Sample records for accumulated strain energy

  1. Energy-Dependent Accumulation of Fluoroquinolones in Quinolone-Resistant Klebsiella pneumoniae Strains

    PubMed Central

    Martínez-Martínez, Luis; García, Isabel; Ballesta, Sofía; Benedí, Vicente Javier; Hernández-Allés, Santiago; Pascual, Alvaro

    1998-01-01

    The intracellular accumulation of norfloxacin and pefloxacin in Klebsiella pneumoniae was evaluated. The roles of lipopolysaccharide, capsule, and outer membrane proteins were not important for the intrabacterial accumulation of fluoroquinolones in isogenic strains with known outer membrane alterations. In fluoroquinolone-resistant clinical isolates also expressing GyrA alterations, an active efflux leading to decreased accumulation of the drugs enhanced their resistance to these agents. PMID:9661034

  2. Episodic strain accumulation in southern california.

    PubMed

    Thatcher, W

    1976-11-12

    Reexamination of horizontal geodetic data in the region of recently discovered aseismic uplift has demonstrated that equally unusual horizontal crustal deformation accompanied the development of the uplift. During this time interval compressive strains were oriented roughly normal to the San Andreas fault, suggesting that the uplift produced little shear strain accumulation across this fault. On the other hand, the orientation of the anomalous shear straining is consistent with strain accumulation across northdipping range-front thrusts like the San Fernando fault. Accordingly, the horizontal and vertical crustal deformation disclosed by geodetic observation is interpreted as a short epoch of rapid strain accumulation on these frontal faults. If this interpretation is correct, thrust-type earthquakes will eventually release the accumulated strains, but the geodetic data examined here cannot be used to estimate when these events might occur. However, observation of an unusual sequence of tilts prior to 1971 on a level line lying to the north of the magnitude 6.4 San Fernando earthquake offers some promise for precursor monitoring. The data are adequately explained by a simple model of up-dip aseismic slip propagation toward the 1971 epicentral region. These observations and the simple model that accounts for them suggest a conceptually straightforward monitoring scheme to search for similar uplift and tilt precursors within the uplifted region. Such premonitory effects could be detected by a combination of frequenlty repeated short (30 to 70 km in length) level line measurements, precise gravity traverses, and continuously recording gravimeters sited to the north of the active frontal thrust faults. Once identified, such precursors could be closely followed in space and time, and might then provide effective warnings of impending potentially destructive earth-quakes.

  3. Accumulated financial strain and women's health over three decades.

    PubMed

    Shippee, Tetyana Pylypiv; Wilkinson, Lindsay R; Ferraro, Kenneth F

    2012-09-01

    Drawing from cumulative inequality theory, this research examines how accumulated financial strain affects women's self-rated health in middle and later life. Using data from the National Longitudinal Survey of Mature Women (1967-2003), we employ random-coefficient growth curve models to examine whether recurring financial strain influences women's health, above and beyond several measures of objective social status. Predicted probabilities of poor health were estimated by the frequency of financial strain. Financial strain is associated with rapid declines in women's health during middle and later life, especially for those women who reported recurrent strain. Changes in household income and household wealth were also associated with women's health but did not eliminate the effects due to accumulated financial strain. Accumulated financial strain has long-term effects on women's health during middle and later life. The findings demonstrate the importance of measuring life course exposure to stressors in studies of health trajectories.

  4. The effect of energy substrates on PHB accumulation of Acidiphilium cryptum DX1-1.

    PubMed

    Xu, Ai-ling; Xia, Jin-lan; Song, Zhi-wen; Jiang, Peng; Xia, Yan; Wan, Min-xi; Zhang, Rui-yong; Yang, Yi; Liu, Ke-ke

    2013-09-01

    The effect of glucose and elemental sulfur on the growth and PHB accumulation of Acidiphilium cryptum DX1-1 was investigated. Meanwhile, the differential expressions of 19 genes related with PHB accumulation, sulfur metabolism and carbon fixed in heterotrophy, phytotrophy and mixotrophy were studied by RT-qPCR. The results showed that strain DX1-1 could accumulate PHB with sulfur as the energy substance and atmospheric CO2 as carbon resource. Glucose could improve the growth of strain DX1-1 cultured in medium with sulfur as the energy substance, and almost all the key enzyme-encoding genes related with PHB, sulfur metabolism and carbon fixed were basically up-regulated. PHB polymerase (Arcy_3030), ribulose-bisphosphate carboxylase (Acry_0825), ribulose-phosphate-epimerase (Acry_0022), and cysteine synthase A (Acry_2560) played important role in PHB accumulation, the modified expression of which could influence the PHB yield. With CO2 as carbon resource, the main initial substance of PHB accumulation for strain DX1-1 was acetyl-CoA, instead of acetate with the glucose as the carbon resource. Because of accumulating PHB by fixed atmospheric CO2 while independent of light, A. cryptum DX1-1 may have specifically potential in production of PHB.

  5. Strain accumulation and rotation in the Eastern California Shear Zone

    USGS Publications Warehouse

    Savage, J.C.; Gan, Weijun; Svarc, J.L.

    2001-01-01

    Although the Eastern California Shear Zone (ECSZ) (strike ???N25??W) does not quite coincide with a small circle drawn about the Pacific-North America pole of rotation, trilateration and GPS measurements demonstrate that the motion within the zone corresponds to right-lateral simple shear across a vertical plane (strike N33??W??5??) roughly parallel to the tangent to that local small circle (strike ???N40??W). If the simple shear is released by slip on faults subparallel to the shear zone, the accumulated rotation is also released, leaving no secular rotation. South of the Garlock fault the principal faults (e.g., Calico-Blackwater fault) strike ???N40??W, close enough to the strike of the vertical plane across which maximum right-lateral shear accumulates to almost wholly accommodate that accumulation of both strain and rotation by right-lateral slip. North of the Garlock fault dip slip as well as strike slip on the principal faults (strike ???N20??W) is required to accommodate the simple shear accumulation. In both cases the accumulated rotation is released with the shear strain. The Garlock fault, which transects the ECSZ, is not offset by north-northwest striking faults nor, despite geological evidence for long-term left-lateral slip, does it appear at the present time to be accumulating left-lateral simple shear strain across the fault due to slip at depth. Rather the motion is explained by right-lateral simple shear across the orthogonal ECSZ. Left-lateral slip on the Garlock fault will release the shear strain accumulating there but would augment the accumulating rotation, resulting in a secular clockwise rotation rate ???80 nrad yr-1 (4.6?? Myr-1).

  6. Characterization of a S-adenosyl-l-methionine (SAM)-accumulating strain of Scheffersomyces stipitis.

    PubMed

    Križanović, Stela; Butorac, Ana; Mrvčić, Jasna; Krpan, Maja; Cindrić, Mario; Bačun-Družina, Višnja; Stanzer, Damir

    2015-06-01

    S-adenosyl-l-methionine (SAM) is an important molecule in the cellular metabolism of mammals. In this study, we examined several of the physiological characteristics of a SAM-accumulating strain of the yeast Scheffersomyces stipitis (M12), including SAM production, ergosterol content, and ethanol tolerance. S. stipitis M12 accumulated up to 52.48 mg SAM/g dry cell weight. Proteome analyses showed that the disruption of C-24 methylation in ergosterol biosynthesis, a step mediated by C-24 sterol methyltransferase (Erg6p), results in greater SAM accumulation by S. stipitis M12 compared to the wild-type strain. A comparative proteome-wide analysis identified 25 proteins that were differentially expressed by S. stipitis M12. These proteins are involved in ribosome biogenesis, translation, the stress response, ubiquitin-dependent catabolic processes, the cell cycle, ethanol tolerance, posttranslational modification, peroxisomal membrane stability, epigenetic regulation, the actin cytoskeleton and cell morphology, iron and copper homeostasis, cell signaling, and energy metabolism. Copyright© by the Spanish Society for Microbiology and Institute for Catalan Studies.

  7. Constant strain accumulation rate between major earthquakes on the North Anatolian Fault.

    PubMed

    Hussain, Ekbal; Wright, Tim J; Walters, Richard J; Bekaert, David P S; Lloyd, Ryan; Hooper, Andrew

    2018-04-11

    Earthquakes are caused by the release of tectonic strain accumulated between events. Recent advances in satellite geodesy mean we can now measure this interseismic strain accumulation with a high degree of accuracy. But it remains unclear how to interpret short-term geodetic observations, measured over decades, when estimating the seismic hazard of faults accumulating strain over centuries. Here, we show that strain accumulation rates calculated from geodetic measurements around a major transform fault are constant for its entire 250-year interseismic period, except in the ~10 years following an earthquake. The shear strain rate history requires a weak fault zone embedded within a strong lower crust with viscosity greater than ~10 20  Pa s. The results support the notion that short-term geodetic observations can directly contribute to long-term seismic hazard assessment and suggest that lower-crustal viscosities derived from postseismic studies are not representative of the lower crust at all spatial and temporal scales.

  8. Himalayan Strain Accumulation 100 ka Timescales

    NASA Astrophysics Data System (ADS)

    Cannon, J. M.; Murphy, M. A.; Liu, Y.

    2015-12-01

    Crustal scale fault systems and tectonostratigraphic units in the Himalaya can be traced for 2500 km along strike. However regional studies have shown that there is variability in the location and rate of strain accumulation which appears to be driven by Main Himalayan Thrust (MHT) geometry and convergence obliquity. GPS illuminates the modern interseismic strain rate and the historical record of great earthquakes elucidates variations in strain accumulation over 103 years. To connect these patterns with the 106 year structural and thermochronometric geologic record we examine normalized river channel steepness (ksn), a proxy for rock uplift rate, which develops over 104 - 105 years. Here we present a ksn map of the Himalaya and compare it with bedrock geology, precipitation, the historic earthquake record, GPS, seismicity, and seismotectonic models. Our map shows significant along strike changes in the magnitude of channel steepness, the areal extent of swaths of high ksn channels, and their location with respect to the range front. Differences include the juxtaposition of two narrow (30 - 40 km) range parallel belts of high ksn in west Nepal and Bhutan coincident with MHT duplexes and belts of microseismcity, with a single broad (70 km) swath of high ksn and microseismicity in central and eastern Nepal. Separating west and central Nepal a band of low ksn crosses the range coincident with the West Nepal Fault (WNF) and the lowest rate of microseismicity in Nepal. To the west the orogen is obliquely convergent and has less high ksn channels, while the orthogonally convergent region to the east contains the highest concentration of oversteepened channels in the Himalaya supporting the idea that the WNF is a strain partitioning boundary. The syntaxes are characterized by locally high channel steepness surrounded by low to moderate ksn channels consistent with the hypothesis that rapid exhumation within the syntaxes is sustained by an influx of lower crust.

  9. Strain accumulation in southern California, 1973-1980.

    USGS Publications Warehouse

    Savage, J.C.; Prescott, W.H.; Lisowski, M.; King, N.E.

    1981-01-01

    Frequent surveys of seven trilateration networks in southern California over the interval 1973-1980 suggest that a regional increment in strain may have occurred in 1978-1979. Prior to 1978 and after late 1979 the strain accumulation has been predominantly a uniaxial north-south compression. This secular trend was interrupted sometime in 1978-1979 by an increment in both north-south and east-west extension in five of the seven networks. The onset of this change appears to have occurred first in the networks farthest south. The changes occurred without any unusual seismicity within the networks, but the overall seismicity in southern California was unusually low prior to and has been unusually high since the occurrence. The average principal strain rates for the seven networks in the 1973-1980 interval are 0.17 mu strain/yr north- south contraction and 0.08 mu strain/yr east-west extension. Although the observed increment in strain could be related to unidentified systematic error in the measuring system, a careful review of the measurements and comparisons with three other measuring systems reveal no appreciable cumulative systematic error. -Authors

  10. Rapid intraplate strain accumulation in the New Madrid seismic zone

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

    Liu, L.; Zoback, M.D.; Segall, P.

    1992-09-01

    Remeasurement of a triangulation network in the southern part of the New Madrid seismic zone with the Global Positioning System has revealed rapid crustal strain accumulation since the 1950s. This area experienced three large (moment magnitudes greater than 8) earthquakes in 1811 to 1812. The orientation and sense of shear is consistent with right-lateral strike slip motion along a northeast-trending fault zone (as indicated by current seismicity). Detection of crustal strain accumulation may be a useful discriminant for identifying areas where potentially damaging intraplate earthquakes may occur despite the absence of large earthquakes during historic time. 34 refs.

  11. Relationship of trehalose accumulation with ethanol fermentation in industrial Saccharomyces cerevisiae yeast strains.

    PubMed

    Wang, Pin-Mei; Zheng, Dao-Qiong; Chi, Xiao-Qin; Li, Ou; Qian, Chao-Dong; Liu, Tian-Zhe; Zhang, Xiao-Yang; Du, Feng-Guang; Sun, Pei-Yong; Qu, Ai-Min; Wu, Xue-Chang

    2014-01-01

    The protective effect and the mechanisms of trehalose accumulation in industrial Saccharomyces cerevisiae strains were investigated during ethanol fermentation. The engineered strains with more intercellular trehalose achieved significantly higher fermentation rates and ethanol yields than their wild strain ZS during very high gravity (VHG) fermentation, while their performances were not different during regular fermentation. The VHG fermentation performances of these strains were consistent with their growth capacity under osmotic stress and ethanol stress, the key stress factors during VHG fermentation. These results suggest that trehalose accumulation is more important for VHG fermentation of industrial yeast strains than regular one. The differences in membrane integrity and antioxidative capacity of these strains indicated the possible mechanisms of trehalose as a protectant under VHG condition. Therefore, trehalose metabolic engineering may be a useful strategy for improving the VHG fermentation performance of industrial yeast strains. Copyright © 2013 Elsevier Ltd. All rights reserved.

  12. A new strain of Claviceps purpurea accumulating tetracyclic clavine alkaloids.

    PubMed

    Schumann, B; Erge, D; Maier, W; Gröger, D

    1982-05-01

    A new strain of Claviceps was isolated from a blokked mutant of Claviceps purpurea. This strain accumulates substantial amounts of clavine alkaloids (2 g/l). The alkaloid fraction is composed of chanoclavine-I ( approximately 10%) and a mixture of agroclavine/elymoclavine (90%). Most suitable for alkaloid production in submerged culture is an ammoncitrate/sucrose medium. The genealogy of the new strain, designated Pepty 695/ch-I is the following one: Pepty 695/S (ergotoxine producer) --> Pepty 695/ch (secoergoline producer) --> Pepty 695/ch-I (tetracyclic clavine producer).

  13. Lipid Accumulation from Glucose and Xylose in an Engineered, Naturally Oleaginous Strain of Saccharomyces cerevisiae

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

    Knoshaug, Eric P; Van Wychen, Stefanie R; Zhang, Min

    Saccharomyces cerevisiae, a well-known industrial yeast for alcoholic fermentation, is not historically known to accumulate lipids. Four S. cerevisiae strains used in industrial applications were screened for their ability to accumulate neutral lipids. Only one, D5A, was found to accumulate up to 20% dry cell weight (dcw) lipids. This strain was further engineered by knocking out ADP-activated serine/threonine kinase (SNF1) which increased lipid accumulation to 35% dcw lipids. In addition, we engineered D5A to utilize xylose and found that D5A accumulates up to 37% dcw lipids from xylose as the sole carbon source. Further we over-expressed different diacylglycerol acyltransferase (DGA1)more » genes and boosted lipid accumulation to 50%. Fatty acid speciation showed that 94% of the extracted lipids consisted of 5 fatty acid species, C16:0 (palmitic), C16:1n7 (palmitoleic), C18:0 (stearic), C18:1n7 (vaccenic), and C18:1n9 (oleic), while the relative distributions changed depending on growth conditions. In addition, this strain accumulated lipids concurrently with ethanol production.« less

  14. Modal strain energies in COSMIC NASTRAN

    NASA Technical Reports Server (NTRS)

    Snyder, B. D.; Venkayya, V. B.

    1989-01-01

    A computer program was developed to take a NASTRAN output file from a normal modes analysis and calculate the modal strain energies of selected elements. The FORTRAN program can determine the modal strain energies for CROD, CBAR, CELAS, CTRMEM, CQDMEM2, and CSHEAR elements. Modal strain energies are useful in estimating damping in structures.

  15. Fusarium proliferatum strains change fumonisin biosynthesis and accumulation when exposed to host plant extracts.

    PubMed

    Górna, Karolina; Pawłowicz, Izabela; Waśkiewicz, Agnieszka; Stępień, Łukasz

    2016-01-01

    Fumonisin concentrations in mycelia and media were studied in liquid Fusarium proliferatum cultures supplemented with host plant extracts. Furthermore, the kinetics of fumonisin accumulation in media and mycelia collected before and after extract addition was analysed as well as the changes in the expression of the FUM1 gene. Fumonisin content in culture media increased in almost all F. proliferatum strains shortly after plant extracts were added. The asparagus extract induced the highest FB level increase and the garlic extract was the second most effective inducer. Fumonisin level decreased constantly until 14th day of culturing, though for some strains also at day 8th an elevated FB level was observed. Pineapple extract induced the highest increase of fum1 transcript levels as well as fumonisin synthesis in many strains, and the peas extract inhibited fungal growth and fumonisin biosynthesis. Moreover, fumonisins were accumulated in mycelia of studied strains and in the respective media. Copyright © 2016 British Mycological Society. Published by Elsevier Ltd. All rights reserved.

  16. Mutation Breeding of β-carotene Producing Strain B. trispora by Low Energy Ion Implantation

    NASA Astrophysics Data System (ADS)

    Zhang, Ning; Yu, Long

    2009-02-01

    Ion beam bioengineering technology as a new mutation approach has been widely used in the biological breeding field. In this paper the application of low energy nitrogen ion implantation in the β-carotene producing strain, Blakeslea trispora(-) was investigated. The effects of different fermentation conditions on β-carotene production by a high yield strain were examined. Results showed that two β-carotene high yielding strains B.trispora(-) BH3-701 and BH3-728 were screened out and the averaged production of β-carotene was raised by 178.7% and 164.6% respectively after five passages in the shaking flasks. Compared with the original strain, the highest yield strain BH3-701 was potent in accumulating β-carotene, especially in the later stage, and greatly increased production efficiency.

  17. Starch and lipid accumulation in eight strains of six Chlorella species under comparatively high light intensity and aeration culture conditions.

    PubMed

    Takeshita, Tsuyoshi; Ota, Shuhei; Yamazaki, Tomokazu; Hirata, Aiko; Zachleder, Vilém; Kawano, Shigeyuki

    2014-04-01

    The microalgae family Chlorella species are known to accumulate starch and lipids. Although nitrogen or phosphorous deficiencies promote starch and lipids formation in many microalgae, these deficiencies also limit their growth and productivity. Therefore, the Chlorellaceae strains were attempted to increase starch and lipids productivity under high-light-intensity conditions (600-μmol photons m(-2)s(-1)). The 12:12-h light-dark (LD) cycle conditions elicited more stable growth than the continuous light (LL) conditions, whereas the starch and lipids yields increased in LL conditions. The amount of starch and lipids per cell increased in Chlorella viscosa and Chlorella vulgaris in sulfur-deficient medium, and long-chain fatty acids with 20 or more carbon atoms accumulated in cells grown in sulfur-deficient medium. Accumulation of starch and lipids was investigated in eight strains. The accumulation was strain-dependent, and varied according to the medium and light conditions. Five of the eight Chlorella strains exhibited similar accumulation patterns. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Factors influencing the accumulation of ciprofloxacin in Pseudomonas aeruginosa.

    PubMed Central

    Celesk, R A; Robillard, N J

    1989-01-01

    Ciprofloxacin accumulation in Pseudomonas aeruginosa was measured by a bioassay. Drug accumulation in strain PAO2 was compared with that of three spontaneous ciprofloxacin-resistant mutants selected with 0.5 micrograms of ciprofloxacin per ml. PAO4701 cfxA2 contains a mutation in the gyrA gene, PAO4742 cfxB5 may represent a permeability mutant based on pleiotropic drug resistance, and PAO4700 cfxA1 cfxB1 contains both types of mutations. In all strains, drug accumulation was similar, reaching steady state during the first minute of exposure. Drug accumulation was unsaturable over a range of 5 to 80 micrograms/ml, suggesting that ciprofloxacin accumulates by diffusion in P. aeruginosa. Although all four strains accumulated two- to sevenfold more ciprofloxacin in the presence of the inhibitor carbonyl cyanide m-chlorophenylhydrazone, the cfxB mutants accumulated two- to fourfold less drug than either PAO2 or the cfxA2 mutant. Polyacrylamide gel analysis revealed a protein common to cfxB mutants only, while all strains had similar lipopolysaccharide profiles. The results suggest that ciprofloxacin accumulation in P. aeruginosa is a complex phenomenon that may be affected by both an energy-dependent drug efflux process and outer envelope composition. Images PMID:2514623

  19. A theoretical insight into H accumulation and bubble formation by applying isotropic strain on the W-H system under a fusion environment

    NASA Astrophysics Data System (ADS)

    Han, Quan-Fu; Liu, Yue-Lin; Zhang, Ying; Ding, Fang; Lu, Guang-Hong

    2018-04-01

    The solubility and bubble formation of hydrogen (H) in tungsten (W) are crucial factors for the application of W as a plasma-facing component under a fusion environment, but the data and mechanism are presently scattered, indicating some important factors might be neglected. High-energy neutron-irradiated W inevitably causes a local strain, which may change the solubility of H in W. Here, we performed first-principles calculations to predict the H solution behaviors under isotropic strain combined with temperature effect in W and found that the H solubility in interstitial lattice can be promoted/impeded by isotropic tensile/compressive strain over the temperature range 300-1800 K. The calculated H solubility presents good agreement with the experiment. Together, our previous results of anisotropic strain, except for isotropic compression, both isotropic tension and anisotropic tension/compression enhance H solution so as to reveal an important physical implication for H accumulation and bubble formation in W: strain can enhance H solubility, resulting in the preliminary nucleation of H bubble that further causes the local strain of W lattice around H bubble, which in turn improves the H solubility at the strained region that promotes continuous growth of the H bubble via a chain-reaction effect in W. This result can also interpret the H bubble formation even if no radiation damage is produced in W exposed to low-energy H plasma.

  20. The effects of abscisic acid, salicylic acid and jasmonic acid on lipid accumulation in two freshwater Chlorella strains.

    PubMed

    Wu, Guanxun; Gao, Zhengquan; Du, Huanmin; Lin, Bin; Yan, Yuchen; Li, Guoqiang; Guo, Yanyun; Fu, Shenggui; Wei, Gongxiang; Wang, Miaomiao; Cui, Meng; Meng, Chunxiao

    2018-03-27

    Sustainable renewable energy is being hotly debated globally because the continued use of finite fossil fuels is now widely recognized as being unsustainable. Microalgae potentially offer great opportunities for resolving this challenge. Abscisic acid (ABA), jasmonic acid (JA) and salicylic acid (SA) are involved in regulating many physiological properties and have been widely used in higher plants. To test if phytohormones have an impact on accumulating lipid for microalgae, ABA, JA and SA were used to induce two Chlorella strains in the present study. The results showed 1.0 mg/L ABA, 10 mg/L SA, and 0.5 mg/L JA, led strain C. vulgaris ZF strain to produce a 45%, 42% and 49% lipid content that was 1.8-, 1.7- and 2.0-fold that of controls, respectively. For FACHB 31 (number 31 of the Freshwater Algae Culture Collection at the Institute of Hydrobiology, Chinese Academy of Sciences), the addition of 1.0 mg/L ABA, 10 mg/L SA, and 0.5 mg/L, JA produced 33%, 30% and 38% lipid content, which was 1.8-, 1.6- and 2.1-fold that of controls, respectively. As for lipid productivity, 1.0 mg/L ABA increased the lipid productivity of C. vulgaris ZF strain and FACHB-31 by 123% and 44%; 10 mg/L SA enhanced lipid productivity by 100% and 33%; the best elicitor, 0.5 mg/L JA, augmented lipid productivity by 127% and 75% compared to that of controls, respectively. The results above suggest that the three phytohormones at physiological concentrations play crucial roles in inducing lipid accumulation in Chlorella.

  1. Strain accumulation across the Coast Ranges at the latitude of San Francisco, 1994-2000

    USGS Publications Warehouse

    Savage, J.C.; Gan, Weijun; Prescott, W.H.; Svarc, J.L.

    2004-01-01

    A 66-monument geodetic array spanning the Coast Ranges near San Francisco has been surveyed more than eight times by GIPS between late 1993 and early 2001. The measured horizontal velocities of the monuments are well represented by uniform, right-lateral, simple shear parallel to N29??W. (The local strike of the San Andreas Fault is ???N34??W. The observed areal dilatation rate of 6.9 ?? 10.0 nstrain yr-1 (quoted uncertainty is one standard deviation and extension is reckoned positive) is not significantly different from zero, which implies that the observed strain accumulation could be released by strike-slip faulting alone. Our results are consistent with the slip rates assigned by the Working Group on California Earthquake Probabilities [2003] to the principal faults (San Gregorio, San Andreas, Hayward-Rodgers Creek, Calaveras-Concord-Green Valley, and Greenville Faults) cutting across the GPS array. The vector sum of those slip rates is 39.8 ?? 2.6 mm yr-1 N29.8??W ?? 2.8??, whereas the motion across the GPS array (breadth 120 km) inferred from the uniform strain rate approximation is 38.7 ?? 1.2 mm yr-1 N29.0?? ?? 0.9?? right-lateral shear and 0.4 ?? 0.9 mm yr-1 N61??E ?? 0.9?? extension. We interpret the near coincidence of these rates and the absence of significant accumulation of areal dilatation to imply that right-lateral slip on the principal faults can release the accumulating strain; major strain release on reverse faults subparallel to the San Andreas Fault within the Coast Ranges is not required. Copyright 2004 by the American Geophysical union.

  2. Strain accumulation in bituminous binders under repeated creep-recovery loading predicted from small-amplitude oscillatory shear (SAOS) experiments

    NASA Astrophysics Data System (ADS)

    Laukkanen, Olli-Ville; Winter, H. Henning

    2017-11-01

    The creep-recovery (CR) test starts out with a period of shearing at constant stress (creep) and is followed by a period of zero-shear stress where some of the accumulated shear strain gets reversed. Linear viscoelasticity (LVE) allows one to predict the strain response to repeated creep-recovery (RCR) loading from measured small-amplitude oscillatory shear (SAOS) data. Only the relaxation and retardation time spectra of a material need to be known and these can be determined from SAOS data. In an application of the Boltzmann superposition principle (BSP), the strain response to RCR loading can be obtained as a linear superposition of the strain response to many single creep-recovery tests. SAOS and RCR data were collected for several unmodified and modified bituminous binders, and the measured and predicted RCR responses were compared. Generally good agreement was found between the measured and predicted strain accumulation under RCR loading. However, in the case of modified binders, the strain accumulation was slightly overestimated (≤20% relative error) due to the insufficient SAOS information at long relaxation times. Our analysis also demonstrates that the evolution in the strain response under RCR loading, caused by incomplete recovery, can be reasonably well predicted by the presented methodology. It was also shown that the outlined modeling framework can be used, as a first approximation, to estimate the rutting resistance of bituminous binders by predicting the values of the Multiple Stress Creep Recovery (MSCR) test parameters.

  3. Storing wind energy into electrical accumulators

    NASA Astrophysics Data System (ADS)

    Dordescu, M.; Petrescu, D. I.; Erdodi, G. M.

    2016-12-01

    Shall be determined, in this work, the energy stored in the accumulators electrical, AE, at a wind system operating at wind speeds time-varying. mechanical energy caught in the turbine from the wind, (TV), is transformed into electrical energy by the generator synchronous with the permanent magnets, GSMP. The Generator synchronous with the permanent magnets saws, via a rectifier, energy in a battery AE, finished in a choice of two: variant 1-unregulated rectifier and variant of the 2-controlled rectifier and task adapted. Through simulation determine the differences between the two versions

  4. Physiological diversity and trehalose accumulation in Schizosaccharomyces pombe strains isolated from spontaneous fermentations during the production of the artisanal Brazilian cachaça.

    PubMed

    Gomes, Fátima C O; Pataro, Carla; Guerra, Juliana B; Neves, Maria J; Corrêa, Soraya R; Moreira, Elizabeth S A; Rosa, Carlos A

    2002-05-01

    Twenty-seven Schizosaccharomyces pombe isolates from seven cachaça distilleries were tested for maximum temperature of growth and fermentation, osmotolerance, ethanol resistance, invertase production, and trehalose accumulation. Two isolates were selected for studies of trehalose accumulation under heat shock and ethanol stress. The S. pombe isolates were also characterized by RAPD-PCR. The isolates were able to grow and ferment at 41 degrees C, resisted concentrations of 10% ethanol, and grew on 50% glucose medium. Four isolates yielded invertase activity of more than 100 micromol of reducing sugar x mg(-1) x min(-1). The S. pombe isolates were able to accumulate trehalose during stationary phase. Two isolates, strains UFMG-A533 and UFMG-A1000, submitted to a 15 min heat shock, were able to accumulate high trehalose levels. Strain UFMG-A533 had a marked reduction in viability during heat shock, but strain UFMG-A1000 preserved a viability rate of almost 20% after 15 min at 48 degrees C. No clear correlation was observed between trehalose accumulation and cell survival during ethanol stress. Strain UFMG-A1000 had higher trehalose accumulation levels than strain UFMG-A533 under conditions of combined heat treatment and ethanol stress. Molecular analysis showed that some strains are maintained during the whole cachaça production period; using the RAPD-PCR profiles, it was possible to group the isolates according to their isolation sites.

  5. Role of Cations in Accumulation and Release of Phosphate by Acinetobacter Strain 210A

    PubMed Central

    van Groenestijn, Johan W.; Vlekke, Gerard J. F. M.; Anink, Désirée M. E.; Deinema, Maria H.; Zehnder, Alexander J. B.

    1988-01-01

    Cells of the strictly aerobic Acinetobacter strain 210A, containing aerobically large amounts of polyphosphate (100 mg of phosphorus per g [dry weight] of biomass), released in the absence of oxygen 1.49 mmol of Pi, 0.77 meq of Mg2+, 0.48 meq of K+, 0.02 meq of Ca2+, and 0.14 meq of NH4+ per g (dry weight) of biomass. The drop in pH during this anaerobic phase was caused by the release of 1.8 protons per PO43− molecule. Cells of Acinetobacter strain 132, which do not accumulate polyphosphate aerobically, released only 0.33 mmol of Pi and 0.13 meq of Mg2+ per g (dry weight) of biomass but released K+ in amounts comparable to those released by strain 210A. Stationary-phase cultures of Acinetobacter strain 210A, in which polyphosphate could not be detected by Neisser staining, aerobically took up phosphate simultaneously with Mg2+, the most important counterion in polyphosphate. In the absence of dissolved phosphate in the medium, no Mg2+ was taken up. Cells containing polyphosphate granules were able to grow in a Mg-free medium, whereas cells without these granules were not. Mg2+ was not essential as a counterion because it could be replaced by Ca2+. The presence of small amounts of K+ was essential for polyphosphate formation in cells of strain 210A. During continuous cultivation under K+ limitation, cells of Acinetobacter strain 210A contained only 14 mg of phosphorus per g (dry weight) of biomass, whereas this element was accumulated in amounts of 59 mg/g under substrate limitation and 41 mg/g under Mg2+ limitation. For phosphate uptake in activated sludge, the presence of K+ seemed to be crucial. PMID:16347788

  6. Prion Strain Differences in Accumulation of PrPSc on Neurons and Glia Are Associated with Similar Expression Profiles of Neuroinflammatory Genes: Comparison of Three Prion Strains

    PubMed Central

    Carroll, James A.; Striebel, James F.; Rangel, Alejandra; Woods, Tyson; Phillips, Katie; Peterson, Karin E.; Race, Brent; Chesebro, Bruce

    2016-01-01

    Misfolding and aggregation of host proteins are important features of the pathogenesis of neurodegenerative diseases including Alzheimer’s disease, Parkinson’s disease, frontotemporal dementia and prion diseases. In all these diseases, the misfolded protein increases in amount by a mechanism involving seeded polymerization. In prion diseases, host prion protein is misfolded to form a pathogenic protease-resistant form, PrPSc, which accumulates in neurons, astroglia and microglia in the CNS. Here using dual-staining immunohistochemistry, we compared the cell specificity of PrPSc accumulation at early preclinical times post-infection using three mouse scrapie strains that differ in brain regional pathology. PrPSc from each strain had a different pattern of cell specificity. Strain 22L was mainly associated with astroglia, whereas strain ME7 was mainly associated with neurons and neuropil. In thalamus and cortex, strain RML was similar to 22L, but in substantia nigra, RML was similar to ME7. Expression of 90 genes involved in neuroinflammation was studied quantitatively using mRNA from thalamus at preclinical times. Surprisingly, despite the cellular differences in PrPSc accumulation, the pattern of upregulated genes was similar for all three strains, and the small differences observed correlated with variations in the early disease tempo. Gene upregulation correlated with activation of both astroglia and microglia detected in early disease prior to vacuolar pathology or clinical signs. Interestingly, the profile of upregulated genes in scrapie differed markedly from that seen in two acute viral CNS diseases (LaCrosse virus and BE polytropic Friend retrovirus) that had reactive gliosis at levels similar to our prion-infected mice. PMID:27046083

  7. Slip distribution, strain accumulation and aseismic slip on the Chaman Fault system

    NASA Astrophysics Data System (ADS)

    Amelug, F.

    2015-12-01

    The Chaman fault system is a transcurrent fault system developed due to the oblique convergence of the India and Eurasia plates in the western boundary of the India plate. To evaluate the contemporary rates of strain accumulation along and across the Chaman Fault system, we use 2003-2011 Envisat SAR imagery and InSAR time-series methods to obtain a ground velocity field in radar line-of-sight (LOS) direction. We correct the InSAR data for different sources of systematic biases including the phase unwrapping errors, local oscillator drift, topographic residuals and stratified tropospheric delay and evaluate the uncertainty due to the residual delay using time-series of MODIS observations of precipitable water vapor. The InSAR velocity field and modeling demonstrates the distribution of deformation across the Chaman fault system. In the central Chaman fault system, the InSAR velocity shows clear strain localization on the Chaman and Ghazaband faults and modeling suggests a total slip rate of ~24 mm/yr distributed on the two faults with rates of 8 and 16 mm/yr, respectively corresponding to the 80% of the total ~3 cm/yr plate motion between India and Eurasia at these latitudes and consistent with the kinematic models which have predicted a slip rate of ~17-24 mm/yr for the Chaman Fault. In the northern Chaman fault system (north of 30.5N), ~6 mm/yr of the relative plate motion is accommodated across Chaman fault. North of 30.5 N where the topographic expression of the Ghazaband fault vanishes, its slip does not transfer to the Chaman fault but rather distributes among different faults in the Kirthar range and Sulaiman lobe. Observed surface creep on the southern Chaman fault between Nushki and north of City of Chaman, indicates that the fault is partially locked, consistent with the recorded M<7 earthquakes in last century on this segment. The Chaman fault between north of the City of Chaman to North of Kabul, does not show an increase in the rate of strain

  8. Time-dependent constitutive modeling of drive belts—II. The effect of the shape of material retardation spectrum on the strain accumulation process

    NASA Astrophysics Data System (ADS)

    Zupančič, B.; Emri, I.

    2009-11-01

    This is the second paper in the series addressing the constitutive modeling of dynamically loaded elastomeric products such as power transmission belts. During the normal operation of such belts certain segments of the belt structure are loaded via tooth-like cyclical loading. When the time-dependent properties of the elastomeric material “match” the time-scale of the dynamic loading a strain accumulation (incrementation) process occurs. It was shown that the location of a critical rotation speed strongly depends on the distribution (shape) of the retardation spectrum, whereas the magnitude of the accumulated strain is governed by the strength of the corresponding spectrum lines. These interrelations are extremely non-linear. The strain accumulation process is most intensive at the beginning of the drive belt operation, and is less intensive for longer belts. The strain accumulation process is governed by the spectrum lines that are positioned within a certain region, which we call the Strain Accumulation Window (SAW). An SAW is always located to the right of the spectrum line, L i , at log ( ω λ i )=0, where ω is the operational angular velocity. The width of the SAW depends on the width of the material spectrum. Based on the following analysis a new designing criterion is proposed for use in engineering applications for selecting a proper material for general drive-belt operations.

  9. On the strain energy of laminated composite plates

    NASA Technical Reports Server (NTRS)

    Atilgan, Ali R.; Hodges, Dewey H.

    1991-01-01

    The present effort to obtain the asymptotically correct form of the strain energy in inhomogeneous laminated composite plates proceeds from the geometrically nonlinear elastic theory-based three-dimensional strain energy by decomposing the nonlinear three-dimensional problem into a linear, through-the-thickness analysis and a nonlinear, two-dimensional analysis analyzing plate formation. Attention is given to the case in which each lamina exhibits material symmetry about its middle surface, deriving closed-form analytical expressions for the plate elastic constants and the displacement and strain distributions through the plate's thickness. Despite the simplicity of the plate strain energy's form, there are no restrictions on the magnitudes of displacement and rotation measures.

  10. Determining Recoverable and Irrecoverable Contributions to Accumulated Strain in a NiTiPd High-Temperature Shape Memory Alloy During Thermomechanical Cycling

    NASA Technical Reports Server (NTRS)

    Monroe, J. A.; Karaman, I.; Lagoudas, D. C.; Bigelow, G.; Noebe, R. D.; Padula, S., II

    2011-01-01

    When Ni(29.5)Ti(50.5)Pd30 shape memory alloy is thermally cycled under stress, significant strain can accumulate due to elasticity, remnant oriented martensite and plasticity. The strain due to remnant martensite can be recovered by further thermal cycling under 0 MPa until the original transformation-induced volume change and martensite coefficient of thermal expansion are obtained. Using this technique, it was determined that the 8.15% total accumulated strain after cycling under 200 MPa consisted of 0.38%, 3.97% and 3.87% for elasticity, remnant oriented martensite and creep/plasticity, respectively.

  11. Spacecraft Dynamic Characterization by Strain Energies Method

    NASA Astrophysics Data System (ADS)

    Bretagne, J.-M.; Fragnito, M.; Massier, S.

    2002-01-01

    In the last years the significant increase in satellite broadcasting demand, with the wide band communication dawn, has given a great impulse to the telecommunication satellite market. The big demand is translated from operators (such as SES/Astra, Eutelsat, Intelsat, Inmarsat, EuroSkyWay etc.) in an increase of orders of telecom satellite to the world industrials. The largest part of these telecom satellite orders consists of Geostationary platforms which grow more and more in mass (over 5 tons) due to an ever longer demanded lifetime (up to 20 years), and become more complex due to the need of implementing an ever larger number of repeaters, antenna reflectors and feeds, etc... In this frame, the mechanical design and verification of these large spacecraft become difficult and ambitious at the same time, driven by the dry mass limitation objective. By the Finite Element Method (FEM), and on the basis of the telecom satellite heritage of a world leader constructor such as Alcatel Space Industries it is nowadays possible to model these spacecraft in a realistic and confident way in order to identify the main global dynamic aspects such as mode shapes, mass participation and/or dynamic responses. But on the other hand, one of the main aims consists in identifying soon in a program the most critical aspects of the system behavior in the launch dynamic environment, such as possible dynamic coupling between the different subsystems and secondary structures of the spacecraft (large deployable reflectors, thrusters, etc.). To this aim a numerical method has been developed in the frame of the Alcatel SPACEBUS family program, using MSC/Nastran capabilities and it is presented in this paper. The method is based on Spacecraft sub-structuring and strain energy calculation. The method mainly consists of two steps : 1) subsystem modal strain energy ratio (with respect to the global strain energy); 2) subsystem strain energy calculation for each mode according to the base driven

  12. Strain accumulation in the Shumagin Islands: Results of initial GPS measurements

    USGS Publications Warehouse

    Larson, Kristine M.; Lisowski, Michael

    1994-01-01

    Deformation in the Shumagin seismic gap has been monitored with repeated trilateration (EDM) in the 1980–1987 interval and with the Global Positioning System (GPS) in the 1987–1991 interval. The geodetic network extends for 100-km across the Shumagin Islands to the Alaska Peninsula. Results from the GPS surveys are consistent with those previously reported for the EDM surveys: we failed to detect significant strain accumulation in the N30°W direction of plate convergence. Using the method of simultaneous reduction for position and strain rates, we found the average rate of extension in the direction of plate convergence to be −25±25 nanostrain/yr (nstrain/yr) during the 1987–1991 interval of GPS surveys compared with −20±15 nstrain/yr during the 1981–1987 interval of complete EDM surveys. We found a marginally significant −26±12 nstrain/yr extension rate in the 1981–1991 interval covered by the combined EDM and GPS surveys. Strain rates are higher, but not significantly so, in the part of the network closest to the trench. Spatial variation in the deformation is observed in the 1980–1991 average station velocities, where three of the four stations closest to the trench have an arcward velocity of a few mm/yr. The observed strain rates are an order of magnitude lower than the −200 nstrain/yr rate predicted by dislocation models.

  13. Oil accumulation in the model green alga Chlamydomonas reinhardtii: characterization, variability between common laboratory strains and relationship with starch reserves.

    PubMed

    Siaut, Magali; Cuiné, Stéphan; Cagnon, Caroline; Fessler, Boris; Nguyen, Mai; Carrier, Patrick; Beyly, Audrey; Beisson, Fred; Triantaphylidès, Christian; Li-Beisson, Yonghua; Peltier, Gilles

    2011-01-21

    When cultivated under stress conditions, many microalgae species accumulate both starch and oil (triacylglycerols). The model green microalga Chlamydomonas reinhardtii has recently emerged as a model to test genetic engineering or cultivation strategies aiming at increasing lipid yields for biodiesel production. Blocking starch synthesis has been suggested as a way to boost oil accumulation. Here, we characterize the triacylglycerol (TAG) accumulation process in Chlamydomonas and quantify TAGs in various wild-type and starchless strains. In response to nitrogen deficiency, Chlamydomonas reinhardtii produced TAGs enriched in palmitic, oleic and linoleic acids that accumulated in oil-bodies. Oil synthesis was maximal between 2 and 3 days following nitrogen depletion and reached a plateau around day 5. In the first 48 hours of oil deposition, a ~80% reduction in the major plastidial membrane lipids occurred. Upon nitrogen re-supply, mobilization of TAGs started after starch degradation but was completed within 24 hours. Comparison of oil content in five common laboratory strains (CC124, CC125, cw15, CC1690 and 11-32A) revealed a high variability, from 2 μg TAG per million cell in CC124 to 11 μg in 11-32A. Quantification of TAGs on a cell basis in three mutants affected in starch synthesis (cw15sta1-2, cw15sta6 and cw15sta7-1) showed that blocking starch synthesis did not result in TAG over-accumulation compared to their direct progenitor, the arginine auxotroph strain 330. Moreover, no significant correlation was found between cellular oil and starch levels among the twenty wild-type, mutants and complemented strains tested. By contrast, cellular oil content was found to increase steeply with salt concentration in the growth medium. At 100 mM NaCl, oil level similar to nitrogen depletion conditions could be reached in CC124 strain. A reference basis for future genetic studies of oil metabolism in Chlamydomonas is provided. Results highlight the importance of using

  14. Accumulation of astaxanthin by a new Haematococcus pluvialis strain BM1 from the white sea coastal rocks (Russia).

    PubMed

    Chekanov, Konstantin; Lobakova, Elena; Selyakh, Irina; Semenova, Larisa; Sidorov, Roman; Solovchenko, Alexei

    2014-08-15

    We report on a novel arctic strain BM1 of a carotenogenic chlorophyte from a coastal habitat with harsh environmental conditions (wide variations in solar irradiance, temperature, salinity and nutrient availability) identified as Haematococcus pluvialis Flotow. Increased (25‰) salinity exerted no adverse effect on the growth of the green BM1 cells. Under stressful conditions (high light, nitrogen and phosphorus deprivation), green vegetative cells of H. pluvialis BM1 grown in BG11 medium formed non-motile palmelloid cells and, eventually, hematocysts capable of a massive accumulation of the keto-carotenoid astaxanthin with a high nutraceutical and therapeutic potential. Routinely, astaxanthin was accumulated at the level of 4% of the cell dry weight (DW), reaching, under prolonged stress, 5.5% DW. Astaxanthin was predominantly accumulated in the form of mono- and diesters of fatty acids from C16 and C18 families. The palmelloids and hematocysts were characterized by the formation of red-colored cytoplasmic lipid droplets, increasingly large in size and number. The lipid droplets tended to merge and occupied almost the entire volume of the cell at the advanced stages of stress-induced carotenogenesis. The potential application of the new strain for the production of astaxanthin is discussed in comparison with the H. pluvialis strains currently employed in microalgal biotechnology.

  15. Accumulation of Astaxanthin by a New Haematococcus pluvialis Strain BM1 from the White Sea Coastal Rocks (Russia)

    PubMed Central

    Chekanov, Konstantin; Lobakova, Elena; Selyakh, Irina; Semenova, Larisa; Sidorov, Roman; Solovchenko, Alexei

    2014-01-01

    We report on a novel arctic strain BM1 of a carotenogenic chlorophyte from a coastal habitat with harsh environmental conditions (wide variations in solar irradiance, temperature, salinity and nutrient availability) identified as Haematococcus pluvialis Flotow. Increased (25‰) salinity exerted no adverse effect on the growth of the green BM1 cells. Under stressful conditions (high light, nitrogen and phosphorus deprivation), green vegetative cells of H. pluvialis BM1 grown in BG11 medium formed non-motile palmelloid cells and, eventually, hematocysts capable of a massive accumulation of the keto-carotenoid astaxanthin with a high nutraceutical and therapeutic potential. Routinely, astaxanthin was accumulated at the level of 4% of the cell dry weight (DW), reaching, under prolonged stress, 5.5% DW. Astaxanthin was predominantly accumulated in the form of mono- and diesters of fatty acids from C16 and C18 families. The palmelloids and hematocysts were characterized by the formation of red-colored cytoplasmic lipid droplets, increasingly large in size and number. The lipid droplets tended to merge and occupied almost the entire volume of the cell at the advanced stages of stress-induced carotenogenesis. The potential application of the new strain for the production of astaxanthin is discussed in comparison with the H. pluvialis strains currently employed in microalgal biotechnology. PMID:25196836

  16. Synthesis and accumulation of aromatic aldehydes in an engineered strain of Escherichia coli.

    PubMed

    Kunjapur, Aditya M; Tarasova, Yekaterina; Prather, Kristala L J

    2014-08-20

    Aromatic aldehydes are useful in numerous applications, especially as flavors, fragrances, and pharmaceutical precursors. However, microbial synthesis of aldehydes is hindered by rapid, endogenous, and redundant conversion of aldehydes to their corresponding alcohols. We report the construction of an Escherichia coli K-12 MG1655 strain with reduced aromatic aldehyde reduction (RARE) that serves as a platform for aromatic aldehyde biosynthesis. Six genes with reported activity on the model substrate benzaldehyde were rationally targeted for deletion: three genes that encode aldo-keto reductases and three genes that encode alcohol dehydrogenases. Upon expression of a recombinant carboxylic acid reductase in the RARE strain and addition of benzoate during growth, benzaldehyde remained in the culture after 24 h, with less than 12% conversion of benzaldehyde to benzyl alcohol. Although individual overexpression results demonstrated that all six genes could contribute to benzaldehyde reduction in vivo, additional experiments featuring subset deletion strains revealed that two of the gene deletions were dispensable under the conditions tested. The engineered strain was next investigated for the production of vanillin from vanillate and succeeded in preventing formation of the byproduct vanillyl alcohol. A pathway for the biosynthesis of vanillin directly from glucose was introduced and resulted in a 55-fold improvement in vanillin titer when using the RARE strain versus the wild-type strain. Finally, synthesis of the chiral pharmaceutical intermediate L-phenylacetylcarbinol (L-PAC) was demonstrated from benzaldehyde and glucose upon expression of a recombinant mutant pyruvate decarboxylase in the RARE strain. Beyond allowing accumulation of aromatic aldehydes as end products in E. coli, the RARE strain expands the classes of chemicals that can be produced microbially via aldehyde intermediates.

  17. Strain of Escherichia coli with a temperature-sensitive mutation affecting ribosomal ribonucleic acid accumulation.

    PubMed Central

    Frey, T; Newlin, L L; Atherly, A G

    1975-01-01

    A mutant of Escherichia coli has been isolated that has a temperature-sensitive mutation that results in specific loss of ribosomal ribonucleic acid (RNA) synthesis and some reduction in messenger RNA synthesis. When the strain was grown in glucose medium at a restrictive temperature, RNA accumulation ceased, but both messenger RNA and protein synthesis continued for an extended time. Because carbon metabolism was slowed drastically when strain AA-157 was placed at the restrictive temperature, this phenotype can be compared with carbon depletion conditions present during diauxic lag. However, the phenotype of mutant AA-157 differs from shift-down conditions in that guanosine-3',5'-tetraphosphate levels are unaffected; therefore, a different site is affected. This mutant strain (AA-157) thus shows many characteristics similar to an aldolase mutant previously reported (Böck and Neidhardt, 1966). However, the mutation occurred in a different position on the E. coli genetic map, and furthermore, aldolase was not temperature sensitive in strain AA-157. In this paper we present a study of macromolecular biosynthesis in this mutant. PMID:1090609

  18. Interseismic Strain Accumulation Across Metropolitan Los Angeles: Puente Hills Thrust

    NASA Astrophysics Data System (ADS)

    Argus, D.; Liu, Z.; Heflin, M. B.; Moore, A. W.; Owen, S. E.; Lundgren, P.; Drake, V. G.; Rodriguez, I. I.

    2012-12-01

    Twelve years of observation of the Southern California Integrated GPS Network (SCIGN) are tightly constraining the distribution of shortening across metropolitan Los Angeles, providing information on strain accumulation across blind thrust faults. Synthetic Aperture Radar Interferometry (InSAR) and water well records are allowing the effects of water and oil management to be distinguished. The Mojave segment of the San Andreas fault is at a 25° angle to Pacific-North America plate motion. GPS shows that NNE-SSW shortening due to this big restraining bend is fastest not immediately south of the San Andreas fault across the San Gabriel mountains, but rather 50 km south of the fault in northern metropolitan Los Angeles. The GPS results we quote next are for a NNE profile through downtown Los Angeles. Just 2 mm/yr of shortening is being taken up across the San Gabriel mountains, 40 km wide (0.05 micro strain/yr); 4 mm/yr of shortening is being taken up between the Sierra Madre fault, at the southern front of the San Gabriel mountains, and South Central Los Angeles, also 40 km wide (0.10 micro strain/yr). We find shortening to be more evenly distributed across metropolitan Los Angeles than we found before [Argus et al. 2005], though within the 95% confidence limits. An elastic models of interseismic strain accumulation is fit to the GPS observations using the Back Slip model of Savage [1983]. Rheology differences between crystalline basement and sedimentary basin rocks are incorporated using the EDGRN/EDCMP algorithm of Wang et al. [2003]. We attempt to place the Back Slip model into the context of the Elastic Subducting Plate Model of Kanda and Simons [2010]. We find, along the NNE profile through downtown, that: (1) The deep Sierra Madre Thrust cannot be slipping faster than 2 mm/yr, and (2) The Puente Hills Thrust and nearby thrust faults (such as the upper Elysian Park Thrust) are slipping at 9 ±2 mm/yr beneath a locking depth of 12 ±5 km (95% confidence limits

  19. [Lorenz was right, or does aggressive energy accumulate?].

    PubMed

    Kudriavtseva, N N

    2004-06-01

    Evidence supporting the fact that inherited mechanisms of regulation of aggressive behavior as a result of a repeated experience of aggression ending in victories are transformed into pathological mechanisms based on accumulation of neurochemical shifts in the brain, enhancing aggressiveness, and forming aggressive motivation in aggressive winners. This confirms the concept by Lorenz on the existence of a mechanism (but not instinct) of a spontaneous accumulation of aggressive energy that needs a discharge and formation of permanent attraction to manifestation of aggression.

  20. Oil accumulation in the model green alga Chlamydomonas reinhardtii: characterization, variability between common laboratory strains and relationship with starch reserves

    PubMed Central

    2011-01-01

    Background When cultivated under stress conditions, many microalgae species accumulate both starch and oil (triacylglycerols). The model green microalga Chlamydomonas reinhardtii has recently emerged as a model to test genetic engineering or cultivation strategies aiming at increasing lipid yields for biodiesel production. Blocking starch synthesis has been suggested as a way to boost oil accumulation. Here, we characterize the triacylglycerol (TAG) accumulation process in Chlamydomonas and quantify TAGs in various wild-type and starchless strains. Results In response to nitrogen deficiency, Chlamydomonas reinhardtii produced TAGs enriched in palmitic, oleic and linoleic acids that accumulated in oil-bodies. Oil synthesis was maximal between 2 and 3 days following nitrogen depletion and reached a plateau around day 5. In the first 48 hours of oil deposition, a ~80% reduction in the major plastidial membrane lipids occurred. Upon nitrogen re-supply, mobilization of TAGs started after starch degradation but was completed within 24 hours. Comparison of oil content in five common laboratory strains (CC124, CC125, cw15, CC1690 and 11-32A) revealed a high variability, from 2 μg TAG per million cell in CC124 to 11 μg in 11-32A. Quantification of TAGs on a cell basis in three mutants affected in starch synthesis (cw15sta1-2, cw15sta6 and cw15sta7-1) showed that blocking starch synthesis did not result in TAG over-accumulation compared to their direct progenitor, the arginine auxotroph strain 330. Moreover, no significant correlation was found between cellular oil and starch levels among the twenty wild-type, mutants and complemented strains tested. By contrast, cellular oil content was found to increase steeply with salt concentration in the growth medium. At 100 mM NaCl, oil level similar to nitrogen depletion conditions could be reached in CC124 strain. Conclusion A reference basis for future genetic studies of oil metabolism in Chlamydomonas is provided. Results

  1. Strain Engineering to Modify the Electrochemistry of Energy Storage Electrodes

    PubMed Central

    Muralidharan, Nitin; Carter, Rachel; Oakes, Landon; Cohn, Adam P.; Pint, Cary L.

    2016-01-01

    Strain engineering has been a critical aspect of device design in semiconductor manufacturing for the past decade, but remains relatively unexplored for other applications, such as energy storage. Using mechanical strain as an input parameter to modulate electrochemical potentials of metal oxides opens new opportunities intersecting fields of electrochemistry and mechanics. Here we demonstrate that less than 0.1% strain on a Ni-Ti-O based metal-oxide formed on superelastic shape memory NiTi alloys leads to anodic and cathodic peak potential shifts by up to ~30 mV in an electrochemical cell. Moreover, using the superelastic properties of NiTi to enable strain recovery also recovers the electrochemical potential of the metal oxide, providing mechanistic evidence of strain-modified electrochemistry. These results indicate that mechanical energy can be coupled with electrochemical systems to efficiently design and optimize a new class of strain-modulated energy storage materials. PMID:27283872

  2. An Analysis of Strain Accumulation in the Western Part of Black Sea Region in Turkey

    NASA Astrophysics Data System (ADS)

    Deniz, I.; Avsar, N. B.; Deniz, R.; Mekik, C.; Kutoglu, S.

    2014-12-01

    Turkish National Horizontal Control Network (TNHCN) based on the European Datum 1950 (ED50) was used as the principal geodetic network until 2005 in Turkey. Since 2005, Turkish Large Scale Map and Map Information Production Regulation have required that that all the densification points have been produced within the same datum of Turkish National Fundamental GPS Network (TNFGN) put into practise in 2002 and based on International Terrestrial Reference Frame (ITRF). Hence, the common points were produced in both European Datum 1950 (ED50), and TNFGN.It is known that the geological and geophysical information about the network area can be obtained by the evaluation of the coordinate and scale variations in a geodetic network. For one such evaluation, the coordinate variations and velocities of network points, and also the strains are investigated. However, the principal problem in derivation of velocities arises from two different datums. In this context, the computation of velocities using the coordinate data of the ED50 and TNFGN is not accurate and reliable. Likewise, the analysis of strain from the coordinate differences is not reliable. However, due to the fact that the scale of a geodetic network is independent from datum, the strains can be derived from scale variations accurately and reliably.In this study, a test area limited 39.5°-42.0° northern latitudes and 31.0°-37.0° eastern longitudes was chosen. The benchmarks in this test area are composed of 30 geodetic control points derived with the aim of cadastral and engineering applications. We used data mining to investigate the common benchmarks in both reference systems for this area. Accordingly, the ED50 and TNFGN coordinates refer 1954 and 2005, respectively. Thus, it has been investigated the strain accumulation of 51 years in this region. It should be also noted that since 1954, the earthquakes have not registered greater than magnitude 6.0 in the test area. It is a considerable situation for this

  3. Estimating Strain Accumulation in the New Madrid and Wabash Valley Seismic Zones

    NASA Astrophysics Data System (ADS)

    Craig, T. J.; Calais, E.

    2014-12-01

    The mechanical behaviour -- and hence earthquake potential -- of faults in continental interiors is a question of critical importance for the resultant seismic hazard, but no consensus has yet been reached on this controversial topic. The debate has focused on the central and eastern United States, in particular the New Madrid Seismic Zone, struck by three magnitude 7 or greater earthquakes in 1811--1812, and to a lesser extent the Wabash Valley Seismic Zone just to the north. A key aspect of this issue is the rate at which strain is currently accruing on those faults in the plate interior, a quantity that remains debated. Understanding if the present-day strain rates indicate sufficient motion to account for the historical and paleoseismological earthquakes by steady-state fault behaviour, or if strain accumulation is time-dependent in this area, is critical for investigating the causative process driving this seismicity in the plate interior, and how regional strain reflects the interplay between stresses arising from different geological processes. Here we address this issue with an analysis of up to 14 years of continuous GPS data from a network of 200 sites in the central United States centred on the New Madrid and Wabash Valley seismic zones. We find that high-quality sites in these regions show motions that are consistently within the 95% confidence limit of zero deformation relative to a rigid background. These results place an upper bound on regional strain accrual of 0.2 mm/yr and 0.5 mm/yr in the New Madrid and Wabash Valley Seismic Zones, respectively. These results, together with increasing evidence for temporal clustering and spatial migration of earthquake sequences in continental interiors, indicate that either tectonic loading rates or fault properties vary with time in the NMSZ and possibly plate-wide.

  4. Increased accumulation of polyhydroxybutyrate in divergent cyanobacteria under nutrient-deprived photoautotrophy: An efficient conversion of solar energy and carbon dioxide to polyhydroxybutyrate by Calothrix scytonemicola TISTR 8095.

    PubMed

    Kaewbai-Ngam, Auratai; Incharoensakdi, Aran; Monshupanee, Tanakarn

    2016-07-01

    The cellular PHB content was determined in 137 strains of cyanobacteria representing 88 species in 26 genera under six photoautotrophic nutrient conditions. One hundred and thirty-four strains were PHB producers. The PHB contents of these 134 strains were subtle under normal growth condition, but were significantly increased in 63 strains under nitrogen deprivation (-N), a higher frequency than with phosphate and/or potassium and all-nutrient deprivation. A high PHB accumulation was not associated with any particular evolutionary groups, but was strain specific. The filamentous Calothrix scytonemicola TISTR 8095 produced 356.5±63.4mg/L PHB under -N from a biomass of 1396.6±66.1mg/L, giving a PHB content of 25.4±3.5% (w/w dry weight). This PHB productivity is equivalent to the CO2 consumption of 729.2±129.8mg/L. The maximum energy conversion from solar energy to PHB obtained by C. scytonemicola TISTR 8095 was 1.42±0.30%. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. The strain capacitor: A novel energy storage device

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

    Deb Shuvra, Pranoy; McNamara, Shamus, E-mail: shamus.mcnamara@louisville.edu

    2014-12-15

    A novel electromechanical energy storage device is reported that has the potential to have high energy densities. It can efficiently store both mechanical strain energy and electrical energy in the form of an electric field between the electrodes of a strain-mismatched bilayer capacitor. When the charged device is discharged, both the electrical and mechanical energy are extracted in an electrical form. The charge-voltage profile of the device is suitable for energy storage applications since a larger portion of the stored energy can be extracted at higher voltage levels compared to a normal capacitor. Its unique features include the potential formore » long lifetime, safety, portability, wide operating temperature range, and environment friendliness. The device can be designed to operate over varied operating voltage ranges by selecting appropriate materials and by changing the dimensions of the device. In this paper a finite element model of the device is developed to verify and demonstrate the potential of the device as an energy storage element. This device has the potential to replace conventional energy storage devices.« less

  6. Growth and lipid accumulation in three Chlorella strains from different regions in response to diurnal temperature fluctuations.

    PubMed

    Yang, Weinan; Zou, Shanmei; He, Meilin; Fei, Cong; Luo, Wei; Zheng, Shiyan; Chen, Bo; Wang, Changhai

    2016-02-01

    It was economically feasible to screen strains adaptive to wide temperature fluctuation for outdoor cultivation without temperature control. In this research, three Chlorella strains from arctic glacier, desert soil and temperate native lake were isolated and identified. The growth, biochemical composition, lipid content and fatty acid composition of each strain cultured under the mode of diurnal temperature fluctuations were compared. All the three Chlorella strains showed desirable abilities of accumulating lipid under diurnal temperature fluctuations and their fatty acid profiles were suitable for biodiesel production, although the growth and biochemical composition were seemed to be region-specific. The highest lipid content was at 51.83±2.49% DW, 42.80±2.97% DW and 36.13±2.27% DW under different temperature fluctuation of 11 °C, 25 °C, 7 °C, respectively. The results indicated that the three Chlorella strains could be promising biodiesel feedstock for outdoor cultivation by the cultural mode of diurnal temperature fluctuations. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Fluorescence resonance energy transfer sensors for quantitative monitoring of pentose and disaccharide accumulation in bacteria

    PubMed Central

    Kaper, Thijs; Lager, Ida; Looger, Loren L; Chermak, Diane; Frommer, Wolf B

    2008-01-01

    Background Engineering microorganisms to improve metabolite flux requires detailed knowledge of the concentrations and flux rates of metabolites and metabolic intermediates in vivo. Fluorescence resonance energy transfer sensors represent a promising technology for measuring metabolite levels and corresponding rate changes in live cells. These sensors have been applied successfully in mammalian and plant cells but potentially could also be used to monitor steady-state levels of metabolites in microorganisms using fluorimetric assays. Sensors for hexose and pentose carbohydrates could help in the development of fermentative microorganisms, for example, for biofuels applications. Arabinose is one of the carbohydrates to be monitored during biofuels production from lignocellulose, while maltose is an important degradation product of starch that is relevant for starch-derived biofuels production. Results An Escherichia coli expression vector compatible with phage λ recombination technology was constructed to facilitate sensor construction and was used to generate a novel fluorescence resonance energy transfer sensor for arabinose. In parallel, a strategy for improving the sensor signal was applied to construct an improved maltose sensor. Both sensors were expressed in the cytosol of E. coli and sugar accumulation was monitored using a simple fluorimetric assay of E. coli cultures in microtiter plates. In the case of both nanosensors, the addition of the respective ligand led to concentration-dependent fluorescence resonance energy transfer responses allowing quantitative analysis of the intracellular sugar levels at given extracellular supply levels as well as accumulation rates. Conclusion The nanosensor destination vector combined with the optimization strategy for sensor responses should help to accelerate the development of metabolite sensors. The new carbohydrate fluorescence resonance energy transfer sensors can be used for in vivo monitoring of sugar levels in

  8. A physical model for strain accumulation in the San Francisco Bay Region

    USGS Publications Warehouse

    Pollitz, F.F.; Nyst, M.

    2005-01-01

    Strain accumulation in tectonically active regions is generally a superposition of the effects of background tectonic loading, steady-state dislocation processes, such as creep, and transient deformation. In the San Francisco Bay region (SFBR), the most uncertain of these processes is transient deformation, which arises primarily in association with large earthquakes. As such, it depends upon the history of faulting and the rheology of the crust and mantle, which together determine the pattern of longer term (decade-scale) post-seismic response to earthquakes. We utilize a set of 102 GPS velocity vectors in the SFBR in order to characterize the strain rate field and construct a physical model of its present deformation. We first perform an inversion for the continuous velocity gradient field from the discrete GPS velocity field, from which both tensor strain rate and rotation rate may be extracted. The present strain rate pattern is well described as a nearly uniform shear strain rate oriented approximately N34??W (140 nanostrain yr-1) plus a N56??E uniaxial compression rate averaging 20 nanostrain yr-1 across the shear zone. We fit the velocity and strain rate fields to a model of time-dependent deformation within a 135-kin-wide, arcuate shear zone bounded by strong Pacific Plate and Sierra Nevada block lithosphere to the SW and NE, respectively. Driving forces are purely lateral, consisting of shear zone deformation imposed by the relative motions between the thick Pacific Plate and Sierra Nevada block lithospheres. Assuming a depth-dependent viscoelastic structure within the shear zone, we account for the effects of steady creep on faults and viscoelastic relaxation following the 1906 San Francisco and 1989 Loma Prieta earthquakes, subject to constant velocity boundary conditions on the edges of the shear zone. Fault creep is realized by evaluating dislocations on the creeping portions of faults in the fluid limit of the viscoelastic model. A priori plate

  9. The accumulation of femtosecond laser radiation energy in crystals of lithium fluoride

    NASA Astrophysics Data System (ADS)

    Dresvyanskiy, V. P.; Glazunov, D. S.; Alekseev, S. V.; Losev, V. F.; Chadraa, B.; Bukhtsooj, O.; Baasankhuu, N.; Zandan, B.; Martynovich, E. F.

    2015-12-01

    We present the results of studies of energy accumulation during the non-destructive interaction of extremely intense near infrared laser radiation with model wide band gap dielectric crystals of lithium fluoride, when the intensity of pulses is sufficient for effective highly nonlinear absorption of light and for the excitation of the electron subsystem of matter and the energy of pulses is still not sufficient for significant heating, evaporation, laser breakdown or other destruction to occur. We studied the emission of energy in the form of light sum of thermally stimulated luminescence accumulated under conditions of self-focusing and multiple filamentation of femtosecond laser radiation. It was established that it's the F2 and F3+ color centers and supplementary to them centers of interstitial type which accumulate energy under the action of a single femtosecond laser pulses. When irradiated by series of pulses the F3, F3- and F4 centers additionally appear. F2 centers are the main centers of emission in the process of thermally stimulated luminescence of accumulated energy. The interstitial fluoride ions (I-centers) are the kinetic particles. They split off from the X3- centers in the result of thermal decomposition of latter on the I-centers and molecules X20. I-centers recombine with F3+ centers and form F2 centers in excited state. The latter produce the characteristic emission spectrum emitted in the form of thermally stimulated luminescence.

  10. Energy scavenging strain absorber: application to kinetic dielectric elastomer generator

    NASA Astrophysics Data System (ADS)

    Jean-Mistral, C.; Beaune, M.; Vu-Cong, T.; Sylvestre, A.

    2014-03-01

    Dielectric elastomer generators (DEGs) are light, compliant, silent energy scavengers. They can easily be incorporated into clothing where they could scavenge energy from the human kinetic movements for biomedical applications. Nevertheless, scavengers based on dielectric elastomers are soft electrostatic generators requiring a high voltage source to polarize them and high external strain, which constitutes the two major disadvantages of these transducers. We propose here a complete structure made up of a strain absorber, a DEG and a simple electronic power circuit. This new structure looks like a patch, can be attached on human's wear and located on the chest, knee, elbow… Our original strain absorber, inspired from a sailing boat winch, is able to heighten the external available strain with a minimal factor of 2. The DEG is made of silicone Danfoss Polypower and it has a total area of 6cm per 2.5cm sustaining a maximal strain of 50% at 1Hz. A complete electromechanical analytical model was developed for the DEG associated to this strain absorber. With a poling voltage of 800V, a scavenged energy of 0.57mJ per cycle is achieved with our complete structure. The performance of the DEG can further be improved by enhancing the imposed strain, by designing a stack structure, by using a dielectric elastomer with high dielectric permittivity.

  11. Analysis of energy states where electrons and holes coexist in pseudomorphically strained InAs high-electron-mobility transistors

    NASA Astrophysics Data System (ADS)

    Nishio, Yui; Sato, Takato; Hirayama, Naomi; Iida, Tsutomu; Takanashi, Yoshifumi

    2016-04-01

    In strained high-electron-mobility transistors (HEMTs) with InAs as the channel, excess electrons and holes are generated in the drain region by impact ionization. In the source region, electrons are injected to recombine with accumulated holes by the Auger process. This causes the shift of the gate potential, V GS,shift, for HEMTs. For a system where electrons and holes coexist, we established a theory taking into account the nonparabolicity of the conduction band in the InAs channel. This theory enables us to rigorously determine not only the energy states and the concentration profiles for both carriers but also the V GS,shift due to an accumulation of holes. We have derived the Auger recombination theory which takes into account the Fermi-Dirac statistics and is applicable to an arbitrary shape of potential energy. The Auger recombination lifetime τA for InAs-PHEMTs was estimated as a function of the sheet hole concentration, p s, and τA was on the order of psec for p s exceeding 1012 cm-2.

  12. Formation Energies of Native Point Defects in Strained-Layer Superlattices (Postprint)

    DTIC Science & Technology

    2017-06-05

    AFRL-RX-WP-JA-2017-0217 FORMATION ENERGIES OF NATIVE POINT DEFECTS IN STRAINED-LAYER SUPERLATTICES (POSTPRINT) Zhi-Gang Yu...2016 Interim 11 September 2013 – 5 November 2016 4. TITLE AND SUBTITLE FORMATION ENERGIES OF NATIVE POINT DEFECTS IN STRAINED-LAYER SUPERLATTICES...native point defect (NPD) formation energies and absence of mid-gap levels. In this Letter we use first-principles calculations to study the formation

  13. Generation of lycopene-overproducing strains of the fungus Mucor circinelloides reveals important aspects of lycopene formation and accumulation.

    PubMed

    Zhang, Yingtong; Chen, Haiqin; Navarro, Eusebio; López-García, Sergio; Chen, Yong Q; Zhang, Hao; Chen, Wei; Garre, Victoriano

    2017-03-01

    To generate lycopene-overproducing strains of the fungus Mucor circinelloides with interest for industrial production and to gain insight into the catalytic mechanism of lycopene cyclase and regulatory process during lycopene overaccumulation. Three lycopene-overproducing mutants were generated by classic mutagenesis techniques from a β-carotene-overproducing strain. They carried distinct mutations in the carRP gene encoding lycopene cyclase that produced loss of enzymatic activity to different extents. In one mutant (MU616), the lycopene cyclase was completely destroyed, and a 43.8% (1.1 mg/g dry mass) increase in lycopene production was observed in comparison to that by the previously existing lycopene overproducer. In addition, feedback regulation of the end product was suggested in lycopene-overproducing strains. A lycopene-overaccumulating strain of the fungus M. circinelloides was generated that could be an alternative for the industrial production of lycopene. Vital catalytic residues for lycopene cyclase activity and the potential mechanism of lycopene formation and accumulation were identified.

  14. Accumulator for Low-Energy Laser-Cooled Particles

    NASA Astrophysics Data System (ADS)

    Mertes, Kevin; Walstrom, Peter; di Rosa, Michael; LANL Collaboration

    2017-04-01

    An accumulator builds phase-space density by use of a non-Hamiltonian process, thereby circumventing Liouville's theorem, which states that phase-space density is preserved in processes governed by Hamilton's equations. We have built an accumulator by a simple magneto-static cusp trap formed from two ring shaped permanent magnets. In traps with a central minimum of | B | , the stored particles are in a field-repelled (FR) Zeeman state, pushed away by | B | and oscillating about its minimum. After laser-cooling our particles and before entering the trap, we employ the non-hamiltonian process of optical pumping: A FR particle approaches the trap and climbs to the top of the confining potential with a finite velocity. There, it is switched to a field seeking (FS) state. As the switch does not change the velocity, the particle proceeds into the trap but continues to lose momentum because, now in the FS state, the particles sees the decreasing field as a potential hill to climb. Before it comes to a halt, the particle is switched back to a FR state for storage. The process repeats, building the trapped number and density. A simple consideration of potential and kinetic energies would show the trapped particles to have less kinetic energy than those injected. Los Alamos National Laboratory's Office of Laboratory Directed Research and Development.

  15. Formation Energies of Native Point Defects in Strained layer Superlattices (Postprint)

    DTIC Science & Technology

    2017-06-05

    AFRL-RX-WP-JA-2017-0440 FORMATION ENERGIES OF NATIVE POINT DEFECTS IN STRAINED-LAYER SUPERLATTICES (POSTPRINT) Zhi Gang Yu...2017 Interim 11 September 2013 – 31 May 2017 4. TITLE AND SUBTITLE FORMATION ENERGIES OF NATIVE POINT DEFECTS IN STRAINED-LAYER SUPERLATTICES...Hamiltonian, tight-binding Hamiltonian, and Green’s function techniques to obtain energy levels arising from native point defects (NPDs) in InAs-GaSb and

  16. Tuning the Energy Gap of SiCH3 Nanomaterials Under Elastic Strain

    NASA Astrophysics Data System (ADS)

    Ma, Shengqian; Li, Feng; Geng, Jiguo; Zhu, Mei; Li, Suyan; Han, Juguang

    2018-05-01

    SiCH3 nanomaterials have been studied using the density functional theory. When the nanosheets and nanoribbons (armchair and zigzag) are introduced, their energy gap is modulated under elastic strain and width. The results show that the band gap of SiCH3 nanomaterials can be easily tuned using elastic strains and widths. Surprisingly, the band gap can be modulated along two directions, namely, compressing and stretching. The band gap decreases when increasing stretching strain or decreasing compressing strain. In addition, the band gap decreases when increasing the nanoribbon width. For energy gap engineering, the band gap can be tuned by strains and widths. Therefore, the SiCH3 nanomaterials play important roles in potential applications for strain sensors, electronics, and optical electronics.

  17. Strain controlled ferromagnetic-ferrimagnetic transition and vacancy formation energy of defective graphene.

    PubMed

    Zhang, Yajun; Sahoo, Mpk; Wang, Jie

    2016-09-23

    Single vacancy (SV)-induced magnetism in graphene has attracted much attention motivated by its potential in achieving new functionalities. However, a much higher vacancy formation energy limits its direct application in electronic devices and the dependency of spin interaction on the strain is unclear. Here, through first-principles density-functional theory calculations, we investigate the possibility of strain engineering towards lowering vacancy formation energy and inducing new magnetic states in defective graphene. It is found that the SV-graphene undergoes a phase transition from an initial ferromagnetic state to a ferrimagnetic state under a biaxial tensile strain. At the same time, the biaxial tensile strain significantly lowers the vacancy formation energy. The charge density, density of states and band theory successfully identify the origin and underlying physics of the transition. The predicted magnetic phase transition is attributed to the strain driven spin flipping at the C-atoms nearest to the SV-site. The magnetic semiconducting graphene induced by defect and strain engineering suggests an effective way to modulate both spin and electronic degrees of freedom in future spintronic devices.

  18. Identification of oleaginous yeast strains able to accumulate high intracellular lipids when cultivated in alkaline pretreated corn stover

    PubMed Central

    Sitepu, Irnayuli R.; Jin, Mingjie; Fernandez, J. Enrique; da Costa Sousa, Leonardo; Balan, Venkatesh; Boundy-Mills, Kyria L.

    2015-01-01

    Microbial oil is a potential alternative to food/plant-derived biodiesel fuel. Our previous screening studies identified a wide range of oleaginous yeast species, using a defined laboratory medium known to stimulate lipid accumulation. In this study, the ability of these yeasts to grow and accumulate lipids was further investigated in synthetic hydrolysate (SynH) and authentic ammonia fiber expansion (AFEX™)-pretreated corn stover hydrolysate (ACSH). Most yeast strains tested were able to accumulate lipids in SynH, but only a few were able to grow and accumulate lipids in ACSH medium. Cryptococcus humicola UCDFST 10-1004 was able to accumulate as high as 15.5 g/L lipids, out of a total of 36 g/L cellular biomass when grown in ACSH, with a cellular lipid content of 40% of cell dry weight. This lipid production is among the highest reported values for oleaginous yeasts grown in authentic hydrolysate. Pre-culturing in SynH media with xylose as sole carbon source enabled yeasts to assimilate both glucose and xylose more efficiently in the subsequent hydrolysate medium. This study demonstrates that ACSH is a suitable medium for certain oleaginous yeasts to convert lignocellullosic sugars to triacylglycerols for production of biodiesel and other valuable oleochemicals. PMID:25052467

  19. Accumulation of 10 Fluoroquinolones by Wild-Type or Efflux Mutant Streptococcus pneumoniae

    PubMed Central

    Piddock, Laura J. V.; Johnson, M. M.

    2002-01-01

    A method for measuring fluoroquinolone accumulation by Streptococcus pneumoniae was rigorously examined. The accumulation of ciprofloxacin, clinafloxacin, gatifloxacin, grepafloxacin, levofloxacin, moxifloxacin, norfloxacin, ofloxacin, sitafloxacin, and trovafloxacin in the presence and absence of either carbonyl cyanide m-chlorophenyl-hydrazone (CCCP) or reserpine was determined for two wild-type fluoroquinolone-susceptible capsulated S. pneumoniae strains (M3 and M4) and the noncapsulated strain R6. Two efflux mutants, R6N (which overexpresses PmrA) and a mutant of M4, M22 (no expression of PmrA), were also examined. Essentially, the fluoroquinolones fell into two groups. (i) One group consisting of ciprofloxacin, grepafloxacin, and norfloxacin accumulated to 72 to 92 ng/mg (dry weight) of cells in all strains. (ii) The remainder of the agents accumulated to 3 to 30 ng/mg (dry weight) of cells. With a decrease in hydrophobicity, there was a decrease in the concentration accumulated. With an increase in the molecular weight of the free form of each agent, there was also a decrease in the concentration accumulated. The strains differed in their responses to reserpine and CCCP. For the three fluoroquinolone-susceptible strains, only reserpine had a significant effect upon accumulation of moxifloxacin and clinafloxacin by M3 and showed no effect for the other agents and strains. For M3 and M4, CCCP enhanced the concentration of ciprofloxacin and norfloxacin accumulated, whereas for R6, the effect was only statistically significant for ofloxacin. Efflux mutant M22 accumulated less ciprofloxacin, gatifloxacin, and ofloxacin than M4 did. M22 accumulated more norfloxacin than M4 did. Reserpine and CCCP had variable effects as for the other strains. Differences in the accumulation of fluoroquinolones by R6 and R6N were highly dependent upon growth phase, and only for norfloxacin was there a significant difference between two strains. PMID:11850266

  20. Genetically based population divergence in overwintering energy mobilization in brook charr (Salvelinus fontinalis).

    PubMed

    Crespel, Amélie; Bernatchez, Louis; Garant, Dany; Audet, Céline

    2013-03-01

    Investigating the nature of physiological traits potentially related to fitness is important towards a better understanding of how species and/or populations may respond to selective pressures imposed by contrasting environments. In northern species in particular, the ability to mobilize energy reserves to compensate for the low external energy intake during winter is crucial. However, the phenotypic and genetic bases of energy reserve accumulation and mobilization have rarely been investigated, especially pertaining to variation in strategy adopted by different populations. In the present study, we documented variation in several energy reserve variables and estimated their quantitative genetic basis to test the null hypothesis of no difference in variation at those traits among three strains of brook charr (Salvelinus fontinalis) and their reciprocal hybrids. Our results indicate that the strategy of winter energy preparation and mobilization was specific to each strain, whereby (1) domestic fish accumulated a higher amount of energy reserves before winter and kept accumulating liver glycogen during winter despite lower feeding; (2) Laval fish used liver glycogen and lipids during winter and experienced a significant decrease in condition factor; (3) Rupert fish had relatively little energy reserves accumulated at the end of fall and preferentially mobilized visceral fat during winter. Significant heritability for traits related to the accumulation and use of energy reserves was found in the domestic and Laval but not in the Rupert strain. Genetic and phenotypic correlations also varied among strains, which suggested population-specific genetic architecture underlying the expression of these traits. Hybrids showed limited evidence of non-additive effects. Overall, this study provides the first evidence of a genetically based-and likely adaptive-population-specific strategy for energy mobilization related to overwinter survival.

  1. Crustal strain accumulation on Southern Basin and Range Province faults modulated by distant plate boundary earthquakes? Evidence from geodesy, seismic imaging, and paleoseismology

    NASA Astrophysics Data System (ADS)

    Bennett, R. A.; Shirzaei, M.; Broermann, J.; Spinler, J. C.; Holland, A. A.; Pearthree, P.

    2014-12-01

    GPS in Arizona reveals a change in the pattern of crustal strain accumulation in 2010 and based on viscoelastic modeling appears to be associated with the distant M7.2 El Mayor-Cucapah (EMC) earthquake in Baja California, Mexico. GPS data collected between 1999 and 2009 near the Santa Rita normal fault in SE Arizona reveal a narrow zone of crustal deformation coincident with the fault trace, delineated by W-NW facing Pleistocene fault scarps of heights 1 to 7 m. The apparent deformation zone is also seen in a preliminary InSAR interferogram. Total motion across the zone inferred using an elastic block model constrained by the pre-2010 GPS measurements is ~1 mm/yr in a sense consistent with normal fault motion. However, continuous GPS measurements throughout Arizona reveal pronounced changes in crustal velocity following the EMC earthquake, such that the relative motion across the Santa Rita fault post-2010 is negligible. Paleoseismic evidence indicates that mapped Santa Rita fault scarps were formed by two or more large magnitude (M6.7 to M7.6) surface rupturing normal-faulting earthquakes 60 to 100 kyrs ago. Seismic refraction and reflection data constrained by deep (~800 m) well log data provide evidence of progressive, possibly intermittent, displacement on the fault through time. The rate of strain accumulation observed geodetically prior to 2010, if constant over the past 60 to 100 kyrs, would imply an untenable minimum slip rate deficit of 60 to 100 m since the most recent earthquake. One explanation for the available geodetic, seismic, and paleoseismic evidence is that strain accumulation is modulated by viscoelastic relaxation associated with frequent large magnitude earthquakes in the Salton Trough region, episodically inhibiting the accumulation of elastic strain required to generate large earthquakes on the Santa Rita and possibly other faults in the Southern Basin and Range. An important question is thus for how long the postseismic velocity changes

  2. Residual thermal and moisture influences on the strain energy release rate analysis of edge delamination

    NASA Technical Reports Server (NTRS)

    Obrien, T. K.; Raju, I. S.; Garber, D. P.

    1985-01-01

    A laminated plate theory analysis is developed to calculate the strain energy release rate associated with edge delamination growth in a composite laminate. The analysis includes the contribution of residual thermal and moisture stresses to the strain energy released. The strain energy release rate, G, increased when residual thermal effects were combined with applied mechanical strains, but then decreased when increasing moisture content was included. A quasi-three-dimensional finite element analysis indicated identical trends and demonstrated these same trends for the individual strain energy release rate components, G sub I and G sub II, associated with interlaminar tension and shear. An experimental study indicated that for T300/5208 graphite-epoxy composites, the inclusion of residual thermal and moisture stresses did not significantly alter the calculation of interlaminar fracture toughness from strain energy release rate analysis of edge delamination data taken at room temperature, ambient conditions.

  3. Using strain rates to forecast seismic hazards

    USGS Publications Warehouse

    Evans, Eileen

    2017-01-01

    One essential component in forecasting seismic hazards is observing the gradual accumulation of tectonic strain accumulation along faults before this strain is suddenly released as earthquakes. Typically, seismic hazard models are based on geologic estimates of slip rates along faults and historical records of seismic activity, neither of which records actively accumulating strain. But this strain can be estimated by geodesy: the precise measurement of tiny position changes of Earth’s surface, obtained from GPS, interferometric synthetic aperture radar (InSAR), or a variety of other instruments.

  4. Satellite Monitoring of Accumulation of Strain in the Earth's Crust Related to Seismic and Volcanic Activity

    NASA Astrophysics Data System (ADS)

    Arellano-Baeza, A. A.

    2009-12-01

    Our studies have shown that the strain energy accumulation deep in the Earth’s crust that precedes seismic and volcanic activity can be detected by applying a lineament extraction technique to the high-resolution multispectral satellite images. A lineament is a straight or a somewhat curved feature in a satellite image, which it is possible to detect by a special processing of images based on directional filtering and or Hough transform. We analyzed tens of earthquakes occurred in the Pacific coast of the South America with the magnitude > 4 Mw, using ASTER/TERRA multispectral satellite images for detection and analysis of changes in the system of lineaments previous to a strong earthquake. All events were located in the regions with small seasonal variations and limited vegetation to facilitate the tracking of features associated with the seismic activity only. It was found that the number and orientation of lineaments changed significantly about one month before an earthquake approximately, and a few months later the system returns to its initial state. This effect increases with the earthquake magnitude. It also was shown that the behavior of lineaments associated to the volcano seismic activity is opposite to that obtained previously for earthquakes. This discrepancy can be explained assuming that in the last case the main reason of earthquakes is compression and accumulation of strength in the Earth’s crust due to subduction of tectonic plates, whereas in the first case we deal with the inflation of a volcano edifice due to elevation of pressure and magma intrusion. The results obtained made it possible to include this research as a part of scientific program of Chilean Remote Sensing Satellite mission to be launched in 2010.

  5. Isolation and identification of poly beta hydroxybutyric acid accumulating bacteria of Staphylococcal sp. and characterization of biodegradable polyester.

    PubMed

    Roy, Bappaditya; Banerjee, Rajat; Chatterjee, Sumana

    2009-04-01

    Staphylococcus sp. strain BP/SU1, capable of degrading the biopolymer and utilize it as a source of carbon and energy, was isolated from activated sludge using METABOLIX (MBX D411G). It was found that this strain was capable of accumulating poly(3-hydroxybutyric acid) P(3-HB), as granule poly (3-hydroxybutyric acid), p(3-HB), inclusion bodies when grown under suitable nutrient conditions. These strains could sustain cell growth up to a dry mass of 9.24 g/l with a doubling time of 8 to 10 hr and could accumulate P(3-HB) as granular inclusion bodies to a cell dry weight of more than 12%. P(3-HB) accumulated by this organism was isolated and characterized through NMR, FT-IR spectroscopy, UV Spectroscopy, Mass spectroscopy and Differential Scanning Calorimetry. P(3-HB) granules so isolated showed physical and chemical properties that should be possessed by a superior quality thermoplastic biopolymer.

  6. EFFECT OF STRAIN FIELD ON THRESHOLD DISPLACEMENT ENERGY OF TUNGSTEN STUDIED BY MOLECULAR DYNAMICS SIMULATION

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

    Wang, D.; Gao, Ning; Setyawan, Wahyu

    The influence of hydrostatic strain on point defect formation energy and threshold displacement energy (Ed) in body-centered cubic (BCC) tungsten was studied with molecular dynamics simulations. Two different tungsten potentials (Fikar and Juslin) were used. The minimum Ed direction calculated with the Fikar-potential was <100>, but with the Juslin-potential it was <111>. The most stable self-interstitial (SIA) configuration was a <111>-crowdion for both potentials. The stable SIA configuration did not change with applied strain. Varying the strain from compression to tension increased the vacancy formation energy but decreased the SIA formation energy. The SIA formation energy changed more significantly thanmore » for a vacancy such that Ed decreased with applied strain from compression to tension.« less

  7. Strain Rate Dependency of Fracture Toughness, Energy Release Rate and Geomechanical Attributes of Select Indian Shales

    NASA Astrophysics Data System (ADS)

    Mahanta, B.; Vishal, V.; Singh, T. N.; Ranjith, P.

    2016-12-01

    In addition to modern improved technology, it requires detailed understanding of rock fractures for the purpose of enhanced energy extraction through hydraulic fracturing of gas shales and geothermal energy systems. The understanding of rock fracture behavior, patterns and properties such as fracture toughness; energy release rate; strength and deformation attributes during fracturing hold significance. Environmental factors like temperature, pressure, humidity, water vapor and experimental condition such as strain rate influence the estimation of these properties. In this study, the effects of strain rates on fracture toughness, energy release rate as well as geomechanical properties like uniaxial compressive strength, Young's modulus, failure strain, tensile strength, and brittleness index of gas shales were investigated. In addition to the rock-mechanical parameters, the fracture toughness and the energy release rates were measured for three different modes viz. mode I, mixed mode (I-II) and mode II. Petrographic and X-ray diffraction (XRD) analyses were performed to identify the mineral composition of the shale samples. Scanning electron microscope (SEM) analyses were conducted to have an insight about the strain rate effects on micro-structure of the rock. The results suggest that the fracture toughness; the energy release rate as well as other geomechanical properties are a function of strain rates. At high strain rates, the strength and stiffness of shale increases which in turn increases the fracture toughness and the energy release rate of shale that may be due to stress redistribution during grain fracturing. The fracture toughness and the strain energy release rates for all the modes (I/I-II/II) are comparable at lower strain rates, but they vary considerably at higher strain rates. In all the cases, mode I and mode II fracturing requires minimum and maximum applied energy, respectively. Mode I energy release rate is maximum, compared to the other modes.

  8. Metabolic engineering of sugarcane to accumulate energy-dense triacylglycerols in vegetative biomass

    DOE PAGES

    Zale, Janice; Jung, Je Hyeong; Kim, Jae Yoon; ...

    2015-06-08

    Elevating the lipid content in vegetative tissues has emerged as a new strategy for increasing energy density and biofuel yield of crops. Storage lipids in contrast to structural and signaling lipids are mainly composed of glycerol esters of fatty acids, also known as triacylglycerol (TAG). TAGs are one of the most energy-rich and abundant forms of reduced carbon available in nature. Therefore, altering the carbon-partitioning balance in favour of TAG in vegetative tissues of sugarcane, one of the highest yielding biomass crops, is expected to drastically increase energy yields. We report metabolic engineering to elevate TAG accumulation in vegetative tissuesmore » of sugarcane. Constitutive co-expression of WRINKLED1 (WRI1), diacylglycerol acyltransferase1-2 (DGAT1-2) and oleosin1 (OLE1) and simultaneous cosuppression of ADP-glucose pyrophosphorylase (AGPase) and a subunit of the peroxisomal ABC transporter1 (PXA1) in transgenic sugarcane elevated TAG accumulation in leaves or stems by 95- or 43-fold to 1.9% or 0.9% of dry weight (DW), respectively, while expression or suppression of one to three of the target genes increased TAG levels by 1.5- to 9.5-fold. Accumulation of TAG in vegetative progeny plants was consistent with the results from primary transgenics and contributed to a total fatty acid content of up to 4.7% or 1.7% of DW in mature leaves or stems, respectively. We saw lipid droplets in mesophyll cells of transgenic leaves by confocal fluorescence microscopy. These results provide the basis for optimizations of TAG accumulation in sugarcane and other high yielding biomass grasses and will open new prospects for biofuel applications.« less

  9. Functional photosystem I maintains proper energy balance during nitrogen depletion in Chlamydomonas reinhardtii, promoting triacylglycerol accumulation

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

    Gargouri, Mahmoud; Bates, Philip D.; Park, Jeong-Jin

    dynamically regulated by alterations in PSI function, which concomitantly alters the immediate ATP/NADPH demand. This occurs even without removal of nitrogen from the medium, but sufficient external carbon must nevertheless be available. Our efforts to increase lipid accumulation in algae such as Chlamydomonas need to consider carefully how the energy balance of the cell is involved in or affected by such efforts and that numerous layers of metabolic and genetic regulatory control are likely to interfere with such efforts to control oil biosynthesis. Such knowledge will enable synthetic biology approaches to alter the response to the N depletion stress, leading to rewiring of the regulatory networks so that lipid accumulation could be turned on in the absence of N deprivation, allowing for the development of algal production strains with highly enhanced lipid accumulation profiles.« less

  10. Functional photosystem I maintains proper energy balance during nitrogen depletion in Chlamydomonas reinhardtii, promoting triacylglycerol accumulation

    DOE PAGES

    Gargouri, Mahmoud; Bates, Philip D.; Park, Jeong-Jin; ...

    2017-04-13

    dynamically regulated by alterations in PSI function, which concomitantly alters the immediate ATP/NADPH demand. This occurs even without removal of nitrogen from the medium, but sufficient external carbon must nevertheless be available. Our efforts to increase lipid accumulation in algae such as Chlamydomonas need to consider carefully how the energy balance of the cell is involved in or affected by such efforts and that numerous layers of metabolic and genetic regulatory control are likely to interfere with such efforts to control oil biosynthesis. Such knowledge will enable synthetic biology approaches to alter the response to the N depletion stress, leading to rewiring of the regulatory networks so that lipid accumulation could be turned on in the absence of N deprivation, allowing for the development of algal production strains with highly enhanced lipid accumulation profiles.« less

  11. Increased ethanol accumulation from glucose via reduction of ATP level in a recombinant strain of Saccharomyces cerevisiae overexpressing alkaline phosphatase.

    PubMed

    Semkiv, Marta V; Dmytruk, Kostyantyn V; Abbas, Charles A; Sibirny, Andriy A

    2014-05-15

    The production of ethyl alcohol by fermentation represents the largest scale application of Saccharomyces cerevisiae in industrial biotechnology. Increased worldwide demand for fuel bioethanol is anticipated over the next decade and will exceed 200 billion liters from further expansions. Our working hypothesis was that the drop in ATP level in S. cerevisiae cells during alcoholic fermentation should lead to an increase in ethanol production (yield and productivity) with a greater amount of the utilized glucose converted to ethanol. Our approach to achieve this goal is to decrease the intracellular ATP level via increasing the unspecific alkaline phosphatase activity. Intact and truncated versions of the S. cerevisiae PHO8 gene coding for vacuolar or cytosolic forms of alkaline phosphatase were fused with the alcohol dehydrogenase gene (ADH1) promoter. The constructed expression cassettes used for transformation vectors also contained the dominant selective marker kanMX4 and S. cerevisiae δ-sequence to facilitate multicopy integration to the genome. Laboratory and industrial ethanol producing strains BY4742 and AS400 overexpressing vacuolar form of alkaline phosphatase were characterized by a slightly lowered intracellular ATP level and biomass accumulation and by an increase in ethanol productivity (13% and 7%) when compared to the parental strains. The strains expressing truncated cytosolic form of alkaline phosphatase showed a prolonged lag-phase, reduced biomass accumulation and a strong defect in ethanol production. Overexpression of vacuolar alkaline phosphatase leads to an increased ethanol yield in S. cerevisiae.

  12. Observations of strain accumulation across the San Andreas fault near Palmdale, California, with a two-color geodimeter

    USGS Publications Warehouse

    Langbein, J.O.; Linker, M.F.; McGarr, A.; Slater, L.E.

    1982-01-01

    Two-color laser ranging measurements during a 15-month period over a geodetic network spanning the San Andreas fault near Palmdale, California, indicate that the crust expands and contracts aseismically in episodes as short as 2 weeks. Shear strain parallel to the fault has accumulated monotonically since November 1980, but at a variable rate. Improvements in measurement precision and temporal resolution over those of previous geodetic studies near Palmdale have resulted in the definition of a time history of crustal deformation that is much more complex than formerly realized. Copyright ?? 1982 AAAS.

  13. Formation and Migration Energies of Interstitials in Silicon Under Strain Conditions

    NASA Technical Reports Server (NTRS)

    Halicioglu, Timur; Barnett, David M.

    1999-01-01

    Simulation calculations are conducted for Si substrates to analyze formation and diffusion energies of interstitials under strain condition using statics methods .based on a Stillinger-Weber type potential function. Defects in the vicinity of the surface region and in the bulk are examined, and the role played by compressive and tensile strains on the energetics of interstitials is investigated. Results indicate that strain alters defect energetics which, in turn, modifies their diffusion characteristics.

  14. Convergence of strain energy release rate components for edge-delaminated composite laminates

    NASA Technical Reports Server (NTRS)

    Raju, I. S.; Crews, J. H., Jr.; Aminpour, M. A.

    1987-01-01

    Strain energy release rates for edge delaminated composite laminates were obtained using quasi 3 dimensional finite element analysis. The problem of edge delamination at the -35/90 interfaces of an 8-ply composite laminate subjected to uniform axial strain was studied. The individual components of the strain energy release rates did not show convergence as the delamination tip elements were made smaller. In contrast, the total strain energy release rate converged and remained unchanged as the delamination tip elements were made smaller and agreed with that calculated using a classical laminated plate theory. The studies of the near field solutions for a delamination at an interface between two dissimilar isotropic or orthotropic plates showed that the imaginary part of the singularity is the cause of the nonconvergent behavior of the individual components. To evaluate the accuracy of the results, an 8-ply laminate with the delamination modeled in a thin resin layer, that exists between the -35 and 90 plies, was analyzed. Because the delamination exists in a homogeneous isotropic material, the oscillatory component of the singularity vanishes.

  15. The mechanical consequences of load bearing in the equine third metacarpal across speed and gait: the nonuniform distributions of normal strain, shear strain, and strain energy density

    PubMed Central

    Rubin, Clinton T.; Seeherman, Howard; Qin, Yi-Xian; Gross, Ted S.

    2013-01-01

    Distributions of normal strain, shear strain, and strain energy density (SED) were determined across the midshaft of the third metacarpal (MCIII, or cannon bone) of 3 adult thoroughbred horses as a function of speed and gait. A complete characterization of the mechanical demands of the bone made through the stride and from mild through the extremes of locomotion was possible by using three 3-element rosette strain gauges bonded at the diaphyseal midshaft of the MCIII and evaluating the strain output with beam theory and finite element analysis. Mean ± sd values of normal strain, shear strain, and SED increased with speed and peaked during a canter (−3560±380 microstrain, 1760±470 microstrain, and 119±23 kPa, respectively). While the location of these peaks was similar across animals and gaits, the resulting strain distributions across the cortex were consistently nonuniform, establishing between a 73-fold (slow trot) to a 330-fold (canter) disparity between the sites of maximum and minimum SED for each gait cycle. Using strain power density as an estimate of strain history across the bone revealed a 154-fold disparity between peak and minimum at the walk but fell to ∼32-fold at the canter. The nonuniform, minimally varying, strain environment suggests either that bone homeostasis is mediated by magnitude-independent mechanical signals or that the duration of stimuli necessary to establish and maintain tissue integrity is relatively brief, and thus the vast majority of strain information is disregarded.—Rubin, C. T., Seeherman, H., Qin, Y.-X., Gross, T. S., The mechanical consequences of load bearing in the equine third metacarpal across speed and gait: the nonuniform distributions of normal strain, shear strain, and strain energy density. PMID:23355269

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

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

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

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

  17. A Novel Creep-Fatigue Life Prediction Model for P92 Steel on the Basis of Cyclic Strain Energy Density

    NASA Astrophysics Data System (ADS)

    Ji, Dongmei; Ren, Jianxing; Zhang, Lai-Chang

    2016-11-01

    A novel creep-fatigue life prediction model was deduced based on an expression of the strain energy density in this study. In order to obtain the expression of the strain energy density, the load-controlled creep-fatigue (CF) tests of P92 steel at 873 K were carried out. Cyclic strain of P92 steel under CF load was divided into elastic strain, applying and unloading plastic strain, creep strain, and anelastic strain. Analysis of cyclic strain indicates that the damage process of P92 steel under CF load consists of three stages, similar to pure creep. According to the characteristics of the strains above, an expression was defined to describe the strain energy density for each cycle. The strain energy density at stable stage is inversely proportional to the total strain energy density dissipated by P92 steel. However, the total strain energy densities under different test conditions are proportional to the fatigue life. Therefore, the expression of the strain energy density at stable stage was chosen to predict the fatigue life. The CF experimental data on P92 steel were employed to verify the rationality of the novel model. The model obtained from the load-controlled CF test of P92 steel with short holding time could predict the fatigue life of P92 steel with long holding time.

  18. Significant strain accumulation between the deformation front and landward out-of-sequence thrusts in accretionary wedge of SW Taiwan revealed by cGPS and SAR interferometry

    NASA Astrophysics Data System (ADS)

    Tsai, M. C.

    2017-12-01

    High strain accumulation across the fold-and-thrust belt in Southwestern Taiwan are revealed by the Continuous GPS (cGPS) and SAR interferometry. This high strain is generally accommodated by the major active structures in fold-and-thrust belt of western Foothills in SW Taiwan connected to the accretionary wedge in the incipient are-continent collision zone. The active structures across the high strain accumulation include the deformation front around the Tainan Tableland, the Hochiali, Hsiaokangshan, Fangshan and Chishan faults. Among these active structures, the deformation pattern revealed from cGPS and SAR interferometry suggest that the Fangshan transfer fault may be a left-lateral fault zone with thrust component accommodating the westward differential motion of thrust sheets on both side of the fault. In addition, the Chishan fault connected to the splay fault bordering the lower-slope and upper-slope of the accretionary wedge which could be the major seismogenic fault and an out-of-sequence thrust fault in SW Taiwan. The big earthquakes resulted from the reactivation of out-of-sequence thrusts have been observed along the Nankai accretionary wedge, thus the assessment of the major seismogenic structures by strain accumulation between the frontal décollement and out-of-sequence thrusts is a crucial topic. According to the background seismicity, the low seismicity and mid-crust to mantle events are observed inland and the lower- and upper- slope domain offshore SW Taiwan, which rheologically implies the upper crust of the accretionary wedge is more or less aseimic. This result may suggest that the excess fluid pressure from the accretionary wedge not only has significantly weakened the prism materials as well as major fault zone, but also makes the accretionary wedge landward extension, which is why the low seismicity is observed in SW Taiwan area. Key words: Continuous GPS, SAR interferometry, strain rate, out-of-sequence thrust.

  19. Sensitivity of inelastic response to numerical integration of strain energy. [for cantilever beam

    NASA Technical Reports Server (NTRS)

    Kamat, M. P.

    1976-01-01

    The exact solution to the quasi-static, inelastic response of a cantilever beam of rectangular cross section subjected to a bending moment at the tip is obtained. The material of the beam is assumed to be linearly elastic-linearly strain-hardening. This solution is then compared with three different numerical solutions of the same problem obtained by minimizing the total potential energy using Gaussian quadratures of two different orders and a Newton-Cotes scheme for integrating the strain energy of deformation. Significant differences between the exact dissipative strain energy and its numerical counterpart are emphasized. The consequence of this on the nonlinear transient responses of a beam with solid cross section and that of a thin-walled beam on elastic supports under impulsive loads are examined.

  20. Characterization of a Bacillus amyloliquefaciens strain for reduction of citrulline accumulation during soy sauce fermentation.

    PubMed

    Zhang, Jiran; Du, Guocheng; Chen, Jian; Fang, Fang

    2016-10-01

    To reduce the amount of citrulline produced by arginine-consuming bacteria in the moromi mash during soy sauce production. Bacillus amyloliquefaciens JY06, a salt-tolerant strain with high arginine consumption ability and low citrulline accumulation capacity, was isolated from moromi mash. The concentration of citrulline was decreased from 26.8 to 5.1 mM and ethyl carbamate in soy sauce, after sterilization, decreased from 97 to 17 μg kg(-1) when B. amyloliquefaciens JY06 was added during fermentation. The aroma of the sauce was improved by increasing the ester content. B. amyloliquefaciens JY06 is a beneficial bacterium that can be used in soy sauce fermentation to eliminate ethyl carbonate and enhance the flavor of the sauce.

  1. The exponentiated Hencky-logarithmic strain energy. Part II: Coercivity, planar polyconvexity and existence of minimizers

    NASA Astrophysics Data System (ADS)

    Neff, Patrizio; Lankeit, Johannes; Ghiba, Ionel-Dumitrel; Martin, Robert; Steigmann, David

    2015-08-01

    We consider a family of isotropic volumetric-isochoric decoupled strain energies based on the Hencky-logarithmic (true, natural) strain tensor log U, where μ > 0 is the infinitesimal shear modulus, is the infinitesimal bulk modulus with the first Lamé constant, are dimensionless parameters, is the gradient of deformation, is the right stretch tensor and is the deviatoric part (the projection onto the traceless tensors) of the strain tensor log U. For small elastic strains, the energies reduce to first order to the classical quadratic Hencky energy which is known to be not rank-one convex. The main result in this paper is that in plane elastostatics the energies of the family are polyconvex for , extending a previous finding on its rank-one convexity. Our method uses a judicious application of Steigmann's polyconvexity criteria based on the representation of the energy in terms of the principal invariants of the stretch tensor U. These energies also satisfy suitable growth and coercivity conditions. We formulate the equilibrium equations, and we prove the existence of minimizers by the direct methods of the calculus of variations.

  2. Improved bounds on the energy-minimizing strains in martensitic polycrystals

    NASA Astrophysics Data System (ADS)

    Peigney, Michaël

    2016-07-01

    This paper is concerned with the theoretical prediction of the energy-minimizing (or recoverable) strains in martensitic polycrystals, considering a nonlinear elasticity model of phase transformation at finite strains. The main results are some rigorous upper bounds on the set of energy-minimizing strains. Those bounds depend on the polycrystalline texture through the volume fractions of the different orientations. The simplest form of the bounds presented is obtained by combining recent results for single crystals with a homogenization approach proposed previously for martensitic polycrystals. However, the polycrystalline bound delivered by that procedure may fail to recover the monocrystalline bound in the homogeneous limit, as is demonstrated in this paper by considering an example related to tetragonal martensite. This motivates the development of a more detailed analysis, leading to improved polycrystalline bounds that are notably consistent with results for single crystals in the homogeneous limit. A two-orientation polycrystal of tetragonal martensite is studied as an illustration. In that case, analytical expressions of the upper bounds are derived and the results are compared with lower bounds obtained by considering laminate textures.

  3. Strain-dependent activation energy of shear transformation in metallic glasses

    NASA Astrophysics Data System (ADS)

    Xu, Bin; Falk, Michael; Li, Jinfu; Kong, Lingti

    2017-04-01

    Shear transformation (ST) plays a decisive role in determining the mechanical behavior of metallic glasses, which is believed to be a stress-assisted thermally activated process. Understanding the dependence in its activation energy on the stress imposed on the material is of central importance to model the deformation process of metallic glasses and other amorphous solids. Here a theoretical model is proposed to predict the variation of the minimum energy path (MEP) associated with a particular ST event upon further deformation. Verification based on atomistic simulations and calculations are also conducted. The proposed model reproduces the MEP and activation energy of an ST event under different imposed macroscopic strains based on a known MEP at a reference strain. Moreover, an analytical approach is proposed based on the atomistic calculations, which works well when the stress varies linearity along the MEP. These findings provide necessary background for understanding the activation processes and, in turn, the mechanical behavior of metallic glasses.

  4. Where is the magnetic energy for the expansion phase of auroral substorms accumulated? 2. The main body, not the magnetotail

    NASA Astrophysics Data System (ADS)

    Akasofu, Syun-Ichi

    2017-08-01

    It is suggested that the magnetosphere tries to stabilize itself by quickly unloading the magnetic energy accumulated within its main body, when the accumulated magnetic energy exceeds a limited amount, which can be identified as the energy for the expansion phase. It is this process which manifests as the impulsive expansion phase, during which auroral arcs advance well beyond the presubstorm latitude in the midnight sector. It was shown in the previous paper that the magnetotail does not have enough magnetic energy for a medium substorm (energy 5 × 1015 J; AE = 1000 nT). In this paper, it is shown that (1) the reason of the short lifetime (1-1.5 h) of the expansion phase is due to the fact that a limited amount of magnetic energy accumulated during the growth phase is dissipated in a period similar to the duration of the growth phase (1-1.5 h); the accumulation rate is similar to the dissipation rate during the expansion phase: (2) when the main body of the magnetosphere accumulates the magnetic energy, it is inflated; β (= (nkT/B2/8π)) even at XGSM = -6 RE becomes close to 1.0 for magnetic energy (2.9 × 1014 J) which is less than the amount consumed by a medium intensity substorm. (3) As a result, the plasma sheet current and thus the magnetosphere are expected to become unstable, unloading the accumulated excess magnetic energy and resulting in current reduction and deflation. (4) The resulting deflation can cause an earthward electric field of 5-50 mV/m, which can generate Bostrom's current system, which is mainly responsible in producing various phenomena of the expansion phase. (5) The large range of substorm intensity (AE = 100-2000 nT) is likely to be due to the location where the energy is accumulated; the closer is the distance to the Earth (XGSM between -10 RE and -4 RE), the more intense the substorm intensity is.

  5. Proline accumulation in baker's yeast enhances high-sucrose stress tolerance and fermentation ability in sweet dough.

    PubMed

    Sasano, Yu; Haitani, Yutaka; Ohtsu, Iwao; Shima, Jun; Takagi, Hiroshi

    2012-01-03

    During bread-making processes, yeast cells are exposed to various baking-associated stresses. High-sucrose concentrations exert severe osmotic stress that seriously damages cellular components by generation of reactive oxygen species (ROS). Previously, we found that the accumulation of proline conferred freeze-thaw stress tolerance and the baker's yeast strain that accumulated proline retained higher-level fermentation abilities in frozen doughs than the wild-type strain. In this study, we constructed self-cloning diploid baker's yeast strains that accumulate proline. These resultant strains showed higher cell viability and lower intracellular oxidation levels than that observed in the wild-type strain under high-sucrose stress condition. Proline accumulation also enhanced the fermentation ability in high-sucrose-containing dough. These results demonstrate the usefulness of proline-accumulating baker's yeast for sweet dough baking. Copyright © 2011 Elsevier B.V. All rights reserved.

  6. Leveraging algal omics to reveal potential targets for augmenting TAG accumulation

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

    Arora, Neha; Pienkos, Philip T.; Pruthi, Vikas

    Ongoing global efforts to commercialize microalgal biofuels have expedited the use of multi-omics techniques to gain insights into lipid biosynthetic pathways. Functional genomics analyses have recently been employed to complement existing sequence-level omics studies, shedding light on the dynamics of lipid synthesis and its interplay with other cellular metabolic pathways, thus revealing possible targets for metabolic engineering. Here, we review the current status of algal omics studies to reveal potential targets to augment TAG accumulation in various microalgae. Here, this review specifically aims to examine and catalog systems level data related to stress-induced TAG accumulation in oleaginous microalgae and informmore » future metabolic engineering strategies to develop strains with enhanced bioproductivity, which could pave a path for sustainable green energy.« less

  7. Leveraging Algal Omics to Reveal Potential Targets for Augmenting TAG Accumulation

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

    Guarnieri, Michael T; Pienkos, Philip T; Arora, Neha

    2018-04-18

    Ongoing global efforts to commercialize microalgal biofuels have expedited the use of multi-omics techniques to gain insights into lipid biosynthetic pathways. Functional genomics analyses have recently been employed to complement existing sequence-level omics studies, shedding light on the dynamics of lipid synthesis and its interplay with other cellular metabolic pathways, thus revealing possible targets for metabolic engineering. Here, we review the current status of algal omics studies to reveal potential targets to augment TAG accumulation in various microalgae. This review specifically aims to examine and catalog systems level data related to stress-induced TAG accumulation in oleaginous microalgae and inform futuremore » metabolic engineering strategies to develop strains with enhanced bioproductivity, which could pave a path for sustainable green energy.« less

  8. Leveraging algal omics to reveal potential targets for augmenting TAG accumulation

    DOE PAGES

    Arora, Neha; Pienkos, Philip T.; Pruthi, Vikas; ...

    2018-04-18

    Ongoing global efforts to commercialize microalgal biofuels have expedited the use of multi-omics techniques to gain insights into lipid biosynthetic pathways. Functional genomics analyses have recently been employed to complement existing sequence-level omics studies, shedding light on the dynamics of lipid synthesis and its interplay with other cellular metabolic pathways, thus revealing possible targets for metabolic engineering. Here, we review the current status of algal omics studies to reveal potential targets to augment TAG accumulation in various microalgae. Here, this review specifically aims to examine and catalog systems level data related to stress-induced TAG accumulation in oleaginous microalgae and informmore » future metabolic engineering strategies to develop strains with enhanced bioproductivity, which could pave a path for sustainable green energy.« less

  9. DEM code-based modeling of energy accumulation and release in structurally heterogeneous rock masses

    NASA Astrophysics Data System (ADS)

    Lavrikov, S. V.; Revuzhenko, A. F.

    2015-10-01

    Based on discrete element method, the authors model loading of a physical specimen to describe its capacity to accumulate and release elastic energy. The specimen is modeled as a packing of particles with viscoelastic coupling and friction. The external elastic boundary of the packing is represented by particles connected by elastic springs. The latter means introduction of an additional special potential of interaction between the boundary particles, that exercises effect even when there is no direct contact between the particles. On the whole, the model specimen represents an element of a medium capable of accumulation of deformation energy in the form of internal stresses. The data of the numerical modeling of the physical specimen compression and the laboratory testing results show good qualitative consistency.

  10. Shear-strain energy rate distribution caused by the interplate locking along the Nankai Trough, southwest Japan: An integration analysis using stress tensor inversion and slip deficit inversion

    NASA Astrophysics Data System (ADS)

    Saito, T.; Noda, A.; Yoshida, K.; Tanaka, S.

    2017-12-01

    In the Nankai Trough, southwest Japan, the Philippine Sea Plate descends beneath the Eurasian plate. The locking, or the slip deficit, on the plate interface causes stress fluctuation in the inland area. The interplate locking does not always result in stress accumulation but also causes stress release. The stress increase/decrease is not determined only from the stress fluctuation but also depends on the background stress, in particular, its orientation. This study proposes a method to estimate the shear-strain energy increase/decrease distribution caused by the interplate locking. We at first investigated the background stress field in and around the Nankai Trough. The spatial distribution of the principal stress orientations and the stress ratio were estimated by analysis of 130,000 focal mechanisms of small earthquakes (e.g., Yoshida et al. 2015 Tectonophysics). For example, in an area called Chugoku region, the maximum and minimum compression axes were E-W and N-S directions, respectively. We also estimated the slip-deficit rate at the plate interface by analyzing GNSS data and calculated the stress fluctuation due to the deficit (e.g., Noda et al. 2013 GJI). The interplate locking causes the maximum compression in the direction of plate convergence. This is significantly different from the orientations of the background stress characterized by the E-W compressional strike-slip stress regime.. By combining the results of the background stress and the stress fluctuation, we made a map indicating the shear-strain energy change due to the interplate locking. In the Chugoku region, the shear-strain energy decreases due to the interplate locking. This is because the N-S compressional stress caused by the interplate locking compensates the N-S extensional stress in the background. The shear-strain energy increases in some parts of the analyzed areas. By statistically comparing the shear strain energy rate with the seismicity in the inland area, we found that the

  11. Elastic strain relaxation in interfacial dislocation patterns: I. A parametric energy-based framework

    NASA Astrophysics Data System (ADS)

    Vattré, A.

    2017-08-01

    A parametric energy-based framework is developed to describe the elastic strain relaxation of interface dislocations. By means of the Stroh sextic formalism with a Fourier series technique, the proposed approach couples the classical anisotropic elasticity theory with surface/interface stress and elasticity properties in heterogeneous interface-dominated materials. For any semicoherent interface of interest, the strain energy landscape is computed using the persistent elastic fields produced by infinitely periodic hexagonal-shaped dislocation configurations with planar three-fold nodes. A finite element based procedure combined with the conjugate gradient and nudged elastic band methods is applied to determine the minimum-energy paths for which the pre-computed energy landscapes yield to elastically favorable dislocation reactions. Several applications on the Au/Cu heterosystems are given. The simple and limiting case of a single set of infinitely periodic dislocations is introduced to determine exact closed-form expressions for stresses. The second limiting case of the pure (010) Au/Cu heterophase interfaces containing two crossing sets of straight dislocations investigates the effects due to the non-classical boundary conditions on the stress distributions, including separate and appropriate constitutive relations at semicoherent interfaces and free surfaces. Using the quantized Frank-Bilby equation, it is shown that the elastic strain landscape exhibits intrinsic dislocation configurations for which the junction formation is energetically unfavorable. On the other hand, the mismatched (111) Au/Cu system gives rise to the existence of a minimum-energy path where the fully strain-relaxed equilibrium and non-regular intrinsic hexagonal-shaped dislocation rearrangement is accompanied by a significant removal of the short-range elastic energy.

  12. Strain accumulation across the central Nevada seismic zone, 1973-1994

    NASA Astrophysics Data System (ADS)

    Savage, J. C.; Lisowski, M.; Svarc, J. L.; Gross, W. K.

    1995-10-01

    Five trilateration networks extending for 280 km along the central Nevada seismic zone (1915 Pleasant Valley, M = 7.3; 1954 Dixie Valley, M = 6.8; 1954 Stillwater, M = 6.8; 1954 Rainbow Mountain, M = 6.6; 1954 Fairview Peak, M = 7.1; and 1932 Cedar Mountain, M = 7.2) have been surveyed 6 times since 1973 to determine deformation along the zone. Within the precision of measurement the deformation appears uniform along the zone and is described by the principal strain rates 0.036±0.008 μstrain/yr N60°W±3° and -0.031±0.008 μstrain/yr N30°E±3°, extension reckoned positive. The observed strain rates are consistent with simple, right-lateral, tensor shear at the rate of 0.033 μstrain/yr across a shear zone striking N15°W. This central Nevada shear zone appears to be the northward continuation of the eastern California shear zone. The orientation of the strike-slip and normal-slip ruptures within the central Nevada seismic zone are consistent with principal stress axes parallel to the measured principal strain rate axes. Space-based geodetic measurements (very long baseline interferometry) indicate that the relative motion accommodated across the Basin and Range province west of Ely, Nevada, is about 9.1±1.5 mm/yr N16°W±8° (Dixon et al., 1995.) Notice that the right-lateral shear zone postulated to explain deformation in the central Nevada seismic zone is properly oriented to accommodate that relative motion. However, a 135-km effective width of the shear zone would be required to accommodate all of the 9.1 mm/yr relative motion at the strain rates observed in the Nevada seismic zone; only about 3 mm/yr of that relative motion is accommodated within the span of the trilateration networks.

  13. Photo-Oxidative Stress-Driven Mutagenesis and Adaptive Evolution on the Marine Diatom Phaeodactylum tricornutum for Enhanced Carotenoid Accumulation.

    PubMed

    Yi, Zhiqian; Xu, Maonian; Magnusdottir, Manuela; Zhang, Yuetuan; Brynjolfsson, Sigurdur; Fu, Weiqi

    2015-09-29

    Marine diatoms have recently gained much attention as they are expected to be a promising resource for sustainable production of bioactive compounds such as carotenoids and biofuels as a future clean energy solution. To develop photosynthetic cell factories, it is important to improve diatoms for value-added products. In this study, we utilized UVC radiation to induce mutations in the marine diatom Phaeodactylum tricornutum and screened strains with enhanced accumulation of neutral lipids and carotenoids. Adaptive laboratory evolution (ALE) was also used in parallel to develop altered phenotypic and biological functions in P. tricornutum and it was reported for the first time that ALE was successfully applied on diatoms for the enhancement of growth performance and productivity of value-added carotenoids to date. Liquid chromatography-mass spectrometry (LC-MS) was utilized to study the composition of major pigments in the wild type P. tricornutum, UV mutants and ALE strains. UVC radiated strains exhibited higher accumulation of fucoxanthin as well as neutral lipids compared to their wild type counterpart. In addition to UV mutagenesis, P. tricornutum strains developed by ALE also yielded enhanced biomass production and fucoxanthin accumulation under combined red and blue light. In short, both UV mutagenesis and ALE appeared as an effective approach to developing desired phenotypes in the marine diatoms via electromagnetic radiation-induced oxidative stress.

  14. Photo-Oxidative Stress-Driven Mutagenesis and Adaptive Evolution on the Marine Diatom Phaeodactylum tricornutum for Enhanced Carotenoid Accumulation

    PubMed Central

    Yi, Zhiqian; Xu, Maonian; Magnusdottir, Manuela; Zhang, Yuetuan; Brynjolfsson, Sigurdur; Fu, Weiqi

    2015-01-01

    Marine diatoms have recently gained much attention as they are expected to be a promising resource for sustainable production of bioactive compounds such as carotenoids and biofuels as a future clean energy solution. To develop photosynthetic cell factories, it is important to improve diatoms for value-added products. In this study, we utilized UVC radiation to induce mutations in the marine diatom Phaeodactylum tricornutum and screened strains with enhanced accumulation of neutral lipids and carotenoids. Adaptive laboratory evolution (ALE) was also used in parallel to develop altered phenotypic and biological functions in P. tricornutum and it was reported for the first time that ALE was successfully applied on diatoms for the enhancement of growth performance and productivity of value-added carotenoids to date. Liquid chromatography-mass spectrometry (LC-MS) was utilized to study the composition of major pigments in the wild type P. tricornutum, UV mutants and ALE strains. UVC radiated strains exhibited higher accumulation of fucoxanthin as well as neutral lipids compared to their wild type counterpart. In addition to UV mutagenesis, P. tricornutum strains developed by ALE also yielded enhanced biomass production and fucoxanthin accumulation under combined red and blue light. In short, both UV mutagenesis and ALE appeared as an effective approach to developing desired phenotypes in the marine diatoms via electromagnetic radiation-induced oxidative stress. PMID:26426027

  15. Effects of Thermal Damage on Strain Burst Mechanism for Brittle Rocks Under True-Triaxial Loading Conditions

    NASA Astrophysics Data System (ADS)

    Akdag, Selahattin; Karakus, Murat; Taheri, Abbas; Nguyen, Giang; Manchao, He

    2018-06-01

    Strain burst is a common problem encountered in brittle rocks in deep, high-stress mining applications. Limited research focuses on the effects of temperature on the strain burst mechanism and the kinetic energies of rocks. This study aims to investigate the effects of thermal damage on the strain burst characteristics of brittle rocks under true-triaxial loading-unloading conditions using the acoustic emission (AE) and kinetic energy analyses. The time-domain and frequency-domain responses related to strain burst were studied, and the damage evolution was quantified by b-values, cumulative AE energy and events rates. The ejection velocities of the rock fragments from the free face of the granite specimens were used to calculate kinetic energies. The experimental results showed that thermal damage resulted in a delay in bursting but increased the bursting rate at 95% of normalised stress level. This is believed to be due to the micro-cracks induced by temperature exposure, and thus the accumulated AE energy (also supported by cumulative AE counts) at the initial loading stage was reduced, causing a delay in bursting. The strain burst stress, initial rock fragment ejection velocity, and kinetic energy decreased from room temperature (25 °C) to 100 °C, whereas they resulted in a gradual rise from 100 to 150 °C demonstrating more intense strain burst behaviour.

  16. Self-cloning baker's yeasts that accumulate proline enhance freeze tolerance in doughs.

    PubMed

    Kaino, Tomohiro; Tateiwa, Tetsuya; Mizukami-Murata, Satomi; Shima, Jun; Takagi, Hiroshi

    2008-09-01

    We constructed self-cloning diploid baker's yeast strains by disrupting PUT1, encoding proline oxidase, and replacing the wild-type PRO1, encoding gamma-glutamyl kinase, with a pro1(D154N) or pro1(I150T) allele. The resultant strains accumulated intracellular proline and retained higher-level fermentation abilities in the frozen doughs than the wild-type strain. These results suggest that proline-accumulating baker's yeast is suitable for frozen-dough baking.

  17. Improved incorporation of strain gradient elasticity in the flexoelectricity based energy harvesting from nanobeams

    NASA Astrophysics Data System (ADS)

    Zhou, Yarong; Yang, Xu; Pan, Dongmei; Wang, Binglei

    2018-04-01

    Flexoelectricity, the coupling of strain gradient and polarization, exists in all the dielectric materials and numerous models have been proposed to study this mechanism. However, the contribution of strain gradient elasticity has typically been underestimated. In this work, inspired by the one-length scale parameter model developed by Deng et al. [19], we incorporate three length-scale parameters to carefully capture the contribution of the purely mechanical strain gradients on flexoelectricity. This three-parameter model is more flexible and could be applied to investigate the flexoelectricity in a wide range of complicated deformations. Accordingly, we carry out our analysis by studying a dielectric nanobeam under different boundary conditions. We show that the strain gradient elasticity and flexoelectricity have apparent size effects and significant influence on the electromechanical response. In particular, the strain gradient effects could significantly reduce the energy efficiency, indicating their importance and necessity. This work may be helpful in understanding the mechanism of flexoelectricity at the nanoscale and sheds light on the flexoelectricity energy harvesting.

  18. Residual thermal and moisture influences on the strain energy release rate analysis of local delaminations from matrix cracks

    NASA Technical Reports Server (NTRS)

    Obrien, T. K.

    1991-01-01

    An analysis utilizing laminated plate theory is developed to calculate the strain energy release rate associated with local delaminations originating at off-axis, single ply, matrix cracks in laminates subjected to uniaxial loads. The analysis includes the contribution of residual thermal and moisture stresses to the strain energy released. Examples are calculated for the strain energy release rate associated with local delaminations originating at 90 degrees and angle-ply (non-90 degrees) matrix ply cracks in glass epoxy and graphite epoxy laminates. The solution developed may be used to assess the relative contribution of mechanical, residual thermal, and moisture stresses on the strain energy release rate for local delamination for a variety of layups and materials.

  19. Strain Partitioning and Accumulation across Overlapping Spreading Centers: Geodetic GPS Measurements in South Iceland

    NASA Astrophysics Data System (ADS)

    La Femina, P. C.; Dixon, T. H.; Malservisi, R.; Árnadóttir, T.; Sigmundsson, F.; Sturkell, E.

    2004-12-01

    Overlapping spreading centers (OSCs) and propagating ridges are important classes of mid-ocean ridges. Kinematic models of OSCs predict along strike variability in spreading rate associated with the propagation of one center and deactivation of the other. Iceland offers a unique opportunity to investigate strain accumulation and partitioning across slow, overlapping spreading centers, and the influence of a ridge centered hotspot on ridge kinematics and morphology. We present results of detailed GPS observations across the Eastern and Western Volcanic Zones, south Iceland, spanning a seven to nine year inter-rifting period, and compare our observations with two-dimensional elastic half-space models that simulate the long-term spreading process. We then compare the elastic half-space models with simple viscoelastic coupling models. We model three velocity profiles across the EVZ-WVZ system, solving for the spreading rate, locking depth and horizontal location of each spreading center. Our spreading rate estimates indicate along strike variations as expected in an OSC system and total spreading rates consistent with geodetic and geologic plate motion models. Spreading rates in the WVZ increase from northeast (3 ±1 mm/yr) to southwest (7 ±1 mm/yr). Spreading rates in the southwest propagating EVZ decrease from northeast (17 ±1 mm/yr) to southwest (12 ±1 mm/yr). These results are consistent with a model whereby the WVZ is deactivating in the direction of EVZ propagation. The morphology of the two spreading centers reflects the spreading rate differences and their location relative to the Iceland hotspot. The predicted locations of the spreading axis for each zone are consistent with mapped Holocene fissure swarms. The neovolcanic zone of the slower WVZ consists of a narrow (10-20 km wide) axial graben and has had few Holocene eruptions. The faster EVZ consists of two parallel neovolcanic zones separated by a 20 km gap of inactivity, little normal faulting, higher

  20. GPS measurements of strain accumulation across the Imperial Valley, California: 1986-1989

    NASA Technical Reports Server (NTRS)

    Larsen, Shawn; Reilinger, Robert

    1989-01-01

    The Global Positioning System (GPS) data collected in southern California from 1986 to 1989 indicate considerable strain accumulation across the Imperial Valley. Displacements are computed at 29 stations in and near the valley from 1986 to 1988, and at 11 sites from 1988 to 1989. The earlier measurements indicate 5.9 +/- 1.0 cm/yr right-lateral differential velocity across the valley, although the data are heavily influenced by the 1987 Superstition Hills earthquake sequence. Some measurements, especially the east-trending displacements, are suspects for large errors. The 1988 to 1989 GPS displacements are best modeled by 5.2 +/- 0.9 cm/yr of valley crossing deformation, but rates calculated from conventional geodetic measurements (3.4 to 4.3 cm/yr) fit the data nearly as well. There is evidence from GPS and Very Long Base Interferometry (VLBI) observations that the present slip rate along the southern San Andreas fault is smaller than the long-term geologic estimate, suggesting a lower earthquake potential than is currently assumed. Correspondingly, a higher earthquake potential is indicated for the San Jacinto fault. The Imperial Valley GPS sites form part of a 183 station network in southern California and northern Baja California, which spans a cross-section of the North American-Pacific plate boundary.

  1. Streptomyces sp. ASBV-1 reduces aflatoxin accumulation by Aspergillus parasiticus in peanut grains.

    PubMed

    Zucchi, T D; de Moraes, L A B; de Melo, I S

    2008-12-01

    To evaluate the ability of Streptomyces sp. (strain ASBV-1) to restrict aflatoxin accumulation in peanut grains. In the control of many phytopathogenic fungi the Streptomyces sp. ASBV-1 strain showed promise. An inhibitory test using this strain and A. parasiticus was conducted in peanut grains to evaluate the effects of this interaction on spore viability and aflatoxin accumulation. In some treatments the Streptomyces sp ASBV-1 strain reduced the viability of A. parasiticus spores by c. 85%, and inhibited aflatoxin accumulation in peanut grains. The values of these reductions ranged from 63 to 98% and from 67% to 96% for aflatoxins B(1) and G(1), respectively. It was demonstrated that Streptomyces sp. ASBV-1 is able to colonize peanut grains and thus inhibit the spore viability of A. parasiticus, as well as reducing aflatoxin production. The positive finding for aflatoxin accumulation reduction in peanut grains seems promising and suggests a wider use of this actinobacteria in biological control programmes.

  2. Leveraging algal omics to reveal potential targets for augmenting TAG accumulation.

    PubMed

    Arora, Neha; Pienkos, Philip T; Pruthi, Vikas; Poluri, Krishna Mohan; Guarnieri, Michael T

    2018-04-18

    Ongoing global efforts to commercialize microalgal biofuels have expedited the use of multi-omics techniques to gain insights into lipid biosynthetic pathways. Functional genomics analyses have recently been employed to complement existing sequence-level omics studies, shedding light on the dynamics of lipid synthesis and its interplay with other cellular metabolic pathways, thus revealing possible targets for metabolic engineering. Here, we review the current status of algal omics studies to reveal potential targets to augment TAG accumulation in various microalgae. This review specifically aims to examine and catalog systems level data related to stress-induced TAG accumulation in oleaginous microalgae and inform future metabolic engineering strategies to develop strains with enhanced bioproductivity, which could pave a path for sustainable green energy. Copyright © 2018. Published by Elsevier Inc.

  3. Comminution of solids caused by kinetic energy of high shear strain rate, with implications for impact, shock, and shale fracturing.

    PubMed

    Bazant, Zdenek P; Caner, Ferhun C

    2013-11-26

    Although there exists a vast literature on the dynamic comminution or fragmentation of rocks, concrete, metals, and ceramics, none of the known models suffices for macroscopic dynamic finite element analysis. This paper outlines the basic idea of the macroscopic model. Unlike static fracture, in which the driving force is the release of strain energy, here the essential idea is that the driving force of comminution under high-rate compression is the release of the local kinetic energy of shear strain rate. The density of this energy at strain rates >1,000/s is found to exceed the maximum possible strain energy density by orders of magnitude, making the strain energy irrelevant. It is shown that particle size is proportional to the -2/3 power of the shear strain rate and the 2/3 power of the interface fracture energy or interface shear stress, and that the comminution process is macroscopically equivalent to an apparent shear viscosity that is proportional (at constant interface stress) to the -1/3 power of this rate. A dimensionless indicator of the comminution intensity is formulated. The theory was inspired by noting that the local kinetic energy of shear strain rate plays a role analogous to the local kinetic energy of eddies in turbulent flow.

  4. Comminution of solids caused by kinetic energy of high shear strain rate, with implications for impact, shock, and shale fracturing

    PubMed Central

    Bažant, Zdeněk P.; Caner, Ferhun C.

    2013-01-01

    Although there exists a vast literature on the dynamic comminution or fragmentation of rocks, concrete, metals, and ceramics, none of the known models suffices for macroscopic dynamic finite element analysis. This paper outlines the basic idea of the macroscopic model. Unlike static fracture, in which the driving force is the release of strain energy, here the essential idea is that the driving force of comminution under high-rate compression is the release of the local kinetic energy of shear strain rate. The density of this energy at strain rates >1,000/s is found to exceed the maximum possible strain energy density by orders of magnitude, making the strain energy irrelevant. It is shown that particle size is proportional to the −2/3 power of the shear strain rate and the 2/3 power of the interface fracture energy or interface shear stress, and that the comminution process is macroscopically equivalent to an apparent shear viscosity that is proportional (at constant interface stress) to the −1/3 power of this rate. A dimensionless indicator of the comminution intensity is formulated. The theory was inspired by noting that the local kinetic energy of shear strain rate plays a role analogous to the local kinetic energy of eddies in turbulent flow. PMID:24218624

  5. Synergic effects of tactolimus and azole antifungal agents against azole-resistant Candida albican strains.

    PubMed

    Maesaki, S; Marichal, P; Hossain, M A; Sanglard, D; Vanden Bossche, H; Kohno, S

    1998-12-01

    We investigated the effects of combining tacrolimus and azole antifungal agents in azole-resistant strains of Candida albicans by comparing the accumulation of [3H]itraconazole. The CDR1-expressing resistant strain C26 accumulated less itraconazole than the CaMDR-expressing resistant strain C40 or the azole-sensitive strain B2630. A CDR1-expressing Saccharomyces cerevisiae mutant, DSY415, showed a marked reduction in the accumulation of both fluconazole and itraconazole. A CaMDR-expressing S. cerevisiae mutant, DSY416, also showed lower accumulation of fluconazole, but not of itraconazole. The addition of sodium azide, an electron-transport chain inhibitor, increased the intracellular accumulation of itraconazole only in the C26 strain, and not in the C40 or B2630 strains. Addition of tacrolimus, an inhibitor of multidrug resistance proteins, resulted in the highest increase in itraconazole accumulation in the C26 strain. The combination of itraconazole and tacrolimus was synergic in azole-resistant C. albicans strains. In the C26 strain, the MIC of itraconazole decreased from >8 to 0.5 mg/L when combined with tacrolimus. Our results showed that two multidrug resistance phenotypes (encoded by the CDR1 and CaMDR genes) in C. albicans have different substrate specificity for azole antifungal agents and that a combination of tacrolimus and azole antifungal agents is effective against azole-resistant strains of C. albicans.

  6. THE SOURCE OF LIPID ACCUMULATION IN L CELLS

    PubMed Central

    Bensch, Klaus G.; King, Donald W.; Socolow, Edward L.

    1961-01-01

    Strain L cells accumulate lipid, concurrent with cessation of protein synthesis, in the stationary phase of growth from the extracellular medium and as a result of de novo synthesis. Cells which have been more severely damaged with an amino acid analogue also accumulate lipid from the extracellular medium, but synthesize very little lipid from labeled acetate. The possible roles which lipid accumulation may play in the cell are discussed. PMID:19866577

  7. Theoretical Investigations of Transition Metal Surface Energies under Lattice Strain and CO Environment

    DOE PAGES

    Tang, Michael T.; Ulissi, Zachary W.; Chan, Karen

    2018-05-30

    Here, an understanding of the relative stability of surface facets is crucial to develop predictive models of catalyst activity and to fabricate catalysts with a controlled morphology. In this work, we present a systematic density functional theory study of the effect of lattice strain and CO environment on the surface formation energies of Cu, Pt, and Ni. First, we show that both compressive and tensile lattice strains favor the formation of stepped versus low-index terraces such as (111) and (100). Then, we investigate the effect of the CO environment using configurations of CO at various coverages, determined using a greedy,more » systematic approach, inspired by forward stepwise feature selection. We find that the CO environment favors stepped facets on Ni, Cu, and Pt. These trends are illustrated with the corresponding equilibrium Wulff shapes at various strains and CO pressures. In general, the surface energies of the studied transition metals are highly sensitive to strain and CO coverage, which should be considered when rationalizing trends in the catalytic activity.« less

  8. Theoretical Investigations of Transition Metal Surface Energies under Lattice Strain and CO Environment

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

    Tang, Michael T.; Ulissi, Zachary W.; Chan, Karen

    Here, an understanding of the relative stability of surface facets is crucial to develop predictive models of catalyst activity and to fabricate catalysts with a controlled morphology. In this work, we present a systematic density functional theory study of the effect of lattice strain and CO environment on the surface formation energies of Cu, Pt, and Ni. First, we show that both compressive and tensile lattice strains favor the formation of stepped versus low-index terraces such as (111) and (100). Then, we investigate the effect of the CO environment using configurations of CO at various coverages, determined using a greedy,more » systematic approach, inspired by forward stepwise feature selection. We find that the CO environment favors stepped facets on Ni, Cu, and Pt. These trends are illustrated with the corresponding equilibrium Wulff shapes at various strains and CO pressures. In general, the surface energies of the studied transition metals are highly sensitive to strain and CO coverage, which should be considered when rationalizing trends in the catalytic activity.« less

  9. Secondary Metabolism and Interspecific Competition Affect Accumulation of Spontaneous Mutants in the GacS-GacA Regulatory System in Pseudomonas protegens

    PubMed Central

    Yan, Qing; Lopes, Lucas D.; Shaffer, Brenda T.; Kidarsa, Teresa A.; Vining, Oliver; Philmus, Benjamin; Song, Chunxu; Stockwell, Virginia O.; Raaijmakers, Jos M.; McPhail, Kerry L.; Andreote, Fernando D.; Chang, Jeff H.

    2018-01-01

    ABSTRACT Secondary metabolites are synthesized by many microorganisms and provide a fitness benefit in the presence of competitors and predators. Secondary metabolism also can be costly, as it shunts energy and intermediates from primary metabolism. In Pseudomonas spp., secondary metabolism is controlled by the GacS-GacA global regulatory system. Intriguingly, spontaneous mutations in gacS or gacA (Gac− mutants) are commonly observed in laboratory cultures. Here we investigated the role of secondary metabolism in the accumulation of Gac− mutants in Pseudomonas protegens strain Pf-5. Our results showed that secondary metabolism, specifically biosynthesis of the antimicrobial compound pyoluteorin, contributes significantly to the accumulation of Gac− mutants. Pyoluteorin biosynthesis, which poses a metabolic burden on the producer cells, but not pyoluteorin itself, leads to the accumulation of the spontaneous mutants. Interspecific competition also influenced the accumulation of the Gac− mutants: a reduced proportion of Gac− mutants accumulated when P. protegens Pf-5 was cocultured with Bacillus subtilis than in pure cultures of strain Pf-5. Overall, our study associated a fitness trade-off with secondary metabolism, with metabolic costs versus competitive benefits of production influencing the evolution of P. protegens, assessed by the accumulation of Gac− mutants. PMID:29339425

  10. Project Hotspot: Linear accumulation rates of late Cenozoic basalt at Kimama, Idaho, and implications for crustal strain and subsidence rates of the central Snake River Plain

    NASA Astrophysics Data System (ADS)

    Rodgers, D. W.; Potter, K. E.; Shervais, J. W.; Champion, D. E.; Duncan, R. A.

    2013-12-01

    Project Hotspot's Kimama drill hole on the Snake River Plain, Idaho recovered a 1912 m thick section of basalt core that ranges in age from ~700 ka to at least 6.14 Ma, based on five 40Ar/39Ar analyses and twenty paleomagnetic age assignments. Fifty-four flow groups comprising 510 individual flows were defined, yielding an average recurrence interval of ~11,400 years between flows. Age-depth analysis indicate that, over thicknesses >150 m and age spans >500 k.y., accumulation rates were constant at 30 m/100 k.y. The existence and persistence of this linear accumulation rate for greater than 5 m.y. documents an external tectonic control on eruption dynamics. One conceptual model relates accumulation rates to horizontal crustal strain, such that far-field extension rate controls the periodicity of dikes that feed basalt flows. In this model, each of the 54 flow groups would have a deep-seated, relatively wide (1-10m) dike that branches upward into a network of narrow (10-100 cm) dikes feeding individual lava flows. Assuming an east-west lateral lava flow extent of up to 50 km, the Kimama data record a steady-state crustal strain rate of 10-9 to 10-10 y-1. This rate is comparable to modern, decadal strain rates measured with GPS in the adjacent Basin & Range province, but exceeds decadal strain rates of zero measured in the eastern Snake River Plain. Linear accumulation rates also provide insight into basalt subsidence history. In this model, the middle-upper crust subsides due to the added weight of lava flows, the added weight of mid-crustal sills/dikes, and thermal contraction in the wake of the Yellowstone hot spot. Isostatic compensation would occur in the (nearly) molten lower crust. Assuming constant surface elevation and a basalt density of 2.6 g/cm3, the lava flow weight would account for 87% of the burial through time, yielding a steady-state "tectonic" subsidence rate of 4 m/100 k.y. attributed to the driving forces of mid-crustal injection and/or thermal

  11. The Bibenzyl Canniprene Inhibits the Production of Pro-Inflammatory Eicosanoids and Selectively Accumulates in Some Cannabis sativa Strains.

    PubMed

    Allegrone, Gianna; Pollastro, Federica; Magagnini, Gianmaria; Taglialatela-Scafati, Orazio; Seegers, Julia; Koeberle, Andreas; Werz, Oliver; Appendino, Giovanni

    2017-03-24

    Canniprene (1), an isoprenylated bibenzyl unique to Cannabis sativa, can be vaporized and therefore potentially inhaled from marijuana. Canniprene (1) potently inhibited the production of inflammatory eicosanoids via the 5-lipoxygenase pathway (IC 50 0.4 μM) and also affected the generation of prostaglandins via the cyclooxygenase/microsomal prostaglandin E 2 synthase pathway (IC 50 10 μM), while the related spiranoid bibenzyls cannabispiranol (2) and cannabispirenone (3) were almost inactive in these bioassays. The concentration of canniprene (1) was investigated in the leaves of 160 strains of C. sativa, showing wide variations, from traces to >0.2%, but no correlation was found between its accumulation and a specific phytocannabinoid profile.

  12. Pressure-strain energy redistribution in compressible turbulence: return-to-isotropy versus kinetic-potential energy equipartition

    NASA Astrophysics Data System (ADS)

    Lee, Kurnchul; Venugopal, Vishnu; Girimaji, Sharath S.

    2016-08-01

    Return-to-isotropy and kinetic-potential energy equipartition are two fundamental pressure-moderated energy redistributive processes in anisotropic compressible turbulence. Pressure-strain correlation tensor redistributes energy among various Reynolds stress components and pressure-dilatation is responsible for energy reallocation between dilatational kinetic and potential energies. The competition and interplay between these pressure-based processes are investigated in this study. Direct numerical simulations (DNS) of low turbulent Mach number dilatational turbulence are performed employing the hybrid thermal Lattice Boltzman method (HTLBM). It is found that a tendency towards equipartition precedes proclivity for isotropization. An evolution towards equipartition has a collateral but critical effect on return-to-isotropy. The preferential transfer of energy from strong (rather than weak) Reynolds stress components to potential energy accelerates the isotropization of dilatational fluctuations. Understanding of these pressure-based redistributive processes is critical for developing insight into the character of compressible turbulence.

  13. Viscous dissipation of energy at the stage of accumulation of the Earth

    NASA Astrophysics Data System (ADS)

    Yurie Khachay, Professor; Olga Hachay, Professor; Antipin, Alexandr

    2017-04-01

    In the papers [1,2] it is published the differentiation model of the proto planet cloud during the accumulation of the Earth's group planets. In [2] it was shown that the energy released during the decay of short-lived radioactive elements in the small size more than 50 km, it is enough that the temperature inside of the protoplanet becomes larger than the temperature of iron melting. It provides a realization of the matter differentiation process and convection development inside the inner envelopes. With increasing of the Earth, the forming region of the outer core remains in a molten state, although the power and viscosity of the layer changed. In [3] it is shown that during the sequence of growth changes of accumulated protoplanets, the main contribution of heat is provided first by radioactive sources, and then heated from above by converting the kinetic energy during the growing impact inside the Earth, and finally heated from below. That provides three types of driving mechanisms of convection: internal heat sources; heated top; heated from bottom and chemical-thermal convection. At all stages of proto Earth's development the convective heat-mass transfer becomes a most significant factor in the dynamics of the planet. However, the heat release due to friction in the viscous liquid of the outer core up to now was not still considered, or it was considered only for the formed planetary envelopes with a constant radius. In this paper we present the first results of thermal evolution numerical modeling of 3D spherical segment for a protoplanet with increasing radius and accounting random falling of bodies and particles. To describe the planetary accumulation Safronov equation is used [4]. For the quantitative account of the released heat by viscous friction a system of hydro dynamic equations for a viscous liquid is used. The obtained results show that the heat input due to viscous friction heat release at the early stage of planetary accumulation was very

  14. Tensile-strain effect of inducing the indirect-to-direct band-gap transition and reducing the band-gap energy of Ge

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

    Inaoka, Takeshi, E-mail: inaoka@phys.u-ryukyu.ac.jp; Furukawa, Takuro; Toma, Ryo

    By means of a hybrid density-functional method, we investigate the tensile-strain effect of inducing the indirect-to-direct band-gap transition and reducing the band-gap energy of Ge. We consider [001], [111], and [110] uniaxial tensility and (001), (111), and (110) biaxial tensility. Under the condition of no normal stress, we determine both normal compression and internal strain, namely, relative displacement of two atoms in the primitive unit cell, by minimizing the total energy. We identify those strain types which can induce the band-gap transition, and evaluate the critical strain coefficient where the gap transition occurs. Either normal compression or internal strain operatesmore » unfavorably to induce the gap transition, which raises the critical strain coefficient or even blocks the transition. We also examine how each type of tensile strain decreases the band-gap energy, depending on its orientation. Our analysis clearly shows that synergistic operation of strain orientation and band anisotropy has a great influence on the gap transition and the gap energy.« less

  15. Edge effects on band gap energy in bilayer 2H-MoS{sub 2} under uniaxial strain

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

    Dong, Liang; Wang, Jin; Dongare, Avinash M., E-mail: dongare@uconn.edu

    2015-06-28

    The potential of ultrathin MoS{sub 2} nanostructures for applications in electronic and optoelectronic devices requires a fundamental understanding in their electronic structure as a function of strain. Previous experimental and theoretical studies assume that an identical strain and/or stress state is always maintained in the top and bottom layers of a bilayer MoS{sub 2} film. In this study, a bilayer MoS{sub 2} supercell is constructed differently from the prototypical unit cell in order to investigate the layer-dependent electronic band gap energy in a bilayer MoS{sub 2} film under uniaxial mechanical deformations. The supercell contains an MoS{sub 2} bottom layer andmore » a relatively narrower top layer (nanoribbon with free edges) as a simplified model to simulate the as-grown bilayer MoS{sub 2} flakes with free edges observed experimentally. Our results show that the two layers have different band gap energies under a tensile uniaxial strain, although they remain mutually interacting by van der Waals interactions. The deviation in their band gap energies grows from 0 to 0.42 eV as the uniaxial strain increases from 0% to 6% under both uniaxial strain and stress conditions. The deviation, however, disappears if a compressive uniaxial strain is applied. These results demonstrate that tensile uniaxial strains applied to bilayer MoS{sub 2} films can result in distinct band gap energies in the bilayer structures. Such variations need to be accounted for when analyzing strain effects on electronic properties of bilayer or multilayered 2D materials using experimental methods or in continuum models.« less

  16. Interseismic Strain Accumulation of the Gazikoy-Saros segment (Ganos fault) of the North Anatolian Fault Zone

    NASA Astrophysics Data System (ADS)

    Havazli, E.; Wdowinski, S.; Amelung, F.

    2017-12-01

    The North Anatolian Fault Zone (NAFZ) is one of the most active continental transform faults in the world. A westward migrating earthquake sequence has started in 1939 in Erzincan and the last two events of this sequence occurred in 1999 in Izmit and Duzce manifesting the importance of NAFZ on the seismic hazard potential of the region. NAFZ exhibits slip rates ranging from 14-30 mm/yr along its 1500 km length with a right lateral strike slip characteristic. In the East of the Marmara Sea, the NAFZ splits into two branches. The Gazikoy-Saros segment (Ganos Fault) is the westernmost and onshore segment of the northern branch. The ENE-WSW oriented Ganos Fault is seismically active. It produced a Ms 7.2 earthquake in 1912, which was followed by several large aftershocks, including Ms 6.3 and Ms 6.9 events. Since 1912, the Ganos Fault did not produce any significant earthquakes (> M 5), in contrast to its adjacent segments, which produced 20 M>5 earthquakes, including a M 6.7 event, offshore in Gulf of Saros. Interseismic strain accumulation along the Ganos Fault was assessed from sparse GPS measurements along a single transect located perpendicular to the fault zone, suggesting strain accumulation rate of 20-25 mm/yr. Insofar, InSAR studies, based on C-band data, didn't produce conclusive results due to low coherence over the fault zone area, which is highly vegetated. In this study, we present a detailed interseismic velocity map of the Ganos Fault zone derived from L-band InSAR observations. We use 21 ALOS PALSAR scenes acquired over a 5-year period, from 2007 to 2011. We processed the ALOS data using the PySAR software, which is the University of Miami version of the Small Baseline (SB) method. The L-band observations enabled us to overcome the coherence issue in the study area. Our initial results indicate a maximum velocity of 15 mm/yr across the fault zone. The high spatial resolution of the InSAR-based interseismic velocity map will enable us to better to

  17. Saccharification of Cellulose by Recombinant Rhodococcus opacus PD630 Strains

    PubMed Central

    Hetzler, Stephan; Bröker, Daniel

    2013-01-01

    The noncellulolytic actinomycete Rhodococcus opacus strain PD630 is the model oleaginous prokaryote with regard to the accumulation and biosynthesis of lipids, which serve as carbon and energy storage compounds and can account for as much as 87% of the dry mass of the cell in this strain. In order to establish cellulose degradation in R. opacus PD630, we engineered strains that episomally expressed six different cellulase genes from Cellulomonas fimi ATCC 484 (cenABC, cex, cbhA) and Thermobifida fusca DSM43792 (cel6A), thereby enabling R. opacus PD630 to degrade cellulosic substrates to cellobiose. Of all the enzymes tested, five exhibited a cellulase activity toward carboxymethyl cellulose (CMC) and/or microcrystalline cellulose (MCC) as high as 0.313 ± 0.01 U · ml−1, but recombinant strains also hydrolyzed cotton, birch cellulose, copy paper, and wheat straw. Cocultivations of recombinant strains expressing different cellulase genes with MCC as the substrate were carried out to identify an appropriate set of cellulases for efficient hydrolysis of cellulose by R. opacus. Based on these experiments, the multicellulase gene expression plasmid pCellulose was constructed, which enabled R. opacus PD630 to hydrolyze as much as 9.3% ± 0.6% (wt/vol) of the cellulose provided. For the direct production of lipids from birch cellulose, a two-step cocultivation experiment was carried out. In the first step, 20% (wt/vol) of the substrate was hydrolyzed by recombinant strains expressing the whole set of cellulase genes. The second step was performed by a recombinant cellobiose-utilizing strain of R. opacus PD630, which accumulated 15.1% (wt/wt) fatty acids from the cellobiose formed in the first step. PMID:23793636

  18. Strain Accumulation Estimated from Seafloor Crustal Deformation at the Nankai Trough, Japan

    NASA Astrophysics Data System (ADS)

    Tadokoro, K.; Watanabe, T.; Nagai, S.; Ikuta, R.; Okuda, T.; Kenji, Y.; Sakata, T.

    2012-12-01

    Our research has developed an observation system for seafloor crustal deformation composed of the kinematic GPS and acoustic ranging techniques [Tadokoro et al., 2006; Ikuta et al., 2008]. We monitored crustal deformation at the Nankai Trough, Japan, where the Philippine Sea Plate subducts beneath the Amurian Plate. The convergence rate is predicted at 60 mm/y in the N59W direction by the Euler vector of REVEL [Sella et al., 2002]. We installed three monitoring sites (named KMN, KMS, and KME) on the seafloor at depths of about 1920-2030 m. The sites KMN and KMS are installed perpendicular to the trough axis with a spacing of 20 km; the site KME is 50 km from KMN and KMS in the direction parallel to the trough axis. The monitoring was started in 2004, 2005, and 2008 at KMS, KMN, and KME, respectively. The numbers of measurements are 16, 20, and 5 times at KMN, KMS, and KME, respectively. We obtained 3-7 years averaged horizontal site velocities within ITRF2000 adopting a robust estimation method with Tukey's biweight function to the time series of site position measured until the end of 2011. Substituting the synthetic rigid block motions of the Amurian Plate from the velocities within ITRF2000, we obtained the following site velocities with respect to the Amurian Plate [Tadokoro et al., 2012]: KMN 41±4 mm/y, N77±7W KMS 43±5 mm/y, N80±6W KME 42±5 mm/y, N80±7W In contrast, the on-land GPS horizontal velocities along the coast is 23-33 mm/y toward N74-80W. The present observational results show: (1) the velocity vectors are all the same length and direction, which indicates no internal deformation in this region; (2) the back-slip model predicts that the plate interface beneath the region is uniformly locked with coupling ratios of 60-80 %, indicating strain accumulation that will be released during the anticipated mega-thrust Tonankai earthquake; and (3) the directions of site velocities differ from that of convergence vector by 20 degrees, which is affected by

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

    NASA Astrophysics Data System (ADS)

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

    2018-05-01

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

  20. Intersubband energies in strain-compensated InGaN/AlInN quantum well structures

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

    Park, Seoung-Hwan, E-mail: shpark@cu.ac.kr; Ahn, Doyeol

    2016-01-15

    Intersubband transition energies in the conduction band for strain-compensated InGaN/AlInN quantum well (QW) structures were investigated as a function of strain based on an effective mass theory with the nonparabolicity taken into account. In the case of an InGaN/AlInN QW structure lattice-matched to GaN, the wavelength is shown to be longer than 1.55 μm. On the other hand, strain-compensated QW structures show that the wavelength of 1.55 μm can be reached even for the QW structure with a relatively small strain of 0.3 %. Hence, the strain-compensated QW structures can be used for telecommunication applications at 1.55 μm with amore » small strain, compared to conventional GaN/AlN QW structure.« less

  1. The Breeding of a Pigment Mutant Strain of Steroid Hydroxylation Aspergillus Flavus by Low Energy Ion Implantation

    NASA Astrophysics Data System (ADS)

    Ye, Hui; Ma, Jingming; Feng, Chun; Cheng, Ying; Zhu, Suwen; Cheng, Beijiu

    2009-02-01

    In the process of the fermentation of steroid C11α-hydroxylgenation strain Aspergillus flavus AF-ANo208, a red pigment is derived, which will affect the isolation and purification of the target product. Low energy ion beam implantation is a new tool for breeding excellent mutant strains. In this study, the ion beam implantation experiments were performed by infusing two different ions: argon ion (Ar+) and nitrogen ion (N+). The results showed that the optimal ion implantation was N+ with an optimum dose of 2.08 × 1015 ions/cm2, with which the mutant strain AF-ANm16 that produced no red pigment was obtained. The strain had high genetic stability and kept the strong capacity of C11α-hydroxylgenation, which could be utilized in industrial fermentation. The differences between the original strain and the mutant strain at a molecular level were analyzed by randomly amplified polymorphic DNA (RAPD). The results indicated that the frequency of variation was 7.00%, which would establish the basis of application investigation into the breeding of pigment mutant strains by low energy ion implantation.

  2. InSAR observations of strain accumulation and fault creep along the Chaman Fault system, Pakistan and Afghanistan

    NASA Astrophysics Data System (ADS)

    Fattahi, Heresh; Amelung, Falk

    2016-08-01

    We use 2004-2011 Envisat synthetic aperture radar imagery and InSAR time series methods to estimate the contemporary rates of strain accumulation in the Chaman Fault system in Pakistan and Afghanistan. At 29 N we find long-term slip rates of 16 ± 2.3 mm/yr for the Ghazaband Fault and of 8 ± 3.1 mm/yr for the Chaman Fault. This makes the Ghazaband Fault one of the most hazardous faults of the plate boundary zone. We further identify a 340 km long segment displaying aseismic surface creep along the Chaman Fault, with maximum surface creep rate of 8.1 ± 2 mm/yr. The observation that the Chaman Fault accommodates only 30% of the relative plate motion between India and Eurasia implies that the remainder is accommodated south and east of the Katawaz block microplate.

  3. Energy harvesting from vibration of Timoshenko nanobeam under base excitation considering flexoelectric and elastic strain gradient effects

    NASA Astrophysics Data System (ADS)

    Managheb, S. A. M.; Ziaei-Rad, S.; Tikani, R.

    2018-05-01

    The coupling between polarization and strain gradients is called flexoelectricity. This phenomenon exists in all dielectrics with any symmetry. In this paper, energy harvesting from a Timoshenko beam is studied by considering the flexoelectric and strain gradient effects. General governing equations and related boundary conditions are derived using Hamilton's principle. The flexoelectric effects are defined by gradients of normal and shear strains which lead to a more general model. The developed model also covers the classical Timoshenko beam theory by ignoring the flexoelectric effect. Based on the developed model, flexoelectricity effect on dielectric beams and energy harvesting from cantilever beam under harmonic base excitation is investigated. A parametric study was conducted to evaluate the effects of flexoelectric coefficients, strain gradient constants, base acceleration and the attaching tip mass on the energy harvested from a cantilever Timoshenko beam. Results show that the flexoelectricity has a significant effect on the energy harvester performance, especially in submicron and nano scales. In addition, this effect makes the beam to behave softer than before and also it changes the harvester first resonance frequency. The present study provides guidance for flexoelectric nano-beam analysis and a method to evaluate the performance of energy harvester in nano-dielectric devices.

  4. 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.

  5. Dynamic behaviour analysis of an energy accumulation system comprising a composite flywheel

    NASA Astrophysics Data System (ADS)

    Portnov, G. G.; Kulakov, V. L.; Barinov, I. N.

    1994-01-01

    A simple system for energy accumulation comprising a rim and a massive shaft with elastic couplings was considered; the shaft runs in elastic damping bearings. Forced vibrations of the flywheel system induced by linear and angular eccentricities of composite rim were investigated. The effect of variation of different parameters of the system (stiffness of bearings, viscous friction coefficients of bearings, mass and moment of inertia of the shaft) on damping of radial and angular forced vibrations has been estimated.

  6. Paenibacillus pabuli strain P7S promotes plant growth and induces anthocyanin accumulation in Arabidopsis thaliana.

    PubMed

    Trinh, Cao Son; Jeong, Chan Young; Lee, Won Je; Truong, Hai An; Chung, Namhyun; Han, Juhyeong; Hong, Suk-Whan; Lee, Hojoung

    2018-06-01

    In this study, a novel plant growth-promoting rhizobacteria (PGPR), the bacterial strain Paenibacillus pabuli P7S (PP7S), showed promising plant growth-promoting effects. Furthermore, it induced anthocyanin accumulation in Arabidopsis. When co-cultivated with PP7S, there was a significant increase in anthocyanin content and biomass of Arabidopsis seedlings compared with those of the control. The quantitative reverse transcription-polymerase chain reaction analysis revealed higher expression of many key genes regulating anthocyanin and flavonoid biosynthesis pathways in PP7S-treated seedlings when compared with that of the control. Furthermore, higher expression of pathogen-related genes and microbe-associated molecular pattern genes was also observed in response to PP7S, indicating that the PGPR triggered the induced systemic response (ISR) in A. thaliana. These results suggest that PP7S promotes plant growth in A. thaliana and increases anthocyanin biosynthesis by triggering specific ISRs in plant. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

  7. Strain energy density and surface layer energy for a crack-like ellipse

    NASA Technical Reports Server (NTRS)

    Kipp, M. E.; Sih, G. C.

    1973-01-01

    Some of the fundamental concepts of sharp crack fracture criteria are applied to cracks and narrow ellipses. The strain energy density theory is extended to notch boundaries, where the energy in a surface layer is calculated and the location of failure initiation is determined. The concept of a core region near the notch tip, and its consequences, are examined in detail. The example treated is that of an elliptical cavity loaded uniformly at a large distance from the hole, and at an angle to the hole; the results are shown to approach that of the crack solution for narrow ellipses, and to display quite satisfactory agreement with recently published experimental data under both tensile and compressive loading conditions. Results also indicate that in globally unstable configurations in brittle materials, the original loading and notch geometry are sufficient to predict the subsequent crack trajectory with considerable accuracy.

  8. Characterization of Scenedesmus obtusiusculus AT-UAM for high-energy molecules accumulation: deeper insight into biotechnological potential of strains of the same species.

    PubMed

    Toledo-Cervantes, Alma; Garduño Solórzano, Gloria; Campos, Jorge E; Martínez-García, Martha; Morales, Marcia

    2018-03-01

    Scenedesmus obtusiusculus AT-UAM, isolated from Cuatro Ciénegas wetlands in Mexico was taxonomically, molecularly and biochemically compared to S. obtusiusculus CCAP 276/25 (Culture Collection of Algae and Protozoa, Scotland, UK). Analysis of Internal Transcribed Spacer 2 (ITS2) secondary structures confirmed that the mexican strain belongs to S. obtusiusculus with one change in the ITS2 nucleotide sequence. However, both strains exhibited different biochemical and fatty acid profiles and therefore biotechnological potential, emphasizing the need for deeper studies among strains of the same species. Furthermore, the biochemical variations of S. obtusiusculus AT-UAM under nitrogen starvation and different levels of irradiance were evaluated. The maximum lipid production (1730 mg L -1 ) was obtained at 613 μmol m -2  s -1 while the highest carbohydrate content (49%) was achieved at 896 μmol m -2  s -1 . Additionally, this strain was capable of storing lipids (∼52%) and carbohydrates (∼40%) under outdoor condition depending on the light availability in the cultivation broth.

  9. Arsenic accumulation by the aquatic fern Azolla: comparison of arsenate uptake, speciation and efflux by A. caroliniana and A. filiculoides.

    PubMed

    Zhang, Xin; Lin, Ai-Jun; Zhao, Fang-Jie; Xu, Guo-Zhong; Duan, Gui-Lan; Zhu, Yong-Guan

    2008-12-01

    This study investigates As accumulation and tolerance of the aquatic fern Azolla. Fifty strains of Azolla showed a large variation in As accumulation. The highest- and lowest-accumulating ferns among the 50 strains were chosen for further investigations. Azolla caroliniana accumulated two times more As than Azolla filiculoides owing to a higher influx velocity for arsenate. A. filiculoides was more resistant to external arsenate due to a lower uptake. Both strains showed a similar degree of tolerance to internal As. Arsenate and arsenite were the dominant As species in both Azolla strains, with methylated As species accounting for <5% of the total As. A. filiculoides had a higher proportion of arsenite than A. caroliniana. Both strains effluxed more arsenate than arsenite, and the amount of As efflux was proportional to the amount of As accumulation. The potential of growing Azolla in paddy fields to reduce As transfer from soil and water to rice should be further evaluated.

  10. Strain energy storage and dissipation rate in active cell mechanics

    NASA Astrophysics Data System (ADS)

    Agosti, A.; Ambrosi, D.; Turzi, S.

    2018-05-01

    When living cells are observed at rest on a flat substrate, they can typically exhibit a rounded (symmetric) or an elongated (polarized) shape. Although the cells are apparently at rest, the active stress generated by the molecular motors continuously stretches and drifts the actin network, the cytoskeleton of the cell. In this paper we theoretically compare the energy stored and dissipated in this active system in two geometric configurations of interest: symmetric and polarized. We find that the stored energy is larger for a radially symmetric cell at low activation regime, while the polar configuration has larger strain energy when the active stress is beyond a critical threshold. Conversely, the dissipation of energy in a symmetric cell is always larger than that of a nonsymmetric one. By a combination of symmetry arguments and competition between surface and bulk stress, we argue that radial symmetry is an energetically expensive metastable state that provides access to an infinite number of lower-energy states, the polarized configurations.

  11. Strain energy storage and dissipation rate in active cell mechanics.

    PubMed

    Agosti, A; Ambrosi, D; Turzi, S

    2018-05-01

    When living cells are observed at rest on a flat substrate, they can typically exhibit a rounded (symmetric) or an elongated (polarized) shape. Although the cells are apparently at rest, the active stress generated by the molecular motors continuously stretches and drifts the actin network, the cytoskeleton of the cell. In this paper we theoretically compare the energy stored and dissipated in this active system in two geometric configurations of interest: symmetric and polarized. We find that the stored energy is larger for a radially symmetric cell at low activation regime, while the polar configuration has larger strain energy when the active stress is beyond a critical threshold. Conversely, the dissipation of energy in a symmetric cell is always larger than that of a nonsymmetric one. By a combination of symmetry arguments and competition between surface and bulk stress, we argue that radial symmetry is an energetically expensive metastable state that provides access to an infinite number of lower-energy states, the polarized configurations.

  12. Peptostreptococcus productus strain that grows rapidly with CO as the energy source.

    PubMed Central

    Lorowitz, W H; Bryant, M P

    1984-01-01

    Anaerobic bacteria were enriched with a sewage digestor sludge inoculum and a mineral medium supplemented with B-vitamins and 0.05% yeast extract and with a 50% CO-30% N2-20% CO2 (2 atm [202 kPa]) gas phase. Microscopic observation revealed an abundance of gram-positive cocci, 1.0 by 1.4 micron, which occurred in pairs or chains. The coccus, strain U-1, was isolated by using roll tubes with CO as the energy source. Based on morphology, sugars fermented, fermentation products from glucose (H2, acetate, lactate, and succinate), and other features, strain U-1 was identified as Peptostreptococcus productus IIb (similar to the type strain). The doubling time with up to 50% CO was 1.5 h; acetate and CO2 were the major products. In addition, no significant change in the doubling time was observed with 90% CO. Some stock strains were also able to use CO, although not as well. Strain U-1 produced acetate during growth with H2-CO2. Other C1 compounds did not support growth. Most probable numbers of CO utilizers morphologically identical with strain U-1 were 7.5 X 10(6) and 1.1 X 10(5) cells per g for anaerobic digestor sludge and human feces, respectively. PMID:6430231

  13. Accumulation of intra-cellular polyphosphate in Chlorella vulgaris cells is related to indole-3-acetic acid produced by Azospirillum brasilense.

    PubMed

    Meza, Beatriz; de-Bashan, Luz E; Hernandez, Juan-Pablo; Bashan, Yoav

    2015-06-01

    Accumulation of intra-cellular phosphate, as polyphosphate, was measured when the microalga Chlorella vulgaris was immobilized in alginate with either of two wild-type strains of the microalgae growth-promoting bacterium Azospirillum brasilense or their corresponding IAA-attenuated mutants. Wild type strains of A. brasilense induced higher amounts of intra-cellular phosphate in Chlorella than their respective mutants. Calculations comparing intra-cellular phosphate accumulation by culture or net accumulation by the cell and the amount of IAA that was produced by each of these strains revealed that higher IAA was linked to higher accumulations of intra-cellular phosphate. Application of four levels of exogenous IAA reported for A. brasilense and their IAA-attenuated mutants to cultures of C. vulgaris enhanced accumulation of intra-cellular phosphate; the higher the content of IAA per culture or per single cell, the higher was the amount of accumulated phosphate. When an IAA-attenuated mutant was complemented with exogenous IAA, accumulation of intra-cellular phosphate at the culture level was even higher than phosphate accumulation with the respective wild type strains. When calculating the net accumulation of intra-cellular phosphate in the complementation experiment, net intra-cellular phosphate induced by the IAA-attenuated mutant was completely restored and was similar to the wild strains. We propose that IAA produced by A. brasilense is linked to polyphosphate accumulation in C. vulgaris. Copyright © 2015 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

  14. Changing Surface-Atmosphere Energy Exchange and Refreezing Capacity of the Lower Accumulation Area, West Greenland

    NASA Astrophysics Data System (ADS)

    Charalampidis, C.; van As, D.; Machguth, H.; Smeets, P.; van den Broeke, M. R.; Box, J. E.

    2014-12-01

    We present five years (2009-2013) of automatic weather station (AWS) data from the lower accumulation area (1840 m above sea level) of the Kangerlussuaq region, western Greenland ice sheet. The summers of 2010 and 2012 were both exceptionally warm, but only 2012 resulted in negative surface mass budget (SMB) and surface runoff. The observed runoff was due to a large ice fraction in the upper 10 m of firn that prevented melt water from percolating to available pore space below. Analysis of the in situ data reveals a relatively low 2012 summer albedo of ~0.7 as melt water was present at the surface. Consequently, during the 2012 melt season the surface absorbed 30% (213 MJ m-2) more solar radiation than in 2010. We drive a surface energy balance model with the AWS data to evaluate the seasonal and interannual variability of all surface energy fluxes. The model is able to reproduce the observed melt rates as well as the SMB for each season. While the drive for melt is solar radiation, year-to-year differences are controlled by terrestrial radiation, apart from 2012 when solar radiation dominated melt. Sensitivity tests reveal that 72% of the excess solar energy in 2012 was used for melt, corresponding to 40% (0.67 m) of the 2012 surface ablation. The remaining ablation (0.99 m) was primarily due to the relatively high atmospheric temperatures up to +2.6 °C daily average, indicating that 2012 would have been a negative SMB year in the lower accumulation area even without the melt-albedo feedback. Longer time series of SMB, regional temperature and remotely sensed albedo (MODIS) suggest that 2012 was the first negative SMB year with the lowest albedo at this elevation on record. The warming conditions of the last years resulted in enhanced melt and reduction of the refreezing capacity of the lower accumulation area. If the warming continues the lower accumulation area will be transformed into superimposed ice.

  15. Fungal accumulation of metals from building materials during brown rot wood decay.

    PubMed

    Hastrup, Anne Christine Steenkjær; Jensen, Bo; Jellison, Jody

    2014-08-01

    This study analyzes the accumulation and translocation of metal ions in wood during the degradation performed by one strain of each of the three brown rot fungi; Serpula lacrymans, Meruliporia incrassata and Coniophora puteana. These fungi species are inhabitants of the built environment where the prevention and understanding of fungal decay is of high priority. This study focuses on the influence of various building materials in relation to fungal growth and metal uptake. Changes in the concentration of iron, manganese, calcium and copper ions in the decayed wood were analyzed by induced coupled plasma spectroscopy and related to wood weight loss and oxalic acid accumulation. Metal transport into the fungal inoculated wood was found to be dependent on the individual strain/species. The S. lacrymans strain caused a significant increase in total iron whereas the concentration of copper ions in the wood appeared decreased after 10 weeks of decay. Wood inoculated with the M. incrassata isolate showed the contrary tendency with high copper accumulation and low iron increase despite similar weight losses for the two strains. However, significantly lower oxalic acid accumulation was recorded in M. incrassata degraded wood. The addition of a building material resulted in increased weight loss in wood degraded by C. puteana in the soil-block test; however, this could not be directly linked specifically to the accumulation of any of the four metals recorded. The accumulation of oxalic acid seemed to influence the iron uptake. The study assessing the influence of the presence of soil and glass in the soil-block test revealed that soil contributed the majority of the metals for uptake by the fungi and contributed to increased weight loss. The varying uptake observed among the three brown rot fungi strains toward the four metals analyzed may be related to the specific non-enzymatic and enzymatic properties including bio-chelators employed by each of the species during wood

  16. Work patterns dictate energy demands and thermal strain during wildland firefighting.

    PubMed

    Cuddy, John S; Sol, Joseph A; Hailes, Walter S; Ruby, Brent C

    2015-06-01

    The purpose of this investigation was to characterize the effects of self-selected work activity on energy expenditure, water turnover, and thermal strain during wildland fire suppression. A secondary aim was to contrast current data with data collected 15 years ago using similar methods to determine whether job demands have changed. Participants (n=15, 26±3 years, 179±6 cm, 78.3±8.6 kg) were monitored for 3 days for total energy expenditure, water turnover, core and chest skin temperature, physical activity, and heart rate. Participants arrived to the mobile laboratory each morning, submitted a nude weight, ingested a temperature transmitter, provided a urine sample, and were equipped with a physiological and activity monitor. Participants completed live wildland fire suppression during their work shifts. Mean core temperature was 37.6°±0.2°C, mean chest skin temperature was 34.1°±1.0°C, mean heart rate was 112±13 beats/min, and the mean physiological strain index score was 3.3±1.0. Wildland firefighters spent 49±8%, 39±6%, and 12±2% in the sedentary, light, and moderate-vigorous intensity categories, respectively. The mean total energy expenditure was 19.1±3.9 MJ/d, similar to 1997 (17.5±6.9 MJ/d). The mean water turnover in 2012 was 9.5±1.7 L/d, which was higher (P<.05) compared with 1997-98 (7.0±1.7 L/d). Wildland firefighters do not induce consistently high cardiovascular and thermal strain while completing arduous work in a hot environment despite fairly high chest skin temperatures. The total energy expenditure in the current study suggests job demands are similar to those of 15 years ago, while the increased water turnover may reflect a change in drinking habits. Copyright © 2015 Wilderness Medical Society. Published by Elsevier Inc. All rights reserved.

  17. Heterologous expression of a thermophilic diacylglycerol acyltransferase triggers triglyceride accumulation in Escherichia coli.

    PubMed

    Lázaro, Beatriz; Villa, Juan A; Santín, Omar; Cabezas, Matilde; Milagre, Cintia D F; de la Cruz, Fernando; Moncalián, Gabriel

    2017-01-01

    Triglycerides (TAGs), the major storage molecules of metabolic energy and source of fatty acids, are produced as single cell oil by some oleogenic microorganisms. However, these microorganisms require strict culture conditions, show low carbon source flexibilities, lack efficient genetic modification tools and in some cases pose safety concerns. TAGs have essential applications such as behaving as a source for added-value fatty acids or giving rise to the production of biodiesel. Hence, new alternative methods are urgently required for obtaining these oils. In this work we describe TAG accumulation in the industrially appropriate microorganism Escherichia coli expressing the heterologous enzyme tDGAT, a wax ester synthase/triacylglycerol:acylCoA acyltranferase (WS/DGAT). With this purpose, we introduce a codon-optimized gene from the thermophilic actinomycete Thermomonospora curvata coding for a WS/DGAT into different E. coli strains, describe the metabolic effects associated to the expression of this protein and evaluate neutral lipid accumulation. We observe a direct relation between the expression of this WS/DGAT and TAG production within a wide range of culture conditions. More than 30% TAGs were detected within the bacterial neutral lipids in 90 minutes after induction. TAGs were observed to be associated with the hydrophobic enzyme while forming round intracytoplasmic bodies, which could represent a bottleneck for lipid accumulation in E. coli. We detected an increase of almost 3-fold in the monounsaturated fatty acids (MUFA) occurring in the recombinant strains. These MUFA were predominant in the accumulated TAGs achieving 46% of the TAG fatty acids. These results set the basis for further research on the achievement of a suitable method towards the sustainable production of these neutral lipids.

  18. Epilepsy, regulation of brain energy metabolism and neurotransmission.

    PubMed

    Cloix, Jean-François; Hévor, Tobias

    2009-01-01

    Seizures are the result of a sudden and temporary synchronization of neuronal activity, the reason for which is not clearly understood. Astrocytes participate in the control of neurotransmitter storage and neurotransmission efficacy. They provide fuel to neurons, which need a high level of energy to sustain normal and pathological neuronal activities, such as during epilepsy. Various genetic or induced animal models have been developed and used to study epileptogenic mechanisms. Methionine sulfoximine induces both seizures and the accumulation of brain glycogen, which might be considered as a putative energy store to neurons in various animals. Animals subjected to methionine sulfoximine develop seizures similar to the most striking form of human epilepsy, with a long pre-convulsive period of several hours, a long convulsive period during up to 48 hours and a post convulsive period during which they recover normal behavior. The accumulation of brain glycogen has been demonstrated in both the cortex and cerebellum as early as the pre-convulsive period, indicating that this accumulation is not a consequence of seizures. The accumulation results from an activation of gluconeogenesis specifically localized to astrocytes, both in vivo and in vitro. Both seizures and brain glycogen accumulation vary when using different inbred strains of mice. C57BL/6J is the most "resistant" strain to methionine sulfoximine, while CBA/J is the most "sensitive" one. The present review describes the data obtained on methionine sulfoximine dependent seizures and brain glycogen in the light of neurotransmission, highlighting the relevance of brain glycogen content in epilepsies.

  19. Enhanced saturated fatty acids accumulation in cultures of newly-isolated strains of Schizochytrium sp. and Thraustochytriidae sp. for large-scale biodiesel production.

    PubMed

    Wang, Qiuzhen; Sen, Biswarup; Liu, Xianhua; He, Yaodong; Xie, Yunxuan; Wang, Guangyi

    2018-08-01

    Heterotrophic marine protists (Thraustochytrids) have received increasingly global attention as a renewable, sustainable and alternative source of biodiesel because of their high ability of saturated fatty acids (SFAs) accumulation. Yet, the influence of extrinsic factors (nutrients and environmental conditions) on thraustochytrid culture and optimal conditions for high SFAs production are poorly described. In the present study, two different thraustochytrid strains, Schizochytrium sp. PKU#Mn4 and Thraustochytriidae sp. PKU#Mn16 were studied for their growth and SFAs production profiles under various conditions (carbon, nitrogen, temperature, pH, KH 2 PO 4 , salinity, and agitation speed). Of the culture conditions, substrates (C and N) source and conc., temperature, and agitation speed significantly influenced the cell growth and SFAs production of both strains. Although both the strains were capable of growth and SFAs production in the broad range of culture conditions, their physiological responses to KH 2 PO 4 , pH, and salinity were dissimilar. Under their optimal batch culture conditions, peak SFAs productions of 3.3g/L and 2.2g/L with 62% and 49% SFAs contents (relative to total fatty acids) were achieved, respectively. The results of 5-L fed-batch fermentation under optimal conditions showed a nearly 4.5-fold increase in SFAs production (i.e., 7.5g/L) by both strains compared to unoptimized conditions. Of the two strains, the quality of biodiesel produced from the fatty acids of PKU#Mn4 met the biodiesel standard defined by ASTM6751. This study, to the knowledge of the authors, is the first comprehensive report of optimal fermentation conditions demonstrating enhanced SFAs production by strains belonging to two different thraustochytrid genera and provides the basis for large-scale biodiesel production. Copyright © 2018. Published by Elsevier B.V.

  20. Screening of bacterial strains isolated from uranium mill tailings porewaters for bioremediation purposes.

    PubMed

    Sánchez-Castro, Iván; Amador-García, Ahinara; Moreno-Romero, Cristina; López-Fernández, Margarita; Phrommavanh, Vannapha; Nos, Jeremy; Descostes, Michael; Merroun, Mohamed L

    2017-01-01

    The present work characterizes at different levels a number of bacterial strains isolated from porewaters sampled in the vicinity of two French uranium tailing repositories. The 16S rRNA gene from 33 bacterial isolates, corresponding to the different morphotypes recovered, was almost fully sequenced. The resulting sequences belonged to 13 bacterial genera comprised in the phyla Firmicutes, Actinobacteria and Proteobacteria. Further characterization at physiological level and metals/metalloid tolerance provided evidences for an appropriate selection of bacterial strains potentially useful for immobilization of uranium and other common contaminants. By using High Resolution Transmission Electron Microscope (HRTEM), this potential ability to immobilize uranium as U phosphate mineral phases was confirmed for the bacterial strains Br3 and Br5 corresponding to Arthrobacter sp. and Microbacterium oxydans, respectively. Scanning Transmission Electron Microscope- High-Angle Annular Dark-Field (STEM-HAADF) analysis showed U accumulates on the surface and within bacterial cytoplasm, in addition to the extracellular space. Energy Dispersive X-ray (EDX) element-distribution maps demonstrated the presence of U and P within these accumulates. These results indicate the potential of certain bacterial strains isolated from porewaters of U mill tailings for immobilizing uranium, likely as uranium phosphates. Some of these bacterial isolates might be considered as promising candidates in the design of uranium bioremediation strategies. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. Steroid catechol degradation: disecoandrostane intermediates accumulated by Pseudomonas transposon mutant strains.

    PubMed

    Leppik, R A

    1989-07-01

    Eleven transposon mutant strains affected in bile acid catabolism were each found to form yellow, muconic-like intermediates from bile acids. To characterize these unstable intermediates, media from the growth of one of these mutants with deoxycholic acid was treated with ammonia, then the crude product was methylated with diazomethane. Four compounds were subsequently isolated; spectral evidence suggested that they were methyl 12 alpha-hydroxy-3-oxo-23,24-dinorchola-1,4-dien-22-oate, methyl 4-aza-12 beta-hydroxy-9(10)-secoandrosta-1,3,5-triene-9,17-dione-3-carboxyl ate, 4-aza-9 alpha, 12 beta-dihydroxy-9(10)-secoandrosta-1,3,5-trien-17-one-3- methyl carboxylate and 4 alpha-[3'-propionic acid]-5-amino-7 beta-hydroxy-7 alpha beta-methyl- 3a alpha, 4,7,7a-tetrahydro-1-indanone-delta-lactam. It is proposed that the mutants are blocked in the utilization of such muconic-like compounds as the 3,12 beta-dihydroxy-5,9,17-trioxo-4(5),9(10)- disecoandrostal (10),2-dien-4-oic acid formed from deoxycholic acid. A further mutant was examined, which converted deoxycholic acid to 12 alpha-hydroxyandrosta-1,4-dien-3,17-dione, but accumulated yellow products from steroids which lacked a 12 alpha-hydroxy function, such as chenodeoxycholic acid. The products from the latter acid were treated as above; spectral evidence suggested that the two compounds isolated were methyl 4-aza-7-hydroxy-9(10)-secoandrosta-1,3,5- triene-9,17-dione-3-carboxylate and 4 alpha-[1'alpha-hydroxy-3'-propionic acid]-5-amino-7a beta-methyl-3a alpha,4,7,7a-tetrahydro-1-indanone-delta-lactam.

  2. Rock Fracture Toughness Under Mode II Loading: A Theoretical Model Based on Local Strain Energy Density

    NASA Astrophysics Data System (ADS)

    Rashidi Moghaddam, M.; Ayatollahi, M. R.; Berto, F.

    2018-01-01

    The values of mode II fracture toughness reported in the literature for several rocks are studied theoretically by using a modified criterion based on strain energy density averaged over a control volume around the crack tip. The modified criterion takes into account the effect of T-stress in addition to the singular terms of stresses/strains. The experimental results are related to mode II fracture tests performed on the semicircular bend and Brazilian disk specimens. There are good agreements between theoretical predictions using the generalized averaged strain energy density criterion and the experimental results. The theoretical results reveal that the value of mode II fracture toughness is affected by the size of control volume around the crack tip and also the magnitude and sign of T-stress.

  3. Accumulation of radionuclides from radioactive substrata by some micromycetes.

    PubMed

    Zhdanova, N N; Redchits, T I; Zheltonozhsky, V A; Sadovnikov, L V; Gerzabek, M H; Olsson, S; Strebl, F; Mück, K

    2003-01-01

    Overgrowing (interaction) and dissolution of intact and milled hot particles by various micromycetes were studied under laboratory conditions. Hot particles used for the investigation originated from the Chernobyl accident release and atomic bomb testing sites. The micromycetes investigated were mitosporic fungi mainly isolated from the Chernobyl site and vicinity. Most of the fungal species and strains showed a tendency to grow towards the hot particle, overgrow it and dissolve it after prolonged contact. The accumulation (absorption and adsorption) of radionuclides from intact hot particles was generally more intensive for (152)Eu than for (137)Cs by a factor of about 2.6-134, while in experiments with milled samples the (152)Eu and (137)Cs accumulation was similar, except for some fungal species, which showed higher (152)Eu than (137)Cs sorption. It could be shown that the main factors influencing Cs and Eu accumulation in fungi are: fungal species and strains and the size and composition of the hot particle.

  4. Nondestructive strain depth profiling with high energy X-ray diffraction: System capabilities and limitations

    NASA Astrophysics Data System (ADS)

    Zhang, Zhan; Wendt, Scott; Cosentino, Nicholas; Bond, Leonard J.

    2018-04-01

    Limited by photon energy, and penetration capability, traditional X-ray diffraction (XRD) strain measurements are only capable of achieving a few microns depth due to the use of copper (Cu Kα1) or molybdenum (Mo Kα1) characteristic radiation. For deeper strain depth profiling, destructive methods are commonly necessary to access layers of interest by removing material. To investigate deeper depth profiles nondestructively, a laboratory bench-top high-energy X-ray diffraction (HEXRD) system was previously developed. This HEXRD method uses an industrial 320 kVp X-Ray tube and the Kα1 characteristic peak of tungsten, to produces a higher intensity X-ray beam which enables depth profiling measurement of lattice strain. An aluminum sample was investigated with deformation/load provided using a bending rig. It was shown that the HEXRD method is capable of strain depth profiling to 2.5 mm. The method was validated using an aluminum sample where both the HEXRD method and the traditional X-ray diffraction method gave data compared with that obtained using destructive etching layer removal, performed by a commercial provider. The results demonstrate comparable accuracy up to 0.8 mm depth. Nevertheless, higher attenuation capabilities in heavier metals limit the applications in other materials. Simulations predict that HEXRD works for steel and nickel in material up to 200 µm, but experiment results indicate that the HEXRD strain profile is not practical for steel and nickel material, and the measured diffraction signals are undetectable when compared to the noise.

  5. Developmental accumulation of inorganic polyphosphate affects germination and energetic metabolism in Dictyostelium discoideum

    PubMed Central

    Livermore, Thomas Miles; Chubb, Jonathan Robert; Saiardi, Adolfo

    2016-01-01

    Inorganic polyphosphate (polyP) is composed of linear chains of phosphate groups linked by high-energy phosphoanhydride bonds. However, this simple, ubiquitous molecule remains poorly understood. The use of nonstandardized analytical methods has contributed to this lack of clarity. By using improved polyacrylamide gel electrophoresis we were able to visualize polyP extracted from Dictyostelium discoideum. We established that polyP is undetectable in cells lacking the polyphosphate kinase (DdPpk1). Generation of this ppk1 null strain revealed that polyP is important for the general fitness of the amoebae with the mutant strain displaying a substantial growth defect. We discovered an unprecedented accumulation of polyP during the developmental program, with polyP increasing more than 100-fold. The failure of ppk1 spores to accumulate polyP results in a germination defect. These phenotypes are underpinned by the ability of polyP to regulate basic energetic metabolism, demonstrated by a 2.5-fold decrease in the level of ATP in vegetative ppk1. Finally, the lack of polyP during the development of ppk1 mutant cells is partially offset by an increase of both ATP and inositol pyrophosphates, evidence for a model in which there is a functional interplay between inositol pyrophosphates, ATP, and polyP. PMID:26755590

  6. Characterization of cadmium-resistant bacteria and their potential for reducing accumulation of cadmium in rice grains.

    PubMed

    Lin, Xiaoyan; Mou, Renxiang; Cao, Zhaoyun; Xu, Ping; Wu, Xiaoliang; Zhu, Zhiwei; Chen, Mingxue

    2016-11-01

    Cadmium (Cd) pollution is a serious widespread environmental problem that not only destroys the microbial ecology of soil and decreases crop production, but also poses a serious risk to human health. Many methods have been used for the remediation of Cd pollution but none of these is totally satisfactory. Microbial remediation strategies have attracted increasing interest since they are environmentally friendly and cost-effective. In the present study, three Cd-resistant bacteria were isolated and evaluated for potential application in Cd bioremediation. Based on their morphological, physiological and biochemical characteristics, together with 16S rDNA gene sequence analyses, bacteria were identified as Stenotrophomonas acidaminiphila (2#), Pseudomonas aeruginosa (9#) and Delftia tsuruhatensis (12#). Pseudomonas aeruginosa showed very high tolerance to metals, especially Cd (2200mg/L), Zn (1800mg/L) and Pb (1200mg/L), and is thought to be a multi-metal-resistant bacterium. Pseudomonas aeruginosa was also sensitive to 13 different antibiotics. The effects of the bacterial strains on the growth of rice plants and their ability to reduce Cd accumulation from Cd-contaminated soils in pot experiments were also evaluated. For Oryza sativa L. A grown in contaminated soil (3mg/kg Cd), the accumulation of Cd was decreased by 31.2 and 25.5% in brown rice and polished rice, respectively, by strain 9#; Pseudomonas aeruginosa was more effective in reducing Cd accumulation in rice grains than a mixture of strains. For Oryza sativa L. B, a mixture of strains acting synergistically was more effective than a single strain in reducing Cd accumulation; treatment with mixed strains (strains+3mg/kg Cd) resulted in 41.3, 35.9, and 32.6% reductions in Cd accumulation in unhulled rice, brown rice and polished rice, respectively. Although different results were obtained for two rice varieties, it can still be concluded that Cd-resistant bacteria are suitable for reducing Cd accumulation in

  7. Accumulation of Polyphosphate in Lactobacillus spp. and Its Involvement in Stress Resistance

    PubMed Central

    Alcántara, Cristina; Blasco, Amalia; Zúñiga, Manuel

    2014-01-01

    Polyphosphate (poly-P) is a polymer of phosphate residues synthesized and in some cases accumulated by microorganisms, where it plays crucial physiological roles such as the participation in the response to nutritional stringencies and environmental stresses. Poly-P metabolism has received little attention in Lactobacillus, a genus of lactic acid bacteria of relevance for food production and health of humans and animals. We show that among 34 strains of Lactobacillus, 18 of them accumulated intracellular poly-P granules, as revealed by specific staining and electron microscopy. Poly-P accumulation was generally dependent on the presence of elevated phosphate concentrations in the culture medium, and it correlated with the presence of polyphosphate kinase (ppk) genes in the genomes. The ppk gene from Lactobacillus displayed a genetic arrangement in which it was flanked by two genes encoding exopolyphosphatases of the Ppx-GppA family. The ppk functionality was corroborated by its disruption (LCABL_27820 gene) in Lactobacillus casei BL23 strain. The constructed ppk mutant showed a lack of intracellular poly-P granules and a drastic reduction in poly-P synthesis. Resistance to several stresses was tested in the ppk-disrupted strain, showing that it presented a diminished growth under high-salt or low-pH conditions and an increased sensitivity to oxidative stress. These results show that poly-P accumulation is a characteristic of some strains of lactobacilli and may thus play important roles in the physiology of these microorganisms. PMID:24375133

  8. Screening high oleaginous Chlorella strains from different climate zones.

    PubMed

    Xu, Jin; Hu, Hanhua

    2013-09-01

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

  9. Proteomics analysis of high lipid-producing strain Mucor circinelloides WJ11: an explanation for the mechanism of lipid accumulation at the proteomic level.

    PubMed

    Tang, Xin; Zan, Xinyi; Zhao, Lina; Chen, Haiqin; Chen, Yong Q; Chen, Wei; Song, Yuanda; Ratledge, Colin

    2016-02-11

    The oleaginous fungus, Mucor circinelloides, is attracting considerable interest as it produces oil rich in γ-linolenic acid. Nitrogen (N) deficiency is a common strategy to trigger the lipid accumulation in oleaginous microorganisms. Although a simple pathway from N depletion in the medium to lipid accumulation has been elucidated at the enzymatic level, global changes at protein levels upon N depletion have not been investigated. In this study, we have systematically analyzed the changes at the levels of protein expression in M. circinelloides WJ11, a high lipid-producing strain (36 %, lipid/cell dry weight), during lipid accumulation. Proteomic analysis demonstrated that N depletion increased the expression of glutamine synthetase, involved in ammonia assimilation, for the supply of cellular nitrogen but decreased the metabolism of amino acids. Upon N deficiency, many proteins (e.g., fructose-bisphosphate aldolase, glyceraldehyde-3-phosphate dehydrogenase, enolase, pyruvate kinase) involved in glycolytic pathway were up-regulated while proteins involved in the tricarboxylic acid cycle (e.g., isocitrate dehydrogenase, succinyl-CoA ligase, succinate dehydrogenase, fumarate hydratase) were down-regulated, indicating this activity was retarded thereby leading to a greater flux of carbon into fatty acid biosynthesis. Moreover, glucose-6-phosphate dehydrogenase, transaldolase and transketolase, which participate in the pentose phosphate pathway, were up-regulated, leading to the increased production of NADPH, the reducing power for fatty acid biosynthesis. Furthermore, protein and nucleic acid metabolism were down-regulated and some proteins involved in energy metabolism, signal transduction, molecular chaperone and redox homeostasis were up-regulated upon N depletion, which may be the cellular response to the stress produced by the onset of N deficiency. N limitation increased those expressions of the proteins involved in ammonia assimilation but decreased that

  10. Interseismic strain accumulation across the Ashkabad fault (NE Iran) from MERIS-corrected ASAR data

    NASA Astrophysics Data System (ADS)

    Walters, R. J.; Elliott, J. R.; Li, Z.; Parsons, B. E.

    2011-12-01

    The right-lateral Ashkabad Fault separates deforming NE Iran from the stable Turkmenistan platform to the north, and also facilitates the north-westwards extrusion of the South Caspian block (along with the left-lateral Shahrud fault zone). The fault represents the northernmost boundary of significant deformation of the Arabia-Eurasia collision in NE Iran. The 1948 M 7.3 Ashkabad earthquake, which killed around 110,000 people and was the deadliest earthquake to hit Europe or the Middle East in the 20th Century, also possibly occurred on this fault. However, the slip rate and therefore the seismic hazard that the Ashkabad fault represents are not well known. GPS data in NE Iran are sparse, and there are no direct geological or quaternary rates for the main strand of the fault. We use Envisat ASAR data acquired between 2003 and 2010 to measure interseismic strain accumulation across the fault, and hence estimate the slip rate across it. Due to the proximity of this region to the Caspian Sea and the presence of highly variable weather systems, we use data from Envisat's Medium Resolution Imaging Spectrometer (MERIS) instrument, as well as modelled weather data from the European Centre for Medium-Range Weather Forecasting (ECMWF), to correct interferograms for differences in water vapour and atmospheric pressure. We mitigate the effects of remaining noise by summing the 13 corrected interferograms that cover the fault, effectively creating a 30 year interferogram with improved signal-to-noise ratio, and we empirically correct for orbital errors. Our measurements of rates of displacement are consistent with an interseismic model for the Ashkabad fault where deformation occurs at depth on a narrow shear zone below a layer in which the fault is locked. We invert the data to solve for best fitting model parameters, estimating both the slip rate and the depth to which the fault is locked. Our measurements show that the Ashkabad fault is accumulating strain at a rate of 9 mm

  11. Slow slip events in Guerrero, Mexico, and consequences on strain accumulation over the past 15 years.

    NASA Astrophysics Data System (ADS)

    Radiguet, M.; Cotton, F.; Cavalié, O.; Pathier, E.; Kostoglodov, V.; Vergnolle, M.; Campillo, M.; Walpersdorf, A.; Cotte, N.; Santiago, J.; Franco, S.

    2012-12-01

    Continuous Global Positioning System (cGPS) time series in Guerrero, Mexico, reveal the widespread existence of large Slow Slip Events (SSEs) at the boundary between the Cocos and North American plates. The existence of these SSEs asks the question of how seismic and aseismic slips complement each other in subduction zones. We examined the last three SSEs that occurred in 2001/2002, 2006 and 2009/2010, and their impact on the strain accumulation along the Guerrero subduction margin. We use continuous cGPS time series and InSAR images to evaluate the surface displacement during SSEs and inter-SSE periods. The slip distributions on the plate interface associated with each SSE, as well as the inter-SSE (short-term) coupling rates are evaluated by inverting these surface displacements. Our results reveal that the three analyzed SSEs have equivalent moment magnitudes of around 7.5 and their lateral extension is variable.The slip distributions for the three SSEs show that in the Guerrero gap area, the slow slip occurs at shallower depth (updip limit around 15-20 km) than in surrounding regions. The InSAR data provide additional information for the 2006 SSE. The joint inversion of InSAR and cGPS data confirms the lateral variation of the slip distribution along the trench, with shallower slip in the Guerrero seismic gap, west of Acapulco, and deeper slip further east. Inversion of inter-SSE displacement rates reveal that during the inter-SSE time intervals, the interplate coupling is high in the area where the slow slip subsequently occurs. Over a 12 year period, corresponding to three cycles of SSEs, our results reveal that the accumulated slip deficit in the Guerrero gap area is only ¼ of the slip deficit accumulated on both sides of the gap. Moreover, the regions of large slip deficit coincide with the rupture areas of recent large earthquakes. We conclude that the SSEs account for a major portion of the overall moment release budget in the Guerrero gap. If large

  12. Evaluation of elastic strain energy of spheroidal inclusions with uniform volumetric and shear eigenstrains

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

    Boehm, H.J.; Fischer, F.D.; Reisner, G.

    The calculation of the elastic strain energy due to a uniform eigenstrain in an inclusion continues to be of high concern for various problems in material science such as nucleation conditions or transformation conditions for the inclusion. It is the main goal of this note to show that very easily programmable equations can be formulated for a general uniform eigenstrain tensor consisting of three different normal and three different shear strains. Although the authors appreciate the recently published results very much, they do not see any necessity to demonstrate in detail specific results since the following derivation presents a consistentmore » way to calculate the specific strain energy in very few steps. Specifically, a modified notation helps to split the usually lengthy expression into a group of easily expressible terms multiplied by the mixed product terms of the normal eigenstrains and the squares of the shear eigenstrains. Since all entities are expressed with respect to a coordinate frame attached to the inclusion any coordinate transformation can be avoided.« less

  13. GPS measurement of relative motion of the Cocos and Caribbean Plates and strain accumulation across the Middle America Trench

    NASA Astrophysics Data System (ADS)

    Dixon, Timothy H.

    1993-10-01

    Global Positioning System (GPS) measurements in 1988 and 1991 on Cocos Island (Cocos plate), San Andres Island (Caribbean plate), and Liberia (Caribbean plate, mainland Costa Rica) provide an estimate of relative motion between the Cocos and Caribbean plates. The data for Cocos and San Andres Islands, both located more than 400 km from the Middle America Trench, define a velocity that is equivalent within two standard errors (7 mm/yr rate, 5 degrees azimuth) to the NUVEL-1 plate motion model. The data for Liberia, 120 km from the trench, define a velocity that is similar in azimuth but substantially different in rate from NUVEL-1. The discrepancy can be explained with a simple model of elastic strain accumulation with a subduction zone that is locked to a relatively shallow (20±5 km) depth.

  14. Dislocation pileup as a representation of strain accumulation on a strike-slip fault

    USGS Publications Warehouse

    Savage, J.C.

    2006-01-01

    The conventional model of strain accumulation on a vertical transform fault is a discrete screw dislocation in an elastic half-space with the Burgers vector of the dislocation increasing at the rate of relative plate motion. It would be more realistic to replace that discrete dislocation by a dislocation distribution, presumably a pileup in which the individual dislocations are in equilibrium. The length of the pileup depends upon the applied stress and the amount of slip that has occurred at depth. I argue here that the dislocation pileup (the transition on the fault from no slip to slip at the full plate rate) occupies a substantial portion of the lithosphere thickness. A discrete dislocation at an adjustable depth can reproduce the surface deformation profile predicted by a pileup so closely that it will be difficult to distinguish between the two models. The locking depth (dislocation depth) of that discrete dislocation approximation is substantially (???30%) larger than that (depth to top of the pileup) in the pileup model. Thus, in inverting surface deformation data using the discrete dislocation model, the locking depth in the model should not be interpreted as the true locking depth. Although dislocation pileup models should provide a good explanation of the surface deformation near the fault trace, that explanation may not be adequate at greater distances from the fault trace because approximating the expected horizontally distributed deformation at subcrustal depths by uniform slip concentrated on the fault is not justified.

  15. Attenuated Escherichia coli strains expressing the colonization factor antigen I (CFA/I) and a detoxified heat-labile enterotoxin (LThK63) enhance clearance of ETEC from the lungs of mice and protect mice from intestinal ETEC colonization and LT-induced fluid accumulation.

    PubMed

    Byrd, Wyatt; Boedeker, Edgar C

    2013-03-15

    Although enterotoxigenic Escherichia coli (ETEC) infections are important causes of infantile and traveler's diarrhea there is no licensed vaccine available for those at-risk. Our goal is to develop a safe, live attenuated ETEC vaccine. We used an attenuated E. coli strain (O157:H7, Δ-intimin, Stx1-neg, Stx2-neg) as a vector (ZCR533) to prepare two vaccine strains, one strain expressing colonization factor antigen I (ZCR533-CFA/I) and one strain expressing CFA/I and a detoxified heat-labile enterotoxin (ZCR533-CFA/I+LThK63) to deliver ETEC antigens to mucosal sites in BALB/c mice. Following intranasal and intragastric immunization with the vaccine strains, serum IgG and IgA antibodies were measured to the CFA/I antigen, however, only serum IgG antibodies were detected to the heat-labile enterotoxin. Intranasal administration of the vaccine strains induced respiratory and intestinal antibody responses to the CFA/I and LT antigens, while intragastric administration induced only intestinal antibody responses with no respiratory antibodies detected to the CFA/I and LT antigens. Mice immunized intranasally with the vaccine strains showed enhanced clearance of wild-type (wt) ETEC bacteria from the lungs. Mice immunized intranasally and intragastrically with the vaccine strains were protected from intestinal colonization following oral challenge with ETEC wt bacteria. Mice immunized intragastrically with the ZCR533-CFA/I+LThK63 vaccine strain had less fluid accumulate in their intestine following challenge with ETEC wt bacteria or with purified LT as compared to the sham mice indicating that the immunized mice were protected from LT-induced intestinal fluid accumulation. Thus, mice intragastrically immunized with the ZCR533-CFA/I+LThK63 vaccine strain were able to effectively neutralize the activity of the LT enterotoxin. However, no difference in intestinal fluid accumulation was detected in the mice immunized intranasally with the vaccine strain as compared to the sham

  16. Shear-strain gradient induced polarization reversal in ferroelectric BaTiO3 thin films: A first-principles total-energy study

    NASA Astrophysics Data System (ADS)

    Li, Guannan; Huang, Xiaokun; Hu, Jingsan; Zhang, Weiyi

    2017-04-01

    Based on the first-principles total-energy calculation, we have studied the shear-strain gradient effect on the polarization reversal of ferroelectric BaTiO3 thin films. By calculating the energies of double-domain supercells for different electric polarization, shear-strain gradients, and domain-wall displacement, we extracted, in addition to the domain-wall energy, the polarization energy, elastic energy, and flexoelectric coefficient of a single domain. The constructed Landau-Devonshire phenomenological theory yields a critical shear-strain gradient of 9.091 ×107/m (or a curvature radius (R ) of 110 Å) for reversing the 180∘ domain at room temperature, which is on the same order of the experimentally estimated value of 3.333 ×107/m (R =300 Å ). In contrast to the commonly used linear response theory, the flexoelectric coefficient derived from fitting the total energy to a Landau-Devonshire energy functional does not depend on the specific pseudopotential. Thus, our method offers an alternative numerical approach to study the flexoelectric effect.

  17. A Lactobacillus mutant capable of accumulating long-chain polyphosphates that enhance intestinal barrier function.

    PubMed

    Saiki, Asako; Ishida, Yasuaki; Segawa, Shuichi; Hirota, Ryuichi; Nakamura, Takeshi; Kuroda, Akio

    2016-05-01

    Inorganic polyphosphate (polyP) was previously identified as a probiotic-derived substance that enhances intestinal barrier function. PolyP-accumulating bacteria are expected to have beneficial effects on the human gastrointestinal tract. In this study, we selected Lactobacillus paracasei JCM 1163 as a strain with the potential to accumulate polyP, because among the probiotic bacteria stored in our laboratory, it had the largest amount of polyP. The chain length of polyP accumulated in L. paracasei JCM 1163 was approximately 700 phosphate (Pi) residues. L. paracasei JCM 1163 accumulated polyP when Pi was added to Pi-starved cells. We further improved the ability of L. paracasei JCM 1163 to accumulate polyP by nitrosoguanidine mutagenesis. The mutant accumulated polyP at a level of 1500 nmol/mg protein-approximately 190 times that of the wild-type strain. PolyP extracted from the L. paracasei JCM 1163 significantly suppressed the oxidant-induced intestinal permeability in mouse small intestine. In conclusion, we have succeeded in breeding the polyP-accumulating Lactobacillus mutant that is expected to enhance intestinal barrier function.

  18. Self-adaptive strain-relaxation optimization for high-energy lithium storage material through crumpling of graphene.

    PubMed

    Zhao, Yunlong; Feng, Jiangang; Liu, Xue; Wang, Fengchao; Wang, Lifen; Shi, Changwei; Huang, Lei; Feng, Xi; Chen, Xiyuan; Xu, Lin; Yan, Mengyu; Zhang, Qingjie; Bai, Xuedong; Wu, Hengan; Mai, Liqiang

    2014-08-01

    High-energy lithium battery materials based on conversion/alloying reactions have tremendous potential applications in new generation energy storage devices. However, these applications are limited by inherent large volume variations and sluggish kinetics. Here we report a self-adaptive strain-relaxed electrode through crumpling of graphene to serve as high-stretchy protective shells on metal framework, to overcome these limitations. The graphene sheets are self-assembled and deeply crumpled into pinecone-like structure through a contraction-strain-driven crumpling method. The as-prepared electrode exhibits high specific capacity (2,165 mAh g(-1)), fast charge-discharge rate (20 A g(-1)) with no capacity fading in 1,000 cycles. This kind of crumpled graphene has self-adaptive behaviour of spontaneous unfolding-folding synchronized with cyclic expansion-contraction volumetric variation of core materials, which can release strain and maintain good electric contact simultaneously. It is expected that such findings will facilitate the applications of crumpled graphene and the self-adaptive materials.

  19. Hormesis enables cells to handle accumulating toxic metabolites during increased energy flux.

    PubMed

    Zemva, Johanna; Fink, Christoph Andreas; Fleming, Thomas Henry; Schmidt, Leonard; Loft, Anne; Herzig, Stephan; Knieß, Robert André; Mayer, Matthias; Bukau, Bernd; Nawroth, Peter Paul; Tyedmers, Jens

    2017-10-01

    Energy production is inevitably linked to the generation of toxic metabolites, such as reactive oxygen and carbonyl species, known as major contributors to ageing and degenerative diseases. It remains unclear how cells can adapt to elevated energy flux accompanied by accumulating harmful by-products without taking any damage. Therefore, effects of a sudden rise in glucose concentrations were studied in yeast cells. This revealed a feedback mechanism initiated by the reactive dicarbonyl methylglyoxal, which is formed non-enzymatically during glycolysis. Low levels of methylglyoxal activate a multi-layered defence response against toxic metabolites composed of prevention, detoxification and damage remission. The latter is mediated by the protein quality control system and requires inducible Hsp70 and Btn2, the aggregase that sequesters misfolded proteins. This glycohormetic mechanism enables cells to pre-adapt to rising energy flux and directly links metabolic to proteotoxic stress. Further data suggest the existence of a similar response in endothelial cells. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  20. Role of malate transporter in lipid accumulation of oleaginous fungus Mucor circinelloides.

    PubMed

    Zhao, Lina; Cánovas-Márquez, José T; Tang, Xin; Chen, Haiqin; Chen, Yong Q; Chen, Wei; Garre, Victoriano; Song, Yuanda; Ratledge, Colin

    2016-02-01

    Fatty acid biosynthesis in oleaginous fungi requires the supply of reducing power, NADPH, and the precursor of fatty acids, acetyl-CoA, which is generated in the cytosol being produced by ATP: citrate lyase which requires citrate to be, transported from the mitochondrion by the citrate/malate/pyruvate transporter. This transporter, which is within the mitochondrial membrane, transports cytosolic malate into the mitochondrion in exchange for mitochondrial citrate moving into the cytosol (Fig. 1). The role of malate transporter in lipid accumulation in oleaginous fungi is not fully understood, however. Therefore, the expression level of the mt gene, coding for a malate transporter, was manipulated in the oleaginous fungus Mucor circinelloides to analyze its effect on lipid accumulation. The results showed that mt overexpression increased the lipid content for about 70 % (from 13 to 22 % dry cell weight, CDW), whereas the lipid content in mt knockout mutant decreased about 27 % (from 13 to 9.5 % CDW) compared with the control strain. Furthermore, the extracellular malate concentration was decreased in the mt overexpressing strain and increased in the mt knockout strain compared with the wild-type strain. This work suggests that the malate transporter plays an important role in regulating lipid accumulation in oleaginous fungus M. circinelloides.

  1. Comparison of Biochemical Activities between High and Low Lipid-Producing Strains of Mucor circinelloides: An Explanation for the High Oleaginicity of Strain WJ11.

    PubMed

    Tang, Xin; Chen, Haiqin; Chen, Yong Q; Chen, Wei; Garre, Victoriano; Song, Yuanda; Ratledge, Colin

    2015-01-01

    The oleaginous fungus, Mucor circinelloides, is one of few fungi that produce high amounts of γ-linolenic acid (GLA); however, it usually only produces <25% lipid. Nevertheless, a new strain (WJ11) isolated in this laboratory can produce lipid up to 36% (w/w) cell dry weight (CDW). We have investigated the potential mechanism of high lipid accumulation in M. circinelloides WJ11 by comparative biochemical analysis with a low lipid-producing strain, M. circinelloides CBS 277.49, which accumulates less than 15% (w/w) lipid. M. circinelloides WJ11 produced more cell mass than that of strain CBS 277.49, although with slower glucose consumption. In the lipid accumulation phase, activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase in strain WJ11 were greater than in CBS 277.49 by 46% and 17%, respectively, and therefore may provide more NADPH for fatty acid biosynthesis. The activities of NAD+:isocitrate dehydrogenase and NADP+:isocitrate dehydrogenase, however, were 43% and 54%, respectively, lower in WJ11 than in CBS 277.49 and may retard the tricarboxylic acid cycle and thereby provide more substrate for ATP:citrate lyase (ACL) to produce acetyl-CoA. Also, the activities of ACL and fatty acid synthase in the high lipid-producing strain, WJ11, were 25% and 56%, respectively, greater than in strain CBS 277.49. These enzymes may therefore cooperatively regulate the fatty acid biosynthesis in these two strains.

  2. Strain Accumulation and Release of the Gorkha, Nepal, Earthquake (M w 7.8, 25 April 2015)

    NASA Astrophysics Data System (ADS)

    Morsut, Federico; Pivetta, Tommaso; Braitenberg, Carla; Poretti, Giorgio

    2017-08-01

    The near-fault GNSS records of strong-ground movement are the most sensitive for defining the fault rupture. Here, two unpublished GNSS records are studied, a near-fault-strong-motion station (NAGA) and a distant station in a poorly covered area (PYRA). The station NAGA, located above the Gorkha fault, sensed a southward displacement of almost 1.7 m. The PYRA station that is positioned at a distance of about 150 km from the fault, near the Pyramid station in the Everest, showed static displacements in the order of some millimeters. The observed displacements were compared with the calculated displacements of a finite fault model in an elastic halfspace. We evaluated two slips on fault models derived from seismological and geodetic studies: the comparison of the observed and modelled fields reveals that our displacements are in better accordance with the geodetic derived fault model than the seismologic one. Finally, we evaluate the yearly strain rate of four GNSS stations in the area that were recording continuously the deformation field for at least 5 years. The strain rate is then compared with the strain released by the Gorkha earthquake, leading to an interval of 235 years to store a comparable amount of elastic energy. The three near-fault GNSS stations require a slightly wider fault than published, in the case of an equivalent homogeneous rupture, with an average uniform slip of 3.5 m occurring on an area of 150 km × 60 km.

  3. Looking for Off-Fault Deformation and Measuring Strain Accumulation During the Past 70 years on a Portion of the Locked San Andreas Fault

    NASA Astrophysics Data System (ADS)

    Vadman, M.; Bemis, S. P.

    2017-12-01

    Even at high tectonic rates, detection of possible off-fault plastic/aseismic deformation and variability in far-field strain accumulation requires high spatial resolution data and likely decades of measurements. Due to the influence that variability in interseismic deformation could have on the timing, size, and location of future earthquakes and the calculation of modern geodetic estimates of strain, we attempt to use historical aerial photographs to constrain deformation through time across a locked fault. Modern photo-based 3D reconstruction techniques facilitate the creation of dense point clouds from historical aerial photograph collections. We use these tools to generate a time series of high-resolution point clouds that span 10-20 km across the Carrizo Plain segment of the San Andreas fault. We chose this location due to the high tectonic rates along the San Andreas fault and lack of vegetation, which may obscure tectonic signals. We use ground control points collected with differential GPS to establish scale and georeference the aerial photograph-derived point clouds. With a locked fault assumption, point clouds can be co-registered (to one another and/or the 1.7 km wide B4 airborne lidar dataset) along the fault trace to calculate relative displacements away from the fault. We use CloudCompare to compute 3D surface displacements, which reflect the interseismic strain accumulation that occurred in the time interval between photo collections. As expected, we do not observe clear surface displacements along the primary fault trace in our comparisons of the B4 lidar data against the aerial photograph-derived point clouds. However, there may be small scale variations within the lidar swath area that represent near-fault plastic deformation. With large-scale historical photographs available for the Carrizo Plain extending back to at least the 1940s, we can potentially sample nearly half the interseismic period since the last major earthquake on this portion of

  4. Strain energy release rate analysis of the end-notched flexure specimen using the finite-element method

    NASA Technical Reports Server (NTRS)

    Salpekar, S. A.; Raju, I. S.; O'Brien, T. K.

    1988-01-01

    Two-dimensional finite-element analysis of the end-notched flexure specimen was performed using 8-node isoparametric, parabolic elements to evaluate compliance and mode II strain energy release rates, G sub II. The G sub II values were computed using two different techniques: the virtual crack-closure technique (VCCT) and the rate of change of compliance with crack length (compliance derivative method). The analysis was performed for various crack-length-to-semi-span (a/L) ratios ranging from 0.2 to 0.9. Three material systems representing a wide range of material properties were analyzed. The compliance and strain energy release rates of the specimen calculated with the present finite-element analysis agree very well with beam theory equations including transverse shear. The G sub II values calculated using the compliance derivative method compared extremely well with those calculated using the VCCT. The G sub II values obtained by the compliance derivative method using the top or bottom beam deflections agreed closely with each other. The strain energy release rates from a plane-stress analysis were higher than the plane-strain values by only a small percentage, indicating that either assumption may be used in the analysis. The G sub II values for one material system calculated from the finte-element analysis agreed with one solution in the literature and disagreed with the other solution in the literature.

  5. Strain-energy-release rate analysis of the end-notched flexure specimen using the finite-element method

    NASA Technical Reports Server (NTRS)

    Salpekar, S. A.; Raju, I. S.; Obrien, T. K.

    1987-01-01

    Two-dimensional finite-element analysis of the end-notched flexure specimen was performed using 8-node isoparametric, parabolic elements to evaluate compliance and mode II strain energy release rates, G sub II. The G sub II values were computed using two different techniques: the virtural crack-closure technique (VCCT) and the rate of change of compliance with crack length (compliance derivative method). The analysis was performed for various crack-length-to-semi-span (a/L) ratios ranging from 0.2 to 0.9. Three material systems representing a wide range of material properties were analyzed. The compliance and strain energy release rates of the specimen calculated with the present finite-element analysis agree very well with beam theory equations including transverse shear. The G sub II values calculated using the compliance derivative method compared extremely well with those calculated using the VCCT. The G sub II values obtained by the compliance derivative method using the top or bottom beam deflections agreed closely with each other. The strain energy release rates from a plane-stress analysis were higher than the plane-strain values by only a small percentage, indicating that either assumption may be used in the analysis. The G sub II values for one material system calculated from the finite-element analysis agreed with one solution in the literature and disagreed with the other solution in the literature.

  6. Mechanical strain energy shuttle for aircraft morphing via wing twist or structural deformation

    NASA Astrophysics Data System (ADS)

    Clingman, Dan J.; Ruggeri, Robert T.

    2004-07-01

    Direct structural deformation to achieve aerodynamic benefit is difficult because large actuators must supply energy for structural strain and aerodynamic loads. This ppaer presents a mechanism that allows most of the energy required to twist or deform a wing to be stored in descrete springs. When this device is used, only sufficient energy is provided to control the position of the wing. This concept allows lightweight actuators to perform wing twisting and other structural distortions, and it reduces the onboard mass of the wing-twist system. The energy shuttle can be used with any actuator and it has been adapted for used with shape memory alloy, piezoelectric, and electromagnetic actuators.

  7. PC index as a proxy of the solar wind energy that entered into the magnetosphere and energy accumulated in the magnetosphere

    NASA Astrophysics Data System (ADS)

    Troshichev, Oleg; Sormakov, Dmitry

    The PC index has been approved by the International Association of Geomagnetism and Aeronomy (Merida, Mexico, 2013) as a new international index of magnetic activity. Application of the PC index as a proxy of a solar wind energy that entered into the magnetosphere determines a principal distinction of the PC index from AL and Dst indices, which are regarded as characteristics of the energy that realized in magnetosphere in form of substorms and magnetic storms. This conclusion is based on results of analysis of relationships between the polar cap magnetic activity (PC-index) and parameters of the solar wind, on the one hand, relationships between changes of PC and development of magnetospheric substorms (AL-index) and magnetic storms (Dst-index), on the other hand. In this study the relationships between the PC and Dst indices in course of more than 200 magnetic storms observed in epoch of solar maximum (1998-2004) have been examined for different classes of storms separated by their kind and intensity. Results of statistical analysis demonstrate that depression of geomagnetic field starts to develop as soon as PC index steadily excess the threshold level ~1.5 mV/m; the storm intensity (DstMIN) follows, with delay ~ 1 hour, the maximum of PC in course of the storm. Main features of magnetic storms are determined, irrespective of their class and intensity, by the accumulated-mean PC value (PCAM): storm is developed as long as PCAM increases, comes to maximal intensity when PCAM attains the maximum, and starts to decay as soon as PCAM value displays decline. The run of “anomalous” magnetic storm on January 21-22, 2005, lasting many hours (with intensity of ≈ -100 nT) under conditions of northward or close to zero BZ component, is perfectly governed by behavior of the accumulated-mean PCAM index and, therefore, this storm should be regarded as an ordinary phenomenon. The conclusion is made that the PC index provides the unique on-line information on solar wind

  8. Accumulate-Repeat-Accumulate-Accumulate-Codes

    NASA Technical Reports Server (NTRS)

    Divsalar, Dariush; Dolinar, Sam; Thorpe, Jeremy

    2004-01-01

    Inspired by recently proposed Accumulate-Repeat-Accumulate (ARA) codes [15], in this paper we propose a channel coding scheme called Accumulate-Repeat-Accumulate-Accumulate (ARAA) codes. These codes can be seen as serial turbo-like codes or as a subclass of Low Density Parity Check (LDPC) codes, and they have a projected graph or protograph representation; this allows for a high-speed iterative decoder implementation using belief propagation. An ARAA code can be viewed as a precoded Repeat-and-Accumulate (RA) code with puncturing in concatenation with another accumulator, where simply an accumulator is chosen as the precoder; thus ARAA codes have a very fast encoder structure. Using density evolution on their associated protographs, we find examples of rate-lJ2 ARAA codes with maximum variable node degree 4 for which a minimum bit-SNR as low as 0.21 dB from the channel capacity limit can be achieved as the block size goes to infinity. Such a low threshold cannot be achieved by RA or Irregular RA (IRA) or unstructured irregular LDPC codes with the same constraint on the maximum variable node degree. Furthermore by puncturing the accumulators we can construct families of higher rate ARAA codes with thresholds that stay close to their respective channel capacity thresholds uniformly. Iterative decoding simulation results show comparable performance with the best-known LDPC codes but with very low error floor even at moderate block sizes.

  9. Intramolecular energies of the cytotoxic protein CagA of Helicobacter pylori as a possible descriptor of strains' pathogenicity level.

    PubMed

    Rojas-Rengifo, Diana F; Alvarez-Silva, Maria Camila; Ulloa-Guerrero, Cindy P; Nuñez-Velez, Vanessa Lucía; Del Pilar Delgado, Maria; Aguilera, Sonia Milena; Castro, Harold; Jaramillo, Carlos Alberto; Fernando González Barrios, Andrés

    2018-05-25

    The Helicobacter pylori cytotoxin-associated gene A (CagA) is known for causing gastroduodenal diseases, such as atrophic gastritis and peptic ulcerations. Furthermore Helicobacter pylori CagA positive strains has been reported as one of the main risk factors for gastric cancer (Parsonnet et al., 1997). Structural variations in the CagA structure can alter its affinity with the host proteins, inducing differences in the pathogenicity of H. pylori. CagA N-terminal region is characterized for be conserved among all H. pylori strains since the C-terminal region is characterized by an intrinsically disorder behavior. We generated complete structural models of CagA using different conformations of the C-terminal region for two H. pylori strains. These models contain the same EPIYA (ABC 1 C 2 ) motifs but different level of pathogenicity: gastric cancer and duodenal ulcer. Using these structural models we evaluated the pathogenicity level of the H. pylori strain, based on the affinity of the interaction with SHP-2 and Grb2 receptors and on the number of interactions with the EPIYA motif. We found that the main differences in the interaction was due to the contributions of certain types of energies from each strain and not from the total energy of the molecule. Specifically, the electrostatic energy, helix dipole energy, Wander Waals clashes, torsional clash, backbone clash and cis bond energy allowed a separation between severe and mild pathology for the interaction of only CagA with SHP2. Copyright © 2018 Elsevier Ltd. All rights reserved.

  10. Physiological-biochemical properties and the ability to synthesize polyhydroxyalkanoates of the glucose-utilizing strain of the hydrogen bacterium Ralstonia eutropha B8562.

    PubMed

    Volova, T G; Trusova, M Y; Kalacheva, G S; Kozhevnicov, I V

    2006-11-01

    Physiological-biochemical, genetic, and cultural properties of the glucose-utilizing mutant strain Ralstonia eutropha B8562 have been compared with those of its parent strain R. eutropha B5786. It has been shown that growth characteristics of the strain cultured on glucose as the sole carbon and energy source are comparable with those of the parent strain. Strain B8562 is characterized by high polyhydroxyalkanoate (PHA) yields on different carbon sources (CO(2), fructose, and glucose). PHA accumulation in the strain batch cultured on glucose under nitrogen deficiency reaches 90 %. The major monomer in the PHA is beta-hydroxybutyric acid (more than 99 mol %); the identified minor components are beta-hydroxyvaleric acid (0.25-0.72 mol %) and beta-hydroxyhexanoic acid (0.08-1.5 mol %). The strain is a promising PHA producer on available sugar-containing media with glucose.

  11. The Csr System Regulates Escherichia coli Fitness by Controlling Glycogen Accumulation and Energy Levels.

    PubMed

    Morin, Manon; Ropers, Delphine; Cinquemani, Eugenio; Portais, Jean-Charles; Enjalbert, Brice; Cocaign-Bousquet, Muriel

    2017-10-31

    In the bacterium Escherichia coli , the posttranscriptional regulatory system Csr was postulated to influence the transition from glycolysis to gluconeogenesis. Here, we explored the role of the Csr system in the glucose-acetate transition as a model of the glycolysis-to-gluconeogenesis switch. Mutations in the Csr system influence the reorganization of gene expression after glucose exhaustion and disturb the timing of acetate reconsumption after glucose exhaustion. Analysis of metabolite concentrations during the transition revealed that the Csr system has a major effect on the energy levels of the cells after glucose exhaustion. This influence was demonstrated to result directly from the effect of the Csr system on glycogen accumulation. Mutation in glycogen metabolism was also demonstrated to hinder metabolic adaptation after glucose exhaustion because of insufficient energy. This work explains how the Csr system influences E. coli fitness during the glycolysis-gluconeogenesis switch and demonstrates the role of glycogen in maintenance of the energy charge during metabolic adaptation. IMPORTANCE Glycogen is a polysaccharide and the main storage form of glucose from bacteria such as Escherichia coli to yeasts and mammals. Although its function as a sugar reserve in mammals is well documented, the role of glycogen in bacteria is not as clear. By studying the role of posttranscriptional regulation during metabolic adaptation, for the first time, we demonstrate the role of sugar reserve played by glycogen in E. coli Indeed, glycogen not only makes it possible to maintain sufficient energy during metabolic transitions but is also the key component in the capacity of cells to resume growth. Since the essential posttranscriptional regulatory system Csr is a major regulator of glycogen accumulation, this work also sheds light on the central role of posttranscriptional regulation in metabolic adaptation. Copyright © 2017 Morin et al.

  12. Chlorella for protein and biofuels: from strain selection to outdoor cultivation in a Green Wall Panel photobioreactor

    PubMed Central

    2014-01-01

    Background Chlorella is one of the few microalgae employed for human consumption. It typically has a high protein content, but it can also accumulate high amounts of lipids or carbohydrates under stress conditions and, for this reason, it is of interest in the production of biofuels. High production costs and energy consumption are associated with its cultivation. This work describes a strategy to reduce costs and environmental impact of Chlorella biomass production for food, biofuels and other applications. Results The growth of four Chlorella strains, selected after a laboratory screening, was investigated outdoors in a low-cost 0.25 m2 GWP-II photobioreactor. The capacity of the selected strains to grow at high temperature was tested. On the basis of these results, in the nitrogen starvation trials the culture was cooled only when the temperature exceeded 40°C to allow for significant energy savings, and performed in a seawater-based medium to reduce the freshwater footprint. Under nutrient sufficiency, strain CH2 was the most productive. In all the strains, nitrogen starvation strongly reduced productivity, depressed protein and induced accumulation of carbohydrate (about 50%) in strains F&M-M49 and IAM C-212, and lipid (40 - 45%) in strains PROD1 and CH2. Starved cultures achieved high storage product productivities: 0.12 g L−1 d−1 of lipids for CH2 and 0.19 g L−1 d−1 of carbohydrates for F&M-M49. When extrapolated to large-scale in central Italy, CH2 showed a potential productivity of 41 t ha−1 y−1 for biomass, 16 t ha−1 y−1 for protein and 11 t ha−1 y−1 for lipid under nutrient sufficiency, and 8 t ha−1 y−1 for lipid under nitrogen starvation. Conclusions The environmental and economic sustainability of Chlorella production was enhanced by growing the organisms in a seawater-based medium, so as not to compete with crops for freshwater, and at high temperatures, so as to reduce energy consumption for cooling. All the four

  13. Secondary Metabolism and Interspecific Competition Affect Accumulation of Spontaneous Mutants in the GacS-GacA Regulatory System in Pseudomonas protegens.

    PubMed

    Yan, Qing; Lopes, Lucas D; Shaffer, Brenda T; Kidarsa, Teresa A; Vining, Oliver; Philmus, Benjamin; Song, Chunxu; Stockwell, Virginia O; Raaijmakers, Jos M; McPhail, Kerry L; Andreote, Fernando D; Chang, Jeff H; Loper, Joyce E

    2018-01-16

    Secondary metabolites are synthesized by many microorganisms and provide a fitness benefit in the presence of competitors and predators. Secondary metabolism also can be costly, as it shunts energy and intermediates from primary metabolism. In Pseudomonas spp., secondary metabolism is controlled by the GacS-GacA global regulatory system. Intriguingly, spontaneous mutations in gacS or gacA (Gac - mutants) are commonly observed in laboratory cultures. Here we investigated the role of secondary metabolism in the accumulation of Gac - mutants in Pseudomonas protegens strain Pf-5. Our results showed that secondary metabolism, specifically biosynthesis of the antimicrobial compound pyoluteorin, contributes significantly to the accumulation of Gac - mutants. Pyoluteorin biosynthesis, which poses a metabolic burden on the producer cells, but not pyoluteorin itself, leads to the accumulation of the spontaneous mutants. Interspecific competition also influenced the accumulation of the Gac - mutants: a reduced proportion of Gac - mutants accumulated when P. protegens Pf-5 was cocultured with Bacillus subtilis than in pure cultures of strain Pf-5. Overall, our study associated a fitness trade-off with secondary metabolism, with metabolic costs versus competitive benefits of production influencing the evolution of P. protegens , assessed by the accumulation of Gac - mutants. IMPORTANCE Many microorganisms produce antibiotics, which contribute to ecologic fitness in natural environments where microbes constantly compete for resources with other organisms. However, biosynthesis of antibiotics is costly due to the metabolic burdens of the antibiotic-producing microorganism. Our results provide an example of the fitness trade-off associated with antibiotic production. Under noncompetitive conditions, antibiotic biosynthesis led to accumulation of spontaneous mutants lacking a master regulator of antibiotic production. However, relatively few of these spontaneous mutants

  14. Trehalose accumulation enhances tolerance of Saccharomyces cerevisiae to acetic acid.

    PubMed

    Yoshiyama, Yoko; Tanaka, Koichi; Yoshiyama, Kohei; Hibi, Makoto; Ogawa, Jun; Shima, Jun

    2015-02-01

    Trehalose confers protection against various environmental stresses on yeast cells. In this study, trehalase gene deletion mutants that accumulate trehalose at high levels showed significant stress tolerance to acetic acid. The enhancement of trehalose accumulation can thus be considered a target in the breeding of acetic acid-tolerant yeast strains. Copyright © 2014 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  15. Accumulate-Repeat-Accumulate-Accumulate Codes

    NASA Technical Reports Server (NTRS)

    Divsalar, Dariush; Dolinar, Samuel; Thorpe, Jeremy

    2007-01-01

    Accumulate-repeat-accumulate-accumulate (ARAA) codes have been proposed, inspired by the recently proposed accumulate-repeat-accumulate (ARA) codes. These are error-correcting codes suitable for use in a variety of wireless data-communication systems that include noisy channels. ARAA codes can be regarded as serial turbolike codes or as a subclass of low-density parity-check (LDPC) codes, and, like ARA codes they have projected graph or protograph representations; these characteristics make it possible to design high-speed iterative decoders that utilize belief-propagation algorithms. The objective in proposing ARAA codes as a subclass of ARA codes was to enhance the error-floor performance of ARA codes while maintaining simple encoding structures and low maximum variable node degree.

  16. Simultaneous accumulation of proline and trehalose in industrial baker's yeast enhances fermentation ability in frozen dough.

    PubMed

    Sasano, Yu; Haitani, Yutaka; Hashida, Keisuke; Ohtsu, Iwao; Shima, Jun; Takagi, Hiroshi

    2012-05-01

    Freeze tolerance is a necessary characteristic for industrial baker's yeast because frozen-dough baking is one of the key technologies for supplying oven-fresh bakery products to consumers. Both proline and trehalose are known to function as cryoprotectants in yeast cells. In order to enhance the freeze tolerance of yeast cells, we constructed a self-cloning diploid baker's yeast strain with simultaneous accumulation of proline, by expressing the PRO1-I150T allele, encoding the proline-feedback inhibition-less sensitive γ-glutamyl kinase, and trehalose, by disrupting the NTH1 gene, encoding neutral trehalase. The resultant strain retained higher tolerance to oxidative and freezing stresses than did the single proline- or trehalose-accumulating strain. Interestingly, our results suggest that proline and trehalose protect yeast cells from short-term and long-term freezing, respectively. Simultaneous accumulation of proline and trehalose in industrial baker's yeast also enhanced the fermentation ability in the frozen dough compared with the single accumulation of proline or trehalose. These results indicate that baker's yeast that accumulates both proline and trehalose is applicable for frozen-dough baking. Copyright © 2012 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  17. Conformational locking by design: relating strain energy with luminescence and stability in rigid metal-organic frameworks.

    PubMed

    Shustova, Natalia B; Cozzolino, Anthony F; Dincă, Mircea

    2012-12-05

    Minimization of the torsional barrier for phenyl ring flipping in a metal-organic framework (MOF) based on the new ethynyl-extended octacarboxylate ligand H(8)TDPEPE leads to a fluorescent material with a near-dark state. Immobilization of the ligand in the rigid structure also unexpectedly causes significant strain. We used DFT calculations to estimate the ligand strain energies in our and all other topologically related materials and correlated these with empirical structural descriptors to derive general rules for trapping molecules in high-energy conformations within MOFs. These studies portend possible applications of MOFs for studying fundamental concepts related to conformational locking and its effects on molecular reactivity and chromophore photophysics.

  18. Measurement of the Spin Relaxation Lifetime (T 1) in a One-Electron Strained-Si Accumulation-Mode Quantum Dot

    NASA Astrophysics Data System (ADS)

    Croke, Edward; Borselli, Matthew; Kiselev, Andrey; Deelman, Peter; Milosavljevic, Ivan; Alvarado-Rodriguez, Ivan; Ross, Richard; Schmitz, Adele; Gyure, Mark; Hunter, Andrew

    2011-03-01

    We report measurements of the spin-relaxation lifetime (T1) as a function of magnetic field in a strained-Si, accumulation-mode quantum dot. An integrated quantum-point contact (QPC) charge sensor was used to detect changes in dot occupancy as a function of bias applied to a single gate electrode. The addition spectra we obtained are consistent with theoretical predictions starting at N=0. The conductance of the charge sensor was measured by applying an AC voltage across the QPC and a 3 k Ω resistor. Lifetime measurements were conducted using a three-pulse technique consisting of a load, read, and flush sequence. T1 was measured by observing the decay of the spin bump amplitude as a function of the load pulse length. We measured decay times ranging from approximately 75 msec at 2T to 12 msec at 3T, consistent with previous reports and theoretical predictions. Sponsored by United States Department of Defense. Approved for Public Release, Distribution Unlimited.

  19. Damage Accumulation in Cyclically-Loaded Glass-Ceramic Matrix Composites Monitored by Acoustic Emission

    PubMed Central

    Aggelis, D. G.; Dassios, K. G.; Kordatos, E. Z.; Matikas, T. E.

    2013-01-01

    Barium osumilite (BMAS) ceramic matrix composites reinforced with SiC-Tyranno fibers are tested in a cyclic loading protocol. Broadband acoustic emission (AE) sensors are used for monitoring the occurrence of different possible damage mechanisms. Improved use of AE indices is proposed by excluding low-severity signals based on waveform parameters, rather than only threshold criteria. The application of such improvements enhances the accuracy of the indices as accumulated damage descriptors. RA-value, duration, and signal energy follow the extension cycles indicating moments of maximum or minimum strain, while the frequency content of the AE signals proves very sensitive to the pull-out mechanism. PMID:24381524

  20. Microstructure, accumulated strain, and mechanical behavior of AA6061 Al alloy severely deformed at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Magalhães, D. C.; Kliauga, A. M.; Ferrante, M.; Sordi, V. L.

    2017-05-01

    The combination of Severe Plastic Deformation (SPD) and cryogenic temperatures can be an efficient way to obtain metals and alloys with very refined microstructure and thus optimize the strength-ductility pair. However, there is still a lack of studies on cryogenic SPD process and their effects on microstructure and mechanical properties, especially in precipitation-hardenable aluminum alloys. This study describes the effect of low temperature processing on microstructure, aging kinetic and tensile properties of AA6061 Al alloy after cryo-SPD. Samples of AA6061 Al alloy in the solutionized state was processed by Equal-channel angular pressing (ECAP) at 77 K and 298 K, up to accumulate true strains up to 4.2. Results indicated that the aging kinetic is accelerated when deformation is performed at cryogenic temperature, dislocation density measurement by x-ray and diffraction analysis at TEM achieved a saturation level of 2×1015 m-2 by ECAP at 298K and 5×1015 m-2 after cryogenic ECAP plus precipitation hardening. The same level of yield strength was observed in both deformation procedures but an improvement in uniform elongation was achieved by cryogenic ECAP followed by a T6 treatment

  1. Corticosterone administration and high-energy feed results in enhanced fat accumulation and insulin resistance in broiler chickens.

    PubMed

    Yuan, L; Lin, H; Jiang, K J; Jiao, H C; Song, Z G

    2008-07-01

    1. Two experiments were conducted to investigate the effects of exogenous corticosterone administration (30 mg/kg diet) and dietary energy level on feed or energy intake and fat deposition in broiler chickens of 1 and 4 weeks of age. 2. Corticosterone treatment significantly suppressed body weight (BW) gain and reduced feed and caloric efficiencies. The retarded growth may conceal the stimulatory effect of corticosterone on feed consumption or metabolisable energy (ME) intake. A high-energy diet may increase energy intake and partially alleviate the suppressing effect of corticosterone on growth of broilers. 3. Corticosterone administration promoted the conservation of energy stores as fat at both abdominal and subcutaneous sites and this process occurred regardless of dietary energy level in ad libitum feeding status. A high-energy diet increased fat accumulation and showed no significant interaction with corticosterone treatment. 4. The suppressed development of breast and thigh muscles by corticosterone treatment was observed only in 1-week-old chickens fed on the low-energy diet. In contrast, the yield of breast muscle but not thigh muscle was significantly decreased by corticosterone in 4-week-old chickens, suggesting that the tissue specificity to corticosterone challenge is age dependent. 5. Plasma concentrations of glucose, insulin, triglyceride, non-esterified fatty acids (NEFA) and very low density lipoprotein were increased by corticosterone treatment regardless of diet treatment. A high-energy diet increased plasma levels of NEFA and resulted in hyperinsulinism in 4-week-old chickens but not in 1-week-old chickens. 6. Lipoprotein lipase (LPL) activities in adipose tissues may have been up-regulated by corticosterone treatment and showed tissue specificity. The increased LPL activities at ad libitum feeding status were not necessarily linked with the increased fat accumulation in corticosterone challenged chickens. 7. Corticosterone resulted in augmented

  2. Current strain accumulation in the hinterland of the northwest Himalaya constrained by landscape analyses, basin-wide denudation rates, and low temperature thermochronology

    NASA Astrophysics Data System (ADS)

    Morell, Kristin D.; Sandiford, Mike; Kohn, Barry; Codilean, Alexandru; Fülöp, Réka-H.; Ahmad, Talat

    2017-11-01

    Rupture associated with the 25 April 2015 Mw 7.8 Gorkha (Nepal) earthquake highlighted our incomplete understanding of the structural architecture and seismic cycle processes that lead to Himalayan mountain building in Central Nepal. In this paper we investigate the style and kinematics of active mountain building in the Himalayan hinterland of Northwest India, approximately 400 km to the west of the hypocenter of the Nepal earthquake, via a combination of landscape metrics and long- (Ma) and short-term (ka) erosion rate estimates (from low temperature thermochronometry and basin-wide denudation rate estimates from 10Be concentrations). We focus our analysis on the area straddling the PT2, the physiographic transition between the Lesser and High Himalaya that has yielded important insights into the nature of hinterland deformation across much of the Himalaya. Our results from Northwest India reveal a distinctive PT2 that separates a Lesser Himalaya region with moderate relief (∼1000 m) and relatively slow erosion (<1 mm/yr) from a High Himalaya with extreme relief (∼2500 m), steep channels, and erosion rates that approach or exceed 1 mm/yr. The close spatial similarity in relative rates of long- and short-term erosion suggests that the gradient in rock uplift rates inferred from the landscape metrics across the PT2 has persisted in the same relative position since at least the past 1.5 Ma. We interpret these observations to suggest that strain accumulation in this hinterland region throughout at least the past 1.5 Ma has been accomplished both by crustal thickening via duplexing and overthrusting along transient emergent faults. Despite the >400 km distance between them, similar spatiotemporal patterns of erosion and deformation observed in Northwest India and Central Nepal suggest both regions experience similar styles of active strain accumulation and both are susceptible to large seismic events.

  3. Improving methionine and ATP availability by MET6 and SAM2 co-expression combined with sodium citrate feeding enhanced SAM accumulation in Saccharomyces cerevisiae.

    PubMed

    Chen, Hailong; Wang, Zhou; Wang, Zhilai; Dou, Jie; Zhou, Changlin

    2016-04-01

    S-adenosyl-L-methionine (SAM), biosynthesized from methionine and ATP, exhibited diverse pharmaceutical applications. To enhance SAM accumulation in S. cerevisiae CGMCC 2842 (wild type), improvement of methionine and ATP availability through MET6 and SAM2 co-expression combined with sodium citrate feeding was investigated here. Feeding 6 g/L methionine at 12 h into medium was found to increase SAM accumulation by 38 % in wild type strain. Based on this result, MET6, encoding methionine synthase, was overexpressed, which caused a 59 % increase of SAM. To redirect intracellular methionine into SAM, MET6 and SAM2 (encoding methionine adenosyltransferase) were co-expressed to obtain the recombinant strain YGSPM in which the SAM accumulation was 2.34-fold of wild type strain. The data obtained showed that co-expression of MET6 and SAM2 improved intracellular methionine availability and redirected the methionine to SAM biosynthesis. To elevate intracellular ATP levels, 6 g/L sodium citrate, used as an auxiliary energy substrate, was fed into the batch fermentation medium, and an additional 19 % increase of SAM was observed after sodium citrate addition. Meanwhile, it was found that addition of sodium citrate improved the isocitrate dehydrogenase activity which was associated with the intracellular ATP levels. The results demonstrated that addition of sodium citrate improved intracellular ATP levels which promoted conversion of methionine into SAM. This study presented a feasible approach with considerable potential for developing highly SAM-productive strains based on improving methionine and ATP availability.

  4. A Comparison of Quantum and Molecular Mechanical Methods to Estimate Strain Energy in Druglike Fragments.

    PubMed

    Sellers, Benjamin D; James, Natalie C; Gobbi, Alberto

    2017-06-26

    Reducing internal strain energy in small molecules is critical for designing potent drugs. Quantum mechanical (QM) and molecular mechanical (MM) methods are often used to estimate these energies. In an effort to determine which methods offer an optimal balance in accuracy and performance, we have carried out torsion scan analyses on 62 fragments. We compared nine QM and four MM methods to reference energies calculated at a higher level of theory: CCSD(T)/CBS single point energies (coupled cluster with single, double, and perturbative triple excitations at the complete basis set limit) calculated on optimized geometries using MP2/6-311+G**. The results show that both the more recent MP2.X perturbation method as well as MP2/CBS perform quite well. In addition, combining a Hartree-Fock geometry optimization with a MP2/CBS single point energy calculation offers a fast and accurate compromise when dispersion is not a key energy component. Among MM methods, the OPLS3 force field accurately reproduces CCSD(T)/CBS torsion energies on more test cases than the MMFF94s or Amber12:EHT force fields, which struggle with aryl-amide and aryl-aryl torsions. Using experimental conformations from the Cambridge Structural Database, we highlight three example structures for which OPLS3 significantly overestimates the strain. The energies and conformations presented should enable scientists to estimate the expected error for the methods described and we hope will spur further research into QM and MM methods.

  5. Metal Accumulation and Vanadium-Induced Multidrug Resistance by Environmental Isolates of Escherichia hermannii and Enterobacter cloacae

    PubMed Central

    Hernández, Alicia; Mellado, Rafael P.; Martínez, José L.

    1998-01-01

    Contaminated soils from an oil refinery were screened for the presence of microorganisms capable of accumulating either nickel, vanadium, or both metals. Three strains of bacteria that belonged to the family Enterobacteriaceae were selected. Two of them were Escherichia hermannii strains, and outer membrane profile (OMP) analysis showed that they were similar to a strain of clinical origin; the other one was an Enterobacter cloacae strain that differed from clinical isolates. The selected bacteria accumulated both nickel and vanadium. Growth in the presence of vanadium induced multidrug resistance phenotypes in E. hermannii and E. cloacae. Incubation with this metal changed the OMP profile of E. hermannii but did not produce variations in the expression of the major OMPs of E. cloacae. PMID:9797283

  6. Proteomic analysis of Chlorella vulgaris: Potential targets for enhanced lipid accumulation

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

    Guarnieri, Michael T.; Nag, Ambarish; Yang, Shihui

    2013-11-01

    Oleaginous microalgae are capable of producing large quantities of fatty acids and triacylglycerides. As such, they are promising feedstocks for the production of biofuels and bioproducts. Genetic strain-engineering strategies offer a means to accelerate the commercialization of algal biofuels by improving the rate and total accumulation of microalgal lipids. However, the industrial potential of these organisms remains to be met, largely due to the incomplete knowledgebase surrounding the mechanisms governing the induction of algal lipid biosynthesis. Such strategies require further elucidation of genes and gene products controlling algal lipid accumulation. In this study, we have set out to examine thesemore » mechanisms and identify novel strain-engineering targets in the oleaginous microalga, Chlorella vulgaris. Comparative shotgun proteomic analyses have identified a number of novel targets, including previously unidentified transcription factors and proteins involved in cell signaling and cell cycle regulation. These results lay the foundation for strain-improvement strategies and demonstrate the power of translational proteomic analysis.« less

  7. Preferential Osmolyte Accumulation: a Mechanism of Osmotic Stress Adaptation in Diazotrophic Bacteria

    PubMed Central

    Madkour, Magdy A.; Smith, Linda Tombras; Smith, Gary M.

    1990-01-01

    A common cellular mechanism of osmotic-stress adaptation is the intracellular accumulation of organic solutes (osmolytes). We investigated the mechanism of osmotic adaptation in the diazotrophic bacteria Azotobacter chroococcum, Azospirillum brasilense, and Klebsiella pneumoniae, which are adversely affected by high osmotic strength (i.e., soil salinity and/or drought). We used natural-abundance 13C nuclear magnetic resonance spectroscopy to identify all the osmolytes accumulating in these strains during osmotic stress generated by 0.5 M NaCl. Evidence is presented for the accumulation of trehalose and glutamate in Azotobacter chroococcum ZSM4, proline and glutamate in Azospirillum brasilense SHS6, and trehalose and proline in K. pneumoniae. Glycine betaine was accumulated in all strains grown in culture media containing yeast extract as the sole nitrogen source. Alternative nitrogen sources (e.g., NH4Cl or casamino acids) in the culture medium did not result in measurable glycine betaine accumulation. We suggest that the mechanism of osmotic adaptation in these organisms entails the accumulation of osmolytes in hyperosmotically stressed cells resulting from either enhanced uptake from the medium (of glycine betaine, proline, and glutamate) or increased net biosynthesis (of trehalose, proline, and glutamate) or both. The preferred osmolyte in Azotobacter chroococcum ZSM4 shifted from glutamate to trehalose as a consequence of a prolonged osmotic stress. Also, the dominant osmolyte in Azospirillum brasilense SHS6 shifted from glutamate to proline accumulation as the osmotic strength of the medium increased. PMID:16348295

  8. Hardness depth profile of lattice strained cemented carbide modified by high-energy boron ion implantation

    NASA Astrophysics Data System (ADS)

    Yoshida, Y.; Matsumura, A.; Higeta, K.; Inoue, T.; Shimizu, S.; Motonami, Y.; Sato, M.; Sadahiro, T.; Fujii, K.

    1991-07-01

    The hardness depth profiles of cemented carbides which were implanted with high-energy B + ions have been estimated using a dynamic microhardness tester. The B + implantations into (16% Co)-cemented WC alloys were carried out under conditions where the implantation energies were 1-3 MeV and the fluences 1 × 10 17-1 × 10 18ions/cm 2. The profiles show that the implanted layer becomes harder as fluences are chosen at higher values and there is a peak at a certain depth which depends on the implantation energy. In X-ray diffraction (XRD) studies of the implanted surface the broadened refraction peaks of only WC and Co are detected and the increments of lattice strain and of residual stress in the near-surface region are observed. It is supposed that the hardening effect should be induced by an increase in residual stress produced by lattice strain. The hardness depth profile in successive implantation of ions with different energies agrees with the compounded profile of each one of the implantations. It is concluded that the hardness depth profile can be controlled under adequate conditions of implantation.

  9. Direct dose mapping versus energy/mass transfer mapping for 4D dose accumulation: fundamental differences and dosimetric consequences.

    PubMed

    Li, Haisen S; Zhong, Hualiang; Kim, Jinkoo; Glide-Hurst, Carri; Gulam, Misbah; Nurushev, Teamour S; Chetty, Indrin J

    2014-01-06

    The direct dose mapping (DDM) and energy/mass transfer (EMT) mapping are two essential algorithms for accumulating the dose from different anatomic phases to the reference phase when there is organ motion or tumor/tissue deformation during the delivery of radiation therapy. DDM is based on interpolation of the dose values from one dose grid to another and thus lacks rigor in defining the dose when there are multiple dose values mapped to one dose voxel in the reference phase due to tissue/tumor deformation. On the other hand, EMT counts the total energy and mass transferred to each voxel in the reference phase and calculates the dose by dividing the energy by mass. Therefore it is based on fundamentally sound physics principles. In this study, we implemented the two algorithms and integrated them within the Eclipse treatment planning system. We then compared the clinical dosimetric difference between the two algorithms for ten lung cancer patients receiving stereotactic radiosurgery treatment, by accumulating the delivered dose to the end-of-exhale (EE) phase. Specifically, the respiratory period was divided into ten phases and the dose to each phase was calculated and mapped to the EE phase and then accumulated. The displacement vector field generated by Demons-based registration of the source and reference images was used to transfer the dose and energy. The DDM and EMT algorithms produced noticeably different cumulative dose in the regions with sharp mass density variations and/or high dose gradients. For the planning target volume (PTV) and internal target volume (ITV) minimum dose, the difference was up to 11% and 4% respectively. This suggests that DDM might not be adequate for obtaining an accurate dose distribution of the cumulative plan, instead, EMT should be considered.

  10. Direct dose mapping versus energy/mass transfer mapping for 4D dose accumulation: fundamental differences and dosimetric consequences

    NASA Astrophysics Data System (ADS)

    Li, Haisen S.; Zhong, Hualiang; Kim, Jinkoo; Glide-Hurst, Carri; Gulam, Misbah; Nurushev, Teamour S.; Chetty, Indrin J.

    2014-01-01

    The direct dose mapping (DDM) and energy/mass transfer (EMT) mapping are two essential algorithms for accumulating the dose from different anatomic phases to the reference phase when there is organ motion or tumor/tissue deformation during the delivery of radiation therapy. DDM is based on interpolation of the dose values from one dose grid to another and thus lacks rigor in defining the dose when there are multiple dose values mapped to one dose voxel in the reference phase due to tissue/tumor deformation. On the other hand, EMT counts the total energy and mass transferred to each voxel in the reference phase and calculates the dose by dividing the energy by mass. Therefore it is based on fundamentally sound physics principles. In this study, we implemented the two algorithms and integrated them within the Eclipse treatment planning system. We then compared the clinical dosimetric difference between the two algorithms for ten lung cancer patients receiving stereotactic radiosurgery treatment, by accumulating the delivered dose to the end-of-exhale (EE) phase. Specifically, the respiratory period was divided into ten phases and the dose to each phase was calculated and mapped to the EE phase and then accumulated. The displacement vector field generated by Demons-based registration of the source and reference images was used to transfer the dose and energy. The DDM and EMT algorithms produced noticeably different cumulative dose in the regions with sharp mass density variations and/or high dose gradients. For the planning target volume (PTV) and internal target volume (ITV) minimum dose, the difference was up to 11% and 4% respectively. This suggests that DDM might not be adequate for obtaining an accurate dose distribution of the cumulative plan, instead, EMT should be considered.

  11. Optimization of Stability Constrained Geometrically Nonlinear Shallow Trusses Using an Arc Length Sparse Method with a Strain Energy Density Approach

    NASA Technical Reports Server (NTRS)

    Hrinda, Glenn A.; Nguyen, Duc T.

    2008-01-01

    A technique for the optimization of stability constrained geometrically nonlinear shallow trusses with snap through behavior is demonstrated using the arc length method and a strain energy density approach within a discrete finite element formulation. The optimization method uses an iterative scheme that evaluates the design variables' performance and then updates them according to a recursive formula controlled by the arc length method. A minimum weight design is achieved when a uniform nonlinear strain energy density is found in all members. This minimal condition places the design load just below the critical limit load causing snap through of the structure. The optimization scheme is programmed into a nonlinear finite element algorithm to find the large strain energy at critical limit loads. Examples of highly nonlinear trusses found in literature are presented to verify the method.

  12. Single-shot full strain tensor determination with microbeam X-ray Laue diffraction and a two-dimensional energy-dispersive detector.

    PubMed

    Abboud, A; Kirchlechner, C; Keckes, J; Conka Nurdan, T; Send, S; Micha, J S; Ulrich, O; Hartmann, R; Strüder, L; Pietsch, U

    2017-06-01

    The full strain and stress tensor determination in a triaxially stressed single crystal using X-ray diffraction requires a series of lattice spacing measurements at different crystal orientations. This can be achieved using a tunable X-ray source. This article reports on a novel experimental procedure for single-shot full strain tensor determination using polychromatic synchrotron radiation with an energy range from 5 to 23 keV. Microbeam X-ray Laue diffraction patterns were collected from a copper micro-bending beam along the central axis (centroid of the cross section). Taking advantage of a two-dimensional energy-dispersive X-ray detector (pnCCD), the position and energy of the collected Laue spots were measured for multiple positions on the sample, allowing the measurement of variations in the local microstructure. At the same time, both the deviatoric and hydrostatic components of the elastic strain and stress tensors were calculated.

  13. Energy dependence of the spin excitation anisotropy in uniaxial-strained BaFe 1.9Ni 0.1As 2

    DOE PAGES

    Song, Yu; Lu, Xingye; Abernathy, Douglas L.; ...

    2015-11-06

    In this study, we use inelastic neutron scattering to study the temperature and energy dependence of the spin excitation anisotropy in uniaxial-strained electron-doped iron pnictide BaFe 1.9Ni 0.1As 2 near optimal superconductivity (T c = 20K). Our work has been motivated by the observation of in-plane resistivity anisotropy in the paramagnetic tetragonal phase of electron-underdoped iron pnictides under uniaxial pressure, which has been attributed to a spin-driven Ising-nematic state or orbital ordering. Here we show that the spin excitation anisotropy, a signature of the spin-driven Ising-nematic phase, exists for energies below 60 meV in uniaxial-strained BaFe 1.9Ni 0.1As 2. Sincemore » this energy scale is considerably larger than the energy splitting of the d xz and d yz bands of uniaxial-strained Ba(Fe 1–xCox) 2As 2 near optimal superconductivity, spin Ising-nematic correlations are likely the driving force for the resistivity anisotropy and associated electronic nematic correlations.« less

  14. Residual strain gradient determination in metal matrix composites by synchrotron X-ray energy dispersive diffraction

    NASA Technical Reports Server (NTRS)

    Kuntz, Todd A.; Wadley, Haydn N. G.; Black, David R.

    1993-01-01

    An X-ray technique for the measurement of internal residual strain gradients near the continuous reinforcements of metal matrix composites has been investigated. The technique utilizes high intensity white X-ray radiation from a synchrotron radiation source to obtain energy spectra from small (0.001 cu mm) volumes deep within composite samples. The viability of the technique was tested using a model system with 800 micron Al203 fibers and a commercial purity titanium matrix. Good agreement was observed between the measured residual radial and hoop strain gradients and those estimated from a simple elastic concentric cylinders model. The technique was then used to assess the strains near (SCS-6) silicon carbide fibers in a Ti-14Al-21Nb matrix after consolidation processing. Reasonable agreement between measured and calculated strains was seen provided the probe volume was located 50 microns or more from the fiber/matrix interface.

  15. Osmoregulation in Agrobacterium tumefaciens: accumulation of a novel disaccharide is controlled by osmotic strength and glycine betaine.

    PubMed Central

    Smith, L T; Smith, G M; Madkour, M A

    1990-01-01

    We have investigated the mechanism of osmotic stress adaptation (osmoregulation) in Agrobacterium tumefaciens biotype I (salt-tolerant) and biotype II (salt-sensitive) strains. Using natural-abundance 13C nuclear magnetic resonance spectroscopy, we identified all organic solutes that accumulated to significant levels in osmotically stressed cultures. When stressed, biotype I strains (C58, NT1, and A348) accumulated glutamate and a novel disaccharide, beta-fructofuranosyl-alpha-mannopyranoside, commonly known as mannosucrose. In the salt-sensitive biotype II strain K84, glutamate was observed but mannosucrose was not. We speculate that mannosucrose confers the extra osmotic tolerance observed in the biotype I strains. In addition to identifying the osmoregulated solutes that this species synthesizes, we investigated the ability of A. tumefaciens to utilize the powerful osmotic stress protectant glycine betaine when it is supplied in the medium. Results from growth experiments, nuclear magnetic resonance spectroscopy, and a 14C labeling experiment demonstrated that in the absence of osmotic stress, glycine betaine was metabolized, while in stressed cultures, glycine betaine accumulated intracellularly and conferred enhanced osmotic stress tolerance. Furthermore, when glycine betaine was taken up in stressed cells, its accumulation caused the intracellular concentration of mannosucrose to drop significantly. The possible role of osmoregulation of A. tumefaciens in the transformation of plants is discussed. PMID:2254260

  16. Energy approach to brittle fracture in strain-gradient modelling.

    PubMed

    Placidi, Luca; Barchiesi, Emilio

    2018-02-01

    In this paper, we exploit some results in the theory of irreversible phenomena to address the study of quasi-static brittle fracture propagation in a two-dimensional isotropic continuum. The elastic strain energy density of the body has been assumed to be geometrically nonlinear and to depend on the strain gradient. Such generalized continua often arise in the description of microstructured media. These materials possess an intrinsic length scale, which determines the size of internal boundary layers. In particular, the non-locality conferred by this internal length scale avoids the concentration of deformations, which is usually observed when dealing with local models and which leads to mesh dependency. A scalar Lagrangian damage field, ranging from zero to one, is introduced to describe the internal state of structural degradation of the material. Standard Lamé and second-gradient elastic coefficients are all assumed to decrease as damage increases and to be locally zero if the value attained by damage is one. This last situation is associated with crack formation and/or propagation. Numerical solutions of the model are provided in the case of an obliquely notched rectangular specimen subjected to monotonous tensile and shear loading tests, and brittle fracture propagation is discussed.

  17. Lattice model calculation of the strain energy density and other properties of crystalline LiCoO{sub 2}

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

    Hart, F.X.; Bates, J.B.

    1998-06-01

    The strain energy densities for various crystalline planes of LiCoO{sub 2} were calculated from the stiffness tensors obtained from lattice model calculations using the program GULP. In addition to Coulomb and Buckingham potentials, it was necessary to include shell models for the oxygen and cobalt ions in order to obtain acceptable agreement between the observed and calculated structural parameters and high frequency dielectric constant. The strain energy densities u due to differential thermal expansion were calculated using the theoretical stiffness tensors and estimated values for the thermal expansion coefficients of LiCoO{sub 2}. For a temperature change of 675thinsp{degree}C, these rangedmore » from 0.5 to 1.3{times}10{sup 8}thinsperg/cm{sup 3} or 5 to 13thinspJ/m{sup 2} for 1-{mu}m-thick films on alumina substrates. In particular, the energies for the (003), (101), and (104) planes were ordered as u(003){gt}u(104){gt}u(101). This suggests that the strong (101) preferred orientation of LiCoO{sub 2} films ({ge}1thinsp{mu}m thick) is due to the tendency to minimize volume strain energy that arises from differential thermal expansion between the film and the substrate. Additional properties obtained from the GULP calculations include the free energy, heat capacity, and the k=0 vibrational modes. thinsp« less

  18. Decreasing Distortion Energies without Strain: Diazo-Selective 1,3-Dipolar Cycloadditions.

    PubMed

    Gold, Brian; Aronoff, Matthew R; Raines, Ronald T

    2016-07-15

    The diazo group has attributes that complement those of the azido group for applications in chemical biology. Here, we use computational analyses to provide insights into the chemoselectivity of the diazo group in 1,3-dipolar cycloadditions. Dipole distortion energies are responsible for ∼80% of the overall energetic barrier for these reactions. Here, we show that diazo compounds, unlike azides, provide an opportunity to decrease that barrier substantially without introducing strain into the dipolarophile. The ensuing rate enhancement is due to the greater nucleophilic character of a diazo group compared to that of an azido group, which can accommodate decreased distortion energies without predistortion. The tuning of distortion energies with substituents in a diazo compound or dipolarophile can enhance reactivity and selectivity in a predictable manner. Notably, these advantages of diazo groups are amplified in water. Our findings provide a theoretical framework that can guide the design and application of both diazo compounds and azides in "orthogonal" contexts, especially for biological investigations.

  19. Creation of High-Yield Polyhydroxyalkanoates Engineered Strains by Low Energy Ion Implantation

    NASA Astrophysics Data System (ADS)

    Qian, Shiquan; Cheng, Ying; Zhu, Suwen; Cheng, Beijiu

    2008-12-01

    Polyhydroxyalkanoates (PHAs), as a candidate for biodegradable plastic materials, can be synthesized by numerous microorganisms. However, as its production cost is high in comparison with those of chemically synthesized plastics, a lot of research has been focused on the efficient production of PHAs using different methods. In the present study, the mutation effects of PHAs production in strain pCB4 were investigated with implantation of low energy ions. It was found that under the implantation conditions of 7.8 × 1014 N+/cm2 at 10 keV, a high-yield PHAs strain with high genetic stability was generated from many mutants. After optimizing its fermentation conditions, the biomass, PHAs concentration and PHAs content of pCBH4 reached 2.26 g/L, 1.81 g/L, and 80.08% respectively, whereas its wild type controls were about 1.24 g/L, 0.61 g/L, and 49.20%. Moreover, the main constituent of PHAs was identified as poly-3-hydroxybutyrates (PHB) in the mutant stain and the yield of this compound was increased up to 41.33% in contrast to that of 27.78% in the wild type strain.

  20. Tyrosine decarboxylase activity of enterococci grown in media with different nutritional potential: tyramine and 2-phenylethylamine accumulation and tyrDC gene expression.

    PubMed

    Bargossi, Eleonora; Tabanelli, Giulia; Montanari, Chiara; Lanciotti, Rosalba; Gatto, Veronica; Gardini, Fausto; Torriani, Sandra

    2015-01-01

    The ability to accumulate tyramine and 2-phenylethylamine by two strains of Enterococcus faecalis and two strains Enterococcus faecium was evaluated in two cultural media added or not with tyrosine. All the enterococcal strains possessed a tyrosine decarboxylase (tyrDC) which determined tyramine accumulation in all the conditions tested, independently on the addition of high concentration of free tyrosine. Enterococci differed in rate and level of biogenic amines accumulation. E. faecalis EF37 and E. faecium FC12 produced tyramine in high amount since the exponential growth phase, while 2-phenylethylamine was accumulated when tyrosine was depleted. E. faecium FC12 and E. faecalis ATCC 29212 showed a slower tyraminogenic activity which took place mainly in the stationary phase up to 72 h of incubation. Moreover, E. faecalis ATCC 29212 produced 2-phenylethylamine only in the media without tyrosine added. In BHI added or not with tyrosine the tyrDC gene expression level differed considerably depending on the strains and the growth phase. In particular, the tyrDC gene expression was high during the exponential phase in rich medium for all the strains and subsequently decreased except for E. faecium FC12. Even if tyrDC presence is common among enterococci, this study underlines the extremely variable decarboxylating potential of strains belonging to the same species, suggesting strain-dependent implications in food safety.

  1. Dinuclear polypyridylruthenium(II) complexes: flow cytometry studies of their accumulation in bacteria and the effect on the bacterial membrane.

    PubMed

    Li, Fangfei; Feterl, Marshall; Warner, Jeffrey M; Keene, F Richard; Collins, J Grant

    2013-12-01

    To determine the energy dependency of and the contribution of the membrane potential to the cellular accumulation of the dinuclear complexes [{Ru(phen)2}2{μ-bbn}](4+) (Rubbn) and the mononuclear complexes [Ru(Me4phen)3](2+) and [Ru(phen)2(bb7)](2+) in Staphylococcus aureus and Escherichia coli, and to examine their effect on the bacterial membrane. The accumulation of the ruthenium complexes in bacteria was determined using flow cytometry at a range of temperatures. The cellular accumulation of the ruthenium complexes was also determined in cells that had been incubated with the metal complexes in the presence or absence of metabolic stimulators or inhibitors and/or commercial dyes to determine the membrane potential or membrane permeability. The accumulation of ruthenium complexes in the two bacterial strains was shown to increase with increasing incubation temperature, with the relative increase in accumulation greater with E. coli, particularly for Rubb12 and Rubb16. No decrease in accumulation was observed for Rubb12 in ATP-inhibited cells. While carbonyl cyanide m-chlorophenyl hydrazone (CCCP) did depolarize the cell membrane, no reduction in the accumulation of Rubb12 was observed; however, all ruthenium complexes, when incubated with S. aureus at concentrations twice their MIC, depolarized the membrane to a similar extent to CCCP. Except for the mononuclear complex [Ru(Me4phen)3](2+), incubation of any of the other ruthenium complexes allowed a greater quantity of the membrane-impermeable dye TO-PRO-3 to be taken up by S. aureus. The results indicate that the potential new antimicrobial Rubbn complexes enter the cell in an energy-independent manner, depolarize the cell membrane and significantly permeabilize the cellular membrane.

  2. Strain dependence of In incorporation in m-oriented GaInN/GaN multi quantum well structures

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

    Horenburg, Philipp, E-mail: p.horenburg@tu-braunschweig.de; Buß, Ernst Ronald; Rossow, Uwe

    We demonstrate a strong dependence of the indium incorporation efficiency on the strain state in m-oriented GaInN/GaN multi quantum well (MQW) structures. Insertion of a partially relaxed AlInN buffer layer opens up the opportunity to manipulate the strain situation in the MQW grown on top. By lattice-matching this AlInN layer to the c- or a-axis of the underlying GaN, relaxation towards larger a- or smaller c-lattice constants can be induced, respectively. This results in a modified template for the subsequent MQW growth. From X-ray diffraction and photoluminescence measurements, we derive significant effects on the In incorporation efficiency and In concentrationsmore » in the quantum well (QW) up to x = 38% without additional accumulation of strain energy in the QW region. This makes strain manipulation a very promising method for growth of high In-containing MQW structures for efficient, long wavelength light-emitting devices.« less

  3. Effect of fault roughness on aftershock distribution and post co-seismic strain accumulation.

    NASA Astrophysics Data System (ADS)

    Aslam, K.; Daub, E. G.

    2017-12-01

    We perform physics-based simulations of earthquake rupture propagation on geometrically complex strike-slip faults. We consider many different realization of the fault roughness and obtain heterogeneous stress fields by performing dynamic rupture simulation of large earthquakes. We calculate the Coulomb failure function (CFF) for all these realizations so that we can quantify zones of stress increase/shadows surrounding the main fault and compare our results to seismic catalogs. To do this comparison, we use relocated earthquake catalogs from Northern and Southern California. We specify the range of fault roughness parameters based on past observational studies. The Hurst exponent (H) varies in range from 0.5 to 1 and RMS height to wavelength ratio ( RMS deviation of a fault profile from planarity) has values between 10-2 to 10-3. For any realization of fault roughness, the Probability density function (PDF) values relative to the mean CFF change show a wider spread near the fault and this spread squeezes into a narrow band as we move away from fault. For lower value of RMS ratio ( 10-3), we see bigger zones of stress change near the hypocenter and for higher value of RMS ratio ( 10-2), we see alternate zones of stress increase/decrease surrounding the fault to have comparable lengths. We also couple short-term dynamic rupture simulation with long-term tectonic modelling. We do this by giving the stress output from one of the dynamic rupture simulation (of a single realization of fault roughness) to long term tectonic model (LTM) as initial condition and then run LTM over duration of seismic cycle. This short term and long term coupling enables us to understand how heterogeneous stresses due to fault geometry influence the dynamics of strain accumulation in the post-seismic and inter-seismic phase of seismic cycle.

  4. Bioprocessing of Stichococcus bacillaris strain siva2011

    PubMed Central

    2014-01-01

    Background Globally, the development of a cost-effective long-term renewable energy infrastructure is one of the most challenging problems faced by society today. Microalgae are rich in potential biofuel substrates such as lipids, including triacylglycerols (TAGs). Some of these algae also biosynthesize small molecule hydrocarbons. These hydrocarbons can often be used as liquid fuels, often with more versatility and by a more direct approach than some TAGs. However, the appropriate TAGs, accumulated from microalgae biomass, can be used as substrates for different kinds of renewable liquid fuels such as biodiesel and jet fuel. Results This article describes the isolation and identification of a lipid-rich, hydrocarbon-producing alga, Stichococcus bacillaris strain siva2011, together with its bioprocessing, hydrocarbon and fatty acid methyl ester (FAME) profiles. The S. bacillaris strain siva2011 was scaled-up in an 8 L bioreactor with 0.2% CO2. The C16:0, C16:3, C18:1, C18:2 and C18:3 were 112.2, 9.4, 51.3, 74.1 and 69.2 mg/g dry weight (DW), respectively. This new strain produced a significant amount of biomass of 3.79 g/L DW on day 6 in the 8 L bioreactor and also produced three hydrocarbons. Conclusions A new oil-rich microalga S. bacillaris strain siva2011 was discovered and its biomass has been scaled-up in a newly designed balloon-type bioreactor. The TAGs and hydrocarbons produced by this organism could be used as substrates for jet fuel or biodiesel. PMID:24731690

  5. Bioprocessing of Stichococcus bacillaris strain siva2011.

    PubMed

    Sivakumar, Ganapathy; Jeong, Kwangkook; Lay, Jackson O

    2014-01-01

    Globally, the development of a cost-effective long-term renewable energy infrastructure is one of the most challenging problems faced by society today. Microalgae are rich in potential biofuel substrates such as lipids, including triacylglycerols (TAGs). Some of these algae also biosynthesize small molecule hydrocarbons. These hydrocarbons can often be used as liquid fuels, often with more versatility and by a more direct approach than some TAGs. However, the appropriate TAGs, accumulated from microalgae biomass, can be used as substrates for different kinds of renewable liquid fuels such as biodiesel and jet fuel. This article describes the isolation and identification of a lipid-rich, hydrocarbon-producing alga, Stichococcus bacillaris strain siva2011, together with its bioprocessing, hydrocarbon and fatty acid methyl ester (FAME) profiles. The S. bacillaris strain siva2011 was scaled-up in an 8 L bioreactor with 0.2% CO2. The C16:0, C16:3, C18:1, C18:2 and C18:3 were 112.2, 9.4, 51.3, 74.1 and 69.2 mg/g dry weight (DW), respectively. This new strain produced a significant amount of biomass of 3.79 g/L DW on day 6 in the 8 L bioreactor and also produced three hydrocarbons. A new oil-rich microalga S. bacillaris strain siva2011 was discovered and its biomass has been scaled-up in a newly designed balloon-type bioreactor. The TAGs and hydrocarbons produced by this organism could be used as substrates for jet fuel or biodiesel.

  6. Breeding of D(-)-lactic acid high producing strain by low-energy ion implantation and preliminary analysis of related metabolism.

    PubMed

    Xu, Ting-Ting; Bai, Zhong-Zhong; Wang, Li-Juan; He, Bing-Fang

    2010-01-01

    The low-energy nitrogen ion beam implantation technique was used in the breeding of mutant D(-)-lactic-acid-producing strains. The wild strain Sporolactobacillus sp. DX12 was mutated by an N(+) ion beam with energy of 10keV and doses ranging from 0.4 x 10(15) to 6.60 x 10(15) ions/cm(2). Combined with an efficient screening method, an efficient mutant Y2-8 was selected after two times N(+) ion beam implantation. By using the mutant Y2-8, 121.6g/l of D-lactic acid was produced with the molar yields of 162.1% to the glucose. The yield of D-lactic acid by strain Y2-8 was 198.8% higher than the wild strain. Determination of anaerobic metabolism by Biolog MT2 was used to analyze the activities of the concerned enzymes in the lactic acid metabolic pathway. The results showed that the activities of the key enzymes responded on the substrates such as 6-phosphofructokinase, pyruvate kinase, and D-lactate dehydrogenase were considerably higher in the mutants than the wild strain. These might be affected by ion beam implantation.

  7. Strain relaxation of CdTe on Ge studied by medium energy ion scattering

    NASA Astrophysics Data System (ADS)

    Pillet, J. C.; Pierre, F.; Jalabert, D.

    2016-10-01

    We have used the medium energy ion scattering (MEIS) technique to assess the strain relaxation in molecular-beam epitaxial (MBE) grown CdTe (2 1 1)/Ge (2 1 1) system. A previous X-ray diffraction study, on 10 samples of the same heterostructure having thicknesses ranging from 25 nm to 10 μm has allowed the measurement of the strain relaxation on a large scale. However, the X-ray diffraction measurements cannot achieve a stress measurement in close proximity to the CdTe/Ge interface at the nanometer scale. Due to the huge lattice misfit between the CdTe and Ge, a high degree of disorder is expected at the interface. The MEIS in channeling mode is a good alternative in order to profile defects with a high depth resolution. For a 21 nm thick CdTe layer, we observed, at the interface, a high density of Cd and/or Te atoms moved from their expected crystallographic positions followed by a rapid recombination of defects. Strain relaxation mechanisms in the vicinity of the interface are discussed

  8. Effect of Hydraulic Accumulator on Pressure Surge of a Hydrostatic Transmission System

    NASA Astrophysics Data System (ADS)

    Kumar, Ajit; Das, Jayanta; Dasgupta, Kabir; Barnwal, Manish Kumar

    2018-04-01

    Hydraulic power system is generally used in off-road vehicles for power transmission such as Heavy Earth Moving Machineries (HEMM). Their energy efficiency and unsubstantial failure becomes an extensive subject of analysis. Various arrangements in the system are compassed along with the utilization of some appropriate components. Application of a hydraulic accumulator is one among them. Benefits of accumulator is its multi-purpose usages like energy saving and pressure surge damping. This paper deals with the control of pressure surges in the hydraulic system and energy saving from the surges by using accumulator. For this purpose, the simulation of the hydraulic system is done in MATLAB/SimulinkR environment and an external disturbance is introduced to generate the pressure surge. The surge absorptivity of the accumulator is studied for different sizes at different pre-charged conditions of the accumulator. The discharge characteristics of different sized accumulators are also analyzed in this paper. It is observed that the ability to absorb the surge and stabilize the system is high in the smaller capacity accumulator. However the energy delivery time of larger sized accumulator is high.

  9. Tuning the energy gap of bilayer α-graphyne by applying strain and electric field

    NASA Astrophysics Data System (ADS)

    Yang, Hang; Wu, Wen-Zhi; Jin, Yu; Wan-Lin, Guo

    2016-02-01

    Our density functional theory calculations show that the energy gap of bilayer α-graphyne can be modulated by a vertically applied electric field and interlayer strain. Like bilayer graphene, the bilayer α-graphyne has electronic properties that are hardly changed under purely mechanical strain, while an external electric field can open the gap up to 120 meV. It is of special interest that compressive strain can further enlarge the field induced gap up to 160 meV, while tensile strain reduces the gap. We attribute the gap variation to the novel interlayer charge redistribution between bilayer α-graphynes. These findings shed light on the modulation of Dirac cone structures and potential applications of graphyne in mechanical-electric devices. Project supported by the National Key Basic Research Program of China (Grant Nos. 2013CB932604 and 2012CB933403), the National Natural Science Foundation of China (Grant Nos. 51472117 and 51535005), the Research Fund of State Key Laboratory of Mechanics and Control of Mechanical Structures, China (Grant No. 0414K01), the Nanjing University of Aeronautics and Astronautics (NUAA) Fundamental Research Funds, China (Grant No. NP2015203), and the Priority Academic Program Development of Jiangsu Higher Education Institutions.

  10. Absence of ppGpp Leads to Increased Mobilization of Intermediately Accumulated Poly(3-Hydroxybutyrate) in Ralstonia eutropha H16

    PubMed Central

    Juengert, Janina R.; Borisova, Marina; Wolz, Christiane; Brigham, Christopher J.; Sinskey, Anthony J.

    2017-01-01

    ABSTRACT In this study, we constructed a set of Ralstonia eutropha H16 strains with single, double, or triple deletions of the (p)ppGpp synthase/hydrolase (spoT1), (p)ppGpp synthase (spoT2), and/or polyhydroxybutyrate (PHB) depolymerase (phaZa1 or phaZa3) gene, and we determined the impact on the levels of (p)ppGpp and on accumulated PHB. Mutants with deletions of both the spoT1 and spoT2 genes were unable to synthesize detectable amounts of (p)ppGpp and accumulated only minor amounts of PHB, due to PhaZa1-mediated depolymerization of PHB. In contrast, unusually high levels of PHB were found in strains in which the (p)ppGpp concentration was increased by the overexpression of (p)ppGpp synthase (SpoT2) and the absence of (p)ppGpp hydrolase. Determination of (p)ppGpp levels in wild-type R. eutropha under different growth conditions and induction of the stringent response by amino acid analogs showed that the concentrations of (p)ppGpp during the growth phase determine the amount of PHB remaining in later growth phases by influencing the efficiency of the PHB mobilization system in stationary growth. The data reported for a previously constructed ΔspoT2 strain (C. J. Brigham, D. R. Speth, C. Rha, and A. J. Sinskey, Appl Environ Microbiol 78:8033–8044, 2012, https://doi.org/10.1128/AEM.01693-12) were identified as due to an experimental error in strain construction, and our results are in contrast to the previous indication that the spoT2 gene product is essential for PHB accumulation in R. eutropha. IMPORTANCE Polyhydroxybutyrate (PHB) is an important intracellular carbon and energy storage compound in many prokaryotes and helps cells survive periods of starvation and other stress conditions. Research activities in several laboratories over the past 3 decades have shown that both PHB synthase and PHB depolymerase are constitutively expressed in most PHB-accumulating bacteria, such as Ralstonia eutropha. This implies that PHB synthase and depolymerase activities

  11. Accumulate repeat accumulate codes

    NASA Technical Reports Server (NTRS)

    Abbasfar, A.; Divsalar, D.; Yao, K.

    2004-01-01

    In this paper we propose an innovative channel coding scheme called Accumulate Repeat Accumulate codes. This class of codes can be viewed as trubo-like codes, namely a double serial concatenation of a rate-1 accumulator as an outer code, a regular or irregular repetition as a middle code, and a punctured accumulator as an inner code.

  12. Hydrocarbon productivities in different Botryococcus strains: comparative methods in product quantification.

    PubMed

    Eroglu, Ela; Okada, Shigeru; Melis, Anastasios

    2011-08-01

    Six different strains of the green microalgae Botryococcus belonging to the A-race or B-race, accumulating alkadiene or botryococcene hydrocarbons, respectively, were compared for biomass and hydrocarbon productivities. Biomass productivity was assessed gravimetrically upon strain growth in the laboratory under defined conditions. Hydrocarbon productivities were measured by three different and independent experimental approaches, including density equilibrium of the intact cells and micro-colonies, spectrophotometric analysis of hydrocarbon extracts, and gravimetric quantitation of eluted hydrocarbons. All three hydrocarbon-quantitation methods yielded similar results for each of the strains examined. The B-race microalgae Botryococcus braunii var. Showa and Kawaguchi-1 constitutively accumulated botryococcene hydrocarbons equivalent to 30% and 20%, respectively, of their overall biomass. The A-race microalgae Botryococcus braunii, varieties Yamanaka, UTEX 2441 and UTEX LB572 constitutively accumulated alkadiene hydrocarbons ranging from 14% to 13% and 10% of their overall biomass, respectively. Botryococcus sudeticus (UTEX 2629), a morphologically different green microalga, had the lowest hydrocarbon accumulation, equal to about 3% of its overall biomass. Results validate the density equilibrium and spectrophotometric analysis methods in the quantitation of botryococcene-type hydrocarbons. These analytical advances will serve in the screening and selection of B. braunii and of other microalgae in efforts to identify those having a high hydrocarbon content for use in commercial applications.

  13. [Physiological and biochemical characteristics and capacity for polyhydroxyalkanoates synthesis in a glucose-utilizing strain of hydrogen-oxidizing bacteria, Ralstonia eutropha B8562].

    PubMed

    Volova, T G; Kozhevnikov, I V; Dolgopolova, Iu B; Trusova, M Iu; Kalacheva, G S; Aref'eva, Iu V

    2005-01-01

    The physiological, biochemical, genetic, and cultural characteristics of the glucose-utilizing mutant strain Ralstonia eutropha B8562 were investigated in comparison with the parent strain R. eutropha B5786. The morphological, cultural, and biochemical characteristics of strain R. eutropha B8562 were similar to those of strain R. eutropha B5786. Genetic analysis revealed differences between the 16S rRNA gene sequences of these strains. The growth characteristics of the mutant using glucose as the sole carbon and energy source were comparable with those of the parent strain grown on fructose. Strain B8562 was characterized by high yields of polyhydroxyalkanoate (PHA) from different carbon sources (CO2, fructose, and glucose). In batch culture with glucose under nitrogen limitation, PHA accumulation reached 90% of dry weight. In PHA, beta-hydroxybutyrate was predominant (over 99 mol %); beta-hydroxyvalerate (0.25-0.72 mol %) and beta-hydroxyhexanoate (0.008-1.5 mol %) were present as minor components. The strain has prospects as a PHA producer on glucose-containing media.

  14. Stringent control during carbon starvation of marine Vibrio sp. strain S14: molecular cloning, nucleotide sequence, and deletion of the relA gene.

    PubMed Central

    Flärdh, K; Axberg, T; Albertson, N H; Kjelleberg, S

    1994-01-01

    In order to evaluate the role of the stringent response in starvation adaptations of the marine Vibrio sp. strain S14, we have cloned the relA gene and generated relaxed mutants of this organism. The Vibrio relA gene was selected from a chromosomal DNA library by complementation of an Escherichia coli delta relA strain. The nucleotide sequence contains a 743-codon open reading frame that encodes a polypeptide that is identical in length and highly homologous to the E. coli RelA protein. The amino acid sequences are 64% identical, and they share some completely conserved regions. A delta relA::kan allele was generated by replacing 53% of the open reading frame with a kanamycin resistance gene. The Vibrio relA mutants displayed a relaxed control of RNA synthesis and failed to accumulate ppGpp during amino acid limitation. During carbon and energy starvation, a relA-dependent burst of ppGpp synthesis concomitant with carbon source depletion and growth arrest was observed. Also, in the absence of the relA gene, there was an accumulation of ppGpp during carbon starvation, but this was slower and smaller than that which occurred in the stringent strains, and it was preceded by a marked decrease in the [ATP]/[ADP] ratio. In both the wild-type and the relaxed strains, carbon source depletion caused an immediate decrease in the size of the GTP pool and a block of net RNA accumulation. The relA mutation did not affect long-term survival or the development of resistance against heat, ethanol, and oxidative stress during carbon starvation of Vibrio sp. strain S14. PMID:7928955

  15. Characterization of a selenium-tolerant rhizosphere strain from a novel Se-hyperaccumulating plant Cardamine hupingshanesis.

    PubMed

    Tong, Xinzhao; Yuan, Linxi; Luo, Lei; Yin, Xuebin

    2014-01-01

    A novel selenium- (Se-) hyperaccumulating plant, Cardamine hupingshanesis, accumulating Se as a form of SeCys2, was discovered in Enshi, Hubei, China, which could not be explained by present selenocysteine methyltransferase (SMT) theory. However, it is interesting to investigate if rhizosphere bacteria play some roles during SeCys2 accumulation. Here, one Se-tolerant rhizosphere strain, Microbacterium oxydans, was isolated from C. hupingshanesis. Phylogenetic analysis and 16S rRNA gene sequences determined the strain as a kind of Gram positive bacillus and belonged to the family Brevibacterium frigoritolerans. Furthermore, Se tolerance test indicated the strain could grow in extreme high Se level of 15.0 mg Se L(-1). When exposed to 1.5 mg Se L(-1), SeCys2 was the predominant Se species in the bacteria, consistent with the Se species in C. hupingshanesis. This coincidence might reveal that this strain played some positive effect in SeCys2 accumulation of C. hupingshanesis. Moreover, when exposed to 1.5 mg Se L(-1) or 15.0 mg Se L(-1), As absorption diminished in the logarithmic phase. In contrast, As absorption increased when exposed to 7.5 mg Se L(-1), indicating As metabolism processes could be affected by Se on this strain. The present study provided a sight on the role of rhizosphere bacteria during Se accumulation for Se-hyperaccumulating plant.

  16. Shear-wave Velocity Structure and Inter-Seismic Strain Accumulation in the Up-Dip Region of the Cascadia Subduction Zone: Similarities to Tohoku?

    NASA Astrophysics Data System (ADS)

    Collins, J. A.; McGuire, J. J.; Wei, M.

    2013-12-01

    the measured compliances in this frequency band using a genetic algorithm that solves for the S-wave velocity, P-wave velocity, and density in a layered structure. By including constraints on the Vp distribution from active-source studies, these parameters appear well constrained down to about 4 km depth from our dataset. There is a clear difference in observed compliance values between stations close to the deformation front (~10 km) and those further up the continental slope (~30-40 km) indicating a region of unconsolidated, high-porosity sediment similar to the off-Tohoku region. The low S-wave velocities and high Vp/Vs ratios in the up-dip region correspond to unconsolidated high-porosity sediments. We calculated the effect of this material property contrast on the inter-seismic strain accumulation in the up-dip region of the subduction zone using a finite element model and find that the sediments can increase the amount of inter-seismic strain accumulated in the up-dip region by >100% relative to a homogenous elastic model.

  17. Characterization of Clostridium thermocellum strains with disrupted fermentation end product pathways

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

    Van Der Veen, Douwe; Lo, Jonathan; Brown, Steven D

    2013-01-01

    Clostridium thermocellum is a thermophilic, cellulolytic anaerobe that is a candidate microorganism for industrial biofuels production. Strains with mutations in genes associated with production of Llactate ( ldh) and/or acetate ( pta) were characterized to gain insight into the intracellular processes that convert cellobiose to ethanol and other fermentation end products. Cellobiose-grown cultures of the ldh strain had identical biomass accumulation, fermentation end products, transcription profile and intracellular metabolite concentrations compared to its parent strain (DSM1313 hpt spo0A). The pta-deficient strain grew slower and had 30% lower final biomass concentration compared to the parent strain, yet produced 75% more ethanol.more » A ldh pta double mutant strain evolved for faster growth had growth rate and ethanol yield comparable to the parent strain, whereas its biomass accumulation was comparable to pta. Free amino acids were secreted by all examined strains, with both pta strains secreting higher amounts of alanine, valine, isoleucine, proline, glutamine, and threonine. Valine concentration for ldh pta reached 5 mM by the end of growth, or 2.7% of the substrate carbon utilized. These secreted amino acid concentrations correlate with increased intracellular pyruvate concentrations, up to 6-fold in the pta and 16-fold in the ldh pta strain. We hypothesize that the deletions in fermentation end product pathways result in an intracellular redox imbalance, which the organism attempts to relieve, in part by recycling NADP+ through increased production of amino acids.« less

  18. Characterization of Clostridium thermocellum strains with disrupted fermentation end-product pathways

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

    Van Der Veen, Douwe; Lo, Jonathan; Brown, Steven D

    2013-01-01

    Clostridium thermocellum is a thermophilic, cellulolytic anaerobe that is a candidate microorganism for industrial biofuels production. Strains with mutations in genes associated with production of L-lactate (Dldh) and/or acetate (Dpta) were characterized to gain insight into the intracellular processes that convert cellobiose to ethanol and other fermentation end-products. Cellobiose-grown cultures of the Dldh strain had identical biomass accumulation, fermentation end-products, transcription profile, and intracellular metabolite concentrations compared to its parent strain (DSM1313 Dhpt Dspo0A). The Dpta-deficient strain grew slower and had 30 % lower final biomass concentration compared to the parent strain, yet produced 75% more ethanol. A Dldh Dptamore » double-mutant strain evolved for faster growth had a growth rate and ethanol yield comparable to the parent strain, whereas its biomass accumulation was comparable to Dpta. Free amino acids were secreted by all examined strains, with both Dpta strains secreting higher amounts of alanine, valine, isoleucine, proline, glutamine, and threonine. Valine concentration for Dldh Dpta reached 5 mM by the end of growth, or 2.7 % of the substrate carbon utilized. These secreted amino acid concentrations correlate with increased intracellular pyruvate concentrations, up to sixfold in the Dpta and 16-fold in the Dldh Dpta strain. We hypothesize that the deletions in fermentation end-product pathways result in an intracellular redox imbalance, which the organism attempts to relieve, in part by recycling NADP* through increased production of amino acids.« less

  19. Influence of the Strain History on TWIP Steel Deformation Mechanisms in the Deep-Drawing Process

    NASA Astrophysics Data System (ADS)

    Lapovok, R.; Timokhina, I.; Mester, A.-K.; Weiss, M.; Shekhter, A.

    2018-03-01

    A study of preferable deformation modes on strain path and strain level in a TWIP steel sheet was performed. Different strain paths were obtained by stretch forming of specimens with various shapes and tensile tests. TEM analysis was performed on samples cut from various locations in the deformed specimens, which had different strain paths and strain levels and the preferable deformation modes were identified. Stresses caused by various strain paths were considered and an analytical analysis performed to identify the preferable deformation modes for the case of single crystal. For a single crystal, in assumption of the absence of lattice rotation, the strain path and the level of accumulated equivalent strain define the preferable deformation mode. For a polycrystalline material, such analytical analysis is not possible due to the large number of grains and, therefore, numerical simulation was employed. For the polycrystalline material, the role of strain path diminishes due to the presence of a large number of grains with random orientations and the effect of accumulated strain becomes dominant. However, at small strains the strain path still defines the level of twinning activity. TEM analysis experimentally confirmed that various deformation modes lead to different deformation strengthening mechanisms.

  20. Influence of the Strain History on TWIP Steel Deformation Mechanisms in the Deep-Drawing Process

    NASA Astrophysics Data System (ADS)

    Lapovok, R.; Timokhina, I.; Mester, A.-K.; Weiss, M.; Shekhter, A.

    2018-06-01

    A study of preferable deformation modes on strain path and strain level in a TWIP steel sheet was performed. Different strain paths were obtained by stretch forming of specimens with various shapes and tensile tests. TEM analysis was performed on samples cut from various locations in the deformed specimens, which had different strain paths and strain levels and the preferable deformation modes were identified. Stresses caused by various strain paths were considered and an analytical analysis performed to identify the preferable deformation modes for the case of single crystal. For a single crystal, in assumption of the absence of lattice rotation, the strain path and the level of accumulated equivalent strain define the preferable deformation mode. For a polycrystalline material, such analytical analysis is not possible due to the large number of grains and, therefore, numerical simulation was employed. For the polycrystalline material, the role of strain path diminishes due to the presence of a large number of grains with random orientations and the effect of accumulated strain becomes dominant. However, at small strains the strain path still defines the level of twinning activity. TEM analysis experimentally confirmed that various deformation modes lead to different deformation strengthening mechanisms.

  1. Changing surface-atmosphere energy exchange and refreezing capacity of the lower accumulation area, West Greenland

    NASA Astrophysics Data System (ADS)

    Charalampidis, C.; van As, D.; Box, J. E.; van den Broeke, M. R.; Colgan, W. T.; Doyle, S. H.; Hubbard, A. L.; MacFerrin, M.; Machguth, H.; Smeets, C. J. P. P.

    2015-11-01

    We present 5 years (2009-2013) of automatic weather station measurements from the lower accumulation area (1840 m a.s.l. - above sea level) of the Greenland ice sheet in the Kangerlussuaq region. Here, the summers of 2010 and 2012 were both exceptionally warm, but only 2012 resulted in a strongly negative surface mass budget (SMB) and surface meltwater run-off. The observed run-off was due to a large ice fraction in the upper 10 m of firn that prevented meltwater from percolating to available pore volume below. Analysis reveals an anomalously low 2012 summer-averaged albedo of 0.71 (typically ~ 0.78), as meltwater was present at the ice sheet surface. Consequently, during the 2012 melt season, the ice sheet surface absorbed 28 % (213 MJ m-2) more solar radiation than the average of all other years. A surface energy balance model is used to evaluate the seasonal and interannual variability of all surface energy fluxes. The model reproduces the observed melt rates as well as the SMB for each season. A sensitivity analysis reveals that 71 % of the additional solar radiation in 2012 was used for melt, corresponding to 36 % (0.64 m) of the 2012 surface lowering. The remaining 64 % (1.14 m) of surface lowering resulted from high atmospheric temperatures, up to a +2.6 °C daily average, indicating that 2012 would have been a negative SMB year at this site even without the melt-albedo feedback. Longer time series of SMB, regional temperature, and remotely sensed albedo (MODIS) show that 2012 was the first strongly negative SMB year, with the lowest albedo, at this elevation on record. The warm conditions of recent years have resulted in enhanced melt and reduction of the refreezing capacity in the lower accumulation area. If high temperatures continue, the current lower accumulation area will turn into a region with superimposed ice in coming years.

  2. Degradation of carbazole, dibenzothiophene, and dibenzofuran at low temperature by Pseudomonas sp. strain C3211.

    PubMed

    Jensen, Anne-Mette; Finster, Kai Waldemar; Karlson, Ulrich

    2003-04-01

    Pseudomonas sp. strain C3211 was isolated from a temperate climate soil contaminated with creosote. This strain was able to degrade carbazole, dibenzothiophene and dibenzofuran at 10 degrees C with acetone as a co-substrate. When dibenzothiophene was degraded by strain C3211, an orange compound, which absorbed at 472 nm, accumulated in the medium. Degradation of dibenzofuran was followed by accumulation of a yellowish compound, absorbing at 462 nm. The temperature optimum of strain C3211 for degradation of dibenzothiophene and dibenzofuran was at 20 to 21 degrees C, while the maximum temperature for degradation was at 27 degrees C. Both compounds were degraded at 4 degrees C. Degradation at 10 degrees C was faster than degradation at 25 degrees C. This indicates that strain C3211 is adapted to life at low temperatures.

  3. Inoculation of Ni-resistant plant growth promoting bacterium Psychrobacter sp. strain SRS8 for the improvement of nickel phytoextraction by energy crops.

    PubMed

    Ma, Y; Rajkumar, M; Vicente, J A F; Freitas, H

    2011-02-01

    This study was conducted to elucidate effects of inoculating plant growth-promoting bacterium Psychrobacter sp. SRS8 on the growth and phytoextraction potential of energy crops Ricinus communis and Helianthus annuus in artificially Ni contaminated soils. The toxicity symptom in plants under Ni stress expressed as chlorophyll, protein content, growth inhibition, and Fe, P concentrations were studied, and the possible relationship among them were also discussed. The PGPB SRS8 was found capable of stimulating plant growth and Ni accumulation in both plant species. Further, the stimulation effect on plant biomass, chlorophyll, and protein content was concomitant with increased Fe and P assimilation from soil to plants. Further, the induction of catalase and peroxidase activities was also involved in the ability of SRS8 to increase the tolerance in both plant species under Ni stress. The findings suggest that strain SRS8 play an important role in promoting the growth and phytoextraction efficiency of R. communis and H. annuus, which may be used for remediation of metal contaminated sites.

  4. Sensitivity of Texas strains of Ceratocystis fagacearum to triazole fungicides

    Treesearch

    A. Dan Wilson; L.B. Forse

    1997-01-01

    Ten geographically diverse Texas strains of the oak wilt fungus Ceratocystis fagacearum were tested in vitro for their sensitivity to five triazole fungicides based on accumulated linear growth, linear growth rates, and dry weight accumulation in response to fungicide concentrations of 0.1 to 600 parts per billion (ppb). None of the triazoles inhibited growth at 0.1...

  5. Predicting the Drop Performance of Solder Joints by Evaluating the Elastic Strain Energy from High-Speed Ball Pull Tests

    NASA Astrophysics Data System (ADS)

    You, Taehoon; Kim, Yunsung; Kim, Jina; Lee, Jaehong; Jung, Byungwook; Moon, Jungtak; Choe, Heeman

    2009-03-01

    Despite being expensive and time consuming, board-level drop testing has been widely used to assess the drop or impact resistance of the solder joints in handheld microelectronic devices, such as cellphones and personal digital assistants (PDAs). In this study, a new test method, which is much simpler and quicker, is proposed. The method involves evaluating the elastic strain energy and relating it to the impact resistance of the solder joint by considering the Young’s modulus of the bulk solder and the fracture stress of the solder joint during a ball pull test at high strain rates. The results show that solder joints can be ranked in order of descending elastic strain energy as follows: Sn-37Pb, Sn-1Ag-0.5Cu, Sn-3Ag-0.5Cu, and Sn-4Ag-0.5Cu. This order is consistent with the actual drop performances of the samples.

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

    PubMed

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

    2007-01-01

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

  7. Strain accumulation and rotation in western Nevada, 1993-2000

    NASA Astrophysics Data System (ADS)

    Svarc, J. L.; Savage, J. C.; Prescott, W. H.; Ramelli, A. R.

    2002-05-01

    The positions of 44 GPS monuments in an array extending from the Sierra Nevada at the latitude of Reno to near Austin, Nevada, have been measured several times in the 1993-2000 interval. The western half of the array spans the Walker Lane belt, whereas the eastern half spans the central Nevada seismic zone (CNSZ). The principal strain rates in the Walker Lane belt are 29.6 +/- 5.3 nstrain yr-1 N88.4°E +/- 5.4° and -12.8 +/- 6.0 nanostrain yr-1 N01.6°W +/- 5.4°, extension reckoned positive, and the clockwise (as seen from above the Earth) rotation rate about a vertical axis is 13.6 +/- 4.0 nrad yr-1. The quoted uncertainties are standard deviations. The motion in the Walker Lane belt can then be represented by a zone striking N35°W subject to 16.8 +/- 4.9 nstrain yr-1 extension perpendicular to it and 19.5 +/- 4.0 nstrain yr-1 right-lateral, simple shear across it. The N35°W strike of the zone is the same as the direction of the local tangent to the small circle drawn about the Pacific-North America pole of rotation. The principal strain rates for the CNSZ are 46.2 +/- 11.0 nstrain yr-1 N49.9°W +/- 6.0° and -13.6 +/- 6.1 nstrain yr-1 N40.1°E +/- 6.0°, and the clockwise rotation rate about a vertical axis is 20.3 +/- 6.3 nrad yr-1. The motion across the CNSZ can then be represented by a zone striking N12°E subject to 32.6 +/- 11.0 nstrain yr-1 extension perpendicular to it and 25.1 +/- 6.3 nstrain yr-1 right-lateral, simple shear across it. The N12°E strike of the zone is similar to the strikes of the faults (Rainbow Mountain, Fairview Peak, and Dixie Valley) within it.

  8. Strain accumulation and rotation in western Nevada, 1993-2000

    USGS Publications Warehouse

    Svarc, J.L.; Savage, J.C.; Prescott, W.H.; Ramelli, A.R.

    2002-01-01

    The positions of 44 GPS monuments in an array extending from the Sierra Nevada at the latitude of Reno to near Austin, Nevada, have been measured several times in the 1993-2000 interval. The western half of the array spans the Walker Lane belt, whereas the eastern half spans the central Nevada seismic zone (CNSZ). The principal strain rates in the Walker Lane belt are 29.6 ?? 5.3 nstrain yr-1 N88.4??E ?? 5.4?? and -12.8 ?? 6.0 nanostrain yr-1 N01.6??W ?? 5.4??, extension reckoned positive, and the clockwise (as seen from above the Earth) rotation rate about a vertical axis is 13.6 ?? 4.0 nrad yr-1. The quoted uncertainties are standard deviations. The motion in the Walker Lane belt can then be represented by a zone striking N35??W subject to 16.8 ?? 4.9 nstrain yr-1 extension perpendicular to it and 19.5 ?? 4.0 nstrain yr-1 right-lateral, simple shear across it. The N35??W strike of the zone is the same as the direction of the local tangent to the small circle drawn about the Pacific-North America pole of rotation. The principal strain rates for the CNSZ are 46.2 ?? 11.0 nstrain yr-1 N49.9??W ?? 6.0?? and -13.6 ?? 6.1 nstrain yr-1 N40.1??E ?? 6.0??, and the clockwise rotation rate about a vertical axis is 20.3 ?? 6.3 nrad yr-1. The motion across the CNSZ can then be represented by a zone striking N12??E subject to 32.6 ?? 11.0 nstrain yr-1 extension perpendicular to it and 25.1 ?? 6.3 nstrain yr-1 right-lateral, simple shear across it. The N12??E strike of the zone is similar to the strikes of the faults (Rainbow Mountain, Fairview Peak, and Dixie Valley) within it.

  9. (13)C-metabolic flux analysis of lipid accumulation in the oleaginous fungus Mucor circinelloides.

    PubMed

    Zhao, Lina; Zhang, Huaiyuan; Wang, Liping; Chen, Haiqin; Chen, Yong Q; Chen, Wei; Song, Yuanda

    2015-12-01

    The oleaginous fungus Mucor circinelloides is of industrial interest because it can produce high levels of polyunsaturated fatty acid γ-linolenic acid. M. circinelloides CBS 277.49 is able to accumulate less than 15% of cell dry weight as lipids, while M. circinelloides WJ11 can accumulate lipid up to 36%. In order to better understand the mechanisms behind the differential lipid accumulation in these two strains, tracer experiments with (13)C-glucose were performed with the growth of M. circinelloides and subsequent gas chromatography-mass spectrometric detection of (13)C-patterns in proteinogenic amino acids was carried out to identify the metabolic network topology and estimate intracellular fluxes. Our results showed that the high oleaginous strain WJ11 had higher flux of pentose phosphate pathway and malic enzyme, lower flux in tricarboxylic acid cycle, higher flux in glyoxylate cycle and ATP: citrate lyase, together, it might provide more NADPH and substrate acetyl-CoA for fatty acid synthesis. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Characterization of a Selenium-Tolerant Rhizosphere Strain from a Novel Se-Hyperaccumulating Plant Cardamine hupingshanesis

    PubMed Central

    Yuan, Linxi; Luo, Lei; Yin, Xuebin

    2014-01-01

    A novel selenium- (Se-) hyperaccumulating plant, Cardamine hupingshanesis, accumulating Se as a form of SeCys2, was discovered in Enshi, Hubei, China, which could not be explained by present selenocysteine methyltransferase (SMT) theory. However, it is interesting to investigate if rhizosphere bacteria play some roles during SeCys2 accumulation. Here, one Se-tolerant rhizosphere strain, Microbacterium oxydans, was isolated from C. hupingshanesis. Phylogenetic analysis and 16S rRNA gene sequences determined the strain as a kind of Gram positive bacillus and belonged to the family Brevibacterium frigoritolerans. Furthermore, Se tolerance test indicated the strain could grow in extreme high Se level of 15.0 mg Se L−1. When exposed to 1.5 mg Se L−1, SeCys2 was the predominant Se species in the bacteria, consistent with the Se species in C. hupingshanesis. This coincidence might reveal that this strain played some positive effect in SeCys2 accumulation of C. hupingshanesis. Moreover, when exposed to 1.5 mg Se L−1 or 15.0 mg Se L−1, As absorption diminished in the logarithmic phase. In contrast, As absorption increased when exposed to 7.5 mg Se L−1, indicating As metabolism processes could be affected by Se on this strain. The present study provided a sight on the role of rhizosphere bacteria during Se accumulation for Se-hyperaccumulating plant. PMID:25478582

  11. Comparative Polygenic Analysis of Maximal Ethanol Accumulation Capacity and Tolerance to High Ethanol Levels of Cell Proliferation in Yeast

    PubMed Central

    Pais, Thiago M.; Foulquié-Moreno, María R.; Hubmann, Georg; Duitama, Jorge; Swinnen, Steve; Goovaerts, Annelies; Yang, Yudi; Dumortier, Françoise; Thevelein, Johan M.

    2013-01-01

    The yeast Saccharomyces cerevisiae is able to accumulate ≥17% ethanol (v/v) by fermentation in the absence of cell proliferation. The genetic basis of this unique capacity is unknown. Up to now, all research has focused on tolerance of yeast cell proliferation to high ethanol levels. Comparison of maximal ethanol accumulation capacity and ethanol tolerance of cell proliferation in 68 yeast strains showed a poor correlation, but higher ethanol tolerance of cell proliferation clearly increased the likelihood of superior maximal ethanol accumulation capacity. We have applied pooled-segregant whole-genome sequence analysis to identify the polygenic basis of these two complex traits using segregants from a cross of a haploid derivative of the sake strain CBS1585 and the lab strain BY. From a total of 301 segregants, 22 superior segregants accumulating ≥17% ethanol in small-scale fermentations and 32 superior segregants growing in the presence of 18% ethanol, were separately pooled and sequenced. Plotting SNP variant frequency against chromosomal position revealed eleven and eight Quantitative Trait Loci (QTLs) for the two traits, respectively, and showed that the genetic basis of the two traits is partially different. Fine-mapping and Reciprocal Hemizygosity Analysis identified ADE1, URA3, and KIN3, encoding a protein kinase involved in DNA damage repair, as specific causative genes for maximal ethanol accumulation capacity. These genes, as well as the previously identified MKT1 gene, were not linked in this genetic background to tolerance of cell proliferation to high ethanol levels. The superior KIN3 allele contained two SNPs, which are absent in all yeast strains sequenced up to now. This work provides the first insight in the genetic basis of maximal ethanol accumulation capacity in yeast and reveals for the first time the importance of DNA damage repair in yeast ethanol tolerance. PMID:23754966

  12. Conversion of light-energy into molecular strain in the photocycle of the photoactive yellow protein.

    PubMed

    Gamiz-Hernandez, Ana P; Kaila, Ville R I

    2016-01-28

    The Photoactive Yellow Protein (PYP) is a light-driven photoreceptor, responsible for the phototaxis of halophilic bacteria. Recently, a new short-lived intermediate (pR0) was characterized in the PYP photocycle using combined time-resolved X-ray crystallography and density functional theory calculations. The pR0 species was identified as a highly contorted cis-intermediate, which is stabilized by hydrogen bonds with protein residues. Here we show by hybrid quantum mechanics/classical mechanics (QM/MM) molecular dynamics simulations, and first-principles calculations of optical properties, that the optical shifts in the early steps of the PYP photocycle originate from the conversion of light energy into molecular strain, stored in the pR0 state, and its relaxation in subsequent reaction steps. Our calculations quantitatively reproduce experimental data, which enables us to identify molecular origins of the optical shifts. Our combined approach suggests that the short-lived pR0 intermediate stores ∼1/3 of the photon energy as molecular strain, thus providing the thermodynamic driving force for later conformational changes in the protein.

  13. How strained are carbomeric-cycloalkanes?

    PubMed

    Wodrich, Matthew D; Gonthier, Jérôme F; Steinmann, Stephan N; Corminboeuf, Clémence

    2010-06-24

    The ring strain energies of carbomeric-cycloalkanes (molecules with one or more acetylene spacer units placed into carbon single bonds) are assessed using a series of isodesmic, homodesmotic, and hyperhomodesmotic chemical equations. Isodesmic bond separation reactions and other equations derived from the explicitly defined hierarchy of homodesmotic equations are insufficient for accurately determining these values, since not all perturbing effects (i.e., conjugation and hyperconjugation) are fully balanced. A set of homodesmotic reactions is proposed, which succeeds in balancing all stereoelectronic effects present within the carbomeric rings, allowing for a direct assessment of the strain energies. Values calculated from chemical equations are validated using an increment/additivity approach. The ring strain energy decreases as acetylene units are added, manifesting from the net stabilization gained by opening the C-CH(2)-C angle around the methylene groups and the destabilization arising from bending the C-C identical withC angles of the spacer groups. This destabilization vanishes with increasing parent ring size (i.e., the angle distortion is less in the carbomeric-cyclobutanes than in the carbomeric-cyclopropanes), leading to strain energies near zero for carbo(n)-cyclopentanes and carbo(n)-cyclohexanes.

  14. Near-freezing effects on the proteome of industrial yeast strains of Saccharomyces cerevisiae.

    PubMed

    Ballester-Tomás, Lidia; Pérez-Torrado, Roberto; Rodríguez-Vargas, Sonia; Prieto, Jose A; Randez-Gil, Francisca

    2016-03-10

    At near-freezing temperatures (0-4°C), the growth of the yeast Saccharomyces cerevisiae stops or is severely limited, and viability decreases. Under these conditions, yeast cells trigger a biochemical response, in which trehalose and glycerol accumulate and protect them against severe cold and freeze injury. However, the mechanisms that allow yeast cells to sustain this response have been not clarified. The effects of severe cold on the proteome of S. cerevisiae have been not investigated and its importance in providing cell survival at near-freezing temperatures and upon freezing remains unknown. Here, we have compared the protein profile of two industrial baker's yeast strains at 30°C and 4°C. Overall, a total of 16 proteins involved in energy-metabolism, translation and redox homeostasis were identified as showing increased abundance at 4°C. The predominant presence of glycolytic proteins among those upregulated at 4°C, likely represents a mechanism to maintain a constant supply of ATP for the synthesis of glycerol and other protective molecules. Accumulation of these molecules is by far the most important component in enhancing viability of baker's yeast strains upon freezing. Overexpression of genes encoding certain proteins associated with translation or redox homeostasis provided specifically protection against extreme cold damage, underlying the importance of these functions in the near-freezing response. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Oxidation of Molecular Hydrogen by a Chemolithoautotrophic Beggiatoa Strain

    PubMed Central

    2016-01-01

    ABSTRACT A chemolithoautotrophic strain of the family Beggiatoaceae, Beggiatoa sp. strain 35Flor, was found to oxidize molecular hydrogen when grown in a medium with diffusional gradients of oxygen, sulfide, and hydrogen. Microsensor profiles and rate measurements suggested that the strain oxidized hydrogen aerobically when oxygen was available, while hydrogen consumption under anoxic conditions was presumably driven by sulfur respiration. Beggiatoa sp. 35Flor reached significantly higher biomass in hydrogen-supplemented oxygen-sulfide gradient media, but hydrogen did not support growth of the strain in the absence of reduced sulfur compounds. Nevertheless, hydrogen oxidation can provide Beggiatoa sp. 35Flor with energy for maintenance and assimilatory purposes and may support the disposal of internally stored sulfur to prevent physical damage resulting from excessive sulfur accumulation. Our knowledge about the exposure of natural populations of Beggiatoaceae to hydrogen is very limited, but significant amounts of hydrogen could be provided by nitrogen fixation, fermentation, and geochemical processes in several of their typical habitats such as photosynthetic microbial mats and submarine sites of hydrothermal fluid flow. IMPORTANCE Reduced sulfur compounds are certainly the main electron donors for chemolithoautotrophic Beggiatoaceae, but the traditional focus on this topic has left other possible inorganic electron donors largely unexplored. In this paper, we provide evidence that hydrogen oxidation has the potential to strengthen the ecophysiological plasticity of Beggiatoaceae in several ways. Moreover, we show that hydrogen oxidation by members of this family can significantly influence biogeochemical gradients and therefore should be considered in environmental studies. PMID:26896131

  16. Identification and Characterization of Oleaginous Yeast Isolated from Kefir and Its Ability to Accumulate Intracellular Fats in Deproteinated Potato Wastewater with Different Carbon Sources

    PubMed Central

    Kieliszek, Marek; Jermacz, Karolina; Błażejak, Stanisław

    2017-01-01

    The search for efficient oleaginous microorganisms, which can be an alternative to fossil fuels and biofuels obtained from oilseed crops, has been going on for many years. The suitability of microorganisms in this regard is determined by their ability to biosynthesize lipids with preferred fatty acid profile along with the concurrent utilization of energy-rich industrial waste. In this study, we isolated, characterized, and identified kefir yeast strains using molecular biology techniques. The yeast isolates identified were Candida inconspicua, Debaryomyces hansenii, Kluyveromyces marxianus, Kazachstania unispora, and Zygotorulaspora florentina. We showed that deproteinated potato wastewater, a starch processing industry waste, supplemented with various carbon sources, including lactose and glycerol, is a suitable medium for the growth of yeast, which allows an accumulation of over 20% of lipid substances in its cells. Fatty acid composition primarily depended on the yeast strain and the carbon source used, and, based on our results, most of the strains met the criteria required for the production of biodiesel. In particular, this concerns a significant share of saturated fatty acids, such as C16:0 and C18:0, and unsaturated fatty acids, such as C18:1 and C18:2. The highest efficiency in lipid biosynthesis exceeded 6.3 g L−1. Kazachstania unispora was able to accumulate the high amount of palmitoleic acid. PMID:29098157

  17. Identification and Characterization of Oleaginous Yeast Isolated from Kefir and Its Ability to Accumulate Intracellular Fats in Deproteinated Potato Wastewater with Different Carbon Sources.

    PubMed

    Gientka, Iwona; Kieliszek, Marek; Jermacz, Karolina; Błażejak, Stanisław

    2017-01-01

    The search for efficient oleaginous microorganisms, which can be an alternative to fossil fuels and biofuels obtained from oilseed crops, has been going on for many years. The suitability of microorganisms in this regard is determined by their ability to biosynthesize lipids with preferred fatty acid profile along with the concurrent utilization of energy-rich industrial waste. In this study, we isolated, characterized, and identified kefir yeast strains using molecular biology techniques. The yeast isolates identified were Candida inconspicua , Debaryomyces hansenii , Kluyveromyces marxianus , Kazachstania unispora , and Zygotorulaspora florentina . We showed that deproteinated potato wastewater, a starch processing industry waste, supplemented with various carbon sources, including lactose and glycerol, is a suitable medium for the growth of yeast, which allows an accumulation of over 20% of lipid substances in its cells. Fatty acid composition primarily depended on the yeast strain and the carbon source used, and, based on our results, most of the strains met the criteria required for the production of biodiesel. In particular, this concerns a significant share of saturated fatty acids, such as C16:0 and C18:0, and unsaturated fatty acids, such as C18:1 and C18:2. The highest efficiency in lipid biosynthesis exceeded 6.3 g L -1 . Kazachstania unispora was able to accumulate the high amount of palmitoleic acid.

  18. 5-Fluorouracil-resistant strain of Methanobacterium thermoautotrophicum.

    PubMed

    Nagle, D P; Teal, R; Eisenbraun, A

    1987-09-01

    Growth of Methanobacterium thermoautotrophicum Marburg is inhibited by the pyrimidine, 5-fluorouracil (FU). It was shown previously that methanogenesis is not inhibited to the same extent as growth. A spontaneously occurring FU-resistant strain (RTAE-1) was isolated from a culture of strain Marburg. The growth of both strains was inhibited by 5-fluorodeoxyuridine but not 5-fluorocytosine, and the wild type was more susceptible to inhibition by 5-azauracil and 6-azauracil than was strain RTAE-1. The cellular targets for the pyrimidine analogs are not known. When the accumulation of 14C-labeled uracil or FU by the two strains was compared, the wild type took up 15-fold more radiolabel per cell than did the FU-resistant strain. In the wild type, radiolabel from uracil was incorporated into the soluble pool, RNA, and DNA. The metabolism of uracil appeared to involve a uracil phosphoribosyltransferase activity. Strain Marburg extracts contained this enzyme, whereas FU-resistant strain RTAE-1 extracts had less than 1/10 as much activity. Although it is possible that a change in permeability to the compounds plays a role in the stable resistance of strain RTAE-1, the fact that it lacks the ability to metabolize pyrimidines to nucleotides is sufficient to account for its phenotype.

  19. 5-Fluorouracil-resistant strain of Methanobacterium thermoautotrophicum.

    PubMed Central

    Nagle, D P; Teal, R; Eisenbraun, A

    1987-01-01

    Growth of Methanobacterium thermoautotrophicum Marburg is inhibited by the pyrimidine, 5-fluorouracil (FU). It was shown previously that methanogenesis is not inhibited to the same extent as growth. A spontaneously occurring FU-resistant strain (RTAE-1) was isolated from a culture of strain Marburg. The growth of both strains was inhibited by 5-fluorodeoxyuridine but not 5-fluorocytosine, and the wild type was more susceptible to inhibition by 5-azauracil and 6-azauracil than was strain RTAE-1. The cellular targets for the pyrimidine analogs are not known. When the accumulation of 14C-labeled uracil or FU by the two strains was compared, the wild type took up 15-fold more radiolabel per cell than did the FU-resistant strain. In the wild type, radiolabel from uracil was incorporated into the soluble pool, RNA, and DNA. The metabolism of uracil appeared to involve a uracil phosphoribosyltransferase activity. Strain Marburg extracts contained this enzyme, whereas FU-resistant strain RTAE-1 extracts had less than 1/10 as much activity. Although it is possible that a change in permeability to the compounds plays a role in the stable resistance of strain RTAE-1, the fact that it lacks the ability to metabolize pyrimidines to nucleotides is sufficient to account for its phenotype. PMID:3624203

  20. Assessment of Hip Fracture Risk Using Cross-Section Strain Energy Determined by QCT-Based Finite Element Modeling

    PubMed Central

    Kheirollahi, Hossein

    2015-01-01

    Accurate assessment of hip fracture risk is very important to prevent hip fracture and to monitor the effect of a treatment. A subject-specific QCT-based finite element model was constructed to assess hip fracture risk at the critical locations of femur during the single-leg stance and the sideways fall. The aim of this study was to improve the prediction of hip fracture risk by introducing a novel failure criterion to more accurately describe bone failure mechanism. Hip fracture risk index was defined using cross-section strain energy, which is able to integrate information of stresses, strains, and material properties affecting bone failure. It was found that the femoral neck and the intertrochanteric region have higher fracture risk than other parts of the femur, probably owing to the larger content of cancellous bone in these regions. The study results also suggested that women are more prone to hip fracture than men. The findings in this study have a good agreement with those clinical observations reported in the literature. The proposed hip fracture risk index based on strain energy has the potential of more accurate assessment of hip fracture risk. However, experimental validation should be conducted before its clinical applications. PMID:26601105

  1. Triacylglycerol Metabolism, Function, and Accumulation in Plant Vegetative Tissues.

    PubMed

    Xu, Changcheng; Shanklin, John

    2016-04-29

    Oils in the form of triacylglycerols are the most abundant energy-dense storage compounds in eukaryotes, and their metabolism plays a key role in cellular energy balance, lipid homeostasis, growth, and maintenance. Plants accumulate oils primarily in seeds and fruits. Plant oils are used for food and feed and, increasingly, as feedstocks for biodiesel and industrial chemicals. Although plant vegetative tissues do not accumulate significant levels of triacylglycerols, they possess a high capacity for their synthesis, storage, and metabolism. The development of plants that accumulate oil in vegetative tissues presents an opportunity for expanded production of triacylglycerols as a renewable and sustainable bioenergy source. Here, we review recent progress in the understanding of triacylglycerol synthesis, turnover, storage, and function in leaves and discuss emerging genetic engineering strategies targeted at enhancing triacylglycerol accumulation in biomass crops. Such plants could potentially be modified to produce oleochemical feedstocks or nutraceuticals.

  2. Metabolism of dimethylphthalate by Micrococcus sp. strain 12B.

    PubMed Central

    Eaton, R W; Ribbons, D W

    1982-01-01

    During growth of Micrococcus sp. strain 12B with dimethylphthalate, 4-carboxy-2-hydroxymuconate lactone (CHML, X) and 3,4-dihydroxyphthalate-2-methyl ester (XI) were isolated from culture filtrates. CHML is the lactone of intermediate 4-carboxy-2-hydroxymuconate (IX). Accumulation of XI which is not a substrate for 3,4-dihydroxyphthalate-2-decarboxylase in strain 12B afforded an easy access to the preparation of 3,4-dihydroxyphthalate. PMID:7085569

  3. Induced Protoporphyrin IX Accumulation by the δ-Aminolevulinic Acid in Bacteria and its Potential Use in the Photodynamic Therapy

    NASA Astrophysics Data System (ADS)

    Brígido-Aparicio, Cyntiha; Ramón-Gallegos, Eva; Arenas-Huertero, Francisco Jesús; Uribe-Hernández, Raúl

    2008-08-01

    The increasing incident of resistant strains to antibiotic has encouraged the search of new antibacterial treatments, such as the photodynamic therapy. In recent years, photodynamic therapy has demonstrated being a good technology for the treatment of recurrent bacteria infection. PDT presents a hopeful approach to eliminate Gram positive and negative bacteria in immunological compromised patients. This therapy uses a laser in combination with a photosensibilizer in presence of intracellular molecular oxygen. The process generates an effect of phototoxicity in bacterial cells. The aim of this work was to determine the in vitro conditions to accumulate PpIX in effective concentrations in Staphylococcus aureus ATCC25923 and Streptococcus pyogenes, which are responsible of human cutaneous diseases. A cellular suspension of both strains was prepared in TSB to obtain growth in Log-phase, then, the suspensions were adjusted to a final concentration of 2.61×108 cells/mL. The strains were exposed to increasing concentrations from 0 to 160μg/mL of δ-ALA in order to determinate the concentration that induces the biggest accumulation of PpIX. PpIX was measured using the Piomelli method modified for bacteria. The concentration selected was 40 mg/mL of ALA. It was found that in basal concentration of δ-ALA (0 μg/mL) both strains accumulated similar amount of PpIX. In concentrations of 5 mg/mL of δ-ALA it was observed a significant (p<0.001) increment in PpIX concentration. Finally it was realized a kinetic to determinate the optimal accumulation over the time at 0, 5, 10, 15 and 30 min, and 1, 2, 4, 8, 16 and 32 h. It was found that the ideal time for PDT application, in both strains, was 24 h because in smaller times there was not statistically significant difference. The S. aureus ATCC25923 accumulated significantly the biggest concentration of PpIX with regard to S. pyogenes. In conclusion, it was found that the optimal conditions to apply PDT will be to expose both

  4. Carbon Monoxide, Hydrogen, and Formate Metabolism during Methanogenesis from Acetate by Thermophilic Cultures of Methanosarcina and Methanothrix Strains.

    PubMed

    Zinder, S H; Anguish, T

    1992-10-01

    CO and H(2) have been implicated in methanogenesis from acetate, but it is unclear whether they are directly involved in methanogenesis or electron transfer in acetotrophic methanogens. We compared metabolism of H(2), CO, and formate by cultures of the thermophilic acetotrophic methanogens Methanosarcina thermophila TM-1 and Methanothrix sp. strain CALS-1. M. thermophila accumulated H(2) to partial pressures of 40 to 70 Pa (1 Pa = 0.987 x 10 atm), as has been previously reported for this and other Methanosarcina cultures. In contrast, Methanothrix sp. strain CALS-1 accumulated H(2) to maximum partial pressures near 1 Pa. Growing cultures of Methanothrix sp. strain CALS-1 initially accumulated CO, which reached partial pressures near 0.6 Pa (some CO came from the rubber stopper) during the middle of methanogenesis; this was followed by a decrease in CO partial pressures to less than 0.01 Pa by the end of methanogenesis. Accumulation or consumption of CO by cultures of M. thermophila growing on acetate was not detected. Late-exponential-phase cultures of Methanothrix sp. strain CALS-1, in which the CO partial pressure was decreased by flushing with N(2)-CO(2), accumulated CO to 0.16 Pa, whereas cultures to which ca. 0.5 Pa of CO was added consumed CO until it reached this partial pressure. Cyanide (1 mM) blocked CO consumption but not production. High partial pressures of H(2) (40 kPa) inhibited methanogenesis from acetate by M. thermophila but not by Methanothrix sp. strain CALS-1, and 2 kPa of CO was not inhibitory to M. thermophila but was inhibitory to Methanothrix sp. strain CALS-1. Levels of CO dehydrogenase, hydrogenase, and formate dehydrogenase in Methanothrix sp. strain CALS-1 were 9.1, 0.045, and 5.8 mumol of viologen reduced min mg of protein. These results suggest that CO plays a role in Methanothrix sp. strain CALS-1 similar to that of H(2) in M. thermophila and are consistent with the conclusion that CO is an intermediate in a catabolic or anabolic

  5. Carbon Monoxide, Hydrogen, and Formate Metabolism during Methanogenesis from Acetate by Thermophilic Cultures of Methanosarcina and Methanothrix Strains

    PubMed Central

    Zinder, S. H.; Anguish, T.

    1992-01-01

    CO and H2 have been implicated in methanogenesis from acetate, but it is unclear whether they are directly involved in methanogenesis or electron transfer in acetotrophic methanogens. We compared metabolism of H2, CO, and formate by cultures of the thermophilic acetotrophic methanogens Methanosarcina thermophila TM-1 and Methanothrix sp. strain CALS-1. M. thermophila accumulated H2 to partial pressures of 40 to 70 Pa (1 Pa = 0.987 × 10-5 atm), as has been previously reported for this and other Methanosarcina cultures. In contrast, Methanothrix sp. strain CALS-1 accumulated H2 to maximum partial pressures near 1 Pa. Growing cultures of Methanothrix sp. strain CALS-1 initially accumulated CO, which reached partial pressures near 0.6 Pa (some CO came from the rubber stopper) during the middle of methanogenesis; this was followed by a decrease in CO partial pressures to less than 0.01 Pa by the end of methanogenesis. Accumulation or consumption of CO by cultures of M. thermophila growing on acetate was not detected. Late-exponential-phase cultures of Methanothrix sp. strain CALS-1, in which the CO partial pressure was decreased by flushing with N2-CO2, accumulated CO to 0.16 Pa, whereas cultures to which ca. 0.5 Pa of CO was added consumed CO until it reached this partial pressure. Cyanide (1 mM) blocked CO consumption but not production. High partial pressures of H2 (40 kPa) inhibited methanogenesis from acetate by M. thermophila but not by Methanothrix sp. strain CALS-1, and 2 kPa of CO was not inhibitory to M. thermophila but was inhibitory to Methanothrix sp. strain CALS-1. Levels of CO dehydrogenase, hydrogenase, and formate dehydrogenase in Methanothrix sp. strain CALS-1 were 9.1, 0.045, and 5.8 μmol of viologen reduced min-1 mg of protein-1. These results suggest that CO plays a role in Methanothrix sp. strain CALS-1 similar to that of H2 in M. thermophila and are consistent with the conclusion that CO is an intermediate in a catabolic or anabolic pathway in

  6. Intercellular salicylic acid accumulation during compatible and incompatible Arabidopsis-Pseudomonas syringae interactions

    PubMed Central

    Wilson, Daniel C; Carella, Philip; Cameron, Robin K

    2014-01-01

    The phytohormone salicylic acid (SA) plays an important role in several disease resistance responses. During the Age-Related Resistance (ARR) response that occurs in mature Arabidopsis responding to Pseudomonas syringae pv tomato (Pst), SA accumulates in the intercellular space where it may act as an antimicrobial agent. Recently we measured intracellular and intercellular SA levels in young, ARR-incompetent plants responding to virulent and avirulent strains of Pst to determine if intercellular SA accumulation is a component of additional defense responses to Pst. In young plants virulent Pst suppressed both intra- and intercellular SA accumulation in a coronatine-dependent manner. In contrast, high levels of intra- and intercellular SA accumulated in response to avirulent Pst. Our results support the idea that SA accumulation in the intercellular space is an important component of multiple defense responses. Future research will include understanding how mature plants counteract the effects of coronatine during the ARR response. PMID:25763618

  7. Solitary waves in morphogenesis: Determination fronts as strain-cued strain transformations among automatous cells

    NASA Astrophysics Data System (ADS)

    Cox, Brian N.; Landis, Chad M.

    2018-02-01

    We present a simple theory of a strain pulse propagating as a solitary wave through a continuous two-dimensional population of cells. A critical strain is assumed to trigger a strain transformation, while, simultaneously, cells move as automata to tend to restore a preferred cell density. We consider systems in which the strain transformation is a shape change, a burst of proliferation, or the commencement of growth (which changes the shape of the population sheet), and demonstrate isomorphism among these cases. Numerical and analytical solutions describe a strain pulse whose height does not depend on how the strain disturbance was first launched, or the rate at which the strain transformation is achieved, or the rate constant in the rule for the restorative cell motion. The strain pulse is therefore very stable, surviving the imposition of strong perturbations: it would serve well as a timing signal in development. The automatous wave formulation is simple, with few model parameters. A strong case exists for the presence of a strain pulse during amelogenesis. Quantitative analysis reveals a simple relationship between the velocity of the leading edge of the pulse in amelogenesis and the known speed of migration of ameloblast cells. This result and energy arguments support the depiction of wave motion as an automatous cell response to strain, rather than as a response to an elastic energy gradient. The theory may also contribute to understanding the determination front in somitogenesis, moving fronts of convergent-extension transformation, and mitotic wavefronts in the syncytial drosophila embryo.

  8. Whole Genome Re-Sequencing Identifies a Quantitative Trait Locus Repressing Carbon Reserve Accumulation during Optimal Growth in Chlamydomonas reinhardtii

    PubMed Central

    Goold, Hugh Douglas; Nguyen, Hoa Mai; Kong, Fantao; Beyly-Adriano, Audrey; Légeret, Bertrand; Billon, Emmanuelle; Cuiné, Stéphan; Beisson, Fred; Peltier, Gilles; Li-Beisson, Yonghua

    2016-01-01

    Microalgae have emerged as a promising source for biofuel production. Massive oil and starch accumulation in microalgae is possible, but occurs mostly when biomass growth is impaired. The molecular networks underlying the negative correlation between growth and reserve formation are not known. Thus isolation of strains capable of accumulating carbon reserves during optimal growth would be highly desirable. To this end, we screened an insertional mutant library of Chlamydomonas reinhardtii for alterations in oil content. A mutant accumulating five times more oil and twice more starch than wild-type during optimal growth was isolated and named constitutive oil accumulator 1 (coa1). Growth in photobioreactors under highly controlled conditions revealed that the increase in oil and starch content in coa1 was dependent on light intensity. Genetic analysis and DNA hybridization pointed to a single insertional event responsible for the phenotype. Whole genome re-sequencing identified in coa1 a >200 kb deletion on chromosome 14 containing 41 genes. This study demonstrates that, 1), the generation of algal strains accumulating higher reserve amount without compromising biomass accumulation is feasible; 2), light is an important parameter in phenotypic analysis; and 3), a chromosomal region (Quantitative Trait Locus) acts as suppressor of carbon reserve accumulation during optimal growth. PMID:27141848

  9. Accumulation of Dissolved DMSP by Marine Bacteria and its Degradation Via Bacterivory

    NASA Technical Reports Server (NTRS)

    Wolfe, Gordon V.

    1996-01-01

    Several bacterial isolates enriched from seawater using complex media were able to accumulate dimethylsulfoniopropionate (DMSP) from media into cells over several hours without degrading it. Uptake only occurred in metabolically active cells, and was repressed in some strains by the presence of additional carbon sources. Accumulation was also more rapid in osmotically-stressed cells, suggesting DMSP is used as an osmotic solute. Uptake could be blocked by inhibitors of active transport systems (2,4-dinitrophenol, azide, arsenate) and of protein synthesis (chloramphenicol). Some structural analogs such as glycine betaine and S-methyl methionine also blocked DMSP uptake, suggesting that the availability of alternate organic osmolytes may influence DMSP uptake. Stresses such as freezing, heating, or osmotic down shock resulted in partial release of DMSP back to the medium. One strain which contained a DMSP-lyase was also able to accumulate DMSP, and DMS was only produced in the absence of alternate carbon sources. Bacteria containing DMSP were prepared as prey for bacterivorous ciliates and flagellates, to examine the fate of the DMSP during grazing. In all cases, predators metabolized the DMSP in bacteria. In some cases, DMS was produced, but it is not clear if this was due to the predators or to associated bacteria in the non-axenic grazer cultures. Bacterivores may influence DMSP cycling by either modulating populations of DMSP-metabolizing bacteria, or by metabolizing DMSP accumulated by bacterial prey.

  10. Earthquake potential in California-Nevada implied by correlation of strain rate and seismicity

    USGS Publications Warehouse

    Zeng, Yuehua; Petersen, Mark D.; Shen, Zheng-Kang

    2018-01-01

    Rock mechanics studies and dynamic earthquake simulations show that patterns of seismicity evolve with time through (1) accumulation phase, (2) localization phase, and (3) rupture phase. We observe a similar pattern of changes in seismicity during the past century across California and Nevada. To quantify these changes, we correlate GPS strain rates with seismicity. Earthquakes of M > 6.5 are collocated with regions of highest strain rates. By contrast, smaller magnitude earthquakes of M ≥ 4 show clear spatiotemporal changes. From 1933 to the late 1980s, earthquakes of M ≥ 4 were more diffused and broadly distributed in both high and low strain rate regions (accumulation phase). From the late 1980s to 2016, earthquakes were more concentrated within the high strain rate areas focused on the major fault strands (localization phase). In the same time period, the rate of M > 6.5 events also increased significantly in the high strain rate areas. The strong correlation between current strain rate and the later period of seismicity indicates that seismicity is closely related to the strain rate. The spatial patterns suggest that before the late 1980s, the strain rate field was also broadly distributed because of the stress shadows from previous large earthquakes. As the deformation field evolved out of the shadow in the late 1980s, strain has refocused on the major fault systems and we are entering a period of increased risk for large earthquakes in California.

  11. Earthquake Potential in California-Nevada Implied by Correlation of Strain Rate and Seismicity

    NASA Astrophysics Data System (ADS)

    Zeng, Yuehua; Petersen, Mark D.; Shen, Zheng-Kang

    2018-02-01

    Rock mechanics studies and dynamic earthquake simulations show that patterns of seismicity evolve with time through (1) accumulation phase, (2) localization phase, and (3) rupture phase. We observe a similar pattern of changes in seismicity during the past century across California and Nevada. To quantify these changes, we correlate GPS strain rates with seismicity. Earthquakes of M > 6.5 are collocated with regions of highest strain rates. By contrast, smaller magnitude earthquakes of M ≥ 4 show clear spatiotemporal changes. From 1933 to the late 1980s, earthquakes of M ≥ 4 were more diffused and broadly distributed in both high and low strain rate regions (accumulation phase). From the late 1980s to 2016, earthquakes were more concentrated within the high strain rate areas focused on the major fault strands (localization phase). In the same time period, the rate of M > 6.5 events also increased significantly in the high strain rate areas. The strong correlation between current strain rate and the later period of seismicity indicates that seismicity is closely related to the strain rate. The spatial patterns suggest that before the late 1980s, the strain rate field was also broadly distributed because of the stress shadows from previous large earthquakes. As the deformation field evolved out of the shadow in the late 1980s, strain has refocused on the major fault systems and we are entering a period of increased risk for large earthquakes in California.

  12. Triacylglycerol Metabolism, Function, and Accumulation in Plant Vegetative Tissues

    DOE PAGES

    Xu, Changcheng; Shanklin, John

    2016-02-03

    One of the most abundant energy-dense storage compounds in eukaryotes are oils in the form of triacylglycerols , and their metabolism plays a key role in cellular energy balance, lipid homeostasis, growth, and maintenance. Plants accumulate oils primarily in seeds and fruits. Moreover, plant oils are used for food and feed and, increasingly, as feedstocks for biodiesel and industrial chemicals. Although plant vegetative tissues do not accumulate significant levels of triacylglycerols, they possess a high capacity for their synthesis, storage, and metabolism. The development of plants that accumulate oil in vegetative tissues presents an opportunity for expanded production of triacylglycerolsmore » as a renewable and sustainable bioenergy source. We review recent progress in the understanding of triacylglycerol synthesis, turnover, storage, and function in leaves and discuss emerging genetic engineering strategies targeted at enhancing triacylglycerol accumulation in biomass crops. Such plants could potentially be modified to produce oleochemical feedstocks or nutraceuticals.« less

  13. Induction of Osmoadaptive Mechanisms and Modulation of Cellular Physiology Help Bacillus licheniformis Strain SSA 61 Adapt to Salt Stress

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

    Paul, Sangeeta; Aggarwal, Chetana; Thakur, Jyoti Kumar

    Bacillus licheniformis strain SSA 61, originally isolated from Sambhar salt lake, was observed to grow even in the presence of 25 % salt stress. Osmoadaptive mechanisms of this halotolerant B. licheniformis strain SSA 61, for long-term survival and growth under salt stress, were determined. Proline was the preferentially accumulated compatible osmolyte. There was also increased accumulation of antioxidants ascorbic acid and glutathione. Among the different antioxidative enzymes assayed, superoxide dismutase played the most crucial role in defense against salt-induced stress in the organism. Adaptation to stress by the organism involved modulation of cellular physiology at various levels. There was enhancedmore » expression of known proteins playing essential roles in stress adaptation, such as chaperones DnaK and GroEL, and general stress protein YfkM and polynucleotide phosphorylase/polyadenylase. Proteins involved in amino acid biosynthetic pathway, ribosome structure, and peptide elongation were also overexpressed. Salt stress-induced modulation of expression of enzymes involved in carbon metabolism was observed. There was up-regulation of a number of enzymes involved in generation of NADH and NADPH, indicating increased cellular demand for both energy and reducing power.« less

  14. Accumulate repeat accumulate codes

    NASA Technical Reports Server (NTRS)

    Abbasfar, Aliazam; Divsalar, Dariush; Yao, Kung

    2004-01-01

    In this paper we propose an innovative channel coding scheme called 'Accumulate Repeat Accumulate codes' (ARA). This class of codes can be viewed as serial turbo-like codes, or as a subclass of Low Density Parity Check (LDPC) codes, thus belief propagation can be used for iterative decoding of ARA codes on a graph. The structure of encoder for this class can be viewed as precoded Repeat Accumulate (RA) code or as precoded Irregular Repeat Accumulate (IRA) code, where simply an accumulator is chosen as a precoder. Thus ARA codes have simple, and very fast encoder structure when they representing LDPC codes. Based on density evolution for LDPC codes through some examples for ARA codes, we show that for maximum variable node degree 5 a minimum bit SNR as low as 0.08 dB from channel capacity for rate 1/2 can be achieved as the block size goes to infinity. Thus based on fixed low maximum variable node degree, its threshold outperforms not only the RA and IRA codes but also the best known LDPC codes with the dame maximum node degree. Furthermore by puncturing the accumulators any desired high rate codes close to code rate 1 can be obtained with thresholds that stay close to the channel capacity thresholds uniformly. Iterative decoding simulation results are provided. The ARA codes also have projected graph or protograph representation that allows for high speed decoder implementation.

  15. Genetic Regulation of Grass Biomass Accumulation and Biological Conversion Quality (2013 DOE JGI Genomics of Energy and Environment 8th Annual User Meeting)

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

    Hazen, Sam

    2013-03-01

    Sam Hazen of the University of Massachusetts on "Genetic Regulation of Grass Biomass Accumulation and Biological Conversion Quality" at the 8th Annual Genomics of Energy & Environment Meeting on March 27, 2013 in Walnut Creek, CA.

  16. 46 CFR 58.30-25 - Accumulators.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... pressure vessel in which energy is stored under high pressure in the form of a gas or a gas and hydraulic... pressures not exceeding the maximum allowable working pressures. When an accumulator forms an integral part...

  17. On strain and stress in living cells

    NASA Astrophysics Data System (ADS)

    Cox, Brian N.; Smith, David W.

    2014-11-01

    Recent theoretical simulations of amelogenesis and network formation and new, simple analyses of the basic multicellular unit (BMU) allow estimation of the order of magnitude of the strain energy density in populations of living cells in their natural environment. A similar simple calculation translates recent measurements of the force-displacement relation for contacting cells (cell-cell adhesion energy) into equivalent volume energy densities, which are formed by averaging the changes in contact energy caused by a cell's migration over the cell's volume. The rates of change of these mechanical energy densities (energy density rates) are then compared to the order of magnitude of the metabolic activity of a cell, expressed as a rate of production of metabolic energy per unit volume. The mechanical energy density rates are 4-5 orders of magnitude smaller than the metabolic energy density rate in amelogenesis or bone remodeling in the BMU, which involve modest cell migration velocities, and 2-3 orders of magnitude smaller for innervation of the gut or angiogenesis, where migration rates are among the highest for all cell types. For representative cell-cell adhesion gradients, the mechanical energy density rate is 6 orders of magnitude smaller than the metabolic energy density rate. The results call into question the validity of using simple constitutive laws to represent living cells. They also imply that cells need not migrate as inanimate objects of gradients in an energy field, but are better regarded as self-powered automata that may elect to be guided by such gradients or move otherwise. Thus Ġel=d/dt 1/2 >[(C11+C12)ɛ02+2μγ02]=(C11+C12)ɛ0ɛ˙0+2μγ0γ˙0 or Ġel=ηEɛ0ɛ˙0+η‧Eγ0γ˙0 with 1.4≤η≤3.4 and 0.7≤η‧≤0.8 for Poisson's ratio in the range 0.2≤ν≤0.4 and η=1.95 and η‧=0.75 for ν=0.3. The spatial distribution of shear strains arising within an individual cell as cells slide past one another during amelogenesis is not known

  18. Complex toxin profile of French Mediterranean Ostreopsis cf. ovata strains, seafood accumulation and ovatoxins prepurification.

    PubMed

    Brissard, Charline; Herrenknecht, Christine; Séchet, Véronique; Hervé, Fabienne; Pisapia, Francesco; Harcouet, Jocelyn; Lémée, Rodolphe; Chomérat, Nicolas; Hess, Philipp; Amzil, Zouher

    2014-05-13

    Ostreopsis cf. ovata produces palytoxin analogues including ovatoxins (OVTXs) and a putative palytoxin (p-PLTX), which can accumulate in marine organisms and may possibly lead to food intoxication. However, purified ovatoxins are not widely available and their toxicities are still unknown. The aim of this study was to improve understanding of the ecophysiology of Ostreopsis cf. ovata and its toxin production as well as to optimize the purification process for ovatoxin. During Ostreopsis blooms in 2011 and 2012 in Villefranche-sur-Mer (France, NW Mediterranean Sea), microalgae epiphytic cells and marine organisms were collected and analyzed both by LC-MS/MS and hemolysis assay. Results obtained with these two methods were comparable, suggesting ovatoxins have hemolytic properties. An average of 223 μg·kg-1 of palytoxin equivalent of whole flesh was found, thus exceeding the threshold of 30 μg·kg-1 in shellfish recommended by the European Food Safety Authority (EFSA). Ostreopsis cells showed the same toxin profile both in situ and in laboratory culture, with ovatoxin-a (OVTX-a) being the most abundant analogue (~50%), followed by OVTX-b (~15%), p-PLTX (12%), OVTX-d (8%), OVTX-c (5%) and OVTX-e (4%). Ostreopsis cf. ovata produced up to 2 g of biomass per L of culture, with a maximum concentration of 300 pg PLTX equivalent cell-1. Thus, an approximate amount of 10 mg of PLTX-group toxins may be produced with 10 L of this strain. Toxin extracts obtained from collected biomass were purified using different techniques such as liquid-liquid partition or size exclusion. Among these methods, open-column chromatography with Sephadex LH20 phase yielded the best results with a cleanup efficiency of 93% and recovery of about 85%, representing an increase of toxin percentage by 13 fold. Hence, this purification step should be incorporated into future isolation exercises.

  19. 46 CFR 58.30-25 - Accumulators.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... pressure vessel in which energy is stored under high pressure in the form of a gas or a gas and hydraulic... result in contamination of the hydraulic fluid and loss of gas through absorption. (c) Each accumulator...

  20. 46 CFR 58.30-25 - Accumulators.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... pressure vessel in which energy is stored under high pressure in the form of a gas or a gas and hydraulic... result in contamination of the hydraulic fluid and loss of gas through absorption. (c) Each accumulator...

  1. 46 CFR 58.30-25 - Accumulators.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... pressure vessel in which energy is stored under high pressure in the form of a gas or a gas and hydraulic... result in contamination of the hydraulic fluid and loss of gas through absorption. (c) Each accumulator...

  2. 46 CFR 58.30-25 - Accumulators.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... pressure vessel in which energy is stored under high pressure in the form of a gas or a gas and hydraulic... result in contamination of the hydraulic fluid and loss of gas through absorption. (c) Each accumulator...

  3. Accumulation of peptidyl tRNA is lethal to Escherichia coli.

    PubMed Central

    Menninger, J R

    1979-01-01

    A mutant strain of Escherichia coli with temperature-sensitive peptidyl-tRNA hydrolase grows at 30 degrees C but, when shifted to 40 degrees C, dies at rates affected by physiological, pharmacological, and genetical perturbations. The rate of killing correlates with the relative accumulation of peptidyl-tRNA, suggesting that it is responsible for the death of the cells. PMID:368041

  4. Molecular chaperone accumulation as a function of stress evidences adaptation to high hydrostatic pressure in the piezophilic archaeon Thermococcus barophilus.

    PubMed

    Cario, Anaïs; Jebbar, Mohamed; Thiel, Axel; Kervarec, Nelly; Oger, Phil M

    2016-07-05

    The accumulation of mannosyl-glycerate (MG), the salinity stress response osmolyte of Thermococcales, was investigated as a function of hydrostatic pressure in Thermococcus barophilus strain MP, a hyperthermophilic, piezophilic archaeon isolated from the Snake Pit site (MAR), which grows optimally at 40 MPa. Strain MP accumulated MG primarily in response to salinity stress, but in contrast to other Thermococcales, MG was also accumulated in response to thermal stress. MG accumulation peaked for combined stresses. The accumulation of MG was drastically increased under sub-optimal hydrostatic pressure conditions, demonstrating that low pressure is perceived as a stress in this piezophile, and that the proteome of T. barophilus is low-pressure sensitive. MG accumulation was strongly reduced under supra-optimal pressure conditions clearly demonstrating the structural adaptation of this proteome to high hydrostatic pressure. The lack of MG synthesis only slightly altered the growth characteristics of two different MG synthesis deletion mutants. No shift to other osmolytes was observed. Altogether our observations suggest that the salinity stress response in T. barophilus is not essential and may be under negative selective pressure, similarly to what has been observed for its thermal stress response.

  5. Molecular chaperone accumulation as a function of stress evidences adaptation to high hydrostatic pressure in the piezophilic archaeon Thermococcus barophilus

    PubMed Central

    Cario, Anaïs; Jebbar, Mohamed; Thiel, Axel; Kervarec, Nelly; Oger, Phil M.

    2016-01-01

    The accumulation of mannosyl-glycerate (MG), the salinity stress response osmolyte of Thermococcales, was investigated as a function of hydrostatic pressure in Thermococcus barophilus strain MP, a hyperthermophilic, piezophilic archaeon isolated from the Snake Pit site (MAR), which grows optimally at 40 MPa. Strain MP accumulated MG primarily in response to salinity stress, but in contrast to other Thermococcales, MG was also accumulated in response to thermal stress. MG accumulation peaked for combined stresses. The accumulation of MG was drastically increased under sub-optimal hydrostatic pressure conditions, demonstrating that low pressure is perceived as a stress in this piezophile, and that the proteome of T. barophilus is low-pressure sensitive. MG accumulation was strongly reduced under supra-optimal pressure conditions clearly demonstrating the structural adaptation of this proteome to high hydrostatic pressure. The lack of MG synthesis only slightly altered the growth characteristics of two different MG synthesis deletion mutants. No shift to other osmolytes was observed. Altogether our observations suggest that the salinity stress response in T. barophilus is not essential and may be under negative selective pressure, similarly to what has been observed for its thermal stress response. PMID:27378270

  6. A Method for Calculating Strain Energy Release Rates in Preliminary Design of Composite Skin/Stringer Debonding Under Multi-Axial Loading

    NASA Technical Reports Server (NTRS)

    Krueger, Ronald; Minguet, Pierre J.; OBrien, T. Kevin

    1999-01-01

    Three simple procedures were developed to determine strain energy release rates, G, in composite skin/stringer specimens for various combinations of unaxial and biaxial (in-plane/out-of-plane) loading conditions. These procedures may be used for parametric design studies in such a way that only a few finite element computations will be necessary for a study of many load combinations. The results were compared with mixed mode strain energy release rates calculated directly from nonlinear two-dimensional plane-strain finite element analyses using the virtual crack closure technique. The first procedure involved solving three unknown parameters needed to determine the energy release rates. Good agreement was obtained when the external loads were used in the expression derived. This superposition technique was only applicable if the structure exhibits a linear load/deflection behavior. Consequently, a second technique was derived which was applicable in the case of nonlinear load/deformation behavior. The technique involved calculating six unknown parameters from a set of six simultaneous linear equations with data from six nonlinear analyses to determine the energy release rates. This procedure was not time efficient, and hence, less appealing. A third procedure was developed to calculate mixed mode energy release rates as a function of delamination lengths. This procedure required only one nonlinear finite element analysis of the specimen with a single delamination length to obtain a reference solution for the energy release rates and the scale factors. The delamination was extended in three separate linear models of the local area in the vicinity of the delamination subjected to unit loads to obtain the distribution of G with delamination lengths. This set of sub-problems was Although additional modeling effort is required to create the sub- models, this local technique is efficient for parametric studies.

  7. Photoswitchable Dihydroazulene Macrocycles for Solar Energy Storage: The Effects of Ring Strain.

    PubMed

    Vlasceanu, Alexandru; Frandsen, Benjamin N; Skov, Anders B; Hansen, Anne Schou; Rasmussen, Mads Georg; Kjaergaard, Henrik G; Mikkelsen, Kurt V; Nielsen, Mogens Brøndsted

    2017-10-06

    Efficient energy storage and release are two major challenges of solar energy harvesting technologies. The development of molecular solar thermal systems presents one approach to address these issues by tuning the isomerization reactions of photo/thermoswitches. Here we show that the incorporation of photoswitches into macrocyclic structures is a particularly attractive solution for increasing the storage time. We present the synthesis and properties of a series of macrocycles incorporating two dihydroazulene (DHA) photoswitching subunits, bridged by linkers of varying chain length. Independent of ring size, all macrocycles exhibit stepwise, light-induced, ring-opening reactions (DHA-DHA to DHA-VHF to VHF-VHF; VHF = vinylheptafulvene) with the first DHA undergoing isomerization with a similar efficiency as the uncyclized parent system while the second (DHA-VHF to VHF-VHF) is significantly slower. The energy-releasing, VHF-to-DHA, ring closures also occur in a stepwise manner and are systematically found to proceed slower in the more strained (smaller) cycles, but in all cases with a remarkably slow conversion of the second VHF to DHA. We managed to increase the half-life of the second VHF-to-DHA conversion from 65 to 202 h at room temperature by simply decreasing the ring size. A computational study reveals the smallest macrocycle to have the most energetic VHF-VHF state and hence highest energy density.

  8. Synergistic Degradation of Linuron by a Bacterial Consortium and Isolation of a Single Linuron-Degrading Variovorax Strain

    PubMed Central

    Dejonghe, Winnie; Berteloot, Ellen; Goris, Johan; Boon, Nico; Crul, Katrien; Maertens, Siska; Höfte, Monica; De Vos, Paul; Verstraete, Willy; Top, Eva M.

    2003-01-01

    The bacterial community composition of a linuron-degrading enrichment culture and the role of the individual strains in linuron degradation have been determined by a combination of methods, such as denaturing gradient gel electrophoresis of the total 16S rRNA gene pool, isolation and identification of strains, and biodegradation assays. Three strains, Variovorax sp. strain WDL1, Delftia acidovorans WDL34, and Pseudomonas sp. strain WDL5, were isolated directly from the linuron-degrading culture. In addition, subculture of this enrichment culture on potential intermediates in the degradation pathway of linuron (i.e., N,O-dimethylhydroxylamine and 3-chloroaniline) resulted in the isolation of, respectively, Hyphomicrobium sulfonivorans WDL6 and Comamonas testosteroni WDL7. Of these five strains, only Variovorax sp. strain WDL1 was able to use linuron as the sole source of C, N, and energy. WDL1 first converted linuron to 3,4-dichloroaniline (3,4-DCA), which transiently accumulated in the medium but was subsequently degraded. To the best of our knowledge, this is the first report of a strain that degrades linuron further than the aromatic intermediates. Interestingly, the rate of linuron degradation by strain WDL1 was lower than that for the consortium, but was clearly increased when WDL1 was coinoculated with each of the other four strains. D. acidovorans WDL34 and C. testosteroni WDL7 were found to be responsible for degradation of the intermediate 3,4-DCA, and H. sulfonivorans WDL6 was the only strain able to degrade N,O-dimethylhydroxylamine. The role of Pseudomonas sp. strain WDL5 needs to be further elucidated. The degradation of linuron can thus be performed by a single isolate, Variovorax sp. strain WDL1, but is stimulated by a synergistic interaction with the other strains isolated from the same linuron-degrading culture. PMID:12620840

  9. Pressure-strain-rate events in homogeneous turbulent shear flow

    NASA Technical Reports Server (NTRS)

    Brasseur, James G.; Lee, Moon J.

    1988-01-01

    A detailed study of the intercomponent energy transfer processes by the pressure-strain-rate in homogeneous turbulent shear flow is presented. Probability density functions (pdf's) and contour plots of the rapid and slow pressure-strain-rate show that the energy transfer processes are extremely peaky, with high-magnitude events dominating low-magnitude fluctuations, as reflected by very high flatness factors of the pressure-strain-rate. A concept of the energy transfer class was applied to investigate details of the direction as well as magnitude of the energy transfer processes. In incompressible flow, six disjoint energy transfer classes exist. Examination of contours in instantaneous fields, pdf's and weighted pdf's of the pressure-strain-rate indicates that in the low magnitude regions all six classes play an important role, but in the high magnitude regions four classes of transfer processes, dominate. The contribution to the average slow pressure-strain-rate from the high magnitude fluctuations is only 50 percent or less. The relative significance of high and low magnitude transfer events is discussed.

  10. Degradation of 1,2-Dibromoethane by Mycobacterium sp. Strain GP1

    PubMed Central

    Poelarends, Gerrit J.; van Hylckama Vlieg, Johan E. T.; Marchesi, Julian R.; Freitas Dos Santos, Luisa M.; Janssen, Dick B.

    1999-01-01

    The newly isolated bacterial strain GP1 can utilize 1,2-dibromoethane as the sole carbon and energy source. On the basis of 16S rRNA gene sequence analysis, the organism was identified as a member of the subgroup which contains the fast-growing mycobacteria. The first step in 1,2-dibromoethane metabolism is catalyzed by a hydrolytic haloalkane dehalogenase. The resulting 2-bromoethanol is rapidly converted to ethylene oxide by a haloalcohol dehalogenase, in this way preventing the accumulation of 2-bromoethanol and 2-bromoacetaldehyde as toxic intermediates. Ethylene oxide can serve as a growth substrate for strain GP1, but the pathway(s) by which it is further metabolized is still unclear. Strain GP1 can also utilize 1-chloropropane, 1-bromopropane, 2-bromoethanol, and 2-chloroethanol as growth substrates. 2-Chloroethanol and 2-bromoethanol are metabolized via ethylene oxide, which for both haloalcohols is a novel way to remove the halide without going through the corresponding acetaldehyde intermediate. The haloalkane dehalogenase gene was cloned and sequenced. The dehalogenase (DhaAf) encoded by this gene is identical to the haloalkane dehalogenase (DhaA) of Rhodococcus rhodochrous NCIMB 13064, except for three amino acid substitutions and a 14-amino-acid extension at the C terminus. Alignments of the complete dehalogenase gene region of strain GP1 with DNA sequences in different databases showed that a large part of a dhaA gene region, which is also present in R. rhodochrous NCIMB 13064, was fused to a fragment of a haloalcohol dehalogenase gene that was identical to the last 42 nucleotides of the hheB gene found in Corynebacterium sp. strain N-1074. PMID:10094681

  11. Degradation of 1,2-dibromoethane by Mycobacterium sp. strain GP1.

    PubMed

    Poelarends, G J; van Hylckama Vlieg, J E; Marchesi, J R; Freitas Dos Santos, L M; Janssen, D B

    1999-04-01

    The newly isolated bacterial strain GP1 can utilize 1, 2-dibromoethane as the sole carbon and energy source. On the basis of 16S rRNA gene sequence analysis, the organism was identified as a member of the subgroup which contains the fast-growing mycobacteria. The first step in 1,2-dibromoethane metabolism is catalyzed by a hydrolytic haloalkane dehalogenase. The resulting 2-bromoethanol is rapidly converted to ethylene oxide by a haloalcohol dehalogenase, in this way preventing the accumulation of 2-bromoethanol and 2-bromoacetaldehyde as toxic intermediates. Ethylene oxide can serve as a growth substrate for strain GP1, but the pathway(s) by which it is further metabolized is still unclear. Strain GP1 can also utilize 1-chloropropane, 1-bromopropane, 2-bromoethanol, and 2-chloroethanol as growth substrates. 2-Chloroethanol and 2-bromoethanol are metabolized via ethylene oxide, which for both haloalcohols is a novel way to remove the halide without going through the corresponding acetaldehyde intermediate. The haloalkane dehalogenase gene was cloned and sequenced. The dehalogenase (DhaAf) encoded by this gene is identical to the haloalkane dehalogenase (DhaA) of Rhodococcus rhodochrous NCIMB 13064, except for three amino acid substitutions and a 14-amino-acid extension at the C terminus. Alignments of the complete dehalogenase gene region of strain GP1 with DNA sequences in different databases showed that a large part of a dhaA gene region, which is also present in R. rhodochrous NCIMB 13064, was fused to a fragment of a haloalcohol dehalogenase gene that was identical to the last 42 nucleotides of the hheB gene found in Corynebacterium sp. strain N-1074.

  12. Identification of FadAB Complexes Involved in Fatty Acid β-Oxidation in Streptomyces coelicolor and Construction of a Triacylglycerol Overproducing strain

    PubMed Central

    Menendez-Bravo, Simón; Paganini, Julián; Avignone-Rossa, Claudio; Gramajo, Hugo; Arabolaza, Ana

    2017-01-01

    Oleaginous microorganisms represent possible platforms for the sustainable production of oleochemicals and biofuels due to their metabolic robustness and the possibility to be engineered. Streptomyces coelicolor is among the narrow group of prokaryotes capable of accumulating triacylglycerol (TAG) as carbon and energy reserve. Although the pathways for TAG biosynthesis in this organism have been widely addressed, the set of genes required for their breakdown have remained elusive so far. Here, we identified and characterized three gene clusters involved in the β-oxidation of fatty acids (FA). The role of each of the three different S. coelicolor FadAB proteins in FA catabolism was confirmed by complementation of an Escherichia coliΔfadBA mutant strain deficient in β-oxidation. In S. coelicolor, the expression profile of the three gene clusters showed variation related with the stage of growth and the presence of FA in media. Flux balance analyses using a corrected version of the current S. coelicolor metabolic model containing detailed TAG biosynthesis reactions suggested the relevance of the identified fadAB genes in the accumulation of TAG. Thus, through the construction and analysis of fadAB knockout mutant strains, we obtained an S. coelicolor mutant that showed a 4.3-fold increase in the TAG content compared to the wild type strain grown under the same culture conditions. PMID:28824562

  13. The effect of energy accumulation and boundary slip on laminar flow between rotating plates

    NASA Astrophysics Data System (ADS)

    Wu, Zhenpeng; Zeng, Liangcai; Chen, Keying; Jin, Xiaohong; Wu, Shiqian

    2018-02-01

    The poor operating conditions of fluid lubrication equipment during the start-up process are due to the resistance of the high-viscosity lubricating liquid. Moreover, the excessive reduction in fluid viscosity due to the elevated temperature resulting from power consumption during prolonged operation is not conducive to the generation of dynamic pressure. In this study, we examine the effect of energy accumulation and boundary slip on the laminar flow of a liquid between a pair of rotating plates. The experiments are conducted using a rotary rheometer, with polymethyl methacrylate (PMMA) as the thermal insulation material and polytetrafluoroethylene (PTFE) as the slip drag reduction material, and a three-dimensional simulation model is established. This model is derived by combining the energy equation including the slip length and the heat conduction equation. Thus, the temperature changes over time are predicted by this model, and the model accuracy is verified by experiments. The results reveal the following points: 1) boundary slips function as a drag reduction mechanism for short-time continuous operation; 2) under prolonged operation, the slip reduces the extent of the oil viscosity decrease and clear control of the elevated temperature by the boundary slip is observed.

  14. Algal dual-specificity tyrosine phosphorylation-regulated kinase, triacylglycerol accumulation regulator1, regulates accumulation of triacylglycerol in nitrogen or sulfur deficiency.

    PubMed

    Kajikawa, Masataka; Sawaragi, Yuri; Shinkawa, Haruka; Yamano, Takashi; Ando, Akira; Kato, Misako; Hirono, Masafumi; Sato, Naoki; Fukuzawa, Hideya

    2015-06-01

    Although microalgae accumulate triacylglycerol (TAG) and starch in response to nutrient-deficient conditions, the regulatory mechanisms are poorly understood. We report here the identification and characterization of a kinase, triacylglycerol accumulation regulator1 (TAR1), that is a member of the yeast (Saccharomyces cerevisiae) Yet another kinase1 (Yak1) subfamily in the dual-specificity tyrosine phosphorylation-regulated kinase family in a green alga (Chlamydomonas reinhardtii). The kinase domain of TAR1 showed auto- and transphosphorylation activities. A TAR1-defective mutant, tar1-1, accumulated TAG to levels 0.5- and 0.1-fold of those of a wild-type strain in sulfur (S)- and nitrogen (N)-deficient conditions, respectively. In N-deficient conditions, tar1-1 showed more pronounced arrest of cell division than the wild type, had increased cell size and cell dry weight, and maintained chlorophyll and photosynthetic activity, which were not observed in S-deficient conditions. In N-deficient conditions, global changes in expression levels of N deficiency-responsive genes in N assimilation and tetrapyrrole metabolism were noted between tar1-1 and wild-type cells. These results indicated that TAR1 is a regulator of TAG accumulation in S- and N-deficient conditions, and it functions in cell growth and repression of photosynthesis in conditions of N deficiency. © 2015 American Society of Plant Biologists. All Rights Reserved.

  15. Reduction of the Mg acceptor activation energy in GaN, AlN, Al0.83Ga0.17N and MgGa δ-doping (AlN)5/(GaN)1: the strain effect

    NASA Astrophysics Data System (ADS)

    Jiang, Xin-He; Shi, Jun-Jie; Zhang, Min; Zhong, Hong-Xia; Huang, Pu; Ding, Yi-Min; He, Ying-Ping; Cao, Xiong

    2015-12-01

    To resolve the p-type doping problem of Al-rich AlGaN alloys, we investigate the influence of biaxial and hydrostatic strains on the activation energy, formation energy and band gap of Mg-doped GaN, AlN, Al0.83Ga0.17N disorder alloy and (AlN)5/(GaN)1 superlattice based on first-principles calculations by combining the standard DFT and hybrid functional. We find that the Mg acceptor activation energy {{E}\\text{A}} , the formation energy {{E}\\text{f}} and the band gap {{E}\\text{g}} decrease with increasing the strain ɛ. The hydrostatic strain has a more remarkable impact on {{E}\\text{g}} and {{E}\\text{A}} than the biaxial strain. Both {{E}\\text{A}} and {{E}\\text{g}} have a linear dependence on the hydrostatic strain. For the biaxial strain, {{E}\\text{g}} shows a parabolic dependence on ɛ if \\varepsilon ≤slant 0 while it becomes linear if \\varepsilon ≥slant 0 . In GaN and (AlN)5/(GaN)1, {{E}\\text{A}} parabolically depends on the biaxial compressive strain and linearly depends on the biaxial tensible strain. However, the dependence is approximately linear over the whole biaxial strain range in AlN and Al0.83Ga0.17N. The Mg acceptor activation energy in (AlN)5/(GaN)1 can be reduced from 0.26 eV without strain to 0.16 (0.22) eV with the hydrostatic (biaxial) tensible strain 3%.

  16. Direct measurement of conformational strain energy in protofilaments curling outward from disassembling microtubule tips.

    PubMed

    Driver, Jonathan W; Geyer, Elisabeth A; Bailey, Megan E; Rice, Luke M; Asbury, Charles L

    2017-06-19

    Disassembling microtubules can generate movement independently of motor enzymes, especially at kinetochores where they drive chromosome motility. A popular explanation is the 'conformational wave' model, in which protofilaments pull on the kinetochore as they curl outward from a disassembling tip. But whether protofilaments can work efficiently via this spring-like mechanism has been unclear. By modifying a previous assay to use recombinant tubulin and feedback-controlled laser trapping, we directly demonstrate the spring-like elasticity of curling protofilaments. Measuring their mechanical work output suggests they carry ~25% of the energy of GTP hydrolysis as bending strain, enabling them to drive movement with efficiency similar to conventional motors. Surprisingly, a β-tubulin mutant that dramatically slows disassembly has no effect on work output, indicating an uncoupling of disassembly speed from protofilament strain. These results show the wave mechanism can make a major contribution to kinetochore motility and establish a direct approach for measuring tubulin mechano-chemistry.

  17. Differential accumulation of nif structural gene mRNA in Azotobacter vinelandii.

    PubMed

    Hamilton, Trinity L; Jacobson, Marty; Ludwig, Marcus; Boyd, Eric S; Bryant, Donald A; Dean, Dennis R; Peters, John W

    2011-09-01

    Northern analysis was employed to investigate mRNA produced by mutant strains of Azotobacter vinelandii with defined deletions in the nif structural genes and in the intergenic noncoding regions. The results indicate that intergenic RNA secondary structures effect the differential accumulation of transcripts, supporting the high Fe protein-to-MoFe protein ratio required for optimal diazotrophic growth.

  18. Strain energy release rate analysis of delamination in a tapered laminate subjected to tension load

    NASA Technical Reports Server (NTRS)

    Salpekar, S. A.; Raju, I. S.; Obrien, T. K.

    1990-01-01

    A tapered composite laminate subjected to tension load was analyzed using the finite-element method. The glass/epoxy laminate has a (+ or - 45)sub 3 group of plies dropped in three distinct steps, each 20 ply-thicknesses apart, thus forming a taper angle of 5.71 degrees. Steep gradients of interlaminar normal and shear stress on a potential delamination interface suggest the existence of stress singularities at the points of material and geometric discontinuities created by the internal plydrops. The delamination was assumed to initiate at the thin end of the taper on a -45/+45 interface and the delamination growth was simulated in both directions, i.e., along the taper and into the thin region. The strain-energy-release rate for a delamination growing into the thin laminate consisted predominantly of mode I (opening) component. For a delamination growing along the tapered region, the strain-energy-release rate was initially all mode I, but the proportion of mode I decreased with increase in delamination size until eventually total G was all mode II. The total G for both delamination tips increased with increase in delamination size, indicating that a delamination initiating at the end of the taper will grow unstably along the taper and into the thin laminate simultaneously.

  19. High-energy x-ray scattering quantification of in-situ-loading-related strain gradients spanning the dentinoenamel junction (DEJ) in bovine tooth specimens.

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

    Almer, J. D.; Stock, S. R.; Northeastern Univ.

    2010-08-26

    High energy X-ray scattering (80.7keV photons) at station 1-ID of the Advanced Photon Source quantified internal strains as a function of applied stress in mature bovine tooth. These strains were mapped from dentin through the dentinoenamel junction (DEJ) into enamel as a function of applied compressive stress in two small parallelepiped specimens. One specimen was loaded perpendicular to the DEJ and the second parallel to the DEJ. Internal strains in enamel and dentin increased and, as expected from the relative values of the Young's modulus, the observed strains were much higher in dentin than in enamel. Large strain gradients weremore » observed across the DEJ, and the data suggest that the mantle dentin-DEJ-aprismatic enamel structure may shield the near-surface volume of the enamel from large strains. In the enamel, drops in internal strain for applied stresses above 40MPa also suggest that this structure had cracked.« less

  20. A physical model for strain accumulation in the San Francisco Bay region: Stress evolution since 1838

    USGS Publications Warehouse

    Pollitz, F.; Bakun, W.H.; Nyst, M.

    2004-01-01

    Understanding of the behavior of plate boundary zones has progressed to the point where reasonably comprehensive physical models can predict their evolution. The San Andreas fault system in the San Francisco Bay region (SFBR) is dominated by a few major faults whose behavior over about one earthquake cycle is fairly well understood. By combining the past history of large ruptures on SFBR faults with a recently proposed physical model of strain accumulation in the SFBR, we derive the evolution of regional stress from 1838 until the present. This effort depends on (1) an existing compilation of the source properties of historic and contemporary SFBR earthquakes based on documented shaking, geodetic data, and seismic data (Bakun, 1999) and (2) a few key parameters of a simple regional viscoelastic coupling model constrained by recent GPS data (Pollitz and Nyst, 2004). Although uncertainties abound in the location, magnitude, and fault geometries of historic ruptures and the physical model relies on gross simplifications, the resulting stress evolution model is sufficiently detailed to provide a useful window into the past stress history. In the framework of Coulomb failure stress, we find that virtually all M ??? 5.8 earthquakes prior to 1906 and M ??? 5.5 earthquakes after 1906 are consistent with stress triggering from previous earthquakes. These events systematically lie in zones of predicted stress concentration elevated 5-10 bars above the regional average. The SFBR is predicted to have emerged from the 1906 "shadow" in about 1980, consistent with the acceleration in regional seismicity at that time. The stress evolution model may be a reliable indicator of the most likely areas to experience M ??? 5.5 shocks in the future.

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

    NASA Astrophysics Data System (ADS)

    Xia, K.; Wang, J.

    2001-10-01

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

  2. Bioprospecting for hyper-lipid producing microalgal strains for sustainable biofuel production.

    PubMed

    Mutanda, T; Ramesh, D; Karthikeyan, S; Kumari, S; Anandraj, A; Bux, F

    2011-01-01

    Global petroleum reserves are shrinking at a fast pace, increasing the demand for alternate fuels. Microalgae have the ability to grow rapidly, and synthesize and accumulate large amounts (approximately 20-50% of dry weight) of neutral lipid stored in cytosolic lipid bodies. A successful and economically viable algae based biofuel industry mainly depends on the selection of appropriate algal strains. The main focus of bioprospecting for microalgae is to identify unique high lipid producing microalgae from different habitats. Indigenous species of microalgae with high lipid yields are especially valuable in the biofuel industry. Isolation, purification and identification of natural microalgal assemblages using conventional techniques is generally time consuming. However, the recent use of micromanipulation as a rapid isolating tool allows for a higher screening throughput. The appropriate media and growth conditions are also important for successful microalgal proliferation. Environmental parameters recorded at the sampling site are necessary to optimize in vitro growth. Identification of species generally requires a combination of morphological and genetic characterization. The selected microalgal strains are grown in upscale systems such as raceway ponds or photobireactors for biomass and lipid production. This paper reviews the recent methodologies adopted for site selection, sampling, strain selection and identification, optimization of cultural conditions for superior lipid yield for biofuel production. Energy generation routes of microalgal lipids and biomass are discussed in detail. Copyright © 2010 Elsevier Ltd. All rights reserved.

  3. Law of damage accumulation and fracture criteria in highly filled polymer materials

    NASA Astrophysics Data System (ADS)

    Bykov, D. L.; Kazakov, A. V.; Konovalov, D. N.; Mel'nikov, V. P.; Milyokhin, Yu. M.; Peleshko, V. A.; Sadovnichii, D. N.

    2014-09-01

    We present the results of a large series of experiments aimed at the study of laws of damage accumulation and fracture in highly filled polymer materials under loading conditions of various types: monotone, repeated, low- and high-cycle, with varying type of stress state, dynamic (in general, more than 50 programs implemented on specimens from one lot of material). The data obtained in these test allow one to make conclusions about the constitutive role of the attained maximum of strain intensity when estimating the accumulated damage in the process of uniaxial tension by various programs (in particular, an additional cyclic deformation below the preliminary attained strain maximum does not affect the limit values of strain and stress in the subsequent active extension), about the strong influence of the stress state on the deformation and fracture, about the specific features of the nonlinear behavior of the material under the shock loading conditions and its influence on the repeated deformation. All tests are described (with an accuracy acceptable in practical calculations, both with respect to stresses and strains in the process of loading and at the moment of fracture) in the framework of the same model of nonlinear viscoelasticity with the same set of constants. The constants of the proposed model are calculated according to a relatively simple algorithm by using the results of standard uniaxial tension tests with constant values of the strain rate and hydrostatic pressure (each test for 2-3 levels of these parameters chosen from the ranges proposed in applications, each loading lasts until the fracture occurs, and one of the tests contains an intermediate interval of total loading and repeated loading) and one axial shock compression test if there are dynamic problems in the applications. The model is based on the use of the criterion fracture parameter which, in the class of proportional loading processes, is the sum of partial increments of the strain

  4. Optimized inorganic carbon regime for enhanced growth and lipid accumulation in Chlorella vulgaris.

    PubMed

    Lohman, Egan J; Gardner, Robert D; Pedersen, Todd; Peyton, Brent M; Cooksey, Keith E; Gerlach, Robin

    2015-01-01

    Large-scale algal biofuel production has been limited, among other factors, by the availability of inorganic carbon in the culture medium at concentrations higher than achievable with atmospheric CO2. Life cycle analyses have concluded that costs associated with supplying CO2 to algal cultures are significant contributors to the overall energy consumption. A two-phase optimal growth and lipid accumulation scenario is presented, which (1) enhances the growth rate and (2) the triacylglyceride (TAG) accumulation rate in the oleaginous Chlorophyte Chlorella vulgaris strain UTEX 395, by growing the organism in the presence of low concentrations of NaHCO3 (5 mM) and controlling the pH of the system with a periodic gas sparge of 5 % CO2 (v/v). Once cultures reached the desired cell densities, which can be "fine-tuned" based on initial nutrient concentrations, cultures were switched to a lipid accumulation metabolism through the addition of 50 mM NaHCO3. This two-phase approach increased the specific growth rate of C. vulgaris by 69 % compared to cultures sparged continuously with 5 % CO2 (v/v); further, biomass productivity (g L(-1) day(-1)) was increased by 27 %. Total biodiesel potential [assessed as total fatty acid methyl ester (FAME) produced] was increased from 53.3 to 61 % (FAME biomass(-1)) under the optimized conditions; biodiesel productivity (g FAME L(-1) day(-1)) was increased by 7.7 %. A bicarbonate salt screen revealed that American Chemical Society (ACS) and industrial grade NaHCO3 induced the highest TAG accumulation (% w/w), whereas Na2CO3 did not induce significant TAG accumulation. NH4HCO3 had a negative effect on cell health presumably due to ammonia toxicity. The raw, unrefined form of trona, NaHCO3∙Na2CO3 (sodium sesquicarbonate) induced TAG accumulation, albeit to a slightly lower extent than the more refined forms of sodium bicarbonate. The strategic addition of sodium bicarbonate was found to enhance growth and lipid accumulation rates in

  5. Cholic acid accumulation and its diminution by short-chain fatty acids in bifidobacteria.

    PubMed

    Kurdi, Peter; Tanaka, Hiroshi; Van Veen, Hendrik W; Asano, Kozo; Tomita, Fusao; Yokota, Atsushi

    2003-08-01

    Cholic acid (CA) transport was investigated in nine intestinal Bifidobacterium strains. Upon energization with glucose, all of the bifidobacteria accumulated CA. The driving force behind CA accumulation was found to be the transmembrane proton gradient (Delta pH, alkaline interior). The levels of accumulated CA generally coincided with the theoretical values, which were calculated by the Henderson-Hasselbalch equation using the measured internal pH values of the bifidobacteria, and a pK(a) value of 6.4 for CA. These results suggest that the mechanism of CA accumulation is based on the diffusion of a hydrophobic weak acid across the bacterial cell membrane, and its dissociation according to the Delta pH value. A mixture of short-chain fatty acids (acetate, propionate and butyrate) at the appropriate colonic concentration (117 mM in total) reduced CA accumulation in Bifidobacterium breve JCM 1192(T). These short-chain fatty acids, which are weak acids, reduced the Delta pH, thereby decreasing CA accumulation in a dose-dependent manner. The bifidobacteria did not alter or modify the CA molecule. The probiotic potential of CA accumulation in vivo is discussed in relation to human bile acid metabolism.

  6. Static and dynamic strain energy release rates in toughened thermosetting composite laminates

    NASA Technical Reports Server (NTRS)

    Cairns, Douglas S.

    1992-01-01

    In this work, the static and dynamic fracture properties of several thermosetting resin based composite laminates are presented. Two classes of materials are explored. These are homogeneous, thermosetting resins and toughened, multi-phase, thermosetting resin systems. Multi-phase resin materials have shown enhancement over homogenous materials with respect to damage resistance. The development of new dynamic tests are presented for composite laminates based on Width Tapered Double Cantilevered Beam (WTDCB) for Mode 1 fracture and the End Notched Flexure (ENF) specimen. The WTDCB sample was loaded via a low inertia, pneumatic cylinder to produce rapid cross-head displacements. A high rate, piezo-electric load cell and an accelerometer were mounted on the specimen. A digital oscilloscope was used for data acquisition. Typical static and dynamic load versus displacement plots are presented. The ENF specimen was impacted in three point bending with an instrumented impact tower. Fracture initiation and propagation energies under static and dynamic conditions were determined analytically and experimentally. The test results for Mode 1 fracture are relatively insensitive to strain rate effects for the laminates tested in this study. The test results from Mode 2 fracture indicate that the toughened systems provide superior fracture initiation and higher resistance to propagation under dynamic conditions. While the static fracture properties of the homogeneous systems may be relatively high, the apparent Mode 2 dynamic critical strain energy release rate drops significantly. The results indicate that static Mode 2 fracture testing is inadequate for determining the fracture performance of composite structures subjected to conditions such as low velocity impact. A good correlation between the basic Mode 2 dynamic fracture properties and the performance is a combined material/structural Compression After Impact (CAI) test is found. These results underscore the importance of

  7. Leucine Biosynthesis Is Involved in Regulating High Lipid Accumulation in Yarrowia lipolytica

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

    Kerkhoven, Eduard J.; Kim, Young-Mo; Wei, Siwei

    ABSTRACT The yeastYarrowia lipolyticais a potent accumulator of lipids, and lipogenesis in this organism can be influenced by a variety of factors, such as genetics and environmental conditions. Using a multifactorial study, we elucidated the effects of both genetic and environmental factors on regulation of lipogenesis inY. lipolyticaand identified how two opposite regulatory states both result in lipid accumulation. This study involved comparison of a strain overexpressing diacylglycerol acyltransferase (DGA1) with a control strain grown under either nitrogen or carbon limitation conditions. A strong correlation was observed between the responses on the transcript and protein levels. Combination ofDGA1overexpression with nitrogen limitationmore » resulted in a high level of lipid accumulation accompanied by downregulation of several amino acid biosynthetic pathways, including that of leucine in particular, and these changes were further correlated with a decrease in metabolic fluxes. This downregulation was supported by the measured decrease in the level of 2-isopropylmalate, an intermediate of leucine biosynthesis. Combining the multi-omics data with putative transcription factor binding motifs uncovered a contradictory role for TORC1 in controlling lipid accumulation, likely mediated through 2-isopropylmalate and a Leu3-like transcription factor. IMPORTANCEThe ubiquitous metabolism of lipids involves refined regulation, and an enriched understanding of this regulation would have wide implications. Various factors can influence lipid metabolism, including the environment and genetics. We demonstrated, using a multi-omics and multifactorial experimental setup, that multiple factors affect lipid accumulation in the yeastYarrowia lipolytica. Using integrative analysis, we identified novel interactions between nutrient restriction and genetic factors involving regulators that are highly conserved among eukaryotes. Given that lipid metabolism is involved in many

  8. Characterization of Amphora sp., a newly isolated diatom wild strain, potentially usable for biodiesel production.

    PubMed

    Chtourou, Haifa; Dahmen, Ines; Jebali, Ahlem; Karray, Fatma; Hassairi, Ilem; Abdelkafi, Slim; Ayadi, Habib; Sayadi, Sami; Dhouib, Abdelhafidh

    2015-07-01

    Microalgae as feedstock for biofuel production have attracted serious consideration as an important sustainable source of energy. For biodiesel production with microalgae, a series of consecutive processes should be performed as selection of adequate microalgal strains, mass culture, cell harvesting, oil extraction and transesterification. The aim of this study was to investigate the growth and lipid accumulation of a new isolated marine microalgal strain by optimizing culture medium composition and applying different stressful culture conditions. Microalga CTM 20023 was isolated from the evaporating salt-ponds at Sfax, Tunisia, using serial-dilution technique from enriched cultures. Phylogenetic analysis based on SSU rDNA and rbcL-3P sequences attributed this isolate to a new species of the Amphora genus. This wild strain possesses rapid gravity sedimentation of 2.91 m h(-1), suitable for an easy and low-cost biomass harvest. The optimization of the composition of the culture medium through statistical experimental designs improved the specific growth rate of Amphora sp. from 0.149 to 0.262 day(-1) and increased its 15-day culture biomass production from 465 to 2200 mg L(-1) (dw) and its lipid content from 140 to 370 mg g(-1) (dw). Highest biomass productivity of 178 mg L(-1) day(-1) was achieved at the 10th day of culture. Highest lipid content of 530 mg g(-1) (dw) was obtained under phosphorus starvation and 64.34% of these lipids were saturated fatty acids. A first growth stage, in optimized condition, would thus offer the maximum productivity for an algal biomass feed stream, followed by second stressful stage for lipid accumulation, thus suitable for biodiesel production.

  9. Production of novel antibacterial liamocins by strains of Aureobasidium pullulans

    USDA-ARS?s Scientific Manuscript database

    Certain strains of Aureobasidium pullulans produce liamocins, heavier-than-water “oils” that accumulate in liquid cultures. Liamocins are surface active, and inhibit mammalian cancer cell lines. Recently, we discovered that liamocins have antibacterial activity with specificity against Streptococcus...

  10. Survival Strategies of the Plant-Associated Bacterium Enterobacter sp. Strain EG16 under Cadmium Stress

    PubMed Central

    Chen, Yanmei; Li, Yaying; Lin, Qingqi; Bai, Jun; Tang, Lu; Wang, Shizhong; Ying, Rongrong

    2016-01-01

    Plant-associated bacteria are of great interest because of their potential use in phytoremediation. However, their ability to survive and promote plant growth in metal-polluted soils remains unclear. In this study, a soilborne Cd-resistant bacterium was isolated and identified as Enterobacter sp. strain EG16. It tolerates high external Cd concentrations (Cd2+ MIC, >250 mg liter−1) and is able to produce siderophores and the plant hormone indole-3-acetic acid (IAA), both of which contribute to plant growth promotion. Surface biosorption in this strain accounted for 31% of the total Cd accumulated. The potential presence of cadmium sulfide, shown by energy-dispersive X-ray (EDX) analysis, suggested intracellular Cd binding as a Cd response mechanism of the isolate. Cd exposure resulted in global regulation at the transcriptomic level, with the bacterium switching to an energy-conserving mode by inhibiting energy-consuming processes while increasing the production of stress-related proteins. The stress response system included increased import of sulfur and iron, which become deficient under Cd stress, and the redirection of sulfur metabolism to the maintenance of intracellular glutathione levels in response to Cd toxicity. Increased production of siderophores, responding to Cd-induced Fe deficiency, not only is involved in the Cd stress response systems of EG16 but may also play an important role in promoting plant growth as well as alleviating the Cd-induced inhibition of IAA production. The newly isolated strain EG16 may be a suitable candidate for microbially assisted phytoremediation due to its high resistance to Cd and its Cd-induced siderophore production, which is likely to contribute to plant growth promotion. PMID:26729719

  11. Multifunctional Woven Structure Operating as Triboelectric Energy Harvester, Capacitive Tactile Sensor Array, and Piezoresistive Strain Sensor Array

    PubMed Central

    Kim, Kihong; Song, Giyoung; Park, Cheolmin; Yun, Kwang-Seok

    2017-01-01

    This paper presents a power-generating sensor array in a flexible and stretchable form. The proposed device is composed of resistive strain sensors, capacitive tactile sensors, and a triboelectric energy harvester in a single platform. The device is implemented in a woven textile structure by using proposed functional threads. A single functional thread is composed of a flexible hollow tube coated with silver nanowires on the outer surface and a conductive silver thread inside the tube. The total size of the device is 60 × 60 mm2 having a 5 × 5 array of sensor cell. The touch force in the vertical direction can be sensed by measuring the capacitance between the warp and weft functional threads. In addition, because silver nanowire layers provide piezoresistivity, the strain applied in the lateral direction can be detected by measuring the resistance of each thread. Last, with regard to the energy harvester, the maximum power and power density were measured as 201 μW and 0.48 W/m2, respectively, when the device was pushed in the vertical direction. PMID:29120363

  12. Global Existence Results for Viscoplasticity at Finite Strain

    NASA Astrophysics Data System (ADS)

    Mielke, Alexander; Rossi, Riccarda; Savaré, Giuseppe

    2018-01-01

    We study a model for rate-dependent gradient plasticity at finite strain based on the multiplicative decomposition of the strain tensor, and investigate the existence of global-in-time solutions to the related PDE system. We reveal its underlying structure as a generalized gradient system, where the driving energy functional is highly nonconvex and features the geometric nonlinearities related to finite-strain elasticity as well as the multiplicative decomposition of finite-strain plasticity. Moreover, the dissipation potential depends on the left-invariant plastic rate, and thus depends on the plastic state variable. The existence theory is developed for a class of abstract, nonsmooth, and nonconvex gradient systems, for which we introduce suitable notions of solutions, namely energy-dissipation-balance and energy-dissipation-inequality solutions. Hence, we resort to the toolbox of the direct method of the calculus of variations to check that the specific energy and dissipation functionals for our viscoplastic models comply with the conditions of the general theory.

  13. Do Anti-Bredt Natural Products Exist? Olefin Strain Energy as a Predictor of Isolability.

    PubMed

    Krenske, Elizabeth H; Williams, Craig M

    2015-09-01

    Bredt's rule holds a special place in the realm of physical organic chemistry, but its application to natural products chemistry—the field in which the rule was originally formulated—is not well defined. Herein, the use of olefin strain (OS) energy as a readily calculated predictor of the stability of natural products containing a bridgehead alkene is introduced. Schleyer first used OS energies to classify parent bridgehead alkenes into "isolable", "observable", and "unstable" classes. OS calculations on natural products, using contemporary forcefield methods, unequivocally predict all structurally verified bridgehead alkene natural products to be "isolable". Thus, when one assigns the structure of a putative bridgehead alkene natural product, an OS in the "observable" or "unstable" ranges is a red flag for error. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Strain Anomalies during an Earthquake Sequence in the South Iceland Seismic Zone

    NASA Astrophysics Data System (ADS)

    Arnadottir, T.; Haines, A. J.; Geirsson, H.; Hreinsdottir, S.

    2017-12-01

    The South Iceland Seismic Zone (SISZ) accommodates E-W translation due to oblique spreading between the North American/Hreppar microplate and Eurasian plate, in South Iceland. Strain is released in the SISZ during earthquake sequences that last days to years, at average intervals of 80-100 years. The SISZ is currently in the midst of an earthquake sequence that started with two M6.5 earthquakes in June 2000, and continued with two M6 earthquakes in May 2008. Estimates of geometric strain accumulation, and seismic strain release in these events indicate that they released at most only half of the strain accumulated since the last earthquake cycle in 1896-1912. Annual GPS campaigns and continuous measurements during 2001-2015 were used to calculate station velocities and strain rates from a new method using the vertical derivatives of horizontal stress (VDoHS). This new method allows higher resolution of strain rates than other (older) approaches, as the strain rates are estimated by integrating VDoHS rates obtained by inversion rather than differentiating interpolated GPS velocities. Estimating the strain rates for eight 1-2 year intervals indicates temporal and spatial variation of strain rates in the SISZ. In addition to earthquake faulting, the strain rates in the SISZ are influenced by anthropogenic signals due to geothermal exploitation, and magma movements in neighboring volcanoes - Hekla and Eyjafjallajökull. Subtle signals of post-seismic strain rate changes are seen following the June 2000 M6.5 main shocks, but interestingly, much larger strain rate variations are observed after the two May 2008 M6 main shocks. A prominent strain anomaly is evident in the epicentral area prior to the May 2008 earthquake sequence. The strain signal persists over at least 4 years in the epicentral area, leading up to the M6 main shocks. The strain is primarily extension in ESE-WNW direction (sub-parallel to the direction of plate spreading), but overall shear across the N

  15. Accumulation of rare earth elements by siderophore-forming Arthrobacter luteolus isolated from rare earth environment of Chavara, India.

    PubMed

    Emmanuel, E S Challaraj; Ananthi, T; Anandkumar, B; Maruthamuthu, S

    2012-03-01

    In this study, Arthrobacter luteolus, isolated from rare earth environment of Chavara (Quilon district, Kerala, India), were found to produce catechol-type siderophores. The bacterial strain accumulated rare earth elements such as samarium and scandium. The siderophores may play a role in the accumulation of rare earth elements. Catecholate siderophore and low-molecular-weight organic acids were found to be present in experiments with Arthrobacter luteolus. The influence of siderophore on the accumulation of rare earth elements by bacteria has been extensively discussed.

  16. Elastic block and strain modeling of GPS data around the Haiyuan-Liupanshan fault, northeastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Li, Yanchuan; Shan, Xinjian; Qu, Chunyan; Zhang, Yingfeng; Song, Xiaogang; Jiang, Yu; Zhang, Guohong; Nocquet, Jean-Mathieu; Gong, Wenyu; Gan, Weijun; Wang, Chisheng

    2017-12-01

    Based on the dense GPS velocity field in the northeastern margin of the Tibetan Plateau from 1999 to 2016, we have produced the deformation and strain characteristics of the Haiyuan fault and the Liupanshan fault. Estimated long-term slip rate along the Haiyuan-Liupanshan fault zones show a gradual decrease from 6.4 ± 1.6 mm/yr at the Tuolaishan fault to 2.9 ± 1.2 mm/yr at the Southern Liupanshan fault. Left-lateral thrusting movement was inverted for the Xiangshan-Tianjingshan fault (XS-TJS), which has an average slip rate of 2.1 ± 3.4 mm/yr during the study period. We also calculated the heterogeneous distribution of interseismic coupling along the fault zones. Our result also shows the locking depth of the Tianzhu seismic gap is ∼22 km. The slip rate deficit, the seismic moment accumulation rate, and the Coulomb stress accumulation rate are high on the fault planes, whereas the second invariant of the strain rate is low at the surface. The Liupanshan fault is locked to a depth of ∼23 km, and the corresponding seismic moment accumulation rate on the fault plane is high, while the strain rate at the surface is low. The accumulated strain along the Tianzhu seismic gap and the Liupanshan fault could be balanced by earthquakes with magnitudes of Mw7.9 and Mw7.4, considering the absence of large earthquakes over the last 1000 years and 1400 years respectively. The Haiyuan segments had ruptured during 1920 Haiyuan earthquake, and the estimated locking depth for period 1999-2016 is 5-10 km. Its seismic moment accumulation rate at depth is low and the strain rate at the surface is high. Our result indicates that 70% of the strike-slip along the Haiyuan segments transforms into thrusting along the Liupanshan fault, while the remaining 30% is related to the orogeny of the Liupanshan. For slip between the Haiyuan fault and the XS-TJS, about 27-34% of the slip is partitioned on the XS-TJS.

  17. Proline accumulation protects Saccharomyces cerevisiae cells in stationary phase from ethanol stress by reducing reactive oxygen species levels.

    PubMed

    Takagi, Hiroshi; Taguchi, Junpei; Kaino, Tomohiro

    2016-08-01

    During fermentation processes, Saccharomyces cerevisiae cells are exposed to multiple stresses, including a high concentration of ethanol that represents toxicity through intracellular reactive oxygen species (ROS) generation. We previously reported that proline protected yeast cells from damage caused by various stresses, such as freezing and ethanol. As an anti-oxidant, proline is suggested to scavenge intracellular ROS. In this study, we examined the role of intracellular proline during ethanol treatment in S. cerevisiae strains that accumulate different concentrations of proline. When cultured in YPD medium, there was a significant accumulation of proline in the put1 mutant strain, which is deficient in proline oxidase, in the stationary phase. Expression of the mutant PRO1 gene, which encodes the γ-glutamyl kinase variant (Asp154Asn or Ile150Thr) with desensitization to feedback inhibition by proline in the put1 mutant strain, showed a prominent increase in proline content as compared with that of the wild-type strain. The oxidation level was clearly increased in wild-type cells after exposure to ethanol, indicating that the generation of ROS occurred. Interestingly, proline accumulation significantly reduces the ROS level and increases the survival rate of yeast cells in the stationary phase under ethanol stress conditions. However, there was not a clear correlation between proline content and survival rate in yeast cells. An appropriate level of intracellular proline in yeast might be important for its stress-protective effect. Hence, the engineering of proline metabolism could be promising for breeding stress-tolerant industrial yeast strains. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  18. Phylogenetic study of recombinant strains of Potato virus Y

    USDA-ARS?s Scientific Manuscript database

    Potato virus Y (PVY) exists as a complex of strains, including a growing number of recombinants. Evolution of PVY proceeds through accumulation of mutations and more rapidly through recombination. Here, the role of recombination in PVY evolution and the origin of common PVY recombinants were studied...

  19. Multilevel modeling of damage accumulation processes in metals

    NASA Astrophysics Data System (ADS)

    Kurmoiartseva, K. A.; Trusov, P. V.; Kotelnikova, N. V.

    2017-12-01

    To predict the behavior of components and constructions it is necessary to develop the methods and mathematical models which take into account the self-organization of microstructural processes and the strain localization. The damage accumulation processes and the evolution of material properties during deformation are important to take into account. The heterogeneity of the process of damage accumulation is due to the appropriate physical mechanisms at the scale levels, which are lower than the macro-level. The purpose of this work is to develop a mathematical model for analyzing the behavior of polycrystalline materials that allows describing the damage accumulation processes. Fracture is the multistage and multiscale process of the build-up of micro- and mesodefects over the wide range of loading rates. The formation of microcracks by mechanisms is caused by the interactions of the dislocations of different slip systems, barriers, boundaries and the inclusions of the secondary phase. This paper provides the description of some of the most well-known models of crack nucleation and also suggests the structure of a mathematical model based on crystal plasticity and dislocation models of crack nucleation.

  20. Thickness effects on the texture development of fluorine-doped SnO2 thin films: The role of surface and strain energy

    NASA Astrophysics Data System (ADS)

    Consonni, V.; Rey, G.; Roussel, H.; Bellet, D.

    2012-02-01

    Polycrystalline fluorine-doped SnO2 thin films have been grown by ultrasonic spray pyrolysis with a thickness varying in the range of 40 to 600 nm. A texture transition from ⟨110⟩ to ⟨100⟩ and ⟨301⟩ crystallographic orientations has experimentally been shown by x-ray diffraction measurements as film thickness is increased, showing that a process of abnormal grain growth has occurred. The texture effects are considered within a thermodynamic approach, in which the minimization of total free energy constitutes the driving force for grain growth. For very small film thickness, it is found that the ⟨110⟩ preferred orientation is due to surface energy minimization, as the (110) planes have the lowest surface energy in the rutile structure. In contrast, as film thickness is increased, the ⟨100⟩ and ⟨301⟩ crystallographic orientations are progressively predominant, owing to elastic strain energy minimization in which the anisotropic character is considered in the elastic biaxial modulus. A texture map is eventually determined, revealing the expected texture as a function of elastic strain and film thickness.

  1. Isolation of baker's yeast mutants with proline accumulation that showed enhanced tolerance to baking-associated stresses.

    PubMed

    Tsolmonbaatar, Ariunzaya; Hashida, Keisuke; Sugimoto, Yukiko; Watanabe, Daisuke; Furukawa, Shuhei; Takagi, Hiroshi

    2016-12-05

    During bread-making processes, yeast cells are exposed to baking-associated stresses such as freeze-thaw, air-drying, and high-sucrose concentrations. Previously, we reported that self-cloning diploid baker's yeast strains that accumulate proline retained higher-level fermentation abilities in both frozen and sweet doughs than the wild-type strain. Although self-cloning yeasts do not have to be treated as genetically modified yeasts, the conventional methods for breeding baker's yeasts are more acceptable to consumers than the use of self-cloning yeasts. In this study, we isolated mutants resistant to the proline analogue azetidine-2-carboxylate (AZC) derived from diploid baker's yeast of Saccharomyces cerevisiae. Some of the mutants accumulated a greater amount of intracellular proline, and among them, 5 mutants showed higher cell viability than that observed in the parent wild-type strain under freezing or high-sucrose stress conditions. Two of them carried novel mutations in the PRO1 gene encoding the Pro247Ser or Glu415Lys variant of γ-glutamyl kinase (GK), which is a key enzyme in proline biosynthesis in S. cerevisiae. Interestingly, we found that these mutations resulted in AZC resistance of yeast cells and desensitization to proline feedback inhibition of GK, leading to intracellular proline accumulation. Moreover, baker's yeast cells expressing the PRO1 P247S and PRO1 E415K gene were more tolerant to freezing stress than cells expressing the wild-type PRO1 gene. The approach described here could be a practical method for the breeding of proline-accumulating baker's yeasts with higher tolerance to baking-associated stresses. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. A Monte Carlo-finite element model for strain energy controlled microstructural evolution - 'Rafting' in superalloys

    NASA Technical Reports Server (NTRS)

    Gayda, J.; Srolovitz, D. J.

    1989-01-01

    This paper presents a specialized microstructural lattice model, MCFET (Monte Carlo finite element technique), which simulates microstructural evolution in materials in which strain energy has an important role in determining morphology. The model is capable of accounting for externally applied stress, surface tension, misfit, elastic inhomogeneity, elastic anisotropy, and arbitrary temperatures. The MCFET analysis was found to compare well with the results of analytical calculations of the equilibrium morphologies of isolated particles in an infinite matrix.

  3. Absorption of Radionuclides from the Fukushima Nuclear Accident by a Novel Algal Strain

    PubMed Central

    Shimura, Hiroki; Itoh, Katsuhiko; Sugiyama, Atsushi; Ichijo, Sayaka; Ichijo, Masashi; Furuya, Fumihiko; Nakamura, Yuji; Kitahara, Ken; Kobayashi, Kazuhiko; Yukawa, Yasuhiro; Kobayashi, Tetsuro

    2012-01-01

    Large quantities of radionuclides have leaked from the Fukushima Daiichi Nuclear Power Plant into the surrounding environment. Effective prevention of health hazards resulting from radiation exposure will require the development of efficient and economical methods for decontaminating radioactive wastewater and aquatic ecosystems. Here we describe the accumulation of water-soluble radionuclides released by nuclear reactors by a novel strain of alga. The newly discovered green microalgae, Parachlorella sp. binos (Binos) has a thick alginate-containing extracellular matrix and abundant chloroplasts. When this strain was cultured with radioiodine, a light-dependent uptake of radioiodine was observed. In dark conditions, radioiodine uptake was induced by addition of hydrogen superoxide. High-resolution secondary ion mass spectrometry (SIMS) showed a localization of accumulated iodine in the cytosol. This alga also exhibited highly efficient incorporation of the radioactive isotopes strontium and cesium in a light-independent manner. SIMS analysis showed that strontium was distributed in the extracellular matrix of Binos. Finally we also showed the ability of this strain to accumulate radioactive nuclides from water and soil samples collected from a heavily contaminated area in Fukushima. Our results demonstrate that Binos could be applied to the decontamination of iodine, strontium and cesium radioisotopes, which are most commonly encountered after nuclear reactor accidents. PMID:22984475

  4. Production of biodegradable plastic by polyhydroxybutyrate (PHB) accumulating bacteria using low cost agricultural waste material.

    PubMed

    Getachew, Anteneh; Woldesenbet, Fantahun

    2016-12-12

    Polyhydroxybutyrates (PHBs) are macromolecules synthesized by bacteria. They are inclusion bodies accumulated as reserve materials when the bacteria grow under different stress conditions. Because of their fast degradability under natural environmental conditions, PHBs are selected as alternatives for production of biodegradable plastics. The aim of this work was to isolate potential PHB producing bacteria, evaluate PHB production using agro-residues as carbon sources. Among fifty bacterial strains isolated from different localities, ten PHB accumulating strains were selected and compared for their ability to accumulate PHB granules inside their cells. Isolate Arba Minch Waste Water (AWW) identified as Bacillus spp was found to be the best producer. The optimum pH, temperature, and incubation period for best PHB production by the isolate were 7, 37 °C, and 48 h respectively at 150 rpm. PHB production was best with glucose as carbon source and peptone as nitrogen source. The strain was able to accumulate 55.6, 51.6, 37.4 and 25% PHB when pretreated sugar cane bagasse, corn cob, teff straw (Eragrostis tef) and banana peel were used as carbon sources respectively. Fourier transform-infrared authentication results of the extracted and purified PHB identified its functional units as C-H, CH 2 , C=O and C-O groups. UV-Vis spectrophotometric analysis and biodegradability test confirmed the similarity of the extract with standard PHB and its suitability for bioplastic production. The isolated Bacillus sp can be used for feasible production of PHB using agro-residues especially sugarcane bagasse which can reduce the production cost in addition to reducing the disposal problem of these substrates. The yield of PHB can further be boosted by optimization of production parameters as substrates.

  5. Damage Assessment of Heat Resistant Steels through Electron BackScatter Diffraction Strain Analysis under Creep and Creep-Fatigue Conditions

    NASA Astrophysics Data System (ADS)

    Fujiyama, Kazunari; Kimachi, Hirohisa; Tsuboi, Toshiki; Hagiwara, Hiroyuki; Ogino, Shotaro; Mizutani, Yoshiki

    EBSD(Electron BackScatter Diffraction) analyses were conducted for studying the quantitative microstructural metrics of creep and creep-fatigue damage for austenitic SUS304HTB boiler tube steel and ferritic Mod.9Cr piping steel. KAM(Kernel Average Misorientation) maps and GOS(Grain Orientation Spread) maps were obtained for these samples and the area averaged values KAMave and GOSave were obtained. While the increasing trends of these misorientation metrics were observed for SUS304HTB steel, the decreasing trends were observed for damaged Mod.9Cr steel with extensive recovery of subgrain structure. To establish more universal parameter representing the accumulation of damage to compensate these opposite trends, the EBSD strain parameters were introduced for converting the misorientation changes into the quantities representing accumulated permanent strains during creep and creep-fatigue damage process. As KAM values were dependent on the pixel size (inversely proportional to the observation magnification) and the permanent strain could be expressed as the shear strain which was the product of dislocation density, Burgers vector and dislocation movement distance, two KAM strain parameters MεKAMnet and MεδKAMave were introduced as the sum of product of the noise subtracted KAMnet and the absolute change from initial value δKAMave with dislocation movement distance divided by pixel size. MεδKAMave parameter showed better relationship both with creep strain in creep tests and accumulated creep strain range in creep-fatigue tests. This parameter can be used as the strain-based damage evaluation and detector of final failure.

  6. In situ strain profiling of elastoplastic bending in Ti-6Al-4V alloy by synchrotron energy dispersive x-ray diffraction

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

    Croft, M.; National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973; Shukla, V.

    Elastic and plastic strain evolution under four-point bending has been studied by synchrotron energy dispersive x-ray diffraction. Measured strain profiles across the specimen thickness showed an increasing linear elastic strain gradient under increasing four-point bending load up to approx2 kN. The bulk elastic modulus of Ti-6Al-4V was determined as 118 GPa. The onset of plastic deformation was found to set in at a total in-plane strain of approx0.008, both under tension and compression. Plastic deformation under bending is initiated in the vicinity of the surface and at a stress of 1100 MPa, and propagates inward, while a finite core regionmore » remains elastically deformed up to 3.67 kN loading. The onset of the plastic regime and the plastic regime itself has been verified by monitoring the line broadening of the (100) peak of alpha-Ti. The effective compression/tension stress-strain curve has been obtained from the scaling collapse of strain profile data taken at seven external load levels. A similar multiple load scaling collapse of the plastic strain variation has also been obtained. The level of precision in strain measurement reported herein was evaluated and found to be 1.5x10{sup -5} or better.« less

  7. Effect of crude and pure glycerol on biomass production and trehalose accumulation by Propionibacterium freudenreichii ssp. shermanii 1.

    PubMed

    Pawlicka-Kaczorowska, Joanna; Czaczyk, Katarzyna

    2017-01-01

    The dairy propionibacteria, which are traditionally used for the production of Swiss cheeses, are able to synthesize valuable biomolecules, e.g. B group vitamins, propionic acid, and trehalose with unique chemical and physical properties. Both, dairy propionibacteria cells and trehalose, have found many applications as attractive and effective components in food, beauty and health care products. This study confirmed the ability of several strains from the Propionibacterium genus to create trehalose from glycerol. The research aimed to investigate the effect of crude and pure glycerol on biomass production and on trehalose accumulation by Propionibacterium freudenreichii ssp. shermanii 1. The results indicated that the capacity for trehalose accumulation by Propionibacterium spp. was strain dependent. Propionibacterium freudenreichii ssp. shermanii 1 was able to grow on crude glycerol. For both, pure and crude glycerol, the highest amount of dry biomass leveled off at about 4 g/L. While the use of crude glycerol had no effect on the final concentration of biomass, it reduced the accumulation of trehalose in the cells. An increase in the concentration of carbon source (2-8%) resulted in more than a 5-fold rise in trehalose production. The highest trehalose concentration of 195.04 mg/L was obtained with cultures of the said strain supplemented to 8% with pure glycerol.

  8. Longitudinal compressive behaviour of 3D braided composite under various temperatures and strain rates

    NASA Astrophysics Data System (ADS)

    Pan, Zhongxiang; Gu, Bohong; Sun, Baozhong

    2015-03-01

    This paper reports the longitudinal compressive behaviour of 3D braided basalt fibre tows/epoxy composite materials under strain-rate range of 1,200-2,400 s-1 and temperature range of 23-210 °C both in experimental and finite element analyses (FEA). A split Hopkinson pressure bar system with a heating device was designed to test the longitudinal compressive behaviour of 3D braided composite materials. Testing results indicate that longitudinal compression modulus, specific energy absorption and peak stress decreased with elevated temperatures, whereas the failure strain increased with elevated temperatures. At some temperatures above the T g of epoxy resin, such as at 120 and 150 °C, strain distributions and deformations in fibre tows and epoxy resin tended to be the same. It results in relatively slighter damage status of the 3D braided composite material. The FEA results reveal that heating of the material due to the dissipative energy of the inelastic deformation and damage processes generated in resin is more than that in fibre tows. The braiding structure has a significant influence on thermomechanical failure via two aspects: distribution and accumulation of the heating leads to the development of the shear band paths along braiding angle; the buckling inflection segment rather than the straight segment generates the maximum of the heating in each fibre tows. The damage occurs at the early stage when the temperature is below T g, while at the temperature above T g, damage stage occurs at the rear of plastic deformation.

  9. Engineering Saccharomyces cerevisiae for improvement in ethanol tolerance by accumulation of trehalose.

    PubMed

    Divate, Nileema R; Chen, Gen-Hung; Wang, Pei-Ming; Ou, Bor-Rung; Chung, Yun-Chin

    2016-11-01

    A genetic recombinant Saccharomyces cerevisiae starter with high ethanol tolerance capacities was constructed. In this study, the gene of trehalose-6-phosphate synthase (encoded by tps1), which catalyzes the first step in trehalose synthesis, was cloned and overexpressed in S. cerevisiae. Moreover, the gene of neutral trehalase (encoded by nth1, trehalose degrading enzyme) was deleted by using a disruption cassette, which contained long flanking homology regions of nth1 gene (the upstream 0.26 kb and downstream 0.4 kb). The engineered strain increased its tolerance against ethanol and glucose stress. The growth of the wild strain was inhibited when the medium contained 6 % or more ethanol, whereas growth of the engineered strain was affected when the medium contained 10 % or more ethanol. There was no significant difference in the ethanol yield between the wild strain and the engineered strain when the fermentation broth contained 10 % glucose (p > 0.05). The engineered strain showed greater ethanol yield than the wild type strain when the medium contained more than 15 % glucose (p < 0.05). Higher intracellular trehalose accumulation by overexpression of tps1 and deletion of nth1 might provide the ability for yeast to protect against environmental stress.

  10. Engineering Saccharomyces cerevisiae for improvement in ethanol tolerance by accumulation of trehalose

    PubMed Central

    Divate, Nileema R.; Chen, Gen-Hung; Wang, Pei-Ming; Ou, Bor-Rung; Chung, Yun-Chin

    2016-01-01

    ABSTRACT A genetic recombinant Saccharomyces cerevisiae starter with high ethanol tolerance capacities was constructed. In this study, the gene of trehalose-6-phosphate synthase (encoded by tps1), which catalyzes the first step in trehalose synthesis, was cloned and overexpressed in S. cerevisiae. Moreover, the gene of neutral trehalase (encoded by nth1, trehalose degrading enzyme) was deleted by using a disruption cassette, which contained long flanking homology regions of nth1 gene (the upstream 0.26 kb and downstream 0.4 kb). The engineered strain increased its tolerance against ethanol and glucose stress. The growth of the wild strain was inhibited when the medium contained 6 % or more ethanol, whereas growth of the engineered strain was affected when the medium contained 10 % or more ethanol. There was no significant difference in the ethanol yield between the wild strain and the engineered strain when the fermentation broth contained 10 % glucose (p > 0.05). The engineered strain showed greater ethanol yield than the wild type strain when the medium contained more than 15 % glucose (p < 0.05). Higher intracellular trehalose accumulation by overexpression of tps1 and deletion of nth1 might provide the ability for yeast to protect against environmental stress. PMID:27484300

  11. Mn accumulation in a submerged plant Egeria densa (Hydrocharitaceae) is mediated by epiphytic bacteria.

    PubMed

    Tsuji, Kousuke; Asayama, Takuma; Shiraki, Nozomi; Inoue, Shota; Okuda, Erina; Hayashi, Chizuru; Nishida, Kazuma; Hasegawa, Hiroshi; Harada, Emiko

    2017-07-01

    Many aquatic plants act as biosorbents, removing and recovering metals from the environment. To assess the biosorbent activity of Egeria densa, a submerged freshwater macrophyte, plants were collected monthly from a circular drainage area in Lake Biwa basin and the Mn concentrations of the plants were analysed. Mn concentrations in these plants were generally above those of terrestrial hyperaccumulators, and were markedly higher in spring and summer than in autumn. Mn concentrations were much lower in plants incubated in hydroponic medium at various pH levels with and without Mn supplementation than in field-collected plants. The precipitation of Mn oxides on the leaves was determined by variable pressure scanning electron microscopy-energy dispersive X-ray analysis and Leucoberbelin blue staining. Several strains of epiphytic bacteria were isolated from the field-collected E. densa plants, with many of these strains, including those of the genera Acidovorax, Comamonas, Pseudomonas and Rhizobium, found to have Mn-oxidizing activity. High Mn concentrations in E. densa were mediated by the production of biogenic Mn oxide in biofilms on leaf surfaces. These findings provide new insights into plant epidermal bacterial flora that affect metal accumulation in plants and suggest that these aquatic plants may have use in Mn phytomining. © 2017 John Wiley & Sons Ltd.

  12. Silica-Based and Borate-Based, Titania-Containing Bioactive Coatings Characterization: Critical Strain Energy Release Rate, Residual Stresses, Hardness, and Thermal Expansion.

    PubMed

    Rodriguez, Omar; Matinmanesh, Ali; Phull, Sunjeev; Schemitsch, Emil H; Zalzal, Paul; Clarkin, Owen M; Papini, Marcello; Towler, Mark R

    2016-12-01

    Silica-based and borate-based glass series, with increasing amounts of TiO₂ incorporated, are characterized in terms of their mechanical properties relevant to their use as metallic coating materials. It is observed that borate-based glasses exhibit CTE (Coefficient of Thermal Expansion) closer to the substrate's (Ti6Al4V) CTE, translating into higher mode I critical strain energy release rates of glasses and compressive residual stresses and strains at the coating/substrate interface, outperforming the silica-based glasses counterparts. An increase in the content of TiO₂ in the glasses results in an increase in the mode I critical strain energy release rate for both the bulk glass and for the coating/substrate system, proving that the addition of TiO₂ to the glass structure enhances its toughness, while decreasing its bulk hardness. Borate-based glass BRT3, with 15 mol % TiO₂ incorporated, exhibits superior properties overall compared to the other proposed glasses in this work, as well as 45S5 Bioglass ® and Pyrex.

  13. Silica-Based and Borate-Based, Titania-Containing Bioactive Coatings Characterization: Critical Strain Energy Release Rate, Residual Stresses, Hardness, and Thermal Expansion

    PubMed Central

    Rodriguez, Omar; Matinmanesh, Ali; Phull, Sunjeev; Schemitsch, Emil H.; Zalzal, Paul; Clarkin, Owen M.; Papini, Marcello; Towler, Mark R.

    2016-01-01

    Silica-based and borate-based glass series, with increasing amounts of TiO2 incorporated, are characterized in terms of their mechanical properties relevant to their use as metallic coating materials. It is observed that borate-based glasses exhibit CTE (Coefficient of Thermal Expansion) closer to the substrate’s (Ti6Al4V) CTE, translating into higher mode I critical strain energy release rates of glasses and compressive residual stresses and strains at the coating/substrate interface, outperforming the silica-based glasses counterparts. An increase in the content of TiO2 in the glasses results in an increase in the mode I critical strain energy release rate for both the bulk glass and for the coating/substrate system, proving that the addition of TiO2 to the glass structure enhances its toughness, while decreasing its bulk hardness. Borate-based glass BRT3, with 15 mol % TiO2 incorporated, exhibits superior properties overall compared to the other proposed glasses in this work, as well as 45S5 Bioglass® and Pyrex. PMID:27916951

  14. Photoactuators for Direct Optical-to-Mechanical Energy Conversion: From Nanocomponent Assembly to Macroscopic Deformation.

    PubMed

    Hu, Ying; Li, Zhe; Lan, Tian; Chen, Wei

    2016-12-01

    Photoactuators with integrated optical-to-mechanical energy conversion capacity have attracted growing research interest in the last few decades due to their unique features of remote control and their wide applications ranging from bionic robots, biomedical devices, and switches to motors. For the photoactuator design, the energy conversion route and structure assembly are two important parts, which directly affect the performance of the photoactuators. In particular, the architectural designs at the molecular, nano-, micro-, and macro- level, are found to play a significant role in accumulating molecular-scale strain/stress to macroscale strain/stress. Here, recent progress on photoactuators based on photochemical and photothermal effects is summarized, followed by a discussion of the important assembly strategies for the amplification of the photoresponsive components at nanoscale to macroscopic scale motions. The application advancement of current photoactuators is also presented. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Strain accumulation and rotation in western Oregon and southwestern Washington

    USGS Publications Warehouse

    Svarc, J.L.; Savage, J.C.; Prescott, W.H.; Murray, M.H.

    2002-01-01

    Velocities of 75 geodetic monuments in western Oregon and southwestern Washington extending from the coast to more than 300 km inland have been determined from GPS surveys over the interval 1992-2000. The average standard deviation in each of the horizontal velocity components is ??? 1 mm yr-1. The observed velocity field is approximated by a combination of rigid rotation (Euler vector relative to interior North America: 43. 40??N ?? 0.14??, 119.33??W ?? 0.28??, and 0.822 ?? 0.057?? Myr-1 clockwise; quoted uncertainties are standard deviations), uniform regional strain rate (??EE = -7.4 ?? 1.8, ??EN = -3.4 ?? 1.0, and ??NN = -5.0 ?? 0.8 nstrain yr-1, extension reckoned positive), and a dislocation model representing subduction of the Juan de Fuca plate beneath North America. Subduction south of 44.5??N was represented by a 40-km-wide locked thrust and subduction north of 44.5??N by a 75-km-wide locked thrust.

  16. Direct measurement of conformational strain energy in protofilaments curling outward from disassembling microtubule tips

    PubMed Central

    Driver, Jonathan W; Geyer, Elisabeth A; Bailey, Megan E; Rice, Luke M; Asbury, Charles L

    2017-01-01

    Disassembling microtubules can generate movement independently of motor enzymes, especially at kinetochores where they drive chromosome motility. A popular explanation is the ‘conformational wave’ model, in which protofilaments pull on the kinetochore as they curl outward from a disassembling tip. But whether protofilaments can work efficiently via this spring-like mechanism has been unclear. By modifying a previous assay to use recombinant tubulin and feedback-controlled laser trapping, we directly demonstrate the spring-like elasticity of curling protofilaments. Measuring their mechanical work output suggests they carry ~25% of the energy of GTP hydrolysis as bending strain, enabling them to drive movement with efficiency similar to conventional motors. Surprisingly, a β-tubulin mutant that dramatically slows disassembly has no effect on work output, indicating an uncoupling of disassembly speed from protofilament strain. These results show the wave mechanism can make a major contribution to kinetochore motility and establish a direct approach for measuring tubulin mechano-chemistry. DOI: http://dx.doi.org/10.7554/eLife.28433.001 PMID:28628007

  17. Strain-rate/temperature behavior of high density polyethylene in compression

    NASA Technical Reports Server (NTRS)

    Clements, L. L.; Sherby, O. D.

    1978-01-01

    The compressive strain rate/temperature behavior of highly linear, high density polyethylene was analyzed in terms of the predictive relations developed for metals and other crystalline materials. For strains of 5 percent and above, the relationship between applied strain rate, dotted epsilon, and resulting flow stress, sigma, was found to be: dotted epsilon exp times (Q sub f/RT) = k'(sigma/sigma sub c) to the nth power; the left-hand side is the activation-energy-compensated strain rate, where Q sub f is activation energy for flow, R is gas constant, and T is temperature; k is a constant, n is temperature-independent stress exponent, and sigma/sigma sub c is structure-compensated stress. A master curve resulted from a logarithmic plot of activation-energy-compensated strain rate versus structure-compensated stress.

  18. Estimate of tephra accumulation probabilities for the U.S. Department of Energy's Hanford Site, Washington

    USGS Publications Warehouse

    Hoblitt, Richard P.; Scott, William E.

    2011-01-01

    In response to a request from the U.S. Department of Energy, we estimate the thickness of tephra accumulation that has an annual probability of 1 in 10,000 of being equaled or exceeded at the Hanford Site in south-central Washington State, where a project to build the Tank Waste Treatment and Immobilization Plant is underway. We follow the methodology of a 1987 probabilistic assessment of tephra accumulation in the Pacific Northwest. For a given thickness of tephra, we calculate the product of three probabilities: (1) the annual probability of an eruption producing 0.1 km3 (bulk volume) or more of tephra, (2) the probability that the wind will be blowing toward the Hanford Site, and (3) the probability that tephra accumulations will equal or exceed the given thickness at a given distance. Mount St. Helens, which lies about 200 km upwind from the Hanford Site, has been the most prolific source of tephra fallout among Cascade volcanoes in the recent geologic past and its annual eruption probability based on this record (0.008) dominates assessment of future tephra falls at the site. The probability that the prevailing wind blows toward Hanford from Mount St. Helens is 0.180. We estimate exceedance probabilities of various thicknesses of tephra fallout from an analysis of 14 eruptions of the size expectable from Mount St. Helens and for which we have measurements of tephra fallout at 200 km. The result is that the estimated thickness of tephra accumulation that has an annual probability of 1 in 10,000 of being equaled or exceeded is about 10 centimeters. It is likely that this thickness is a maximum estimate because we used conservative estimates of eruption and wind probabilities and because the 14 deposits we used probably provide an over-estimate. The use of deposits in this analysis that were mostly compacted by the time they were studied and measured implies that the bulk density of the tephra fallout we consider here is in the range of 1,000-1,250 kg/m3. The

  19. Analyzing Reaction Rates with the Distortion/Interaction‐Activation Strain Model

    PubMed Central

    2017-01-01

    Abstract The activation strain or distortion/interaction model is a tool to analyze activation barriers that determine reaction rates. For bimolecular reactions, the activation energies are the sum of the energies to distort the reactants into geometries they have in transition states plus the interaction energies between the two distorted molecules. The energy required to distort the molecules is called the activation strain or distortion energy. This energy is the principal contributor to the activation barrier. The transition state occurs when this activation strain is overcome by the stabilizing interaction energy. Following the changes in these energies along the reaction coordinate gives insights into the factors controlling reactivity. This model has been applied to reactions of all types in both organic and inorganic chemistry, including substitutions and eliminations, cycloadditions, and several types of organometallic reactions. PMID:28447369

  20. Q3DG: A computer program for strain-energy-release rates for delamination growth in composite laminates

    NASA Technical Reports Server (NTRS)

    Raju, I. S.

    1986-01-01

    The Q3DG is a computer program developed to perform a quasi-three-dimensional stress analysis for composite laminates which may contain delaminations. The laminates may be subjected to mechanical, thermal, and hygroscopic loads. The program uses the finite element method and models the laminates with eight-noded parabolic isoparametric elements. The program computes the strain-energy-release components and the total strain-energy release in all three modes for delamination growth. A rectangular mesh and data file generator, DATGEN, is included. The DATGEN program can be executed interactively and is user friendly. The documentation includes sections dealing with the Q3D analysis theory, derivation of element stiffness matrices and consistent load vectors for the parabolic element. Several sample problems with the input for Q3DG and output from the program are included. The capabilities of the DATGEN program are illustrated with examples of interactive sessions. A microfiche of all the examples is included. The Q3DG and DATGEN programs have been implemented on CYBER 170 class computers. Q3DG and DATGEN were developed at the Langley Research Center during the early eighties and documented in 1984 to 1985.

  1. Energy transfer in turbulence under rotation

    NASA Astrophysics Data System (ADS)

    Buzzicotti, Michele; Aluie, Hussein; Biferale, Luca; Linkmann, Moritz

    2018-03-01

    It is known that rapidly rotating turbulent flows are characterized by the emergence of simultaneous upscale and downscale energy transfer. Indeed, both numerics and experiments show the formation of large-scale anisotropic vortices together with the development of small-scale dissipative structures. However the organization of interactions leading to this complex dynamics remains unclear. Two different mechanisms are known to be able to transfer energy upscale in a turbulent flow. The first is characterized by two-dimensional interactions among triads lying on the two-dimensional, three-component (2D3C)/slow manifold, namely on the Fourier plane perpendicular to the rotation axis. The second mechanism is three-dimensional and consists of interactions between triads with the same sign of helicity (homochiral). Here, we present a detailed numerical study of rotating flows using a suite of high-Reynolds-number direct numerical simulations (DNS) within different parameter regimes to analyze both upscale and downscale cascade ranges. We find that the upscale cascade at wave numbers close to the forcing scale is generated by increasingly dominant homochiral interactions which couple the three-dimensional bulk and the 2D3C plane. This coupling produces an accumulation of energy in the 2D3C plane, which then transfers energy to smaller wave numbers thanks to the two-dimensional mechanism. In the forward cascade range, we find that the energy transfer is dominated by heterochiral triads and is dominated primarily by interaction within the fast manifold where kz≠0 . We further analyze the energy transfer in different regions in the real-space domain. In particular, we distinguish high-strain from high-vorticity regions and we uncover that while the mean transfer is produced inside regions of strain, the rare but extreme events of energy transfer occur primarily inside the large-scale column vortices.

  2. Adhesive-Bonded Composite Joint Analysis with Delaminated Surface Ply Using Strain-Energy Release Rate

    NASA Technical Reports Server (NTRS)

    Chadegani, Alireza; Yang, Chihdar; Smeltzer, Stanley S. III

    2012-01-01

    This paper presents an analytical model to determine the strain energy release rate due to an interlaminar crack of the surface ply in adhesively bonded composite joints subjected to axial tension. Single-lap shear-joint standard test specimen geometry with thick bondline is followed for model development. The field equations are formulated by using the first-order shear-deformation theory in laminated plates together with kinematics relations and force equilibrium conditions. The stress distributions for the adherends and adhesive are determined after the appropriate boundary and loading conditions are applied and the equations for the field displacements are solved. The system of second-order differential equations is solved to using the symbolic computation tool Maple 9.52 to provide displacements fields. The equivalent forces at the tip of the prescribed interlaminar crack are obtained based on interlaminar stress distributions. The strain energy release rate of the crack is then determined by using the crack closure method. Finite element analyses using the J integral as well as the crack closure method are performed to verify the developed analytical model. It has been shown that the results using the analytical method correlate well with the results from the finite element analyses. An attempt is made to predict the failure loads of the joints based on limited test data from the literature. The effectiveness of the inclusion of bondline thickness is justified when compared with the results obtained from the previous model in which a thin bondline and uniform adhesive stresses through the bondline thickness are assumed.

  3. Survival Strategies of the Plant-Associated Bacterium Enterobacter sp. Strain EG16 under Cadmium Stress.

    PubMed

    Chen, Yanmei; Chao, Yuanqing; Li, Yaying; Lin, Qingqi; Bai, Jun; Tang, Lu; Wang, Shizhong; Ying, Rongrong; Qiu, Rongliang

    2016-01-04

    Plant-associated bacteria are of great interest because of their potential use in phytoremediation. However, their ability to survive and promote plant growth in metal-polluted soils remains unclear. In this study, a soilborne Cd-resistant bacterium was isolated and identified as Enterobacter sp. strain EG16. It tolerates high external Cd concentrations (Cd(2+) MIC, >250 mg liter(-1)) and is able to produce siderophores and the plant hormone indole-3-acetic acid (IAA), both of which contribute to plant growth promotion. Surface biosorption in this strain accounted for 31% of the total Cd accumulated. The potential presence of cadmium sulfide, shown by energy-dispersive X-ray (EDX) analysis, suggested intracellular Cd binding as a Cd response mechanism of the isolate. Cd exposure resulted in global regulation at the transcriptomic level, with the bacterium switching to an energy-conserving mode by inhibiting energy-consuming processes while increasing the production of stress-related proteins. The stress response system included increased import of sulfur and iron, which become deficient under Cd stress, and the redirection of sulfur metabolism to the maintenance of intracellular glutathione levels in response to Cd toxicity. Increased production of siderophores, responding to Cd-induced Fe deficiency, not only is involved in the Cd stress response systems of EG16 but may also play an important role in promoting plant growth as well as alleviating the Cd-induced inhibition of IAA production. The newly isolated strain EG16 may be a suitable candidate for microbially assisted phytoremediation due to its high resistance to Cd and its Cd-induced siderophore production, which is likely to contribute to plant growth promotion. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

  4. Strain-Specific Induction of Endometrial Periglandular Fibrosis in Mice Exposed During Adulthood to the Endocrine Disrupting Chemical Bisphenol A

    PubMed Central

    Kendziorski, Jessica A.; Belcher, Scott M.

    2015-01-01

    The aim of this study was to compare effects of bisphenol A (BPA) on collagen accumulation in uteri of two mouse strains. Adult C57Bl/6N and CD-1 mice were exposed to dietary BPA (0.004–40 mg/kg/day) or 17α-ethinyl estradiol (0.00002–0.001 mg/kg/day) as effect control. An equine endometrosis-like phenotype with increased gland nesting and periglandular collagen accumulation was characteristic of unexposed C57Bl/6N, but not CD-1, endometrium. BPA non-monotonically increased gland nest density and periglandular collagen accumulation in both strains. Increased collagen I and III expression, decreased matrix metalloproteinase 2 (MMP2) and MMP14 expression, and increased immune response were associated with the endometrosis phenotype in the C57Bl/6N strain and the 30 ppm BPA CD-1 group. The association between the pro-collagen shift in increased collagen expression and decreased MMP2 expression and activity implies that strain differences and BPA exposure salter regulation of endometrial remodeling and contributes to increased fibrosis, a component of several human uterine diseases. PMID:26307436

  5. Strain-controlled electrocatalysis on multimetallic nanomaterials

    NASA Astrophysics Data System (ADS)

    Luo, Mingchuan; Guo, Shaojun

    2017-11-01

    Electrocatalysis is crucial for the development of clean and renewable energy technologies, which may reduce our reliance on fossil fuels. Multimetallic nanomaterials serve as state-of-the-art electrocatalysts as a consequence of their unique physico-chemical properties. One method of enhancing the electrocatalytic performance of multimetallic nanomaterials is to tune or control the surface strain of the nanomaterials, and tremendous progress has been made in this area in the past decade. In this Review, we summarize advances in the introduction, tuning and quantification of strain in multimetallic nanocrystals to achieve more efficient energy conversion by electrocatalysis. First, we introduce the concept of strain and its correlation with other key physico-chemical properties. Then, using the electrocatalytic reduction of oxygen as a model reaction, we discuss the underlying mechanisms behind the strain-adsorption-reactivity relationship based on combined classical theories and models. We describe how this knowledge can be harnessed to design multimetallic nanocrystals with optimized strain to increase the efficiency of oxygen reduction. In particular, we highlight the unexpectedly beneficial (and previously overlooked) role of tensile strain from multimetallic nanocrystals in improving electrocatalysis. We conclude by outlining the challenges and offering our perspectives on the research directions in this burgeoning field.

  6. Anchoring plant metallothioneins to the inner face of the plasma membrane of Saccharomyces cerevisiae cells leads to heavy metal accumulation.

    PubMed

    Ruta, Lavinia Liliana; Lin, Ya-Fen; Kissen, Ralph; Nicolau, Ioana; Neagoe, Aurora Daniela; Ghenea, Simona; Bones, Atle M; Farcasanu, Ileana Cornelia

    2017-01-01

    In this study we engineered yeast cells armed for heavy metal accumulation by targeting plant metallothioneins to the inner face of the yeast plasma membrane. Metallothioneins (MTs) are cysteine-rich proteins involved in the buffering of excess metal ions, especially Cu(I), Zn(II) or Cd(II). The cDNAs of seven Arabidopsis thaliana MTs (AtMT1a, AtMT1c, AtMT2a, AtMT2b, AtMT3, AtMT4a and AtMT4b) and four Noccaea caerulescens MTs (NcMT1, NcMT2a, NcMT2b and NcMT3) were each translationally fused to the C-terminus of a myristoylation green fluorescent protein variant (myrGFP) and expressed in Saccharomyces cerevisiae cells. The myrGFP cassette introduced a yeast myristoylation sequence which allowed directional targeting to the cytosolic face of the plasma membrane along with direct monitoring of the intracellular localization of the recombinant protein by fluorescence microscopy. The yeast strains expressing plant MTs were investigated against an array of heavy metals in order to identify strains which exhibit the (hyper)accumulation phenotype without developing toxicity symptoms. Among the transgenic strains which could accumulate Cu(II), Zn(II) or Cd(II), but also non-canonical metal ions, such as Co(II), Mn(II) or Ni(II), myrGFP-NcMT3 qualified as the best candidate for bioremediation applications, thanks to the robust growth accompanied by significant accumulative capacity.

  7. Finite-strain analysis of Metavolcano-sedimentary rocks at Gabel El Mayet area, Central Eastern Desert, Egypt

    NASA Astrophysics Data System (ADS)

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

    2010-09-01

    Finite strain was estimated in the metavolcano-sedimentary rocks, which surround by serpentinites of Gabel El Mayet area. Finite strain shows a relationship to nappe contacts between the metavolcano-sedimentary rocks and serpentinite and sheds light on the nature of the subhorizontal foliation typical for the Gable Mayet shear zone. We used the Rf/ ϕ and Fry methods on feldspar porphyroclasts and mafic grains from 10 metasedimentary and six metavolcanic samples in Gabel El Mayet region. Our finite-strain data show that the metavolcano-sedimentary rocks were moderately deformed and axial ratios in the XZ section range from 1.9 to 3.9. The long axes of the finite-strain ellipsoids trend W/WNW in the north and W/WSW in the south of the Gabel El Mayet shear zone. Furthermore, the short axes are subvertical to a subhorizontal foliation. The strain magnitudes increase towards the tectonic contacts between the metavolcano-sedimentary rocks and serpentinite. The data indicate oblate strain symmetry in the metavolcano-sedimentary rocks. Hence, our strain data also indicate flattening strain. We assume that the metasedimentary and metavolcanics rocks have similar deformation behaviour. The fact that finite strain accumulated during the metamorphism indicates that the nappe contacts formed during the accumulation of finite strain and thus during thrusting. We conclude that the nappe contacts formed during progressive thrusting under brittle to semi-brittle deformation conditions by simple shear and involved a component of vertical shortening, which caused the subhorizontal foliation in the Gabel El Mayet shear zone.

  8. 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.

  9. Measurement of large strains in ropes using plastic optical fibers

    DOEpatents

    Williams, Jerry Gene; Smith, David Barton; Muhs, Jeffrey David

    2006-02-14

    A method for the direct measurement of large strains in ropes in situ using a plastic optical fiber, for example, perfluorocarbon or polymethyl methacrylate and Optical Time-Domain Reflectometer or other light time-of-flight measurement instrumentation. Protective sheaths and guides are incorporated to protect the plastic optical fiber. In one embodiment, a small rope is braided around the plastic optical fiber to impose lateral compressive forces to restrain the plastic optical fiber from slipping and thus experience the same strain as the rope. Methods are described for making reflective interfaces along the length of the plastic optical fiber and to provide the capability to measure strain within discrete segments of the rope. Interpretation of the data allows one to calculate the accumulated strain at any point in time and to determine if the rope has experienced local damage.

  10. The Formation of Ganymede's Grooved Terrain: Importance of Strain Weakening

    NASA Astrophysics Data System (ADS)

    Bland, M. T.; McKinnon, W. B.; Showman, A. P.

    2008-12-01

    Nearly two-thirds of Ganymede's surface consists of relatively bright, young, tectonically deformed terrain dubbed grooved terrain. The grooved terrain consists of sets of parallel, undulatory ridges and troughs with peak to trough amplitudes of several hundred meters and periodic spacings that range from 3 to 10~km. The low slopes and periodic spacing of the grooves suggest that they formed via unstable extension of the ice lithosphere [e.g. Fink and Fletcher 1981, LPS XII; Pappalardo et al. 1998, Icarus 135]. Application of analytical models of unstable extension to Ganymede suggest that large amplitude grooves with appropriate wavelengths can form if the lithosphere is in pervasive brittle failure and if the lithospheric thermal gradient was relatively high (~45K km-1) [Dombard and McKinnon 2001, Icarus 154]; however, numerical models of unstable extension struggle to produce topographic amplitudes consistent with Ganymede's grooves (maximum amplitudes are a factor of five less than typical large amplitude grooves) [Bland and Showman 2007, Icarus 189]. The difficulties in producing large amplitude deformation may be overcome by the inclusion of strain weakening in models of groove formation. Strain weakening effects account for a material's tendency to strain more easily as viscous and/or plastic deformation accumulates, and as strain localizes in shear zones or along faults. When included in models of terrestrial extension, such effects can increase deformation amplitudes by up to several orders of magnitude [e.g. Fredericksen and Braun 2001, EPSL 188; Behn et al. 2002, EPSL 202]. Here we present the results of simulations of Ganymede's groove formation that include various strain weakening processes. Incorporation of a simple damage rheology, in which the yield strength of the ice lithosphere decreases as plastic strain accumulates, permits a factor of three increase in the amplitude of the simulated grooves, generating topography of 200~m or more. Such groove

  11. [New strains of basidiomycetes that produce bioethanol from lignocellulose biomass].

    PubMed

    Kozhevnikova, E Yu; Petrova, D A; Kopitsyn, D S; Nivikov, A A; Shnyreva, A V; Barkov, A V; Vinokurov, V A

    2016-01-01

    Sixty six isolates were screened for ability of bioethanol production; dynamics of product accumulation and substrate utilization were investigated for two selected strains Trametes hirsuta MT-24.24 and Trametes versicolor IT-1. The strains’ efficiency was evaluated as bioethanol production by 1 g biomass. Strain T. versicolor IT-1 producing over 33 g/L of the ethanol for 9 d was selected. Direct conversion of Na-carboxymethyl cellulose, microcrystalline cellulose and straw was shown with ethanol yields of 2.1, 1.6 and 1.7 g/L, respectively, for 9 d fermentation time.

  12. A wireless strain sensor consumes less than 10 mW

    NASA Astrophysics Data System (ADS)

    Hew, Y.; Deshmukh, S.; Huang, H.

    2011-10-01

    This paper presents a wireless strain sensor that consumes about 9 mW. To achieve such an ultra-low power operation, a voltage-controlled oscillator (VCO) is utilized to convert the direct-current (DC) strain signal to a high frequency oscillatory signal. This oscillatory signal is then transmitted using an unpowered wireless transponder (Huang et al 2011 Smart Mater. Struct. 20 015017). A photocell-based energy harvester was developed to power the wireless strain sensor. The energy harvested from a flash light placed at 65 cm away is sufficient to power the wireless strain sensor continuously. The implementation of the wireless strain sensor and its characterization are presented.

  13. Misfit strain of oxygen precipitates in Czochralski silicon studied with energy-dispersive X-ray diffraction

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

    Gröschel, A., E-mail: alexander.groeschel@fau.de; Will, J.; Bergmann, C.

    Annealed Czochralski Silicon wafers containing SiO{sub x} precipitates have been studied by high energy X-ray diffraction in a defocused Laue setup using a laboratory tungsten tube. The energy dispersive evaluation of the diffracted Bragg intensity of the 220 reflection within the framework of the statistical dynamical theory yields the static Debye-Waller factor E of the crystal, which gives access to the strain induced by the SiO{sub x} precipitates. The results are correlated with precipitate densities and sizes determined from transmission electron microscopy measurements of equivalent wafers. This allows for the determination of the constrained linear misfit ε between precipitate andmore » crystal lattice. For samples with octahedral precipitates the values ranging from ε = 0.39 (+0.28/−0.12) to ε = 0.48 (+0.34/−0.16) indicate that self-interstitials emitted into the matrix during precipitate growth contribute to the lattice strain. In this case, the expected value calculated from literature values is ε = 0.26 ± 0.05. Further, the precise evaluation of Pendellösung oscillations in the diffracted Bragg intensity of as-grown wafers reveals a thermal Debye-Waller parameter for the 220 reflection B{sup 220}(293 K) of 0.5582 ± 0.0039 Å{sup 2} for a structure factor based on spherically symmetric scattering contributions.« less

  14. 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

  15. 40 CFR 610.51 - Mileage accumulation procedure.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 31 2013-07-01 2013-07-01 false Mileage accumulation procedure. 610.51 Section 610.51 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) ENERGY POLICY FUEL ECONOMY RETROFIT DEVICES Test Procedures and Evaluation Criteria Durability Test Procedures § 610.51...

  16. 40 CFR 610.51 - Mileage accumulation procedure.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 30 2011-07-01 2011-07-01 false Mileage accumulation procedure. 610.51 Section 610.51 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) ENERGY POLICY FUEL ECONOMY RETROFIT DEVICES Test Procedures and Evaluation Criteria Durability Test Procedures § 610.51...

  17. 40 CFR 610.51 - Mileage accumulation procedure.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 31 2012-07-01 2012-07-01 false Mileage accumulation procedure. 610.51 Section 610.51 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) ENERGY POLICY FUEL ECONOMY RETROFIT DEVICES Test Procedures and Evaluation Criteria Durability Test Procedures § 610.51...

  18. 40 CFR 610.51 - Mileage accumulation procedure.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 30 2014-07-01 2014-07-01 false Mileage accumulation procedure. 610.51 Section 610.51 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) ENERGY POLICY FUEL ECONOMY RETROFIT DEVICES Test Procedures and Evaluation Criteria Durability Test Procedures § 610.51...

  19. 40 CFR 610.51 - Mileage accumulation procedure.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 29 2010-07-01 2010-07-01 false Mileage accumulation procedure. 610.51 Section 610.51 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) ENERGY POLICY FUEL ECONOMY RETROFIT DEVICES Test Procedures and Evaluation Criteria Durability Test Procedures § 610.51...

  20. Strain effects on oxygen migration in perovskites.

    PubMed

    Mayeshiba, Tam; Morgan, Dane

    2015-01-28

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

  1. Mechanical deformation model of the western United States instantaneous strain-rate field

    USGS Publications Warehouse

    Pollitz, F.F.; Vergnolle, M.

    2006-01-01

    We present a relationship between the long-term fault slip rates and instantaneous velocities as measured by Global Positioning System (GPS) or other geodetic measurements over a short time span. The main elements are the secularly increasing forces imposed by the bounding Pacific and Juan de Fuca (JdF) plates on the North American plate, viscoelastic relaxation following selected large earthquakes occurring on faults that are locked during their respective interseismic periods, and steady slip along creeping portions of faults in the context of a thin-plate system. In detail, the physical model allows separate treatments of faults with known geometry and slip history, faults with incomplete characterization (i.e. fault geometry but not necessarily slip history is available), creeping faults, and dislocation sources distributed between the faults. We model the western United States strain-rate field, derived from 746 GPS velocity vectors, in order to test the importance of the relaxation from historic events and characterize the tectonic forces imposed by the bounding Pacific and JdF plates. Relaxation following major earthquakes (M ??? 8.0) strongly shapes the present strain-rate field over most of the plate boundary zone. Equally important are lateral shear transmitted across the Pacific-North America plate boundary along ???1000 km of the continental shelf, downdip forces distributed along the Cascadia subduction interface, and distributed slip in the lower lithosphere. Post-earthquake relaxation and tectonic forcing, combined with distributed deep slip, constructively interfere near the western margin of the plate boundary zone, producing locally large strain accumulation along the San Andreas fault (SAF) system. However, they destructively interfere further into the plate interior, resulting in smaller and more variable strain accumulation patterns in the eastern part of the plate boundary zone. Much of the right-lateral strain accumulation along the SAF

  2. Don't soil your chances with solar energy: Experiments of natural dust accumulation on solar modules and the effect on light transmission

    NASA Astrophysics Data System (ADS)

    Boyle, Liza

    Dust accumulation, or soiling, on solar energy harvesting systems can cause significant losses that reduce the power output of the system, increase pay-back time of the system, and reduce confidence in solar energy overall. Developing a method of estimating soiling losses could greatly improve estimates of solar energy system outputs, greatly improve operation and maintenance of solar systems, and improve siting of solar energy systems. This dissertation aims to develop a soiling model by collecting ambient soiling data as well as other environmental data and fitting a model to these data. In general a process-level approach is taken to estimating soiling. First a comparison is made between mass of deposited particulates and transmission loss. Transmission loss is the reduction in light that a solar system would see due to soiling, and mass accumulation represents the level of soiling in the system. This experiment is first conducted at two sites in the Front Range of Colorado and then expanded to three additional sites. Second mass accumulation is examined as a function of airborne particulate matter (PM) concentrations, airborne size distributions, and meteorological data. In depth analysis of this process step is done at the first two sites in Colorado, and a more general analysis is done at the three additional sites. This step is identified as less understood step, but with results still allowing for a general soiling model to be developed. Third these two process steps are combined, and spatial variability of these steps are examined. The three additional sites (an additional site in the Front Range of Colorado, a site in Albuquerque New Mexico, and a site in Cocoa Florida) represent a much more spatially and climatically diverse set of locations than the original two sites and provide a much broader sample space in which to develop the combined soiling model. Finally a few additional parameters, precipitation, micro-meteorology, and some sampling artifacts

  3. Sugar versus fat: elimination of glycogen storage improves lipid accumulation in Yarrowia lipolytica.

    PubMed

    Bhutada, Govindprasad; Kavšcek, Martin; Ledesma-Amaro, Rodrigo; Thomas, Stéphane; Rechberger, Gerald N; Nicaud, Jean-Marc; Natter, Klaus

    2017-05-01

    Triacylglycerol (TAG) and glycogen are the two major metabolites for carbon storage in most eukaryotic organisms. We investigated the glycogen metabolism of the oleaginous Yarrowia lipolytica and found that this yeast accumulates up to 16% glycogen in its biomass. Assuming that elimination of glycogen synthesis would result in an improvement of lipid accumulation, we characterized and deleted the single gene coding for glycogen synthase, YlGSY1. The mutant was grown under lipogenic conditions with glucose and glycerol as substrates and we obtained up to 60% improvement in TAG accumulation compared to the wild-type strain. Additionally, YlGSY1 was deleted in a background that was already engineered for high lipid accumulation. In this obese background, TAG accumulation was also further increased. The highest lipid content of 52% was found after 3 days of cultivation in nitrogen-limited glycerol medium. Furthermore, we constructed mutants of Y. lipolytica and Saccharomyces cerevisiae that are deleted for both glycogen and TAG synthesis, demonstrating that the ability to store carbon is not essential. Overall, this work showed that glycogen synthesis is a competing pathway for TAG accumulation in oleaginous yeasts and that deletion of the glycogen synthase has beneficial effects on neutral lipid storage. © FEMS 2017.

  4. Accumulation of Citrulline by Microbial Arginine Metabolism during Alcoholic Fermentation of Soy Sauce.

    PubMed

    Fang, Fang; Zhang, Jiran; Zhou, Jingwen; Zhou, Zhaohui; Li, Tieqiao; Lu, Liling; Zeng, Weizhu; Du, Guocheng; Chen, Jian

    2018-03-07

    Citrulline, the major precursor of ethyl carbamate in soy sauce, is an intermediate catabolite of arginine produced by bacteria present in soy sauce moromi mash. Pediococcus acidilactici is responsible for the formation of citrulline during the lactic acid fermentation process of soy sauce. However, citrulline accumulation during the alcoholic fermentation process and the corresponding bacteria involved have not been identified. Salt-tolerant, arginine-utilizing bacteria were isolated from moromi mash during the alcoholic fermentation process. Under normal cultivation conditions, arginine utilization by these strains did not contribute to citrulline accumulation. However, the conversion of arginine to citrulline by these bacteria increased when cultivated during the alcoholic fermentation process. Additionally, the ethanol-enhanced solubility of free fatty acids in moromi mash stimulated the accumulation of citrulline. Staphylococcus exhibited the highest capability in the conversion of arginine to citrulline.

  5. Pseudoalteromonas haloplanktis produces methylamine, a volatile compound active against Burkholderia cepacia complex strains.

    PubMed

    Sannino, Filomena; Parrilli, Ermenegilda; Apuzzo, Gennaro Antonio; de Pascale, Donatella; Tedesco, Pietro; Maida, Isabel; Perrin, Elena; Fondi, Marco; Fani, Renato; Marino, Gennaro; Tutino, Maria Luisa

    2017-03-25

    The Antarctic marine bacterium Pseudoalteromonas haloplanktis TAC125 has been reported to produce several Volatile Organic Compounds (VOCs), which are able to inhibit the growth of Burkholderia cepacia complex (Bcc) strains, opportunistic pathogens responsible for the infection of immune-compromised patients. However, no specific antibacterial VOCs have been identified to date. The purpose of the present study was to identify specific VOCs that contribute to Bcc inhibition by the Antarctic strain. When grown on defined medium containing D-gluconate and L-glutamate as carbon, nitrogen and energy sources, P. haloplanktis TAC125 is unable to inhibit the growth of Bcc strains. However, single addition of several amino acids to the defined medium restores the P. haloplanktis TAC125 inhibition ability. With the aim of identifying specific volatile compound/s responsible for Bcc inhibition, we set up an apparatus for VOC capture, accumulation, and storage. P. haloplanktis TAC125 was grown in an automatic fermenter which was connected to a cooling system to condense VOCs present in the exhaust air outlet. Upon addition of methionine to the growth medium, the VOC methylamine was produced by P. haloplanktis TAC125. Methylamine was found to inhibit the growth of several Bcc strains in a dose-dependent way. Although it was reported that P. haloplanktis TAC125 produces VOCs endowed with antimicrobial activity, this is the first demonstration that methylamine probably contributes to the anti-Bcc activity of P. haloplanktis TAC125 VOCs. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Zeaxanthin Accumulation in the Absence of a Functional Xanthophyll Cycle Protects Chlamydomonas reinhardtii from Photooxidative Stress

    PubMed Central

    Baroli, Irene; Do, An D.; Yamane, Tomoko; Niyogi, Krishna K.

    2003-01-01

    Xanthophylls participate in light harvesting and are essential in protecting the chloroplast from photooxidative damage. To investigate the roles of xanthophylls in photoprotection, we isolated and characterized extragenic suppressors of the npq1 lor1 double mutant of Chlamydomonas reinhardtii, which lacks zeaxanthin and lutein and undergoes irreversible photooxidative bleaching and cell death at moderate to high light intensities. Here, we describe three suppressor strains that carry point mutations in the coding sequence of the zeaxanthin epoxidase gene, resulting in the constitutive accumulation of zeaxanthin in a range of concentrations. The presence of zeaxanthin in these strains was sufficient to prevent photooxidative damage in the npq1 lor1 background. The size of the light-harvesting antenna in the suppressors decreased in high light in a manner that was proportional to the relative content of zeaxanthin, with the strain having the most zeaxanthin showing a severe reduction in levels of the major light-harvesting complex II proteins in high light. We show that the effect of constitutive zeaxanthin on light harvesting is not the main cause of increased photoprotection, because in the absence of zeaxanthin, a strain with a smaller light-harvesting antenna showed only minor protection against photobleaching in high light. Furthermore, the zeaxanthin-accumulating suppressors were able to tolerate higher levels of exogenous reactive oxygen than their parental strain under conditions that did not affect light harvesting. Our results are consistent with an antioxidant role of zeaxanthin in the quenching of singlet oxygen and/or free radicals in the thylakoid membrane in vivo. PMID:12671093

  7. Mutational landscape of yeast mutator strains.

    PubMed

    Serero, Alexandre; Jubin, Claire; Loeillet, Sophie; Legoix-Né, Patricia; Nicolas, Alain G

    2014-02-04

    The acquisition of mutations is relevant to every aspect of genetics, including cancer and evolution of species on Darwinian selection. Genome variations arise from rare stochastic imperfections of cellular metabolism and deficiencies in maintenance genes. Here, we established the genome-wide spectrum of mutations that accumulate in a WT and in nine Saccharomyces cerevisiae mutator strains deficient for distinct genome maintenance processes: pol32Δ and rad27Δ (replication), msh2Δ (mismatch repair), tsa1Δ (oxidative stress), mre11Δ (recombination), mec1Δ tel1Δ (DNA damage/S-phase checkpoints), pif1Δ (maintenance of mitochondrial genome and telomere length), cac1Δ cac3Δ (nucleosome deposition), and clb5Δ (cell cycle progression). This study reveals the diversity, complexity, and ultimate unique nature of each mutational spectrum, composed of punctual mutations, chromosomal structural variations, and/or aneuploidies. The mutations produced in clb5Δ/CCNB1, mec1Δ/ATR, tel1Δ/ATM, and rad27Δ/FEN1 strains extensively reshape the genome, following a trajectory dependent on previous events. It comprises the transmission of unstable genomes that lead to colony mosaicisms. This comprehensive analytical approach of mutator defects provides a model to understand how genome variations might accumulate during clonal evolution of somatic cell populations, including tumor cells.

  8. Poly(3-hydroxybutyrate) hyperproduction by a global nitrogen regulator NtrB mutant strain of Paracoccus denitrificans PD1222

    PubMed Central

    Olaya-Abril, Alfonso; Luque-Almagro, Víctor M; Manso, Isabel; Gates, Andrew J; Moreno-Vivián, Conrado; Richardson, David J

    2017-01-01

    Abstract Paracoccus denitrificans PD1222 accumulates short-length polyhydroxyalkanoates, poly(3-hydroxybutyrate), under nitrogen-deficient conditions. Polyhydroxybutyrate metabolism requires the 3-ketoacyl-CoA thiolase PhaA, the acetoacetyl-CoA dehydrogenase/reductase PhaB and the synthase PhaC for polymerization. Additionally, P. denitrificans PD1222 grows aerobically with nitrate as sole nitrogen source. Nitrate assimilation is controlled negatively by ammonium through the two-component NtrBC system. NtrB is a sensor kinase that autophosphorylates a histidine residue under low-nitrogen concentrations and, in turn, transfers a phosphoryl group to an aspartate residue of the response regulator NtrC protein, which acts as a transcriptional activator of the P. denitrificans PD1222 nasABGHC genes. The P. denitrificans PD1222 NtrB mutant was unable to use nitrate efficiently as nitrogen source when compared to the wild-type strain, and it also overproduced poly(3-hydroxybutyrate). Acetyl-CoA concentration in the P. denitrificans PD1222 NtrB mutant strain was higher than in the wild-type strain. The expression of the phaC gene was also increased in the NtrB mutant when compared to the wild-type strain. These results suggest that accumulation of poly(3-hydroxybutyrate) in the NtrB mutant strain of PD1222 responds to the high levels of acetyl-CoA that accumulate in the cytoplasm as consequence of its inability to efficiently use nitrate as nitrogen source. PMID:29228177

  9. [Completed sequences analysis on the Chinese attenuated yellow fever 17D vaccine strain and the WHO standard yellow fever 17D vaccine strain].

    PubMed

    Li, Jing; Yu, Yong-Xin; Dong, Guan-Mu

    2009-04-01

    To compare the molecular characteristics of the Chinese attenuated yellow fever 17D vaccine strain and the WHO reference yellow fever 17D vaccine strain. The primers were designed according to the published nucleotide sequences of YFV 17D strains in GenBank. Total RNA of was extracted by the Trizol and reverse transcripted. The each fragments of the YFV genome were amplified by PCR and sequenced subsequently. The fragments of the 5' and 3' end of the two strains were cloned into the pGEM T-easy vector and then sequenced. The nucleotide acid and amino acid sequences of the homology to both strains were 99% with each other. No obvious nulceotide changes were found in the sequences of the entire genome of each 17D strains. Moreover, there was no obvious changes in the E protein genes. But the E173 of YF17D Tiantan, associted with the virulence, had mutantions. And the two live attenuated yellow fever 17D vaccine strains fell to the same lineage by the phylogenetic analysis. The results indicated that the two attenuated yellow fever 17D vaccine viruses accumulates mutations at a very low frequency and the genomes were relative stable.

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

    NASA Astrophysics Data System (ADS)

    Wang, Yunfei; Cui, Fang

    2018-07-01

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

  11. Thick film wireless and powerless strain sensor

    NASA Astrophysics Data System (ADS)

    Jia, Yi; Sun, Ke

    2006-03-01

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

  12. Investigation of the interface characteristics of Y2O3/GaAs under biaxial strain, triaxial strain, and non-strain conditions

    NASA Astrophysics Data System (ADS)

    Shi, Li-Bin; Liu, Xu-Yang; Dong, Hai-Kuan

    2016-09-01

    We investigate the interface behaviors of Y2O3/GaAs under biaxial strain, triaxial strain, and non-strain conditions. This study is performed by first principles calculations based on density functional theory (DFT). First of all, the biaxial strain is realized by changing the lattice constants in ab plane. Averaged electrostatic potential (AEP) is aligned by establishing Y2O3 and GaAs (110) surfaces. The band offsets of Y2O3/GaAs interface under biaxial strain are investigated by generalized gradient approximation and Heyd-Scuseria-Ernzerhof (HSE) functionals. The interface under biaxial strain is suitable for the design of metal oxide semiconductor (MOS) devices because the valence band offsets (VBO) and conduction band offsets (CBO) are larger than 1 eV. Second, the triaxial strain is applied to Y2O3/GaAs interface by synchronously changing the lattice constants in a, b, and c axis. The band gaps of Y2O3 and GaAs under triaxial strain are investigated by HSE functional. We compare the VBO and CBO under triaxial strain with those under biaxial strain. Third, in the absence of lattice strain, the formation energies, charge state switching levels, and migration barriers of native defects in Y2O3 are assessed. We investigate how they will affect the MOS device performance. It is found that VO+2 and Oi-2 play a very dangerous role in MOS devices. Finally, a direct tunneling leakage current model is established. The model is used to analyze current and voltage characteristics of the metal/Y2O3/GaAs.

  13. Structural and electronic properties of armchair graphene nanoribbons under uniaxial strain

    NASA Astrophysics Data System (ADS)

    Qu, Li-Hua; Zhang, Jian-Min; Xu, Ke-Wei; Ji, Vincent

    2014-02-01

    We theoretically investigate the structures, relative stabilities and electronic properties of the armchair graphene nanoribbons (AGNRs) under uniaxial strain via first-principles calculations. The results show that, although each bond length decreases (increases) with increasing compression (tension) strain especially for the axial bonds a1, a4 and a7, the ribbon geometrical width d increases (decreases) with increasing compression (tension) strain due to the rotation of the zigzag bonds a2, a3, a5 and a6. For each nanoribbon, as expected, the lowest average energy corresponds to the unstrained state and the larger contract (elongate) deformation corresponds to the higher average energy. At a certain strain, the average energy increases with decreasing the ribbon width n. The average energy increases quadratically with the absolute value of the uniaxial strain, showing an elastic behavior. The dependence of the band gap on the strain is sensitive to the ribbon width n which can be classified into three distinct families n=3I, 3I+1 and 3I+2, where I is an integer. The ribbon width leads to oscillatory band gaps due to quantum confinement effect.

  14. Snow Densification and Recent Accumulation Along the iSTAR Traverse, Pine Island Glacier, Antarctica

    NASA Astrophysics Data System (ADS)

    Morris, E. M.; Mulvaney, R.; Arthern, R. J.; Davies, D.; Gurney, R. J.; Lambert, P.; De Rydt, J.; Smith, A. M.; Tuckwell, R. J.; Winstrup, M.

    2017-12-01

    Neutron probe measurements of snow density from 22 sites in the Pine Island Glacier basin have been used to determine mean annual accumulation using an automatic annual layer identification routine. A mean density profile which can be used to convert radar two-way travel times to depth has been derived, and the effect of annual fluctuations in density on estimates of the depth of radar reflectors is shown to be insignificant, except very near the surface. Vertical densification rates have been derived from the neutron probe density profiles and from deeper firn core density profiles available at 9 of the sites. These rates are consistent with the rates predicted by the Herron and Langway model for stage 1 densification (by grain-boundary sliding, grain growth and intracrystalline deformation) and stage 2 densification (predominantly by sintering), except in a transition zone extending from ≈8 to ≈13 m from the surface in which 10-14% of the compaction occurs. Profiles of volumetric strain rate at each site show that in this transition zone the rates are consistent with the Arthern densification model. Comparison of the vertical densification rates and volumetric strain rates indicates that the expected relation to mean annual accumulation breaks down at high accumulation rates even when corrections are made for horizontal ice velocity divergence.

  15. A Constitutive Model for Strain-Controlled Strength Degradation of Rockmasses (SDR)

    NASA Astrophysics Data System (ADS)

    Kalos, A.; Kavvadas, M.

    2017-11-01

    The paper describes a continuum, rate-independent, incremental plasticity constitutive model applicable in weak rocks and heavily fractured rockmasses, where mechanical behaviour is controlled by rockmass strength rather than structural features (discontinuities). The model describes rockmass structure by a generalised Hoek-Brown Structure Envelope (SE) in the stress space. Stress paths inside the SE are nonlinear and irreversible to better simulate behaviour at strains up to peak strength and under stress reversals. Stress paths on the SE have user-controlled volume dilatancy (gradually reducing to zero at large shear strains) and can model post-peak strain softening of brittle rockmasses via a structure degradation (damage) mechanism triggered by accumulated plastic shear strains. As the SE may strain harden with plastic strains, ductile behaviour can also be modelled. The model was implemented in the Finite Element Code Simulia ABAQUS and was applied in plane strain (2D) excavation of a cylindrical cavity (tunnel) to predict convergence-confinement curves. It is shown that small-strain nonlinearity, variable volume dilatancy and post-peak hardening/softening strongly affect the predicted curves, resulting in corresponding differences of lining pressures in real tunnel excavations.

  16. Role of Wax Ester Synthase/Acyl Coenzyme A:Diacylglycerol Acyltransferase in Oleaginous Streptomyces sp. Strain G25

    PubMed Central

    Röttig, Annika; Strittmatter, Carl Simon; Schauer, Jennifer; Hiessl, Sebastian; Daniel, Rolf

    2016-01-01

    ABSTRACT Recently, we isolated a novel Streptomyces strain which can accumulate extraordinarily large amounts of triacylglycerol (TAG) and consists of 64% fatty acids (dry weight) when cultivated with glucose and 50% fatty acids (dry weight) when cultivated with cellobiose. To identify putative gene products responsible for lipid storage and cellobiose utilization, we analyzed its draft genome sequence. A single gene encoding a wax ester synthase/acyl coenzyme A (CoA):diacylglycerol acyltransferase (WS/DGAT) was identified and heterologously expressed in Escherichia coli. The purified enzyme AtfG25 showed acyltransferase activity with C12- or C16-acyl-CoA, C12 to C18 alcohols, or dipalmitoyl glycerol. This acyltransferase exhibits 24% amino acid identity to the model enzyme AtfA from Acinetobacter baylyi but has high sequence similarities to WS/DGATs from other Streptomyces species. To investigate the impact of AtfG25 on lipid accumulation, the respective gene, atfG25, was inactivated in Streptomyces sp. strain G25. However, cells of the insertion mutant still exhibited DGAT activity and were able to store TAG, albeit in lower quantities and at lower rates than the wild-type strain. These findings clearly indicate that AtfG25 has an important, but not exclusive, role in TAG biosynthesis in the novel Streptomyces isolate and suggest the presence of alternative metabolic pathways for lipid accumulation which are discussed in the present study. IMPORTANCE A novel Streptomyces strain was isolated from desert soil, which represents an extreme environment with high temperatures, frequent drought, and nutrient scarcity. We believe that these harsh conditions promoted the development of the capacity for this strain to accumulate extraordinarily large amounts of lipids. In this study, we present the analysis of its draft genome sequence with a special focus on enzymes potentially involved in its lipid storage. Furthermore, the activity and importance of the detected

  17. Effect of Strain Restored Energy on Abnormal Grain Growth in Mg Alloy Simulated by Phase Field Methods

    NASA Astrophysics Data System (ADS)

    Wu, Yan; Huang, Yuan-yuan

    2018-03-01

    Abnormal grain growth of single phase AZ31 Mg alloy in the spatio-temporal process has been simulated by phase field models, and the influencing factors of abnormal grain growth are studied in order to find the ways to control secondary recrystallization in the microstructure. The study aims to find out the mechanisms for abnormal grain growth in real alloys. It is shown from the simulated results that the abnormal grain growth can be controlled by the strain restored energy. Secondary recrystallization after an annealing treatment can be induced if there are grains of a certain orientation in the microstructure with local high restored energy. However, if the value of the local restored energy at a certain grain orientation is not greater than 1.1E 0, there may be no abnormal grain growth in the microstructure.

  18. Characterization of Vibrio fluvialis-Like Strains Implicated in Limp Lobster Disease

    PubMed Central

    Tall, B. D.; Fall, S.; Pereira, M. R.; Ramos-Valle, M.; Curtis, S. K.; Kothary, M. H.; Chu, D. M. T.; Monday, S. R.; Kornegay, L.; Donkar, T.; Prince, D.; Thunberg, R. L.; Shangraw, K. A.; Hanes, D. E.; Khambaty, F. M.; Lampel, K. A.; Bier, J. W.; Bayer, R. C.

    2003-01-01

    Studies were undertaken to characterize and determine the pathogenic mechanisms involved in a newly described systemic disease in Homarus americanus (American lobster) caused by a Vibrio fluvialis-like microorganism. Nineteen isolates were obtained from eight of nine lobsters sampled. Biochemically, the isolates resembled V. fluvialis, and the isolates grew optimally at 20°C; none could grow at temperatures above 23°C. The type strain (1AMA) displayed a thermal reduction time (D value) of 5.77 min at 37°C. All of the isolates required at least 1% NaCl for growth. Collectively, the data suggest that these isolates may embody a new biotype. Pulsed-field gel electrophoresis (PFGE) analysis of the isolates revealed five closely related subgroups. Some isolates produced a sheep hemagglutinin that was neither an outer membrane protein nor a metalloprotease. Several isolates possessed capsules. The isolates were highly susceptible to a variety of antibiotics tested. However, six isolates were resistant to erythromycin. Seventeen isolates harbored plasmids. Lobster challenge studies revealed that the 50% lethal dose of a plasmid-positive strain was 100-fold lower than that of a plasmid-negative strain, suggesting that the plasmid may enhance the pathogenicity of these microorganisms in lobsters. Microorganisms that were recovered from experimentally infected lobsters exhibited biochemical and PFGE profiles that were indistinguishable from those of the challenge strain. Tissue affinity studies demonstrated that the challenge microorganisms accumulated in heart and midgut tissues as well as in the hemolymph. Culture supernatants and polymyxin B lysates of the strains caused elongation of CHO cells in tissue culture, suggesting the presence of a hitherto unknown enterotoxin. Both plasmid-positive and plasmid-negative strains caused significant dose-related intestinal fluid accumulations in suckling mice. Absence of viable organisms in the intestinal contents of mice

  19. Increasing β-catenin/Wnt3A activity levels drive mechanical strain-induced cell cycle progression through mitosis

    PubMed Central

    Benham-Pyle, Blair W; Sim, Joo Yong; Hart, Kevin C; Pruitt, Beth L; Nelson, William James

    2016-01-01

    Mechanical force and Wnt signaling activate β-catenin-mediated transcription to promote proliferation and tissue expansion. However, it is unknown whether mechanical force and Wnt signaling act independently or synergize to activate β-catenin signaling and cell division. We show that mechanical strain induced Src-dependent phosphorylation of Y654 β-catenin and increased β-catenin-mediated transcription in mammalian MDCK epithelial cells. Under these conditions, cells accumulated in S/G2 (independent of DNA damage) but did not divide. Activating β-catenin through Casein Kinase I inhibition or Wnt3A addition increased β-catenin-mediated transcription and strain-induced accumulation of cells in S/G2. Significantly, only the combination of mechanical strain and Wnt/β-catenin activation triggered cells in S/G2 to divide. These results indicate that strain-induced Src phosphorylation of β-catenin and Wnt-dependent β-catenin stabilization synergize to increase β-catenin-mediated transcription to levels required for mitosis. Thus, local Wnt signaling may fine-tune the effects of global mechanical strain to restrict cell divisions during tissue development and homeostasis. DOI: http://dx.doi.org/10.7554/eLife.19799.001 PMID:27782880

  20. Interactions between accumulation of trace elements and major nutrients in Salix caprea after inoculation with rhizosphere microorganisms

    PubMed Central

    De Maria, Susanna; Rivelli, Anna Rita; Kuffner, Melanie; Sessitsch, Angela; Wenzel, Walter W.; Gorfer, Markus; Strauss, Joseph; Puschenreiter, Markus

    2015-01-01

    Although the beneficial effects on growth and trace element accumulation in Salix inoculated with microbes are well known, little information is available on the interactions among trace elements and major nutrients. The main purpose of this study was to assess the effect of inoculation with rhizobacteria Agromyces sp. AR33, Streptomyces sp. AR17, and the combination of each of them with the fungus Cadophora finlandica PRF15 on biomass production and the accumulation of selected trace elements and major nutrients (Cd, Zn, Fe, Ca, K and Mg) in Salix caprea grown on a moderately polluted soil. Dry matter production was significantly enhanced only upon inoculation with Agromyces AR33. Microbial treatments differently affected the accumulation of Zn and Cd in plants. Both the inoculation with Streptomyces AR17 and the co-inoculation of C. finlandica with Agromyces AR33 were most efficient in enhancing the accumulation of Zn and Cd in leaves. These two treatments showed also a higher translocation factor from roots to the leaves for both Cd and Zn. Concentrations of major nutrients in shoots were generally increased in the treatments with the fungus compared to those without, except for K in plants inoculated with bacterial strain Streptomyces AR17. Co-inoculation of C. finlandica plus Agromyces AR33 resulted in a better accumulation of both Zn and Cd and Ca, K and Mg in shoots. This study suggests that the phytoextraction of Zn and Cd can be improved by inoculation with selected microbial strains. PMID:21612812

  1. Is policy well-targeted to remedy financial strain among caregivers of severely injured U.S. service members?

    PubMed

    Van Houtven, Courtney Harold; Friedemann-Sánchez, Greta; Clothier, Barbara; Levison, Deborah; Taylor, Brent C; Jensen, Agnes C; Phelan, Sean M; Griffin, Joan M

    U.S. military service members have sustained severe injuries since the start of the wars in Iraq and Afghanistan. This paper aims to determine the factors associated with financial strain of their caregivers and establish whether recent federal legislation targets caregivers experiencing financial strain. In our national survey, 62.3% of caregivers depleted assets and/or accumulated debt, and 41% of working caregivers left the labor force. If a severely injured veteran needed intensive help, the primary caregiver faced odds 4.63 times higher of leaving the labor force, and used $27,576 more in assets and/or accumulated debt compared to caregivers of veterans needing little or no assistance.

  2. 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.

  3. Comparative Proteome Analysis between High Lipid-Producing Strain Mucor circinelloides WJ11 and Low Lipid-Producing Strain CBS 277.49.

    PubMed

    Tang, Xin; Chen, Haiqin; Gu, Zhennan; Zhang, Hao; Chen, Yong Q; Song, Yuanda; Chen, Wei

    2017-06-21

    Mucor circinelloides is one of few oleaginous fungi that produces a useful oil rich in γ-linolenic acid, but it usually only produces <25% total lipid. Nevertheless, we isolated a new strain WJ11 that can produce up to 36% lipid of cell dry weight. In this study, we have systematically analyzed the global changes in protein levels between the high lipid-producing strain WJ11 and the low lipid-producing strain CBS 277.49 (15%, lipid/cell dry weight) at lipid accumulation phase through comparative proteome analysis. Proteome analysis demonstrated that the branched-chain amino acid and lysine metabolism, glycolytic pathway, and pentose phosphate pathway in WJ11 were up-regulated, while the activities of tricarboxylic acid cycle and branch point enzyme for synthesis of isoprenoids were retarded compared with CBS 277.49. The coordinated regulation at proteome level indicate that more acetyl-CoA and NADPH are provided for fatty acid biosynthesis in WJ11 compared with CBS 277.49.

  4. Experimental study of strained and destrained turbulence

    NASA Astrophysics Data System (ADS)

    Chen, Jun; Meneveau, Charles; Katz, Joseph

    2003-11-01

    Planar Particle Image Velocimetry measurements are performed in a water tank facility in which high Reynolds number turbulence is generated by an array of spinning grids. Straining fields are applied using a piston with rectangular cross-section which is pushed towards the bottom of the tank, setting up a planar straining field there. The facility can also be used to reverse the distortion ("destraining'') by pulling the piston upwards. We present calibration tests characterizing the flow in the facility. The initial turbulent state is characterized by means of ditributions of rms values and energy spectra, and corresponds closely to isotropic, homogeneous turbulence. The applied straining is characterized using high-speed camera and PIV measurements of the mean flow without turbulence. Initial results of turbulence subjected to a sequence of straining and destraining motions are presented, with particular emphasis on the flux of kinetic energy from large to small scales and possible backscatter during destraining.

  5. Enhanced Toxic Metal Accumulation in Engineered Bacterial Cells Expressing Arabidopsis thaliana Phytochelatin Synthase

    PubMed Central

    Sauge-Merle, Sandrine; Cuiné, Stéphan; Carrier, Patrick; Lecomte-Pradines, Catherine; Luu, Doan-Trung; Peltier, Gilles

    2003-01-01

    Phytochelatins (PCs) are metal-binding cysteine-rich peptides, enzymatically synthesized in plants and yeasts from glutathione in response to heavy metal stress by PC synthase (EC 2.3.2.15). In an attempt to increase the ability of bacterial cells to accumulate heavy metals, the Arabidopsis thaliana gene encoding PC synthase (AtPCS) was expressed in Escherichia coli. A marked accumulation of PCs was observed in vivo together with a decrease in the glutathione cellular content. When bacterial cells expressing AtPCS were placed in the presence of heavy metals such as cadmium or the metalloid arsenic, cellular metal contents were increased 20- and 50-fold, respectively. We discuss the possibility of using genes of the PC biosynthetic pathway to design bacterial strains or higher plants with increased abilities to accumulate toxic metals, and also arsenic, for use in bioremediation and/or phytoremediation processes. PMID:12514032

  6. Increased risk of cataract development in WNIN-obese rats due to accumulation of intralenticular sorbitol.

    PubMed

    Reddy, Paduru Yadagiri; Giridharan, Nappan Veettil; Balakrishna, Nagalla; Validandi, Vakdevi; Pullakhandam, Raghu; Reddy, Geereddy Bhanuprakash

    2013-05-01

    Epidemiological studies have reported an association between obesity and increased incidence of ocular complications including cataract, yet the underlying biochemical and molecular mechanisms remained unclear. Previously we had demonstrated accumulation of sorbitol in the lens of obese rats (WNIN/Ob) and more so in a related strain with impaired glucose tolerance (WNIN/GR-Ob). However, only a few (15-20%) WNIN/Ob and WNIN/GR-Ob rats develop cataracts spontaneously with age. To gain further insights, we investigated the susceptibility of eye lens proteins of these obese rat strains to heat- and UV-induced aggregation in vitro, lens opacification upon glucose-mediated sorbitol accumulation ex vivo, and onset and progression of cataract was followed by galactose feeding and streptozotocin (STZ) injection. The results indicated increased susceptibility toward heat- or UV-induced aggregation of lens proteins in obese animals compared to their littermate lean controls. Further, in organ culture studies glucose-induced sorbitol accumulation was found to be higher and thus the lens opacification was faster in obese animals compared to their lean littermates. Also, the onset and progression of galactose- or STZ-induced cataractogenesis was faster in obese animals compared to lean control. These results together with our previous observations suggest that obesity status could lead to hyperaccumulation of sorbitol in eye lens, predisposing them to cataract, primarily by increasing their susceptibility to environmental and/or physiological factors. Further, intralenticular sorbitol accumulation beyond a threshold level could lead to cataract in WNIN/Ob and WNIN/GR-Ob rats. Copyright © 2013 International Union of Biochemistry and Molecular Biology, Inc.

  7. Chemicals to enhance microalgal growth and accumulation of high-value bioproducts

    PubMed Central

    Yu, Xinheng; Chen, Lei; Zhang, Weiwen

    2015-01-01

    Photosynthetic microalgae have attracted significant attention as they can serve as important sources for cosmetic, food and pharmaceutical products, industrial materials and even biofuel biodiesels. However, current productivity of microalga-based processes is still very low, which has restricted their scale-up application. In addition to various efforts in strain improvement and cultivation optimization, it was proposed that the productivity of microalga-based processes can also be increased using various chemicals to trigger or enhance cell growth and accumulation of bioproducts. Herein, we summarized recent progresses in applying chemical triggers or enhancers to improve cell growth and accumulation of bioproducts in algal cultures. Based on their enhancing mechanisms, these chemicals can be classified into four categories:chemicals regulating biosynthetic pathways, chemicals inducing oxidative stress responses, phytohormones and analogs regulating multiple aspects of microalgal metabolism, and chemicals directly as metabolic precursors. Taken together, the early researches demonstrated that the use of chemical stimulants could be a very effective and economical way to improve cell growth and accumulation of high-value bioproducts in large-scale cultivation of microalgae. PMID:25741321

  8. GLUTAMATE METABOLISM IN BRUCELLA ABORTUS STRAINS OF LOW AND HIGH VIRULENCE

    PubMed Central

    Dasinger, B. L.; Wilson, J. B.

    1962-01-01

    Dasinger, B. L. (University of Wisconsin, Madison) and J. B. Wilson. Glutamate metabolism in Brucella abortus strains of low and high virulence. J. Bacteriol. 84:911–915. 1962.—Brucella abortus strains of low virulence oxidize glutamate at a high rate, whereas strains of high virulence oxidize glutamate at a relatively low rate. Results indicated that this observation was not related to differences in pathway of glutamate oxidation or to differences in total enzyme activity. Permeability studies showed that the maximal rates of glutamate accumulation were 2.8 μmoles per 2 min per g (wet wt) for a strain of high virulence and 6.2 μmoles per 2 min per g for a strain of low virulence, but equal intracellular steady-state concentrations were attained by both types of strains. Evidence is presented which suggests that the site of glutamate oxidation is separate from the pool of glutamate being measured. Unequal rates of permeability at these sites could be the reason for the differences in rate of glutamate oxidation. PMID:14028057

  9. Laboratory evolution of copper tolerant yeast strains

    PubMed Central

    2012-01-01

    Background Yeast strains endowed with robustness towards copper and/or enriched in intracellular Cu might find application in biotechnology processes, among others in the production of functional foods. Moreover, they can contribute to the study of human diseases related to impairments of copper metabolism. In this study, we investigated the molecular and physiological factors that confer copper tolerance to strains of baker's yeasts. Results We characterized the effects elicited in natural strains of Candida humilis and Saccharomyces cerevisiae by the exposure to copper in the culture broth. We observed that, whereas the growth of Saccharomyces cells was inhibited already at low Cu concentration, C. humilis was naturally robust and tolerated up to 1 g · L-1 CuSO4 in the medium. This resistant strain accumulated over 7 mg of Cu per gram of biomass and escaped severe oxidative stress thanks to high constitutive levels of superoxide dismutase and catalase. Both yeasts were then "evolved" to obtain hyper-resistant cells able to proliferate in high copper medium. While in S. cerevisiae the evolution of robustness towards Cu was paralleled by the increase of antioxidative enzymes, these same activities decreased in evolved hyper-resistant Candida cells. We also characterized in some detail changes in the profile of copper binding proteins, that appeared to be modified by evolution but, again, in a different way in the two yeasts. Conclusions Following evolution, both Candida and Saccharomyces cells were able to proliferate up to 2.5 g · L-1 CuSO4 and to accumulate high amounts of intracellular copper. The comparison of yeasts differing in their robustness, allowed highlighting physiological and molecular determinants of natural and acquired copper tolerance. We observed that different mechanisms contribute to confer metal tolerance: the control of copper uptake, changes in the levels of enzymes involved in oxidative stress response and changes in the copper

  10. Accumulation of Poly(3-hydroxybutyrate) Helps Bacterial Cells to Survive Freezing

    PubMed Central

    Krzyzanek, Vladislav; Mravec, Filip; Hrubanova, Kamila; Samek, Ota; Kucera, Dan; Benesova, Pavla; Marova, Ivana

    2016-01-01

    Accumulation of polyhydroxybutyrate (PHB) seems to be a common metabolic strategy adopted by many bacteria to cope with cold environments. This work aimed at evaluating and understanding the cryoprotective effect of PHB. At first a monomer of PHB, 3-hydroxybutyrate, was identified as a potent cryoprotectant capable of protecting model enzyme (lipase), yeast (Saccharomyces cerevisiae) and bacterial cells (Cupriavidus necator) against the adverse effects of freezing-thawing cycles. Further, the viability of the frozen–thawed PHB accumulating strain of C. necator was compared to that of the PHB non-accumulating mutant. The presence of PHB granules in cells was revealed to be a significant advantage during freezing. This might be attributed to the higher intracellular level of 3-hydroxybutyrate in PHB accumulating cells (due to the action of parallel PHB synthesis and degradation, the so-called PHB cycle), but the cryoprotective effect of PHB granules seems to be more complex. Since intracellular PHB granules retain highly flexible properties even at extremely low temperatures (observed by cryo-SEM), it can be expected that PHB granules protect cells against injury from extracellular ice. Finally, thermal analysis indicates that PHB-containing cells exhibit a higher rate of transmembrane water transport, which protects cells against the formation of intracellular ice which usually has fatal consequences. PMID:27315285

  11. The genetic architecture of NAFLD among inbred strains of mice

    PubMed Central

    Hui, Simon T; Parks, Brian W; Org, Elin; Norheim, Frode; Che, Nam; Pan, Calvin; Castellani, Lawrence W; Charugundla, Sarada; Dirks, Darwin L; Psychogios, Nikolaos; Neuhaus, Isaac; Gerszten, Robert E; Kirchgessner, Todd; Gargalovic, Peter S; Lusis, Aldons J

    2015-01-01

    To identify genetic and environmental factors contributing to the pathogenesis of non-alcoholic fatty liver disease, we examined liver steatosis and related clinical and molecular traits in more than 100 unique inbred mouse strains, which were fed a diet rich in fat and carbohydrates. A >30-fold variation in hepatic TG accumulation was observed among the strains. Genome-wide association studies revealed three loci associated with hepatic TG accumulation. Utilizing transcriptomic data from the liver and adipose tissue, we identified several high-confidence candidate genes for hepatic steatosis, including Gde1, a glycerophosphodiester phosphodiesterase not previously implicated in triglyceride metabolism. We confirmed the role of Gde1 by in vivo hepatic over-expression and shRNA knockdown studies. We hypothesize that Gde1 expression increases TG production by contributing to the production of glycerol-3-phosphate. Our multi-level data, including transcript levels, metabolite levels, and gut microbiota composition, provide a framework for understanding genetic and environmental interactions underlying hepatic steatosis. DOI: http://dx.doi.org/10.7554/eLife.05607.001 PMID:26067236

  12. Inorganic phosphate accumulation and cadmium detoxification in Klebsiella aerogenes NCTC 418 growing in continuous culture

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

    Aiking, H.; Stijnman, A.; van Garderen, C.

    1984-02-01

    Klebsiella aerogenes NCTC-418, growing in the presence of cadmium under glucose-, sulfate-, or phosphate-limited conditions in continuous culture, exhibits two different cadmium detoxifying mechanisms. In addition to sulfide formation, increased accumulation of P/sub i/ is demonstrated as a novel mechanism. Intracellular cadmium is always quantitatively counterbalanced by a concerted increase in both inorganic sulfide and P/sub i/ contents of the cells. This led to the conclusion that production of sulfide and accumulation of P/sub i/ are detoxification mechanisms present in K. aerogenes but that their relative importance is crucially dependent on the strain and the growth conditions employed.

  13. Accumulation of 1-deoxynojirimycin in silkworm, Bombyx mori L.

    PubMed

    Yin, Hao; Shi, Xin-qin; Sun, Bo; Ye, Jing-jing; Duan, Zu-an; Zhou, Xiao-ling; Cui, Wei-zheng; Wu, Xiao-feng

    2010-04-01

    1-deoxynojirimycin (1-DNJ) contents in the silkworm, Bombyx mori, at different developmental stages and tissues were investigated by using reverse-phase high-performance liquid chromatography. The 1-DNJ contents of silkworm larvae change significantly with their developmental stages. The male larvae showed higher accumulation efficiency of 1-DNJ than the females and also a significant variation was observed among the silkworm strains. The present results show that tissue distribution of 1-DNJ was significantly higher in blood, digestive juice, and alimentary canal, but no 1-DNJ was observed in the silkgland. Moreover, 1-DNJ was not found in silkworms fed with artificial diet that does not contain mulberry leaf powder. This proves that silkworms obtain 1-DNJ from mulberry leaves; they could not synthesize 1-DNJ by themselves. The accumulation and excretion of 1-DNJ change periodically during the larval stage. There was no 1-DNJ in the newly-hatched larvae and 1-DNJ was mainly accumulated during the early and middle stages of every instar, while excreted at later stages of larval development. Further, it is possible to extract 1-DNJ from the larval feces and it is optimal to develop the 1-DNJ related products for diabetic auxiliary therapy.

  14. Chlamydomonas reinhardtii PsbS Protein Is Functional and Accumulates Rapidly and Transiently under High Light.

    PubMed

    Tibiletti, Tania; Auroy, Pascaline; Peltier, Gilles; Caffarri, Stefano

    2016-08-01

    Photosynthetic organisms must respond to excess light in order to avoid photo-oxidative stress. In plants and green algae the fastest response to high light is non-photochemical quenching (NPQ), a process that allows the safe dissipation of the excess energy as heat. This phenomenon is triggered by the low luminal pH generated by photosynthetic electron transport. In vascular plants the main sensor of the low pH is the PsbS protein, while in the green alga Chlamydomonas reinhardtii LhcSR proteins appear to be exclusively responsible for this role. Interestingly, Chlamydomonas also possesses two PsbS genes, but so far the PsbS protein has not been detected and its biological function is unknown. Here, we reinvestigated the kinetics of gene expression and PsbS and LhcSR3 accumulation in Chlamydomonas during high light stress. We found that, unlike LhcSR3, PsbS accumulates very rapidly but only transiently. In order to determine the role of PsbS in NPQ and photoprotection in Chlamydomonas, we generated transplastomic strains expressing the algal or the Arabidopsis psbS gene optimized for plastid expression. Both PsbS proteins showed the ability to increase NPQ in Chlamydomonas wild-type and npq4 (lacking LhcSR3) backgrounds, but no clear photoprotection activity was observed. Quantification of PsbS and LhcSR3 in vivo indicates that PsbS is much less abundant than LhcSR3 during high light stress. Moreover, LhcSR3, unlike PsbS, also accumulates during other stress conditions. The possible role of PsbS in photoprotection is discussed. © 2016 American Society of Plant Biologists. All Rights Reserved.

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

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

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

  16. Oleaginous yeasts from Antarctica: Screening and preliminary approach on lipid accumulation.

    PubMed

    Viñarta, Silvana C; Angelicola, M Virginia; Barros, J Maximiliano; Fernández, Pablo M; Mac Cormak, Walter; Aybar, Manuel J; de Figueroa, Lucía I C

    2016-12-01

    The capability of 17 Rhodotorula spp. isolated from Antarctica to accumulate intracellular lipids in nitrogen-limited medium was investigated. As results, 10 isolates were selected by Nile red staining, while 12 isolates were selected as oleaginous by analysis of total lipid content (20.4-73%, w/w of dry biomass). The higher lipid production and accumulation was exhibited for six strains belonging to three species of Rhodotorula (Rhodotorula glutinis, Rhodotorula glacialis, and Rhodotorula laryngis). This is the first report where R. laryngis have been identified within oleaginous specie. Lipid accumulation was evaluated comparatively in two nitrogen-limited glucose-based media (MI and MII). MI (low C/N ratio) was more suitable for biomass and lipid production while in MII (high C/N ratio) total lipid content was improved. R. glutinis R4, R. glacialis R15, and R. glutinis R48 showed high lipid concentrations (4.65-6.93 g L -1 ) and they were able to accumulate large amounts of lipids per gram of biomass (47-77%, w/w). A similar profile in fatty acids composition and content of neutral lipids to vegetable oils was observed, indicating that lipids produced by oleaginous Antarctic yeasts can be considered an alternative feedstock for biodiesel production. Antarctica represents an important source of oleaginous yeasts with adaptive capabilities to accumulate considerable amounts of lipids with biotechnological interest at 15 °C and 25 °C. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Energy Transfer in Turbulence under Rotation

    NASA Astrophysics Data System (ADS)

    Aluie, Hussein; Buzzicotti, Michele; Biferale, Luca; Linkmann, Moritz

    2017-11-01

    It is known that rapidly rotating turbulent flows are characterized by the emergence of simultaneous direct and inverse energy cascades. However, the organization of interactions which leads to this complex dynamics remains unclear. Two different mechanisms are known to be able to transfer energy upscale in a turbulent flow: (i) 2-dimensional interactions amongst triads lying on the 2D3C (or slow) manifold, and (ii) purely 3-dimensional interactions between a sub-set of triads with the same sign of helicity (homo-chiral). Here, we perform a numerical study of high Reynolds rotating flows by means of direct numerical simulations (DNS), in different parameter regimes to highlight both forward and inverse cascade regimes. We find that the inverse cascade at wavenumbers close to the forcing scale is generated by the dominance of homo-chiral interactions which couple the 3-dimensional bulk and the 2D3C plane. This coupling produces an accumulation of energy in the 2D3C plane, which then transfers energy to smaller wavenumbers thanks to a 2-dimensional mechanism. We further analyze the energy transfer that occurs in different regions in the real-space domain. In particular we distinguish high strain from high vorticity regions and quantify their contributions to the cascade.

  18. Response of turbulence subjected to a straining-relaxation-destraining cycle

    NASA Astrophysics Data System (ADS)

    Chen, Jun; Meneveau, Charles; Katz, Joseph

    2004-11-01

    The response of turbulence subjected to planar straining and de-straining is studied experimentally, and the impact of the applied distortions on the energy transfer across different length scales is quantified. The data are obtained using Planar Particle Image Velocimetry (PIV) in a water tank, in which high Reynolds number turbulence with very low mean velocity is generated by an array of spinning grids. Planar straining and de-straining mean flows are produced by pushing and pulling a rectangular piston towards, and away from, the bottom wall of the tank. The data are processed to yield the time evolution of Reynolds stresses, anisotropy tensors, turbulence kinetic energy production, and mean subgrid dissipation rate at various scales. During straining, the production rises rapidly. After the relaxation period the small-scale SGS stresses recover isotropy, but the Reynolds stresses at large scales still display significant anisotropy. When destraining is applied, a strong negative production (back-scattering) is observed, by which turbulence fluctuations return kinetic energy to the mean flow. Reversed energy transfer is also revealed in the vorticity fluctuations history. The experiment allows to disentangle in detail the causes for this global backscatter phenomenon in terms of non-equilibrium conditions of the Reynolds stresses, and to follow the trends as function of scale.

  19. Strain energy release rate analysis of cyclic delamination growth in compressively loaded laminates

    NASA Technical Reports Server (NTRS)

    Whitcomb, J. D.

    1983-01-01

    Delamination growth in compressively loaded composite laminates was studied analytically and experimentally. The configuration used was a laminate with an across-the-width delamination. An approximate super-position stress analysis was developed to quantify the effects of various geometric, material, and load parameters on mode 2 and mode 2 strain energy release rates G sub/1 and G sub 2, respectively. Calculated values of G sub 1 and G sub 2 were then compared with measured cyclic delamination growth rates to determine the relative importance of G sub 1 and G sub 2. High growth rates were observed only when G sub 1 was large. However, slow growth was observed even when G sub 1 was negligibly small. This growth apparently was due to a large value of G sub 2.

  20. Strain improvement and metabolic flux analysis in the wild-type and a mutant Lactobacillus lactis strain for L(+)-lactic acid production.

    PubMed

    Bai, Dong-Mei; Zhao, Xue-Ming; Li, Xin-Gang; Xu, Shi-Min

    2004-12-20

    The effects of initial glucose concentration and calcium lactate concentration on the lactic acid production by the parent strain, Lactobacillus lactis BME5-18, were studied. The results of the experiments indicated that glucose and lactate repressed the cell growth and the lactic acid production by Lactobacillus lactis BME5-18. A L(+)-lactic acid overproducing strain, Lactobacillus lactis BME5-18M, was screened by mutagenizing the parent strain with ultraviolet (UV) light irradiation and selecting the high glucose and lactate calcium concentration repression resistant mutant. Starting with a concentration of 100g L(-1) glucose, the mutant produced 98.6 g L(-1) lactic acid after 60 h in flasks, 73.9% higher than that of the parent strain. The L(+)-lactic acid purity was 98.1% by weight based on the amount of total lactic acid. The culture of the parent strain could not be analyzed well by conventional metabolic flux analysis techniques, since some pyruvate were accumulated intracellularly. Therefore, a revised flux analysis method was proposed by introducing intracellular pyruvate pool. Further studies demonstrate that there is a high level of NADH oxidase activity (12.11 mmol mg(-1) min(-1)) in the parent strain. The molecular mechanisms of the strain improvement were proposed, i.e., the high level of NADH oxidase activity was eliminated and the uptake rate of glucose was increased from 82.1 C-mmol (g DW h)(-1) to 98.9 C-mmol (g DW h)(-1) by mutagenizing the parent strain with UV, and therefore the mutant strain converts mostly pyruvate to lactic acid with a higher productivity (1.76 g L(-1) h(-1)) than the parent strain (0.95 g L(-1) h(-1)).

  1. Accumulate Repeat Accumulate Coded Modulation

    NASA Technical Reports Server (NTRS)

    Abbasfar, Aliazam; Divsalar, Dariush; Yao, Kung

    2004-01-01

    In this paper we propose an innovative coded modulation scheme called 'Accumulate Repeat Accumulate Coded Modulation' (ARA coded modulation). This class of codes can be viewed as serial turbo-like codes, or as a subclass of Low Density Parity Check (LDPC) codes that are combined with high level modulation. Thus at the decoder belief propagation can be used for iterative decoding of ARA coded modulation on a graph, provided a demapper transforms the received in-phase and quadrature samples to reliability of the bits.

  2. A strain energy filter for 3D vessel enhancement with application to pulmonary CT images.

    PubMed

    Xiao, Changyan; Staring, Marius; Shamonin, Denis; Reiber, Johan H C; Stolk, Jan; Stoel, Berend C

    2011-02-01

    The traditional Hessian-related vessel filters often suffer from detecting complex structures like bifurcations due to an over-simplified cylindrical model. To solve this problem, we present a shape-tuned strain energy density function to measure vessel likelihood in 3D medical images. This method is initially inspired by established stress-strain principles in mechanics. By considering the Hessian matrix as a stress tensor, the three invariants from orthogonal tensor decomposition are used independently or combined to formulate distinctive functions for vascular shape discrimination, brightness contrast and structure strength measuring. Moreover, a mathematical description of Hessian eigenvalues for general vessel shapes is obtained, based on an intensity continuity assumption, and a relative Hessian strength term is presented to ensure the dominance of second-order derivatives as well as suppress undesired step-edges. Finally, we adopt the multi-scale scheme to find an optimal solution through scale space. The proposed method is validated in experiments with a digital phantom and non-contrast-enhanced pulmonary CT data. It is shown that our model performed more effectively in enhancing vessel bifurcations and preserving details, compared to three existing filters. Copyright © 2010 Elsevier B.V. All rights reserved.

  3. A downstream box fusion allows stable accumulation of a bacterial cellulase in Chlamydomonas reinhardtii chloroplasts.

    PubMed

    Richter, Lubna V; Yang, Huijun; Yazdani, Mohammad; Hanson, Maureen R; Ahner, Beth A

    2018-01-01

    We investigated strategies to improve foreign protein accumulation in the chloroplasts of the model algae Chlamydomonas reinhardtii and tested the outcome in both standard culture conditions as well as one pertinent to algal biofuel production. The downstream box (DB) of the TetC or NPTII genes, the first 15 codons following the start codon, was N -terminally fused to the coding region of cel6A , an endoglucanase from Thermobifida fusca . We also employed a chimeric regulatory element, consisting of the 16S rRNA promoter and the atpA 5'UTR, previously reported to enhance protein expression, to regulate the expression of the TetC- cel6A gene. We further investigated the accumulation of TetC-Cel6A under N -deplete growth conditions. Both of the DB fusions improved intracellular accumulation of Cel6A in transplastomic C. reinhardtii strains though the TetC DB was much more effective than the NPTII DB. Furthermore, using the chimeric regulatory element, the TetC-Cel6A protein accumulation displayed a significant increase to 0.3% total soluble protein (TSP), whereas NPTII-Cel6A remained too low to quantify. Comparable levels of TetC- and NPTII- cel6A transcripts were observed, which suggests that factors other than transcript abundance mediate the greater TetC-Cel6A accumulation. The TetC-Cel6A accumulation was stable regardless of the growth stage, and the transplastomic strain growth rate was not altered. When transplastomic cells were suspended in N -deplete medium, cellular levels of TetC-Cel6A increased over time along with TSP, and were greater than those in cells suspended in N -replete medium. The DB fusion holds great value as a tool to enhance foreign protein accumulation in C. reinhardtii chloroplasts and its influence is related to translation or other post-transcriptional processes. Our results also suggest that transplastomic protein production can be compatible with algal biofuel production strategies. Cells displayed a consistent accumulation of

  4. Interplay between strain, quantum confinement, and ferromagnetism in strained ferromagnetic semiconductor (In,Fe)As thin films

    NASA Astrophysics Data System (ADS)

    Sasaki, Daisuke; Anh, Le Duc; Nam Hai, Pham; Tanaka, Masaaki

    2014-04-01

    We systematically investigated the influence of strain on the electronic structure and ferromagnetism of (In,Fe)As thin films. It is found that while the shift of the critical point energies of compressive-strained (In,Fe)As layers grown on (In1-y,Gay)As (y = 0.05, 0.1) buffer layers can be explained by the hydrostatic deformation effect (HDE) alone, those of tensile-strained (In,Fe)As layers grown on (Ga1-z,Alz)Sb (z = 0, 0.5, 1) buffer layers can be explained by the combination of HDE and the quantum confinement effect (QCE). The Curie temperature TC of the (In,Fe)As layers strongly depends on the strain, and shows a maximum for the (In,Fe)As layer grown on a GaSb buffer layer. The strain dependence of TC can be explained by the s-d exchange mechanism taking into account HDE and QCE.

  5. Goldstone-like phonon modes in a (111)-strained perovskite

    NASA Astrophysics Data System (ADS)

    Marthinsen, A.; Griffin, S. M.; Moreau, M.; Grande, T.; Tybell, T.; Selbach, S. M.

    2018-01-01

    Goldstone modes are massless particles resulting from spontaneous symmetry breaking. Although such modes are found in elementary particle physics as well as in condensed-matter systems like superfluid helium, superconductors, and magnons, structural Goldstone modes are rare. Epitaxial strain in thin films can induce structures and properties not accessible in bulk and has been intensively studied for (001)-oriented perovskite oxides. Here we predict Goldstone-like phonon modes in (111)-strained SrMn O3 by first-principles calculations. Under compressive strain the coupling between two in-plane rotational instabilities gives rise to a Mexican hat-shaped energy surface characteristic of a Goldstone mode. Conversely, large tensile strain induces in-plane polar instabilities with no directional preference, giving rise to a continuous polar ground state. Such phonon modes with U (1) symmetry could emulate structural condensed-matter Higgs modes. The mass of this Higgs boson, given by the shape of the Mexican hat energy surface, can be tuned by strain through proper choice of substrate.

  6. High-Resolution SNP/CGH Microarrays Reveal the Accumulation of Loss of Heterozygosity in Commonly Used Candida albicans Strains

    PubMed Central

    Abbey, Darren; Hickman, Meleah; Gresham, David; Berman, Judith

    2011-01-01

    Phenotypic diversity can arise rapidly through loss of heterozygosity (LOH) or by the acquisition of copy number variations (CNV) spanning whole chromosomes or shorter contiguous chromosome segments. In Candida albicans, a heterozygous diploid yeast pathogen with no known meiotic cycle, homozygosis and aneuploidy alter clinical characteristics, including drug resistance. Here, we developed a high-resolution microarray that simultaneously detects ∼39,000 single nucleotide polymorphism (SNP) alleles and ∼20,000 copy number variation loci across the C. albicans genome. An important feature of the array analysis is a computational pipeline that determines SNP allele ratios based upon chromosome copy number. Using the array and analysis tools, we constructed a haplotype map (hapmap) of strain SC5314 to assign SNP alleles to specific homologs, and we used it to follow the acquisition of loss of heterozygosity (LOH) and copy number changes in a series of derived laboratory strains. This high-resolution SNP/CGH microarray and the associated hapmap facilitated the phasing of alleles in lab strains and revealed detrimental genome changes that arose frequently during molecular manipulations of laboratory strains. Furthermore, it provided a useful tool for rapid, high-resolution, and cost-effective characterization of changes in allele diversity as well as changes in chromosome copy number in new C. albicans isolates. PMID:22384363

  7. Target of rapamycin (TOR) plays a critical role in triacylglycerol accumulation in microalgae.

    PubMed

    Imamura, Sousuke; Kawase, Yasuko; Kobayashi, Ikki; Sone, Toshiyuki; Era, Atsuko; Miyagishima, Shin-Ya; Shimojima, Mie; Ohta, Hiroyuki; Tanaka, Kan

    2015-10-01

    Most microalgae produce triacylglycerol (TAG) under stress conditions such as nitrogen depletion, but the underlying molecular mechanism remains unclear. In this study, we focused on the role of target of rapamycin (TOR) in TAG accumulation. TOR is a serine/threonine protein kinase that is highly conserved and plays pivotal roles in nitrogen and other signaling pathways in eukaryotes. We previously constructed a rapamycin-susceptible Cyanidioschyzon merolae, a unicellular red alga, by expressing yeast FKBP12 protein to evaluate the results of TOR inhibition (Imamura et al. in Biochem Biophys Res Commun 439:264-269, 2013). By using this strain, we here report that rapamycin-induced TOR inhibition results in accumulation of cytoplasmic lipid droplets containing TAG. Transcripts for TAG synthesis-related genes, such as glycerol-3-phosphate acyltransferase and acyl-CoA:diacylglycerol acyltransferase (DGAT), were increased by rapamycin treatment. We also found that fatty acid synthase-dependent de novo fatty acid synthesis was required for the accumulation of lipid droplets. Induction of TAG and up-regulation of DGAT gene expression by rapamycin were similarly observed in the unicellular green alga, Chlamydomonas reinhardtii. These results suggest the general involvement of TOR signaling in TAG accumulation in divergent microalgae.

  8. Mechanism of axial strain effects on friction in carbon nanotube rotating bearings.

    PubMed

    Huang, Jianzhang; Han, Qiang

    2018-08-10

    A systematic study of axial strain effects on friction in carbon nanotube bearings is conducted in this paper. The relationships between friction and axial strains are determined by implementing molecular dynamics simulations. It is found that the dependence of friction on velocity and temperature is altered by axial strains. The mechanism of strain effects is revealed through numerical and theoretical analyses. Based on phonon computations, axial strain effects tune friction by adjusting the distribution of the phonon frequency density, which affects the transfer efficiency of orderly kinetic energy into disorderly thermal energy. The findings in this work advance the understanding of friction in carbon nanotubes and suggest the great potential of axial strain effects on tuning friction in nanodevice applications.

  9. Non-Q-wave myocardial infarction: impaired myocardial energy metabolism in regions with reduced 99mTc-MIBI accumulation.

    PubMed

    Moka, D; Baer, F M; Theissen, P; Schneider, C A; Dietlein, M; Erdmann, E; Schicha, H

    2001-05-01

    Reduced regional technetium-99m methoxyisobutylisonitrile (99mTc-MIBI) accumulation in patients with chronic non-Q-wave infarction (NQWI) but without significant coronary artery stenosis indicates non-transmural damage of the myocardial wall. The aim of this study was to characterise cardiac energy metabolism after NQWI using phosphorus-31 magnetic resonance spectroscopy (31P-MRS) and to compare the biochemical remodelling with changes in regional 99mTc-MIBI uptake and with morphological and functional parameters assessed by magnetic resonance imaging (MRI). Fifteen patients with a history of NQWI, exclusion of significant coronary artery stenosis (<50% diameter stenosis) and hypokinesia of the anterior wall (group A) were examined with 31P-MRS to study the effects of NQWI on myocardial energy metabolism. Spectroscopic measurements were performed in the infarct-related myocardial region. Corresponding gradient-echo MR images and myocardial 99mTc-MIBI single-photon emission tomography images were acquired for exact localisation of the infarct region. All examinations were performed at rest under anti-ischaemic medication. Data were compared with those of patients in whom coronary artery disease had been excluded by angiography (group B, n=10). All patients of group A displayed anterior wall hypokinesia in the infarcted area on both ventriculography and MRI, with a reduced myocardial accumulation of 99mTc-MIBI (66.3%+/-11.8% vs 95.6%+/-2.2% in group B). The mean wall thickness during the complete cardiac cycle (9.5+/-1.8 mm vs 13.1+/-1.1 mm in group B, P<0.001), the systolic wall thickening (2.6+/-1.4 mm vs 5.8+/-1.5 mm in group B, P<0.01) and the phosphocreatine/adenosine triphosphate ratio (1.12+/-0.22 vs 1.74+/-0.23 in group B, P<0.01) in the hypokinetic area were all significantly reduced. It is concluded that persisting hypokinetic myocardium after NQWI combined with reduced myocellular uptake of 99mTc-MIBI displays a reduced PCr/ATP ratio. Our results indicate

  10. Functional analysis RaZIP1 transporter of the ZIP family from the ectomycorrhizal Zn-accumulating Russula atropurpurea.

    PubMed

    Leonhardt, Tereza; Sácký, Jan; Kotrba, Pavel

    2018-04-01

    A search of R. atropurpurea transcriptome for sequences encoding the transporters of the Zrt-, Irt-like Protein (ZIP) family, which are in eukaryotes integral to Zn supply into cytoplasm, allowed the identification of RaZIP1 cDNA with a predicted product belonging to ZIP I subfamily; it was subjected to functional studies in mutant Saccharomyces cerevisiae strains. The expression of RaZIP1, but not RaZIP1 H208A or RaZIP1 H232A mutants lacking conserved-among-ZIPs transmembrane histidyls, complemented Zn uptake deficiency in zrt1Δzrt2Δ yeasts. RaZIP1 substantially increased cellular Zn uptake in this strain and added to Zn sensitivity in zrc1Δcot1Δ mutant. The Fe uptake deficiency in ftr1Δ strain was not rescued and Mn uptake was insufficient for toxicity in Mn-sensitive pmr1Δ yeasts. By contrast, RaZIP1 increased Cd sensitivity in yap1Δ strain and conferred Cd transport activity in yeasts, albeit with substantially lower efficiency compared to Zn transport. In metal uptake assays, the accumulation of Zn in zrt1Δzrt2Δ strain remained unaffected by Cd, Fe, and Mn present in 20-fold molar excess over Zn. Immunofluorescence microscopy detected functional hemagglutinin-tagged HA::RaZIP1 on the yeast cell protoplast periphery. Altogether, these data indicate that RaZIP1 is a high-affinity plasma membrane transporter specialized in Zn uptake, and improve the understanding of the cellular and molecular biology of Zn in R. atropurpurea that is known for its ability to accumulate remarkably high concentrations of Zn.

  11. The impact of nutrient density in terms of energy and/or protein on live performance, metabolism and carcass composition of female and male broiler chickens of two commercial broiler strains.

    PubMed

    Delezie, E; Bruggeman, V; Swennen, Q; Decuypere, E; Huyghebaert, G

    2010-08-01

    The objective of this study was to investigate the effects of diet composition on performance, slaughter yield and plasma metabolites, as different modern broiler strains show different responses to feed intake. Broilers of two commercial strains and of both sexes received one of three diets being different in energy and/or protein level [control diet, low energy/low protein diet (LM/LP) and low protein diet (LP)]. Low energy/low protein diet chickens were characterized by significantly lower body weights and feed intake compared with their LP and control counterparts. Broilers of the Cobb strain or broilers that were fed the control diet were most efficient in converting energy to body weight. No significant differences in plasma metabolites were detected due to diet composition or genotype. The diet with the lower energy and crude protein levels reached the lowest slaughter yield but the highest drumstick and wing percentages. The lowest mortality percentages were observed for broilers fed the LM/LP diet, and Cobb birds appeared to be more sensitive for metabolic disorders resulting in death. It is obvious from this study that different genotypes respond differently to changes in diet composition and therefore have adjusted nutritional requirements.

  12. The influence of rock strength on erosion processes and river morphology in central Arizona: the accumulation of damage from macro-abrasion

    NASA Astrophysics Data System (ADS)

    Larimer, J. E.; Yanites, B.

    2017-12-01

    River morphology reflects the interaction between the driving forces of erosion and the resisting properties of bedrock that limit erosion. Changes in energy dissipation at the riverbed are indicated by differences in channel geometry. To erode at the same rate, stronger rocks require more energy, and thus, an adjustment in river slope or width is necessary to accomplish this work. Therefore, morphological changes should reflect differences in the rock strength properties most relevant to the dominant erosion process. We investigate this hypothesis by comparing river morphology and rock-strength properties of reaches subject to different processes. Streams in Prescott National Forest, AZ expose bedrock through a variety of lithologies, which provides a natural testing ground. Measurements include channel geometry, surface P-wave velocity, fracture spacing, and bedload grain size distribution of 150 individual reaches, as well as 260 tensile and compressive-strength tests and P-wave velocity of cores up to depths of 20 cm. Based on observations, we infer that fluvial erosion processes in this region generally fall into three domains: (1) grain by grain abrasion, (2) progressive failure by damage accumulation due to bedload impacts or `macro-abrasion', and (3) `plucking' of jointed rocks. We focus analyses on the accumulation of damage from sub-critical stresses that weakens the surface of the bedrock, potentially leading to macroscopic fractures, fatigue, and rock failure. This plays a dual role facilitating the ease with which abrasion removes material and increasing the rate of production of pluck-able particles. We estimate the `damage potential' of saltating bedload using water discharge time-series, sediment transport models and grain size distribution. To determine the resistance to damage accumulation among different rocks, we measure the evolution of damage in core samples under uniaxial loading using strain energy and inherent flaw theory. Preliminary

  13. A flex-compressive-mode piezoelectric transducer for mechanical vibration/strain energy harvesting.

    PubMed

    Li, Xiaotian; Guo, Mingsen; Dong, Shuxiang

    2011-04-01

    A piezoelectric transducer for harvesting energy from ambient mechanical vibrations/strains under pressure condition was developed. The proposed transducer was made of two ring-type piezoelectric stacks, one pair of bow-shaped elastic plates, and one shaft that pre-compresses them. This transducer works in flex-compressive (F-C) mode, which is different from a conventional flex-tensional (F-T) one, to transfer a transversely applied force F into an amplified longitudinal force N pressing against the two piezo-stacks via the two bowshaped elastic plates, generating a large electric voltage output via piezoelectric effect. Our experimental results show that without an electric load, an F-C mode piezo-transducer could generate a maximum electric voltage output of up to 110 Vpp, and with an electric load of 40 κΩ, it a maximum power output of 14.6 mW under an acceleration excitation of 1 g peak-peak at the resonance frequency of 87 Hz. © 2011 IEEE

  14. Physiological characterization of strain DCB-1, a unique dehalogenating sulfidogenic bacterium.

    PubMed Central

    Stevens, T O; Linkfield, T G; Tiedje, J M

    1988-01-01

    Strain DCB-1 is an obligately anaerobic bacterium which carries out the reductive dehalogenation of halobenzoates and was previously known to grow only on pyruvate plus 20% ruminal fluid. When various electron acceptors were supplied, thiosulfate and sulfite were found to stimulate growth. Sulfide was produced from thiosulfate. Cytochrome c and desulfoviridin were detected. The mol% G+C was 49 (at the thermal denaturation temperature). Of 55 carbon sources tested, only pyruvate supported growth as the sole carbon source in mineral medium. Lactate, acetate, L- and D-malate, glycerol, and L- and D-arabinose stimulated growth when supplemented with 10% ruminal fluid and 20 mM thiosulfate. In mineral medium, pyruvate was converted to acetate and lactate, with small amounts of succinate and fumarate accumulating transiently. During growth with thiosulfate, all of these products accumulated transiently. Addition of excess hydrogen to pyruvate-grown cultures resulted in diversion of carbon to formate, lactate, and butyrate, which caused a decrease in cell yield. We conclude that strain DCB-1 is a new type of sulfidogenic bacterium. PMID:3223760

  15. High-power density piezoelectric energy harvesting using radially strained ultrathin trigonal tellurium nanowire assembly.

    PubMed

    Lee, Tae Il; Lee, Sangmin; Lee, Eungkyu; Sohn, Sungwoo; Lee, Yean; Lee, Sujeong; Moon, Geondae; Kim, Dohyang; Kim, Youn Sang; Myoung, Jae Min; Wang, Zhong Lin

    2013-06-04

    A high-yield solution-processed ultrathin (<10 nm) trigonal tellurium (t-Te) nanowire (NW) is introduced as a new class of piezoelectric nanomaterial with a six-fold higher piezoelectric constant compared to conventional ZnO NWs for a high-volume power-density nanogenerator (NG). While determining the energy-harvesting principle in a NG consisting of t-Te NW, it is theoretically and experimentally found that t-Te NW is piezoelectrically activated only by creating strain in its radial direction, along which it has an asymmetric crystal structure. Based upon this mechanism, a NG with a monolayer consisting of well-aligned t-Te NWs and a power density of 9 mW/cm(3) is fabricated. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Chlamydomonas reinhardtii PsbS Protein Is Functional and Accumulates Rapidly and Transiently under High Light1

    PubMed Central

    Tibiletti, Tania; Auroy, Pascaline; Peltier, Gilles; Caffarri, Stefano

    2016-01-01

    Photosynthetic organisms must respond to excess light in order to avoid photo-oxidative stress. In plants and green algae the fastest response to high light is non-photochemical quenching (NPQ), a process that allows the safe dissipation of the excess energy as heat. This phenomenon is triggered by the low luminal pH generated by photosynthetic electron transport. In vascular plants the main sensor of the low pH is the PsbS protein, while in the green alga Chlamydomonas reinhardtii LhcSR proteins appear to be exclusively responsible for this role. Interestingly, Chlamydomonas also possesses two PsbS genes, but so far the PsbS protein has not been detected and its biological function is unknown. Here, we reinvestigated the kinetics of gene expression and PsbS and LhcSR3 accumulation in Chlamydomonas during high light stress. We found that, unlike LhcSR3, PsbS accumulates very rapidly but only transiently. In order to determine the role of PsbS in NPQ and photoprotection in Chlamydomonas, we generated transplastomic strains expressing the algal or the Arabidopsis psbS gene optimized for plastid expression. Both PsbS proteins showed the ability to increase NPQ in Chlamydomonas wild-type and npq4 (lacking LhcSR3) backgrounds, but no clear photoprotection activity was observed. Quantification of PsbS and LhcSR3 in vivo indicates that PsbS is much less abundant than LhcSR3 during high light stress. Moreover, LhcSR3, unlike PsbS, also accumulates during other stress conditions. The possible role of PsbS in photoprotection is discussed. PMID:27329221

  17. Recrystallization texture in nickel heavily deformed by accumulative roll bonding

    NASA Astrophysics Data System (ADS)

    Mishin, O. V.; Zhang, Y. B.; Godfrey, A.

    2017-07-01

    The recrystallization behavior of Ni processed by accumulative roll bonding to a total accumulated von Mises strain of 4.8 has been examined, and analyzed with respect to heterogeneity in the deformation microstructure. The regions near the bonding interface are found to be more refined and contain particle deformation zones around fragments of the steel wire brush used to prepare the surface for bonding. Sample-scale gradients are also observed, manifested as differences between the subsurface, intermediate and central layers, where the distributions of texture components are different. These heterogeneities affect the progress of recrystallization. While the subsurface and near-interface regions typically contain lower frequencies of cube-oriented grains than anywhere else in the sample, a strong cube texture forms in the sample during recrystallization, attributed to both a high nucleation rate and fast growth rate of cube-oriented grains. The observations highlight the sensitivity of recrystallization to heterogeneity in the deformation microstructure and demonstrate the importance of characterizing this heterogeneity over several length scales.

  18. Changes in the physiological properties and kinetics of citric acid accumulation via carbon ion irradiation mutagenesis of Aspergillus niger *

    PubMed Central

    Hu, Wei; Chen, Ji-hong; Wang, Shu-yang; Liu, Jing; Song, Yuan; Wu, Qing-feng; Li, Wen-jian

    2016-01-01

    The objective of this work was to produce citric acid from corn starch using a newly isolated mutant of Aspergillus niger, and to analyze the relationship between changes in the physiological properties of A. niger induced by carbon ion irradiation and citric acid accumulation. Our results showed that the physiological characteristics of conidia in A. niger were closely related to citric acid accumulation and that lower growth rate and viability of conidia may be beneficial to citric acid accumulation. Using corn starch as a raw material, a high-yielding citric acid mutant, named HW2, was obtained. In a 10-L bioreactor, HW2 can accumulate 118.9 g/L citric acid with a residual total sugar concentration of only 14.4 g/L. This represented an 18% increase in citric acid accumulation and a 12.5% decrease in sugar utilization compared with the original strain.

  19. Involvement of indole-3-acetic acid produced by Azospirillum brasilense in accumulating intracellular ammonium in Chlorella vulgaris.

    PubMed

    Meza, Beatriz; de-Bashan, Luz E; Bashan, Yoav

    2015-01-01

    Accumulation of intracellular ammonium and activities of the enzymes glutamine synthetase (GS) and glutamate dehydrogenase (GDH) were measured when the microalgae Chlorella vulgaris was immobilized in alginate with either of two wild type strains of Azospirillum brasilense or their corresponding indole-3-acetic acid (IAA)-attenuated mutants. After 48 h of immobilization, both wild types induced higher levels of intracellular ammonium in the microalgae than their respective mutants; the more IAA produced, the higher the intracellular ammonium accumulated. Accumulation of intracellular ammonium in the cells of C. vulgaris followed application of four levels of exogenous IAA reported for A. brasilense and its IAA-attenuated mutants, which had a similar pattern for the first 24 h. This effect was transient and disappeared after 48 h of incubation. Immobilization of C. vulgaris with any bacteria strain induced higher GS activity. The bacterial strains also had GS activity, comparable to the activity detected in C. vulgaris, but weaker than when immobilized with the bacteria. When net activity was calculated, the wild type always induced higher GS activity than IAA-attenuated mutants. GDH activity in most microalgae/bacteria interactions resembled GS activity. When complementing IAA-attenuated mutants with exogenous IAA, GS activity in co-immobilized cultures matched those of the wild type A. brasilense immobilized with the microalga. Similarity occurred when the net GS activity was measured, and was higher with greater quantities of exogenous IAA. It is proposed that IAA produced by A. brasilense is involved in ammonium uptake and later assimilation by C. vulgaris. Copyright © 2014 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

  20. Size effects and strain localization in atomic-scale cleavage modeling

    NASA Astrophysics Data System (ADS)

    Elsner, B. A. M.; Müller, S.

    2015-09-01

    In this work, we study the adhesion and decohesion of Cu(1 0 0) surfaces using density functional theory (DFT) calculations. An upper stress to surface decohesion is obtained via the universal binding energy relation (UBER), but the model is limited to rigid separation of bulk-terminated surfaces. When structural relaxations are included, an unphysical size effect arises if decohesion is considered to occur as soon as the strain energy equals the energy of the newly formed surfaces. We employ the nudged elastic band (NEB) method to show that this size effect is opposed by a size-dependency of the energy barriers involved in the transition. Further, we find that the transition occurs via a localization of bond strain in the vicinity of the cleavage plane, which resembles the strain localization at the tip of a sharp crack that is predicted by linear elastic fracture mechanics.

  1. Size effects and strain localization in atomic-scale cleavage modeling.

    PubMed

    Elsner, B A M; Müller, S

    2015-09-04

    In this work, we study the adhesion and decohesion of Cu(1 0 0) surfaces using density functional theory (DFT) calculations. An upper stress to surface decohesion is obtained via the universal binding energy relation (UBER), but the model is limited to rigid separation of bulk-terminated surfaces. When structural relaxations are included, an unphysical size effect arises if decohesion is considered to occur as soon as the strain energy equals the energy of the newly formed surfaces. We employ the nudged elastic band (NEB) method to show that this size effect is opposed by a size-dependency of the energy barriers involved in the transition. Further, we find that the transition occurs via a localization of bond strain in the vicinity of the cleavage plane, which resembles the strain localization at the tip of a sharp crack that is predicted by linear elastic fracture mechanics.

  2. Dirac points and van Hove singularities of silicene under uniaxial strain

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

    Lin, Xianqing, E-mail: xqlin@zjut.edu.cn; College of Science, Zhejiang University of Technology, Hangzhou 310023; Ni, Jun

    2015-04-28

    First-principles calculations have been performed to investigate the low energy electronic properties and van Hove singularities (VHSs) of silicene under uniaxial strain. The Dirac points (DPs) persist when silicene is stretched uniaxially, while they are shifted away from the corners (K points) of the first Brillouin zone (FBZ). The relative positions of DPs with respect to the K points for silicene strained along the armchair (AC) or zigzag (ZZ) direction show opposite tendency compared with strained graphene, which is due to the larger deformation of the unit cell of strained silicene than that of strained graphene. Moreover, for silicene undermore » AC or ZZ strain, the Fermi velocities around DPs along the positive and negative directions of the FBZ show rather significant difference. The nature of the VHS just above the Fermi energy undergoes a transition from the π* band to the σ* band for silicene under increasing AC or ZZ strain. These observations suggest uniaxial strain as an effective route to tune the electronic properties of silicene for potential applications in future electronic devices.« less

  3. Mitochondrial accumulation of APP and Aβ: significance for Alzheimer disease pathogenesis

    PubMed Central

    Pavlov, Pavel F; Petersen, Camilla Hansson; Glaser, Elzbieta; Ankarcrona, Maria

    2009-01-01

    Accumulating evidence suggest that alterations in energy metabolism are among the earliest events that occur in the Alzheimer disease (AD) affected brain. Energy consumption is drastically decreased in the AD-affected regions of cerebral cortex and hippocampus pointing towards compromised mitochondrial function of neurons within specific brain regions. This is accompanied by an elevated production of reactive oxygen species contributing to increased rates of neuronal loss in the AD-affected brain regions. In this review, we will discuss the role of mitochondrial function and dysfunction in AD. We will focus on the consequences of amyloid precursor protein and amyloid-β peptide accumulation in mitochondria and their involvement in AD pathogenesis. PMID:19725915

  4. Photoluminescence and electroluminescence from Ge/strained GeSn/Ge quantum wells

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

    Lin, Chung-Yi; Chang, Chih-Chiang; Huang, Chih-Hsiung

    2016-08-29

    Ge/strained GeSn/Ge quantum wells are grown on a 300 mm Si substrate by chemical vapor deposition. The direct bandgap emission from strained GeSn is observed in the photoluminescence spectra and is enhanced by Al{sub 2}O{sub 3}/SiO{sub 2} passivation due to the field effect. The electroluminescence of the direct bandgap emission of strained GeSn is also observed from the Ni/Al{sub 2}O{sub 3}/GeSn metal-insulator-semiconductor tunneling diodes. Electroluminescence is a good indicator of GeSn material quality, since defects in GeSn layers degrade the electroluminescence intensity significantly. At the accumulation bias, the holes in the Ni gate electrode tunnel to the strained n-type GeSn layermore » through the ultrathin Al{sub 2}O{sub 3} and recombine radiatively with electrons. The emission wavelength of photoluminescence and electroluminescence can be tuned by the Sn content.« less

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

    NASA Astrophysics Data System (ADS)

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

    2018-04-01

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

  6. Changes in lymphocyte accumulation and proliferation in the lymph nodes draining the pregnant uterus.

    PubMed Central

    Ansell, J D; McDougall, C M; Speedy, G; Inchley, C J

    1978-01-01

    Changes in weight, lymphocyte accumulation and cellular proliferation have been measured in the lymph nodes draining the uterus during inter- and intra-strain pregnancies and compared with similar effects after other antigenic stimuli. From the data obtained it was concluded that "paternal" antigenic stimulation from the conceptus initiated an immune response in these nodes. The mechanisms of the subsequent suppression of this response are discussed. PMID:657586

  7. Atomistic simulations of focused ion beam machining of strained silicon

    NASA Astrophysics Data System (ADS)

    Guénolé, J.; Prakash, A.; Bitzek, E.

    2017-09-01

    The focused ion beam (FIB) technique has established itself as an indispensable tool in the material science community, both to analyze samples and to prepare specimens by FIB milling. In combination with digital image correlation (DIC), FIB milling can, furthermore, be used to evaluate intrinsic stresses by monitoring the strain release during milling. The irradiation damage introduced by such milling, however, results in a change in the stress/strain state and elastic properties of the material; changes in the strain state in turn affect the bonding strength, and are hence expected to implicitly influence irradiation damage formation and sputtering. To elucidate this complex interplay between strain, irradiation damage and sputtering, we perform TRIM calculations and molecular dynamics simulations on silicon irradiated by Ga+ ions, with slab and trench-like geometries, whilst simultaneously applying uniaxial tensile and compressive strains up to 4%. In addition we calculate the threshold displacement energy (TDE) and the surface binding energy (SBE) for various strain states. The sputter rate and amount of damage produced in the MD simulations show a clear influence of the strain state. The SBE shows no significant dependence on strain, but is strongly affected by surface reconstructions. The TDE shows a clear strain-dependence, which, however, cannot explain the influence of strain on the extent of the induced irradiation damage or the sputter rate.

  8. Plasmid-borne Tn5 insertion mutation resulting in accumulation of gentisate from salicylate.

    PubMed Central

    Monticello, D J; Bakker, D; Schell, M; Finnerty, W R

    1985-01-01

    Plasmid-borne Tn5 insertion mutants of a Pseudomonas species which accumulated 2,5-dihydroxybenzoate (gentisate) following growth on 2-hydroxybenzoate (salicylate) were obtained from a pool of mutants that were unable to grow on naphthalene. One such mutant was characterized further. The ability of this mutant to oxidize gentisate was 100-fold less than the ability of a Nah+ Sal+ strain harboring the unmutagenized plasmid, although both strains oxidized and grew on salicylate. These bacteria were presumably able to metabolize salicylate via catechol, since they possessed an inducible, plasmid-encoded catechol 2,3-dioxygenase. Our results suggest that there is an alternate, plasmid-encoded route of salicylate degradation via gentisate and that some plasmid-associated relationship between this pathway and naphthalene oxidation exists. PMID:2988437

  9. Increased growth and root Cu accumulation of Sorghum sudanense by endophytic Enterobacter sp. K3-2: Implications for Sorghum sudanense biomass production and phytostabilization.

    PubMed

    Li, Ya; Wang, Qi; Wang, Lu; He, Lin-Yan; Sheng, Xia-Fang

    2016-02-01

    Endophytic bacterial strain K3-2 was isolated from the roots of Sorghum sudanense (an bioenergy plant) grown in a Cu mine wasteland soils and characterized. Strain K3-2 was identified as Enterobacter sp. based on 16S rRNA gene sequence analysis. Strain K3-2 exhibited Cu resistance and produced 1-aminocyclopropane-1-carboxylate (ACC) deaminase, indole-3-acetic acid (IAA), siderophores, and arginine decarboxylase. Pot experiments showed that strain K3-2 significantly increased the dry weight and root Cu accumulation of Sorghum sudanense grown in the Cu mine wasteland soils. Furthermore, increase in total Cu uptake (ranging from 49% to 95%) of the bacterial inoculated-Sorghum sudanense was observed compared to the control. Notably, most of Cu (83-86%) was accumulated in the roots of Sorghum sudanense. Furthermore, inoculation with strain K3-2 was found to significantly increase Cu bioconcentration factors and the proportions of IAA- and siderophore-producing bacteria in the root interiors and rhizosphere soils of Sorghum sudanense compared with the control. Significant decrease in the available Cu content was also observed in the rhizosphere soils of the bacterial-inoculated Sorghum sudanense. The results suggest that the endophytic bacterial strain K3-2 may be exploited for promoting Sorghum sudanense biomass production and Cu phytostabilization in the Cu mining wasteland soils. Copyright © 2015 Elsevier Inc. All rights reserved.

  10. Ultrasonic enhancement of waste activated sludge hydrolysis and volatile fatty acids accumulation at pH 10.0.

    PubMed

    Yan, Yuanyuan; Feng, Leiyu; Zhang, Chaojie; Wisniewski, Christelle; Zhou, Qi

    2010-06-01

    Volatile fatty acids (VFA), the preferred carbon source for biological nutrients removal, can be produced by waste activated sludge (WAS) anaerobic fermentation. However, because the rate of VFA accumulation is limited by that of WAS hydrolysis and VFA is always consumed by methanogens at acidic or neutral pHs, the ultrasonic pretreatment which can accelerate the rate of WAS hydrolysis, and alkaline adjustment which can inhibit the activities of methanogens, were, therefore, used to improve WAS hydrolysis and VFA accumulation in this study. Experiment results showed that the combination of ultrasonic pretreatment and alkaline adjustment caused significant enhancements of WAS hydrolysis and VFA accumulation. The study of ultrasonic energy density effect revealed that energy density influenced not only the total VFA accumulation but also the percentage of individual VFA. The maximal VFA accumulation (3109.8mg COD/L) occurred at ultrasonic energy density of 1.0kW/L and fermentation time of 72h, which was more than two times that without ultrasonic treatment (1275.0mg COD/L). The analysis of VFA composition showed that the percentage of acetic acid ranked the first (more than 40%) and those of iso-valeric and propionic acids located at the second and third places, respectively. Thus, the suitable ultrasonic conditions combined with alkaline adjustment for VFA accumulation from WAS were ultrasonic energy density of 1.0kW/L and fermentation time of 72h. Also, the key enzymes related to VFA formation exhibited the highest activities at ultrasonic energy density of 1.0kW/L, which resulted in the greatest VFA production during WAS fermentation at pH 10.0. Copyright 2010 Elsevier Ltd. All rights reserved.

  11. Prion propagation and toxicity occur in vitro with two-phase kinetics specific to strain and neuronal type.

    PubMed

    Hannaoui, Samia; Maatouk, Layal; Privat, Nicolas; Levavasseur, Etienne; Faucheux, Baptiste A; Haïk, Stéphane

    2013-03-01

    Prion diseases, or transmissible spongiform encephalopathies (TSEs), are fatal neurodegenerative disorders that occur in humans and animals. The neuropathological hallmarks of TSEs are spongiosis, glial proliferation, and neuronal loss. The only known specific molecular marker of TSEs is the abnormal isoform (PrP(Sc)) of the host-encoded prion protein (PrP(C)), which accumulates in the brain of infected subjects and forms infectious prion particles. Although this transmissible agent lacks a specific nucleic acid component, several prion strains have been isolated. Prion strains are characterized by differences in disease outcome, PrP(Sc) distribution patterns, and brain lesion profiles at the terminal stage of the disease. The molecular factors and cellular mechanisms involved in strain-specific neuronal tropism and toxicity remain largely unknown. Currently, no cellular model exists to facilitate in vitro studies of these processes. A few cultured cell lines that maintain persistent scrapie infections have been developed, but only two of them have shown the cytotoxic effects associated with prion propagation. In this study, we have developed primary neuronal cultures to assess in vitro neuronal tropism and toxicity of different prion strains (scrapie strains 139A, ME7, and 22L). We have tested primary neuronal cultures enriched in cerebellar granular, striatal, or cortical neurons. Our results showed that (i) a strain-specific neuronal tropism operated in vitro; (ii) the cytotoxic effect varied among strains and neuronal cell types; (iii) prion propagation and toxicity occurred in two kinetic phases, a replicative phase followed by a toxic phase; and (iv) neurotoxicity peaked when abnormal PrP accumulation reached a plateau.

  12. Prion Propagation and Toxicity Occur In Vitro with Two-Phase Kinetics Specific to Strain and Neuronal Type

    PubMed Central

    Hannaoui, Samia; Maatouk, Layal; Privat, Nicolas; Levavasseur, Etienne; Faucheux, Baptiste A.

    2013-01-01

    Prion diseases, or transmissible spongiform encephalopathies (TSEs), are fatal neurodegenerative disorders that occur in humans and animals. The neuropathological hallmarks of TSEs are spongiosis, glial proliferation, and neuronal loss. The only known specific molecular marker of TSEs is the abnormal isoform (PrPSc) of the host-encoded prion protein (PrPC), which accumulates in the brain of infected subjects and forms infectious prion particles. Although this transmissible agent lacks a specific nucleic acid component, several prion strains have been isolated. Prion strains are characterized by differences in disease outcome, PrPSc distribution patterns, and brain lesion profiles at the terminal stage of the disease. The molecular factors and cellular mechanisms involved in strain-specific neuronal tropism and toxicity remain largely unknown. Currently, no cellular model exists to facilitate in vitro studies of these processes. A few cultured cell lines that maintain persistent scrapie infections have been developed, but only two of them have shown the cytotoxic effects associated with prion propagation. In this study, we have developed primary neuronal cultures to assess in vitro neuronal tropism and toxicity of different prion strains (scrapie strains 139A, ME7, and 22L). We have tested primary neuronal cultures enriched in cerebellar granular, striatal, or cortical neurons. Our results showed that (i) a strain-specific neuronal tropism operated in vitro; (ii) the cytotoxic effect varied among strains and neuronal cell types; (iii) prion propagation and toxicity occurred in two kinetic phases, a replicative phase followed by a toxic phase; and (iv) neurotoxicity peaked when abnormal PrP accumulation reached a plateau. PMID:23255799

  13. Growth of Chlamydomonas reinhardtii in acetate-free medium when co-cultured with alginate-encapsulated, acetate-producing strains of Synechococcus sp. PCC 7002.

    PubMed

    Therien, Jesse B; Zadvornyy, Oleg A; Posewitz, Matthew C; Bryant, Donald A; Peters, John W

    2014-01-01

    The model alga Chlamydomonas reinhardtii requires acetate as a co-substrate for optimal production of lipids, and the addition of acetate to culture media has practical and economic implications for algal biofuel production. Here we demonstrate the growth of C. reinhardtii on acetate provided by mutant strains of the cyanobacterium Synechococcus sp. PCC 7002. Optimal growth conditions for co-cultivation of C. reinhardtii with wild-type and mutant strains of Synechococcus sp. 7002 were established. In co-culture, acetate produced by a glycogen synthase knockout mutant of Synechococcus sp. PCC 7002 was able to support the growth of a lipid-accumulating mutant strain of C. reinhardtii defective in starch production. Encapsulation of Synechococcus sp. PCC 7002 using an alginate matrix was successfully employed in co-cultures to limit growth and maintain the stability. The ability of immobilized strains of the cyanobacterium Synechococcus sp. PCC 7002 to produce acetate at a level adequate to support the growth of lipid-accumulating strains of C. reinhartdii offers a potentially practical, photosynthetic alternative to providing exogenous acetate into growth media.

  14. Compatibility of a wild type and its genetically modified Sinorhizobium strain with two mycorrhizal fungi on Medicago species as affected by drought stress.

    PubMed

    Vázquez, M M.; Azcón, R; Barea, J M.

    2001-07-01

    The effect of double inoculation with two strains of Sinorhizobium meliloti [the wild type (WT) strain GR4 and its genetically modified (GM) derivative GR4(pCK3)], and two species of arbuscular mycorrhizal (AM) fungi (Glomus deserticola and Glomus intraradices) was examined in a microcosm system on three species of Medicago (M. nolana, M. rigidula, M. rotata). Two water regimes (80 and 100% water holding capacity, WHC) were assayed. The efficiency of each AM fungus increasing plant growth, nutrient content, nodulation and water-stress tolerance was related to the Sinorhizobium strains and Medicago species. This indicates selective and specific compatibilities between microsymbionts and the common host plant. Differential effects of the mycorrhizal isolates were not associated with their colonizing ability. Nodulation and mycorrhizal dependency (MD) changed in each plant genotype in accordance with the Sinorhizobium strain and AM fungi involved. Generally, Medicago sp. MD decreased under water-stress conditions even when these conditions did not affect AM colonization (%). Proline accumulation in non-mycorrhizal plant leaves was increased by water stress, except in M. rotata plants. Differences in proline accumulation in AM-colonized plants suggest that both the AM fungus and the Sinorhizobium strain were able to induce different degrees of osmotic adjustment. Mycorrhizal plants nodulated by the WT strain accumulated more proline in M. rigidula and M. rotata under water stress than non-mycorrhizal plants. Conversely, mycorrhizal plants nodulated by the GM strain accumulated less proline in response to both AM colonization and drought. These results indicated changes in the synthesis of this nitrogenous osmoregulator product associated with microbial inoculation and drought tolerance. Mycorrhizal plants nodulated by the GM Sinorhizobium strain seem to suffer less from the detrimental effect of water stress, since under water limitation relative plant growth

  15. Rapid genome resequencing of an atoxigenic strain of Aspergillus carbonarius

    DOE PAGES

    Cabañes, F. Javier; Sanseverino, Walter; Castellá, Gemma; ...

    2015-03-13

    In microorganisms, Ion Torrent sequencing technology has been proved to be useful in whole-genome sequencing of bacterial genomes (5 Mbp). In our study, for the first time we used this technology to perform a resequencing approach in a whole fungal genome (36 Mbp), a non-ochratoxin A producing strain of Aspergillus carbonarius. Ochratoxin A (OTA) is a potent nephrotoxin which is found mainly in cereals and their products, but it also occurs in a variety of common foods and beverages. Due to the fact that this strain does not produce OTA, we focused some of the bioinformatics analyses in genes involvedmore » in OTA biosynthesis, using a reference genome of an OTA producing strain of the same species. This study revealed that in the atoxigenic strain there is a high accumulation of nonsense and missense mutations in several genes. Importantly, a two fold increase in gene mutation ratio was observed in PKS and NRPS encoding genes which are suggested to be involved in OTA biosynthesis.« less

  16. Rapid genome resequencing of an atoxigenic strain of Aspergillus carbonarius

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

    Cabañes, F. Javier; Sanseverino, Walter; Castellá, Gemma

    In microorganisms, Ion Torrent sequencing technology has been proved to be useful in whole-genome sequencing of bacterial genomes (5 Mbp). In our study, for the first time we used this technology to perform a resequencing approach in a whole fungal genome (36 Mbp), a non-ochratoxin A producing strain of Aspergillus carbonarius. Ochratoxin A (OTA) is a potent nephrotoxin which is found mainly in cereals and their products, but it also occurs in a variety of common foods and beverages. Due to the fact that this strain does not produce OTA, we focused some of the bioinformatics analyses in genes involvedmore » in OTA biosynthesis, using a reference genome of an OTA producing strain of the same species. This study revealed that in the atoxigenic strain there is a high accumulation of nonsense and missense mutations in several genes. Importantly, a two fold increase in gene mutation ratio was observed in PKS and NRPS encoding genes which are suggested to be involved in OTA biosynthesis.« less

  17. Strain effects on the electronic properties in δ-doped oxide superlattices

    NASA Astrophysics Data System (ADS)

    You, Jeong Ho; Lee, Jun Hee; Okamoto, Satoshi; Cooper, Valentino; Lee, Ho Nyung

    2015-03-01

    Strain effects on the electronic properties of (LaTiO3)1/(SrTiO3)N superlattices were investigated using density functional theory. Under biaxial in-plane strain within the range of -5% ≤ ɛ// ≤ 5%, the dxy orbital electrons are highly localized at the interfaces whereas the dyz and dxz orbital electrons are more distributed in the SrTiO3 (STO) spacer layers. For STO thickness N ≥ 3 unit cells (u.c.), the dxy orbital electrons form two-dimensional (2D) electron gases (2DEGs). The quantized energy levels of the 2DEG are insensitive to the STO spacer thickness, but are strongly dependent on the applied biaxial in-plane strain. As the in-plane strain changes from compressive to tensile, the quantized energy levels of the dxy orbitals decrease thereby creating more states with 2D character. In contrast to the dxy orbital, the dyz and dxz orbitals always have three-dimensional (3D) transport characteristics and their energy levels increase as the strain changes from compressive to tensile. Since the charge densities in the dxy orbital and the dyz and dxz orbitals respond to biaxial in-plane strain in an opposite way, the transport dimensionality of the majority carriers can be controlled between 2D and 3D by applying biaxial in-plane strain.

  18. Excessive by-product formation: A key contributor to low isobutanol yields of engineered Saccharomyces cerevisiae strains.

    PubMed

    Milne, N; Wahl, S A; van Maris, A J A; Pronk, J T; Daran, J M

    2016-12-01

    It is theoretically possible to engineer Saccharomyces cerevisiae strains in which isobutanol is the predominant catabolic product and high-yielding isobutanol-producing strains are already reported by industry. Conversely, isobutanol yields of engineered S. cerevisiae strains reported in the scientific literature typically remain far below 10% of the theoretical maximum. This study explores possible reasons for these suboptimal yields by a mass-balancing approach. A cytosolically located, cofactor-balanced isobutanol pathway, consisting of a mosaic of bacterial enzymes whose in vivo functionality was confirmed by complementation of null mutations in branched-chain amino acid metabolism, was expressed in S. cerevisiae . Product formation by the engineered strain was analysed in shake flasks and bioreactors. In aerobic cultures, the pathway intermediate isobutyraldehyde was oxidized to isobutyrate rather than reduced to isobutanol. Moreover, significant concentrations of the pathway intermediates 2,3-dihydroxyisovalerate and α-ketoisovalerate, as well as diacetyl and acetoin, accumulated extracellularly. While the engineered strain could not grow anaerobically, micro-aerobic cultivation resulted in isobutanol formation at a yield of 0.018±0.003 mol/mol glucose. Simultaneously, 2,3-butanediol was produced at a yield of 0.649±0.067 mol/mol glucose. These results identify massive accumulation of pathway intermediates, as well as overflow metabolites derived from acetolactate, as an important, previously underestimated contributor to the suboptimal yields of 'academic' isobutanol strains. The observed patterns of by-product formation is consistent with the notion that in vivo activity of the iron-sulphur-cluster-requiring enzyme dihydroxyacid dehydratase is a key bottleneck in the present and previously described 'academic' isobutanol-producing yeast strains.

  19. Blood orange juice inhibits fat accumulation in mice.

    PubMed

    Titta, L; Trinei, M; Stendardo, M; Berniakovich, I; Petroni, K; Tonelli, C; Riso, P; Porrini, M; Minucci, S; Pelicci, P G; Rapisarda, P; Reforgiato Recupero, G; Giorgio, M

    2010-03-01

    To analyze the effect of the juice obtained from two varieties of sweet orange (Citrus sinensis L. Osbeck), Moro (a blood orange) and Navelina (a blond orange), on fat accumulation in mice fed a standard or a high-fat diet (HFD). Obesity was induced in male C57/Bl6 mice by feeding a HFD. Moro and Navelina juices were provided instead of water. The effect of an anthocyanin-enriched extract from Moro oranges or purified cyanidin-3-glucoside (C3G) was also analyzed. Body weight and food intake were measured regularly over a 12-week period. The adipose pads were weighted and analyzed histologically; total RNA was also isolated for microarray analysis. Dietary supplementation of Moro juice, but not Navelina juice significantly reduced body weight gain and fat accumulation regardless of the increased energy intake because of sugar content. Furthermore, mice drinking Moro juice were resistant to HFD-induced obesity with no alterations in food intake. Only the anthocyanin extract, but not the purified C3G, slightly affected fat accumulation. High-throughput gene expression analysis of fat tissues confirmed that Moro juice could entirely rescue the high fat-induced transcriptional reprogramming. Moro juice anti-obesity effect on fat accumulation cannot be explained only by its anthocyanin content. Our findings suggest that multiple components present in the Moro orange juice might act synergistically to inhibit fat accumulation.

  20. Heavy metals accumulation affects bone microarchitecture in osteoporotic patients.

    PubMed

    Scimeca, Manuel; Feola, Maurizio; Romano, Lorenzo; Rao, Cecilia; Gasbarra, Elena; Bonanno, Elena; Brandi, Maria Luisa; Tarantino, Umberto

    2017-04-01

    Bone metabolism is affected by mechanical, genetic, and environmental factors and plays a major role in osteoporosis. Nevertheless, the influence of environmental pollution on the occurrence of osteoporosis is still unclear and controversial. In this context, heavy metals are the most important pollutants capable to affect bone mass. The aim of this study was to investigate whether heavy metals accumulation in bone tissues could be related to the altered bone metabolism and architecture of osteoporotic patients. To this end, we analyzed 25 bone head biopsies osteoporotic patients and 25 bone head biopsies of osteoarthritic patients. Moreover we enrolled 15 patients underwent hip arthroplasty for high-energy hip fracture or osteonecrosis of the femoral head as a control group. Bone head biopsies were studied by BioQuant-osteo software, scanning electron microscopy and Energy Dispersive X-ray microanalysis. We found a prevalence of lead, cadmium and chromium accumulation in osteoporotic patients. Noteworthy, high levels of sclerostin, detected by immunohistochemistry, correlate with the accumulation of heavy metal found in the bone of osteoporotic patients, suggesting a molecular link between heavy metal accumulation and bone metabolism impairment. In conclusion, the presence of heavy metals into bone shed new light on the comprehension of the pathogenesis of osteoporosis since these elements could play a non redundant role in the development of osteoporosis at cellular/molecular and epigenetic level. Nevertheless, in vivo and in vitro studies need to better elucidate the molecular mechanism in which heavy metals can participate to osteoporosis. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1333-1342, 2017. © 2016 Wiley Periodicals, Inc.

  1. Metabolism of hydroxydibenzofurans, methoxydibenzofurans, acetoxydibenzofurans, and nitrodibenzofurans by Sphingomonas sp. strain HH69

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

    Harms, H.; Wittich, R.M.; Fortnagel, P.

    The metabolism of 11 substituted dibenzofurans by the dibenzofuran-degrading Sphingomonas sp. strain HH69 was investigated. Strain HH69 utilizes 2-, 3-, and 4-acetoxydibenzofuran as well as 2-, 3-, and 4-hydroxydibenzofuran as sole sources of carbon and energy. The degradation of acetoxydibenzofurans is initiated by hydrolysis of the ester bonds, yielding the corresponding hydroxydibenzofurans and acetate. Strain HH69 grew on 2-methoxydibenzofuran only after it was adapted to the utilization of 5-methoxysalicylic acid, whereas 3- and 4-methoxydibenzofuran as well as 2- and 3-nitrodibenzofuran were only cooxidized. During the breakdown of all eight hydroxy-, methoxy-, and nitrodibenzofurans studied here, the corresponding substituted salicylic acidsmore » accumulated in the culture broth. In the cases of 2- and 3-hydroxydibenzofuran as well as 2- and 3-nitrodibenzofuran, salicylic acid was also formed. Those four dibenzofurans which did not serve as carbon sources for strain HH69 were converted to a nonutilizable salicylic acid derivative. From turnover experiments with the mutant HH69/II, which is deficient in meta-cleavage, 2,2{prime}, 3,4{prime}-tetrahydroxybiphenyl, 2,2{prime},3-trihydroxy-5{prime}-methoxybiphenyl, 2,2{prime},3-trihydroxy-5{prime}-nitrobiphenyl, and 2,2{prime},3-trihydroxy-4{prime}-nitrobiphenyl were isolated as the main products formed from 3-hydroxydibenzofuran, 2-methoxydibenzofuran, and 2- and 3-nitrodibenzo-furan, respectively. These results indicate significant regioselectivity for the dioxygenolytic cleavage of the ether bond of these monosubstituted dibenzofurans, with a preference for the nonsubstituted aromatic nucleus. Substituted trihydroxybiphenyls are converted further by meta-cleavage followed by the removal of the side chain of the resulting product. A stepwise degradation of this side chain was found to be involved in the metabolism of 2-hydroxydibenzofuran. 34 refs., 5 figs., 2 tabs.« less

  2. The premixed flame in uniform straining flow

    NASA Technical Reports Server (NTRS)

    Durbin, P. A.

    1982-01-01

    Characteristics of the premixed flame in uniform straining flow are investigated by the technique of activation-energy asymptotics. An inverse method is used, which avoids some of the restrictions of previous analyses. It is shown that this method recovers known results for adiabatic flames. New results for flames with heat loss are obtained, and it is shown that, in the presence of finite heat loss, straining can extinguish flames. A stability analysis shows that straining can suppress the cellular instability of flames with Lewis number less than unity. Strain can produce instability of flames with Lewis number greater than unity. A comparison shows quite good agreement between theoretical deductions and experimental observations of Ishizuka, Miyasaka & Law (1981).

  3. Sealing glass-ceramics with near-linear thermal strain, part III: Stress modeling of strain and strain rate matched glass-ceramic to metal seals

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

    Dai, Steve; Elisberg, Brenton; Calderone, James

    Thermal mechanical stresses of glass-ceramic to stainless steel (GCtSS) seals are analyzed using finite element modeling over a temperature cycle from a set temperature (T set) 500°C to -55°C, and then back to 600°C. There are two glass-ceramics that have an identical coefficient of thermal expansion (CTE) at ~16 ppm/°C but have very different linearity of thermal strains, designated as near-linear NL16 and step-like SL16, and were formed from the same parent glass using different crystallization processes. Stress modeling reveals much higher plastic strain in the stainless steel using SL16 glass-ceramic when the GCtSS seal cools from T set. Uponmore » heating tensile stresses start to develop at the GC-SS interface before the temperature reaches T set. On the other hand, the much lower plastic deformation in stainless steel accumulated during cooling using NL16 glass-ceramic allows for radially compressive stress at the GC-SS interface to remain present when the seal is heated back to T set. Finally, the qualitative stress comparison suggests that with a better match of thermal strain rate to that of stainless steel, the NL16 glass-ceramic not only improves the hermeticity of the GCtSS seals, but would also improve the reliability of the seals exposed to high-temperature and/or high-pressure abnormal environments.« less

  4. Sealing glass-ceramics with near-linear thermal strain, part III: Stress modeling of strain and strain rate matched glass-ceramic to metal seals

    DOE PAGES

    Dai, Steve; Elisberg, Brenton; Calderone, James; ...

    2017-04-21

    Thermal mechanical stresses of glass-ceramic to stainless steel (GCtSS) seals are analyzed using finite element modeling over a temperature cycle from a set temperature (T set) 500°C to -55°C, and then back to 600°C. There are two glass-ceramics that have an identical coefficient of thermal expansion (CTE) at ~16 ppm/°C but have very different linearity of thermal strains, designated as near-linear NL16 and step-like SL16, and were formed from the same parent glass using different crystallization processes. Stress modeling reveals much higher plastic strain in the stainless steel using SL16 glass-ceramic when the GCtSS seal cools from T set. Uponmore » heating tensile stresses start to develop at the GC-SS interface before the temperature reaches T set. On the other hand, the much lower plastic deformation in stainless steel accumulated during cooling using NL16 glass-ceramic allows for radially compressive stress at the GC-SS interface to remain present when the seal is heated back to T set. Finally, the qualitative stress comparison suggests that with a better match of thermal strain rate to that of stainless steel, the NL16 glass-ceramic not only improves the hermeticity of the GCtSS seals, but would also improve the reliability of the seals exposed to high-temperature and/or high-pressure abnormal environments.« less

  5. Quantification of carotid artery plaque stability with multiple region of interest based ultrasound strain indices and relationship with cognition

    NASA Astrophysics Data System (ADS)

    Meshram, N. H.; Varghese, T.; Mitchell, C. C.; Jackson, D. C.; Wilbrand, S. M.; Hermann, B. P.; Dempsey, R. J.

    2017-08-01

    Vulnerability and instability in carotid artery plaque has been assessed based on strain variations using noninvasive ultrasound imaging. We previously demonstrated that carotid plaques with higher strain indices in a region of interest (ROI) correlated to patients with lower cognition, probably due to cerebrovascular emboli arising from these unstable plaques. This work attempts to characterize the strain distribution throughout the entire plaque region instead of being restricted to a single localized ROI. Multiple ROIs are selected within the entire plaque region, based on thresholds determined by the maximum and average strains in the entire plaque, enabling generation of additional relevant strain indices. Ultrasound strain imaging of carotid plaques, was performed on 60 human patients using an 18L6 transducer coupled to a Siemens Acuson S2000 system to acquire radiofrequency data over several cardiac cycles. Patients also underwent a battery of neuropsychological tests under a protocol based on National Institute of Neurological Disorders and Stroke and Canadian Stroke Network guidelines. Correlation of strain indices with composite cognitive index of executive function revealed a negative association relating high strain to poor cognition. Patients grouped into high and low cognition groups were then classified using these additional strain indices. One of our newer indices, namely the average L  -  1 norm with plaque (AL1NWP) presented with significantly improved correlation with executive function when compared to our previously reported maximum accumulated strain indices. An optimal combination of three of the new indices generated classifiers of patient cognition with an area under the curve (AUC) of 0.880, 0.921 and 0.905 for all (n  =  60), symptomatic (n  =  33) and asymptomatic patients (n  =  27) whereas classifiers using maximum accumulated strain indices alone provided AUC values of 0.817, 0.815 and 0

  6. Quantification of carotid artery plaque stability with multiple region of interest based ultrasound strain indices and relationship with cognition.

    PubMed

    Meshram, N H; Varghese, T; Mitchell, C C; Jackson, D C; Wilbrand, S M; Hermann, B P; Dempsey, R J

    2017-07-17

    Vulnerability and instability in carotid artery plaque has been assessed based on strain variations using noninvasive ultrasound imaging. We previously demonstrated that carotid plaques with higher strain indices in a region of interest (ROI) correlated to patients with lower cognition, probably due to cerebrovascular emboli arising from these unstable plaques. This work attempts to characterize the strain distribution throughout the entire plaque region instead of being restricted to a single localized ROI. Multiple ROIs are selected within the entire plaque region, based on thresholds determined by the maximum and average strains in the entire plaque, enabling generation of additional relevant strain indices. Ultrasound strain imaging of carotid plaques, was performed on 60 human patients using an 18L6 transducer coupled to a Siemens Acuson S2000 system to acquire radiofrequency data over several cardiac cycles. Patients also underwent a battery of neuropsychological tests under a protocol based on National Institute of Neurological Disorders and Stroke and Canadian Stroke Network guidelines. Correlation of strain indices with composite cognitive index of executive function revealed a negative association relating high strain to poor cognition. Patients grouped into high and low cognition groups were then classified using these additional strain indices. One of our newer indices, namely the average L  -  1 norm with plaque (AL1NWP) presented with significantly improved correlation with executive function when compared to our previously reported maximum accumulated strain indices. An optimal combination of three of the new indices generated classifiers of patient cognition with an area under the curve (AUC) of 0.880, 0.921 and 0.905 for all (n  =  60), symptomatic (n  =  33) and asymptomatic patients (n  =  27) whereas classifiers using maximum accumulated strain indices alone provided AUC values of 0.817, 0.815 and 0

  7. The Role of Trabecular Microarchitecture in the Formation, Accumulation, and Morphology of Microdamage in Human Cancellous Bone

    PubMed Central

    Karim, Lamya; Vashishth, Deepak

    2011-01-01

    Alterations in microdamage morphology and accumulation are typically attributed to impaired remodeling, but may also result from changes in microdamage initiation and propagation. Such alterations are relevant for cancellous bone with high metabolic activity and numerous bone quality changes. This study investigates the role of trabecular microarchitecture on morphology and accumulation of microdamage in human cancellous bone. Trabecular bone cores from donors of varying ages and bone volume fraction (BV/TV) were separated into high and low BV/TV groups. Samples were subjected to no load or uniaxial compression to 0.6% (pre-yield) or 1.1% (post-yield) strain. Microdamage was stained with lead uranyl acetate and specimens were imaged via microcomputed tomography to quantify microdamage and determine its morphology in three-dimensions (3D). Donors with high BV/TV had greater post yield strain and were tougher than low BV/TV donors. High BV/TV bone had less microdamage than low BV/TV bone under post- but not pre-yield loading. Microdamage under both loading conditions showed significant correlations with microarchitecture and BV/TV, but the key predictor was structure model index (SMI). As SMI increased (more trabecular rods), microdamage morphology became crack-like. Thus, low BV/TV and increased SMI have strong influences on microdamage accumulation in bone through altered initiation. PMID:21538510

  8. Plasmon modes in monolayer and double-layer black phosphorus under applied uniaxial strain

    NASA Astrophysics Data System (ADS)

    Saberi-Pouya, S.; Vazifehshenas, T.; Saleh, M.; Farmanbar, M.; Salavati-fard, T.

    2018-05-01

    We study the effects of an applied in-plane uniaxial strain on the plasmon dispersions of monolayer, bilayer, and double-layer black phosphorus structures in the long-wavelength limit within the linear elasticity theory. In the low-energy limit, these effects can be modeled through the change in the curvature of the anisotropic energy band along the armchair and zigzag directions. We derive analytical relations of the plasmon modes under uniaxial strain and show that the direction of the applied strain is important. Moreover, we observe that along the armchair direction, the changes of the plasmon dispersion with strain are different and larger than those along the zigzag direction. Using the analytical relations of two-layer phosphorene systems, we found that the strain-dependent orientation factor of layers could be considered as a means to control the variations of the plasmon energy. Furthermore, our study shows that the plasmonic collective modes are more affected when the strain is applied equally to the layers compared to the case in which the strain is applied asymmetrically to the layers. We also calculate the effect of strain on the drag resistivity in a double-layer black phosphorus structure and obtain that the changes in the plasmonic excitations, due to an applied strain, are mainly responsible for the predicted results. This study can be readily extended to other anisotropic two-dimensional materials.

  9. Influences of misfit strains on liquid phase heteroepitaxial growth

    NASA Astrophysics Data System (ADS)

    Lu, Yanli; Peng, Yingying; Yu, Genggeng; Chen, Zheng

    2017-10-01

    Influences of misfit strains with different signs on liquid phase heteroepitaxial growth are studied by binary phase field crystal model. It is amazing to find that double islands are formed because of lateral and vertical separation. The morphological evolution of epitaxial layer depends on signs of misfit strains. The maximum atomic layer thickness of double islands under negative misfit strain is larger than that of under positive misfit strain at the same evolutional time, and size differences between light and dark islands is much smaller under negative misfit strain than that of under positive misfit strain. In addition, concentration field and density field approximately have similar variational law along x direction under the same misfit strain but show opposite variational trend under misfit strains with different signs. Generally, free energy of epitaxial growth systems keeps similar variational trend under misfit strains with different signs.

  10. Evaluation of GE-167 Silicone Rubber (RTV) For Possible Service As A Moisture-Barrier For Certain Strain Gage Applications

    NASA Technical Reports Server (NTRS)

    Hare, David A.; Moore, Thomas C., Sr.

    2000-01-01

    The Langley Research Center uses strain gages in a wide variety of demanding test environments. Strain gage installations, depending on the testing scenario, may see high temperatures, cryogenic temperature, moisture accumulation, mechanical abuse, or any combination of these conditions. At Langley, there is often a need to provide protection for strain gages against moisture and mechanical abuse, especially when large-scale, harsh environment testing is to be encountered. This technical memorandum discusses the evaluation of a room temperature curing silicone rubber sealant manufactured by the General Electric Company for consideration as a moisture-barrier for certain strain gage installations.

  11. Scale interactions of turbulence subjected to a straining relaxation destraining cycle

    NASA Astrophysics Data System (ADS)

    Chen, Jun; Meneveau, Charles; Katz, Joseph

    2006-09-01

    The response of turbulence subjected to planar straining and de-straining is studied experimentally, and the impact of the applied distortions on the energy transfer across different length scales is quantified. The data are obtained using planar particle image velocimetry (PIV) in a water tank, in which high-Reynolds-number turbulence with very low mean velocity is generated by an array of spinning grids. Planar straining and de-straining mean flows are produced by pushing and pulling a rectangular piston towards, and away from, the bottom wall of the tank. The data are processed to yield the time evolution of Reynolds stresses, anisotropy tensors, turbulence kinetic energy production, and mean subgrid-scale (SGS) dissipation rate at various scales. During straining, the production rises rapidly. After the relaxation period the small-scale SGS stresses recover isotropy, but the Reynolds stresses still display significant anisotropy. Thus when destraining is applied, a strong negative production (mean backscatter) occurs, i.e. the turbulence returns kinetic energy to the mean flow. The SGS dissipation displays similar behaviour at large filter scales, but the mean backscatter gradually disappears with decreasing filter scales. Energy spectra are compared to predictions of rapid distortion theory (RDT). Good agreement is found for the initial response but, as expected for the time-scale ratios of the experiment, turbulence relaxation causes discrepancies between measurements and RDT at later times.

  12. Electronic and phononic modulation of MoS2 under biaxial strain

    NASA Astrophysics Data System (ADS)

    Moghadasi, A.; Roknabadi, M. R.; Ghorbani, S. R.; Modarresi, M.

    2017-12-01

    Dichalcogenides of transition metals are attractive material due to its unique properties. In this work, it has been investigated the electronic band structure, phonon spectrum and heat capacity of MoS2 under the applied tensile and compressive biaxial strain using the density functional theory. The Molybdenum disulfide under compressive (tensile) strain up to 6% (10%) has stable atomic structure without any negative frequency in the phonon dispersion curves. The tensile biaxial strain reduces the energy gap in the electronic band structure and the optical-acoustic gap in phonon dispersion curves. The tensile biaxial strain also increases the specific heat capacity. On the other hand, the compressive biaxial strain in this material increases phonon gap and reduces the heat capacity and the electronic band gap. The phonon softening/hardening is reported for tensile/compressive biaxial strain in MoS2. We report phonon hardening for out of plane ZA mode in the presence of both tensile and compressive strains. Results show that the linear variation of specific heat with strain (CV ∝ε) and square dependency of specific heat with the temperature (CV ∝T2) for low temperature regime. The results demonstrate that the applied biaxial strain tunes the electronic energy gap and modifies the phonon spectrum of MoS2.

  13. Increase of chromium tolerance in Scenedesmus acutus after sulfur starvation: Chromium uptake and compartmentalization in two strains with different sensitivities to Cr(VI).

    PubMed

    Marieschi, M; Gorbi, G; Zanni, C; Sardella, A; Torelli, A

    2015-10-01

    In photosynthetic organisms sulfate constitutes the main sulfur source for the biosynthesis of GSH and its precursor Cys. Hence, sulfur availability can modulate the capacity to cope with environmental stresses, a phenomenon known as SIR/SED (Sulfur Induced Resistance or Sulfur Enhanced Defence). Since chromate may compete for sulfate transport into the cells, in this study chromium accumulation and tolerance were investigated in relation to sulfur availability in two strains of the unicellular green alga Scenedesmus acutus with different Cr-sensitivities. Paradoxically, sulfur deprivation has been demonstrated to induce a transient increase of Cr-tolerance in both strains. Sulfur deprivation is known to enhance the sulfate uptake/assimilation pathway leading to important consequences on Cr-tolerance: (i) reduced chromate uptake due to the induction of high affinity sulfate transporters (ii) higher production of cysteine and GSH which can play a role both through the formation of unsoluble complexes and their sequestration in inert compartments. To investigate the role of the above mentioned mechanisms, Cr accumulation in total cells and in different cell compartments (cell wall, membranes, soluble and miscellaneous fractions) was analyzed in both sulfur-starved and unstarved cells. Both strains mainly accumulated chromium in the soluble fraction, but the uptake was higher in the wild-type. In this type a short period of sulfur starvation before Cr(VI) treatment lowered chromium accumulation to the level observed in the unstarved Cr-tolerant strain, in which Cr uptake seems instead less influenced by S-starvation, since no significant decrease was observed. The increase in Cr-tolerance following S-starvation seems thus to rely on different mechanisms in the two strains, suggesting the induction of a mechanism constitutively active in the Cr-tolerant strain, maybe a high affinity sulfate transporter also in the wild-type. Changes observed in the cell wall and

  14. Natural convection during heat energy accumulation by substances that change their state of aggregation

    NASA Astrophysics Data System (ADS)

    Chukaev, A. G.; Kuks, A. M.

    Heat transfer calculations are presented for a heat accumulator using the melting heat of a substance which changes its state of aggregation. It is shown that the approach adopted here makes it possible to evaluate the efficiency of using heat-storage materials in the pipe-tank system. The calculations, which allow for the effect of free convection in the liquid phase, have been made using the Boussinesq approximation. Results of a numerical experiment for NaNO3 salt show that the effect of natural convection on heat transfer is significant and that the heat flux to the material decreases as heat accumulates.

  15. The strain-encoded relationship between PrP replication, stability and processing in neurons is predictive of the incubation period of disease.

    PubMed

    Ayers, Jacob I; Schutt, Charles R; Shikiya, Ronald A; Aguzzi, Adriano; Kincaid, Anthony E; Bartz, Jason C

    2011-03-01

    Prion strains are characterized by differences in the outcome of disease, most notably incubation period and neuropathological features. While it is established that the disease specific isoform of the prion protein, PrP(Sc), is an essential component of the infectious agent, the strain-specific relationship between PrP(Sc) properties and the biological features of the resulting disease is not clear. To investigate this relationship, we examined the amplification efficiency and conformational stability of PrP(Sc) from eight hamster-adapted prion strains and compared it to the resulting incubation period of disease and processing of PrP(Sc) in neurons and glia. We found that short incubation period strains were characterized by more efficient PrP(Sc) amplification and higher PrP(Sc) conformational stabilities compared to long incubation period strains. In the CNS, the short incubation period strains were characterized by the accumulation of N-terminally truncated PrP(Sc) in the soma of neurons, astrocytes and microglia in contrast to long incubation period strains where PrP(Sc) did not accumulate to detectable levels in the soma of neurons but was detected in glia similar to short incubation period strains. These results are inconsistent with the hypothesis that a decrease in conformational stability results in a corresponding increase in replication efficiency and suggest that glia mediated neurodegeneration results in longer survival times compared to direct replication of PrP(Sc) in neurons.

  16. Strain-Gradient Modulated Exciton Emission in Bent ZnO Wires Probed by Cathodoluminescence.

    PubMed

    Fu, Xue-Wen; Li, Cai-Zhen; Fang, Liang; Liu, Da-Meng; Xu, Jun; Yu, Da-Peng; Liao, Zhi-Min

    2016-12-27

    Photoelectrical properties of semiconductor nanostructures are expected to be improved significantly by strain engineering. Besides the local strain, the strain gradient is promising to tune the luminescence properties by modifying the crystal symmetry. Here, we report the investigation of strain-gradient induced symmetry-breaking effect on excitonic states in pure bending ZnO microwires by high spatial-resolved cathodoluminescence at low temperature of 80 K. In addition to the local-strain induced light emission peak shift, the bound exciton emission photon energy shows an extraordinary jump of ∼16.6 meV at a high strain-gradient of 1.22% μm -1 , which is ascribed to the strain gradient induced symmetry-breaking. Such a symmetry-breaking lifts the energy degeneracy of the electronic band structures, which significantly modifies the electron-hole interactions and the fine structures of the bound exciton states. These results provide a further understanding of the strain gradient effect on the excitonic states and possess a potential for the applications in optoelectronic devices.

  17. Synchronized growth and neutral lipid accumulation in Chlorella sorokiniana FC6 IITG under continuous mode of operation.

    PubMed

    Kumar, Vikram; Muthuraj, Muthusivaramapandian; Palabhanvi, Basavaraj; Das, Debasish

    2016-01-01

    Synchronized growth and neutral lipid accumulation with high lipid productivity under mixotrophic growth of the strain Chlorella sorokiniana FC6 IITG was achieved via manipulation of substrates feeding mode and supplementation of lipid elicitors in the growth medium. Screening and optimization of lipid elicitors resulted in lipid productivity of 110.59mgL(-1)day(-1) under the combined effect of lipid inducers sodium acetate and sodium chloride. Fed-batch cultivation of the strain in bioreactor with intermittent feeding of limiting nutrients and lipid inducer resulted in maximum biomass and lipid productivity of 2.08 and 0.97gL(-1)day(-1) respectively. Further, continuous production of biomass with concomitant lipid accumulation was demonstrated via continuous feeding of BG11 media supplemented with lipid inducers sodium acetate and sodium chloride. The improved biomass and lipid productivity in chemostat was found to be 2.81 and 1.27gL(-1)day(-1) respectively operated at a dilution rate of 0.54day(-1). Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. Theoretical Modeling of Molecular Mechanisms, Strains, and Time Scales in Prion Diseases

    DTIC Science & Technology

    2005-07-01

    oversimplification) displays a linear relationship between the change in the free energy difference between cellular and scrapies form of the protein and...and show with molecular dynamics (MD) that the DSTP has more favorable intermonomer hydrogen bonding and proline dihedral strain energy than the BPT...ramping of the overall free energy surface slope in favor of the scrapies form. In Fig. 5 we illustrate two ways in which strains might breed true if

  19. Strain effects on the electronic properties in δ -doped oxide superlattices

    DOE PAGES

    You, Jeong Ho; Lee, Jun Hee; Okamoto, Satoshi; ...

    2015-02-07

    We investigated strain effects on the electronic properties of (LaTiO 3) 1/(SrTiO 3)N superlattices using density functional theory. Under biaxial in-plane strain within the range of -5% ≤ ε// ≤ 5%, the d xy orbital electrons are highly localized at the interfaces whereas the d yz and d xz orbital electrons are more distributed in the SrTiO 3 (STO) spacer layers. For STO thickness N ≥ 3 unit cells (u.c.), the d xy orbital electrons form two-dimensional (2D) electron gases (2DEGs). The quantized energy levels of the 2DEG are insensitive to the STO spacer thickness, but are strongly dependent onmore » the applied biaxial in-plane strain. As the in-plane strain changes from compressive to tensile, the quantized energy levels of the dxy orbitals decrease thereby creating more states with 2D character. In contrast to the d xy orbital, the d yz and dxz orbitals always have three-dimensional (3D) transport characteristics and their energy levels increase as the strain changes from compressive to tensile. In conclusion, since the charge densities in the d xy orbital and the d yz and d xz orbitals respond to biaxial in-plane strain in an opposite way, the transport dimensionality of the majority carriers can be controlled between 2D and 3D by applying biaxial in-plane strain.« less

  20. Draft Genome Sequence of the Tyramine Producer Enterococcus durans Strain IPLA 655

    PubMed Central

    Ladero, Victor; Linares, Daniel M.; del Rio, Beatriz; Fernandez, Maria; Martin, M. Cruz

    2013-01-01

    We here report a 3.059-Mbp draft assembly for the genome of Enterococcus durans strain IPLA 655. This dairy isolate provides a model for studying the regulation of the biosynthesis of tyramine (a toxic compound). These results should aid our understanding of tyramine production and allow tyramine accumulation in food to be reduced. PMID:23682153

  1. Role of Prion Replication in the Strain-dependent Brain Regional Distribution of Prions*

    PubMed Central

    Hu, Ping Ping; Morales, Rodrigo; Duran-Aniotz, Claudia; Moreno-Gonzalez, Ines; Khan, Uffaf; Soto, Claudio

    2016-01-01

    One intriguing feature of prion diseases is their strain variation. Prion strains are differentiated by the clinical consequences they generate in the host, their biochemical properties, and their potential to infect other animal species. The selective targeting of these agents to specific brain structures have been extensively used to characterize prion strains. However, the molecular basis dictating strain-specific neurotropism are still elusive. In this study, isolated brain structures from animals infected with four hamster prion strains (HY, DY, 139H, and SSLOW) were analyzed for their content of protease-resistant PrPSc. Our data show that these strains have different profiles of PrP deposition along the brain. These patterns of accumulation, which were independent of regional PrPC production, were not reproduced by in vitro replication when different brain regions were used as substrate for the misfolding-amplification reaction. On the contrary, our results show that in vitro replication efficiency depended exclusively on the amount of PrPC present in each part of the brain. Our results suggest that the variable regional distribution of PrPSc in distinct strains is not determined by differences on prion formation, but on other factors or cellular pathways. Our findings may contribute to understand the molecular mechanisms of prion pathogenesis and strain diversity. PMID:27056328

  2. Use of De Novo Transcriptome Libraries to Characterize a Novel Oleaginous Marine Chlorella Species during the Accumulation of Triacylglycerols

    PubMed Central

    Ahner, Beth A.; Cochlan, William P.; Richardson, Ruth E.

    2016-01-01

    Marine chlorophytes of the genus Chlorella are unicellular algae capable of accumulating a high proportion of cellular lipids that can be used for biodiesel production. In this study, we examined the broad physiological capabilities of a subtropical strain (C596) of Chlorella sp. “SAG-211-18” including its heterotrophic growth and tolerance to low salt. We found that the alga replicates more slowly at diluted salt concentrations and can grow on a wide range of carbon substrates in the dark. We then sequenced the RNA of Chlorella strain C596 to elucidate key metabolic genes and investigate the transcriptomic response of the organism when transitioning from a nutrient-replete to a nutrient-deficient condition when neutral lipids accumulate. Specific transcripts encoding for enzymes involved in both starch and lipid biosynthesis, among others, were up-regulated as the cultures transitioned into a lipid-accumulating state whereas photosynthesis-related genes were down-regulated. Transcripts encoding for two of the up-regulated enzymes—a galactoglycerolipid lipase and a diacylglyceride acyltransferase—were also monitored by reverse transcription quantitative polymerase chain reaction assays. The results of these assays confirmed the transcriptome-sequencing data. The present transcriptomic study will assist in the greater understanding, more effective application, and efficient design of Chlorella-based biofuel production systems. PMID:26840425

  3. Use of De Novo Transcriptome Libraries to Characterize a Novel Oleaginous Marine Chlorella Species during the Accumulation of Triacylglycerols.

    PubMed

    Mansfeldt, Cresten B; Richter, Lubna V; Ahner, Beth A; Cochlan, William P; Richardson, Ruth E

    2016-01-01

    Marine chlorophytes of the genus Chlorella are unicellular algae capable of accumulating a high proportion of cellular lipids that can be used for biodiesel production. In this study, we examined the broad physiological capabilities of a subtropical strain (C596) of Chlorella sp. "SAG-211-18" including its heterotrophic growth and tolerance to low salt. We found that the alga replicates more slowly at diluted salt concentrations and can grow on a wide range of carbon substrates in the dark. We then sequenced the RNA of Chlorella strain C596 to elucidate key metabolic genes and investigate the transcriptomic response of the organism when transitioning from a nutrient-replete to a nutrient-deficient condition when neutral lipids accumulate. Specific transcripts encoding for enzymes involved in both starch and lipid biosynthesis, among others, were up-regulated as the cultures transitioned into a lipid-accumulating state whereas photosynthesis-related genes were down-regulated. Transcripts encoding for two of the up-regulated enzymes-a galactoglycerolipid lipase and a diacylglyceride acyltransferase-were also monitored by reverse transcription quantitative polymerase chain reaction assays. The results of these assays confirmed the transcriptome-sequencing data. The present transcriptomic study will assist in the greater understanding, more effective application, and efficient design of Chlorella-based biofuel production systems.

  4. Production of xylitol by a Coniochaeta ligniaria strain tolerant of inhibitors and defective in growth on xylose.

    PubMed

    Nichols, Nancy N; Saha, Badal C

    2016-05-01

    In conversion of biomass to fuels or chemicals, inhibitory compounds arising from physical-chemical pretreatment of the feedstock can interfere with fermentation of the sugars to product. Fungal strain Coniochaeta ligniaria NRRL30616 metabolizes the furan aldehydes furfural and 5-hydroxymethylfurfural, as well as a number of aromatic and aliphatic acids and aldehydes. Use of NRRL30616 to condition biomass sugars by metabolizing the inhibitors improves their fermentability. Wild-type C. ligniaria has the ability to grow on xylose as sole source of carbon and energy, with no accumulation of xylitol. Mutants of C. ligniaria unable to grow on xylose were constructed. Xylose reductase and xylitol dehydrogenase activities were reduced by approximately two thirds in mutant C8100. The mutant retained ability to metabolize inhibitors in biomass hydrolysates. Although C. ligniaria C8100 did not grow on xylose, the strain converted a portion of xylose to xylitol, producing 0.59 g xylitol/g xylose in rich medium and 0.48 g xylitol/g xylose in corn stover dilute acid hydrolysate. 2016 American Institute of Chemical Engineers Biotechnol. Prog., 2016 © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:606-612, 2016. © 2016 American Institute of Chemical Engineers.

  5. Earthquakes and strain in subhorizontal slabs

    NASA Astrophysics Data System (ADS)

    Brudzinski, Michael R.; Chen, Wang-Ping

    2005-08-01

    Using an extensive database of fault plane solutions and precise locations of hypocenters, we show that the classic patterns of downdip extension (DDE) or downdip compression (DDC) in subduction zones deteriorate when the dip of the slab is less than about 20°. This result is depth-independent, demonstrated by both intermediate-focus (depths from 70 to 300 km) and deep-focus (depths greater than 300 km) earthquakes. The absence of pattern in seismic strain in subhorizontal slabs also occurs locally over scales of about 10 km, as evident from a detailed analysis of a large (Mw 7.1) earthquake sequence beneath Fiji. Following the paradigm that a uniform strain of DDE/DDC results from sinking of the cold, dense slab as it encounters resistance from the highly viscous mantle at depth, breakdown of DDE/DDC in subhorizontal slabs reflects waning negative buoyancy ("slab pull") in the downdip direction. Our results place a constraint on the magnitude of slab pull that is required to dominate over localized sources of stress and to align seismic strain release in dipping slabs. Under the condition of a vanishing slab pull, eliminating the only obvious source of regional stress, the abundance of earthquakes in subhorizontal slabs indicates that a locally variable source of stress is both necessary and sufficient to sustain the accumulation of elastic strain required to generate intermediate- and deep-focus seismicity. Evidence is growing that the process of seismogenesis under high pressures, including localized sources of stress, is tied to the presence of petrologic anomalies.

  6. Strain Release Amination

    PubMed Central

    Gianatassio, Ryan; Lopchuk, Justin M.; Wang, Jie; Pan, Chung-Mao; Malins, Lara R.; Prieto, Liher; Brandt, Thomas A.; Collins, Michael R.; Gallego, Gary M.; Sach, Neal W.; Spangler, Jillian E.; Zhu, Huichin; Zhu, Jinjiang; Baran, Phil S.

    2015-01-01

    To optimize drug candidates, modern medicinal chemists are increasingly turning to an unconventional structural motif: small, strained ring systems. However, the difficulty of introducing substituents such as bicyclo[1.1.1]pentanes, azetidines, or cyclobutanes often outweighs the challenge of synthesizing the parent scaffold itself. Thus, there is an urgent need for general methods to rapidly and directly append such groups onto core scaffolds. Here we report a general strategy to harness the embedded potential energy of effectively spring-loaded C–C and C–N bonds with the most oft-encountered nucleophiles in pharmaceutical chemistry, amines. Strain release amination can diversify a range of substrates with a multitude of desirable bioisosteres at both the early and late-stages of a synthesis. The technique has also been applied to peptide labeling and bioconjugation. PMID:26816372

  7. Characterization of genome-reduced Bacillus subtilis strains and their application for the production of guanosine and thymidine.

    PubMed

    Li, Yang; Zhu, Xujun; Zhang, Xueyu; Fu, Jing; Wang, Zhiwen; Chen, Tao; Zhao, Xueming

    2016-06-03

    Genome streamlining has emerged as an effective strategy to boost the production efficiency of bio-based products. Many efforts have been made to construct desirable chassis cells by reducing the genome size of microbes. It has been reported that the genome-reduced Bacillus subtilis strain MBG874 showed clear advantages for the production of several heterologous enzymes including alkaline cellulase and protease. In addition to enzymes, B. subtilis is also used for the production of chemicals. To our best knowledge, it is still unknown whether genome reduction could be used to optimize the production of chemicals such as nucleoside products. In this study, we constructed a series of genome-reduced strains by deleting non-essential regions in the chromosome of B. subtilis 168. These strains with genome reductions ranging in size from 581.9 to 814.4 kb displayed markedly decreased growth rates, sporulation ratios, transformation efficiencies and maintenance coefficients, as well as increased cell yields. We re-engineered the genome-reduced strains to produce guanosine and thymidine, respectively. The strain BSK814G2, in which purA was knocked out, and prs, purF and guaB were co-overexpressed, produced 115.2 mg/L of guanosine, which was 4.4-fold higher compared to the control strain constructed by introducing the same gene modifications into the parental strain. We also constructed a thymidine producer by deleting the tdk gene and overexpressing the prs, ushA, thyA, dut, and ndk genes from Escherichia coli in strain BSK756, and the resulting strain BSK756T3 accumulated 151.2 mg/L thymidine, showing a 5.2-fold increase compared to the corresponding control strain. Genome-scale genetic manipulation has a variety of effects on the physiological characteristics and cell metabolism of B. subtilis. By introducing specific gene modifications related to guanosine and thymidine accumulation, respectively, we demonstrated that genome-reduced strains had greatly improved

  8. Effect of strain and deformation route on grain boundary characteristics and recrystallization behavior of aluminum

    NASA Astrophysics Data System (ADS)

    Sakai, Tetsuo; Utsunomiya, Hiroshi; Takahashi, Yasuo

    2014-08-01

    The effect of strain and deformation route on the recrystallization behavior of aluminum sheets has been investigated using well lubricated cold rolling and continuous equal channel angular extrusion. Three different deformation routes in plane strain corresponding to (1) simple shear, (2) compression, and (3) the combination of simple shear and compression were performed on 1100 aluminum sheet. Fixed amounts of the equivalent strain of 1.28 and 1.06 were accumulated in each route. In case of the combined deformation route, the ratio of shear strain to the total equivalent strain was varied. The recrystallized grain size was finer if the combined deformation route was employed instead of the monotonic route under the same amount of equivalent strain at either strain level. The density of high angle grain boundaries that act as nucleation sites for recrystallization was higher in materials deformed by the combined route. The orientation imaging micrographs revealed that the change in deformation route is effective for introducing a larger number of new high angle grain boundaries with relatively low misorientation angle.

  9. Early Mitochondrial Adaptations in Skeletal Muscle to Diet-Induced Obesity Are Strain Dependent and Determine Oxidative Stress and Energy Expenditure But Not Insulin Sensitivity

    PubMed Central

    Sena, Sandra; Sloan, Crystal; Tebbi, Ali; Han, Yong Hwan; O'Neill, Brian T.; Cooksey, Robert C.; Jones, Deborah; Holland, William L.; McClain, Donald A.; Abel, E. Dale

    2012-01-01

    This study sought to elucidate the relationship between skeletal muscle mitochondrial dysfunction, oxidative stress, and insulin resistance in two mouse models with differential susceptibility to diet-induced obesity. We examined the time course of mitochondrial dysfunction and insulin resistance in obesity-prone C57B and obesity-resistant FVB mouse strains in response to high-fat feeding. After 5 wk, impaired insulin-mediated glucose uptake in skeletal muscle developed in both strains in the absence of any impairment in proximal insulin signaling. Impaired mitochondrial oxidative capacity preceded the development of insulin resistant glucose uptake in C57B mice in concert with increased oxidative stress in skeletal muscle. By contrast, mitochondrial uncoupling in FVB mice, which prevented oxidative stress and increased energy expenditure, did not prevent insulin resistant glucose uptake in skeletal muscle. Preventing oxidative stress in C57B mice treated systemically with an antioxidant normalized skeletal muscle mitochondrial function but failed to normalize glucose tolerance and insulin sensitivity. Furthermore, high fat-fed uncoupling protein 3 knockout mice developed increased oxidative stress that did not worsen glucose tolerance. In the evolution of diet-induced obesity and insulin resistance, initial but divergent strain-dependent mitochondrial adaptations modulate oxidative stress and energy expenditure without influencing the onset of impaired insulin-mediated glucose uptake. PMID:22510273

  10. Nanostructure formation during accumulative roll bonding of commercial purity titanium

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

    Karimi, Mohsen, E-mail: m.karimi@shahroodut.ac.ir

    2016-12-15

    In this investigation, commercial purity titanium (CP–Ti) was subjected to accumulative roll bonding (ARB) process up to 8 cycles (equivalent strain of 6.4) at the ambient temperature. Transmission electron microscopy (TEM) and X–ray diffraction line profile analysis (XRDLPA) were utilized to investigate the microstructure and grain size evolution. Both characterization techniques could clarify the non–uniform microstructure in the early stages and the uniform microstructure in the final stages of the process. The effectiveness of ARB for the fabrication of the nano–grained structure in CP–Ti was revealed. It was found that the SFE is not the only factor affecting grain refinement,more » as compared with other studies on ARB of FCC materials. Influence of other factors such as the melting temperature and the crystalline structure of the material was determined on the grain refinement. - Highlights: •Nano–grained commercial purity titanium was produced by accumulative roll bonding. •TEM and XRDLPA were used for the characterization of the microstructure. •Important factors affecting the grain size of ARBed materials were discussed.« less

  11. Strain engineering of van der Waals heterostructures.

    PubMed

    Vermeulen, Paul A; Mulder, Jefta; Momand, Jamo; Kooi, Bart J

    2018-01-18

    Modifying the strain state of solids allows control over a plethora of functional properties. The weak interlayer bonding in van der Waals (vdWaals) materials such as graphene, hBN, MoS 2 , and Bi 2 Te 3 might seem to exclude strain engineering, since strain would immediately relax at the vdWaals interfaces. Here we present direct observations of the contrary by showing growth of vdWaals heterostructures with persistent in-plane strains up to 5% and we show that strain relaxation follows a not yet reported process distinctly different from strain relaxation in three-dimensionally bonded (3D) materials. For this, 2D bonded Bi 2 Te 3 -Sb 2 Te 3 and 2D/3D bonded Bi 2 Te 3 -GeTe multilayered films are grown using Pulsed Laser Deposition (PLD) and their structure is monitored in situ using Reflective High Energy Electron Diffraction (RHEED) and post situ analysis is performed using Transmission Electron Microscopy (TEM). Strain relaxation is modeled and found to solely depend on the layer being grown and its initial strain. This insight demonstrates that strain engineering of 2D bonded heterostructures obeys different rules than hold for epitaxial 3D materials and opens the door to precise tuning of the strain state of the individual layers to optimize functional performance of vdWaals heterostructures.

  12. An integrated approach to model strain localization bands in magnesium alloys

    NASA Astrophysics Data System (ADS)

    Baxevanakis, K. P.; Mo, C.; Cabal, M.; Kontsos, A.

    2018-02-01

    Strain localization bands (SLBs) that appear at early stages of deformation of magnesium alloys have been recently associated with heterogeneous activation of deformation twinning. Experimental evidence has demonstrated that such "Lüders-type" band formations dominate the overall mechanical behavior of these alloys resulting in sigmoidal type stress-strain curves with a distinct plateau followed by pronounced anisotropic hardening. To evaluate the role of SLB formation on the local and global mechanical behavior of magnesium alloys, an integrated experimental/computational approach is presented. The computational part is developed based on custom subroutines implemented in a finite element method that combine a plasticity model with a stiffness degradation approach. Specific inputs from the characterization and testing measurements to the computational approach are discussed while the numerical results are validated against such available experimental information, confirming the existence of load drops and the intensification of strain accumulation at the time of SLB initiation.

  13. [Genetic modification of Methylobacterium extorquens G10 producer strain of polyhydroxybutyrate].

    PubMed

    Fedorov, D N; Zamakhaeva, S A; Ezhov, V A; Doronina, N V; Trotsenko, Iu A

    2014-01-01

    The effect of the increased copy number of polyhydroxybutyrate (PHB) biosynthesis genes in pink-pigmented methylobacterium Methylobacterium extorquens G10 on properties of the biopolymer was studied. The activity of poly-3-hydroxybutyril-synthase (PHB-synthase) was shown to increase and the molecular weight of synthesized PHB decreases twofold (150 --> 79 kDa) after insertion of extra copies of phaC and phaCAB genes into cells of the producer strain, whereas the physicochemical properties of the plastic changed insignificantly. White mutant M. extorquens G10-W with disrupted synthesis of the carotenoid pigment (defect by the crtI gene, which codes for phytoene desaturase) was established to have the same rate of growth and level of PHB accumulation as the initial strain G10. The G10-W strain is a promising producer of PHB, with decreased expenses for purification and PHB biosynthesis.

  14. Canthaxanthin production with modified Mucor circinelloides strains.

    PubMed

    Papp, Tamás; Csernetics, Arpád; Nagy, Gábor; Bencsik, Ottó; Iturriaga, Enrique A; Eslava, Arturo P; Vágvölgyi, Csaba

    2013-06-01

    Canthaxanthin is a natural diketo derivative of β-carotene primarily used by the food and feed industries. Mucor circinelloides is a β-carotene-accumulating zygomycete fungus and one of the model organisms to study the carotenoid biosynthesis in fungi. In this study, the β-carotene ketolase gene (crtW) of the marine bacterium Paracoccus sp. N81106 fused with fungal promoter and terminator regions was integrated into the M. circinelloides genome to construct stable canthaxanthin-producing strains. Different transformation methods including polyethylene glycol-mediated transformation with linear DNA fragments, restriction enzyme-mediated integration and Agrobacterium tumefaciens-mediated transformation were tested to integrate the crtW gene into the Mucor genome. Mitotic stability, site of integration and copy number of the transferred genes were analysed in the transformants, and several stable strains containing the crtW gene in high copy number were isolated. Carotenoid composition of selected transformants and effect of culturing conditions, such as temperature, carbon sources and application of certain additives in the culturing media, on their carotenoid content were analysed. Canthaxanthin-producing transformants were able to survive at higher growth temperature than the untransformed strain, maybe due to the effect of canthaxanthin on the membrane fluidity and integrity. With the application of glucose, trehalose, dihydroxyacetone and L-aspartic acid as sole carbon sources in minimal medium, the crtW-expressing M. circinelloides strain, MS12+pCA8lf/1, produced more than 200 μg/g (dry mass) of canthaxanthin.

  15. Genetic analysis of fructan-hyperproducing strains of Streptococcus mutans.

    PubMed Central

    Kiska, D L; Macrina, F L

    1994-01-01

    Fructan polymer, synthesized from sucrose by the extracellular fructosyltransferase of Streptococcus mutans, is thought to contribute to the progression of dental caries. It may serve as an extracellular storage polysaccharide facilitating survival and acid production. It may also have a role in adherence or accumulation of bacterial cells on the tooth surface. A number of clinical isolates of S. mutans which produce large, mucoid colonies on sucrose-containing agar as a result of increased production of fructan have been discovered. By using eight independent isolates, we sought to determine if such fructan-hyperproducing strains represented a genetically homogeneous group of organisms. Restriction fragment patterns of total cellular DNA were examined by using pulsed-field and conventional gel electrophoresis. Four genetic types which appeared to correlate with the serotype of the organism and the geographic site of isolation were evident. Southern blot analysis of several genetic loci for extracellular enzymes revealed some minor differences between the strains, but the basic genomic organizations of these loci were similar. To evaluate whether the excess fructan produced by these strains enhanced the virulence of these organisms in the oral cavity, it was of interest to create mutants deficient in fructosidase (FruA), the extracellular enzyme which degrades this polymer. The fruA gene was inactivated by allelic exchange in two fructan-hyperproducing strains as well as in S. mutans GS5, a strain which does not hyperproduce fructan. All of the fruA mutant strains were devoid of fructan hydrolase activity when levan was used as a substrate. However, the fructan-hyperproducing strains retained the ability to hydrolyze inulin, suggesting the presence of a second fructosidase with specificity for inulin in these strains. Images PMID:7911782

  16. Energy expended and knee joint load accumulated when walking, running, or standing for the same amount of time.

    PubMed

    Miller, Ross H; Edwards, W Brent; Deluzio, Kevin J

    2015-01-01

    Evidence suggests prolonged bouts of sitting are unhealthy, and some public health messages have recently recommended replacing sitting with more standing. However, the relative benefits of replacing sitting with standing compared to locomotion are not known. Specifically, the biomechanical consequences of standing compared to other sitting-alternatives like walking and running are not well known and are usually not considered in studies on sitting. We compared the total knee joint load accumulated (TKJLA) and the total energy expended (TEE) when performing either walking, running, or standing for a common exercise bout duration (30 min). Walking and running both (unsurprisingly) had much more TEE than standing (+300% and +1100%, respectively). TKJLA was similar between walking and standing and 74% greater in running. The results suggest that standing is a poor replacement for walking and running if one wishes to increases energy expenditure, and may be particularly questionable for use in individuals at-risk for knee osteoarthritis due to its surprisingly high TKJLA (just as high as walking, 56% of the load in running) and the type of loading (continuous compression) it places on cartilage. However, standing has health benefits as an "inactivity interrupter" that extend beyond its direct energy expenditure. We suggest that future studies on standing as an inactivity intervention consider the potential biomechanical consequences of standing more often throughout the day, particularly in the case of prolonged bouts of standing. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Probabilistic assessment methodology for continuous-type petroleum accumulations

    USGS Publications Warehouse

    Crovelli, R.A.

    2003-01-01

    The analytic resource assessment method, called ACCESS (Analytic Cell-based Continuous Energy Spreadsheet System), was developed to calculate estimates of petroleum resources for the geologic assessment model, called FORSPAN, in continuous-type petroleum accumulations. The ACCESS method is based upon mathematical equations derived from probability theory in the form of a computer spreadsheet system. ?? 2003 Elsevier B.V. All rights reserved.

  18. Maximum likelihood decoding analysis of Accumulate-Repeat-Accumulate Codes

    NASA Technical Reports Server (NTRS)

    Abbasfar, Aliazam; Divsalar, Dariush; Yao, Kung

    2004-01-01

    Repeat-Accumulate (RA) codes are the simplest turbo-like codes that achieve good performance. However, they cannot compete with Turbo codes or low-density parity check codes (LDPC) as far as performance is concerned. The Accumulate Repeat Accumulate (ARA) codes, as a subclass of LDPC codes, are obtained by adding a pre-coder in front of RA codes with puncturing where an accumulator is chosen as a precoder. These codes not only are very simple, but also achieve excellent performance with iterative decoding. In this paper, the performance of these codes with (ML) decoding are analyzed and compared to random codes by very tight bounds. The weight distribution of some simple ARA codes is obtained, and through existing tightest bounds we have shown the ML SNR threshold of ARA codes approaches very closely to the performance of random codes. We have shown that the use of precoder improves the SNR threshold but interleaving gain remains unchanged with respect to RA code with puncturing.

  19. Mechanism of Na accumulation at extended defects in Si from first-principles

    NASA Astrophysics Data System (ADS)

    Park, Ji-Sang; Chan, Maria K. Y.

    2018-04-01

    Sodium (Na) impurities in silicon solar cells are considered to play an important role in potential-induced degradation (PID), a significant cause of solar cell degradation and failure. Shorting due to Na accumulation at extended defects has been suggested as a culprit for PID. However, it is not clear how the extended defects are decorated by Na impurities. Using first-principles density functional theory calculations, we find that Na impurities segregate from the bulk into extended defects such as intrinsic stacking faults and Σ3 (111) grain boundaries. The energy barrier required for Na to escape from the extended defects is substantial and similar to the sum of the barrier energy in bulk Si (1.1-1.2 eV) and the segregation energy to the stacking fault (˜0.7 eV). Surprisingly, the migration barrier for Na diffusion within the extended defects is even higher than the energy barrier for escaping. The results suggest that the extended defects likely accumulate Na as the impurities segregate to the defects from the bulk, rather than because of migration through the extended defects.

  20. Microscopic full-field three-dimensional strain measurement during the mechanical testing of additively manufactured porous biomaterials.

    PubMed

    Genovese, Katia; Leeflang, Sander; Zadpoor, Amir A

    2017-05-01

    A custom-designed micro-digital image correlation system was used to track the evolution of the full-surface three-dimensional strain field of Ti6Al4V additively manufactured lattice samples under mechanical loading. The high-magnification capabilities of the method allowed to resolve the strain distribution down to the strut level and disclosed a highly heterogeneous mechanical response of the lattice structure with local strain concentrations well above the nominal global strain level. In particular, we quantified that strain heterogeneity appears at a very early stage of the deformation process and increases with load, showing a strain accumulation pattern with a clear correlation to the later onset of the fracture. The obtained results suggest that the unique opportunities offered by the proposed experimental method, in conjunction with analytical and computational models, could serve to provide novel important information for the rational design of additively manufactured porous biomaterials. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Electronic origin of strain effects on solute stabilities in iron

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

    Liu, Wei; Li, Xiangyan; Xu, Yichun, E-mail: xuyichun@issp.ac.cn, E-mail: csliu@issp.ac.cn

    2016-08-21

    Nonuniform strain fields might induce the segregation of alloying solutes and ultimately lead to the mechanical performance degradation of body-centered-cubic (bcc) Fe based steels serving in extreme environments, which is worthy of investigation. In this paper, two typical volume-conserving strains, shear strain (SS) and normal strain (NS), are proposed to investigate the strain effects on solute stabilities in bcc iron by first-principles calculations. For solutes in each transition metal group, the calculated substitution energy change due to SS exhibits a linear dependence on the valence d radius of the solutes, and the slope decreases in an exponential manner as amore » function of the absolute difference between the Watson's electronegativity of iron and the averaged value of each transition metal group. This regularity is attributed to the Pauli repulsion between the solutes and the nearest neighboring Fe ions modulated by the hybridization of valence d bands and concluded to be originated from the characteristics of valence d bonding between the transition-metal solutes and Fe ions under SS. For main-group and post transition-metal solutes, the considerable drop of substitution energy change due to NS is concluded to be originated from the low-energy side shift of the widened valence s and p bands of the solutes. Our results indicate that the stabilities of substitutional solutes in iron under volume-conserving strain directly correlate with the intrinsic properties of the alloying elements, such as the valence d radius and occupancy, having or not having valence s and p bands.« less

  2. Effect of minerals on accumulation of Cs by fungus Saccaromyces cerevisiae.

    PubMed

    Ohnuki, Toshihiko; Sakamoto, Fuminori; Yamasaki, Shinya; Kozai, Naofumi; Shiotsu, Hiroyuki; Utsunomiya, Satoshi; Watanabe, Naoko; Kozaki, Tamotsu

    2015-06-01

    The accumulation of Cs by unicellular fungus of Saccharomyces cerevisiae in the presence of minerals has been studied to elucidate the role of microorganisms in the migration of radioactive Cs in the environment. Two different types of experiments were employed: experiments using stable Cs to examine the effect of a carbon source on the accumulation of Cs, and accumulation experiments of radioactive Cs from agar medium containing (137)Cs and zeolite, vermiculite, phlogopite, smectite, mica, or illite as mineral supplements. In the former type of experiments, the Cs-accumulated cells were analyzed by scanning electron microscopy equipped with energy dispersive X-ray analysis (SEM-EDS). In the latter type, the radioactivity in the yeast cells was measured by an autoradiography technique. When a carbon source was present, higher amounts of Cs accumulated in the cells than in the resting condition without a carbon source. Analyses with SEM-EDS showed that no mineral formed on the cell surface. These results indicate that the yeast cells accumulate Cs by adsorption on the cell surface and intracellular accumulation. In the presence of minerals in the agar medium, the radioactivity in the yeast cells was in the order of mica > smectite, illite > vermiculite, phlogopite, zeolite. This order is inversely correlated to the ratio of the concentration of radioactive Cs between the minerals and the medium solution. These results strongly suggest that the yeast accumulates radioactive Cs competitively with minerals. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Variable characteristics of bacteriocin-producing Streptococcus salivarius strains isolated from Malaysian subjects.

    PubMed

    Barbour, Abdelahhad; Philip, Koshy

    2014-01-01

    Salivaricins are bacteriocins produced by Streptococcus salivarius, some strains of which can have significant probiotic effects. S. salivarius strains were isolated from Malaysian subjects showing variable antimicrobial activity, metabolic profile, antibiotic susceptibility and lantibiotic production. In this study we report new S. salivarius strains isolated from Malaysian subjects with potential as probiotics. Safety assessment of these strains included their antibiotic susceptibility and metabolic profiles. Genome sequencing using Illumina's MiSeq system was performed for both strains NU10 and YU10 and demonstrating the absence of any known streptococcal virulence determinants indicating that these strains are safe for subsequent use as probiotics. Strain NU10 was found to harbour genes encoding salivaricins A and 9 while strain YU10 was shown to harbour genes encoding salivaricins A3, G32, streptin and slnA1 lantibiotic-like protein. Strain GT2 was shown to harbour genes encoding a large non-lantibiotic bacteriocin (salivaricin-MPS). A new medium for maximum biomass production buffered with 2-(N-morpholino)ethanesulfonic acid (MES) was developed and showed better biomass accumulation compared with other commercial media. Furthermore, we extracted and purified salivaricin 9 (by strain NU10) and salivaricin G32 (by strain YU10) from S. salivarius cells grown aerobically in this medium. In addition to bacteriocin production, S. salivarius strains produced levan-sucrase which was detected by a specific ESI-LC-MS/MS method which indicates additional health benefits from the developed strains. The current study established the bacteriocin, levan-sucrase production and basic safety features of S. salivarius strains isolated from healthy Malaysian subjects demonstrating their potential for use as probiotics. A new bacteriocin-production medium was developed with potential scale up application for pharmaceuticals and probiotics from S. salivarius generating different

  4. Strain localization parameters of AlCu4MgSi processed by high-energy electron beams

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

    Lunev, A. G., E-mail: agl@ispms.ru; Nadezhkin, M. V., E-mail: mvn@ispms.ru; National Research Tomsk Polytechnic University, Tomsk, 634050

    2015-10-27

    The influence of the electron beam surface treatment of AlCu4MgSi on the strain localization parameters and on the critical strain value of the Portevin–Le Chatelier effect has been considered. The strain localization parameters were measured using speckle imaging of the specimens subjected to the constant strain rate uniaxial tension at a room temperature. Impact of the surface treatment on the Portevin–Le Chatelier effect has been investigated.

  5. Temperature dependence of strain energy and thermodynamic properties of V2 O5 -based single-walled nanotubes: Zone-folding approach.

    PubMed

    Porsev, Vitaly V; Bandura, Andrei V; Evarestov, Robert A

    2016-06-15

    A zone-folding approach is applied to estimate the thermodynamic properties of V2 O5 -based nanotubes. The results obtained are compared with those from the direct calculations. It is shown that the zone-folding approximation allows an accurate estimation of nanotube thermodynamic properties and gives a gain in computation time compared to their direct calculations. Both approaches show that temperature effects do not change the relative stability of V2 O5 free layers and nanotubes derived from the α- and γ-phase. The internal energy thermal contributions into the strain energy of nanotubes are small and can be ignored. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  6. An Outbreak of Diarrhea in Mandera, Kenya, Due to Escherichia coli Serogroup O-Nontypable Strain That Had a Coding Gene for Enteroaggregative E. coli Heat-Stable Enterotoxin 1

    PubMed Central

    Ochi, Sadayuki; Shah, Mohammad; Odoyo, Erick; Bundi, Martin; Miringu, Gabriel; Guyo, Sora; Wandera, Ernest; Kathiiko, Cyrus; Kariuki, Samuel; Karama, Mohamed; Tsuji, Takao; Ichinose, Yoshio

    2017-01-01

    In an outbreak of gastroenteritis in December 2009, in Mandera, Kenya, Escherichia coli O-nontypable (ONT) strain was isolated from stool specimens of patients (18/24, 75%). The E. coli ONT organisms could not be assigned to any of the recognized diarrheagenic groups of E. coli. However, they possessed the enteroaggregative E. coli heat-stable enterotoxin-1 gene. The cell-free culture filtrates of the E. coli ONT strain isolated from the outbreak cases induced considerable amount of fluid accumulation in suckling mouse intestine, indicating production of an enterotoxic factor(s). These results identify E. coli that did not have any diarrheagenic characteristics except astA as the etiological agent of the diarrheal outbreak in Mandera. It is however considered necessary to characterize the fluid accumulation factor(s) to determine whether any novel toxins were responsible for the fluid accumulation. Moreover, it is important to study dissemination of strains producing the enterotoxic factor(s) to assess their public health significance distribution in the environment. PMID:27994101

  7. Studying damage accumulation in martensitic corrosion-resistant steel under cold radial reduction

    NASA Astrophysics Data System (ADS)

    Karamyshev, A. P.; Nekrasov, I. I.; Nesterenko, A. V.; Parshin, V. S.; Smirnov, S. V.; Shveikin, V. P.; Fedulov, A. A.

    2017-12-01

    Cold radial reduction of specimens made of the Kh17N2 corrosion-resistant martensitic steel is studied on a lever-type radial-forging machine (RFM). The mechanical properties of the deformed specimens, the "damage accumulation - strain" relation in the specimens are obtained with the application of hydrostatic and fractographic methods for fractured specimens. The damage of the Kh17N2 corrosion-resistant steel is evaluated as a result of an experimental study considering the data of simulation by a complex finite element model of cold deformation on a lever-type RFM.

  8. Comparative proteomic analysis of engineered Saccharomyces cerevisiae with enhanced free fatty acid accumulation.

    PubMed

    Chen, Liwei; Lee, Jaslyn Jie Lin; Zhang, Jianhua; Chen, Wei Ning

    2016-02-01

    The engineered Saccharomyces cerevisiae strain △faa1△faa4 [Acot5s] was demonstrated to accumulate more free fatty acids (FFA) previously. Here, comparative proteomic analysis was performed to get a global overview of metabolic regulation in the strain. Over 500 proteins were identified, and 82 of those proteins were found to change significantly in the engineered strains. Proteins involved in glycolysis, acetate metabolism, fatty acid synthesis, TCA cycle, glyoxylate cycle, the pentose phosphate pathway, respiration, transportation, and stress response were found to be upregulated in △faa1△faa4 [Acot5s] as compared to the wild type. On the other hand, proteins involved in glycerol, ethanol, ergosterol, and cell wall synthesis were downregulated. Taken together with our metabolite analysis, our results showed that the disruption of Faa1 and Faa4 and expression of Acot5s in the engineered strain △faa1△faa4 [Acot5s] not only relieved the feedback inhibition of fatty acyl-CoAs on fatty acid synthesis, but also caused a major metabolic rearrangement. The rearrangement redirected carbon flux toward the pathways which generate the essential substrates and cofactors for fatty acid synthesis, such as acetyl-CoA, ATP, and NADPH. Therefore, our results help shed light on the mechanism for the increased production of fatty acids in the engineered strains, which is useful in providing information for future studies in biofuel production.

  9. Constraint-Based Modeling Highlights Cell Energy, Redox Status and α-Ketoglutarate Availability as Metabolic Drivers for Anthocyanin Accumulation in Grape Cells Under Nitrogen Limitation

    PubMed Central

    Soubeyrand, Eric; Colombié, Sophie; Beauvoit, Bertrand; Dai, Zhanwu; Cluzet, Stéphanie; Hilbert, Ghislaine; Renaud, Christel; Maneta-Peyret, Lilly; Dieuaide-Noubhani, Martine; Mérillon, Jean-Michel; Gibon, Yves; Delrot, Serge; Gomès, Eric

    2018-01-01

    Anthocyanin biosynthesis is regulated by environmental factors (such as light, temperature, and water availability) and nutrient status (such as carbon, nitrogen, and phosphate nutrition). Previous reports show that low nitrogen availability strongly enhances anthocyanin accumulation in non carbon-limited plant organs or cell suspensions. It has been hypothesized that high carbon-to-nitrogen ratio would lead to an energy excess in plant cells, and that an increase in flavonoid pathway metabolic fluxes would act as an “energy escape valve,” helping plant cells to cope with energy and carbon excess. However, this hypothesis has never been tested directly. To this end, we used the grapevine Vitis vinifera L. cultivar Gamay Teinturier (syn. Gamay Freaux or Freaux Tintorier, VIVC #4382) cell suspension line as a model system to study the regulation of anthocyanin accumulation in response to nitrogen supply. The cells were sub-cultured in the presence of either control (25 mM) or low (5 mM) nitrate concentration. Targeted metabolomics and enzyme activity determinations were used to parametrize a constraint-based model describing both the central carbon and nitrogen metabolisms and the flavonoid (phenylpropanoid) pathway connected by the energy (ATP) and reducing power equivalents (NADPH and NADH) cofactors. The flux analysis (2 flux maps generated, for control and low nitrogen in culture medium) clearly showed that in low nitrogen-fed cells all the metabolic fluxes of central metabolism were decreased, whereas fluxes that consume energy and reducing power, were either increased (upper part of glycolysis, shikimate, and flavonoid pathway) or maintained (pentose phosphate pathway). Also, fluxes of flavanone 3β-hydroxylase, flavonol synthase, and anthocyanidin synthase were strongly increased, advocating for a regulation of the flavonoid pathway by alpha-ketoglutarate levels. These results strongly support the hypothesis of anthocyanin biosynthesis acting as an energy

  10. Constraint-Based Modeling Highlights Cell Energy, Redox Status and α-Ketoglutarate Availability as Metabolic Drivers for Anthocyanin Accumulation in Grape Cells Under Nitrogen Limitation.

    PubMed

    Soubeyrand, Eric; Colombié, Sophie; Beauvoit, Bertrand; Dai, Zhanwu; Cluzet, Stéphanie; Hilbert, Ghislaine; Renaud, Christel; Maneta-Peyret, Lilly; Dieuaide-Noubhani, Martine; Mérillon, Jean-Michel; Gibon, Yves; Delrot, Serge; Gomès, Eric

    2018-01-01

    Anthocyanin biosynthesis is regulated by environmental factors (such as light, temperature, and water availability) and nutrient status (such as carbon, nitrogen, and phosphate nutrition). Previous reports show that low nitrogen availability strongly enhances anthocyanin accumulation in non carbon-limited plant organs or cell suspensions. It has been hypothesized that high carbon-to-nitrogen ratio would lead to an energy excess in plant cells, and that an increase in flavonoid pathway metabolic fluxes would act as an "energy escape valve," helping plant cells to cope with energy and carbon excess. However, this hypothesis has never been tested directly. To this end, we used the grapevine Vitis vinifera L. cultivar Gamay Teinturier (syn. Gamay Freaux or Freaux Tintorier, VIVC #4382) cell suspension line as a model system to study the regulation of anthocyanin accumulation in response to nitrogen supply. The cells were sub-cultured in the presence of either control (25 mM) or low (5 mM) nitrate concentration. Targeted metabolomics and enzyme activity determinations were used to parametrize a constraint-based model describing both the central carbon and nitrogen metabolisms and the flavonoid (phenylpropanoid) pathway connected by the energy (ATP) and reducing power equivalents (NADPH and NADH) cofactors. The flux analysis (2 flux maps generated, for control and low nitrogen in culture medium) clearly showed that in low nitrogen-fed cells all the metabolic fluxes of central metabolism were decreased, whereas fluxes that consume energy and reducing power, were either increased (upper part of glycolysis, shikimate, and flavonoid pathway) or maintained (pentose phosphate pathway). Also, fluxes of flavanone 3β-hydroxylase, flavonol synthase, and anthocyanidin synthase were strongly increased, advocating for a regulation of the flavonoid pathway by alpha-ketoglutarate levels. These results strongly support the hypothesis of anthocyanin biosynthesis acting as an energy

  11. Mercury toxicokinetics-dependency on strain and gender

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

    Ekstrand, Jimmy; Nielsen, Jesper B.; Havarinasab, Said

    Mercury (Hg) exposure from dental amalgam fillings and thimerosal in vaccines is not a major health hazard, but adverse health effects cannot be ruled out in a small and more susceptible part of the exposed population. Individual differences in toxicokinetics may explain susceptibility to mercury. Inbred, H-2-congenic A.SW and B10.S mice and their F1- and F2-hybrids were given HgCl{sub 2} with 2.0 mg Hg/L drinking water and traces of {sup 203}Hg. Whole-body retention (WBR) was monitored until steady state after 5 weeks, when the organ Hg content was assessed. Despite similar Hg intake, A.SW males attained a 20-30% significantly highermore » WBR and 2- to 5-fold higher total renal Hg retention/concentration than A.SW females and B10.S mice. A selective renal Hg accumulation but of lower magnitude was seen also in B10.S males compared with females. Differences in WBR and organ Hg accumulation are therefore regulated by non-H-2 genes and gender. Lymph nodes lacked the strain- and gender-dependent Hg accumulation profile of kidney, liver and spleen. After 15 days without Hg A.SW mice showed a 4-fold higher WBR and liver Hg concentration, but 11-fold higher renal Hg concentration, showing the key role for the kidneys in explaining the slower Hg elimination in A.SW mice. The trait causing higher mercury accumulation was not dominantly inherited in the F1 hybrids. F2 mice showed a large inter-individual variation in Hg accumulation, showing that multiple genetic factors influence the Hg toxicokinetics in the mouse. The genetically heterogeneous human population may therefore show a large variation in mercury toxicokinetics.« less

  12. Polyhydroxyalkanoate production from sucrose by Cupriavidus necator strains harboring csc genes from Escherichia coli W.

    PubMed

    Arikawa, Hisashi; Matsumoto, Keiji; Fujiki, Tetsuya

    2017-10-01

    Cupriavidus necator H16 is the most promising bacterium for industrial production of polyhydroxyalkanoates (PHAs) because of their remarkable ability to accumulate them in the cells. With genetic modifications, this bacterium can produce poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx), which has better physical properties, as well as poly(3-hydroxybutyrate) (PHB) using plant oils and sugars as a carbon source. Considering production cost, sucrose is a very attractive raw material because it is inexpensive; however, this bacterium cannot assimilate sucrose. Here, we used the sucrose utilization (csc) genes of Escherichia coli W to generate C. necator strains that can assimilate sucrose. Especially, glucose-utilizing recombinant C. necator strains harboring the sucrose hydrolase gene (cscA) and sucrose permease gene (cscB) of E. coli W grew well on sucrose as a sole carbon source and accumulated PHB. In addition, strains introduced with a crotonyl-CoA reductase gene (ccr), ethylmalonyl-CoA decarboxylase gene (emd), and some other genetic modifications besides the csc genes and the glucose-utilizing mutations produced PHBHHx with a 3-hydroxyhexanoate (3HHx) content of maximum approximately 27 mol% from sucrose. Furthermore, when one of the PHBHHx-producing strains was cultured with sucrose solution in a fed-batch fermentation, PHBHHx with a 3HHx content of approximately 4 mol% was produced and reached 113 g/L for 65 h, which is approximately 1.5-fold higher than that produced using glucose solution.

  13. Spoilage potential of brettanomyces bruxellensis strains isolated from Italian wines.

    PubMed

    Guzzon, Raffaele; Larcher, Roberto; Guarcello, Rosa; Francesca, Nicola; Settanni, Luca; Moschetti, Giancarlo

    2018-03-01

    Brettanomyces bruxellensis is an important wine spoilage agent. In this study a population of Brettanomyces strains isolated from Italian wines was thoroughly investigated to evaluate adaptability to wine conditions and spoilage potential. The presumptive isolates of Brettanomyces were identified at species level with 26S rRNA gene sequencing and species-specific PCR, and subsequently subjected to analysis of intra-species variability through the study of intron splice sites (ISS-PCR). Although, some strains were tracked in wines from different regions, extensive genetic biodiversity was observed within the B. bruxellensis population investigated. All strains were evaluated for their growth ability in the presence of ethanol, high sugar content, low pH, different temperatures and sulphur dioxide, using optical density and flow cytometry measurement. The ability of yeasts to produce ethyl phenols in red wines with different chemical compositions was evaluated by means of high performance liquid chromatography with electrochemical detection (HPLC-ECD). The results highlighted wide variability in B. bruxellensis in response to wine limiting factors and in terms of the accumulation of ethyl phenols. As regards this last aspect, the differences found among strains were closely related to chemical composition of wine and strain resistance to environmental stress factors, making a priori evaluation of risk of wine alteration quite difficult. These results suggest that strategies for the control of Brettanomyces should be tailored on the basis of strain distribution and wine characteristics. Copyright © 2017. Published by Elsevier Ltd.

  14. Multiple layers of temporal and spatial control regulate accumulation of the fruiting body-specific protein APP in Sordaria macrospora and Neurospora crassa.

    PubMed

    Nowrousian, Minou; Piotrowski, Markus; Kück, Ulrich

    2007-07-01

    During fungal fruiting body development, specialized cell types differentiate from vegetative mycelium. We have isolated a protein from the ascomycete Sordaria macrospora that is not present during vegetative growth but accumulates in perithecia. The protein was sequenced by mass spectrometry and the corresponding gene was termed app (abundant perithecial protein). app transcript occurs only after the onset of sexual development; however, the formation of ascospores is not a prerequisite for APP accumulation. The transcript of the Neurospora crassa ortholog is present prior to fertilization, but the protein accumulates only after fertilization. In crosses of N. crassa Deltaapp strains with the wild type, APP accumulates when the wild type serves as female parent, but not in the reciprocal cross; thus, the presence of a functional female app allele is necessary and sufficient for APP accumulation. These findings highlight multiple layers of temporal and spatial control of gene expression during fungal development.

  15. Strain coupling of oxygen non-stoichiometry in perovskite thin films

    NASA Astrophysics Data System (ADS)

    Herklotz, Andreas; Lee, Dongkyu; Guo, Er-Jia; Meyer, Tricia L.; Petrie, Jonathan R.; Lee, Ho Nyung

    2017-12-01

    The effects of strain and oxygen vacancies on perovskite thin films have been studied in great detail over the past decades and have been treated separately from each other. While epitaxial strain has been realized as a tuning knob to tailor the functional properties of correlated oxides, oxygen vacancies are usually regarded as undesirable and detrimental. In transition metal oxides, oxygen defects strongly modify the properties and functionalities via changes in oxidation states of the transition metals. However, such coupling is not well understood in epitaxial films, but rather deemed as cumbersome or experimental artifact. Only recently it has been recognized that lattice strain and oxygen non-stoichiometry are strongly correlated in a vast number of perovskite systems and that this coupling can be beneficial for information and energy technologies. Recent experimental and theoretical studies have focused on understanding the correlated phenomena between strain and oxygen vacancies for a wide range of perovskite systems. These correlations not only include the direct relationship between elastic strain and the formation energy of oxygen vacancies, but also comprise highly complex interactions such as strain-induced phase transitions due to oxygen vacancy ordering. Therefore, we aim in this review to give a comprehensive overview on the coupling between strain and oxygen vacancies in perovskite oxides and point out the potential applications of the emergent functionalities strongly coupled to oxygen vacancies.

  16. Laser speckle technique for burner liner strain measurements

    NASA Technical Reports Server (NTRS)

    Stetson, K. A.

    1982-01-01

    Thermal and mechanical strains were measured on samples of a common material used in jet engine burner liners, which were heated from room temperature to 870 C and cooled back to 220 C, in a laboratory furnance. The physical geometry of the sample surface was recorded at selected temperatures by a set of 12 single exposure speckle-grams. Sequential pairs of specklegrams were compared in a heterodyne interferometer which give high precision measurement of differential displacements. Good speckle correlation between the first and last specklegrams is noted which allows a check on accumulate errors.

  17. Bakken, Three Forks largest continuous US oil accumulation

    USGS Publications Warehouse

    Gaswirth, Stephanie B.; Marra, Kristen R.

    2013-01-01

    The recent reversal of the declining trend of US oil production is largely due to production from unconventional or "continuous" low-permeability reservoirs by use of multistage hydraulic fracturing of horizontal legs of exploration wells. The US currently produces about 7.4 million bo/d, and the increasing trend in domestic production has led to speculation that the US could become energy independent in oil in the near future.The US still imports an additional 11 million bo/d to meet consumption requirements).1 Critical to the discussion of energy independence are estimates of resources contained in low-porosity and low-permeability (or "tight") continuous oil and gas accumulations, which have formed a critical component of national energy policies in recent years.

  18. Monolithic, multi-bandgap, tandem, ultra-thin, strain-counterbalanced, photovoltaic energy converters with optimal subcell bandgaps

    DOEpatents

    Wanlass, Mark W [Golden, CO; Mascarenhas, Angelo [Lakewood, CO

    2012-05-08

    Modeling a monolithic, multi-bandgap, tandem, solar photovoltaic converter or thermophotovoltaic converter by constraining the bandgap value for the bottom subcell to no less than a particular value produces an optimum combination of subcell bandgaps that provide theoretical energy conversion efficiencies nearly as good as unconstrained maximum theoretical conversion efficiency models, but which are more conducive to actual fabrication to achieve such conversion efficiencies than unconstrained model optimum bandgap combinations. Achieving such constrained or unconstrained optimum bandgap combinations includes growth of a graded layer transition from larger lattice constant on the parent substrate to a smaller lattice constant to accommodate higher bandgap upper subcells and at least one graded layer that transitions back to a larger lattice constant to accommodate lower bandgap lower subcells and to counter-strain the epistructure to mitigate epistructure bowing.

  19. Isotropic and anisotropic strain-induced self-assembled oxide nanostructures

    NASA Astrophysics Data System (ADS)

    Gibert, Marta; Abellan, Patricia; Benedetti, Alessandro; Sandiumenge, Felip; Puig, Teresa; Obradors, Xavier

    2009-03-01

    The apparition of new functionalities based on size- and shape-dependent properties requires strategies for the formation of well-defined structures at nanometric scale. We present a bottom-up low-cost chemically-derived methodology based on the control of strain and surface energies anisotropies in CeO2/LAO system to tune the lateral aspect ratio, orientation and kinetics of interfacial oxide nanostructures. Self-organized uniform square-based nanopyramids form under isotropic strain [1]. In contrast, highly elongated nanostructures (long/short axis ˜20) grow induced by biaxial anisotropic strain and anisotropic surface energies. Island's distinct crystallographic orientation is the clue of their differentiated shape, and also influences their distinct evolution. The kinetically-limited coarsening of isotropic nanodots contrasts with the ultrafast kinetics of anisotropic islands. Experimental analyses are based on AFM, TEM, XRD and RHEED, and simulations based on a thermodynamic model enables us to confirm the equilibrium shape of each sort of island's shape in relation to its misfit strain and surface characteristics. [1] Gibert, M. et al., Adv.Materials 19 (22), 3937 (2007).

  20. Ignition Delay Associated with a Strained Strip

    NASA Technical Reports Server (NTRS)

    Gerk, T. J.; Karagozian, A. R.

    1996-01-01

    Ignition processes associated with two adjacent fuel-oxidizer interferences bounding a strained fuel strip are explored here using single-step activation energy asymptotics. Calculations are made for constant as well as temporally decaying strain fields. There possible models of ignition are determined: one in which the two interfaces ignite independently as diffusion flames; one in which the two interfaces ignite dependently and in which ignition occurs to form a single , premixed flame at very high strain rates before ignition is completely prevented. In contrast to a single, isolated interface in which ignition can be prevented by overmatching heat production with heat convection due to strain, ignition of a strained fuel strip can also be prevented if the finite extend of fuel is diluted by oxidizer more quickly than heat production can cause a positive feedback thermal runaway. These behaviors are dependent on the relative sizes of timescales associated with species and heat diffusion, with convection due to strain, and with the chemical reaction. The result here indicate that adjacent, strained species interfaces may ignite quite differently in nature from ignition of a single, strained intrface and that their interdependence should be considered as the interfaces are brought closer together in complex strain fields. Critical strain rates leading to complete ignition delay are found to be considerably smaller for the fuel strip than those for single interfaces as the fuel strip is made thin in comparison to diffusion and chemical length scales.

  1. Role of Prion Replication in the Strain-dependent Brain Regional Distribution of Prions.

    PubMed

    Hu, Ping Ping; Morales, Rodrigo; Duran-Aniotz, Claudia; Moreno-Gonzalez, Ines; Khan, Uffaf; Soto, Claudio

    2016-06-10

    One intriguing feature of prion diseases is their strain variation. Prion strains are differentiated by the clinical consequences they generate in the host, their biochemical properties, and their potential to infect other animal species. The selective targeting of these agents to specific brain structures have been extensively used to characterize prion strains. However, the molecular basis dictating strain-specific neurotropism are still elusive. In this study, isolated brain structures from animals infected with four hamster prion strains (HY, DY, 139H, and SSLOW) were analyzed for their content of protease-resistant PrP(Sc) Our data show that these strains have different profiles of PrP deposition along the brain. These patterns of accumulation, which were independent of regional PrP(C) production, were not reproduced by in vitro replication when different brain regions were used as substrate for the misfolding-amplification reaction. On the contrary, our results show that in vitro replication efficiency depended exclusively on the amount of PrP(C) present in each part of the brain. Our results suggest that the variable regional distribution of PrP(Sc) in distinct strains is not determined by differences on prion formation, but on other factors or cellular pathways. Our findings may contribute to understand the molecular mechanisms of prion pathogenesis and strain diversity. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

  2. 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.

  3. Mercury bioremediation by mercury accumulating Enterobacter sp. cells and its alginate immobilized application.

    PubMed

    Sinha, Arvind; Khare, Sunil Kumar

    2012-02-01

    The effective microbial remediation of the mercury necessitates the mercury to be trapped within the cells without being recycled back to the environment. The study describes a mercury bioaccumulating strain of Enterobacter sp., which remediated mercury from the medium simultaneous to its growth. The transmission electron micrographs and electron dispersive X-ray analysis revealed the accumulation of remediated mercury as nano-size particles in the cytoplasm as well as on the cell wall. The Enterobacter sp. in the present work was able to accumulate mercury, without being engineered in its native form. The possibility of recovering the accumulated mercury from the cells is also indicated. The applicability of the alginate immobilized cells in removing mercury from synthetic and complex industrial effluent in a batch mode was amply demonstrated. The initial load of 7.3 mg l(-1) mercury in the industrial effluent was completely removed in 72 h. The cells immobilized in calcium alginate were similarly effective in the complete removal of 5 mg l(-1) HgCl(2) of mercury from the synthetic effluent in less than 72 h. The immobilized cells could be reused for multiple cycles.

  4. A Food-Grade Cloning System for Industrial Strains of Lactococcus lactis

    PubMed Central

    Sørensen, Kim I.; Larsen, Rasmus; Kibenich, Annette; Junge, Mette P.; Johansen, Eric

    2000-01-01

    We have previously reported the construction of a food-grade cloning vector for Lactococcus using the ochre suppressor, supB, as the selective marker. This vector, pFG1, causes only a slight growth inhibition in the laboratory strain MG1363 but is unstable in the industrial strains tested. As supB suppresses both amber and ochre stop codons, which are present in 82% of all known lactococcal genes, this undesirable finding may result from the accumulation of elongated mistranslated polypeptides. Here, we report the development of a new food-grade cloning vector, pFG200, which is suitable for overexpressing a variety of genes in industrial strains of Lactococcus lactis. The vector uses an amber suppressor, supD, as selectable marker and consists entirely of Lactococcus DNA, with the exception of a small polylinker region. Using suppressible pyrimidine auxotrophs, selection and maintenance are efficient in any pyrimidine-free medium including milk. Importantly, the presence of this vector in a variety of industrial strains has no significant effect on the growth rate or the rate of acidification in milk, making this an ideal system for food-grade modification of industrially relevant L. lactis strains. The usefulness of this system is demonstrated by overexpressing the pepN gene in a number of industrial backgrounds. PMID:10742196

  5. Metabolic Engineering of Synechocystis sp. Strain PCC 6803 for Isobutanol Production

    PubMed Central

    Varman, Arul M.; Xiao, Yi; Pakrasi, Himadri B.

    2013-01-01

    Global warming and decreasing fossil fuel reserves have prompted great interest in the synthesis of advanced biofuels from renewable resources. In an effort to address these concerns, we performed metabolic engineering of the cyanobacterium Synechocystis sp. strain PCC 6803 to develop a strain that can synthesize isobutanol under both autotrophic and mixotrophic conditions. With the expression of two heterologous genes from the Ehrlich pathway, the engineered strain can accumulate 90 mg/liter of isobutanol from 50 mM bicarbonate in a gas-tight shaking flask. The strain does not require any inducer (i.e., isopropyl β-d-1-thiogalactopyranoside [IPTG]) or antibiotics to maintain its isobutanol production. In the presence of glucose, isobutanol synthesis is only moderately promoted (titer = 114 mg/liter). Based on isotopomer analysis, we found that, compared to the wild-type strain, the mutant significantly reduced its glucose utilization and mainly employed autotrophic metabolism for biomass growth and isobutanol production. Since isobutanol is toxic to the cells and may also be degraded photochemically by hydroxyl radicals during the cultivation process, we employed in situ removal of the isobutanol using oleyl alcohol as a solvent trap. This resulted in a final net concentration of 298 mg/liter of isobutanol under mixotrophic culture conditions. PMID:23183979

  6. Effects of Trophic Modes, Carbon Sources, and Salinity on the Cell Growth and Lipid Accumulation of Tropic Ocean Oilgae Strain Desmodesmus sp. WC08.

    PubMed

    Zhao, Zhenyu; Ma, Shasha; Li, Ang; Liu, Pinghuai; Wang, Meng

    2016-10-01

    The effects of trophic modes, carbon sources, and salinity on the growth and lipid accumulation of a marine oilgae Desmodesmus sp. WC08 in different trophic cultures were assayed by single factor experiment based on the blue-green algae medium (BG-11). The results implied that biomass and lipid accumulation culture process were optimized depending on the tophic modes, sorts, and concentration of carbon sources and salinity in the cultivation. There was no significant difference in growth or lipid accumulation with Na 2 CO 3 amendment or NaHCO 3 amendment. However, Na 2 CO 3 amendment did enhance the biomass and lipid accumulation to some extent. The highest Desmodesmus sp. WC08 biomass and lipid accumulation was achieved in the growth medium with photoautotrophic cultivation, 0.08 g L -1 Na 2 CO 3 amendment and 15 g L -1 sea salt, respectively.

  7. Strain-induced friction anisotropy between graphene and molecular liquids

    NASA Astrophysics Data System (ADS)

    Liao, Meng; To, Quy-Dong; Léonard, Céline; Monchiet, Vincent; Vo, Van-Hoang

    2017-01-01

    In this paper, we study the friction behavior of molecular liquids with anisotropically strained graphene. Due to the changes of lattice and the potential energy surface, the friction is orientation dependent and can be computed by tensorial Green-Kubo formula. Simple quantitative estimations are also proposed for the zero-time response and agree reasonably well with the molecular dynamics results. From simulations, we can obtain the information of structures, dynamics of the system, and study the influence of strain and molecular shapes on the anisotropy degree. It is found that unilateral strain can increase friction in all directions but the strain direction is privileged. Numerical evidences also show that nonspherical molecules are more sensitive to strain and give rise to more pronounced anisotropy effects.

  8. Dissolved organic matter reduces algal accumulation of methylmercury

    USGS Publications Warehouse

    Luengen, Allison C.; Fisher, Nicholas S.; Bergamaschi, Brian A.

    2012-01-01

    Dissolved organic matter (DOM) significantly decreased accumulation of methylmercury (MeHg) by the diatom Cyclotella meneghiniana in laboratory experiments. Live diatom cells accumulated two to four times more MeHg than dead cells, indicating that accumulation may be partially an energy-requiring process. Methylmercury enrichment in diatoms relative to ambient water was measured by a volume concentration factor (VCF). Without added DOM, the maximum VCF was 32 x 104, and the average VCF (from 10 to 72 h) over all experiments was 12.6 x 104. At very low (1.5 mg/L) added DOM, VCFs dropped by approximately half. At very high (20 mg/L) added DOM, VCFs dropped 10-fold. Presumably, MeHg was bound to a variety of reduced sulfur sites on the DOM, making it unavailable for uptake. Diatoms accumulated significantly more MeHg when exposed to transphilic DOM extracts than hydrophobic ones. However, algal lysate, a labile type of DOM created by resuspending a marine diatom in freshwater, behaved similarly to a refractory DOM isolate from San Francisco Bay. Addition of 67 μM L-cysteine resulted in the largest drop in VCFs, to 0.28 x 104. Although the DOM composition influenced the availability of MeHg to some extent, total DOM concentration was the most important factor in determining algal bioaccumulation of MeHg.

  9. Energy band-gap calculations of short-period (ZnTe)m(ZnSe)n and (ZnS)m(ZnSe)n strained-layer superlattices

    NASA Astrophysics Data System (ADS)

    Wu, Yi-hong; Fujita, Shizuo; Fujita, Shigeo

    1990-01-01

    We report on the calculations of energy band gaps based on the semiempirical tight-binding model for short-period (ZnTe)m(ZnSe)n and (ZnS)m(ZnSe)n strained-layer superlattices (SLSs). During the calculation, much attention has been paid to the modeling of strain effect. It is found that (ZnTe)m(ZnSe)n superlattices grown on InAs, InP, and GaAs substrates show very different electronic properties from each other, which is consistent with experimental results now available. Assuming that the emission observed for (ZnTe)m(ZnSe)n SLS originates from intrinsic luminescence, we obtain an unstrained valence-band offset of 1.136±0.1 eV for this superlattice. On the other hand, the band gap of (ZnS)m(ZnSe)n superlattice grown coherently on GaP is found to exhibit a much stronger structure dependence than that grown coherently on GaAs. The difference of energy gap between superlattice with equal monolayers (m=n) and the corresponding alloy with equal chalcogenide composition is also discussed.

  10. Regional Greenland accumulation variability from Operation IceBridge airborne accumulation radar

    NASA Astrophysics Data System (ADS)

    Lewis, Gabriel; Osterberg, Erich; Hawley, Robert; Whitmore, Brian; Marshall, Hans Peter; Box, Jason

    2017-03-01

    The mass balance of the Greenland Ice Sheet (GrIS) in a warming climate is of critical interest to scientists and the general public in the context of future sea-level rise. An improved understanding of temporal and spatial variability of snow accumulation will reduce uncertainties in GrIS mass balance models and improve projections of Greenland's contribution to sea-level rise, currently estimated at 0.089 ± 0.03 m by 2100. Here we analyze 25 NASA Operation IceBridge accumulation radar flights totaling > 17 700 km from 2013 to 2014 to determine snow accumulation in the GrIS dry snow and percolation zones over the past 100-300 years. IceBridge accumulation rates are calculated and used to validate accumulation rates from three regional climate models. Averaged over all 25 flights, the RMS difference between the models and IceBridge accumulation is between 0.023 ± 0.019 and 0.043 ± 0.029 m w.e. a-1, although each model shows significantly larger differences from IceBridge accumulation on a regional basis. In the southeast region, for example, the Modèle Atmosphérique Régional (MARv3.5.2) overestimates by an average of 20.89 ± 6.75 % across the drainage basin. Our results indicate that these regional differences between model and IceBridge accumulation are large enough to significantly alter GrIS surface mass balance estimates. Empirical orthogonal function analysis suggests that the first two principal components account for 33 and 19 % of the variance, and correlate with the Atlantic Multidecadal Oscillation (AMO) and wintertime North Atlantic Oscillation (NAO), respectively. Regions that disagree strongest with climate models are those in which we have the fewest IceBridge data points, requiring additional in situ measurements to verify model uncertainties.

  11. Utilization of simultaneous saccharification and fermentation residues as feedstock for lipid accumulation in Rhodococcus opacus.

    PubMed

    Le, Rosemary K; Das, Parthapratim; Mahan, Kristina M; Anderson, Seth A; Wells, Tyrone; Yuan, Joshua S; Ragauskas, Arthur J

    2017-09-29

    Use of oleaginous microorganisms as "micro-factories" for accumulation of single cell oils for biofuel production has increased significantly to mitigate growing energy demands, resulting in efforts to upgrade industrial waste, such as second-generation lignocellulosic residues, into potential feedstocks. Dilute-acid pretreatment (DAP) is commonly used to alter the physicochemical properties of lignocellulosic materials and is typically coupled with simultaneous saccharification and fermentation (SSF) for conversion of sugars into ethanol. The resulting DAP residues are usually processed as a waste stream, e.g. burned for power, but this provides minimal value. Alternatively, these wastes can be utilized as feedstock to generate lipids, which can be converted to biofuel. DAP-SSF residues were generated from pine, poplar, and switchgrass. High performance liquid chromatography revealed less than 0.13% monomeric sugars in the dry residue. Fourier transform infrared spectroscopy was indicative of the presence of lignin and polysaccharides. Gel permeation chromatography suggested the bacterial strains preferred molecules with molecular weight ~ 400-500 g/mol. DAP-SSF residues were used as the sole carbon source for lipid production by Rhodococcus opacus DSM 1069 and PD630 in batch fermentations. Depending on the strain of Rhodococcus employed, 9-11 lipids for PD630 and DSM 1069 were observed, at a final concentration of ~ 15 mg/L fatty acid methyl esters (FAME) detected. Though the DAP-SSF substrate resulted in low FAME titers, novel analysis of solid-state fermentations was investigated, which determined that DAP-SSF residues could be a viable feedstock for lipid generation.

  12. Improving the productivity of S-adenosyl-l-methionine by metabolic engineering in an industrial Saccharomyces cerevisiae strain.

    PubMed

    Zhao, Weijun; Hang, Baojian; Zhu, Xiangcheng; Wang, Ri; Shen, Minjie; Huang, Lei; Xu, Zhinan

    2016-10-20

    S-Adenosyl-l-methionine (SAM) is an important metabolite having prominent roles in treating various diseases. In order to improve the production of SAM, the regulation of three metabolic pathways involved in SAM biosynthesis were investigated in an industrial yeast strain ZJU001. GLC3 encoded glycogen-branching enzyme (GBE), SPE2 encoded SAM decarboxylase, as well as ERG4 and ERG6 encoded key enzymes in ergosterol biosynthesis, were knocked out in ZJU001 accordingly. The results indicated that blocking of either glycogen pathway or SAM decarboxylation pathway could improve the SAM accumulation significantly in ZJU001, while single disruption of either ERG4 or ERG6 gene had no obvious effect on SAM production. Moreover, the double mutant ZJU001-GS with deletion of both GLC3 and SPE2 genes was also constructed, which showed further improvement of SAM accumulation. Finally, SAM2 was overexpressed in ZJU001-GS to give the best SAM-producing recombinant strain ZJU001-GS-SAM2, in which 12.47g/L SAM was produced by following our developed pseudo-exponential fed-batch cultivation strategy, about 81.0% increase comparing to its parent strain ZJU001. The present work laid a solid base for large-scale SAM production with the industrial Saccharomyces cerevisiae strain. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Biotechnological conversion of waste cooking olive oil into lipid-rich biomass using Aspergillus and Penicillium strains.

    PubMed

    Papanikolaou, S; Dimou, A; Fakas, S; Diamantopoulou, P; Philippoussis, A; Galiotou-Panayotou, M; Aggelis, G

    2011-05-01

    In this study, we have investigated the biochemical behaviour of Aspergillus sp. (five strains) and Penicillium expansum (one strain) fungi cultivated on waste cooking olive oil. The production of lipid-rich biomass was the main target of the work. In parallel, the biosynthesis of other extracellular metabolites (organic acids) and enzyme (lipase) and the substrate fatty acid specificity of the strains were studied. Carbon-limited cultures were performed on waste oil, added in the growth medium at 15g l(-1) , and high biomass quantities were produced (up to c.18g l(-1) , conversion yield of c. 1·0 g of dry biomass formed per g of fat consumed or higher). Cellular lipids were accumulated in notable quantities in almost all cultures. Aspergillus sp. ATHUM 3482 accumulated lipid up to 64·0% (w/w) in dry fungal mass. In parallel, extracellular lipase activity was quantified, and it was revealed to be strain and fermentation time dependent, with a maximum quantity of 645 U ml(-1) being obtained by Aspergillus niger NRRL 363. Storage lipid content significantly decreased at the stationary growth phase. Some differences in the fatty acid composition of both cellular and residual lipids when compared with the initial substrate fat used were observed; in various cases, cellular lipids more saturated and enriched with arachidic acid were produced. Aspergillus strains produced oxalic acid up to 5·0 g l(-1) . Aspergillus and Penicillium strains are able to convert waste cooking olive oil into high-added-value products.   Increasing fatty wastes amounts are annually produced. The current study provided an alternative way of biovalourization of these materials, by using them as substrates, to produce added-value compounds. © 2011 The Authors. Journal of Applied Microbiology © 2011 The Society for Applied Microbiology.

  14. Elastic strain budget and inelastic deformation in northeast Japan

    NASA Astrophysics Data System (ADS)

    Sagiya, T.; Meneses Gutierrez, A. D. V.

    2016-12-01

    A degree of magnitude discrepancy between geodetic and geologic strain rates of the Japan islands has been debated for a long time. Ikeda (1996) hypothesized that geodetic strain rate is affected by interseismic locking at the plate interface, which was later supported by the occurrence of the 2011 Tohoku-oki earthquake. The hypothesis also predicts that the interseismic elastic strain must be fully released in association with large earthquakes and do not accumulates in time. However, there has been no such quantitative discussion about the elastic strain budget of the Japan Islands so far. A 261 km-long baseline connecting GEONET stations Ryotsu (950232) and Oshika (960550) runs across the northeast Japan in the E-W direction. The baseline length change shows interseismic contraction at 0.11 ppm/yr before 2011, and coseismic extension of about 20 ppm, which comprises only 200 years of interseismic strain. Geologically the recurrence interval of 2011-type giant earthquakes is estimated as 400-800 years, much longer than a prediction from the elastic strain budget. Menese-Gutierrez and Sagiya (2016) recently identified persistent crustal shortening of 4-10 mm/yr along the Japan Sea coastal area from continuous GPS data. This contribution of inelastic deformation corresponds to 10 30% of the total interseismic shortening. The discrepancy can be also partly resolved by considering the effects of M7-class earthquakes and inelastic deformation of the island arc. M7-class earthquakes such as the 1978 and 2005 Miyagi-oki earthquakes cause 0.05-0.10 cm of baseline extension every about 40 years, releasing about 10 % of the totals strain. In addition, a postseismic extension still continues after 5 years from the main shock. By assuming this postseismic phase continues for about 50-100 years, the total elastic strain budget is balanced for a recurrence interval of about 400 yrs. If we assume a longer recurrence interval, we need additional ingredients such as inelastic

  15. Use of De Novo transcriptome libraries to characterize a novel oleaginous marine Chlorella species during the accumulation of triacylglycerols

    DOE PAGES

    Mansfeldt, Cresten B.; Richter, Lubna V.; Ahner, Beth A.; ...

    2016-02-03

    Here, marine chlorophytes of the genus Chlorella are unicellular algae capable of accumulating a high proportion of cellular lipids that can be used for biodiesel production. In this study, we examined the broad physiological capabilities of a subtropical strain (C596) of Chlorella sp. “SAG-211-18” including its heterotrophic growth and tolerance to low salt.We found that the alga replicates more slowly at diluted salt concentrations and can grow on a wide range of carbon substrates in the dark.We then sequenced the RNA of Chlorella strain C596 to elucidate key metabolic genes and investigate the transcriptomic response of the organism when transitioningmore » from a nutrient-replete to a nutrient-deficient condition when neutral lipids accumulate. Specific transcripts encoding for enzymes involved in both starch and lipid biosynthesis, among others, were up-regulated as the cultures transitioned into a lipid-accumulating state whereas photosynthesis-related genes were down-regulated. Transcripts encoding for two of the up-regulated enzymes—a galactoglycerolipid lipase and a diacylglyceride acyltransferase—were also monitored by reverse transcription quantitative polymerase chain reaction assays. The results of these assays confirmed the transcriptome-sequencing data. The present transcriptomic study will assist in the greater understanding, more effective application, and efficient design of Chlorella-based biofuel production systems.« less

  16. Insights into accumulation variability over the last 2000 years at James Ross Island, Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Massam, A.; Mulvaney, R.; McConnell, J.; Abram, N.; Arienzo, M. M.; Whitehouse, P. L.

    2016-12-01

    The James Ross Island ice core, drilled to 364 m on the northern tip of the Antarctic Peninsula, preserves a climate record that spans beyond the Holocene period to the end of the last glacial maximum (LGM). Reanalysis of the ice core using high-resolution continuous flow analysis (CFA) highlighted errors in the identification of events of known age that had been used to constrain the earlier chronology. The new JRI2 chronology is annual layer counted to 300 years, with the remaining profile reconstructed using a new age-depth model that is tied to age horizons identified in the annual-layer counted WAIS Divide ice core record. An accurate age-depth profile requires reliable known-age horizons along the ice core profile. In addition, these allow us to determine a solution for the accumulation history and rate of compaction due to vertical strain. The accuracy of the known-age constraints used in JRI2 allows only a small uncertainty in the reconstruction of the most recent 2000 years of accumulation variability. Independently, the surface temperature profile has been estimated from the stable water isotope profile and calibrated to borehole temperature observations. We present the accumulation, vertical thinning and temperature history interpreted from the James Ross Island ice core for the most recent 2000 years. JRI2 reconstructions show accumulation variability on a decadal to centennial timescale up to 20% from the present-day mean annual accumulation rate of 0.63 m yr-1. Analysis of the accumulation profile for James Ross Island offers insight into the sensitivity of accumulation to a change in surface temperature, as well as the reliability of the assumed relationship between accumulation and surface temperature in climate reconstructions using stable water isotope proxies.

  17. Accumulation and subsequent utilization of waste heat

    NASA Astrophysics Data System (ADS)

    Koloničný, Jan; Richter, Aleš; Pavloková, Petra

    2016-06-01

    This article aims to introduce a special way of heat accumulation and primary operating characteristics. It is the unique way in which the waste heat from flue gas of biogas cogeneration station is stored in the system of storage tanks, into the heat transfer oil. Heat is subsequently transformed into water, from which is generated the low-pressure steam. Steam, at the time of peak electricity needs, spins the special designed turbine generator and produces electrical energy.

  18. Microstructural Evolution of Al-1Fe (Weight Percent) Alloy During Accumulative Continuous Extrusion Forming

    NASA Astrophysics Data System (ADS)

    Wang, Xiang; Guan, Ren-Guo; Tie, Di; Shang, Ying-Qiu; Jin, Hong-Mei; Li, Hong-Chao

    2018-04-01

    As a new microstructure refining method, accumulative continuous extrusion forming (ACEF) cannot only refine metal matrix but also refine the phases that exist in it. In order to detect the refinements of grain and second phase during the process, Al-1Fe (wt pct) alloy was processed by ACEF, and the microstructural evolution was analyzed by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Results revealed that the average grain size of Al-1Fe (wt pct) alloy decreased from 13 to 1.2 μm, and blocky Al3Fe phase with an average length of 300 nm was granulated to Al3Fe particle with an average diameter of 200 nm, after one pass of ACEF. Refinement of grain was attributed to continuous dynamic recrystallization (CDRX), and the granulation of Al3Fe phase included the spheroidization resulting from deformation heat and the fragmentation caused by the coupling effects of strain and thermal effect. The spheroidization worked in almost the entire deformation process, while the fragmentation required strain accumulation. However, fragmentation contributed more than spheroidization. Al3Fe particle stimulated the formation of substructure and retarded the migration of recrystallized grain boundary, but the effect of Al3Fe phase on refinement of grain could only be determined by the contrastive investigation of Al-1Fe (wt pct) alloy and pure Al.

  19. Static Strain Aging Behavior of a Manganese-Silicon Steel After Single and Multi-stage Straining

    NASA Astrophysics Data System (ADS)

    Seraj, P.; Serajzadeh, S.

    2016-03-01

    In this work, static strain aging behavior of an alloy steel containing high amounts of silicon and manganese was examined while the influences of initial microstructure and pre-strain on the aging kinetics were evaluated as well. The rate of strain aging in a low carbon steel was also determined and compared with that occurred in the alloy steel. The rates of static strain aging in the steels were defined at room temperature and at 95 °C by means of double-hit tensile testing and hardness measurements. In addition, three-stage aging experiments at 80 °C were carried out to estimate aging behavior under multi-pass deformation processing. The results showed that in-solution manganese and silicon atoms could significantly affect the aging behavior of the steel and reduce the kinetics of static strain aging as compared to the low carbon steel. The initial microstructure also played an important role on the aging behavior. The rapidly cooled steel having mean ferrite grain size of 9.7 μm showed the least aging susceptibility index during the aging experiments. Accordingly, the activation energies for static strain aging were calculated as 93.2 and 85.7 kJ/mole for the alloy steel having fine and coarse ferrite-pearlite structures, respectively while it was computed as 79.1 kJ/mole for the low carbon steel with ferrite mean grain size of about 16.2 μm.

  20. Strained Cyclophane Macrocycles: Impact of Progressive Ring Size Reduction on Synthesis and Structure

    PubMed Central

    Bogdan, Andrew R.; Jerome, Steven V.; Houk, K. N.; James, Keith

    2012-01-01

    The synthesis, X-ray crystal structures, and calculated strain energies are reported for a homologous series of 11- to 14-membered drug-like cyclophane macrocycles, representing an unusual region of chemical space that can be difficult to access synthetically. The ratio of macrocycle to dimer, generated via a copper catalyzed azide-alkyne cycloaddition macrocyclization in flow at elevated temperature, could be rationalized in terms of the strain energy in the macrocyclic product. The progressive increase in strain resulting from reduction in macrocycle ring size, or the introduction of additional conformational constraints, results in marked deviations from typical geometries. These strained cyclophane macrocyclic systems provide access to spatial orientations of functionality that would not be readily available in unstrained or acyclic analogs. The most strained system prepared represents the first report of an 11-membered cyclophane containing a 1,4-disubstituted 1,2,3-triazole ring, and establishes a limit to the ring strain that can be generated using this macrocycle synthesis methodology. PMID:22133103