 steel is stronger than the softening effect induced by increasing temperatures, the process of simulation cold-beating cause the grain shape of 1020 steel significant change and microstructure elongate significantly to form a fibrous tissue parallel to the direction of deformation, the higher strain rate, the more obvious grain refinement and the more hardening effect. Additionally, the change law of the work hardening rate is investigated, the relationship between dislocation density and strain, the relationship between work hardening rate and dislocation density is obtained. Results show that the change trend of the work hardening rate of 1020 steel is divided into two stages, the work hardening rate decreases dramatically in the first stage and slowly decreases in the second stage, finally tending toward zero. Dislocation density increases with increasing strain and strain rate, work hardening rate decreases with increasing dislocation density. The research results provide the basis for solving the problem of improving the surface quality and performance of workpieces under cold-beating formation of 1020 steel.

Revisiting the Cramér Rao Lower Bound for Elastography: Predicting the Performance of Axial, Lateral and Polar Strain Elastograms.

PubMed

Verma, Prashant; Doyley, Marvin M

2017-09-01

We derived the Cramér Rao lower bound for 2-D estimators employed in quasi-static elastography. To illustrate the theory, we modeled the 2-D point spread function as a sinc-modulated sine pulse in the axial direction and as a sinc function in the lateral direction. We compared theoretical predictions of the variance incurred in displacements and strains when quasi-static elastography was performed under varying conditions (different scanning methods, different configuration of conventional linear array imaging and different-size kernels) with those measured from simulated or experimentally acquired data. We performed studies to illustrate the application of the derived expressions when performing vascular elastography with plane wave and compounded plane wave imaging. Standard deviations in lateral displacements were an order higher than those in axial. Additionally, the derived expressions predicted that peak performance should occur when 2% strain is applied, the same order of magnitude as observed in simulations (1%) and experiments (1%-2%). We assessed how different configurations of conventional linear array imaging (number of active reception and transmission elements) influenced the quality of axial and lateral strain elastograms. The theoretical expressions predicted that 2-D echo tracking should be performed with wide kernels, but the length of the kernels should be selected using knowledge of the magnitude of the applied strain: specifically, longer kernels for small strains (<5%) and shorter kernels for larger strains. Although the general trends of theoretical predictions and experimental observations were similar, biases incurred during beamforming and subsample displacement estimation produced noticeable differences. Copyright © 2017 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Damage localisation and fracture propagation in granite: 4D synchrotron x-ray microtomographic observations from an in-situ triaxial deformation experiment at SOLEIL

NASA Astrophysics Data System (ADS)

Cartwright-Taylor, Alexis; Fusseis, Florian; Butler, Ian; Flynn, Michael; King, Andrew

2017-04-01

To date, most studies of damage localisation and failure have utilised indirect techniques to visualise the pathway to failure. The advent of synchrotron tomography and x-ray transparent experimental cells provides for the first time the opportunity to image localisation and fracture propagation in-situ, in real time with spatial resolutions of a few microns. We present 4D x-ray microtomographic data collected during a triaxial deformation experiment carried out at the imaging beamline PSICHE at the French Synchrotron SOLEIL. The data document damage localisation and fracture propagation in a microgranite. The sample was deformed at 15 MPa confining pressure and 3x10-5 s-1 strain rate, in a novel, miniature, x-ray transparent, triaxial deformation apparatus, designed and built at the University of Edinburgh. We used a 2.97 mm diameter x 9.46 mm long cylindrical sample of Ailsa Craig microgranite, heat treated to 600 ˚ C to introduce flaws in the form of pervasive crack damage. As the sample was loaded to failure, 21 microtomographic volumes were acquired in intervals of 5-20 MPa (decreasing as failure approached), including one scan at peak differential stress of 200 MPa (1.4 kN end load) and three post-failure scans. The scan at peak stress contained the incipient fault, and the sample failed immediately when loading continued afterwards. During scanning, a constant stress level was maintained. Individual datasets were collected in ˜10 minutes using a white beam with an energy maximum at 66 keV in a spiral configuration. Reconstructions yielded image stacks with a dimension of 1700x1700x4102 voxels with a voxel size of 2.7 μm. We analysed damage localisation and fracture propagation in the time series data. Fractures were segmented from the image data using a Multiscale Hessian fracture filter [1] and analysed for their orientations, dimensions and spatial distributions and changes in these properties during loading. Local changes in volumetric and shear strains between time steps were quantified using 3D digital image correlation [2]. In combination, these analyses show the extent and evolution of local aseismic deformation and that related to microcracking. Our results provide direct evidence of ongoing deformation processes such as micro-fracture nucleation at pre-existing flaws, in the form of cracks, grain boundaries and pores, and coalescence of en-echelon tensile micro-fractures along a shear fault in response to changes in the local stress field. These direct 4D observations of damage evolution and strain localisation complement the seminal results of Lockner et al. [3], who first imaged the process of fault growth using acoustic emissions locations. Our data provide further insight into the aseismic mechanisms that dissipate 99% of the total accumulated strain energy [4] and the interactions between these mechanisms and the developing microcracks. Our results also provide experimental verification of models for shear fracture formation whereby pre-existing flaws become connected by en-echelon tensile cracks that extend from their edges. _________________________________________ [1] Voorn et al., 2015, J. Petroleum Sci. Eng. 127, 270-285. [2] Hall, S. et al., 2010, Geotechnique 60, 315-322. [3] Lockner, D., et al., 1991, Nature 350, 39-42. [4] Byerlee, J., 1993, Geology 21, 303-306.

Small scale mechanical characterization of thin foil materials via pin load microtesting

DOE PAGES

Wheeler, Robert; Pandey, Amit; Shyam, Amit; ...

2015-05-06

In situ scanning electron microscope (SEM) experiments, where small-scale mechanical tests are conducted on micro- and nanosized specimens, allow direct visualization of elastic and plastic responses over the entirety of the volume being deformed. This enables precise spatial and temporal correlation of slip events contributing to the plastic flow evidenced in a stress–strain curve. A new pin-loading methodology has been employed, in situ within the SEM, to conduct microtensile tests on thin polycrystalline metal foils. This approach can be tailored to a specific foil whose particular grain size may range from microns to tens of microns. Manufacture of the specializedmore » pin grip was accomplished via silicon photolithography-based processing followed by subsequent focused ion beam finishing. Microtensile specimen preparation was achieved by combining a stencil mask methodology employing broad ion beam sputtering along with focused ion beam milling in the study of several metallic foil materials. Finite-element analyses were performed to characterize the stress and strain distributions in the pin grip and micro-specimen under load. Furthermore, under appropriately conceived test conditions, uniaxial stress–strain responses measured within these foils by pin-load microtensile testing exhibit properties consistent with larger scale tests.« less

X-ray scattering to probe cracks in rubbers

NASA Astrophysics Data System (ADS)

Creton, Costantino; Demassieux, Quentin; Berghezan, Daniel

Natural rubber is a well-known very tough elastomer and its toughness is generally attributed to its aptitude to crystallize under strain. Yet the mechanism linking the extent of strain induced crystallization to the toughness gamma is still unclear. We mapped by scanning microbeam X-ray diffraction (20 microns resolution), the strain induced crystallization near the crack tip of highly crosslinked and carbon-black filled natural rubbers. Experiments were carried out on static cracks loaded at different values of energy release rates G and for different filler and crosslinker concentrations. We specifically investigated the effect of the crosslinking density, the effect of thermal (oxygen-free) aging and the effect of temperature (between 23 and 100 °C). Several novel findings are reported : a significant amount of crystallization was still present at the crack tip at 100°C, thermal aging (in the absence of oxygen) greatly reduces the amount of crystallization at the crack tip without much effect on the room temperature resistance to fatigue crack propagation of the material, and an increase in crosslinking density reduces the extent of crystallinity at the crack tip for the same applied G. We acknowledge the financial support of Michelin.

Local nanoscale strain mapping of a metallic glass during in situ testing

NASA Astrophysics Data System (ADS)

Gammer, Christoph; Ophus, Colin; Pekin, Thomas C.; Eckert, Jürgen; Minor, Andrew M.

2018-04-01

The local elastic strains during tensile deformation in a CuZrAlAg metallic glass are obtained by fitting an elliptic shape function to the characteristic amorphous ring in electron diffraction patterns. Scanning nanobeam electron diffraction enables strain mapping with a resolution of a few nanometers. Here, a fast direct electron detector is used to acquire the diffraction patterns at a sufficient speed to map the local transient strain during continuous tensile loading in situ in the transmission electron microscope. The elastic strain in tensile direction was found to increase during loading. After catastrophic fracture, a residual elastic strain that relaxes over time was observed.

Research on Fracture of Aluminum Foil in Microscale Laser Peen Forming

NASA Astrophysics Data System (ADS)

Zheng, Chao; Sun, Sheng; Liu, Jing; Ji, Zhong

2010-06-01

A novel numerical method for dynamic fracture in microscale laser peen forming (μLPF) of aluminum foils was presented and the role of the die diameter on fracture behavior at the ultra high strain rate was investigated via both experimental and numerical methods. μLPF is a process in which the plastic deformation is generated through laser-induced shock wave and compressive residual stresses can be imparted to improve the fatigue life of micro parts. During μLPF, the pressure exerted on the target is higher than 1 GPa and the strain rate is greater than 106s-1, so the mechanical behavior of materials in this dynamic process is very different from that under static or quasi-static conditions. In the present study, the finite element method with grain and grain boundary elements was used to analyze the μLPF process of aluminum foils with a thickness of 60 μm. The onset and propagation of crack were simulated in this way that the specified nodes were tied together until the equivalent plastic strain exceeded a certain value. Under a given value of plastic strain, the influence of die diameters of 0.6, 1.0, and 1.6 mm on the fracture mode of the material was predicted. A series of experiments were carried out to verify the numerical model. The geometrical morphologies of fracture regions were observed via optical microscope and scan electron microscope. In results from both experiments and simulations, the size of the die diameter affects the location of the fracture: (I) Fracture appeared at the entrance of the die for die diameters of 0.6 and 1.0 mm. (II) Fracture occurred near the centre of the formed dome for 1.6 mm die diameter. The generation mechanism of two fracture modes was explained. This work provides a preliminary insight into the fracture behavior of materials under the ultra high strain rate and lays the ground work for more in-depth simulations in the future study.

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

PubMed

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

2004-11-01

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

The response of single human cells to zero gravity

NASA Technical Reports Server (NTRS)

Montgomery, P. O., Jr.; Cook, J. E.; Reynolds, R. C.; Paul, J. S.; Hayflick, L.; Stock, D.; Schulz, W. W.; Kimzey, S. L.; Thirolf, R. G.; Rogers, T.

1974-01-01

The SO15 experiment was designed to extend observations of the effects of zero-gravity to living human cells during and subsequent to a 59-day flight on Skylab 3. A strain of diploid human embryonic lung cells, WI-38, was chosen for this purpose. The studies were concerned with observations designed to detect the effects of zero-gravity on cell growth rates and on cell structure as observed by light microscopy, transmission and scanning electron microscopy and histochemistry. Studies of the effects of zero-gravity on the cell function and the cell cycle were performed by time lapse motion picture photography and microspectrophotometry. Subsequent study of the returned living cells included karotyping, G- and C-banding, and analyses of the culture media used. Some of the living cells returned were banked by deep freeze techniques for possible future experiments.

Sensitivity and ex vivo validation of finite element models of the domestic pig cranium

PubMed Central

Bright, Jen A; Rayfield, Emily J

2011-01-01

A finite element (FE) validation and sensitivity study was undertaken on a modern domestic pig cranium. Bone strain data were collected ex vivo from strain gauges, and compared with results from specimen-specific FE models. An isotropic, homogeneous model was created, then input parameters were altered to investigate model sensitivity. Heterogeneous, isotropic models investigated the effects of a constant-thickness, stiffer outer layer (representing cortical bone) atop a more compliant interior (representing cancellous bone). Loading direction and placement of strain gauges were also varied, and the use of 2D membrane elements at strain gauge locations as a method of projecting 3D model strains into the plane of the gauge was investigated. The models correctly estimate the loading conditions of the experiment, yet at some locations fail to reproduce correct principal strain magnitudes, and hence strain ratios. Principal strain orientations are predicted well. The initial model was too stiff by approximately an order of magnitude. Introducing a compliant interior reported strain magnitudes more similar to the ex vivo results without notably affecting strain orientations, ratios or contour patterns, suggesting that this simple heterogeneity was the equivalent of reducing the overall stiffness of the model. Models were generally insensitive to moderate changes in loading direction or strain gauge placement, except in the squamosal portion of the zygomatic arch. The use of membrane elements made negligible differences to the reported strains. The models therefore seem most sensitive to changes in material properties, and suggest that failure to model local heterogeneity in material properties and structure of the bone may be responsible for discrepancies between the experimental and model results. This is partially attributable to a lack of resolution in the CT scans from which the model was built, and partially due to an absence of detailed material properties data for pig cranial bone. Thus, caution is advised when using FE models to estimate absolute numerical values of breaking stress and bite force unless detailed input parameters are available. However, if the objective is to compare relative differences between models, the fact that the strain environment is replicated well means that such investigations can be robust. PMID:21718316

Static FBG strain sensor with high resolution and large dynamic range by dual-comb spectroscopy.

PubMed

Kuse, Naoya; Ozawa, Akira; Kobayashi, Yohei

2013-05-06

We demonstrate a fiber Bragg grating (FBG) strain sensor with optical frequency combs. To precisely characterize the optical response of the FBG when strain is applied, dual-comb spectroscopy is used. Highly sensitive dual-comb spectroscopy of the FBG enabled strain measurements with a resolution of 34 nε. The optical spectral bandwidth of the measurement exceeds 1 THz. Compared with conventional FBG strain sensor using a continuous-wave laser that requires rather slow frequency scanning with a limited range, the dynamic range and multiplexing capability are significantly improved by using broadband dual-comb spectroscopy.

The relationship between biofilm formations and capsule in Haemophilus influenzae.

PubMed

Qin, Liang; Kida, Yutaka; Ishiwada, Naruhiko; Ohkusu, Kiyofumi; Kaji, Chiharu; Sakai, Yoshiro; Watanabe, Kiwao; Furumoto, Akitsugu; Ichinose, Akitoyo; Watanabe, Hiroshi

2014-03-01

To evaluate the biofilm formation of non-typeable Haemophilus influenzae (NTHi) and H. influenzae type b (Hib) clinical isolates, we conducted the following study. Serotyping and polymerase chain reaction were performed to identify β-lactamase-negative ampicillin (ABPC)-susceptible (BLNAS), β-lactamase-negative ABPC-resistant (BLNAR), TEM-1 type β-lactamase-producing ABPC-resistant (BLPAR)-NTHi, and Hib. Biofilm formation was investigated by microtiter biofilm assay, as well as visually observation with a scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) in a continuous-flow chamber. As a result, totally 99 strains were investigated, and were classified into 4 groups which were 26 gBLNAS, 22 gBLNAR, 28 gBLPAR-NTHi and 23 Hib strains. The mean OD600 in the microtiter biofilm assay of gBLNAS, gBLNAR, gBLPAR-NTHi, and Hib strains were 0.57, 0.50, 0.34, and 0.08, respectively. NTHi strains were similar in terms of biofilm formations, which were observed by SEM and CLSM. Five Hib strains with the alternated type b cap loci showed significantly increased biofilm production than the other Hib strains. In conclusion, gBLNAS, gBLNAR, and gBLPAR-NTHi strains were more capable to produce biofilms compared to Hib strains. Our data suggested that resistant status may not be a key factor but capsule seemed to play an important role in H. influenzae biofilm formation. Copyright © 2013 Japanese Society of Chemotherapy and the Japanese Association for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

Antibacterial activity of extracellular compounds produced by a Pseudomonas strain against methicillin-resistant Staphylococcus aureus (MRSA) strains

PubMed Central

2013-01-01

Background The emergence of multidrug-resistant bacteria is a world health problem. Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA) strains, is one of the most important human pathogens associated with hospital and community-acquired infections. The aim of this work was to evaluate the antibacterial activity of a Pseudomonas aeruginosa-derived compound against MRSA strains. Methods Thirty clinical MRSA strains were isolated, and three standard MRSA strains were evaluated. The extracellular compounds were purified by vacuum liquid chromatography. Evaluation of antibacterial activity was performed by agar diffusion technique, determination of the minimal inhibitory concentration, curve of growth and viability and scanning electron microscopy. Interaction of an extracellular compound with silver nanoparticle was studied to evaluate antibacterial effect. Results The F3 (ethyl acetate) and F3d (dichloromethane- ethyl acetate) fractions demonstrated antibacterial activity against the MRSA strains. Phenazine-1-carboxamide was identified and purified from the F3d fraction and demonstrated slight antibacterial activity against MRSA, and synergic effect when combined with silver nanoparticles produced by Fusarium oxysporum. Organohalogen compound was purified from this fraction showing high antibacterial effect. Using scanning electron microscopy, we show that the F3d fraction caused morphological changes to the cell wall of the MRSA strains. Conclusions These results suggest that P. aeruginosa-produced compounds such as phenazines have inhibitory effects against MRSA and may be a good alternative treatment to control infections caused by MRSA. PMID:23773484

Differential Scanning Calorimetric (DSC) Analysis of Rotary Nickel-Titanium (NiTi) Endodontic File (RNEF)

NASA Astrophysics Data System (ADS)

Wu, Ray Chun Tung; Chung, C. Y.

2012-12-01

To determine the variation of A f along the axial length of rotary nickel-titanium endodontic files (RNEF). Three commercial brands of 4% taper RNEF: GTX (#20, 25 mm, Dentsply Tulsa Dental Specialties, Tulsa, OK, USA), K3 (#25, 25 mm) and TF (Twisted File #25, 27 mm) (Sybron Kerr, Orange, CA, USA) were cut into segments at 4 mm increment from the working tip. Regional specimens were measured for differential heat-flow over thermal cycling, generally with continuous heating or cooling (5 °C/min) and 5 min hold at set temperatures (start, finish temperatures): GTX: -55, 90 °C; K3: -55, 45 °C; TF: -55, 60 °C; using differential scanning calorimeter. This experiment demonstrated regional differences in A f along the axial length of GTX and K3 files. Similar variation was not obvious in the TF samples. A contributory effect of regional difference in strain-hardening due to grinding and machining during manufacturing is proposed.

Strain-induced structure transformations on Si(111) and Ge(111) surfaces: a combined density-functional and scanning tunneling microscopy study.

PubMed

Zhachuk, R; Teys, S; Coutinho, J

2013-06-14

Si(111) and Ge(111) surface formation energies were calculated using density functional theory for various biaxial strain states ranging from -0.04 to 0.04, and for a wide set of experimentally observed surface reconstructions: 3 × 3, 5 × 5, 7 × 7 dimer-adatom-stacking fault reconstructions and c(2 × 8), 2 × 2, and √3×√3 adatoms based surfaces. The calculations are compared with scanning tunneling microscopy data obtained on stepped Si(111) surfaces and on Ge islands grown on a Si(111) substrate. It is shown that the surface structure transformations observed in these strained systems are accounted for by a phase diagram that relates the equilibrium surface structure to the applied strain. The calculated formation energy of the unstrained Si(111)-9 × 9 dimer-adatom-stacking fault surface is reported for the first time and it is higher than corresponding energies of Si(111)-5 × 5 and Si(111)-7 × 7 dimer-adatom-stacking fault surfaces as expected. We predict that the Si(111) surface should adopt a c(2 × 8) reconstruction when tensile strain is above 0.03.

Disorganization of cell division of methicillin-resistant Staphylococcus aureus by methanolic extract from Phyllanthus columnaris stem bark

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

Adnalizawati, A. Siti Noor; Nazlina, I.; Yaacob, W. A.

The in vitro activity of methanolic extract from Phyllanthus columnaris stem bark was studied against Methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300 and MRSA BM1 (clinical strain) using time-kill curves in conjunction with scanning and transmission electron microscopy. The extract showed more markedly bactericidal activity in MRSA BM1 clinical strain within less than 4 h by 6.25-12.5 mg/mL and within 6 h by 1.56 mg/mL. Scanning electron microscopy of MRSA BM1 revealed distortion of cell whilst transmission electron microscopy revealed disruption in cell wall division.

Disorganization of cell division of methicillin-resistant Staphylococcus aureus by methanolic extract from Phyllanthus columnaris stem bark

NASA Astrophysics Data System (ADS)

Adnalizawati, A. Siti Noor; Nazlina, I.; Yaacob, W. A.

2013-11-01

The in vitro activity of methanolic extract from Phyllanthus columnaris stem bark was studied against Methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300 and MRSA BM1 (clinical strain) using time-kill curves in conjunction with scanning and transmission electron microscopy. The extract showed more markedly bactericidal activity in MRSA BM1 clinical strain within less than 4 h by 6.25-12.5 mg/mL and within 6 h by 1.56 mg/mL. Scanning electron microscopy of MRSA BM1 revealed distortion of cell whilst transmission electron microscopy revealed disruption in cell wall division.

View of the bacterial strains of Escherichia coli M-17 and its interaction with the nanoparticles of zinc oxide by means of atomic force microscopy

NASA Astrophysics Data System (ADS)

Sagitova, A.; Yaminsky, I.; Meshkov, G.

2016-08-01

Visualization of the structure of biological objects plays a key role in medicine, biotechnology, nanotechnology and IT-technology. Atomic force microscopy (AFM) is a promising method of studying of objects’ morphology and structure. In this work, AFM was used to determine the size and shape of the bacterial strains of Escherichia coli M-17 and visualization its interaction with the nanoparticles of zinc oxide. The suspension of E.coli bacteria was applied to natural mica and studied by contact mode using the FemtoScan multifunctional scanning probe microscope.

Rotating-unbalanced-mass Devices for Scanning Balloon-borne Experiments, Free-flying Spacecraft, and Space Shuttle/space Station Experiments

NASA Technical Reports Server (NTRS)

Polites, Michael E.

1990-01-01

A new method is presented for scanning balloon-borne experiments, free-flying spacecraft, and gimballed experiments mounted to the space shuttle or the space station. It uses rotating-unbalanced-mass (RUM) devices for generating circular, line, or raster scan patterns and an auxiliary control system for target acquisition, keeping the scan centered on the target, and producing complementary motion for raster scanning. It is ideal for applications where the only possible way to accomplish the required scan is to physically scan the entire experiment or spacecraft as in x ray and gamma ray experiments. In such cases, this new method should have advantages over prior methods in terms of either power, weight, cost, performance, stability, or a combination of these.

Noninvasive characterization of carotid plaque strain.

PubMed

Khan, Amir A; Sikdar, Siddhartha; Hatsukami, Thomas; Cebral, Juan; Jones, Michael; Huston, John; Howard, George; Lal, Brajesh K

2017-06-01

Current risk stratification of internal carotid artery plaques based on diameter-reducing percentage stenosis may be unreliable because ischemic stroke results from plaque disruption with atheroembolization. Biomechanical forces acting on the plaque may render it vulnerable to rupture. The feasibility of ultrasound-based quantification of plaque displacement and strain induced by hemodynamic forces and their relationship to high-risk plaques have not been determined. We studied the feasibility and reliability of carotid plaque strain measurement from clinical B-mode ultrasound images and the relationship of strain to high-risk plaque morphology. We analyzed carotid ultrasound B-mode cine loops obtained in patients with asymptomatic ≥50% stenosis during routine clinical scanning. Optical flow methods were used to quantify plaque motion and shear strain during the cardiac cycle. The magnitude (maximum absolute shear strain rate [MASSR]) and variability (entropy of shear strain rate [ESSR] and variance of shear strain rate [VSSR]) of strain were combined into a composite shear strain index (SSI), which was assessed for interscan repeatability and correlated with plaque echolucency. Nineteen patients (mean age, 70 years) constituting 36 plaques underwent imaging; 37% of patients (n = 7) showed high strain (SSI ≥0.5; MASSR, 2.2; ESSR, 39.7; VSSR, 0.03) in their plaques; the remaining clustered into a low-strain group (SSI <0.5; MASSR, 0.58; ESSR, 21.2; VSSR, 0.002). The area of echolucent morphology was greater in high-strain plaques vs low-strain plaques (28% vs 17%; P = .018). Strain measurements showed low variability on Bland-Altman plots with cluster assignment agreement of 76% on repeated scanning. Two patients developed a stroke during 2 years of follow-up; both demonstrated high SSI (≥0.5) at baseline. Carotid plaque strain is reliably computed from routine B-mode imaging using clinical ultrasound machines. High plaque strain correlates with known high-risk echolucent morphology. Strain measurement can complement identification of patients at high risk for plaque disruption and stroke. Copyright © 2017 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.

Characterization and comparison of biofilm development by pathogenic and commensal isolates of Histophilus somni.

PubMed

Sandal, Indra; Hong, Wenzhou; Swords, W Edward; Inzana, Thomas J

2007-11-01

Histophilus somni (Haemophilus somnus) is an obligate inhabitant of the mucosal surfaces of bovines and sheep and an opportunistic pathogen responsible for respiratory disease, meningoencephalitis, myocarditis, arthritis, and other systemic infections. The identification of an exopolysaccharide produced by H. somni prompted us to evaluate whether the bacterium was capable of forming a biofilm. After growth in polyvinyl chloride wells a biofilm was formed by all strains examined, although most isolates from systemic sites produced more biofilm than commensal isolates from the prepuce. Biofilms of pneumonia isolate strain 2336 and commensal isolate strain 129Pt were grown in flow cells, followed by analysis by confocal laser scanning microscopy and scanning electron microscopy. Both strains formed biofilms that went through stages of attachment, growth, maturation, and detachment. However, strain 2336 produced a mature biofilm that consisted of thick, homogenous mound-shaped microcolonies encased in an amorphous extracellular matrix with profound water channels. In contrast, strain 129Pt formed a biofilm of cell clusters that were tower-shaped or distinct filamentous structures intertwined with each other by strands of extracellular matrix. The biofilm of strain 2336 had a mass and thickness that was 5- to 10-fold greater than that of strain 129Pt and covered 75 to 82% of the surface area, whereas the biofilm of strain 129Pt covered 35 to 40% of the surface area. Since H. somni is an obligate inhabitant of the bovine and ovine host, the formation of a biofilm may be crucial to its persistence in vivo, and our in vitro evidence suggests that formation of a more robust biofilm may provide a selective advantage for strains that cause systemic disease.

Characterization and Comparison of Biofilm Development by Pathogenic and Commensal Isolates of Histophilus somni▿

PubMed Central

Sandal, Indra; Hong, Wenzhou; Swords, W. Edward; Inzana, Thomas J.

2007-01-01

Histophilus somni (Haemophilus somnus) is an obligate inhabitant of the mucosal surfaces of bovines and sheep and an opportunistic pathogen responsible for respiratory disease, meningoencephalitis, myocarditis, arthritis, and other systemic infections. The identification of an exopolysaccharide produced by H. somni prompted us to evaluate whether the bacterium was capable of forming a biofilm. After growth in polyvinyl chloride wells a biofilm was formed by all strains examined, although most isolates from systemic sites produced more biofilm than commensal isolates from the prepuce. Biofilms of pneumonia isolate strain 2336 and commensal isolate strain 129Pt were grown in flow cells, followed by analysis by confocal laser scanning microscopy and scanning electron microscopy. Both strains formed biofilms that went through stages of attachment, growth, maturation, and detachment. However, strain 2336 produced a mature biofilm that consisted of thick, homogenous mound-shaped microcolonies encased in an amorphous extracellular matrix with profound water channels. In contrast, strain 129Pt formed a biofilm of cell clusters that were tower-shaped or distinct filamentous structures intertwined with each other by strands of extracellular matrix. The biofilm of strain 2336 had a mass and thickness that was 5- to 10-fold greater than that of strain 129Pt and covered 75 to 82% of the surface area, whereas the biofilm of strain 129Pt covered 35 to 40% of the surface area. Since H. somni is an obligate inhabitant of the bovine and ovine host, the formation of a biofilm may be crucial to its persistence in vivo, and our in vitro evidence suggests that formation of a more robust biofilm may provide a selective advantage for strains that cause systemic disease. PMID:17644581

New method for scanning spacecraft and balloon-borne/space-based experiments

NASA Technical Reports Server (NTRS)

Polites, Michael E.

1991-01-01

A new method is presented for scanning balloon-borne experiments, free-flying spacecraft, and gimballed experiments mounted to the space shuttle or the space station. It uses rotating-unbalanced-mass (RUM) devices for generating circular, line, or raster scan patterns and an auxiliary control system for target acquisition, keeping the scan centered on the target, and producing complementary motion for raster scanning. It is ideal for applications where the only possible way to accomplish the required scan is to physically scan the entire experiment or spacecraft as in X-ray and gamma ray experiments. In such cases, this new method should have advantages over prior methods in terms of either power, weight, cost, performance, stability, or a combination of these.

Silver nanoparticle production by Rhizopus stolonifer and its antibacterial activity against extended spectrum {beta}-lactamase producing (ESBL) strains of Enterobacteriaceae

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

Banu, Afreen; Rathod, Vandana, E-mail: drvandanarathod@rediffmail.com; Ranganath, E.

Highlights: {yields} Silver nanoparticle production by using Rhizopus stolonifer. {yields} Antibacterial activity of silver nanoparticles against extended spectrum {beta}-lactamase producing (ESBL) strains of Enterobacteriaceae. {yields} Synergistic effect of antibiotics with silver nanoparticles towards ESBL-strains. {yields} Characterization of silver nanoparticles made by UV-vis spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformed infrared (FTIR) spectroscopy, atomic force microscopy (AFM). -- Abstract: This report focuses on the synthesis of silver nanoparticles using the fungus, Rhizopus stolonifer and its antimicrobial activity. Research in nanotechnology highlights the possibility of green chemistry pathways to produce technologically important nanomaterials. Characterization of newly synthesized silvermore » nanoparticles was made by UV-visible absorption spectroscopy, scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared (FTIR) spectroscopy and atomic force microscope (AFM). TEM micrograph revealed the formation of spherical nanoparticles with size ranging between 3 and 20 nm. The biosynthesized silver nanoparticles (AgNPs) showed excellent antibacterial activity against ESBL-strains which includes E. coli, Proteus. sp. and Klebsiella sp.« less

X-ray μ-Laue diffraction analysis of Cu through-silicon vias: A two-dimensional and three-dimensional study

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

Sanchez, Dario Ferreira; Weleguela, Monica Larissa Djomeni; Audoit, Guillaume

2014-10-28

Here, white X-ray μ-beam Laue diffraction is developed and applied to investigate elastic strain distributions in three-dimensional (3D) materials, more specifically, for the study of strain in Cu 10 μm diameter–80 μm deep through-silicon vias (TSVs). Two different approaches have been applied: (i) two-dimensional μ-Laue scanning and (ii) μ-beam Laue tomography. 2D μ-Laue scans provided the maps of the deviatoric strain tensor integrated along the via length over an array of TSVs in a 100 μm thick sample prepared by Focused Ion Beam. The μ-beam Laue tomography analysis enabled to obtain the 3D grain and elemental distribution of both Cu and Si. Themore » position, size (about 3 μm), shape, and orientation of Cu grains were obtained. Radial profiles of the equivalent deviatoric strain around the TSVs have been derived through both approaches. The results from both methods are compared and discussed.« less

About the inevitable compromise between spatial resolution and accuracy of strain measurement for bone tissue: a 3D zero-strain study.

PubMed

Dall'Ara, E; Barber, D; Viceconti, M

2014-09-22

The accurate measurement of local strain is necessary to study bone mechanics and to validate micro computed tomography (µCT) based finite element (FE) models at the tissue scale. Digital volume correlation (DVC) has been used to provide a volumetric estimation of local strain in trabecular bone sample with a reasonable accuracy. However, nothing has been reported so far for µCT based analysis of cortical bone. The goal of this study was to evaluate accuracy and precision of a deformable registration method for prediction of local zero-strains in bovine cortical and trabecular bone samples. The accuracy and precision were analyzed by comparing scans virtually displaced, repeated scans without any repositioning of the sample in the scanner and repeated scans with repositioning of the samples. The analysis showed that both precision and accuracy errors decrease with increasing the size of the region analyzed, by following power laws. The main source of error was found to be the intrinsic noise of the images compared to the others investigated. The results, once extrapolated for larger regions of interest that are typically used in the literature, were in most cases better than the ones previously reported. For a nodal spacing equal to 50 voxels (498 µm), the accuracy and precision ranges were 425-692 µε and 202-394 µε, respectively. In conclusion, it was shown that the proposed method can be used to study the local deformation of cortical and trabecular bone loaded beyond yield, if a sufficiently high nodal spacing is used. Copyright © 2014 Elsevier Ltd. All rights reserved.

In-situ microscale through-silicon via strain measurements by synchrotron x-ray microdiffraction exploring the physics behind data interpretation

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

Liu, Xi; School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332; Thadesar, Paragkumar A.

2014-09-15

In-situ microscale thermomechanical strain measurements have been performed in combination with synchrotron x-ray microdiffraction to understand the fundamental cause of failures in microelectronics devices with through-silicon vias. The physics behind the raster scan and data analysis of the measured strain distribution maps is explored utilizing the energies of indexed reflections from the measured data and applying them for beam intensity analysis and effective penetration depth determination. Moreover, a statistical analysis is performed for the beam intensity and strain distributions along the beam penetration path to account for the factors affecting peak search and strain refinement procedure.

Performance of automatic scanning microscope for nuclear emulsion experiments

NASA Astrophysics Data System (ADS)

Güler, A. Murat; Altınok, Özgür

2015-12-01

The impressive improvements in scanning technology and methods let nuclear emulsion to be used as a target in recent large experiments. We report the performance of an automatic scanning microscope for nuclear emulsion experiments. After successful calibration and alignment of the system, we have reached 99% tracking efficiency for the minimum ionizing tracks that penetrating through the emulsions films. The automatic scanning system is successfully used for the scanning of emulsion films in the OPERA experiment and plan to use for the next generation of nuclear emulsion experiments.

Performance of automatic scanning microscope for nuclear emulsion experiments

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

Güler, A. Murat, E-mail: mguler@newton.physics.metu.edu.tr; Altınok, Özgür; Tufts University, Medford, MA 02155

The impressive improvements in scanning technology and methods let nuclear emulsion to be used as a target in recent large experiments. We report the performance of an automatic scanning microscope for nuclear emulsion experiments. After successful calibration and alignment of the system, we have reached 99% tracking efficiency for the minimum ionizing tracks that penetrating through the emulsions films. The automatic scanning system is successfully used for the scanning of emulsion films in the OPERA experiment and plan to use for the next generation of nuclear emulsion experiments.

Dephosphorization of High-Phosphorus Iron Ore Using Different Sources of Aspergillus niger Strains.

PubMed

Xiao, Chunqiao; Wu, Xiaoyan; Chi, Ruan

2015-05-01

High-phosphorus iron ore is traditionally dephosphorized by chemical process with inorganic acids. However, this process is not recommended nowadays because of its high cost and consequent environmental pollution. With the current tendency for development of a low-cost and eco-friendly process, dephosphorization of high-phosphorus iron ore through microbial process with three different sources of Aspergillus niger strains was studied in this study. Results show that the three strains of A. niger could grow well in the broth, and effectively remove phosphate from high-phosphorus iron ore during the experiments. Meanwhile, the total iron in the broth was also increased. Acidification of the broth seemed to be the major mechanism for the dephosphorization by these strains. High-pressure liquid chromatography analysis indicated that various organic acids were secreted in the broth, which caused a significant drop of the broth pH. Scanning electron microscopy of ore residues revealed that the high-phosphorus iron ore was obviously destroyed by the actions of these strains. Ore residues by energy-dispersive X-ray microanalysis and Fourier transform infrared spectroscopy indicated that the phosphate was obviously removed from the high-phosphorus iron ore. The optimization of the dephosphorization by these strains was also investigated, and the maximum percentages of phosphate removal were recorded at temperature 27-30 °C, initial pH 5.0-6.5, particle size 0.07-0.1 mm, and pulp density of 2-3% (w/v), respectively. The fungus A. niger was found to have good potential for the dephosphorization of high-phosphorus iron ore, and this microbial process seems to be economic and effective in the future industrial application.

Scanning the landscape of genome architecture of non-O1 and non-O139 Vibrio cholerae by whole genome mapping reveals extensive population genetic diversity

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

Chapman, Carol; Henry, Matthew; Bishop-Lilly, Kimberly A.

Historically, cholera outbreaks have been linked to V. cholerae O1 serogroup strains or its derivatives of the O37 and O139 serogroups. A genomic study on the 2010 Haiti cholera outbreak strains highlighted the putative role of non O1/non-O139 V. cholerae in causing cholera and the lack of genomic sequences of such strains from around the world. Here we address these gaps by scanning a global collection of V. cholerae strains as a first step towards understanding the population genetic diversity and epidemic potential of non O1/non-O139 strains. Whole Genome Mapping (Optical Mapping) based bar coding produces a high resolution, orderedmore » restriction map, depicting a complete view of the unique chromosomal architecture of an organism. To assess the genomic diversity of non-O1/non-O139 V. cholerae, we applied a Whole Genome Mapping strategy on a well-defined and geographically and temporally diverse strain collection, the Sakazaki serogroup type strains. Whole Genome Map data on 91 of the 206 serogroup type strains support the hypothesis that V. cholerae has an unprecedented genetic and genomic structural diversity. Interestingly, we discovered chromosomal fusions in two unusual strains that possess a single chromosome instead of the two chromosomes usually found in V. cholerae. We also found pervasive chromosomal rearrangements such as duplications and indels in many strains. The majority of Vibrio genome sequences currently in public databases are unfinished draft sequences. The Whole Genome Mapping approach presented here enables rapid screening of large strain collections to capture genomic complexities that would not have been otherwise revealed by unfinished draft genome sequencing and thus aids in assembling and finishing draft sequences of complex genomes. Furthermore, Whole Genome Mapping allows for prediction of novel V. cholerae non-O1/non-O139 strains that may have the potential to cause future cholera outbreaks.« less

Scanning the landscape of genome architecture of non-O1 and non-O139 Vibrio cholerae by whole genome mapping reveals extensive population genetic diversity.

PubMed

Chapman, Carol; Henry, Matthew; Bishop-Lilly, Kimberly A; Awosika, Joy; Briska, Adam; Ptashkin, Ryan N; Wagner, Trevor; Rajanna, Chythanya; Tsang, Hsinyi; Johnson, Shannon L; Mokashi, Vishwesh P; Chain, Patrick S G; Sozhamannan, Shanmuga

2015-01-01

Historically, cholera outbreaks have been linked to V. cholerae O1 serogroup strains or its derivatives of the O37 and O139 serogroups. A genomic study on the 2010 Haiti cholera outbreak strains highlighted the putative role of non O1/non-O139 V. cholerae in causing cholera and the lack of genomic sequences of such strains from around the world. Here we address these gaps by scanning a global collection of V. cholerae strains as a first step towards understanding the population genetic diversity and epidemic potential of non O1/non-O139 strains. Whole Genome Mapping (Optical Mapping) based bar coding produces a high resolution, ordered restriction map, depicting a complete view of the unique chromosomal architecture of an organism. To assess the genomic diversity of non-O1/non-O139 V. cholerae, we applied a Whole Genome Mapping strategy on a well-defined and geographically and temporally diverse strain collection, the Sakazaki serogroup type strains. Whole Genome Map data on 91 of the 206 serogroup type strains support the hypothesis that V. cholerae has an unprecedented genetic and genomic structural diversity. Interestingly, we discovered chromosomal fusions in two unusual strains that possess a single chromosome instead of the two chromosomes usually found in V. cholerae. We also found pervasive chromosomal rearrangements such as duplications and indels in many strains. The majority of Vibrio genome sequences currently in public databases are unfinished draft sequences. The Whole Genome Mapping approach presented here enables rapid screening of large strain collections to capture genomic complexities that would not have been otherwise revealed by unfinished draft genome sequencing and thus aids in assembling and finishing draft sequences of complex genomes. Furthermore, Whole Genome Mapping allows for prediction of novel V. cholerae non-O1/non-O139 strains that may have the potential to cause future cholera outbreaks.

Scanning the landscape of genome architecture of non-O1 and non-O139 Vibrio cholerae by whole genome mapping reveals extensive population genetic diversity

DOE PAGES

Chapman, Carol; Henry, Matthew; Bishop-Lilly, Kimberly A.; ...

2015-03-20

Historically, cholera outbreaks have been linked to V. cholerae O1 serogroup strains or its derivatives of the O37 and O139 serogroups. A genomic study on the 2010 Haiti cholera outbreak strains highlighted the putative role of non O1/non-O139 V. cholerae in causing cholera and the lack of genomic sequences of such strains from around the world. Here we address these gaps by scanning a global collection of V. cholerae strains as a first step towards understanding the population genetic diversity and epidemic potential of non O1/non-O139 strains. Whole Genome Mapping (Optical Mapping) based bar coding produces a high resolution, orderedmore » restriction map, depicting a complete view of the unique chromosomal architecture of an organism. To assess the genomic diversity of non-O1/non-O139 V. cholerae, we applied a Whole Genome Mapping strategy on a well-defined and geographically and temporally diverse strain collection, the Sakazaki serogroup type strains. Whole Genome Map data on 91 of the 206 serogroup type strains support the hypothesis that V. cholerae has an unprecedented genetic and genomic structural diversity. Interestingly, we discovered chromosomal fusions in two unusual strains that possess a single chromosome instead of the two chromosomes usually found in V. cholerae. We also found pervasive chromosomal rearrangements such as duplications and indels in many strains. The majority of Vibrio genome sequences currently in public databases are unfinished draft sequences. The Whole Genome Mapping approach presented here enables rapid screening of large strain collections to capture genomic complexities that would not have been otherwise revealed by unfinished draft genome sequencing and thus aids in assembling and finishing draft sequences of complex genomes. Furthermore, Whole Genome Mapping allows for prediction of novel V. cholerae non-O1/non-O139 strains that may have the potential to cause future cholera outbreaks.« less

Micro/Nano-scale Strain Distribution Measurement from Sampling Moiré Fringes.

PubMed

Wang, Qinghua; Ri, Shien; Tsuda, Hiroshi

2017-05-23

This work describes the measurement procedure and principles of a sampling moiré technique for full-field micro/nano-scale deformation measurements. The developed technique can be performed in two ways: using the reconstructed multiplication moiré method or the spatial phase-shifting sampling moiré method. When the specimen grid pitch is around 2 pixels, 2-pixel sampling moiré fringes are generated to reconstruct a multiplication moiré pattern for a deformation measurement. Both the displacement and strain sensitivities are twice as high as in the traditional scanning moiré method in the same wide field of view. When the specimen grid pitch is around or greater than 3 pixels, multi-pixel sampling moiré fringes are generated, and a spatial phase-shifting technique is combined for a full-field deformation measurement. The strain measurement accuracy is significantly improved, and automatic batch measurement is easily achievable. Both methods can measure the two-dimensional (2D) strain distributions from a single-shot grid image without rotating the specimen or scanning lines, as in traditional moiré techniques. As examples, the 2D displacement and strain distributions, including the shear strains of two carbon fiber-reinforced plastic specimens, were measured in three-point bending tests. The proposed technique is expected to play an important role in the non-destructive quantitative evaluations of mechanical properties, crack occurrences, and residual stresses of a variety of materials.

Evaluation of a New Entomopathogenic Strain of Beauveria bassiana and a New Field Delivery Method against Solenopsis invicta

PubMed Central

Li, Jun; Guo, Qiang; Lin, Miaofeng; Jiang, Lu; Ye, Jingwen; Chen, Dasong; Li, Zhigang; Dai, Jianqing; Han, Shichou

2016-01-01

Solenopsis invicta Buren is one of the most important pests in China, and control measures are mainly based on the use of synthetic pesticides, which may be inadequate and unsustainable. Hence, there is a growing interest in developing biological control alternatives for managing S. invicta, such as the use of entomopathogenic fungi. To facilitate the commercialization of entomopathogenic fungi against S. invicta, 10 Beauveria bassiana isolates originating from different hosts were tested for virulence in laboratory bioassays, and the most pathogenic strain, ZGNKY-5, was tested in field studies using an improved pathogen delivery system. The cumulative mortality rate reached 93.40% at 1×108 mL-1 conidia after 504 h. The germination and invasion of the spores were observed under a scanning electron microscope, and several conidia adhered to the cuticle of S. invicta after 2 h. Furthermore, the germ tubes of the conidia oriented toward the cuticle after 48 h, and the mycelium colonized the entire body after 96 h. Based on the efficacy observed in the laboratory trials, further experiments were performed with ZGNKY-5 strain to evaluate its utility in an injection control technology against S. invicta in the field. We found that three dosage treatments of ZGNKY-5 strain (500 mL, 750 mL, and 1,000 mL per nest) had significant control effects. Our results show that this strain of Beauveria bassiana and our control method were effective against S. invicta in both laboratory and field settings. PMID:27341441

18 GHz electromagnetic field induces permeability of Gram-positive cocci

PubMed Central

Nguyen, The Hong Phong; Shamis, Yury; Croft, Rodney J.; Wood, Andrew; McIntosh, Robert L.; Crawford, Russell J.; Ivanova, Elena P.

2015-01-01

The effect of electromagnetic field (EMF) exposures at the microwave (MW) frequency of 18 GHz, on four cocci, Planococcus maritimus KMM 3738, Staphylococcus aureus CIP 65.8T, S. aureus ATCC 25923 and S. epidermidis ATCC 14990T, was investigated. We demonstrate that exposing the bacteria to an EMF induced permeability in the bacterial membranes of all strains studied, as confirmed directly by transmission electron microscopy (TEM), and indirectly via the propidium iodide assay and the uptake of silica nanospheres. The cells remained permeable for at least nine minutes after EMF exposure. It was shown that all strains internalized 23.5 nm nanospheres, whereas the internalization of the 46.3 nm nanospheres differed amongst the bacterial strains (S. epidermidis ATCC 14990T~ 0%; Staphylococcus aureus CIP 65.8T S. aureus ATCC 25923, ~40%; Planococcus maritimus KMM 3738, ~80%). Cell viability experiments indicated that up to 84% of the cells exposed to the EMF remained viable. The morphology of the bacterial cells was not altered, as inferred from the scanning electron micrographs, however traces of leaked cytosolic fluids from the EMF exposed cells could be detected. EMF-induced permeabilization may represent an innovative, alternative cell permeability technique for applications in biomedical engineering, cell drug delivery and gene therapy. PMID:26077933

18 GHz electromagnetic field induces permeability of Gram-positive cocci.

PubMed

Nguyen, The Hong Phong; Shamis, Yury; Croft, Rodney J; Wood, Andrew; McIntosh, Robert L; Crawford, Russell J; Ivanova, Elena P

2015-06-16

The effect of electromagnetic field (EMF) exposures at the microwave (MW) frequency of 18 GHz, on four cocci, Planococcus maritimus KMM 3738, Staphylococcus aureus CIP 65.8(T), S. aureus ATCC 25923 and S. epidermidis ATCC 14990(T), was investigated. We demonstrate that exposing the bacteria to an EMF induced permeability in the bacterial membranes of all strains studied, as confirmed directly by transmission electron microscopy (TEM), and indirectly via the propidium iodide assay and the uptake of silica nanospheres. The cells remained permeable for at least nine minutes after EMF exposure. It was shown that all strains internalized 23.5 nm nanospheres, whereas the internalization of the 46.3 nm nanospheres differed amongst the bacterial strains (S. epidermidis ATCC 14990(T) ~  0%; Staphylococcus aureus CIP 65.8(T) S. aureus ATCC 25923, ~40%; Planococcus maritimus KMM 3738, ~ 80%). Cell viability experiments indicated that up to 84% of the cells exposed to the EMF remained viable. The morphology of the bacterial cells was not altered, as inferred from the scanning electron micrographs, however traces of leaked cytosolic fluids from the EMF exposed cells could be detected. EMF-induced permeabilization may represent an innovative, alternative cell permeability technique for applications in biomedical engineering, cell drug delivery and gene therapy.

Results of a laboratory experiment that tests rotating unbalanced-mass devices for scanning gimbaled payloads and free-flying spacecraft

NASA Technical Reports Server (NTRS)

Alhorn, D. C.; Polites, M. E.

1994-01-01

Rotating unbalanced-mass (RUM) devices are a new way to scan space-based, balloon-borne, and ground-based gimbaled payloads, like x-ray and gamma-ray telescopes. They can also be used to scan free-flying spacecraft. Circular scans, linear scans, and raster scans can be generated. A pair of RUM devices generates the basic scan motion and an auxiliary control system using torque motors, control moment gyros, or reaction wheels keeps the scan centered on the target and produces some complementary motion for raster scanning. Previous analyses and simulation results show that this approach offers significant power savings compared to scanning only with the auxiliary control system, especially with large payloads and high scan frequencies. However, these claims have never been proven until now. This paper describes a laboratory experiment which tests the concept of scanning a gimbaled payload with RUM devices. A description of the experiment is given and test results that prove the concept are presented. The test results are compared with those from a computer simulation model of the experiment and the differences are discussed.

An Assessment of Subsurface Residual Stress Analysis in SLM Ti-6Al-4V

PubMed Central

Mishurova, Tatiana; Cabeza, Sandra; Artzt, Katia; Haubrich, Jan; Klaus, Manuela; Genzel, Christoph; Requena, Guillermo; Bruno, Giovanni

2017-01-01

Ti-6Al-4V bridges were additively fabricated by selective laser melting (SLM) under different scanning speed conditions, to compare the effect of process energy density on the residual stress state. Subsurface lattice strain characterization was conducted by means of synchrotron diffraction in energy dispersive mode. High tensile strain gradients were found at the frontal surface for samples in an as-built condition. The geometry of the samples promotes increasing strains towards the pillar of the bridges. We observed that the higher the laser energy density during fabrication, the lower the lattice strains. A relief of lattice strains takes place after heat treatment. PMID:28772706

Stretchable and flexible high-strain sensors made using carbon nanotubes and graphite films on natural rubber.

PubMed

Tadakaluru, Sreenivasulu; Thongsuwan, Wiradej; Singjai, Pisith

2014-01-06

Conventional metallic strain sensors are flexible, but they can sustain maximum strains of only ~5%, so there is a need for sensors that can bear high strains for multifunctional applications. In this study, we report stretchable and flexible high-strain sensors that consist of entangled and randomly distributed multiwall carbon nanotubes or graphite flakes on a natural rubber substrate. Carbon nanotubes/graphite flakes were sandwiched in natural rubber to produce these high-strain sensors. Using field emission scanning electron microscopy, the morphology of the films for both the carbon nanotube and graphite sensors were assessed under different strain conditions (0% and 400% strain). As the strain was increased, the films fractured, resulting in an increase in the electrical resistance of the sensor; this change was reversible. Strains of up to 246% (graphite sensor) and 620% (carbon nanotube sensor) were measured; these values are respectively ~50 and ~120 times greater than those of conventional metallic strain sensors.

Stretchable and Flexible High-Strain Sensors Made Using Carbon Nanotubes and Graphite Films on Natural Rubber

PubMed Central

Tadakaluru, Sreenivasulu; Thongsuwan, Wiradej; Singjai, Pisith

2014-01-01

Conventional metallic strain sensors are flexible, but they can sustain maximum strains of only ∼5%, so there is a need for sensors that can bear high strains for multifunctional applications. In this study, we report stretchable and flexible high-strain sensors that consist of entangled and randomly distributed multiwall carbon nanotubes or graphite flakes on a natural rubber substrate. Carbon nanotubes/graphite flakes were sandwiched in natural rubber to produce these high-strain sensors. Using field emission scanning electron microscopy, the morphology of the films for both the carbon nanotube and graphite sensors were assessed under different strain conditions (0% and 400% strain). As the strain was increased, the films fractured, resulting in an increase in the electrical resistance of the sensor; this change was reversible. Strains of up to 246% (graphite sensor) and 620% (carbon nanotube sensor) were measured; these values are respectively ∼50 and ∼120 times greater than those of conventional metallic strain sensors. PMID:24399158

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.

Strain and lattice orientation distribution in SiN/Ge complementary metal–oxide–semiconductor compatible light emitting microstructures by quick x-ray nano-diffraction microscopy

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

Chahine, G. A.; Schülli, T. U.; Zoellner, M. H.

2015-02-16

This paper presents a study of the spatial distribution of strain and lattice orientation in CMOS-fabricated strained Ge microstripes using high resolution x-ray micro-diffraction. The recently developed model-free characterization tool, based on a quick scanning x-ray diffraction microscopy technique can image strain down to levels of 10{sup −5} (Δa/a) with a spatial resolution of ∼0.5 μm. Strain and lattice tilt are extracted using the strain and orientation calculation software package X-SOCS. The obtained results are compared with the biaxial strain distribution obtained by lattice parameter-sensitive μ-Raman and μ-photoluminescence measurements. The experimental data are interpreted with the help of finite element modelingmore » of the strain relaxation dynamics in the investigated structures.« less

Comparative Survival Rates of Human-Derived Probiotic Lactobacillus paracasei and L. salivarius Strains during Heat Treatment and Spray Drying

PubMed Central

Gardiner, G. E.; O'Sullivan, E.; Kelly, J.; Auty, M. A. E.; Fitzgerald, G. F.; Collins, J. K.; Ross, R. P.; Stanton, C.

2000-01-01

Spray drying of skim milk was evaluated as a means of preserving Lactobacillus paracasei NFBC 338 and Lactobacillus salivarius UCC 118, which are human-derived strains with probiotic potential. Our initial experiments revealed that NFBC 338 is considerably more heat resistant in 20% (wt/vol) skim milk than UCC 118 is; the comparable decimal reduction times were 11.1 and 1.1 min, respectively, at 59°C. An air outlet temperature of 80 to 85°C was optimal for spray drying; these conditions resulted in powders with moisture contents of 4.1 to 4.2% and viable counts of 3.2 × 109 CFU/g for NFBC 338 and 5.2 × 107 CFU/g for UCC 118. Thus, L. paracasei NFBC 338 survived better than L. salivarius UCC 118 during spray drying; similar results were obtained when we used confocal scanning laser microscopy and LIVE/DEAD BacLight viability staining. In addition, confocal scanning laser microscopy revealed that the probiotic lactobacilli were located primarily in the powder particles. Although both spray-dried cultures appeared to be stressed, as shown by increased sensitivity to NaCl, bacteriocin production by UCC 118 was not affected by the process, nor was the activity of the bacteriocin peptide. The level of survival of NFBC 338 remained constant at ∼1 × 109 CFU/g during 2 months of powder storage at 4°C, while a decline in the level of survival of approximately 1 log (from 7.2 × 107 to 9.5 × 106 CFU/g) was observed for UCC 118 stored under the same conditions. However, survival of both Lactobacillus strains during powder storage was inversely related to the storage temperature. Our data demonstrate that spray drying may be a cost-effective way to produce large quantities of some probiotic cultures. PMID:10831444

Mathematical Modeling in Support of Military Operational Medicine

DTIC Science & Technology

2006-07-01

of PBPK models in toxicol- ogy research and chemical risk assessment today is pri- marily related to their ability to make more quantitative ...derived earlier. The biomechanical basis of SFC is established by its correlation with strain. (a) Pretest Scan (b) Posttest Fracture...Three-Dimensional Reconstruction of Pretest and Posttest CT Scans Cited References Vander Vorst, M., Stuhmiller, J., et al., (2003). Biomechanically

[Effects of ammonium sulfate on the metabolism and K-feldspar weathering of two potassium-bearing mineral-solubilizing bacteria].

PubMed

Huang, Zhi; Ma, Guangyou; He, Linyan; Sheng, Xiafang

2012-02-04

To determine the best conditions for Bacillus globisporus Q12 and Rhizobium sp. Q32 to produce organic acids and extracellular polysaccharides, respectively, and further elucidate the weathering mechanism of the two potassium-bearing mineral-solubilizing bacteria. Different contents (0-1.2 g/L) of (NH4)2SO4 were added to media to analyze the ability of the strains to produce organic acids and extracellular polysaccharides, and assess the ability of Q12, Q32 and their mixture to dissolve potassium feldspar. Scanning electron microscope (SEM) was also used to observe the distribution of the bacterial cells on the surfaces of the feldspar and the mineral weathering. Results show that Bacillus globisporus Q12 produced more organic acids, when the contents of (NH4)2SO4 were 0.6 g/L; Rhizobium sp. Q32 produced more extracellular polysaccharides, when there was no (NH4)2SO4 in the media; and the mixture of two strains produced more organic acids and extracellular polysaccharides, when the contents of (NH4)2SO4 were 0.3 g/L. Mineral dissolution experiment showed that Bacillus globisporus Q12, Rhizobium sp. Q32 and the mixture (Q12 + Q32) significantly dissolved the feldspar and released the elements from the mineral, of which the mixture of Q12 and Q32 had the best weathering ability than strain Q12 or Q32; SEM also indicated that the mixture of Q12 and Q32 had more ability to weather feldspar than each tested strain. The contents of (NH4)2SO4 in the media could affect the growth and metabolites of the strains Q12 and Q32 and the mineral bioweathering, the mixture of strains Q12 and Q32 had the more potential of feldspar weathering through the combined action of organic acids and extracellular polysaccharides produced by strains Q12 and Q32.

Mechanical characterization of an additively manufactured Inconel 718 theta-shaped specimen

DOE PAGES

Cakmak, Ercan; Watkins, Thomas R.; Bunn, Jeffrey R.; ...

2015-11-20

Two sets of “theta”-shaped specimens were additively manufactured with Inconel 718 powders using an electron beam melting technique with two distinct scan strategies. Light optical microscopy, mechanical testing coupled with a digital image correlation (DIC) technique, finite element modeling, and neutron diffraction with in situ loading characterizations were conducted. The cross-members of the specimens were the focus. Light optical micrographs revealed that different microstructures were formed with different scan strategies. Ex situ mechanical testing revealed each build to be stable under load until ductility was observed on the cross-members before failure. The elastic moduli were determined by forming a correlationmore » between the elastic tensile stresses determined from FEM, and the elastic strains obtained from DIC. The lattice strains were mapped with neutron diffraction during in situ elastic loading; and a good correlation between the average axial lattice strains on the cross-member and those determined from the DIC analysis was found. Lastly, the spatially resolved stresses in the elastic deformation regime are derived from the lattice strains and increased with applied load, showing a consistent distribution along the cross-member.« less

Minimization of spurious strains by using a Si bent-perfect-crystal monochromator: neutron surface strain scanning of a shot-peened sample

NASA Astrophysics Data System (ADS)

Rebelo Kornmeier, Joana; Gibmeier, Jens; Hofmann, Michael

2011-06-01

Neutron strain measurements are critical at the surface. When scanning close to a sample surface, aberration peak shifts arise due to geometrical and divergence effects. These aberration peak shifts can be of the same order as the peak shifts related to residual strains. In this study it will be demonstrated that by optimizing the horizontal bending radius of a Si (4 0 0) monochromator, the aberration peak shifts from surface effects can be strongly reduced. A stress-free sample of fine-grained construction steel, S690QL, was used to find the optimal instrumental conditions to minimize aberration peak shifts. The optimized Si (4 0 0) monochromator and instrument settings were then applied to measure the residual stress depth gradient of a shot-peened SAE 4140 steel sample to validate the effectiveness of the approach. The residual stress depth profile is in good agreement with results obtained by x-ray diffraction measurements from an international round robin test (BRITE-EURAM-project ENSPED). The results open very promising possibilities to bridge the gap between x-ray diffraction and conventional neutron diffraction for non-destructive residual stress analysis close to surfaces.

Mechanical characterization of an additively manufactured Inconel 718 theta-shaped specimen

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

Cakmak, Ercan; Watkins, Thomas R.; Bunn, Jeffrey R.

Two sets of “theta”-shaped specimens were additively manufactured with Inconel 718 powders using an electron beam melting technique with two distinct scan strategies. Light optical microscopy, mechanical testing coupled with a digital image correlation (DIC) technique, finite element modeling, and neutron diffraction with in situ loading characterizations were conducted. The cross-members of the specimens were the focus. Light optical micrographs revealed that different microstructures were formed with different scan strategies. Ex situ mechanical testing revealed each build to be stable under load until ductility was observed on the cross-members before failure. The elastic moduli were determined by forming a correlationmore » between the elastic tensile stresses determined from FEM, and the elastic strains obtained from DIC. The lattice strains were mapped with neutron diffraction during in situ elastic loading; and a good correlation between the average axial lattice strains on the cross-member and those determined from the DIC analysis was found. Lastly, the spatially resolved stresses in the elastic deformation regime are derived from the lattice strains and increased with applied load, showing a consistent distribution along the cross-member.« less

Stress and strain distribution in three different mini dental implant designs using in implant retained overdenture: a finite element analysis study.

PubMed

Aunmeungtong, W; Khongkhunthian, P; Rungsiyakull, P

2016-01-01

Finite Element Analysis (FEA) has been used for prediction of stress and strain between dental implant components and bone in the implant design process. Purpose of this study was to characterize and analyze stress and strain distribution occurring in bone and implants and to compare stress and strain of three different implant designs. Three different mini dental implant designs were included in this study: 1. a mini dental implant with an internal implant-abutment connection (MDIi); 2. a mini dental implant with an external implant-abutment connection (MDIe); 3. a single piece mini dental implant (MDIs). All implant designs were scanned using micro-CT scans. The imaging details of the implants were used to simulate models for FEA. An artificial bone volume of 9×9 mm in size was constructed and each implant was placed separately at the center of each bone model. All bone-implant models were simulatively loaded under an axial compressive force of 100 N and a 45-degree force of 100 N loading at the top of the implants using computer software to evaluate stress and strain distribution. There was no difference in stress or strain between the three implant designs. The stress and strain occurring in all three mini dental implant designs were mainly localized at the cortical bone around the bone-implant interface. Oblique 45° loading caused increased deformation, magnitude and distribution of stress and strain in all implant models. Within the limits of this study, the average stress and strain in bone and implant models with MDIi were similar to those with MDIe and MDIs. The oblique 45° load played an important role in dramatically increased average stress and strain in all bone-implant models. Mini dental implants with external or internal connections have similar stress distribution to single piece mini dental implants. In clinical situations, the three types of mini dental implant should exhibit the same behavior to chewing force.

Creep of Bridgmanite Analog, Neighborite (NaMgF3), and Implications for Viscous Flow in the Lower Mantle

NASA Astrophysics Data System (ADS)

Kaercher, P. M.; Mecklenburgh, J.; Mariani, E.; Wheeler, J.

2016-12-01

The rheology of the lower mantle directly influences mantle viscosity and strength and therefore affects a number of geophysical processes including mantle mixing, formation of mantle plumes and hotspots, slab subduction and stagnation, and plate motion. Experimental flow laws of lower mantle minerals, which quantify rheology of the lower mantle, are needed to help resolve discrepancies in estimates of lower mantle viscosity, better constrain geophysical models, and answer a number of outstanding questions such as, why slabs descend to different depths, and why the lower mantle is mostly isotropic despite large strains predicted by convection models. However, we lack natural lower mantle samples from which to infer deformation history. Furthermore, deformation experiments at lower mantle pressures and temperatures are challenging, and strain rates and stress cannot always be precisely controlled or measured. As a valuable alternative we have synthesized and deformed neighborite (NaMgF3), a low pressure analog of bridgmanite (MgSiO3), the most abundant mineral in the lower mantle and the Earth. Neighborite was deformed at 200 MPa confining pressure and between 500-700°C in compression using a fluid-medium deformation apparatus, and in torsion using a Patterson rig. In these experiments strain rate and stress can be accurately controlled and measured, and flow laws reliably determined. In addition we have recovered samples and examined deformation microstructures in a scanning electron microscope using electron backscatter diffraction. Preliminary mechanical results show a switch from linear-viscous deformation at lower stress (<50 MPa) to power law creep accommodated by grain boundary sliding at higher stress (>50 MPa). We also see strain weakening. Microstructures of samples deformed at a range of stress steps show grain boundary migration recrystallization (likely from lower stress) and crystallographic preferred orientation with poles to (100) planes parallel to compression (likely from higher stress). Further work is in progress to obtain microstructures that can be univocally associated with the observed mechanical behavior. We compare our results to those of other bridgmanite analogs and bridgmanite itself and extrapolate to geologic strain rates.

In vitro antagonism of Thielaviopsis paradoxa by Trichoderma longibrachiatum.

PubMed

Sánchez, Vladimir; Rebolledo, Oscar; Picaso, Rosa M; Cárdenas, Elizabeth; Córdova, Jesús; González, Orfil; Samuels, Gary J

2007-01-01

Seventy-nine Trichoderma strains were isolated from soil taken from 28 commercial plantations of Agave tequilana cv. 'Azul' in the State of Jalisco, Mexico. Nine of these isolates produced nonvolatile metabolites that completely inhibited the growth of Thielaviopsis paradoxa on potato dextrose agar plates. These isolates were identified as Trichoderma longibrachiatum on the basis of their morphology and DNA sequence analysis of two genes (ITS rDNA and translation elongation factor EF-1alpha). Mycoparasitism of Th. paradoxa by T. longibrachiatum strains in dual cultures was examined by scanning electron microscopy. The Trichoderma hyphae grew alongside the Th. paradoxa hyphae, but penetration of Thielaviopsis hyphae by Trichoderma was no apparent. Aleurioconidia of Th. paradoxa were parasitized by Trichoderma. Both hyphae and aleurioconidia of Th. paradoxa lost turgor pressure, wrinkled, collapsed and finally disintegrated. In liquid cultures, all nine Trichoderma isolates produced proteases, beta-1,3-glucanases and chitinases that would be responsible for the degradation of Thielaviopsis hyphae. These results demonstrate that the modes of action of T. longibrachiatum involved against Th. paradoxa in vitro experiments are mycoparasitism and the production of nonvolatile toxic metabolites.

Amorphization and Frictional Processes in Smectite-Quartz Gouge Mixtures Sheared from Sub-seismic to Seismic Slip Rates

NASA Astrophysics Data System (ADS)

Aretusini, S.; Mittempergher, S.; Spagnuolo, E.; Di Toro, G.; Gualtieri, A.; Plümper, O.

2015-12-01

Slipping zones in shallow sections of megathrusts and large landslides are often made of smectite and quartz gouge mixtures. Experiments aimed at investigating the frictional processes operating at high slip rates (>1 m/s) may unravel the mechanics of these natural phenomena. Here we present a new dataset obtained with two rotary shear apparatus (ROSA, Padua University; SHIVA, INGV-Rome). Experiments were performed at room humidity and temperature on four mixtures of smectite (Ca-Montmorillonite) and quartz with 68, 50, 25, 0 wt% of smectite. The gouges were slid for 3 m at normal stress of 5 MPa and slip rate V from 300 µm/s to 1.5 m/s. Temperature during the experiments was monitored with four thermocouples and modeled with COMSOL Multiphysics. In smectite-rich mixtures, the friction coefficient µ evolved with slip according to three slip rate regimes: in regime 1 (V<0.1 m/s) initial slip-weakening was followed by slip-strengthening; in regime 2 (0.10.3 m/s) µ had strong slip-weakening behavior. Instead, in quartz-rich mixtures the gouge had a monotonic slip-weakening behavior, independently of V. Temperature modelling showed that the fraction of work rate converted into heat decreased with increasing smectite content and slip rate. Quantitative X-ray powder diffraction (Rietveld method) indicates that the production of amorphous material from smectite breakdown increased with frictional work but was independent of work rate. Scanning Electron Microscopy investigation evidenced strain localization and presence of dehydrated clays for V≥0.3 m/s; instead, for V<0.3 m/s, strain was distributed and the gouge layer pervasively foliated. In conclusion, amorphization of the sheared gouges was not responsible of the measured frictional weakening. Instead, slip-weakening was concomitant to strain localization and possible vaporization of water adsorbed on smectite grain surfaces.

International Seminar on Laser and Opto-Electronic Technology in Industry: State-of-the-Art Review, Xiamen, People's Republic of China, June 25-28, 1986, Proceedings

NASA Astrophysics Data System (ADS)

Ke, Jingtang; Pryputniewicz, Ryszard J.

Various papers on the state of the art in laser and optoelectronic technology in industry are presented. Individual topics addressed include: wavelength compensation for holographic optical element, optoelectronic techniques for measurement and inspection, new optical measurement methods in Western Europe, applications of coherent optics at ISL, imaging techniques for gas turbine development, the Rolls-Royce experience with industrial holography, panoramic holocamera for tube and borehole inspection, optical characterization of electronic materials, optical strain measurement of rotating components, quantitative interpretation of holograms and specklegrams, laser speckle technique for hydraulic structural model test, study of holospeckle interferometry, common path shearing fringe scanning interferometer, and laser interferometry applied to nondestructive testing of tires.

Development of a parallel demodulation system used for extrinsic Fabry-Perot interferometer and fiber Bragg grating sensors.

PubMed

Jiang, Junfeng; Liu, Tiegen; Zhang, Yimo; Liu, Lina; Zha, Ying; Zhang, Fan; Wang, Yunxin; Long, Pin

2006-01-20

A parallel demodulation system for extrinsic Fabry-Perot interferometer (EFPI) and fiber Bragg grating (FBG) sensors is presented, which is based on a Michelson interferometer and combines the methods of low-coherence interference and a Fourier-transform spectrum. The parallel demodulation theory is modeled with Fourier-transform spectrum technology, and a signal separation method with an EFPI and FBG is proposed. The design of an optical path difference scanning and sampling method without a reference light is described. Experiments show that the parallel demodulation system has good spectrum demodulation and low-coherence interference demodulation performance. It can realize simultaneous strain and temperature measurements while keeping the whole system configuration less complex.

Characteristics of InN epilayers grown with H2-assistance

NASA Astrophysics Data System (ADS)

Zhou, Jin; Li, Jinchai; Lu, Shiqiang; Kang, Junyong; Lin, Wei

2017-11-01

A series of InN films were grown on GaN-on-sapphire template with H2 pulse flow by metal organic vapor phase epitaxy. The scanning electron microscopy and atomic force microscopy observations demonstrate that the smooth surface has been achieved. The X-ray diffraction and Raman spectra measurements indicate that InN layers experience stronger accommodated compressive stress, resulting in a larger fraction of (002) oriented InN grains. On the basics of the first-principles calculations, these features can be understand as competition between N-penetrating effect with the assistance of the H atom and the etching effect of H2. Finally, the absorption spectra in conjunction with simulated results reveal that the band gap energy predominantly increase with increasing compressive strain.

The Bulk Nanocrystalline zn Produced by Mechanical Attrition

NASA Astrophysics Data System (ADS)

Zhu, X. K.; Zhao, K. Y.; Li, C. J.; Tao, J. M.; Chan, T. L.; Koch, C. C.

The purpose of experiment was to produce bulk nanocrystalline Zn by mechanical attrition. The bulk nanocrystalline Zn produced by mechanical attrition was studied. The microstructural evolution during cryomilling and subsequent room temperature milling was characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). In this paper, Nanocrystalline Zn was produced by insitu consolidation of Zn elemental powder using mechanical attrition at liquid nitrogen and room temperature. For the samples studied, the longest elongation of 65% and highest stress of 200 MPa is obtained in nanocrystalline Zn during tensile testing at the condition of strain rate (10-3 sec-1) and 20°C which is equal to 0.43 Tm (Tm is the melting temperature of pure Zn).

Strain measurement of abdominal aortic aneurysm with real-time 3D ultrasound speckle tracking.

PubMed

Bihari, P; Shelke, A; Nwe, T H; Mularczyk, M; Nelson, K; Schmandra, T; Knez, P; Schmitz-Rixen, T

2013-04-01

Abdominal aortic aneurysm rupture is caused by mechanical vascular tissue failure. Although mechanical properties within the aneurysm vary, currently available ultrasound methods assess only one cross-sectional segment of the aorta. This study aims to establish real-time 3-dimensional (3D) speckle tracking ultrasound to explore local displacement and strain parameters of the whole abdominal aortic aneurysm. Validation was performed on a silicone aneurysm model, perfused in a pulsatile artificial circulatory system. Wall motion of the silicone model was measured simultaneously with a commercial real-time 3D speckle tracking ultrasound system and either with laser-scan micrometry or with video photogrammetry. After validation, 3D ultrasound data were collected from abdominal aortic aneurysms of five patients and displacement and strain parameters were analysed. Displacement parameters measured in vitro by 3D ultrasound and laser scan micrometer or video analysis were significantly correlated at pulse pressures between 40 and 80 mmHg. Strong local differences in displacement and strain were identified within the aortic aneurysms of patients. Local wall strain of the whole abdominal aortic aneurysm can be analysed in vivo with real-time 3D ultrasound speckle tracking imaging, offering the prospect of individual non-invasive rupture risk analysis of abdominal aortic aneurysms. Copyright © 2013 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.

Environmental scanning electron microscopy analysis of Proteus mirabilis biofilms grown on chitin and stainless steel.

PubMed

Fernández-Delgado, Milagro; Duque, Zoilabet; Rojas, Héctor; Suárez, Paula; Contreras, Monica; García-Amado, María A; Alciaturi, Carlos

Proteus mirabilis is a human pathogen able to form biofilms on the surface of urinary catheters. Little is known about P. mirabilis biofilms on natural or industrial surfaces and the potential consequences for these settings. The main aim of this work was to assess and compare the adhesion and biofilm formation of P. mirabilis strains from different origins on chitin and stainless steel surfaces within 4 to 96 h. Using environmental scanning electron microscopy, the biofilms of a clinical strain grown on chitin at 4 h showed greater adhesion, aggregation, thickness, and extracellular matrix production than those grown on stainless steel, whereas biofilms of an environmental strain had less aggregation on both surfaces. Biofilms of both P. mirabilis strains developed different structures on chitin, such as pillars, mushrooms, channels, and crystalline-like precipitates between 24 and 96 h, in contrast with flat-layer biofilms produced on stainless steel. Significant differences ( p  < 0.05) were found in the frequency of pillars and channels. Images of transmission electron microscopy demonstrated abundant fimbriae in 100 % of cells from both strains, which could be related to surface adherence and biofilm formation. This represents the first study of P. mirabilis showing adhesion, biofilm formation, and development of different structures on surfaces found outside the human host.

Evaluation of Pathogenicity of the Fungi Metarhizium anisopliae and Beauveria bassiana in Hazelnut Weevil (Curculio nucum L., Coleoptera, Curculionidae) Larvae.

PubMed

Cheng, Yunqing; Liu, Ting; Zhao, Yixin; Geng, Wanting; Chen, Longtao; Liu, Jianfeng

2016-12-01

The nut weevil ( Curculio nucum ) is one of the most important and widespread pests in hazelnut orchards. In order to screen entomopathogenic fungal strains with high virulence against C. nucum , the growth rate, sporulation, and cumulative mortality of different Metarhizium anisopliae and Beauveria bassiana strains were investigated, and the process by which M. anisopliae CoM 02 infects C. nucum larvae was observed using scanning electron microscopy. The results indicated that the growth rate and sporulation of different fungal strains significantly differed. Thirteen days after inoculation with M. anisopliae CoM 02, the cumulative mortality of C. nucum larvae reached 100 %, which was considerably higher than that of the other five strains. As the most virulent of the six test strains, the cadaver rate, LT 50 , and LT 90 of M. anisopliae CoM 02 were 93.4 %, 7.05 and 11.90 days, respectively. Analysis of the infection process by scanning electron microscopy showed that the spore attachment, hyphal germination, hyphal rapid growth, and sporulation of M. anisopliae CoM 02 occurred on the 3rd, 5th, 7th, and 11th day after inoculation, respectively, indicating that the infection cycle takes approximately 11 days. This finding suggests that the highly virulent M. anisopliae plays an important role in the biocontrol of C. nucum in China.

The Deformation Behavior and Microstructure Evolution of a Mn- and Cr-Containing Al-Mg-Si-Cu Alloy During Hot Compression and Subsequent Heat Treatment

NASA Astrophysics Data System (ADS)

Xu, Yi; Nagaumi, Hiromi; Han, Yi; Zhang, Gongwang; Zhai, Tongguang

2017-03-01

Hot compression tests on a newly developed Mn- and Cr-containing Al-Mg-Si-Cu alloy were carried out at temperatures ranging from 623 K (350 °C) to 823 K (550 °C) and strain rates between 0.001 and 1 s-1 after casting and subsequent homogenization heat treatment. The true stress-true strain curves of the alloy exhibited a peak stress at a small plastic strain followed by dynamic flow softening. Using the constitutive equation containing the strain rate, peak stress, and temperature, the activation energy for hot deformation in the alloy was determined to be 249.67 kJ/mol, much higher than that (143.4 kJ/mol) for self-diffusion in pure Al. Scanning transmission electron microscopy experiments revealed that Mn- and Cr-containing α-dispersoids formed during homogenization showed a strong pinning effect on dislocations and grain boundaries, which was responsible for the increase in activation energy for hot deformation in the alloy. A threshold stress was consequently introduced and determined in the constitutive equation to count for the dispersoid hardening effect on hot deformation in the alloy. Electron back-scatter diffraction measurements revealed that the softening occurred in the alloy was mainly due to dynamic recovery taking place at relatively large Z values, and that it was dominated by continuous dynamic recrystallization at relatively low Z. In subsequent annealing after hot deformation at large Z, abnormal grain growth could occur, as a result of the critical strain-annealing effect. After upsetting at higher temperatures, the alloy showed superior tensile properties due to a high non-recrystallized area fraction.

Peeking under the Iron Curtain: Development of a Microcosm for Imaging the Colonization of Steel Surfaces by Mariprofundus sp. Strain DIS-1, an Oxygen-Tolerant Fe-Oxidizing Bacterium

PubMed Central

Adaktylou, Irini J.; Emerson, David

2016-01-01

ABSTRACT Microbially influenced corrosion (MIC) is a major cause of damage to steel infrastructure in the marine environment. Despite their ability to grow directly on Fe(II) released from steel, comparatively little is known about the role played by neutrophilic iron-oxidizing bacteria (FeOB). Recent work has shown that FeOB grow readily on mild steel (1018 MS) incubated in situ or as a substrate for pure cultures in vitro; however, details of how they colonize steel surfaces are unknown yet are important for understanding their effects. In this study, we combine a novel continuously upwelling microcosm with confocal laser scanning microscopy (CLSM) to determine the degree of colonization of 1018 MS by the marine FeOB strain DIS-1. 1018 MS coupons were incubated with sterile seawater (pH 8) inoculated with strain DIS-1. Incubations were performed both under oxic conditions and in an anoxic-to-oxic gradient. Following incubations of 1 to 10 days, the slides were removed from the microcosms and stained to visualize both cells and stalk structures. Stained coupons were visualized by CLSM after being mounted in a custom frame to preserve the three-dimensional structure of the biofilm. The incubation of 1018 MS coupons with strain DIS-1 under oxic conditions resulted in initial attachment of cells within 2 days and nearly total coverage of the coupon with an ochre film within 5 days. CLSM imaging revealed a nonadherent biofilm composed primarily of the Fe-oxide stalks characteristic of strain DIS-1. When incubated with elevated concentrations of Fe(II), DIS-1 colonization of 1018 MS was inhibited. IMPORTANCE These experiments describe the growth of a marine FeOB in a continuous culture system and represent direct visualizations of steel colonization by FeOB. We anticipate that these experiments will lay the groundwork for studying the mechanisms by which FeOB colonize steel and help to elucidate the role played by marine FeOB in MIC. These observations of the interaction between an FeOB, strain DIS-1, and steel suggest that this experimental system will provide a useful model for studying the interactions between microbes and solid substrates. PMID:27637877

Peeking under the Iron Curtain: Development of a Microcosm for Imaging the Colonization of Steel Surfaces by Mariprofundus sp. Strain DIS-1, an Oxygen-Tolerant Fe-Oxidizing Bacterium.

PubMed

Mumford, Adam C; Adaktylou, Irini J; Emerson, David

2016-11-15

Microbially influenced corrosion (MIC) is a major cause of damage to steel infrastructure in the marine environment. Despite their ability to grow directly on Fe(II) released from steel, comparatively little is known about the role played by neutrophilic iron-oxidizing bacteria (FeOB). Recent work has shown that FeOB grow readily on mild steel (1018 MS) incubated in situ or as a substrate for pure cultures in vitro; however, details of how they colonize steel surfaces are unknown yet are important for understanding their effects. In this study, we combine a novel continuously upwelling microcosm with confocal laser scanning microscopy (CLSM) to determine the degree of colonization of 1018 MS by the marine FeOB strain DIS-1. 1018 MS coupons were incubated with sterile seawater (pH 8) inoculated with strain DIS-1. Incubations were performed both under oxic conditions and in an anoxic-to-oxic gradient. Following incubations of 1 to 10 days, the slides were removed from the microcosms and stained to visualize both cells and stalk structures. Stained coupons were visualized by CLSM after being mounted in a custom frame to preserve the three-dimensional structure of the biofilm. The incubation of 1018 MS coupons with strain DIS-1 under oxic conditions resulted in initial attachment of cells within 2 days and nearly total coverage of the coupon with an ochre film within 5 days. CLSM imaging revealed a nonadherent biofilm composed primarily of the Fe-oxide stalks characteristic of strain DIS-1. When incubated with elevated concentrations of Fe(II), DIS-1 colonization of 1018 MS was inhibited. These experiments describe the growth of a marine FeOB in a continuous culture system and represent direct visualizations of steel colonization by FeOB. We anticipate that these experiments will lay the groundwork for studying the mechanisms by which FeOB colonize steel and help to elucidate the role played by marine FeOB in MIC. These observations of the interaction between an FeOB, strain DIS-1, and steel suggest that this experimental system will provide a useful model for studying the interactions between microbes and solid substrates. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Nanoscale interplay of strain and doping in a high-temperature superconductor

DOE PAGES

Zeljkovic, Ilija; Gu, Genda; Nieminen, Jouko; ...

2014-11-07

The highest temperature superconductors are electronically inhomogeneous at the nanoscale, suggesting the existence of a local variable which could be harnessed to enhance the superconducting pairing. Here we report the relationship between local doping and local strain in the cuprate superconductor Bi₂Sr₂CaCu₂O₈₊ x. We use scanning tunneling microscopy to discover that the crucial oxygen dopants are periodically distributed, in correlation with local strain. Our picoscale investigation of the intra-unit-cell positions of all oxygen dopants provides essential structural input for a complete microscopic theory.

High-resolution spatiotemporal strain mapping reveals non-uniform deformation in micropatterned elastomers

NASA Astrophysics Data System (ADS)

Aksoy, B.; Rehman, A.; Bayraktar, H.; Alaca, B. E.

2017-04-01

Micropatterns are generated on a vast selection of polymeric substrates for various applications ranging from stretchable electronics to cellular mechanobiological systems. When these patterned substrates are exposed to external loading, strain field is primarily affected by the presence of microfabricated structures and similarly by fabrication-related defects. The capturing of such nonhomogeneous strain fields is of utmost importance in cases where study of the mechanical behavior with a high spatial resolution is necessary. Image-based non-contact strain measurement techniques are favorable and have recently been extended to scanning tunneling microscope and scanning electron microscope images for the characterization of mechanical properties of metallic materials, e.g. steel and aluminum, at the microscale. A similar real-time analysis of strain heterogeneity in elastomers is yet to be achieved during the entire loading sequence. The available measurement methods for polymeric materials mostly depend on cross-head displacement or precalibrated strain values. Thus, they suffer either from the lack of any real-time analysis, spatiotemporal distribution or high resolution in addition to a combination of these factors. In this work, these challenges are addressed by integrating a tensile stretcher with an inverted optical microscope and developing a subpixel particle tracking algorithm. As a proof of concept, the patterns with a critical dimension of 200 µm are generated on polydimethylsiloxane substrates and strain distribution in the vicinity of the patterns is captured with a high spatiotemporal resolution. In the field of strain measurement, there is always a tradeoff between minimum measurable strain value and spatial resolution. Current noncontact techniques on elastomers can deliver a strain resolution of 0.001% over a minimum length of 5 cm. More importantly, inhomogeneities within this quite large region cannot be captured. The proposed technique can overcome this challenge and provides a displacement measurement resolution of 116 nm and a strain resolution of 0.04% over a gage length of 300 µm. Similarly, the ability to capture inhomogeneities is demonstrated by mapping strain around a thru-hole. The robustness of the technique is also evaluated, where no appreciable change in strain measurement is observed despite the significant variations imposed on the measurement mesh. The proposed approach introduces critical improvements for the determination of displacement and strain gradients in elastomers regarding the real-time nature of strain mapping with a microscale spatial resolution.

A scanning electron microscopic evaluation of in vitro dentinal tubules penetration by selected anaerobic bacteria.

PubMed

Siqueira, J F; De Uzeda, M; Fonseca, M E

1996-06-01

In vitro root canal dentinal tubule invasion by selected anaerobic bacteria commonly isolated from endodontic infections was evaluated. Dentinal cylinders obtained from bovine incisors were inoculated with bacteria, and microbial penetration into tubules was demonstrated by scanning electron microscopy. The results indicated that all bacterial strains tested were able to penetrate into dentinal tubules, but to different extents.

Failure of the MicroScan WalkAway System To Detect Heteroresistance to Carbapenems in a Patient with Enterobacter aerogenes Bacteremia▿

PubMed Central

Gordon, N. C.; Wareham, D. W.

2009-01-01

We report the failure of the automated MicroScan WalkAway system to detect carbapenem heteroresistance in Enterobacter aerogenes. Carbapenem resistance has become an increasing concern in recent years, and robust surveillance is required to prevent dissemination of resistant strains. Reliance on automated systems may delay the detection of emerging resistance. PMID:19641071

The Photosensitivity of Rhodopsin Bleaching and Light-Induced Increases of Fundus Reflectance in Mice Measured In Vivo With Scanning Laser Ophthalmoscopy

PubMed Central

Zhang, Pengfei; Goswami, Mayank; Zawadzki, Robert J.; Pugh, Edward N.

2016-01-01

Purpose To quantify bleaching-induced changes in fundus reflectance in the mouse retina. Methods Light reflected from the fundus of albino (Balb/c) and pigmented (C57Bl/6J) mice was measured with a multichannel scanning laser ophthalmoscopy optical coherence tomography (SLO-OCT) optical system. Serial scanning of small retinal regions was used for bleaching rhodopsin and measuring reflectance changes. Results Serial scanning generated a saturating reflectance increase centered at 501 nm with a photosensitivity of 1.4 × 10−8 per molecule μm2 in both strains, 2-fold higher than expected were irradiance at the rod outer segment base equal to that at the retinal surface. The action spectrum of the reflectance increase corresponds to the absorption spectrum of mouse rhodopsin in situ. Spectra obtained before and after bleaching were fitted with a model of fundus reflectance, quantifying contributions from loss of rhodopsin absorption with bleaching, absorption by oxygenated hemoglobin (HbO2) in the choroid (Balb/c), and absorption by melanin (C57Bl/6J). Both mouse strains exhibited light-induced broadband reflectance changes explained as bleaching-induced reflectivity increases at photoreceptor inner segment/outer segment (IS/OS) junctions and OS tips. Conclusions The elevated photosensitivity of rhodopsin bleaching in vivo is explained by waveguide condensing of light in propagation from rod inner segment (RIS) to rod outer segment (ROS). The similar photosensitivity of rhodopsin in the two strains reveals that little light backscattered from the sclera can enter the ROS. The bleaching-induced increases in reflectance at the IS/OS junctions and OS tips resemble results previously reported in human cones, but are ascribed to rods due to their 30/1 predominance over cones in mice and to the relatively minor amount of cone M-opsin in the regions scanned. PMID:27403994

Temperature measurement by thermal strain imaging with diagnostic power ultrasound, with potential for thermal index determination.

PubMed

Liang, Hai-Dong; Zhou, Li-Xia; Wells, Peter N T; Halliwell, Michael

2009-05-01

Over the years, there has been a substantial increase in acoustic exposure in diagnostic ultrasound as new imaging modalities with higher intensities and frame rates have been introduced; and more electronic components have been packed into the probe head, so that there is a tendency for it to become hotter. With respect to potential thermal effects, including those which may be hazardous occurring during ultrasound scanning, there is a correspondingly growing need for in vivo techniques to guide the operator as to the actual temperature rise occurring in the examined tissues. Therefore, an in vivo temperature estimator would be of considerable practical value. The commonly-used method of tissue thermal index (TI) measurement with a hydrophone in water could underestimate the actual value of TI (in one report by as much as 2.9 times). To obtain meaningful results, it is necessary to map the temperature elevation in 2-D (or 3-D) space. We present methodology, results and validation of a 2-D spatial and temporal thermal strain ultrasound temperature estimation technique in phantoms, and its apparently novel application in tracking the evolution of heat deposition at diagnostic exposure levels. The same ultrasound probe is used for both transmission and reception. The displacement and thermal strain estimation methods are similar to those used in high-intensity focused ultrasound thermal monitoring. The use of radiofrequency signals permits the application of cross correlation as a similarity measurement for tracking feature displacement. The displacement is used to calculate the thermal strain directly related to the temperature rise. Good agreement was observed between the temperature rise and the ultrasound power and scan duration. Thermal strain up to 1.4% was observed during 4000-s scan. Based on the results obtained for the temperature range studied in this work, the technique demonstrates potential for applicability in phantom (and possibly in vivo tissue) temperature measurement for the determination of TI.

Strategy for reliable strain measurement in InAs/GaAs materials from high-resolution Z-contrast STEM images

NASA Astrophysics Data System (ADS)

Vatanparast, Maryam; Vullum, Per Erik; Nord, Magnus; Zuo, Jian-Min; Reenaas, Turid W.; Holmestad, Randi

2017-09-01

Geometric phase analysis (GPA), a fast and simple Fourier space method for strain analysis, can give useful information on accumulated strain and defect propagation in multiple layers of semiconductors, including quantum dot materials. In this work, GPA has been applied to high resolution Z-contrast scanning transmission electron microscopy (STEM) images. Strain maps determined from different g vectors of these images are compared to each other, in order to analyze and assess the GPA technique in terms of accuracy. The SmartAlign tool has been used to improve the STEM image quality getting more reliable results. Strain maps from template matching as a real space approach are compared with strain maps from GPA, and it is discussed that a real space analysis is a better approach than GPA for aberration corrected STEM images.

Effects of age and loading rate on equine cortical bone failure.

PubMed

Kulin, Robb M; Jiang, Fengchun; Vecchio, Kenneth S

2011-01-01

Although clinical bone fractures occur predominantly under impact loading (as occurs during sporting accidents, falls, high-speed impacts or other catastrophic events), experimentally validated studies on the dynamic fracture behavior of bone, at the loading rates associated with such events, remain limited. In this study, a series of tests were performed on femoral specimens obtained post-mortem from equine donors ranging in age from 6 months to 28 years. Fracture toughness and compressive tests were performed under both quasi-static and dynamic loading conditions in order to determine the effects of loading rate and age on the mechanical behavior of the cortical bone. Fracture toughness experiments were performed using a four-point bending geometry on single and double-notch specimens in order to measure fracture toughness, as well as observe differences in crack initiation between dynamic and quasi-static experiments. Compressive properties were measured on bone loaded parallel and transverse to the osteonal growth direction. Fracture propagation was then analyzed using scanning electron and scanning confocal microscopy to observe the effects of microstructural toughening mechanisms at different strain rates. Specimens from each horse were also analyzed for dry, wet and mineral densities, as well as weight percent mineral, in order to investigate possible influences of composition on mechanical behavior. Results indicate that bone has a higher compressive strength, but lower fracture toughness when tested dynamically as compared to quasi-static experiments. Fracture toughness also tends to decrease with age when measured quasi-statically, but shows little change with age under dynamic loading conditions, where brittle "cleavage-like" fracture behavior dominates. Copyright © 2010 Elsevier Ltd. All rights reserved.

Comprehensive Cardiovascular magnetic resonance of myocardial mechanics in mice using three-dimensional cine DENSE

PubMed Central

2011-01-01

Background Quantitative noninvasive imaging of myocardial mechanics in mice enables studies of the roles of individual genes in cardiac function. We sought to develop comprehensive three-dimensional methods for imaging myocardial mechanics in mice. Methods A 3D cine DENSE pulse sequence was implemented on a 7T small-bore scanner. The sequence used three-point phase cycling for artifact suppression and a stack-of-spirals k-space trajectory for efficient data acquisition. A semi-automatic 2D method was adapted for 3D image segmentation, and automated 3D methods to calculate strain, twist, and torsion were employed. A scan protocol that covered the majority of the left ventricle in a scan time of less than 25 minutes was developed, and seven healthy C57Bl/6 mice were studied. Results Using these methods, multiphase normal and shear strains were measured, as were myocardial twist and torsion. Peak end-systolic values for the normal strains at the mid-ventricular level were 0.29 ± 0.17, -0.13 ± 0.03, and -0.18 ± 0.14 for Err, Ecc, and Ell, respectively. Peak end-systolic values for the shear strains were 0.00 ± 0.08, 0.04 ± 0.12, and 0.03 ± 0.07 for Erc, Erl, and Ecl, respectively. The peak end-systolic normalized torsion was 5.6 ± 0.9°. Conclusions Using a 3D cine DENSE sequence tailored for cardiac imaging in mice at 7 T, a comprehensive assessment of 3D myocardial mechanics can be achieved with a scan time of less than 25 minutes and an image analysis time of approximately 1 hour. PMID:22208954

Quantitative Tracking of Salmonella Enteritidis Transmission Routes Using Barcode-Tagged Isogenic Strains in Chickens: Proof-of-Concept Study

PubMed Central

Yang, Yichao; Ricke, Steven C.; Tellez, Guillermo; Kwon, Young Min

2017-01-01

Salmonella is an important foodborne bacterial pathogen, however, a fundamental understanding on Salmonella transmission routes within a poultry flock remains unclear. In this study, a series of barcode-tagged strains were constructed by inserting six random nucleotides into a functionally neutral region on the chromosome of S. Enteritidis as a tool for quantitative tracking of Salmonella transmission in chickens. Six distinct barcode-tagged strains were used for infection or contamination at either low dose (103 CFUs; three strains) or high dose (105 CFUs; three strains) in three independent experiments (Experiment 1 oral gavage; Experiment 2 contaminated feed; Experiment 3 contaminated water). For all chick experiments, cecal and foot-wash samples were collected from a subset of the chickens at days 7 or/and 14, from which genomic DNA was extracted and used to amplify the barcode regions. After the resulting PCR amplicons were pooled and analyzed by MiSeq sequencing, a total of approximately 1.5 million reads containing the barcode sequences were analyzed to determine the relative frequency of every barcode-tagged strain in each sample. In Experiment 1, the high dose of oral infection was correlated with greater dominance of the strains in the ceca of the respective seeder chickens and also in the contact chickens yet at lesser degrees. When chicks were exposed to contaminated feed (Experiment 2) or water (Experiment 3), there were no clear patterns of the barcode-tagged strains in relation to the dosage, except that the strains introduced at low dose required a longer time to colonize the ceca with contaminated feed. Most foot-wash samples contained only one to three strains for the majority of the samples, suggesting potential existence of an unknown mechanism(s) for strain exclusion. These results demonstrated the proof of concept of using barcode tagged to investigate transmission dynamics of Salmonella in chickens in a quantitative manner. PMID:28261587

Strain-induced phase transformation at the surface of an AISI-304 stainless steel irradiated to 4.4 dpa and deformed to 0.8% strain

NASA Astrophysics Data System (ADS)

Gussev, M. N.; Field, K. G.; Busby, J. T.

2014-03-01

Surface relief due to localized deformation in a 4.4-dpa neutron-irradiated AISI 304 stainless steel was investigated using scanning electron microscopy coupled with electron backscattering diffraction and scanning transmission electron microscopy. It was found a body-centered-cubic (BCC) phase (deformation-induced martensite) had formed at the surface of the deformed specimen along the steps generated from dislocation channels. Martensitic hill-like formations with widths of ˜1 μm and depths of several microns were observed at channels with heights greater than ˜150 nm above the original surface. Martensite at dislocation channels was observed in grains along the [0 0 1]-[1 1 1] orientation but not in those along the [1 0 1] orientation.

Evaluation of MALDI-TOF mass spectrometry for the competitiveness analysis of selected indigenous cowpea (Vigna unguiculata L. Walp.) Bradyrhizobium strains from Kenya.

PubMed

Ndungu, Samuel Mathu; Messmer, Monika M; Ziegler, Dominik; Thuita, Moses; Vanlauwe, Bernard; Frossard, Emmanuel; Thonar, Cécile

2018-06-01

Cowpea N 2 fixation and yield can be enhanced by selecting competitive and efficient indigenous rhizobia. Strains from contrasting agro-ecologies of Kilifi and Mbeere (Kenya) were screened. Two pot experiments were established consisting of 13 Bradyrhizobium strains; experiment 1 (11 Mbeere + CBA + BK1 from Burkina Faso), experiment 2 (12 Kilifi + CBA). Symbiotic effectiveness was assessed (shoot biomass, SPAD index and N uptake). Nodule occupancy of 13 simultaneously co-inoculated strains in each experiment was analyzed by matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry (MS) to assess competitiveness. Strains varied in effectiveness and competitiveness. The four most efficient strains were further evaluated in a field trial in Mbeere during the 2014 short rains. Strains from bacteroids of cowpea nodules from pot and field experiments were accurately identified as Bradyrhizobium by MALDI-TOF based on the SARAMIS™ database. In the field, abundant indigenous populations 7.10 × 10 3 rhizobia g -1 soil, outcompeted introduced strains. As revealed by MALDI-TOF, indigenous strains clustered into six distinct groups (I, II, III, IV, V and VI), group III were most abundant occupying 80% of nodules analyzed. MALDI-TOF was rapid, affordable and reliable to identify Bradyrhizobium strains directly from nodule suspensions in competition pot assays and in the field with abundant indigenous strains thus, its suitability for future competition assays. Evaluating strain competitiveness and then symbiotic efficacy is proposed in bioprospecting for potential cowpea inoculant strains.

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

Li, D.F.; Zhang, X.M.; Gautier, E.

The morphology and crystallography of deformation-induced martensites formed during isothermal tensile tests in Fe-30Ni-0.34C and Fe-25Ni-0.66C alloys were investigated by means of optical, transmission electron and scanning electron microscopy. Transitions in morphology from thin plate to coupled plate, to lenticular coupled-plate martensite and from thin plate to lenticular to compact martensite have been observed with increasing deformation. Stress favors the growth of martensite when concurrent plastic strain allows accommodation of macroscopic transformation strains and the change of the Bain strain accommodation mechanism. Mobile dislocations and emission dislocations are directly related to the change of the Bain strain accommodation mechanism frommore » twinning to slip.« less

Strain effects on the work function of an organic semiconductor

PubMed Central

Wu, Yanfei; Chew, Annabel R.; Rojas, Geoffrey A.; Sini, Gjergji; Haugstad, Greg; Belianinov, Alex; Kalinin, Sergei V.; Li, Hong; Risko, Chad; Brédas, Jean-Luc; Salleo, Alberto; Frisbie, C. Daniel

2016-01-01

Establishing fundamental relationships between strain and work function (WF) in organic semiconductors is important not only for understanding electrical properties of organic thin films, which are subject to both intrinsic and extrinsic strains, but also for developing flexible electronic devices. Here we investigate tensile and compressive strain effects on the WF of rubrene single crystals. Mechanical strain induced by thermal expansion mismatch between the substrate and rubrene is quantified by X-ray diffraction. The corresponding WF change is measured by scanning Kelvin probe microscopy. The WF of rubrene increases (decreases) significantly with in-plane tensile (compressive) strain, which agrees qualitatively with density functional theory calculations. An elastic-to-plastic transition, characterized by a steep rise of the WF, occurs at ∼0.05% tensile strain along the rubrene π-stacking direction. The results provide the first concrete link between mechanical strain and WF of an organic semiconductor and have important implications for understanding the connection between structural and electronic disorder in soft organic electronic materials. PMID:26831362

Strain effects on the work function of an organic semiconductor

NASA Astrophysics Data System (ADS)

Wu, Yanfei; Chew, Annabel R.; Rojas, Geoffrey A.; Sini, Gjergji; Haugstad, Greg; Belianinov, Alex; Kalinin, Sergei V.; Li, Hong; Risko, Chad; Brédas, Jean-Luc; Salleo, Alberto; Frisbie, C. Daniel

2016-02-01

Establishing fundamental relationships between strain and work function (WF) in organic semiconductors is important not only for understanding electrical properties of organic thin films, which are subject to both intrinsic and extrinsic strains, but also for developing flexible electronic devices. Here we investigate tensile and compressive strain effects on the WF of rubrene single crystals. Mechanical strain induced by thermal expansion mismatch between the substrate and rubrene is quantified by X-ray diffraction. The corresponding WF change is measured by scanning Kelvin probe microscopy. The WF of rubrene increases (decreases) significantly with in-plane tensile (compressive) strain, which agrees qualitatively with density functional theory calculations. An elastic-to-plastic transition, characterized by a steep rise of the WF, occurs at ~0.05% tensile strain along the rubrene π-stacking direction. The results provide the first concrete link between mechanical strain and WF of an organic semiconductor and have important implications for understanding the connection between structural and electronic disorder in soft organic electronic materials.

Strain effects on the work function of an organic semiconductor.

PubMed

Wu, Yanfei; Chew, Annabel R; Rojas, Geoffrey A; Sini, Gjergji; Haugstad, Greg; Belianinov, Alex; Kalinin, Sergei V; Li, Hong; Risko, Chad; Brédas, Jean-Luc; Salleo, Alberto; Frisbie, C Daniel

2016-02-01

Establishing fundamental relationships between strain and work function (WF) in organic semiconductors is important not only for understanding electrical properties of organic thin films, which are subject to both intrinsic and extrinsic strains, but also for developing flexible electronic devices. Here we investigate tensile and compressive strain effects on the WF of rubrene single crystals. Mechanical strain induced by thermal expansion mismatch between the substrate and rubrene is quantified by X-ray diffraction. The corresponding WF change is measured by scanning Kelvin probe microscopy. The WF of rubrene increases (decreases) significantly with in-plane tensile (compressive) strain, which agrees qualitatively with density functional theory calculations. An elastic-to-plastic transition, characterized by a steep rise of the WF, occurs at ∼0.05% tensile strain along the rubrene π-stacking direction. The results provide the first concrete link between mechanical strain and WF of an organic semiconductor and have important implications for understanding the connection between structural and electronic disorder in soft organic electronic materials.

Strain measurement in semiconductor heterostructures by scanning transmission electron microscopy.

PubMed

Müller, Knut; Rosenauer, Andreas; Schowalter, Marco; Zweck, Josef; Fritz, Rafael; Volz, Kerstin

2012-10-01

This article deals with the measurement of strain in semiconductor heterostructures from convergent beam electron diffraction patterns. In particular, three different algorithms in the field of (circular) pattern recognition are presented that are able to detect diffracted disc positions accurately, from which the strain in growth direction is calculated. Although the three approaches are very different as one is based on edge detection, one on rotational averages, and one on cross correlation with masks, it is found that identical strain profiles result for an In x Ga1-x N y As1-y /GaAs heterostructure consisting of five compressively and tensile strained layers. We achieve a precision of strain measurements of 7-9·10-4 and a spatial resolution of 0.5-0.7 nm over the whole width of the layer stack which was 350 nm. Being already very applicable to strain measurements in contemporary nanostructures, we additionally suggest future hardware and software designs optimized for fast and direct acquisition of strain distributions, motivated by the present studies.

Strain effects on the work function of an organic semiconductor

DOE PAGES

Wu, Yanfei; Chew, Annabel R.; Rojas, Geoffrey A.; ...

2016-02-01

Establishing fundamental relationships between strain and work function (WF) in organic semiconductors is important not only for understanding the electrical properties of organic thin films, which are subject to both intrinsic and extrinsic strains, but also for developing flexible electronic devices. Here we investigate tensile and compressive strain effects on the WF of rubrene single crystals. Mechanical strain induced by thermal expansion mismatch between the substrate and rubrene is quantified by X-ray diffraction. The corresponding WF change is measured by scanning Kelvin probe microscopy. The WF of rubrene increases (decreases) significantly with in-plane tensile (compressive) strain, which agrees qualitatively withmore » density functional theory calculations. An elastic-to-plastic transition, characterized by a steep rise of the WF, occurs at ~0.05% tensile strain along the rubrene -stacking direction. The results provide the first concrete link between mechanical strain and the WF of an organic semiconductor and have important implications for understanding the connection between structural and electronic disorder (charge traps) in soft organic electronic materials.« less

Dynamic Response and Microstructure Evolution of AA2219-T4 and AA2219-T6 Aluminum Alloys

NASA Astrophysics Data System (ADS)

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

2018-02-01

In this study, the dynamic deformation behavior of AA2219 aluminum alloy was investigated in two different temper conditions: T4 and T6, with a view to determining the effect of heat treatment on the microstructure and flow behavior of the material under high strain rates. Split Hopkinson pressure bar experiment was used in determining the dynamic response of the alloy while a digital image correlation system was employed in visualizing and tracking the surface deformation of the specimens. Optical microscopy and scanning electron microscopy were used to assess the microstructure of the material after following standard metallographic specimen preparation techniques. The results obtained showed heterogeneous deformation of the alloy in the two temper conditions. It was observed that the dynamic mechanical behavior of each sample preparation was dependent on its strength properties due to aging type, which in turn controls the metamorphosis of the strengthening precipitates and the initial microstructure. At the maximum strain rate of 3500 s-1, transformed bands leading to crack nucleation was observed in the AA2219-T4 aluminum alloy while AA2219-T6 had fractured at the same strain rate. The modes of crack formation and growth in the two alloys were found to be similar: nucleation, growth and coalescence of voids. However, shear band bifurcation phenomenon was observed only in the AA2219-T6 alloy.

Weathering of a Roman Mosaic—A Biological and Quantitative Study on In Vitro Colonization of Calcareous Tesserae by Phototrophic Microorganisms

PubMed Central

Nocerino, Simona; Pinto, Gabriele; Pollio, Antonino; Trojsi, Giorgio; Natale, Antonino De

2016-01-01

The potential impact of cyanobacteria and microalgae on the weathering of calcareous tesserae from a Roman mosaic of the II Century CE has been followed through in vitro experiments. Laboratory tests were carried out by inoculating mosaic tiles with single strains of Cyanobacteria or Chlorophyta to evaluate the roles of pioneer phototrophic microrganism on the resulting architecture of biofilms. The interaction between tesserae and strains was assessed at the whole substratum and micrometer scales, by image analysis and Confocal Laser Scanning (CLS) microscopy, respectively. The biofilm surface coverage on each tessera varied from 19% (Fischerella ambigua) to 97% (Microcoleus autumnalis). Cyanobacteria showed a better growth on calcareous tesserae, whereas the only green alga attaining a superficial coverage higher than 50% was Coelastrella rubescens. CLS microscopy evidenced two different types of spatial arrangement of the phototrophic organisms on the tesserae, that were defined as compact or porous, respectively. In the first one was measured a reduced number of empty spaces between cells or filaments, whereas in the second type, a reticulate texture allowed the presence of numerous empty volumes. The colonization processes observed are an intrinsic characteristic of each strain. We have proposed a colonization index IC as a sensible tool to describe, in a quantitative way, the pioneering attitude of each photosynthetic microorganism to colonize lithic substrates under laboratory conditions. PMID:27783631

Weathering of a Roman Mosaic-A Biological and Quantitative Study on In Vitro Colonization of Calcareous Tesserae by Phototrophic Microorganisms.

PubMed

Marasco, Addolorata; Nocerino, Simona; Pinto, Gabriele; Pollio, Antonino; Trojsi, Giorgio; Natale, Antonino De

2016-01-01

The potential impact of cyanobacteria and microalgae on the weathering of calcareous tesserae from a Roman mosaic of the II Century CE has been followed through in vitro experiments. Laboratory tests were carried out by inoculating mosaic tiles with single strains of Cyanobacteria or Chlorophyta to evaluate the roles of pioneer phototrophic microrganism on the resulting architecture of biofilms. The interaction between tesserae and strains was assessed at the whole substratum and micrometer scales, by image analysis and Confocal Laser Scanning (CLS) microscopy, respectively. The biofilm surface coverage on each tessera varied from 19% (Fischerella ambigua) to 97% (Microcoleus autumnalis). Cyanobacteria showed a better growth on calcareous tesserae, whereas the only green alga attaining a superficial coverage higher than 50% was Coelastrella rubescens. CLS microscopy evidenced two different types of spatial arrangement of the phototrophic organisms on the tesserae, that were defined as compact or porous, respectively. In the first one was measured a reduced number of empty spaces between cells or filaments, whereas in the second type, a reticulate texture allowed the presence of numerous empty volumes. The colonization processes observed are an intrinsic characteristic of each strain. We have proposed a colonization index IC as a sensible tool to describe, in a quantitative way, the pioneering attitude of each photosynthetic microorganism to colonize lithic substrates under laboratory conditions.

Dynamic Response and Microstructure Evolution of AA2219-T4 and AA2219-T6 Aluminum Alloys

NASA Astrophysics Data System (ADS)

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

2018-06-01

In this study, the dynamic deformation behavior of AA2219 aluminum alloy was investigated in two different temper conditions: T4 and T6, with a view to determining the effect of heat treatment on the microstructure and flow behavior of the material under high strain rates. Split Hopkinson pressure bar experiment was used in determining the dynamic response of the alloy while a digital image correlation system was employed in visualizing and tracking the surface deformation of the specimens. Optical microscopy and scanning electron microscopy were used to assess the microstructure of the material after following standard metallographic specimen preparation techniques. The results obtained showed heterogeneous deformation of the alloy in the two temper conditions. It was observed that the dynamic mechanical behavior of each sample preparation was dependent on its strength properties due to aging type, which in turn controls the metamorphosis of the strengthening precipitates and the initial microstructure. At the maximum strain rate of 3500 s-1, transformed bands leading to crack nucleation was observed in the AA2219-T4 aluminum alloy while AA2219-T6 had fractured at the same strain rate. The modes of crack formation and growth in the two alloys were found to be similar: nucleation, growth and coalescence of voids. However, shear band bifurcation phenomenon was observed only in the AA2219-T6 alloy.

Quantitative In Situ TEM Studies of Small-Scale Plasticity in Irradiated and Unirradiated Metals

NASA Astrophysics Data System (ADS)

Chisholm, Claire

In this work, unirradiated and irradiated model body centered cubic (BCC) and face centered cubic (FCC) materials are investigated using advanced electron microscopy techniques to quantitatively measure local stresses and strains around defects, with the overarching goal of obtaining a fundamental understanding of defect physics. Quantitative in-situ transmission electron microscopy (TEM) tensile tests are performed with Molybdenum-alloy nano-fibers, functioning as a model BCC structural material. Local true stress and strain around an active Frank-Read type dislocation source are obtained using quantitative load-displacement data and digital image correlation. A mixed Frank-Read dislocation source, b=a/2[-1-11](112) with a line direction 20° from a screw orientation and length 177 nm, is observed to begin operating at a measured local stress of 1.38 GPa. The measured local true stress values compare very well to estimated stresses using dislocation radius of curvature, and a line-tension model of a large bow-out configuration, with differences of only ˜1%. The degree to which the local true stresses can be measured is highly promising. However, the ultimate failure mode of these fibers, sudden strain softening after dislocation starvation and exhaustion, cannot be captured at the typical camera frame rate of 30 frames per second. Thus, fibers are mechanically tested while under observation with the Gatan K2-IS direct electron detector camera, where the frame rate is an order of magnitude larger at 400 fps. Though the increase in frame rate adds to the overall understanding of the sudden failure, by definitively showing that the nano-fibers break rather than strain soften, the failure mechanism still operates too quickly to be observed. In the final investigation of this BCC model structural alloy, the mechanical behavior of heavily dislocated, but unirradiated, and He1+ and Ni 2+ irradiated nano-fibers are compared. Remarkable similarities are found in the mechanical data, as the two defect conditions exhibit similar yield strengths, ultimate tensile strengths, and number and size of load-drops. This similarity implies that, even if materials contain dissimilar individual defects, the collective defect behavior can result in similar mechanical properties. Thus, the origin of mechanical properties can be ambiguous and caution should be taken when extrapolating to different size scales. Furthermore, such similarities highlight the importance of in-situ observation during deformation. These experiments provide a key test of theory, by providing a local test of behavior, which is much more stringent than testing behaviors averaged over many regions. Advanced electron microscopy imaging techniques and quantitative in-situ TEM tensile tests are performed with Au thin-film as a model FCC structural material. These investigations highlight the various hurdles experimental studies must overcome in order to probe defect behavior at a fundamental level. Two novelly-applied strain mapping techniques are performed to directly measure the matrix strain around helium bubbles in He1+ implanted Au thin-film. Dark-field inline holography (DFIH) is applied here for the first time to a metal, and nano-beam electron diffraction (NBED) transient strain mapping is shown to be experimentally feasible using the high frame rate Gatan K2 camera. The K2 camera reduces scan times from ˜18 minutes to 82 seconds for a 128x256 pixel scan at 400 fps. Both methods measure a peak strain around 10 nm bubbles of 0.7%, correlating to an internal pressure of 580 MPa, or a vacancy to helium ion ratio of 1V:2.4He. Previous studies have relied on determining the appropriate equation of state to relate measured or approximated helium density to internal bubble pressure and thus strain. Direct measurement of the surrounding matrix strain through DFIH and NBED methods effectively bypasses this step, allowing for easier defect interaction modeling as the bubble can be effectively simplified to its matrix strain. Furthermore, this study demonstrates the feasibility of fully strain mapping, in four dimensions, any in-situ TEM experiment. The final set of experiments with this model FCC structural material shows the attempted correlation of defect interactions and deformation behavior at the nano-scale. Experimental comparison of mechanical behavior from quantitative in-situ TEM tensile tests of focused ion beam (FIB) shaped, He1+ implanted, and FIB-shaped He1+ implanted Au thin-film show a wide range of behavior that could not be directly linked to irradiation condition. This is due to the large role that overall microstructural features, such as grain boundary orientation and texture, play in mechanical behavior at this size scale. However, these tests are some of the first to in-situ TEM mechanically strain single grain-boundaries free of FIB-damage. It is expected that, with well-defined grain orientations and boundaries, real conclusions can be made.

A genome scan for selection signatures comparing farmed Atlantic salmon with two wild populations: Testing colocalization among outlier markers, candidate genes, and quantitative trait loci for production traits.

PubMed

Liu, Lei; Ang, Keng Pee; Elliott, J A K; Kent, Matthew Peter; Lien, Sigbjørn; MacDonald, Danielle; Boulding, Elizabeth Grace

2017-03-01

Comparative genome scans can be used to identify chromosome regions, but not traits, that are putatively under selection. Identification of targeted traits may be more likely in recently domesticated populations under strong artificial selection for increased production. We used a North American Atlantic salmon 6K SNP dataset to locate genome regions of an aquaculture strain (Saint John River) that were highly diverged from that of its putative wild founder population (Tobique River). First, admixed individuals with partial European ancestry were detected using STRUCTURE and removed from the dataset. Outlier loci were then identified as those showing extreme differentiation between the aquaculture population and the founder population. All Arlequin methods identified an overlapping subset of 17 outlier loci, three of which were also identified by BayeScan. Many outlier loci were near candidate genes and some were near published quantitative trait loci (QTLs) for growth, appetite, maturity, or disease resistance. Parallel comparisons using a wild, nonfounder population (Stewiacke River) yielded only one overlapping outlier locus as well as a known maturity QTL. We conclude that genome scans comparing a recently domesticated strain with its wild founder population can facilitate identification of candidate genes for traits known to have been under strong artificial selection.

Robust intravascular optical coherence elastography driven by acoustic radiation pressure

NASA Astrophysics Data System (ADS)

van Soest, Gijs; Bouchard, Richard R.; Mastik, Frits; de Jong, Nico; van der Steen, Anton F. W.

2007-07-01

High strain spots in the vessel wall indicate the presence of vulnerable plaques. The majority of acute cardiovascular events are preceded by rupture of such a plaque in a coronary artery. Intracoronary optical coherence tomography (OCT) can be extended, in principle, to an elastography technique, mapping the strain in the vascular wall. However, the susceptibility of OCT to frame-to-frame decorrelation, caused by tissue and catheter motion, inhibits reliable tissue displacement tracking and has to date obstructed the development of OCT-based intravascular elastography. We introduce a new technique for intravascular optical coherence elastography, which is robust against motion artifacts. Using acoustic radiation force, we apply a pressure to deform the tissue synchronously with the line scan rate of the OCT instrument. Radial tissue displacement can be tracked based on the correlation between adjacent lines, instead of subsequent frames in conventional elastography. The viability of the method is demonstrated with a simulation study. The root mean square (rms) error of the displacement estimate is 0.55 μm, and the rms error of the strain is 0.6%. It is shown that high-strain spots in the vessel wall, such as observed at the sites of vulnerable atherosclerotic lesions, can be detected with the technique. Experiments to realize this new elastographic method are presented. Simultaneous optical and ultrasonic pulse-echo tracking demonstrate that the material can be put in a high-frequency oscillatory motion with an amplitude of several micrometers, more than sufficient for accurate tracking with OCT. The resulting data are used to optimize the acoustic pushing sequence and geometry.

Study on biofilm-forming properties of clinical isolates of Staphylococcus aureus.

PubMed

Taj, Yasmeen; Essa, Farhan; Aziz, Faisal; Kazmi, Shahana Urooj

2012-05-14

The purpose of this study was to observe the formation of biofilm, an important virulence factor, by isolates of Staphylococcus aureus (S. aureus) in Pakistan by different conventional methods and through electron microscopy. We screened 115 strains of S. aureus isolated from different clinical specimens by tube method (TM), air-liquid interface coverslip assay method, Congo red agar (CRA) method, and scanning electron microscopy (SEM). Out of 115 S. aureus isolates, 63 (54.78%) showed biofilm formation by tube method. Biofilm forming bacteria were further categorized as high producers (n = 23, 20%) and moderate producers (n = 40, 34.78%). TM coordinated well with the coverslip assay for strong biofilm-producing strains in 19 (16.5%) isolates. By coverslip method, weak producers were difficult to differentiate from biofilm negative isolates. Screening on CRA showed biofilm formation only in four (3.47%) strains. Scanning electron micrographs showed the biofilm-forming strains of S. aureus arranged in a matrix on the propylene surface and correlated well with the TM. Biofilm production is a marker of virulence for clinically relevant staphylococcal infections. It can be studied by various methods but screening on CRA is not recommended for investigation of biofilm formation in Staphylococcus aureus. Electron micrograph images correlate well with the biofilm production as observed by TM.

Room temperature ferrimagnetism and ferroelectricity in strained, thin films of BiFe 0.5Mn 0.5O 3

DOE PAGES

Choi, Eun -Mi; Fix, Thomas; Kursumovic, Ahmed; ...

2014-10-14

In this study, highly strained films of BiFe 0.5Mn 0.5O 3 (BFMO) grown at very low rates by pulsed laser deposition were demonstrated to exhibit both ferrimagnetism and ferroelectricity at room temperature and above. Magnetization measurements demonstrated ferrimagnetism (T C ~ 600K), with a room temperature saturation moment (M S) of up to 90 emu/cc (~0.58μ B/f.u) on high quality (001) SrTiO 3. X-ray magnetic circular dichroism showed that the ferrimagnetism arose from antiferromagnetically coupled Fe 3+ and Mn 3+ . While scanning transmission electron microscope studies showed there was no long range ordering of Fe and Mn, the magneticmore » properties were found to be strongly dependent on the strain state in the films. The magnetism is explained to arise from one of three possible mechanisms with Bi polarization playing a key role. A signature of room temperature ferroelectricity in the films was measured by piezoresponse force microscopy and was confirmed using angular dark field scanning transmission electron microscopy. The demonstration of strain induced, high temperature multiferroism is a promising development for future spintronic and memory applications at room temperature and above.« less

SEA domain autoproteolysis accelerated by conformational strain: mechanistic aspects.

PubMed

Johansson, Denny G A; Macao, Bertil; Sandberg, Anders; Härd, Torleif

2008-04-04

A subclass of SEA (sea urchin sperm protein, enterokinase, and agrin) domain proteins undergoes autoproteolysis between glycine and serine in a conserved G(-1)S+1VVV motif to generate stable heterodimers. Autoproteolysis has been suggested to involve only the intramolecular catalytic action of the conserved serine hydroxyl in combination with conformational strain of the glycine-serine peptide bond. We conducted a number of experiments and simulations on the SEA domain from the MUC1 mucin to test this mechanism. Alanine-scanning mutagenesis of polar residues in the vicinity of the cleavage site demonstrates that only the nucleophile at position +1 is required for efficient proteolysis. Molecular modeling shows that an uncleaved trans peptide is incompatible with the native heterodimeric structure, resulting in disruption of secondary structure elements and distortion of the scissile peptide bond. Insertion of glycine residues (to obtain G(n)G(-1)S+1VVV motifs) appears to relieve strain, and autoproteolysis is 100 times slower in a 1G (n=1) mutant and not measurable in 2G and 4G mutants. Removal of the catalytic serine hydroxyl hampers cleavage considerably, but measurable autoproteolysis of this S1098A mutant still proceeds in the presence of strain alone. The uncleaved SEA precursor populates interconverting partially folded conformations, and autoproteolysis coincides with adoption of proper beta-sheet secondary structure and completed folding. Molecular dynamics simulations of the precursor show that the serine hydroxyl and the preceding glycine carbonyl carbon can be in van der Waals contact at the same time as the scissile peptide bond becomes strained. These observations are all consistent with autoproteolysis accelerated by N-->O acyl shift and conformational strain imposed upon protein folding in a reaction for which the free-energy barrier is decreased by substrate destabilization rather than by transition-state stabilization. The energetics of this coupled folding and autoproteolysis mechanism is accounted for in an accompanying article.

Optimized phase gradient measurements and phase-amplitude interplay in optical coherence elastography

NASA Astrophysics Data System (ADS)

Zaitsev, Vladimir Y.; Matveyev, Alexander L.; Matveev, Lev A.; Gelikonov, Grigory V.; Sovetsky, Aleksandr A.; Vitkin, Alex

2016-11-01

In compressional optical coherence elastography, phase-variation gradients are used for estimating quasistatic strains created in tissue. Using reference and deformed optical coherence tomography (OCT) scans, one typically compares phases from pixels with the same coordinates in both scans. Usually, this limits the allowable strains to fairly small values < to 10-3, with the caveat that such weak phase gradients may become corrupted by stronger measurement noises. Here, we extend the OCT phase-resolved elastographic methodology by (1) showing that an order of magnitude greater strains can significantly increase the accuracy of derived phase-gradient differences, while also avoiding error-phone phase-unwrapping procedures and minimizing the influence of decorrelation noise caused by suprapixel displacements, (2) discussing the appearance of artifactual stiff inclusions in resultant OCT elastograms in the vicinity of bright scatterers due to the amplitude-phase interplay in phase-variation measurements, and (3) deriving/evaluating methods of phase-gradient estimation that can outperform conventionally used least-square gradient fitting. We present analytical arguments, numerical simulations, and experimental examples to demonstrate the advantages of the proposed optimized phase-variation methodology.

Template assisted strain tuning and phase stabilization in epitaxial BiFeO3 thin films

NASA Astrophysics Data System (ADS)

Saj Mohan M., M.; Ramadurai, Ranjith

2018-04-01

Strain engineering is a key to develop novel properties in functional materials. We report a strain mediated phase stabilization and epitaxial growth of bismuth ferrite(BiFeO3) thin films on LaAlO3 (LAO) substrates. The strain in the epitaxial layer is controlled by controlling the thickness of bottom electrode where the thickness of the BFO is kept constant. The thickness of La0.7Sr0.3MnO3(LSMO) template layer was optimized to grow completely strained tetragonal, tetragonal/rhombohedral mixed phase and fully relaxed rhombohedral phase of BFO layers. The results were confirmed with coupled-θ-2θ scan, and small area reciprocal space mapping. The piezoelectric d33 (˜ 45-48 pm/V) coefficient of the mixed phase was relatively larger than the strained tetragonal and relaxed rhombohedral phase for a given thickness.

Effects of mechanical strain amplitude on the isothermal fatigue behavior of H13

NASA Astrophysics Data System (ADS)

Zeng, Yan; Zuo, Peng-peng; Wu, Xiao-chun; Xia, Shu-wen

2017-09-01

Isothermal fatigue (IF) tests were performed on H13 tool steel subjected to three different mechanical strain amplitudes at a constant temperature to determine the effects of mechanical strain amplitude on the microstructure of the steel samples. The samples' extent of damage after IF tests was compared by observation of their cracks and calculation of their damage parameters. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to observe the microstructure of the samples. Cracks were observed to initiate at the surface because the strains and stresses there were the largest during thermal cycling. Mechanical strain accelerated the damage and softening of the steel. A larger mechanical strain caused greater deformation of the steel, which made the precipitated carbides easier to gather and grow along the deformation direction, possibly resulting in softening of the material or the initiation of cracks.

Analysis of Crushing Response of Composite Crashworthy Structures

NASA Astrophysics Data System (ADS)

David, Matthew; Johnson, Alastair F.; Voggenreiter, H.

2013-10-01

The paper describes quasi-static and dynamic tests to characterise the energy absorption properties of polymer composite crash energy absorbing segment elements under axial loads. Detailed computer tomography scans of failed specimens are used to identify local compression crush failure mechanisms at the crush front. The varied crushing morphology between the compression strain rates identified in this paper is observed to be due to the differences in the response modes and mechanical properties of the strain dependent epoxy matrix. The importance of understanding the role of strain rate effects in composite crash energy absorbing structures is highlighted in this paper.

Stress and strain distribution in three different mini dental implant designs using in implant retained overdenture: a finite element analysis study

PubMed Central

AUNMEUNGTONG, W.; KHONGKHUNTHIAN, P.; RUNGSIYAKULL, P.

2016-01-01

SUMMARY Finite Element Analysis (FEA) has been used for prediction of stress and strain between dental implant components and bone in the implant design process. Purpose Purpose of this study was to characterize and analyze stress and strain distribution occurring in bone and implants and to compare stress and strain of three different implant designs. Materials and methods Three different mini dental implant designs were included in this study: 1. a mini dental implant with an internal implant-abutment connection (MDIi); 2. a mini dental implant with an external implant-abutment connection (MDIe); 3. a single piece mini dental implant (MDIs). All implant designs were scanned using micro-CT scans. The imaging details of the implants were used to simulate models for FEA. An artificial bone volume of 9×9 mm in size was constructed and each implant was placed separately at the center of each bone model. All bone-implant models were simulatively loaded under an axial compressive force of 100 N and a 45-degree force of 100 N loading at the top of the implants using computer software to evaluate stress and strain distribution. Results There was no difference in stress or strain between the three implant designs. The stress and strain occurring in all three mini dental implant designs were mainly localized at the cortical bone around the bone-implant interface. Oblique 45° loading caused increased deformation, magnitude and distribution of stress and strain in all implant models. Conclusions Within the limits of this study, the average stress and strain in bone and implant models with MDIi were similar to those with MDIe and MDIs. The oblique 45° load played an important role in dramatically increased average stress and strain in all bone-implant models. Clinical implications Mini dental implants with external or internal connections have similar stress distribution to single piece mini dental implants. In clinical situations, the three types of mini dental implant should exhibit the same behavior to chewing force. PMID:28042449

A study on the effect of surface topography on the actuation performance of stacked-rolled dielectric electro active polymer actuator

NASA Astrophysics Data System (ADS)

Sait, Usha; Muthuswamy, Sreekumar

2016-05-01

Dielectric electro active polymer (DEAP) is a suitable actuator material that finds wide applications in the field of robotics and medical areas. This material is highly controllable, flexible, and capable of developing large strain. The influence of geometrical behavior becomes critical when the material is used as miniaturized actuation devices in robotic applications. The present work focuses on the effect of surface topography on the performance of flat (single sheet) and stacked-rolled DEAP actuators. The non-active areas in the form of elliptical spots that affect the performance of the actuator are identified using scanning electron microscope (SEM) and energy dissipated X-ray (EDX) experiments. Performance of DEAP actuation is critically evaluated, compared, and presented with analytical and experimental results.

The pros and cons of code validation

NASA Technical Reports Server (NTRS)

Bobbitt, Percy J.

1988-01-01

Computational and wind tunnel error sources are examined and quantified using specific calculations of experimental data, and a substantial comparison of theoretical and experimental results, or a code validation, is discussed. Wind tunnel error sources considered include wall interference, sting effects, Reynolds number effects, flow quality and transition, and instrumentation such as strain gage balances, electronically scanned pressure systems, hot film gages, hot wire anemometers, and laser velocimeters. Computational error sources include math model equation sets, the solution algorithm, artificial viscosity/dissipation, boundary conditions, the uniqueness of solutions, grid resolution, turbulence modeling, and Reynolds number effects. It is concluded that, although improvements in theory are being made more quickly than in experiments, wind tunnel research has the advantage of the more realistic transition process of a right turbulence model in a free-transition test.

Phenotypic and genotypic characterization of Prototheca zopfii in a dog with enteric signs.

PubMed

Ribeiro, Márcio Garcia; Rodrigues de Farias, Marconi; Roesler, Uwe; Roth, Katja; Rodigheri, Sabrina Mari; Ostrowsky, Marco Antonio; Salerno, Tatiana; Siqueira, Amanda Keller; Fernandes, Marta Catarina

2009-12-01

This is a case report of enteric protothecosis caused by Prototheca zopfii in an eight-year-old male mixed breed dog with a history of chronic bloody diarrhea, loss of appetite and weight loss. Algae were isolated from rectal scrapings in defibrinated sheep blood agar and dextrose Sabouraud agar. Cytological evaluation showed the presence of globular and cylindrical organisms with a defined capsule and variable number of endospores, characteristic of the genus Prototheca, in the rectum of the animal. Scanning electron microscopy of P. zopfii strains at different development stages confirmed the diagnosis of algal infection. Molecular identification using a conserved 18S rDNA gene sequence determined that the strain belonged to genotype 2. This report describes success on treatment of canine protothecosis, diagnosed based on clinical, cytological, microbiological, scanning electron microscopy and genotypical findings.

Ultra-sensitive Chip-based Photonic Temperature Sensor Using Ring Resonator Structures

DTIC Science & Technology

2014-02-10

273.15 K to 373 K [15]. An optical analog of this, using infrared light to probe strain- free fiber Bragg gratings ( FBG ), exhibits temperature...sensors [9, 12, 13]. However, FBGs are susceptible to strain and are relatively large. Instead, we consider the use of ring resonators. In recent years...Traditionally, photonic thermometers such as those based on Fiber Bragg gratings ( FBG ) employ continuous wavelength scanning techniques to measure

Effect of strain on structure and charge order transitions in epitaxial Bi0.4Ca0.6MnO3 films on perovskite (001) and (011) substrates

NASA Astrophysics Data System (ADS)

Kim, Dae Ho; Christen, Hans M.; Varela, Maria; Lee, Ho Nyung; Lowndes, Douglas H.

2006-05-01

The effect of epitaxial strain on the charge order (CO) transition in Bi0.4Ca0.6MnO3 films was studied by varying the strain's strength and symmetry via the use of SrTiO3 and LaAlO3 substrates having different crystallographic orientations. The film on pseudocubic (001) LaAlO3, under symmetric compressive strain, exhibits a clear CO transition. In the film on a (001) SrTiO3 substrate, under symmetric tensile strain, highly segregated line-shaped features in the Bi distribution are seen in Z-contrast scanning transmission microscopy, accompanied by a strongly broadened CO transition. The asymmetric tensile stress on (011) SrTiO3 results in an apparent compressive strain state with a deviation from tetragonality (i.e., γ ≠90°), accompanied by the sharpest CO transition. These comparisons illustrate the importance of considering both the strength and symmetry of epitaxial strain.

Role of strained nano-regions in the formation of subgrains in CaCu3Ti4O12

NASA Astrophysics Data System (ADS)

Fang, Tsang-Tse; Wang, Yong-Huei; Kuo, Jui-Chao

2011-07-01

Single-phase CaCu3Ti4O12 (CCTO) was synthesized by solid-state reaction. Electron backscatter diffraction, scanning electron microscopy, and atomic force microscopy were adopted to characterize the grain orientation, microstructure, and surface morphology of the CCTO samples with or without thermal etching. Bump strained nano-regions induced by the local compositional disorder at a nano-scale have been discovered, being the origin of the formation of subgrains in CCTO. The proposed mechanism for the formation of subgrains involves the formation of etched pits and subboundaries pertaining to the strained nano-regions rather than dislocation displacement. The dielectric response inside the grains of CCTO relevant to the strained nano-regions is also discussed.

Rapid Bacterial Testing for Spacecraft Water

NASA Technical Reports Server (NTRS)

Lisle, John T.; Pyle, Barry H.; McFeters, Gordon A.

1996-01-01

Evaluations of the fluorogenic stains and probes will continue. E. coli 0157:H7 will be used as the reference strain for optimizing protocols. We anticipate the continued use of the fluorescent antibodies (TRITC and FITC labeled) in conjunction with CTC, Rhl23, DiBAC4(3), DAPI and acridine orange. Chemunex, the manufacturer of the ChemScan analyzer system, also makes a fluorogenic probe, Chemchrome B, which will be incorporated into the suite of probes to evaluate once their system is on site. Regardless of the combination of stains and probes all will be evaluated on membrane filters. Development of a FISH protocol that will be applicable to our conditions will be continued. Complimentary 16s rRNA probes to Ps. aeruginosa and currently in our laboratory will be evaluated first. Once this protocol has been adequately optimized other probes will be ordered for u a select number of other species. Currently, protocols to evaluate the effects of disinfection and the resulting lethality, injury on stain and/or probe specificity and reliability are being developed. E. coli 0157:H7 is the reference strain and chlorine the disinfectant the reference protocol is being developed around. Upon completion of this work, the resulting protocol will be extended to other species and disinfectants (e.g., iodine). Similar disinfectant experiments will then be conducted on the same species after starvation to evaluate the effects of starvation on disinfection resistance and the applicability of the stains and probes. Development of the immunomagnetic separation system will continue. Combined with the rapid methods described above, with enumeration by the ChemScan, we anticipate that this will provide a highly sensitive technique for the detection of specific, active bacteria.

SU-E-T-594: Preliminary Active Scanning Results of KHIMA

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

Kim, C; Yang, T; Chang, S

Purpose: To verify the design criteria on heavy ion beam irradiation, developing a proto type active scanning system was purposed. The active scanning system consists of scanning magnet, power supplies, beam monitors, energy modulation system, and irradiation control system. Methods: Each components of the active scanning system was designed for carbon beam first. For the fast ramping a laminated yoke was purposed. To measure incoming dose and profile, a plate and strip type of ion chambers were designed. Also, ridge filter and range shifter was manufactured. And, the scanning system was modified to adopt 45 MeV of proton beam becausemore » of the absence of carbon ion beam in Korea. The system was installed in a beam line at MC-50, KIRAMS. Also, the irradiation control system and planning software was provided. Results: The scanning experiment was performed by drawing KHIMA logo on GaF film. The logo was scanned by 237 scanning points through time normalized intensity modulation. Also, a grid points scanning was performed to measure the scanning resolution and intensity resolution. Conclusion: A prototype active scanning system was successfully designed and manufactured. Also, an initial experiment to print out a drawing on GaF film through the scanning system was completed. More experiments would be required to specify the system performance.« less

Detection of Macromolecules in Desert Cyanobacteria Mixed with a Lunar Mineral Analogue After Space Simulations

NASA Astrophysics Data System (ADS)

Baqué, Mickael; Verseux, Cyprien; Rabbow, Elke; de Vera, Jean-Pierre Paul; Billi, Daniela

2014-09-01

In the context of future exposure missions in Low Earth Orbit and possibly on the Moon, two desert strains of the cyanobacterium Chroococcidiopsis, strains CCMEE 029 and 057, mixed or not with a lunar mineral analogue, were exposed to fractionated fluencies of UVC and polychromatic UV (200-400 nm) and to space vacuum. These experiments were carried out within the framework of the BIOMEX (BIOlogy and Mars EXperiment) project, which aims at broadening our knowledge of mineral-microorganism interaction and the stability/degradation of their macromolecules when exposed to space and simulated Martian conditions. The presence of mineral analogues provided a protective effect, preserving survivability and integrity of DNA and photosynthetic pigments, as revealed by testing colony-forming abilities, performing PCR-based assays and using confocal laser scanning microscopy. In particular, DNA and pigments were still detectable after 500 kJ/m2 of polychromatic UV and space vacuum (10-4 Pa), corresponding to conditions expected during one-year exposure in Low Earth Orbit on board the EXPOSE-R2 platform in the presence of 0.1 % Neutral Density (ND) filter. After exposure to high UV fluencies (800 MJ/m2) in the presence of minerals, however, altered fluorescence emission spectrum of the photosynthetic pigments were detected, whereas DNA was still amplified by PCR. The present paper considers the implications of such findings for the detection of biosignatures in extraterrestrial conditions and for putative future lunar missions.

Damage Evolution in Complex-Phase and Dual-Phase Steels during Edge Stretching.

PubMed

Pathak, Nikky; Butcher, Cliff; Worswick, Michael James; Bellhouse, Erika; Gao, Jeff

2017-03-27

The role of microstructural damage in controlling the edge stretchability of Complex-Phase (CP) and Dual-Phase (DP) steels was evaluated using hole tension experiments. The experiments considered a tensile specimen with a hole at the center of specimen that is either sheared (sheared edge condition) or drilled and then reamed (reamed edge condition). The damage mechanism and accumulation in the CP and DP steels were systematically characterized by interrupting the hole tension tests at different strain levels using scanning electron microscope (SEM) analysis and optical microscopy. Martensite cracking and decohesion of ferrite-martensite interfaces are the dominant nucleation mechanisms in the DP780. The primary source of void nucleation in the CP800 is nucleation at TiN particles, with secondary void formation at martensite/bainite interfaces near the failure strain. The rate of damage evolution is considerably higher for the sheared edge in contrast with the reamed edge since the shearing process alters the microstructure in the shear affected zone (SAZ) by introducing work-hardening and initial damage behind the sheared edge. The CP microstructures were shown to be less prone to shear-induced damage than the DP materials resulting in much higher sheared edge formability. Microstructural damage in the CP and DP steels was characterized to understand the interaction between microstructure, damage evolution and edge formability during edge stretching. An analytical model for void evolution and coalescence was developed and applied to predict the damage rate in these rather diverse microstructures.

Detection of macromolecules in desert cyanobacteria mixed with a lunar mineral analogue after space simulations.

PubMed

Baqué, Mickael; Verseux, Cyprien; Rabbow, Elke; de Vera, Jean-Pierre Paul; Billi, Daniela

2014-09-01

In the context of future exposure missions in Low Earth Orbit and possibly on the Moon, two desert strains of the cyanobacterium Chroococcidiopsis, strains CCMEE 029 and 057, mixed or not with a lunar mineral analogue, were exposed to fractionated fluencies of UVC and polychromatic UV (200-400 nm) and to space vacuum. These experiments were carried out within the framework of the BIOMEX (BIOlogy and Mars EXperiment) project, which aims at broadening our knowledge of mineral-microorganism interaction and the stability/degradation of their macromolecules when exposed to space and simulated Martian conditions. The presence of mineral analogues provided a protective effect, preserving survivability and integrity of DNA and photosynthetic pigments, as revealed by testing colony-forming abilities, performing PCR-based assays and using confocal laser scanning microscopy. In particular, DNA and pigments were still detectable after 500 kJ/m(2) of polychromatic UV and space vacuum (10(-4) Pa), corresponding to conditions expected during one-year exposure in Low Earth Orbit on board the EXPOSE-R2 platform in the presence of 0.1 % Neutral Density (ND) filter. After exposure to high UV fluencies (800 MJ/m(2)) in the presence of minerals, however, altered fluorescence emission spectrum of the photosynthetic pigments were detected, whereas DNA was still amplified by PCR. The present paper considers the implications of such findings for the detection of biosignatures in extraterrestrial conditions and for putative future lunar missions.

Damage Evolution in Complex-Phase and Dual-Phase Steels during Edge Stretching

PubMed Central

Pathak, Nikky; Butcher, Cliff; Worswick, Michael James; Bellhouse, Erika; Gao, Jeff

2017-01-01

The role of microstructural damage in controlling the edge stretchability of Complex-Phase (CP) and Dual-Phase (DP) steels was evaluated using hole tension experiments. The experiments considered a tensile specimen with a hole at the center of specimen that is either sheared (sheared edge condition) or drilled and then reamed (reamed edge condition). The damage mechanism and accumulation in the CP and DP steels were systematically characterized by interrupting the hole tension tests at different strain levels using scanning electron microscope (SEM) analysis and optical microscopy. Martensite cracking and decohesion of ferrite-martensite interfaces are the dominant nucleation mechanisms in the DP780. The primary source of void nucleation in the CP800 is nucleation at TiN particles, with secondary void formation at martensite/bainite interfaces near the failure strain. The rate of damage evolution is considerably higher for the sheared edge in contrast with the reamed edge since the shearing process alters the microstructure in the shear affected zone (SAZ) by introducing work-hardening and initial damage behind the sheared edge. The CP microstructures were shown to be less prone to shear-induced damage than the DP materials resulting in much higher sheared edge formability. Microstructural damage in the CP and DP steels was characterized to understand the interaction between microstructure, damage evolution and edge formability during edge stretching. An analytical model for void evolution and coalescence was developed and applied to predict the damage rate in these rather diverse microstructures. PMID:28772707

Strain Dependent Electronic Structure and Band Offset Tuning at Heterointerfaces of ASnO3 (A=Ca, Sr, and Ba) and SrTiO3

PubMed Central

Baniecki, John D.; Yamazaki, Takashi; Ricinschi, Dan; Van Overmeere, Quentin; Aso, Hiroyuki; Miyata, Yusuke; Yamada, Hiroaki; Fujimura, Norifumi; Maran, Ronald; Anazawa, Toshihisa; Valanoor, Nagarajan; Imanaka, Yoshihiko

2017-01-01

The valence band (VB) electronic structure and VB alignments at heterointerfaces of strained epitaxial stannate ASnO3 (A=Ca, Sr, and Ba) thin films are characterized using in situ X-ray and ultraviolet photoelectron spectroscopies, with band gaps evaluated using spectroscopic ellipsometry. Scanning transmission electron microscopy with geometric phase analysis is used to resolve strain at atomic resolution. The VB electronic structure is strain state dependent in a manner that correlated with a directional change in Sn-O bond lengths with strain. However, VB offsets are found not to vary significantly with strain, which resulted in ascribing most of the difference in band alignment, due to a change in the band gaps with strain, to the conduction band edge. Our results reveal significant strain tuning of conduction band offsets using epitaxial buffer layers, with strain-induced offset differences as large as 0.6 eV possible for SrSnO3. Such large conduction band offset tunability through elastic strain control may provide a pathway to minimize the loss of charge confinement in 2-dimensional electron gases and enhance the performance of photoelectrochemical stannate-based devices. PMID:28195149

Imaging of high-angle annular dark-field scanning transmission electron microscopy and observations of GaN-based violet laser diodes.

PubMed

Shiojiri, M; Saijo, H

2006-09-01

The first part of this paper is devoted to physics, to explain high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging and to interpret why HAADF-STEM imaging is incoherent, instructing a strict definition of interference and coherence of electron waves. Next, we present our recent investigations of InGaN/GaN multiple quantum wells and AlGaN/GaN strained-layer superlattice claddings in GaN-based violet laser diodes, which have been performed by HAADF-STEM and high-resolution field-emission gun scanning electron microscopy.

Power-law viscous materials for analogue experiments: New data on the rheology of highly-filled silicone polymers

NASA Astrophysics Data System (ADS)

Boutelier, D.; Schrank, C.; Cruden, A.

2008-03-01

The selection of appropriate analogue materials is a central consideration in the design of realistic physical models. We investigate the rheology of highly-filled silicone polymers in order to find materials with a power-law strain-rate softening rheology suitable for modelling rock deformation by dislocation creep and report the rheological properties of the materials as functions of the filler content. The mixtures exhibit strain-rate softening behaviour but with increasing amounts of filler become strain-dependent. For the strain-independent viscous materials, flow laws are presented while for strain-dependent materials the relative importance of strain and strain rate softening/hardening is reported. If the stress or strain rate is above a threshold value some highly-filled silicone polymers may be considered linear visco-elastic (strain independent) and power-law strain-rate softening. The power-law exponent can be raised from 1 to ˜3 by using mixtures of high-viscosity silicone and plasticine. However, the need for high shear strain rates to obtain the power-law rheology imposes some restrictions on the usage of such materials for geodynamic modelling. Two simple shear experiments are presented that use Newtonian and power-law strain-rate softening materials. The results demonstrate how materials with power-law rheology result in better strain localization in analogue experiments.

Analysis of strain-induced crystallinity in neutron-irradiated amorphous PET fiber

NASA Astrophysics Data System (ADS)

Mallick, B.

2015-05-01

Polyethylene terephthalate (PET) fiber of 2.2 denier per filament has been irradiated with 4.44-MeV fast neutron beam at different low doses: 0.58-2,513.5 mGy. The variation of crystallinity because of neutron irradiation straining in PET filaments has been investigated. Study of the effects of irradiation by using X-ray diffraction and differential scanning calorimetry technique confirms the radiation-induced microstrain-dependent crystallinity of PET fiber.

Inhibition of quorum-sensing-mediated biofilm formation in Cronobacter sakazakii strains.

PubMed

Singh, Niharika; Patil, Amrita; Prabhune, Asmita; Goel, Gunjan

2016-09-01

The present study investigated plant extracts for their anti-quorum-sensing (QS) potential to inhibit the biofilm formation in Cronobacter sakazakii strains. The bioassay based on loss of pigment production by Chromobacterium violaceum 026 and Agrobacterium tumefaciens NTL4(pZLR4) was used for initial screening of the extracts. Further, the effect of extracts on the inhibition of QS-mediated biofilm in C. sakazakii isolates was evaluated using standard crystal violet assay. The effect on biofilm texture was studied using SYTO9 staining and light and scanning electron microscopy. Among the tested extracts, Piper nigrum and Cinnamomum verum at 100 ppm resulted in 78 and 68 % reduction in the production of violacein as well as blue-green colour in both biosensor strains. A higher inhibitory activity (>50 %) on biofilm formation in C. sakazakii was observed for Pip. nigrum and Cin. verum, whereas the other extracts possessed moderate (25-50 %) and minimal (<25 %) inhibitory activities. Further, the fluorescent and scanning electron microscopic images indicated a major disruption in the architecture of biofilms of tested strains by Pip. nigrum. This study points to the possibility of using Pip. nigrum and Cin. verum as inhibitor of QS-mediated biofilm formation by C. sakazakii that could be further explored for novel bioactive molecules to limit the emerging infections of C. sakazakii.

Enhancing adhesion of yeast brewery strains to chamotte carriers through aminosilane surface modification.

PubMed

Berlowska, Joanna; Kregiel, Dorota; Ambroziak, Wojciech

2013-07-01

The adhesion of cells to solid supports is described as surface-dependent, being largely determined by the properties of the surface. In this study, ceramic surfaces modified using different organosilanes were tested for proadhesive properties using industrial brewery yeast strains in different physiological states. Eight brewing strains were tested: bottom-fermenting Saccharomyces pastorianus and top-fermenting Saccharomyces cerevisiae. To determine adhesion efficiency light microscopy, scanning electron microscopy and the fluorymetric method were used. Modification of chamotte carriers by 3-(3-anino-2-hydroxy-1-propoxy) propyldimethoxysilane and 3-(N, N-dimethyl-N-2-hydroxyethyl) ammonium propyldimethoxysilane groups increased their biomass load significantly.

Destructive behavior of iron oxide in projectile impact

NASA Astrophysics Data System (ADS)

Shang, Wang; Xiaochen, Wang; Quan, Yang; Zhongde, Shan

2017-12-01

The damage strain values of Q235-A surface oxide scale were obtained by scanning electron microscopy (SEM/EDS) and universal tensile testing machine. The finite element simulation was carried out to study the destruction effects of oxidation at different impact rates. The results show that the damage value of the oxide strain is 0.08%. With the increase of the projectile velocity, the damage area of the oxide scale is increased, and the damage area is composed of the direct destruction area and the indirect failure area. The indirect damage area is caused by the stress/strain to the surrounding expansion after the impact of the steel body.

Mechanical suitability of glycerol-preserved human dura mater for construction of prosthetic cardiac valves.

PubMed

McGarvey, K A; Lee, J M; Boughner, D R

1984-03-01

We have examined the tensile viscoelastic properties of fresh and glycerol-preserved human dura mater, and correlated the results with structural information from the scanning electron microscope. The interwoven laminar structure of dura produces rather high flexural stiffness, while the crossed-fibrillar laminae produce planar mechanical isotropy. Glycerol storage shifts the stress-strain curve to lower strain, reduces stress relaxation and creep, and lowers the ultimate tensile strength and strain at fracture. These changes may be due to glyceraldehyde crosslinking, or to increased interfibrillar friction. The latter hypothesis suggests that glycerol storage may reduce the fatigue lifetime of the tissue.

Atomic scale study of strain relaxation in Sn islands on Sn-induced Si(111)-(2√3 ×2√3 ) surface

NASA Astrophysics Data System (ADS)

Wang, L. L.; Ma, X. C.; Ning, Y. X.; Ji, S. H.; Fu, Y. S.; Jia, J. F.; Kelly, K. F.; Xue, Q. K.

2009-04-01

Surface structure of the Sn islands 5 ML high, prepared on Si(111)-(2√3 ×2√3 )-Sn substrate, is investigated by low temperature scanning tunneling microscopy/spectroscopy. Due to the elastic strain relaxation in the islands, the in-plane unit cell structure distorts and the apparent height of the surface atoms varies regularly to form an overall modulated strip structure. The quantum well states are observed to depend on the relative position within this structure, which implies the change of the surface chemical potential induced by the elastic strain relaxation as well.

The influence of strain rate and hydrogen on the plane-strain ductility of Zircaloy cladding

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

Link, T.M.; Motta, A.T.; Koss, D.A.

1998-03-01

The authors studied the ductility of unirradiated Zircaloy-4 cladding under loading conditions prototypical of those found in reactivity-initiated accidents (RIA), i.e.: near plane-strain deformation in the hoop direction (transverse to the cladding axis) at room temperature and 300 C and high strain rates. To conduct these studies, they developed a specimen configuration in which near plane-strain deformation is achieved in the gage section, and a testing methodology that allows one to determine both the limit strain at the onset of localized necking and the fracture strain. The experiments indicate that there is little effect of strain rate (10{sup {minus}3} tomore » 10{sup 2} s{sup {minus}1}) on the ductility of unhydrided Zircaloy tubing deformed under near plane-strain conditions at either room temperature or 300 C. Preliminary experiments on cladding containing 190 ppm hydrogen show only a small loss of fracture strain but no clear effect on limit strain. The experiments also indicate that there is a significant loss of Zircaloy ductility when surface flaws are present in the form of thickness imperfections.« less

Rapid Antimicrobial Susceptibility Testing Using Forward Laser Light Scatter Technology

PubMed Central

Clinton, Lani K.; Hewitt, Carolyn; Koyamatsu, Terri; Sun, Yilun; Jamison, Ginger; Perkins, Rosalie; Tang, Li; Pounds, Stanley; Bankowski, Matthew J.

2016-01-01

The delayed reporting of antimicrobial susceptibility testing remains a limiting factor in clinical decision-making in the treatment of bacterial infection. This study evaluates the use of forward laser light scatter (FLLS) to measure bacterial growth for the early determination of antimicrobial susceptibility. Three isolates each (two clinical isolates and one reference strain) of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa were tested in triplicate using two commercial antimicrobial testing systems, the Vitek2 and the MicroScan MIC panel, to challenge the BacterioScan FLLS. The BacterioScan FLLS showed a high degree of categorical concordance with the commercial methods. Pairwise comparison with each commercial system serving as a reference standard showed 88.9% agreement with MicroScan (two minor errors) and 72.2% agreement with Vitek (five minor errors). FLLS using the BacterioScan system shows promise as a novel method for the rapid and accurate determination of antimicrobial susceptibility. PMID:27558176

SURVIVAL OF SALMONELLA SPECIES IN RIVER WATER.

EPA Science Inventory

The survival of four Salmonella strains in river water microcosms was monitored using culturing techniques, direct counts, whole cell hybridization, scanning electron microscopy, and resuscitation techniques via the direct viable count method and flow cytrometry. Plate counts of...

Differentiating Pseudomonas sp. strain ADP cells in suspensions and biofilms using Raman spectroscopy and scanning electron microscopy.

PubMed

Henry, Victoria A; Jessop, Julie L P; Peeples, Tonya L

2017-02-01

High quality spectra of Pseudomonas sp. strain ADP in the planktonic and biofilm state were obtained using Raman microspectroscopy. These spectra enabled the identification of key differences between free and biofilm cells in the fingerprint region of Raman spectra in the nucleic acid, carbohydrate, and protein regions. Scanning electron microscopy (SEM) enabled detailed visualization of ADP biofilm with confirmation of associated extracellular matrix structure. Following extraction and Raman analysis of extracellular polymeric substances, Raman spectral differences between free and biofilm cells were largely attributed to the contribution of extracellular matrix components produced in mature biofilms. Raman spectroscopy complemented with SEM proves to be useful in distinguishing physiological properties among cells of the same species. Graphical Abstract Raman spectroscopy complemented with SEM proves to be useful in distinguishing physiological properties among cells of the same species.

Experimental stress–strain analysis of tapered silica optical fibers with nanofiber waist

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

Holleis, S.; Hoinkes, T.; Wuttke, C.

2014-04-21

We experimentally determine tensile force–elongation diagrams of tapered optical fibers with a nanofiber waist. The tapered optical fibers are produced from standard silica optical fibers using a heat and pull process. Both, the force–elongation data and scanning electron microscope images of the rupture points indicate a brittle material. Despite the small waist radii of only a few hundred nanometers, our experimental data can be fully explained by a nonlinear stress–strain model that relies on material properties of macroscopic silica optical fibers. This is an important asset when it comes to designing miniaturized optical elements as one can rely on themore » well-founded material characteristics of standard optical fibers. Based on this understanding, we demonstrate a simple and non-destructive technique that allows us to determine the waist radius of the tapered optical fiber. We find excellent agreement with independent scanning electron microscope measurements of the waist radius.« less

Genomic analysis of thermophilic Bacillus coagulans strains: efficient producers for platform bio-chemicals.

PubMed

Su, Fei; Xu, Ping

2014-01-29

Microbial strains with high substrate efficiency and excellent environmental tolerance are urgently needed for the production of platform bio-chemicals. Bacillus coagulans has these merits; however, little genetic information is available about this species. Here, we determined the genome sequences of five B. coagulans strains, and used a comparative genomic approach to reconstruct the central carbon metabolism of this species to explain their fermentation features. A novel xylose isomerase in the xylose utilization pathway was identified in these strains. Based on a genome-wide positive selection scan, the selection pressure on amino acid metabolism may have played a significant role in the thermal adaptation. We also researched the immune systems of B. coagulans strains, which provide them with acquired resistance to phages and mobile genetic elements. Our genomic analysis provides comprehensive insights into the genetic characteristics of B. coagulans and paves the way for improving and extending the uses of this species.

Genomic analysis of thermophilic Bacillus coagulans strains: efficient producers for platform bio-chemicals

PubMed Central

Su, Fei; Xu, Ping

2014-01-01

Microbial strains with high substrate efficiency and excellent environmental tolerance are urgently needed for the production of platform bio-chemicals. Bacillus coagulans has these merits; however, little genetic information is available about this species. Here, we determined the genome sequences of five B. coagulans strains, and used a comparative genomic approach to reconstruct the central carbon metabolism of this species to explain their fermentation features. A novel xylose isomerase in the xylose utilization pathway was identified in these strains. Based on a genome-wide positive selection scan, the selection pressure on amino acid metabolism may have played a significant role in the thermal adaptation. We also researched the immune systems of B. coagulans strains, which provide them with acquired resistance to phages and mobile genetic elements. Our genomic analysis provides comprehensive insights into the genetic characteristics of B. coagulans and paves the way for improving and extending the uses of this species. PMID:24473268

Characterization of Thermo-Mechanical and Fracture Behaviors of Thermoplastic Polymers

PubMed Central

Ghorbel, Elhem; Hadriche, Ismail; Casalino, Giuseppe; Masmoudi, Neila

2014-01-01

In this paper the effects of the strain rate on the inelastic behavior and the self-heating under load conditions are presented for polymeric materials, such as polymethyl methacrylate (PMMA), polycarbonate (PC), and polyamide (PA66). By a torsion test, it was established that the shear yield stress behavior of PMMA, PC, and PA66 is well-described by the Ree-Eyring theory in the range of the considered strain rates. During the investigation, the surface temperature was monitored using an infrared camera. The heat release appeared at the early stage of the deformation and increased with the strain and strain rate. This suggested that the external work of deformation was dissipated into heat so the torsion tests could not be considered isothermal. Eventually, the effect of the strain rate on the failure modes was analyzed by scanning electron microscopy. PMID:28788462

Making the invisible body visible. Bone scans, osteoporosis and women's bodily experiences.

PubMed

Reventlow, Susanne Dalsgaard; Hvas, Lotte; Malterud, Kirsti

2006-06-01

The imaging technology of bone scans allows visualization of the bone structure, and determination of a numerical value. Both these are subjected to professional interpretation according to medical (epidemiological) evidence to estimate the individual's risk of fractures. But when bodily experience is challenged by a visual diagnosis, what effect does this have on an individual? The aim of this study was to explore women's bodily experiences after a bone scan and to analyse how the scan affects women's self-awareness, sense of bodily identity and integrity. We interviewed 16 Danish women (aged 61-63) who had had a bone scan for osteoporosis. The analysis was based on Merleau-Ponty's perspective of perception as an embodied experience in which bodily experience is understood to be the existential ground of culture and self. Women appeared to take the scan literally and planned their lives accordingly. They appeared to believe that the 'pictures' revealed some truth in themselves. The information supplied by the scan fostered a new body image. The women interpreted the scan result (a mark on a curve) to mean bodily fragility which they incorporated into their bodily perception. The embodiment of this new body image produced new symptom interpretations and preventive actions, including caution. The result of the bone scan and its cultural interpretation triggered a reconstruction of the body self as weak with reduced capacity. Women's interpretation of the bone scan reorganized their lived space and time, and their relations with others and themselves. Technological information about osteoporosis appeared to leave most affected women more uncertain and restricted rather than empowered. The findings raise some fundamental questions concerning the use of medical technology for the prevention of asymptomatic disorders.

Nucleation, growth, and strain relaxation of lattice-mismatched 3-5 semiconductor epitaxial layers

NASA Technical Reports Server (NTRS)

Welser, R. E.; Guido, L. J.

1994-01-01

We have investigated the early stages of evolution of highly strained 2-D InAs layers and 3-D InAs islands grown by metal-organic chemical vapor deposition (MOCVD) on (100) and (111)B GaAs substrates. The InAs epilayer/GaAs substrate combination has been chosen because the lattice-mismatch is severe (approximately 7.2 percent), yet these materials are otherwise very similar. By examining InAs-on-GaAs composites instead of the more common In(x)Ga(1-x)As alloy we remove an additional degree of freedom (x) and thereby simplify data interpretation. A matrix of experiments is described in which the MOCVD growth parameters - susceptor temperature, Thin flux, and AsH3 flux - have been varied over a wide range. Scanning electron microscopy, atomic force microscopy, transmission electron microscopy, and electron microprobe analysis have been employed to observe the thin film surface morphology. In the case of 3-D growth, we have extracted activation energies and power-dependent exponents that characterize the nucleation process. As a consequence, optimized growth conditions have been identified for depositing approximately 250 A thick (100) and (111)B oriented InAs layers with relatively smooth surfaces. Together with preliminary data on the strain relaxation of these layers, the above results on the evolution of thin InAs films indicate that the (111)B orientation is particularly promising for yielding lattice-mismatched films that are fully relaxed with only misfit dislocations at the epilayer/substrate interface.

Influence of Bacillus spp. strains on seedling growth and physiological parameters of sorghum under moisture stress conditions.

PubMed

Grover, Minakshi; Madhubala, R; Ali, Sk Z; Yadav, S K; Venkateswarlu, B

2014-09-01

Microorganisms isolated from stressed ecosystem may prove as ideal candidates for development of bio-inoculants for stressed agricultural production systems. In the present study, moisture stress tolerant rhizobacteria were isolated from the rhizosphere of sorghum, pigeonpea, and cowpea grown under semiarid conditions in India. Four isolates KB122, KB129, KB133, and KB142 from sorghum rhizosphere exhibited plant growth promoting traits and tolerance to salinity, high temperature, and moisture stress. These isolates were identified as Bacillus spp. by 16S rDNA sequence analysis. The strains were evaluated for growth promotion of sorghum seedlings under two different moisture stress conditions (set-I, continuous 50% soil water holding capacity (WHC) throughout the experiment and set-II, 75% soil WHC for 27 days followed by no irrigation for 5 days) under greenhouse conditions. Plate count and scanning electron microscope studies indicated successful root surface colonization by inoculated bacteria. Plants inoculated with Bacillus spp. strains showed better growth in terms of shoot length and root biomass with dark greenish leaves due to high chlorophyll content while un-inoculated plants showed rolling of the leaves, stunted appearance, and wilting under both stress conditions. Inoculation also improved leaf relative water content and soil moisture content. However, variation in proline and sugar content in the different treatments under two stress conditions indicated differential effect of microbial treatments on plant physiological parameters under stress conditions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Achromobacter xylosoxidans as a new microorganism strain colonizing high-density polyethylene as a key step to its biodegradation.

PubMed

Kowalczyk, Anna; Chyc, Marek; Ryszka, Przemysław; Latowski, Dariusz

2016-06-01

This study presents results of research on isolation new bacteria strain Achromobacter xylosoxidans able to effect on the structure of high-density polyethylene (HDPE), polymer resistant to degradation in environment. New strain of A. xylosoxidans PE-1 was isolated from the soil and identified by analysis of the 16S ribosome subunit coding sequences. The substance to be degraded was HDPE in the form of thin foil films. The foil samples were analyzed with Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) as well as scanning electron microscope (SEM), and the results revealed degradation of chemical structure of HDPE. About 9 % loss of weight was also detected as a result of A. xylosoxidans PE-1 effect on HDPE foil. On the basis of comparative spectral analysis of the raw material before the bacteria treatment and the spectrum from a spectra database, it was assumed that the HDPE was the only source of carbon and energy for the microorganisms. No fillers or other additives used in the plastic processing were observed in HDPE before experiments. This is the first communication showing that A. xylosoxidans is able to modify chemical structure of HDPE, what was observed both on FTIR, in mass reduction of HDPE and SEM analysis. We also observed quite good growth of the bacteria also when the HDPE was the sole carbon source in the medium. These results prove that A. xylosoxidans is an organism worth applying in future HDPE biodegradation studies.

Application of four novel fungal strains to remove arsenic from contaminated water in batch and column modes.

PubMed

Jaiswal, Virendra; Saxena, Sangeeta; Kaur, Ispreet; Dubey, Priya; Nand, Sampurna; Naseem, Mariya; Singh, Suman B; Srivastava, Pankaj Kumar; Barik, Saroj Kanta

2018-08-15

Immobilized biomass of novel indigenous fungal strains FNBR_3, FNBR_6, FNBR_13, and FNBR_19 were evaluated for arsenic (As) removal from aqueous solution. Alginate beads containing 0.1 g biomass were used in a batch experiment (200 mg l -1 As; pH 6). Biosorption equilibrium established in first 2 h with As adsorption (mg g -1 ) as 70, 68, 113 and 90 by FNBR_3, FNBR_6, FNBR_13 and FNBR_19, respectively. The equilibrium was fitted to the Langmuir model (r 2  = 0. 90-0.97). The absorption kinetic followed the pseudo second order. Changes in the surface of fungal cells and intracellular As-uptake by fungal biomass were also confirmed by scanning electron microscopy combined with X-ray energy dispersive spectrometer. The presence of different functional groups on fungal cells capable of As-binding was investigated by FTIR. The As-removal by immobilized fungal beads tested in the packed columns also. The As-adsorption by biomass (qe as mg g -1 ) were recorded as 59.5 (FNBR_3 and FNBR_6), 74.8 (FNBR_13), and 66.3 (FNBR_19) in the column and validated by Thomas model. This is the first report concerning the arsenic removal by immobilized biomass of these novel fungal strains from aqueous solution both in batch and column studies with a prospect of their further industrial application. Copyright © 2018 Elsevier B.V. All rights reserved.

Substantial tensile ductility in sputtered Zr-Ni-Al nano-sized metallic glass

DOE PAGES

Liontas, Rachel; Jafary-Zadeh, Mehdi; Zeng, Qiaoshi; ...

2016-08-04

We investigate the mechanical behavior and atomic-level structure of glassy Zr-Ni-Al nano-tensile specimens with widths between 75 and 215 nm. We focus our studies on two different energy states: (1) as-sputtered and (2) sputtered then annealed below the glass transition temperature (T g). In-situ tensile experiments conducted inside a scanning electron microscope (SEM) reveal substantial tensile ductility in some cases reaching >10% engineering plastic strains, >150% true plastic strains, and necking down to a point during tensile straining in specimens as wide as ~150 nm. We found the extent of ductility depends on both the specimen size and the annealingmore » conditions. Using molecular dynamics (MD) simulations, transmission electron microscopy (TEM), and synchrotron x-ray diffraction (XRD), we explain the observed mechanical behavior through changes in free volume as well as short- and medium-range atomic-level order that occur upon annealing. This work demonstrates the importance of carefully choosing the metallic glass fabrication method and post-processing conditions for achieving a certain atomic-level structure and free volume within the metallic glass, which then determine the overall mechanical response. Lastly, an important implication is that sputter deposition may be a particularly promising technique for producing thin coatings of metallic glasses with significant ductility, due to the high level of disorder and excess free volume resulting from the sputtering process and to the suitability of sputtering for producing thin coatings that may exhibit enhanced size-induced ductility.« less

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

Heo, Yooun; Lee, Jin Hong; Xie, Lin

Enhanced properties in modern functional materials can often be found at structural transition regions, such as morphotropic phase boundaries (MPB), owing to the coexistence of multiple phases with nearly equivalent energies. Strain-engineered MPBs have emerged in epitaxially grown BiFeO 3 (BFO) thin films by precisely tailoring a compressive misfit strain, leading to numerous intriguing phenomena, such as a massive piezoelectric response, magnetoelectric coupling, interfacial magnetism and electronic conduction. Recently, an orthorhombic–rhombohedral (O–R) phase boundary has also been found in tensile-strained BFO. In this study, we characterise the crystal structure and electronic properties of the two competing O and R phasesmore » using X-ray diffraction, scanning probe microscope and scanning transmission electron microscopy (STEM). We observe the temperature evolution of R and O domains and find that the domain boundaries are highly conductive. Temperature-dependent measurements reveal that the conductivity is thermally activated for R–O boundaries. STEM observations point to structurally wide boundaries, significantly wider than in other systems. Furthermore, we reveal a strong correlation between the highly conductive domain boundaries and structural material properties. These findings provide a pathway to use phase boundaries in this system for novel nanoelectronic applications.« less

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

NASA Astrophysics Data System (ADS)

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

2018-01-01

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

Relative importance of bacteriocin-like genes in antagonism of Xanthomonas perforans tomato race 3 to Xanthomonas euvesicatoria tomato race 1 strains.

PubMed

Hert, A P; Roberts, P D; Momol, M T; Minsavage, G V; Tudor-Nelson, S M; Jones, J B

2005-07-01

In a previous study, tomato race 3 (T3) strains of Xanthomonas perforans became predominant in fields containing both X. euvesicatoria and X. perforans races T1 and T3, respectively. This apparent ability to take over fields led to the discovery that there are three bacteriocin-like compounds associated with T3 strains. T3 strain 91-118 produces at least three different bacteriocin-like compounds (BCN-A, BCN-B, and BCN-C) antagonistic toward T1 strains. We determined the relative importance of the bacteriocin-like compounds by constructing the following mutant forms of a wild-type (WT) T3 strain to evaluate the antagonism to WT T1 strains: Mut-A (BCN-A-), Mut-B (BCN-B-), Mut-C (BCN-C-), Mut-AB, Mut-BC, and Mut-ABC. Although all mutant and WT T3 strains reduced the T1 populations in in planta growth room experiments, Mut-B and WT T3 were significantly more effective. Mutants expressing BCN-B and either BCN-A or BCN-C reduced T1 populations less than mutants expressing only BCN-A or BCN-C. The triple-knockout mutant Mut-ABC also had a significant competitive advantage over the T1 strain. In pairwise-inoculation field experiments where plants were coinoculated with an individual mutant or WT T3 strain and the T1 strain, the mutant strains and the WT T3 strain were reisolated from more than 70% of the lesions. WT T3 and Mut-B were the most frequently reisolated strains. In field experiments where plants were group inoculated with Mut-A, Mut-B, Mut-C, Mut-ABC, and WT T1 and T3 strains, Mut-B populations dominated all three seasons. In greenhouse and field experiments, the WT and mutant T3 strains had a selective advantage over T1 strains. Bacterial strains expressing both BCN-A and BCN-C appeared to have a competitive advantage over all other mutant and WT strains. Furthermore, BCN-B appeared to be a negative factor, with mutant T3 strains lacking BCN-B having a selective advantage in the field.

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

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

NASA Astrophysics Data System (ADS)

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

2016-01-01

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

Correlation between von Mises strain and material thinning in a hydroformed sample of Ti35A aerospace grade titanium

NASA Astrophysics Data System (ADS)

Bell, Colin; Jump, Ellen; Kerr, William; Corney, Jonathan; Zuelli, Nicola; Savings, David

2017-10-01

This paper presents the results of an experimental investigation of the strain measured on a sample of Ti35A (commercially pure) titanium that was formed past the point of failure in a hydroforming operation. The sample was etched prior to forming to allow for a strain map of the exterior to be created and examined by using a circle grid analysis (CGA) technique. The sample was scanned post forming with precise optical inspection to ascertain an accurate model of its geometry. This paper discusses the results of the analyses including the full geometric and surface strain measurements. This paper then compares material thinning properties to strain values and finds a linear relationship of approximately 3:1 between Von Mises strain and material thinning percentage throughout the sample. The slope of the line appears to correlate strongly with the material's Poisson's ratio and could have potential uses in process planning.

Plasmid-dependent attachment of Agrobacterium tumefaciens to plant tissue culture cells.

PubMed

Matthysse, A G; Wyman, P M; Holmes, K V

1978-11-01

Kinetic, microscopic, and biochemical studies show that virulent Ti (tumor inducing)-plasmid-containing strains of Agrobacterium attach to normal tobacco and carrot tissue culture cells. Kinetic studies showed that virulent strains of A. tumefaciens attach to the plant tissue culture cells in increasing numbers during the first 1 to 2 h of incubation of the bacteria with the plant cells. Five Ti-plasmid-containing virulent Agrobacterium strains showed greater attachment to tobacco cells than did five avirulent strains. Light and scanning electron microscopic observations confirmed that virulent strains showed little attachment. Bacterial attachment was blocked by prior incubation of the plant cells with lipopolysaccharide extracted from A. tumefaciens, but not from A. radiobacter, suggesting that bacterial lipopolysaccharide is one of the components involved in the attachment process. At least one other bacterial product may be required for attachment in tissue culture because the virulent A. tumefaciens NT1, which lacks the Ti plasmid, does not itself attach to tobacco cells, but its lipopolysaccharide does inhibit the attachment of virulent strains.

Low cycle fatigue behavior of a ferritic reactor pressure vessel steel

NASA Astrophysics Data System (ADS)

Sarkar, Apu; Kumawat, Bhupendra K.; Chakravartty, J. K.

2015-07-01

The cyclic stress-strain response and the low cycle fatigue (LCF) behavior of 20MnMoNi55 pressure vessel steel were studied. Tensile strength and LCF properties were examined at room temperature (RT) using specimens cut from rolling direction of a rolled block. The fully reversed strain-controlled LCF tests were conducted at a constant total strain rate with different axial strain amplitude levels. The cyclic strain-stress relationships and the strain-life relationships were obtained through the test results, and related LCF parameters of the steel were calculated. The studied steel exhibits cyclic softening behavior. Furthermore, analysis of stabilized hysteresis loops showed that the steel exhibits non-Masing behavior. Complementary scanning electron microscopy examinations were also carried out on fracture surfaces to reveal dominant damage mechanisms during crack initiation, propagation and fracture. Multiple crack initiation sites were observed on the fracture surface. The investigated LCF behavior can provide reference for pressure vessel life assessment and fracture mechanisms analysis.

Transport processes and mutual interactions of three bacterial strains in saturated porous media

NASA Astrophysics Data System (ADS)

Stumpp, Christine; Lawrence, John R.; Hendry, M. Jim; Maloszewski, Pitor

2010-05-01

Transport processes of the bacterial strains Klebsiella oxytoca, Burkholderia cepacia G4PR-1 and Pseudomonas sp #5 were investigated in saturated column experiments to study the differences in transport characteristics and the mutual interactions of these strains during transport. Soil column experiments (114 mm long x 33 mm in diameter) were conducted with constant water velocities (3.9-5.7 cm/h) through a medium to coarse grained silica sand. All experiments were performed in freshly packed columns in quadruplicate. Chloride was used as tracer to determine the mean transit time, dispersivity and flow rate. It was injected as a pulse into the columns together with the bacterial strains suspended in artificial groundwater medium. In the first setup, each strain was investigated alone. In the second setup, transport processes were performed injecting two strains simultaneously. Finally, the transport characteristics were studied in successive experiments when one bacterium was resident on the sand grains prior to the introduction of the second strain. In all experiments the peak C/Co bacterial concentrations were attenuated with respect to the conservative tracer chloride and a well defined tailing was observed. A one dimensional mathematical model for advective-dispersive transport that accounts for irreversible and reversible sorption was used to analyze the bacterial breakthrough curves and tailing patterns. It was shown that the sorption parameters were different for the three strains that can be explained by the properties of the bacteria. For the species Klebsiella oxytoca and Burkholderia cepacia G4PR-the transport parameters were mostly in the same range independent of the experimental setup. However, Pseudomonas sp #5, which is a motile bacterium, showed differences in the breakthrough curves and sorption parameters during the experiments. The simultaneous and successive experiments indicated an influence on the reversible sorption processes when another strain was present during the transport processes.

Definition and design of an experiment to test raster scanning with rotating unbalanced-mass devices on gimbaled payloads

NASA Technical Reports Server (NTRS)

Lightsey, W. D.; Alhorn, D. C.; Polites, M. E.

1992-01-01

An experiment designed to test the feasibility of using rotating unbalanced-mass (RUM) devices for line and raster scanning gimbaled payloads, while expending very little power is described. The experiment is configured for ground-based testing, but the scan concept is applicable to ground-based, balloon-borne, and space-based payloads, as well as free-flying spacecraft. The servos used in scanning are defined; the electronic hardware is specified; and a computer simulation model of the system is described. Simulation results are presented that predict system performance and verify the servo designs.

Fast-scan EM with digital image processing for dynamic experiments

Treesearch

C.W. McMillin; F.C. Billingsley; R.E. Frazer

1974-01-01

The recent introduction of accessory instrumentation capable of display at television scan rates suggests a broadened application for the scanning electron microscope- the direct observation of motion (dynamic events) at magnifications otherwise unattainable. In one illustrative experiment, the transverse surface of southern pine was observed when subjected to large...

Fast-scan em with digital image processing for dynamic experiments

Treesearch

Charles W. McMillin; Fred C. Billingsley; Robert E. Frazer

1973-01-01

The recent introduction of accessory instrumentation capable of display at television scan rates suggests a broadened application for the scanning electron microscope - the direct observation of motion (dynamic events) at magnifactions otherwise unattainable. In one illustrative experiment, the transverse surface of southern pine was observed when subjected to large...

Stress-strain characteristics of rubber-like materials: Experiment and analysis

NASA Technical Reports Server (NTRS)

Allen, David J.

1992-01-01

The objectives are: (1) to demonstrate tensile testing of materials and the application of the concepts of stress and strain; and (2) to yield a mathematical relationship between stress and strain for many artificial rubbers and plastics. The experiment, supplies, and procedure are presented.

Fatigue behavior of ULTIMETRTM alloy: Experiment and theoretical modeling

NASA Astrophysics Data System (ADS)

Jiang, Liang

ULTIMETRTM alloy is a commercial Co-26Cr-9Ni (weight percent) superalloy, which possesses excellent resistance to both wear and corrosion. In order to extend the structural applications of this alloy and improve the fundamental understanding of the fatigue damage mechanisms, stress- and strain-controlled fatigue tests were performed at various temperatures and in different environments. The stress- and strain-life data were developed for the structural design and engineering applications of this material. Fractographic studies characterized the crack-initiation and propagation behavior of the alloy. Microstructure evolution during fatigue was revealed by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Specifically, it was found that the metastable face-centered-cubic structure of this alloy in the as-received condition could be transformed into a hexagonal-close-packed structure either under the action of plastic deformation at room temperature, or due to the aging and cyclic deformation at intermediate temperatures. This interesting observation constructed a sound basis for the alloy development. The dominant mechanisms, which control the fatigue behavior of ULTIMET alloy, were characterized. High-speed, high-resolution infrared (IR) thermography, as a non-contact, full-field, and nondestructive technique, was used to characterize the damage during fatigue. The temperature variations during each fatigue cycle, which were due to the thermal-elastic-plastic effect, were observed and related to stress-strain analyses. The temperature evolution during fatigue manifested the cumulative fatigue damage process. A constitutive model was developed to predict thermal and mechanical responses of ULTIMET alloy subjected to cyclic deformation. The predicted cyclic stress-strain responses and temperature variations were found to be in good agreement with the experimental results. In addition, a fatigue life prediction model was developed based on the strain-energy consideration, and the measured temperature could be utilized as an index for fatigue-life prediction.

Compression behavior of delaminated composite plates

NASA Technical Reports Server (NTRS)

Peck, Scott O.; Springer, George S.

1989-01-01

The response of delaminated composite plates to compressive in-plane loads was investigated. The delaminated region may be either circular or elliptical, and may be located between any two plies of the laminate. For elliptical delaminations, the axes of the ellipse may be arbitrarily oriented with respect to the applied loads. A model was developed that describes the stresses, strains, and deformation of the sublaminate created by the delamination. The mathematical model is based on a two dimensional nonlinear plate theory that includes the effects of transverse shear deformation. The model takes into account thermal and moisture induced strains, transverse pressures acting on the sublaminate, and contact between the sublaminate and plate. The solution technique used is the Ritz method. A computationally efficient computer implementation of the model was developed. The code can be used to predict the nonlinear-load-strain behavior of the sublaminate including the buckling load, postbuckling behavior, and the onset of delamination growth. The accuracy of the code was evaluated by comparing the model results to benchmark analytical solutions. A series of experiments was conducted on Fiberite T300/976 graphite/epoxy laminates bonded to an aluminum honeycomb core forming a sandwich panel. Either circles or ellipses made from Teflon film were embedded in the laminates, simulating the presence of a delamination. Each specimen was loaded in compression and the strain history of the sublaminate was recorded far into the postbuckling regime. The extent of delamination growth was evaluated by C-scan examination of each specimen. The experimental data were compared to code predictions. The code was found to describe the data with reasonable accuracy. A sensitivity study examined the relative importance of various material properties, the delamination dimensions, the contact model, the transverse pressure differential, the critical strain energy release rate, and the relative growth direction on the buckling load, the postbuckling behavior, and the growth load of the sublaminate.

[Isolation of an excellent bio-flocculant-producing strain and its application in the treatment of cold-rolling waste oily water].

PubMed

Lei, Guo-Yuan; Ding, Cui-Ping; Yang, Jia-Xuan

2011-09-01

An excellent strain (designated as T-3) which produces bio-flocculants was isolated from soil samples, and identified as Klebsiella sp. species based on the analysis of morphology, physiology and biochemistry and 16S rDNA sequences measurement. The effects of culture conditions such as pH values, temperature, carbon sources and nitrogen sources on bio-flocculants production by T-3 strain were studied. The experiment results show that T-3 strain has better adaptability to carbon sources and nitrogen sources, and higher capacity of bio-flocculants was obtained when the initial pH value of culture and temperature were 9 and 25 degrees C respectively. Based on the colorimetric reactions of proteins and polysaccharide substance, ultraviolet scanning analysis and Fourier Transform Infrared Spectroscopy analysis, it is found that the bio-flocculants produced by T-3 strain contains -OH and -COO(-) groups and belongs to anionic type flocculant. Moreover, the main component is polysaccharides. The treatment of oily cold-rolling wastewater by the bio-flocculant was investigated and the better result was obtained. When the dosages of CaCl2, bio-flocculants and poly aluminium chloride were 4 g x L(-1), 10% (volume fraction) and 1 g x L(-1) respectively, and the pH value was 7.0, the oil concentration, COD and turbidity were decreased to 10 mg x L(-1), 218.4 mg x L(-1) and 1.36 from 4 819 mg x L(-1), 28 456.8 mg x L(-1) and 3 950 with the removal efficiencies of 99.79%, 92.32% and 99.97% respectively. The interaction between flocculant and oily droplets is achieved by the interaction of Van der Waals force, hydrogen bond and the bridged coordination of Ca2+, in which the bridged coordination of Ca2+ is the dominant.

Change in coccolith size and morphology due to response to temperature and salinity in coccolithophore Emiliania huxleyi (Haptophyta) isolated from the Bering and Chukchi seas

NASA Astrophysics Data System (ADS)

Saruwatari, Kazuko; Satoh, Manami; Harada, Naomi; Suzuki, Iwane; Shiraiwa, Yoshihiro

2016-05-01

Strains of the coccolithophore Emiliania huxleyi (Haptophyta) collected from the subarctic North Pacific and Arctic oceans in 2010 were established as clone cultures and have been maintained in the laboratory at 15 °C and 32 ‰ salinity. To study the physiological responses of coccolith formation to changes in temperature and salinity, growth experiments and morphometric investigations were performed on two strains, namely MR57N isolated from the northern Bering Sea and MR70N at the Chukchi Sea. This is the first report of a detailed morphometric and morphological investigation of Arctic Ocean coccolithophore strains. The specific growth rates at the logarithmic growth phases in both strains markedly increased as temperature was elevated from 5 to 20 °C, although coccolith productivity (estimated as the percentage of calcified cells) was similar at 10-20 % at all temperatures. On the other hand, the specific growth rate of MR70N was affected less by changes in salinity in the range 26-35 ‰, but the proportion of calcified cells decreased at high and low salinities. According to scanning electron microscopy (SEM) observations, coccolith morphotypes can be categorized into Type B/C on the basis of their biometrical parameters. The central area elements of coccoliths varied from thin lath type to well-calcified lath type when temperature was increased or salinity was decreased, and coccolith size decreased simultaneously. Coccolithophore cell size also decreased with increasing temperature, although the variation in cell size was slightly greater at the lower salinity level. This indicates that subarctic and arctic coccolithophore strains can survive in a wide range of seawater temperatures and at lower salinities with change in their morphology. Because all coccolith biometric parameters followed the scaling law, the decrease in coccolith size was caused simply by the reduced calcification. Taken together, our results suggest that calcification productivity may be used to predict future oceanic environmental conditions in the polar regions.

Helix handedness of Leptospira interrogans as determined by scanning electron microscopy.

PubMed Central

Carleton, O; Charon, N W; Allender, P; O'Brien, S

1979-01-01

Representative serovars and strains of the seven genetic groups of Leptospira interrogans, and two previously studied serovars, were all found to form exclusively right-handed helices as determined by scanning electron microscopy. No change in handedness occurred in cells grown in a minimal medium (Tween-80 albumin) compared to cells grown in a rich medium (rabbit serum). The right-handedness of the organisms was related to the evolution, cell wall structure, and the mechanism of motility of L. interrogans. Images PMID:438122

Candida parapsilosis biofilm identification by Raman spectroscopy.

PubMed

Samek, Ota; Mlynariková, Katarina; Bernatová, Silvie; Ježek, Jan; Krzyžánek, Vladislav; Šiler, Martin; Zemánek, Pavel; Růžička, Filip; Holá, Veronika; Mahelová, Martina

2014-12-22

Colonies of Candida parapsilosis on culture plates were probed directly in situ using Raman spectroscopy for rapid identification of specific strains separated by a given time intervals (up to months apart). To classify the Raman spectra, data analysis was performed using the approach of principal component analysis (PCA). The analysis of the data sets generated during the scans of individual colonies reveals that despite the inhomogeneity of the biological samples unambiguous associations to individual strains (two biofilm-positive and two biofilm-negative) could be made.

Candida parapsilosis Biofilm Identification by Raman Spectroscopy

PubMed Central

Samek, Ota; Mlynariková, Katarina; Bernatová, Silvie; Ježek, Jan; Krzyžánek, Vladislav; Šiler, Martin; Zemánek, Pavel; Růžička, Filip; Holá, Veronika; Mahelová, Martina

2014-01-01

Colonies of Candida parapsilosis on culture plates were probed directly in situ using Raman spectroscopy for rapid identification of specific strains separated by a given time intervals (up to months apart). To classify the Raman spectra, data analysis was performed using the approach of principal component analysis (PCA). The analysis of the data sets generated during the scans of individual colonies reveals that despite the inhomogeneity of the biological samples unambiguous associations to individual strains (two biofilm-positive and two biofilm-negative) could be made. PMID:25535081

Development of tube-packaged FBG strain sensor and application in the vibration experiment of submarine pipeline model

NASA Astrophysics Data System (ADS)

Ren, Liang; Li, Hong-Nan; Sun, Li; Li, Dong-Sheng

2005-05-01

Optical fiber sensors have received increasing attention in the fields of aeronautic and civil engineering for their superior ability of explosion proof, immunity to electromagnetic interference and high accuracy, especially fitting for measurement applications in harsh environment. In this paper, a novel FBG (fiber Bragg grating) strain sensor, which was packaged in a 1.2mm stainless steel tube by epoxy resin, was developed. Experiments were conducted on the universal material testing machine to calibrate its strain transferring characteristics. The sensor has the advantages of small size, high precision and flexible use, and demonstrates promising potentials. Ten of tube-packaged strain FBG sensors were applied in the vibration experiment of submarine pipeline model. The strain measured by FBG sensor agrees well with the electric resistance strain sensor.

Development of tube-packaged FBG strain sensor and application in the vibration experiment of submarine pipeline model

NASA Astrophysics Data System (ADS)

Ren, Liang; Li, Hong-Nan; Sun, Li; Li, Dong-Sheng

2005-02-01

Optical fiber sensors have received increasing attention in the fields of aeronautic and civil engineering for their superior ability of explosion proof, immunity to electromagnetic interference and high accuracy, especially fitting for measurement applications in harsh environment. In this paper, a novel FBG (fiber Bragg grating) strain sensor, which was packaged in a 1.2mm stainless steel tube by epoxy resin, was developed. Experiments were conducted on the universal material testing machine to calibrate its strain transferring characteristics. The sensor has the advantages of small size, high precision and flexible use, and demonstrates promising potentials. Ten of tube-packaged strain FBG sensors were applied in the vibration experiment of submarine pipeline model. The strain measured by FBG sensor agrees well with the electric resistance strain sensor.

SURVIVAL OF SALMONELLA SPECIES IN RIVER WATER

EPA Science Inventory

The survival of four Salmonella strains in river water microcosms was monitored by culturing techniques, direct counts, whole-cell hybridization, scanning electron microscopy, and resuscitation techniques via the direct viable count method and flow cytometry. Plate counts of bact...

A multivariate approach using attenuated total reflectance mid-infrared spectroscopy to measure the surface mannoproteins and β-glucans of yeast cell walls during wine fermentations.

PubMed

Moore, John P; Zhang, Song-Lei; Nieuwoudt, Hélène; Divol, Benoit; Trygg, Johan; Bauer, Florian F

2015-11-18

Yeast cells possess a cell wall comprising primarily glycoproteins, mannans, and glucan polymers. Several yeast phenotypes relevant for fermentation, wine processing, and wine quality are correlated with cell wall properties. To investigate the effect of wine fermentation on cell wall composition, a study was performed using mid-infrared (MIR) spectroscopy coupled with multivariate methods (i.e., PCA and OPLS-DA). A total of 40 yeast strains were evaluated, including Saccharomyces strains (laboratory and industrial) and non-Saccharomyces species. Cells were fermented in both synthetic MS300 and Chardonnay grape must to stationery phase, processed, and scanned in the MIR spectrum. PCA of the fingerprint spectral region showed distinct separation of Saccharomyces strains from non-Saccharomyces species; furthermore, industrial wine yeast strains separated from laboratory strains. PCA loading plots and the use of OPLS-DA to the data sets suggested that industrial strains were enriched with cell wall proteins (e.g., mannoproteins), whereas laboratory strains were composed mainly of mannan and glucan polymers.

Visual scanning with or without spatial uncertainty and time-sharing performance

NASA Technical Reports Server (NTRS)

Liu, Yili; Wickens, Christopher D.

1989-01-01

An experiment is reported that examines the pattern of task interference between visual scanning as a sequential and selective attention process and other concurrent spatial or verbal processing tasks. A distinction is proposed between visual scanning with or without spatial uncertainty regarding the possible differential effects of these two types of scanning on interference with other concurrent processes. The experiment required the subject to perform a simulated primary tracking task, which was time-shared with a secondary spatial or verbal decision task. The relevant information that was needed to perform the decision tasks were displayed with or without spatial uncertainty. The experiment employed a 2 x 2 x 2 design with types of scanning (with or without spatial uncertainty), expected scanning distance (low/high), and codes of concurrent processing (spatial/verbal) as the three experimental factors. The results provide strong evidence that visual scanning as a spatial exploratory activity produces greater task interference with concurrent spatial tasks than with concurrent verbal tasks. Furthermore, spatial uncertainty in visual scanning is identified to be the crucial factor in producing this differential effect.

Thermal cycling reliability of Cu/SnAg double-bump flip chip assemblies for 100 μm pitch applications

NASA Astrophysics Data System (ADS)

Son, Ho-Young; Kim, Ilho; Lee, Soon-Bok; Jung, Gi-Jo; Park, Byung-Jin; Paik, Kyung-Wook

2009-01-01

A thick Cu column based double-bump flip chip structure is one of the promising alternatives for fine pitch flip chip applications. In this study, the thermal cycling (T/C) reliability of Cu/SnAg double-bump flip chip assemblies was investigated, and the failure mechanism was analyzed through the correlation of T/C test and the finite element analysis (FEA) results. After 1000 thermal cycles, T/C failures occurred at some Cu/SnAg bumps located at the edge and corner of chips. Scanning acoustic microscope analysis and scanning electron microscope observations indicated that the failure site was the Cu column/Si chip interface. It was identified by a FEA where the maximum stress concentration was located during T/C. During T/C, the Al pad between the Si chip and a Cu column bump was displaced due to thermomechanical stress. Based on the low cycle fatigue model, the accumulation of equivalent plastic strain resulted in thermal fatigue deformation of the Cu column bumps and ultimately reduced the thermal cycling lifetime. The maximum equivalent plastic strains of some bumps at the chip edge increased with an increased number of thermal cycles. However, equivalent plastic strains of the inner bumps did not increase regardless of the number of thermal cycles. In addition, the z-directional normal plastic strain ɛ22 was determined to be compressive and was a dominant component causing the plastic deformation of Cu/SnAg double bumps. As the number of thermal cycles increased, normal plastic strains in the perpendicular direction to the Si chip and shear strains were accumulated on the Cu column bumps at the chip edge at low temperature region. Thus it was found that the Al pad at the Si chip/Cu column interface underwent thermal fatigue deformation by compressive normal strain and the contact loss by displacement failure of the Al pad, the main T/C failure mode of the Cu/SnAg flip chip assembly, then occurred at the Si chip/Cu column interface shear strain deformation during T/C.

Analytical and Experimental Nanomechanical Approaches to Understanding the Ductile-to-Brittle Transition

NASA Astrophysics Data System (ADS)

Hintsala, Eric Daniel

This dissertation presents progress towards understanding the ductile-to-brittle transition (DBT) using a mixture of nanomechanical experiments and an analytical model. The key concept is dislocation shielding of crack tips, which is occurs due to a dislocation back stress. In order to properly evaluate the role of these interactions, in-situ experiments are ideal by reducing the number of interacting dislocations and allowing direct observation of cracking behavior and the dislocations themselves. First, in-situ transmission electron microscope (TEM) compression experiments of plasma-synthesized silicon nanocubes (NCs) are presented which shows plastic strains greater than 50% in a semi-brittle material. The mechanical properties are discussed and plasticity mechanisms are identified using post-mortem imaging with a combination of dark field and high-resolution imaging. This observations help to develop a back stress model which is used to fit the hardening regime. This represents the first study of its kind where back stresses are used in a discrete manner to match hardening rates. However, the important measurable quantities for evaluating the DBT include fracture toughness values and energetic activation parameters for cracking and plasticity. In order to do this, a new method for doing in-situ fracture experiments is explored. This method is pre-notched three point bending experiments, which were fabricated by focused ion beam (FIB) milling. Two different materials are evaluated: a model ductile material, Nitronic 50, an austenitic steel alloy, and a model brittle material, silicon. These experiments are performed in-situ scanning electron microscope (SEM) and TEM and explore different aspects including electron backscatter diffraction (EBSD) to track deformation in SEM scale experiments, pre-notching using a converged TEM beam to produce sharper notches better replicating natural cracks, etching procedures to reduce residual FIB damage and elevated temperature experiments. Lastly, an analytical method to predict DBTs is presented which can account for effects of strain rate, temperature and impurity presence. The model is tested by pre-existing data on macroscopic compact tension specimens of single crystal Fe-3%Si. Next, application of the model to nano/micro scale fracture toughness experiments is explored and the large number of confounding variables is discussed in detail. A first attempt at fitting is also presented.

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.

Passive Thermal Design Approach for the Space Communications and Navigation (SCaN) Testbed Experiment on the International Space Station (ISS)

NASA Technical Reports Server (NTRS)

Siamidis, John; Yuko, Jim

2014-01-01

The Space Communications and Navigation (SCaN) Program Office at NASA Headquarters oversees all of NASAs space communications activities. SCaN manages and directs the ground-based facilities and services provided by the Deep Space Network (DSN), Near Earth Network (NEN), and the Space Network (SN). Through the SCaN Program Office, NASA GRC developed a Software Defined Radio (SDR) testbed experiment (SCaN testbed experiment) for use on the International Space Station (ISS). It is comprised of three different SDR radios, the Jet Propulsion Laboratory (JPL) radio, Harris Corporation radio, and the General Dynamics Corporation radio. The SCaN testbed experiment provides an on-orbit, adaptable, SDR Space Telecommunications Radio System (STRS) - based facility to conduct a suite of experiments to advance the Software Defined Radio, Space Telecommunications Radio Systems (STRS) standards, reduce risk (Technology Readiness Level (TRL) advancement) for candidate Constellation future space flight hardware software, and demonstrate space communication links critical to future NASA exploration missions. The SCaN testbed project provides NASA, industry, other Government agencies, and academic partners the opportunity to develop and field communications, navigation, and networking technologies in the laboratory and space environment based on reconfigurable, software defined radio platforms and the STRS Architecture.The SCaN testbed is resident on the P3 Express Logistics Carrier (ELC) on the exterior truss of the International Space Station (ISS). The SCaN testbed payload launched on the Japanese Aerospace Exploration Agency (JAXA) H-II Transfer Vehicle (HTV) and was installed on the ISS P3 ELC located on the inboard RAM P3 site. The daily operations and testing are managed out of NASA GRC in the Telescience Support Center (TSC).

Characterization of homologous and heterologous adaptive immune responses in porcine reproductive and respiratory syndrome virus infection

PubMed Central

2012-01-01

The present study characterized the homologous and heterologous immune response in type-I porcine reproductive and respiratory syndrome virus (PRRSV) infection. Two experiments were conducted: in experiment 1, eight pigs were inoculated with PRRSV strain 3262 and 84 days post-inoculation (dpi) they were challenged with either strain 3262 or strain 3267 and followed for the next 14 days (98 dpi). In experiment 2, eight pigs were inoculated with strain 3267 and challenged at 84 dpi as above. Clinical course, viremia, humoral response (neutralizing and non-neutralizing antibodies, NA) and virus-specific IFN-γ responses (ELISPOT) were evaluated all throughout the study. Serum levels of IL-1, IL-6, IL-8, TNF-α and TGF-β were determined (ELISA) after the second challenge. In experiment 1 primo-inoculation with strain 3262 induced viremia of ≤ 28 days, low titres of homologous NA but strong IFN-γ responses. In contrast, strain 3267 induced longer viremias (up to 56 days), higher NA titres (≤ 6 log2) and lower IFN-γ responses. Inoculation with 3267 produced higher serum IL-8 levels. After the re-challenge at 84 dpi, pigs in experiment 1 developed mostly a one week viremia regardless of the strain used. In experiment 2, neither the homologous nor the heterologous challenge resulted in detectable viremia although PRRSV was present in tonsils of some animals. Homologous re-inoculation with 3267 produced elevated TGF-β levels in serum for 7–14 days but this did not occur with the heterologous re-inoculation. In conclusion, inoculation with different PRRSV strains result in different virological and immunological outcomes and in different degrees of homologous and heterologous protection. PMID:22515169

Tension and fatigue behavior of 316LVM 1x7 multi-strand cables used as implantable electrodes.

PubMed

Lewandowski, John J; Varadarajan, Ravikumar; Smith, Brian; Tuma, Chris; Shazly, Mostafa; Vatamanu, Luciano O

2008-07-15

The mechanical behavior of 316LVM 1x7 cables were evaluated in uniaxial tension, and in cyclic strain-controlled fatigue with the use of a Flex tester operated to provide fully reversed bending fatigue. The magnitude of cyclic strains imparted to each cable tested was controlled via the use of different diameter mandrels. Smaller diameter mandrels produced higher values of cyclic strain and lower fatigue life. Multiple samples were tested and analyzed via scanning electron microscopy. The fatigue results were analyzed via a Coffin-Manson-Basquin approach and compared to fatigue data obtained from the literature where testing was conducted on similar materials, but under rotating bending fatigue conditions.

Surface roughening transition and critical layer thickness in strained-layer heteroepitaxy of EuTe on PbTe (111)

NASA Astrophysics Data System (ADS)

Springholz, G.; Frank, N.; Bauer, G.

1994-05-01

Heteroepitaxial growth of 2% lattice-mismatched EuTe on PbTe (111) by molecular beam epitaxy is investigated in the two-dimensional layer-by-layer growth regime combining in situ reflection high-energy electron diffraction and scanning tunneling microscopy (STM). At the critical layer thickness a distinct surface roughening is observed. The quantitative analysis of STM images yields an increase of the root mean square roughness by a factor of 4 at this roughening transition. Strong evidence is presented that for the used growth conditions this roughening is not caused by strain induced coherent islanding but by misfit dislocations at the onset of strain relaxation.

Utilization of Sugarcane Bagasse by Halogeometricum borinquense Strain E3 for Biosynthesis of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

PubMed Central

Salgaonkar, Bhakti B.; Bragança, Judith M.

2017-01-01

Sugarcane bagasse (SCB), one of the major lignocellulosic agro-industrial waste products, was used as a substrate for biosynthesis of polyhydroxyalkanoates (PHA) by halophilic archaea. Among the various wild-type halophilic archaeal strains screened, Halogeometricum borinquense strain E3 showed better growth and PHA accumulation as compared to Haloferaxvolcanii strain BBK2, Haloarcula japonica strain BS2, and Halococcus salifodinae strain BK6. Growth kinetics and bioprocess parameters revealed the maximum PHA accumulated by strain E3 to be 50.4 ± 0.1 and 45.7 ± 0.19 (%) with specific productivity (qp) of 3.0 and 2.7 (mg/g/h) using NaCl synthetic medium supplemented with 25% and 50% SCB hydrolysate, respectively. PHAs synthesized by strain E3 were recovered in chloroform using a Soxhlet apparatus. Characterization of the polymer using crotonic acid assay, X-ray diffraction (XRD), differential scanning calorimeter (DSC), Fourier transform infrared (FT-IR), and proton nuclear magnetic resonance (1H-NMR) spectroscopy analysis revealed the polymer obtained from SCB hydrolysate to be a co-polymer of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] comprising of 13.29 mol % 3HV units. PMID:28952529

Development of the radiation-resistant strain of Moraxella osloensis and effect of penicillin G on its growth

NASA Astrophysics Data System (ADS)

Lim, Sangyong; Yun, Hyejeong; Joe, Minho; Kim, Dongho

2009-07-01

A series of repeated exposures to γ-radiation with intervening outgrowth of survivors was used to develop radioresistant cultures of Moraxella osloensis that have been recognized as potential pathogenic microorganism. The D10 value of the radiation-resistant strain, 5.903±0.006 kGy, was increased by four-fold compared to the parent wild-type strain, 1.637±0.004 kGy. Since most strains of M. osloensis are sensitive to penicillin, we have surveyed the sensitivity of radiation-resistant strain to this antibiotic. When the optical density was monitored after the addition of penicillin G, the radioresistant strain appeared to be more resistant to only a low concentration of penicillin G (0.5 U/ml) than the parent strain. Interestingly, however, there was no apparent difference in the number of viable cells between both strains. Scanning electron microscope data showed that the resistance cells were generally larger than the parent cells, suggesting that this increase in size may cause a higher optical density of radioresistant cells. In conclusion, radiation mutation does not affect the penicillin resistance of M. osloensis.

Ductility of Advanced High-Strength Steel in the Presence of a Sheared Edge

NASA Astrophysics Data System (ADS)

Ruggles, Tim; Cluff, Stephen; Miles, Michael; Fullwood, David; Daniels, Craig; Avila, Alex; Chen, Ming

2016-07-01

The ductility of dual-phase (DP) 980 and transformation-induced plasticity (TRIP) assisted bainitic ferritic (TBF) 980 steels was studied in the presence of a sheared edge. Specimens were tested in uniaxial tension in a standard test frame as well as in situ in the scanning electron microscope (SEM). Incremental tensile straining was done in the SEM with images taken at each strain increment. Then digital image correlation (DIC) was used to compute the effective strain at the level of the individual phases in the microstructure. Shear banding across multiple phases was seen in strained TBF specimens, while the DP specimens exhibited more of a patchwork strain pattern, with high strains concentrated in ferrite and low strains observed in the martensite. Two-point statistics were applied to the strain data from the DIC work and the corresponding microstructure images to evaluate the effect of phase hardness on localization and fracture. It was observed that the DP 980 material had a greater tendency for localization around hard phases compared to the TBF 980. This at least partially explains the greater ductility of the TBF material, especially in specimens where a sheared edge was present.

Personality Impact on Experiences of Strain among Staff Exposed to Violence in Care of People with Intellectual Disabilities

ERIC Educational Resources Information Center

Lundstrom, Mats; Graneheim, Ulla H.; Eisemann, Martin; Richter, Jorg; Astrom, Sture

2007-01-01

Explored are the relationships among personality and emotional reactions, work-related strain, and experiences of burnout among staff exposed vs. not exposed to violence when caring for people with intellectual disabilities (ID). Questionnaires measuring personality, emotional reactions, strain and burnout, and exposure to violence were…

The inhomogeneous microstructure and deformation of similar and dissimilar Al-Zn containing Mg friction stir welds

NASA Astrophysics Data System (ADS)

Hiscocks, Jessica

The magnesium-based aluminum-zinc alloys have excellent stiffness to weight ratios, and may be combined by friction stir welding to expand the possible applications. The high aluminum alloy AZ80 in particular has the advantage of being relatively stiff but still extrudable. However limited friction stir welding research is available for this alloy and extrapolation from the extensive work in aluminum alloys is impractical due differences in precipitation behaviour, and magnesium's high plastic anisotropy and tendency to form strong textures during friction stir welding. This work investigates the correlations between local friction stir welded microstructures, textures, residual strains, and the local deformation behaviour based on strain mapping during tensile tests. Covering bead-on-plate and butt configurations, joining of similar and dissimilar materials, and a range of processing conditions, many findings of interest for deformation modelling and industrial applications are presented. Synchrotron x-ray diffraction study of an entire friction stir weld was used to determine texture, residual strain and dislocation density data from a single experiment. A number of unique findings were made, mainly related to the asymmetric distribution of properties both between sides of the weld and through the depth. Particularly in the case of strain measurements, features not detectable at coarser measurement spacing or by line scan are presented and compared for multiple processing conditions. Investigation of the longitudinal material flow during welding showed that even when periodicity in grain size, precipitate distribution, or texture was not observed, periodic changes in texture intensity resulting from compaction of material behind the tool were present, providing evidence that movement of nugget material remained periodic. Strain localisation and fracture behaviour were found to be completely different between good quality similar and dissimilar friction stir welds. For similar magnesium friction stir welds, higher heat input was shown to improve mechanical performance by reducing the residual strain, while for dissimilar friction stir welds, deformation behaviour was found to be more sensitive to the final material distribution in the friction stir weld nugget. For dissimilar welds, even minor changes to the material flow were shown to have a major impact on the tensile performance.

Strain-induced formation of fourfold symmetric SiGe quantum dot molecules.

PubMed

Zinovyev, V A; Dvurechenskii, A V; Kuchinskaya, P A; Armbrister, V A

2013-12-27

The strain field distribution at the surface of a multilayer structure with disklike SiGe nanomounds formed by heteroepitaxy is exploited to arrange the symmetric quantum dot molecules typically consisting of four elongated quantum dots ordered along the [010] and [100] directions. The morphological transition from fourfold quantum dot molecules to continuous fortresslike quantum rings with an increasing amount of deposited Ge is revealed. We examine key mechanisms underlying the formation of lateral quantum dot molecules by using scanning tunneling microscopy and numerical calculations of the strain energy distribution on the top of disklike SiGe nanomounds. Experimental data are well described by a simple thermodynamic model based on the accurate evaluation of the strain dependent part of the surface chemical potential. The spatial arrangement of quantum dots inside molecules is attributed to the effect of elastic property anisotropy.

Flexible Sensing Arrays Fabricated with Carbon Nanofiber Composite Thin Films for Posture Monitoring

NASA Astrophysics Data System (ADS)

Chang, Fuh-Yu; Wang, Ruoh-Huey; Lin, Yu-Hsien; Chen, Tse-Min; Lee, Yueh-Feng; Huang, Shu-Jiuan; Liu, Chia-Ming

2011-06-01

Faulty posture increases joint stress and causes postural pain syndrome. In this paper, we present a portable strain sensing system with flexible sensor arrays to warn patients to correct inappropriate posture. A 3×3 flexible strain sensing array system was fabricated using patterned surface treatment and the tilted-drop process with carbon nanofiber composite solutions on polyimide substrates. Atmospheric plasma was used to enhance or reduce the surface energy in specific areas for patterned surface treatment. A scanning circuit was also developed to capture the signal from the flexible sensing array. The developed system has been used to measure the bent angle of the human neck from 15 to 60°. The results indicate that human posture can be successfully captured by analyzing the measured strains from a flexible strain sensing array.

Internal state variable plasticity-damage modeling of AISI 4140 steel including microstructure-property relations: temperature and strain rate effects

NASA Astrophysics Data System (ADS)

Nacif el Alaoui, Reda

Mechanical structure-property relations have been quantified for AISI 4140 steel. under different strain rates and temperatures. The structure-property relations were used. to calibrate a microstructure-based internal state variable plasticity-damage model for. monotonic tension, compression and torsion plasticity, as well as damage evolution. Strong stress state and temperature dependences were observed for the AISI 4140 steel. Tension tests on three different notched Bridgman specimens were undertaken to study. the damage-triaxiality dependence for model validation purposes. Fracture surface. analysis was performed using Scanning Electron Microscopy (SEM) to quantify the void. nucleation and void sizes in the different specimens. The stress-strain behavior exhibited. a fairly large applied stress state (tension, compression dependence, and torsion), a. moderate temperature dependence, and a relatively small strain rate dependence.

Identifying suitable substrates for high-quality graphene-based heterostructures

NASA Astrophysics Data System (ADS)

Banszerus, L.; Janssen, H.; Otto, M.; Epping, A.; Taniguchi, T.; Watanabe, K.; Beschoten, B.; Neumaier, D.; Stampfer, C.

2017-06-01

We report on a scanning confocal Raman spectroscopy study investigating the strain-uniformity and the overall strain and doping of high-quality chemical vapour deposited (CVD) graphene-based heterostuctures on a large number of different substrate materials, including hexagonal boron nitride (hBN), transition metal dichalcogenides, silicon, different oxides and nitrides, as well as polymers. By applying a hBN-assisted, contamination free, dry transfer process for CVD graphene, high-quality heterostructures with low doping densities and low strain variations are assembled. The Raman spectra of these pristine heterostructures are sensitive to substrate-induced doping and strain variations and are thus used to probe the suitability of the substrate material for potential high-quality graphene devices. We find that the flatness of the substrate material is a key figure for gaining, or preserving high-quality graphene.

Structural analysis of LaVO3 thin films under epitaxial strain

NASA Astrophysics Data System (ADS)

Meley, H.; Karandeep, Oberson, L.; de Bruijckere, J.; Alexander, D. T. L.; Triscone, J.-M.; Ghosez, Ph.; Gariglio, S.

2018-04-01

Rare earth vanadate perovskites exhibit a phase diagram in which two different types of structural distortions coexist: the strongest, the rotation of the oxygen octahedra, comes from the small tolerance factor of the perovskite cell (t = 0.88 for LaVO3) and the smaller one comes from inter-site d-orbital interactions manifesting as a cooperative Jahn-Teller effect. Epitaxial strain acts on octahedral rotations and crystal field symmetry to alter this complex lattice-orbit coupling. In this study, LaVO3 thin film structures have been investigated by X-ray diffraction and scanning transmission electron microscopy. The analysis shows two different orientations of octahedral tilt patterns, as well as two distinct temperature behaviors, for compressive and tensile film strain states. Ab initio calculations capture the strain effect on the tilt pattern orientation in agreement with experimental data.

Structure and Composition of Isolated Core-Shell (In ,Ga )N /GaN Rods Based on Nanofocus X-Ray Diffraction and Scanning Transmission Electron Microscopy

NASA Astrophysics Data System (ADS)

Krause, Thilo; Hanke, Michael; Nicolai, Lars; Cheng, Zongzhe; Niehle, Michael; Trampert, Achim; Kahnt, Maik; Falkenberg, Gerald; Schroer, Christian G.; Hartmann, Jana; Zhou, Hao; Wehmann, Hergo-Heinrich; Waag, Andreas

2017-02-01

Nanofocus x-ray diffraction is used to investigate the structure and local strain field of an isolated (In ,Ga )N /GaN core-shell microrod. Because the high spatial resolution of the x-ray beam is only 80 ×90 nm2, we are able to investigate several distinct volumes on one individual side facet. Here, we find a drastic increase in thickness of the outer GaN shell along the rod height. Additionally, we performed high-angle annular dark-field scanning-transmission-electron-microscopy measurements on several rods from the same sample showing that (In,Ga)N double-quantum-well and GaN barrier thicknesses also increase strongly along the height. Moreover, plastic relaxation is observed in the top part of the rod. Based on the experimentally obtained structural parameters, we simulate the strain-induced deformation using the finite-element method, which serves as the input for subsequent kinematic scattering simulations. The simulations reveal a significant increase of elastic in-plane relaxation along the rod height. However, at a certain height, the occurrence of plastic relaxation yields a decrease of the elastic strain. Because of the experimentally obtained structural input for the finite-element simulations, we can exclude unknown structural influences on the strain distribution, and we are able to translate the elastic relaxation into an indium concentration which increases by a factor of 4 from the bottom to the height where plastic relaxation occurs.

Studies on drug metabolism by fungi colonizing decomposing human cadavers. Part II: biotransformation of five model drugs by fungi isolated from post-mortem material.

PubMed

Martínez-Ramírez, Jorge A; Walther, Grit; Peters, Frank T

2015-04-01

The present study investigated the in vitro metabolic capacity of 28 fungal strains isolated from post-mortem material towards five model drugs: amitriptyline, metoprolol, mirtazapine, promethazine, and zolpidem. Each fungal strain was incubated at 25 °C for up to 120 h with each of the five models drugs. Cunninghamella elegans was used as positive control. Aliquots of the incubation mixture were centrifuged and 50 μL of the supernatants were diluted and directly analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) with product ion scanning. The remaining mixture was analyzed by full scan gas chromatography-mass spectrometry (GC-MS) after liquid-liquid extraction and acetylation. The metabolic activity was evaluated through the total number of detected metabolites (NDM) produced in each model and fungal strains and the percentage of parent drug remaining (%RPD) after up to five days of incubation. All the tested fungal strains were capable of forming mammalian phase I metabolites. Fungi from the normal fungal flora of the human body such as Candida sp., Geotrichum candidum, and Trichosporon asahii) formed up to seven metabolites at %RPD values greater than 52% but no new fungal metabolites (NFM). In contrast, some airborne fungal strains like Bjerkandera adusta, Chaetomium sp, Coriolopsis sp., Fusarium solani and Mucor plumbeus showed NDM values exceeding those of the positive control, complete metabolism of the parent drug in some models and formation of NFM. NFM (numbers in brackets) were detected in four of the five model drugs: amitriptyline (18), metoprolol (4), mirtazapine (8), and zolpidem (2). The latter NFM are potential candidates for marker substances indicating post-mortem fungal metabolism. Copyright © 2014 John Wiley & Sons, Ltd.

Cyclic fatigue behavior of nickel-titanium dental rotary files in clinical simulated root canals.

PubMed

Chi, Chih-Wen; Li, Chun-Chieh; Lin, Chun-Pin; Shin, Chow-Shing

2017-04-01

Dental rotary instruments can be applied in multiple conditions of canals, but unpredictable fatigue fracture may happen. This study evaluated the fatigue lives of two batches of nickel-titanium (NiTi) dental rotary files operating in clinically simulated root canals. Single-step cyclic fatigue tests were carried out to assess the performance of two batches of NiTi files (ProTaper and ProFile) in nine combinations of simulated canals (cylinder radii 5 mm, 7.5 mm, and 10 mm, and insertion angles 20°, 40°, and 60°). Two-step cyclic fatigue tests were carried out in simulated root canals with the same radius by using the following two sets of insertion angles: (20°, 40°), (20°, 60°), (40°, 20°), and (60°, 20°). Fracture surfaces were observed by scanning electron microscopy. The single-step cyclic fatigue results showed that cyclic fatigue lives of the files decreased with increasing insertion angles or decreasing cylinder radius. The ProFile #25 .04 file was more fatigue resistant than the ProTaper F2 file. In two-step cyclic fatigue tests, the total fatigue lives were usually more than 100% when the files operated at a lower strain and then at a higher strain. By scanning electron microscopy, a larger area of fatigue striation corresponded to a longer fatigue life. Cyclic fatigue life can be influenced by the strains and geometries of files. The fatigue life was prolonged when the files operated at a lower strain and then at a higher strain. However, the fatigue life was shortened if the loading sequence was reversed. Copyright © 2016. Published by Elsevier B.V.

Measurement of Ring Strain Using Butanols: A Physical Chemistry Lab Experiment

ERIC Educational Resources Information Center

Martin, William R.; Davidson, Ada S.; Ball, David W.

2016-01-01

In this article, a bomb calorimeter experiment and subsequent calculations aimed at determining the strain energy of the cyclobutane backbone are described. Students use several butanol isomers instead of the parent hydrocarbons, and they manipulate liquids instead of gases, which makes the experiment much easier to perform. Experiments show that…

Research on the novel FBG detection system for temperature and strain field distribution

NASA Astrophysics Data System (ADS)

Liu, Zhi-chao; Yang, Jin-hua

2017-10-01

In order to collect the information of temperature and strain field distribution information, the novel FBG detection system was designed. The system applied linear chirped FBG structure for large bandwidth. The structure of novel FBG cover was designed as a linear change in thickness, in order to have a different response at different locations. It can obtain the temperature and strain field distribution information by reflection spectrum simultaneously. The structure of novel FBG cover was designed, and its theoretical function is calculated. Its solution is derived for strain field distribution. By simulation analysis the change trend of temperature and strain field distribution were analyzed in the conditions of different strain strength and action position, the strain field distribution can be resolved. The FOB100 series equipment was used to test the temperature in experiment, and The JSM-A10 series equipment was used to test the strain field distribution in experiment. The average error of experimental results was better than 1.1% for temperature, and the average error of experimental results was better than 1.3% for strain. There were individual errors when the strain was small in test data. It is feasibility by theoretical analysis, simulation calculation and experiment, and it is very suitable for application practice.

Effect of high strain rates on peak stress in a Zr-based bulk metallic glass

NASA Astrophysics Data System (ADS)

Sunny, George; Yuan, Fuping; Prakash, Vikas; Lewandowski, John

2008-11-01

The mechanical behavior of Zr41.25Ti13.75Cu12.5Ni10Be22.5 (LM-1) has been extensively characterized under quasistatic loading conditions; however, its mechanical behavior under dynamic loading conditions is currently not well understood. A Split-Hopkinson pressure bar (SHPB) and a single-stage gas gun are employed to characterize the mechanical behavior of LM-1 in the strain-rate regime of 102-105/s. The SHPB experiments are conducted with a tapered insert design to mitigate the effects of stress concentrations and preferential failure at the specimen-insert interface. The higher strain-rate plate-impact compression-and-shear experiments are conducted by impacting a thick tungsten carbide (WC) flyer plate with a sandwich sample comprising a thin bulk metallic glass specimen between two thicker WC target plates. Specimens employed in the SHPB experiments failed in the gage-section at a peak stress of approximately 1.8 GPa. Specimens in the high strain-rate plate-impact experiments exhibited a flow stress in shear of approximately 0.9 GPa, regardless of the shear strain-rate. The flow stress under the plate-impact conditions was converted to an equivalent flow stress under uniaxial compression by assuming a von Mises-like material behavior and accounting for the plane strain conditions. The results of these experiments, when compared to the previous work conducted at quasistatic loading rates, indicate that the peak stress of LM-1 is essentially strain rate independent over the strain-rate range up to 105/s.

Propagation of a finite-amplitude elastic pulse in a bar of Berea sandstone: A detailed look at the mechanisms of classical nonlinearity, hysteresis, and nonequilibrium dynamics: Nonlinear propagation of elastic pulse

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

Remillieux, Marcel C.; Ulrich, T. J.; Goodman, Harvey E.

Here, we study the propagation of a finite-amplitude elastic pulse in a long thin bar of Berea sandstone. In previous work, this type of experiment has been conducted to quantify classical nonlinearity, based on the amplitude growth of the second harmonic as a function of propagation distance. To greatly expand on that early work, a non-contact scanning 3D laser Doppler vibrometer was used to track the evolution of the axial component of the particle velocity over the entire surface of the bar as functions of the propagation distance and source amplitude. With these new measurements, the combined effects of classicalmore » nonlinearity, hysteresis, and nonequilibrium dynamics have all been measured simultaneously. We then show that the numerical resolution of the 1D wave equation with terms for classical nonlinearity and attenuation accurately captures the spectral features of the waves up to the second harmonic. But, for higher harmonics the spectral content is shown to be strongly influenced by hysteresis. This work also shows data which not only quantifies classical nonlinearity but also the nonequilibrium dynamics based on the relative change in the arrival time of the elastic pulse as a function of strain and distance from the source. Finally, a comparison is made to a resonant bar measurement, a reference experiment used to quantify nonequilibrium dynamics, based on the relative shift of the resonance frequencies as a function of the maximum dynamic strain in the sample.« less

Propagation of a finite-amplitude elastic pulse in a bar of Berea sandstone: A detailed look at the mechanisms of classical nonlinearity, hysteresis, and nonequilibrium dynamics: Nonlinear propagation of elastic pulse

DOE PAGES

Remillieux, Marcel C.; Ulrich, T. J.; Goodman, Harvey E.; ...

2017-10-18

Here, we study the propagation of a finite-amplitude elastic pulse in a long thin bar of Berea sandstone. In previous work, this type of experiment has been conducted to quantify classical nonlinearity, based on the amplitude growth of the second harmonic as a function of propagation distance. To greatly expand on that early work, a non-contact scanning 3D laser Doppler vibrometer was used to track the evolution of the axial component of the particle velocity over the entire surface of the bar as functions of the propagation distance and source amplitude. With these new measurements, the combined effects of classicalmore » nonlinearity, hysteresis, and nonequilibrium dynamics have all been measured simultaneously. We then show that the numerical resolution of the 1D wave equation with terms for classical nonlinearity and attenuation accurately captures the spectral features of the waves up to the second harmonic. But, for higher harmonics the spectral content is shown to be strongly influenced by hysteresis. This work also shows data which not only quantifies classical nonlinearity but also the nonequilibrium dynamics based on the relative change in the arrival time of the elastic pulse as a function of strain and distance from the source. Finally, a comparison is made to a resonant bar measurement, a reference experiment used to quantify nonequilibrium dynamics, based on the relative shift of the resonance frequencies as a function of the maximum dynamic strain in the sample.« less

Deformation and Failure Mechanisms of Shape Memory Alloys

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

Daly, Samantha Hayes

2015-04-15

The goal of this research was to understand the fundamental mechanics that drive the deformation and failure of shape memory alloys (SMAs). SMAs are difficult materials to characterize because of the complex phase transformations that give rise to their unique properties, including shape memory and superelasticity. These phase transformations occur across multiple length scales (one example being the martensite-austenite twinning that underlies macroscopic strain localization) and result in a large hysteresis. In order to optimize the use of this hysteretic behavior in energy storage and damping applications, we must first have a quantitative understanding of this transformation behavior. Prior resultsmore » on shape memory alloys have been largely qualitative (i.e., mapping phase transformations through cracked oxide coatings or surface morphology). The PI developed and utilized new approaches to provide a quantitative, full-field characterization of phase transformation, conducting a comprehensive suite of experiments across multiple length scales and tying these results to theoretical and computational analysis. The research funded by this award utilized new combinations of scanning electron microscopy, diffraction, digital image correlation, and custom testing equipment and procedures to study phase transformation processes at a wide range of length scales, with a focus at small length scales with spatial resolution on the order of 1 nanometer. These experiments probe the basic connections between length scales during phase transformation. In addition to the insights gained on the fundamental mechanisms driving transformations in shape memory alloys, the unique experimental methodologies developed under this award are applicable to a wide range of solid-to-solid phase transformations and other strain localization mechanisms.« less

2pBAb5. Validation of three-dimensional strain tracking by volumetric ultrasound image correlation in a pubovisceral muscle model

PubMed Central

Nagle, Anna S.; Nageswaren, Ashok R.; Haridas, Balakrishna; Mast, T. D.

2014-01-01

Little is understood about the biomechanical changes leading to pelvic floor disorders such as stress urinary incontinence. In order to measure regional biomechanical properties of the pelvic floor muscles in vivo, a three dimensional (3D) strain tracking technique employing correlation of volumetric ultrasound images has been implemented. In this technique, local 3D displacements are determined as a function of applied stress and then converted to strain maps. To validate this approach, an in vitro model of the pubovisceral muscle, with a hemispherical indenter emulating the downward stress caused by intra-abdominal pressure, was constructed. Volumetric B-scan images were recorded as a function of indenter displacement while muscle strain was measured independently by a sonomicrometry system (Sonometrics). Local strains were computed by ultrasound image correlation and compared with sonomicrometry-measured strains to assess strain tracking accuracy. Image correlation by maximizing an exponential likelihood function was found more reliable than the Pearson correlation coefficient. Strain accuracy was dependent on sizes of the subvolumes used for image correlation, relative to characteristic speckle length scales of the images. Decorrelation of echo signals was mapped as a function of indenter displacement and local tissue orientation. Strain measurement accuracy was weakly related to local echo decorrelation. PMID:24900165

Strain tolerance in technical Nb3Al superconductors

NASA Astrophysics Data System (ADS)

Banno, N.; Takeuchi, T.; Kitaguchi, H.; Tagawa, K.

2006-10-01

We observed crack formation in transformation-processed Nb3Al wires at room temperature, the wire being bent with a small clamp fixture with a curvature. The polished cross-section parallel to the longitudinal axis was observed, using a high power optical microscope or a field-emission scanning electron microscope. The bend strain limit for microcrack formation is found, changing the radius of the curvature of the clamp. The bend strain limit was found to be around 0.3% for standard Nb3Al wires. This corresponds to the irreversible tensile strain limit of the Ic characteristics determined with a 0.1 µV cm-1 criterion. Reduction of the barrier thickness should be avoided to keep to the bend strain limit. A new configuration of the Nb3Al wire is demonstrated to improve the bend strain limit. The filament is divided into segments in the transverse cross-section. The wire is fabricated by a double-stacking method. The bend strain limit is enhanced to about 0.85% for the wire surface; the equivalent strain of the outermost filament location is about 0.66%. A simple react and wind test for this wire was performed, where the wire experienced 0.86% bend strain. The degradation of Jc was found to be very small.

Development of a multi-cycle shear-compression testing for the modeling of severe plastic deformation

NASA Astrophysics Data System (ADS)

Pesin, A.; Pustovoytov, D.; Lokotunina, N.

2017-12-01

The mechanism of severe plastic deformation comes from very significant shear strain. Shear-compression testing of materials is complicated by the fact that a state of large equivalent strain with dominant shear strain is not easily achievable. This paper presents the novel technique of laboratory simulation of severe plastic deformation by multi-cycle shear-compression testing at room temperature with equivalent strain e=1…5. The specimen consisted of a parallelepiped having an inclined gauge section created by two diametrically opposed semi-circular slots which were machined at 45°. Height of the specimen was 50 mm, section dimensions were 25×25 mm, gauge thickness was 5.0 mm and gauge width was 6.0 mm. The specimen provided dominant shear strain in an inclined gauge-section. The level of shear strain and equivalent strain was controlled through adjustment of the height reduction of the specimen, load application direction and number of cycles of shear-compression. Aluminium alloy Al-6.2Mg-0.7Mn was used as a material for specimen. FE simulation and analysis of the stress-strain state were performed. The microstructure of the specimen after multi-cycle shear-compression testing with equivalent strain e=1…5 was examined by optical and scanning electron microscope.

Influence of Additive Manufactured Scaffold Architecture on the Distribution of Surface Strains and Fluid Flow Shear Stresses and Expected Osteochondral Cell Differentiation.

PubMed

Hendrikson, Wim J; Deegan, Anthony J; Yang, Ying; van Blitterswijk, Clemens A; Verdonschot, Nico; Moroni, Lorenzo; Rouwkema, Jeroen

2017-01-01

Scaffolds for regenerative medicine applications should instruct cells with the appropriate signals, including biophysical stimuli such as stress and strain, to form the desired tissue. Apart from that, scaffolds, especially for load-bearing applications, should be capable of providing mechanical stability. Since both scaffold strength and stress-strain distributions throughout the scaffold depend on the scaffold's internal architecture, it is important to understand how changes in architecture influence these parameters. In this study, four scaffold designs with different architectures were produced using additive manufacturing. The designs varied in fiber orientation, while fiber diameter, spacing, and layer height remained constant. Based on micro-CT (μCT) scans, finite element models (FEMs) were derived for finite element analysis (FEA) and computational fluid dynamics (CFD). FEA of scaffold compression was validated using μCT scan data of compressed scaffolds. Results of the FEA and CFD showed a significant impact of scaffold architecture on fluid shear stress and mechanical strain distribution. The average fluid shear stress ranged from 3.6 mPa for a 0/90 architecture to 6.8 mPa for a 0/90 offset architecture, and the surface shear strain from 0.0096 for a 0/90 offset architecture to 0.0214 for a 0/90 architecture. This subsequently resulted in variations of the predicted cell differentiation stimulus values on the scaffold surface. Fluid shear stress was mainly influenced by pore shape and size, while mechanical strain distribution depended mainly on the presence or absence of supportive columns in the scaffold architecture. Together, these results corroborate that scaffold architecture can be exploited to design scaffolds with regions that guide specific tissue development under compression and perfusion. In conjunction with optimization of stimulation regimes during bioreactor cultures, scaffold architecture optimization can be used to improve scaffold design for tissue engineering purposes.

Influence of Additive Manufactured Scaffold Architecture on the Distribution of Surface Strains and Fluid Flow Shear Stresses and Expected Osteochondral Cell Differentiation

PubMed Central

Hendrikson, Wim J.; Deegan, Anthony J.; Yang, Ying; van Blitterswijk, Clemens A.; Verdonschot, Nico; Moroni, Lorenzo; Rouwkema, Jeroen

2017-01-01

Scaffolds for regenerative medicine applications should instruct cells with the appropriate signals, including biophysical stimuli such as stress and strain, to form the desired tissue. Apart from that, scaffolds, especially for load-bearing applications, should be capable of providing mechanical stability. Since both scaffold strength and stress–strain distributions throughout the scaffold depend on the scaffold’s internal architecture, it is important to understand how changes in architecture influence these parameters. In this study, four scaffold designs with different architectures were produced using additive manufacturing. The designs varied in fiber orientation, while fiber diameter, spacing, and layer height remained constant. Based on micro-CT (μCT) scans, finite element models (FEMs) were derived for finite element analysis (FEA) and computational fluid dynamics (CFD). FEA of scaffold compression was validated using μCT scan data of compressed scaffolds. Results of the FEA and CFD showed a significant impact of scaffold architecture on fluid shear stress and mechanical strain distribution. The average fluid shear stress ranged from 3.6 mPa for a 0/90 architecture to 6.8 mPa for a 0/90 offset architecture, and the surface shear strain from 0.0096 for a 0/90 offset architecture to 0.0214 for a 0/90 architecture. This subsequently resulted in variations of the predicted cell differentiation stimulus values on the scaffold surface. Fluid shear stress was mainly influenced by pore shape and size, while mechanical strain distribution depended mainly on the presence or absence of supportive columns in the scaffold architecture. Together, these results corroborate that scaffold architecture can be exploited to design scaffolds with regions that guide specific tissue development under compression and perfusion. In conjunction with optimization of stimulation regimes during bioreactor cultures, scaffold architecture optimization can be used to improve scaffold design for tissue engineering purposes. PMID:28239606

Thermomechanical characterization of one-way shape memory Nitinol as an actuator for active surgical needle

NASA Astrophysics Data System (ADS)

Honarvar, Mohammad

Needle-based intervention insertion is one of the common surgical techniques used in many diagnostic and therapeutic percutaneous procedures. The success of such procedures highly depends on the accuracy of needle placement at target locations. An active needle has the potential to enhance the accuracy of needle placement as well as to improve clinical outcome. Bending forces provided by the attached actuators can assist the maneuverability in order to reach the targets following a desired trajectory. There are three major research parts in the development of active needle project in the Composites Laboratory of Temple University. They are thermomechanical characterization of shape memory alloy (SMA) or Nitinol as an actuator for smart needle, mechanical modeling and design of smart needles, and study of tissue needle interaction. The characterization of SMA is the focus of this dissertation. Unique thermomechanical properties of Nitinol known as shape memory effect and superelasticity make it applicable for different fields such as biomedical, structural and aerospace engineering. These unique behaviors are due to the comparatively large amount of recoverable strain which is being produced in a martensitic phase transformation. However, under certain ranges of stresses and temperatures, Nitinol wires exhibit unrecovered strain (also known as residual strain); which limits their applicability. Therefore, for applications that rely on the strain response in repetitive loading and unloading cycles, it is important to understand the generation of the unrecovered strain in the Nitinol wires. In this study, the unrecovered strain of Nitinol wires with various diameters was investigated, using two experimental approaches: constant stress and uniaxial tensile tests. Moreover, a critical range of stress was found beyond which the unrecovered strain was negligible at temperatures of 70 to 80°C depending on the wire diameter. Wire diameters varied from 0.10 to 0.29 mm were tested and different ranges of critical stress were found for different wire diameters. The transformation temperatures of different wire diameters at zero stress have been achieved by performing the Differential Scanning Calorimetry (DSC) test. The actuation force created by Nitinol wire is measured through constant strain experiment. X-Ray Diffraction (XRD) study was also performed to investigate the phase of Nitinol wires under various thermomechanical loading conditions. In summary, the effect of wire diameter on the required critical stresses to avoid the unrecovered strain between first and second cycle of heating and cooling are presented and the results of both mechanical tests are justified by the results obtained from the XRD study.

Re-evaluation of differential phase contrast (DPC) in a scanning laser microscope using a split detector as an alternative to differential interference contrast (DIC) optics.

PubMed

Amos, W B; Reichelt, S; Cattermole, D M; Laufer, J

2003-05-01

In this paper, differential phase imaging (DPC) with transmitted light is implemented by adding a suitable detection system to a standard commercially available scanning confocal microscope. DPC, a long-established method in scanning optical microscopy, depends on detecting the intensity difference between opposite halves or quadrants of a split photodiode detector placed in an aperture plane. Here, DPC is compared with scanned differential interference contrast (DIC) using a variety of biological specimens and objective lenses of high numerical aperture. While DPC and DIC images are generally similar, DPC seems to have a greater depth of field. DPC has several advantages over DIC. These include low cost (no polarizing or strain-free optics are required), absence of a double scanning spot, electronically variable direction of shading and the ability to image specimens in plastic dishes where birefringence prevents the use of DIC. DPC is also here found to need 20 times less laser power at the specimen than DIC.

Rapid Antimicrobial Susceptibility Testing Using Forward Laser Light Scatter Technology.

PubMed

Hayden, Randall T; Clinton, Lani K; Hewitt, Carolyn; Koyamatsu, Terri; Sun, Yilun; Jamison, Ginger; Perkins, Rosalie; Tang, Li; Pounds, Stanley; Bankowski, Matthew J

2016-11-01

The delayed reporting of antimicrobial susceptibility testing remains a limiting factor in clinical decision-making in the treatment of bacterial infection. This study evaluates the use of forward laser light scatter (FLLS) to measure bacterial growth for the early determination of antimicrobial susceptibility. Three isolates each (two clinical isolates and one reference strain) of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa were tested in triplicate using two commercial antimicrobial testing systems, the Vitek2 and the MicroScan MIC panel, to challenge the BacterioScan FLLS. The BacterioScan FLLS showed a high degree of categorical concordance with the commercial methods. Pairwise comparison with each commercial system serving as a reference standard showed 88.9% agreement with MicroScan (two minor errors) and 72.2% agreement with Vitek (five minor errors). FLLS using the BacterioScan system shows promise as a novel method for the rapid and accurate determination of antimicrobial susceptibility. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Fabrication and modeling of shape memory alloy springs

NASA Astrophysics Data System (ADS)

Heidari, B.; Kadkhodaei, M.; Barati, M.; Karimzadeh, F.

2016-12-01

In this paper, shape memory alloy (SMA) helical springs are produced by shape setting two sets of NiTi (Ti-55.87 at% Ni) wires, one of which showing shape memory effect and another one showing pseudoelasticity at the ambient temperature. Different pitches as well as annealing temperatures are tried to investigate the effect of such parameters on the thermomechanical characteristics of the fabricated springs. Phase transformation temperatures of the products are measured by differential scanning calorimetry and are compared with those of the original wires. Compression tests are also carried out, and stiffness of each spring is determined. The desired pitches are so that a group of springs experiences phase transition during loading while the other does not. The former shows a varying stiffness upon the application of compression, but the latter acts as passive springs with a predetermined stiffness. Based on the von-Mises effective stress and strain, an enhanced one-dimensional constitutive model is further proposed to describe the shear stress-strain response within the coils of an SMA spring. The theoretically predicted force-displacement responses of the produced springs are shown to be in a reasonable agreement with the experimental results. Finally, effects of variations in geometric parameters on the axial force-displacement response of an SMA spring are investigated.

Static viscoelasticity of biomass polyethylene composites

NASA Astrophysics Data System (ADS)

Yang, Keyan; Cai, Hongzhen; Yi, Weiming; Zhang, Qingfa; Zhao, Kunpeng

The biomass polyethylene composites filled with poplar wood flour, rice husk, cotton stalk or corn stalk were prepared by extrusion molding. The static viscoelasticity of composites was investigated by the dynamic thermal mechanical analyzer (DMA). Through the stress-strain scanning, it is found that the linear viscoelasticity interval of composites gradually decreases as the temperature rises, and the critical stress and strain values are 0.8 MPa and 0.03% respectively. The experiment shows that as the temperature rises, the creep compliance of biomass polyethylene composites is increased; under the constant temperature, the creep compliance decreases with the increase of content of biomass and calcium carbonate. The biomass and calcium carbonate used to prepare composites as filler can improve damping vibration attenuation and reduce stress deformation of composites. The stress relaxation modulus of composites is reduced and the relaxation rate increases at the higher temperature. The biomass and calcium carbonate used to prepare composites as filler not only can reduce costs, but also can increase stress relaxation modulus and improve the size thermostability of composites. The corn stalk is a good kind of biomass raw material for composites since it can improve the creep resistance property and the stress relaxation resistance property of composites more effectively than other three kinds of biomass (poplar wood flour, rice husk and cotton stalk).

Negative pressure and spallation in graphite targets under nano- and picosecond laser irradiation

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

Belikov, R S; Khishchenko, K V; Krasyuk, I K

We present the results of experiments on the spallation phenomena in graphite targets under shock-wave nano- and picosecond irradiation, which have been performed on Kamerton-T (GPI, Moscow, Russia) and PHELIX (GSI, Darmstadt, Germany) laser facilities. In the range of the strain rates of 10{sup 6} – 10{sup 7} s{sup -1}, the data on the dynamic mechanical strength of the material at rapure (spallation) have been for the first time obtained. With a maximal strain rate of 1.4 × 10{sup 7} s{sup -1}, the spall strength of 2.1 GPa is obtained, which constitutes 64% of the theoretical ultimate tensile strength ofmore » graphite. The effect of spallation is observed not only on the rear side of the target, but also on its irradiated (front) surface. With the use of optical and scanning electron microscopes, the morphology of the front and rear surfaces of the targets is studied. By means of Raman scattering of light, the graphite structure both on the target front surface under laser exposure and on its rear side in the spall zone is investigated. A comparison of the dynamic strength of graphite and synthetic diamond is performed. (extreme light fields and their applications)« less

Residual stresses in a stainless steel - titanium alloy joint made with the explosive technique

NASA Astrophysics Data System (ADS)

Taran, Yu V.; Balagurov, A. M.; Sabirov, B. M.; Evans, A.; Davydov, V.; Venter, A. M.

2012-02-01

Joining of pipes from stainless steel (SS) and titanium (Ti) alloy still experience serious technical problems. Recently, reliable and hermetic joining of SS and Ti pipes has been achieved with the explosive bonding technique in the Russian Federal Nuclear Center. Such adapters are earmarked for use at the future International Linear Collider. The manufactured SS-Ti adapters have excellent mechanical behavior at room and liquid nitrogen temperatures, during high-pressure tests and thermal cycling. We here report the first neutron diffraction investigation of the residual stresses in a SS-Ti adapter on the POLDI instrument at the SINQ spallation source. The strain scanning across the adapter walls into the SS-SS and SS-Ti pipes sections encompassed measurement of the axial, radial and hoop strain components, which were transformed into residual stresses. The full stress information was successfully determined for the three steel pipes involved in the joint. The residual stresses do not exceed 300 MPa in magnitude. All stress components have tensile values close to the adapter internal surface, whilst they are compressive close to the outer surface. The strong incoherent and weak coherent neutron scattering cross-sections of Ti did not allow for the reliable determination of stresses inside the titanic pipe.

Complex conductivity response to microbial growth and biofilm formation on phenanthrene spiked medium

NASA Astrophysics Data System (ADS)

Albrecht, Remy; Gourry, Jean Christophe; Simonnot, Marie-Odile; Leyval, Corinne

2011-11-01

Several laboratory studies have recently demonstrated the utility of geophysical methods for the investigation of microbial-induced changes over contaminated sites. However, it remains difficult to distinguish the effects due to the new physical properties imparted by microbial processes, to bacterial growth, or to the development of bacterial biofilm. We chose to study the influence of biofilm formation on geophysical response using complex conductivity measurements (0.1-1000 Hz) in phenanthrene-contaminated media. Biotic assays were conducted with two phenanthrene (PHE) degrading bacterial strains: Burkholderia sp (NAH1), which produced biofilm and Stenophomonas maltophilia (MATE10), which did not, and an abiotic control. Results showed that bacterial densities for NAH1 and MATE10 strains continuously increased at the same rate during the experiment. However, the complex conductivity signature showed noticeable differences between the two bacteria, with a phase shift of 50 mrad at 4 Hz for NAH1, which produced biofilm. Biofilm volume was quantified by Scanning Confocal Laser Microscopy (SCLM). Significant correlations were established between phase shift decrease and biofilm volume for NAH1 assays. Results suggest that complex conductivity measurements, specifically phase shift, can be a useful indicator of biofilm formation inside the overall signal of microbial activity on contaminated sites.

A microbial transformation using Bacillus subtilis B7-S to produce natural vanillin from ferulic acid

PubMed Central

Chen, Peng; Yan, Lei; Wu, Zhengrong; Li, Suyue; Bai, Zhongtian; Yan, Xiaojuan; Wang, Ningbo; Liang, Ning; Li, Hongyu

2016-01-01

Bacillus subtilis strain B7-S screened from18 strains is an aerobic, endospore-forming, model organism of Gram-positive bacteria which is capable to form vanillin during ferulic acid bioconversion. The bioconversion of ferulic acid to vanillin by Bacillus subtilis B7-S (B. subtilis B7-S) was investigated. Based on our results, the optimum bioconversion conditions for the production of vanillin by B. subtilis B7-S can be summarized as follows: temperature 35 °C; initial pH 9.0; inoculum volume 5%; ferulic acid concentration 0.6 g/L; volume of culture medium 20%; and shaking speed 200 r/min. Under these conditions, several repeated small-scale batch experiments showed that the maximum conversion efficiency was 63.30% after 3 h of bioconversion. The vanillin products were confirmed by spectral data achieved from UV–vis, inductively coupled plasma atomic emission spectroscope (ICP-AES) and Fourier transform infrared spectrometer (FT-IR) spectra. Scanning electron microscopy (SEM) and transmission electron spectroscopy (TEM) results confirmed that the cell surface of B. subtilis plays a role in the induction of ferulic acid tolerance. These results demonstrate that B. subtilis B7-S has the potential for use in vanillin production through bioconversion of ferulic acid. PMID:26841717

A microbial transformation using Bacillus subtilis B7-S to produce natural vanillin from ferulic acid.

PubMed

Chen, Peng; Yan, Lei; Wu, Zhengrong; Li, Suyue; Bai, Zhongtian; Yan, Xiaojuan; Wang, Ningbo; Liang, Ning; Li, Hongyu

2016-02-04

Bacillus subtilis strain B7-S screened from18 strains is an aerobic, endospore-forming, model organism of Gram-positive bacteria which is capable to form vanillin during ferulic acid bioconversion. The bioconversion of ferulic acid to vanillin by Bacillus subtilis B7-S (B. subtilis B7-S) was investigated. Based on our results, the optimum bioconversion conditions for the production of vanillin by B. subtilis B7-S can be summarized as follows: temperature 35 °C; initial pH 9.0; inoculum volume 5%; ferulic acid concentration 0.6 g/L; volume of culture medium 20%; and shaking speed 200 r/min. Under these conditions, several repeated small-scale batch experiments showed that the maximum conversion efficiency was 63.30% after 3 h of bioconversion. The vanillin products were confirmed by spectral data achieved from UV-vis, inductively coupled plasma atomic emission spectroscope (ICP-AES) and Fourier transform infrared spectrometer (FT-IR) spectra. Scanning electron microscopy (SEM) and transmission electron spectroscopy (TEM) results confirmed that the cell surface of B. subtilis plays a role in the induction of ferulic acid tolerance. These results demonstrate that B. subtilis B7-S has the potential for use in vanillin production through bioconversion of ferulic acid.

Residual Ductility and Microstructural Evolution in Continuous-Bending-under-Tension of AA-6022-T4

PubMed Central

Zecevic, Milovan; Roemer, Timothy J.; Knezevic, Marko; Korkolis, Yannis P.; Kinsey, Brad L.

2016-01-01

A ubiquitous experiment to characterize the formability of sheet metal is the simple tension test. Past research has shown that if the material is repeatedly bent and unbent during this test (i.e., Continuous-Bending-under-Tension, CBT), the percent elongation at failure can significantly increase. In this paper, this phenomenon is evaluated in detail for AA-6022-T4 sheets using a custom-built CBT device. In particular, the residual ductility of specimens that are subjected to CBT processing is investigated. This is achieved by subjecting a specimen to CBT processing and then creating subsize tensile test and microstructural samples from the specimens after varying numbers of CBT cycles. Interestingly, the engineering stress initially increases after CBT processing to a certain number of cycles, but then decreases with less elongation achieved for increasing numbers of CBT cycles. Additionally, a detailed microstructure and texture characterization are performed using standard scanning electron microscopy and electron backscattered diffraction imaging. The results show that the material under CBT preserves high integrity to large plastic strains due to a uniform distribution of damage formation and evolution in the material. The ability to delay ductile fracture during the CBT process to large plastic strains, results in formation of a strong <111> fiber texture throughout the material. PMID:28773257

Growth kinetics and biodeterioration of polypropylene microplastics by Bacillus sp. and Rhodococcus sp. isolated from mangrove sediment.

PubMed

Auta, H S; Emenike, C U; Jayanthi, B; Fauziah, S H

2018-02-01

Interest in the biodegradation of microplastics is due to their ubiquitous distribution, availability, high persistence in the environment and deleterious impact on marine biota. The present study evaluates the growth response and mechanism of polypropylene (PP) degradation by Bacillus sp. strain 27 and Rhodococcus sp. strain 36 isolated from mangrove sediments upon exposure to PP microplastics. Both bacteria strains were able to utilise PP microplastic for growth as confirmed by the reduction of the polymer mass. The weight loss was 6.4% by Rhodococcus sp. strain 36 and 4.0% by Bacillus sp. strain 27 after 40days of incubation. PP biodegradation was further confirmed using Fourier-transform infrared spectroscopy and scanning electron microscopy analyses, which revealed structural and morphological changes in the PP microplastics with microbial treatment. These analyses showed that the isolates can colonise, modify and utilise PP microplastics as carbon source. Copyright © 2017 Elsevier Ltd. All rights reserved.

Strain-Driven Stacking Faults in CdSe/CdS Core/Shell Nanorods.

PubMed

Demortière, Arnaud; Leonard, Donovan N; Petkov, Valeri; Chapman, Karena; Chattopadhyay, Soma; She, Chunxing; Cullen, David A; Shibata, Tomohiro; Pelton, Matthew; Shevchenko, Elena V

2018-04-19

Colloidal semiconductor nanocrystals are commonly grown with a shell of a second semiconductor material to obtain desired physical properties, such as increased photoluminescence quantum yield. However, the growth of a lattice-mismatched shell results in strain within the nanocrystal, and this strain has the potential to produce crystalline defects. Here, we study CdSe/CdS core/shell nanorods as a model system to investigate the influence of core size and shape on the formation of stacking faults in the nanocrystal. Using a combination of high-angle annular dark-field scanning transmission electron microscopy and pair-distribution-function analysis of synchrotron X-ray scattering, we show that growth of the CdS shell on smaller, spherical CdSe cores results in relatively small strain and few stacking faults. By contrast, growth of the shell on larger, prolate spheroidal cores leads to significant strain in the CdS lattice, resulting in a high density of stacking faults.

Carbon nanotube thin film strain sensors: comparison between experimental tests and numerical simulations

NASA Astrophysics Data System (ADS)

Lee, Bo Mi; Loh, Kenneth J.

2017-04-01

Carbon nanotubes can be randomly deposited in polymer thin film matrices to form nanocomposite strain sensors. However, a computational framework that enables the direct design of these nanocomposite thin films is still lacking. The objective of this study is to derive an experimentally validated and two-dimensional numerical model of carbon nanotube-based thin film strain sensors. This study consisted of two parts. First, multi-walled carbon nanotube (MWCNT)-Pluronic strain sensors were fabricated using vacuum filtration, and their physical, electrical, and electromechanical properties were evaluated. Second, scanning electron microscope images of the films were used for identifying topological features of the percolated MWCNT network, where the information obtained was then utilized for developing the numerical model. Validation of the numerical model was achieved by ensuring that the area ratios (of MWCNTs relative to the polymer matrix) were equivalent for both the experimental and modeled cases. Strain sensing behavior of the percolation-based model was simulated and then compared to experimental test results.

Effect of strain rate and notch geometry on tensile properties and fracture mechanism of creep strength enhanced ferritic P91 steel

NASA Astrophysics Data System (ADS)

Pandey, Chandan; Mahapatra, M. M.; Kumar, Pradeep; Saini, N.

2018-01-01

Creep strength enhanced ferritic (CSEF) P91 steel were subjected to room temperature tensile test for quasi-static (less than 10-1/s) strain rate by using the Instron Vertical Tensile Testing Machine. Effect of different type of notch geometry, notch depth and angle on mechanical properties were also considered for different strain rate. In quasi-static rates, the P91 steel showed a positive strain rate sensitivity. On the basis of tensile data, fracture toughness of P91 steel was also calculated numerically. For 1 mm notch depth (constant strain rate), notch strength and fracture toughness were found to be increased with increase in notch angle from 45° to 60° while the maximum value attained in U-type notch. Notch angle and notch depth has found a minute effect on P91 steel strength and fracture toughness. The fracture surface morphology was studied by field emission scanning electron microscopy (FESEM).

Use of Digital Volume Correlation to Measure Deformation of Shale Using Natural Markers

NASA Astrophysics Data System (ADS)

Dewers, T. A.; Quintana, E.; Ingraham, M. D.; Jacques, C. L.

2016-12-01

We apply digital volume correlation (DVC) to interpreting deformation as influenced by shale heterogeneity. An extension of digital image correlation, DVC uses 3D images (CT Scans) of a sample before, during and after loading to determine deformation in terms of a 3D strain map. The technology tracks the deformation of high and low density regions within the sample to determine full field 3D strains within the sample. High pyrite shales (Woodford and Marcellus in this study) are being used as the high density pyrite serves as an excellent point to track in the volume correlation. Preliminary results indicate that this technology is promising for measuring true volume strains, strain localization, and strain portioning by microlithofacies within specimens during testing. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

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

Nelson, K.M.; Manson, J.A.E.; Seferis, J.C.

Consolidation of thermoplastic prepregs was measured with an integrally-heated parallel platen apparatus attached to a servo-hydraulic mechanical testing machine. The apparatus was designed as a small-scale, well-instrumented press. The lamination or consolidation process was viewed as a superposition of three distinctly occurring events identified as void volume reduction, fiber spreading, and autohesion. Consolidation was measured in relation to the original prepreg thickness and was reported as compressive or consolidation strain as a function of temperature. The derivative of the consolidation strain, the consolidation strain rate, was found to be qualitatively descriptive of viscoelastic phenomena occurring in the prepreg stack duringmore » consolidation. The apparatus was sensitive enough to identify glass and melt transitions of the polymer matrix, and to provide a measure of the net consolidation for a given processing cycle. The strain and the strain rate data were compared to thermoanalytical prepreg data obtained by Differential Scanning Calorimetry, and Dynamic Mechanical Analysis. Three different thermoplastic matrix composite systems were examined with this apparatus: Poly (etheretherketone), Poly(etherimide), and Poly(ethylene terephthalate). 21 refs.« less

Calcium Carbonate Precipitation by Bacillus and Sporosarcina Strains Isolated from Concrete and Analysis of the Bacterial Community of Concrete.

PubMed

Kim, Hyun Jung; Eom, Hyo Jung; Park, Chulwoo; Jung, Jaejoon; Shin, Bora; Kim, Wook; Chung, Namhyun; Choi, In-Geol; Park, Woojun

2016-03-01

Microbially induced calcium carbonate precipitation (CCP) is a long-standing but re-emerging environmental engineering process for production of self-healing concrete, bioremediation, and long-term storage of CO2. CCP-capable bacteria, two Bacillus strains (JH3 and JH7) and one Sporosarcina strain (HYO08), were isolated from two samples of concrete and characterized phylogenetically. Calcium carbonate crystals precipitated by the three strains were morphologically distinct according to field emission scanning electron microscopy. Energy dispersive X-ray spectrometry mapping confirmed biomineralization via extracellular calcium carbonate production. The three strains differed in their physiological characteristics: growth at alkali pH and high NaCl concentrations, and urease activity. Sporosarcina sp. HYO08 and Bacillus sp. JH7 were more alkali- and halotolerant, respectively. Analysis of the community from the same concrete samples using barcoded pyrosequencing revealed that the relative abundance of Bacillus and Sporosarcina species was low, which indicated low culturability of other dominant bacteria. This study suggests that calcium carbonate crystals with different properties can be produced by various CCP-capable strains, and other novel isolates await discovery.

Iron-Corroding Methanogen Isolated from a Crude-Oil Storage Tank ▿

PubMed Central

Uchiyama, Taku; Ito, Kimio; Mori, Koji; Tsurumaru, Hirohito; Harayama, Shigeaki

2010-01-01

Microbiologically influenced corrosion of steel in anaerobic environments has been attributed to hydrogenotrophic microorganisms. A sludge sample collected from the bottom plate of a crude-oil storage tank was used to inoculate a medium containing iron (Fe0) granules, which was then incubated anaerobically at 37°C under an N2-CO2 atmosphere to enrich for microorganisms capable of using iron as the sole source of electrons. A methanogen, designated strain KA1, was isolated from the enrichment culture. An analysis of its 16S rRNA gene sequence revealed that strain KA1 is a Methanococcus maripaludis strain. Strain KA1 produced methane and oxidized iron much faster than did the type strain of M. maripaludis, strain JJT, which produced methane at a rate expected from the abiotic H2 production rate from iron. Scanning electron micrographs of iron coupons that had been immersed in either a KA1 culture, a JJT culture, or an aseptic medium showed that only coupons from the KA1 culture had corroded substantially, and these were covered with crystalline deposits that consisted mainly of FeCO3. PMID:20118376

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

PubMed

Sivakami, R; Dhanuskodi, S; Karvembu, R

2016-01-05

RuO2 nanoparticles (RuO2 NPs) have been successfully synthesized by the hydrothermal method. Structure and the particle size have been determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM). UV-Vis spectra reveal that the optical band gap of RuO2 nanoparticles is red shifted from 3.95 to 3.55eV. BET measurements show a high specific surface area (SSA) of 118-133m(2)/g and pore diameter (10-25nm) has been estimated by Barret-Joyner-Halenda (BJH) method. The crystallite size and lattice strain in the samples have been investigated by Williamson-Hall (W-H) analysis assuming uniform deformation, deformation stress and deformation energy density, and the size-strain plot method. All other relevant physical parameters including stress, strain and energy density have been calculated. The average crystallite size and the lattice strain evaluated from XRD measurements are in good agreement with the results of TEM. Copyright © 2015 Elsevier B.V. All rights reserved.

Plasmid-dependent attachment of Agrobacterium tumefaciens to plant tissue culture cells.

PubMed Central

Matthysse, A G; Wyman, P M; Holmes, K V

1978-01-01

Kinetic, microscopic, and biochemical studies show that virulent Ti (tumor inducing)-plasmid-containing strains of Agrobacterium attach to normal tobacco and carrot tissue culture cells. Kinetic studies showed that virulent strains of A. tumefaciens attach to the plant tissue culture cells in increasing numbers during the first 1 to 2 h of incubation of the bacteria with the plant cells. Five Ti-plasmid-containing virulent Agrobacterium strains showed greater attachment to tobacco cells than did five avirulent strains. Light and scanning electron microscopic observations confirmed that virulent strains showed little attachment. Bacterial attachment was blocked by prior incubation of the plant cells with lipopolysaccharide extracted from A. tumefaciens, but not from A. radiobacter, suggesting that bacterial lipopolysaccharide is one of the components involved in the attachment process. At least one other bacterial product may be required for attachment in tissue culture because the virulent A. tumefaciens NT1, which lacks the Ti plasmid, does not itself attach to tobacco cells, but its lipopolysaccharide does inhibit the attachment of virulent strains. Images PMID:730370

Iron-corroding methanogen isolated from a crude-oil storage tank.

PubMed

Uchiyama, Taku; Ito, Kimio; Mori, Koji; Tsurumaru, Hirohito; Harayama, Shigeaki

2010-03-01

Microbiologically influenced corrosion of steel in anaerobic environments has been attributed to hydrogenotrophic microorganisms. A sludge sample collected from the bottom plate of a crude-oil storage tank was used to inoculate a medium containing iron (Fe(0)) granules, which was then incubated anaerobically at 37 degrees C under an N(2)-CO(2) atmosphere to enrich for microorganisms capable of using iron as the sole source of electrons. A methanogen, designated strain KA1, was isolated from the enrichment culture. An analysis of its 16S rRNA gene sequence revealed that strain KA1 is a Methanococcus maripaludis strain. Strain KA1 produced methane and oxidized iron much faster than did the type strain of M. maripaludis, strain JJ(T), which produced methane at a rate expected from the abiotic H(2) production rate from iron. Scanning electron micrographs of iron coupons that had been immersed in either a KA1 culture, a JJ(T) culture, or an aseptic medium showed that only coupons from the KA1 culture had corroded substantially, and these were covered with crystalline deposits that consisted mainly of FeCO(3).

Minority Carrier Lifetime in Beryllium-Doped InAs/InAsSb Strained Layer Superlattices

DTIC Science & Technology

2014-06-03

FTIR) spectrometer, operating in either continuous-scan or step-scan mode with a 14-lm cut-off wavelength external HgCdTe photo- detector . The PL...was collected by reflective optics and detected with a Vigo 10-lm cut-off, HgCdTe detector with a 3-ns time constant. The laser emission scattered from...45 ns and 8 ns were measured. The 6 × 10^16 cm?3 doping level is a factor of 6 greater than the typical background doping level in long-wave infrared

Enhanced conductivity at orthorhombic–rhombohedral phase boundaries in BiFeO 3 thin films

DOE PAGES

Heo, Yooun; Lee, Jin Hong; Xie, Lin; ...

2016-08-26

Enhanced properties in modern functional materials can often be found at structural transition regions, such as morphotropic phase boundaries (MPB), owing to the coexistence of multiple phases with nearly equivalent energies. Strain-engineered MPBs have emerged in epitaxially grown BiFeO 3 (BFO) thin films by precisely tailoring a compressive misfit strain, leading to numerous intriguing phenomena, such as a massive piezoelectric response, magnetoelectric coupling, interfacial magnetism and electronic conduction. Recently, an orthorhombic–rhombohedral (O–R) phase boundary has also been found in tensile-strained BFO. In this study, we characterise the crystal structure and electronic properties of the two competing O and R phasesmore » using X-ray diffraction, scanning probe microscope and scanning transmission electron microscopy (STEM). We observe the temperature evolution of R and O domains and find that the domain boundaries are highly conductive. Temperature-dependent measurements reveal that the conductivity is thermally activated for R–O boundaries. STEM observations point to structurally wide boundaries, significantly wider than in other systems. Furthermore, we reveal a strong correlation between the highly conductive domain boundaries and structural material properties. These findings provide a pathway to use phase boundaries in this system for novel nanoelectronic applications.« less

Antibacterial activity of moxifloxacin on bacteria associated with periodontitis within a biofilm.

PubMed

Tsaousoglou, Phoebus; Nietzsche, Sandor; Cachovan, Georg; Sculean, Anton; Eick, Sigrun

2014-02-01

The activity of moxifloxacin was compared with ofloxacin and doxycycline against bacteria associated with periodontitis within a biofilm (single strain and mixed population) in vitro. MICs and minimal bactericidal concentrations (MBCs) of moxifloxacin, ofloxacin and doxycyline were determined against single strains and mixed populations in a planktonic state. Single-species biofilms of two Porphyromonas gingivalis and two Aggregatibacter actinomycetemcomitans strains and a multispecies biofilm consisting of 12 species were formed for 3 days. The minimal biofilm eradication concentrations (MBECs) were determined after exposing the biofilms to the antibacterials (0.002-512 µg ml(-1)) for 18 h, addition of nutrient broth for 3 days and subsequent subcultivation. Photographs were taken using confocal laser-scanning microscopy and scanning electron microscopy. The MICs and MBCs did not differ between ofloxacin and moxifloxacin against A. actinomycetemcomitans, whilst moxifloxacin was more active than the other tested antibacterials against anaerobes and the mixed population. The single-species biofilms were eradicated by moderate concentrations of the antibacterials, and the lowest MBECs were always found for moxifloxacin (2-8 µg ml(-1)). MBECs against the multispecies biofilms were 128, >512 and >512 µg ml(-1) for moxifloxacin, ofloxacin and doxycycline, respectively. In summary, moxifloxacin in a topical formulation may have potential as an adjunct to mechanical removal of the biofilms.

Unraveling the origins of electromechanical response in mixed-phase Bismuth Ferrite

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

Vasudevan, Rama K; Okatan, M. B.; Liu, Y. Y.

The origin of giant electromechanical response in a mixed-phase rhombohedral-tetragonal BiFeO3 thin film is probed using sub-coercive scanning probe microscopy based multiple-harmonic measurements. Significant contributions to the strain arise from a second-order harmonic response localized at the phase boundaries. Strain and dissipation data, backed by thermodynamic calculations suggest that the source of the enhanced electromechanical response is the motion of phase boundaries. These findings elucidate the key role of labile phase boundaries, both natural and artificial, in achieving thin films with giant electromechanical properties.

Maternal antibody transfer to broiler progeny varies among strains and is affected by grain source and cage density.

PubMed

Leandro, N M; Ali, R; Koci, M; Moraes, V; Eusebio-Balcazar, P E; Jornigan, J; Malheiros, R D; Wineland, M J; Brake, J; Oviedo-Rondón, E O

2011-12-01

Two experiments were conducted to examine the effects of broiler breeder dietary grain source and cage density on maternal antibody (MatAb) transfer to progeny in 2 genetic strains (A and B). Broiler breeders were assigned to 16 litter floor pens and fed either corn- or wheat-based diets. Breeders were administered 4 live vaccines against Newcastle disease virus (NDV). At 23 wk of age, pullets and cocks, which reflected the full BW distribution from each treatment, were moved to a cage breeder house and placed at 1 or 2 hens/cage. Breeders were artificially inseminated at 44 wk (experiment 1) and 52 wk of age (experiment 2). Eggs were collected for 8 d, incubated, and placed in individual pedigree bags at d 19 of incubation. Blood samples from 5 chicks per treatment combination were collected at hatch in both experiments. Spleen and bursa were collected from the same chicks for histomorphometry analyses in experiment 2. In the second experiment, 12 chicks per treatment were placed in cages. Progeny were provided diets based on the same grain (corn or wheat) as their parents. Serum samples were collected at 5, 9, and 13 d of age and analyzed for anti-NDV MatAb. Data were analyzed as a 2 × 2 × 2 factorial design considering strain, dietary grain source, and cage density as main factors. Interaction effects were observed in breeders and progeny. Experiment 1 showed that strain A chicks had lower levels of MatAb when hens were housed at 2 hens/cage rather than 1 hen/cage. The MatAb levels of strain B chickens were not affected by cage density in either experiment. Experiment 2 demonstrated similar effects of cage density on MatAb levels and the area of bursa follicles for both strains. Progeny of breeders fed corn-based diets had smaller spleen white pulp only when hens were housed at 2 hens/cage compared with 1 hen/cage. The results of these experiments suggest that breeder strain and cage-density conditions affected MatAb transfer to progeny and embryo development of spleen and bursa.

Improvement in the Shape Memory Response of Ti50.5Ni24.5Pd25 High-Temperature Shape Memory Alloy with Scandium Microalloying

NASA Technical Reports Server (NTRS)

Atli, K. C.; Karaman, I; Noebe, R. D.; Garg, A.; Chumlyakov, Y. I.; Kireeva, I. V.

2010-01-01

A Ti(50.5)Ni(24.5)Pd25 high-temperature shape memory alloy (HTSMA) is microalloyed with 0.5 at. pct scandium (Sc) to enhance its shape-memory characteristics, in particular, dimensional stability under repeated thermomechanical cycles. For both Ti(50.5)Ni(24.5)Pd25 and the Sc-alloyed material, differential scanning calorimetry is conducted for multiple cycles to characterize cyclic stability of the transformation temperatures. The microstructure is evaluated using electron microscopy, X-ray diffractometry, and wavelength dispersive spectroscopy. Isobaric thermal cycling experiments are used to determine transformation temperatures, dimensional stability, and work output as a function of stress. The Sc-doped alloy displays more stable shape memory response with smaller irrecoverable strain and narrower thermal hysteresis than the baseline ternary alloy. This improvement in performance is attributed to the solid solution hardening effect of Sc.

The Deformation Mechanism of Fatigue Behaviour in a N36 Zirconium Alloy

NASA Astrophysics Data System (ADS)

Wang, Yingzhu

2018-05-01

Zirconium alloys are widely used as claddings in nuclear reactor. A N36 zirconium alloy has been deformed into a sheet with highly texture according to the result of electron back scatter diffraction test. Then this N36 zirconium alloy sheet has been cut into small beam samples with 12 x 3 x 3 mm3 in size. In this experiment, a three-point bending test was carried out to investigate the fatigue behaviour of N36 zirconium alloy. Cyclic loadings were applied on the top middle of the beam samples. The region of interest (ROI) is located at the middle bottom of the front face of the beam sample where slip band was observed in deformed beam sample due to strain concentration by using scanning electron microscopy. Twinning also plays an important role to accommodate the plastic deformation of N36 zirconium alloy in fatigue, which displays competition with slip.

Reproducibility of cine displacement encoding with stimulated echoes (DENSE) cardiovascular magnetic resonance for measuring left ventricular strains, torsion, and synchrony in mice.

PubMed

Haggerty, Christopher M; Kramer, Sage P; Binkley, Cassi M; Powell, David K; Mattingly, Andrea C; Charnigo, Richard; Epstein, Frederick H; Fornwalt, Brandon K

2013-08-27

Advanced measures of cardiac function are increasingly important to clinical assessment due to their superior diagnostic and predictive capabilities. Cine DENSE cardiovascular magnetic resonance (CMR) is ideal for quantifying advanced measures of cardiac function based on its high spatial resolution and streamlined post-processing. While many studies have utilized cine DENSE in both humans and small-animal models, the inter-test and inter-observer reproducibility for quantification of advanced cardiac function in mice has not been evaluated. This represents a critical knowledge gap for both understanding the capabilities of this technique and for the design of future experiments. We hypothesized that cine DENSE CMR would show excellent inter-test and inter-observer reproducibility for advanced measures of left ventricular (LV) function in mice. Five normal mice (C57BL/6) and four mice with depressed cardiac function (diet-induced obesity) were imaged twice, two days apart, on a 7T ClinScan MR system. Images were acquired with 15-20 frames per cardiac cycle in three short-axis (basal, mid, apical) and two long-axis orientations (4-chamber and 2-chamber). LV strain, twist, torsion, and measures of synchrony were quantified. Images from both days were analyzed by one observer to quantify inter-test reproducibility, while inter-observer reproducibility was assessed by a second observer's analysis of day-1 images. The coefficient of variation (CoV) was used to quantify reproducibility. LV strains and torsion were highly reproducible on both inter-observer and inter-test bases with CoVs ≤ 15%, and inter-observer reproducibility was generally better than inter-test reproducibility. However, end-systolic twist angles showed much higher variance, likely due to the sensitivity of slice location within the sharp longitudinal gradient in twist angle. Measures of synchrony including the circumferential (CURE) and radial (RURE) uniformity of strain indices, showed excellent reproducibility with CoVs of 1% and 3%, respectively. Finally, peak measures (e.g., strains) were generally more reproducible than the corresponding rates of change (e.g., strain rate). Cine DENSE CMR is a highly reproducible technique for quantification of advanced measures of left ventricular cardiac function in mice including strains, torsion and measures of synchrony. However, myocardial twist angles are not reproducible and future studies should instead report torsion.

Influence of strain on the corrosion of magnesium alloys and zinc in physiological environments.

PubMed

Törne, Karin; Örnberg, Andreas; Weissenrieder, Jonas

2017-01-15

During implantation load-bearing devices experience stress that may influence its mechanical and corrosion profile and potentially lead to premature rupture. The susceptibility to stress corrosion cracking (SCC) of the Mg-Al alloy AZ61 and Zn was studied in simulated body fluid (m-SBF) and whole blood by slow strain rate (SSR) testing in combination with electrochemical impedance spectroscopy (EIS) and further ex situ analysis including scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. AZ61 was found to be highly susceptible to SCC. EIS analysis show that although the majority of cracking occurred during the apparent plastic straining, cracking initiation occurs already in the elastic region at ∼50% of the ultimate tensile strength (UTS). Shifts in EIS phase angle and open circuit potential can be used to detect the onset of SCC. Zinc demonstrated a highly ductile behavior with limited susceptibility to SCC. No significant decrease in UTS was observed in m-SBF but a decrease in time to failure by ∼25% compared to reference samples indicates some effect on the mechanical properties during the ductile straining. The formation of micro cracks, ∼10μm deep, was indicated by the EIS analysis and later confirmed by ex situ SEM. The results of SSR analysis of zinc in whole blood showed a reduced effect compared to m-SBF and no cracks were detected. It appears that formation of an organic surface layer protects the corroding surface from cracking. These results highlight the importance of considering the effect of biological species on the degradation of implants in the clinical situation. Strain may deteriorate the corrosion properties of metallic implants drastically. We study the influence of load on the corrosion properties of a magnesium alloy and zinc by a combination of electrochemical impedance spectroscopy (EIS) and slow strain rate analysis. This combination of techniques has previously not been used for studying degradation in physiological relevant electrolytes. EIS provide valuable information on the initial formation of cracks, detecting crack nucleation before feasible in slow strain rate analysis. This sensitivity of EIS shows the potential for electrochemical methods to be used for in situ monitoring crack formation of implants in more applied studies. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

[Development of Staphylococcus Haemolyticus multilocus sequencing scheme and its use for molecular-epidemiologic analysis of strains isolated in hospitals in Russian federation in 2009-2010].

PubMed

Voronina, O L; Kunda, M S; Dmitrenko, O A; Lunin, V G; Gintsburg, A L

2011-01-01

Development of Staphylococcus haemolyticus strain typing method based on multilocus sequencing for resolving problems of molecular epidemiology. 102 strains of coagulase negative staphylococci (CNS) isolated in hospitals of various specialization in N. Novgorod and Moscow were studied. Species identification of strain was performed by using tuf gene fragment sequencing, S. haemolyticus strain differentiation--by MLST results. eBURST approach was used for cluster analysis of MLST data; structural changes in tagatose-6-phosphate kinase were studied by using InterProScan platform and SWISS-MODEL site programs; MLST scheme gene allele variability analysis was performed by using MEGA4.0 program package. In the 102 strains sampled CNS was detected in 28 strains of the S. haemolyticus species. The MLST scheme developed for the first time for S. haemolyticus including mvaK, rphE, tphK, gtr, arcC, triA, aroE genes allowed the differentiation of the sampled strains by 11 genotypes. Strains with ST 3, 8, 6, 1, 4, 5 and 11 differed by highest epidemiologic significance. Cluster and phylogenetic analysis of the data obtained showed a high adaptive ability of the nosocomial S. haemolyticus strains. Multiresistance to antibacterial preparations was detected in the analyzed strains. The MLST method developed was effective in the differentiation of S. haemolyticus strains that circulate in hospitals and threaten both neonates and hospitalized adult patients.

Ultrastructure and molecular characterization of Fusobacterium necrophorum biovars.

PubMed Central

Garcia, M M; Becker, S A; Brooks, B W; Berg, J N; Finegold, S M

1992-01-01

The ultrastructural features and molecular components of 18 strains of Fusobacterium necrophorum biovars A, AB and B, isolated from animal and human infections, were examined by electron microscopy, multilocus enzyme electrophoresis (MEE) and by sodium dodecyl sulfate-gradient polyacrylamide gel electrophoresis (SDS-PAGE). High resolution scanning electron microscopy revealed that the strains possessed a convoluted surface pattern. Transmission electron microscopy showed that all strains possessed a cell wall structure typical of gram-negative bacteria. Bleb formation was not uncommon. Numerous extracellular materials, resembling lipopolysaccharide (LPS) fragments, surrounded cells of both human strains and biovar B animal strains. Biovar A field strains revealed capsules as stained by ruthenium red whereas a stock culture strain showed the capsule only when immunostabilized with hyperimmune serum. Starch gel electrophoresis showed all strains to possess adenyl kinase, glutamate dehydrogenases and lactate dehydrogenase; each enzyme migrated uniformly (monomorphic) among the strains and represented an electrotype. However, SDS-PAGE indicated differences in the protein profiles between all of the strains; the most distinctly different was a human isolate (FN 606). Silver staining to detect LPS showed extensive "ladder" patterns among the majority of biovar A strains but not in the animal biovar B strains. Immunoblotting of LPS with a rabbit antiserum prepared against phenol extracted LPS from a biovar A animal isolate (LA 19) suggested marked variability in the LPS antigens among the isolates studied. Images Fig. 1. Fig. 2. Fig. 3. Fig. 4. Fig. 5. Fig. 7. Fig. 8. Fig. 9. PMID:1477801

Biosorption characteristic of Alcaligenes sp. BAPb.1 for removal of lead(II) from aqueous solution.

PubMed

Jin, Yu; Yu, Sumei; Teng, Chunying; Song, Tao; Dong, Liying; Liang, Jinsong; Bai, Xin; Xu, Xiuhong; Qu, Juanjuan

2017-06-01

In this study, strain BAPb.1 was isolated from lead mining area and used as an adsorbent to remove lead(II) ions from aqueous solution. The physicochemical characteristics, heavy metal resistance and antibiotic sensitivity of strain BAPb.1 were investigated. Biosorption capacity was evaluated by batch biosorption experiments, and isothermal characteristics were discussed. Atomic force microscopy (AFM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectrometry (FTIR) were conducted to explore the mechanism for lead(II) adsorption. Based on morphological and physiological characteristics as well as the phylogenetic analysis of 16S rDNA sequences, strain BAPb.1 was identified as a member of the genus Alcaligenes. It exhibited high resistances to multiple heavy metals such as lead(II), copper(II), zinc(II), nickel(II) and chromium(VI), and to antibiotics such as kanamycin, ampicillin, streptomycin, chloramphenicol, and tetracycline. The optimum conditions for maximum biosorption rate of 85.2% and maximum capacity of 56.8 mg g -1 were found at pH of 5, adsorbent dosage of 1.5 g L -1 (dry weight), initial lead(II) concentration of 100 mg L -1 , and contact time of 30 min at 30 °C. Biosorption isotherms were well fitted with Langmuir isotherm model. Mechanism analysis reveals that the lead(II) ions may exchange with sodium and potassium ions, and the hydroxyl, carbonyl and phosphate groups on the cell surface can chelate the lead(II) ions, therefore, surface adsorption play significant role in the biosorption process.

QLT091001, a 9-cis-Retinal Analog, Is Well-Tolerated by Retinas of Mice with Impaired Visual Cycles

PubMed Central

Maeda, Tadao; Dong, Zhiqian; Jin, Hui; Sawada, Osamu; Gao, Songqi; Utkhede, Deepank; Monk, Wendy; Palczewska, Grazyna; Palczewski, Krzysztof

2013-01-01

Purpose. Investigate whether retinas of mice with impaired retinal cycles exposed to light or kept in the dark tolerate prolonged high-dose administration of QLT091001, which contains as an active ingredient, the 9-cis-retinal precursor, 9-cis-retinyl acetate. Methods. Four- to six-week-old Lrat−/− and Rpe65−/− mice (n = 126) as well as crossbred Gnat1−/− mice lacking rod phototransduction (n = 110) were gavaged weekly for 6 months with 50 mg/kg QLT091001, either after being kept in the dark or after light bleaching for 30 min/wk followed by maintenance in a 12-hour light ≤ 10 lux)/12-hour dark cycle. Retinal health was monitored by spectral-domain optical coherent tomography (SD-OCT) and scanning laser ophthalmoscopy (SLO) every other month and histological, biochemical, and visual functional analyses were performed at the end of the experiment. Two-photon microscopy (TPM) was used to observe retinoid-containing retinosome structures in the RPE. Results. Retinal thickness and morphology examined by SD-OCT were well maintained in all strains treated with QLT091001. No significant increases of fundus autofluorescence were detected by SLO imaging of any strain. Accumulation of all-trans-retinyl esters varied with genetic background, types of administered compounds and lighting conditions but retinal health was not compromised. TPM imaging clearly revealed maintenance of retinosomes in the RPE of all mouse strains tested. Conclusions. Retinas of Lrat−/−, Rpe65−/−, and crossbred Gnat1−/− mice tolerated prolonged high-dose QLT091001 treatment well. PMID:23249702

Optical fabrication and testing; Proceedings of the Meeting, Singapore, Oct. 22-27, 1990

NASA Astrophysics Data System (ADS)

Lorenzen, Manfred; Campbell, Duncan R.; Johnson, Craig W.

1991-03-01

Various papers on optical fabrication and testing are presented. Individual topics addressed include: interferometry with laser diodes, new methods for economic production of prisms and lenses, interferometer accuracy and precision, optical testing with wavelength scanning interferometer, digital Talbot interferometer, high-sensitivity interferometric technique for strain measurements, absolute interferometric testing of spherical surfaces, contouring using gratings created on an LCD panel, three-dimensional inspection using laser-based dynamic fringe projection, noncontact optical microtopography, laser scan microscope and infrared laser scan microscope, photon scanning tunneling microscopy. Also discussed are: combination-matching problems in the layout design of minilaser rangefinder, design and testing of a cube-corner array for laser ranging, mode and far-field pattern of diode laser-phased arrays, new glasses for optics and optoelectronics, optical properties of Li-doped ZnO films, application and machining of Zerodur for optical purposes, finish machining of optical components in mass production.

Optical fabrication and testing; Proceedings of the Meeting, Singapore, Oct. 22-27, 1990

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

Lorenzen, M.; Campbell, D.R.; Johnson, C.W.

1991-01-01

Various papers on optical fabrication and testing are presented. Individual topics addressed include: interferometry with laser diodes, new methods for economic production of prisms and lenses, interferometer accuracy and precision, optical testing with wavelength scanning interferometer, digital Talbot interferometer, high-sensitivity interferometric technique for strain measurements, absolute interferometric testing of spherical surfaces, contouring using gratings created on an LCD panel, three-dimensional inspection using laser-based dynamic fringe projection, noncontact optical microtopography, laser scan microscope and infrared laser scan microscope, photon scanning tunneling microscopy. Also discussed are: combination-matching problems in the layout design of minilaser rangefinder, design and testing of a cube-corner arraymore » for laser ranging, mode and far-field pattern of diode laser-phased arrays, new glasses for optics and optoelectronics, optical properties of Li-doped ZnO films, application and machining of Zerodur for optical purposes, finish machining of optical components in mass production.« less

Strain detection in crystalline heterostructures using bidimensional blocking patterns of channelled particles

NASA Astrophysics Data System (ADS)

Redondo-Cubero, A.; David-Bosne, E.; Wahl, U.; Miranda, P.; da Silva, M. R.; Correia, J. G.; Lorenz, K.

2018-03-01

Strain is a critical parameter affecting the growth and the performance of many semiconductor systems but, at the same time, the accurate determination of strain profiles in heterostructures can be challenging, especially at the nanoscale. Ion channelling/blocking is a powerful technique for the detection of the strain state of thin films, normally carried out through angular scans with conventional particle detectors. Here we report the novel application of position sensitive detectors for the evaluation of the strain in a series of AlInN/GaN heterostructures with different compositions and thicknesses. The tetragonal strain is varied from compressive to tensile and analysed through bidimensional blocking patterns. The results demonstrate that strain can be correctly quantified when compared to Monte Carlo channelling simulations, which are essential because of the presence of ion steering effects at the interface between the layer and the substrate. Despite this physical limitation caused by ion steering, our results show that full bidimensional patterns can be applied to detect fingerprints and enhance the accuracy for most critical cases, in which the angular shift associated to the lattice distortion is below the critical angle for channelling.

Biofilm density and detection of biofilm-producing genes in methicillin-resistant Staphylococcus aureus strains.

PubMed

Szczuka, Ewa; Urbańska, Katarzyna; Pietryka, Marta; Kaznowski, Adam

2013-01-01

Many serious diseases caused by Staphylococcus aureus appear to be associated with biofilms. Therefore, we investigated the biofilm-forming ability of the methicillin-resistant S. aureus (MRSA) isolates collected from hospitalized patients. As many as 96 % strains had the ability to form biofilm in vitro. The majority of S. aureus strains formed biofilm in ica-dependent mechanism. However, 23 % of MRSA isolates formed biofilm in ica-independent mechanism. Half of these strains carried fnbB genes encoding surface proteins fibronectin-binding protein B involved in intercellular accumulation and biofilm development in S. aureus strains. The biofilm structures were examined via confocal laser scanning microscopy (CLSM) and three-dimensional structures were reconstructed. The images obtained in CLSM revealed that the biofilm created by ica-positive strains was different from biofilm formed by ica-negative strains. The MRSA population showed a large genetic diversity and we did not find a single clone that occurred preferentially in hospital environment. Our results demonstrated the variation in genes encoding adhesins for the host matrix proteins (elastin, laminin, collagen, fibronectin, and fibrinogen) and in the gene involved in biofilm formation (icaA) within the majority of S. aureus clones.

Transcriptomic analysis for genetic mechanisms of the factors related to biofilm formation in Escherichia coli O157:H7.

PubMed

Lee, Jin-Hyung; Kim, Yong-Guy; Cho, Moo Hwan; Wood, Thomas K; Lee, Jintae

2011-04-01

Two lineages of enterohemorrhagic Escherichia coli O157:H7 (EDL933, Stx1(+) and Stx2(+)) and 86-24 (Stx2(+)) were investigated to determine the genetic basis of biofilm formation on abiotic surfaces. Strain EDL933 formed a robust biofilm while strain 86-24 formed almost no biofilm on either polystyrene plates or polyethylene tubes. Whole-transcriptome profiles of EDL933 versus 86-24 revealed that in the strong biofilm-forming strain, genes involved in curli biosynthesis and cellulose production were significantly induced, whereas genes involved in indole signaling were most repressed. Additionally, 49 phage genes were highly induced and repressed between the two strains. Curli assays using Congo red plates and scanning electron microscopy corroborated the microarray data as the EDL933 strain produced a large amount of curli, while strain 86-24 formed much less curli. Moreover, EDL933 produced 19-fold more cellulose than 86-24, and indole production in EDL933 was two times lower than that of the strain 86-24. Therefore, it appears E. coli O157:H7 EDL933 produces more biofilm because of its increased curli and cellulose production and reduced indole production.

Haemophilus parasuis serovar 5 Nagasaki strain adheres and invades PK-15 cells.

PubMed

Frandoloso, Rafael; Martínez-Martínez, Sonia; Gutiérrez-Martín, César B; Rodríguez-Ferri, Elías F

2012-01-27

Haemophilus parasuis is the agent responsible for causing Glässer's disease, which is characterized by fibrinous polyserositis, polyarthritis and meningitis in pigs. The purpose of this study was to investigate the in vitro ability of two H. parasuis serovars of different virulence (serovar 5, Nagasaki strain, highly virulent, belonging to serovar 5, and SW114 strain, nonvirulent, belonging to serovar 3) to adhere to and invade porcine kidney epithelial cells (PK-15 line). Nagasaki strain was able to attach at high levels from 60 to 180 min of incubation irrespective of the concentrations compared (10(7)-10(10)CFU), and a substantial increase of surface projections could be seen in PK-15 cells by scanning electron microscopy. This virulent strain was also able to invade effectively these epithelial cells, and the highest invasion capacity was reached at 180 min of infection. On the contrary, nonvirulent SW114 strain hardly adhered to PK-15 cells, and it did not invade these cells, thus suggesting that adherence and invasion of porcine kidney epithelial cells could be a virulence mechanism involved in the lesions caused by H. parasuis Nagasaki strain in this organ. Copyright © 2011 Elsevier B.V. All rights reserved.

PhybalSIT — Fatigue Assessment and Life Time Calculation of the Ductile Cast Iron EN-GJS-600 at Ambient and Elevated Temperatures

NASA Astrophysics Data System (ADS)

Jost, Benjamin; Klein, Marcus; Eifler, Dietmar

This paper focuses on the ductile cast iron EN-GJS-600 which is often used for components of combustion engines. Under service conditions, those components are mechanically loaded at different temperatures. Therefore, this investigation targets at the fatigue behavior of EN-GJS-600 at ambient and elevated temperatures. Light and scanning electron microscopic investigations were done to characterize the sphericity of the graphite as well as the ferrite, pearlite and graphite fraction. At elevated temperatures, the consideration of dynamic strain ageing effects is of major importance. In total strain increase, temperature increase and constant total strain amplitude tests, the plastic strain amplitude, the stress amplitude, the change in temperature and the change in electrical resistance were measured. The measured values depend on plastic deformation processes in the bulk of the specimens and at the interfaces between matrix and graphite. The fatigue behavior of EN-GJS-600 is dominated by cyclic hardening processes. The physically based fatigue life calculation "PHYBALSIT" (SIT = strain increase test) was developed for total strain controlled fatigue tests. Only one temperature increase test is necessary to determine the temperature interval of pronounced dynamic strain ageing effects.

Evidence of sharp and diffuse domain walls in BiFeO3 by means of unit-cell-wise strain and polarization maps obtained with high resolution scanning transmission electron microscopy.

PubMed

Lubk, A; Rossell, M D; Seidel, J; He, Q; Yang, S Y; Chu, Y H; Ramesh, R; Hÿtch, M J; Snoeck, E

2012-07-27

Domain walls (DWs) substantially influence a large number of applications involving ferroelectric materials due to their limited mobility when shifted during polarization switching. The discovery of greatly enhanced conduction at BiFeO(3) DWs has highlighted yet another role of DWs as a local material state with unique properties. However, the lack of precise information on the local atomic structure is still hampering microscopical understanding of DW properties. Here, we examine the atomic structure of BiFeO(3) 109° DWs with pm precision by a combination of high-angle annular dark-field scanning transmission electron microscopy and a dedicated structural analysis. By measuring simultaneously local polarization and strain, we provide direct experimental proof for the straight DW structure predicted by ab initio calculations as well as the recently proposed theory of diffuse DWs, thus resolving a long-standing discrepancy between experimentally measured and theoretically predicted DW mobilities.

[Rapid test for detection of susceptibility to cefotaxime in Enterobacteriaceae].

PubMed

Jiménez-Guerra, Gemma; Hoyos-Mallecot, Yannik; Rodríguez-Granger, Javier; Navarro-Marí, José María; Gutiérrez-Fernández, José

In this work an "in house" rapid test based on the change in pH that is due to hydrolysis for detecting Enterobacteriaceae susceptible to cefotaxime is evaluated. The strains of Enterobacteriaceae from 1947 urine cultures were assessed using MicroScan panels and the "in house" test. This rapid test includes red phenol solution and cefotaxime. Using MicroScan panels, 499 Enterobacteriaceae isolates were evaluated, which included 27 isolates of Escherichia coli producing extended-spectrum beta-lactamases (ESBL), 16 isolates of Klebsiella pneumoniae ESBL and 1 isolate of Klebsiella oxytoca ESBL. The "in house" test offers the following values: sensitivity 98% and specificity 97%, with negative predictive value 100% and positive predictive value 78%. The "in house" test based on the change of pH is useful in our area for detecting presumptively cefotaxime-resistant Enterobacteriaceae strains. Copyright © 2016 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.

Nucleic Acid Homologies Among Oxidase-Negative Moraxella Species

PubMed Central

Johnson, John L.; Anderson, Robert S.; Ordal, Erling J.

1970-01-01

The deoxyribonucleic acid (DNA) base composition and DNA homologies of more than 40 strains of oxidase-negative Moraxella species were determined. These bacteria have also been identified as belonging to the Mima-Herellea-Acinetobacter group and the Bacterium anitratum group, as well as to several other genera including Achromobacter and Alcaligenes. The DNA base content of these strains ranged from 40 to 46% guanine plus cytosine. DNA–DNA competition experiments distinguished five groups whose members were determined by showing 50% or more homology to one of the reference strains: B. anitratum type B5W, Achromobacter haemolyticus var. haemolyticus, Alcaligenes haemolysans, Achromobacter metalcaligenes, and Moraxella lwoffi. A sixth group comprised those strains showing less than 50% homology to any of the reference strains. Negligible homology was found between strains of oxidase-negative and oxidase-positive Moraxella species in DNA–DNA competition experiments. However, evidence of a distant relationship between the two groups was obtained in competition experiments by using ribosomal ribonucleic acid. PMID:5413826

Characterization of LiMn 2O 4 cathodes by electrochemical strain microscopy

DOE PAGES

Alikin, D. O.; Ievlev, A. V.; Luchkin, S. Yu.; ...

2016-03-15

Electrochemical strain microscopy (ESM) is a scanning probe microscopy(SPM) method in which the local electrodiffusion is probed via application of AC voltage to the SPM tip and registration of resulting electrochemical strain. In this study, we implemented ESM to measure local strain in bulk LiMn 2O 4 cathodes of a commercial Li-battery in different states of charge to investigate distribution of Li-ion mobility and concentration. Ramped AC ESM imaging and voltage spectroscopy were used to find the most reliable regime of measurements allowing separating and diminishing different contributions to ESM. This is not a trivial task due to complex geometrymore » of the sample and various obstacles resulting in less predictable contributions of different origins into ESM response: electrostatic tip–surface interactions, charge injection, electrostriction, and flexoelectricity. Finally, understanding and control of these contributions is an important step towards quantitative interpretation of ESM data.« less

Bacteroides fragilis induce necrosis on mice peritoneal macrophages: In vitro and in vivo assays

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

Vieira, J.M.B.D., E-mail: jmanya@terra.com.br; Laboratorio de Biologia de Anaerobios, IMPPG, UFRJ, Rio de Janeiro; Seabra, S.H.

Bacteroides fragilis is an anaerobic bacteria component of human intestinal microbiota and agent of infections. In the host B. fragilis interacts with macrophages, which produces toxic radicals like NO. The interaction of activated mice peritoneal macrophages with four strains of B. fragilis was evaluated on this study. Previously was shown that such strains could cause metabolic and morphologic alterations related to macrophage death. In this work propidium iodide staining showed the strains inducing macrophage necrosis in that the labeling was evident. Besides nitroblue tetrazolium test showed that B. fragilis stimulates macrophage to produce oxygen radicals. In vivo assays performed inmore » BalbC mice have results similar to those for in vitro tests as well as scanning electron microscopy, which showed the same surface pore-like structures observed in vitro before. The results revealed that B. fragilis strains studied lead to macrophage death by a process similar to necrosis.« less

Lead-resistant Providencia alcalifaciens strain 2EA bioprecipitates Pb+2 as lead phosphate.

PubMed

Naik, M M; Khanolkar, D; Dubey, S K

2013-02-01

A lead-resistant bacteria isolated from soil contaminated with car battery waste were identified as Providencia alcalifaciens based on biochemical characteristics, FAME profile and 16S rRNA sequencing and designated as strain 2EA. It resists lead nitrate up to 0·0014 mol l(-1) by precipitating soluble lead as insoluble light brown solid. Scanning electron microscopy coupled with energy-dispersive X-ray spectrometric analysis (SEM-EDX) and X-ray diffraction spectroscopy (XRD) revealed extracellular light brown precipitate as lead orthophosphate mineral, that is, Pb(9) (PO(4))(6) catalysed by phosphatase enzyme. This lead-resistant bacterial strain also demonstrated tolerance to high levels of cadmium and mercury along with multiple antibiotic resistance. Providencia alcalifaciens strain 2EA could be used for bioremediation of lead-contaminated environmental sites, as it can efficiently precipitate lead as lead phosphate. © 2012 The Society for Applied Microbiology.

Observation of a periodic array of flux-closure quadrants in strained ferroelectric PbTiO 3 films

DOE PAGES

Tang, Y. L.; Zhu, Y. L; Ma, Xiuliang; ...

2015-05-01

Nanoscale ferroelectrics are expected to exhibit various exotic domain configurations, such as the full flux-closure pattern that is well known in ferromagnetic materials. Here we observe not only the atomic morphology of the flux-closure quadrant but also a periodic array of flux closures in ferroelectric PbTiO 3 films, mediated by tensile strain on a GdScO 3 substrate. Using aberration-corrected scanning transmission electron microscopy, we directly visualize an alternating array of clockwise and counterclockwise flux closures, whose periodicity depends on the PbTiO 3 film thickness. In the vicinity of the core, the strain is sufficient to rupture the lattice, with strainmore » gradients up to 10 9 per meter. We found engineering strain at the nanoscale may facilitate the development of nanoscale ferroelectric devices.« less

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.

Preparation of Chemically Etched Tips for Ambient Instructional Scanning Tunneling Microscopy

ERIC Educational Resources Information Center

Zaccardi, Margot J.; Winkelmann, Kurt; Olson, Joel A.

2010-01-01

A first-year laboratory experiment that utilizes concepts of electrochemical tip etching for scanning tunneling microscopy (STM) is described. This experiment can be used in conjunction with any STM experiment. Students electrochemically etch gold STM tips using a time-efficient method, which can then be used in an instructional grade STM that…

Interferon in resistance to bacterial and protozoan infections

NASA Technical Reports Server (NTRS)

Sonnenfeld, Gerald; Gould, Cheryl L.; Kierszenbaum, Felipe; Degee, Antonie L. W.; Mansfield, John M.

1986-01-01

The effects of genetic differences in mouse strains on the modulation of protozoan infections by interferon (IFN) were investigated. In one set of experiments, three different strains of mice were injected with T. cruzi, and their sera were assayed at five time intervals for IFN titer. A greater quantity of IFN was produced by mouse strains that were susceptible to T. cruzi infection than by the more resistant strain. In another set of experiments, spleen cell cultures from inbred strains of mice were challenged with an antigen made from T.b. rhodesiense. The cells from mice resistant to infection, produced greater amounts of IFN-gamma than did cells from the susceptible mice. In a third set of experiments, it was found that mice injected with T.b. rhodesiense before being infected with a diabetogenic virus (EMC-D) were resistant to the effects of the virus and did not produce virus-specific antibody.

Modeling of grain size strengthening in tantalum at high pressures and strain rates

DOE PAGES

Rudd, Robert E.; Park, H. -S.; Cavallo, R. M.; ...

2017-01-01

Laser-driven ramp wave compression experiments have been used to investigate the strength (flow stress) of tantalum and other metals at high pressures and high strain rates. Recently this kind of experiment has been used to assess the dependence of the strength on the average grain size of the material, finding no detectable variation with grain size. The insensitivity to grain size has been understood theoretically to result from the dominant effect of the high dislocation density generated at the extremely high strain rates of the experiment. Here we review the experiments and describe in detail the multiscale strength model usedmore » to simulate them. The multiscale strength model has been extended to include the effect of geometrically necessary dislocations generated at the grain boundaries during compatible plastic flow in the polycrystalline metal. Lastly, we use the extended model to make predictions of the threshold strain rates and grain sizes below which grain size strengthening would be observed in the laser-driven Rayleigh-Taylor experiments.« less

Colonization of spinach (Spinacia oleracea L.) by GFP-tagged verticillium dahliae.

USDA-ARS?s Scientific Manuscript database

The soilborne fungus, Verticillium dahliae, causes wilt in a wide range of hosts, including spinach (Spinacia oleracea L.). The interaction between a green fluorescent protein (GFP)-tagged V. dahliae strain and spinach was studied by confocal laser scanning microscopy. The roots of spinach seedlings...

Control of bone remodelling by applied dynamic loads

NASA Technical Reports Server (NTRS)

Lanyon, L. E.; Rubin, C. T.

1984-01-01

The data showing the relationship between bone mass and peak strain magnitude prepared and submitted for publication. The data from experiments relating remodelling activity with static or dynamic loads were prepared and submitted for publication. Development of programs to relate the location of remodelling activity with he natural and artificial dynamic strain distributions continued. Experiments on the effect of different strain rates on the remodelling response continued.

The experience of patients participating in a small randomised control trial that explored two different interventions to reduce anxiety prior to an MRI scan.

PubMed

Tugwell-Allsup, J; Pritchard, A W

2018-05-01

This paper reports qualitative findings from within a larger randomised control trial where a video clip or telephone conversation with a radiographer was compared to routine appointment letter and information sheet to help alleviate anxiety prior to their MRI scan. Questionnaires consisting of three free-text response questions were administered to all of the 74 patients recruited to the MRI anxiety clinical trial. The questionnaire was designed to establish patients' experiences of the intervention they had received. These questionnaires were administered post-scan. Two participants from each trial arm were also interviewed. A thematic approach was utilised for identifying recurrent categories emerging from the qualitative data which are supported by direct quotations. Participants in the interventional groups commented positively about the provision of pre-MRI scan information they received and this was contrastable with the relatively indifferent responses observed among those who received the standard information letter. Many important themes were identified including the patients needs for clear and simplified information, the experience of anticipation when waiting for the scan, and also the informally acquired information about having an MRI scan i.e. the shared experiences of friends and family. All themes highlighted the need for an inclusive and individually tailored approach to pre-scan information provision. Qualitative data collected throughout the trial is supportive of the statistical findings, where it is asserted that the use of a short video clip or a radiographer having a short conversation with patients before their scan reduces pre-scan anxiety. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Microstructure and critical strain of dynamic recrystallization of 6082 aluminum alloy in thermal deformation

NASA Astrophysics Data System (ADS)

Ren, W. W.; Xu, C. G.; Chen, X. L.; Qin, S. X.

2018-05-01

Using high temperature compression experiments, true stress true strain curve of 6082 aluminium alloy were obtained at the temperature 460°C-560°C and the strain rate 0.01 s-1-10 s-1. The effects of deformation temperature and strain rate on the microstructure are investigated; (‑∂lnθ/∂ε) ‑ ε curves are plotted based on σ-ε curve. Critical strains of dynamic recrystallization of 6082 aluminium alloy model were obtained. The results showed lower strain rates were beneficial to increase the volume fraction of recrystallization, the average recrystallized grain size was coarse; High strain rates are beneficial to refine average grain size, the volume fraction of dynamic recrystallized grain is less than that by using low strain rates. High temperature reduced the dislocation density and provided less driving force for recrystallization so that coarse grains remained. Dynamic recrystallization critical strain model and thermal experiment results can effectively predict recrystallization critical point of 6082 aluminium alloy during thermal deformation.

An entomopathogenic strain of Beauveria bassiana against Frankliniella occidentalis with no detrimental effect on the predatory mite Neoseiulus barkeri: evidence from laboratory bioassay and scanning electron microscopic observation.

PubMed

Wu, Shengyong; Gao, Yulin; Zhang, Yaping; Wang, Endong; Xu, Xuenong; Lei, Zhongren

2014-01-01

Among 28 isolates of Beauveria bassiana tested for virulence against F. occidentalis in laboratory bioassays, we found strain SZ-26 as the most potent, causing 96% mortality in adults at 1×10(7) mL(-1)conidia after 4 days. The effect of the strain SZ-26 on survival, longevity and fecundity of the predatory mite Neoseiulus (Amblyseius) barkeri Hughes were studied under laboratory conditions. The bioassay results showed that the corrected mortalities were less than 4 and 8% at 10 days following inoculation of the adult and the larvae of the predator, respectively, with 1×10(7) conidia mL(-1) of SZ-26. Furthermore, no fungal hyphae were found in dead predators. The oviposition and postoviposition durations, longevity, and fecundity displayed no significant differences after inoculation with SZ-26 using first-instar larvae of F. occidentalis as prey in comparison with untreated predator. In contrast, the preoviposition durations were significantly longer. Observations with a scanning electron microscope, revealed that many conidia were attached to the cuticles of F. occidentalis at 2 h after treatment with germ tubes oriented toward cuticle at 24 h, penetration of the insect cuticle at 36 h, and finally, fungal colonization of the whole insect body at 60 h. In contrast, we never observed penetration of the predator's cuticle and conidia were shed gradually from the body, further demonstrating that B. bassiana strain SZ-26 show high toxicity against F. occidentalis but no pathogenicity to predatory mite.

An Entomopathogenic Strain of Beauveria bassiana against Frankliniella occidentalis with no Detrimental Effect on the Predatory Mite Neoseiulus barkeri: Evidence from Laboratory Bioassay and Scanning Electron Microscopic Observation

PubMed Central

Wu, Shengyong; Gao, Yulin; Zhang, Yaping; Wang, Endong; Xu, Xuenong; Lei, Zhongren

2014-01-01

Among 28 isolates of Beauveria bassiana tested for virulence against F. occidentalis in laboratory bioassays, we found strain SZ-26 as the most potent, causing 96% mortality in adults at 1×107 mL−1conidia after 4 days. The effect of the strain SZ-26 on survival, longevity and fecundity of the predatory mite Neoseiulus (Amblyseius) barkeri Hughes were studied under laboratory conditions. The bioassay results showed that the corrected mortalities were less than 4 and 8% at 10 days following inoculation of the adult and the larvae of the predator, respectively, with 1×107 conidia mL−1 of SZ-26. Furthermore, no fungal hyphae were found in dead predators. The oviposition and postoviposition durations, longevity, and fecundity displayed no significant differences after inoculation with SZ-26 using first-instar larvae of F. occidentalis as prey in comparison with untreated predator. In contrast, the preoviposition durations were significantly longer. Observations with a scanning electron microscope, revealed that many conidia were attached to the cuticles of F. occidentalis at 2 h after treatment with germ tubes oriented toward cuticle at 24 h, penetration of the insect cuticle at 36 h, and finally, fungal colonization of the whole insect body at 60 h. In contrast, we never observed penetration of the predator's cuticle and conidia were shed gradually from the body, further demonstrating that B. bassiana strain SZ-26 show high toxicity against F. occidentalis but no pathogenicity to predatory mite. PMID:24454744

Isolation and Characterization of China Isolates of Duddingtonia flagrans, a Candidate of the Nematophagous Fungi for Biocontrol of Animal Parasitic Nematodes.

PubMed

Wang, Bo-Bo; Liu, Wei; Chen, Ming-Yue; Li, Xuan; Han, Yuan; Xu, Qiang; Sun, Long-Jie; Xie, De-Qiong; Cai, Kui-Zheng; Liu, Yi-Zhong; Liu, Jun-Lin; Yi, Lin-Xin; Wang, Hui; Zhao, Ming-Wang; Li, Xiao-Shan; Wu, Jia-Yan; Yang, Jing; Wang, Yue-Ying

2015-08-01

The nematophagous fungus Duddingtonia flagrans has been investigated as a biological agent for the control of gastrointestinal nematodes infecting domestic animals in other countries. However, D. flagrans has not been detected in China. In this study 1,135 samples were examined from 2012 to 2014; 4 D. flagrans isolates (SDH 035, SDH 091, SFH 089, SFG 170) were obtained from the feces of domestic animals and dung compost. The 4 isolates were then characterized morphologically. The SDH 035 strain was characterized by sequencing the ITS1-5.8S rDNA-ITS2 region. A BLAST search showed that the SDH 035 strain (GenBank KP257593) was 100% identical to Arthrobotrys flagrans (AF106520) and was identified as D. flagrans. The morphological plasticity of the isolated strain and the interaction of this strain with the nematode targets were observed by subjecting the infected trichostrongylide L3 to scanning electron microscopy. At 6 and 8 hr after trichostrongylide L(3) was added, hyphal ramifications were observed and L(3) were captured, respectively. Scanning electron micrographs were obtained at 0, 6, 12, 18, 24, 30, 36, 42, and 48 hr, where 0 is the time when trichostrongylide L(3) were first captured by the fungus. The details of the capture process by the fungus are also described. Chlamydospores were observed in the body of L(3) in the late stage of digestion. A sticky substance and bacteria could be observed in contact areas between predation structures and nematode cuticle.

Nondestructive monitoring of fatigue damage evolution in austenitic stainless steel by positron-lifetime measurements

NASA Astrophysics Data System (ADS)

Holzwarth, Uwe; Schaaff, Petra

2004-03-01

Positron-lifetime measurements have been performed on austenitic stainless steel during (i) stress- and (ii) strain-controlled fatigue experiments for different applied stress and strain amplitudes, respectively. For this purpose a generator-detector assembly with a 72Se/72As positron generator [maximum activity 25 μCi (0.9 MBq)] has been mounted on mechanical testing machines in order to measure the positron lifetime without removing the specimens from the load train. The average positron lifetime has been determined by a β+-γ coincidence. The feasibility to use the average positron lifetime for monitoring the evolution of fatigue damage and to predict early failure has been examined. In strain- and stress-controlled experiments the average positron lifetime shows a pronounced increase within the first 10% and 40% of the fatigue life, respectively. In stress-controlled experiments the average positron lifetime at failure depends significantly on the applied stress amplitude. In strain-controlled experiments significantly different positron lifetimes for different applied plastic strain amplitudes are obtained within the first 1.000 fatigue cycles, whereas differences get wiped out during further cycling until failure.

Mapping the ductile-brittle transition of magma

NASA Astrophysics Data System (ADS)

Kendrick, J. E.; Lavallee, Y.; Dingwell, D. B.

2010-12-01

During volcanic unrest, eruptive activity can switch rapidly from effusive to explosive. Explosive eruptions require the fragmentation of magma, in which, if deformation rate is too fast to be relaxed, magma undergoes a transition in deformation mechanism from viscous and/or ductile to brittle. Our knowledge of the deformation mechanisms of magma ascent and eruption remains, to date, poor. Many studies have constrained the glass transition (Tg) of the interstitial melt phase; yet the effect of crystals and bubbles are unresolved. During ascent, magma undergoes P-T changes which induce crystallization, thereby inducing a transition from viscous to ductile and, in some cases, to brittle deformation. Here, we explore the deformation mechanisms of magma involved in the dome-building eruptions and explosions that occurred at Volcán de Colima (Mexico) since 1998. For this purpose, we investigated the rheology of dome lavas, containing 10-45 vol.% rhyolitic interstitial melt, 55-90 vol.% crystals and 5-20 vol.% bubbles. The interstitial glass is characterized by electron microprobe and Tg is characterized using a differential scanning calorimeter and a dilatometer. The population of crystals (fraction, shape and size distribution) is described optically and quantified using ImageJ and AMOCADO. The rheological effects of crystals on the deformation of magmas are constrained via acoustic emission (AE) and uniaxial deformation experiments at temperature above Tg (900-980 °C) and at varied applied stresses (and strain rates: 10-6 to 10-2 s-1). The ratio of ductile to brittle deformation across the ductile-brittle transition is quantified using the output AE energy and optical and SEM analysis. We find that individual dome lava sample types have different mechanical responses, yielding a significant range of measured strain rates under a given temperature and applied stress. Optical analysis suggests that at low strain rates, ductile deformation is mainly controlled by the groundmass, whereas fractures initiate sporadically in phenocrysts. At high strain rates continuous fracture initiate in the phenocrysts and propagate through the groundmass. AE analysis suggests the ductile-brittle transition to approximate two orders of magnitude of strain rate and that it is temperature dependent. Within the transition, the different ratio of ductile to brittle deformation processes controls the strain to failure. This study shows that the presence of crystals widens the range of strain rates of the ductile-brittle transition and the failure of magma becomes dependent on total strain. Our findings will be discussed in the context of different eruptive scenarios.

The ACEII recombinant Trichoderma reesei QM9414 strains with enhanced xylanase production and its applications in production of xylitol from tree barks.

PubMed

Xiong, Lili; Kameshwar, Ayyappa Kumar Sista; Chen, Xi; Guo, Zhiyun; Mao, Canquan; Chen, Sanfeng; Qin, Wensheng

2016-12-28

ACEII transcription factor plays a significant role in regulating the expression of cellulase and hemicellulase encoding genes. Apart from ACEII, transcription factors such as XYR1, CRE1, HAP2/3/5 complex and ACEI function in a coordinated pattern for regulating the gene expression of cellulases and hemicellulases. Studies have demonstrated that ACEII gene deletion results in decreased total cellulase and xylanase activities with reduced transcript levels of lignocellulolytic enzymes. In this study, we have successfully transformed the ACEII transcription factor encoding gene in Trichoderma reesei to significantly improve its degrading abilities. Transformation experiments on parental strain T. reesei QM9414 has resulted in five genetically engineered strains T/Ace2-2, T/Ace2-5, T/Ace2-8, T/Ace5-4 and T/Ace10-1. Among which, T/Ace2-2 has exhibited significant increase in enzyme activity by twofolds, when compared to parental strain. The T/Ace2-2 was cultured on growth substrates containing 2% bark supplemented with (a) sugar free + MA medium (b) glucose + MA medium and (c) xylose + MA medium. The bark degradation efficiency of genetically modified T/Ace2-2 strain was assessed by analyzing the xylitol production yield using HPAEC. By 6th day, about 10.52 g/l of xylitol was produced through enzymatic conversion of bark (2% bark + MA + xylose) by the T/Ace2-2 strain and by 7th day the conversion rate was found to be 0.21 g/g. Obtained results confirmed that bark growth medium supplemented with D-xylose has profoundly increased the conversion rate of bark by T/Ace2-2 strain when compared to sugar free and glucose supplemented growth media. Results obtained from scanning electron microscopy has endorsed our current results. Bark samples inoculated with T/Ace2-2 strain has showed large number of degraded cells with clearly visible cavities and fractures, by exposing the microfibrillar interwoven complex. We propose a cost effective and ecofriendly method for the degradation of lignocellulosic biomass such as bark to produce xylitol by using genetically modified T. reesei. Efficient conversion rate and production yield obtained in our current study provides a great scope for the xylitol industries, as our method bypasses the pretreatment of bark achieving clean and low-cost xylitol production.

Virtual experiments, physical validation: dental morphology at the intersection of experiment and theory

PubMed Central

Anderson, P. S. L.; Rayfield, E. J.

2012-01-01

Computational models such as finite-element analysis offer biologists a means of exploring the structural mechanics of biological systems that cannot be directly observed. Validated against experimental data, a model can be manipulated to perform virtual experiments, testing variables that are hard to control in physical experiments. The relationship between tooth form and the ability to break down prey is key to understanding the evolution of dentition. Recent experimental work has quantified how tooth shape promotes fracture in biological materials. We present a validated finite-element model derived from physical compression experiments. The model shows close agreement with strain patterns observed in photoelastic test materials and reaction forces measured during these experiments. We use the model to measure strain energy within the test material when different tooth shapes are used. Results show that notched blades deform materials for less strain energy cost than straight blades, giving insights into the energetic relationship between tooth form and prey materials. We identify a hypothetical ‘optimal’ blade angle that minimizes strain energy costs and test alternative prey materials via virtual experiments. Using experimental data and computational models offers an integrative approach to understand the mechanics of tooth morphology. PMID:22399789

Brittle Creep of Tournemire Shale: Orientation, Temperature and Pressure Dependences

NASA Astrophysics Data System (ADS)

Geng, Zhi; Bonnelye, Audrey; Dick, Pierre; David, Christian; Chen, Mian; Schubnel, Alexandre

2017-04-01

Time and temperature dependent rock deformation has both scientific and socio-economic implications for natural hazards, the oil and gas industry and nuclear waste disposal. During the past decades, most studies on brittle creep have focused on igneous rocks and porous sedimentary rocks. To our knowledge, only few studies have been carried out on the brittle creep behavior of shale. Here, we conducted a series of creep experiments on shale specimens coming from the French Institute for Nuclear Safety (IRSN) underground research laboratory located in Tournemire, France. Conventional tri-axial experiments were carried under two different temperatures (26˚ C, 75˚ C) and confining pressures (10 MPa, 80 MPa), for three orientations (σ1 along, perpendicular and 45˚ to bedding). Following the methodology developed by Heap et al. [2008], differential stress was first increased to ˜ 60% of the short term peak strength (10-7/s, Bonnelye et al. 2016), and then in steps of 5 to 10 MPa every 24 hours until brittle failure was achieved. In these long-term experiments (approximately 10 days), stress and strains were recorded continuously, while ultrasonic acoustic velocities were recorded every 1˜15 minutes, enabling us to monitor the evolution of elastic wave speed anisotropy. Temporal evolution of anisotropy was illustrated by inverting acoustic velocities to Thomsen parameters. Finally, samples were investigated post-mortem using scanning electron microscopy. Our results seem to contradict our traditional understanding of loading rate dependent brittle failure. Indeed, the brittle creep failure stress of our Tournemire shale samples was systematically observed ˜50% higher than its short-term peak strength, with larger final axial strain accumulated. At higher temperatures, the creep failure strength of our samples was slightly reduced and deformation was characterized with faster 'steady-state' creep axial strain rates at each steps, and larger final axial strain accumulated. At each creep step, ultrasonic wave velocities first decreased, and then increased gradually. The magnitude of elastic wave velocity variations showed an important orientation and temperature dependence. Velocities measured perpendicular to bedding showed increased variation, variation that was enhanced at higher temperature and higher pressure. The case of complete elastic anisotropy reversal was even observed for sample deformed perpendicular to bedding, with a reduction amount of axial strain needed to reach anisotropy reversal at higher temperature. Our data were indicative of competition between crack growth, sealing/healing, and possibly mineral rotation or anisotropic compaction during creep. SEM investigation confirmed evidence of time dependent pressure solution and crack sealing/healing. Our research not only has practical engineering consequence but, more importantly, can provide valuable insights into the underlying mechanisms of creep in complex media like shale. In particular, our study highlights that the short-term peak strength has little meaning in shale material, which can over-consolidate importantly by 'plastic' flow. In addition, we showed that elastic anisotropy can switch and even reverse over relatively short time periods (<10 days) and for relatively small amount of plastic deformation (<5%).

Some unique features of alkaliphilic anaerobes

NASA Astrophysics Data System (ADS)

Roof, Erin; Pikuta, Elena; Otto, Christopher; Williams, George; Hoover, Richard

2013-09-01

This article explores two topics involving the examination of four strains of alkaliphilic anaerobes. The first topic was dedicated to detection of the ability of microorganisms to metabolize alternative chirality substrates. Two saccharolytic anaerobic bacteria were chosen for the first experiment: Anaerovirgula multivorans strain SCAT, which is gram positive and spore-forming; and Spirochaeta dissipatitropha, strain ASpC2T, which is gram negative. It was found that both checked sugarlytics were able to use L-ribose and L-arabinose, as growth substrates. The second part was concerned of study a chemolithotrophy in two halo-alkaliphilic sulfate reducing bacteria: Desulfonatornum thiodismutans strain MLF1T and Desulfonatronum lacustre strain Z-7951T. The experiments with lithotrophs had demonstrated that strain MLF1T was capable to grow without any organic source of carbon, while strain Z-7951T had required at least 2 mM sodium acetate for growth. Anaerobic technique was used for preparation of the growth media and maintenance of these bacterial cultures. Standard methods for Gram, spore, and flagella staining were applied for characterization of cytomorphology. In this article, the results of the experiments performed on cytological, physiological, and biochemical levels are presented and discussed.

Hierarchical and Multifunctional Three-dimensional Network of Carbon Nanotubes for Supercapacitor and Strain Sensor Applications

DTIC Science & Technology

2016-05-19

cycles at 100 mV/s scan rate. 15. SUBJECT TERMS Carbon nano tubes, Nanotechnology , supercapacitor 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF...5. Lee, H., Hierarchical and Multifunctional Three-dimensional Network of Carbon Nanotubes of Sensor Applications, College of Engineering Forum on

Bill McMahon | NREL

Science.gov Websites

career at NREL in 1995 by conducting scanning tunneling microscope (STM) studies of the atomic structure revealed a new strain-induced step structure and contributed to the development of world-record-efficiency NREL's Computational Materials Science team, probing the atomic structure of dislocations in III-V

Continuous modulations of femtosecond laser-induced periodic surface structures and scanned line-widths on silicon by polarization changes.

PubMed

Han, Weina; Jiang, Lan; Li, Xiaowei; Liu, Pengjun; Xu, Le; Lu, YongFeng

2013-07-01

Large-area, uniform laser-induced periodic surface structures (LIPSS) are of wide potential industry applications. The continuity and processing precision of LIPSS are mainly determined by the scanning intervals of adjacent scanning lines. Therefore, continuous modulations of LIPSS and scanned line-widths within one laser scanning pass are of great significance. This study proposes that by varying the laser (800 nm, 50 fs, 1 kHz) polarization direction, LIPSS and the scanned line-widths on a silicon (111) surface can be continuously modulated with high precision. It shows that the scanned line-width reaches the maximum when the polarization direction is perpendicular to the scanning direction. As an application example, the experiments show large-area, uniform LIPSS can be fabricated by controlling the scanning intervals based on the one-pass scanned line-widths. The simulation shows that the initially formed LIPSS structures induce directional surface plasmon polaritons (SPP) scattering along the laser polarization direction, which strengthens the subsequently anisotropic LIPSS fabrication. The simulation results are in good agreement with the experiments, which both support the conclusions of continuous modulations of the LIPSS and scanned line-widths.

Geographic Variation in Sexual Attraction of Spodoptera frugiperda Corn- and Rice-Strain Males to Pheromone Lures

PubMed Central

Unbehend, Melanie; Hänniger, Sabine; Vásquez, Gissella M.; Juárez, María Laura; Reisig, Dominic; McNeil, Jeremy N.; Meagher, Robert L.; Jenkins, David A.; Heckel, David G.; Groot, Astrid T.

2014-01-01

The corn- and rice-strains of Spodoptera frugiperda exhibit several genetic and behavioral differences and appear to be undergoing ecological speciation in sympatry. Previous studies reported conflicting results when investigating male attraction to pheromone lures in different regions, but this could have been due to inter-strain and/or geographic differences. Therefore, we investigated whether corn- and rice-strain males differed in their response to different synthetic pheromone blends in different regions in North America, the Caribbean and South America. All trapped males were strain-typed by two strain-specific mitochondrial DNA markers. In the first experiment, we found a nearly similar response of corn- and rice-strain males to two different 4-component blends, resembling the corn- and rice-strain female blend we previously described from females in Florida. This response showed some geographic variation in fields in Canada, North Carolina, Florida, Puerto Rico, and South America (Peru, Argentina). In dose-response experiments with the critical secondary sex pheromone component (Z)-7-dodecenyl acetate (Z7-12:OAc), we found some strain-specific differences in male attraction. While the response to Z7-12:OAc varied geographically in the corn-strain, rice-strain males showed almost no variation. We also found that the minor compound (Z)-11-hexadecenyl acetate (Z11-16:OAc) did not increase attraction of both strains in Florida and of corn-strain males in Peru. In a fourth experiment, where we added the stereo-isomer of the critical sex pheromone component, (E)-7-dodecenyl acetate, to the major pheromone component (Z)-9-tetradecenyl acetate (Z9-14:OAc), we found that this compound was attractive to males in North Carolina, but not to males in Peru. Overall, our results suggest that both strains show rather geographic than strain-specific differences in their response to pheromone lures, and that regional sexual communication differences might cause geographic differentiation between populations. PMID:24586634

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

Gradient Echo MRI Characterization of Development of Atherosclerosis in the Abdominal Aorta in Watanabe Heritable Hyperlipidemic Rabbits

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

Wang, Yi-Xiang J., E-mail: yi-xiang.wang@astrazeneca.com; Kuribayashi, Hideto; Wagberg, Maria

Purpose. The Watanabe Heritable Hyperlipidemic (WHHL) rabbit provides an important model of spontaneous atherosclerosis. With a strain of WHHL rabbits which do not develop abdominal aorta lumen stenosis even with advanced atherosclerosis, we studied the MRI-histology correlation, and the natural progression of atherosclerosis in the abdominal aorta. In addition, intra-reader segmentation repeatability and scan-rescan reproducibility were assessed. Methods. Two batches of female WHHL rabbits were used. The first batch of 6 rabbits was scanned at 20 weeks old. A second batch of 17 rabbits was scanned at 50 weeks old and then randomly divided into two subgroups: 8 were killedmore » for histologic investigation; 9 were kept alive for follow-up, with repeat scanning a week later to assess scan-rescan reproducibility, and again at 73 weeks old to assess disease progression. MR images were acquired at 4.7 T using a chemical shift selective fat suppression gradient echo with a saturation band suppressing blood signal within the aortic lumen. Five slices per animal were acquired, centered around the renal artery region of the abdominal aorta, with in-plane resolution of 0.195 mm and slice thickness of 3 mm. Results. The coefficient of variation for intra-reader reproducibility for aortic wall thickness measurements was 2.5% for repeat segmentations of the same scans on the same day, but segmentations of these same scans made 8 months later showed a systematic change, suggesting that intra-reader bias as well as increased variability could compromise assessments made over time. Comparative analyses were therefore performed in one postprocessing session. The coefficient of variation for scan-rescan reproducibility for aortic wall thickness was 5.5% for nine pairs of scans acquired a week apart and segmented on the same day. Good MRI-histology correlation was obtained. The MRI-measured mean aortic wall thickness of animals at 20 weeks of age was 76% that of animals at 50 weeks of age (p < 0.001). There was a small increase in aortic wall thickness between 50 and 73 weeks of age, but this was not significant (p > 0.05). The corresponding differences in lumen cross-sectional areas at 20, 50, and 73 weeks of age were not significant. These results were consistent with in-house historical histology data on this strain of rabbits. Conclusions. High-resolution gradient echo MRI can follow disease progression in the WHHL rabbit spontaneous atherosclerosis disease model.« less

Nanoheteroepitaxy of gallium arsenide on strain-compliant silicon-germanium nanowires

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

Chin, Hock-Chun; Gong, Xiao; Yeo, Yee-Chia

Heterogeneous integration of high-quality GaAs on Si-based substrates using a selective migration-enhanced epitaxy (MEE) of GaAs on strain-compliant SiGe nanowires was demonstrated for the first time. The physics of compliance in nanoscale heterostructures was captured and studied using finite-element simulation. It is shown that nanostructures can provide additional substrate compliance for strain relief and therefore contribute to the formation of defect-free GaAs on SiGe. Extensive characterization using scanning electron microscopy and cross-sectional transmission electron microscopy was performed to illustrate the successful growth of GaAs on SiGe nanowire. Raman and Auger electron spectroscopy measurements further confirmed the quality of the GaAsmore » grown and the high growth selectivity of the MEE process.« less

High temperature strain gages

NASA Technical Reports Server (NTRS)

Gregory, Otto J. (Inventor); You, Tao (Inventor)

2011-01-01

A ceramic strain gage based on reactively sputtered indium-tin-oxide (ITO) thin films is used to monitor the structural integrity of components employed in aerospace propulsion systems operating at temperatures in excess of 1500.degree. C. A scanning electron microscopy (SEM) of the thick ITO sensors reveals a partially sintered microstructure comprising a contiguous network of submicron ITO particles with well defined necks and isolated nanoporosity. Densification of the ITO particles was retarded during high temperature exposure with nitrogen thus stabilizing the nanoporosity. ITO strain sensors were prepared by reactive sputtering in various nitrogen/oxygen/argon partial pressures to incorporate more nitrogen into the films. Under these conditions, sintering and densification of the ITO particles containing these nitrogen rich grain boundaries was retarded and a contiguous network of nano-sized ITO particles was established.

Tip-induced local strain on Mo S 2 / graphite detected by inelastic electron tunneling spectroscopy

DOE PAGES

Ko, Wonhee; Hus, Saban M.; Li, Xufan; ...

2018-03-02

We report the detection of tip-induced local strain applied to the monolayer MoS 2 grown on a graphite substrate by scanning tunneling microscope. Monolayer MoS 2 behaves as both mechanical and tunneling barriers that prevent the tip from contacting the graphite while maintaining the tunneling current. Inelastic tunneling electron spectroscopy (IETS) is utilized to probe the phonon modes in graphite. As the tip pushes the sample, IETS reveals a continuous phonon softening in graphite, corroborated by a downward shift of the phonon energy as calculated by density-functional theory. Finally, our results demonstrate a way to apply local mechanical strain andmore » simultaneously detect the induced change in phonon modes by unitizing IETS with two-dimensional materials as a tunneling barrier.« less

Tip-induced local strain on Mo S 2 / graphite detected by inelastic electron tunneling spectroscopy

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

Ko, Wonhee; Hus, Saban M.; Li, Xufan

We report the detection of tip-induced local strain applied to the monolayer MoS 2 grown on a graphite substrate by scanning tunneling microscope. Monolayer MoS 2 behaves as both mechanical and tunneling barriers that prevent the tip from contacting the graphite while maintaining the tunneling current. Inelastic tunneling electron spectroscopy (IETS) is utilized to probe the phonon modes in graphite. As the tip pushes the sample, IETS reveals a continuous phonon softening in graphite, corroborated by a downward shift of the phonon energy as calculated by density-functional theory. Finally, our results demonstrate a way to apply local mechanical strain andmore » simultaneously detect the induced change in phonon modes by unitizing IETS with two-dimensional materials as a tunneling barrier.« less

Tip-induced local strain on Mo S2/graphite detected by inelastic electron tunneling spectroscopy

NASA Astrophysics Data System (ADS)

Ko, Wonhee; Hus, Saban M.; Li, Xufan; Berlijn, Tom; Nguyen, Giang D.; Xiao, Kai; Li, An-Ping

2018-03-01

We report the detection of tip-induced local strain applied to the monolayer Mo S2 grown on a graphite substrate by scanning tunneling microscope. Monolayer Mo S2 behaves as both mechanical and tunneling barriers that prevent the tip from contacting the graphite while maintaining the tunneling current. Inelastic tunneling electron spectroscopy (IETS) is utilized to probe the phonon modes in graphite. As the tip pushes the sample, IETS reveals a continuous phonon softening in graphite, corroborated by a downward shift of the phonon energy as calculated by density-functional theory. Our results demonstrate a way to apply local mechanical strain and simultaneously detect the induced change in phonon modes by unitizing IETS with two-dimensional materials as a tunneling barrier.

Nanoscale self-templating for oxide epitaxy with large symmetry mismatch

DOE PAGES

Gao, Xiang; Lee, Shinbuhm; Nichols, John A.; ...

2016-12-02

Direct observations using scanning transmission electron microscopy unveil an intriguing interfacial bi-layer that enables epitaxial growth of a strain-free, monoclinic, bronze-phase VO 2(B) thin film on a perovskite SrTiO 3 (STO) substrate. For this study, we observe an ultrathin (2–3 unit cells) interlayer best described as highly strained VO 2(B) nanodomains combined with an extra (Ti,V)O 2 layer on the TiO 2 terminated STO (001) surface. By forming a fully coherent interface with the STO substrate and a semi-coherent interface with the strain-free epitaxial VO 2(B) film above, the interfacial bi-layer enables the epitaxial connection of the two materials despitemore » their large symmetry and lattice mismatch.« less

(Full field) optical coherence tomography and applications

NASA Astrophysics Data System (ADS)

Buchroithner, Boris; Hannesschläger, Günther; Leiss-Holzinger, Elisabeth; Prylepa, Andrii; Heise, Bettina

2018-03-01

This paper illustrates specific features and use of optical coherence tomography (OCT) in the raster-scanning and in comparison in the full field version of this imaging technique. Cases for nondestructive testing are discussed alongside other application schemes. In particular monitoring time-dependent processes and probing of birefringent specimens are considered here. In the context of polymer testing birefringence mapping may often provide information about internal strain and stress states. Recent results obtained with conventional raster-scanning OCT systems, with (dual and single-shot) full field OCT configurations, and with polarization-sensitive versions of (full field) OCT are presented here.

Akkermansia glycaniphila sp. nov., an anaerobic mucin-degrading bacterium isolated from reticulated python faeces.

PubMed

Ouwerkerk, Janneke P; Aalvink, Steven; Belzer, Clara; de Vos, Willem M

2016-11-01

A Gram-stain-negative, non-motile, strictly anaerobic, oval-shaped, non-spore-forming bacterium (strain PytT) was isolated from reticulated python faeces. Strain PytT was capable of using mucin as sole carbon, energy and nitrogen source. Cells could grow singly, in pairs, and were also found to aggregate. Scanning electron microscopy revealed the presence of filamentous structures connecting individual bacterial cells. Strain PytT could grow on a limited number of single sugars, including N-acetylglucosamine, N-acetylgalactosamine, glucose, lactose and galactose, but only when a plentiful protein source was provided. Phylogenetic analysis based on 16S rRNA gene sequencing showed strain PytT to belong to the Verrucomicrobiae class I, family Akkermansiaceae, genus Akkermansia, with Akkermansia muciniphila MucT as the closest relative (94.4 % sequence similarity). DNA-DNA hybridization revealed low relatedness of 28.3 % with A. muciniphila MucT. The G+C content of DNA from strain PytT was 58.2 mol%. The average nucleotide identity (ANI) of the genome of strain PytT compared to the genome of strain MucT was 79.7 %. Chemotaxonomic data supported the affiliation of strain PytT to the genus Akkermansia. Based on phenotypic, phylogenetic and genetic characteristics, strain PytT represents a novel species of the genus Akkermansia, for which the name Akkermansia glycaniphila sp. nov. is proposed. The type strain is PytT (=DSM 100705T=CIP 110913T).

Impacts of Pantoea agglomerans strain and cation-modified clay minerals on the adsorption and biodegradation of phenanthrene.

PubMed

Tao, Kelin; Zhao, Song; Gao, Pin; Wang, Lijin; Jia, Hanzhong

2018-06-06

Interactions between microorganisms and minerals have the potential contribution to remove polycyclic aromatic hydrocarbons (PAHs) in model systems. In this study, phenanthrene (PHE) was used as a probe molecule to explore the potential adsorption and biotransformation processes in the presence of microorganisms and various reference clays, such as montmorillonite (M), kaolinite (K), and pyrophyllite (P). Equilibrium adsorption experiments and scanning electron microscopy (SEM) technique were used to investigate the sorption of Pantoea agglomerans strains on clay minerals saturated with cations (Na + and Fe 3+ ). The adsorption isotherms of PHE and Pantoea agglomerans strains on cation-modified clay minerals fitted to Langmuir equation, and their adsorbed amounts both followed the sequence: montmorillonite > kaolinite > pyrophyllite. For six types of cation-modified minerals, the behavior of PHE adsorbed and Pantoea agglomerans adhered onto mentioned minerals was in the order of Na(I)-M > Fe(Ⅲ)-M, Na(I)-K > Fe(Ⅲ)-K and Fe(Ⅲ)-P > Na(I)-P, respectively. The biodegradation results showed that cation-modified clay minerals could enhance the biodegradation of PHE, ascribing to their large specific surface area, and cation exchange capability, as well as the difference in zeta potential between minerals and Pantoea agglomerans strains. Comparison of biodegradation rates displayed that PHE was degraded the highest in the presence of Na-M (93.285%). In addition, the obtained results suggested that the adhesion of bacteria onto cation-exchanged clay minerals was beneficial to the biodegradation of PHE. Anthracen-9-ylmethanol and 3,4-dimethyl-2-(3-methylbutanoyl)benzoic acid were detected as the main intermediate compounds, which can be further biodegraded into small molecules. The overall results obtained in this study are of valuable significance for the understanding of the behavior of PHE in soil and associated environment. Copyright © 2018 Elsevier Inc. All rights reserved.

The FhaB/FhaC two-partner secretion system is involved in adhesion of Acinetobacter baumannii AbH12O-A2 strain

PubMed Central

Pérez, A.; Merino, M.; Rumbo-Feal, S.; Álvarez-Fraga, L.; Vallejo, J. A.; Beceiro, A.; Ohneck, E. J.; Mateos, J.; Fernández-Puente, P.; Actis, L. A.; Poza, M.; Bou, G.

2017-01-01

ABSTRACT Acinetobacter baumannii is a hospital-acquired pathogen that shows an extraordinary capacity to stay in the hospital environment. Adherence of the bacteria to eukaryotic cells or to abiotic surfaces is the first step for establishing an infection. The A. baumannii strain AbH12O-A2 showed an exceptional ability to adhere to A549 epithelial cells. The AbFhaB/FhaC 2-partner secretion (TPS) system involved in adhesion was discovered after the screening of the recently determined A. baumannii AbH12O-A2 strain genome (CP009534.1). The AbFhaB is a large exoprotein which transport to the bacterial surface is mediated by the AbFhaC protein. In the present study, the role of this TPS system in the AbH12O-A2 adherence phenotype was investigated. The functional inactivation of this 2-partner secretion system was addressed by analyzing the outer membrane vesicles (OMV) proteomic profile from the wild-type strain and its derivative mutant AbH12O-A2ΔfhaC demonstrating that AbFhaB is no longer detected in the absence of AbFhaC. Scanning electron microscopy (SEM) and adhesion experiments demonstrated that inactivation of the AbFhaB/FhaC system significantly decreases bacterial attachment to A549 alveolar epithelial cells. Moreover, it has been demonstrated that this 2-partner secretion system is involved in fibronectin-mediated adherence of the A. baumannii AbH12O-A2 isolate. Finally, we report that the AbFhaB/FhaC system is involved in virulence when tested using invertebrate and vertebrate hosts. These data suggest the potential role that this AbFhaB/FhaC secretion system could play in the pathobiology of A. baumannii. PMID:27858524

The FhaB/FhaC two-partner secretion system is involved in adhesion of Acinetobacter baumannii AbH12O-A2 strain.

PubMed

Pérez, A; Merino, M; Rumbo-Feal, S; Álvarez-Fraga, L; Vallejo, J A; Beceiro, A; Ohneck, E J; Mateos, J; Fernández-Puente, P; Actis, L A; Poza, M; Bou, G

2017-08-18

Acinetobacter baumannii is a hospital-acquired pathogen that shows an extraordinary capacity to stay in the hospital environment. Adherence of the bacteria to eukaryotic cells or to abiotic surfaces is the first step for establishing an infection. The A. baumannii strain AbH12O-A2 showed an exceptional ability to adhere to A549 epithelial cells. The AbFhaB/FhaC 2-partner secretion (TPS) system involved in adhesion was discovered after the screening of the recently determined A. baumannii AbH12O-A2 strain genome (CP009534.1). The AbFhaB is a large exoprotein which transport to the bacterial surface is mediated by the AbFhaC protein. In the present study, the role of this TPS system in the AbH12O-A2 adherence phenotype was investigated. The functional inactivation of this 2-partner secretion system was addressed by analyzing the outer membrane vesicles (OMV) proteomic profile from the wild-type strain and its derivative mutant AbH12O-A2ΔfhaC demonstrating that AbFhaB is no longer detected in the absence of AbFhaC. Scanning electron microscopy (SEM) and adhesion experiments demonstrated that inactivation of the AbFhaB/FhaC system significantly decreases bacterial attachment to A549 alveolar epithelial cells. Moreover, it has been demonstrated that this 2-partner secretion system is involved in fibronectin-mediated adherence of the A. baumannii AbH12O-A2 isolate. Finally, we report that the AbFhaB/FhaC system is involved in virulence when tested using invertebrate and vertebrate hosts. These data suggest the potential role that this AbFhaB/FhaC secretion system could play in the pathobiology of A. baumannii.

A non-contact measurement technique at the micro scale

NASA Astrophysics Data System (ADS)

Ghosh, Santaneel

During their production and normal use, electronic packages experience large temperature excursions, leading to high thermo-mechanical stress gradients that cause fatigue failure of the solder joints. In order to prevent premature failure and prolong the fatigue life of solder joints, there is a pressing need for the characterization of the solder, especially lead-free solder, at the micro-level (joint size). The characterization and modeling of solder behavior at the appropriate scale is a major issue. However, direct measurement techniques are not applicable to characterize the deformation response of solder joints because of their micro scale dimensions. Therefore, a non-contact measurement technique utilizing a Scanning Electron Microscope (SEM) in conjunction with Digital Image Correlation (DIC) has been developed. Validation was achieved by performing a four-point bending test in both an in-house optical system with DIC and inside the SEM. This non-contact measurement technique was then used to extract the stress-strain response of the solder. Mechanical tests were performed on solder joints that were created using the same type of solder balls used in the electronic industry and were representative of normal joint scales. The SEM-DIC technique has been proven to be applicable for the determining the stress-strain response of solder material at the micro-scale. This study resulted in a validated material characterization technique specifically designed for micro-scale material response. One of the main contributions of this study is that the method is a lot simpler and cheaper, yet highly effective, compared to the previous methods. This technique is also readily applicable to the measurement of the stress-strain response of any micro-scale specimen, such as other metals, polymers, etc. Also, the measured displacement field by obtained by DIC can be used as the base for calculating the strain field on the surface of a specimen.

Age-related changes in fear, sociality and pecking behaviours in two strains of laying hen.

PubMed

Hocking, P M; Channing, C E; Waddington, D; Jones, R B

2001-09-01

1. Two lines of commercial hybrid layers (Tetra and ISA Brown) were reared from hatch to 30 weeks of age in groups of 8. The objectives of the experiment were to evaluate the significance of the different selection practices involved in the development of the lines and to assess the potential association between selected behavioural states and the potential for feather damage and cannibalism. 2. Behavioural tests related to fear (tonic immobility, novel object, open field), sociality (runway, proximity in the home pen) and pecking (feather bunch and focal observations of inter-bird and environmental pecking) were conducted at 0 to 2, 5 to 7, 12 to 14, 19 to 21 and 29 to 31 weeks of age. Scan sampling of general behaviour was also conducted at these ages. 3. Underlying sociality was greater in Tetras than in ISA Brown hens. 4. There were no apparent overall strain differences in fearfulness although ISA Brown hens showed significantly longer tonic immobility fear reactions than Tetras at 31 weeks of age. 5. ISA Brown hens gave and received more gentle pecks than Tetra hens whereas preening was commoner among Tetras. There were no strain differences in the number of pecks at litter or food. 6. As birds aged they showed less avoidance of novel objects and Tetras, though not ISA Browns, showed progressively shorter tonic immobility responses. Birds of both strains spent less time resting, more foraging (pecking and scratching) and pecked more at the feather bunch at older ages. 7. Measures taken in the TI, open field, runway (social affiliation) and feather bunch tests were stable over time whereas focal observations of pecking at hens and the environment were not. 8. Factor Analysis showed that 3 factors defined by the novel object test, environmental pecking and pecking ata feather bunch explained most of the variation in the correlation matrix between summary measures for the 8 behavioural traits.

Covalent nitrogen doping in molecular beam epitaxy-grown and bulk WSe2

NASA Astrophysics Data System (ADS)

Khosravi, Ava; Addou, Rafik; Smyth, Christopher M.; Yue, Ruoyu; Cormier, Christopher R.; Kim, Jiyoung; Hinkle, Christopher L.; Wallace, Robert M.

2018-02-01

Covalent p-type doping of WSe2 thin films grown by molecular beam epitaxy and WSe2 exfoliated from bulk crystals is achieved via remote nitrogen plasma exposure. X-ray photoelectron and Raman spectroscopies indicate covalently bonded nitrogen in the WSe2 lattice as well as tunable nitrogen concentration with N2 plasma exposure time. Furthermore, nitrogen incorporation induces compressive strain on the WSe2 lattice after N2 plasma exposure. Finally, atomic force microscopy and scanning tunneling microscopy reveal that N2 plasma treatment needs to be carefully tuned to avoid any unwanted strain or surface damage.

Hydromechanics in dentine: role of dentinal tubules and hydrostatic pressure on mechanical stress-strain distribution.

PubMed

Kishen, A; Vedantam, S

2007-10-01

This investigation is to understand the role of free water in the dentinal tubules on the mechanical integrity of bulk dentine. Three different experiments were conducted in this study. In experiment 1, three-dimensional models of dentine with gradient elastic modulus, homogenous elastic modulus, and with and without hydrostatic pressure were simulated using the finite element method. Static compressive loads of 15, 50 and 100 N were applied and the distribution of the principal stresses, von Mises stresses, and strains in loading direction were determined. In experiment 2, experimental compression testing of fully hydrated and partially dehydrated dentine (21 degrees C for 72 h) was conducted using a Universal testing machine. In experiment 3, Fourier transform infrared spectroscopic analysis of hydrated and partially dehydrated dentine was carried out. The finite element analysis revealed that the dentine model with simulated hydrostatic pressure displayed residual tensile stresses and strains in the inner region adjacent to the root canal. When external compressive loads were applied to the model, the residual stresses and strains counteracted the applied loads. Similarly the hydrated specimens subjected to experimental compression loads showed greater toughness when compared to the partially dehydrated specimens. The stress at fracture was significantly higher in partially dehydrated specimens (p=0.014), while the strain at fracture was significantly higher in hydrated dentine specimens (p=0.037). These experiments highlighted the distinct role of free water in the dentinal tubules and hydrostatic pressure on the stress-strain distribution within the bulk dentine.

Biosorption of multi-heavy metals by coral associated phosphate solubilising bacteria Cronobacter muytjensii KSCAS2.

PubMed

Saranya, Kailasam; Sundaramanickam, Arumugam; Shekhar, Sudhanshu; Meena, Moorthy; Sathishkumar, Rengasamy Subramaniyan; Balasubramanian, Thangavel

2018-06-02

This paper examines the potential detoxification efficiency of heavy metals by phosphate solubilising bacteria (PSB) that were isolated from coral, sea grass and mangrove environment. Initially, four potential bacterial isolates were selected based on their phosphate solubilisation index from 42 strains and were used for the metal tolerance test. Among the four isolates, KSCAS2 exhibited maximum tolerance to heavy metals and the phenotype indicated the production of extra polymeric substances. In a multi-heavy metal experimental setup at two concentrations (100 and 200 mg L -l ), it has been demonstrated that the bacteria have extracellularly sequestered metal ions in amorphous deposits and this has been confirmed by scanning electron microscopy. In experiments with a 100 mg L -1 initial metal concentration, the percentages of metal removal by bacteria were 55.23% of Cd, 72.45% of Cr, 76.51% of Cu and 61.51% of Zn, respectively. In subsequent experiments, when the metal concentration was increased up to 200 mg L -l , the metal removal capacity decreased as follows: 44.62%, 63.1%, 67% and 52.80% for Cd, Cr, Cu and Zn, respectively. In addition, the biosorption of heavy metals was confirmed by the Fourier transform infrared Spectroscopy (FT-IR) and scanning electron microscopy (SEM) analysis. The heavy metal concentrations in a broth culture were analysed by inductively coupled plasma-optical emission spectroscopy (ICP-OES). The study suggests that PSB Cronobacter muytjensii KSCAS2 can efficiently remove the heavy metals and these bacteria could be used for the metal removal from the agricultural soils. Copyright © 2018. Published by Elsevier Ltd.

Combining Digital Image Correlation and Acoustic Emission for Monitoring of the Strain Distribution until Yielding During Compression of Bovine Cancellous Bone

NASA Astrophysics Data System (ADS)

Tsirigotis, Athanasios; Deligianni, Despoina D.

2017-12-01

In this work, the surface heterogeneity in mechanical compressive strain of cancellous bone was investigated with digital image correlation (DIC). Moreover, the onset and progression of failure was studied by acoustic emission (AE). Cubic cancellous bone specimens, with side of 15 mm, were obtained from bovine femur and kept frozen at -20ºC until testing. Specimen strain was analyzed by measuring the change of distance between the platens (crosshead) and via an optical method, by following the strain evolution with a camera. Simultaneously, AE monitoring was performed. The experiments showed that compressive Young’s modulus determined by crosshead strain is underestimated at 23% in comparison to optically determined strain. However, surface strain fields defined by DIC displayed steep strain gradients, which can be attributed to cancellous bone porosity and inhomogeneity. The cumulative number of events for the total AE activity recorded from the sensors showed that the activity started at a mean load level of 36% of the maximum load and indicated the initiation of micro-cracking phenomena. Further experiments, determining 3D strain with μCT apart from surface strain, are necessary to clarify the issue of strain inhomogeneity in cancellous bone.

Effects of selected pectinolytic bacterial strains on water-retting of hemp and fibre properties.

PubMed

Di Candilo, M; Bonatti, P M; Guidetti, C; Focher, B; Grippo, C; Tamburini, E; Mastromei, G

2010-01-01

To study the effect of selected bacterial strains on hemp water-retting and properties of retted fibre. The trials were performed in laboratory tanks. The traditional water-retting process, without inoculum addition, was compared to a process modified by inoculating water tanks with two selected pectinolytic bacteria: the anaerobic strain Clostridium sp. L1/6 and the aerobic strain Bacillus sp. ROO40B. Six different incubation times were compared. Half the fibre obtained from each tank was combed. Micromorphological analyses were performed by scanning electron microscopy on uncombed and combed fibres. Moreover, organoleptic and chemical analyses of uncombed fibres were performed. The inoculum, besides speeding up the process, significantly improved the fibre quality. The fibre was not damaged by mechanical hackling, thanks to the good retting level obtained by the addition of selected strains, differently to what happened with the traditionally retted fibre. The best fibre quality was obtained after 3-4 days of retting with the addition of the bacterial inoculum. Retting is the major limitation to an efficient production of high-quality hemp fibres. The water-retting process and fibre quality were substantially improved by simultaneously inoculating water tanks with two selected pectinolytic strains.

Evidence for a plant-associated natural habitat for Cronobacter spp.

PubMed

Schmid, Michael; Iversen, Carol; Gontia, Iti; Stephan, Roger; Hofmann, Andreas; Hartmann, Anton; Jha, Bhavanath; Eberl, Leo; Riedel, Kathrin; Lehner, Angelika

2009-10-01

Cronobacter (Enterobacter sakazakii) species are responsible for rare cases of necrotising enterocolitis and bacteraemia in infants, as well as cases of meningitis with high case fatality rates in neonates and immunocompromised infants. Some physiological features, such as the production of a yellow pigment, the formation of a gum-like extracellular polysaccharide and the ability to persist in a desiccated state, suggest an environmental niche for these organisms. To date, the natural habitat of Cronobacter spp. remains unknown. In this report, the isolation and characterisation of two Cronobacter sakazakii strains from plant roots is described. Also, the root colonisation behaviour of Cronobacter strains originating from clinical and plant sources is assessed. The nine strains investigated showed features often found in plant-associated and rhizosphere microorganisms, including solubilisation of mineral phosphate and production of indole acetic acid. Siderophore production was observed for all except one strain. In addition, the capability to endophytically colonise tomato and maize roots was demonstrated for several strains, either by fluorescence in situ hybridisation, using fluorescently labelled oligonucleotide probes, or by using strains tagged with green fluorescent protein and confocal laser scanning microscopy. The results provide evidence that plants may be the natural habitat of Cronobacter spp.

Biofilm formation by Staphylococcus hominis strains isolated from human clinical specimens.

PubMed

Szczuka, Ewa; Telega, Kinga; Kaznowski, Adam

2015-01-01

Staphylococcus hominis is the third species of coagulase-negative staphylococci (CoNS) most frequently isolated from specimens of patients with hospital-acquired infections. Many infections caused by CoNS appeared to be associated with biofilms. Nevertheless, the knowledge of the ability of S. hominis to form a biofilm is limited. The aim of this study was to analyze the formation of the biofilm by 56 S. hominis strains isolated from clinical cases. The biofilm three-dimensional structure was reconstructed by confocal laser scanning microscopy. We found that most of S. hominis strains carried icaADBC genes encoding polysaccharide intercellular adhesin (PIA), which plays a crucial role in the formation of biofilms in staphylococci strains. However, only a half of the ica-positive strains had an ability to form a biofilm in vitro. In this study, we also accessed the sensitivity of biofilms of S. hominis strains to sodium metaperiodate, proteinase K and DNase. We found that polysaccharides and proteins are the major components of the extracellular matrix of the biofilm formed by S. hominis. DNase did not have a significant effect on biofilms, which suggested that nucleic acid plays a minor role in the mature biofilm.

Direct Three-Dimensional Myocardial Strain Tensor Quantification and Tracking using zHARP★

PubMed Central

Abd-Elmoniem, Khaled Z.; Stuber, Matthias; Prince, Jerry L.

2008-01-01

Images of myocardial strain can be used to diagnose heart disease, plan and monitor treatment, and to learn about cardiac structure and function. Three-dimensional (3-D) strain is typically quantified using many magnetic resonance (MR) images obtained in two or three orthogonal planes. Problems with this approach include long scan times, image misregistration, and through-plane motion. This article presents a novel method for calculating cardiac 3-D strain using a stack of two or more images acquired in only one orientation. The zHARP pulse sequence encodes in-plane motion using MR tagging and out-of-plane motion using phase encoding, and has been previously shown to be capable of computing 3D displacement within a single image plane. Here, data from two adjacent image planes are combined to yield a 3-D strain tensor at each pixel; stacks of zHARP images can be used to derive stacked arrays of 3D strain tensors without imaging multiple orientations and without numerical interpolation. The performance and accuracy of the method is demonstrated in-vitro on a phantom and in-vivo in four healthy adult human subjects. PMID:18511332

Tuning the Pseudospin Polarization of Graphene by a Pseudomagnetic Field

NASA Astrophysics Data System (ADS)

Georgi, Alexander; Nemes-Incze, Peter; Carrillo-Bastos, Ramon; Faria, Daiara; Viola Kusminskiy, Silvia; Zhai, Dawei; Schneider, Martin; Subramaniam, Dinesh; Mashoff, Torge; Freitag, Nils M.; Liebmann, Marcus; Pratzer, Marco; Wirtz, Ludger; Woods, Colin R.; Gorbachev, Roman V.; Cao, Yang; Novoselov, Kostya S.; Sandler, Nancy; Morgenstern, Markus

2017-04-01

One of the intriguing characteristics of honeycomb lattices is the appearance of a pseudo-magnetic field as a result of mechanical deformation. In the case of graphene, the Landau quantization resulting from this pseudo-magnetic field has been measured using scanning tunneling microscopy. Here we show that a signature of the pseudo-magnetic field is a local sublattice symmetry breaking observable as a redistribution of the local density of states. This can be interpreted as a polarization of graphene's pseudospin due to a strain induced pseudo-magnetic field, in analogy to the alignment of a real spin in a magnetic field. We reveal this sublattice symmetry breaking by tunably straining graphene using the tip of a scanning tunneling microscope. The tip locally lifts the graphene membrane from a SiO$_2$ support, as visible by an increased slope of the $I(z)$ curves. The amount of lifting is consistent with molecular dynamics calculations, which reveal a deformed graphene area under the tip in the shape of a Gaussian. The pseudo-magnetic field induced by the deformation becomes visible as a sublattice symmetry breaking which scales with the lifting height of the strained deformation and therefore with the pseudo-magnetic field strength. Its magnitude is quantitatively reproduced by analytic and tight-binding models, revealing fields of 1000 T. These results might be the starting point for an effective THz valley filter, as a basic element of valleytronics.

Isolation and identification of Aeromonas caviae strain KS-1 as TBTC- and lead-resistant estuarine bacteria.

PubMed

Shamim, Kashif; Naik, Milind Mohan; Pandey, Anju; Dubey, Santosh Kumar

2013-06-01

Tributyltin chloride (TBTC)- and lead-resistant estuarine bacterium from Mandovi estuary, Goa, India was isolated and identified as Aeromonas caviae strain KS-1 based on biochemical characteristics and FAME analysis. It tolerates TBTC and lead up to 1.0 and 1.4 mM, respectively, in the minimal salt medium (MSM) supplemented with 0.4 % glucose. Scanning electron microscopy clearly revealed a unique morphological pattern in the form of long inter-connected chains of bacterial cells on exposure to 1 mM TBTC, whereas cells remained unaltered in presence of 1.4 mM Pb(NO₃)₂ but significant biosorption of lead (8 %) on the cell surface of this isolate was clearly revealed by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. SDS-PAGE analysis of whole-cell proteins of this lead-resistant isolate interestingly demonstrated three lead-induced proteins with molecular mass of 15.7, 16.9 and 32.4 kDa, respectively, when bacterial cells were grown under the stress of 1.4 mM Pb (NO₃)₂. This clearly demonstrated their possible involvement exclusively in lead resistance. A. caviae strain KS-1 also showed tolerance to several other heavy metals, viz. zinc, cadmium, copper and mercury. Therefore, we can employ this TBTC and lead-resistant bacterial isolate for lead bioremediation and also for biomonitoring TBTC from lead and TBTC contaminated environment.

A investigation on unixial and quasi-biaxial tensile mechanical properties of aging HTPB propellant under dynamic loading at low temperature

NASA Astrophysics Data System (ADS)

Duan, Leiguang; Wang, Guang; Zhang, Guoxing; Sun, Xinya; Shang, Hehao

2018-06-01

In order to study the uniaxial and quasi-biaxial mechanical properties of aging solid propellants under low temperature and high strain rate, stress-strain curves and tensile fracture surfaces of HTPB propellant were obtained in a wide range of temperature (-30,25 °C) and strain rates (0.4,4.0 and 14.29 s-1), respectively, by means of uniaxial and biaxial tensile tests and electron microscopy scanning on the fracture cross section. The results indicate that the quasi-biaxial tensile mechanical properties of aging HTPB propellant is same as the uniaxial tensile mechanical properties influenced distinctly by temperature and strain rate. With decreasing temperature and increasing strain rate, the mechanical properties gradually strengthen. The damage for HTPB propellant changes from "dehumidification" to grain fracture. The initial elastic modulus E and maximum tensile stress σ of the uniaxial and biaxial tensile increase gradually with decreasing temperature and increasing strain rate, and well present linear-log function relation with strain rate. The ratio of quasi-biaxial and uniaxial stretching under different loading conditions was obtained so that the researchers could predict the quasi-biaxial tensile mechanical properties of the propellant based on the uniaxial test data.

Screening of biofilm formation by beneficial vaginal lactobacilli and influence of culture media components.

PubMed

Terraf, M C Leccese; Juárez Tomás, M S; Nader-Macías, M E F; Silva, C

2012-12-01

To assess the ability of vaginal lactobacilli to form biofilm under different culture conditions and to determine the relationship between their growth and the capability of biofilm formation by selected strains. Fifteen Lactobacillus strains from human vagina were tested for biofilm formation by crystal violet staining. Only Lactobacillus rhamnosus Centro de Referencia para Lactobacilos Culture Collection (CRL) 1332, Lact. reuteri CRL 1324 and Lact. delbrueckii CRL 1510 were able to grow and form biofilm in culture media without Tween 80. However, Lact. gasseri CRL 1263 (a non-biofilm-forming strain) did not grow in these media. Scanning electron microscopy showed that Lact. rhamnosus CRL 1332 and Lact. reuteri CRL 1324 formed a highly structured biofilm, but only Lact. reuteri CRL 1324 showed a high amount of extracellular material in medium without Tween. Biofilm formation was significantly influenced by the strain, culture medium, inoculum concentration, microbial growth and chemical nature of the support used for the assay. The results allow the selection of biofilm-forming vaginal Lactobacillus strains and the conditions and factors that affect this phenomenon. © 2012 The Society for Applied Microbiology.

[Improvement of butanol production by Escherichia coli via Tn5 transposon mediated mutagenesis].

PubMed

Lin, Zhao; Dong, Hongjun; Li, Yin

2015-12-01

For engineering an efficient butanol-producing Escherichia coli strain, many efforts have been paid on the known genes or pathways based on current knowledge. However, many genes in the genome could also contribute to butanol production in an unexpected way. In this work, we used Tn5 transposon to construct a mutant library including 1 196 strains in a previously engineered butanol-producing E. coli strain. To screen the strains with improved titer of butanol production, we developed a high-throughput method for pyruvate detection based on dinitrophenylhydrazine reaction using 96-well microplate reader, because pyruvate is the precursor of butanol and its concentration is inversely correlated with butanol in the fermentation broth. Using this method, we successfully screened three mutants with increased butanol titer. The insertion sites of Tn5 transposon was in the ORFs of pykA, tdk, and cadC by inverse PCR and sequencing. These found genes would be efficient targets for further strain improvement. And the genome scanning strategy described here will be helpful for other microbial cell factory construction.

Simultaneous Myocardial Strain and Dark-Blood Perfusion Imaging Using a Displacement-Encoded MRI Pulse Sequence

PubMed Central

Le, Yuan; Stein, Ashley; Berry, Colin; Kellman, Peter; Bennett, Eric E.; Taylor, Joni; Lucas, Katherine; Kopace, Rael; Chefd’Hotel, Christophe; Lorenz, Christine H.; Croisille, Pierre; Wen, Han

2010-01-01

The purpose of this study is to develop and evaluate a displacement-encoded pulse sequence for simultaneous perfusion and strain imaging. Displacement-encoded images in 2–3 myocardial slices were repeatedly acquired using a single shot pulse sequence for 3 to 4 minutes, which covers a bolus infusion of Gd. The magnitudes of the images were T1 weighted and provided quantitative measures of perfusion, while the phase maps yielded strain measurements. In an acute coronary occlusion swine protocol (n=9), segmental perfusion measurements were validated against microsphere reference standard with a linear regression (slope 0.986, R2 = 0.765, Bland-Altman standard deviation = 0.15 ml/min/g). In a group of ST-elevation myocardial infarction(STEMI) patients (n=11), the scan success rate was 76%. Short-term contrast washout rate and perfusion are highly correlated (R2=0.72), and the pixel-wise relationship between circumferential strain and perfusion was better described with a sigmoidal Hill curve than linear functions. This study demonstrates the feasibility of measuring strain and perfusion from a single set of images. PMID:20544714

Application of metal hydride paper to simple pressure generator for use in soft actuator systems.

PubMed

Ino, Shuichi; Sakaki, Kouji; Hosono, Minako; Doi, Kouki; Shimada, Shigenobu; Chikai, Manabu

2015-01-01

Metal hydride (MH) actuators have a simple structure and a number of features that make them attractive for use in rehabilitation engineering and assistive technology. The MH actuator provides a high power-to-weight ratio, high-strain actuation, human-compatible softness, and noiseless operation, while being environmentally benign. On the other hand, there remain technical challenges to be overcome to improve the MH actuator regarding its speed of operation and energy efficiency, given the low heat conductivity of the MH powder that is used as the pressure generator for soft actuation. To overcome the issues of low heat conductivity and the handling of MH powder, we developed an MH paper, which is a special paper incorporating MH powder and carbon fiber, for use as a new pressure-generating element for a soft MH actuator system. In addition, the basic properties and structure of the proposed MH paper were investigated through scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and several thermodynamic experiments. The results of these experiments showed that the hydrogen absorption and desorption rates of the MH paper were significantly higher than those of the MH powder around room temperature.

OPERA experiment and its releted emulsion techniques

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

Ariga, Akitaka

2008-02-21

The OPERA experiment is designed to clarify neutrino oscillation by detecting appearance of {nu}{sub {tau}} in pure {nu}{sub {mu}} beam through a long baseline method (CNGS beam from cern to the Gran Sasso laboratory). The key technique is the use of emulsion films and their scanning. We developed a new high speed scanning system with speed of 50 cm{sup 2}/h and it was successfully demonstrated in 2006 CNGS commissioning. The new scanning system is not only meant for the OPERA experiment, but it has large potential of applications. For example, measurement of {nu}{sub e} with strong separation power against {pi}{supmore » 0}. Or a compact emulsion spectrometer for future neutrino experiments.« less

Released products of pathogenic bacteria stimulate biofilm formation by Escherichia coli K-12 strains.

PubMed

Vacheva, Anna; Ivanova, Radka; Paunova-Krasteva, Tsvetelina; Stoitsova, Stoyanka

2012-06-01

It has recently been shown that pathogens with a limited capacity for sessile growth (like some Escherichia coli O157 strains) can benefit from the presence of other bacteria and form mixed biofilms with companion strains. This study addresses the question whether pathogens may influence attached growth of E. coli non-pathogenic strains via secreted factors. We compared the biofilm-modulating effects of sterile stationary-phase culture media of a biofilm non-producing strain of E. coli O157:H, a laboratory biofilm-producing E. coli K-12 strain and a biofilm-forming strain of the pathogen Yersina enterocolitica O:3. Sessile growth was monitored as biomass (crystal violet assay), exopolysaccharide (ELLA) and morphology (scanning electron and confocal laser microscopy). With two of the E. coli K-12 strains stimulation of biofilm formation by all supernatants was achieved, but only the pathogens' secreted products induced biomass increase in some 'biofilm-deficient' K-12 strains. Lectin-peroxidase labeling indicated changes in colanic acid and poly-N-acetylglucosamine amounts in extracellular matrices. The contribution of indole, protein and polysaccharide to the biofilm-modulating activities of the supernatants was compared. Indole, in concentrations equal to those established in the supernatants, suppressed sessile growth in one K-12 strain. Proteinase K significantly reduced the stimulatory effects of all supernatants, indicating a prominent role of protein/peptide factor(s) in biofilm promotion. The amount of released polysaccharides (rPS) in the supernatants was quantitated then comparable quantities of isolated rPS were applied during biofilm growth. The three rPS had notable strain-specific effects with regard to both the strain-source of the rPS and the E. coli K-12 target strain.

Factors associated with occupational strain among Chinese teachers: a cross-sectional study.

PubMed

Yang, X; Wang, L; Ge, C; Hu, B; Chi, T

2011-02-01

With the reform of the education system in China, teachers are suffering from more occupational strain, which is believed to impair their working state indirectly and affect their health. This study assessed occupational strain and explored the related factors among Chinese teachers. Cross-sectional with cluster sampling. The study population was composed of 3570 school teachers working in 64 primary and middle schools in Heping District in Shenyang, China. Data were collected using a self-administered questionnaire (the Chinese version of the Occupational Stress Inventory scale). Multivariate linear regression analyses were performed to study the factors related to occupational strain. The average score on the Personal Strain Questionnaire (PSQ) for the whole study population was 106.5 (107.5 in men and 106.3 in women). Teachers with chronic disease, a greater number of days of sick leave, recent experience of a stressful life event and divorced/separated/widowed status tended to suffer greater strain than their peers. Regression analyses showed that the PSQ score was significantly associated with role overload, role boundary, responsibility and physical environment, and inversely associated with recreation and rational coping. The most crucial predictors of occupational strain were chronic disease, days of sick leave, recent experience of a stressful life event and marital status. Being a class teacher was the strongest indicator of interpersonal strain. Self-care was associated with vocational strain and psychological strain, and inversely associated with physical strain. Most teachers in this study experienced a high degree of occupational strain. Chronic disease, days of sick leave, recent experience of a stressful life event and divorced/separated/widowed status played prominent roles in occupational strain. In addition, role overload, role boundary, responsibility and physical environment induce occupational strain, while recreation and rational coping have a positive effect on occupational strain. Interventions such as proper management of chronic diseases and establishment of a balanced work-family life are crucial to reduce occupational strain. Recreation and training in coping abilities are needed to enhance positive working environments and attenuate the occupational strain imposed on teachers. Copyright © 2010 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.

Microstructure characterization of Al matrix composite reinforced with Ti-6Al-4V meshes after compression by scanning electron microscope and transmission electron microscope.

PubMed

Guo, Q; Sun, D L; Han, X L; Cheng, S R; Chen, G Q; Jiang, L T; Wu, G H

2012-02-01

Compressive properties of Al matrix composite reinforced with Ti-6Al-4V meshes (TC4(m)/5A06 Al composite) under the strain rates of 10(-3)S(-1) and 1S(-1) at different temperature were measured and microstructure of composites after compression was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). Compressive strength decreased with the test temperature increased and the strain-rate sensitivity (R) of composite increased with the increasing temperature. SEM observations showed that grains of Al matrix were elongated severely along 45° direction (angle between axis direction and fracture surface) and TC4 fibres were sheared into several parts in composite compressed under the strain rate of 10(-3)S(-1) at 25°C and 250°C. Besides, amounts of cracks were produced at the interfacial layer between TC4 fibre and Al matrix and in (Fe, Mn)Al(6) phases. With the compressive temperature increasing to 400°C, there was no damage at the interfacial layer between TC4 fibre and Al matrix and in (Fe, Mn)Al(6) phases, while equiaxed recrystal grains with sizes about 10 μm at the original grain boundaries of Al matrix were observed. However, interface separation of TC4 fibres and Al matrix occurred in composite compressed under the strain rate of 1S(-1) at 250°C and 400°C. With the compressive temperature increasing from 25°C to 100°C under the strain rate of 10(-3) S(-1), TEM microstructure in Al matrix exhibited high density dislocations and slipping bands (25°C), polygonized dislocations and dynamic recovery (100°C), equiaxed recrystals with sizes below 500 μm (250°C) and growth of equiaxed recrystals (400°C), respectively. Copyright © 2011 Elsevier Ltd. All rights reserved.

The effect of a scanning flat fold mirror on a cosmic microwave background B-mode experiment.

PubMed

Grainger, William F; North, Chris E; Ade, Peter A R

2011-06-01

We investigate the possibility of using a flat-fold beam steering mirror for a cosmic microwave background B-mode experiment. An aluminium flat-fold mirror is found to add ∼0.075% polarization, which varies in a scan synchronous way. Time-domain simulations of a realistic scanning pattern are performed, and the effect on the power-spectrum illustrated, and a possible method of correction applied. © 2011 American Institute of Physics

Change in coccolith morphology by responding to temperature and salinity in coccolithophore Emiliania huxleyi (Haptophyta) isolated from the Bering and Chukchi Seas

NASA Astrophysics Data System (ADS)

Saruwatari, K.; Satoh, M.; Harada, N.; Suzuki, I.; Shiraiwa, Y.

2015-11-01

Strains of the coccolithophore Emiliania huxleyi (Haptophyta) collected from the subarctic North Pacific and Arctic Oceans during the R/V MIRAI cruise in 2010 (MR10-05) were established as clone cultures and have been maintained in the laboratory at 15 °C and 32 ‰ salinity. To study the physiological responses of coccolith formation to changes in temperature and salinity, growth experiments and morphometric investigations were performed on two strains of MR57N isolated from the northern Bering Sea (56°58' N, 167°11' W) and MR70N at the Chukchi Sea (69°99' N, 168° W). This is the first report of a detailed morphometric and morphological investigation of Arctic Ocean coccolithophore strains. The specific growth rates at the logarithmic growth phases in both strains markedly increased as temperature was elevated from 5 to 20 °C, although coccolith productivity (the percentage of calcified cells) was similar at 10-20 % at all temperatures. On the other hand, the specific growth rate of strain MR70N was affected less by changes in salinity in the range 26-35 ‰, but the proportion of calcified cells decreased at high and low salinities. According to scanning electron microscopy (SEM) observations, coccolith morphotypes can be categorized into Type B/C on the basis of their biometrical parameters, such as length of the distal shield (LDS), length of the inner central area (LICA), and the thickness of distal shield elements. The central area elements of coccoliths varied from grilled type to closed type when temperature was increased or salinity was decreased, and coccolith size decreased simultaneously. Coccolithophore cell size also decreased with increasing temperature, although the variation in cell size was slightly greater at the lower salinity level. This indicates that subarctic and arctic coccolithophore strains can survive in a wide range of seawater temperatures and at lower salinities due to their marked morphometric adaptation ability. Because all coccolith biometric parameters followed the scaling law, the decrease in coccolith size was caused simply by the reduced calcification. Taken together, our results suggest that calcification productivity may be used to predict future oceanic environmental conditions in the Polar Regions.

The effect of vaccination with the PAV-250 strain classical swine fever (CSF) virus on the airborne transmission of CSF virus.

PubMed

Gonzalez, C; Pijoan, C; Ciprian, A; Correa, P; Mendoza, S

2001-09-01

The airborne transmission of Classical Swine Fever (CSF) virus to susceptible pigs, as well as the effect of vaccination with the CSF virus PAV-250 strain was investigated on this mode of transmission. Experiment I: four pigs were inoculated with the ALD CSFV strain (10(4.3) 50% TCID) by the intramuscular route, and at the onset of fever, they were introduced into an enclosed chamber. At the end of the experiment surviving pigs were sedated, anesthetized and euthanatized. Experiment II: four pigs were previously vaccinated with the CSF virus PAV-250 strain, and at 14 days post-vaccination they were challenged with the CSF virus ALD strain. In both experiments, four susceptible pigs were exposed to infectious aerosols by placing them in a chamber connected by a duct to the adjacent pen containing the infected animals and were kept there for 86 hs. In Experiment I, pigs exposed to contaminated air died as a result of infection with CSF virus on days 14, 21 and 28 post-inhalation. These four pigs seroconverted from day 12 post-inhalation. CSF virus was isolated from these animals, and the fluorescent antibody test on tonsils was positive. In Experiment II, a vaccinated pig exposed to contaminated air did not seroconvert, nor was CSF virus isolated from lymphoid tissues. However, mild fluorescence in tonsil sections from these pigs was observed. In conclusion, CSF virus was shown to be transmitted by air at a distance of 1 m to susceptible pigs. Vaccination with the PAV-250 CSF virus strain protected the pigs from clinical disease under the same conditions.

Physically-based strength model of tantalum incorporating effects of temperature, strain rate and pressure

DOE PAGES

Lim, Hojun; Battaile, Corbett C.; Brown, Justin L.; ...

2016-06-14

In this work, we develop a tantalum strength model that incorporates e ects of temperature, strain rate and pressure. Dislocation kink-pair theory is used to incorporate temperature and strain rate e ects while the pressure dependent yield is obtained through the pressure dependent shear modulus. Material constants used in the model are parameterized from tantalum single crystal tests and polycrystalline ramp compression experiments. It is shown that the proposed strength model agrees well with the temperature and strain rate dependent yield obtained from polycrystalline tantalum experiments. Furthermore, the model accurately reproduces the pressure dependent yield stresses up to 250 GPa.more » The proposed strength model is then used to conduct simulations of a Taylor cylinder impact test and validated with experiments. This approach provides a physically-based multi-scale strength model that is able to predict the plastic deformation of polycrystalline tantalum through a wide range of temperature, strain and pressure regimes.« less

Inferring Strength of Tantalum from Hydrodynamic Instability Recovery Experiments

NASA Astrophysics Data System (ADS)

Sternberger, Z.; Maddox, B.; Opachich, Y.; Wehrenberg, C.; Kraus, R.; Remington, B.; Randall, G.; Farrell, M.; Ravichandran, G.

2018-05-01

Hydrodynamic instability experiments allow access to material properties at extreme conditions, where strain rates exceed 105 s-1 and pressures reach 100 GPa. Current hydrodynamic instability experimental methods require in-flight radiography to image the instability growth at high pressure and high strain rate, limiting the facilities where these experiments can be performed. An alternate approach, recovering the sample after loading, allows measurement of the instability growth with profilometry. Tantalum samples were manufactured with different 2D and 3D initial perturbation patterns and dynamically compressed by a blast wave generated by laser ablation. The samples were recovered from peak pressures between 30 and 120 GPa and strain rates on the order of 107 s-1, providing a record of the growth of the perturbations due to hydrodynamic instability. These records are useful validation points for hydrocode simulations using models of material strength at high strain rate. Recovered tantalum samples were analyzed, providing an estimate of the strength of the material at high pressure and strain rate.

Effects of polyaluminum chloride and lanthanum-modified bentonite on the growth rates of three Cylindrospermopsis raciborskii strains

PubMed Central

van Oosterhout, Frank; Becker, Vanessa; Attayde, José Luiz; Lürling, Miquel

2018-01-01

In tropical and subtropical lakes, eutrophication often leads to nuisance blooms of Cylindrospermopsis raciborskii. In laboratory experiments, we tested the combined effects of flocculant polyaluminum chloride (PAC) and lanthanum-modified bentonite (LMB) on the sinking and growth rates of three C. raciborskii strains. We tested the hypothesis that the combination of PAC and LMB would (1) effectively sink C. raciborskii in a test tube experiment and (2) impair C. raciborskii growth, irrespective of the biomass of the inoculum (bloom) and the strain in the growth experiment. We tested the recommended (LMB1) and a three-times higher dose of LMB (LMB3). The combined addition of PAC and LMB enhanced the sedimentation of all C. raciborskii strains. Moreover, both the PAC and LMB doses decreased the phosphate concentration. PAC and LMB1 decreased the growth rate of all strains, but the efficacy depended on the biomass and strain. The combined addition of PAC and LMB3 inhibited the growth of all strains independently of the biomass and strain. We conclude that a low dose of PAC in combination with the recommended dose of LMB decreases C. raciborskii blooms and that the efficiency of the technique depends on the biomass of the bloom. A higher dose of LMB is needed to obtain a more efficient control of C. raciborskii blooms. PMID:29614118

Effects of polyaluminum chloride and lanthanum-modified bentonite on the growth rates of three Cylindrospermopsis raciborskii strains.

PubMed

Araújo, Fabiana; van Oosterhout, Frank; Becker, Vanessa; Attayde, José Luiz; Lürling, Miquel

2018-01-01

In tropical and subtropical lakes, eutrophication often leads to nuisance blooms of Cylindrospermopsis raciborskii. In laboratory experiments, we tested the combined effects of flocculant polyaluminum chloride (PAC) and lanthanum-modified bentonite (LMB) on the sinking and growth rates of three C. raciborskii strains. We tested the hypothesis that the combination of PAC and LMB would (1) effectively sink C. raciborskii in a test tube experiment and (2) impair C. raciborskii growth, irrespective of the biomass of the inoculum (bloom) and the strain in the growth experiment. We tested the recommended (LMB1) and a three-times higher dose of LMB (LMB3). The combined addition of PAC and LMB enhanced the sedimentation of all C. raciborskii strains. Moreover, both the PAC and LMB doses decreased the phosphate concentration. PAC and LMB1 decreased the growth rate of all strains, but the efficacy depended on the biomass and strain. The combined addition of PAC and LMB3 inhibited the growth of all strains independently of the biomass and strain. We conclude that a low dose of PAC in combination with the recommended dose of LMB decreases C. raciborskii blooms and that the efficiency of the technique depends on the biomass of the bloom. A higher dose of LMB is needed to obtain a more efficient control of C. raciborskii blooms.

Heterogeneity effects in visual search predicted from the group scanning model.

PubMed

Macquistan, A D

1994-12-01

The group scanning model of feature integration theory (Treisman & Gormican, 1988) suggests that subjects search visual displays serially by groups, but process items within each group in parallel. The size of these groups is determined by the discriminability of the targets in the background of distractors. When the target is poorly discriminable, the size of the scanned group will be small, and search will be slow. The model predicts that group size will be smallest when targets of an intermediate value on a perceptual dimension are presented in a heterogeneous background of distractors that have higher and lower values on the same dimension. Experiment 1 demonstrates this effect. Experiment 2 controls for a possible confound of decision complexity in Experiment 1. For simple feature targets, the group scanning model provides a good account of the visual search process.

Quantification of atrial dynamics using cardiovascular magnetic resonance: inter-study reproducibility.

PubMed

Kowallick, Johannes T; Morton, Geraint; Lamata, Pablo; Jogiya, Roy; Kutty, Shelby; Hasenfuß, Gerd; Lotz, Joachim; Nagel, Eike; Chiribiri, Amedeo; Schuster, Andreas

2015-05-17

Cardiovascular magnetic resonance (CMR) offers quantification of phasic atrial functions based on volumetric assessment and more recently, on CMR feature tracking (CMR-FT) quantitative strain and strain rate (SR) deformation imaging. Inter-study reproducibility is a key requirement for longitudinal studies but has not been defined for CMR-based quantification of left atrial (LA) and right atrial (RA) dynamics. Long-axis 2- and 4-chamber cine images were acquired at 9:00 (Exam A), 9:30 (Exam B) and 14:00 (Exam C) in 16 healthy volunteers. LA and RA reservoir, conduit and contractile booster pump functions were quantified by volumetric indexes as derived from fractional volume changes and by strain and SR as derived from CMR-FT. Exam A and B were compared to assess the inter-study reproducibility. Morning and afternoon scans were compared to address possible diurnal variation of atrial function. Inter-study reproducibility was within acceptable limits for all LA and RA volumetric, strain and SR parameters. Inter-study reproducibility was better for volumetric indexes and strain than for SR parameters and better for LA than for RA dynamics. For the LA, reservoir function showed the best reproducibility (intraclass correlation coefficient (ICC) 0.94-0.97, coefficient of variation (CoV) 4.5-8.2%), followed by conduit (ICC 0.78-0.97, CoV 8.2-18.5%) and booster pump function (ICC 0.71-0.95, CoV 18.3-22.7). Similarly, for the RA, reproducibility was best for reservoir function (ICC 0.76-0.96, CoV 7.5-24.0%) followed by conduit (ICC 0.67-0.91, CoV 13.9-35.9) and booster pump function (ICC 0.73-0.90, CoV 19.4-32.3). Atrial dynamics were not measurably affected by diurnal variation between morning and afternoon scans. Inter-study reproducibility for CMR-based derivation of LA and RA functions is acceptable using either volumetric, strain or SR parameters with LA function showing higher reproducibility than RA function assessment. Amongst the different functional components, reservoir function is most reproducibly assessed by either technique followed by conduit and booster pump function, which needs to be considered in future longitudinal research studies.

Plastic flow modeling in glassy polymers

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

Clements, Brad

2010-12-13

Glassy amorphous and semi-crystalline polymers exhibit strong rate, temperature, and pressure dependent polymeric yield. As a rule of thumb, in uniaxial compression experiments the yield stress increases with the loading rate and applied pressure, and decreases as the temperature increases. Moreover, by varying the loading state itself complex yield behavior can be observed. One example that illustrates this complexity is that most polymers in their glassy regimes (i.e., when the temperature is below their characteristic glass transition temperature) exhibit very pronounced yield in their uniaxial stress stress-strain response but very nebulous yield in their uniaxial strain response. In uniaxial compression,more » a prototypical glassy-polymer stress-strain curve has a stress plateau, often followed by softening, and upon further straining, a hardening response. Uniaxial compression experiments of this type are typically done from rates of 10{sup -5} s{sup -1} up to about 1 s{sup -1}. At still higher rates, say at several thousands per second as determined from Split Hopkinson Pressure Bar experiments, the yield can again be measured and is consistent with the above rule of thumb. One might expect that that these two sets of experiments should allow for a successful extrapolation to yet higher rates. A standard means to probe high rates (on the order of 105-107 S-I) is to use a uniaxial strain plate impact experiment. It is well known that in plate impact experiments on metals that the yield stress is manifested in a well-defined Hugoniot Elastic Limit (HEL). In contrast however, when plate impact experiments are done on glassy polymers, the HEL is arguably not observed, let alone observed at the stress estimated by extrapolating from the lower strain rate experiments. One might argue that polymer yield is still active but somehow masked by the experiment. After reviewing relevant experiments, we attempt to address this issue. We begin by first presenting our recently developed glassy polymer model. While polymers are well known for their non-equilibrium deviatoric behavior we have found the need for incorporating both equilibrium and non-equilibrium volumetric behavior into our theory. Experimental evidence supporting the notion of non-equilibrium volumetric behavior will be summarized. Our polymer yield model accurately captures the stress plateau, softening and hardening and its yield stress predictions agree well with measured values for several glassy polymers including PMMA, PC, and an epoxy resin. We then apply our theory to plate impact experiments in an attempt to address the questions associated with high rate polymer yield in uniaxial strain configurations.« less

Integration of Vibrio vulnificus into Marine Aggregates and Its Subsequent Uptake by Crassostrea virginica Oysters

PubMed Central

Froelich, Brett; Ayrapetyan, Mesrop

2013-01-01

Marine aggregates are naturally forming conglomerations of larvacean houses, phytoplankton, microbes, and inorganics adhered together by exocellular polymers. In this study, we show in vitro that the bacterial pathogen Vibrio vulnificus can be concentrated into laboratory-generated aggregates from surrounding water. We further show that environmental (E-genotype) strains exhibit significantly more integration into these aggregates than clinical (C-genotype) strains. Experiments where marine aggregates with attached V. vulnificus cells were fed to oysters (Crassostrea virginica) resulted in greater uptake of both C and E types than nonaggregated controls. When C- and E-genotype strains were cocultured in competitive experiments, the aggregated E-genotype strains exhibited significantly greater uptake by oyster than the C-genotype strains. PMID:23263962

Suppression of Prostate Tumor Progression by Bin 1

DTIC Science & Technology

2006-02-01

experiment). The full protocol was approved by IACUC review. Cohort A. Castration + Testostrone propionate s.c. + MNU i.v. Cohort B. Castration... Testostrone propionate s.c. + MNU i.v. + testosterone pellet Strain 1. mosaic Bin1 flox)/KO  Strain 2. Bin1 flox/+ (control for strain 1) Strain

Structural, compositional, mechanical characterization and biological assessment of bovine-derived hydroxyapatite coatings reinforced with MgF2 or MgO for implants functionalization.

PubMed

Mihailescu, Natalia; Stan, G E; Duta, L; Chifiriuc, Mariana Carmen; Bleotu, Coralia; Sopronyi, M; Luculescu, C; Oktar, F N; Mihailescu, I N

2016-02-01

Hydroxyapatite (HA) is a consecrated biomaterial for bone reconstruction. In the form of thin films deposited by pulsed laser technologies, it can be used to cover metallic implants aiming to increase biocompatibility and osseointegration rate. HA of animal origin (bovine, BHA) reinforced with MgF2 (2wt.%) or MgO (5wt.%) were used for deposition of thin coatings with improved adherence, biocompatibility and antimicrobial activity. For pulsed laser deposition experiments, a KrF* (λ=248nm, τFWHM≤25ns) excimer laser source was used. The deposited structures were characterized from a physical-chemical point of view by X-Ray Diffraction, Fourier Transform Infra-Red Spectroscopy, Scanning Electron Microscopy in top- and cross-view modes, Energy Dispersive X-Ray Spectroscopy and Pull-out adherence tests. The microbiological assay using the HEp-2 cell line revealed that all target materials and deposited thin films are non-cytotoxic. We conducted tests on three strains isolated from patients with dental implants failure, i.e. Microccocus sp., Enterobacter sp. and Candida albicans sp. The most significant anti-biofilm effect against Microcococcus sp. strain, at 72h, was obtained in the presence of BHA:MgO thin films. For Enterobacter sp. strain a superior antimicrobial activity at 72h was noticed, in respect with simple BHA or Ti control. The enhanced antimicrobial performances, correlated with good cytocompatibility and mechanical properties recommend these biomaterials as an alternative to synthetic HA for the fabrication of reliable implant coatings for dentistry and other applications. Copyright © 2015 Elsevier B.V. All rights reserved.

An extractive membrane biofilm reactor as alternative technology for the treatment of methyl tert-butyl ether contaminated water.

PubMed

Guisado, I M; Purswani, J; González-López, J; Pozo, C

2016-09-01

Among the strategies developed for contaminated groundwater bioremediation, those based on the use of bacteria adhering to inert supports and establishing biofilms have gained great importance in this field. Extractive membrane biofilm reactor (EMBFR) technology offers productive solutions for the removal of volatile and semi-volatile compounds. EMBFR technology is based on the use of extractive semipermeable membranes through which contaminants migrate to the biological compartment in which microorganisms with pollutant biotransformation and/or mineralization capacities can grow, forming an active biofilm on the membrane surface. The objective of this study was to assess the use of three bacterial strains (Paenibacillus sp. SH7 CECT 8558, Agrobacterium sp. MS2 CECT 8557, and Rhodococcus ruber EE6 CECT 8612), as inoculum in a lab-scale EMBFR running for 28 days under aerobic conditions to eliminate methyl tert-butyl ether (MTBE) from water samples. Three different hydraulic retention times (1, 6, and 12 h) were employed. MTBE degradation values were determined daily by a gas GC-MS technique, as well as suspended bacterial growth. The biofilm established by the bacterial strains on the semipermeable membrane was detected by Field-Emission Scanning Electron Microscopy (FESEM) at the end of each experiment. The acute toxicity of the treated effluents and biomedium was determined by Microtox © assay (EC 50 ).The results achieved from the MTBE degradation, biofilm formation, and toxicity analysis indicated that bacterial strains MS2 and EE6 were the best options as selective inoculum, although further research is needed, particularly with regard to their possible use as a mixed culture. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1238-1245, 2016. © 2016 American Institute of Chemical Engineers.

Strength and microstructure characteristics of the recycled rubber tire-sand mixtures as lightweight backfill.

PubMed

Zhang, Tao; Cai, Guojun; Duan, Weihong

2018-02-01

The disposal of scrap rubber tires has induced critical environmental issue worldwide due to the rapid increase in the number of vehicles. Recycled scrap tires as a construction material in civil engineering have significant environmental benefits from a waste management perspective. A systematic study that deals with strength and microstructure characteristics of the rubber-sand mixtures is initiated, and mechanical response of the mixtures is discussed in this investigation. Experiments were conducted to evaluate the effects of rubber fraction on the basic properties including mass density (ρ), stress-strain characteristics, shear strength, and unconfined compression strength (q u ) of the rubber-sand mixtures. Additionally, scanning electron microscopy (SEM) was carried out to reveal the microstructure characteristics of the mixtures with various rubber fractions. A discussion on the micromechanics of the mixtures also was conducted. This study demonstrates that the ρ, friction angle, and q u decrease linearly with an increase in rubber fraction, whereas shear strain at peak increases. The stress-strain characteristics of the rubber-sand mixtures shift from brittle to ductile as the rubber fraction increase. These changes are attributed to remarkably lower stiffness and higher compressibility of the rubber particle compared with those of the conventional mineral aggregates. With an increase in the rubber fraction, the mechanical response of rubber-sand mixtures exhibits two types: sand-like material and rubber-like material. Rubber particle possesses the capacity to prevent the contacted sand particles from sliding at lower rubber fraction, whereas it transmits the applied loadings as the rubber fraction increased. This outcome reinforces the practicability of using recycled rubber tire-sand mixtures as a lightweight backfill in subbase/base applications.

Inhibition of adherence of C. albicans to dental implants and cover screws by Cymbopogon nardus essential oil and citronellal.

PubMed

Trindade, Leonardo Antunes; de Araújo Oliveira, Julyana; de Castro, Ricardo Dias; de Oliveira Lima, Edeltrudes

2015-12-01

This study investigated the biological activity of the essential oil from Cymbopogon nardus and of the phytoconstituent citronellal on Candida strains as to the inhibition of adherence to dental implants and cover screws. The essential oil was analyzed by gas chromatography coupled to mass spectrometry (GC-MS) and had its MIC and MFC determined against 12 strains of Candida. Then, tests of inhibition of adherence to the dental implants and cover screws were carried out using the MIC of the substances, followed by scanning electron microscopy analysis. Nystatin and chlorhexidine were used as positive controls, and experiments were performed in triplicate. The analysis by GC-MS of the essential oil identified citronellal as the major compound. The MICs of the essential oil, citronellal, chlorhexidine, and nystatin--able to inhibit 100 % of the strains--were found to be 64, 512, 64, and 32 μg/ml, respectively. The essential oil significantly inhibited the adherence of Candida albicans to the dental implants and cover screws (p < 0.001). Citronellal inhibited yeast adherence only to the dental implants (p < 0.001), and no significant results were found for the cover screws (p > 0.05) compared to the growth control. The essential oil and citronellal have proven antifungal activity and are able to inhibit the in vitro adherence of C. albicans. There has been a search for alternative natural product-containing formulations that should be effective in inhibiting adherence of yeasts to the surfaces of materials and also able to treat oral fungal infections. Further trials could make these products an alternative to chemical removal of peri-implant biofilm.

Protective Mechanisms of Respiratory Tract Streptococci against Streptococcus pyogenes Biofilm Formation and Epithelial Cell Infection

PubMed Central

Fiedler, Tomas; Riani, Catur; Koczan, Dirk; Standar, Kerstin

2013-01-01

Streptococcus pyogenes (group A streptococci [GAS]) encounter many streptococcal species of the physiological microbial biome when entering the upper respiratory tract of humans, leading to the question how GAS interact with these bacteria in order to establish themselves at this anatomic site and initiate infection. Here we show that S. oralis and S. salivarius in direct contact assays inhibit growth of GAS in a strain-specific manner and that S. salivarius, most likely via bacteriocin secretion, also exerts this effect in transwell experiments. Utilizing scanning electron microscopy documentation, we identified the tested strains as potent biofilm producers except for GAS M49. In mixed-species biofilms, S. salivarius dominated the GAS strains, while S. oralis acted as initial colonizer, building the bottom layer in mixed biofilms and thereby allowing even GAS M49 to form substantial biofilms on top. With the exception of S. oralis, artificial saliva reduced single-species biofilms and allowed GAS to dominate in mixed biofilms, although the overall two-layer structure was unchanged. When covered by S. oralis and S. salivarius biofilms, epithelial cells were protected from GAS adherence, internalization, and cytotoxic effects. Apparently, these species can have probiotic effects. The use of Affymetrix array technology to assess HEp-2 cell transcription levels revealed modest changes after exposure to S. oralis and S. salivarius biofilms which could explain some of the protective effects against GAS attack. In summary, our study revealed a protection effect of respiratory tract bacteria against an important airway pathogen and allowed a first in vitro insight into local environmental processes after GAS enter the respiratory tract. PMID:23241973

Multi-fiber strains measured by micro-Raman spectroscopy: Principles and experiments

NASA Astrophysics Data System (ADS)

Lei, Zhenkun; Wang, Yunfeng; Qin, Fuyong; Qiu, Wei; Bai, Ruixiang; Chen, Xiaogang

2016-02-01

Based on widely used axial strain measurement method of Kevlar single fiber, an original theoretical model and measurement principle of application of micro-Raman spectroscopy to multi-fiber strains in a fiber bundle were established. The relationship between the nominal Raman shift of fiber bundle and the multi-fiber strains was deduced. The proposed principle for multi-fiber strains measurement is consistent with two special cases: single fiber deformation and multi-fiber deformation under equal strain. It is found experimentally that the distribution of Raman scattering intensity of a Kevlar 49 fiber as a function of distance between a fiber and the laser spot center follows a Gaussian function. Combining the Raman-shift/strain relationship of the Kevlar 49 single fiber and the uniaxial tension measured by micro-Raman spectroscopy, the Raman shift as a function of strain was obtained. Then the Raman peak at 1610 cm-1 for the Kevlar 49 fiber was fitted to a Lorentzian function and the FWHM showed a quadratic increase with the fiber strain. Finally, a dual-fiber tensile experiment was performed to verify the adequacy of the Raman technique for the measurement of multi-fiber strains.

Generation of volcanic ash: a textural study of ash produced in various laboratory experiments

NASA Astrophysics Data System (ADS)

Lavallée, Yan; Kueppers, Ulrich; Dingwell, Donald B.

2010-05-01

In volcanology, ash is commonly understood as a fragment of a bubble wall that gets disrupted during explosive eruptions. Most volcanic ashes are indeed the product of explosive eruptions, but the true definition is however that of a particle size being inferior to 2 mm. The term does not hold any information about its genesis. During fragmentation, particles of all sizes in various amounts are generated. In nature, fragmentation is a brittle response of the material (whether a rock or magma) caused by changes in 1) strain rate and 2) temperature, and/or 3) chemical composition. Here we used different experimental techniques to produce ash and study their physical characteristics. The effects of strain rate were investigated by deforming volcanic rocks and magma (pure silicate melt and crystal-bearing magma) at different temperatures and stresses in a uniaxial compression apparatus. Failure of pure silicate melts is spontaneous and generates more ash particles than fragmentation of crystal-bearing melts. In the latter, the abundance of generated ash correlates positively with the strain rate. We complemented this investigation with a study of particles generated during rapid decompression of porous rocks, using a fragmentation apparatus. Products of decompression experiments at different initial applied pore pressure show that the amount of ash generated by bubble burst increase with the initial applied pressure and the open porosity. The effects of temperature were investigated by dropping pure silicate melts and crystal-bearing magma at 900 and 1100°C in water at room temperature. Quenching of the material is accompanied by rapid contraction and near instantaneous fragmentation. Pure silicate melts respond more violently to the interaction with water and completely fragmented into small particles, including a variety of ash morphologies and surface textures. Crystal-bearing magmas however fragmented only very partially when in contact with water and produced a few ash particles (< 0.05 g). The morphology and surface textures of the experimentally generated ash particles were imaged through scanning electron microscopy, and the observations will be discussed in terms of fragmentation processes.

Evaluation of the correctness of the feed selection based on the analysis of chip's shape

NASA Astrophysics Data System (ADS)

Chodor, Jaroslaw; Kukielka, Leon; Kaldunski, Pawel; Bohdal, Lukasz; Patyk, Radoslaw; Kulakowska, Agnieszka

2018-05-01

For the experiment needs, the own experiment plan was developed. The researches were carried out to determine the effect of variable, small feed on the chip's shape. To provide orthogonal free cutting special specimens were prepared. Obtained chips were divided according to shapes and also scanned using a scanning electron microscope (SEM). Conclusions from the experiments were given.

Thermal Analysis of Plastics

ERIC Educational Resources Information Center

D'Amico, Teresa; Donahue, Craig J.; Rais, Elizabeth A.

2008-01-01

This lab experiment illustrates the use of differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) in the measurement of polymer properties. A total of seven exercises are described. These are dry exercises: students interpret previously recorded scans. They do not perform the experiments. DSC was used to determine the…

Microscopic and Spectroscopic Analyses of Chlorhexidine Tolerance in Delftia acidovorans Biofilms

PubMed Central

Rema, Tara; Lawrence, John R.; Dynes, James J.; Hitchcock, Adam P.

2014-01-01

The physicochemical responses of Delftia acidovorans biofilms exposed to the commonly used antimicrobial chlorhexidine (CHX) were examined in this study. A CHX-sensitive mutant (MIC, 1.0 μg ml−1) was derived from a CHX-tolerant (MIC, 15.0 μg ml−1) D. acidovorans parent strain using transposon mutagenesis. D. acidovorans mutant (MT51) and wild-type (WT15) strain biofilms were cultivated in flow cells and then treated with CHX at sub-MIC and inhibitory concentrations and examined by confocal laser scanning microscopy (CLSM), scanning transmission X-ray microscopy (STXM), and infrared (IR) spectroscopy. Specific morphological, structural, and chemical compositional differences between the CHX-treated and -untreated biofilms of both strains were observed. Apart from architectural differences, CLSM revealed a negative effect of CHX on biofilm thickness in the CHX-sensitive MT51 biofilms relative to those of the WT15 strain. STXM analyses showed that the WT15 biofilms contained two morphochemical cell variants, whereas only one type was detected in the MT51 biofilms. The cells in the MT51 biofilms bioaccumulated CHX to a similar extent as one of the cell types found in the WT15 biofilms, whereas the other cell type in the WT15 biofilms did not bioaccumulate CHX. STXM and IR spectral analyses revealed that CHX-sensitive MT51 cells accumulated the highest levels of CHX. Pretreating biofilms with EDTA promoted the accumulation of CHX in all cells. Thus, it is suggested that a subpopulation of cells that do not accumulate CHX appear to be responsible for greater CHX resistance in D. acidovorans WT15 biofilm in conjunction with the possible involvement of bacterial membrane stability. PMID:25022584

Mechanical performance of PPy helix tube microactuator

NASA Astrophysics Data System (ADS)

Bahrami Samani, Mehrdad; Spinks, Geoffrey M.; Cook, Christopher

2004-02-01

Conducting polymer actuators with favourable properties such as linearity, high power density and compliance are of increasing demand in micro applications. These materials generate forces over two times larger than produced by mammalian skeletal muscles. They operate to convert electro chemical energy to mechanical stress and strain. On the other hand, the application of conducting polymers is limited by the lack of a full description of the relation between four essential parameters: stress, strain, voltage and current. In this paper, polypyrrole helix tube micro actuator mechanical characteristics are investigated. The electrolyte is propylene carbonate and the dopant is TBA. PF6. The experiments are both in isotonic and isometric conditions and the input parameters are both electrical and mechanical. A dual mode force and length control and potentiostat / galvanostat are utilized for this purpose. Ultimately, the viscoelastic behaviour of the actuator is presented in this paper by a standard stress relaxation test. The effect of electrical stimulus on mechanical parameters is also explored by cyclic voltametry at different scan rates to obtain the best understanding of the actuation mechanism. The results demonstrate that the linear viscoelastic model, which performed well on conducting polymer film actuators, has to be modified to explain the mechanical behaviour of PPy helix tube fibre micro actuators. Secondly, the changes in mechanical properties of PPy need to be considered when modelling electromechanical behaviour.

Sinorhizobium meliloti chemotaxis to quaternary ammonium compounds is mediated by the chemoreceptor McpX.

PubMed

Webb, Benjamin A; Karl Compton, K; Castañeda Saldaña, Rafael; Arapov, Timofey D; Keith Ray, W; Helm, Richard F; Scharf, Birgit E

2017-01-01

The bacterium Sinorhizobium meliloti is attracted to seed exudates of its host plant alfalfa (Medicago sativa). Since quaternary ammonium compounds (QACs) are exuded by germinating seeds, we assayed chemotaxis of S. meliloti towards betonicine, choline, glycine betaine, stachydrine and trigonelline. The wild type displayed a positive response to all QACs. Using LC-MS, we determined that each germinating alfalfa seed exuded QACs in the nanogram range. Compared to the closely related nonhost species, spotted medic (Medicago arabica), unique profiles were released. Further assessments of single chemoreceptor deletion strains revealed that an mcpX deletion strain displayed little to no response to these compounds. Differential scanning fluorimetry showed interaction of the isolated periplasmic region of McpX (McpX PR and McpX 34-306 ) with QACs. Isothermal titration calorimetry experiments revealed tight binding to McpX PR with dissociation constants (K d ) in the nanomolar range for choline and glycine betaine, micromolar K d for stachydrine and trigonelline and a K d in the millimolar range for betonicine. Our discovery of S. meliloti chemotaxis to plant-derived QACs adds another role to this group of compounds, which are known to serve as nutrient sources, osmoprotectants and cell-to-cell signalling molecules. This is the first report of a chemoreceptor that mediates QACs taxis through direct binding. © 2016 John Wiley & Sons Ltd.

Nanostructured composite material graphite/TiO2 and its antibacterial activity under visible light irradiation.

PubMed

Dědková, Kateřina; Lang, Jaroslav; Matějová, Kateřina; Peikertová, Pavlína; Holešinský, Jan; Vodárek, Vlastimil; Kukutschová, Jana

2015-08-01

The paper addresses laboratory preparation, characterization and in vitro evaluation of antibacterial activity of graphite/TiO2 nanocomposites. Composites graphite/TiO2 with various ratio of TiO2 nanoparticles (30wt.%, and 50wt.%) to graphite were prepared using a thermal hydrolysis of titanylsulfate in the presence of graphite particles, and subsequently dried at 80°C. X-ray powder diffraction, transmission electron microscopy and Raman microspectroscopy served as phase-analytical methods distinguishing anatase and rutile phases in the prepared composites. Scanning and transmission electron microscopy techniques were used for characterization of morphology of the prepared samples. A developed modification of the standard microdilution test was used for in vitro evaluation of daylight induced antibacterial activity, using four common human pathogenic bacterial strains (Staphylococcus aureus, Escherichia coli, Enterococcus faecalis and Pseudomonas aeruginosa). Antibacterial activity of the graphite/TiO2 nanocomposites could be based mainly on photocatalytic reaction with subsequent potential interaction of reactive oxygen species with bacterial cells. During the antibacterial activity experiments, the graphite/TiO2 nanocomposites exhibited antibacterial activity, where differences in the onset of activity and activity against bacterial strains were observed. The highest antibacterial activity evaluated as minimum inhibitory concentration was observed against P. aeruginosa after 180min of irradiation. Copyright © 2015 Elsevier B.V. All rights reserved.

Porosity evolution at the brittle-ductile transition in the continental crust: Implications for deep hydro-geothermal circulation.

PubMed

Violay, M; Heap, M J; Acosta, M; Madonna, C

2017-08-09

Recently, projects have been proposed to engineer deep geothermal reservoirs in the ductile crust. To examine their feasibility, we performed high-temperature (up to 1000 °C), high-pressure (130 MPa) triaxial experiments on granite (initially-intact and shock-cooled samples) in which we measured the evolution of porosity during deformation. Mechanical data and post-mortem microstuctural characterisation (X-ray computed tomography and scanning electron microscopy) indicate that (1) the failure mode was brittle up to 900 °C (shear fracture formation) but ductile at 1000 °C (no strain localisation); (2) only deformation up to 800 °C was dilatant; (3) deformation at 900 °C was brittle but associated with net compaction due to an increase in the efficiency of crystal plastic processes; (4) ductile deformation at 1000 °C was compactant; (5) thermally-shocking the granite did not influence strength or failure mode. Our data show that, while brittle behaviour increases porosity, porosity loss is associated with both ductile behaviour and transitional behaviour as the failure mode evolves from brittle to ductile. Extrapolating our data to geological strain rates suggests that the brittle-ductile transition occurs at a temperature of 400 ± 100 °C, and is associated with the limit of fluid circulation in the deep continental crust.

Calcium carbonate precipitation by strain Bacillus licheniformis AK01, newly isolated from loamy soil: a promising alternative for sealing cement-based materials.

PubMed

Vahabi, Ali; Ramezanianpour, Ali Akbar; Sharafi, Hakimeh; Zahiri, Hossein Shahbani; Vali, Hojatollah; Noghabi, Kambiz Akbari

2015-01-01

The relevant experiments were designed to determine the ability of indigenous bacterial strains isolated from limestone caves, mineral springs, and loamy soils to induce calcium carbonate precipitation. Among all isolates examined in this study, an efficient carbonate-precipitating soil bacterium was selected from among the isolates and identified by 16S rRNA gene sequences as Bacillus licheniformis AK01. The ureolytic isolate was able to grow well on alkaline carbonate-precipitation medium and precipitate calcium carbonate more than 1 g L(-1). Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analyses, and scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX) examinations were performed in order to confirm the presence of calcium carbonate in the precipitate and to determine which polymorphs were present. The selected isolate was determined to be an appropriate candidate for application in a surface treatment of cement-based material to improve the properties of the mortar. Biodeposition of a layer of calcite on the surface of cement specimens resulted in filling in pore spaces. This could be an alternative method to improve the durability of the mortar. The kind of bacterial culture and medium composition had a profound impact on the resultant CaCO(3) crystal morphology. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Multiphase nanodomains in a strained BaTiO3 film on a GdScO3 substrate

NASA Astrophysics Data System (ADS)

Kobayashi, Shunsuke; Inoue, Kazutoshi; Kato, Takeharu; Ikuhara, Yuichi; Yamamoto, Takahisa

2018-02-01

Controlling the crystal structure of ferroelectric materials via epitaxial strain, which is a well-known technique in strain engineering, can lead to the formation of unique domain structures generating non-intrinsic phenomena such as electronic conductivity, photovoltages, and enhanced piezoelectric characteristics. Strained BaTiO3 films are promising ferroelectric materials as theoretical modeling predicts that different domain morphologies can introduce additional properties not observed in conventional BaTiO3 ceramics. To rationally design materials for practical application, a thorough understanding of the formation mechanisms and stabilities of different domain structures in strained BaTiO3 films is required. However, there have been very few experimental reports on this topic, and details about the domain structures in strained BaTiO3 films are currently lacking. In this paper, we report multiphase nanodomains in a strained BaTiO3 film deposited on an orthorhombic GdScO3 substrate. The phase-transition behavior of the strained BaTiO3 film reveals that it contains multiple phases at room temperature; the film first undergoes a phase-transition upon heating at around 550 K, and then a paraelectric phase forms at temperatures above 690 K. A picometer-scale analysis of the Ti ion displacements, using an advanced scanning transmission electron microscopy technique, is used to characterize the complex multiphase nanodomains, providing useful insights into the control of domain structures in BaTiO3 films by applying epitaxial strain.

Influences of strain rate on yield strength aluminum alloys

NASA Astrophysics Data System (ADS)

Rizal, Samsul; Firdaus, Hamdani Teuku; Thaib, Razali; Homma, Hiroomi

2005-04-01

The simulation of aircraft has often been performing by implementing finite element code on supercomputers. The reliability an accuracy of simulation depends mainly on the material model as well as on structural model used in calculations. Consequently, an accurate knowledge of mechanical behavior of materials under impact loading is essential for safety performance evaluation of structure. Impact tension tests on specimens for aircrafts and automotive structural applications are conduct by means of the split Hopkinson bar apparatus. Small specimens having diameter 4 mm are use in the test. Tensile stress-strain relations at strain rates of 102 s-1 to over 103 s-1 are present and compared with those obtained at quasi-static strain rates. The limitations on the applicability of apparatus are also discusses. The other importance of the reference of strain, while studying void growth in elastic-viscoplastic material, is emphasized. In the present paper, a simplified plane-symmetrical two-dimensional finite element model for a SHPB with a plate specimen made of an elastic material is first established. The used of strain gage mounted at the specimens to be monitored strain during the course of impact test. Comparisons may then be made between the numerical predicted and experimentally observed of load and a specimen strain. This report also describes the apparatus and instrumentation, and also be discusses the advantages and limitations of experimental technique. Fractograph is taken by scanning electron microscope on the center of the specimens for judgment of the fracture mechanism and strain rates influences on the materials.

Sensitivity of Heterointerfaces on Emission Wavelength in Quantum Cascade Lasers

DTIC Science & Technology

2016-10-31

as expected, and all scans exhibit sharp satellite peaks and highly resolved thickness interference fringes. The full- width at half-maximum of the n...K. Watanabe , M. Sugiyama, and Y. Nakano, "Effect of hetero-interfaces on in situ wafer curvature behavior in InGaAs/GaAsP strain-balanced MQWs

[A study on space mutation of Streptomyces fradiae].

PubMed

Fang, Xiao-mei; Zhao, Zhi-jia; Gu, Hai-ke

2005-04-01

To study the rule of mutation of Streptomyces fradiae during spaceflight, and to select efficient tylosin producing strains for industrial production. Streptomyces fradiae 9940S(+)-86 were carried on-board spaceship "Shenzhou" I, "Shenzhou" III and "Shenzhou" IV sequentially to achieve spaceflight mutation breeding experiment. After space experiments and the screening tests in the lab, 48 strains were obtained which promoted production by +20% or more at shaker level. And the highest production of a strain was 14950 micrograms/ml, which means an increase of 91.5%. Comparing the results of three tests, it is found that the outer space environment can lead to a cumulative mutation. After the medium scale tests and production experiments, strain T1-156-84-23 was finally selected to be used for sample production. And its output was increased by 18%.

Strain and culture medium optimization for production enhancement of prodiginines from marine-derived Streptomyces sp. GQQ-10

NASA Astrophysics Data System (ADS)

Li, Xueping; Zhang, Guojian; Zhu, Tianjiao; Li, Dehai; Gu, Qianqun

2012-09-01

A mutant (GQQ-M6) of a Sponge-Derived streptomyces sp. GQQ-10 obtained by UV-induced mutation was used for producing prodiginines (PGs). Single factor experiments and orthogonal array design (OAD) methods were employed for medium optimization. In the single factor method, the effects of soluble starch, glucose, soybean flour, yeast extract and sodium acetate on PGs production were investigated individually. In the subsequent OAD experiments, the concentrations of these 5 key nutritional components combined with salinity were further adjusted. The mutant strain GQQ-M6 gave a 2.2-fold higher PGs production than that of the parent strain; OAD experiments offered a PGs yield of 61mg L-1, which was 10 times higher than that of the initial GQQ-10 strain under the original cultivation mode.

Deformation-induced speckle-pattern evolution and feasibility of correlational speckle tracking in optical coherence elastography.

PubMed

Zaitsev, Vladimir Y; Matveyev, Alexandr L; Matveev, Lev A; Gelikonov, Grigory V; Gelikonov, Valentin M; Vitkin, Alex

2015-07-01

Feasibility of speckle tracking in optical coherence tomography (OCT) based on digital image correlation (DIC) is discussed in the context of elastography problems. Specifics of applying DIC methods to OCT, compared to processing of photographic images in mechanical engineering applications, are emphasized and main complications are pointed out. Analytical arguments are augmented by accurate numerical simulations of OCT speckle patterns. In contrast to DIC processing for displacement and strain estimation in photographic images, the accuracy of correlational speckle tracking in deformed OCT images is strongly affected by the coherent nature of speckles, for which strain-induced complications of speckle “blinking” and “boiling” are typical. The tracking accuracy is further compromised by the usually more pronounced pixelated structure of OCT scans compared with digital photographic images in classical DIC applications. Processing of complex-valued OCT data (comprising both amplitude and phase) compared to intensity-only scans mitigates these deleterious effects to some degree. Criteria of the attainable speckle tracking accuracy and its dependence on the key OCT system parameters are established.

Polyacrylonitrile nanofibers with added zeolitic imidazolate frameworks (ZIF-7) to enhance mechanical and thermal stability

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

Lee, Min Wook; An, Seongpil; Song, Kyo Yong

2015-12-28

Zeolitic imidazolate framework 7/polyacrylonitrile (ZIF-7/PAN) nanofiber mat of high porosity and surface area can be used as a flexible fibrous filtration membrane that is subjected to various modes of mechanical loading resulting in stresses and strains. Therefore, the stress-strain relation of ZIF-7/PAN nanofiber mats in the elastic and plastic regimes of deformation is of significant importance for numerous practical applications, including hydrogen storage, carbon dioxide capture, and molecular sensing. Here, we demonstrated the fabrication of ZIF-7/PAN nanofiber mats via electrospinning and report their mechanical properties measured in tensile tests covering the elastic and plastic domains. The effect of the matmore » fabrication temperature on the mechanical properties is elucidated. We showed the superior mechanical strength and thermal stability of the compound ZIF-7/PAN nanofiber mats in comparison with that of pure PAN nanofiber mats. Material characterization including scanning electron microscope, energy-dispersive X-ray spectroscopy, tensile tests, differential scanning calorimetry, and Fourier transform infrared spectroscopy revealed the enhanced chemical bonds of the ZIF-7/PAN complex.« less

Effects of physical exercise and social isolation on anxiety-related behaviors in two inbred rat strains.

PubMed

Mazur, F G; Oliveira, L F G; Cunha, M P; Rodrigues, A L S; Pértile, R A N; Vendruscolo, L F; Izídio, G S

2017-09-01

We investigated the effects of physical exercise (PE) on locomotor activity and anxiety-like behavior in Lewis (LEW) and Spontaneously Hypertensive Rats (SHR) male rats. Rats received either four weeks of forced training, 5days/week, on a treadmill (experiment 1) or were given 21days of free access to running wheels (experiment 2). We also tested the effects of social isolation (SI) (seven days of isolation - experiment 3) on behavior. In experiment 1, 20% of LEW rats and 63% of SHR rats completed the training protocol. PE significantly increased central and peripheral locomotion in the open field (OF) and entries into the open arms in the elevated plus-maze (EPM) in both strains. In experiment 2, the distance traveled by SHR rats on running wheels was significantly higher compared with LEW rats. PE on running wheels also increased the time spent in the center of the OF in SHR rats only. In experiment 3, SI decreased central and peripheral locomotion in the OF in both strains. In summary, forced PE on a treadmill reduced anxiety-like behavior and increased locomotion in male rats of both strains, whereas voluntary PE on running wheels decreased anxiety-like behavior in SHR rats only. SI decreased locomotion in both strains in the OF. This study suggests that spontaneous activity levels are genotype-dependent and the effects of PE depend on the type of exercise performed. Copyright © 2017 Elsevier B.V. All rights reserved.

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

Liu, Jiyuan; Zhang, Zicheng, E-mail: zhangzicheng2004@126.com; Manabe, Ken-ichi

Transformation-induced plasticity aided seamless steel tube comprising of ferrite, bainite, and metastable austenite was processed through forging, piercing, cold-drawing, and two-stage heat treatment. T-shape hydroforming is a classic forming method for experimental research and practical production. The current work studied austenite-to-martensite transformation and microcrack initiation and propagation of the tube during T-shape hydroforming using electron backscattering diffraction, scanning electron microscopy, and transmission electron microscopy. The strain distribution in the bcc-phase and fcc-phase was studied by evaluating changes in the average local misorientation. Compared to the compressive stress, metastable austenite with similar strain surrounding or inside the grains transformed easier undermore » tensile loading conditions. The inclusions were responsible for microcrack initiation. The propagation of the cracks is hindered by martensite/austenite constituent due to transformation induced plasticity effect. The volume fraction of untransformed retained austenite decreased with increase in strain implying transformation-induced plasticity effect. - Highlights: • Hydroformed tubes processed via TRIP concept • EBSD provided estimate of micro local strain. • Retained austenite hinders propagation of microcracks.« less

Unusual polyphosphate inclusions observed in a marine Beggiatoa strain.

PubMed

Brock, Jörg; Rhiel, Erhard; Beutler, Martin; Salman, Verena; Schulz-Vogt, Heide N

2012-02-01

Sulfide-oxidizing bacteria of the genus Beggiatoa are known to accumulate phosphate intracellularly as polyphosphate but little is known about the structure and properties of these inclusions. Application of different staining techniques revealed the presence of unusually large polyphosphate inclusions in the marine Beggiatoa strain 35Flor. The inclusions showed a co-occurrence of polyphosphate, calcium and magnesium when analyzed by scanning electron microscopy and energy dispersive X-ray analysis. Similar to polyphosphate-enriched acidocalcisomes of prokaryotes and eukaryotes, the polyphosphate inclusions in Beggiatoa strain 35Flor are enclosed by a lipid layer and store cations. However, they are not notably acidic. 16S rRNA gene sequence-based phylogenetic reconstruction showed an affiliation of Beggiatoa strain 35Flor to a monophyletic branch, comprising other narrow vacuolated and non-vacuolated Beggiatoa species. The polyphosphate inclusions represent a new type of membrane surrounded storage compartment within the genus Beggiatoa, distinct from the mostly nitrate-storing vacuoles known from other marine sulfide-oxidizing bacteria of the family Beggiatoaceae.

Optimizing disk registration algorithms for nanobeam electron diffraction strain mapping

DOE PAGES

Pekin, Thomas C.; Gammer, Christoph; Ciston, Jim; ...

2017-01-28

Scanning nanobeam electron diffraction strain mapping is a technique by which the positions of diffracted disks sampled at the nanoscale over a crystalline sample can be used to reconstruct a strain map over a large area. However, it is important that the disk positions are measured accurately, as their positions relative to a reference are directly used to calculate strain. Here in this study, we compare several correlation methods using both simulated and experimental data in order to directly probe susceptibility to measurement error due to non-uniform diffracted disk illumination structure. We found that prefiltering the diffraction patterns with amore » Sobel filter before performing cross correlation or performing a square-root magnitude weighted phase correlation returned the best results when inner disk structure was present. Lastly, we have tested these methods both on simulated datasets, and experimental data from unstrained silicon as well as a twin grain boundary in 304 stainless steel.« less

Control of Attachment of Pseudomonas aeruginosa and Burkholderia cepacia to Surfaces by Shear Force.

PubMed

Hui, Yew Woh; Narayanan, Kumaran; Dykes, Gary A

2016-11-01

  The effect of physical shearing on the attachment of six Pseudomonas aeruginosa strains and six Burkholderia cepacia strains to glass, stainless steel, polystyrene and Teflon® was determined. A significant (p < 0.05) decrease in hydrophobicity was apparent for all P. aeruginosa strains (17-36%) and B. cepacia, MS 5 (20%) after shearing. A significant (p < 0.05) decrease in attachment of some P. aeruginosa (0.2-0.5 log CFU/cm2) and B. cepacia (0.2-0.4 log CFU/cm2) strains to some surface types was apparent after shearing. Significant (p < 0.05) correlation was observed for both numbers of flagellated cells and hydrophobicity against attachment to glass, stainless steel and polystyrene for P. aeruginosa while only hydrophobicity showed significant correlation against the same surfaces for B. cepacia. Scanning electron microscopy and protein analysis showed that shearing removed surface proteins from the cells and may have led to the observed changes in hydrophobicity and attachment to abiotic surfaces.

Time-dependent crashworthiness of polyurethane foam

NASA Astrophysics Data System (ADS)

Basit, Munshi Mahbubul; Cheon, Seong Sik

2018-05-01

Time-dependent stress-strain relationship as well as crashworthiness of polyurethane foam was investigated under constant impact energy with different velocities, considering inertia and strain-rate effects simultaneously during the impact testing. Even though the impact energies were same, the percentage in increase in densification strain due to higher impact velocities was found, which yielded the wider plateau region, i.e. growth in crashworthiness. This phenomenon is analyzed by the microstructure of polyurethane foam obtained from scanning electron microscopy. The equations, coupled with the Sherwood-Frost model and the impulse-momentum theory, were employed to build the constitutive equation of the polyurethane foam and calculate energy absorption capacity of the foam. The nominal stress-strain curves obtained from the constitutive equation were compared with results from impact tests and were found to be in good agreement. This study is dedicated to guiding designer use polyurethane foam in crashworthiness structures such as an automotive bumper system by providing crashworthiness data, determining the crush mode, and addressing a mathematical model of the crashworthiness.

Key role of lattice symmetry in the metal-insulator transition of NdNiO 3 films

DOE PAGES

Zhang, Jack Y.; Kim, Honggyu; Mikheev, Evgeny; ...

2016-04-01

Here, bulk NdNiO 3 exhibits a metal-to-insulator transition (MIT) as the temperature is lowered that is also seen in tensile strained films. In contrast, films that are under a large compressive strain typically remain metallic at all temperatures. To clarify the microscopic origins of this behavior, we use position averaged convergent beam electron diffraction in scanning transmission electron microscopy to characterize strained NdNiO 3 films both above and below the MIT temperature. We show that a symmetry lowering structural change takes place in case of the tensile strained film, which undergoes an MIT, but is absent in the compressively strainedmore » film. Using space group symmetry arguments, we show that these results support the bond length disproportionation model of the MIT in the rare-earth nickelates. Furthermore, the results provide insights into the non-Fermi liquid phase that is observed in films for which the MIT is absent.« less

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.

Using an ultrasound elasticity microscope to map three-dimensional strain in a porcine cornea.

PubMed

Hollman, Kyle W; Shtein, Roni M; Tripathy, Sakya; Kim, Kang

2013-08-01

An ultrasound elasticity microscope was used to map 3-D strain volume in an ex vivo porcine cornea to illustrate its ability to measure the mechanical properties of this tissue. Mechanical properties of the cornea play an important role in its function and, therefore, also in ophthalmic diseases such as kerataconus and corneal ectasia. The ultrasound elasticity microscope combines a tightly focused high-frequency transducer with confocal scanning to produce high-quality speckle over the entire volume of tissue. This system and the analysis were able to generate volume maps of compressional strain in all three directions for porcine corneal tissue, more information than any previous study has reported. Strain volume maps indicated features of the cornea and mechanical behavior as expected. These results constitute a step toward better understanding of corneal mechanics and better treatment of corneal diseases. Copyright © 2013 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Acceleration of the formation of biofilms on contact lens surfaces in the presence of neutrophil-derived cellular debris is conserved across multiple genera

PubMed Central

Patel, Naiya B.; Hinojosa, Jorge A.; Zhu, Meifang

2018-01-01

Purpose We have previously shown that invasive strains of Pseudomonas aeruginosa exploit the robust neutrophil response to form biofilms on contact lens surfaces and invade the corneal epithelium. The present study investigated the ability of multiple bacterial genera, all commonly recovered during contact lens–related infectious events, to adhere to and form biofilms on contact lens surfaces in the presence of neutrophils. Methods Five reference strains from the American Type Culture Collection were used: P. aeruginosa, Serratia marcescens, Stenotrophomonas maltophilia, Staphylococcus aureus, and Staphylococcus epidermidis. Each bacterial strain was incubated overnight with or without stimulated human neutrophils in the presence of an unworn contact lens. Standard colony counts and laser scanning confocal microscopy of BacLight-stained contact lenses were used to assess bacterial viability. Three-dimensional modeling of lens-associated biofilms with Imaris software was used to determine the biofilm volume. Lenses were further examined using scanning electron microscopy. Results Less than 1% of the starting inoculum adhered to the contact lens surface incubated with bacteria alone. There were no differences in adhesion rates to contact lens surfaces between bacteria in the absence of neutrophils for either the Gram-negative or Gram-positive test strains. Bacterial adhesion to contact lens surfaces was accelerated in the presence of human neutrophils for all test strains. This effect was least evident with S. epidermidis. There was also an increase in the number of viable bacteria recovered from contact lens surfaces (p<0.001 for the Gram-negative and Gram-positive test strains, respectively) and in biofilm volume (p<0.001 for the Gram-negative test strains, p = 0.005 for S. aureus). Conclusions These results show that in addition to P. aeruginosa, other bacteria commonly encountered during contact lens wear possess the capacity to utilize neutrophil-derived cellular debris to facilitate colonization of the lens surface. These data suggest that this phenomenon is conserved among multiple genera. Thus, during contact lens wear, the presence of inflammation and the accumulation of neutrophil debris under the posterior lens surface likely contribute to colonization of the lens. Further studies are needed to correlate these findings with risk for infection in an animal model. PMID:29422767

Complementation studies in Niemann-Pick disease type C indicate the existence of a second group.

PubMed Central

Steinberg, S J; Ward, C P; Fensom, A H

1994-01-01

Niemann-Pick disease type C is a clinically heterogeneous storage disorder with an unknown primary metabolic defect. We have undertaken somatic cell hybridisation experiments using skin fibroblast strains from 12 patients representing a wide clinical spectrum. Preliminary experiments using filipin staining of free cholesterol as a marker for complementation indicated the existence of one major group (group alpha) and one minor group (group beta) represented by one mutant strain. Subsequent experiments in which sphingomyelinase activity was measured as a marker for complementation using five mutant strains showing activity consistently < 40% control levels confirmed the existence of the second group. Images PMID:8071958

Draft Genome Sequences from a Novel Clade of Bacillus cereus Sensu Lato Strains, Isolated from the International Space Station.

PubMed

Venkateswaran, Kasthuri; Checinska Sielaff, Aleksandra; Ratnayake, Shashikala; Pope, Robert K; Blank, Thomas E; Stepanov, Victor G; Fox, George E; van Tongeren, Sandra P; Torres, Clinton; Allen, Jonathan; Jaing, Crystal; Pierson, Duane; Perry, Jay; Koren, Sergey; Phillippy, Adam; Klubnik, Joy; Treangen, Todd J; Rosovitz, M J; Bergman, Nicholas H

2017-08-10

The draft genome sequences of six Bacillus strains, isolated from the International Space Station and belonging to the Bacillus anthracis - B. cereus - B. thuringiensis group, are presented here. These strains were isolated from the Japanese Experiment Module (one strain), U.S. Harmony Node 2 (three strains), and Russian Segment Zvezda Module (two strains). Copyright © 2017 Venkateswaran et al.

Isotropic thin-walled pressure vessel experiment

NASA Technical Reports Server (NTRS)

Denton, Nancy L.; Hillsman, Vernon S.

1992-01-01

The objectives are: (1) to investigate the stress and strain distributions on the surface of a thin walled cylinder subject to internal pressure and/or axial load; and (2) to relate stress and strain distributions to material properties and cylinder geometry. The experiment, supplies, and procedure are presented.

[Surveillance of Antimicrobial Resistant Esherichia coli by Rectal Swab Method--Annual Change of Prevalence of Quinolone-resistant and ESBL Producing Strains from 2009 to 2013].

PubMed

Nasu, Yoshitsugu; Sako, Shinichi; Yano, Tomofumi; Kosaka, Noriko

2015-09-01

Although most of commonly used antimicrobial agents had been susceptible to Esherichia coli, recently there are a lot of reports concerning about community-acquired infection caused by resistant E. coli. The aim of this study is to define the prevalence of resistant E. coli in normal flora colonization by the rectal swab method. From June 2009 to December 2013, 251 male patients (50-85 year-old, median 68) planned to transrectal prostate biopsy participated in this study. Stools stuck on the glove at the digital examination were provided for culture specimen. Identification of E. coli and determination of MIC was performed by MicroScan WalkAway40plus (Siemens). Isolated E. coli were deemed quinolone-resistant strains when their MIC of levofloxacine was 4 μg/mL or above according to the breakpoint MIC by the CLSI criteria. ESBL producing ability was determined by the double disk method used by CVA contained ESBL definition disc (Eikenkagaku). Of the 251 study patients, 224 patients had positive cultures of E. coli. Twenty-four patients had quinolone-resistant strains and 9 patients had ESBL producing strains. The prevalence of quinolone-resistant strains in 2009, 2010, 2011, 2012 and 2013 were 5.9% (2 out of 34 strains), 13.5% (5 out of 37 strains), 12.5% (4 out of 32 strains), 9.0% (6 out of 67) and 13.0% (7 out of 54 strains), respectively. The prevalence of ESBL producing strains in 2009, 2010, 2011, 2012 and 2013 were 0% (0 out of 34 strains), 5.4% (2 out of 37 strains), 3.1% (1 out of 32 strains), 3.0% (2 out of 67 strains) and 7.4% (4 out of 54 strains), respectively. In 2013, the prevalence of antimicrobial resistant E. coli, both quinolone-resistant and ESBL producing strains, were increasing. We have to pay a close attention to the increase of resistant E. coli.

Effect of strain hardening on friction behavior of iron lubricated with benzyl structures

NASA Technical Reports Server (NTRS)

Buckley, D. H.; Brainard, W. A.

1974-01-01

Sliding friction experiments were conducted with iron, copper, and aluminum in contact with iron in various states of strain. The surfaces were examined in dry sliding and with various benzyl compounds applied as lubricants. Friction experiments were conducted with a hemispherical rider contacting a flat disk at loads of from 50 to 600 grams with a sliding speed of 0.15 cm/min. Results indicate that straining increases friction for dry sliding and for surfaces lubricated with certain benzyl structures such as dibenzyl disulfide. With other benzyl compounds (e.g., benzyl formate), friction coefficients are lower for strained than for annealed iron.

Plasmid analyses in clinical isolates of Bacteroides fragilis and other Bacteroides species.

PubMed Central

Wallace, B L; Bradley, J E; Rogolsky, M

1981-01-01

Plasmid analyses were performed on Bacteroides strains isolated from clinical specimens. Of 32 Bacteroides strains, 8 were found to contain plasmids. Seven of these eight strains were B. fragilis, and the other one was B. distasonis. Three of these eight strains harbored only a 3.0-megadalton plasmid. Two strains had only a 2.0-megadalton plasmid, and one had 2.0-, 3.0-megadalton plasmid. Of the remaining two strains, one had 2.0-, 3.0-, and 5.0-megadalton plasmids, and the other had 3.0- and 5.0-megadalton plasmids. Beta-Lactamase was produced by 93% of the clinical isolates. Seven of the eight plasmid-carrying strains were cadmium resistant, five were zinc resistant, four were mercury resistant, and two expressed a brick-red fluorescence under ultraviolet light. None of these traits could be associated with a plasmid after performing either curing experiments or genetic transfer experiments by cell-to-cell contact. Images PMID:6974737

[Molecular and biologic characteristics of attenuated rubella viruses].

PubMed

Lavrent'eva, I N

2008-01-01

To study stability/variability of rubella virus vaccine strain "Orlov-B" during its adaptation to other tissue substrate. Vaccine strains of rubella virus Wistar 27/3 and "Orlov-B" as well as wild type strains "Orlov-D" and "Lebedev" were used. Rhesus monkeys were used as laboratory animals. Standard virological, molecular and statistical methods were applied. Obtained as a result of adaptation to other tissue substrate - diploid human cell line M-22 - strain "Orlov-D" demonstrated stability on RCT40 sign in in vitro experiments. Comparative genotyping of "Orlov-B" and "Orlov-D" strains on gene E1 showed identity of nucleotide sequences of both variants. Genetic stability of virus on the gene coding the most immunogenic protein E1 was confirmed in vivo: the stable high immunogenic and protective activity of both "Orlov-B" and "Orlov- D" strains was demonstrated in experiments on rhesus macaques. New data on stability of attenuated rubella virus vaccine strains have practical significance for the development of new vaccines.

Effects of value strains on psychopathology of Chinese rural youths.

PubMed

Zhang, Jie; Zhao, Sibo

2013-12-01

The Strain Theory of Suicide postulates that psychological strains usually precede mental disorders including suicidal behavior. This paper focuses on the effect of conflicting social value strains on the individual's psychopathology. We analyzed the data of 2031 respondents who were proxy informants for suicides and community living controls in a large scale psychological autopsy study in rural China, with the CES-D depression measure for the psychopathology. Individuals having experienced value conflicts between Confucian gender role and gender equalitarianism in modern society scored on depression significantly higher than the individuals who do not experience the value conflict, and it is also true when several other relevant variables were held constant in the multiple regression model. This study supports the hypotheses that people who confront value conflicts are likely to experience psychopathological strain, and the higher the level of strain, the stronger the depression. Copyright © 2013 Elsevier B.V. All rights reserved.

Mesoscopic Metal-Insulator Transition at Ferroelastic Domain Walls in VO2

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

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

2010-01-01

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

Genetic influences on ovulation of primary oocytes in LT/Sv strain mice.

PubMed

Everett, Clare A; Auchincloss, Catherine A; Kaufman, Matthew H; Abbott, Catherine M; West, John D

2004-11-01

A high proportion of LT/Sv strain oocytes arrest in meiotic metaphase I (MI) and are ovulated as diploid primary oocytes rather than haploid secondary oocytes. (Mus musculus castaneus x LT/SvKau)F1 x LT/SvKau backcross females were analysed for the proportion of oocytes that arrested in MI and typed by PCR for a panel of microsatellite DNA sequences (simple sequence repeat polymorphisms) that differed between strain LT/SvKau and M. m. castaneus. This provided a whole genome scan of 86 genetic markers distributed over all 19 autosomes and the X chromosome, and revealed genetic linkage of the MI arrest phenotype to markers on chromosomes 1 and 9. Identification of these two chromosomal regions should facilitate the identification of genes involved in mammalian oocyte maturation and the control of meiosis.

Composite time-lapse computed tomography and micro finite element simulations: A new imaging approach for characterizing cement flows and mechanical benefits of vertebroplasty.

PubMed

Stadelmann, Vincent A; Zderic, Ivan; Baur, Annick; Unholz, Cynthia; Eberli, Ursula; Gueorguiev, Boyko

2016-02-01

Vertebroplasty has been shown to reinforce weak vertebral bodies and reduce fracture risks, yet cement leakage is a major problem that can cause severe complications. Since cement flow is nearly impossible to control during surgery, small volumes of cement are injected, but then mechanical benefits might be limited. A better understanding of cement flows within bone structure is required to further optimize vertebroplasty and bone augmentation in general. We developed a novel imaging method, composite time-lapse CT, to characterize cement flow during injection. In brief, composite-resolution time-lapse CT exploits the qualities of microCT and clinical CT. The method consists in overlaying low-resolution time-lapse CT scans acquired during injection onto pre-operative high-resolution microCT scans, generating composite-resolution time-lapse CT series of cement flow within bone. In this in vitro study, composite-resolution time-lapse CT was applied to eight intact and five artificially fractured cadaveric vertebrae during vertebroplasty. The time-lapse scans were acquired at one-milliliter cement injection steps until a total of 10 ml cement was injected. The composite-resolution series were then converted into micro finite element models to compute strains distribution under virtual axial loading. Relocation of strain energy density within bone structure was observed throughout the progression of the procedure. Interestingly, the normalized effect of cement injection on the overall stiffness of the vertebrae was similar between intact and fractured specimens, although at different orders of magnitude. In conclusion, composite time-lapse CT can picture cement flows during bone augmentation. The composite images can also be easily converted into finite element models to compute virtual strain distributions under loading at every step of an injection, providing deeper understanding on the biomechanics of vertebroplasty. Copyright © 2015 IPEM. Published by Elsevier Ltd. All rights reserved.

Deciphering the Possible Role of Strain Path on the Evolution of Microstructure, Texture, and Magnetic Properties in a Fe-Cr-Ni Alloy

NASA Astrophysics Data System (ADS)

Kumar, Amit; Khatirkar, Rajesh Kisni; Gupta, Aman; Shekhawat, Satish K.; Suwas, Satyam

2018-06-01

In the present work, the influence of strain path on the evolution of microstructure, crystallographic texture, and magnetic properties of a two-phase Fe-Cr-Ni alloy was investigated. The Fe-Cr-Ni alloy had nearly equal proportion of austenite and ferrite and was cold rolled up to a true strain of 1.6 (thickness reduction) using two different strain paths—unidirectional rolling and multi-step cross rolling. The microstructures were characterized by scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD), while crystallographic textures were determined using X-ray diffraction. For magnetic characterization, B-H loops and M-H curves were measured and magnetic force microscopy was performed. After unidirectional rolling, ferrite showed the presence of strong α-fiber (rolling direction, RD//<110>) and austenite showed strong brass type texture (consisting of Brass (Bs) ({110}<112>), Goss ({110}<001>), and S ({123}<634>)). After multi-step cross rolling, strong rotated cube ({100}<110>) was developed in ferrite, while austenite showed ND (normal direction) rotated brass ( 10 deg) texture. The strain-induced martensite (SIM) was found to be higher in unidirectionally rolled samples than multi-step cross-rolled samples. The coherently diffracting domain size, micro-strain, coercivity, and core loss also showed a strong correlation with strain and strain path. More strain was partitioned into austenite than ferrite during deformation (unidirectional as well as cross rolling). Further, the strain partitioning (in both austenite and ferrite) was found to be higher in unidirectionally rolled samples.

Biofilm formation by virulent and non-virulent strains of Haemophilus parasuis.

PubMed

Bello-Ortí, Bernardo; Deslandes, Vincent; Tremblay, Yannick D N; Labrie, Josée; Howell, Kate J; Tucker, Alexander W; Maskell, Duncan J; Aragon, Virginia; Jacques, Mario

2014-11-27

Haemophilus parasuis is a commensal bacterium of the upper respiratory tract of healthy pigs. It is also the etiological agent of Glässer's disease, a systemic disease characterized by polyarthritis, fibrinous polyserositis and meningitis, which causes high morbidity and mortality in piglets. The aim of this study was to evaluate biofilm formation by well-characterized virulent and non-virulent strains of H. parasuis. We observed that non-virulent strains isolated from the nasal cavities of healthy pigs formed significantly (p < 0.05) more biofilms than virulent strains isolated from lesions of pigs with Glässer's disease. These differences were observed when biofilms were formed in microtiter plates under static conditions or formed in the presence of shear force in a drip-flow apparatus or a microfluidic system. Confocal laser scanning microscopy using different fluorescent probes on a representative subset of strains indicated that the biofilm matrix contains poly-N-acetylglucosamine, proteins and eDNA. The biofilm matrix was highly sensitive to degradation by proteinase K. Comparison of transcriptional profiles of biofilm and planktonic cells of the non-virulent H. parasuis F9 strain revealed a significant number of up-regulated membrane-related genes in biofilms, and genes previously identified in Actinobacillus pleuropneumoniae biofilms. Our data indicate that non-virulent strains of H. parasuis have the ability to form robust biofilms in contrast to virulent, systemic strains. Biofilm formation might therefore allow the non-virulent strains to colonize and persist in the upper respiratory tract of pigs. Conversely, the planktonic state of the virulent strains might allow them to disseminate within the host.

Biaxial Mechanical Testing of Posterior Sclera using High-Resolution Ultrasound Speckle Tracking for Strain Measurements

PubMed Central

Cruz-Perez, Benjamin; Tang, Junhua; Morris, Hugh J.; Palko, Joel R.; Pan, Xueliang; Hart, Richard T.; Liu, Jun

2014-01-01

This study aimed to characterize the mechanical responses of the sclera, the white outer coat of the eye, under equal-biaxial loading with unrestricted shear. An ultrasound speckle tracking technique was used to measure tissue deformation through sample thickness, expanding the capabilities of surface strain techniques. Eight porcine scleral samples were tested within 72 hours postmortem. High resolution ultrasound scans of scleral cross-sections along the two loading axes were acquired at 25 consecutive biaxial load levels. An additional repeat of the biaxial loading cycle was performed to measure a third normal strain emulating a strain gauge rosette for calculating the in-plane shear. The repeatability of the strain measurements during identical biaxial ramps was evaluated. A correlation-based ultrasound speckle tracking algorithm was used to compute the displacement field and determine the distributive strains in the sample cross-sections. A Fung type constitutive model including a shear term was used to determine the material constants of each individual specimen by fitting the model parameters to the experimental stress-strain data. A non-linear stress-strain response was observed in all samples. The meridian direction had significantly larger strains than the circumferential direction during equal-biaxial loadings (P’s<0.05). The stiffness along the two directions were also significantly different (P=0.02) but highly correlated (R2=0.8). These results showed that the mechanical properties of the porcine sclera were nonlinear and anisotropic under biaxial loading. This work has also demonstrated the feasibility of using ultrasound speckle tracking for strain measurements during mechanical testing. PMID:24438767

The Effects of Academic and Interpersonal Stress on Dating Violence among College Students: A Test of Classical Strain Theory

ERIC Educational Resources Information Center

Mason, Brandon; Smithey, Martha

2012-01-01

This study examines Merton's Classical Strain Theory (1938) as a causative factor in intimate partner violence among college students. We theorize that college students experience general life strain and cumulative strain as they pursue the goal of a college degree. We test this strain on the likelihood of using intimate partner violence. Strain…

Formation of composite polyacrylamide and silicone substrates for independent control of stiffness and strain.

PubMed

Simmons, Chelsey S; Ribeiro, Alexandre J S; Pruitt, Beth L

2013-02-21

Cells that line major tissues in the body such as blood vessels, lungs and gastrointestinal tract experience deformation from mechanical strain with our heartbeat, breathing, and other daily activities. Tissues also remodel in both development and disease, changing their mechanical properties. Taken together, cells can experience vastly different mechanical cues resulting from the combination of these interdependent stimuli. To date, most studies of cellular mechanotransduction have been limited to assays in which variations in substrate stiffness and strain were not combined. Here, we address this technological gap by implementing a method that can simultaneously tune both substrate stiffness and mechanical strain. Substrate stiffness is controlled with different monomer and crosslinker ratios during polyacrylamide gel polymerization, and strain is transferred from the underlying silicone platform when stretched. We demonstrate this platform with polyacrylamide gels with elastic moduli at 6 kPa and 20 kPa in combination with two different silicone formulations. The gels remain attached with up to 50% applied strains. To validate strain transfer through the gels into cells, we employ particle-tracking methods and observe strain transmission via cell morphological changes.

Formation of composite polyacrylamide and silicone substrates for independent control of stiffness and strain

PubMed Central

Simmons, Chelsey S.; Ribeiro, Alexandre J. S.; Pruitt, Beth L.

2013-01-01

Cells that line major tissues in the body such as blood vessels, lungs and gastrointestinal tract experience deformation from mechanical strain with our heartbeat, breathing, and other daily activities. Tissues also remodel in both development and disease, changing their mechanical properties. Taken together, cells can experience vastly different mechanical cues resulting from the combination of these interdependent stimuli. To date, most studies of cellular mechanotransduction have been limited to assays in which variations in substrate stiffness and strain were not combined. Here, we address this technological gap by implementing a method that can simultaneously tune both substrate stiffness and mechanical strain. Substrate stiffness is controlled with different monomer and crosslinker ratios during polyacrylamide gel polymerization, and strain is transferred from the underlying silicone platform when stretched. We demonstrate this platform with polyacrylamide gels with elastic moduli at 6 kPa and 20 kPa in combination with two different silicone formulations. The gels remain attached with up to 50% applied strains. To validate strain transfer through the gels into cells, we employ particle-tracking methods and observe strain transmission via cell morphological changes. PMID:23287818

Measured Radiation Patterns of the Boeing 91-Element ICAPA Antenna With Comparison to Calculations

NASA Technical Reports Server (NTRS)

Lambert, Kevin M.; Burke, Thomas (Technical Monitor)

2003-01-01

This report presents measured antenna patterns of the Boeing 91-Element Integrated Circuit Active Phased Array (ICAPA) Antenna at 19.85 GHz. These patterns were taken in support of various communication experiments that were performed using the antenna as a testbed. The goal here is to establish a foundation of the performance of the antenna for the experiments. An independent variable used in the communication experiments was the scan angle of the antenna. Therefore, the results presented here are patterns as a function of scan angle, at the stated frequency. Only a limited number of scan angles could be measured. Therefore, a computer program was written to simulate the pattern performance of the antenna at any scan angle. This program can be used to facilitate further study of the antenna. The computed patterns from this program are compared to the measured patterns as a means of validating the model.

Methane production from kitchen waste using Escherichia coli.

PubMed

Jayalakshmi, S; Joseph, Kurian; Sukumaran, V

2007-04-01

Escherichia coli (E. coli) strain isolated from biogas plant sludge was examined for its ability to enhance biogas from kitchen waste during solid phase anaerobic digestion. The laboratory experiments were conducted for total solid concentrations of 20% and 22%. Kitchen waste was characterized for physico-chemical parameters and laboratory experiments were conducted with and without E. coli strain. It was found that the reactor with E. coli produced 17% more biogas than the reactors that are operated without E. coli strain.

Scanning drop sensor

DOEpatents

Jin, Jian; Xiang, Chengxiang; Gregoire, John

2017-05-09

Electrochemical experiments are performed on a collection of samples by suspending a drop of electrolyte solution between an electrochemical experiment probe and one of the samples that serves as a test sample. During the electrochemical experiment, the electrolyte solution is added to the drop and an output solution is removed from the drop. The probe and collection of samples can be moved relative to one another so the probe can be scanned across the samples.

Experimental Study and Modelling of Poly (Methyl Methacrylate) and Polycarbonate Compressive Behavior from Low to High Strain Rates

NASA Astrophysics Data System (ADS)

El-Qoubaa, Z.; Colard, L.; Matadi Boumbimba, R.; Rusinek, A.

2018-06-01

This paper concerns an experimental investigation of Polycarbonate and Poly (methyl methacrylate) compressive behavior from low to high strain rates. Experiments were conducted from 0.001/s to ≈ 5000/s for PC and from 0.001/s to ≈ 2000/s for PMMA. The true strain-stress behavior is established and analyzed at various stain rates. Both PC and PMMA mechanical behavior appears as known, to be strain rate and temperature dependent. The DSGZ model is selected for modelling the strain-stress curves while the yield stress is reproduced using the cooperative model and a modified Eyring equation based on Eyring first process theory. All the three models predictions are in agreement with experiments performed on PC and PMMA.

Experimental Study and Modelling of Poly (Methyl Methacrylate) and Polycarbonate Compressive Behavior from Low to High Strain Rates

NASA Astrophysics Data System (ADS)

El-Qoubaa, Z.; Colard, L.; Matadi Boumbimba, R.; Rusinek, A.

2018-03-01

This paper concerns an experimental investigation of Polycarbonate and Poly (methyl methacrylate) compressive behavior from low to high strain rates. Experiments were conducted from 0.001/s to ≈ 5000/s for PC and from 0.001/s to ≈ 2000/s for PMMA. The true strain-stress behavior is established and analyzed at various stain rates. Both PC and PMMA mechanical behavior appears as known, to be strain rate and temperature dependent. The DSGZ model is selected for modelling the strain-stress curves while the yield stress is reproduced using the cooperative model and a modified Eyring equation based on Eyring first process theory. All the three models predictions are in agreement with experiments performed on PC and PMMA.

Nano-scale luminescence characterization of individual InGaN/GaN quantum wells stacked in a microcavity using scanning transmission electron microscope cathodoluminescence

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

Schmidt, Gordon, E-mail: Gordon.Schmidt@ovgu.de; Müller, Marcus; Veit, Peter

2014-07-21

Using cathodoluminescence spectroscopy directly performed in a scanning transmission electron microscope at liquid helium temperatures, the optical and structural properties of a 62 InGaN/GaN multiple quantum well embedded in an AlInN/GaN based microcavity are investigated at the nanometer scale. We are able to spatially resolve a spectral redshift between the individual quantum wells towards the surface. Cathodoluminescence spectral linescans allow directly visualizing the critical layer thickness in the quantum well stack resulting in the onset of plastic relaxation of the strained InGaN/GaN system.

Spatial and Temporal Variations in Slip Partitioning During Oblique Convergence Experiments

NASA Astrophysics Data System (ADS)

Beyer, J. L.; Cooke, M. L.; Toeneboehn, K.

2017-12-01

Physical experiments of oblique convergence in wet kaolin demonstrate the development of slip partitioning, where two faults accommodate strain via different slip vectors. In these experiments, the second fault forms after the development of the first fault. As one strain component is relieved by one fault, the local stress field then favors the development of a second fault with different slip sense. A suite of physical experiments reveals three styles of slip partitioning development controlled by the convergence angle and presence of a pre-existing fault. In experiments with low convergence angles, strike-slip faults grow prior to reverse faults (Type 1) regardless of whether the fault is precut or not. In experiments with moderate convergence angles, slip partitioning is dominantly controlled by the presence of a pre-existing fault. In all experiments, the primarily reverse fault forms first. Slip partitioning then develops with the initiation of strike-slip along the precut fault (Type 2) or growth of a secondary reverse fault where the first fault is steepest. Subsequently, the slip on the first fault transitions to primarily strike-slip (Type 3). Slip rates and rakes along the slip partitioned faults for both precut and uncut experiments vary temporally, suggesting that faults in these slip-partitioned systems are constantly adapting to the conditions produced by slip along nearby faults in the system. While physical experiments show the evolution of slip partitioning, numerical simulations of the experiments provide information about both the stress and strain fields, which can be used to compute the full work budget, providing insight into the mechanisms that drive slip partitioning. Preliminary simulations of precut experiments show that strain energy density (internal work) can be used to predict fault growth, highlighting where fault growth can reduce off-fault deformation in the physical experiments. In numerical simulations of uncut experiments with a first non-planar oblique slip fault, strain energy density is greatest where the first fault is steepest, as less convergence is accommodated along this portion of the fault. The addition of a second slip-partitioning fault to the system decreases external work indicating that these faults increase the mechanical efficiency of the system.

Faulting of rocks in three-dimensional strain fields I. Failure of rocks in polyaxial, servo-control experiments

USGS Publications Warehouse

Reches, Z.; Dieterich, J.H.

1983-01-01

The dependence of the number of sets of faults and their orientation on the intermediate strain axis is investigated through polyaxial tests, reported here, and theoretical analysis, reported in an accompanying paper. In the experiments, cubic samples of Berea sandstone, Sierra-White and Westerly granites, and Candoro and Solnhofen limestones were loaded on their three pairs of faces by three independent, mutually perpendicular presses at room temperature. Two of the presses were servo-controlled and applied constant displacement rates throughout the experiment. Most samples display three or four sets of faults in orthorhombic symmetry. These faults form in several yielding events that follow a stage of elastic deformation. In many experiments, the maximum and the intermediate compressive stresses interchange orientations during the yielding events, where the corresponding strains are constant. The final stage of most experiments is characterized by slip along the faults. ?? 1983.

Faulting of rocks in three-dimensional strain fields I. Failure of rocks in polyaxial, servo-control experiments

NASA Astrophysics Data System (ADS)

Reches, Ze'ev; Dieterich, James H.

1983-05-01

The dependence of the number of sets of faults and their orientation on the intermediate strain axis is investigated through polyaxial tests, reported here, and theoretical analysis, reported in an accompanying paper. In the experiments, cubic samples of Berea sandstone, Sierra-White and Westerly granites, and Candoro and Solnhofen limestones were loaded on their three pairs of faces by three independent, mutually perpendicular presses at room temperature. Two of the presses were servo-controlled and applied constant displacement rates throughout the experiment. Most samples display three or four sets of faults in orthorhombic symmetry. These faults form in several yielding events that follow a stage of elastic deformation. In many experiments, the maximum and the intermediate compressive stresses interchange orientations during the yielding events, where the corresponding strains are constant. The final stage of most experiments is characterized by slip along the faults.

Impact of the introduction of emergency ultrasound to one large UK emergency department: the REBUS study.

PubMed

Kwok, T'ng Choong; Johnson, Sue; Reed, Matthew James

2013-02-01

Firstly, to detail the experiences of one UK training region in establishing an emergency ultrasound (EU) training programme and secondly, to report the initial 30 months of EU scanning experience. Prospective study of all documented emergency department (ED) ultrasound scans. Results were extracted from written paper reports and/or electronically saved images. Details of scan date, time, type of scan, grade of operator, supervision status (whether supervised by a level 1 competent scanner) and whether the scan was clinical (performed or supervised by a level 1 operator) or training, were recorded. EU scans were reviewed for quality (internal quality assurance) and for diagnostic accuracy (external quality assurance). Between 14 January 2009 and 4 July 2011, 626 scans were performed by 41 operators. 263 (42%) scans were completed outside of normal working hours (09:00 to 17:00). There were 251 abdominal aorta and inferior vena cava scans (40% of all scans) and 198 focused assessment with sonography in trauma scans (32%). The number of scans performed by each operator varied widely. 87 scans (14%) were supervised but the majority (459; 73%) were not. 484 (77%) scans were for training purposes, 124 (20%) were clinical scans and the majority (401; 63%) were performed by either speciality registrars (ST4-6) or specialist registrars (SpR). When the three commonest types of scans performed were analysed, eight false positives and 11 false negatives were identified. Only seven of these were deemed of poor quality and none led to poor patient outcome. Since the acquisition of our ED ultrasound machine and the development of a quality assured training programme, on average 20 scans per month have been performed in the ED, with no known adverse patient outcomes.

Reduction in radiation dose with reconstruction technique in the brain perfusion CT

NASA Astrophysics Data System (ADS)

Kim, H. J.; Lee, H. K.; Song, H.; Ju, M. S.; Dong, K. R.; Chung, W. K.; Cho, M. S.; Cho, J. H.

2011-12-01

The principal objective of this study was to verify the utility of the reconstruction imaging technique in the brain perfusion computed tomography (PCT) scan by assessing reductions in the radiation dose and analyzing the generated images. The setting used for image acquisition had a detector coverage of 40 mm, a helical thickness of 0.625 mm, a helical shuttle mode scan type and a rotation time of 0.5 s as the image parameters used for the brain PCT scan. Additionally, a phantom experiment and an animal experiment were carried out. In the phantom and animal experiments, noise was measured in the scanning with the tube voltage fixed at 80 kVp (kilovolt peak) and the level of the adaptive statistical iterative reconstruction (ASIR) was changed from 0% to 100% at 10% intervals. The standard deviation of the CT coefficient was measured three times to calculate the mean value. In the phantom and animal experiments, the absorbed dose was measured 10 times under the same conditions as the ones for noise measurement before the mean value was calculated. In the animal experiment, pencil-type and CT-dedicated ionization chambers were inserted into the central portion of pig heads for measurement. In the phantom study, as the level of the ASIR changed from 0% to 100% under identical scanning conditions, the noise value and dose were proportionally reduced. In our animal experiment, the noise value was lowest when the ASIR level was 50%, unlike in the phantom study. The dose was reduced as in the phantom study.

Effect of Chitosan Acetate on Bacteria Occurring on Neungee Mushrooms, Sarcodon aspratus

PubMed Central

Park, Bom Soo; Koo, Chang-Duck; Ka, Kang Hyeon

2008-01-01

Minimal growth inhibitory concentrations (MICs) of chitosan acetate (M.W. 60 kDa) on heterotrophic bacteria (strains MK1, S, and R) isolated from the soft-rotten tissues of Neungee mushroom (Sarcodon aspratus) were measured. The slimy substance produced by the MK1 strain was responsible for the diseased mushroom's appearance. The S and R strains were members of the Burkholderia cepacia complex. These strains showed different levels of susceptibility toward chitosan acetate. The MIC of chitosan acetate against the MK1 and S strains was 0.06%. The MIC against the R strain was greater than 0.10%. Survival fractions of the MK1 and S strains at the MIC were 3 × 10-4 and 1.4 × 10-3 after 24 h, and 2 × 10-4 and 7 × 10-4 after 48 h, respectively. Survival fractions of the R strain after 24 and 48 hr at 0.1% chitosan acetate were 1 × 10-2 and 6.9 × 10-3, respectively. Compared to the MK1 and S strains, the low susceptibility of the R stain towards chitosan acetate could be due to the ability of the R strain to utilize chitosan as a carbon source. Thirty-eight percent of Neungee pieces treated in a 0.06% chitosan acetate solution for 2~3 second did not show any bacterial growth at 4 days, whereas bacterial growth around untreated mushroom pieces occurred within 2 days. These data suggest that chitosan acetate is highly effective in controlling growth of indigenous microorganisms on Neungee. The scanning electron micrographs of the MK1 strain treated with chitosan revealed a higher degree of disintegrated and distorted cellular structures. PMID:23997635

Resistance of extremely halophilic archaea to zinc and zinc oxide nanoparticles

NASA Astrophysics Data System (ADS)

Salgaonkar, Bhakti B.; Das, Deepthi; Bragança, Judith Maria

2016-02-01

Industrialization as well as other anthropogenic activities have resulted in addition of high loads of metal and/or metal nanoparticles to the environment. In this study, the effect of one of the widely used heavy metal, zinc (Zn) and zinc oxide nanoparticles (ZnO NPs) on extremely halophilic archaea was evaluated. One representative member from four genera namely Halococcus, Haloferax, Halorubrum and Haloarcula of the family Halobacteriaceae was taken as the model organism. All the haloarchaeal genera investigated were resistant to both ZnCl2 and ZnO NPs at varying concentrations. Halococcus strain BK6 and Haloferax strain BBK2 showed the highest resistance in complex/minimal medium of up to 2.0/1.0 mM ZnCl2 and 2.0/1.0-0.5 mM ZnO NP. Accumulation of ZnCl2/ZnO NPs was seen as Haloferax strain BBK2 (287.2/549.6 mg g-1) > Halococcus strain BK6 (165.9/388.5 mg g-1) > Haloarcula strain BS2 (93.2/28.5 mg g-1) > Halorubrum strain BS17 (29.9/16.2 mg g-1). Scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDX) analysis revealed that bulk ZnCl2 was sorbed at a higher concentration (21.77 %) on the cell surface of Haloferax strain BBK2 as compared to the ZnO NPs (14.89 %).

High-temperature deformation and processing maps of Zr-4 metal matrix with dispersed coated surrogate nuclear fuel particles

NASA Astrophysics Data System (ADS)

Chen, Jing; Liu, Huiqun; Zhang, Ruiqian; Li, Gang; Yi, Danqing; Lin, Gaoyong; Guo, Zhen; Liu, Shaoqiang

2018-06-01

High-temperature compression deformation of a Zr-4 metal matrix with dispersed coated surrogate nuclear fuel particles was investigated at 750 °C-950 °C with a strain rate of 0.01-1.0 s-1 and height reduction of 20%. Scanning electron microscopy was utilized to investigate the influence of the deformation conditions on the microstructure of the composite and damage to the coated surrogate fuel particles. The results indicated that the flow stress of the composite increased with increasing strain rate and decreasing temperature. The true stress-strain curves showed obvious serrated oscillation characteristics. There were stable deformation ranges at the initial deformation stage with low true strain at strain rate 0.01 s-1 for all measured temperatures. Additionally, the coating on the surface of the surrogate nuclear fuel particles was damaged when the Zr-4 matrix was deformed at conditions of high strain rate and low temperature. The deformation stability was obtained from the processing maps and microstructural characterization. The high-temperature deformation activation energy was 354.22, 407.68, and 433.81 kJ/mol at true strains of 0.02, 0.08, and 0.15, respectively. The optimum deformation parameters for the composite were 900-950 °C and 0.01 s-1. These results are expected to provide guidance for subsequent determination of possible hot working processes for this composite.

Degradation of polyester polyurethane by a newly isolated soil bacterium, Bacillus subtilis strain MZA-75.

PubMed

Shah, Ziaullah; Krumholz, Lee; Aktas, Deniz Fulya; Hasan, Fariha; Khattak, Mutiullah; Shah, Aamer Ali

2013-11-01

A polyurethane (PU) degrading bacterial strain MZA-75 was isolated from soil through enrichment technique. The bacterium was identified through 16S rRNA gene sequencing, the phylogenetic analysis indicated the strain MZA-75 belonged to genus Bacillus having maximum similarity with Bacillus subtilis strain JBE0016. The degradation of PU films by strain MZA-75 in mineral salt medium (MSM) was analyzed by scanning electron microscopy (SEM), fourier transform infra-red spectroscopy (FT-IR) and gel permeation chromatography (GPC). SEM revealed the appearance of widespread cracks on the surface. FTIR spectrum showed decrease in ester functional group. Increase in polydispersity index was observed in GPC, which indicates chain scission as a result of microbial treatment. CO2 evolution and cell growth increased when PU was used as carbon source in MSM in Sturm test. Increase in both cell associated and extracellular esterases was observed in the presence of PU indicated by p-Nitrophenyl acetate (pNPA) hydrolysis assay. Analysis of cell free supernatant by gas chromatography-mass spectrometry (GC-MS) revealed that 1,4-butanediol and adipic acid monomers were produced. Bacillus subtilis strain MZA-75 can degrade the soft segment of polyester polyurethane, unfortunately no information about the fate of hard segment could be obtained. Growth of strain MZA-75 in the presence of these metabolites indicated mineralization of ester hydrolysis products into CO2 and H2O.

Influence of Stimulus Symmetry and Complexity upon Haptic Scanning Strategies During Detection, Learning and Recognition Tasks.

ERIC Educational Resources Information Center

Locher, Paul J.; Simmons, Roger W.

Two experiments were conducted to investigate the perceptual processes involved in haptic exploration of randomly generated shapes. Experiment one required subjects to detect symmetrical or asymmetrical characteristics of individually presented plastic shapes, also varying in complexity. Scanning time for both symmetrical and asymmetrical shapes…

Repeated batch fermentation of immobilized E. coli expressing Vitreoscilla hemoglobin for long-term use

PubMed Central

Sar, Taner; Seker, Gamze; Erman, Ayse Gokce; Stark, Benjamin C.; Yesilcimen Akbas, Meltem

2017-01-01

ABSTRACT This study describes an efficient and reusable process for ethanol production from medium containing whey powder, using alginate immobilized ethanologenic E. coli strains either expressing (TS3) or not expressing (FBR5) Vitreoscilla hemoglobin. Reuseabilities of the FBR5 and TS3 strains were investigated regarding their ethanol production capacities over the course of 15 successive 96-h batch fermentations. The ethanol production was fairly stable over the entire duration of the experiment, with strain TS3 maintaining a substantial advantage over strain FBR5. Storage of both strains in 2 different solutions for up to 60 d resulted in only a modest loss of ethanol production, with strain TS3 consistently outperforming strain FBR5 by a substantial amount. Strains stored for 15 or 30 d maintained their abilities to produce ethanol without dimunition over the course of 8 successive batch fermentations; again strain TS3 maintained a substantial advantage over strain FBR5 throughout the entire experiment. Thus, immobilization is a useful strategy to maintain the advantage in ethanol productivity afforded by expression of Vitreoscilla hemoglobin over long periods of time and large numbers of repeated batch fermentations, including, as in this case, using media with food processing wastes as the carbon source. PMID:28394725

Repeated batch fermentation of immobilized E. coli expressing Vitreoscilla hemoglobin for long-term use.

PubMed

Sar, Taner; Seker, Gamze; Erman, Ayse Gokce; Stark, Benjamin C; Yesilcimen Akbas, Meltem

2017-09-03

This study describes an efficient and reusable process for ethanol production from medium containing whey powder, using alginate immobilized ethanologenic E. coli strains either expressing (TS3) or not expressing (FBR5) Vitreoscilla hemoglobin. Reuseabilities of the FBR5 and TS3 strains were investigated regarding their ethanol production capacities over the course of 15 successive 96-h batch fermentations. The ethanol production was fairly stable over the entire duration of the experiment, with strain TS3 maintaining a substantial advantage over strain FBR5. Storage of both strains in 2 different solutions for up to 60 d resulted in only a modest loss of ethanol production, with strain TS3 consistently outperforming strain FBR5 by a substantial amount. Strains stored for 15 or 30 d maintained their abilities to produce ethanol without dimunition over the course of 8 successive batch fermentations; again strain TS3 maintained a substantial advantage over strain FBR5 throughout the entire experiment. Thus, immobilization is a useful strategy to maintain the advantage in ethanol productivity afforded by expression of Vitreoscilla hemoglobin over long periods of time and large numbers of repeated batch fermentations, including, as in this case, using media with food processing wastes as the carbon source.

Relations between scanning and recognition of own- and other-race faces in 6- and 9-month-old infants.

PubMed

Liu, Shaoying; Quinn, Paul C; Xiao, Naiqi G; Wu, Zhijun; Liu, Guangxi; Lee, Kang

2018-06-01

Infants typically see more own-race faces than other-race faces. Existing evidence shows that this difference in face race experience has profound consequences for face processing: as early as 6 months of age, infants scan own- and other-race faces differently and display superior recognition for own- relative to other-race faces. However, it is unclear whether scanning of own-race faces is related to the own-race recognition advantage in infants. To bridge this gap in the literature, the current study used eye tracking to investigate the relation between own-race face scanning and recognition in 6- and 9-month-old Asian infants (N = 82). The infants were familiarized with dynamic own- and other-race faces, and then their face recognition was tested with static face images. Both age groups recognized own- but not other-race faces. Also, regardless of race, the more infants scanned the eyes of the novel versus familiar faces at test, the better their face-recognition performance. In addition, both 6- and 9-month-olds fixated significantly longer on the nose of own-race faces, and greater fixation on the nose during test trials correlated positively with individual novelty preference scores in the own- but not other-race condition. The results suggest that some aspects of the relation between recognition and scanning are independent of differential experience with face race, whereas other aspects are affected by such experience. More broadly, the findings imply that scanning and recognition may become linked during infancy at least in part through the influence of perceptual experience. © 2018 The Institute of Psychology, Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd.

Strained enabled Ferroelectricity in CaTiO3 Thin Films Probed by Nonlinear Optics and Scanning Probe Microscopy

NASA Astrophysics Data System (ADS)

Vlahos, Eftihia; Kumar, Amit; Denev, Sava; Brooks, Charles; Schlom, Darrell; Eklund, Carl-Johan; Rabe, Karin M.; Fennie, Craig J.; Gopalan, Venkatraman

2009-03-01

Calcium titanate, CaTiO3 is not a ferroelectric in its bulk form. However, first principles calculations predict that biaxially tensile strained CaTiO3 thin films should become ferroelectric. Here, we indeed confirm that strained CaTiO3 films become ferroelectric with a Curie temperature of ˜125K. Optical second harmonic generation (SHG) measurements, polarization studies, and in-situ electric-field measurements for a number of films with different strain values will be presented: CaTiO3/DyScO3(110), CaTiO3/SrTiO3 (100),CaTiO3/GdScO3/NdGaO3(110), CaTiO3/LaSrAlO3(001) as well as for a single crystal CaTiO3. From these studies, we conclude that strained CaTiO3 films are ferroelectric with a point group symmetry of mm2, and show reversible domain switching characteristics under an electric field. We also present results of variable temperature piezoelectric force microscopy for imaging the polar domains in the ferroelectric phase. These results suggest that strain is a valuable tool for inducing polar, long range ferroelectric order in even non-polar ceramic materials such as CaTiO3.

Exploration of the antioxidant system and photosynthetic system of a marine algicidal Bacillus and its effect on four harmful algal bloom species.

PubMed

Hou, Shaoling; Shu, Wanjiao; Tan, Shuo; Zhao, Ling; Yin, Pinghe

2016-01-01

A novel marine bacterium, strain B1, initially showed 96.4% algicidal activity against Phaeocystis globosa. Under this situation, 3 other harmful algal species (Skeletonema costatum, Heterosigma akashiwo, and Prorocentrum donghaiense) were chosen to study the algicidal effects of strain B1, and the algicidal activities were 91.4%, 90.7%, and 90.6%, respectively. To explore the algicidal mechanism of strain B1 on these 4 harmful algal species, the characteristics of the antioxidant system and photosynthetic system were studied. Sensitivity to strain B1 supernatant, enzyme activity, and gene expression varied with algal species, while the algicidal patterns were similar. Strain B1 supernatant increased malondialdehyde contents; decreased chlorophyll a contents; changed total antioxidant and superoxide dismutase activity; and restrained psbA, psbD, and rbcL genes expression, which eventually resulted in the algal cells death. The algicidal procedure was observed using field emission scanning electron microscopy, which indicated that algal cells were lysed and cellular substances were released. These findings suggested that the antioxidant and photosynthetic system of these 4 algal species was destroyed under strain B1 supernatant stress. This is the first report to explore and compare the mechanism of a marine Bacillus against harmful algal bloom species of covered 4 phyla.

Preliminary evaluation of infrared spectroscopy for the differentiation of Brettanomyces bruxellensis strains isolated from red wines.

PubMed

Oelofse, A; Malherbe, S; Pretorius, I S; Du Toit, M

2010-10-15

The objective of this study was to evaluate different infrared spectroscopy methods in combination with chemometrics for the differentiation between Brettanomyces bruxellensis strains. These methods of discrimination were applied to intact yeast cells of B. bruxellensis strains and on wines spoiled by the same strains. Eleven wine isolates of B. bruxellensis were evaluated for volatile phenol production in red wine and their genetic diversity was determined by Restriction Endonuclease Analysis-Pulsed Field Gel Electrophoresis (REA-PFGE). Fourier transform mid-infrared (FTMIR) spectroscopy was used to obtain spectral fingerprints of the spoiled wines. Attenuated total reflectance (ATR) was used to obtain spectral fingerprints from the intact cells of the 11 B. bruxellensis strains. The groupings from the genetic fingerprints obtained with REA-PFGE were used as reference firstly for comparison with the groupings observed with the FTMIR spectral fingerprint of the wines and secondly for the FTIR-ATR spectral fingerprints from the whole cells. Results indicated that ATR-IR spectra obtained by scanning whole cells of B. bruxellensis could be useful for rapid strain typing in comparison or complementary to molecular techniques and FTMIR spectra from wines provide a useful resource for the discrimination between B. bruxellensis contaminated wines. Copyright © 2010 Elsevier B.V. All rights reserved.

Identifying Deformation and Strain Hardening Behaviors of Nanoscale Metallic Multilayers Through Nano-wear Testing

DOE PAGES

Economy, David Ross; Mara, Nathan A.; Schoeppner, R.; ...

2016-01-13

In complex loading conditions (e.g. sliding contact), mechanical properties, such as strain hardening and initial hardness, will dictate the long-term performance of materials systems. With this in mind, the strain hardening behaviors of Cu/Nb nanoscale metallic multilayer systems were examined by performing nanoindentation tests within nanoscratch wear boxes and undeformed, as-deposited regions. Both the architecture and substrate influence were examined by utilizing three different individual layer thicknesses (2, 20, and 100 nm) and two total film thicknesses (1 and 10 μm). After nano-wear deformation, multilayer systems with thinner layers showed less volume loss as measured by laser scanning microscopy. Additionally,more » the hardness of the deformed regions significantly rose with respect to the as-deposited measurements, which further increased with greater wear loads. Strain hardening exponents for multilayers with thinner layers (2 and 20 nm, n ≈ 0.018 and n ≈ 0.022 respectively) were less than was determined for 100 nm systems (n ≈ 0.041). These results suggest that singledislocation based deformation mechanisms observed for the thinner systems limit the extent of achievable strain hardening. This conclusion indicates that impacts of both architecture strengthening and strain hardening must be considered to accurately predict multilayer performance during sliding contact across varying length scales.« less

Application of VitaVallis dressing for infected wounds

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

Kirilova, N. V., E-mail: n.kirilova@vitavallis.com; Fomenko, A. N., E-mail: alserova@ispms.tsc.ru; Korovin, M. S., E-mail: msk@ispms.tsc.ru

Today there is a growing demand for safe and efficient antimicrobial dressings for infected wound treatment. The antimicrobial sorption material for VitaVallis dressings was produced by one-stage oxidation of aluminum nanopowder in water in the presence of fibrous acetylcellulose matrix. Scanning electron microscopy revealed that the material is made up of fibers of diameter 1.5–3.0 µm with adhered agglomerated alumina nanosheets. An antimicrobial study revealed a high inhibitory effect of VitaVallis against the growth of gram-negative (E.coli, P. aeruginosa) and gram-positive (S. aureus) strains. The antimicrobial activity of the dressing against microbial pathogens on the wound surface was demonstrated in inmore » vivo experiments on male rats. The dressing was also tested on volunteer patients. The testing showed reduction of the wound healing period, accelerated cleaning of the infected wound and enhanced tissue regeneration in the wound. The results demonstrate that the VitaVallis dressing can be used for the treatment of deep infected wounds.« less

Thermal Cycling and Isothermal Deformation Response of Polycrystalline NiTi: Simulations vs. Experiment

NASA Technical Reports Server (NTRS)

Manchiraju, Sivom; Gaydosh, Darrell; Benafan, Othmane; Noebe, Ronald; Vaidyanathan, Raj; Anderson, Peter M.

2011-01-01

A recent microstructure-based FEM model that couples crystal-based plasticity, the B2<-> MB190 phase transformation and anisotropic elasticity at the grain scale is calibrated to recent data for polycrystalline NiTi (49.9 at.% Ni). Inputs include anisotropic elastic properties, texture and differential scanning calorimetry data, as well as a subset of recent isothermal deformation and load-biased thermal cycling data. The model is assessed against additional experimental data. Several experimental trends are captured - in particular, the transformation strain during thermal cycling monotonically increases and reaches a peak with increasing bias stress. This is achieved, in part, by modifying the martensite hardening matrix proposed by Patoor et al. [Patoor E, Eberhardt A, Berveiller M. J Phys IV 1996;6:277]. Some experimental trends are underestimated - in particular, the ratcheting of macrostrain during thermal cycling. This may reflect a model limitation that transformation-plasticity coupling is captured on a coarse (grain) scale but not on a fine (martensitic plate) scale.

Out-of-Plane Piezoelectricity and Ferroelectricity in Layered α-In2Se3 Nanoflakes.

PubMed

Zhou, Yu; Wu, Di; Zhu, Yihan; Cho, Yujin; He, Qing; Yang, Xiao; Herrera, Kevin; Chu, Zhaodong; Han, Yu; Downer, Michael C; Peng, Hailin; Lai, Keji

2017-09-13

Piezoelectric and ferroelectric properties in the two-dimensional (2D) limit are highly desired for nanoelectronic, electromechanical, and optoelectronic applications. Here we report the first experimental evidence of out-of-plane piezoelectricity and ferroelectricity in van der Waals layered α-In 2 Se 3 nanoflakes. The noncentrosymmetric R3m symmetry of the α-In 2 Se 3 samples is confirmed by scanning transmission electron microscopy, second-harmonic generation, and Raman spectroscopy measurements. Domains with opposite polarizations are visualized by piezo-response force microscopy. Single-point poling experiments suggest that the polarization is potentially switchable for α-In 2 Se 3 nanoflakes with thicknesses down to ∼10 nm. The piezotronic effect is demonstrated in two-terminal devices, where the Schottky barrier can be modulated by the strain-induced piezopotential. Our work on polar α-In 2 Se 3 , one of the model 2D piezoelectrics and ferroelectrics with simple crystal structures, shows its great potential in electronic and photonic applications.

A major protein component of the Bacillus subtilis biofilm matrix.

PubMed

Branda, Steven S; Chu, Frances; Kearns, Daniel B; Losick, Richard; Kolter, Roberto

2006-02-01

Microbes construct structurally complex multicellular communities (biofilms) through production of an extracellular matrix. Here we present evidence from scanning electron microscopy showing that a wild strain of the Gram positive bacterium Bacillus subtilis builds such a matrix. Genetic, biochemical and cytological evidence indicates that the matrix is composed predominantly of a protein component, TasA, and an exopolysaccharide component. The absence of TasA or the exopolysaccharide resulted in a residual matrix, while the absence of both components led to complete failure to form complex multicellular communities. Extracellular complementation experiments revealed that a functional matrix can be assembled even when TasA and the exopolysaccharide are produced by different cells, reinforcing the view that the components contribute to matrix formation in an extracellular manner. Having defined the major components of the biofilm matrix and the control of their synthesis by the global regulator SinR, we present a working model for how B. subtilis switches between nomadic and sedentary lifestyles.

Bacterial Transport Experiments in Fractured Crystalline Bedrock

USGS Publications Warehouse

Becker, M.W.; Metge, D.W.; Collins, S.A.; Shapiro, A.M.; Harvey, R.W.

2003-01-01

The efficiency of contaminant biodegradation in ground water depends, in part, on the transport properties of the degrading bacteria. Few data exist concerning the transport of bacteria in saturated bedrock, particularly at the field scale. Bacteria and microsphere tracer experiments were conducted in a fractured crystalline bedrock under forced-gradient conditions over a distance of 36 m. Bacteria isolated from the local ground water were chosen on the basis of physicochemical and physiological differences (shape, cell-wall type, motility), and were differentially stained so that their transport behavior could be compared. No two bacterial strains transported in an identical manner, and microspheres produced distinctly different breakthrough curves than bacteria. Although there was insufficient control in this field experiment to completely separate the effects of bacteria shape, reaction to Gram staining, cell size, and motility on transport efficiency, it was observed that (1) the nonmotile, mutant strain exhibited better fractional recovery than the motile parent strain; (2) Gram-negative rod-shaped bacteria exhibited higher fractional recovery relative to the Gram-positive rod-shaped strain of similar size; and (3) coccoidal (spherical-shaped) bacteria transported better than all but one strain of the rod-shaped bacteria. The field experiment must be interpreted in the context of the specific bacterial strains and ground water environment in which they were conducted, but experimental results suggest that minor differences in the physical properties of bacteria can lead to major differences in transport behavior at the field scale.

TU-CD-207-05: A Novel Digital Tomosynthesis System Using Orthogonal Scanning Technique: A Feasibility Study

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

Kim, J; Park, C; Kauweloa, K

2015-06-15

Purpose: As an alternative to full tomographic imaging technique such as cone-beam computed tomography (CBCT), there is growing interest to adopt digital tomosynthesis (DTS) for the use of diagnostic as well as therapeutic applications. The aim of this study is to propose a new DTS system using novel orthogonal scanning technique, which can provide superior image quality DTS images compared to the conventional DTS scanning system. Methods: Unlike conventional DTS scanning system, the proposed DTS is reconstructed with two sets of orthogonal patient scans. 1) X-ray projections that are acquired along transverse trajectory and 2) an additional sets of X-raymore » projections acquired along the vertical direction at the mid angle of the previous transverse scan. To reconstruct DTS, we have used modified filtered backprojection technique to account for the different scanning directions of each projection set. We have evaluated the performance of our method using numerical planning CT data of liver cancer patient and a physical pelvis phantom experiment. The results were compared with conventional DTS techniques with single transverse and vertical scanning. Results: The experiments on both numerical simulation as well as physical experiment showed that the resolution as well as contrast of anatomical structures was much clearer using our method. Specifically, the image quality comparing with transversely scanned DTS showed that the edge and contrast of anatomical structures along Left-Right (LR) directions was comparable however, considerable discrepancy and enhancement could be observed along Superior-Inferior (SI) direction using our method. The opposite was observed when vertically scanned DTS was compared. Conclusion: In this study, we propose a novel DTS system using orthogonal scanning technique. The results indicated that the image quality of our novel DTS system was superior compared to conventional DTS system. This makes our DTS system potentially useful in various on-line clinical applications.« less

Preliminary evidence on photoreactivation of Frankia spores with visible light after exposure to UV-C radiation.

PubMed

Sayed, W F

2011-06-01

Spores of four Frankia strains, the nitrogen-fixing actinomycete, were exposed to short wavelength UV-C radiation of 254 nm at 1 lux cm(2) (0.24 mw cm2 of energy) for 10 min. The used strains were HFP020203, UGL020604, UGL020602q and ORS021001. Exposure to UV was followed by reactivation with visible white light at 327.4 lux cm(2) for the same period of time. Spore germination percentage, spore protein content, and cell growth were damaged by this treatment. The lower and higher percentages of reduction in spore germination were 32 and 63% and, for the same strains, the recovery by white light was 7.2 and 37%. The lower percentages of UV damage and subsequent low recovery were recorded for strain ORS021001 that is considered more resistant to UV than the other strains. The higher percentages were recorded for strain HFP020203 that is more sensitive to UV but having more efficient repairing mechanisms. All the tested strains showed repairing activity induced by white light as indicated from the increase in their spore germination, protein content and almost restoring the normal shape of Frankia hyphae, after being damaged, as revealed by scanning electron microscope. This is the first evidence that photo-repairing systems are present in Frankia strains although there are variations in their response to both UV-C and photoreactivation by white light.

Scanning drop sensor

DOEpatents

Jin, Jian; Xiang, Chengxiang; Gregoire, John M.; Shinde, Aniketa A.; Guevarra, Dan W.; Jones, Ryan J.; Marcin, Martin R.; Mitrovic, Slobodan

2017-05-09

Electrochemical or electrochemical and photochemical experiments are performed on a collection of samples by suspending a drop of electrolyte solution between an electrochemical experiment probe and one of the samples that serves as a test sample. During the electrochemical experiment, the electrolyte solution is added to the drop and an output solution is removed from the drop. The probe and collection of samples can be moved relative to one another so the probe can be scanned across the samples.

Automatic image analysis and spot classification for detection of pathogenic Escherichia coli on glass slide DNA microarrays

USDA-ARS?s Scientific Manuscript database

A computer algorithm was created to inspect scanned images from DNA microarray slides developed to rapidly detect and genotype E. Coli O157 virulent strains. The algorithm computes centroid locations for signal and background pixels in RGB space and defines a plane perpendicular to the line connect...

A technique to measure strain distributions in single wood pulp fibers

Treesearch

Laurence Mott; Stephen M. Shaler; Leslie H. Groom

1996-01-01

Environmental scanning electron microscopy (ESEM) and digital image correlation (DIC) were used to measure microstrain distributions on the surface of wood pulp fibers. A loading stage incorporating a fiber gripping system was designed and built by the authors. Fitted to the tensile substage of an ESEM or a Polymer Laboratories MINIMAT tester, it provided a reliable...

Investigation of the Optical and Electronic Properties of Crystalline Organic Materials

DTIC Science & Technology

1990-06-14

38 (A) EFFECTS OF DEPOSTION RATE ---------------- 38 0 (B) EFFECTS OF SUBSTRATE TEMPERATURE ------ 40 11.5 ANISOTROPIES IN CRYSTALLINE ORGANIC THIN...depostion rate .- ------------------------------------------------------------------ 41 Fig. 2.10: Scanning electron micrographs showing the surface...materials grown be lattice-matched. Hence, relatively strain -free heterostructures using materials with large lattice-mismatch can be realized by the

Homology between genes for aromatic hydrocarbon degradation in surface and deep-subsurface sphingomonas strains

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

Kim, E.; Aversano, P.J.; Zylstra, G.J.

The cloned genes for aromatic hydrocarbon degradation from Sphingomonas yanoikuyae B1 were utilized in Southern hybridization experiments with Sphingomonas strains from the surface and deep-subsurface environments. One hybridization pattern was obtained with BamHI-digested genomic DNAs for two surface strains, while a differing pattern was seen for five deep-subsurface strains. The cross-hybridizing genes were located in the chromosomes of the surface strains and on plasmids in the deep-subsurface strains. 31 refs., 3 figs., 1 tab.

Electronic and mechanical properties of graphene-germanium interfaces grown by chemical vapor deposition

DOE PAGES

Kiraly, Brian T.; Jacobberger, Robert M.; Mannix, Andrew J.; ...

2015-10-27

Epitaxially oriented wafer-scale graphene grown directly on semiconducting Ge substrates is of high interest for both fundamental science and electronic device applications. To date, however, this material system remains relatively unexplored structurally and electronically, particularly at the atomic scale. To further understand the nature of the interface between graphene and Ge, we utilize ultrahigh vacuum scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) along with Raman and X-ray photoelectron spectroscopy to probe interfacial atomic structure and chemistry. STS reveals significant differences in electronic interactions between graphene and Ge(110)/Ge(111), which is consistent with a model of stronger interaction on Ge(110)more » leading to epitaxial growth. Raman spectra indicate that the graphene is considerably strained after growth, with more point-to-point variation on Ge(111). Furthermore, this native strain influences the atomic structure of the interface by inducing metastable and previously unobserved Ge surface reconstructions following annealing. These nonequilibrium reconstructions cover >90% of the surface and, in turn, modify both the electronic and mechanical properties of the graphene overlayer. Finally, graphene on Ge(001) represents the extreme strain case, where graphene drives the reorganization of the Ge surface into [107] facets. From this study, it is clear that the interaction between graphene and the underlying Ge is not only dependent on the substrate crystallographic orientation, but is also tunable and strongly related to the atomic reconfiguration of the graphene–Ge interface.« less

Antimicrobial Activity and Possible Mechanism of Action of Citral against Cronobacter sakazakii.

PubMed

Shi, Chao; Song, Kaikuo; Zhang, Xiaorong; Sun, Yi; Sui, Yue; Chen, Yifei; Jia, Zhenyu; Sun, Huihui; Sun, Zheng; Xia, Xiaodong

2016-01-01

Citral is a flavor component that is commonly used in food, beverage and fragrance industries. Cronobacter sakazakii is a food-borne pathogen associated with severe illness and high mortality in neonates and infants. The objective of the present study was to evaluate antimicrobial effect of citral against C. sakazakii strains. The minimum inhibitory concentration (MIC) of citral against C. sakazakii was determined via agar dilution method, then Gompertz models were used to quantitate the effect of citral on microbial growth kinetics. Changes in intracellular pH (pHin), membrane potential, intracellular ATP concentration, and membrane integrity were measured to elucidate the possible antimicrobial mechanism. Cell morphology changes were also examined using a field emission scanning electron microscope. The MICs of citral against C. sakazakii strains ranged from 0.27 to 0.54 mg/mL, and citral resulted in a longer lag phase and lower growth rate of C. sakazakii compared to the control. Citral affected the cell membrane of C. sakazakii, as evidenced by decreased intracellular ATP concentration, reduced pHin, and cell membrane hyperpolarization. Scanning electron microscopy analysis further confirmed that C. sakazakii cell membranes were damaged by citral. These findings suggest that citral exhibits antimicrobial effect against C. sakazakii strains and could be potentially used to control C. sakazakii in foods. However, how it works in food systems where many other components may interfere with its efficacy should be tested in future research before its real application.

Antimicrobial Activity and Possible Mechanism of Action of Citral against Cronobacter sakazakii

PubMed Central

Shi, Chao; Song, Kaikuo; Zhang, Xiaorong; Sun, Yi; Sui, Yue; Chen, Yifei; Jia, Zhenyu; Sun, Huihui; Sun, Zheng; Xia, Xiaodong

2016-01-01

Citral is a flavor component that is commonly used in food, beverage and fragrance industries. Cronobacter sakazakii is a food-borne pathogen associated with severe illness and high mortality in neonates and infants. The objective of the present study was to evaluate antimicrobial effect of citral against C. sakazakii strains. The minimum inhibitory concentration (MIC) of citral against C. sakazakii was determined via agar dilution method, then Gompertz models were used to quantitate the effect of citral on microbial growth kinetics. Changes in intracellular pH (pHin), membrane potential, intracellular ATP concentration, and membrane integrity were measured to elucidate the possible antimicrobial mechanism. Cell morphology changes were also examined using a field emission scanning electron microscope. The MICs of citral against C. sakazakii strains ranged from 0.27 to 0.54 mg/mL, and citral resulted in a longer lag phase and lower growth rate of C. sakazakii compared to the control. Citral affected the cell membrane of C. sakazakii, as evidenced by decreased intracellular ATP concentration, reduced pHin, and cell membrane hyperpolarization. Scanning electron microscopy analysis further confirmed that C. sakazakii cell membranes were damaged by citral. These findings suggest that citral exhibits antimicrobial effect against C. sakazakii strains and could be potentially used to control C. sakazakii in foods. However, how it works in food systems where many other components may interfere with its efficacy should be tested in future research before its real application. PMID:27415761

Determination of strain fields in porous shape memory alloys using micro-computed tomography

NASA Astrophysics Data System (ADS)

Bormann, Therese; Friess, Sebastian; de Wild, Michael; Schumacher, Ralf; Schulz, Georg; Müller, Bert

2010-09-01

Shape memory alloys (SMAs) belong to 'intelligent' materials since the metal alloy can change its macroscopic shape as the result of the temperature-induced, reversible martensite-austenite phase transition. SMAs are often applied for medical applications such as stents, hinge-less instruments, artificial muscles, and dental braces. Rapid prototyping techniques, including selective laser melting (SLM), allow fabricating complex porous SMA microstructures. In the present study, the macroscopic shape changes of the SMA test structures fabricated by SLM have been investigated by means of micro computed tomography (μCT). For this purpose, the SMA structures are placed into the heating stage of the μCT system SkyScan 1172™ (SkyScan, Kontich, Belgium) to acquire three-dimensional datasets above and below the transition temperature, i.e. at room temperature and at about 80°C, respectively. The two datasets were registered on the basis of an affine registration algorithm with nine independent parameters - three for the translation, three for the rotation and three for the scaling in orthogonal directions. Essentially, the scaling parameters characterize the macroscopic deformation of the SMA structure of interest. Furthermore, applying the non-rigid registration algorithm, the three-dimensional strain field of the SMA structure on the micrometer scale comes to light. The strain fields obtained will serve for the optimization of the SLM-process and, more important, of the design of the complex shaped SMA structures for tissue engineering and medical implants.

Evaluation of the infection process by Lecanicillium fungicola in Agaricus bisporus by scanning electron microscopy.

PubMed

Santana Nunes, Janaira; Rocha de Brito, Manuela; Cunha Zied, Diego; Aparecida das Graças Leite, Eloisa; Souza Dias, Eustáquio; Alves, Eduardo

Lecanicillium fungicola causes dry bubble disease in Agaricus bisporus mushrooms leading to significant economic losses in commercial production. To monitor the infection process of L. fungicola in Brazilian strains of A. bisporus. The interaction between the mycelium of L. fungicola (LF.1) and three strains of A. bisporus (ABI 7, ABI 11/14 and ABI 11/21) was studied. Electron microscopy and X-ray microanalyses of vegetative growth and basidiocarp infection were evaluated. Micrographs show that the vegetative mycelium of the Brazilian strains of A. bisporus is not infected by the parasite. The images show that the pathogen can interlace the hyphae of A. bisporus without causing damage, which contributes to the presence of L. fungicola during the substrate colonization, allowing their presence during primordial formation of A. bisporus. In the basidiocarp, germ tubes form within 16h of infection with L. fungicola and the beginning of penetration takes place within 18h, both without the formation of specialized structures. Scanning electron microscopy enabled the process of colonization and reproduction to be observed within the formation of phialides, conidiophores and verticils of L. fungicola. The formation of calcium oxalate crystals by the pathogen was also visible using the X-ray microanalysis, both at the hyphae in the Petri plate and at basidiocarp infection site. Copyright © 2016 Asociación Española de Micología. Publicado por Elsevier España, S.L.U. All rights reserved.

Towards large dynamic range and ultrahigh measurement resolution in distributed fiber sensing based on multicore fiber.

PubMed

Dang, Yunli; Zhao, Zhiyong; Tang, Ming; Zhao, Can; Gan, Lin; Fu, Songnian; Liu, Tongqing; Tong, Weijun; Shum, Perry Ping; Liu, Deming

2017-08-21

Featuring a dependence of Brillouin frequency shift (BFS) on temperature and strain changes over a wide range, Brillouin distributed optical fiber sensors are however essentially subjected to the relatively poor temperature/strain measurement resolution. On the other hand, phase-sensitive optical time-domain reflectometry (Φ-OTDR) offers ultrahigh temperature/strain measurement resolution, but the available frequency scanning range is normally narrow thereby severely restricts its measurement dynamic range. In order to achieve large dynamic range and high measurement resolution simultaneously, we propose to employ both the Brillouin optical time domain analysis (BOTDA) and Φ-OTDR through space-division multiplexed (SDM) configuration based on the multicore fiber (MCF), in which the two sensors are spatially separately implemented in the central core and a side core, respectively. As a proof of concept, the temperature sensing has been performed for validation with 2.5 m spatial resolution over 1.565 km MCF. Large temperature range (10 °C) has been measured by BOTDA and the 0.1 °C small temperature variation is successfully identified by Φ-OTDR with ~0.001 °C resolution. Moreover, the temperature changing process has been recorded by continuously performing the measurement of Φ-OTDR with 80 s frequency scanning period, showing about 0.02 °C temperature spacing at the monitored profile. The proposed system enables the capability to see finer and/or farther upon requirement in distributed optical fiber sensing.

Disruption of methicillin-resistant Staphylococcus aureus protein synthesis by tannins

PubMed Central

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

2017-01-01

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

Dynamic Crushing Response of Closed-cell Aluminium Foam at Variable Strain Rates

NASA Astrophysics Data System (ADS)

Islam, M. A.; Kader, M. A.; Escobedo, J. P.; Hazell, P. J.; Appleby-Thomas, G. J.; Quadir, M. Z.

2015-06-01

The impact response of aluminium foams is essential for assessing their crashworthiness and energy absorption capacity for potential applications. The dynamic compactions of closed-cell aluminium foams (CYMAT) have been tested at variable strain rates. Microstructural characterization has also been carried out. The low strain rate impact test has been carried out using drop weight experiments while the high strain compaction test has been carried out via plate impact experiments. The post impacted samples have been examined using optical and electron microscopy to observe the microstructural changes during dynamic loading. This combination of dynamic deformation during impact and post impact microstructural analysis helped to evaluate the pore collapse mechanism and impact energy absorption characteristics.

Differentiation of different mixed Listeria strains and also acid-injured, heat-injured, and repaired cells of Listeria monocytogenes using fourier transform infrared spectroscopy.

PubMed

Nyarko, Esmond; Donnelly, Catherine

2015-03-01

Fourier transform infrared (FT-IR) spectroscopy was used to differentiate mixed strains of Listeria monocytogenes and mixed strains of L. monocytogenes and Listeria innocua. FT-IR spectroscopy was also applied to investigate the hypothesis that heat-injured and acid-injured cells would return to their original physiological integrity following repair. Thin smears of cells on infrared slides were prepared from cultures for mixed strains of L. monocytogenes, mixed strains of L. monocytogenes and L. innocua, and each individual strain. Heat-injured and acid-injured cells were prepared by exposing harvested cells of L. monocytogenes strain R2-764 to a temperature of 56 ± 0.2°C for 10 min or lactic acid at pH 3 for 60 min, respectively. Cellular repair involved incubating aliquots of acid-injured and heat-injured cells separately in Trypticase soy broth supplemented with 0.6% yeast extract for 22 to 24 h; bacterial thin smears on infrared slides were prepared for each treatment. Spectral collection was done using 250 scans at a resolution of 4 cm(-1) in the mid-infrared wavelength region. Application of multivariate discriminant analysis to the wavelength region from 1,800 to 900 cm(-1) separated the individual L. monocytogenes strains. Mixed strains of L. monocytogenes and L. monocytogenes cocultured with L. innocua were successfully differentiated from the individual strains when the discriminant analysis was applied. Different mixed strains of L. monocytogenes were also successfully separated when the discriminant analysis was applied. A data set for injury and repair analysis resulted in the separation of acid-injured, heat-injured, and intact cells; repaired cells clustered closer to intact cells when the discriminant analysis (1,800 to 600 cm(-1)) was applied. FT-IR spectroscopy can be used for the rapid source tracking of L. monocytogenes strains because it can differentiate between different mixed strains and individual strains of the pathogen.

A technique for recording polycrystalline structure and orientation during in situ deformation cycles of rock analogues using an automated fabric analyser.

PubMed

Peternell, M; Russell-Head, D S; Wilson, C J L

2011-05-01

Two in situ plane-strain deformation experiments on norcamphor and natural ice using synchronous recording of crystal c-axis orientations have been performed with an automated fabric analyser and a newly developed sample press and deformation stage. Without interrupting the deformation experiment, c-axis orientations are determined for each pixel in a 5 × 5 mm sample area at a spatial resolution of 5 μm/pixel. In the case of norcamphor, changes in microstructures and associated crystallographic information, at a strain rate of ∼2 × 10(-5) s(-1), were recorded for the first time during a complete in situ deformation-cycle experiment that consisted of an annealing, deformation and post-deformation annealing path. In the case of natural ice, slower external strain rates (∼1 × 10(-6) s(-1)) enabled the investigation of small changes in the polycrystal aggregate's crystallography and microstructure for small amounts of strain. The technical setup and first results from the experiments are presented. © 2010 The Authors Journal of Microscopy © 2010 Royal Microscopical Society.

Assessment of virtual towers performed with scanning wind lidars and Ka-band radars during the XPIA experiment

DOE PAGES

Debnath, Mithu; Iungo, Giacomo Valerio; Brewer, W. Alan; ...

2017-03-29

During the eXperimental Planetary boundary layer Instrumentation Assessment (XPIA) campaign, which was carried out at the Boulder Atmospheric Observatory (BAO) in spring 2015, multiple-Doppler scanning strategies were carried out with scanning wind lidars and Ka-band radars. Specifically, step–stare measurements were collected simultaneously with three scanning Doppler lidars, while two scanning Ka-band radars carried out simultaneous range height indicator (RHI) scans. The XPIA experiment provided the unique opportunity to compare directly virtual-tower measurements performed simultaneously with Ka-band radars and Doppler wind lidars. Furthermore, multiple-Doppler measurements were assessed against sonic anemometer data acquired from the meteorological tower (met-tower) present at the BAOmore » site and a lidar wind profiler. As a result, this survey shows that – despite the different technologies, measurement volumes and sampling periods used for the lidar and radar measurements – a very good accuracy is achieved for both remote-sensing techniques for probing horizontal wind speed and wind direction with the virtual-tower scanning technique.« less

Strain-Engineering of Giant Pseudo-Magnetic Fields in Graphene/Boron Nitride (BN) Periodic Nanostructures

NASA Astrophysics Data System (ADS)

Hsu, Chen-Chih; Wang, Jiaqing; Teague, Marcus; Chen, Chien-Chang; Yeh, Nai-Chang

2015-03-01

Ideal graphene is strain-free whereas non-trivial strain can induce pseudo-magnetic fields as predicted theoretically and manifested experimentally. Here we employ nearly strain-free single-domain graphene, grown by plasma-enhanced chemical vapor deposition (PECVD) at low temperatures, to induce controlled strain by placing the PECVD-graphene on substrates containing engineered nanostructures. We fabricate periodic pyramid nanostructures (typically 100 ~ 200 nm laterally and 10 ~ 60 nm in height) on Si substrates by focused ion beam, and determine the topography of these nanostructures using atomic force microscopy and scanning electron microscopy after we transferred monolayer h-BN followed by PECVD-graphene onto these substrates. We find both layers conform well to the nanostructures so that we can control the size, arrangement, separation, and shape of the nanostructures to generate desirable pseudo-magnetic fields. We also employ molecular dynamics simulation to determine the displacement of carbon atoms under a given nanostructure. The pseudo-magnetic field thus obtained is ~150T in the center, relatively homogeneous over 50% of the area, and drops off precipitously near the edge. These findings are extended to arrays of nanostructures and compared with topographic and spectroscopic studies by STM. Supported by NSF.

Flexible Strain Sensor Based on Layer-by-Layer Self-Assembled Graphene/Polymer Nanocomposite Membrane and Its Sensing Properties

NASA Astrophysics Data System (ADS)

Zhang, Dongzhi; Jiang, Chuanxing; Tong, Jun; Zong, Xiaoqi; Hu, Wei

2018-04-01

Graphene is a potential building block for next generation electronic devices including field-effect transistors, chemical sensors, and radio frequency switches. Investigations of strain application of graphene-based films have emerged in recent years, but the challenges in synthesis and processing achieving control over its fabrication constitute the main obstacles towards device applications. This work presents an alternative approach, layer-by-layer self-assembly, allowing a controllable fabrication of graphene/polymer film strain sensor on flexible substrates of polyimide with interdigital electrodes. Carboxylated graphene and poly (diallyldimethylammonium chloride) (PDDA) were exploited to form hierarchical nanostructure due to electrostatic action. The morphology and structure of the film were inspected by using scanning electron microscopy, x-ray diffraction and Fourier transform infrared spectroscopy. The strain-sensing properties of the graphene/PDDA film sensor were investigated through tuning micrometer caliper exertion and a PC-assisted piezoresistive measurement system. Experimental result shows that the sensor exhibited not only excellent response and reversibility behavior as a function of deflection, but also good repeatability and acceptable linearity. The strain-sensing mechanism of the proposed sensor was attributed to the electrical resistance change resulted from piezoresistive effect.

Compositional and strain analysis of In(Ga)N/GaN short period superlattices

NASA Astrophysics Data System (ADS)

Dimitrakopulos, G. P.; Vasileiadis, I. G.; Bazioti, C.; Smalc-Koziorowska, J.; Kret, S.; Dimakis, E.; Florini, N.; Kehagias, Th.; Suski, T.; Karakostas, Th.; Moustakas, T. D.; Komninou, Ph.

2018-01-01

Extensive high resolution transmission and scanning transmission electron microscopy observations were performed in In(Ga)N/GaN multi-quantum well short period superlattices comprising two-dimensional quantum wells (QWs) of nominal thicknesses 1, 2, and 4 monolayers (MLs) in order to obtain a correlation between their average composition, geometry, and strain. The high angle annular dark field Z-contrast observations were quantified for such layers, regarding the indium content of the QWs, and were correlated to their strain state using peak finding and geometrical phase analysis. Image simulations taking into thorough account the experimental imaging conditions were employed in order to associate the observed Z-contrast to the indium content. Energetically relaxed supercells calculated with a Tersoff empirical interatomic potential were used as the input for such simulations. We found a deviation from the tetragonal distortion prescribed by continuum elasticity for thin films, i.e., the strain in the relaxed cells was lower than expected for the case of 1 ML QWs. In all samples, the QW thickness and strain were confined in up to 2 ML with possible indium enrichment of the immediately abutting MLs. The average composition of the QWs was quantified in the form of alloy content.

Comparative stress distribution of implant-retained mandibular ball-supported and bar-supported overlay dentures: a finite element analysis.

PubMed

Vafaei, Fariborz; Khoshhal, Masoumeh; Bayat-Movahed, Saeed; Ahangary, Ahmad Hassan; Firooz, Farnaz; Izady, Alireza; Rakhshan, Vahid

2011-08-01

Implant-retained mandibular ball-supported and bar-supported overlay dentures are the two most common treatment options for the edentulous mandible. The superior option in terms of strain distribution should be determined. The three-dimensional model of mandible (based on computerized tomography scan) and its overlying implant-retained bar-supported and ball-supported overlay dentures were simulated using SolidWorks, NURBS, and ANSYS Workbench. Loads A (60 N) and B (60 N) were exerted, respectively, in protrusive and laterotrusive motions, on second molar mesial, first molar mesial, and first premolar. The strain distribution patterns were assessed on (1) implant tissue, (2) first implant-bone, and (3) second implant-bone interfaces. Protrusive: Strain was mostly detected in the apical of the fixtures and least in the cervical when bar design was used. On the nonworking side, however, strain was higher in the cervical and lower in the apical compared with the working side implant. Laterotrusive: The strain values were closely similar in the two designs. It seems that both designs are acceptable in terms of stress distribution, although a superior pattern is associated with the application of bar design in protrusive motion.

Ultra-high resolution, polarization sensitive transversal optical coherence tomography for structural analysis and strain mapping

NASA Astrophysics Data System (ADS)

Wiesauer, Karin; Pircher, Michael; Goetzinger, Erich; Hitzenberger, Christoph K.; Engelke, Rainer; Ahrens, Gisela; Pfeiffer, Karl; Ostrzinski, Ute; Gruetzner, Gabi; Oster, Reinhold; Stifter, David

2006-02-01

Optical coherence tomography (OCT) is a contactless and non-invasive technique nearly exclusively applied for bio-medical imaging of tissues. Besides the internal structure, additionally strains within the sample can be mapped when OCT is performed in a polarization sensitive (PS) way. In this work, we demonstrate the benefits of PS-OCT imaging for non-biological applications. We have developed the OCT technique beyond the state-of-the-art: based on transversal ultra-high resolution (UHR-)OCT, where an axial resolution below 2 μm within materials is obtained using a femtosecond laser as light source, we have modified the setup for polarization sensitive measurements (transversal UHR-PS-OCT). We perform structural analysis and strain mapping for different types of samples: for a highly strained elastomer specimen we demonstrate the necessity of UHR-imaging. Furthermore, we investigate epoxy waveguide structures, photoresist moulds for the fabrication of micro-electromechanical parts (MEMS), and the glass-fibre composite outer shell of helicopter rotor blades where cracks are present. For these examples, transversal scanning UHR-PS-OCT is shown to provide important information about the structural properties and the strain distribution within the samples.

Optimal reduction of chemical oxygen demand and NH3-N from landfill leachate using a strongly resistant novel Bacillus salmalaya strain.

PubMed

Dadrasnia, Arezoo; Azirun, Mohd Sofian; Ismail, Salmah Binti

2017-11-28

When the unavoidable waste generation is considered as damaging to our environment, it becomes crucial to develop a sustainable technology to remediate the pollutant source towards an environmental protection and safety. The development of a bioengineering technology for highly efficient pollutant removal is this regard. Given the high ammonia nitrogen content and chemical oxygen demand of landfill leachate, Bacillus salmalaya strain 139SI, a novel resident strain microbe that can survive in high ammonia nitrogen concentrations, was investigated for the bioremoval of ammonia nitrogen from landfill leachate. The treatability of landfill leachate was evaluated under different treatment parameters, such as temperature, inoculum dosage, and pH. Results demonstrated that bioaugmentation with the novel strain can potentially improve the biodegradability of landfill leachate. B. salmalaya strain 139SI showed high potential to enhance biological treatment given its maximum NH 3 -N and COD removal efficiencies. The response surface plot pattern indicated that within 11 days and under optimum conditions (10% v/v inoculant, pH 6, and 35 °C), B. salmalaya strain139SI removed 78% of ammonia nitrogen. At the end of the study, biological and chemical oxygen demands remarkably decreased by 88% and 91.4%, respectively. Scanning electron microscopy images revealed that ammonia ions covered the cell surface of B. salmalaya strain139SI. Therefore, novel resistant Bacillus salmalaya strain139SI significantly reduces the chemical oxygen demand and NH 3 -N content of landfill leachate. Leachate treatment by B. salmalaya strain 139SI within 11 days.

Local and transient nanoscale strain mapping during in situ deformation

DOE PAGES

Gammer, C.; Kacher, J.; Czarnik, C.; ...

2016-08-26

The mobility of defects such as dislocations controls the mechanical properties of metals. This mobility is determined both by the characteristics of the defect and the material, as well as the local stress and strain applied to the defect. Therefore, the knowledge of the stress and strain during deformation at the scale of defects is important for understanding fundamental deformation mechanisms. In this paper, we demonstrate a method of measuring local stresses and strains during continuous in situ deformation with a resolution of a few nanometers using nanodiffraction strain mapping. Finally, our results demonstrate how large multidimensional data sets capturedmore » with high speed electron detectors can be analyzed in multiple ways after an in situ TEM experiment, opening the door for true multimodal analysis from a single electron scattering experiment.« less

Experimental investigation of strain errors in stereo-digital image correlation due to camera calibration

NASA Astrophysics Data System (ADS)

Shao, Xinxing; Zhu, Feipeng; Su, Zhilong; Dai, Xiangjun; Chen, Zhenning; He, Xiaoyuan

2018-03-01

The strain errors in stereo-digital image correlation (DIC) due to camera calibration were investigated using precisely controlled numerical experiments and real experiments. Three-dimensional rigid body motion tests were conducted to examine the effects of camera calibration on the measured results. For a fully accurate calibration, rigid body motion causes negligible strain errors. However, for inaccurately calibrated camera parameters and a short working distance, rigid body motion will lead to more than 50-μɛ strain errors, which significantly affects the measurement. In practical measurements, it is impossible to obtain a fully accurate calibration; therefore, considerable attention should be focused on attempting to avoid these types of errors, especially for high-accuracy strain measurements. It is necessary to avoid large rigid body motions in both two-dimensional DIC and stereo-DIC.

Strain rate dependent calcite microfabric evolution - an experiment carried out by nature

NASA Astrophysics Data System (ADS)

Rogowitz, A.; Huet, B.; Grasemann, B.; Habler, G.

2013-12-01

The deformation behaviour of calcite has been studied extensively in a number of experiments. Different strain rates and pressure and temperature conditions have been used to investigate a wide range of deformation regimes. However, a direct comparison with natural fault rocks remains difficult because of extreme differences between experimental and natural strain rates. A secondary shear zone (flanking structure) developed in almost pure calcite marble on Syros (Greece). Due to rotation of an elliptical inclusion (crack) a heterogeneous strain field in the surrounding area occurred resulting in different strain domains and the formation of the flanking structure. Assuming that deformation was active continuously during the development of the flanking structure, the different strain domains correspond to different strain-rate domains. The outcrop thus represents the final state of a natural experiment and gives us a great opportunity to get natural constraints on strain rate dependent deformation behaviour of calcite. Comparing the microfabrics in the 1 to 2.5 cm thick shear zone and the surrounding host rocks, which formed under the same metamorphic conditions but with different strain rates, is the central focus of this study. Due to the extreme variation in strain and strain rate, different microstructures and textures can be observed corresponding to different deformation mechanisms. With increasing strain rate we observe a change in dominant deformation mechanism from dislocation glide to dislocation creep and finally diffusion creep. Additionally, a change from subgrain rotation (SGR) to bulging (BLG) recrystallization can be observed in the dislocation creep regime. Textures and the degree of intracrystalline deformation have been measured by electron back scatter diffraction (EBSD). At all strain rates clear CPOs developed leading to the assumption that calcite preferentially deforms within the dislocation creep field. However, we can also find clear evidence for grain size sensitive deformation mechanisms at smaller grain sizes (3.6 μm) consistent with experimental observations and determined flaw laws. Although mylonitic layers evolve at high (10^-10 s^-1) and intermediate strain rates (10^-11 s^-1) by SGR recrystallization we observe variations in texture leading to the assumption that at varying strain rates different gliding systems were active. The results of this study are compared with experimental data, closing the gap between experimental and natural geological strain rates.

Creep of Ni(3)Al in the temperature regime of anomalous flow behavior

NASA Astrophysics Data System (ADS)

Uchic, Michael David

Much attention has been paid to understanding the dynamics of dislocation motion and substructure formation in Ni3Al in the anomalous flow regime. However, most of the experimental work that has been performed in the lowest temperatures of the anomalous flow regime has been under constant-strain-rate conditions. An alternative and perhaps more fundamental way to probe the plastic behavior of materials is a monotonic creep test, in which the stress and temperature are held constant while the time-dependent strain is measured. The aim of this study is to use constant-stress experiments to further explore the plastic flow anomaly in L12 alloys at low temperatures. Tension creep experiments have been carried out on <123> oriented single crystals of Ni75Al24Ta1 at temperatures between 293 and 473 K. We have observed primary creep leading to exhaustion at all temperatures and stresses, with creep rates declining faster than predicted by the logarithmic creep law. The total strain and creep strain have an anomalous dependence on temperature, which is consistent with the flow stress anomaly. We have also observed other unusual behavior in our creep experiments; for example, the reinitiation of plastic flow at low temperatures after a modest increment in applied stress shows a sigmoidal response, i.e., there is a significant time delay before the plastic strain rate accelerates to a maximum value. We also examined the ability to reinitiate plastic flow in samples that have been crept to exhaustion by simply lowering the test temperature. In addition, we have also performed conventional constant-displacement-rate experiments in the same temperature range. From these experiments, we have discovered that unlike most metals, Ni3Al displays a negative dependence of the work hardening rate (WHR) with increasing strain rate. For tests at intermediate temperatures (373 and 423 K), the WHRs of crystals tested at moderately high strain rates (10-2 s-1) are half the WHRs of crystals tested at conventional strain rates (10 -5 s-1), and this anomalous dependence has also been shown to be reversible with changes in strain rate. The implications of all results are discussed in light of our efforts to model plastic deformation in these alloys.

Strategies to improve phase-stability of ultrafast swept source optical coherence tomography for single shot imaging of transient mechanical waves at 16 kHz frame rate

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

Song, Shaozhen; Wei, Wei; Hsieh, Bao-Yu

We present single-shot phase-sensitive imaging of propagating mechanical waves within tissue, enabled by an ultrafast optical coherence tomography (OCT) system powered by a 1.628 MHz Fourier domain mode-locked (FDML) swept laser source. We propose a practical strategy for phase-sensitive measurement by comparing the phases between adjacent OCT B-scans, where the B-scan contains a number of A-scans equaling an integer number of FDML buffers. With this approach, we show that micro-strain fields can be mapped with ∼3.0 nm sensitivity at ∼16 000 fps. The system's capabilities are demonstrated on porcine cornea by imaging mechanical wave propagation launched by a pulsed UV laser beam, promisingmore » non-contact, real-time, and high-resolution optical coherence elastography.« less

A novel fermentation strategy for removing the key inhibitor acetic acid and efficiently utilizing the mixed sugars from lignocellulosic hydrolysates

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

Mark A. Eiteman PHD; Elliot Altman Phd

2009-02-11

As part of preliminary research efforts, we have completed several experiments which demonstrate 'proof of concept.' These experiments addressed the following three questions: (1) Can a synthetic mixed sugar solution of glucose and xylose be efficiently consumed using the multi-organism approach? (2) Can this approach be used to accumulate a model product? (3) Can this approach be applied to the removal of an inhibitor, acetate, selectively from mixtures of xylose and glucose? To answer the question of whether this multi-organism approach can effectively consume synthetic mixed sugar solutions, we first tested substrate-selective uptake using two strains, one unable to consumemore » glucose and one unable to consume xylose. The xylose-selective strain ALS998 has mutations in the three genes involved in glucose uptake, rendering it unable to consume glucose: ptsG codes for the Enzyme IICB{sup Glc} of the phosphotransferase system (PTS) for carbohydrate transport (Postma et al., 1993), manZ codes for the IID{sup Man} domain of the mannose PTS permease (Huber, 1996), glk codes for glucokinase (Curtis and Epstein 1975) We also constructed strain ALS1008 which has a knockout in the xylA gene encoding for xylose isomerase, rendering ALS1008 unable to consume xylose. Two batch experiments and one continuous bioprocess were completed. In the first experiment, each strain was grown separately in a defined medium of 8 g/L xylose and 15 g/L glucose which represented xylose and glucose concentrations that can be generated by actual biomass. In the second experiment, the two strains were grown together in batch in the same defined, mixed-sugar medium. In a third experiment, we grew the strains continuously in a 'chemostat', except that we shifted the concentrations of glucose and xylose periodically to observe how the system would respond. (For example, we shifted the glucose concentration suddenly from 15 g/L to 30 g/L in the feed).« less

Elongational flow of polymer melts at constant strain rate, constant stress and constant force

NASA Astrophysics Data System (ADS)

Wagner, Manfred H.; Rolón-Garrido, Víctor H.

2013-04-01

Characterization of polymer melts in elongational flow is typically performed at constant elongational rate or rarely at constant tensile stress conditions. One of the disadvantages of these deformation modes is that they are hampered by the onset of "necking" instabilities according to the Considère criterion. Experiments at constant tensile force have been performed even more rarely, in spite of the fact that this deformation mode is free from necking instabilities and is of considerable industrial relevance as it is the correct analogue of steady fiber spinning. It is the objective of the present contribution to present for the first time a full experimental characterization of a long-chain branched polyethylene melt in elongational flow. Experiments were performed at constant elongation rate, constant tensile stress and constant tensile force by use of a Sentmanat Extensional Rheometer (SER) in combination with an Anton Paar MCR301 rotational rheometer. The accessible experimental window and experimental limitations are discussed. The experimental data are modelled by using the Wagner I model. Predictions of the steady-start elongational viscosity in constant strain rate and creep experiments are found to be identical, albeit only by extrapolation of the experimental data to Hencky strains of the order of 6. For constant stress experiments, a minimum in the strain rate and a corresponding maximum in the elongational viscosity is found at a Hencky strain of the order of 3, which, although larger than the steady-state value, follows roughly the general trend of the steady-state elongational viscosity. The constitutive analysis also reveals that constant tensile force experiments indicate a larger strain hardening potential than seen in constant elongation rate or constant tensile stress experiments. This may be indicative of the effect of necking under constant elongation rate or constant tensile stress conditions according to the Considère criterion.