Relation between academic yield and stress in medical students

Directory of Open Access Journals (Sweden)

Sandra Patricia González Peña

2006-12-01

Full Text Available Objective. To study risk factors that where found as influence in the academic yield (stress, alcohol, friendships, depression and family relations in the students of the Medicine Faculty of the Universidad de Manizales. Materials and methods: Descriptive study integrated by random selected sample, who were attending of II to XI semester of the Medicine faculty. An anonymous survey was conduced about sociodemographic, cultural, academic and motivational characteristics,including stress, depresión, family disfunction and substance abuse. We correlated all variables with academic yield using chi square test, Pearson`s coefficient and lineal regression. Results: 212 students of ages between 17 and 31 years where analyzed, in which the majority where from another city. Some of the factors were detected which affect the academic yield of the students as it is stress, depression, the family function and friendships among others. Conclusions: A significant relation between academic yield and stress was found. In turn, stress variable was influenced by depression, alcohol and family relation.

Yield stress determines bioprintability of hydrogels based on gelatin-methacryloyl and gellan gum for cartilage bioprinting

Science.gov (United States)

Mouser, Vivian H. M.; Melchels, Ferry P.W.; Visser, Jetze; Dhert, Wouter J.A.; Gawlitta, Debby; Malda, Jos

2016-01-01

Bioprinting of chondrocyte-laden hydrogels facilitates the fabrication of constructs with controlled organization and shape for e.g. articular cartilage implants. Gelatin-methacryloyl (gelMA) supplemented with gellan gum is a promising bio-ink. However, the rheological properties governing the printing process, and the influence of gellan gum on the mechanical properties and chondrogenesis of the blend, are still unknown. Here, we investigated the suitability of gelMA/gellan for cartilage bioprinting. Multiple concentrations, ranging from 3-25% gelMA with 0-1.5% gellan gum, were evaluated for their printability, defined as the ability to form filaments and to incorporate cells at 15-37°C. To support the printability assessment, yield stress and viscosity of the hydrogels were measured. Stiffness of UV-cured constructs, as well as cartilage-like tissue formation by embedded chondrocytes, were determined in vitro. A large range of gelMA/gellan concentrations were printable with inclusion of cells and formed the bioprinting window. Addition of gellan gum improved filament deposition by inducing yielding behavior, increased construct stiffness, and supported chondrogenesis. High gellan gum concentrations, however, did compromise cartilage matrix production and distribution, and even higher concentrations resulted in too high yield stresses to allow cell encapsulation. This study demonstrates the high potential of gelMA/gellan blends for cartilage bioprinting and identifies yield stress as dominant factor for bioprintability. PMID:27431733

Yield stress determines bioprintability of hydrogels based on gelatin-methacryloyl and gellan gum for cartilage bioprinting.

Science.gov (United States)

Mouser, Vivian H M; Melchels, Ferry P W; Visser, Jetze; Dhert, Wouter J A; Gawlitta, Debby; Malda, Jos

2016-07-19

Bioprinting of chondrocyte-laden hydrogels facilitates the fabrication of constructs with controlled organization and shape e.g. for articular cartilage implants. Gelatin-methacryloyl (gelMA) supplemented with gellan gum is a promising bio-ink. However, the rheological properties governing the printing process, and the influence of gellan gum on the mechanical properties and chondrogenesis of the blend, are still unknown. Here, we investigated the suitability of gelMA/gellan for cartilage bioprinting. Multiple concentrations, ranging from 3% to 20% gelMA with 0%-1.5% gellan gum, were evaluated for their printability, defined as the ability to form filaments and to incorporate cells at 15 °C-37 °C. To support the printability assessment, yield stress and viscosity of the hydrogels were measured. Stiffness of UV-cured constructs, as well as cartilage-like tissue formation by embedded chondrocytes, were determined in vitro. A large range of gelMA/gellan concentrations were printable with inclusion of cells and formed the bioprinting window. The addition of gellan gum improved filament deposition by inducing yielding behavior, increased construct stiffness and supported chondrogenesis. High gellan gum concentrations, however, did compromise cartilage matrix production and distribution, and even higher concentrations resulted in too high yield stresses to allow cell encapsulation. This study demonstrates the high potential of gelMA/gellan blends for cartilage bioprinting and identifies yield stress as a dominant factor for bioprintability.

Physiological basis of barley yield under near optimal and stress conditions

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Pržulj Novo

2004-01-01

Full Text Available Average barley yield fall below its potential due to incidence of stresses. Water stress is the main environmental factor limiting yield. The component a priori more sensitive to most stresses is the amount of radiation absorbed. The effect of stresses influence on the total amount of radiation absorbed by barley crop during its vegetation and the photosynthetic efficiency of radiation conversion. Growth inhibition is accompanied by reductions in leaf and cell wall extensibility. Grain yield under drought conditions is source limited. Supply of assimilates to the developing inflorescence plays a critical role in establishing final grain number and grain size. Grain weight is negatively affected by drought, high temperature, and any other factors that may reduce grain filling duration and grain filling rate. Awns and glaucousness confer better performance of barley under drought stress conditions. Barley responds with an increased accumulation of a number of proteins when subjected to different stress inducing cell dehydration. Screening techniques that are able to identify desirable genotypes based on the evaluation of physiological traits related to stress evasion and stress resistance maybe useful in breeding barley for resistance to stress, particularly drought stress. Crop management and breeding can reduce the incidence of stress on yield. The effect of these practices is sustained by an understanding of their physiology. In this paper the physiological basis of the processes determining barley yield and the incidence of stresses on photosynthetic metabolism that determine grain yield of barley is discussed. .

Particle debonding using different yield criteria

DEFF Research Database (Denmark)

Legarth, Brian Nyvang; Kuroda, Mitsutoshi

2004-01-01

Effects of plastic anisotropy in relation to debonding of rigid inclusions embedded in an elastic-viscoplastic metal are studied. Full finite strain analyses are carried out for plane cells assuming plane stress or plane strain. The overall stress strain response is calculated, when the cell......-matrix debonding. Keeping all material parameters fixed, the material response of the plane strain cell is considerably affected, due to debonding at a much reduced overall plastic strain compared to the corresponding plane stress cell. (C) 2004 Elsevier SAS. All rights reserved....... extent and shape of the particular yield function considered. The required overall straining of the cell for debonding initiation is related to the extent of the yield surfaces, since a high yield stress promotes debonding. Additionally, the maximum overall stress level for the cell is lower for the Hill...

Yielding to stress: Recent developments in viscoplastic fluid mechanics

OpenAIRE

BALMFORTH, Neil; FRIGAARD, Ian A.; OVARLEZ, Guillaume

2014-01-01

The archetypal feature of a viscoplastic fluid is its yield stress: If the material is not sufficiently stressed, it behaves like a solid, but once the yield stress is exceeded, the material flows like a fluid. Such behavior characterizes materials common in industries such as petroleum and chemical processing, cosmetics, and food processing and in geophysical fluid dynamics. The most common idealization of a viscoplastic fluid is the Bingham model, which has been widely used to rationalize e...

Al-matrix composite materials reinforced by Al-Cu-Fe particles

International Nuclear Information System (INIS)

Bonneville, J; Laplanche, G; Joulain, A; Gauthier-Brunet, V; Dubois, S

2010-01-01

Al-matrix material composites were produced using hot isostatic pressing technique, starting with pure Al and icosahedral (i) Al-Cu-Fe powders. Depending on the processing temperature, the final reinforcement particles are either still of the initial i-phase or transformed into the tetragonal ω-Al0 0.70 Cu 0.20 Fe 0.10 crystalline phase. Compression tests performed in the temperature range 293K - 823K on the two types of composite, i.e. Al/i and Al/ω, indicate that the flow stress of both composites is strongly temperature dependent and exhibit distinct regimes with increasing temperature. Differences exist between the two composites, in particular in yield stress values. In the low temperature regime (T ≤ 570K), the yield stress of the Al/ω composite is nearly 75% higher than that of the Al/i composite, while for T > 570K both composites exhibit similar yield stress values. The results are interpreted in terms of load transfer contribution between the matrix and the reinforcement particles and elementary dislocation mechanisms in the Al matrix.

A new coal-permeability model: Internal swelling stress and fracture-matrix interaction

Energy Technology Data Exchange (ETDEWEB)

Liu, H.H.; Rutqvist, J.

2009-10-01

We have developed a new coal-permeability model for uniaxial strain and constant confining stress conditions. The model is unique in that it explicitly considers fracture-matrix interaction during coal deformation processes and is based on a newly proposed internal-swelling stress concept. This concept is used to account for the impact of matrix swelling (or shrinkage) on fracture-aperture changes resulting from partial separation of matrix blocks by fractures that do not completely cut through the whole matrix. The proposed permeability model is evaluated with data from three Valencia Canyon coalbed wells in the San Juan Basin, where increased permeability has been observed during CH{sub 4} gas production, as well as with published data from laboratory tests. Model results are generally in good agreement with observed permeability changes. The importance of fracture-matrix interaction in determining coal permeability, demonstrated in this work using relatively simple stress conditions, underscores the need for a dual-continuum (fracture and matrix) mechanical approach to rigorously capture coal-deformation processes under complex stress conditions, as well as the coupled flow and transport processes in coal seams.

Evaluating Yield and Drought Stress Indices under End Season Drought Stress in Promising Genotypes of Barley

Directory of Open Access Journals (Sweden)

H. Tajalli

2012-08-01

Full Text Available To study the effects of end season drought stress on yield, yield components and drought stress indices in barley, a split plot experiment arranged in randomized complete block design with three replications was conducted at the Agricultural Research Center of Birjand in 2008-2009 crop years. Drought stress, in 2 levels, consists of control (complete irrigation and stopping irrigation at the 50% of heading stage, and 20 promising genotypes of barley were the treatments of the experiment. Results revealed that stopping irrigation lead to declining of 14.64 and 8.12 percent of seed and forage yields against control condition, respectively. Using stress susceptibility index (SSI indicated that genotypes 2, 3, 7, 9, 10 and 15; using STI and GMP indices, genotypes 5, 8, 18 and 20 using MP, genotypes 8, 18 and 20, and TOL, genotypes 2, 3, 7, 9, and 10, were the most drought tolerant genotypes. Correlation between seed yield and stress evaluation indices showed that MP, GMP and STI are the best indices to be used in selection and introducing drought tolerant genotypes of barley. Considering all indices, and given that the best genotypes are those with high yield under normal condition and minimum yield reduction under drought stress, No. 18 and 20 could be introduced as the most tolerant barley genotypes to drought.

Effect of Drought Stress at Different Growth Stages on Yield and Yield Components of Six Rice (Oryza sativa L. Genotypes

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Sharifunnessa Moonmoon

2017-12-01

Full Text Available Drought stress affects plant growth and development and ultimately, reduced grain yield of rice. But stress at different growth stages may respond differently which is still unclear. Therefore, a pot experiment was carried out with six rice genotypes to determine the critical growth stage where drought stress effect on yield reduction and to find stress tolerance mechanism in rice genotypes. Drought stress (control i.e. no stress and 40% field capacity, FC was imposed on Binadhan-13, Kalizira, BRRI dhan34, Ukunimodhu, RM-100-16 and NERICA mutant rice genotypes at maximum tillering, panicle initiation and grain filling stages and discontinued when the specific stage was over. The experiment was laid out in a complete randomized design with three replications. Drought stress affected number of effective tiller hill-1, number of spikelets panicle-1, filled grains hill-1, 1000-grain weight and grain yield. Binadhan-13 produced the highest grain yield and the lowest sterility under drought stress at grain filling stage. Percentage of spikelet sterility increased under drought stress (40% FC especially at the panicle initiation stage resulting low grain yield. Among the tested genotypes Binadhan-13 performed well by reducing spikelet sterility under drought stress condition. For 1000-grain weight and grain yield, grain filling stage was found more crucial. From the current research, drought tolerance mechanism was found in genotypes Binadhan-13 and NERICA mutant. [Fundam Appl Agric 2017; 2(3.000: 285-289

On a new method to determine the yield stress in lubricating grease

NARCIS (Netherlands)

Cyriac, F.; Lugt, Pieter Martin; Bosman, Rob

2015-01-01

An experimental study using both a controlled stress and a controlled strain rheometer has been undertaken to characterize lubricating grease in shear, creep, stress relaxation, and oscillatory flow, with a main focus on determining the yield stress. The yield stress was examined using a cone–plate

Analysis of the static yield stress for giant electrorheological fluids

Science.gov (United States)

Seo, Youngwook P.; Choi, Hyoung Jin; Seo, Yongsok

2017-08-01

Cheng et al. (2010)'s experimental results for the static yield stress of giant electrorheological (GER) fluids over the full range of electric field strengths were reanalyzed by applying Seo's scaling function which could include both the polarization and the conductivity models. The Seo's scaling function could correctly fit the yield stress behavior of GER suspensions behavior after if a proper normalization of the yield stress data was taken which collapse them onto a single curve. The model predictions were also contrasted with recently proposed Choi et al.'s scaling function to rouse the attention for a proper consideration of the GER fluid mechanisms.

Genotypic Correlation and Path Analysis of Some Traits related to Oil Yield and Grain Yield in Canola (Brassica napus L. under Non-stress and Water Deficit Stress Conditions

Directory of Open Access Journals (Sweden)

A Ismaili

2017-03-01

Full Text Available Introduction Obtaining varieties with acceptable yield and tolerant to different arid and semi-arid climate condition of Iran is an important goal in canola breeding programs. Selection of genotypes base on one or more traits without regarding to correlation between them, could biases the expected results. Therefore, identifying of genetic correlation among traits especially in environmental stress condition is very important. The use of genotypic correlation helps evaluating the magnitude and direction of associations between characters facilitating the application of indirect selection, because genetic changes in a given trait may change other traits, leading to faster and larger genetic gains in plant breeding programs. Therefore, the selection for another trait may result in indirect response in the low heritable trait, provided the following conditions are satisfied: the genetic correlation between them is substantial, and the heritability of the secondary trait is greater than that of the primary trait. The purpose of this study was estimating the total genotypic variability, genotypic correlations, and path analysis among some important traits for selection criteria for improving seed and oil yield in canola under water deficit stress condition. Materials and Methods For evaluation of genetic correlation among traits and identifying important affecting traits on grain yield and oil yield in canola genotypes, an experiment was conducted based on a randomized complete blocks design with three replications in two different conditions of water deficit (stress and non-stress. Different traits were measured including seed yield, 1000-seed weight, number of seeds per pod, number of pods per plant, silique length, oil content, days to maturity, protein content, plant height and water use efficiency. Genotypic and phenotypic correlation coefficients were calculated for ten characters during growing seasons. The genotypic correlation coefficients

Yielding to Stress: Recent Developments in Viscoplastic Fluid Mechanics

Science.gov (United States)

Balmforth, Neil J.; Frigaard, Ian A.; Ovarlez, Guillaume

2014-01-01

The archetypal feature of a viscoplastic fluid is its yield stress: If the material is not sufficiently stressed, it behaves like a solid, but once the yield stress is exceeded, the material flows like a fluid. Such behavior characterizes materials common in industries such as petroleum and chemical processing, cosmetics, and food processing and in geophysical fluid dynamics. The most common idealization of a viscoplastic fluid is the Bingham model, which has been widely used to rationalize experimental data, even though it is a crude oversimplification of true rheological behavior. The popularity of the model is in its apparent simplicity. Despite this, the sudden transition between solid-like behavior and flow introduces significant complications into the dynamics, which, as a result, has resisted much analysis. Over recent decades, theoretical developments, both analytical and computational, have provided a better understanding of the effect of the yield stress. Simultaneously, greater insight into the material behavior of real fluids has been afforded by advances in rheometry. These developments have primed us for a better understanding of the various applications in the natural and engineering sciences.

Yield shear stress model of magnetorheological fluids based on exponential distribution

International Nuclear Information System (INIS)

Guo, Chu-wen; Chen, Fei; Meng, Qing-rui; Dong, Zi-xin

2014-01-01

The magnetic chain model that considers the interaction between particles and the external magnetic field in a magnetorheological fluid has been widely accepted. Based on the chain model, a yield shear stress model of magnetorheological fluids was proposed by introducing the exponential distribution to describe the distribution of angles between the direction of magnetic field and the chain formed by magnetic particles. The main influencing factors were considered in the model, such as magnetic flux density, intensity of magnetic field, particle size, volume fraction of particles, the angle of magnetic chain, and so on. The effect of magnetic flux density on the yield shear stress was discussed. The yield stress of aqueous Fe 3 O 4 magnetreological fluids with volume fraction of 7.6% and 16.2% were measured by a device designed by ourselves. The results indicate that the proposed model can be used for calculation of yield shear stress with acceptable errors. - Highlights: • A yield shear stress model of magnetorheological fluids was proposed. • Use exponential distribution to describe the distribution of magnetic chain angles. • Experimental and predicted results were in good agreement for 2 types of MR

Modified stress intensity factor as a crack growth parameter applicable under large scale yielding conditions

International Nuclear Information System (INIS)

Yasuoka, Tetsuo; Mizutani, Yoshihiro; Todoroki, Akira

2014-01-01

High-temperature water stress corrosion cracking has high tensile stress sensitivity, and its growth rate has been evaluated using the stress intensity factor, which is a linear fracture mechanics parameter. Stress corrosion cracking mainly occurs and propagates around welded metals or heat-affected zones. These regions have complex residual stress distributions and yield strength distributions because of input heat effects. The authors previously reported that the stress intensity factor becomes inapplicable when steep residual stress distributions or yield strength distributions occur along the crack propagation path, because small-scale yielding conditions deviate around those distributions. Here, when the stress intensity factor is modified by considering these distributions, the modified stress intensity factor may be used for crack growth evaluation for large-scale yielding. The authors previously proposed a modified stress intensity factor incorporating the stress distribution or yield strength distribution in front of the crack using the rate of change of stress intensity factor and yield strength. However, the applicable range of modified stress intensity factor for large-scale yielding was not clarified. In this study, the range was analytically investigated by comparison with the J-integral solution. A three-point bending specimen with parallel surface crack was adopted as the analytical model and the stress intensity factor, modified stress intensity factor and equivalent stress intensity factor derived from the J-integral were calculated and compared under large-scale yielding conditions. The modified stress intensity was closer to the equivalent stress intensity factor when compared with the stress intensity factor. If deviation from the J-integral solution is acceptable up to 2%, the modified stress intensity factor is applicable up to 30% of the J-integral limit, while the stress intensity factor is applicable up to 10%. These results showed that

Efficient Return Algorithms For Associated Plasticity With Multiple Yield Planes

DEFF Research Database (Denmark)

Clausen, Johan Christian; Damkilde, Lars; Andersen, Lars

2006-01-01

of such criteria. The return formulae are in closed form and no iteration is required. The method accounts for three types of stress return: Return to a single yield plane, to a discontinuity line at the intersection of two yield planes and to a discontinuity point at the intersection between three or more yield...... planes. The infinitesimal and the consistent elastoplastic constitutive matrix are calculated for each type of stress return, as are the conditions to ascertain which type of return is required. The method is exemplified with the Mohr-Coulomb yield criterion....

Post-heading heat stress and yield impact in winter wheat of China.

Science.gov (United States)

Liu, Bing; Liu, Leilei; Tian, Liying; Cao, Weixing; Zhu, Yan; Asseng, Senthold

2014-02-01

Wheat is sensitive to high temperatures, but the spatial and temporal variability of high temperature and its impact on yield are often not known. An analysis of historical climate and yield data was undertaken to characterize the spatial and temporal variability of heat stress between heading and maturity and its impact on wheat grain yield in China. Several heat stress indices were developed to quantify heat intensity, frequency, and duration between heading and maturity based on measured maximum temperature records of the last 50 years from 166 stations in the main wheat-growing region of China. Surprisingly, heat stress between heading and maturity was more severe in the generally cooler northern wheat-growing regions than the generally warmer southern regions of China, because of the delayed time of heading with low temperatures during the earlier growing season and the exposure of the post-heading phase into the warmer part of the year. Heat stress between heading and maturity has increased in the last decades in most of the main winter wheat production areas of China, but the rate was higher in the south than in the north. The correlation between measured grain yields and post-heading heat stress and average temperature were statistically significant in the entire wheat-producing region, and explained about 29% of the observed spatial and temporal yield variability. A heat stress index considering the duration and intensity of heat between heading and maturity was required to describe the correlation of heat stress and yield variability. Because heat stress is a major cause of yield loss and the number of heat events is projected to increase in the future, quantifying the future impact of heat stress on wheat production and developing appropriate adaptation and mitigation strategies are critical for developing food security policies in China and elsewhere. © 2013 John Wiley & Sons Ltd.

Evaluation of Relationship Between Auxin and Cytokinine Hormones on Yield and Yield Components of Maize under Drought Stress Condition

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A Mahrokh

2016-10-01

Full Text Available Introduction Drought is one of the major environmental conditions that adversely affects plant growth and crop yield. In the face of a global scarcity of water resources, water stress has already become a primary factor in limiting crop production worldwide. Drought is the major restriction in maize production. The plant growth reduction under drought stress conditions could be an outcome of altered hormonal balance and hence the exogenous application of growth regulators under stress conditions could be the possible means for reversing the effects of abiotic stress. Phytohormones such as auxine and cytokinine are known to be involved in the regulation of plant response to the adverse effects of stress conditions. Previous studies have shown that endogenous hormones are essential regulators for translocation and partitioning of photoassimilates for grain filling in cereal crops, and therefore could be involved in the regulation of grain weight and yield. Materials and Methods The experiment was carried out in three separately environments included non-drought stress environment (irrigation after soil moisture reached to 75% field capacity, drought stress in vegetative stage (irrigation after soil moisture reached to 50% field capacity in V4 to tasseling stage, but irrigation after soil moisture reached to 75% field capacity in pollination to physiological maturity stage and drought stress in reproductive stage (irrigation after soil moisture reached to 75% field capacity in V4 to tasseling stage and irrigation after soil moisture reached to 50% field capacity in pollination to physiological maturity stage. Cytokinin hormone in three levels (control, spraying in V5 –V6 and V8-V10 stages and auxin hormone in three levels (control, spraying in silk emergence stage and 15 days after that were laid out as a factorial design based on randomized complete block with three replications in each environment at Seed and Plant Improvement Institute (SPII

Microstructure, Slip Systems and Yield Stress Anisotropy in Plastic Deformation

DEFF Research Database (Denmark)

Winther, Grethe; You, Ze Sheng; Lu, Lei

The highly anisotropic microstructures in nanotwinned copper produced by electrodeposition provide an excellent opportunity to evaluate models for microstructurally induced mechanical anisotropy. A crystal plasticity model originally developed for the integration of deformation induced dislocatio...... boundaries with texture is applied to account for the effects of texture as well as twin and grain boundaries, providing good qualitative agreement with experimental yield stress and yield stress anisotropy data....

Effect of moisture stress and low phosphorus on yield of some ...

African Journals Online (AJOL)

Soybean genotypes belonging to different maturity periods were planted under normal, nutrient (P) and moisture stress conditions in a combined design with three replications. The objective was to determine the effect of phosphorus and moisture stress on yield and yield components of soybean in order to select varieties ...

Crop yield response to water stress imposed at different growth stages

International Nuclear Information System (INIS)

Iqbal, M.; Mahmood Shah, M.; Wisal, M.

1995-01-01

Potato requires sufficient soil moisture and fertilization to produce high yields but the present water resoures are limited compared to the cultivable land, field experiments were conduced from 1991 to 1995 to study relationship between yield and crop water use as a function of water stress imposed at different growth stages. The irrigation treatments involved application of full and stress watering s selectively at four growth stages : Establishment , Flowering Tuber formation and ripening. In full watering, full water requirements of the crop were met, i.e., ET sub a = ET sub m whereas in stress watering about half the amount of full watering was applied, i.e., ET sub a < ET sub m. Changes in moisture content of the soil pre files after irrigation were monitored with the help of neutron moisture probe in order to compute ET sub a by the water balance method. The results obtained showed that the tuber yield was produced by full watering ( T 1) and the lowest by continuous stress watering (T 2). A plot of relative yield against relative evapotranspiration deficit revealed that ripening was the lest sensitive whereas early development followed by flowering the most sensitive growth stage to water stress. The crop water use efficiencies were generally higher in the treatments where a combination of normal and stress watering was applied compared to where all - normal watering s were applied. The traditional irrigation practice resulted in wasteful water application with relatively lower yields, hence the results from this project will have high value for the farming community to get this higher yields with scarce water resources. The studies with labelled fertilizer showed that planting and earthing - up were equally important growth stages of potato for applying fertilizer for its efficient utilization. 3 figs; 25 tabs; 12 refs (Author)

An analytical solution describing the shape of a yield stress material subjected to an overpressure

DEFF Research Database (Denmark)

Hovad, Emil; Spangenberg, Jon; Larsen, P.

2016-01-01

as well as the spread length and height of the material when deformed in a box due to gravity. In the present work, the analytical solution is extended with the addition of an overpressure that acts over the entire body of the material. This extension enables finding the shape of a yield stress material......Many fluids and granular materials are able to withstand a limited shear stress without flowing. These materials are known as yields stress materials. Previously, an analytical solution was presented to quantify the yield stress for such materials. The yields stress is obtained based on the density...... with known density and yield stress when for instance deformed under water or subjected to a forced air pressure....

An investigation on the mechanism of sublimed DHB matrix on molecular ion yields in SIMS imaging of brain tissue.

Science.gov (United States)

Dowlatshahi Pour, Masoumeh; Malmberg, Per; Ewing, Andrew

2016-05-01

We have characterized the use of sublimation to deposit matrix-assisted laser desorption/ionization (MALDI) matrices in secondary ion mass spectrometry (SIMS) analysis, i.e. matrix-enhanced SIMS (ME-SIMS), a common surface modification method to enhance sensitivity for larger molecules and to increase the production of intact molecular ions. We use sublimation to apply a thin layer of a conventional MALDI matrix, 2,5-dihydroxybenzoic acid (DHB), onto rat brain cerebellum tissue to show how this technique can be used to enhance molecular yields in SIMS while still retaining a lateral resolution around 2 μm and also to investigate the mechanism of this enhancement. The results here illustrate that cholesterol, which is a dominant lipid species in the brain, is decreased on the tissue surface after deposition of matrix, particularly in white matter. The decrease of cholesterol is followed by an increased ion yield of several other lipid species. Depth profiling of the sublimed rat brain reveals that the lipid species are de facto extracted by the DHB matrix and concentrated in the top most layers of the sublimed matrix. This extraction/concentration of lipids directly leads to an increase of higher mass lipid ion yield. It is also possible that the decrease of cholesterol decreases the potential suppression of ion yield caused by cholesterol migration to the tissue surface. This result provides us with significant insights into the possible mechanisms involved when using sublimation to deposit this matrix in ME-SIMS.

Understanding the rheology of yield stress materials

NARCIS (Netherlands)

Paredes Rojas, J.F.

2013-01-01

This thesis presents the PhD research on the flow behavior of yield stress materials, using rheological measurements and confocal laser scanning microscopy. Experiments are performed in dispersed systems, such as emulsions, gels and foams; for these, when the amount of the dispersed phase is high

Residual Stress Induced Mechanical Property Enhancement in Steel Encapsulated Light Metal Matrix Composites

Science.gov (United States)

Fudger, Sean James

Macro hybridized systems consisting of steel encapsulated light metal matrix composites (MMCs) were produced with the goal of creating a low cost/light weight composite system with enhanced mechanical properties. MMCs are frequently incorporated into advanced material systems due to their tailorable material properties. However, they often have insufficient ductility for many structural applications. The macro hybridized systems take advantage of the high strength, modulus, and damage tolerance of steels and high specific stiffness and low density of MMCs while mitigating the high density of steels and the poor ductility of MMCs. Furthermore, a coefficient of thermal expansion (CTE) mismatch induced residual compressive stress method is utilized as a means of improving the ductility of the MMCs and overall efficiency of the macro hybridized systems. Systems consisting of an A36, 304 stainless steel, or NitronicRTM 50 stainless steel shell filled with an Al-SiC, Al-Al2O3, or Mg-B4C MMC are evaluated in this work. Upon cooling from processing temperatures, residual strains are generated due to a CTE mismatch between each of the phases. The resulting systems offer higher specific properties and a more structurally efficient system can be attained. Mechanical testing was performed and improvements in yield stress, ultimate tensile stress, and ductility were observed. However, the combination of these dissimilar materials often results in the formation of intermetallic compounds. In certain loading situations, these typically brittle intermetallic layers can result in degraded performance. X-ray Diffraction (XRD), X-ray Energy Dispersive Spectroscopy (EDS), and Electron Backscatter Diffraction (EBSD) are utilized to characterize the intermetallic layer formation at the interface between the steel and MMC. As the residual stress condition in each phase has a large impact on the mechanical property improvement, accurate quantification of these strains/stresses is

Effect of the Yield Stress and r-value Distribution on the Earing Profile of Cup Drawing with Yld2000-2d Yield Function

Science.gov (United States)

Lou, Yanshan; Bae, Gihyun; Lee, Changsoo; Huh, Hoon

2010-06-01

This paper deals with the effect of the yield stress and r-value distribution on the earing in the cup drawing. The anisotropic yield function, Yld2000-2d yield function, is selected to describe the anisotropy of two metal sheets, 719B and AA5182-O. The tool dimension is referred from the Benchmark problem of NUMISHEET'2002. The Downhill Simplex method is applied to identify the anisotropic coefficients in Yld2000-2d yield function. Simulations of the drawing process are performed to investigate the earing profile of two materials. The earing profiles obtained from simulations are compared with the analytical model developed by Hosford and Caddell. Simulations are conducted with respect to the change of the yield stress and r-value distribution, respectively. The correlation between the anisotropy and the earing tendency is investigated based on simulation data. Finally, the earing mechanism is analyzed through the deformation process of the blank during the cup deep drawing. It can be concluded that ears locate at angular positions with lower yield stress and higher r-value while the valleys appear at the angular position with higher yield stress and lower r-value. The effect of the yield stress distribution is more important for the cup height distribution than that of the r-value distribution.

Giant intracranial aneurysm embolization with a yield stress fluid material: insights from CFD analysis.

Science.gov (United States)

Wang, Weixiong; Graziano, Francesca; Russo, Vittorio; Ulm, Arthur J; De Kee, Daniel; Khismatullin, Damir B

2013-01-01

The endovascular treatment of intracranial aneurysms remains a challenge, especially when the aneurysm is large in size and has irregular, non-spherical geometry. In this paper, we use computational fluid dynamics to simulate blood flow in a vertebro-basilar junction giant aneurysm for the following three cases: (1) an empty aneurysm, (2) an aneurysm filled with platinum coils, and (3) an aneurysm filled with a yield stress fluid material. In the computational model, blood and the coil-filled region are treated as a non-Newtonian fluid and an isotropic porous medium, respectively. The results show that yield stress fluids can be used for aneurysm embolization provided the yield stress value is 20 Pa or higher. Specifically, flow recirculation in the aneurysm and the size of the inflow jet impingement zone on the aneurysm wall are substantially reduced by yield stress fluid treatment. Overall, this study opens up the possibility of using yield stress fluids for effective embolization of large-volume intracranial aneurysms.

Characterizing drought stress and trait influence on maize yield under current and future conditions.

Science.gov (United States)

Harrison, Matthew T; Tardieu, François; Dong, Zhanshan; Messina, Carlos D; Hammer, Graeme L

2014-03-01

Global climate change is predicted to increase temperatures, alter geographical patterns of rainfall and increase the frequency of extreme climatic events. Such changes are likely to alter the timing and magnitude of drought stresses experienced by crops. This study used new developments in the classification of crop water stress to first characterize the typology and frequency of drought-stress patterns experienced by European maize crops and their associated distributions of grain yield, and second determine the influence of the breeding traits anthesis-silking synchrony, maturity and kernel number on yield in different drought-stress scenarios, under current and future climates. Under historical conditions, a low-stress scenario occurred most frequently (ca. 40%), and three other stress types exposing crops to late-season stresses each occurred in ca. 20% of cases. A key revelation shown was that the four patterns will also be the most dominant stress patterns under 2050 conditions. Future frequencies of low drought stress were reduced by ca. 15%, and those of severe water deficit during grain filling increased from 18% to 25%. Despite this, effects of elevated CO2 on crop growth moderated detrimental effects of climate change on yield. Increasing anthesis-silking synchrony had the greatest effect on yield in low drought-stress seasonal patterns, whereas earlier maturity had the greatest effect in crops exposed to severe early-terminal drought stress. Segregating drought-stress patterns into key groups allowed greater insight into the effects of trait perturbation on crop yield under different weather conditions. We demonstrate that for crops exposed to the same drought-stress pattern, trait perturbation under current climates will have a similar impact on yield as that expected in future, even though the frequencies of severe drought stress will increase in future. These results have important ramifications for breeding of maize and have implications for

Combined effect of matrix cracking and stress-free edge on delamination

Science.gov (United States)

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

1990-01-01

The effect of the stress-free edge on the growth of local delaminations initiating from a matrix crack in (0 sub 2/90 sub 4) sub s and (+ or - 45.90 sub 4) sub s glass epoxy laminates is investigated using 3-D finite element analysis. The presence of high interlaminar normal stresses at the intersection (corner) of the matrix crack with the stress-free edge, suggests that a mode I delamination may initiate at the corners. The strain energy release rates (G) were calculated by modeling a uniform through-width delamination and two inclined delaminations at 10.6 deg and 45 deg to the matrix crack. All components of G have high values near the free edges. The mode I component of G is high at small delamination length and becomes zero for a delamination length of one-ply thickness. The total G values near the free edge agreed well with previously derived closed form solution. The quasi-3D solutions agreed well with the 3-D interior solutions.

Effect of soil water stress on yield and proline content of four wheat ...

African Journals Online (AJOL)

Effect of soil water stress on yield and proline content of four wheat lines. ... This field study was conducted to evaluate the effect of drought stress after anthesis on proline accumulation and wheat yield during 2008 at ... from 32 Countries:.

Combining ability studies on yield related traits in wheat under normal and water stress conditions

International Nuclear Information System (INIS)

Saeed, A.; Khan, A.S.; Khaliq, I.

2010-01-01

Six diverse wheat cultivars/lines viz; Baviacore, Nesser, 9247, 9252, 9258 and 9267 were crossed in a complete diallel fashion to develop 30 F1 crosses, which were tested along with their parents under normal and water stress conditions. Numerical analysis was made for spike density, number of grains per spike, 100-grain weight, biological yield, grain yield and harvest index. Significant differences among genotypic mean were observed in all of the traits under both conditions. GCA and SCA differences were significant for all the traits under study except spike density and 100-grain weight in both conditions. Wheat variety Nesser showed maximum general combining ability value for spike density under water stress conditions and maximum GCA value for biological yield and grain yield under irrigated condition. The variety Baviacore proved best general combiner for number of grains per spike and harvest index under both conditions while biological yield and grain yield under water stress condition. Variety 9252 found best general combiner for 100-grain weight under both condition. The cross 9252 x Nesser showed maximum specific combining ability value for spike density and biological yield under irrigated while for 100-grain weight under water stress condition. 9258 x 9252 exhibited maximum SCA for number of grains per spike under irrigated while 9258 x Nesser under water stress condition. 9267 x Nesser showed maximum SCA for 100-grain weight under irrigated condition while spike density under water stress condition. 9258 x 9247 was proved best combiner for grain yield and harvest index irrigated while 9267 x 9258 for biological yield, grain yield and harvest index under water stress condition. (author)

Separating heat stress from moisture stress: analyzing yield response to high temperature in irrigated maize

Science.gov (United States)

Carter, Elizabeth K.; Melkonian, Jeff; Riha, Susan J.; Shaw, Stephen B.

2016-09-01

Several recent studies have indicated that high air temperatures are limiting maize (Zea mays L.) yields in the US Corn Belt and project significant yield losses with expected increases in growing season temperatures. Further work has suggested that high air temperatures are indicative of high evaporative demand, and that decreases in maize yields which correlate to high temperatures and vapor pressure deficits (VPD) likely reflect underlying soil moisture limitations. It remains unclear whether direct high temperature impacts on yields, independent of moisture stress, can be observed under current temperature regimes. Given that projected high temperature and moisture may not co-vary the same way as they have historically, quantitative analyzes of direct temperature impacts are critical for accurate yield projections and targeted mitigation strategies under shifting temperature regimes. To evaluate yield response to above optimum temperatures independent of soil moisture stress, we analyzed climate impacts on irrigated maize yields obtained from the National Corn Growers Association (NCGA) corn yield contests for Nebraska, Kansas and Missouri. In irrigated maize, we found no evidence of a direct negative impact on yield by daytime air temperature, calculated canopy temperature, or VPD when analyzed seasonally. Solar radiation was the primary yield-limiting climate variable. Our analyses suggested that elevated night temperature impacted yield by increasing rates of phenological development. High temperatures during grain-fill significantly interacted with yields, but this effect was often beneficial and included evidence of acquired thermo-tolerance. Furthermore, genetics and management—information uniquely available in the NCGA contest data—explained more yield variability than climate, and significantly modified crop response to climate. Thermo-acclimation, improved genetics and changes to management practices have the potential to partially or completely

Influence of polymer charge on the shear yield stress of silica aggregated with adsorbed cationic polymers.

Science.gov (United States)

Zhou, Ying; Yu, Hai; Wanless, Erica J; Jameson, Graeme J; Franks, George V

2009-08-15

Flocs were produced by adding three cationic polymers (10% charge density, 3.0x10(5) g/mol molecular weight; 40% charge density, 1.1x10(5) g/mol molecular weight; and 100% charge density, 1.2x10(5) g/mol molecular weight) to 90 nm diameter silica particles. The shear yield stresses of the consolidated sediment beds from settled and centrifuged flocs were determined via the vane technique. The polymer charge density plays an important role in influencing the shear yield stresses of sediment beds. The shear yield stresses of sediment beds from flocs induced by the 10% charged polymer were observed to increase with an increase in polymer dose, initial solid concentration and background electrolyte concentration at all volume fractions. In comparison, polymer dose has a marginal effect on the shear yield stresses of sediment beds from flocs induced by the 40% and 100% charged polymers. The shear yield stresses of sediments from flocs induced by the 40% charged polymer are independent of salt concentration whereas the addition of salt decreases the shear yield stresses of sediments from flocs induced by the 100% charged polymer. When flocculated at the optimum dose for each polymer (12 mg/g silica for the 10% charged polymer at 0.03 M NaCl, 12 mg/g for 40% and 2 mg/g for 100%), shear yield stress increases as polymer charge increases. The effects observed are related to the flocculation mechanism (bridging, patch attraction or charge neutralisation) and the magnitude of the adhesive force. Comparison of shear and compressive yield stresses show that the network is only slightly weaker in shear than in compression. This is different than many other systems (mainly salt and pH coagulation) which have shear yield stress much less than compressive yield stress. The existing models relating the power law exponent of the volume fraction dependence of the shear yield stress to the network fractal structure are not satisfactory to predict all the experimental behaviour.

Effect of Mulch and Water Stress on Some Physiological Traits, Yield Components and Grain Yield of Red Kidney bean (Phaseolus vulgaris L.

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R Amini

2016-02-01

Full Text Available Introduction Water use in agricultural production as one of the most important environmental factors affecting plant growth and development, especially in arid and semi-arid climatic conditions of Iran is of special importance (21. One of the ways of alleviating water scarcity is by enhancing its use efficiency or productivity. Improving water use efficiency in arid and semi-arid areas depends on effective conservation of moisture and efficient use of limited water. Mulching is one of the management practices for increasing water use efficiency (WUE . Straw mulch is commonly used as mulch. Straw mulching has potential for increasing soil water storage (16. Mulches modify the microclimate and growing conditions of crops (16, conserve more water and increase water use efficiency (34. Red kidney bean (Phaseolus vulgaris L. is the most important food legume (25 and is an important source of proteins and minerals (28. The majority of red kidney bean production is under drought conditions, and thus yield reductions due to drought are very common (29. This research was carried out to evaluate the effect of wheat straw mulch and water stress on physiological traits, yield components and grain yield of red kidney bean cultivars. Materials and Methods A field experiment was conducted in 2012 at the Research Farm of the Faculty of Agriculture, University of Tabriz, Iran (latitude 38°05_N, longitude 46°17_E, altitude 1360 m above sea level. In order to investigate the effect of mulch on grain yield and yield components of red kidney bean (Phaseolus vulgaris L. cultivars at different water stress treatments, a factorial experiment was conducted based on RCB design with three replications. The factors were including water stress treatment (I1 and I2, irrigation after 60 and 120 mm evaporation from class A pan, respectively; mulch application at two levels (M1: (no mulch and M2: 2 ton ha-1 wheat straw mulch and red kidney bean cultivars including Akhtar and

Effects of drought stress condition on the yield of spring wheat ...

African Journals Online (AJOL)

Effects of drought stress condition on the yield of spring wheat ( Triticum aestivum ) lines. ... Drought stress tolerance is seen in almost all plants but its extent varies from species to species and even within species. ... from 32 Countries:.

Yield stress of duplex stainless steel specimens estimated using a compound Hall–Petch equation

Directory of Open Access Journals (Sweden)

Noriaki Hirota, Fuxing Yin, Tsukasa Azuma and Tadanobu Inoue

2010-01-01

Full Text Available In this study, the 0.2% yield stress of duplex stainless steel was evaluated using a compound Hall–Petch equation. The compound Hall–Petch equation was derived from four types of duplex stainless steel, which contained 0.2–64.4 wt% δ-ferrite phase, had different chemical compositions and were annealed at different temperatures. Intragranular yield stress was measured with an ultra-microhardness tester and evaluated with the yield stress model proposed by Dao et al. Grain size, volume fraction and texture were monitored by electron backscattering diffraction measurement. The kγ constant in the compound equation for duplex stainless steel agrees well with that for γ-phase SUS316L steel in the temperature range of 1323–1473 K. The derived compound Hall–Petch equation predicts that the yield stress will be in good agreement with the experimental results for the Cr, Mn, Si, Ni and N solid-solution states. We find that the intragranular yield stress of the δ-phase of duplex stainless steel is rather sensitive to the chemical composition and annealing conditions, which is attributed to the size misfit parameter.

Yield stress determination from miniaturized disk bend test data

International Nuclear Information System (INIS)

Sohn, D.S.; Kohse, G.; Harling, O.K.

1985-04-01

Methodology for testing 3.0 mm diameter by 0.25 mm thick disks by bending in a punch and die has been described previously. This paper describes the analysis of load/deflection data from such miniaturized disk bend tests (MDBT) using a finite element simulation. Good simulation has been achieved up to a point just beyond the predominantly elastic response, linear initial region. The load at which deviation from linearity begins has been found to correlate with yield stress, and yield stress has been successfully extracted from disk bend tests of a number of known materials. Although finite element codes capable of dealing with large strains and large rotations have been used, simulation of the entire load/deflection curve up to fracture of the specimen has not yet been achieved

Predicted strains in austenitic stainless steels at stresses above yield

International Nuclear Information System (INIS)

Hammond, J.P.; Sikka, V.K.

1977-01-01

Tensile results on austenitic stainless steels were analyzed to develop means for predicting strains at stresses above yield for reactor regulatory applications. Eight heats each of types 316 and 304 were tested at 24, 93, 204, and 316 0 C as mill-annealed and at 24 0 C after reannealing. The effects of heat-to-heat variations on total strain (to 5%) at discrete stress levels were portrayed by a rational polynomial incorporating three constants that relate to the basic features of the true-stress-true-strain diagram. Because these constants usually are interrelated, a single parameter, yield strength (YS), proved adequate to predict results. For predictions analytical expressions of yield strength, an average value (YSa), and a lower bound value [YSa - 1.65SEE (standard error of estimate)] were used. Using the rational polynomial with these parameters we determined (1) limits of total maximum strain and (2) ratios of strain of material of lower bound YS to that of average YS. These are recorded at regular increments of stress [34 MPa (5 ksi)] and at ASME Code-related stresses (S/sub y), S/sub m/, 1.2S/sub m/ and 1.5S/sub m/). At intermediate stresses, strain penalties for using material of lower bound strength were large, generally larger for type 316 than type 304. For mill-annealed type 316 at 24, 93, 204, and 316 0 C, the maximum ratios of strain were 8.8, 13.0, 14.1, and 14.9, respectively, whereas for type 304 they were 3.5, 3.4, 5.6, and 4.6. At 1.5S/sub m/ and 316 0 C, a maximum strain of 2.08% was predicted for type 316 and 1.66% for type 304, as contrasted to values of 0.14 and 0.39% for average strain

Nanoscale Roughness of Faults Explained by the Scale-Dependent Yield Stress of Geologic Materials

Science.gov (United States)

Thom, C.; Brodsky, E. E.; Carpick, R. W.; Goldsby, D. L.; Pharr, G.; Oliver, W.

2017-12-01

Despite significant differences in their lithologies and slip histories, natural fault surfaces exhibit remarkably similar scale-dependent roughness over lateral length scales spanning 7 orders of magnitude, from microns to tens of meters. Recent work has suggested that a scale-dependent yield stress may result in such a characteristic roughness, but experimental evidence in favor of this hypothesis has been lacking. We employ an atomic force microscope (AFM) operating in intermittent-contact mode to map the topography of the Corona Heights fault surface. Our experiments demonstrate that the Corona Heights fault exhibits isotropic self-affine roughness with a Hurst exponent of 0.75 +/- 0.05 at all wavelengths from 60 nm to 10 μm. If yield stress controls roughness, then the roughness data predict that yield strength varies with length scale as λ-0.25 +/ 0.05. To test the relationship between roughness and yield stress, we conducted nanoindentation tests on the same Corona Heights sample and a sample of the Yair Fault, a carbonate fault surface that has been previously characterized by AFM. A diamond Berkovich indenter tip was used to indent the samples at a nominally constant strain rate (defined as the loading rate divided by the load) of 0.2 s-1. The continuous stiffness method (CSM) was used to measure the indentation hardness (which is proportional to yield stress) and the elastic modulus of the sample as a function of depth in each test. For both samples, the yield stress decreases with increasing size of the indents, a behavior consistent with that observed for many engineering materials and recently for other geologic materials such as olivine. The magnitude of this "indentation size effect" is best described by a power-law with exponents of -0.12 +/- 0.06 and -0.18 +/- 0.08 for the Corona Heights and Yair Faults, respectively. These results demonstrate a link between surface roughness and yield stress, and suggest that fault geometry is the physical

The Effects of Drought Stress on Yield, Yield Components and Anti-oxidant of Two Garlic (Allium sativum L. Ecotypes with Different Planting Densities

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shiva akbari

2016-07-01

Full Text Available Introduction Drought stress reduces plant growth by affecting various physiological and biochemical processes, such as photosynthesis, respiration, translocation, ion uptake, carbohydrates, nutrient metabolism and growth promoters. Garlic (Allium sativum L. is an annual bulb crop that has been cultivated since ancient times and was used as a spice and condiment for many centuries. Garlic is an important plant because of its pharmaceutical properties. The optimum yield of this bulb crop depends on well-managed irrigation, fertilization and cultivation practices. In the final and middle stages of growth, garlic is sensitive to water stress and low irrigation is unsuitable in these stages. This experiment was established to study the influence of drought stress and planting density on yield and its components and the non-enzymatic anti-oxidant content of two different garlic ecotypes. Materials and methods This study was conducted in 2011-2012 in a farmland at the south east of Semnan city. The experimental layout was a split-plot factorial with a randomized complete block design with three replications. The treatments were comprised of three factors: irrigation rates (60%, 80% and 100% of estimated crop evapotranspiration (ETC as the main plot and the factorial combination of three levels of planting density (30, 40 and 50 plants.m-2 and two ecotypes (Tabas and Toroud as the sub-plots. To estimate the crop water requirement, different meteorological parameters were collected from Semnan weather station and were used based on FAO-56 water irrigation calculation instructions. After harvesting, ten garlic plants were sampled randomly in each plot and bulb yield components were measured. To calculate the leaves anti-oxidant content, DPPH method was used. The statistical significances of mean values were assessed by analysis of variance and LSD tests at p≤0.05. All calculations were performed using SAS and Mstat-C softwares. Results and discussion

Yielding the yield-stress analysis: a study focused on the effects of elasticity on the settling of a single spherical particle in simple yield-stress fluids.

Science.gov (United States)

Fraggedakis, D; Dimakopoulos, Y; Tsamopoulos, J

2016-06-28

The sedimentation of a single particle in materials that exhibit simultaneously elastic, viscous and plastic behavior is examined in an effort to explain phenomena that contradict the nature of purely yield-stress materials. Such phenomena include the loss of the fore-and-aft symmetry with respect to an isolated settling particle under creeping flow conditions and the appearance of the "negative wake" behind it. Despite the fact that similar observations have been reported in studies involving viscoelastic fluids, researchers conjectured that thixotropy is responsible for these phenomena, as the aging of yield-stress materials is another common feature. By means of transient calculations, we study the effect of elasticity on both the fluidized and the solid phase. The latter is considered to behave as an ideal Hookean solid. The material properties of the model are determined under the isotropic kinematic hardening framework via Large Amplitude Oscillatory Shear (LAOS) measurements. In this way, we are able to predict accurately the unusual phenomena observed in experiments with simple yield-stress materials, irrespective of the appearance of slip on the particle surface. Viscoelasticity favors the formation of intense shear and extensional stresses downstream of the particle, significantly changing the entrapment mechanism in comparison to that observed in viscoplastic fluids. Therefore, the critical conditions under which the entrapment of the particle occurs deviate from the well-known criterion established theoretically by Beris et al. (1985) and verified experimentally by Tabuteau et al. (2007) for similar materials under conditions that elastic effects are negligible. Our predictions are in quantitative agreement with published experimental results by Holenberg et al. (2012) on the loss of the fore-aft symmetry and the formation of the negative wake in Carbopol with well-characterized rheology. Additionally, we propose simple expressions for the Stokes drag

Residual Effect of Chemical and Animal Fertilizers and Compost on Yield, YieldComponents, Physiological Characteristics and Essential Oil Content of Matricaria chamomilla L. under Drought Stress conditions

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a Ahmadian

2011-02-01

Full Text Available Abstract The residual effect of inorganic and organic fertilizers on growth and yield of plants is one of the important problems in nutrition. This study was conducted to determine the residual effect of different fertilizers on yield, yield components, physiological parameters and essential oil percentage of Matricaria chamomilla under drought stress. A split plot arrangement based on randomized completely block design (RCBD with three replication was conducted in 2009, at the University of Zabol. Treatments included W1 (non stress, W2 (75% FC and W3 (50% FC as main plot and three types of residual’s fertilizers: F1 (non fertilizer, F2 (chemical fertilizer, F3 (manure fertilizer and F4 (compost as sub plot. Results showed that water stress at W3 treatment reduced dry flower yield. Low water stress increased essential oil percentage and the highest oil was obtained in W2. In this experiment, free proline and total soluble carbohydrate concentration were increased under water stress. The residual’s manure and compost enhanced flower yield, percentage and yield of essential oil of chamomile at the second year. At a glance, animal manure application and light water stress (75% FC was recommended to obtain best quantitative and qualitative yield. Keywords: Water Stress, Fertilizer, Carbohydrate, Proline, Chamomile

Yield Stress Reduction of DWPF Melter Feed Slurries

International Nuclear Information System (INIS)

Stone, M.E.; Smith, M.E.

2007-01-01

The Defense Waste Processing Facility (DWPF) at the Savannah River Site vitrifies High Level Waste for repository internment. The process consists of three major steps: waste pretreatment, vitrification, and canister decontamination/sealing. The HLW consists of insoluble metal hydroxides and soluble sodium salts. The pretreatment process acidifies the sludge with nitric and formic acids, adds the glass formers as glass frit, then concentrates the resulting slurry to approximately 50 weight percent (wt%) total solids. This slurry is fed to the joule-heated melter where the remaining water is evaporated followed by calcination of the solids and conversion to glass. The Savannah River National Laboratory (SRNL) is currently assisting DWPF efforts to increase throughput of the melter. As part of this effort, SRNL has investigated methods to increase the solids content of the melter feed to reduce the heat load required to complete the evaporation of water and allow more of the energy available to calcine and vitrify the waste. The process equipment in the facility is fixed and cannot process materials with high yield stresses, therefore increasing the solids content will require that the yield stress of the melter feed slurries be reduced. Changing the glass former added during pretreatment from an irregularly shaped glass frit to nearly spherical beads was evaluated. The evaluation required a systems approach which included evaluations of the effectiveness of beads in reducing the melter feed yield stress as well as evaluations of the processing impacts of changing the frit morphology. Processing impacts of beads include changing the settling rate of the glass former (which effects mixing and sampling of the melter feed slurry and the frit addition equipment) as well as impacts on the melt behavior due to decreased surface area of the beads versus frit. Beads were produced from the DWPF process frit by fire polishing. The frit was allowed to free fall through a flame

Mean-Field Scenario for the Athermal Creep Dynamics of Yield-Stress Fluids

Science.gov (United States)

Liu, Chen; Martens, Kirsten; Barrat, Jean-Louis

2018-01-01

We develop a theoretical description based on an existent mean-field model for the transient dynamics prior to the steady flow of yielding materials. The mean-field model not only reproduces the experimentally observed nonlinear time dependence of the shear-rate response to an external stress, but also allows for the determination of the different physical processes involved in the onset of the reacceleration phase after the initial slowing down and a distinct fluidization phase. The fluidization time displays a power-law dependence on the distance of the applied stress to an age-dependent yield stress, which is not universal but strongly dependent on initial conditions.

Stress transfer around a broken fiber in unidirectional fiber-reinforced composites considering matrix damage evolution and interface slipping

Science.gov (United States)

Yang, Zhong; Zhang, BoMing; Zhao, Lin; Sun, XinYang

2011-02-01

A shear-lag model is applied to study the stress transfer around a broken fiber within unidirectional fiber-reinforced composites (FRC) subjected to uniaxial tensile loading along the fiber direction. The matrix damage and interfacial debonding, which are the main failure modes, are considered in the model. The maximum stress criterion with the linear damage evolution theory is used for the matrix. The slipping friction stress is considered in the interfacial debonding region using Coulomb friction theory, in which interfacial clamping stress comes from radial residual stress and mismatch of Poisson's ratios of constituents (fiber and matrix). The stress distributions in the fiber and matrix are obtained by the shear-lag theory added with boundary conditions, which includes force continuity and displacement compatibility constraints in the broken and neighboring intact fibers. The result gives axial stress distribution in fibers and shear stress in the interface and compares the theory reasonably well with the measurement by a polarized light microscope. The relation curves between damage, debonding and ineffective region lengths with external strain loading are obtained.

Bubble Formation in Yield Stress Fluids Using Flow-Focusing and T-Junction Devices.

Science.gov (United States)

Laborie, Benoit; Rouyer, Florence; Angelescu, Dan E; Lorenceau, Elise

2015-05-22

We study the production of bubbles inside yield stress fluids (YSFs) in axisymmetric T-junction and flow-focusing devices. Taking advantage of yield stress over capillary stress, we exhibit a robust break-up mechanism reminiscent of the geometrical operating regime in 2D flow-focusing devices for Newtonian fluids. We report that when the gas is pressure driven, the dynamics is unsteady due to hydrodynamic feedback and YSF deposition on the walls of the channels. However, the present study also identifies pathways for potential steady-state production of bubbly YSFs at large scale.

The Bree problem with different yield stresses on-load and off-load and application to creep ratcheting

International Nuclear Information System (INIS)

Bradford, R.A.W.; Ure, J.; Chen, H.F.

2014-01-01

The ratchet boundaries and ratchet strains are derived for the Bree problem and an elastic-perfectly plastic material with different yield stresses on-load and off-load. The Bree problem consists of a constant uniaxial primary membrane stress and a cycling thermal bending stress. The ratchet problem with differing yield stresses is also solved for a modified loading in which both the primary membrane and thermal bending stresses cycle in-phase. The analytic solutions for the ratchet boundaries are compared with the results of deploying the linear matching method (LMM) and excellent agreement is found. Whilst these results are of potential utility for purely elastic–plastic behaviour, since yield stresses will often differ at the two ends of the cycle, the solution is also proposed as a means of assessing creep ratcheting via a creep ductility exhaustion approach. -- Highlights: • The Bree problem is solved for differing yield stresses on and off load. • The modified Bree problem with cycling primary load is also solved. • These solutions can be applied to creep ratcheting using a pseudo-yield stress

The influence of aging stress on the yield point phenomenon in the zirconium alloy, ozhennite 0.5

International Nuclear Information System (INIS)

Dickson, J.I.; Sayar, A.

1977-01-01

The influence of aging stress on the occurrence of yield points during interrupted tensile tests was studied in the temperature range 423 to 623 K for aging times of 2 to 10 min. The results indicate that at the lower temperatures the yield points are produced by dislocation rearrangements, with a minimum yield drop resulting from an aging close to the internal stress estimated by an unloading to zero stress relaxation technique. Above approximately 458 K, solute atoms can play an important role in the formation of the yield points. When this solute strain-aging occurs strongly, a maximum yield drop is at times obtained by aging at a stress close to the measured internal stress. At the higher deformation temperatures, the yield drop decreases more rapidly with increasing plastic strain, which result appears related to the greater amount of tangling of dislocations produced at the higher temperatures. (Auth.)

Non-self-similar cracking in unidirectional metal-matrix composites

International Nuclear Information System (INIS)

Rajesh, G.; Dharani, L.R.

1993-01-01

Experimental investigations on the fracture behavior of unidirectional Metal Matrix Composites (MMC) show the presence of extensive matrix damage and non-self-similar cracking of fibers near the notch tip. These failures are primarily observed in the interior layers of an MMC, presenting experimental difficulties in studying them. Hence an investigation of the matrix damage and fiber fracture near the notch tip is necessary to determine the stress concentration at the notch tip. The classical shear lag (CLSL) assumption has been used in the present study to investigate longitudinal matrix damage and nonself-similar cracking of fibers at the notch tip of an MMC. It is seen that non-self-similar cracking of fibers reduces the stress concentration at the notch tip considerably and the effect of matrix damage is negligible after a large number of fibers have broken beyond the notch tip in a non-self-similar manner. Finally, an effort has been made to include non-self-similar fiber fracture and matrix damage to model the fracture behavior of a unidirectional boron/aluminum composite for two different matrices viz. a 6061-0 fully annealed aluminum matrix and a heat treated 6061-T6 aluminum matrix. Results have been drawn for several characteristics pertaining to the shear stiffnesses and the shear yield stresses of the two matrices and compared with the available experimental results

Influence of cold rolling and fatigue on the residual stress state of a metal matrix composite

International Nuclear Information System (INIS)

Hanus, E.; Ericsson, T.; Lu, J.; Decomps, F.

1993-01-01

The large difference in the coefficient of thermal expansion between the matrix alloy and the particle in a metal matrix composite gives rise to residual stresses in the material. In the present work the effect of cold rolling and four-point bending fatigue on the residual stress state of a silicon carbide particle reinforced aluminium alloy (AA 2014) has been investigated. The three dimensional stress state measured in both phases: matrix and reinforcement, has been determined by using an X-ray diffraction technique. It was found that cold rolling induces surface compressive macrostresses of about -250 MPa, with a penetration depth around 2 mm. The absolute values of the pseudomacrostresses in both phases are significantly reduced due to the single track rolling. Stress relaxation occurs during four-point bending fatigue. (orig.)

Experimental determination of the yield stress curve of the scotch pine wood materials

Science.gov (United States)

Günay, Ezgi; Aygün, Cevdet; Kaya, Şükrü Tayfun

2013-12-01

Yield stress curve is determined for the pine wood specimens by conducting a series of tests. In this work, pinewood is modeled as a composite material with transversely isotropic fibers. Annual rings (wood grain) of the wood specimens are taken as the major fiber directions with which the strain gauge directions are aligned. For this purpose, three types of tests are arranged. These are tensile, compression and torsion loading tests. All of the tests are categorized with respect to fiber orientations and their corresponding loading conditions. Each test within these categories is conducted separately. Tensile and compression tests are conducted in accordance with standards of Turkish Standards Institution (TSE) whereas torsion tests are conducted in accordance with Standards Australia. Specimens are machined from woods of Scotch pine which is widely used in boat building industries and in other structural engineering applications. It is determined that this species behaves more flexibly than the others. Strain gauges are installed on the specimen surfaces in such a way that loading measurements are performed along directions either parallel or perpendicular to the fiber directions. During the test and analysis phase of yield stress curve, orientation of strain gauge directions with respect to fiber directions are taken into account. The diagrams of the normal stress vs. normal strain or the shear stress vs. shear strain are plotted for each test. In each plot, the yield stress is determined by selecting the point on the diagram, the tangent of which is having a slope of 5% less than the slope of the elastic portion of the diagram. The geometric locus of these selected points constitutes a single yield stress curve on σ1-σ2 principal plane. The resulting yield stress curve is plotted as an approximate ellipse which resembles Tsai-Hill failure criterion. The results attained in this work, compare well with the results which are readily available in the literature.

Effect of Filter Cake on Morphophysiological and Yield of Sweet Corn Under Late Season Drought Stress Condition

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S. A. Siadat

2015-06-01

Full Text Available In order to investigate the effect of Filter Cake application on some morpho-physiological characteristics and yield of sweet corn (Zea mays var saccharata under different irrigation regimes, an experiment was conducted in Ramin Agriculture and Natural Resources University, Khuzestan, in 2012. The experiment was arranged in split-plot design in RCBD (Completely Randomized Block Design with three replications. Treatments were drought stress (irrigation after 25, 50 and 75% depletion of available water content in main plots and Filter Cake (0, 10, 20 and 30 tonha-1 arranged in sub-plots. Results showed that drought stress increased electrolyte leakage (EL and proline content (PC while height of plant, relative water content (RWC, chlorophyll stability index and ear and grain yield were decreased. The intensive drought stress had the greatest effect on EL and PC (54% increase, and decreased ear and grain yield by21 and 37% compared to control, respectively. Application of filter cake on non-stress condition increased height of plant and economic yield. But Filter Cake in intensive stress reduced RWC and yield and increased EL compared to control. Also, the application of 30 tonha-1 of Filter Cake in intensive stress condition decreased ear and grain yield by 14.5 and 10.7% respectively. Thus, positive effect of Filter Cake application was clear on non-stress condition, but on drought stress condition it decreased the economic yield.

Mechanical Characterization of Thermomechanical Matrix Residual Stresses Incurred During MMC Processing

Science.gov (United States)

Castelli, Michael G.

1998-01-01

In recent years, much effort has been spent examining the residual stress-strain states of advanced composites. Such examinations are motivated by a number of significant concerns that affect composite development, processing, and analysis. The room-temperature residual stress states incurred in many advanced composite systems are often quite large and can introduce damage even prior to the first external mechanical loading of the material. These stresses, which are induced during the cooldown following high-temperature consolidation, result from the coefficient of thermal expansion mismatch between the fiber and matrix. Experimental techniques commonly used to evaluate composite internal residual stress states are non-mechanical in nature and generally include forms of x-ray and neutron diffraction. Such approaches are usually complex, involving a number of assumptions and limitations associated with a wide range of issues, including the depth of penetration, the volume of material being assessed, and erroneous effects associated with oriented grains. Furthermore, and more important to the present research, these techniques can assess only "single time" stress in the composite. That is, little, if any, information is obtained that addresses the time-dependent point at which internal stresses begin to accumulate, the manner in which the accumulation occurs, and the presiding relationships between thermoelastic, thermoplastic, and thermoviscous behaviors. To address these critical issues, researchers at the NASA Lewis Research Center developed and implemented an innovative mechanical test technique to examine in real time, the time-dependent thermomechanical stress behavior of a matrix alloy as it went through a consolidation cycle.

Yield Stress Model for Molten Composition B-3

Science.gov (United States)

Davis, Stephen; Zerkle, David

2017-06-01

Composition B-3 (Comp B-3) is a melt-castable explosive composed of 60/40 wt% RDX/TNT (hexahydro-1,3,5-trinitro-1,3,5-triazine/2,4,6-trinitrotoluene). During casting operations thermal conditions are controlled which along with the low melting point of TNT and the insensitivity of the mixture to external stimuli leading to safe use. Outside these standard operating conditions a more rigorous model of Comp B-3 rheological properties is necessary to model thermal transport as Comp B-3 evolves from quiescent solid through vaporization/decomposition upon heating. One particular rheological phenomena of interest is Bingham plasticity, where a material behaves as a quiescent solid unless a sufficient load is applied, resulting in fluid flow. In this study falling ball viscometer data is used to model the change in Bingham plastic yield stresses as a function of RDX particle volume fraction; a function of temperature. Results show the yield stress of Comp B-3 (τy) follows the expression τy = B ϕ -ϕc N , where Φ and Φc are the volume fraction of RDX and a critical volume fraction, respectively and B and N are experimentally evaluated constants.

Effects of Methanol Spraying on Qualitative traits, Yield and Yield Components of Soybean (Glycine max L. under Drought Stress Conditions

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J Esazadeh Panjali Kharabasi

2017-12-01

Full Text Available Introduction Soybean (Glycin max L. is one of the most important oilseed crops in the world. It can provide oil and vegetable protein suitable for feeding humans as well as animals. The productivity Increasing of this crop in Iran has been the subject of continuous investigation over the past few years. It is well known that adequate water supply is considered as a very important factor to affect the accumulation of dry matter in the plant as well as vegetative growth of most crops. Irrigation is an important factor affecting soybean growth and yield and its related components. Exposing soybean plants to soil moisture stress at any phase of its life cycle may lead to a detrimental effect on growth, yield and its components. The methanol spraying can lead to increase in yield, expediting in maturity and reduction in drought stress impacts and water requirement of crops. Material and Methods The experiment was conducted as split plots based on randomized complete block design with three replications at the Research Farm, Faculty of Agriculture of Moghan, Iran, in 2011. Treatments included three levels of drought stress as follows irrigation after, 40 (control, 55 and 70 percentage of available soil moisture depletion as main plots, and four levels of methanol spraying including 0 (control, 7, 21 and 35 volumetric percentage as sub plots. The studied traits were included plant height, leaf area, number of pod and seed per plant, 1000 seed weight, biological and seed yield, stomatal conductance and proline contents. Statistical analysis was carried out using SAS version 9.1 software. Significant difference was set at p ≤ 0.05 by using Duncan’s multiple range test. Results and Discussion The results showed that the plant height, leaf area, number of pod and seed per plant, 1000 seed weight, biological and seed yield, stomatal conductance and proline contents as well as number of leaf per plant significantly affected by drought stress and methanol

Effects of magnetized walls on the particle structure and the yield stress of magnetorheological fluids

Energy Technology Data Exchange (ETDEWEB)

Zhou, Jianfeng, E-mail: zhoujianfeng@njtech.edu.cn [School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing 211816, Jiangsu (China); Mo, Jingwen [Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Shao, Chunlei [School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing 211816, Jiangsu (China); Li, Zhigang [Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

2015-09-01

In this work, we investigate the quasi-static shear deformation of magnetic particles (MPs) in a Couette flow of magnetorheological (MR) fluids through Stokesian dynamic simulations. The magnetized walls are modeled by a congregation of magnetic dipoles and their effects on the MPs are considered. The simple shear flow of the base fluid with linear velocity distribution is used to generate the shear deformation of the MP structure and the yield stresses under different shear rates are obtained. Comparing with the relatively long chains forming in base fluid without the effect of magnetized walls, the initial structure of MPs is mainly in the form of short chains due to the attractive force of walls. At the beginning of the shear deformation of the MP structure, the concentration of MPs near the walls is found. As the shear deformation develops, however, the chains concentrate at the center of the simulation domain and the MPs near wall boundaries are attracted to the center. The yield stress depends on the initial structure of MPs which is affected by the magnetized walls. It is revealed that the larger shear rate of base fluid results in the larger yield stress, and the effects of the magnetization intensity of the walls and their space distance on the yield stress are also investigated. - Highlights: • We model a Couette flow of magnetorheological fluid considering magnetized walls. • The walls are modeled by a congregation of magnetic dipoles. • Initial structure of MPs is remarkably affected by the walls, so is yield stress. • Larger base fluid shear rate causes the larger shear deformation and larger yield stress.

Effects of magnetized walls on the particle structure and the yield stress of magnetorheological fluids

International Nuclear Information System (INIS)

Zhou, Jianfeng; Mo, Jingwen; Shao, Chunlei; Li, Zhigang

2015-01-01

In this work, we investigate the quasi-static shear deformation of magnetic particles (MPs) in a Couette flow of magnetorheological (MR) fluids through Stokesian dynamic simulations. The magnetized walls are modeled by a congregation of magnetic dipoles and their effects on the MPs are considered. The simple shear flow of the base fluid with linear velocity distribution is used to generate the shear deformation of the MP structure and the yield stresses under different shear rates are obtained. Comparing with the relatively long chains forming in base fluid without the effect of magnetized walls, the initial structure of MPs is mainly in the form of short chains due to the attractive force of walls. At the beginning of the shear deformation of the MP structure, the concentration of MPs near the walls is found. As the shear deformation develops, however, the chains concentrate at the center of the simulation domain and the MPs near wall boundaries are attracted to the center. The yield stress depends on the initial structure of MPs which is affected by the magnetized walls. It is revealed that the larger shear rate of base fluid results in the larger yield stress, and the effects of the magnetization intensity of the walls and their space distance on the yield stress are also investigated. - Highlights: • We model a Couette flow of magnetorheological fluid considering magnetized walls. • The walls are modeled by a congregation of magnetic dipoles. • Initial structure of MPs is remarkably affected by the walls, so is yield stress. • Larger base fluid shear rate causes the larger shear deformation and larger yield stress

Stress and Damage in Polymer Matrix Composite Materials Due to Material Degradation at High Temperatures

Science.gov (United States)

McManus, Hugh L.; Chamis, Christos C.

1996-01-01

This report describes analytical methods for calculating stresses and damage caused by degradation of the matrix constituent in polymer matrix composite materials. Laminate geometry, material properties, and matrix degradation states are specified as functions of position and time. Matrix shrinkage and property changes are modeled as functions of the degradation states. The model is incorporated into an existing composite mechanics computer code. Stresses, strains, and deformations at the laminate, ply, and micro levels are calculated, and from these calculations it is determined if there is failure of any kind. The rationale for the model (based on published experimental work) is presented, its integration into the laminate analysis code is outlined, and example results are given, with comparisons to existing material and structural data. The mechanisms behind the changes in properties and in surface cracking during long-term aging of polyimide matrix composites are clarified. High-temperature-material test methods are also evaluated.

Effect of drought stress on yield, proline and chlorophyll contents in three chickpea cultivars

NARCIS (Netherlands)

Mafakheri, A.; Siosemardeh, A.; Bahramnejad, B.; Struik, P.C.; Sohrabi, Y.

2010-01-01

Drought stress is one of the major abiotic stresses in agriculture worldwide. This study was carried out to investigate the effect of drought stress on proline content, chlorophyll content, photosynthesis and transpiration, stomatal conductance and yield characteristics in three varieties of

Effect of water stress and harvesting stages on quantitative and qualitative yields of coriander (Coriandrum sativum L.

Directory of Open Access Journals (Sweden)

A. Ahmadian

2016-05-01

Full Text Available In order to study the effect of drought stress and harvesting stages on quantitative and qualitative yields of Coriander (Coriandrum sativum L. this experiment was conducted on split plot based on a randomized completely block design with 3 replications in Torbat-e Heydariyeh University, Iran, during growing season of 2010-2011. Treatments were drought stress (in three levels no stress: control and irrigation in 60 and 30 percentage of FC as main plots and harvesting times (in 3 levels consist of: before flowering, flowering and after flowering as sub plots. Results showed that drought stress and harvesting stages had significant affected on leaf number, height, number of stem, wet and dry weight of plant, SPAD, proline content, carbohydrate content, essential oil yield and percentage and components of essential oil of coriander. Increasing water stress decreased yield and its components while enhanced proline and carbohydrate contents. Maximum of essential oil and its main components (linalool, alpha pentene, gamma terpinene, geranial acetate and camphor were in low stress that had significant difference with other stress treatments. Delaying in harvest enhanced yield and its components and essential oil percentage. Proline content had no significant difference between flowering and after flowering stages. Therefore, we can suggest low stress of water and harvest at after flowering stage to get maximum of yield.

The Effect of Drought Stress on Morphological Characteristics and Yield Components of Medicinal Plant Fenugreek

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N. Bazzazi

2013-06-01

Full Text Available Fenugreek (Trigonella foenum-graecum L. is one of the oldest medicinal plants. In order to study water-stress effects on some morphological characteristics of fenugreek, an experiment was carried out in a strip plots based on randomized complete blocks design with three replicates, at Research Farm of Shahrekord University, Shahrekord, Iran, in 2010. The first factor was allocated to four water stress levels (irrigation after depletion of 20 (as control, 40, 60 and 80% of available soil moisture and the second factor was six fenugreek landraces (Shiraz, Ardestan, Tirancheh, Yazd, Jahrom and Hindi. The results of ANOVA and comparison of means indicated that the effect of water stress was significant for all traits and variation was observed among landraces for all the studied characteristics. Mean comparison showed that drought stress reduced days to flowering, days to maturity, plant height and yield components (number of pods per plant, number of seeds per pod and 1000-kernel weight. It was also revealed that water stress caused reduction in biological yield (43% and grain yield (42.3% of all genotypes. Comparison between landraces indicated that maximum biological and grain yield belonged to Ardestan landrace. Assessment of cluster analysis showed that it was possible to classify Ardestan, Shiraz and Tirancheh as a single group having tolerance to water stress. In general, based on obtained results, the Ardestan landrace, with 22.37 g/plant, had the highest biological yield and Hindi landrace, with 73.83 days to maturity, was the most early-maturing one.

Global crop yield response to extreme heat stress under multiple climate change futures

Science.gov (United States)

Deryng, D.; Conway, D.; Ramankutty, N.; Price, J.; Warren, R.

2014-12-01

Extreme heat stress during the crop reproductive period can be critical for crop productivity. Projected changes in the frequency and severity of extreme climatic events are expected to negatively impact crop yields and global food production. This study applies the global crop model PEGASUS to quantify, for the first time at the global scale, impacts of extreme heat stress on maize, spring wheat and soybean yields resulting from 72 climate change scenarios for the 21st century. Our results project maize to face progressively worse impacts under a range of RCPs but spring wheat and soybean to improve globally through to the 2080s due to CO2 fertilization effects, even though parts of the tropic and sub-tropic regions could face substantial yield declines. We find extreme heat stress at anthesis (HSA) by the 2080s (relative to the 1980s) under RCP 8.5, taking into account CO2 fertilization effects, could double global losses of maize yield (dY = -12.8 ± 6.7% versus -7.0 ± 5.3% without HSA), reduce projected gains in spring wheat yield by half (dY = 34.3 ± 13.5% versus 72.0 ± 10.9% without HSA) and in soybean yield by a quarter (dY = 15.3 ± 26.5% versus 20.4 ± 22.1% without HSA). The range reflects uncertainty due to differences between climate model scenarios; soybean exhibits both positive and negative impacts, maize is generally negative and spring wheat generally positive. Furthermore, when assuming CO2 fertilization effects to be negligible, we observe drastic climate mitigation policy as in RCP 2.6 could avoid more than 80% of the global average yield losses otherwise expected by the 2080s under RCP 8.5. We show large disparities in climate impacts across regions and find extreme heat stress adversely affects major producing regions and lower income countries.

Global crop yield response to extreme heat stress under multiple climate change futures

International Nuclear Information System (INIS)

Deryng, Delphine; Warren, Rachel; Conway, Declan; Ramankutty, Navin; Price, Jeff

2014-01-01

Extreme heat stress during the crop reproductive period can be critical for crop productivity. Projected changes in the frequency and severity of extreme climatic events are expected to negatively impact crop yields and global food production. This study applies the global crop model PEGASUS to quantify, for the first time at the global scale, impacts of extreme heat stress on maize, spring wheat and soybean yields resulting from 72 climate change scenarios for the 21st century. Our results project maize to face progressively worse impacts under a range of RCPs but spring wheat and soybean to improve globally through to the 2080s due to CO 2 fertilization effects, even though parts of the tropic and sub-tropic regions could face substantial yield declines. We find extreme heat stress at anthesis (HSA) by the 2080s (relative to the 1980s) under RCP 8.5, taking into account CO 2 fertilization effects, could double global losses of maize yield (ΔY = −12.8 ± 6.7% versus − 7.0 ± 5.3% without HSA), reduce projected gains in spring wheat yield by half (ΔY = 34.3 ± 13.5% versus 72.0 ± 10.9% without HSA) and in soybean yield by a quarter (ΔY = 15.3 ± 26.5% versus 20.4 ± 22.1% without HSA). The range reflects uncertainty due to differences between climate model scenarios; soybean exhibits both positive and negative impacts, maize is generally negative and spring wheat generally positive. Furthermore, when assuming CO 2 fertilization effects to be negligible, we observe drastic climate mitigation policy as in RCP 2.6 could avoid more than 80% of the global average yield losses otherwise expected by the 2080s under RCP 8.5. We show large disparities in climate impacts across regions and find extreme heat stress adversely affects major producing regions and lower income countries. (paper)

Improving Wheat Growth and Yield Using Chlormequat Chloride, Salicylic Acid and Jasmonic Acid under Water Stress

Directory of Open Access Journals (Sweden)

N Vahabi

2017-06-01

Full Text Available Introduction Drought stress is most important abiotic stress reducing growth and production of wheat worldwide. Protective role of plant growth regulators (PGRs against drought stress has been accepted in general, however, comparison of PGRs types to determine the optimum one is crucial. Many PGRs are known to alleviate the negative effects of drought stress in plants. However, limited research has been conducted to investigate the potential benefits of exogenous application of different PGRs in wheat plants grown under drought stress. Chlormequat chloride (CCC, salicylic acid (SA and jasmonic acid (JA could consider as three major PGRs using in cereals. Materials and Methods To examine the effect of three PGRs consisted of CCC, SA and JA on yield components and grain yield of wheat cv. Roshan under different water stress conditions (a range of light to severe drought levels two separated experiments were conducted at controlled and field conditions at College of Agriculture, Shiraz University during 2012-2013 growing seasons. Concentration of CCC, SA and JA were 19.0, 1.0 and 0.1 mM, respectively. Drought stress levels were 100%, 80%, 60% and 40% of field capacity in greenhouse and were 100%, 2/3 and 1/5 of field capacity in the field experiment. Field capacity was determined as 25% (g g-1 for the experimental field. Greenhouse and field researches were carried out in factorial experiment based on completely randomized design and in split plot experiment based on randomized complete block design, respectively. Four and three replications were used greenhouse and field experiments, respectively. Roshan as a bread wheat cultivar with standard height was used. Foliar application of 3 PGRs was done at double ridges stage in both experiments; however, irrigation treatments were applied at double ridges stage and early anthesis at greenhouse and field experiment, respectively. For plot irrigation a tape system was used and amount of irrigation was

Quantifying the stress fields due to a delta-hydride precipitate in alpha-Zr matrix

Energy Technology Data Exchange (ETDEWEB)

Tummala, Hareesh [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Capolungo, Laurent [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tome, Carlos N. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-10-19

This report is a preliminary study on δ-hydride precipitate in zirconium alloy performed using 3D discrete dislocation dynamics simulations. The ability of dislocations in modifying the largely anisotropic stress fields developed by the hydride particle in a matrix phase is addressed for a specific dimension of the hydride. The influential role of probable dislocation nucleation at the hydride-matrix interface is reported. Dislocation nucleation around a hydride was found to decrease the shear stress (S₁₃) and also increase the normal stresses inside the hydride. We derive conclusions on the formation of stacks of hydrides in zirconium alloys. The contribution of mechanical fields due to dislocations was found to have a non-negligible effect on such process.

Metastability at the Yield-Stress Transition in Soft Glasses

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Matteo Lulli

2018-05-01

Full Text Available We study the solid-to-liquid transition in a two-dimensional fully periodic soft-glassy model with an imposed spatially heterogeneous stress. The model we consider consists of droplets of a dispersed phase jammed together in a continuous phase. When the peak value of the stress gets close to the yield stress of the material, we find that the whole system intermittently tunnels to a metastable “fluidized” state, which relaxes back to a metastable “solid” state by means of an elastic-wave dissipation. This macroscopic scenario is studied through the microscopic displacement field of the droplets, whose time statistics displays a remarkable bimodality. Metastability is rooted in the existence, in a given stress range, of two distinct stable rheological branches, as well as long-range correlations (e.g., large dynamic heterogeneity developed in the system. Finally, we show that a similar behavior holds for a pressure-driven flow, thus suggesting possible experimental tests.

Metastability at the Yield-Stress Transition in Soft Glasses

Science.gov (United States)

Lulli, Matteo; Benzi, Roberto; Sbragaglia, Mauro

2018-04-01

We study the solid-to-liquid transition in a two-dimensional fully periodic soft-glassy model with an imposed spatially heterogeneous stress. The model we consider consists of droplets of a dispersed phase jammed together in a continuous phase. When the peak value of the stress gets close to the yield stress of the material, we find that the whole system intermittently tunnels to a metastable "fluidized" state, which relaxes back to a metastable "solid" state by means of an elastic-wave dissipation. This macroscopic scenario is studied through the microscopic displacement field of the droplets, whose time statistics displays a remarkable bimodality. Metastability is rooted in the existence, in a given stress range, of two distinct stable rheological branches, as well as long-range correlations (e.g., large dynamic heterogeneity) developed in the system. Finally, we show that a similar behavior holds for a pressure-driven flow, thus suggesting possible experimental tests.

Effect of intergranular stress on yielding of 316H during room temperature cyclic loading

International Nuclear Information System (INIS)

Al Mamun, Abdullah; Moat, Richard; Bouchard, John; Kelleher, Joe

2016-01-01

Assessment of cyclic deformation is an integral part of nuclear power plant life assessment code, as many of the components in plant go through scheduled and unscheduled cyclic deformation owing to varying thermal and mechanical stresses. In polycrystalline material like 316H, a type of micro stress known as intergranular stress is generated due to elastic and plastic anisotropies during such cyclic loading. In tension-compression loading cycles, these stresses remain in the material as a residual stress upon unloading to zero stress from the tensile/compressive peak or intermediates stresses. The magnitude of these stresses vary depending on the point in the cycle from which it was unloaded from. When the material is re-loaded either in the same or reverse loading direction these residual stresses increase or decrease the effective stress acting in the material and as such the macroscopic yield stress of the material in subsequent cycle is changed significantly. The magnitude of intergranular stresses in many differently oriented grain families can be measured simultaneously using time of flight (ToF) neutron diffraction technique. In this paper, we have used this technique to experimentally study, how these intergranular stresses affect the yield (proof) stress of 316H at room temperature. (author)

Optimization of MR fluid Yield stress using Taguchi Method and Response Surface Methodology Techniques

Science.gov (United States)

Mangal, S. K.; Sharma, Vivek

2018-02-01

Magneto rheological fluids belong to a class of smart materials whose rheological characteristics such as yield stress, viscosity etc. changes in the presence of applied magnetic field. In this paper, optimization of MR fluid constituents is obtained with on-state yield stress as response parameter. For this, 18 samples of MR fluids are prepared using L-18 Orthogonal Array. These samples are experimentally tested on a developed & fabricated electromagnet setup. It has been found that the yield stress of MR fluid mainly depends on the volume fraction of the iron particles and type of carrier fluid used in it. The optimal combination of the input parameters for the fluid are found to be as Mineral oil with a volume percentage of 67%, iron powder of 300 mesh size with a volume percentage of 32%, oleic acid with a volume percentage of 0.5% and tetra-methyl-ammonium-hydroxide with a volume percentage of 0.7%. This optimal combination of input parameters has given the on-state yield stress as 48.197 kPa numerically. An experimental confirmation test on the optimized MR fluid sample has been then carried out and the response parameter thus obtained has found matching quite well (less than 1% error) with the numerically obtained values.

Modelling climate change impacts on viticultural yield, phenology and stress conditions in Europe.

Science.gov (United States)

Fraga, Helder; García de Cortázar Atauri, Iñaki; Malheiro, Aureliano C; Santos, João A

2016-11-01

Viticulture is a key socio-economic sector in Europe. Owing to the strong sensitivity of grapevines to atmospheric factors, climate change may represent an important challenge for this sector. This study analyses viticultural suitability, yield, phenology, and water and nitrogen stress indices in Europe, for present climates (1980-2005) and future (2041-2070) climate change scenarios (RCP4.5 and 8.5). The STICS crop model is coupled with climate, soil and terrain databases, also taking into account CO 2 physiological effects, and simulations are validated against observational data sets. A clear agreement between simulated and observed phenology, leaf area index, yield and water and nitrogen stress indices, including the spatial differences throughout Europe, is shown. The projected changes highlight an extension of the climatic suitability for grapevines up to 55°N, which may represent the emergence of new winemaking regions. Despite strong regional heterogeneity, mean phenological timings (budburst, flowering, veraison and harvest) are projected to undergo significant advancements (e.g. budburst/harvest can be >1 month earlier), with implications also in the corresponding phenophase intervals. Enhanced dryness throughout Europe is also projected, with severe water stress over several regions in southern regions (e.g. southern Iberia and Italy), locally reducing yield and leaf area. Increased atmospheric CO 2 partially offsets dryness effects, promoting yield and leaf area index increases in central/northern Europe. Future biomass changes may lead to modifications in nitrogen demands, with higher stress in northern/central Europe and weaker stress in southern Europe. These findings are critical decision support systems for stakeholders from the European winemaking sector. © 2016 John Wiley & Sons Ltd.

Effect of drought stress on growth, yield and seed quality of tomato (lycopersicon esculentum L.)

International Nuclear Information System (INIS)

Pervez, M.A.; Ayub, C.M.

2009-01-01

Plant growth is seriously affected by abiotic stresses such as drought, salinity or temperature. Drought is one of the most important limiting factors for agricultural crops and vegetable production in particular all around the world. Drought stress during vegetative or early reproductive growth usually reduces yield by reducing the number of seeds, seed size and seed quality. To assess the effect of drought stress on seed yield, seed quality and growth of tomato, the experiment was conducted in green house in plastic pots at Pen-y-Fridd field station, University of Wales, Bangor, U.K. during 2003-2004. Tomato cv. Moneymaker was used as a test crop. There were four treatments i.e. early stress (when first truss has set the fruits), middle stress (when fruits in first truss were fully matured and started changing their colour), late stress (when fruits on first truss were ripened fully), whereas in control no stress was imposed. Analysis of data regarding various attributes (fruit weight and shoot dry weight per plant, number of seeds per fruit, total number of seeds and seed weight per plant and vigour of seed) showed that drought stress had non-significant effect on vigour, quality and yield of tomato seed. Plant height, number of leaves and number of fruits per plant showed significant results toward drought stress signifying drought effects on growth of tomato. (author)

Postpartum endocrine activities, metabolic attributes and milk yield are influenced by thermal stress in crossbred dairy cows.

Science.gov (United States)

Ihsanullah; Qureshi, Muhammad Subhan; Suhail, Syed Muhammad; Akhtar, Sohail; Khan, Rifat Ullah

2017-09-01

This study was conducted on 30 freshly parturated multiparous crossbred dairy cows possessing three levels of Holstein Frisian genetic makeup (62.5, 75.0, and 87.5%). Data on temperature humidity index (THI) were classified into comfortable (≤ 71), mild stress (72-79), moderate stress (80-89), and stressful (≥90) zone. Results showed that serum cortisol concentration increased significantly (P stressful condition irrespective of genetic makeup compared to the other zones. Daily milk yield (DMY) was significantly (P stressful condition. Triglyceride was significantly higher in cows with genetic makeup 87.5% compared to the others, while total serum protein was significantly (P stressful conditions. The mean concentration of cortisol and protein increased linearly from comfort to the stressful condition, while mean serum triglyceride, glucose, progesterone (P 4 ), and luteinizing hormone (LH) decreased by moving from comfort to stressful conditions. Results also indicated that higher cortisol level in higher grade crossbred cows was adversely associated with LH concentration and milk yield under thermal stress conditions. Greater triglyceride in high-grade crossbred (87.5%) cows indicates higher fat mobilization reflecting a negative energy balance. We concluded that heat stress increased blood cortisol and protein, and reduced milk yield in dairy cows irresptive of the genetic makeup. In addition, there was no significant difference in blood metabolites and daily milk yield in the different levels of genetic makeup cows.

Response of Yield, Yield Components and Nutrient Concentration of Cumin (Cuminum cyminum L. to Mycorrhizal Symbiosis under Salt Stress Conditions

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M. Bijhani

2016-01-01

Full Text Available To study the effects of mycorrhizal inoculation and salinity stress on the growth, yield and nutrient concentrations of cumin (Cuminum cyminum L., an experiment was carried out as split plot in a completely randomized block design at Zabol University Research Farm in 2013. Treatments consisted of three salinity stresses: 1 (control, 5 and 10 dSm-1, was considered as the main treatments, and four levels of mycorrhizal inoculation (Glomus intraradices, G. etanicatum, G. hoi and non-inoculation as control as the sub-treatments. The effects of salinity on all traits under study, except umbers per plant, were significant, and severe stress (10 dSm-1 reduced 100 seed weight, number of seeds per umbel, concentrations of phosphorus, calcium and magnesium in seeds by 17.71, 11.4, 14.95, 46.08, 13.60 %, respectively, as compared to the control. The numbers of seeds per umbel and phosphorus concentration in seed were highest in G. intraradices with 28.4 and 54.4%, respectively as compared to control and umbels per plant was also maximum (9.7 by using G. etanicatum. Mycorrhizal inoculation did not have significant effect on calcium and magnesium concentrations in seeds and 1000 seed weight. However mycorrhiza × salinity stress interaction was significant about concentration of sodium, potassium and sodium to potassium ratio (Na/K in seeds, as well as seed yield and seed number per plant. Among the species of mycorrhiza, applied G. intraradices had better performance in severe salinity (10 dS-1 and increased seed yield and seed number per plant by 28.5 and 47.6%, respectively in comparision control. The results suggested that mycorrhizal inoculation improves water absorption by plant. Yield increases of plants under different salinity regimes dependent on their mycorrhizal inoculation.

The Effect of Stochastically Varying Creep Parameters on Residual Stresses in Ceramic Matrix Composites

Science.gov (United States)

Pineda, Evan J.; Mital, Subodh K.; Bednarcyk, Brett A.; Arnold, Steven M.

2015-01-01

Constituent properties, along with volume fraction, have a first order effect on the microscale fields within a composite material and influence the macroscopic response. Therefore, there is a need to assess the significance of stochastic variation in the constituent properties of composites at the higher scales. The effect of variability in the parameters controlling the time-dependent behavior, in a unidirectional SCS-6 SiC fiber-reinforced RBSN matrix composite lamina, on the residual stresses induced during processing is investigated numerically. The generalized method of cells micromechanics theory is utilized to model the ceramic matrix composite lamina using a repeating unit cell. The primary creep phases of the constituents are approximated using a Norton-Bailey, steady state, power law creep model. The effect of residual stresses on the proportional limit stress and strain to failure of the composite is demonstrated. Monte Carlo simulations were conducted using a normal distribution for the power law parameters and the resulting residual stress distributions were predicted.

Effect of drying and co-matrix addition on the yield and quality of supercritical CO₂ extracted pumpkin (Cucurbita moschata Duch.) oil.

Science.gov (United States)

Durante, Miriana; Lenucci, Marcello S; D'Amico, Leone; Piro, Gabriella; Mita, Giovanni

2014-04-01

In this work a process for obtaining high vitamin E and carotenoid yields by supercritical carbon dioxide (SC-CO₂) extraction from pumpkin (Cucurbita moschata Duch.) is described. The results show that the use of a vacuum oven-dried [residual moisture (∼8%)] and milled (70 mesh sieve) pumpkin flesh matrix increased SC-CO₂ extraction yields of total vitamin E and carotenoids of ∼12.0- and ∼8.5-fold, respectively, with respect to the use of a freeze-dried and milled flesh matrix. The addition of milled (35 mesh) pumpkin seeds as co-matrix (1:1, w/w) allowed a further ∼1.6-fold increase in carotenoid yield, besides to a valuable enrichment of the extracted oil in vitamin E (274 mg/100 g oil) and polyunsaturated fatty acids. These findings encourage further studies in order to scale up the process for possible industrial production of high quality bioactive ingredients from pumpkin useful in functional food or cosmeceutical formulation. Copyright © 2013 Elsevier Ltd. All rights reserved.

Postpartum endocrine activities, metabolic attributes and milk yield are influenced by thermal stress in crossbred dairy cows

Science.gov (United States)

Ihsanullah; Qureshi, Muhammad Subhan; Suhail, Syed Muhammad; Akhtar, Sohail; Khan, Rifat Ullah

2017-09-01

This study was conducted on 30 freshly parturated multiparous crossbred dairy cows possessing three levels of Holstein Frisian genetic makeup (62.5, 75.0, and 87.5%). Data on temperature humidity index (THI) were classified into comfortable (≤ 71), mild stress (72-79), moderate stress (80-89), and stressful (≥90) zone. Results showed that serum cortisol concentration increased significantly ( P cows during stressful condition irrespective of genetic makeup compared to the other zones. Daily milk yield (DMY) was significantly ( P cows during stressful condition. Triglyceride was significantly higher in cows with genetic makeup 87.5% compared to the others, while total serum protein was significantly ( P cows during both moderate and stressful conditions. The mean concentration of cortisol and protein increased linearly from comfort to the stressful condition, while mean serum triglyceride, glucose, progesterone (P4), and luteinizing hormone (LH) decreased by moving from comfort to stressful conditions. Results also indicated that higher cortisol level in higher grade crossbred cows was adversely associated with LH concentration and milk yield under thermal stress conditions. Greater triglyceride in high-grade crossbred (87.5%) cows indicates higher fat mobilization reflecting a negative energy balance. We concluded that heat stress increased blood cortisol and protein, and reduced milk yield in dairy cows irresptive of the genetic makeup. In addition, there was no significant difference in blood metabolites and daily milk yield in the different levels of genetic makeup cows.

Morphological plasticity of root growth under mild water stress increases water use efficiency without reducing yield in maize

Science.gov (United States)

Cai, Qian; Zhang, Yulong; Sun, Zhanxiang; Zheng, Jiaming; Bai, Wei; Zhang, Yue; Liu, Yang; Feng, Liangshan; Feng, Chen; Zhang, Zhe; Yang, Ning; Evers, Jochem B.; Zhang, Lizhen

2017-08-01

A large yield gap exists in rain-fed maize (Zea mays L.) production in semi-arid regions, mainly caused by frequent droughts halfway through the crop-growing period due to uneven distribution of rainfall. It is questionable whether irrigation systems are economically required in such a region since the total amount of rainfall does generally meet crop requirements. This study aimed to quantitatively determine the effects of water stress from jointing to grain filling on root and shoot growth and the consequences for maize grain yield, above- and below-ground dry matter, water uptake (WU) and water use efficiency (WUE). Pot experiments were conducted in 2014 and 2015 with a mobile rain shelter to achieve conditions of no, mild or severe water stress. Maize yield was not affected by mild water stress over 2 years, while severe stress reduced yield by 56 %. Both water stress levels decreased root biomass slightly but shoot biomass substantially. Mild water stress decreased root length but increased root diameter, resulting in no effect on root surface area. Due to the morphological plasticity in root growth and the increase in root / shoot ratio, WU under water stress was decreased, and overall WUE for both above-ground dry matter and grain yield increased. Our results demonstrate that an irrigation system might be not economically and ecologically necessary because the frequently occurring mild water stress did not reduce crop yield much. The study helps us to understand crop responses to water stress during a critical water-sensitive period (middle of the crop-growing season) and to mitigate drought risk in dry-land agriculture.

Morphological plasticity of root growth under mild water stress increases water use efficiency without reducing yield in maize

Directory of Open Access Journals (Sweden)

Q. Cai

2017-08-01

Full Text Available A large yield gap exists in rain-fed maize (Zea mays L. production in semi-arid regions, mainly caused by frequent droughts halfway through the crop-growing period due to uneven distribution of rainfall. It is questionable whether irrigation systems are economically required in such a region since the total amount of rainfall does generally meet crop requirements. This study aimed to quantitatively determine the effects of water stress from jointing to grain filling on root and shoot growth and the consequences for maize grain yield, above- and below-ground dry matter, water uptake (WU and water use efficiency (WUE. Pot experiments were conducted in 2014 and 2015 with a mobile rain shelter to achieve conditions of no, mild or severe water stress. Maize yield was not affected by mild water stress over 2 years, while severe stress reduced yield by 56 %. Both water stress levels decreased root biomass slightly but shoot biomass substantially. Mild water stress decreased root length but increased root diameter, resulting in no effect on root surface area. Due to the morphological plasticity in root growth and the increase in root ∕ shoot ratio, WU under water stress was decreased, and overall WUE for both above-ground dry matter and grain yield increased. Our results demonstrate that an irrigation system might be not economically and ecologically necessary because the frequently occurring mild water stress did not reduce crop yield much. The study helps us to understand crop responses to water stress during a critical water-sensitive period (middle of the crop-growing season and to mitigate drought risk in dry-land agriculture.

The rising motion of spheres in structured fluids with yield stress

Science.gov (United States)

Mirzaagha, S.; Pasquino, R.; Iuliano, E.; D'Avino, G.; Zonfrilli, F.; Guida, V.; Grizzuti, N.

2017-09-01

The rising of spherical bodies in structured fluids with yield stress is studied. The system is a suspension of hydrogenated castor oil colloidal fibers in a surfactant micellar solution. The fiber network confers to the fluid a viscoelastic behavior, with a well-defined yield stress, which increases with increasing fiber concentration. Various fluids with different fiber contents are prepared and rheologically characterized. A home-made time-lapse photography setup is used to monitor the time evolution position of the spherical particles, and the rising motion of both hollow spheres and air bubbles, in the diameter range 65-550 μm, is measured. The experiments last as long as several weeks, corresponding to significantly low measured velocities. Finite element simulations are performed to support the experimental data, assuming both interfacial slip and no slip conditions. The fluid dynamic phenomenon is studied and discussed in terms of dimensionless numbers, such as yield ratio, Bingham number, and Stokes drag coefficient. The results are novel for the system (suspending medium and hollow spheres) and for the covered Bingham number range, which is extended over three orders of magnitude in comparison with already available literature results. Our values provide quantitative data of the mechanical properties (i.e., yield stress value) at very low shear rates, in a prohibitive range for a traditional rheometer, and agree with the macroscopic rheological response. Moreover, the important role of the power law index n of the Herschel-Bulkley model, used to fit the data, has been highlighted. Our results, based on a Bingham-like fluid, are compared with the experimental data already available with Carbopol, treated as a Herschel Bulkley fluid with n = 0.5. The results could have important implications in the fabric and personal care detergency, a technological area where many fluids have composition and show rheological properties similar to those considered in the

Evaluation of Chitosan Nanoparticles Effects on Yield and Yield Components of Barley (Hordeum vulgare L. under Late Season Drought Stress

Directory of Open Access Journals (Sweden)

Faride Behboudi

2018-01-01

Full Text Available As a step towards the profitable employment of nanoparticles (NPs in agriculture, effects of chitosan NPs was probed on barley plants under late season drought stress. A factorial experiment was performed based on a randomized complete block design with three replications. The experimental factors included the chitosan NPs concentrations (0 (control, 30, 60 and 90 ppm, application methods (foliar and soil application and irrigation regimes (well-watered and withholding of irrigation for 15 days after pollination. The barley seeds were separately planted in pots. Then, the NPs were added to them through the soil and foliar application at three stages. The results indicated that using the chitosan NPs, especially 60 and 90 ppm, significantly increased the leaf area (LA, the leaf color (SPAD, the number of grain per spike, the grain yield and the harvest index compared to the control. Also, drought stress significantly decreased the yield and yield components compared to the well-watered plants. In contrast, using the chitosan NPs in plants under drought stress significantly increased the relative water content (RWC, the 1000-grain weight, the grain protein, the proline content, the catalase (CAT and the superoxide dismutase (SOD compared to the control. There was no a significant difference between two methods of using NPs in most studied traits. The results highlighted that using the chitosan NPs, especially 60 and 90 ppm, in both irrigation regimes can significantly improve the majority of the studied traits compared to the control and mitigate the harmful effects of drought stress.

Traits in Spring Wheat Cultivars Associated with Yield Loss Caused by a Heat Stress Episode after Anthesis

DEFF Research Database (Denmark)

Vignjevic, Marija; Wang, Xiao; Olesen, Jørgen E

2015-01-01

with heat tolerance. Fifteen spring wheat (Triticum aestivum L.) cultivars were grown in pots under semifield conditions, and heat stress (35/26 °C) and control treatments (20/12 °C) were applied in growth chambers for 5 days starting 14 days after flowering. The heat stress treatment reduced final yield...... in the grain-filling period was negatively correlated with grain nitrogen yield (r = −0.60). A positive correlation (r = 0.73) was found between the treatment effect on green leaf area (GLA) and the reduction in yield resulting from heat stress. The amount of stem water-soluble carbohydrates (WSC...

Effect of the plate surface characteristics and gap height on yield stresses of a magnetorheological fluid

International Nuclear Information System (INIS)

Jonkkari, I; Syrjala, S; Kostamo, E; Kostamo, J; Pietola, M

2012-01-01

Effects of the plate material, surface roughness and measuring gap height on static and dynamic yield stresses of a magnetorheological (MR) fluid were investigated with a commercial plate–plate magnetorheometer. Magnetic and non-magnetic plates with smooth (Ra ∼ 0.3 μm) and rough (Ra ∼ 10 μm) surface finishes were used. It was shown by Hall probe measurements and finite element simulations that the use of magnetic plates or higher gap heights increases the level of magnetic flux density and changes the shape of the radial flux density profile. The yield stress increase caused by these factors was determined and subtracted from the measured values in order to examine only the effect of the wall characteristics or the gap height. Roughening of the surfaces offered a significant increase in the yield stresses for non-magnetic plates. With magnetic plates the yield stresses were higher to start with, but roughening did not increase them further. A significant part of the difference in measured stresses between rough non-magnetic and magnetic plates was caused by changes in magnetic flux density rather than by better contact of the particles to the plate surfaces. In a similar manner, an increase in gap height from 0.25 to 1.00 mm can lead to over 20% increase in measured stresses due to changes in the flux density profile. When these changes were compensated the dynamic yield stresses generally remained independent of the gap height, even in the cases where it was obvious that the wall slip was present. This suggests that with MR fluids the wall slip cannot be reliably detected by comparison of flow curves measured at different gap heights. (paper)

Tensile Stress Rupture Behavior of a Woven Ceramic Matrix Composite in Humid Environments at Intermediate Temperature

National Research Council Canada - National Science Library

LaRochelle, Kevin J

2005-01-01

Stress rupture tests on the Sylramic(TM) fiber with an in-situ layer of boron nitride, boron nitride interphase, and SiC matrix ceramic matrix composite were performed at 550 degrees C and 750 degrees C with 0.0, 0.2...

Growth and yield response of wheat varieties to water stress at booting and anthesis stages of development

International Nuclear Information System (INIS)

Khakwani, A.A.; Abid, M.

2012-01-01

Plants of 6 bread wheat varieties (Damani, Hashim-8, Gomal-8, DN-73, Zam-04 and Dera-98) were subjected to 2 treatments i.e., control treatment (100% field capacity) and stressed treatment (20 days water stress was given during booting stage and 20 days water stress after anthesis). The findings revealed highly significant differences among means of wheat varieties in all physiological and yield traits. Almost all varieties showed their best adaptation under stressed environment however Hashim-8 and Zam-04 behaved exclusively and indicated higher relative water content (RWC), mean productivity (MP), geometric mean productivity (GMP) and stress tolerance index (STI) whereas stress susceptibility index (SSI) and tolerance (TOL) was estimated at its lowest, as these traits are recognised beneficial drought tolerance indicators for selection of a stress tolerant variety. Similarly, total grain yield per plant, biological yield per plant and harvest index was also higher in the same wheat varieties that put them as good candidates for selection criteria in wheat breeding program for drought resistant. (author)

Evaluation Physiological Characteristics and Grain Yield Canola Cultivars under end Seasonal Drought Stress in Weather Condition of Ahvaz

Directory of Open Access Journals (Sweden)

A Seyed Ahmadi

2015-07-01

Full Text Available To evaluate canola cultivars response to physiological characteristics and grain yield end seasonal drought stress in weather condition of Ahvaz, farm experiments were done at research farm of Khuzestan agriculture and natural resources center. During 2007-2008 and 2008-2009 crop years. Farm test comprised drought stress was done as split plot form with randomize complete block design with four replication, treatments consist of drought stress (main factor including 50, 60 and 70 percent of water use content, which was applied from early heading stage until physiological maturity, and three spring canola cultivar including Shirali, Hayola 401 and R.G.S. were considered as sub plots. Measurements include biological yield, grain yield, harvesting index, number of pod per plant 1000 grain weight, number of grain in pod, plant height, and stem diameter, oil and protein percentage. Results showed that drought stress reduced significantly grain yield, biological yield, harvest index and the average of reduction of them during 2 years for per unit reduce moisture from 50% to 70% were 2, 1.35, and 0.81 percent, respectively. During two years, 1000 grain weight, number of pods per plant and number of grain per pod reduced 27, 36 and 20 percent, respectively. Terminal Drought stress reduced significantly plant height, stem diameter, stem number per plant and pod length, this reduced were 12, 46, 36 and 14 percent, respectively. Stem diameter, and stem number per plant reduced more than other characteristics. In this study oil grain decreased 12 % and protein grain increased 18.5% but oil and protein yield decreased 44.9% and 27.1% respectively..Finally, in weather condition of Khuzestan, terminal drought stress on February and March in which has simultaneous with early flowering stage and filling seed, significantly, reduced yield and compounded yield and affects on stem growth and qualities oil and protein negatively. Therefore, with irrigation

Neglecting rice milling yield and quality underestimates economic losses from high-temperature stress.

Directory of Open Access Journals (Sweden)

Nathaniel B Lyman

Full Text Available Future increases in global surface temperature threaten those worldwide who depend on rice production for their livelihoods and food security. Past analyses of high-temperature stress on rice production have focused on paddy yield and have failed to account for the detrimental impact of high temperatures on milling quality outcomes, which ultimately determine edible (marketable rice yield and market value. Using genotype specific rice yield and milling quality data on six common rice varieties from Arkansas, USA, combined with on-site, half-hourly and daily temperature observations, we show a nonlinear effect of high-temperature stress exposure on yield and milling quality. A 1 °C increase in average growing season temperature reduces paddy yield by 6.2%, total milled rice yield by 7.1% to 8.0%, head rice yield by 9.0% to 13.8%, and total milling revenue by 8.1% to 11.0%, across genotypes. Our results indicate that failure to account for changes in milling quality leads to understatement of the impacts of high temperatures on rice production outcomes. These dramatic losses result from reduced paddy yield and increased percentages of chalky and broken kernels, which together decrease the quantity and market value of milled rice. Recently published estimates show paddy yield reductions of up to 10% across the major rice-producing regions of South and Southeast Asia due to rising temperatures. The results of our study suggest that the often-cited 10% figure underestimates the economic implications of climate change for rice producers, thus potentially threatening future food security for global rice producers and consumers.

Effects of shade and drought stress on soybean hormones and yield ...

African Journals Online (AJOL)

Multiple frequently interactive stress factors naturally influence plant due to global change. The leaf's hormone concentrations, main-stem and branch yield response to the combination of shade and drought were studied in a greenhouse experiment during 2009 and 2010 seasons. Pot experiments were conducted under ...

Macro-mechanical material model for fiber reinforced metal matrix composites

CERN Document Server

Banks-Sills, L

1999-01-01

The stress-strain behavior of a metal matrix composite reinforced with unidirectional, continuous and periodic fibers is investigated. Three-dimensional micro-mechanical analyses of a unit cell by means of the finite element method $9 and homogenization-localization are carried out. These calculations allow the determination of material behavior of the in-plane, as well as the fiber directions. The fibers are assumed to be elastic and the matrix elasto-plastic. $9 The matrix material is governed by a von Mises yield surface, isotropic hardening and an associated flow rule. With the aid of these analyses, the foundation to a macro-mechanical material model is presented which is employed to $9 consider an elementary problem. The model includes an anisotropic yield surface with isotropic hardening and an associated flow rule. A beam in bending containing square fibers under plane strain conditions is analyzed by means of $9 the model. Two cases are considered: one in which the fibers are symmetric with respect t...

The Effect of Chemical, Biological and Organic Nutritional Treatments on Sunflowers Yield and Yield Components under the Influence of Water Deficit Stress

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fatemeh soleymani

2016-07-01

Full Text Available Introduction To achieve the higher economic yield of crop plants, supplying enough nutrients to plants is very important. Moreover, nutrient uptakes by plants is influenced by the soil water contents. However, nowadays chemical fertilizer application is important agronomic factor that has significant effects on growth and quantity and quality of final yield, but traditional nutrient management and excessive use of chemical fertilizers may cause the environmental problems such as contamination of soil and water resources, low quality of agricultural products and reduction of soil fertility. These factors have drawn attention to health and ecological sustainable farming systems (Sharma, 2002. In this context, usage of organic and biological products for plant nutrition is considered as one of the solutions to achieve the goals of sustainable agriculture. Materials and methods To evaluate the effect of various feeding systems on yield and yield components of sunflower (Helianthus annuus L. under the influence of water deficit stress, a split-plot experiment based on randomized complete block design with three replications, was carried out in the Agricultural Faculty of Bu-Ali Sina University during the growing season of 2013-2014. Main plots consisted of two irrigation levels: optimum irrigation and deficit irrigation stress (irrigation after 60 and 120 mm evaporation from evaporation pan, class A, respectively and sub-plots included of nine nutrition systems: 1- no bio or chemical fertilizer application, 2- 100% of the recommended chemical fertilizer , 3- vermicompost, 4- phospho nitro kara, 5- vermicompost+ phospho nitro kara, 6- vermicompost+ ½ chemical fertilizer, 7- phospho nitro kara+ ½ chemical fertilizer, 8- vermicompost+ phospho nitro kara+ ½ chemical fertilizer, 9- ½ proposed chemical fertilizer. Phospho-nitro-kara which contains phosphate solubilizing and nitrogen fixing bacteria (Bacillus coagulans, azotobactr chroocuccum and

The transverse mobility of yield-stress fluids in fibrous media

Science.gov (United States)

Shahsavari, Setareh; McKinley, Gareth H.

2015-11-01

The pressure-drop/flow-rate relationship for fluids that exhibit a yield stress and a shear dependent viscosity flowing through fibrous media is studied numerically. The Cauchy momentum equation along with the Bingham or Herschel-Bulkley constitutive equations are solved for flow transverse to a periodic array of fibers and systematic parametric studies are used to understand the individual roles of geometrical characteristics and fluid rheological properties. We develop a scaling model to predict the fluid mobility as a function of the medium porosity and the Bingham number. In addition, using this scaling model we estimate the width of the unyielded region between two adjacent fibers. Numerical computations are combined with the scaling model to obtain a criterion for the critical pressure gradient required to drive flow. Variations in the size of the yielded zones, the velocity profiles and the resulting stress fields are investigated for the limiting cases of (i) densely packed fiber arrays and (ii) very sparsely distributed fibers, and the hydrodynamic transition between these configurations is investigated. While this work focuses on the flow of inelastic fluids, the methodology can be extended to consider more complex rheology such as flow of elasto-visco-plastic fluids.

Universal rescaling of flow curves for yield-stress fluids close to jamming

Science.gov (United States)

Dinkgreve, M.; Paredes, J.; Michels, M. A. J.; Bonn, D.

2015-07-01

The experimental flow curves of four different yield-stress fluids with different interparticle interactions are studied near the jamming concentration. By appropriate scaling with the distance to jamming all rheology data can be collapsed onto master curves below and above jamming that meet in the shear-thinning regime and satisfy the Herschel-Bulkley and Cross equations, respectively. In spite of differing interactions in the different systems, master curves characterized by universal scaling exponents are found for the four systems. A two-state microscopic theory of heterogeneous dynamics is presented to rationalize the observed transition from Herschel-Bulkley to Cross behavior and to connect the rheological exponents to microscopic exponents for the divergence of the length and time scales of the heterogeneous dynamics. The experimental data and the microscopic theory are compared with much of the available literature data for yield-stress systems.

Response of Barley Double Haploid Lines to the Grain Yield and Morphological Traits under Water Deficit Stress Conditions

Directory of Open Access Journals (Sweden)

Maroof Khalily

2017-04-01

Full Text Available To study the relationships of grain yield and some of agro-morphological traits in 40 doubled haploid (DH lines along with parental and three check genotypes in a randomized complete block design with two replications under two water regimes (normal and stress were evaluated during 2011-2012 and 2012-2013 growing seasons. Combined analysis of variance showed significant difference for all the traits in terms of the year, water regimes, lines, and and line × year. Comparison of group means, between non-stress and stress conditions, showed that DH lines had the lowest reduction percentage for the number of grains per spike, thousand grain weight, grain yield and biological yield as opposed to check genotypes. The correlation between grain yield with biological yield, harvest index, thousand grain weight, and hectoliter of kernel weight in both conditions, were highly significant and positive. Based on stepwise regression the peduncle length, number of seeds per spike, thousand seed weight, and hectoliter of kernel weight had important effect on increasing seed yield. The result of path analysis showed that these traits had the highest direct effect on grain yield. Based on mean comparisons of morphological characters as well as STI and GMP indices it can be concluded that lines No.11, 13, 14, 24, 29, 30, 35 and 39 were distinguished to be desirable lines for grain yield and their related traits and also tolerant lines in terms of response to drought stress conditions.

Effects of drought stress and different densities on oil yield and ...

African Journals Online (AJOL)

For evaluation of water deficit stress and planting density effects on the oil and biological yield attributes of sunflower, an experiment was conducted in a randomized complete block design (RCBD) based split plot factorial design in three replications in the research field of Baku State University, Baku, Azerbaijan, in 2009.

A seed preferential heat shock transcription factor from wheat provides abiotic stress tolerance and yield enhancement in transgenic Arabidopsis under heat stress environment.

Directory of Open Access Journals (Sweden)

Harsh Chauhan

Full Text Available Reduction in crop yield and quality due to various abiotic stresses is a worldwide phenomenon. In the present investigation, a heat shock factor (HSF gene expressing preferentially in developing seed tissues of wheat grown under high temperatures was cloned. This newly identified heat shock factor possesses the characteristic domains of class A type plant HSFs and shows high similarity to rice OsHsfA2d, hence named as TaHsfA2d. The transcription factor activity of TaHsfA2d was confirmed through transactivation assay in yeast. Transgenic Arabidopsis plants overexpressing TaHsfA2d not only possess higher tolerance towards high temperature but also showed considerable tolerance to salinity and drought stresses, they also showed higher yield and biomass accumulation under constant heat stress conditions. Analysis of putative target genes of AtHSFA2 through quantitative RT-PCR showed higher and constitutive expression of several abiotic stress responsive genes in transgenic Arabidopsis plants over-expressing TaHsfA2d. Under stress conditions, TaHsfA2d can also functionally complement the T-DNA insertion mutants of AtHsfA2, although partially. These observations suggest that TaHsfA2d may be useful in molecular breeding of crop plants, especially wheat, to improve yield under abiotic stress conditions.

Yield stress in metallic glasses: The jamming-unjamming transition studied through Monte Carlo simulations based on the activation-relaxation technique

International Nuclear Information System (INIS)

Rodney, David; Schuh, Christopher A.

2009-01-01

A Monte Carlo approach allowing for stress control is employed to study the yield stress of a two-dimensional metallic glass in the limit of low temperatures and long (infinite) time scales. The elementary thermally activated events are determined using the activation-relaxation technique (ART). By tracking the minimum-energy state of the glass for various applied stresses, we find a well-defined jamming-unjamming transition at a yield stress about 30% lower than the steady-state flow stress obtained in conventional strain-controlled quasistatic simulations. ART is then used to determine the evolution of the distribution of thermally activated events in the glass microstructure both below and above the yield stress. We show that aging below the yield stress increases the stability of the glass, both thermodynamically (the internal potential energy decreases) and dynamically (the aged glass is surrounded by higher-energy barriers than the initial quenched configuration). In contrast, deformation above the yield stress brings the glass into a high internal potential energy state that is only marginally stable, being surrounded by a high density of low-energy barriers. The strong influence of deformation on the glass state is also evidenced by the microstructure polarization, revealed here through an asymmetry of the distribution of thermally activated inelastic strains in glasses after simple shear deformation.

Effect of Filter Cake on Physiological Traits and Ear Yield of Sweet Corn under Late Drought Stress Condition

Directory of Open Access Journals (Sweden)

aziz karmollachaab

2017-10-01

Full Text Available Introduction Environmental stresses are one of the main causes of severe yield reductions. Drought is still a serious agronomic problem and also one of the most important factors contributing to crop yield loss in arid and semi-arid areas in the world. Filter Cake is a byproduct of sugarcane industry and experiments on corn showed that the use of 20 tons per hectare Filter Cake increases crop productivity, total amount of dry matter, protein and forage yield compared with the control. Materials and methods This experiment was conducted at the Research Station of the Ramin Agricultural University of Khuzestan in 2012. The experiment was done as a split plot based on randomized complete block design with three replications. Drought stress at the end of the growth period in three levels, non-stress, mild and severe drought stress, respectively irrigated after 25, 50 and 75% depletion of available water, and was considered as the main factor. Drought stress was applied in early stage of the male inflorescence of plants to maturity for 35 days, due to the critical stage of the plant in late spring. Soil moisture was determined by gravimetric method. Different doses of Filter Cake (0, 10, 20 and 30 tons per hectare were considered as subplot factor and was added to the soil two days before the seeding. The final harvest as green corn was performed in the first phase of dough by hand in three times and two midfields of each subplot was considered as the margin of half a meter for each side. Finally, the data were analyzed using SAS 9.1 and means were compared by Duncan’s multiple range test at probability level of 5%. Results and discussion In non-stress conditions, Filter Cake is significantly increased plant height, So the amounts of 20 and 30 tons per hectare increased by 11.7% and 10.1% of the plant’s height, respectively, but the use of 10 tons of Filter Cake did not have a significant effect on it. In severe stress conditions, the use of

Supportability of a High-Yield-Stress Slurry in a New Stereolithography-Based Ceramic Fabrication Process

Science.gov (United States)

He, Li; Song, Xuan

2018-03-01

In recent years, ceramic fabrication using stereolithography (SLA) has gained in popularity because of its high accuracy and density that can be achieved in the final part of production. One of the key challenges in ceramic SLA is that support structures are required for building overhanging features, whereas removing these support structures without damaging the components is difficult. In this research, a suspension-enclosing projection-stereolithography process is developed to overcome this challenge. This process uses a high-yield-stress ceramic slurry as the feedstock material and exploits the elastic force of the material to support overhanging features without the need for building additional support structures. Ceramic slurries with different solid loadings are studied to identify the rheological properties most suitable for supporting overhanging features. An analytical model of a double doctor-blade module is established to obtain uniform and thin recoating layers from a high-yield-stress slurry. Several test cases highlight the feasibility of using a high-yield-stress slurry to support overhanging features in SLA.

Effects of stress concentration on low-temperature fracture behavior of A356 alloy

Energy Technology Data Exchange (ETDEWEB)

Ma, Guanghui; Li, Runxia; Li, Rongde

2016-06-14

The effect of stress concentration on the dislocation motion, the Si particles and the crack propagation path in A356 alloy at the temperature of 20 °C to −60 °C was analyzed by scanning electron microscope and optical microscope using a series of notched tensile specimens and normal tensile specimens. The results show that the sensitivity of A356 alloy to the stress concentration increases, the tensile strength and yield strength of normal specimens and notched specimens increase, and the elongation shows a decreasing trend with the decrease of test temperature from 20 °C to −60 °C. The yield strength is not affected by the notch, and the tensile strength is sensitive to the stress concentration. Stress concentration leads to a large number of dislocation generation. Local plastic deformation occurred in the stress concentration region during the tensile process firstly. With the stress concentration in the aluminum matrix between the Si phase and the crack further increasing, the distribution of cracks along the Si phase leads to the cracking of aluminum matrix particle.

Do maize models capture the impacts of heat and drought stresses on yield? Using algorithm ensembles to identify successful approaches.

Science.gov (United States)

Jin, Zhenong; Zhuang, Qianlai; Tan, Zeli; Dukes, Jeffrey S; Zheng, Bangyou; Melillo, Jerry M

2016-09-01

Stresses from heat and drought are expected to increasingly suppress crop yields, but the degree to which current models can represent these effects is uncertain. Here we evaluate the algorithms that determine impacts of heat and drought stress on maize in 16 major maize models by incorporating these algorithms into a standard model, the Agricultural Production Systems sIMulator (APSIM), and running an ensemble of simulations. Although both daily mean temperature and daylight temperature are common choice of forcing heat stress algorithms, current parameterizations in most models favor the use of daylight temperature even though the algorithm was designed for daily mean temperature. Different drought algorithms (i.e., a function of soil water content, of soil water supply to demand ratio, and of actual to potential transpiration ratio) simulated considerably different patterns of water shortage over the growing season, but nonetheless predicted similar decreases in annual yield. Using the selected combination of algorithms, our simulations show that maize yield reduction was more sensitive to drought stress than to heat stress for the US Midwest since the 1980s, and this pattern will continue under future scenarios; the influence of excessive heat will become increasingly prominent by the late 21st century. Our review of algorithms in 16 crop models suggests that the impacts of heat and drought stress on plant yield can be best described by crop models that: (i) incorporate event-based descriptions of heat and drought stress, (ii) consider the effects of nighttime warming, and (iii) coordinate the interactions among multiple stresses. Our study identifies the proficiency with which different model formulations capture the impacts of heat and drought stress on maize biomass and yield production. The framework presented here can be applied to other modeled processes and used to improve yield predictions of other crops with a wide variety of crop models. © 2016 John

Matrix elements for the anti B{yields}X{sub s}{gamma} decay at NNLO

Energy Technology Data Exchange (ETDEWEB)

Schutzmeier, Thomas Paul

2009-12-17

In the context of the indirect search for non-standard physics in the flavour sector of the Standard Model (SM), one of the most interesting processes is the rare inclusive anti B{yields} X{sub s}{gamma} decay. On the one hand, being a flavour-changing neutral current, this B decay is sensitive to new physics, as it is loop-suppressed in the SM. On the other hand, it is only mildly affected by non-perturbative effects, and thus allows for precise theoretical predictions in the framework of renormalization-group improved perturbation theory. Accurate measurements as well as precise theoretical predictions with a good control over both perturbative and non-perturbative contributions have to be provided in order to derive stringent constraints on the parameter space of physics beyond the SM. On the experimental side, an outstanding accuracy in the measurement of the anti B{yields}X{sub s}{gamma} decay rate has been achieved, which is mainly due the specialized experiments BaBar and Belle at the so-called B factories. To match the small experimental uncertainty, higher order computations within an effective low-energy theory of the SM are mandatory. In fact, next-to-next-to-leading order (NNLO) QCD corrections are required to provide a prediction for the decay rate with the same precision as the measurement. The NNLO evaluation of the anti B{yields}X{sub s}{gamma} decay rate has been pursued by various groups over the last decade. The project was completed to a large extent and a first estimate at this level of perturbation theory was obtained in 2006. This prediction, however, lacks important contributions from yet unknown matrix elements, that were estimated from results which are only partially known to date. In this work, we provide a framework for the systematic study of the missing matrix elements at the NNLO. As main results of this thesis, we determine fermionic corrections to the charm quark mass dependent matrix elements of four-quark operators in the

Improvement of wheat yield grown under drought stress by boron foliar application at different growth stages

Directory of Open Access Journals (Sweden)

F.M.F. Abdel-Motagally

2018-04-01

Full Text Available Two field experiments were conducted to determine the effect of boron foliar application and water stress on yield of wheat plant grown in calcareous soil during 2013/2014 and 2014/2015 seasons. The highest mean values obtained against boron application time were potential contributor to total grains mass by improving the plant height (99.42 and 98.32 cm, spike length (11.86 and 11.72 cm, number of spikelets m−2 (332.65 and 324.35, grain yield plant−1 (21.56 and 20.26 g, 1000-grain weight (35.2 and 37.4 g and grain yield (1.87 and 1.85 ton fed.−1, which were recorded at normal irrigation level (100% from the amount of water consumption for wheat with boron spraying at booting stage (B1 in the first and second seasons, respectively. Furthermore, boron application significantly enhanced all studied growth traits under water stress levels (50% from the amount of water consumption for wheat compared to B-untreated plants. Boron spraying at booting stage enhances also plant pigments contents recording its highest mean values under normal water level (100% from the amount of water consumption for wheat. The reduction in stress markers (proline and H2O2 and the enhancement of plant pigments content under water stress levels (50% from the amount of water consumption for wheat by B spraying suggests an alleviating effect of boron foliar application to water stress in the test plant. This alleviating effect was more pronounced when B applied at booting stage. Therefore, booting stage was found to be the best time for boron application to get higher grains production and consequently, better economic returns of wheat. Keywords: Wheat, Growth stages, Boron application time, Water stress, Crop yield, Plant pigments, Proline, H2O2

Influence of oxidative stress and grains on sclerotial biomass and carotenoid yield of Penicillium sp. PT95.

Science.gov (United States)

Chen, Shu-Jun; Wang, Qi; Han, Jian-Rong

2010-08-01

Oxidative stress and grains were evaluated for carotenoid production by solid-state fermentation using Penicillium sp. PT95. When the fungus was grown at high oxidative stress, its sclerotial biomass and carotenoid content in sclerotia increased significantly with respect to low oxidative stress (P < 0.01). High oxidative stress also caused a statistically significant increase in carotenoid yield as compared with low oxidative stress (P < 0.01). Both the sclerotial biomass and the amount of carotenoid accumulated in sclerotia of strain PT95 were strongly dependent on the grain medium used. Among the grain media tested under high oxidative stress, buckwheat medium gave the highest content of carotenoid in sclerotia (828 microg/g dry sclerotia), millet medium gave respectively the highest sclerotial biomass (12.69 g/100 g grain) and carotenoid yield (10.152 mg/100 g grain). Copyright 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

On Inclusion-Matrix Interfacial Stresses in Composites Containing Phase-Transforming Phases

International Nuclear Information System (INIS)

Wang, Y.-C.; Ko, C.-C.

2010-01-01

Recent development in composites containing phase-transforming particles, such as vanadium dioxide or barium titanate, reveals the overall stiffness and viscoelastic damping of the composites may be unbounded. Negative stiffness is induced from phase transformation predicted by the Landau phase transformation theory. Although this unbounded phenomenon is theoretically supported with the composite homogenization theory, detailed stress analyses of the composites are still lacking. In this work, we analyze the two-dimensional plane stress elasticity problem of a square plate containing a circular inclusion, under the assumption that the Young's modulus of the inclusion is negative. Assumption of negative stiffness is a priori in the present analysis. A static loading condition is adopted to estimate the effective modulus of the composites by the ratio of applied stress to averaged strain on the loading edges. It is found that the interfacial stresses between the circular inclusion and matrix increase dramatically when the negative stiffness is so tuned that overall stiffness is unbounded. Furthermore, it is found that stress distributions in the inclusion are not uniform, contrary to Eshelby's theorem, which states, for two-phase, infinite composites, the inclusion's stress distribution is uniform when the shape of the inclusion has higher symmetry than an ellipse. The rationale for this nonuniform stress distributions is due to nonlocal effects induced from negative stiffness.

Matrix mechanics and fluid shear stress control stem cells fate in three dimensional microenvironment.

Science.gov (United States)

Chen, Guobao; Lv, Yonggang; Guo, Pan; Lin, Chongwen; Zhang, Xiaomei; Yang, Li; Xu, Zhiling

2013-07-01

Stem cells have the ability to self-renew and to differentiate into multiple mature cell types during early life and growth. Stem cells adhesion, proliferation, migration and differentiation are affected by biochemical, mechanical and physical surface properties of the surrounding matrix in which stem cells reside and stem cells can sensitively feel and respond to the microenvironment of this matrix. More and more researches have proven that three dimensional (3D) culture can reduce the gap between cell culture and physiological environment where cells always live in vivo. This review summarized recent findings on the studies of matrix mechanics that control stem cells (primarily mesenchymal stem cells (MSCs)) fate in 3D environment, including matrix stiffness and extracellular matrix (ECM) stiffness. Considering the exchange of oxygen and nutrients in 3D culture, the effect of fluid shear stress (FSS) on fate decision of stem cells was also discussed in detail. Further, the difference of MSCs response to matrix stiffness between two dimensional (2D) and 3D conditions was compared. Finally, the mechanism of mechanotransduction of stem cells activated by matrix mechanics and FSS in 3D culture was briefly pointed out.

Epoxy cracking in the epoxy-impregnated superconducting winding: nonuniform dissipation of stress energy in a wire-epoxy matrix model

International Nuclear Information System (INIS)

Tsukamoto, O.; Iwasa, Y.

1985-01-01

The authors present the epoxy-crack-induced temperature data of copper wires imbedded in wire-epoxy resin composite model at 4.2 K. The experimental results show that the epoxy-crackinduced temperature rise is higher in the copper wires than in the epoxy matrix, indicating that in stress-induced wire-epoxy failure, stress energy stored in the wire-epoxy matrix is preferrentially dissipated in the wire. A plausible mechanism of the nonuniform dissipation is presented

Overall mechanical properties of fiber-reinforced metal matrix composites for fusion applications

International Nuclear Information System (INIS)

You, J.H.; Bolt, H.

2002-01-01

The high-temperature strength and creep properties are among the crucial criteria for the structural materials of plasma facing components (PFC) of fusion reactors, as they will be subjected to severe thermal stresses. The fiber-reinforced metal matrix composites are a potential heat sink material for the PFC application, since the combination of different material properties can lead to versatile performances. In this article, the overall mechanical properties of two model composites based on theoretical predictions are presented. The matrix materials considered were a precipitation hardened CuCrZr alloy and reduced activation martensitic steel 'Eurofer'. Continuous SiC fibers were used for the reinforcement. The results demonstrate that yield stress, ultimate tensile strength, work hardening rate and creep resistance could be extensively improved by the fiber reinforcement up to fiber content of 40 vol.%. The influence of the residual stresses on the plastic behavior of the composites is also discussed

Static yield stress of a magnetorheological fluid containing Pickering emulsion polymerized Fe2O3/polystyrene composite particles.

Science.gov (United States)

Seo, Youngwook P; Kwak, Soonjong; Choi, Hyoung Jin; Seo, Yongsok

2016-02-01

The flow behaviors of magnetorheological (MR) suspensions containing Pickering emulsion polymerized Fe2O3/polystyrene (PS) composite particles were reanalyzed using the Seo-Seo model. The experimental shear stress data obtained experimentally from the magnetorheological fluid fit well to the Seo-Seo model, indicating that this model can describe the structural reformation process of the aligned fibers at various shear rates. Unlike the dynamic yield stress obtained from the Cho-Choi-Jhon (CCJ) model, the static yield stresses obtained from the Seo-Seo model exhibit the same quadratic dependence on the magnetic field strength for both pure Fe2O3 particle suspension and Fe2O3/PS particle suspensions, which is in agreement with the predictions of the polarization model. The static yield stress plausibly explains the difference in underlying mechanism of MR fluids. Copyright © 2015 Elsevier Inc. All rights reserved.

Effect of Drought Stress onYield and Yield Components of Sesame cultivars under Kerman conditions (Sesamum indicum L.

Directory of Open Access Journals (Sweden)

S Farahbakhsh

2015-04-01

Full Text Available To investigate effects of drought stress on yield and yield components of sesame in Kerman region a split-plot experiment based onn compelet randomised block design with three replications was carried out in 1388. Irrigation levels (Normal irrigation in all growth stages, witholding water after 50% flowering, witholding water after 50% pod setting and differen t sesame landraces (Jiroft, Shiraz, Ardestan, Dezful, Shahr babak, Gorgan, Sirjan, Markazi, Birjand and Orzueieh were considered as main plots and sub-plots respectively. Plant height, the biggest pod length, noumber of grain per pod, noumber of pod per plant, grain weight per plant, thousand grain weight and grain yield were the measured traits. Results showed all the measured traits were significantly affected by the irrigation treatments. The effects of different landraces on all traits except noumber of grain per plant were significant. Irrigation × landraces interaction affected all measured traits except the biggest pod length significantly. The highest grain yield was recorde for Markezi landrace (845.2 kg –ha under normal irrigation and the lowest one was obtained from Jiroft landrace (104.8 kg –ha with witholding irrigation after 50% flowering.

Analysis of the yielding behavior of electrorheological suspensions by controlled shear stress experiments

Czech Academy of Sciences Publication Activity Database

Pavlínek, V.; Sáha, P.; Perez-Gonzales, K.; de Vargas, L.; Stejskal, Jaroslav; Quadrat, Otakar

2006-01-01

Roč. 16, 1-2 (2006), s. 14-18 ISSN 1430-6395 R&D Projects: GA ČR GA202/06/0419 Institutional research plan: CEZ:AV0Z40500505 Keywords : electrorheology * yield stress * suspensions * polyaniline Subject RIV: CD - Macromolecular Chemistry

Effect of soil water stress on yield and proline content of four wheat ...

African Journals Online (AJOL)

STORAGESEVER

2010-01-04

Jan 4, 2010 ... Four lines of bread wheat (N-82-9, N-83-5, ... Key words: Water stress, Triticum aestivum, yield, proline, TSS. .... Numbers in the columns followed by the same letters are not significantly different at P .... constituents, Acta Bot.

On the thermally-induced residual stresses in thick fiber-thermoplastic matrix (PEEK) cross-ply laminated plates

Science.gov (United States)

Hu, Shoufeng; Nairn, John A.

1992-01-01

An analytical method for calculating thermally-induced residual stresses in laminated plates is applied to cross-ply PEEK laminates. We considered three cooling procedures: slow cooling (uniform temperature distribution); convective and radiative cooling; and rapid cooling by quenching (constant surface temperature). Some of the calculated stresses are of sufficient magnitude to effect failure properties such as matrix microcracking.

Compressive behavior of wire reinforced bulk metallic glass matrix composites

Energy Technology Data Exchange (ETDEWEB)

Lee, Seung-Yub [Department of Materials Science, M/C 138-78, California Institute of Technology, Pasadena, CA 91125 (United States); Clausen, Bjorn [Lujan Neutron Science Center, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Uestuendag, Ersan [Department of Materials Science and Engineering, Iowa State University, Ames, IA 50011 (United States)]. E-mail: ustundag@iastate.edu; Choi-Yim, Haein [Department of Materials Science, M/C 138-78, California Institute of Technology, Pasadena, CA 91125 (United States); Aydiner, C. Can [Department of Materials Science and Engineering, Iowa State University, Ames, IA 50011 (United States); Bourke, Mark A.M. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

2005-06-15

Bulk metallic glasses (BMGs) possess a unique set of mechanical properties that make them attractive structural materials. However, when loaded without constraint, BMGs fracture catastrophically due to formation of macroscopic shear bands and this behavior reduces their reliability. To address this issue, BMG matrix composites have been developed. In this investigation, neutron diffraction was used during uniaxial compressive loading to measure the internal strains in the second phases of various BMG composites reinforced with Ta, Mo, or stainless steel wires. The diffraction data were then employed to develop a finite element model that deduced the in situ constitutive behavior of each phase. It was found that the reinforcements yielded first and started transferring load to the matrix, which remained elastic during the whole experiment. While the present composites exhibited enhanced ductility, largely due to their ductile reinforcements, they yielded at applied stresses lower than those found in W reinforced composites.

Analysis of heat stress in UK dairy cattle and impact on milk yields

International Nuclear Information System (INIS)

Dunn, Robert J H; Mead, Naomi E; Willett, Kate M; Parker, David E

2014-01-01

Much as humans suffer from heat-stress during periods of high temperature and humidity, so do dairy cattle. Using a temperature-humidity index (THI), we investigate the effect of past heatwaves in the UK on heat-stress in dairy herds. Daily THI data derived from routine meteorological observations show that during the summer, there has been an average of typically 1 day per year per station over the past 40 years when the THI has exceeded the threshold for the onset of mild heat-stress in dairy cattle. However, during the heatwaves of 2003 and 2006, this threshold was exceeded on typically 5 days on average in the Midlands, south and east of England. Most dairy cattle are in the west and north of the country and so did not experience the severest heat. Milk yield data in the south-west of England show that a few herds experienced decreases in yields during 2003 and 2006. We used the 11-member regional climate model ensemble with the A1B scenario from UKCP09 to investigate the possible future change in days exceeding the THI threshold for the onset of mild heat-stress. The number of days where the THI exceeds this threshold could increase to over 20 days yr −1 in southern parts of England by the end of the century. (letters)

Effects of different mycorrhiza species on grain yield, nutrient uptake and oil content of sunflower under water stress

Directory of Open Access Journals (Sweden)

Mostafa Heidari

2014-01-01

Full Text Available The role of arbuscular mycorrhizal fungi in alleviating water stress is well documented. In order to study the effects of water stress and two different mycorrhiza species on grain yield, nutrient uptake and oil content of sunflower, a field experiment as split plot design with three replications was conducted in the Research Field Station, Zabol University, Zabol, Iran in 2011. Water stress treatments included control as 90% of field capacity (W1, 70% field capacity (W2 and 50% field capacity (W3 assigned to the main plots and two different mycorrhiza species, consisting of M1 = control (without any inoculation, M2 = Glumus mossea and M3 = Glumus etanicatum as sub plots. Results showed that by increasing water stress from control (W1 to W3 treatment, grain yield was significantly decreased. The reduction in the level of W3 was 15.05%. The content of potassium in seeds significantly decreased due to water stress but water stress upto W2 treatment increased the content of phosphorus, nitrogen and oil content of seeds. In between two species of mycorrhiza in sunflower plants, Glumus etanicatum had the highest effect on grain yield and these elements in seeds and increased both.

A new macroscopically anisotropic pressure dependent yield function for metal matrix composite based on strain gradient plasticity for the microstructure

DEFF Research Database (Denmark)

Azizi, Reza; Legarth, Brian Nyvang; Niordson, Christian Frithiof

2013-01-01

Metal matrix composites with long aligned elastic fibers are studied using an energetic rate independent strain gradient plasticity theory with an isotropic pressure independent yield function at the microscale. The material response is homogenized to obtain a conventional macroscopic model...... is investigated numerically using a unit cell model with periodic boundary conditions containing a single fiber deformed under generalized plane strain conditions. The homogenized response can be modeled by conventional plasticity with an anisotropic yield surface and a free energy depending on plastic strain...

Genetic Analysis of Yield and Physiological Traits in Sunflower (Helianthus annuus L. under Irrigation and Drought Stress

Directory of Open Access Journals (Sweden)

Azam POURMOHAMMAD

2014-06-01

Full Text Available Implementing appropriate breeding strategies for sunflower, alongside dependable information on heritability and gene effects upon yield and related traits under drought conditions, are all necessary. Thirty sunflower hybrids were produced by line × tester cross of six male-sterile and five restorer lines. Their hybrids were evaluated in three levels of irrigation, as follows: (1 non-stressed plots, irrigated at regular intervals (W1; (2 mild water stress (W2, irrigated from the beginning of the button stage (R4 to seed filling initiation (R6; (3 severe water stress (W3 started from the beginning of button stage (R4 to physiological maturity. Based on observations and specific methods for determination, canopy temperatures, chlorophyll index, relative water content and proline content, were studied by additive effects, under the different irrigation conditions. Canopy temperatures,chlorophyll index, relative water content, leaf water potential, proline content and yield were controlled by additive effects under mild stressed conditions. Under severe stress conditions however, canopy temperatures, leaf water potential and proline content were controlled by additive effects, while chlorophyll index and relative water content were controlled by both additive and dominant effects, as seed yield was mainly influenced by the dominant effects. The narrow sense heritability ranged from 47-97% for all traits, except for chlorophyll fluorescence. Yield correlated positively with chlorophyll index and relative water content, and negatively with canopy temperature and leaf water potential. Therefore, under drought stressed conditions in breeding programs, canopy temperatures, chlorophyll index and relative water content can be reliable criteria for the selection of tolerant genotypes with prospect to higher yields.

Ceramic matrix and resin matrix composites - A comparison

Science.gov (United States)

Hurwitz, Frances I.

1987-01-01

The underlying theory of continuous fiber reinforcement of ceramic matrix and resin matrix composites, their fabrication, microstructure, physical and mechanical properties are contrasted. The growing use of organometallic polymers as precursors to ceramic matrices is discussed as a means of providing low temperature processing capability without the fiber degradation encountered with more conventional ceramic processing techniques. Examples of ceramic matrix composites derived from particulate-filled, high char yield polymers and silsesquioxane precursors are provided.

Ceramic matrix and resin matrix composites: A comparison

Science.gov (United States)

Hurwitz, Frances I.

1987-01-01

The underlying theory of continuous fiber reinforcement of ceramic matrix and resin matrix composites, their fabrication, microstructure, physical and mechanical properties are contrasted. The growing use of organometallic polymers as precursors to ceramic matrices is discussed as a means of providing low temperature processing capability without the fiber degradation encountered with more conventional ceramic processing techniques. Examples of ceramic matrix composites derived from particulate-filled, high char yield polymers and silsesquioxane precursors are provided.

Effect of Silicon application on Morpho-physiological Characteristics, Grain Yield and Nutrient Content of Bread Wheat under Water Stress Conditions

Directory of Open Access Journals (Sweden)

A. Karmollachaab

2015-03-01

Full Text Available In order to investigate the effect of silicon application on some physiological characteristics, yield and yield components, and grain mineral contents of bread wheat (Triticum aestivum under water stress condition, an experiment was conducted in Ramin Agriculture and Natural Resources University, Khuzestan, in 2012. The experiment was arranged in split-plots design in RCBD (Completely Randomized Blocks Design with three replications. Treatments consisted of drought stress (irrigation after 25, 50 and 75% depletion of Available Water Content in main plots and silicon (0, 10, 20 and 30 Kg Si ha-1 arranged in sub-plots. Results showed that the effect of drought stress was significant on most traits and led to the increase of electrolyte leakage (EL, cuticular wax, leaf and grain silicon content and grain nitrogen content. But drought led to negative impacts on grain yield and its components, and leaf potassium content, i.e. moderate and severe stresses reduced yield by 17% and 38% compared to control, respectively. Effect of silicon application was significant on all traits except for spike per square meter. Silicon had the greatest impact on EL and led to 35% decrease in this trait. Also, silicon led to increase in leaf and grain silicon contents and grain K content and grain yield and yield components, when applied at 30 kg ha-1. Generally, application of 30 kg ha-1 of silicon led to 6 and 14% increases of grain yield at the presence of moderate and severe drought stresses, respectively. Thus, given the abundance of silicon it can be used as an ameliorating element for planting bread wheat in drought-prone conditions.

Thermal and mechanical behavior of metal matrix and ceramic matrix composites

Science.gov (United States)

Kennedy, John M. (Editor); Moeller, Helen H. (Editor); Johnson, W. S. (Editor)

1990-01-01

The present conference discusses local stresses in metal-matrix composites (MMCs) subjected to thermal and mechanical loads, the computational simulation of high-temperature MMCs' cyclic behavior, an analysis of a ceramic-matrix composite (CMC) flexure specimen, and a plasticity analysis of fibrous composite laminates under thermomechanical loads. Also discussed are a comparison of methods for determining the fiber-matrix interface frictional stresses of CMCs, the monotonic and cyclic behavior of an SiC/calcium aluminosilicate CMC, the mechanical and thermal properties of an SiC particle-reinforced Al alloy MMC, the temperature-dependent tensile and shear response of a graphite-reinforced 6061 Al-alloy MMC, the fiber/matrix interface bonding strength of MMCs, and fatigue crack growth in an Al2O3 short fiber-reinforced Al-2Mg matrix MMC.

The Effect of Water Deficit stress on Osmotic Metabolites and Anti Oxidant System and Grain and Oil Yield of Amaranth CV. Koniz

Directory of Open Access Journals (Sweden)

Mehrdad Yarnia

2015-01-01

Full Text Available Drought is one of the most important environmental stresses that highly affect crop growth and yield. But the response of crops to stress depending on the timing of crop growth stages is different. The purpose of this study was to investigate effect of different levels of water stress (irrigation after 50, 80, 110, 140 and 170 mm evaporation from pan on different stages of Amaranth growth (establishment, branching, flowering and grain filling. To find the effects of water deficit stress on this plant it was decided to determine its protein percentage, oil and grain yields under drought stress. Evaluation of physiological characteristics as to the extent of osmotic adjustment and antioxidant activity was also carried out. Results showed that water deficit stress,depending on the severity and duration of stress, caused a reduction between between a minimum of 10 to a maximum of 89 percent in yield, 28 to 70 percent in harvest index, 12 to 32 percent in grain protein and 29 to 97 percent in oil yield. This indicates the high sensitivity of grain and oil yields to severe and prolonged drought stresses. Changes in osmotic substances (proline and soluble carbohydrates showed that this crop under water stress conditions increased proline and soluble carbohydrates by 31 and 50 percents, respectively. Thus, if could be said that under severe droughts the ability of crops to cops with drought will be reduced. Similarly, amaranth, to cope with water stress, increases the amount of antioxidant enzymes like catalase, peroxidase and super oxid dismutase up to 53, 23 and 79%, respectively. Higher amount of super oxid dismutase enzyme produce as the result of drought stress may play an important role to cope with reactive oxygen species and oxidative stresses.

Correlation between yield stress and hardness of nickel–silicon–boron-based alloys by nanoindentation

International Nuclear Information System (INIS)

Şerban, Viorel-Aurel; Codrean, Cosmin; Vodă, Mircea; Chicot, Didier; Decoopman, Xavier

2014-01-01

Based on the relation proposed by Tabor in 1951, which connects the ultimate tensile strength and the yield stress of classical materials to the Brinell or Vickers hardness numbers by a simple factor of proportionality, we propose an extended analytical model for the determination of the yield stress of brittle materials using nanoindentation data. This model considers the nanoindentation hardness calculated from the projected actual contact area between the indenter and the material which is representative of the real mean pressure exerted by the indenter compared to classical hardness numbers. A coefficient is introduced in the model to integrate the extent of the elastic recovery of the indented material occurring after the withdrawal of the indenter. This is possible by using the criterion defined by the residual to maximum indenter displacements ratio, this criterion being already related to the deformation mode under indentation. Indeed, this criterion allows identifying the piling-up deformation observed for complete or fully plastic deformation materials or the sinking-in deformation for purely elastic materials. The proposed model thus allows a good estimation of the yield stress of brittle materials for which classical tensile tests are not applicable. The model is validated on a variety of amorphous nickel–silicon-based alloy ribbons, i.e., Ni 89 Si 9 B 2 , Ni 78 Si 9 B 13 and Ni 68 Fe 3 Cr 7 Si 8 B 14 on which both nanoindentation tests and tensile experiments have been performed

Genotype x environment interaction for grain yield of wheat genotypes tested under water stress conditions

International Nuclear Information System (INIS)

Sail, M.A.; Dahot, M.U.; Mangrio, S.M.; Memon, S.

2007-01-01

Effect of water stress on grain yield in different wheat genotypes was studied under field conditions at various locations. Grain yield is a complex polygenic trait influenced by genotype, environment and genotype x environment (GxE) interaction. To understand the stability among genotypes for grain yield, twenty-one wheat genotypes developed Through hybridization and radiation-induced mutations at Nuclear Institute of Agriculture (NIA) TandoJam were evaluated with four local check varieties (Sarsabz, Thori, Margalla-99 and Chakwal-86) in multi-environmental trails (MET/sub s/). The experiments were conducted over 5 different water stress environments in Sindh. Data on grain yield were recorded from each site and statistically analyzed. Combined analysis of variance for all the environments indicated that the genotype, environment and genotype x environment (GxE) interaction were highly significant (P greater then 0.01) for grain yield. Genotypes differed in their response to various locations. The overall highest site mean yield (4031 kg/ha) recorded at Moro and the lowest (2326 kg/ha) at Thatta. Six genotypes produced significantly (P=0.01) the highest grain yield overall the environments. Stability analysis was applied to estimate stability parameters viz., regression coefficient (b), standard error of regression coefficient and variance due to deviation from regression (S/sub 2/d) genotypes 10/8, BWS-78 produced the highest mean yield over all the environments with low regression coefficient (b=0.68, 0.67 and 0.63 respectively and higher S/sup 2/ d value, showing specific adaptation to poor (un favorable) environments. Genotype 8/7 produced overall higher grain yield (3647 kg/ha) and ranked as third high yielding genotype had regression value close to unity (b=0.9) and low S/sup d/ value, indicating more stability and wide adaptation over the all environments. The knowledge of the presence and magnitude of genotype x environment (GE) interaction is important to

Effect of sulfur and iron fertilizers on yield, yield components and ...

African Journals Online (AJOL)

Jane

2011-06-13

Jun 13, 2011 ... per plant. Interaction between water stress and combination of iron and sulfur fertilizers had significant .... Results of analysis of variance (ANOVA) of water stress (W), sulfur (B) and iron (C), and their interaction with gain yield, yield components and ... the soil structure and it increased the usefulness of other.

Suction pressure, yield strength and effective stress of partially saturated unbound granular pavement layers

CSIR Research Space (South Africa)

Theyse, HL

2006-09-01

Full Text Available to the ratio of the imposed stress over the shear strength of the material. Conventionally, the shear strength of the material was characterised with the Mohr-Coulomb shear strength parameters. This paper further develops a recent yield strength model...

A note on hypoplastic yielding

OpenAIRE

Nader, José Jorge

2010-01-01

This note discusses briefly the definition of yield surface in hypoplasticity in connection with the physical notion of yielding. The relation of yielding with the vanishing of the material time derivative of the stress tensor and the vanishing of the corotational stress rate is investigated.

Evolution of Grain Yield and its Components Relationships in Bread Wheat Genotypes under Full Irrigation and Terminal Water Stress Conditions Using Multivariate Statistical Analysis

Directory of Open Access Journals (Sweden)

S Mohammadi

2014-07-01

Full Text Available To study relationships between effective traits on wheat grain yield, the varieties Zarrin and Alvand, and some promising lines i.e. C-81-4, C-81-10, C-81-14 and C-82-12 were investigated at three sowing dates including 10 October, 1 November and 21 November. The experiment was carried out using strip plot in RCBD with three replications under two different water conditions including full-irrigation and terminal water stress at Miyandoab Agricultural Research Station in 2005-06 and 2006-07 cropping seasons. The results showed that under both full irrigation and terminal water stress conditions, grain yield had positive and significant correlation with days to heading, days to maturity, plant height, number of spikes/m2 and 1000 grain weight. Stepwise regression analysis revealed that 83 percent of yield variation under non-stressed conditions could be determined by days to maturity and number of spikes/m2 (R2 = 83% whereas these traits explained 87% of yield variation under stress conditions (R2= 87%. Path analysis indicated that number of spikes/m2 and days to maturity had the greatest positive direct and indirect effect on grain yield, under both conditions. The results of factor analysis under non-stressed condition showed that three factors explained 77% of total variation; these factors were called grain yield components, grain characteristics and plant phonology. Under non-stressed condition two factors (that were called grain yield and phenology, and plant morphology explained 88% of total variation. Cluster analysis through ward method, classified days to maturity and number of spikes/m2 in the same cluster where the grain yield was put under both conditions. It was concluded that under different sowing dates, selection based on days to maturity and number spikes/m2 could indirectly led to higher yield under both normal and water stress conditions.

A study on thermal residual stresses in the matrix and fiber of a misoriented short fiber composite

International Nuclear Information System (INIS)

Son, Bong Jin; Lee, Joon Hyun

1994-01-01

An elastic model is developed to predict the average thermal residual stresses in the matrix and fiber of a misoriented short fiber composite. The thermal residual stresses are induced by the mismatch in the coefficient of the thermal expansion of the matrix and fiber when the composite is subjected to a uniform temperature change. The model considers two special cases of fiber misorientation; two-dimensional in-plane and three-dimensional axisymmetric. The analytical formulation of the model is based on Eshelby's equivalent inclusion method and is unique in that it is able to account for interactions among fibers. The model is more general than past models and it is able to treat prior analyses of the simpler composite systems as extream cases. The present model is to investigate the effects of fiber volume fraction, distribution type, distribution cut-off angle, and aspect ratio on thermal residual stress for both in-plane and axisymmetric fiber misorientation. Fiber volume fraction, aspect ratio, and disturbution cut-off angle are shown to have more significant effects on the magnitude of the thermal residual stresses than fiber distrubution type for both in-plane and axisymmetric misorientation.

Atomistic simulations of the yielding of gold nanowires

International Nuclear Information System (INIS)

Diao Jiankuai; Gall, Ken; Dunn, Martin L.; Zimmerman, Jonathan A.

2006-01-01

We performed atomistic simulations to study the effect of free surfaces on the yielding of gold nanowires. Tensile surface stresses on the surfaces of the nanowires cause them to contract along the length with respect to the bulk face-centered cubic lattice and induce compressive stress in the interior. When the cross-sectional area of a nanowire is less than 2.45 nm x 2.45 nm, the wire yields under its surface stresses. Under external forces and surface stresses, nanowires yield via the nucleation and propagation of the {1 1 1} partial dislocations. The magnitudes of the tensile and compressive yield stress of nanowires increase and decrease, respectively, with a decrease of the wire width. The magnitude of the tensile yield stress is much larger than that of the compressive yield stress for small nanowires, while for small nanowires, tensile and compressive yield stresses have similar magnitudes. The critical resolved shear stress (RSS) by external forces depends on wire width, orientation and loading condition (tension vs. compression). However, the critical RSS in the interior of the nanowires, which is exerted by both the external force and the surface-stress-induced compressive stress, does not change significantly with wire width for same orientation and same loading condition, and can thus serve as a 'local' criterion. This local criterion is invoked to explain the observed size dependence of yield behavior and tensile/compressive yield stress asymmetry, considering surface stress effects and different slip systems active in tensile and compressive yielding

Modeling the Monotonic and Cyclic Tensile Stress-Strain Behavior of 2D and 2.5D Woven C/SiC Ceramic-Matrix Composites

Science.gov (United States)

Li, L. B.

2018-05-01

The deformation of 2D and 2.5 C/SiC woven ceramic-matrix composites (CMCs) in monotonic and cyclic loadings has been investigated. Statistical matrix multicracking and fiber failure models and the fracture mechanics interface debonding approach are used to determine the spacing of matrix cracks, the debonded length of interface, and the fraction of broken fibers. The effects of fiber volume fraction and fiber Weibull modulus on the damage evolution in the composites and on their tensile stress-strain curves are analyzed. When matrix multicracking and fiber/matrix interface debonding occur, the fiber slippage relative to the matrix in the debonded interface region of the 0° warp yarns is the main reason for the emergance of stress-strain hysteresis loops for 2D and 2.5D woven CMCs. A model of these loops is developed, and histeresis loops for the composites in cyclic loadings/unloadings are predicted.

Maximizing Lipid Yield in Neochloris oleoabundans Algae Extraction by Stressing and Using Multiple Extraction Stages with N-Ethylbutylamine as Switchable Solvent

Science.gov (United States)

2017-01-01

The extraction yield of lipids from nonbroken Neochloris oleoabundans was maximized by using multiple extraction stages and using stressed algae. Experimental parameters that affect the extraction were investigated. The study showed that with wet algae (at least) 18 h extraction time was required for maximum yield at room temperature and a solvent/feed ratio of 1:1 (w/w). For fresh water (FW), nonstressed, nonbroken Neochloris oleoabundans, 13.1 wt % of lipid extraction yield (based on dry algae mass) was achieved, which could be improved to 61.3 wt % for FW stressed algae after four extractions, illustrating that a combination of stressing the algae and applying the solvent N-ethylbutylamine in multiple stages of extraction results in almost 5 times higher yield and is very promising for further development of energy-efficient lipid extraction technology targeting nonbroken wet microalgae. PMID:28781427

Infrared thermometry: a remote sensing technique for predicting yield in water-stressed cotton

International Nuclear Information System (INIS)

Pinter, P.J.; Fry, K.E.; Guinn, G.; Mauney, J.R.

1983-01-01

A crop water stress index (CWSI) was derived from air temperatures, air vapor pressure deficits and the midday radiant leaf temperatures of cotton plants that were exposed to different early-season irrigation treatments at Phoenix, AZ, U.S.A. To calculate the CWSI, an infrared thermometer was used to measure leaf temperatures which were then scaled relative to minimum and maximum temperatures expected for no-stress (CWSI=0) and extreme drought-stress conditions (CWSI=1). Results showed the CWSI behaved as expected, dropping to low levels following an irrigation and increasing gradually as the cotton plants depleted soil moisture reserves. The final yield of seed cotton was significantly inversely correlated with the average CWSI observed over the interval from the appearance of the first square until two weeks following the final irrigation

Effect of Water Stress and Sulfur Fertilizer on Grain Yield, Chlorophyll and Nutrient Status of Black Cumin (Nigella Sativa L.

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M. Heidari

2011-04-01

Full Text Available In order to study the effects of water stress and different amounts of sulfur fertilizer on grain yield, nutrient status and chlorophyll content in black cumin (Nigella sativa L. a field experiment as split plot design with three replications was conducted at Ghaen city in 2009. Treatments included three levels of irrigation after 50, 100 and 150 mm evaporation from Class A pan as main plot and four levels of sulfur fertilizer including 0, 75, 150 and 225 kg/ha from bentonite-sulfur source as sub-plot. Statistical analysis of the results showed that water stress has significant effect on grain yield and essential oil of black cumin. At the level of 150 mm evaporation from Class A pan, the grain yield decreased by 22.8% and essential oil by 27.6%. Application of 225 kg/ha sulfur fertilizer increased grain yield up to 7.2%. Water stress and sulfur fertilizer treatments had only significant effect on chlorophyll a content. However, water stress decreased chlorophyll a content, but sulfur fertilizer application up to 225 kg/ha increased the content of chlorophyll a. In this study, water stress decreased potassium content in black cumin leaves, but increased the sodium and calcium accumulation. Although application of sulfur fertilizer affected significantly the potassium and magnesium contents in shoots, but did not have significant effect on sodium and calcium contents.

Boron application improves yield of rice cultivars under high temperature stress during vegetative and reproductive stages

Science.gov (United States)

Shahid, Mohammad; Nayak, Amaresh Kumar; Tripathi, Rahul; Katara, Jawahar Lal; Bihari, Priyanka; Lal, Banwari; Gautam, Priyanka

2018-04-01

It is reported that high temperatures (HT) would cause a marked decrease in world rice production. In tropical regions, high temperatures are a constraint to rice production and the most damaging effect is on spikelet sterility. Boron (B) plays a very important role in the cell wall formation, sugar translocation, and reproduction of the rice crop and could play an important role in alleviating high temperature stress. A pot culture experiment was conducted to study the effect of B application on high temperature tolerance of rice cultivars in B-deficient soil. The treatments comprised of four boron application treatments viz. control (B0), soil application of 1 kg B ha-1 (B1), soil application of 2 kg B ha-1 (B2), and foliar spray of 0.2% B (Bfs); three rice cultivars viz. Annapurna (HT stress tolerant), Naveen, and Shatabdi (both HT stress susceptible); and three temperature regimes viz. ambient (AT), HT at vegetative stage (HTV), and HT at reproductive stage (HTR). The results revealed that high temperature stress during vegetative or flowering stage reduced grain yield of rice cultivars mainly because of low pollen viability and spikelet fertility. The effects of high temperature on the spikelet fertility and grain filling varied among cultivars and the growth stages of plant when exposed to the high temperature stress. Under high temperature stress, the tolerant cultivar displays higher cell membrane stability, less accumulation of osmolytes, more antioxidant enzyme activities, and higher pollen viability and spikelet fertility than the susceptible cultivars. In the present work, soil application of boron was effective in reducing the negative effects of high temperature both at vegetative and reproductive stages. Application of B results into higher grain yield under both ambient and high temperature condition over control for all the three cultivars; however, more increase was observed for the susceptible cultivar over the tolerant one. The results suggest

Boron application improves yield of rice cultivars under high temperature stress during vegetative and reproductive stages.

Science.gov (United States)

Shahid, Mohammad; Nayak, Amaresh Kumar; Tripathi, Rahul; Katara, Jawahar Lal; Bihari, Priyanka; Lal, Banwari; Gautam, Priyanka

2018-04-12

It is reported that high temperatures (HT) would cause a marked decrease in world rice production. In tropical regions, high temperatures are a constraint to rice production and the most damaging effect is on spikelet sterility. Boron (B) plays a very important role in the cell wall formation, sugar translocation, and reproduction of the rice crop and could play an important role in alleviating high temperature stress. A pot culture experiment was conducted to study the effect of B application on high temperature tolerance of rice cultivars in B-deficient soil. The treatments comprised of four boron application treatments viz. control (B0), soil application of 1 kg B ha -1 (B1), soil application of 2 kg B ha -1 (B2), and foliar spray of 0.2% B (Bfs); three rice cultivars viz. Annapurna (HT stress tolerant), Naveen, and Shatabdi (both HT stress susceptible); and three temperature regimes viz. ambient (AT), HT at vegetative stage (HTV), and HT at reproductive stage (HTR). The results revealed that high temperature stress during vegetative or flowering stage reduced grain yield of rice cultivars mainly because of low pollen viability and spikelet fertility. The effects of high temperature on the spikelet fertility and grain filling varied among cultivars and the growth stages of plant when exposed to the high temperature stress. Under high temperature stress, the tolerant cultivar displays higher cell membrane stability, less accumulation of osmolytes, more antioxidant enzyme activities, and higher pollen viability and spikelet fertility than the susceptible cultivars. In the present work, soil application of boron was effective in reducing the negative effects of high temperature both at vegetative and reproductive stages. Application of B results into higher grain yield under both ambient and high temperature condition over control for all the three cultivars; however, more increase was observed for the susceptible cultivar over the tolerant one. The results

Effects of arbuscular mycorrhiza inoculation on growth and yield of tomato (Lycopersicum esculentum Mill. under salinity stress

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D.R.R. Damaiyanti

2015-10-01

Full Text Available Objective of the research was to study the effect mycorrhiza on growth and yield of tomato. The experiment was conducted in screen house 14 m x 10.5 m, in Pasuruan on November 2013 until March 2014, The experiment was conducted as a factorial randomized complete design. The first factor was dose of mycorrhiza (without mycorrhiza, 5 g mycorrhiza, 10 g mycorrhiza, and 20 g mycorrhiza. The second factor was the salinity stress level (without NaCl, 2500 ppm NaCl, 5000 ppm NaCl, and 7500 ppm NaCl. The results showed that salinity stress at the level 7500 ppm decreased the amount of fruit by 30.84% and fresh weight per hectare decreased by 51.72%. Mycorrhizal application was not able to increase the growth and yield in saline stress conditions; it was shown by the level of infection and the number of spores on the roots of tomato plants lower the salinity level 5000 ppm and 7500 ppm. But separately, application of 20 g mycorrhiza enhanced plant growth, such as plant height, leaf area, leaf number and proline. Application of 20 g mycorrhiza increased the yield by 35.99%.

Ectopic expression of specific GA2 oxidase mutants promotes yield and stress tolerance in rice.

Science.gov (United States)

Lo, Shuen-Fang; Ho, Tuan-Hua David; Liu, Yi-Lun; Jiang, Mirng-Jier; Hsieh, Kun-Ting; Chen, Ku-Ting; Yu, Lin-Chih; Lee, Miin-Huey; Chen, Chi-Yu; Huang, Tzu-Pi; Kojima, Mikiko; Sakakibara, Hitoshi; Chen, Liang-Jwu; Yu, Su-May

2017-07-01

A major challenge of modern agricultural biotechnology is the optimization of plant architecture for enhanced productivity, stress tolerance and water use efficiency (WUE). To optimize plant height and tillering that directly link to grain yield in cereals and are known to be tightly regulated by gibberellins (GAs), we attenuated the endogenous levels of GAs in rice via its degradation. GA 2-oxidase (GA2ox) is a key enzyme that inactivates endogenous GAs and their precursors. We identified three conserved domains in a unique class of C 20 GA2ox, GA2ox6, which is known to regulate the architecture and function of rice plants. We mutated nine specific amino acids in these conserved domains and observed a gradient of effects on plant height. Ectopic expression of some of these GA2ox6 mutants moderately lowered GA levels and reprogrammed transcriptional networks, leading to reduced plant height, more productive tillers, expanded root system, higher WUE and photosynthesis rate, and elevated abiotic and biotic stress tolerance in transgenic rice. Combinations of these beneficial traits conferred not only drought and disease tolerance but also increased grain yield by 10-30% in field trials. Our studies hold the promise of manipulating GA levels to substantially improve plant architecture, stress tolerance and grain yield in rice and possibly in other major crops. © 2016 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

A water stress index based on water balance modelling for discrimination of grapevine quality and yield

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Rémi Gaudin

2014-01-01

Significance and impact of the study: This water stress index is a valuable tool for explaining the variations in grape yield and quality among various locations and years because it reflects the vineyard water stress history in relation to rainfall regime and soil conditions. Improvement would come from the simulation of FTSW during winter, notably for soils of high Total Transpirable Soil Water. One potential application is the quantification of water stress change brought by irrigation in Mediterranean vineyards, and its relation to grapevine production.

STATIC ANALYSIS OF STRESSES INDIUCED BY MATRIX BAND IN ROOT CANAL TREATED SECOND PREMOLARS MOD CAVITIES BY FINITE ELEMENTH TECHNIQUE

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K KHOSRAVI

2000-09-01

Full Text Available Introduction. The purpose of this study is measurement the stresses due to matrix bond and their effect on fracture or crock formation in teeth and finally modifying in treatment methods of tooth. Methods. We use a second premolar that was as similar as measurements of wheelers studies. Au mod cavity prepared with buccolingual width 3mm while the roof of pulp chamber has been removed and gingival floor was 1mm higher than CEJ. CTS was prepared in three dimention: crolan, sigital and axial and then tooth model was made based on Nisall program. The forces due to matrix band measured by strain guage and then, this force based on finite element method applied on the prepared model. Results: Inall cases, stresses observed in tensile and shear from tensile stresses was mainly in cervical one third of buccal cups and shear stress was surronded cervical area of the tooth like as circle. The greatest amount of forces were localized in gingival floor in mesial area and in the enamel with increasing the depth and sidth of cavity. The amount of this stresses increased especially in increasing of depth. With increasing the width and depth cuspal displacment was observed especially in colossal on third which localized in buccal cusp. Discussion. Matrix band stresses mainly are destructive and cause fractures or at least crack formation in tooth. So its preffered to use thinner band in shorter time as much as possible. using of anatomic bands were prefeved.

Influence of thermal residual stress on behaviour of metal matrix composites reinforced with particles

Science.gov (United States)

Guzmán, R. E.; Hernández Arroyo, E.

2016-02-01

The properties of a metallic matrix composites materials (MMC's) reinforced with particles can be affected by different events occurring within the material in a manufacturing process. The existence of residual stresses resulting from the manufacturing process of these materials (MMC's) can markedly differentiate the curves obtained in tensile tests obtained from compression tests. One of the themes developed in this work is the influence of residual stresses on the mechanical behaviour of these materials. The objective of this research work presented is numerically estimate the thermal residual stresses using a unit cell model for the Mg ZC71 alloy reinforced with SiC particles with volume fraction of 12% (hot-forging technology). The MMC's microstructure is represented as a three dimensional prismatic cube-shaped with a cylindrical reinforcing particle located in the centre of the prism. These cell models are widely used in predicting stress/strain behaviour of MMC's materials, in this analysis the uniaxial stress/strain response of the composite can be obtained through the calculation using the commercial finite-element code.

Evaluation of Yield and Yield Components of Some Pinto bean (Phaseolus vulgaris L. Genotypes under Late Season Water Deficit Conditions

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somayyeh soheili movahhed

2017-10-01

Full Text Available Introduction Drought or water deficit stress is the most important environmental factor which has severe negative impacts on crop yields, especially when the water stress occurs in the flowering stage. Iran is located in arid and semi-arid areas, therefore, attention to the effects of water deficit stress in different stages of plants growth seems necessary. Bean (Phaseolus vulgaris L. is one of the most important legumes that has a major contribution to human diet and provides an important part of the human protein. According to studies, cultivation areas of legumes in Iran are about 97300 hectares and its total production is about 208350 tons of grain. Bean is a fast-growing plant (Tran and Singh, 2002, thus soil water must be sufficiently available to ensure its desirable growth and yield. The aim of this study was to investigate the effect of drought stress on yield and yield components of some pinto bean (Phaseolus vulgaris L. cultivated in Zanjan province. Materials and methods An experiment was conducted as spilt plot based on randomized complete block design with four replications in Zanjan university research farm. Irrigation levels (control and drought stress and genotypes (Local khomein, Sadri, Ks21193 and Ks21189 were set in the main and subplot, respectively. Water deficit stress was applied during flowering stage (50% of the plants were at anthesis. Sampling was performed to measure yield and yield components at the end of the growth period and final maturity. In this experiment number of pod per Plant, numberof grain per pod, 100 grain weight, grain yield, biological yield and harvest index were measured. Results and Discussion In this experiment it was observed that drought stress, genotype and interact irrigation×genotyps were significantly for all traits except biological yield. Drought stress reduced number of pod perplant, number of grain per pod, 100 grain weight, grain yield, biological yield and Harvest Index. Results

Experimental study on yield behavior of Daqing crude oil

Energy Technology Data Exchange (ETDEWEB)

Hou, Lei [China University of Petroleum, College of Mechanical and Transportation Engineering, Beijing (China)

2012-07-15

The yield behavior of Daqing crude oil was studied by means of multi-mode controlled-stress tests with a high-precision stress controlled rheometer. Two experiments of creep and constant stress loading rate were performed. The yield stress of gelled crude oil was dependent on the test conditions such as the stress loading time and the stress loading rate, but the yield strain did not change with test conditions. The yield strain did exist objectively and it can be used as the criterion for the yielding of the structure of gelled crude oil. The yield strain of gelled oil was studied through experiments of creep, constant stress loading rate, oscillatory shear stress increase, and constant shear rate. The yield strain of gelled crude oil decreased with the increasing gel strength. The experiment of constant speed increase of stress showed the strain softening phenomena for low gel strength oil. (orig.)

Effect of Zeolite, Selenium and Silicon on Yield, Yield Components and Some Physiological Traits of Canola under Salt Stress Conditions

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A Bybordi

2016-07-01

Full Text Available Introduction Canola can be cultivated in large areas of the country due to its specific characteristics such as suitable composition of the fatty acids, its germination ability under low temperature, as well as its good compatibility with different climates. Canola is a high demanding crop in terms of fertilizers so that it uptakes considerable amount of nutrients from the soil during the growing season. Canola cultivation in poor soils or application of imbalanced fertilizers, especially nitrogen, can reduce qualitaty and quantity of final yield. On the other hand, salinity is known as one of the major limiting factors in canola production. Therefore, the aim of this study is the application of zeolite, selenium and silicon treatments to amend soil and increasing salinity tolerance in canola. Materials and Methods In order to study the effect of soil applied zeolite and foliar application of selenium and silicon on yield, yield components and some physiological traits of canola grown under salinity stress, a factorial experiment in randomized complete block design was conducted in Agriculture and Natural Resource Research Center in East Azerbaijan during 2011-2013 cropping seasons. Zeolite was applied at three levels (0, 5 and 10 ton ha-1 and foliar selenium and silicon were applied at three levels as well (each one zero, 2 and 4 g l-1. For this purpose, seedbed was prepared using plow and disk and then plot were designed. Canola seeds, cultivar Okapi, were sown in sandy loam soil with 4 dS.m-1 salinity at the depth of 2-3 cm. Irrigation was performed using local well based on 60% field capacity using the closed irrigation system. Potassium selentae and potassium silicate were used for selenium and silicon treatments. Treatments at rosette and stem elongation stages were sprayed on plants using a calibrated pressurized backpack sprayer. At flowering stage, photosynthesis rate was recorded. Then leaf samples were randomly collected to assay

Comments on the Dutton-Puls model: Temperature and yield stress dependences of crack growth rate in zirconium alloys

International Nuclear Information System (INIS)

Kim, Young S.

2010-01-01

Research highlights: → This study shows first that temperature and yield stress dependences of crack growth rate in zirconium alloys can analytically be understood not by the Dutton-Puls model but by Kim's new DHC model. → It is demonstrated that the driving force for DHC is ΔC, not the stress gradient, which is the core of Kim's DHC model. → The Dutton-Puls model reveals the invalidity of Puls' claim that the crack tip solubility would increase to the cooling solvus. - Abstract: This work was prompted by the publication of Puls's recent papers claiming that the Dutton-Puls model is valid enough to explain the stress and temperature dependences of the crack growth rate (CGR) in zirconium alloys. The first version of the Dutton-Puls model shows that the CGR has positive dependences on the concentration difference ΔC, hydrogen diffusivity D H , and the yield strength, and a negative dependence on the applied stress intensity factor K I , which is one of its critical defects. Thus, the Dutton-Puls model claiming that the temperature dependence of CGR is determined by D H C H turns out to be incorrect. Given that ΔC is independent of the stress, it is evident that the driving force for DHC is ΔC, not the stress gradient, corroborating the validity of Kim's model. Furthermore, the predicted activation energy for CGR in a cold-worked Zr-2.5Nb tube disagrees with the measured one for the Zr-2.5Nb tube, showing that the Dutton-Puls model is too defective to explain the temperature dependence of CGR. It is demonstrated that the revised Dutton-Puls model also cannot explain the yield stress dependence of CGR.

Creep and stress relaxation induced by interface diffusion in metal matrix composites

Science.gov (United States)

Li, Yinfeng; Li, Zhonghua

2013-03-01

An analytical solution is developed to predict the creep rate induced by interface diffusion in unidirectional fiber-reinforced and particle reinforced composites. The driving force for the interface diffusion is the normal stress acting on the interface, which is obtained from rigorous Eshelby inclusion theory. The closed-form solution is an explicit function of the applied stress, volume fraction and radius of the fiber, as well as the modulus ratio between the fiber and the matrix. It is interesting that the solution is formally similar to that of Coble creep in polycrystalline materials. For the application of the present solution in the realistic composites, the scale effect is taken into account by finite element analysis based on a unit cell. Based on the solution, a closed-form solution is also given as a description of stress relaxation induced by interfacial diffusion under constant strain. In addition, the analytical solution for the interface stress presented in this study gives some insight into the relationship between the interface diffusion and interface slip. This work was supported by the financial support from the Nature Science Foundation of China (No. 10932007), the National Basic Research Program of China (No. 2010CB631003/5), and the Doctoral Program of Higher Education of China (No. 20100073110006).

Yield surface evolution for columnar ice

Science.gov (United States)

Zhou, Zhiwei; Ma, Wei; Zhang, Shujuan; Mu, Yanhu; Zhao, Shunpin; Li, Guoyu

A series of triaxial compression tests, which has capable of measuring the volumetric strain of the sample, were conducted on columnar ice. A new testing approach of probing the experimental yield surface was performed from a single sample in order to investigate yield and hardening behaviors of the columnar ice under complex stress states. Based on the characteristic of the volumetric strain, a new method of defined the multiaxial yield strengths of the columnar ice is proposed. The experimental yield surface remains elliptical shape in the stress space of effective stress versus mean stress. The effect of temperature, loading rate and loading path in the initial yield surface and deformation properties of the columnar ice were also studied. Subsequent yield surfaces of the columnar ice have been explored by using uniaxial and hydrostatic paths. The evolution of the subsequent yield surface exhibits significant path-dependent characteristics. The multiaxial hardening law of the columnar ice was established experimentally. A phenomenological yield criterion was presented for multiaxial yield and hardening behaviors of the columnar ice. The comparisons between the theoretical and measured results indicate that this current model is capable of giving a reasonable prediction for the multiaxial yield and post-yield properties of the columnar ice subjected to different temperature, loading rate and path conditions.

The Effect of Silicon on some Morpho-physiological Characteristics and Grain Yield of Sorghum (Sorghum bicolor L. under Salt Stress

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S Hasibi

2016-12-01

Full Text Available Introduction Nowadays, salinity is one of the limiting factors for crop production in arid and semi-arid regions. On the other hand, sorghum (Sorghum bicolor L. is a self-pollinated and short-day plant, which partly has been adapted to salinity and water stress conditions; also play an important role in humans, livestock and poultry nourishments. All studies have showed the positive effects of Silicon on growth and yield of plants in both normal and stress conditions. The aim of this experiment was to improve salinity tolerance of Sorghum by application of Silicon. Materials and Methods A split plot experiment based on randomized complete block design with three replications in both normal and salt stress conditions was carried out at research farm of Shahid Bahonar University of Kerman in 2013. Silicon treatments (0 and 6 mM were considered as main plot and various sorghum genotypes (payam, sepideh, TN-4-70, TN-04-71, TN-04-39, TN-04-107, TN-04-100, TN-04-37, TN-04-68, TN-04-83, TN-04-62 and TN-04-95 were assigned to sub plots. The sodium silicate was used as silica source. The data were analyzed by SAS software using combine analysis. Means comparisons were accomplished by Duncan multiple range test at 5% probability level. Some of the measured traits were as follow: Relative water content (Ritchie and Nguyen, 1990, Relative permeability (33, leaf area index and chlorophyll index (by SPAD. Results and Discussion According to the results, use of silicon led to increase of RWC under salinity stress, while RWC decreased by 13% when no silicon applied. Salinity significantly decreased 1000-grain weight. Maximum grain yield obtained from TN-04-37 (987.6 g m-2 under normal condition with foliar application of silicon. Application of silicon under stress condition led to 38% increase in grain yield of Sepideh compared to control. Under salt stress, silicon also increased shoot dry weight in TN-04-107, TN-04-70, TN-04-37, Payam and Sepideh genotypes

Matrix analysis of the asymmetrical bending of conical shell-beams and their singular assemblies

International Nuclear Information System (INIS)

Kiedrzynski, A.; Coppens, L.

1979-01-01

As an alternative to refined finite element methodology a new method has been derived to investigate in much detail the linear static behaviour of singular assemblies of moderately thick conical shells of revolution submitted to non-axisymmetrical loads at their ends (an assembly of conical sections is said to be singular when the geometrical discontinuities are deformable, i.e. not stiffened by diaphragms). A detailed preliminary study has shown that the currently adopted simplifying assumptions in shell theories for moderate thickness lead to unconsistencies at any departure from axisymmetric loading. Therefore, FLUEGGE's general shell theory has been applied to a conical section, yielding a set of mixed first order differential equations in terms of displacements and conjuguated stress resultants well suited for a matrix formalism. The numerical integration is based on a fourth-order Runge-Kutta method and provides an 8 x 8 mixed matrix. This matrix contains complete information on the distribution of the displacements (exhibiting the warping and ovalization of the cross-section) and of the stress resultants along the meridian; also the stiffness coefficients proceed from it. (orig.)

Effect of Foliar Application of Chelate Iron in Common and Nanoparticles Forms on Yield and Yield Components of Cumin (Cuminum cyminum L. under Drought Stress Conditions

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A Nasiri Dehsorkhi

2018-05-01

Full Text Available Introduction Cumin is a member of Apiaceae family and annual plant which is widely cultivated in arid and semi-arid zone. Iran is one of the main producers of this plant. Water deficit is the major limiting factor in crops production. Proper nutrition management under stress conditions could partly help the plant to tolerate different stresses. Various studies were carried out to understand the effect of nanoparticles on the growth of plants. For example, Hong et al. (2005 and Yang et al. (2006 reported that a proper concentration of nano-TiO2 was found to improve the growth of spinach by promoting photosynthesis and nitrogen metabolism. Iran a country with arid and semi-arid climate, always face water deficiency. Thus the aim of this research was investigate the effect of foliar application of chelate iron in common and nanoparticles forms on yield and yield components of cumin (Cuminum cyminum L. under drought stress conditions. Materials and Methods A field experiment was conducted as a split plot in complete randomized block design with three replications in Esfahan city, during the growing season of 2015-2016. Treatments were included three irrigation intervals (5, 10 and 15 days as main plots and Fe foliar application in four levels (control, 2 g L-1 iron chelate, 2 g L-1 Nano-iron chelate, 4 g L-1 iron chelate, 4 g L-1 nano-iron chelate. Foliar application of Fe chelate on leaves was done two times at before and after flowering stage. The plots were 16 m2 with 4 sowing rows, 4 m long. Seeds were placed at 2 to 4 cm depth in each row. All data collected were subjected of analysis of variance (ANOVA using MSTATC software. Significant differences between means refer to the probability level of 0.05 by LSD test. Results and Discussion The results indicated that drought stress decreased the investigated traits significantly but the effect of irrigation by 15 days interval was more than 10 days. Plots which irrigated by 15 days interval showed

Influence of yield stress on free convective boundary-layer flow of a non-Newtonian nanofluid past a vertical plate in a porous medium

International Nuclear Information System (INIS)

Hady, F. M.; Ibrahim, F. S.; Abdel-Gaied, S. M.; Eid, M. R.

2011-01-01

The effect of yield stress on the free convective heat transfer of dilute liquid suspensions of nanofluids flowing on a vertical plate saturated in porous medium under laminar conditions is investigated considering the nanofluid obeys the mathematical model of power-law. The model used for non-Newtonian nanofluid incorporates the effects of Brownian motion and thermophoresis. The governing boundary- layer equations are cast into dimensionless system which is solved numerically using a deferred correction technique and Newton iteration. This solution depends on yield stress parameter Ω, a power-law index n, Lewis number Le, a buoyancy-ratio number Nr, a Brownian motion number Nb, and a thermophoresis number Nt. Analyses of the results found that the reduced Nusselt and Sherwood numbers are decreasing functions of the higher yield stress parameter for each dimensionless numbers, n and Le, except the reduced Sherwood number is an increasing function of higher Nb for different values of yield stress parameter

Large particles increase viscosity and yield stress of pig cecal contents without changing basic viscoelastic properties.

Science.gov (United States)

Takahashi, Toru; Sakata, Takashi

2002-05-01

The viscosity of gut contents should influence digestion and absorption. Earlier investigators measured the viscosity of intestinal contents after the removal of solid particles. However, we previously found that removal of solid particles from pig cecal contents dramatically lowered the viscosity of the contents. Accordingly, we examined the contribution of large solid particles to viscoelastic parameters of gut contents in the present study. We removed large particles from pig cecal contents by filtration through surgical gauze. Then, we reconstructed the cecal contents by returning all, one half or none of the original amount of the large particles to the filtrate. We measured the viscosity, shear stress and shear rate of these reconstructed cecal contents using a tube-flow viscometer. The coefficient of viscosity was larger when the large-particle content was higher (P Bingham plastic nature irrespective of large-particle content. We calculated the yield stress of these fluids assuming that the fluids behave as Bingham plastic. The yield stress of the cecal contents was greater (P Bingham plastic characteristics to pig cecal contents.

Effect of different N fertilizer forms on antioxidant capacity and grain yield of rice growing under Cd stress

International Nuclear Information System (INIS)

Jalloh, Mohamed Alpha; Chen Jinghong; Zhen Fanrong; Zhang Guoping

2009-01-01

Cadmium contamination in soil has become a serious issue in sustainable agriculture production and food safety. A pot experiment was conducted to study the influence of four N fertilizer forms on grain yield, Cd concentration in plant tissues and oxidative stress under two Cd levels (0 and 100 mg Cd kg -1 soil). The results showed that both N form and Cd stress affected grain yield, with urea-N and NH 4 + -N treatments having significantly higher grain yields, and Cd addition reducing yield. NO 3 - -N and NH 4 + -N treated plants had the highest and lowest Cd concentration in plant tissues, respectively. Urea-N and NH 4 + -N treatments had significantly higher N accumulation in plant tissues than other two N treatments. Cd addition caused a significant increase in leaf superoxide dismutase (SOD) and peroxidase (POD) activities for all N treatments, except for NO 3 - -N treatment, with urea-N and NH 4 + -N treated plants having more increase than organic-N treated ones. The results indicated that growth inhibition, yield reduction and Cd uptake of rice plants in response to Cd addition varied with the N fertilizer form

Effect of different N fertilizer forms on antioxidant capacity and grain yield of rice growing under Cd stress.

Science.gov (United States)

Jalloh, Mohamed Alpha; Chen, Jinghong; Zhen, Fanrong; Zhang, Guoping

2009-03-15

Cadmium contamination in soil has become a serious issue in sustainable agriculture production and food safety. A pot experiment was conducted to study the influence of four N fertilizer forms on grain yield, Cd concentration in plant tissues and oxidative stress under two Cd levels (0 and 100 mg Cd kg(-1)soil). The results showed that both N form and Cd stress affected grain yield, with urea-N and NH(4)(+)-N treatments having significantly higher grain yields, and Cd addition reducing yield. NO(3)(-)-N and NH(4)(+)-N treated plants had the highest and lowest Cd concentration in plant tissues, respectively. Urea-N and NH(4)(+)-N treatments had significantly higher N accumulation in plant tissues than other two N treatments. Cd addition caused a significant increase in leaf superoxide dismutase (SOD) and peroxidase (POD) activities for all N treatments, except for NO(3)(-)-N treatment, with urea-N and NH(4)(+)-N treated plants having more increase than organic-N treated ones. The results indicated that growth inhibition, yield reduction and Cd uptake of rice plants in response to Cd addition varied with the N fertilizer form.

Crop coefficient, yield response to water stress and water productivity of teff (Eragrostis tef (Zucc.)

NARCIS (Netherlands)

Araya, A.; Stroosnijder, L.; Girmay, G.; Keesstra, S.D.

2011-01-01

In the semi-arid region of Tigray, Northen Ethiopia a two season experiment was conducted to measure evapotranspiration, estimate yield response to water stress and derive the crop coefficient of teff using the single crop coefficient approach with simple, locally made lysimeters and field plots.

Reliability analysis for cementless hip prosthesis using a new optimized formulation of yield stress against elasticity modulus relationship

International Nuclear Information System (INIS)

Kharmanda, G.

2015-01-01

Highlights: • We develop a new formulation between the yield stress and Young’s modulus of bone. • We validate the optimized formulation for cortical and trabecular bone. • We integrate the reliability analysis into artificially hip replacement design. - Abstract: Using classical design optimization methods for implant-bone studies does not completely guarantee a safety and satisfactory performance, due in part to the randomness of bone properties and loading. Here, the material properties of the different bone layers are considered as uncertain parameters. So their corresponding yield stress values will not be deterministic, that leads to integrate variable limitations into the optimization process. Here there is a strong need to find a reliable mathematical relationship between yield stress and material properties of the different bone layers. In this work, a new optimized formulation for yield stress against elasticity modulus relationship is first developed. This model is based on some experimental results. A validation of the proposed formulation is next carried out to show its accuracy for both bone layers (cortical and cancellous). A probabilistic sensitivity analysis is then carried out to show the role of each input parameter with respect to the limit state function. The new optimized formulation is next integrated into a reliability analysis problem in order to assess the reliability level of the stem–bone study where we deal with variable boundary limitations. An illustrative application is considered as a bi-dimensional example (contains only two variables) in order to present the results in an illustrative 2D space. Finally, a multi-variable problem considering several daily loading cases on a hip prosthesis shows the applicability of the proposed strategy

A Theoretical Study on Quantitative Prediction and Evaluation of Thermal Residual Stresses in Metal Matrix Composite (Case 1 : Two-Dimensional In-Plane Fiber Distribution)

International Nuclear Information System (INIS)

Lee, Joon Hyun; Son, Bong Jin

1997-01-01

Although discontinuously reinforced metal matrix composite(MMC) is one of the most promising materials for applications of aerospace, automotive industries, the thermal residual stresses developed in the MMC due to the mismatch in coefficients of thermal expansion between the matrix and the fiber under a temperature change has been pointed out as one of the serious problem in practical applications. There are very limited nondestructive techniques to measure the residual stress of composite materials. However, many difficulties have been reported in their applications. Therefore it is important to establish analytical model to evaluate the thermal residual stress of MMC for practical engineering application. In this study, an elastic model is developed to predict the average thermal residual stresses in the matrix and fiber of a misoriented short fiber composite. The thermal residual stresses are induced by the mismatch in the coefficient of the thermal expansion of the matrix and fiber when the composite is subjected to a uniform temperature change. The model considers two-dimensional in-plane fiber misorientation. The analytical formulation of the model is based on Eshelby's equivalent inclusion method and is unique in that it is able to account for interactions among fibers. This model is more general than past models to investigate the effect of parameters which might influence thermal residual stress in composites. The present model is to investigate the effects of fiber volume fraction, distribution type, distribution cut-off angle, and aspect ratio on thermal residual stress for in-plane fiber misorientation. Fiber volume fraction, aspect ratio, and distribution cut-off angle are shown to have more significant effects on the magnitude of the thermal residual stresses than fiber distribution type for in-plane misorientation

Evaluation of Foliar Spraying of Zinc and Calcium Fertilizers on Yield and Physiological Traits of Safflower under Lead Stress

Directory of Open Access Journals (Sweden)

P Jamshidi

2017-10-01

Full Text Available Introduction In order to evaluate the effect of foliar spraying of zinc and calcium on yield and physiological traits of safflower under lead stress, a factorial experiment based on randomized complete block design was performed in Kerman agricultural and natural resource research and education center in 2014-2015 with three replications. The first factorial included three levels (control, and 0.5 and 1 μM lead spraying, whereas the second and third factorials were spraying zinc sulfate at three concentrations (zero, and 10 and 20 μM and spraying calcium chloride at two levels (zero and 20 μM, respectively. According to the results, grain yield, the 1000-grain weight, leaf dry weight, number of seeds per head, head weight and chlorophyll content decreased. On the other hand, a significant increase was observed in the activities of catalase and ascorbate peroxidase enzymes and amount of malondialdehyde in plants. Moreover, spraying zinc fertilizer in lead treatment resulted in a significant increase in activity of catalase enzyme, reduction of membrane lipid peroxidation, prevention of chlorophyll destruction and maintenance of grain yield. However, the effect of spraying calcium fertilize in lead treatment was only significant on chlorophyll content. According to the results of the research, it seems that spraying zinc fertilizer had more effects on improved growth of safflower under lead stress, compared to spraying calcium fertilizer. Therefore, in air pollution with heavy metals (lead, application of zinc sulfate fertilizer can be an effective approach to maintain the growth and production of plants. Among the various heavy metals, lead (Pb is a major anthropogenic pollutant that has been released to the environment since the industrial revolution and accumulated in different terrestrial and aquatic ecosystems These elements will transfer to leaves in polluted areas and will rapidly uptake and cause irreparable damages to the most

Full CKM matrix with lattice QCD

Energy Technology Data Exchange (ETDEWEB)

Okamoto, Masataka; /Fermilab

2004-12-01

The authors show that it is now possible to fully determine the CKM matrix, for the first time, using lattice QCD. |V{sub cd}|, |V{sub cs}|, |V{sub ub}|, |V{sub cb}| and |V{sub us}| are, respectively, directly determined with the lattice results for form factors of semileptonic D {yields} {pi}lv, D {yields} Klv, B {yields} {pi}lv, B {yields} Dlv and K {yields} {pi}lv decays. The error from the quenched approximation is removed by using the MILC unquenced lattice gauge configurations, where the effect of u, d and s quarks is included. The error from the ''chiral'' extrapolation (m{sub l} {yields} m{sub ud}) is greatly reduced by using improved staggered quarks. The accuracy is comparable to that of the Particle Data Group averages. In addition, |V{sub ud}|, |V{sub ts}|, |V{sub ts}| and |V{sub td}| are determined by using unitarity of the CKM matrix and the experimental result for sin (2{beta}). In this way, they obtain all 9 CKM matrix elements, where the only theoretical input is lattice QCD. They also obtain all the Wolfenstein parameters, for the first time, using lattice QCD.

Green's Function and Stress Fields in Stochastic Heterogeneous Continua

Science.gov (United States)

Negi, Vineet

Many engineering materials used today are heterogenous in composition e.g. Composites - Polymer Matrix Composites, Metal Matrix Composites. Even, conventional engineering materials - metals, plastics, alloys etc. - may develop heterogeneities, like inclusions and residual stresses, during the manufacturing process. Moreover, these materials may also have intrinsic heterogeneities at a nanoscale in the form of grain boundaries in metals, crystallinity in amorphous polymers etc. While, the homogenized constitutive models for these materials may be satisfactory at a macroscale, recent studies of phenomena like fatigue failure, void nucleation, size-dependent brittle-ductile transition in polymeric nanofibers reveal a major play of micro/nanoscale physics in these phenomena. At this scale, heterogeneities in a material may no longer be ignored. Thus, this demands a study into the effects of various material heterogeneities. In this work, spatial heterogeneities in two material properties - elastic modulus and yield stress - have been investigated separately. The heterogeneity in the elastic modulus is studied in the context of Green's function. The Stochastic Finite Element method is adopted to get the mean statistics of the Green's function defined on a stochastic heterogeneous 2D infinite space. A study of the elastic-plastic transition in a domain having stochastic heterogenous yield stress was done using Mont-Carlo methods. The statistics for various stress and strain fields during the transition were obtained. Further, the effects of size of the domain and the strain-hardening rate on the stress fields during the heterogeneous elastic-plastic transition were investigated. Finally, a case is made for the role of the heterogenous elastic-plastic transition in damage nucleation and growth.

Fiber/matrix interfaces for SiC/SiC composites: Multilayer SiC coatings

Energy Technology Data Exchange (ETDEWEB)

Halverson, H.; Curtin, W.A. [Virginia Polytechnic Institute and State Univ., Blacksburg, VA (United States)

1996-08-01

Tensile tests have been performed on composites of CVI SiC matrix reinforced with 2-d Nicalon fiber cloth, with either pyrolitic carbon or multilayer CVD SiC coatings [Hypertherm High-Temperature Composites Inc., Huntington Beach, CA.] on the fibers. To investigate the role played by the different interfaces, several types of measurements are made on each sample: (i) unload-reload hysteresis loops, and (ii) acoustic emission. The pyrolitic carbon and multilayer SiC coated materials are remarkably similar in overall mechanical responses. These results demonstrate that low-modulus, or compliant, interface coatings are not necessary for good composite performance, and that complex, hierarchical coating structures may possibly yield enhanced high-temperature performance. Analysis of the unload/reload hysteresis loops also indicates that the usual {open_quotes}proportional limit{close_quotes} stress is actually slightly below the stress at which the 0{degrees} load-bearing fibers/matrix interfaces slide and are exposed to atmosphere.

Assessing and Exploiting Functional Diversity in Germplasm Pools to Enhance Abiotic Stress Adaptation and Yield in Cereals and Food Legumes

Science.gov (United States)

Dwivedi, Sangam L.; Scheben, Armin; Edwards, David; Spillane, Charles; Ortiz, Rodomiro

2017-01-01

There is a need to accelerate crop improvement by introducing alleles conferring host plant resistance, abiotic stress adaptation, and high yield potential. Elite cultivars, landraces and wild relatives harbor useful genetic variation that needs to be more easily utilized in plant breeding. We review genome-wide approaches for assessing and identifying alleles associated with desirable agronomic traits in diverse germplasm pools of cereals and legumes. Major quantitative trait loci and single nucleotide polymorphisms (SNPs) associated with desirable agronomic traits have been deployed to enhance crop productivity and resilience. These include alleles associated with variation conferring enhanced photoperiod and flowering traits. Genetic variants in the florigen pathway can provide both environmental flexibility and improved yields. SNPs associated with length of growing season and tolerance to abiotic stresses (precipitation, high temperature) are valuable resources for accelerating breeding for drought-prone environments. Both genomic selection and genome editing can also harness allelic diversity and increase productivity by improving multiple traits, including phenology, plant architecture, yield potential and adaptation to abiotic stresses. Discovering rare alleles and useful haplotypes also provides opportunities to enhance abiotic stress adaptation, while epigenetic variation has potential to enhance abiotic stress adaptation and productivity in crops. By reviewing current knowledge on specific traits and their genetic basis, we highlight recent developments in the understanding of crop functional diversity and identify potential candidate genes for future use. The storage and integration of genetic, genomic and phenotypic information will play an important role in ensuring broad and rapid application of novel genetic discoveries by the plant breeding community. Exploiting alleles for yield-related traits would allow improvement of selection efficiency and

Assessing and Exploiting Functional Diversity in Germplasm Pools to Enhance Abiotic Stress Adaptation and Yield in Cereals and Food Legumes

Directory of Open Access Journals (Sweden)

Sangam L. Dwivedi

2017-08-01

Full Text Available There is a need to accelerate crop improvement by introducing alleles conferring host plant resistance, abiotic stress adaptation, and high yield potential. Elite cultivars, landraces and wild relatives harbor useful genetic variation that needs to be more easily utilized in plant breeding. We review genome-wide approaches for assessing and identifying alleles associated with desirable agronomic traits in diverse germplasm pools of cereals and legumes. Major quantitative trait loci and single nucleotide polymorphisms (SNPs associated with desirable agronomic traits have been deployed to enhance crop productivity and resilience. These include alleles associated with variation conferring enhanced photoperiod and flowering traits. Genetic variants in the florigen pathway can provide both environmental flexibility and improved yields. SNPs associated with length of growing season and tolerance to abiotic stresses (precipitation, high temperature are valuable resources for accelerating breeding for drought-prone environments. Both genomic selection and genome editing can also harness allelic diversity and increase productivity by improving multiple traits, including phenology, plant architecture, yield potential and adaptation to abiotic stresses. Discovering rare alleles and useful haplotypes also provides opportunities to enhance abiotic stress adaptation, while epigenetic variation has potential to enhance abiotic stress adaptation and productivity in crops. By reviewing current knowledge on specific traits and their genetic basis, we highlight recent developments in the understanding of crop functional diversity and identify potential candidate genes for future use. The storage and integration of genetic, genomic and phenotypic information will play an important role in ensuring broad and rapid application of novel genetic discoveries by the plant breeding community. Exploiting alleles for yield-related traits would allow improvement of selection

Effect of different N fertilizer forms on antioxidant capacity and grain yield of rice growing under Cd stress

Energy Technology Data Exchange (ETDEWEB)

Jalloh, Mohamed Alpha; Chen Jinghong; Zhen Fanrong [Department of Agronomy, Huajiachi Campus, Zhejiang University, Hangzhou 310029 (China); Zhang Guoping [Department of Agronomy, Huajiachi Campus, Zhejiang University, Hangzhou 310029 (China)], E-mail: zhanggp@zju.edu.cn

2009-03-15

Cadmium contamination in soil has become a serious issue in sustainable agriculture production and food safety. A pot experiment was conducted to study the influence of four N fertilizer forms on grain yield, Cd concentration in plant tissues and oxidative stress under two Cd levels (0 and 100 mg Cd kg{sup -1} soil). The results showed that both N form and Cd stress affected grain yield, with urea-N and NH{sub 4}{sup +}-N treatments having significantly higher grain yields, and Cd addition reducing yield. NO{sub 3}{sup -}-N and NH{sub 4}{sup +}-N treated plants had the highest and lowest Cd concentration in plant tissues, respectively. Urea-N and NH{sub 4}{sup +}-N treatments had significantly higher N accumulation in plant tissues than other two N treatments. Cd addition caused a significant increase in leaf superoxide dismutase (SOD) and peroxidase (POD) activities for all N treatments, except for NO{sub 3}{sup -}-N treatment, with urea-N and NH{sub 4}{sup +}-N treated plants having more increase than organic-N treated ones. The results indicated that growth inhibition, yield reduction and Cd uptake of rice plants in response to Cd addition varied with the N fertilizer form.

Yielding and shear banding in soft glassy materials

NARCIS (Netherlands)

Fall, A.; Paredes, J.; Bonn, D.

2010-01-01

Yield stress fluids have proven difficult to characterize, and a reproducible determination of the yield stress is difficult. We study two types of yield stress fluids (YSF) in a single system: simple and thixotropic ones. This allows us to show that simple YSF are simply a special case of

Yielding and flow of sheared colloidal glasses

International Nuclear Information System (INIS)

Petekidis, G; Vlassopoulos, D; Pusey, P N

2004-01-01

We have studied some of the rheological properties of suspensions of hard-sphere colloids with particular reference to behaviour near the concentration of the glass transition. First we monitored the strain on the samples during and after a transient step stress. We find that, at all values of applied step stress, colloidal glasses show a rapid, apparently elastic, recovery of strain after the stress is removed. This recovery is found even in samples which have flowed significantly during stressing. We attribute this behaviour to 'cage elasticity', the recovery of the stress-induced distorted environment of any particle to a more isotropic state when the stress is removed. Second, we monitored the stress as the strain rate dot γ of flowing samples was slowly decreased. Suspensions which are glassy at rest show a stress which becomes independent of dot γ as dot γ →0. This limiting stress can be interpreted as the yield stress of the glass and agrees well both with the yield stress deduced from the step stress and recovery measurements and that predicted by a recent mode coupling theory of sheared suspensions. Thus, the behaviours under steady shearing and transient step stress both support the idea that colloidal glasses have a finite yield stress. We note however that the samples do exhibit a slow accumulation of strain due to creep at stresses below the yield stress

Effects of Saline and Sodic Stress on Yield and Fatty Acid Profile in Sunflower Seeds

Directory of Open Access Journals (Sweden)

Giovanna Cucci

2007-03-01

Full Text Available Among the objectives concerned in this research, much importance has been attached to the assessment of the influence of soil type, irrigation water quality and leaching requirement on the production and composition in fatty acids of sunflower oil. The trial was run in 2001 on a sunflower crop (cv. HS 90 grown in cylindrical pots at the Campus of Bari University (Italy. 36 treatments obtained from the factorial combination of two clay soils with nine types of brackish water and two leaching fractions (10 and 20% were compared. The nine types of irrigation water were obtained by dissolving the proper amounts of NaCl and CaCl2 in de-ionized water, according to the factorial combination of three salt concentration levels (0.01, 0.032 and 0.064 M with three sodium levels (SAR = 5, 15 and 45. At ripening the main yield traits, oil yield and acid composition of seeds were analysed. At the highest salinity level about 70% yield reduction, in terms of seeds per plant was observed. The oil yield and the final acid composition of seeds were significantly affected by soil type, leaching requirement, salinity and the SAR levels of irrigation water. A progressive decline in oil yield was recorded as the salt concentration and sodium level of irrigation solutions increased. As to the fatty acid composition, a gradual increase in oleic and linolenic acid content and a corresponding decrease in the other fatty acids were found as the salinity and sodium levels of irrigation water increased. The oleic/linoleic acid ratio too increased as the salinity increased. The salt and sodium-induced stresses of irrigation water reduced the seed and oil yields while still favouring a progressive increase in the oleic acid content and a slight decrease of linoleic, palmitic and stearic acids, thus improving oil quality. The results point out both the influence of the soil and the positive effect of sodium and salt stress and of the leaching fraction on the food quality of

Effects of Saline and Sodic Stress on Yield and Fatty Acid Profile in Sunflower Seeds

Directory of Open Access Journals (Sweden)

Emanuele Tarantino

2011-02-01

Full Text Available Among the objectives concerned in this research, much importance has been attached to the assessment of the influence of soil type, irrigation water quality and leaching requirement on the production and composition in fatty acids of sunflower oil. The trial was run in 2001 on a sunflower crop (cv. HS 90 grown in cylindrical pots at the Campus of Bari University (Italy. 36 treatments obtained from the factorial combination of two clay soils with nine types of brackish water and two leaching fractions (10 and 20% were compared. The nine types of irrigation water were obtained by dissolving the proper amounts of NaCl and CaCl2 in de-ionized water, according to the factorial combination of three salt concentration levels (0.01, 0.032 and 0.064 M with three sodium levels (SAR = 5, 15 and 45. At ripening the main yield traits, oil yield and acid composition of seeds were analysed. At the highest salinity level about 70% yield reduction, in terms of seeds per plant was observed. The oil yield and the final acid composition of seeds were significantly affected by soil type, leaching requirement, salinity and the SAR levels of irrigation water. A progressive decline in oil yield was recorded as the salt concentration and sodium level of irrigation solutions increased. As to the fatty acid composition, a gradual increase in oleic and linolenic acid content and a corresponding decrease in the other fatty acids were found as the salinity and sodium levels of irrigation water increased. The oleic/linoleic acid ratio too increased as the salinity increased. The salt and sodium-induced stresses of irrigation water reduced the seed and oil yields while still favouring a progressive increase in the oleic acid content and a slight decrease of linoleic, palmitic and stearic acids, thus improving oil quality. The results point out both the influence of the soil and the positive effect of sodium and salt stress and of the leaching fraction on the food quality of

Analytical Modeling of the High Strain Rate Deformation of Polymer Matrix Composites

Science.gov (United States)

Goldberg, Robert K.; Roberts, Gary D.; Gilat, Amos

2003-01-01

The results presented here are part of an ongoing research program to develop strain rate dependent deformation and failure models for the analysis of polymer matrix composites subject to high strain rate impact loads. State variable constitutive equations originally developed for metals have been modified in order to model the nonlinear, strain rate dependent deformation of polymeric matrix materials. To account for the effects of hydrostatic stresses, which are significant in polymers, the classical 5 plasticity theory definitions of effective stress and effective plastic strain are modified by applying variations of the Drucker-Prager yield criterion. To verify the revised formulation, the shear and tensile deformation of a representative toughened epoxy is analyzed across a wide range of strain rates (from quasi-static to high strain rates) and the results are compared to experimentally obtained values. For the analyzed polymers, both the tensile and shear stress-strain curves computed using the analytical model correlate well with values obtained through experimental tests. The polymer constitutive equations are implemented within a strength of materials based micromechanics method to predict the nonlinear, strain rate dependent deformation of polymer matrix composites. In the micromechanics, the unit cell is divided up into a number of independently analyzed slices, and laminate theory is then applied to obtain the effective deformation of the unit cell. The composite mechanics are verified by analyzing the deformation of a representative polymer matrix composite (composed using the representative polymer analyzed for the correlation of the polymer constitutive equations) for several fiber orientation angles across a variety of strain rates. The computed values compare favorably to experimentally obtained results.

Influence of reductant and germanium concentration on the growth and stress development of germanium nanocrystals in silicon oxide matrix

International Nuclear Information System (INIS)

Chew, H G; Zheng, F; Choi, W K; Chim, W K; Foo, Y L; Fitzgerald, E A

2007-01-01

Germanium (Ge) nanocrystals have been synthesized by annealing co-sputtered SiO 2 -Ge samples in N 2 or forming gas (90% N 2 +10% H 2 ) at temperatures ranging from 700 to 1000 deg. C. We concluded that the annealing ambient, temperature and Ge concentration have a significant influence on the formation and evolution of the nanocrystals. We showed that a careful selective etching of the annealed samples in hydrofluoric acid solution enabled the embedded Ge nanocrystals to be liberated from the SiO 2 matrix. From the Raman results of the as-grown and the liberated nanocrystals, we established that the nanocrystals generally experienced compressive stress in the oxide matrix and the evolution of these stress states was intimately linked to the distribution, density, size and quality of the Ge nanocrystals

Satellite-based mapping of field-scale stress indicators for crop yield forecasting: an application over Mead, NE

Science.gov (United States)

Yang, Y.; Anderson, M. C.; Gao, F.; Wardlow, B.; Hain, C.; Otkin, J.; Sun, L.; Dulaney, W.

2017-12-01

In agricultural regions, water is one of the most widely limiting factors of crop performance and production. Evapotranspiration (ET) describes crop water use through transpiration and water lost through direct soil evaporation, which makes it a good indicator of soil moisture availability and vegetation health and thus has been an integral part of many yield estimation efforts. The Evaporative Stress Index (ESI) describes temporal anomalies in a normalized evapotranspiration metric (fRET) as derived from satellite remote sensing and has demonstrated capacity to explain regional yield variability in water limited crop growing regions. However, its performance in some regions where the vegetation cycle is intensively managed appears to be degraded. In this study we generated maps of ET, fRET, and ESI at high spatiotemporal resolution (30-m pixels, daily timesteps) using a multi-sensor data fusion method, integrating information from satellite platforms with good temporal coverage and other platforms that provide field-scale spatial detail. The study was conducted over the period 2010-2014, covering a region around Mead, Nebraska that includes both rainfed and irrigated crops. Correlations between ESI and measurements of corn yield are investigated at both the field and county level to assess the value of ESI as a yield forecasting tool. To examine the role of phenology in ESI-yield correlations, annual input fRET timeseries were aligned by both calendar day and by biophysically relevant dates (e.g. days since planting or emergence). Results demonstrate that mapping of fRET and ESI at 30-m has the advantage of being able to resolve different crop types with varying phenology. The study also suggests that incorporating phenological information significantly improves yield-correlations by accounting for effects of phenology such as variable planting date and emergence date. The yield-ESI relationship in this study well captures the inter-annual variability of yields

Hydrostatic Stress Effects Incorporated Into the Analysis of the High-Strain-Rate Deformation of Polymer Matrix Composites

Science.gov (United States)

Goldberg, Robert K.; Roberts, Gary D.

2003-01-01

Procedures for modeling the effect of high strain rate on composite materials are needed for designing reliable composite engine cases that are lighter than the metal cases in current use. The types of polymer matrix composites that are likely to be used in such an application have a deformation response that is nonlinear and that varies with strain rate. The nonlinearity and strain rate dependence of the composite response is primarily due to the matrix constituent. Therefore, in developing material models to be used in the design of impact-resistant composite engine cases, the deformation of the polymer matrix must be correctly analyzed. However, unlike in metals, the nonlinear response of polymers depends on the hydrostatic stresses, which must be accounted for within an analytical model. An experimental program has been carried out through a university grant with the Ohio State University to obtain tensile and shear deformation data for a representative polymer for strain rates ranging from quasi-static to high rates of several hundred per second. This information has been used at the NASA Glenn Research Center to develop, characterize, and correlate a material model in which the strain rate dependence and nonlinearity (including hydrostatic stress effects) of the polymer are correctly analyzed. To obtain the material data, Glenn s researchers designed and fabricated test specimens of a representative toughened epoxy resin. Quasi-static tests at low strain rates and split Hopkinson bar tests at high strain rates were then conducted at the Ohio State University. The experimental data confirmed the strong effects of strain rate on both the tensile and shear deformation of the polymer. For the analytical model, Glenn researchers modified state variable constitutive equations previously used for the viscoplastic analysis of metals to allow for the analysis of the nonlinear, strain-rate-dependent polymer deformation. Specifically, we accounted for the effects of

The start of ebullition in quiescent, yield-stress fluids

Energy Technology Data Exchange (ETDEWEB)

Sherwood, David J., E-mail: djsherwo@bechtel.com [URS Corporation, Hanford Tank Waste Treatment and Immobilization Plant Project, 2435 Stevens Center Place, Richland, WA 99354 (United States); Eduardo Sáez, A. [Department of Chemical and Environmental Engineering, The University of Arizona, Tucson, AZ 85721 (United States)

2014-04-01

Highlights: • Nuclear waste slurries evolve gases from radiochemical reactions. • Evolved gases form bubbles that rise in the yield-stress slurry. • Bubble buoyancy leads to expansion and ebullition, processes modeled here. - Abstract: Non-Newtonian rheology is typical for the high-level radioactive waste (HLW) slurries to be processed in the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Hydrogen and other flammable gases are generated in the aqueous phase by radiolytic and chemical reactions. HLW slurries have a capacity for retaining gas characterized by the shear strength holding the bubbles still. The sizes and degassing characteristics of flammable gas bubbles in the HLW slurries, expected to be processed by the WTP are important considerations for designing equipment and operating procedures. Slurries become susceptible to degassing as the bubble concentration increases over a maximum value that depends on shear strength. This susceptibility and the process of ebullitive bubble enlargement are described here. When disturbed, the fluid undergoes localized flow around neighboring bubbles which are dragged together and coalesce, producing an enlarged bubble. For the conditions considered in this work, bubble size increase is enough to displace the weight required to overcome the fluid shear strength and yield the surroundings. The buoyant bubble ascends and accumulates others within a zone of influence, enlarging by a few orders of magnitude. This process describes how the first bubbles appear on the surface of a 7 Pa shear strength fluid a few seconds after being jarred.

Micromechanical modeling of tungsten-based bulk metallic glass matrix composites

Energy Technology Data Exchange (ETDEWEB)

Li Hao [Department of Mechanical Engineering-Engineering Mechanics, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 (United States); Li Ke [Department of Mechanical Engineering, Texas A and M University, TAMU 3123, College Station, TX 77843 (United States)]. E-mail: keli@tamu.edu; Subhash, Ghatu [Department of Mechanical Engineering-Engineering Mechanics, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 (United States); Kecskes, Laszlo J. [Weapons and Materials Research Directorate, US Army Research Laboratory, Aberdeen Proving Ground, MD 21005 (United States); Dowding, Robert J. [Weapons and Materials Research Directorate, US Army Research Laboratory, Aberdeen Proving Ground, MD 21005 (United States)

2006-08-15

Micromechanics models are developed for tungsten (W)-based bulk metallic glass (BMG) matrix composites employing the Voronoi tessellation technique and the finite element (FE) method. The simulation results indicate that the computed elastic moduli are close to those measured in the experiments. The predicted stress-strain curves agree well with their experimentally obtained counterparts in the early stage of the plastic deformation. An increase in the W volume fraction leads to a decrease in the yield stress and an increase in the Young's modulus of the composite. In addition, contours of equivalent plastic strain for increasing applied strains provide an explanation why shear bands were observed in the glassy phase, along the W/BMG interface, and in the W phase of failed W/BMG composite specimens.

Genotypic variability in faba bean (vicia faba L.) for seed yield and protein content under drought stress during vegetative and Reproductive Stages

International Nuclear Information System (INIS)

Abdelmula, A. A.; Gasim, S. M.; Link, W.; Mohamed, A. A.; Khalifa, J. E.

2012-01-01

Faba bean (viciafaba L.) is subjected to drought stress during different growth stages. In this study, variability in seed yield and protein content was investigated when drought occurred during the vegetative and reproductive stages. Twenty two genotypes of faba bean were field evaluated under three levels of drought stress at two locations in the Sudan. The three levels of drought were normal watering (non-stress), drought during the vegetative stage and drought during the reproductive stage. Data were collected on yield and vegetative traits and protein content. The results showed that yield, as well as other traits, were reduced by drought. The genotypes exhibited significant differences for 100 seed weight, plant height and protein content. The interaction between the genotypes and drought was significant for yield/plant. Some genotypes were more sensitive when drought occurred during the vegetative stage, some when drought occurred during the vegetative stage, and others were more stable under the three levels of drought. yield/plant showed significant covariance with pods/plant and plant height. The association between different characters varied according to trait and the time of drought incidence. The correlation of yield/plant with protein content was negative under all drought levels, and the average correlation coefficient was 0.32. It could be concluded that the specific adaptation and the wide adaptation have great implication for improving faba bean under drought. To select for high seed yield under drought, secondary characters, such as pods/plant and plant height could be of great importance. Drought could reduce protein content and affect its association with yield/plant.(Author)

Detrimental effect of selection for milk yield on genetic tolerance to heat stress in purebred Zebu cattle: Genetic parameters and trends.

Science.gov (United States)

Santana, M L; Pereira, R J; Bignardi, A B; Filho, A E Vercesi; Menéndez-Buxadera, A; El Faro, L

2015-12-01

In an attempt to determine the possible detrimental effects of continuous selection for milk yield on the genetic tolerance of Zebu cattle to heat stress, genetic parameters and trends of the response to heat stress for 86,950 test-day (TD) milk yield records from 14,670 first lactations of purebred dairy Gir cows were estimated. A random regression model with regression on days in milk (DIM) and temperature-humidity index (THI) values was applied to the data. The most detrimental effect of THI on milk yield was observed in the stage of lactation with higher milk production, DIM 61 to 120 (-0.099kg/d per THI). Although modest variations were observed for the THI scale, a reduction in additive genetic variance as well as in permanent environmental and residual variance was observed with increasing THI values. The heritability estimates showed a slight increase with increasing THI values for any DIM. The correlations between additive genetic effects across the THI scale showed that, for most of the THI values, genotype by environment interactions due to heat stress were less important for the ranking of bulls. However, for extreme THI values, this type of genotype by environment interaction may lead to an important error in selection. As a result of the selection for milk yield practiced in the dairy Gir population for 3 decades, the genetic trend of cumulative milk yield was significantly positive for production in both high (51.81kg/yr) and low THI values (78.48kg/yr). However, the difference between the breeding values of animals at high and low THI may be considered alarming (355kg in 2011). The genetic trends observed for the regression coefficients related to general production level (intercept of the reaction norm) and specific ability to respond to heat stress (slope of the reaction norm) indicate that the dairy Gir population is heading toward a higher production level at the expense of lower tolerance to heat stress. These trends reflect the genetic

Exogenous Cytokinins Increase Grain Yield of Winter Wheat Cultivars by Improving Stay-Green Characteristics under Heat Stress.

Directory of Open Access Journals (Sweden)

Dongqing Yang

Full Text Available Stay-green, a key trait of wheat, can not only increase the yield of wheat but also its resistance to heat stress during active photosynthesis. Cytokinins are the most potent general coordinator between the stay-green trait and senescence. The objectives of the present study were to identify and assess the effects of cytokinins on the photosynthetic organ and heat resistance in wheat. Two winter wheat cultivars, Wennong 6 (a stay-green cultivar and Jimai 20 (a control cultivar, were subjected to heat stress treatment from 1 to 5 days after anthesis (DAA. The two cultivars were sprayed daily with 10 mg L-1 of 6-benzylaminopurine (6-BA between 1 and 3 DAA under ambient and elevated temperature conditions. We found that the heat stress significantly decreased the number of kernels per spike and the grain yield (P < 0.05. Heat stress also decreased the zeatin riboside (ZR content, but increased the gibberellin (GA3, indole-3-acetic acid (IAA, and abscisic acid (ABA contents at 3 to 15 DAA. Application of 6-BA significantly (P < 0.05 increased the grain-filling rate, endosperm cell division rate, endosperm cell number, and 1,000-grain weight under heated condition. 6-BA application increased ZR and IAA contents at 3 to 28 DAA, but decreased GA3 and ABA contents. The contents of ZR, ABA, and IAA in kernels were positively and significantly correlated with the grain-filling rate (P < 0.05, whereas GA3 was counter-productive at 3 to 15 DAA. These results suggest that the decrease in grain yield under heat stress was due to a lower ZR content and a higher GA3 content compared to that at elevated temperature during the early development of the kernels, which resulted in less kernel number and lower grain-filling rate. The results also provide essential information for further utilization of the cytokinin substances in the cultivation of heat-resistant wheat.

Phenological Variation and its Relation with Yield in several Wheat (Triticum aestivum L. Cultivars under Normal and Late Sowing Mediated Heat Stress Condition

Directory of Open Access Journals (Sweden)

Kamrun NAHAR

2010-09-01

Full Text Available Phenological performance in relation to yield of five modern varieties of wheat Sourav, Pradip, Sufi, Shatabdi and Bijoy were evaluated under two growing environments; one is normal growing environment (sowing at November 30 and the other is post anthesis heat stressed environment (sowing at December 30. In case of late seeding, the varieties phased a significant level of high temperature stress that also significantly affected the required days to germination, booting, anthesis, maturity of all varieties including the yield as compared to normal sowing treatment. The temperature during the grain filling or grain maturing period was near 23C in case of normal seeding and it was near about 28C to 30C and sometimes reached above this range in the later period of late seeded treatment. In the normal sowing treatment the germination period was lower than the late sowing treatment as during that time the temperature was higher as compared to late sowing condition where temperature was lower. Days to anthesis and booting decreased due to late sown heat stress condition regardless the cultivars. These phenological characteristics under heat stressed condition led the wheat cultivars to significantly lower the grain yield as compared to normal condition. Due to heat stress, the yield reduction was 69.53% in Sourav, 58.41% in Pradip, 73.01% in Sufi, 55.46% in Shatabdi and 53.42% in Bijoy.

On the superposition of strengthening mechanisms in dispersion strengthened alloys and metal-matrix nanocomposites: Considerations of stress and energy

Science.gov (United States)

Ferguson, J. B.; Schultz, Benjamin F.; Venugopalan, Dev; Lopez, Hugo F.; Rohatgi, Pradeep K.; Cho, Kyu; Kim, Chang-Soo

2014-03-01

Yield strength improvement in dispersion strengthened alloys and nano particle-reinforced composites by well-known strengthening mechanisms such as solid solution, grain refinement, coherent and incoherent dispersed particles, and increased dislocation density resulting from work-hardening can all be described individually. However, there is no agreed upon description of how these mechanisms combine to determine the yield strength. In this work, we propose an analytical yield strength prediction model combining arithmetic and quadratic addition approaches based on the consideration of two types of yielding mechanisms; stress-activated and energy-activated. Using data available in the literature for materials of differing grain sizes, we consider the cases of solid solutions and coherent precipitates to show that they follow stress-activated behavior. Then, we applied our model with some empirical parameters to precipitationhardenable materials of various grain sizes in both coherent and incoherent precipitate conditions, which demonstrated that grain boundary and Orowan-strengthening can be treated as energy-activated mechanisms.

Synchrotron X-ray diffraction measurements of internal stresses during loading of steel-based metal matrix composites reinforced with TiB2 particles

International Nuclear Information System (INIS)

Bacon, D.H.; Edwards, L.; Moffatt, J.E.; Fitzpatrick, M.E.

2011-01-01

Highlights: → Synchrotron X-ray diffraction was used to measure internal stresses in Fe-TiB 2 MMCs. → Samples of the MMCs were loaded to failure in situ in the X-ray beam. → The results show good elastic load transfer from the matrix to the reinforcement. → There is good agreement with the predicted elastic stresses from Eshelby modeling. → During plastic deformation there is increasing load transfer to the reinforcement. - Abstract: High-energy synchrotron X-ray diffraction was used to measure the internal strain evolution in the matrix and reinforcement of steel-based metal matrix composites reinforced with particulate titanium diboride (TiB 2 ). Two systems were studied: a 316L matrix with 25% TiB 2 by volume and a W1.4418 matrix with 10% reinforcement. In situ loading experiments were performed, where the materials were loaded uniaxially in the X-ray beam. The results show the strain partitioning between the phases in the elastic regime, and the evolution of the strain partitioning once plasticity occurs. The results are compared with results from Eshelby modelling, and very good agreement is seen between the measured and modelled response for elastic loading of the material. Heat treatment of the 316-based material did not affect the elastic internal strain response.

Effects of inter-varietal diversity, biotic stresses and environmental productivity on grain yield of spring barley variety mixtures

DEFF Research Database (Denmark)

Kiær, Lars Pødenphant; Skovgaard, Ib M.; Østergård, Hanne

2012-01-01

than their component varieties when accounting also for the general response to environmental productivity. Hence, most mixtures adapted slightly better to environmental productivity and were less sensitive to environmental stress than their component varieties. We conclude that the efficacy of variety...... mixtures may be enhanced by mixing relatively high-yielding varieties differing in responsiveness to environmental productivity.......Varietal seed mixtures tend to increase and stabilize crop yields, yet their application is sparse. Large-scale cultivation of variety mixtures may require a better understanding of how inter-varietal interactions and their interaction with the environment may influence the grain yield of variety...

Chronic mild stress influences nerve growth factor through a matrix metalloproteinase-dependent mechanism.

Science.gov (United States)

Kucharczyk, Mateusz; Kurek, Anna; Detka, Jan; Slusarczyk, Joanna; Papp, Mariusz; Tota, Katarzyna; Basta-Kaim, Agnieszka; Kubera, Marta; Lason, Wladyslaw; Budziszewska, Bogusława

2016-04-01

Stress is generally a beneficial experience that motivates an organism to action to overcome the stressful challenge. In particular situations, when stress becomes chronic might be harmful and devastating. The hypothalamus is a critical coordinator of stress and the metabolic response; therefore, disruptions in this structure may be a significant cause of the hormonal and metabolic disturbances observed in depression. Chronic stress induces adverse changes in the morphology of neural cells that are often associated with a deficiency of neurotrophic factors (NTFs); additionally, many studies indicate that insufficient NTF synthesis may participate in the pathogenesis of depression. The aim of the present study was to determine the expression of the nerve growth factor (NGF) in the hypothalamus of male rats subjected to chronic mild stress (CMS) or to prenatal stress (PS) and to PS in combination with an acute stress event (AS). It has been found that chronic mild stress, but not prenatal stress, acute stress or a combination of PS with AS, decreased the concentration of the mature form of NGF (m-NGF) in the rat hypothalamus. A discrepancy between an increase in the Ngf mRNA and a decrease in the m-NGF levels suggested that chronic mild stress inhibited NGF maturation or enhanced the degradation of this factor. We have shown that NGF degradation in the hypothalamus of rats subjected to chronic mild stress is matrix metalloproteinase-dependent and related to an increase in the active forms of some metalloproteinases (MMP), including MMP2, MMP3, MMP9 and MMP13, while the NGF maturation process does not seem to be changed. We suggested that activated MMP2 and MMP9 potently cleave the mature but not the pro- form of NGF into biologically inactive products, which is the reason for m-NGF decomposition. In turn, the enhanced expression of Ngf in the hypothalamus of these rats is an attempt to overcome the reduced levels of m-NGF. Additionally, the decreased level of m

Compressive yielding of tungsten fiber reinforced bulk metallic glass composites

Energy Technology Data Exchange (ETDEWEB)

Clausen, B.; Lee, S.-Y.; Uestuendag, E.; Aydiner, C.C.; Conner, R.D.; Bourke, M.A.M

2003-07-15

In-situ uniaxial compression tests were conducted on four tungsten fiber reinforced bulk metallic glass matrix composites using neutron diffraction. The results were interpreted with a finite element model. Both phases were seen to approximately obey the von Mises yield criterion. The fibers were observed to yield first and then transfer load to the matrix.

Compressive yielding of tungsten fiber reinforced bulk metallic glass composites

International Nuclear Information System (INIS)

Clausen, B.; Lee, S.-Y.; Uestuendag, E.; Aydiner, C.C.; Conner, R.D.; Bourke, M.A.M.

2003-01-01

In-situ uniaxial compression tests were conducted on four tungsten fiber reinforced bulk metallic glass matrix composites using neutron diffraction. The results were interpreted with a finite element model. Both phases were seen to approximately obey the von Mises yield criterion. The fibers were observed to yield first and then transfer load to the matrix

Thermomechanical behavior of fuel particles in a matrix during reactor power excursions

International Nuclear Information System (INIS)

Brittan, R.O.; Smith, R.S.

1977-01-01

This work determines the largest particle size that can be used in fabricating fuel material without exceeding temperature or stress criteria during transient operation. To do this temperature distribution histories must be determined for various particle sizes and volume fractions using typical power densities histories of transient reactor operation. From these, the critical stresses are calculated. The model chosen to accomplish this is a spherical fuel particle in a spherical matrix shell. Heat flow and temperature continuity conditions are imposed at the interface, and a zero temperature gradient is specified at the outer radius of the matrix shell. The particle power density is assumed to be uniform radially. Provisions are made for uniform power density in the matrix to model gamma heating and power density in interface layers to allow for radiant and fission fragment heating. A computer code was prepared to solve the model performance, yielding the temperature and stress distribution histories. Material property variation with temperature is employed, along with a close mockup of the power density history during self-limiting reactor transients. To date, four fuel systems have been investigated: 1) UC.ZrC particles in graphite; 2) UO 2 particles in graphite; 3) UO 2 particles in chromium 4) UO 2 particles in stainless steel. The study indicates that the maximum allowable particle diameter varies as the square root of the initial transient period and of the particle volume fraction. The critical thermophysical parameter is the thermal diffusivity of the particle, since in all cases studied it is many times smaller than that of the matrix. That of the UC.ZrC solid solution particle is 5 or more times larger than that of the UO 2 particle. It was found that the particles of system 1) above could be about 4 times larger than that of the other sy

Phenological Variation and its Relation with Yield in several Wheat (Triticum aestivum L. Cultivars under Normal and Late Sowing Mediated Heat Stress Condition

Directory of Open Access Journals (Sweden)

Kamrun NAHAR

2010-09-01

Full Text Available Phenological performance in relation to yield of five modern varieties of wheat �Sourav�, �Pradip�, �Sufi�, �Shatabdi� and �Bijoy� were evaluated under two growing environments; one is normal growing environment (sowing at November 30 and the other is post anthesis heat stressed environment (sowing at December 30. In case of late seeding, the varieties phased a significant level of high temperature stress that also significantly affected the required days to germination, booting, anthesis, maturity of all varieties including the yield as compared to normal sowing treatment. The temperature during the grain filling or grain maturing period was near 23�C in case of normal seeding and it was near about 28�C to 30�C and sometimes reached above this range in the later period of late seeded treatment. In the normal sowing treatment the germination period was lower than the late sowing treatment as during that time the temperature was higher as compared to late sowing condition where temperature was lower. Days to anthesis and booting decreased due to late sown heat stress condition regardless the cultivars. These phenological characteristics under heat stressed condition led the wheat cultivars to significantly lower the grain yield as compared to normal condition. Due to heat stress, the yield reduction was 69.53% in �Sourav�, 58.41% in �Pradip�, 73.01% in �Sufi�, 55.46% in �Shatabdi� and 53.42% in �Bijoy�.

Stress-induced martensitic transformations in NiTi and NiTi-TiC composites investigated by neutron diffraction

International Nuclear Information System (INIS)

Vaidyanathan, R.; Dunand, D.C.

1999-01-01

Superelastic NiTi (51.0 at.% Ni) specimens reinforced with 0, 10 and 20 vol.% TiC particles were deformed under uniaxial compression while neutron diffraction spectra were collected. The experiments yielded in-situ measurements of the thermoelastic stress-induced transformation. The evolution of austenite/martensite phase fractions and of elastic strains in the reinforcing TiC particles and the austenite matrix were obtained by Rietveld refinement during the loading cycle as the austenite transforms to martensite (and its subsequent back transformation during unloading). Phase fractions and strains are discussed in terms of load transfer in composites where the matrix undergoes a stress-induced phase transformation. (orig.)

Correlation of microstructure and compressive properties of amorphous matrix composites reinforced with tungsten continuous fibers or porous foams

International Nuclear Information System (INIS)

Son, Chang-Young; Lee, Sang-Bok; Lee, Sang-Kwan; Kim, Choongnyun Paul; Lee, Sunghak

2010-01-01

Zr-based amorphous alloy matrix composites reinforced with tungsten continuous fibers or porous foams were fabricated without pores or defects by liquid pressing process, and their microstructures and compressive properties were investigated. About 65-70 vol.% of tungsten reinforcements were homogeneously distributed inside the amorphous matrix. The compressive test results indicated that the tungsten-reinforced composites showed considerable plastic strain as the compressive load was sustained by fibers or foams. Particularly in the tungsten porous foam-reinforced composite, the compressive stress continued to increase according to the work hardening after the yielding, thereby leading to the maximum strength of 2764 MPa and the plastic strain of 39.4%. This dramatic increase in strength and ductility was attributed to the simultaneous and homogeneous deformation at tungsten foams and amorphous matrix since tungsten foams did not show anisotropy and tungsten/matrix interfaces were excellent.

Multifunctional Nanotube Polymer Nanocomposites for Aerospace Applications: Adhesion between SWCNT and Polymer Matrix

Science.gov (United States)

Park, Cheol; Wise, Kristopher E.; Kang, Jin Ho; Kim, Jae-Woo; Sauti, Godfrey; Lowther, Sharon E.; Lillehei, Peter T.; Smith, Michael W.; Siochi, Emilie J.; Harrison, Joycelyn S.;

Random regression models to account for the effect of genotype by environment interaction due to heat stress on the milk yield of Holstein cows under tropical conditions.

Science.gov (United States)

Santana, Mário L; Bignardi, Annaiza Braga; Pereira, Rodrigo Junqueira; Menéndez-Buxadera, Alberto; El Faro, Lenira

2016-02-01

The present study had the following objectives: to compare random regression models (RRM) considering the time-dependent (days in milk, DIM) and/or temperature × humidity-dependent (THI) covariate for genetic evaluation; to identify the effect of genotype by environment interaction (G×E) due to heat stress on milk yield; and to quantify the loss of milk yield due to heat stress across lactation of cows under tropical conditions. A total of 937,771 test-day records from 3603 first lactations of Brazilian Holstein cows obtained between 2007 and 2013 were analyzed. An important reduction in milk yield due to heat stress was observed for THI values above 66 (-0.23 kg/day/THI). Three phases of milk yield loss were identified during lactation, the most damaging one at the end of lactation (-0.27 kg/day/THI). Using the most complex RRM, the additive genetic variance could be altered simultaneously as a function of both DIM and THI values. This model could be recommended for the genetic evaluation taking into account the effect of G×E. The response to selection in the comfort zone (THI ≤ 66) is expected to be higher than that obtained in the heat stress zone (THI > 66) of the animals. The genetic correlations between milk yield in the comfort and heat stress zones were less than unity at opposite extremes of the environmental gradient. Thus, the best animals for milk yield in the comfort zone are not necessarily the best in the zone of heat stress and, therefore, G×E due to heat stress should not be neglected in the genetic evaluation.

Efficient Brownian Dynamics of rigid colloids in linear flow fields based on the grand mobility matrix

Science.gov (United States)

Palanisamy, Duraivelan; den Otter, Wouter K.

2018-05-01

We present an efficient general method to simulate in the Stokesian limit the coupled translational and rotational dynamics of arbitrarily shaped colloids subject to external potential forces and torques, linear flow fields, and Brownian motion. The colloid's surface is represented by a collection of spherical primary particles. The hydrodynamic interactions between these particles, here approximated at the Rotne-Prager-Yamakawa level, are evaluated only once to generate the body's (11 × 11) grand mobility matrix. The constancy of this matrix in the body frame, combined with the convenient properties of quaternions in rotational Brownian Dynamics, enables an efficient simulation of the body's motion. Simulations in quiescent fluids yield correct translational and rotational diffusion behaviour and sample Boltzmann's equilibrium distribution. Simulations of ellipsoids and spherical caps under shear, in the absence of thermal fluctuations, yield periodic orbits in excellent agreement with the theories by Jeffery and Dorrepaal. The time-varying stress tensors provide the Einstein coefficient and viscosity of dilute suspensions of these bodies.

Cavitation instabilities between fibres in a metal matrix composite

DEFF Research Database (Denmark)

Tvergaard, Viggo

2016-01-01

induced by bonding to the ceramics that only show elastic deformation. In an MMC the stress state in the metal matrix is highly non-uniform, varying between regions where shear stresses are dominant and regions where hydrostatic tension is strong. An Al–SiC whisker composite with a periodic pattern......Short fibre reinforced metal matrix composites (MMC) are studied here to investigate the possibility that a cavitation instability can develop in the metal matrix. The high stress levels needed for a cavitation instability may occur in metal–ceramic systems due to the constraint on plastic flow...... of transversely staggered fibres is here modelled by using an axisymmetric cell model analysis. First the critical stress level is determined for a cavitation instability in an infinite solid made of the Al matrix material. By studying composites with different distributions and aspect ratios of the fibres...

Effect of Different Level of Water Stress and Nitrogen Fertilizer on Yield and Yield Components of Barley in Badjgah (Fars province

Directory of Open Access Journals (Sweden)

ali asghar ghaemi

2016-02-01

Full Text Available Introduction: Barley is very important to feed humans, livestock, medical, industrial uses, especially in fermentation industries. In Iran, barley crop cultivation was nearly 1.4 million hectares withits production of 1.3 million tons in 2003 (2. Barelyis the oldest crops to environmental stresses such as drought and salinity resistance (3.The different barely growth stages with extreme water requirement can benoted in germination stage, stem elongation, heading the production stage, the stage of flowering and seed production. Typically, for spring and autumn barely respectively 3 and 4 to 5 times irrigation is done during the growing season. The barley water requirement over its life is between 4 and 7 thousand cubic meters and 518 liters of water is needed to produce one kilogram of dry matter. Due to limited water resources and low rainfall in Iran, efficient use of water is absolutely essential and the maximum water utilization must be achieved by applying a minimum amount of water in agriculture. One of the ways to increase productivity in agricultural water is deficit irrigation.Deficit irrigation is an optimization strategy for water use efficiency in irrigation.The purpose of this study was to evaluate the simultaneous effect of fertilizer treatments (150, 225 and 75 kg/ ha and water at three different levels (100%, 75% and 50% of crop water requirement at different growth stages on leaf area index, weight fresh and dried herb and plant nitrogen concentration and the effect of irrigation and nitrogen fertilizer on yield, yield components and productivity of water use. Materials and Method: This research was conducted in Shiraz University in fall 2012 to study the effect of interaction of deficit irrigation and nitrogen fertilizer on yield, yield component and water use efficiency and nitrogen concentration in different stages of barley (Bahman species growth. This experiment were evaluated using a randomized complete block design with s

[Impacts of drought stress on the growth and development and grain yield of spring maize in Northeast China].

Science.gov (United States)

Ji, Rui-Peng; Che, Yu-Sheng; Zhu, Yong-Ning; Liang, Tao; Feng, Rui; Yu, Wen-Ying; Zhang, Yu-Shu

2012-11-01

Taking spring maize variety Danyu-39 as test object, an experiment was conducted in a large-scale agricultural water controlling experimental field to study the impacts of drought stress at three key growth stages, i. e. , 3-leaf-jointing, jointing-silking, and silking-milk ripe, on the growth and development and grain yield of spring maize in Northeast China. Two treatments were installed, including moderate drought stress (MS) and re-watering to suitable water (CK). Compared with CK, the MS at 3-leaf-jointing stage postponed the whole growth period of Danyu-39 by 13 d, and the plant height and leaf area at jointing stage were decreased by 29.8% and 41.2%, respectively. After re-watering, the plant height and grain yield recovered obviously, and the differences in ear characteristics and final yield were insignificant. The MS at jointing-silking stage shortened the whole growth period by 7 d, the plant height and leaf area at silking stage were decreased by 18.6% and 14.1%, respectively, the ear length, grain number per ear, ear dry mass, and grain mass per ear decreased by 6.9%, 19.1%, 28.1%, and 29.4%, respectively, and the blank stem rate increased by 13.3%. When the maize suffered from moderate drought stress at silking-milk ripe stage, the whole growth period was shortened by 15 d, the plant height and leaf area at milk ripe stage were decreased by 2.3% and 37.3%, respectively, the ear length, grain number per ear, ear dry mass, and grain mass per ear decreased by 9.2%, 24.1%, 30.8%, and 27.9%, respectively, and the blank stem rate increased by 24.5%. After re-watering at the latter two stages, the recovery of plant height was little, and the grain yield decreased significantly.

Heat waves imposed during early pod development in soybean (Glycine max) cause significant yield loss despite a rapid recovery from oxidative stress.

Science.gov (United States)

Siebers, Matthew H; Yendrek, Craig R; Drag, David; Locke, Anna M; Rios Acosta, Lorena; Leakey, Andrew D B; Ainsworth, Elizabeth A; Bernacchi, Carl J; Ort, Donald R

2015-08-01

Heat waves already have a large impact on crops and are predicted to become more intense and more frequent in the future. In this study, heat waves were imposed on soybean using infrared heating technology in a fully open-air field experiment. Five separate heat waves were applied to field-grown soybean (Glycine max) in central Illinois, three in 2010 and two in 2011. Thirty years of historical weather data from Illinois were analyzed to determine the length and intensity of a regionally realistic heat wave resulting in experimental heat wave treatments during which day and night canopy temperatures were elevated 6 °C above ambient for 3 days. Heat waves were applied during early or late reproductive stages to determine whether and when heat waves had an impact on carbon metabolism and seed yield. By the third day of each heat wave, net photosynthesis (A), specific leaf weight (SLW), and leaf total nonstructural carbohydrate concentration (TNC) were decreased, while leaf oxidative stress was increased. However, A, SLW, TNC, and measures of oxidative stress were no different than the control ca. 12 h after the heat waves ended, indicating rapid physiological recovery from the high-temperature stress. That end of season seed yield was reduced (~10%) only when heat waves were applied during early pod developmental stages indicates the yield loss had more to do with direct impacts of the heat waves on reproductive process than on photosynthesis. Soybean was unable to mitigate yield loss after heat waves given during late reproductive stages. This study shows that short high-temperature stress events that reduce photosynthesis and increase oxidative stress resulted in significant losses to soybean production in the Midwest, U.S. The study also suggests that to mitigate heat wave-induced yield loss, soybean needs improved reproductive and photosynthetic tolerance to high but increasingly common temperatures. Published 2015. This article is a U.S. Government work and is

In-situ stress analysis with X-Ray diffraction for yield locus characterization of sheet metals

Energy Technology Data Exchange (ETDEWEB)

Güner, A.; Tekkaya, A. E. [Institute of Forming Technology and Lightweight Construction, TU Dortmund University, Baroper Str. 301, 44227 Dortmund (Germany); Zillmann, B.; Lampke, T. [Institute of Materials Science and Engineering, Chemnitz University of Technology, Erfenschlager Strasse 73 D-09125 Chemnitz (Germany)

2013-12-16

A main problem in the field of sheet metal characterization is the inhomogeneous plastic deformation in the gauge regions of specimens which causes the analytically calculated stresses to differ from the sought state of stress acting in the middle of the gauge region. To overcome this problem, application of X-Ray diffraction is analyzed. For that purpose a mobile X-ray diffractometer and an optical strain measurement system are mounted on a universal tensile testing machine. This enables the recording of the whole strain and stress history of a material point. The method is applied to uniaxial tension tests, plane strain tension tests and shear tests to characterize the interstitial free steel alloy DC06. The applicability of the concepts of stress factors is verified by uniaxial tension tests. The experimentally obtained values are compared with the theoretical values calculated with crystal elasticity models utilizing the orientation distribution functions (ODF). The relaxation problem is addressed which shows itself as drops in the stress values with the strain kept at a constant level. This drop is analyzed with elasto-viscoplastic material models to correct the measured stresses. Results show that the XRD is applicable to measure the stresses in sheet metals with preferred orientation. The obtained yield locus is expressed with the Yld2000–2D material model and an industry oriented workpiece is analyzed numerically. The comparison of the strain distribution on the workpiece verifies the identified material parameters.

Effects of drought stress and arbuscular mycorrhizal fungi on some morphophysiological traits and yield of savory (Satureja hortensis L.)

OpenAIRE

B. Esmaielpour; P. Jalilvand; J. Hadian

2016-01-01

Water deficit stress permanent or temporary limits the growth and distribution of natural vegetation and performance of plants more than other environmental factors. In order to investigate the effect of drought stress and mycorrhizal-arbuscular fungi inoculation on the growth and yield of savory (Satureja hortensis L.) a factorial experiment based on completely randomized design were conducted in Research Greenhouse of Horticulture Department of Mohaghegh Ardabili University during 2010. Exp...

Cell stiffness, contractile stress and the role of extracellular matrix

International Nuclear Information System (INIS)

An, Steven S.; Kim, Jina; Ahn, Kwangmi; Trepat, Xavier; Drake, Kenneth J.; Kumar, Sarvesh; Ling, Guoyu; Purington, Carolyn; Rangasamy, Tirumalai; Kensler, Thomas W.; Mitzner, Wayne; Fredberg, Jeffrey J.; Biswal, Shyam

2009-01-01

Here we have assessed the effects of extracellular matrix (ECM) composition and rigidity on mechanical properties of the human airway smooth muscle (ASM) cell. Cell stiffness and contractile stress showed appreciable changes from the most relaxed state to the most contracted state: we refer to the maximal range of these changes as the cell contractile scope. The contractile scope was least when the cell was adherent upon collagen V, followed by collagen IV, laminin, and collagen I, and greatest for fibronectin. Regardless of ECM composition, upon adherence to increasingly rigid substrates, the ASM cell positively regulated expression of antioxidant genes in the glutathione pathway and heme oxygenase, and disruption of a redox-sensitive transcription factor, nuclear erythroid 2 p45-related factor (Nrf2), culminated in greater contractile scope. These findings provide biophysical evidence that ECM differentially modulates muscle contractility and, for the first time, demonstrate a link between muscle contractility and Nrf2-directed responses.

Cell stiffness, contractile stress and the role of extracellular matrix

Energy Technology Data Exchange (ETDEWEB)

An, Steven S., E-mail: san@jhsph.edu [Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, Room E-7616, Baltimore, MD 21205 (United States); Kim, Jina [Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, Room E-7616, Baltimore, MD 21205 (United States); Ahn, Kwangmi [Division of Biostatistics, Penn State College of Medicine, Hershey, PA 17033 (United States); Trepat, Xavier [CIBER, Enfermedades Respiratorias, 07110 Bunyola (Spain); Drake, Kenneth J. [Division of Molecular and Integrative Physiological Sciences, Harvard School of Public Health, Boston, MA 02115 (United States); Kumar, Sarvesh; Ling, Guoyu; Purington, Carolyn; Rangasamy, Tirumalai; Kensler, Thomas W.; Mitzner, Wayne [Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, Room E-7616, Baltimore, MD 21205 (United States); Fredberg, Jeffrey J. [Division of Molecular and Integrative Physiological Sciences, Harvard School of Public Health, Boston, MA 02115 (United States); Biswal, Shyam [Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, Room E-7616, Baltimore, MD 21205 (United States); Division of Pulmonary and Critical Care Medicine, Johns Hopkins School of Medicine, Baltimore, MD 21205 (United States)

2009-05-15

Here we have assessed the effects of extracellular matrix (ECM) composition and rigidity on mechanical properties of the human airway smooth muscle (ASM) cell. Cell stiffness and contractile stress showed appreciable changes from the most relaxed state to the most contracted state: we refer to the maximal range of these changes as the cell contractile scope. The contractile scope was least when the cell was adherent upon collagen V, followed by collagen IV, laminin, and collagen I, and greatest for fibronectin. Regardless of ECM composition, upon adherence to increasingly rigid substrates, the ASM cell positively regulated expression of antioxidant genes in the glutathione pathway and heme oxygenase, and disruption of a redox-sensitive transcription factor, nuclear erythroid 2 p45-related factor (Nrf2), culminated in greater contractile scope. These findings provide biophysical evidence that ECM differentially modulates muscle contractility and, for the first time, demonstrate a link between muscle contractility and Nrf2-directed responses.

Drought Stress Effect during Different Growth Stages on Yield, Osmolites and Photosynthetic Pigments Accumulation of Grain Sorghum Genotypes (Sorghum bicolor L.

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A Azari Nasrabad

2017-12-01

Full Text Available Introduction Osmotic adjustment in plants can be achieved by the accumulation of compatible solution or metabolites. These compounds are known as compatible metabolites that accumulate naturally in tolerant plants due to non-interference in the normal metabolic response of plants to adapt or supplement. Proline, soluble sugars and other metabolites accumulation that are involved in osmotic adjustment have been reported for various plants. Different studies show that water absorption in sorghum plant, is due to osmotic adjustment and appropriate and fairly extensive root system. Moreover, there are some differences from genotype to genotype regarding the osmolites accumulation under drought stress conditions. Thus, the aim of this study was to investigate the effects of drought in the vegetative and reproductive growth stages on yield, its components and biochemical traits in grain sorghum genotypes. Materials and Methods In order to evaluate the effect of water stress on grain yield and its components and some biochemical traits in grain sorghum genotypes (Sorghum bicolor L., a field experiment as a split plot design was carried out with 3 replications in 2014 at the research farm of the southern Khorasan Agriculture and natural resources research and education center. Water stress treatments including normal irrigation (control, irrigation cut off in vegetative growth stage (emergence of terminal leaf as rolled and irrigation cut off in generative growth stage (50% of plants in start of flowering as the main plot and 10 genotypes of sorghum including KGS29, MGS2, Sepideh, KGFS27, MGS5, KGFS5, KGFS17, KGFS13 and KGFS30 were considered as sub plots. Each plot consists of 4 rows with a length of 6 m and row spacing of 60 cm, between plants on row was 10 cm. In addition, between each plot and the adjacent plot a row was considered to side effect reduction. To determine the yield components of each plot, half a meter in length was harvested and the

Relations between soil factors and herbage yields of natural ...

African Journals Online (AJOL)

Keywords: Cation exchange capacity; Correlation matrix; Nitrogen supplies; Root mass; Root measurements; Soil acidity; Soil variables; Soil water content; Soil water measurements; Yield measurements; nitrogen supply; ph; herbage yield; grassland; soils; productivity; soil depth; dry matter yield; grasses; water content; n; ...

Application of tungsten-fibre-reinforced copper matrix composites to a high-heat-flux component: A design study by dual scale finite element analysis

International Nuclear Information System (INIS)

Jeong-Ha You

2006-01-01

According to the European Power Plant Conceptual Study, actively cooled tungsten mono-block is one of the divertor design options for fusion reactors. In this study the coolant tube acts as a heat sink and the tungsten block as plasma-facing armour. A key material issue here is how to achieve high temperature strength and high heat conductivity of the heat sink tube simultaneously. Copper matrix composite reinforced with continuous strong fibres has been considered as a candidate material for heat sink of high-heat-flux components. Refractory tungsten wire is a promising reinforcement material due to its high strength, winding flexibility and good interfacial wetting with copper. We studied the applicability of tungsten-fibre-reinforced copper matrix composite heat sink tubes for the tungsten mono-block divertor by means of dual-scale finite element analysis. Thermo-elasto-plastic micro-mechanics homogenisation technique was applied. A heat flux of 15 MW/m 2 with cooling water temperature of 320 o C was considered. Effective stress-free temperature was assumed to be 500 o C. Between the tungsten block and the composite heat sink tube interlayer (1 mm thick) of soft Cu was inserted. The finite element analysis yields the following results: The predicted maximum temperature at steady state is 1223 o C at the surface and 562 o C at the interface between tube and copper layer. On the macroscopic scale, residual stress is generated during fabrication due to differences in thermal expansion coefficients of the materials. Strong compressive stress occurs in the tungsten block around the tube while weak tensile stress is present in the interlayer. The local and global probability of brittle failure of the tungsten block was also estimated using the probabilistic failure theories. The thermal stresses are significantly decreased upon subsequent heat flux loading. Resolving the composite stress on microscopic scale yields a maximum fibre axial stress of 3000 MPa after

Evaluation of Low Pressure Fogging System for Improving Crop Yield of Tomato (Lycopersicon esculentum Mill.: Grown under Heat Stress Conditions

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Kobi Shilo

2013-06-01

Full Text Available In Mediterranean regions, many tomato plants are grown throughout the hot summer period (May–September in sheltered cultivation, mainly for plant protection reasons. Most of the shelters that are used are low cost net houses covered with 50 mesh insect proof net. In most cases these net houses have a flat roof and no ventilation or climate control measures. This insufficient ventilation during the hot summer leads to above optimal air temperatures and causes moderate heat stress inside the shelters, which leads to yield reduction. The aim of this study was to evaluate the ability of a simple and inexpensive low pressure fogging system installed in a naturally ventilated net house to lower temperatures and improve the yield during the summer. The study showed that in areas where relative air humidity (RH during the daytime is less than 60%, tomato plants improved their performance when grown through the summer in net houses under moderate heat stress. Under fogging conditions pollen grain viability and fruit set were significantly improved. This improvement influenced the yield picked during September (104–136 DAP. However, total seasonal yield was not affected by the fogging treatment.

Increasing Crop Yields in Water Stressed Countries by Combining Operations of Freshwater Reservoir and Wastewater Reclamation Plant

Science.gov (United States)

Bhushan, R.; Ng, T. L.

2015-12-01

Freshwater resources around the world are increasing in scarcity due to population growth, industrialization and climate change. This is a serious concern for water stressed countries, including those in Asia and North Africa where future food production is expected to be negatively affected by this. To address this problem, we investigate the potential of combining freshwater reservoir and wastewater reclamation operations. Reservoir water is the cheaper source of irrigation, but is often limited and climate sensitive. Treated wastewater is a more reliable alternative for irrigation, but often requires extensive further treatment which can be expensive. We propose combining the operations of a reservoir and a wastewater reclamation plant (WWRP) to augment the supply from the reservoir with reclaimed water for increasing crop yields in water stressed regions. The joint system of reservoir and WWRP is modeled as a multi-objective optimization problem with the double objective of maximizing the crop yield and minimizing total cost, subject to constraints on reservoir storage, spill and release, and capacity of the WWRP. We use the crop growth model Aquacrop, supported by The Food and Agriculture Organization of the United Nations (FAO), to model crop growth in response to water use. Aquacrop considers the effects of water deficit on crop growth stages, and from there estimates crop yield. We generate results comparing total crop yield under irrigation with water from just the reservoir (which is limited and often interrupted), and yield with water from the joint system (which has the potential of higher supply and greater reliability). We will present results for locations in India and Africa to evaluate the potential of the joint operations for improving food security in those areas for different budgets.

Solid matrix priming with chitosan enhances seed germination and seedling invigoration in mung bean under salinity stress

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Sujoy SEN

2016-09-01

Full Text Available The objective of present study was to evaluate the response of the mung bean seeds of ‘Sonali B1’ variety primed with chitosan in four different concentrations (0, 0.1%, 0.2% and 0.5% under salinity stress of five different concentrations (i.e., 0, 4, 6, 8 and 12 dS*mm-1 and halotolerance pattern by applying Celite as matrix at three different moisture levels (5%, 10% and 20%. Improved germination percentage, germination index, mean germination time, coefficient of velocity of germination along with root and shoot length was observed comparing with control. Germination stress tolerance index (GSI, plant height stress tolerance index (PHSI and root length stress tolerance index (RLSI were used to evaluate the tolerance of the mung bean seeds against salinity stress induced by chitosan. Results of GSI, PHSI, RLSI showing noteworthy inhibitory effect of salinity stress in control set was significantly less pronounced in chitosan treated seedlings. Chitosan can remarkably alleviate the detrimental effect of salinity up to the level of 6 dS*m-1, beyond which no improvement was noticed. In conclusion present investigation revealed that chitosan is an ideal elicitor for enhancing the speed of germination and seedling invigoration that synchronize with emergence of radicle and salinity stress tolerance.

Nanoindentation measurements of the mechanical properties of zirconium matrix and hydrides in unirradiated pre-hydrided nuclear fuel cladding

International Nuclear Information System (INIS)

Rico, A.; Martin-Rengel, M.A.; Ruiz-Hervias, J.; Rodriguez, J.; Gomez-Sanchez, F.J.

2014-01-01

It is well known that the mechanical properties of the nuclear fuel cladding may be affected by the presence of hydrides. The average mechanical properties of hydrided cladding have been extensively investigated from a macroscopic point of view. In addition, the mechanical and fracture properties of bulk hydride samples fabricated from zirconium plates have also been reported. In this paper, Young’s modulus, hardness and yield stress are measured for each phase, namely zirconium hydrides and matrix, of pre-hydrided nuclear fuel cladding. To this end, nanoindentation tests were performed on ZIRLO samples in as-received state, on a hydride blister and in samples with 150 and 1200 ppm of hydrogen homogeneously distributed along the hoop direction of the cladding. The results show that the measured mechanical properties of the zirconium hydrides and ZIRLO matrix (Young’s modulus, hardness and yield stress) are rather similar. From the experimental data, the hydride volume fraction in the cladding samples with 150 and 1200 ppm was estimated and the average mechanical properties were calculated by means of the rule of mixtures. These values were compared with those obtained from ring compression tests. Good agreement between the results obtained by both methods was found

Effects of physical agitation on yield of greenhouse-grown soybean

Science.gov (United States)

Jones, R. S.; Mitchell, C. A.

1992-01-01

Agronomic and horticultural crop species experience reductions in growth and harvestable yield after exposure to physical agitation (also known as mechanical stress), as by wind or rain. A greenhouse study was conducted to test the influence of mechanical stress on soybean yield and to determine if exposure to mechanical stress during discrete growth periods has differential effects on seed yield. A modified rotatory shaker was used to apply seismic (i.e., shaking) stress. Brief, periodic episodes of seismic stress reduced stem length, total seed dry weight, and seed number of soybean [Glycine max (L.) Merr.]. Lodging resistance was greater for plants stressed during vegetative growth or throughout vegetative and reproductive growth than during reproductive growth only. Seed dry weight yield was reduced regardless of the timing or duration of stress application, but was lowest when applied during reproductive development. Seismic stress applied during reproductive growth stages R1 to R2 (Days 3 to 4) was as detrimental to seed dry weight accumulation as was stress applied during growth stages R1 to R6 (Days 39 to 42). Seed dry weight per plant was highly correlated with seed number per plant, and seed number was correlated with the seed number of two- and three-seeded pods. Dry weight per 100 seeds was unaffected by seismic-stress treatment. Growth and yield reductions resulting from treatments applied only during the vegetative stage imply that long-term mechanical effects were induced, from which the plants did not fully recover. It is unclear which yield-controlling physiological processes were affected by mechanical stress. Both transient and long-term effects on yield-controlling processes remain to be elucidated.

Effect of Organic and Chemical Fertilizers on Yield and Essential Oil of Two Ecotypes of Savory (Satureja hortensis L. under Normal and Drought Stress Conditions

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O Akrami nejad

2016-02-01

height, grain and biological yield, chlorophyll index, ionic leakage, relative water content, number of branches, essence percentage and essence amount were evaluated. Data were analyzed with SAS and MSTAT-C software and mean comparison was done using Duncan test at %5 level. Results and Discussion The results showed that drought stress reduced plant height, number of branches, oil yield, relative water content, SPAD index and increased ion leakage. Meanwhile, it had no significant effect on the percent of oil. Fertilizers increased plant height, number of branches, yield, chlorophyll index and oil yield, while it decreased ion leakage in contrast with control. Baher et al (2002 have reported that drought stress reduced plant height, grain yield, and branches number of Savory. As nutrients deficit is one of the main factors in control of plant height and yield, plant that were treated with control had the lowest growth. Organic fertilizers provide appropriate plant growth via gradual release of nutrients during growth season and saving water. Two ecotypes had significant differences for yield, number of branches and ionic leakage. Kerman ecotype showed better yield performance. The results showed that water stress reduced yield, number of branches and plant height of savory. Meanwhile fertilizers (especially cow and hen manure could reduce the effects of drought. Conclusions Generally, organic fertilizers, especially cow manure, produced higher yield and showed a better response to drought stress. It might be for higher moisture maintenance in contrast with chemical fertilizers. It seems that, using cow manure could be helpful to overcome the negative effects of drought stress.

Viscoplastic Matrix Materials for Embedded 3D Printing.

Science.gov (United States)

Grosskopf, Abigail K; Truby, Ryan L; Kim, Hyoungsoo; Perazzo, Antonio; Lewis, Jennifer A; Stone, Howard A

2018-03-16

Embedded three-dimensional (EMB3D) printing is an emerging technique that enables free-form fabrication of complex architectures. In this approach, a nozzle is translated omnidirectionally within a soft matrix that surrounds and supports the patterned material. To optimize print fidelity, we have investigated the effects of matrix viscoplasticity on the EMB3D printing process. Specifically, we determine how matrix composition, print path and speed, and nozzle diameter affect the yielded region within the matrix. By characterizing the velocity and strain fields and analyzing the dimensions of the yielded regions, we determine that scaling relationships based on the Oldroyd number, Od, exist between these dimensions and the rheological properties of the matrix materials and printing parameters. Finally, we use EMB3D printing to create complex architectures within an elastomeric silicone matrix. Our methods and findings will both facilitate future characterization of viscoplastic matrices and motivate the development of new materials for EMB3D printing.

By activating matrix metalloproteinase-7, shear stress promotes chondrosarcoma cell motility, invasion and lung colonization.

Science.gov (United States)

Guan, Pei-Pei; Yu, Xin; Guo, Jian-Jun; Wang, Yue; Wang, Tao; Li, Jia-Yi; Konstantopoulos, Konstantinos; Wang, Zhan-You; Wang, Pu

2015-04-20

Interstitial fluid flow and associated shear stress are relevant mechanical signals in cartilage and bone (patho)physiology. However, their effects on chondrosarcoma cell motility, invasion and metastasis have yet to be delineated. Using human SW1353, HS.819.T and CH2879 chondrosarcoma cell lines as model systems, we found that fluid shear stress induces the accumulation of cyclic AMP (cAMP) and interleukin-1β (IL-1β), which in turn markedly enhance chondrosarcoma cell motility and invasion via the induction of matrix metalloproteinase-7 (MMP-7). Specifically, shear-induced cAMP and IL-1β activate PI3-K, ERK1/2 and p38 signaling pathways, which lead to the synthesis of MMP-7 via transactivating NF-κB and c-Jun in human chondrosarcoma cells. Importantly, MMP-7 upregulation in response to shear stress exposure has the ability to promote lung colonization of chondrosarcomas in vivo. These findings offer a better understanding of the mechanisms underlying MMP-7 activation in shear-stimulated chondrosarcoma cells, and provide insights on designing new therapeutic strategies to interfere with chondrosarcoma invasion and metastasis.

Fibrocartilage tissue engineering: the role of the stress environment on cell morphology and matrix expression.

Science.gov (United States)

Thomopoulos, Stavros; Das, Rosalina; Birman, Victor; Smith, Lester; Ku, Katherine; Elson, Elliott L; Pryse, Kenneth M; Marquez, Juan Pablo; Genin, Guy M

2011-04-01

Although much is known about the effects of uniaxial mechanical loading on fibrocartilage development, the stress fields to which fibrocartilaginous regions are subjected to during development are mutiaxial. That fibrocartilage develops at tendon-to-bone attachments and in compressive regions of tendons is well established. However, the three-dimensional (3D) nature of the stresses needed for the development of fibrocartilage is not known. Here, we developed and applied an in vitro system to determine whether fibrocartilage can develop under a state of periodic hydrostatic tension in which only a single principal component of stress is compressive. This question is vital to efforts to mechanically guide morphogenesis and matrix expression in engineered tissue replacements. Mesenchymal stromal cells in a 3D culture were exposed to compressive and tensile stresses as a result of an external tensile hydrostatic stress field. The stress field was characterized through mechanical modeling. Tensile cyclic stresses promoted spindle-shaped cells, upregulation of scleraxis and type one collagen, and cell alignment with the direction of tension. Cells experiencing a single compressive stress component exhibited rounded cell morphology and random cell orientation. No difference in mRNA expression of the genes Sox9 and aggrecan was observed when comparing tensile and compressive regions unless the medium was supplemented with the chondrogenic factor transforming growth factor beta3. In that case, Sox9 was upregulated under static loading conditions and aggrecan was upregulated under cyclic loading conditions. In conclusion, the fibrous component of fibrocartilage could be generated using only mechanical cues, but generation of the cartilaginous component of fibrocartilage required biologic factors in addition to mechanical cues. These studies support the hypothesis that the 3D stress environment influences cell activity and gene expression in fibrocartilage development.

Particles geometry influence in the thermal stress level in an SiC reinforced aluminum matrix composite considering the material non-linear behavior

International Nuclear Information System (INIS)

Miranda, Carlos A. de J.; Libardi, Rosani M.P.; Boari, Zoroastro de M.

2009-01-01

An analytical methodology was developed to predict the thermal stress level that occurs in a metallic matrix composite reinforced with SiC particles, when the temperature decreases from 600 deg C to 20 deg C during the fabrication process. This analytical development is based on the Eshelby method, dislocation mechanisms, and the Maxwell-Boltzmann distribution model. The material was assumed to have a linear elastic behavior. The analytical results from this formulation were verified against numerical linear analyses that were performed over a set of random non-uniform distribution of particles that covers a wide range of volumetric ratios. To stick with the analytical hypothesis, particles with round geometry were used. Each stress distribution, represented by the isostress curves at ΔT=-580 deg C, was analyzed with an image analyzer. A statistical procedure was applied to obtain the most probable thermal stress level. Analytical and numerical results compared very well. Plastic deformation as well as particle geometry can alter significantly the stress field in the material. To account for these effects, in this work, several numerical analyses were performed considering the non-linear behavior for the aluminum matrix and distinct particle geometries. Two distinct sets of data with were used. To allow a direct comparison, the first set has the same models (particle form, size and distribution) as used previously. The second set analyze quadrilateral particles and present very tight range of volumetric ratio, closer to what is found in actual SiC composites. A simple and fast algorithm was developed to analyze the new results. The comparison of these results with the previous ones shows, as expected, the strong influence of the elastic-plastic behavior of the aluminum matrix on the composite thermal stress distribution due to its manufacturing process and shows, also, a small influence of the particles geometry and volumetric ratio. (author)

Effect of Salinity Stress and Foliar Application of Methyl Jasmonate on Photosynthetic Rate, Stomatal Conductance, Water Use Efficiency and Yield of German Chamomile

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fatemeh Salimi

2014-09-01

Full Text Available Jasmonate is new plant growth regulator that plays an essential role at increasing plants resistance to the environmental stresses like salinity stress. Hence, in this research the effect of foliar application of methyl jasmonate on some physiological indices and yield of German chamomile under salinity conditions was studied. A factorial experiment was laid out based on randomized complete block design (RCBD with three replications in the greenhouse condition. Foliar application of methyl jasmonate was five levels (MJ1; 0, MJ2; 75, MJ3; 150, MJ4; 225 and MJ5; 300 μM and salinity stress was four levels (S1; 2, S2; 6, S3; 10, S4; 14 dS m-1. The effect of methyl jasmonate, salinity condition treatments and their interaction was significant for traits of photosynthesis rate, stomata conductance, transpiration rate, carboxylation efficiency, intercellular CO2 concentration and yield of flower. The highest values of photosynthetic rate, stomata conductance, transpiration rate, carboxylation efficiency and yield of flower (3.76 g pot-1 and the lowest intercellular CO2 concentration were achieved at MJ×S treatment. Maximum value of photosynthetic water use efficiency was revealed at MJ5×S2 treatment. With decreasing stomata conductance, photosynthetic water use efficiency and intercellular CO2 concentration were increased. In general, it seems that application of methyl jasmonate by lower dose (MJ2 under salinity conditions especially mild salinity stress (S2 can improve physiological indices and yield of chamomile.

TECHNICAL NOTE: The strengthening effect of guar gum on the yield stress of magnetorheological fluid

Science.gov (United States)

Wu, Wei Ping; Zhao, Bin Yuan; Wu, Qing; Chen, LeSheng; Hu, Ke Ao

2006-08-01

In this paper we present a novel approach for producing obvious strengthening of the magnetorheological (MR) effect of MR fluids. Carbonyl iron powders coated with guar gum were used as magnetic particles in the MR fluid. Experimental results showed that inducing a guar gum coating not only greatly improved the sedimentation stability but also strengthened the yield stress of the MR fluid. An intermolecular force based model was proposed for explaining the strengthening effect.

Effect of yield stress matching on ductile fracture behavior of girth welds for X line pipe

Energy Technology Data Exchange (ETDEWEB)

Motohashi, Hiroyuki; Hagiwara, Naoto [Tokyo Gas Co., Ltd. (Japan)

2005-07-01

This paper describes the effects of yield stress matching on the ductile fracture behavior of girth welded joints for X linepipes. Three welded joints were made on an X line pipe using several consumables to obtain about a 20% overmatched, even matched and about a 20% under matched weld metal. For these three welded joints, curved wide plate tensile tests were then conducted with a surface notch in the weld metal. To determine the ductile crack initiation from the surface notch, these tests employed a direct-current electric potential (d-c E P) method. Crack opening displacement, gauge length strain and local strain adjacent to the surface notch were also measured. The ductile crack initiation was successfully detected using the d-c E P method. The yield stress matching significantly affected the ductile crack initiation and fracture behavior, that is, the overmatched welded joint had a higher resistance to ductile fracture than that of the under matched welded joint. The allowable strength matching level was determined from the relationship between the strength matching and the gauge length strain at the ductile crack initiation detected using the d-c E P method. (author)

The Effect of Water Stress and Polymer on Water Use Efficiency, Yield and several Morphological Traits of Sunflower under Greenhouse Condition

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Hossein NAZARLI

2010-12-01

Full Text Available In many part of Iran, the reproductive growth stages of sunflower (Helianthus annuus L. are exposed to water deficit stress. Therefore, the investigation of irrigation management in the farm conditions is a necessary element for increasing irrigation efficiency and decreasing water losses. The objective of present study was to investigate the effect of different rates of super absorbent polymer and levels of water stress on water use efficiency (WUE, yield and some morphological traits of sunflower (cultivar Master. Factorial experiment was carried out in completely randomized design with 3 replications. Factors were water stress in three levels (irrigation in 0.75; 0.50 and 0.25% of field capacity and super absorbent polymer in five levels (0; 0.75; 0.150; 2.25; 3 g/kg of soil. Super absorbent polymer was added in eight leaves stage of sunflower to pots in deepness of roots development. Water stress treatment was also applied in this growth stage of sunflower. For stress application, pots were weighted every day and irrigated when soil water received to 0.75; 0.50 and 0.25 of field capacity, respectively. The results of ANOVA indicated that the effect of different rates of super absorbent polymer and different rates of consumed water in all traits were significant. ANOVA also revealed that the interactive effects of two mentioned factors were significant except for seed yield trait. Polynomial model based on the ANOVA results was fitted for each trait. The results indicated that water stress significantly convert in decreasing the number of leaves per plant, chlorophyll content, 100 weight of seeds, seed yield and WUE in sunflower, whereas the application of super absorbent polymer moderated the negative effect of deficit irrigation, especially in high rates of polymer (2.25 and 3 g/kg of soil. The above mentioned rates of polymer have the best effect to all characteristics of sunflower in all levels of water stress treatment. The findings

Extracellular Matrix Modulates Morphology, Growth, Oxidative Stress Response and Functionality of Human Skin Fibroblasts during Aging In Vitro

DEFF Research Database (Denmark)

Jørgensen, Peter; Rattan, Suresh

2014-01-01

recent observations indicate that replicative lifespan, senescence and functionality of cells in vitro can be significantly affected by the quality of the extra cellular matrix (ECM). Following up on those reports, here we show that using the ECM prepared from early passage young cells, partial...... rejuvenation of serially passaged human facial skin fibroblasts was possible in pre-senescent middle-aged cells, but not in fully senescent late passage cells. ECM from young cells improved the appearance, viability, stress tolerance and wound healing ability of skin fibroblasts. Furthermore, young ECM...... modulated the oxidative stress response transcription factor Nrf-2 and its downstream effector haem-oxygenase (HO-1), possibly through the amelioration of the environmental stress induced by the plastic surface of the culturing flasks. Therefore, it is important to consider the role of ECM in modulating...

The Effect of Phosphorus and Zinc Fertilizers on Nutrient Content and Essential Oil Yield of German Chamomile under Drought Stress (Matricaria recutita L.

Directory of Open Access Journals (Sweden)

M. Ghaedi Jeshni

2016-07-01

Full Text Available Introduction: The German chamomile (Matricaria recutita L. is mainly cultivated for essential oil. Nowadays, it is a highly favored and much-used medicinal plant in reqular and traditional medicine. Water deficit is one of the most important limiting factors on crops production in arid and semi-arid regions (Sharafi et al. 2002. Drought stress limits the growth of plants by reducing water content of tissues and causes some metabolic and physiological changes. On the other hand, the availability of nutrients in the soil is affected by drought stress. Thus, nutritional management of plants under drought stress conditions is one of the most important factors in crop production. A better understanding of the role of nutrients in plant resistance to drought is associated with improvement of fertilizer management in arid and semi-arid areas. Our objectives were to investigate the effects of phosphorus and zinc fertilizers on nutrient content and essential oil yield of German chamomile under drought stress. Material and Methods: The experiment was conducted in split plot factorial based on randomized complete block design with three replications at Research farm of University of Zabol in 2013. Drought stress consisted of three levels 75% (control, 50% (mild stress and 25% of field capacity (severe stress as main plots, and factorial combinations of three triple superphosphate fertilizer (CaH4P2O8 levels (0, 150, and 300 kg ha-1 and two zinc sulphate fertilizer (ZnSO4H2O levels (0 and 30 kg ha-1 as sub plots (the fertilizers were applied before planting time. The seeds were sown at 20 cm apart in rows 40 cm wide, on first half of March 2013. Drought stress levels were determined by the Time Domain Reflectometry (TDR. The success of chamomile cultivation as a commercial venture lies in how efficiently and effectively one can collect the flowers at the right stage during the peak flowering season extending over a period of 3–6 weeks. So, flowers were

Increasing influence of heat stress on French maize yields from the 1960s to the 2030s

Science.gov (United States)

Hawkins, Ed; Fricker, Thomas E; Challinor, Andrew J; Ferro, Christopher A T; Kit Ho, Chun; Osborne, Tom M

2013-01-01

Improved crop yield forecasts could enable more effective adaptation to climate variability and change. Here, we explore how to combine historical observations of crop yields and weather with climate model simulations to produce crop yield projections for decision relevant timescales. Firstly, the effects on historical crop yields of improved technology, precipitation and daily maximum temperatures are modelled empirically, accounting for a nonlinear technology trend and interactions between temperature and precipitation, and applied specifically for a case study of maize in France. The relative importance of precipitation variability for maize yields in France has decreased significantly since the 1960s, likely due to increased irrigation. In addition, heat stress is found to be as important for yield as precipitation since around 2000. A significant reduction in maize yield is found for each day with a maximum temperature above 32 °C, in broad agreement with previous estimates. The recent increase in such hot days has likely contributed to the observed yield stagnation. Furthermore, a general method for producing near-term crop yield projections, based on climate model simulations, is developed and utilized. We use projections of future daily maximum temperatures to assess the likely change in yields due to variations in climate. Importantly, we calibrate the climate model projections using observed data to ensure both reliable temperature mean and daily variability characteristics, and demonstrate that these methods work using retrospective predictions. We conclude that, to offset the projected increased daily maximum temperatures over France, improved technology will need to increase base level yields by 12% to be confident about maintaining current levels of yield for the period 2016–2035; the current rate of yield technology increase is not sufficient to meet this target. PMID:23504849

The influence of predeformations and annealings on yield stress and modulus of elongation essentially yttrium doped copper

International Nuclear Information System (INIS)

Neklyudov, I.M.; Sytin, V.I.; Voevodin, V.N.

2003-01-01

The researches results of influence of predeformations and annealings on elastic and plastic characteristics of vacuum melting and yttrium doped copper are given. The interrelation between elastic and plastic characteristics has been shown. It is shown that the yield stress and modulus of elongation essentially depend on predeformations and annealings and they are the structurally sensitive characteristics

Al-based metal matrix composites reinforced with Al–Cu–Fe quasicrystalline particles: Strengthening by interfacial reaction

International Nuclear Information System (INIS)

Ali, F.; Scudino, S.; Anwar, M.S.; Shahid, R.N.; Srivastava, V.C.; Uhlenwinkel, V.; Stoica, M.; Vaughan, G.; Eckert, J.

2014-01-01

Highlights: • Strength of composites is enhanced as the QC-to-ω phase transformation advances. • Yield strength increases from 195 to 400 MPa with QC-to-ω interfacial reaction. • Reducing matrix ligament size explains most of the strengthening. • Improved interfacial bonding and nano ω phase explains divergence from model. - Abstract: The interfacial reaction between the Al matrix and the Al 62.5 Cu 25 Fe 12.5 quasicrystalline (QC) reinforcing particles to form the Al 7 Cu 2 Fe ω-phase has been used to further enhance the strength of the Al/QC composites. The QC-to-ω phase transformation during heating was studied by in situ X-ray diffraction using a high-energy monochromatic synchrotron beam, which permits to follow the structural evolution and to correlate it with the mechanical properties of the composites. The mechanical behavior of these transformation-strengthened composites is remarkably improved as the QC-to-ω phase transformation progresses: the yield strength increases from 195 MPa for the starting material reinforced exclusively with QC particles to 400 MPa for the material where the QC-to-ω reaction is complete. The reduction of the matrix ligament size resulting from the increased volume fraction of the reinforcing phase during the transformation can account for most of the observed improvement in strength, whereas the additional strengthening can be ascribed to the possible presence of nanosized ω-phase particles as well as to the improved interfacial bonding between matrix and particles caused by the compressive stresses arising in the matrix

Al-based metal matrix composites reinforced with Al–Cu–Fe quasicrystalline particles: Strengthening by interfacial reaction

Energy Technology Data Exchange (ETDEWEB)

Ali, F. [IFW Dresden, Institut für Komplexe Materialien, Postfach 27 01 16, D-01171 Dresden (Germany); Materials Processing Group, DMME, Pakistan Institute of Engineering and Applied Sciences, P.O. Nilore, Islamabad (Pakistan); Scudino, S., E-mail: s.scudino@ifw-dresden.de [IFW Dresden, Institut für Komplexe Materialien, Postfach 27 01 16, D-01171 Dresden (Germany); Anwar, M.S.; Shahid, R.N. [Materials Processing Group, DMME, Pakistan Institute of Engineering and Applied Sciences, P.O. Nilore, Islamabad (Pakistan); Srivastava, V.C. [Metal Extraction and Forming Division, National Metallurgical Laboratory, Jamshedpur 831007 (India); Uhlenwinkel, V. [Institut für Werkstofftechnik, Universität Bremen, D-28359 Bremen (Germany); Stoica, M. [IFW Dresden, Institut für Komplexe Materialien, Postfach 27 01 16, D-01171 Dresden (Germany); Vaughan, G. [European Synchrotron Radiation Facilities ESRF, BP 220, 38043 Grenoble (France); Eckert, J. [IFW Dresden, Institut für Komplexe Materialien, Postfach 27 01 16, D-01171 Dresden (Germany); TU Dresden, Institut für Werkstoffwissenschaft, D-01062 Dresden (Germany)

2014-09-01

Highlights: • Strength of composites is enhanced as the QC-to-ω phase transformation advances. • Yield strength increases from 195 to 400 MPa with QC-to-ω interfacial reaction. • Reducing matrix ligament size explains most of the strengthening. • Improved interfacial bonding and nano ω phase explains divergence from model. - Abstract: The interfacial reaction between the Al matrix and the Al{sub 62.5}Cu{sub 25}Fe{sub 12.5} quasicrystalline (QC) reinforcing particles to form the Al{sub 7}Cu{sub 2}Fe ω-phase has been used to further enhance the strength of the Al/QC composites. The QC-to-ω phase transformation during heating was studied by in situ X-ray diffraction using a high-energy monochromatic synchrotron beam, which permits to follow the structural evolution and to correlate it with the mechanical properties of the composites. The mechanical behavior of these transformation-strengthened composites is remarkably improved as the QC-to-ω phase transformation progresses: the yield strength increases from 195 MPa for the starting material reinforced exclusively with QC particles to 400 MPa for the material where the QC-to-ω reaction is complete. The reduction of the matrix ligament size resulting from the increased volume fraction of the reinforcing phase during the transformation can account for most of the observed improvement in strength, whereas the additional strengthening can be ascribed to the possible presence of nanosized ω-phase particles as well as to the improved interfacial bonding between matrix and particles caused by the compressive stresses arising in the matrix.

Effect of Black and Clear Polyethylene Mulch on Yield and Yield Components of Melon in Salinity Stress Condition

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Peyman Jafari

2017-02-01

Full Text Available Introduction: The term of Mulch, is the German word (Molsh means the soft, however, not soft, and made of plant debris or synthetic substances. Many positive effects attributed to the use of plastic mulch such as adjusting the temperature in the root environment, conserve moisture, reduce weeds, increase root growth, reduce soil erosion, and soil condensation and improve germination and early plant establishment. The use of mulch can reduce the harmful effects of salt in plants. Materials and Methods: To evaluate the effects of black and clear polyethylene mulch on yield and yield components of melon in salinity stress condition, a study was conducted in 2011 using split plot randomized based on complete block design with three replications in Varamin region. Three salinity levels of irrigation water of 2, 5 and 8 dS-1 as main factor and three plastic mulch treatments (no mulch, clear mulch and black mulch were considered as sub-plots. At harvest and after determining the yield and number of fruits harvested from each plot, the average number of fruits per plant was measured and fruit pulp thickness was recorded with calipers. Results Discussion The results showed interactive effects of salinity and mulch on fruit yield, number of fruits per plant, average fruit weight, fruit length, days to first harvest and fruit soluble solids percentage were statistically significant. In salinity levels of 2, 5 and 8 dS m-1, fruit yield increased, respectively, 19.6, 59, and 45.4 %in clear mulch compared to control. Similarly these increases for the black mulch were equal to 15.7, 41.9, and 21.4 percent, respectively. With 2, 5 and 8 dS m-1 salinity levels, fruit yield in the first harvest were 7.44, 7.72, and 6.98 t ha -1, respectively, which was significantly higher than without mulch and black mulch. Mulch can reduce evaporation and increase the level of moisture in the soil and thereby dilute the salt and reduce the harmful effects of salinity. Some

Investigation of Tolerance, Yield and Yield Components of Wheat Cultivars to Salinity of Irrigation Water at Sensitive Stages of Growth

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B Saadatian

2013-04-01

Full Text Available This research in order to study of tolerance ability of wheat cultivates yield and yield components to salinity of irrigation water at sensitive stages of growth, was carried out as a factorial based on a randomized complete block design with 3 replications at greenhouse of Agricultural Faculty of Bu-Ali Sina University, in 2009. Treatments were included wheat cultivars of Alvand, Tous, Sayson and Navid and salinity of irrigation water induced by sodium chloride at five levels of 0, 4, 8, 12 and 16 dS m-1. The results showed that percentage and rate of emergence, plant height, 1000-grain weight, number of seed per spike, number of spike per pot, biological and grain yield reduced by increasing salinity level. At all stress levels Navid cv. had highest emergence percentage. In non-stress and 4 dS m-1, Alvand cv. and at higher levels of stress, Tous cv. had high height in reproductive phase. At control and 4 dS m-1, Sayson cv. and at 8, 12 and 16 dS m-1, Tous cv. in majority of yield and yield components traits had significant superior than other cultivars. Tolerance index of Sayson cv. at 4 and 8 dS m-1 was more than other cultivars but at 12 and 16 dS m-1, maximum value of this index was belonged to Tous cv. At all salinity levels, Alvand cv. had least tolerance index to stress. Number of spike per pot had maximum direct effect on grain yield of wheat cultivars in stress condition. Also indirect effect of biological yield via number of spike per pot than other its indirect effects, had maximum share in wheat seed yield.

The Effect of Drought Stress on Grain Yield and Oil Rate and Protein Percentage of Four Varieties Castor in Climatic Conditions of Damghan

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Gh. Laei

2012-08-01

Full Text Available In this study theeffect ofdrought stress was investigated on grain yield and oil rate and protein percentage of four varieties of castor in the climatic conditions of Damghan. The experiment was done in the research farm of Damghan Islamic Azad University(Iranin 2011 assplit plots in a randomized complete block design with three replications. The main plots of drought stress were 5, 10 and15 days and another factor included four varities of castor ( one-flower, two- flower, local and red-flower which were performed in stable density of fivebushes per cultured square meter. Therefore, after gremination, the amount of irrigation water was recorded using volumetric meters. The traits evaluated included oil rate,seed protein percentage, andgrainyield. The results show that two-flower variety with 1241 kg per hectare on 5-day drought stress has the most grain yield. Most oil rate was observed in two-flower variety on 5 day drought stress with 496.4 kg/ha.

Sequential path analysis for determining interrelationships between yield and related traits in tobacco (Nicotiana tabacum L. under normal and abiotic stress conditions

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Bayat Mahdi

2014-01-01

Full Text Available In the present work the relationships between yield and its related traits were investigated in tobacco genotypes under normal and abiotic stress conditions (Orobanche aegyptiaca weed at Urmia Tobacco Research Centre, Iran, during 2006-2009 cropping seasons. The experimental design was a randomized complete block design (RCBD with three replications in each condition every year. Analysis of variance revealed extent genetic variability among the genotypes for most of the traits studied. In comparison with normal condition, the mean value of studied traits decreased in stress condition. LAI and FD showed the maximum and minimum diminution in the mean values under stress condition compared to normal one so known as more sensitive and more tolerant traits, respectively. Based on CV values, the traits FD and DLYP showed the minimum and maximum variation among traits in both normal and stress conditions. Correlation analysis revealed significant and positive correlations between DLYP with all studied traits in both normal and stress conditions. Path analysis detected the traits including biomass, APDW and DWR as the first-order variables at normal condition and biomass, APDW, DWR and harvest index as the first-order variables under abiotic stress condition. Based on results, the traits such as biomass, APDW, DWR detected as more important factors in both conditions can be used in tobacco breeding programs for increasing yield. Abbreviation: aerial part fresh weight without leaves weight (APFW, aerial part dry weight without leaves weight (APDW, biomass (BIO, coefficient of variation (CV, dry weight of root (DWR, flowering date (FD, fresh weight of leaf (FWL, fresh weight of root (FWR, harvest index (HI, leaf area index (LAI, dry leaf yield per plant (DLYP, number of leaf (NL, plant height (PH, randomized complete block design (RCBD, standard deviation (Std.

Photosynthesis and yield reductions from wheat stem sawfly (Hymenoptera: Cephidae): interactions with wheat solidness, water stress, and phosphorus deficiency.

Science.gov (United States)

Delaney, Kevin J; Weaver, David K; Peterson, Robert K D

2010-04-01

The impact of herbivory on plants is variable and influenced by several factors. The current study examined causes of variation in the impact of larval stem mining by the wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), on spring wheat, Triticum aestivum L. We performed greenhouse experiments over 2 yr to (1) study whether biotic (hollow versus solid stemmed host wheat) and abiotic (water, phosphorus stress) factors interact with C. cinctus stem mining to influence degree of mined stem physiological (photosynthesis) and yield (grain weight) reductions; and (2) determine whether whole plant yield compensatory responses occur to offset stem-mining reductions. Flag leaf photosynthetic reduction was not detected 16-20 d after infestation, but were detected at 40-42 d and doubled from water or phosphorus stresses. Main stem grain weight decreased from 10 to 25% from stem mining, largely due to reductions in grain size, with greater reductions under low phosphorus and/or water levels. Phosphorus-deficient plants without water stress were most susceptible to C. cinctus, more than doubling the grain weight reduction due to larval feeding relative to other water and phosphorus treatments. Two solid stemmed varieties with stem mining had less grain weight loss than a hollow stemmed variety, so greater internal mechanical resistance may reduce larval stem mining and plant yield reductions. Our results emphasize the importance of sufficient water and macronutrients for plants grown in regions impacted by C. cinctus. Also, solid stemmed varieties not only reduce wheat lodging from C. cinctus, they may reduce harvested grain losses from infested stems.

Load transfer in short fibre reinforced metal matrix composites

International Nuclear Information System (INIS)

Garces, Gerardo; Bruno, Giovanni; Wanner, Alexander

2007-01-01

The internal load transfer and the deformation behaviour of aluminium-matrix composites reinforced with 2D-random alumina (Saffil) short fibres was studied for different loading modes. The evolution of stress in the metallic matrix was measured by neutron diffraction during in situ uniaxial deformation tests. Tensile and compressive tests were performed with loading axis parallel or perpendicular to the 2D-reinforcement plane. The fibre stresses were computed based on force equilibrium considerations. The results are discussed in light of a model recently established by the co-authors for composites with visco-plastic matrix behaviour and extended to the case of plastic deformation in the present study. Based on that model, the evolution of internal stresses and the macroscopic stress-strain were simulated. Comparison between the experimental and computational results shows a qualitative agreement in all relevant aspects

Investigations on thermal properties, stress and deformation of Al/SiC metal matrix composite based on finite element method

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K. A. Ramesh Kumar

2014-09-01

Full Text Available AlSiC is a metal matrix composite which comprises of aluminium matrix with silicon carbide particles. It is characterized by high thermal conductivity (180-200 W/m K, and its thermal expansion are attuned to match other important materials that finds enormous demand in industrial sectors. Although its application is very common, the physics behind the Al-SiC formation, functionality and behaviors are intricate owing to the temperature gradient of hundreds of degrees, over the volume, occurring on a time scale of a few seconds, involving multiple phases. In this study, various physical, metallurgical and numerical aspects such as equation of continuum for thermal, stress and deformation using finite element (FE matrix formulation, temperature dependent material properties, are analyzed. Modelling and simulation studies of Al/SiC composites are a preliminary attempt to view this research work from computational point of view.

Effectively enhanced load transfer by interfacial reactions in multi-walled carbon nanotube reinforced Al matrix composites

International Nuclear Information System (INIS)

Zhou, Weiwei; Yamaguchi, Tatsuya; Kikuchi, Keiko; Nomura, Naoyuki; Kawasaki, Akira

2017-01-01

The thermal expansion response of multi-walled carbon nanotube (MWCNT) reinforced Al matrix composites was employed to discuss the improvement of the load transfer at the interface between the MWCNTs and the Al matrix. An aluminum carbide (Al_4C_3) nanostructure at the end of the MWCNTs, incorporated in the Al matrix, was produced by appropriate heat-treatment. The stress contrast around the Al_4C_3 observed in the high-resolution transmission electron microscopy (HRTEM) image revealed the evidence of a trace of friction, which would lead to the enhancement of the anchor effect from the Al matrix. This anchor effect of Al_4C_3 may hinder the local interfacial slippage and constrain the deformation of the Al matrix. As a result, the thermal expansion behavior became linear and reversible under cyclic thermal load. It is concluded that the formation of Al_4C_3 could effectively enhance the load transfer in MWCNT/Al composites. The yield strength of MWCNT/Al composites was substantially increased under the appropriate quantity of Al_4C_3 produced at the MWCNT-Al interface by precisely controlled heat-treatment.

Effects of drought stress and bio-fertilizers inoculation on growth, essential oil yield and constituents of thyme (Thymus vulgaris L.

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roghayeh mohammadpour vashvaei

2016-05-01

Full Text Available Thyme (Thymus vulgaris L. is perennial aromatic shrub belonging to the mint family which has anti-spasmodic, antiseptic, carminative, anti-cough, sputum and antioxidant properties. In order to study the effects of drought stress and bio-fertilizer on plant growth, essential oil yield and constituents of thyme plant, an experiment was conducted in a split plot based on randomized complete block design with two replications, at the Research Farm of Zabol University, during growing season of 2012 and 2013. Main plots consisted of irrigation with 30, 50, 70 and 90% field capacity and subplots including plant inoculation with nitroxin, bio-phosphorus and mycorrhiza. Plant traits such as plant height, fresh and dry weight of herb per plant, essential oil percentage, yield and constituents of Thyme were measured. Effects of drought stress, bio-fertilizer and their interactions on all studied traits were significant at the 1% probability level. The highest plant height (35.09 cm, fresh and dry weight of herb per plant (103.52 and 43,27 g.plant-1, respectively and essential oil yield (0.350 ml.plant-1 belong to treatment of irrigation with 90% field capacity and nitroxin bio-fertilizer. The maximum essential oil percentage with 0.413% was obtained by irrigation with 70% field capacity and nitroxin bio-fertilizer. Fresh weight of herb per plant was the most crucial component in determining essential oil yield in Thyme. Plants irrigated with 70% filed capacity gave the highest relative percentage of thymol, which reached 71.32, 50.68 and 47.71% in nitroxin, biophosphorus and mycorrhiza biofertilizer, respectively. This effect was accompanied with decrease in -cymene content. Inoculation with nitroxin bio-fertilizer as compared to other fertilizers could further amend drought stress and improved the plant growth, essential oil percentage and yield and phenolic compound thymol of Thyme. Thus, it appears that in order to achieve sustainable agriculture

Investigations on evaluation method for yield strength of round bar undermatched joint

International Nuclear Information System (INIS)

Matsumoto, Toshimi; Satoh, Hiroshi; Wadayama, Yoshihide

1988-01-01

The objective values of the yield strength and fracture toughness are respectively more than 1200 MPa and 200 MPa √m at 4K on the structural material for the superconducting magnet container in the Fusion Reactor. It should be desirable to assure the above value for the properties of the weld metal used for the containers. The initial yielding behavior of the undermatched joint is investigated in this paper. Results are as follows. (1) On the nominal stress vs. nominal strain relationship at the central section of the undermatched metal of the joint, the stress increases higher than the yield stress of undermatched metal itself then gradually comes up to a constant value, after the whole area of the undermatched metal starts to generate plastic deformation as the stress reaches the yield stress of the metal. (2) The increase in the stress is caused by the restraint effect of the base metal on the plasticity, and the stress becomes larger with the larger strength ratio of the undermatched metal to the basemetal and with the smaller relative thickness of the joint. (3) The strain does not distribute uniformly at the central section of the undermatched metal along the radial direction during the initial yielding process of the joint. (4) In the case that the yield strength of the joints is considered as the proof stress desided for a constant offset strain, the relationship between the dimensionless yield strength of the joint to the yield stress of the base metal and the relative yield strength of the undermatched metal to the base metal cannot be not established consistently. (5) The assumption that the base metal is rigid, causes the excessive evaluation of the joint yield strength of theoretical analysis. (6) As the quantitative evaluation method, the stress vs. strain relationship and then the algebraic expression has been formulated for the initial yielding behavior of the joint. (author)

Rupture of Al matrix in U-Mo/Al dispersion fuel by fission induced creep

Energy Technology Data Exchange (ETDEWEB)

Jeong, Gwan Yoon; Sohn, Dong Seong [UNIST, Daejeon (Korea, Republic of); Kim, Yeon Soo [Argonne National Laboratory, Argonnge (United States); Lee, Kyu Hong [KAERI, Daejeon (Korea, Republic of)

2016-05-15

This phenomenon was found specifically in the dispersion fuel plate with Si addition in the Al matrix to suppress interaction layer (IL) formation between UMo and Al. It is known that the stresses induced by fission induced swelling in U-Mo fuel particles are relieved by creep deformation of the IL, surrounding the fuel particles, that has a much higher creep rate than the Al matrix. Thus, when IL growth is suppressed, the stress is instead exerted on the Al matrix. The observed rupture in the Al matrix is believed to be caused when the stress exceeded the rupture strength of the Al matrix. In this study, the possibility of creep rupture of the Al matrix between the neighboring U-Mo fuel particles was examined using the ABAQUS finite element analysis (FEA) tool. The predicted rupture time for a plate was much shorter than its irradiation life indicating a rupture during the irradiation. The higher stress leads Al matrix to early creep rupture in this plate for which the Al matrix with lower creep strain rate does not effectively relieve the stress caused by the swelling of the U-Mo fuel particles. For the other plate, no rupture was predicted for the given irradiation condition. The effect of creeping of the continuous phase on the state of stress is significant.

Stress-strain effects in alumina-Cu reinforced Nb3Sn wires fabricated by the tube process

International Nuclear Information System (INIS)

Murase, Satoru; Nakayama, Shigeo; Masegi, Tamaki; Koyanagi, Kei; Nomura, Shunji; Shiga, Noriyuki; Kobayashi, Norio; Watanabe, Kazuo.

1997-01-01

In order to fabricate a large-bore, high-field magnet which achieves a low coil weight and volume, a high strength compound superconducting wire is required. For those demands we have developed the reinforced Nb 3 Sn wire using alumina dispersion strengthened copper (alumina-Cu) as a reinforcement material and the tube process of the Nb 3 Sn wire fabrication. The ductility study of the composites which consisted of the reinforcement, Nb tube, Cu, and Cu clad Sn brought a 1 km long alumina-Cu reinforced Nb 3 Sn wire successfully. Using fabricated wires measurements and evaluations of critical current density as parameters of magnetic field, tensile stress, tensile strain, and transverse compressive stress, and those of stress-strain curves at 4.2 K were performed. They showed superior performance such as high 0.3% proof stress (240 MPa at 0.3% strain) and high maximum tolerance stress (320 MPa) which were two times as large as those of conventional Cu matrix Nb 3 Sn wire. The strain sensitivity parameters were obtained for the reinforced Nb 3 Sn wire and the Cu matrix one using the scaling law. Residual stress of the component materials caused by cooling down to 4.2 K from heat-treatment temperature was calculated using equivalent Young's modulus, equivalent yield strength, thermal expansion coefficient and other mechanical parameters. Calculated stress-strain curves at 4.2 K for the reinforced Nb 3 Sn wire and the Cu matrix one based on calculation of residual stress, had good agreement with the experimental values. (author)

The Optimum Plutonium Inert Matrix Fuel Form for Reactor-Based Plutonium Disposition

International Nuclear Information System (INIS)

Tulenko, J.S.; Wang, J.; Acosta, C.

2004-01-01

The University of Florida has underway an ongoing research program to validate the economic, operational and performance benefits of developing an inert matrix fuel (IMF) for the disposition of the U.S. weapons plutonium (Pu) and for the recycle of reprocessed Pu. The current fuel form of choice for Pu disposition for the Department of Energy is as a mixed oxide (MOX) (PuO2/UO2). We will show analyses that demonstrate that a Silicon Carbide (SiC) IMF offers improved performance capabilities as a fuel form for Pu recycle and disposition. The reason that UF is reviewing various materials to serve as an inert matrix fuel is that an IMF fuel form can offer greatly reduced Pu and transuranic isotope (TRU) production and also improved thermal performance characteristics. Our studies showed that the Pu content is reduced by an order of magnitude while centerline fuel temperatures are reduced approximately 380 degrees centigrade compared to MOX. These reduced temperatures result in reduced stored heat and thermal stresses in the pellet. The reduced stored heat reduces the consequences of the loss of coolant accident, while the reduced temperatures and thermal stresses yield greatly improved fuel performance. Silicon Carbide is not new to the nuclear industry, being a basic fuel material in gas cooled reactors

The role of silicon in higher plants under salinity and drought stress

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Devrim Coskun

2016-07-01

Full Text Available Although deemed a non-essential mineral nutrient, silicon (Si is clearly beneficial to plant growth and development, particularly under stress conditions, including salinity and drought. Here, we review recent research on the physiological, biochemical, and molecular mechanisms underlying Si-induced alleviation of osmotic and ionic stresses associated with salinity and drought. We distinguish between changes observed in the apoplast (i.e. suberization, lignification, and silicification of the extracellular matrix; transpirational bypass flow of solutes and water, and those of the symplast (i.e. transmembrane transport of solutes and water; gene expression; oxidative stress; metabolism, and discuss these features in the context of Si biogeochemistry and bioavailability in agricultural soils, evaluating the prospect of using Si fertilization to increase crop yield and stress tolerance under salinity and drought conditions.

Deficit Irrigation Effects on Yield, Yield Components and Seed Production of Three Cultivas of Watermelon (Citrullus lanatus (Thunb Matsum and Nakai

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P. Jafari

2015-09-01

Full Text Available A two-year study (2005 - 2006 was carried out to explore the effect of deficit irrigation treatments according to evaporation from a class A basin, including ET= 1 (T1, ET = 0.75 (T2, and ET = 0.5 (T3, on yield, yield components and seed yield of three varieties of watermelon (Charleston Gray, Sugar Baby and Crimson Suite in the Varamin Agricultural Research Center of Iran. A randomized complete block design with a split plot arrangement with four replications was used. The results showed that fruit yield, yield components and seed yield were not significantly different in T1 and T2 treatments in contrary to T3 treatment. Among the yield components, number of fruits per plant most suffered from the negative impact of severe water stress (T3 (1.20 fruit per plant. Rind thickness, percent soluble solids in fruit and seed yield were not affected by water stress. According to phenotypic traits, and correlation coefficients, a significant positive correlation (1% probability level was observed between the weighted average, and the number of fruit with the fruit yield. Crimson Suite cultivar produced the highest yield (2533 kg ha-1 compared to the cultivars Charleston Gray and Sugar Baby. Sugar Baby and Crimson Suite cultivars, with 311.7 and 298.2 kg ha-1, respectively, produced the highest amount of seed. Crimson Suite cultiavr had the highest percentage of soluble solids in fruit (1.35. Rind thickness in Crimson Suites, Charleston Gray and Sugar Baby cultivars were 1.35, 1.13 and 1.10 cm, respectively. The results of this study showed that under a moderate moisture stress condition (ET = 0.75, fruit and seed yield could be similar to the no-water stress conditions.

Role of aquaporins in determining transpiration and photosynthesis in water-stressed plants: crop water-use efficiency, growth and yield.

Science.gov (United States)

Moshelion, Menachem; Halperin, Ofer; Wallach, Rony; Oren, Ram; Way, Danielle A

2015-09-01

The global shortage of fresh water is one of our most severe agricultural problems, leading to dry and saline lands that reduce plant growth and crop yield. Here we review recent work highlighting the molecular mechanisms allowing some plant species and genotypes to maintain productivity under water stress conditions, and suggest molecular modifications to equip plants for greater production in water-limited environments. Aquaporins (AQPs) are thought to be the main transporters of water, small and uncharged solutes, and CO2 through plant cell membranes, thus linking leaf CO2 uptake from the intercellular airspaces to the chloroplast with water loss pathways. AQPs appear to play a role in regulating dynamic changes of root, stem and leaf hydraulic conductivity, especially in response to environmental changes, opening the door to using AQP expression to regulate plant water-use efficiency. We highlight the role of vascular AQPs in regulating leaf hydraulic conductivity and raise questions regarding their role (as well as tonoplast AQPs) in determining the plant isohydric threshold, growth rate, fruit yield production and harvest index. The tissue- or cell-specific expression of AQPs is discussed as a tool to increase yield relative to control plants under both normal and water-stressed conditions. © 2014 John Wiley & Sons Ltd.

Effects of Heat Treatment on SiC-SiC Ceramic Matrix Composites

Science.gov (United States)

Knauf, Michael W.

Residual stresses resulting from the manufacturing process found within a silicon carbide/silicon carbide (SiC/SiC) ceramic matrix composite were thoroughly investigated through the use of high-energy X-ray diffraction and Raman microspectroscopy. The material system studied was a Rolls-Royce composite produced with Hi-Nicalon fibers woven into a five harness satin weave, coated with boron nitride and silicon carbide interphases, and subsequently infiltrated with silicon carbide particles and a silicon matrix. Constituent stress states were measured before, during, and after heat treatments ranging from 900 °C to 1300 °C for varying times between one and sixty minutes. Stress determination methods developed through these analyses can be utilized in the development of ceramic matrix composites and other materials employing boron-doped silicon. X-ray diffraction experiments were performed at the Argonne National Laboratory Advanced Photon Source to investigate the evolution of constituent stresses through heat treatment, and determine how stress states are affected at high temperature through in situ measurements during heat treatments up to 1250 °C for 30 minutes. Silicon carbide particles in the as-received condition exhibited a nearly isotropic stress state with average tensile stresses of approximately 300 MPa. The silicon matrix exhibited a complimentary average compressive stress of approximately 300 MPa. Strong X-ray diffraction evidence is presented demonstrating solid state boron diffusion and increased boron solubility found in silicon throughout heat treatment. While the constituent stress states did evolve through the heat treatment cycles, including approaching nearly stress-free conditions at temperatures close to the manufacturing temperature, no permanent relaxation of stress was observed. Raman spectroscopy was utilized to investigate stresses found within silicon carbide particles embedded within the matrix and the silicon matrix as an alternate

Dynamics of Strong Interactions and the S-Matrix

Energy Technology Data Exchange (ETDEWEB)

Omnes, R. [Laboratoire de Physique Theorique et Hautes Energies, Universite de Paris, Orsay (France)

1969-08-15

The physical principles underlying the S-matrix theory of strong interactions are reviewed. In particular, the problem of whether these principles are sufficient to completely determine the S-matrix, i.e. to yield a dynamical theory of strong interactions, is discussed. (author)

The effect of pigment matrix, temperature and amount of carrier on the yield and final color properties of spray dried purple corn (Zea mays L.) cob anthocyanin powders.

Science.gov (United States)

Lao, Fei; Giusti, M Monica

2017-07-15

Spray drying is an economic technique to produce anthocyanin-based colorants. High pigments yields with minimum color degradation are desirable to maximize quality and profits. This study evaluated the impacts of purple corncob (PCC) anthocyanin extraction matrices (hot water, 40% ethanol, C18 purified), drying inlet temperature (130, 150, 170°C) and amount of carrier (2%, 5%, 10% maltodextrin) on the yields and quality of PCC anthocyanin powders. Monomeric and polymeric anthocyanins, color properties (CIELch, haze), and pigments composition before and after spray drying were determined. The yield and final color quality of spray dried PCC anthocyanins were affected (p<0.05) by all parameters evaluated. The pigment matrix, inlet temperature, and carrier amount had biggest impacts on product water solubility, pigments degradation and yield, respectively. The optimal combination of hot water extracts spray dried with 5% maltodextrin at 150°C gave the highest pigment yield (∼90%) with good solubility with the least color loss. Copyright © 2017 Elsevier Ltd. All rights reserved.

On the stability of the production of bubbles in yield-stress fluid using flow-focusing and T-junction devices

Science.gov (United States)

Laborie, B.; Rouyer, F.; Angelescu, D. E.; Lorenceau, E.

2016-06-01

We investigate experimentally the stability of bubble production in yield-stress fluids (YSF) and highly viscous silicone oil, using flow-focusing and T-junction devices. When the exit channel is initially pre-filled with the fluid and the gas is pressure-driven, the production is highly unstable, despite a regular frequency of bubble production in the junction. As observed for pressure-driven bubble trains in Newtonian fluids, we report that two mechanisms can explain these observations: (i) drastic reduction of the hydrodynamic pressure drop along the channel during the transient bubble production, which induces a rapid increase of the gas flow rate and (ii) thin film deposition resulting in a cascade of plug break-up and bubble coalescence. While the drastic reduction of the pressure drop is inevitable in such two-phase flows, we show that modifying the surfaces of the channel can help to stabilize the system when the continuous phase is a YSF. To do so, we measure the thickness of the film deposited on the channel wall for rough and smooth channels. Our results are rationalized by introducing the inverse of the Bingham number Bi-1 comparing the viscous stress to the yield stress. For Bi-1 ≥ 1, a fast fluidization process associated to efficient deposition of YSF on the channel wall leads to a rapid destabilization of bubble production. However, for Bi-1 < 1, the deposition driven by capillarity can be hindered by the wall-slip induced by the existence of the yield stress: the thickness of the deposited film is very thin and corresponds to the equivalent roughness of the channels. It is typically 40 μm thick for rough surfaces and below the limit of resolution of our set-up for smooth surfaces. In this regime of Bi-1 and for smooth surfaces, the length of the plugs barely vanishes, thus the start-up flow is less prone to destabilization. These results therefore potentially open routes to steady production of aerated YSF on smooth channels in the regime of

The Effect of Silicon on some Morpho-physiological Characteristics and Grain Yield of Sorghum (Sorghum bicolor L.) under Salt Stress

OpenAIRE

S Hasibi; H Farahbakhsh; Gh Khajoeinejad

2016-01-01

Introduction Nowadays, salinity is one of the limiting factors for crop production in arid and semi-arid regions. On the other hand, sorghum (Sorghum bicolor L.) is a self-pollinated and short-day plant, which partly has been adapted to salinity and water stress conditions; also play an important role in humans, livestock and poultry nourishments. All studies have showed the positive effects of Silicon on growth and yield of plants in both normal and stress conditions. The aim of this exp...

Study of B{sup {+-}} {yields} K{sup {+-}}{pi}{sup 0} and B{sup {+-}} {yields} {pi}{sup {+-}}{pi}{sup 0} decay modes with the BABAR detector and constraints from B {yields} {pi}{pi}, K{pi}, KK modes on the CKM matrix; Etude des desintegrations B{sup {+-}} {yields} K{sup {+-}}{pi}{sup 0} et B{sup {+-}} {yields} {pi}{sup {+-}}{pi}{sup 0} avec le detecteur BABAR et contraintes des modes B {yields} {pi}{pi}, K{pi}, KK sur la matrice CKM

Energy Technology Data Exchange (ETDEWEB)

Malcles, J

2006-04-15

The analysis of B{sup {+-}} {yields} pi{sup {+-}}{pi}{sup 0} and B{sup {+-}} {yields} K{sup {+-}}{pi}{sup 0} modes has been done with a sample of 227 millions of B pairs corresponding to 205 fb{sup -1} of data collected between october 1999 and july 2004 with the BABAR detector. The branching ratios and CP asymmetries obtained are: Br({pi}{pi}{sup 0}) = (5.57 {+-} 0.60 {+-} 0.33)*10{sup -6}; Br(K{pi}{sup 0}) (11.50 {+-} 0.65 {+-} 0.57)*10{sup -6}; A({pi}{pi}{sup 0}) = (-0.007 {+-} 0.104 {+-} 0.023); and A(K{pi}{sup 0}) = (0.066 {+-} 0.055 {+-} 0.010). The constraints on the angle alpha of the unitarity triangle have been derived from the isospin analysis of B {yields} {pi}{pi} modes. The isospin symmetry has also been used to relate B {yields} K{pi} modes in order to constraint the CKM matrix. More significant constraints have been obtained with the SU(3) symmetry for B, Bs {yields} {pi}{pi}/ K{pi}/ KK modes. They are in good agreement with the Standard CKM fit. It has been shown that such an analysis will be competitive with the Standard CKM fit in the future and will allow to determine SU(3) breaking or New Physics parameters from data. (author)

Microstructural analysis and mechanical characterization of aluminum matrix nanocomposites reinforced with uncoated and Cu-coated alumina particles

Energy Technology Data Exchange (ETDEWEB)

Beygi, H., E-mail: hossein.beygi@stu-mail.um.ac.ir; Sajjadi, S.A.; Zebarjad, S.M.

2014-06-01

Aluminum matrix composites used in the aerospace, military and automotive industries are typically fabricated by a stir casting method. However, when nanoparticles are used for reinforcement, fabrication of composite materials by this method leads to the formation of a large number of structural defects. In this study, copper coating of alumina reinforcement particles is investigated as a technique for improving the structure of Al-Al{sub 2}O{sub 3} composites. Microstructural investigations by optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersion spectroscopy (EDS) and transmission electron microscopy (TEM) showed that the alumina particles were coated uniformly with copper shells. Copper coating of the reinforcing particles significantly increased their wettability in the molten aluminum alloy, strengthened the matrix-particle interfaces and improved the distribution of reinforcing particles within the matrix. Due to these microstructural improvements, the hardness, compressive strength, yield stress, tensile strength and elongation of the composites were enhanced by copper coating of the alumina particles.

Microstructural analysis and mechanical characterization of aluminum matrix nanocomposites reinforced with uncoated and Cu-coated alumina particles

International Nuclear Information System (INIS)

Beygi, H.; Sajjadi, S.A.; Zebarjad, S.M.

2014-01-01

Aluminum matrix composites used in the aerospace, military and automotive industries are typically fabricated by a stir casting method. However, when nanoparticles are used for reinforcement, fabrication of composite materials by this method leads to the formation of a large number of structural defects. In this study, copper coating of alumina reinforcement particles is investigated as a technique for improving the structure of Al-Al 2 O 3 composites. Microstructural investigations by optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersion spectroscopy (EDS) and transmission electron microscopy (TEM) showed that the alumina particles were coated uniformly with copper shells. Copper coating of the reinforcing particles significantly increased their wettability in the molten aluminum alloy, strengthened the matrix-particle interfaces and improved the distribution of reinforcing particles within the matrix. Due to these microstructural improvements, the hardness, compressive strength, yield stress, tensile strength and elongation of the composites were enhanced by copper coating of the alumina particles

Matrix-exponential description of radiative transfer

International Nuclear Information System (INIS)

Waterman, P.C.

1981-01-01

By appling the matrix-exponential operator technique to the radiative-transfer equation in discrete form, new analytical solutions are obtained for the transmission and reflection matrices in the limiting cases x >1, where x is the optical depth of the layer. Orthongonality of the eigenvectors of the matrix exponential apparently yields new conditions for determining. Chandrasekhar's characteristic roots. The exact law of reflection for the discrete eigenfunctions is also obtained. Finally, when used in conjuction with the doubling method, the matrix exponential should result in reduction in both computation time and loss of precision

Irrigation offsets wheat yield reductions from warming temperatures

Science.gov (United States)

Tack, Jesse; Barkley, Andrew; Hendricks, Nathan

2017-11-01

Temperature increases due to climate change are expected to cause substantial reductions in global wheat yields. However, uncertainty remains regarding the potential role for irrigation as an adaptation strategy to offset heat impacts. Here we utilize over 7000 observations spanning eleven Kansas field-trial locations, 180 varieties, and 29 years to show that irrigation significantly reduces the negative impact of warming temperatures on winter wheat yields. Dryland wheat yields are estimated to decrease about eight percent for every one-degree Celsius increase in temperature, yet irrigation completely offsets this negative impact in our sample. As in previous studies, we find that important interactions exist between heat stress and precipitation for dryland production. Here, uniquely, we observe both dryland and irrigated trials side-by-side at the same locations and find that precipitation does not provide the same reduction in heat stress as irrigation. This is likely to be because the timing, intensity, and volume of water applications influence wheat yields, so the ability to irrigate—rather than relying on rainfall alone—has a stronger influence on heat stress. We find evidence of extensive differences of water-deficit stress impacts across varieties. This provides some evidence of the potential for adapting to hotter and drier climate conditions using optimal variety selection. Overall, our results highlight the critical role of water management for future global food security. Water scarcity not only reduces crop yields through water-deficit stress, but also amplifies the negative effects of warming temperatures.

Multiscale Modeling of Ceramic Matrix Composites

Science.gov (United States)

Bednarcyk, Brett A.; Mital, Subodh K.; Pineda, Evan J.; Arnold, Steven M.

2015-01-01

Results of multiscale modeling simulations of the nonlinear response of SiC/SiC ceramic matrix composites are reported, wherein the microstructure of the ceramic matrix is captured. This micro scale architecture, which contains free Si material as well as the SiC ceramic, is responsible for residual stresses that play an important role in the subsequent thermo-mechanical behavior of the SiC/SiC composite. Using the novel Multiscale Generalized Method of Cells recursive micromechanics theory, the microstructure of the matrix, as well as the microstructure of the composite (fiber and matrix) can be captured.

Natural convection in Bingham plastic fluids from an isothermal spheroid: Effects of fluid yield stress, viscous dissipation and temperature-dependent viscosity

Science.gov (United States)

Gupta, Anoop Kumar; Gupta, Sanjay; Chhabra, Rajendra Prasad

2017-08-01

In this work, the buoyancy-induced convection from an isothermal spheroid is studied in a Bingham plastic fluid. Extensive results on the morphology of approximate yield surfaces, temperature profiles, and the local and average Nusselt numbers are reported to elucidate the effects of the pertinent dimensionless parameters: Rayleigh number, 102 ≤ Ra ≤ 106; Prandtl number, 20 ≤ Pr ≤ 100; Bingham number, 0 ≤ Bn ≤ 103, and aspect ratio, 0.2 ≤ e ≤ 5. Due to the fluid yield stress, fluid-like (yielded) and solid-like (unyielded) regions coexist in the flow domain depending upon the prevailing stress levels vis-a-vis the value of the fluid yield stress. The yielded parts progressively grow in size with the rising Rayleigh number while this tendency is countered by the increasing Bingham and Prandtl numbers. Due to these two competing effects, a limiting value of the Bingham number ( Bn max) is observed beyond which heat transfer occurs solely by conduction due to the solid-like behaviour of the fluid everywhere in the domain. Such limiting values bear a positive dependence on the Rayleigh number ( Ra) and aspect ratio ( e). In addition to this, oblate shapes ( e 1) impede it. Finally, simple predictive expressions for the maximum Bingham number and the average Nusselt number are developed which can be used to predict a priori the overall heat transfer coefficient in a new application. Also, a criterion is developed in terms of the composite parameter Bn• Gr-1/2 which predicts the onset of convection in such fluids. Similarly, another criterion is developed which delineates the conditions for the onset of settling due to buoyancy effects. The paper is concluded by presenting limited results to delineate the effects of viscous dissipation and the temperature-dependent viscosity on the Nusselt number. Both these effects are seen to be rather small in Bingham plastic fluids.

CCN2/CTGF is required for matrix organization and to protect growth plate chondrocytes from cellular stress.

Science.gov (United States)

Hall-Glenn, Faith; Aivazi, Armen; Akopyan, Lusi; Ong, Jessica R; Baxter, Ruth R; Benya, Paul D; Goldschmeding, Roel; van Nieuwenhoven, Frans A; Hunziker, Ernst B; Lyons, Karen M

2013-08-01

CCN2 (connective tissue growth factor (CTGF/CCN2)) is a matricellular protein that utilizes integrins to regulate cell proliferation, migration and survival. The loss of CCN2 leads to perinatal lethality resulting from a severe chondrodysplasia. Upon closer inspection of Ccn2 mutant mice, we observed defects in extracellular matrix (ECM) organization and hypothesized that the severe chondrodysplasia caused by loss of CCN2 might be associated with defective chondrocyte survival. Ccn2 mutant growth plate chondrocytes exhibited enlarged endoplasmic reticula (ER), suggesting cellular stress. Immunofluorescence analysis confirmed elevated stress in Ccn2 mutants, with reduced stress observed in Ccn2 overexpressing transgenic mice. In vitro studies revealed that Ccn2 is a stress responsive gene in chondrocytes. The elevated stress observed in Ccn2-/- chondrocytes is direct and mediated in part through integrin α5. The expression of the survival marker NFκB and components of the autophagy pathway were decreased in Ccn2 mutant growth plates, suggesting that CCN2 may be involved in mediating chondrocyte survival. These data demonstrate that absence of a matricellular protein can result in increased cellular stress and highlight a novel protective role for CCN2 in chondrocyte survival. The severe chondrodysplasia caused by the loss of CCN2 may be due to increased chondrocyte stress and defective activation of autophagy pathways, leading to decreased cellular survival. These effects may be mediated through nuclear factor κB (NFκB) as part of a CCN2/integrin/NFκB signaling cascade.

Yield strength, shear stress and toughness of YBCO samples textured by Bridgman technique

International Nuclear Information System (INIS)

Roa, J J; Capdevila, X G; Martinez, M; Segarra, M; Jimenez-Pique, E

2008-01-01

Mechanical properties of the orthorhombic phase of YBa 2 Cu 3 O 7-δ (Y-123) at room temperature have been investigated at different applied loads using nanoindentation technique. The study was carried out for several monodomains on the (001) planes for textured Bridgman samples with dispersed Y 2 BaCuO 5 (Y-211) particles as pinning centers. The yield strength (σ ys ), shear stress (τ m ) and toughness (K IC ) of Y123/Y211composite was determined at different applied loads. First and second mechanical properties have been calculated though the Hertz equations and the last one with Lawn et al. equations. Finally, the ultra-low imprints obtained by nanoindentation have been correlated with parameters obtained by Field Emission Scanning Electron Microscope (FE-SEM)

Residual effects of biochar on improving growth, physiology and yield of wheat under salt stress

DEFF Research Database (Denmark)

Akhtar, Saqib Saleem; Andersen, Mathias Neumann; Liu, Fulai

2015-01-01

Salinity is one of the major threats to global food security. Biochar amendment could alleviate the negative impacts of salt stress in crop in the season. However, its long-term residual effect on reducing Na+ uptake in latter crops remains unknown. A pot experiment with wheat was conducted...... in a greenhouse. The soil used was from an earlier experiment on potato where the plants were irrigated with tap water (S0), 25 mM (S1) and 50 mM (S2) NaCl solutions and with 0 and 5% (w/w) biochar amendment. At onset of the experiment, three different EC levels at S0, S1 and S2 were established in the non...... by transient Na+ binding due to its high adsorption capacity, decreasing osmotic stress by enhancing soil moisture content, and by releasing mineral nutrients (particularly K+, Ca++, Mg++) into the soil solution. Growth, physiology and yield of wheat were affected positively with biochar amendment...

Ferroelastic ceramic-reinforced metal matrix composites

OpenAIRE

2006-01-01

Composite materials comprising ferroelastic ceramic particulates dispersed in a metal matrix are capable of vibration damping. When the ferroelastic ceramic particulates are subjected to stress, such as the cyclic stress experienced during vibration of the material, internal stresses in the ceramic cause the material to deform via twinning, domain rotation or domain motion thereby dissipating the vibrational energy. The ferroelastic ceramic particulates may also act as reinforcements to impro...

Bingham viscosity and yield stress of molten (TeO2)0.78(WO3)0.22 glass

International Nuclear Information System (INIS)

Churbanov, M.F.; Snopatin, G.E.; Shaposhnikov, R.M.; Shabarov, V.V.; Plotnichenko, V.G.

2007-01-01

The flow of molten (TeO 2 ) 0.78 (WO 3 ) 0.22 glass in a circular-cylindrical channel has been studied at temperatures from 390 to 430 deg C. The variation of the measured volumetric flow rate with the gas pressure over the melt attests to non-Newtonian flow behavior. The flow rates calculated in the pseudo plastic model were used to determine the yield stress and plastic (Bingham) viscosity of the melt [ru

Drought tolerance indices and their correlation with yield in exotic wheat genotypes

International Nuclear Information System (INIS)

Anwar, J.; Subhani, G.M.; Ahmad, J.; Hussain, M.; Munir, M.

2011-01-01

Performance of nineteen exotic genotypes along with local check variety was studied during 2009-10 at Wheat Research Institute, AARI, Faisalabad, Pakistan. The experiment was conducted under two field conditions i.e., stress and irrigated conditions. In case of water stress experiment, only soaking irrigation was applied for seed bed preparation and no further irrigation was applied up to maturity. While, four irrigations were applied at critical growth stages to the second experiment (irrigated). At maturity, grain yield was recorded in both experiments (stress Y/sub s/ and irrigated Y/sub p/). From grain yield data, some drought tolerance/resistance indices such as tolerance index (TOL), mean productivity (MP), harmonic mean (HM), stress susceptibility index (SSI), geometric mean productivity (GMP), stress tolerance index (STI), yield index (YI), yield stability index (YSI) and modified stress tolerance index (k/sub 1/STI and k/sub 2/STI) were calculated. Genotypic correlation, genetic components and heritability were also calculated for grain yield and all indices. Significant differences among genotypes were observed for Y/sub p/, Y/sub s/ and all other drought tolerance indices. Moderate to high heritability and genetic advance were observed for Y/sub p/, Y/sub s/ and all drought tolerance indices. Grain yield under irrigated environment (Y/sub p/) was positively and significantly correlated with MP, HM, GMP, STI and k/sub 1/STI. Similarly, positive and significant association has also been observed between grain yield under stress condition (Y/sub s/) and MP, HM, GMP, STI, YI and k/sub 2/STI so they were the better predictor of potential yield Y/sub p/ and Y/sub s/ than TOL, SSI and YSI. According to Fernandez model; genotypes No. 2, 4, 6, 7, 9 and 13 have uniform superiority under both conditions (stress and irrigated). Genotypes No. 1, 11, 15, 16, 17, 18 and 19 were recommended for irrigated conditions. Genotypes No. 3 and 5 were identified suitable for

Impact of mild heat stress on dry matter intake, milk yield and milk composition in mid-lactation Holstein dairy cows in a temperate climate.

Science.gov (United States)

Gorniak, Tobias; Meyer, Ulrich; Südekum, Karl-Heinz; Dänicke, Sven

2014-01-01

The aim of the present study was to evaluate the impact of summer temperatures in a temperate climate on mid-lactation Holstein dairy cows. Therefore, a data set was examined comprising five trials with dairy cows conducted at the experimental station of the Friedrich-Loeffler-Institute in Braunschweig, Germany. The temperature-humidity index (THI) was calculated using temperature and humidity data from the barns recorded between January 2010 and July 2012. By using a generalised additive mixed model, the impact of increasing THI on dry matter intake, milk yield and milk composition was evaluated. Dry matter intake and milk yield decreased when THI rose above 60, whilst water intake increased in a linear manner beyond THI 30. Furthermore, milk protein and milk fat content decreased continuously with increasing THI. The present results revealed that heat stress exists in Lower Saxony, Germany. However, further research is necessary to describe the mode of action of heat stress. Especially, mild heat stress has to be investigated in more detail and appropriate heat stress thresholds for temperate climates have to be developed.

Uncovering the local inelastic interactions during manufacture of ductile cast iron: How the substructure of the graphite particles can induce residual stress concentrations in the matrix

Science.gov (United States)

Andriollo, Tito; Hellström, Kristina; Sonne, Mads Rostgaard; Thorborg, Jesper; Tiedje, Niels; Hattel, Jesper

2018-02-01

Recent X-ray diffraction (XRD) measurements have revealed that plastic deformation and a residual elastic strain field can be present around the graphite particles in ductile cast iron after manufacturing, probably due to some local mismatch in thermal contraction. However, as only one component of the elastic strain tensor could be obtained from the XRD data, the shape and magnitude of the associated residual stress field have remained unknown. To compensate for this and to provide theoretical insight into this unexplored topic, a combined experimental-numerical approach is presented in this paper. First, a material equivalent to the ductile cast iron matrix is manufactured and subjected to dilatometric and high-temperature tensile tests. Subsequently, a two-scale hierarchical top-down model is devised, calibrated on the basis of the collected data and used to simulate the interaction between the graphite particles and the matrix during manufacturing of the industrial part considered in the XRD study. The model indicates that, besides the viscoplastic deformation of the matrix, the effect of the inelastic deformation of the graphite has to be considered to explain the magnitude of the XRD strain. Moreover, the model shows that the large elastic strain perturbations recorded with XRD close to the graphite-matrix interface are not artifacts due to e.g. sharp gradients in chemical composition, but correspond to residual stress concentrations induced by the conical sectors forming the internal structure of the graphite particles. In contrast to common belief, these results thus suggest that ductile cast iron parts cannot be considered, in general, as stress-free at the microstructural scale.

Maximizing Lipid Yield in Neochloris oleoabundans Algae Extraction by Stressing and Using Multiple Extraction Stages with N-Ethylbutylamine as Switchable Solvent

NARCIS (Netherlands)

Du, Ying; Schuur, Boelo; Brilman, Derk W.F.

2017-01-01

(Graph Presented) The extraction yield of lipids from nonbroken Neochloris oleoabundans was maximized by using multiple extraction stages and using stressed algae. Experimental parameters that affect the extraction were investigated. The study showed that with wet algae (at least) 18 h extraction

Effect of Fiber Poisson Contraction on Matrix Multicracking Evolution of Fiber-Reinforced Ceramic-Matrix Composites

Science.gov (United States)

Longbiao, Li

2015-12-01

An analytical methodology has been developed to investigate the effect of fiber Poisson contraction on matrix multicracking evolution of fiber-reinforced ceramic-matrix composites (CMCs). The modified shear-lag model incorporated with the Coulomb friction law is adopted to solve the stress distribution in the interface slip region and intact region of the damaged composite. The critical matrix strain energy criterion which presupposes the existence of an ultimate or critical strain energy limit beyond which the matrix fails has been adopted to describe matrix multicracking of CMCs. As more energy is placed into the composite, matrix fractures and the interface debonding occurs to dissipate the extra energy. The interface debonded length under the process of matrix multicracking is obtained by treating the interface debonding as a particular crack propagation problem along the fiber/matrix interface. The effects of the interfacial frictional coefficient, fiber Poisson ratio, fiber volume fraction, interface debonded energy and cycle number on the interface debonding and matrix multicracking evolution have been analyzed. The theoretical results are compared with experimental data of unidirectional SiC/CAS, SiC/CAS-II and SiC/Borosilicate composites.

Effect of elasticity on stress distribution in CAD/CAM dental crowns: Glass ceramic vs. polymer-matrix composite.

Science.gov (United States)

Duan, Yuanyuan; Griggs, Jason A

2015-06-01

Further investigations are required to evaluate the mechanical behaviour of newly developed polymer-matrix composite (PMC) blocks for computer-aided design/computer-aided manufacturing (CAD/CAM) applications. The purpose of this study was to investigate the effect of elasticity on the stress distribution in dental crowns made of glass-ceramic and PMC materials using finite element (FE) analysis. Elastic constants of two materials were determined by ultrasonic pulse velocity using an acoustic thickness gauge. Three-dimensional solid models of a full-coverage dental crown on a first mandibular molar were generated based on X-ray micro-CT scanning images. A variety of load case-material property combinations were simulated and conducted using FE analysis. The first principal stress distribution in the crown and luting agent was plotted and analyzed. The glass-ceramic crown had stress concentrations on the occlusal surface surrounding the area of loading and the cemented surface underneath the area of loading, while the PMC crown had only stress concentration on the occlusal surface. The PMC crown had lower maximum stress than the glass-ceramic crown in all load cases, but this difference was not substantial when the loading had a lateral component. Eccentric loading did not substantially increase the maximum stress in the prosthesis. Both materials are resistant to fracture with physiological occlusal load. The PMC crown had lower maximum stress than the glass-ceramic crown, but the effect of a lateral loading component was more pronounced for a PMC crown than for a glass-ceramic crown. Knowledge of the stress distribution in dental crowns with low modulus of elasticity will aid clinicians in planning treatments that include such restorations. Copyright © 2015 Elsevier Ltd. All rights reserved.

A Piston-Rotaxane with Two Potential Stripes: Force Transitions and Yield Stresses

Directory of Open Access Journals (Sweden)

Edith M. Sevick

2013-10-01

Full Text Available We examine a rod piston-rotaxane system, where the positions of several mobile rings on the axle are controlled by an external force acting on one of the rings. This allows us to access the translational entropy of the rings. For a simple rotaxane molecule with an axle that has uniform ring-axle interactions along its length, the molecule behaves like a miniature piston filled with a one-dimensional ideal gas. We then examine the effect of two stripes on the axle, having different ring-axle interactions with the mobile rings, so that one section is of high energy (repulsive for the rings and another section is of lower energy (or attractive. This kind of rotaxane can exhibit rapid changes in displacement or force, and in particular, this molecule can exhibit a yield stress in which the piston suddenly compresses under a small increase in the applied force.

Heritability and correlates of maize yield ( Zea mays L .) under ...

African Journals Online (AJOL)

Heritability and correlates of maize yield ( Zea mays L .) under varying drought conditions. ... Nigeria Agricultural Journal ... Correlation analysis revealed that days to 50% tasseling and silking under non-stress, ASI and leaf senescence under severe stress exhibited negative and significant correlations with grain yield.

Assesment of economic benefits of foliarly applied osmoprotectants in alleviating the adverse effects of water stress on growth and yield of cotton (gossypium hirsutum L.)

International Nuclear Information System (INIS)

Zafar, Z. U.; Hussain, K.; Athar, H. U. R.

2015-01-01

Water stress reduces crop growth and productivity by affecting various physiological and biochemical processes. Although foliar application of osmoprotectants alleviates the detrimental effects of drought stress growth and productivity of crops, its economic benefits on large scale has not been explored yet. The studies were carried out to quantify the interactive effects of some osmoprotectantsand various watering regimes on cotton crop. The treatments consisted of water stress and osmoprotectant applications ((a) two watering regimes (well watered, 2689m /sup 3/ water; drought stressed, 2078m /sup 3/), and (b) three osmoprotectants (untreated check; water spray containing 0.1 percentage Tween-80; salicylic acid (100 mg L /sup -1/); proline (100 mg L /sup -1/); glycine betaine (100 mg L /sup -1/)) in split plot design. The crop was subjected to drought stress at day 45 after sowing, i.e. at the flowering stage. The solutions of osmoprotectants were foliarly applied after two weeks of imposition of water stress (at the peak flowering stage). The results showed that imposition of water stress caused substantial reduction in plant growth, biological yield, fruit production, and fiber characteristics as compared to fully irrigated cotton crop. However, the application of osmoprotectants was found effective in off-setting the negative impacts of drought stress. The exogenous application of salicylic acid (100 mgL /sup -1/) caused improvement by 47.9 percentage, 36.5 percentage, 17.4 percentage, 4.86 percentage and 9.9 percentage in main stem height, biological yield, fruit production, fiber length and seed cotton yield over an untreated check, respectively. The efficiency of various osmoprotectants was in order of salicylic acid > glycinebetaine > proline in alleviating the harmful effects of drought stress. The usage of osmoprotectants was also found most cost-effective and the value for money. The cost-benefit ratio was 1:9.1, 1:3.9 and 1:1.7 by spraying of salicylic

Interactive effects of high temperature and drought stress during stem elongation, anthesis and early grain filling on the yield formation and photosynthesis of winter wheat

Czech Academy of Sciences Publication Activity Database

Hlaváčová, Marcela; Klem, Karel; Rapantová, Barbora; Novotná, Kateřina; Urban, Otmar; Hlavinka, Petr; Smutná, P.; Horáková, V.; Škarpa, P.; Pohanková, Eva; Wimmerová, Markéta; Orság, Matěj; Jurečka, František; Trnka, Miroslav

2018-01-01

Roč. 221, MAY (2018), s. 182-195 ISSN 0378-4290 R&D Projects: GA MŠk(CZ) LO1415; GA MŠk(CZ) LM2015061; GA MŠk(CZ) EF16_013/0001609 Institutional support: RVO:86652079 Keywords : carbon-isotope discrimination * triticum-aestivum-l. * heat-stress * climate-change * reproductive growth * leaf senescence * gas-exchange * water -stress * durum-wheat * responses * Drought stress * Heat stress * Photosynthesis * Triticum aestivum * Yield formation Subject RIV: GC - Agronomy OBOR OECD: Agronomy, plant breeding and plant protection Impact factor: 3.048, year: 2016

Improvement of antioxidant activities and yield of spring maize through seed priming and foliar application of plant growth regulators under heat stress conditions

Directory of Open Access Journals (Sweden)

Ijaz Ahmad

2017-03-01

Full Text Available Heat stress during reproductive and grain filling phases adversely affects the growth of cereals through reduction in grain’s number and size. However, exogenous application of antioxidants, plant growth regulators and osmoprotectants may be helpful to minimize these heat induced yield losses in cereals. This two year study was conducted to evaluate the role of exogenous application of ascorbic acid (AsA, salicylic acid (SA and hydrogen peroxide (H2O2 applied through seed priming or foliar spray on biochemical, physiological, morphological and yield related traits, grain yield and quality of late spring sown hybrid maize. The experiment was conducted in the spring season of 2007 and 2008. We observed that application of AsA, SA and H2O2 applied through seed priming or foliar spray improved the physiological, biochemical, morphological and yield related traits, grain yield and grain quality of late spring sown maize in both years. In both years, we observed higher superoxide dismutase (SOD, catalase (CAT and peroxidase (POD activity in the plants where AsA, SA and H2O2were applied through seed priming or foliar spray than control. Membrane stability index (MSI, relative water contents (RWC, chlorophyll contents, grain yield and grain oil contents were also improved by exogenous application of AsA, SA and H2O2 in both years. Seed priming of AsA, SA and H2O2was equally effective as the foliar application. In conclusion, seed priming with AsA, SA and H2O2 may be opted to lessen the heat induced yield losses in late sown spring hybrid maize. Heat tolerance induced by ASA, SA and H2O2 may be attributed to increase in antioxidant activities and MSI which maintained RWC and chlorophyll contents in maize resulting in better grain yield in heat stress conditions.

Effect of Water Stress and Spraying of Potassium Iodide on Agronomic Traits and Grain Yield of Bread Wheat (Tiriticum aistivum L. Genotypes

Directory of Open Access Journals (Sweden)

N. Pooladsaz

2011-01-01

Full Text Available Abstract In order to study the effect of water stress and chemical desiccation (potassium iodide on grain yield and agronomic traits of 8 wheat genotypes, a field experiment was conducted using a split split plot design based on a randomized complete block design with three replications in Torogh Agricultural and Natural Resources Research Station (Mashhad, Iran in 2006-2007 and 2007-2008. Main plots were assigned to two levels of water stress treatments; D1: optimum irrigation, and D2: cessation of watering from anthesis to maturity stages. Sub plots were assigned to eight bread wheat genotypes: 9103, 9116, 9203, 9205, 9207, 9212, C-81-10 and Cross Shahi (drought sensitive; and photosynthetic conditions with two levels: P1: using of current photosynthesis and P2: inhibition of current photosynthesis were in sub-sub plots. The results showed that the effects of water stress and photosynthetic conditions on number of total florets per spike (NTF/S, seed set percentage (SSP, spike harvest index (SHI, duration of grain filling (DGF and grain yield (GY were significant. There was a significant difference between genotypes for spike dry weight at anthesis (SDWA, number of spikletes per spike (NSP/S, NTF/S, SSP, SHI, spike partitioning coefficient (SPC, plant height (PLH, spike length (SL, DGF and GY. 9103 genotype produced the most GY (7870 kg/ha under D1P1 treatment. The least GY ( 1114 kg/ha related to Cross Shahi cultivar under D2P2 treatment. Considering that C-81-10, 9103 and 9116 genotypes showed the highest grain yield, potential for reserves and remobilizations of assimilates under different irrigation conditions thus, these genotypes could be introduced as promising in breeding programs for arid and semi-arid regions. Keywords: Triticum aestivum L., Cessation of watering, Chemical Desiccation, Spike, Grain yield

Combining Ability of Pod Yield and Related Traits of Groundnut (Arachis hypogaea L. under Salinity Stress

Directory of Open Access Journals (Sweden)

Md. Abul Kalam Azad

2014-01-01

Full Text Available A study was performed using 6×6 F1 diallel population without reciprocals to assess the mode of inheritance of pod yield and related traits in groundnut with imposed salinity stress. Heterosis was found for pod number and yield. Data on general and specific combining ability (gca and sca indicated additive and nonadditive gene actions. The gca: sca ratios were much less than unity suggesting predominant role of nonadditive gene effects. Cultivars “Binachinabadam-2” and “Dacca-1” and mutant M6/25/64-82 had the highest, second highest, and third highest pod number, as well as gca values, respectively. These two cultivars and another mutant M6/15/70-19 also had the highest, second highest, and third highest pod yield, as well as gca values, respectively. Therefore, “Dacca-1”, “Binachinabadam-2”, M6/25/64-82, and M6/15/70-19 could be used as source of salinity tolerance. Cross combinations showing high sca effects arising from parents with high and low gca values for any trait indicate the influence of nonadditive genes on their expression. Parents of these crosses can be used for biparental mating or reciprocal recurrent selection for developing high yielding varieties. Crosses with high sca effects having both parents with good gca effects could be exploited by pedigree breeding to get transgressive segregants.

Combining Earthquake Focal Mechanism Inversion and Coulomb Friction Law to Yield Tectonic Stress Magnitudes in Strike-slip Faulting Regime

Science.gov (United States)

Soh, I.; Chang, C.

2017-12-01

The techniques for estimating present-day stress states by inverting multiple earthquake focal mechanism solutions (FMS) provide orientations of the three principal stresses and their relative magnitudes. In order to estimate absolute magnitudes of the stresses that are generally required to analyze faulting mechanics, we combine the relative stress magnitude parameter (R-value) derived from the inversion process and the concept of frictional equilibrium of stress state defined by Coulomb friction law. The stress inversion in Korean Peninsula using 152 FMS data (magnitude≥2.5) conducted at regularly spaced grid points yields a consistent strike-slip faulting regime in which the maximum (S1) and the minimum (S3) principal stresses act in horizontal planes (with an S1 azimuth in ENE-WSW) and the intermediate principal stress (S2) close to vertical. However, R-value varies from 0.28 to 0.75 depending on locations, systematically increasing eastward. Based on the assumptions that the vertical stress is lithostatic, pore pressure is hydrostatic, and the maximum differential stress (S1-S3) is limited by Byerlee's friction of optimally oriented faults for slip, we estimate absolute magnitudes of the two horizontal principal stresses using R-value. As R-value increases, so do the magnitudes of the horizontal stresses. Our estimation of the stress magnitudes shows that the maximum horizontal principal stress (S1) normalized by vertical stress tends to increase from 1.3 in the west to 1.8 in the east. The estimated variation of stress magnitudes is compatible with distinct clustering of faulting types in different regions. Normal faulting events are densely populated in the west region where the horizontal stress is relatively low, whereas numerous reverse faulting events prevail in the east offshore where the horizontal stress is relatively high. Such a characteristic distribution of distinct faulting types in different regions can only be explained in terms of stress

Development of an inelastic stress analysis code 'KINE-T' and its evaluations

International Nuclear Information System (INIS)

Kobatake, K.; Takahashi, S.; Suzuki, M.

1977-01-01

Referring to the ASME B and PVC Code Case 1592-7, the inelastic stress analysis is required for the designs of the class 1 components in elevated temperature if the results of the elastic stress analysis and/or simplified inelastic analysis do not satisfy the requirements. Authors programmed a two-dimensional axisymmetric inelastic analysis code 'KINE-T', and carried out its evaluations and an application. This FEM code is based on the incremental method and the following: elastic-plastic constitutive equation (yield condition of von Mises; flow rule of Prandtl-Reuss; Prager's hardening rule); creep constitutive equation (equation of state approach; flow rule of von Mises; strain hardening rule); the temperature dependency of the yield function is considered; solution procedure of the assembled stiffness matrix is the 'initial stress method'. After the completion of the programming, authors compared the output with not only theoretical results but also with those of the MARC code and the ANSYS code. In order to apply the code to the practical designing, authors settled a quasi-component two-dimensional axisymmetric model and a loading cycle (500 cycles). Then, an inelastic analysis and its integrity evaluation are carried out

Effects of High-Temperature Annealing in Air on Hi-Nicalon Fiber-Reinforced Celsian Matrix Composites

Science.gov (United States)

Bansal, Narottam P.

2008-01-01

BN/SiC-coated Hi-Nicalon fiber-reinforced celsian matrix composites (CMC) were annealed for 100 h in air at various temperatures to 1200 C, followed by flexural strength measurements at room temperature. Values of yield stress and strain, ultimate strength, and composite modulus remain almost unchanged for samples annealed up to 1100 C. A thin porous layer formed on the surface of the 1100 C annealed sample and its density decreased from 3.09 to 2.90 g/cu cm. The specimen annealed at 1200 C gained 0.43 wt%, was severely deformed, and was covered with a porous layer of thick shiny glaze which could be easily peeled off. Some gas bubbles were also present on the surface. This surface layer consisted of elongated crystals of monoclinic celsian and some amorphous phase(s). The fibers in this surface ply of the CMC had broken into small pieces. The fiber-matrix interface strength was characterized through fiber push-in technique. Values of debond stress, alpha(sub d), and frictional sliding stress, tau(sub f), for the as-fabricated CMC were 0.31+/-0.14 GPa and 10.4+/-3.1 MPa, respectively. These values compared with 0.53+/-0.47 GPa and 8.33+/-1.72 MPa for the fibers in the interior of the 1200 C annealed sample, indicating hardly any change in fiber-matrix interface strength. The effects of thermal aging on microstructure were investigated using scanning electron microscopy. Only the surface ply of the 1200 C annealed specimens had degraded from oxidation whereas the bulk interior part of the CMC was unaffected. A mechanism is proposed explaining the various steps involved during the degradation of the CMC on annealing in air at 1200 C.

Improving growth and yield of cowpea by foliar application of ...

African Journals Online (AJOL)

Water stress impaired cowpea plant growth and decreased ion percentage and chlorophyll and carbohydrate concentration in the shoot as well as yield and its quality. Foliar-applied chitosan, in particular 250 mg/l, increased plant growth, yield and its quality as well as physiological constituents in plant shoot under stressed ...

Effect of magnetic field and silver nanoparticles on yield and water use efficiency of Carum copticum under water stress conditions

Directory of Open Access Journals (Sweden)

Seghatoleslami Mohammadjavad

2015-03-01

Full Text Available Normally the productivity of cropping systems in arid and semi- arid regions is very low. The sustainable agricultural systems try to find out environmental friendly technologies based on physical and biological treatments to increase crop production. In this study two irrigation treatments (control and water stress and six methods of fertilizer treatment (control, NPK-F, using magnetic band- M, using silver nano particles- N, M+N and M+N+50% F on performance of ajowan were compared. Results showed that treatments with magnetic field or base fertilizer had more yield compared to the control and silver nanoparticles (N treatments. Application of silver nanoparticles had no positive effect on yield. The highest seed and biomass WUE achieved in base fertilizer or magnetic field treatments. Under water stress treatment, seed WUE significantly increased. In conclusion magnetic field exposure, probably by encourage nutrient uptake efficiency could be applied to reduce fertilizer requirement. On the other hand the cultivation of plants under low MF could be an alternative way of WUE improving.

Effects of shade and drought stress on soybean hormones and yield ...

African Journals Online (AJOL)

Jane

2011-10-24

Oct 24, 2011 ... hormone concentrations, main-stem and branch yield response to the combination of shade and drought were studied ... yield primarily by reducing branch growth and branch seed yield per ..... deficit soybean. Yield decrease ...

Stress relaxation and activation volume at the yield point of cold worked and neutron irradiated copper single crystals

International Nuclear Information System (INIS)

Brunner, D.; Diehl, J.

1979-01-01

The effective activation volume of slip is studied after neutron irradiation in as-grown crystals as well as in predeformed ones by means of stress relaxation tests between 20 K and 200 K. The activation volume corresponding to the initial strain rate is found to be always higher in predeformed crystals than in as-grown ones. During stress relaxation the flow stress tau decreases linearly with ln(-dtau/dt) (indicating a constant activation volume) only in rare cases. Depending on predeformation and temperature several types of deviations from straight lines are observed: monotoneously bent curves, strong scattering of data points not fitting smooth curves or systematic deviations from straight lines at the beginning of relaxation. Accordingly the effective activation volumes and their dependences on stress seem to behave in a strange manner. By the aid of a previously proposed model for the deformation within the yield point elongation the results can be interpreted qualitatively by taking into account the inhomogeneity of slip and work hardening, allowing a more reliable judgement on the real activation volumes, on which a better understanding of the superposition of the two hardening mechanisms involved here can be based. (author)

Genotypic Variation in Yield, Yield Components, Root Morphology and Architecture, in Soybean in Relation to Water and Phosphorus Supply

Science.gov (United States)

He, Jin; Jin, Yi; Du, Yan-Lei; Wang, Tao; Turner, Neil C.; Yang, Ru-Ping; Siddique, Kadambot H. M.; Li, Feng-Min

2017-01-01

Water shortage and low phosphorus (P) availability limit yields in soybean. Roots play important roles in water-limited and P-deficient environment, but the underlying mechanisms are largely unknown. In this study we determined the responses of four soybean [Glycine max (L.) Merr.] genotypes [Huandsedadou (HD), Bailudou (BLD), Jindou 21 (J21), and Zhonghuang 30 (ZH)] to three P levels [applied 0 (P0), 60 (P60), and 120 (P120) mg P kg-1 dry soil to the upper 0.4 m of the soil profile] and two water treatment [well-watered (WW) and water-stressed (WS)] with special reference to root morphology and architecture, we compared yield and its components, root morphology and root architecture to find out which variety and/or what kind of root architecture had high grain yield under P and drought stress. The results showed that water stress and low P, respectively, significantly reduced grain yield by 60 and 40%, daily water use by 66 and 31%, P accumulation by 40 and 80%, and N accumulation by 39 and 65%. The cultivar ZH with the lowest daily water use had the highest grain yield at P60 and P120 under drought. Increased root length was positively associated with N and P accumulation in both the WW and WS treatments, but not with grain yield under water and P deficits. However, in the WS treatment, high adventitious and lateral root densities were associated with high N and P uptake per unit root length which in turn was significantly and positively associated with grain yield. Our results suggest that (1) genetic variation of grain yield, daily water use, P and N accumulation, and root morphology and architecture were observed among the soybean cultivars and ZH had the best yield performance under P and water limited conditions; (2) water has a major influence on nutrient uptake and grain yield, while additional P supply can modestly increase yields under drought in some soybean genotypes; (3) while conserved water use plays an important role in grain yield under drought

Spectra of matrix isolated metal atoms and clusters

International Nuclear Information System (INIS)

Meyer, B.

1977-01-01

The matrix isolation spectra of all of the 40 presently known atomic metal species show strong matrix effects. The transition energies are increased, and the bands are broad and exhibit splitting of sublevels which are degenerate in the gas phase. Several models have been proposed for splitting of levels, but basic effects are not yet understood, and spectra cannot be predicted, yet it is possible to correlate gas phase and matrix in many of the systems. Selective production of diatomics and clusters via thermal and optical annealing of atomic species can be monitored by optical spectra, but yields spectroscopically complex systems which, however, especially in the case of transition metals, can be used as precursors in novel chemical reactions. A combination of absorption, emission, ir, Raman, ESR, and other methods is now quickly yielding data which will help correlate the increasing wealth of existing data. 55 references, 6 figures

Statistical evaluation of characteristic SDDLV-induced stress resultants to discriminate between undamaged and damaged elements

DEFF Research Database (Denmark)

Hansen, Lasse Majgaard; Johansen, Rasmus Johan; Ulriksen, Martin Dalgaard

2015-01-01

of modified characteristic stress resultants, which are compared to a pre-defined tolerance value, without any thorough statistical evaluation. In the present paper, it is tested whether three widely-used statistical pattern-recognition-based damage-detection methods can provide an effective statistical...... evaluation of the characteristic stress resultants, hence facilitating general discrimination between damaged and undamaged elements. The three detection methods in question enable outlier analysis on the basis of, respectively, Euclidian distance, Hotelling’s statistics, and Mahalanobis distance. The study...... alternately to an undamaged reference model with known stiffness matrix, hereby, theoretically, yielding characteristic stress resultants approaching zero in the damaged elements. At present, the discrimination between potentially damaged elements and undamaged ones is typically conducted on the basis...

Effect of yield strength on stress corrosion crack propagation under PWR and BWR environments of hardened stainless steels

Energy Technology Data Exchange (ETDEWEB)

Castano, M.L.; Garcia, M.S.; Diego, G. de; Gomez-Briceno, D. [CIEMAT, Nuclear Fission Department, Structural Materials Program, Avda. Complutense 22, 28040 Madrid (Spain)

2004-07-01

stress corrosion cracking of austenitic stainless steels (SS) and to quantify the effect on the crack propagation rate, an experimental research program was performed using cold and warm worked 304, 316L and 347 SS. Stress corrosion crack growth rate tests, under BWR and PWR environments have been carried out. The results obtained have permitted to determine the yield strength effect in the crack propagation of austenitic stainless steels in PWR and BWR conditions. In addition, similarities on cold work and radiation hardening in enhancing the yield strength and the stress corrosion cracking propagation at high temperature water have been evaluated. (authors)

A Modified Eyring Equation for Modeling Yield and Flow Stresses of Metals at Strain Rates Ranging from 10−5 to 5 × 104 s−1

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Ramzi Othman

2015-01-01

Full Text Available In several industrial applications, metallic structures are facing impact loads. Therefore, there is an important need for developing constitutive equations which take into account the strain rate sensitivity of their mechanical properties. The Johnson-Cook equation was widely used to model the strain rate sensitivity of metals. However, it implies that the yield and flow stresses are linearly increasing in terms of the logarithm of strain rate. This is only true up to a threshold strain rate. In this work, a three-constant constitutive equation, assuming an apparent activation volume which decreases as the strain rate increases, is applied here for some metals. It is shown that this equation fits well the experimental yield and flow stresses for a very wide range of strain rates, including quasi-static, high, and very high strain rates (from 10−5 to 5 × 104 s−1. This is the first time that a constitutive equation is showed to be able to fit the yield stress over a so large strain rate range while using only three material constants.

Giant magneto-impedance and stress-impedance effects of microwire composites for sensing applications

Science.gov (United States)

Qin, F. X.; Peng, H. X.; Popov, V. V.; Phan, M. H.

2011-02-01

Composites consisting of glass-coated amorphous microwire Co 68.59Fe 4.84Si 12.41B 14.16 and 913 E-glass prepregs were designed and fabricated. The influences of tensile stress, annealing and number of composite layers on the giant magneto-impedance (GMI) and giant stress-impedance (GSI) effects in these composites were investigated systematically. It was found that the application of tensile stress along the microwire axis or an increase in the number of composite layers reduced the GMI effect and increased the circular anisotropy field, while the annealing treatment had a reverse effect. The value of matrix-wire interfacial stress calculated via the GMI profiles coincided with the value of the applied effective tensile stress to yield similar GMI profiles. Enhancement of the GSI effect was achieved in the composites relative to their single microwire inclusion. These findings are important for the development of functional microwire-based composites for magnetic- and stress-sensing applications. They also open up a new route for probing the interfacial stress in fibre-reinforced polymer (FRP) composites.

Genetic Loci Governing Grain Yield and Root Development under Variable Rice Cultivation Conditions

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Margaret Catolos

2017-10-01

Full Text Available Drought is the major abiotic stress to rice grain yield under unpredictable changing climatic scenarios. The widely grown, high yielding but drought susceptible rice varieties need to be improved by unraveling the genomic regions controlling traits enhancing drought tolerance. The present study was conducted with the aim to identify quantitative trait loci (QTLs for grain yield and root development traits under irrigated non-stress and reproductive-stage drought stress in both lowland and upland situations. A mapping population consisting of 480 lines derived from a cross between Dular (drought-tolerant and IR64-21 (drought susceptible was used. QTL analysis revealed three major consistent-effect QTLs for grain yield (qDTY1.1, qDTY1.3, and qDTY8.1 under non-stress and reproductive-stage drought stress conditions, and 2 QTLs for root traits (qRT9.1 for root-growth angle and qRT5.1 for multiple root traits, i.e., seedling-stage root length, root dry weight and crown root number. The genetic locus qDTY1.1 was identified as hotspot for grain yield and yield-related agronomic and root traits. The study identified significant positive correlations among numbers of crown roots and mesocotyl length at the seedling stage and root length and root dry weight at depth at later stages with grain yield and yield-related traits. Under reproductive stage drought stress, the grain yield advantage of the lines with QTLs ranged from 24.1 to 108.9% under upland and 3.0–22.7% under lowland conditions over the lines without QTLs. The lines with QTL combinations qDTY1.3+qDTY8.1 showed the highest mean grain yield advantage followed by lines having qDTY1.1+qDTY8.1 and qDTY1.1+qDTY8.1+qDTY1.3, across upland/lowland reproductive-stage drought stress. The identified QTLs for root traits, mesocotyl length, grain yield and yield-related traits can be immediately deployed in marker-assisted breeding to develop drought tolerant high yielding rice varieties.

N-acetylcysteine increased rice yield

OpenAIRE

NOZULAIDI, MOHD; JAHAN, MD SARWAR; KHAIRI, MOHD; KHANDAKER, MOHAMMAD MONERUZZAMAN; NASHRIYAH, MAT; KHANIF, YUSOP MOHD

2015-01-01

N-acetylcysteine (NAC) biosynthesized reduced glutathione (GSH), which maintains redox homeostasis in plants under normal and stressful conditions. To justify the effects of NAC on rice production, we measured yield parameters, chlorophyll (Chl) content, minimum Chl fluorescence (Fo), maximum Chl fluorescence (Fm), quantum yield (Fv/Fm), net photosynthesis rate (Pn), photosynthetically active radiation (PAR), and relative water content (RWC). Four treatments, N1G0 (nitrogen (N) with no NAC), ...

Strength and fracture behavior of aluminide matrix composites with ceramic fibers

Energy Technology Data Exchange (ETDEWEB)

Inoue, M.; Suganuma, K.; Niihara, K.

1999-07-01

This paper investigates the fracture behavior of FeAl and Ni{sub 3}Al matrix composites with ceramic continuous fibers 8.5--10 {micro}m in diameter. When stress is applied to these composites, multiple-fracture of fibers predominantly occurs before matrix cracking, because the load carried by the fibers reaches their fracture strength. Fragments which remain longer than the critical length can provide significant strengthening through load bearing even though fiber breaking has occurred. The ultimate fracture strength of the composites also depends on stress relaxation by plastic deformation of the matrix at a crack tip in the multiple-fractured fibers. Ductilizing of the matrix by B doping improves the ultimate strength at ambient temperatures in both composites. However, their mechanical properties at elevated temperatures are quite different. In the case of Ni{sub 3}Al matrix composites, embrittlement of the matrix is undesirable for high strength and reliability at 873--973 K.

Characteristics of hot-pressed fiber-reinforced ceramics with SiC matrix

Science.gov (United States)

Miyoshi, Tadahiko; Kodama, Hironori; Sakamoto, Hiroshi; Goto, Akihiro; Iijima, Shiroo

1989-11-01

Silicon carbide ceramics’ matrix composites with SiC or C filaments were fabricated through hot pressing, and the effects of the filament pullout on their fracture toughness were experimentally investigated. The C-rich coating layers on the SiC filaments were found to have a significant effect on the frictional stress at the filament/matrix interfaces, through assising the filamet pullout from the matrix. Although the coating layers were apt to burn out in the sintering process of SiC matrix compposites, a small addition of carbon to the raw materials was found to be effective for the retention of the layers on the fibers, thus increasing the fracture toughness of the composites. The fracture toughness of the C filament/SiC matrix composite increased with temperature due to the larger interfacial frictional stress at higher temperatures, because of the higher thermal expansion of the filament in the radial direction than that of the matrix.

Kinetics model of bainitic transformation with stress

Science.gov (United States)

Zhou, Mingxing; Xu, Guang; Hu, Haijiang; Yuan, Qing; Tian, Junyu

2018-01-01

Thermal simulations were conducted on a Gleeble 3800 simulator. The main purpose is to investigate the effects of stress on the kinetics of bainitic transformation in a Fe-C-Mn-Si advanced high strength bainitic steel. Previous studies on modeling the kinetics of stress affected bainitic transformation only considered the stress below the yield strength of prior austenite. In the present study, the stress above the yield strength of prior austenite is taken into account. A new kinetics model of bainitic transformation dependent on the stress (including the stresses below and above the yield strength of prior austenite) and the transformation temperature is proposed. The new model presents a good agreement with experimental results. In addition, it is found that the acceleration degree of stress on bainitic transformation increases with the stress whether its magnitude is below or above the yield strength of austenite, but the increasing rate gradually slows down when the stress is above the yield strength of austenite.

Determining the Threshold Value of Basil Yield Reduction and Evaluation of Water Uptake Models under Salinity Stress Condition

Directory of Open Access Journals (Sweden)

M. Sarai Tabrizi

2016-10-01

Full Text Available Introduction: Several mathematical models are being used for assessing the plant response to the salinity of the root zone. The salinity of the soil and water resources is a major challenge for agricultural sector in Iran. Several mathematical models have been developed for plant responses to the salinity stress. However, these models are often applicable in particular conditions. The objectives of this study were to evaluate the threshold value of Basil yield reduction, modeling Basil response to salinity and to evaluate the effectiveness of available mathematical models for the yield estimation of the Basil . Materials and Methods: The extensive experiments were conducted with 13 natural saline water treatments including 1.2, 1.8, 2, 2.2, 2.5, 2.8, 3, 3.5, 4, 5, 6, 8, and 10 dSm-1. Water salinity treatments were prepared by mixing Shoor River water with fresh water. In order to quantify the salinity effect on Basil yield, seven mathematical models including Maas and Hoffman (1977, van Genuchten and Hoffman (1984, Dirksen and Augustijn (1988, and Homaee et al., (2002 were used. One of the relatively recent methods for soil water content measurements is theta probes instrument. Theta probes instrument consists of four probes with 60 mm long and 3 mm diameter, a water proof container (probe structure, and a cable that links input and output signals to the data logger display. The advantages that have been attributed to this method are high precision and direct and rapid measurements in the field and greenhouse. The range of measurements is not limited like tensiometer and is from saturation to wilting point. In this study, Theta probes instrument was calibrated by weighing method for exact irrigation scheduling. Relative transpiration was calculated using daily soil water content changes. A coarse sand layer with 2 centimeters thick was used to decrease evaporation from the surface soil of the pots. Quantity comparison of the used models was done

OASIS/CREB3L1 is induced by endoplasmic reticulum stress in human glioma cell lines and contributes to the unfolded protein response, extracellular matrix production and cell migration.

Directory of Open Access Journals (Sweden)

Ravi N Vellanki

Full Text Available OASIS is a transcription factor similar to ATF6 that is activated by endoplasmic reticulum stress. In this study we investigated the expression of OASIS in human glioma cell lines and the effect of OASIS knock-down on the ER stress response and cell migration. OASIS mRNA was detected in three distinct glioma cell lines (U373, A172 and U87 and expression levels were increased upon treatment with ER stress-inducing compounds in the U373 and U87 lines. OASIS protein, which is glycosylated on Asn-513, was detected in the U373 and U87 glioma lines at low levels in control cells and protein expression was induced by ER stress. Knock-down of OASIS in human glioma cell lines resulted in an attenuated unfolded protein response to ER stress (reduced GRP78/BiP and GRP94 induction and decreased expression of chondroitin sulfate proteoglycan extracellular matrix proteins, but induction of the collagen gene Col1a1 was unaffected. Cells in which OASIS was knocked-down exhibited altered cell morphology and reduced cell migration. These results suggest that OASIS is important for the ER stress response and maintenance of some extracellular matrix proteins in human glioma cells.

Effect of drought stress and sulphur fertilizer on quantity and quality yield of psyllium (Plantago ovata L. in Baluchestan

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M. Mousavi nik

2016-05-01

Full Text Available Management of chemical fertilizers application is very important issues on environment and plant yield especially in arid and-semi arid region. In order to determine the effects of drought stresses and fertilizer levels on quantity and quality yields of psyllium (Plantago ovata L., a study was conducted as split plot based on randomized complete block design with four replications at the Natural Resources and Agriculture Researches Center of Balouchestan, Iran, during growing season of 2009-2010. Treatments included different irrigation regimes (three, five and eight times irrigation during the growing season as main plots and four levels of sulphur fertilizer (0, 75, 150 and 225 kg.ha-1 sulphur as sub plot. The results showed that the irrigation regimes and sulphur fertilizer had significant effects on seed and biological yield of psyllium, so the highest seed and biological yields obtained in eight times irrigation. Also, the maximum of these factors were achieved in 225 kg.ha-1 sulphur. The highest harvest index and 1000- seed weight, No. seed per spike and No. spike per plant were observed in eight times irrigation and 225 kg.ha-1 sulphur. The highest plant height was obtained in eight times irrigation and 225 kg.ha-1 sulphur and the maximum mucilage percentage and proline content were obtained in three times irrigation. The maximum mucilage yield and carbohydrate content were achieved in eight times irrigation. Among sulphur fertilizer, the highest amounts for all factors were achieved in 225 kg.ha-1 sulphur. There was positive and significant correlation between seed yield with spike No. per plant, Seed No. per spike, 1000-Seed, biological yield and mucilage yield.

Determining the Threshold Value of Basil Yield Reduction and Evaluation of Water Uptake Models under Salinity Stress Condition

OpenAIRE

M. Sarai Tabrizi; H. Babazadeh; M. Homaee; F. Kaveh Kaveh; M. Parsinejad

2016-01-01

Introduction: Several mathematical models are being used for assessing the plant response to the salinity of the root zone. The salinity of the soil and water resources is a major challenge for agricultural sector in Iran. Several mathematical models have been developed for plant responses to the salinity stress. However, these models are often applicable in particular conditions. The objectives of this study were to evaluate the threshold value of Basil yield reduction, modeling Basil respon...

Mechanical confinement regulates cartilage matrix formation by chondrocytes

Science.gov (United States)

Lee, Hong-Pyo; Gu, Luo; Mooney, David J.; Levenston, Marc E.; Chaudhuri, Ovijit

2017-12-01

Cartilage tissue equivalents formed from hydrogels containing chondrocytes could provide a solution for replacing damaged cartilage. Previous approaches have often utilized elastic hydrogels. However, elastic stresses may restrict cartilage matrix formation and alter the chondrocyte phenotype. Here we investigated the use of viscoelastic hydrogels, in which stresses are relaxed over time and which exhibit creep, for three-dimensional (3D) culture of chondrocytes. We found that faster relaxation promoted a striking increase in the volume of interconnected cartilage matrix formed by chondrocytes. In slower relaxing gels, restriction of cell volume expansion by elastic stresses led to increased secretion of IL-1β, which in turn drove strong up-regulation of genes associated with cartilage degradation and cell death. As no cell-adhesion ligands are presented by the hydrogels, these results reveal cell sensing of cell volume confinement as an adhesion-independent mechanism of mechanotransduction in 3D culture, and highlight stress relaxation as a key design parameter for cartilage tissue engineering.

Matrix models with γstring>0

International Nuclear Information System (INIS)

Marzban, C.; Viswanathan, R.R.

1990-12-01

Within the framework of c = 1 matrix models, we consider multi-matrix models. A connection is established between a D-dimensional gas of fermions (bosons) for odd (even) values of D. A statistical mechanical analysis yields the scaling law for the free energy, and hence the susceptibility exponents for the various models. The exponents turn out to be positive for the multi-matrix models, suggesting that these could represent models of 2 d-gravity coupled to c>1 matter. Whereas in the c=1 case the density of states itself diverges as one approaches the critical point, in the D-matrix models various derivatives of the density of states diverge, with the order of the derivative depending on D. This qualitatively different behaviour of the density of states could be a signal of the conjectured ''phase transition'' at c=1. (author). 14 refs

The effect of water deficit stress and nitrogen fertilizer levels on morphology traits, yield and leaf area index in maize

International Nuclear Information System (INIS)

Moosavi, S.G.

2012-01-01

In order to study the effect of water deficit stress at different growth stages and N fertilizer levels on morphological traits, yield and yield components of maize cv. Single Cross 704, an experiment was conducted as a split-plot based on a Randomized Complete Block Design with three replications. The main plot included irrigation at four levels (irrigation stop at 10-leaf, tasselling and grain-filling stages and optimum irrigation) and the sub-plot was N fertilizer at three levels (75, 150 and 225 kg N/ha). The results of analysis of variance showed that water-deficit stress and N fertilizer level significantly affected leaf area index at silking stage, ear length, grain number per ear, 1000-grain weight and grain yield. Stem diameter, ear diameter and harvest index were only affected by irrigation treatments and the interaction between irrigation and N level did not significantly affect the studied traits. Means comparison indicated that ear diameter under optimum irrigation was higher than that under the treatments of irrigation stop at 8-leaf, tasselling and grain-filling stages by 29.9, 19.1 and 33.5%, respectively; and ear length was higher than them by 38.1, 28.9 and 25.2%, respectively. Moreover, the highest grain number per ear, 1000-grain weight and grain yield were obtained under optimum irrigation treatment, and irrigation stop at 10-leaf, tasselling and grain-filling stages decreased grain yield by 52.8, 66.4 and 44.9%, respectively; and it decreased grain number/ear by 45.9, 59.3 and 30.1%, respectively. In addition, optimum irrigation treatment with mean 1000-grain weight of 289.2 g was significantly superior over other irrigation stop treatments by 27.6-42.8% and produced the highest leaf area index at silking stage (4.1). Means comparison of traits at different N levels indicated that N level of 225 kg/ha produced the highest ear length (17.82 cm), grain number per ear (401.9), 1000-grain weight (258.8 g), leaf area index at silking stage (4

NLTE steady-state response matrix method.

Science.gov (United States)

Faussurier, G.; More, R. M.

2000-05-01

A connection between atomic kinetics and non-equilibrium thermodynamics has been recently established by using a collisional-radiative model modified to include line absorption. The calculated net emission can be expressed as a non-local thermodynamic equilibrium (NLTE) symmetric response matrix. In the paper, this connection is extended to both cases of the average-atom model and the Busquet's model (RAdiative-Dependent IOnization Model, RADIOM). The main properties of the response matrix still remain valid. The RADIOM source function found in the literature leads to a diagonal response matrix, stressing the absence of any frequency redistribution among the frequency groups at this order of calculation.

Yield response of cotton, maize, soybean, sugar beet, sunflower and wheat to deficit irrigation

International Nuclear Information System (INIS)

Kirda, C.; Kanber, R.; Tulucu, K.

1995-01-01

Results of several field experiments on deficit irrigation programmes in Turkey are discussed. Deficit irrigation of sugar beet with water stress imposed (i e.,irrigation omitted)during ripening,stage saved nearly 22 % water, yet with no significant yield decrease. An experiment, conducted in Turkey Region, the European part of Turkey,and aimed at studying water production functions of sunflower(i e,yield vs water consumption), revealed that water stress imposed at either head forming or seed filling stags influence yield the least , and 40 % savings of irrigation water supply , compared with traditional practices in the region, can be achieved without significant yield reduction. Water stress imposed at vegetative and flowering stages of maize hindered the yield most significantly. The results showed that deficit irrigation can be a feasible option under limited supply of irrigation if stress occurs during yield formation stage. A four year field experiments aiming at developing deficit irrigation strategies for soybean showed that soybean was at the most sensitive to water stress during flowering and pod filling stages, and irrigation during these stages would ensure high yields. Results of experiments on cotton showed that irrigations omitted during yield formation stage did not significantly hinder the yield. Similarly wheat give good yield response if irrigated at booting,heading and milking stages, depending on w heather conditions. In areas where rainfall at planting is limited, supplementary irrigation during this period can ensure good establishment of wheat crop. 1 tab; 9 figs; 59 refs (Author)

An Efficient Formulation of the Elasto-plastic Constitutive Matrix on Yield Surface Corners

DEFF Research Database (Denmark)

Clausen, Johan; Andersen, Lars; Damkilde, Lars

2009-01-01

A formulation for the elasto-plastic constitutive matrices on discontinuities on yield surfaces is presented, for use in finite element calculations. The formulation entails no rounding of the yield surface or the plastic potential, as it is done in most other formulations, and therefore exact an...

The Effect of Vermicompost and Mycorrhizal Inoculation on Grain Yield and some Physiological Characteristics of Soybean (Glycine max L. under Water Stress Condition

Directory of Open Access Journals (Sweden)

Elham Jahangiri nia

2017-08-01

Full Text Available Introduction Moisture limitation is considered as one of the important limiting factors in soybean growth. Drought stress affects different aspects of soybean growth through making anatomical, physiological and biochemical changes (Tarumingkeng & Coto, 2003. Under dry tension condition, there will be a disturbance in transmitting nutrients, but some useful soil fungi such as mycorrhiza improve production of crops under stress through forming colonies in the root and boosting water and nutrient absorption (Al-Karaki et al., 2004. Using vermicompost in sustainable agriculture strengthens support and activities of beneficial soil microorganisms (such as mycorrhizal fungi and phosphate solubilizing microorganisms in order to provide nutrients required by plants like nitrogen, phosphorus and soluble potassium as well as improving the growth and performance of the crops (Arancon et al., 2004. Materials and methods In order to investigate the effects of vermicompost and mycorrhiza fertilizers on grain yield and some physiological characteristics of soybean under water stress condition an experiment was conducted at Agricultural Research Center of Khorramabad during 2013. The field experiment was carried out based on a randomized complete blocks design arranged in split-plot with four replications. The experiment treatments including irrigation in three levels (after 60, 120 and 180 mm evaporation from pan class A pan, nutrient management in six levels (non-use of vermicompost and mycorhiza fertilizer, inoculated with mycorrhiza fertilizer, consumption of 5 and 10 t.ha-1 vermicompost, consumption of 5 and 10 t.ha-1 vermicompost with mycorrhiza were respectively as the main plots and sub. In current study, RWC, LAI, SPAD were measured during 59 days after planting at the beginning of podding of the control treatment. The temperature of plant leaves were measured by the thermometer (model TM-958 LUTRON infrared Thermometers. To analyze the growth of

Statistical study on applied stress dependence of failure time in stress corrosion cracking of Zircaloy-4 alloy

International Nuclear Information System (INIS)

Hirao, Keiichi; Yamane, Toshimi; Minamino, Yoritoshi; Tanaka, Akiei.

1988-01-01

Effects of applied stress on failure time in stress corrosion cracking of Zircaloy-4 alloy were investigated by Weibull distribution method. Test pieces in the evaculated silica tubes were annealed at 1,073 K for 7.2 x 10 3 s, and then quenched into ice-water. These species under constant applied stresses of 40∼90 % yield stress were immersed in CH 3 OH-1 w% I 2 solution at room temperature. The probability distribution of failure times under applied stress of 40 % of yield stress was described as single Weibull distribution, which had one shape parameter. The probability distributions of failure times under applied stress above 60 % of yield stress were described as composite and mixed Weibull distributions, which had the two shape parameters of Weibull distributions for the regions of the shorter time and longer one of failure. The values of these shape parameters in this study were larger than the value of 1 which corresponded to that of wear out failure. The observation of fracture surfaces and the stress dependence of the shape parameters indicated that the shape parameters both for the times of failure under 40 % of yield stress and for the longer ones above 60 % of yield stress corresponded to intergranular cracking, and that for shorter times of failure corresponded to transgranular cracking and dimple fracture. (author)

Hardening of particle/oil/water suspensions due to capillary bridges: Experimental yield stress and theoretical interpretation.

Science.gov (United States)

Danov, Krassimir D; Georgiev, Mihail T; Kralchevsky, Peter A; Radulova, Gergana M; Gurkov, Theodor D; Stoyanov, Simeon D; Pelan, Eddie G

2018-01-01

Suspensions of colloid particles possess the remarkable property to solidify upon the addition of minimal amount of a second liquid that preferentially wets the particles. The hardening is due to the formation of capillary bridges (pendular rings), which connect the particles. Here, we review works on the mechanical properties of such suspensions and related works on the capillary-bridge force, and present new rheological data for the weakly studied concentration range 30-55 vol% particles. The mechanical strength of the solidified capillary suspensions, characterized by the yield stress Y, is measured at the elastic limit for various volume fractions of the particles and the preferentially wetting liquid. A quantitative theoretical model is developed, which relates Y with the maximum of the capillary-bridge force, projected on the shear plane. A semi-empirical expression for the mean number of capillary bridges per particle is proposed. The model agrees very well with the experimental data and gives a quantitative description of the yield stress, which increases with the rise of interfacial tension and with the volume fractions of particles and capillary bridges, but decreases with the rise of particle radius and contact angle. The quantitative description of capillary force is based on the exact theory and numerical calculation of the capillary bridge profile at various bridge volumes and contact angles. An analytical formula for Y is also derived. The comparison of the theoretical and experimental strain at the elastic limit reveals that the fluidization of the capillary suspension takes place only in a deformation zone of thickness up to several hundred particle diameters, which is adjacent to the rheometer's mobile plate. The reported experimental results refer to water-continuous suspension with hydrophobic particles and oily capillary bridges. The comparison of data for bridges from soybean oil and hexadecane surprisingly indicate that the yield strength is

Mechanical properties and fracture mechanism of as-cast Mg77TM12Zn5Y6 (TM = Cu, Ni) bulk amorphous matrix composites

International Nuclear Information System (INIS)

Qiu, K.Q.; Hu, N.N.; Zhang, H.B.; Jiang, W.H.; Ren, Y.L.; Liaw, P.K.

2009-01-01

Comparative investigations on the microstructures, thermal stability and mechanical properties of Mg 77 Cu 12 Zn 5 Y 6 and Mg 77 Ni 12 Zn 5 Y 6 bulk metallic glass matrix composites were carried out by using scanning electron microscopy (SEM), DSC and compressive tester. The results show that the microstructure of as-cast samples with 3 mm in diameter for Cu-containing alloy is consisted of Mg flakes and dotted Mg 2 Cu phase in the amorphous matrix, while the as-cast Ni-containing alloy with the same diameter is mainly consisted of Mg flakes in the amorphous matrix. The glass transition temperature and supercooled liquid region are 413 K and 27 K for the Cu-containing, 443 K and 32 K for the Ni-containing amorphous matrix composites, respectively. The fracture strength, yield strength and plastic strain are 532 MPa, 390 MPa and 2.4% for the Cu-containing alloy, 667 MPa, 412 MPa and 7% for the Ni-containing alloy, respectively. Furthermore, the fracture mechanism for the amorphous matrix composites was discussed according to both the fracture surfaces and the stress-strain curves.

The Effect of Grain Size and Strain on the Tensile Flow Stress of Aluminium at Room Temperature

DEFF Research Database (Denmark)

Hansen, Niels

1977-01-01

stress-grain size relationship was analyzed in terms of matrix strengthening and grain boundary strengthening according to the dislocation concept of Ashby. At intermediate strains this approach gives a good description of the effect of strain, grain size and purity on the flow stress.......Tensile-stress-strain data over a strain range from 0.2 to 30% were obtained at room temperature for 99.999 and 99.5% aluminium as a function of grain size. The yield stress-grain size relationship can be expressed by a Petch-Hall relation with approximately the same slope for the two materials....... The flow stress-grain size relationship can adequately be expressed by a modified Petch-Hall relation; for 99.999% aluminium material the slope increases with strain through a maximum around 15–20%, whereas for 99.5% aluminium the slope decreases with the strain to zero at strains about 10%. The flow...

Equivalence of Stress and Energy Calculations of Mean Stress

DEFF Research Database (Denmark)

Pedersen, Ole Bøcker; Brown, L. M.

1977-01-01

Calculations of the mean stress in a plastically deformed matrix containing randomly distributed elastic inclusions are considered. The mean stress for an elastically homogeneous material is calculated on the basis of an energy consideration which completely accounts for elastic interactions....... The result is shown to be identical to that obtained from a stress calculation. The possibility of including elastic interactions in the case of elastic inhomogeneity is discussed....

AN EXACT ELASTO-PLASTIC SOLUTION OF METAL-MATRIX COMPOSITE CANTILEVER BEAM LOADED BY A SINGLE FORCE AT ITS FREE END

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Onur SAYMAN

2001-03-01

Full Text Available In the present study, an elastic-plastic stress analysis is carried out in a metal matrix composite cantilever beam loaded by a single force at its free end. A composite consisting of stainless-steel reinforced aluminium was produced for this work. The orientation angle of the fibers is chosen as 0°, 30°, 45°, 60° and 90°. The material is assumed to be perfectly plastic in the elasto-plastic solution. An analytical solution is performed for satisfying both the governing differential equation in the plane stress case and boundary conditions for small plastic deformations. The solution is carried out under the assumption of the Bernoulli-Navier hypotheses. The composite material is assumed as hardening linearly. The Tsai-Hill theory is used as a yield criterion.

Influence of Fuel-Matrix Interaction on the Deformation of U-Mo Dispersion Fuel

Energy Technology Data Exchange (ETDEWEB)

Ryu, Ho Jin [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Kim, Yeon Soo [Argonne National Laboratory, Chicago (United States)

2014-05-15

In order to predict the fuel plate failure leading to breakaway swelling in the meat, an understanding of the effects of the fuel-matrix interaction behavior on the deformation of fuel meat is necessary. However, the effects of IL formation on the development of breakaway swelling have not been studied thoroughly. A mechanism that explains large pore growth that leads to breakaway swelling has not been included in the existing fuel performance models. In this study, the effect of the fuel-matrix interaction on large interfacial porosity development at the IL-Al interface is analyzed using both mechanistic correlations and observations from the post-irradiation examination results of U-Mo Dispersion fuels. The effects of fuel-matrix interaction on the fuel performance of U-Mo/Al Dispersion fuel were investigated. Fuel-matrix interaction bears the causes for breakaway swelling that can lead to a fuel failure under a high-power irradiation condition. Fission gas atoms are released from U-Mo particles to the interaction layer via diffusion and recoil. The fission gases released from the U-Mo and produced in the ILs are further released to the IL-Al interface by diffusion in the IL and recoil. Large pore formation at the IL-Al interface is attributed to the active diffusion of fission gas atoms in the ILs and coalescence between the small bubbles there. A model calculation showed that IL growth increases the probability of forming a breakaway swelling condition. ILs are connected to each other and the Al matrix decreases as ILs grow. When more ILs are interconnected, breakaway swelling can occur when the effective stress from the fission gas pressure in the IL-Al interfacial pore becomes larger than the yield strength of the Al matrix.

Unwinding after high salinity stress: Pea DNA helicase 45 over- expression in tobacco confers high salinity tolerance without affecting yield (abstract)

International Nuclear Information System (INIS)

Tuteja, N.

2005-01-01

Soil salinity is an increasing threat for agriculture and is a major factor in reducing plant productivity; therefore, it is necessary to obtain salinity-tolerant varieties. A typical characteristic of soil salinity is the induction of multiple stress- inducible genes. Some of the genes encoding osmolytes, ion channels or enzymes are able to confer salinity-tolerant phenotypes when transferred to sensitive plants. As salinity stress affects the cellular gene-expression machinery, it is evident that molecules involved in nucleic acid processing including helicases, are likely to be affected as well. DNA helicases unwind duplex DNA and are involved in replication, repair, recombination and transcription while RNA helicases unfold the secondary structures in RNA and are involved in transcription, ribosome biogenesis and translation initiation. We have earlier reported the isolation of a pea DNA helicase 45 (PDH45) that exhibits striking homology with eIF-4A (Plant J. 24:219-230,2000). Here we report that PDH45 mRNA is induced in pea seedlings in response to high salt and its over- expression driven by a constitutive CAMV-355-promoter in tobacco plants confers salinity tolerance, thus suggesting a new pathway for manipulating stress tolerance in crop plants. The T0 transgenic plants showed high-levels of PDH45 protein in normal and stress conditions, as compared to wild type (WT) plants. The T0 transgenics also showed tolerance to high salinity as tested by a leaf disc senescence assay. The T1 transgenics were able to grow to maturity and set normal viable seeds under continuous salinity stress, without any reduction in plant yield, in terms of seed weight. Measurement of Na/sup +/ ions in different parts of the plant showed higher accumulation in the old leaves and negligible in seeds of T1 transgenic lines as compared with the WT plants. The possible mechanism of salinity tolerance will be discussed. Over-expression of PDH45 provides a possible example of the

RESPONSE OF CHILE PEPPER (Capsicum annuum L. TO SALT STRESS AND ORGANIC AND INORGANIC NITROGEN SOURCES: I.GROWTH AND YIELD

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Marco Antonio Huez Lopez

2010-10-01

Full Text Available The effect of two sources of nitrogen on plant growth, and fruit yield of chile pepper (Capsicum annuum L. cv. Sandia grown in greenhouse to increased salinity   were evaluated. An organic source extracted from grass clippings in rates of 120 and 200 kg N ha-1, and another inorganic (ammonium nitrate in rate of 120 kg ha-1 were combined with low, moderate and high (1.5, 4.5, and 6.5 dS m-1 salinity levels arranged in a randomized complete block design replicated four times. Salinity treatments reduced dry matter production, leaf area, relative growth rate and net assimilation rate but increased leaf area ratio. Mean fresh fruit yields decreased for each N rate and source combinations as soil salinity increased. The organic fertilizer produced higher fruit yields tan the inorganic fertilizer. The highest fruit yield was obtained with the increased rate of organic N.    The fruit number was more affected by salinity than the individual fruit weight. This organic fertilizer may be an effective N source for chile pepper and other vegetable crops grown under non- and salt-stressed conditions.

Determination of NABE in urine of high-yield dairy cows in early lactation in conditions of moderate heat stress

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Fratrić Natalija

2010-01-01

Full Text Available The work presents the results of investigations of the effect of moderate heat stress on the acidobasal status in high-yield dairy cows in early lactation. Improving performance in high-yield dairy cows increases their inclination toward metabolic disorders. The most likely to be affected is the acid-base balance, in particular when cows are exposed to heat stress. Investigations so far have shown that the taking of urine samples and their analysis is the best and fastest way to diagnose disorders in the acid-base balance. Investigations were carried out on 7 clinically healthy cows of the Holstein- Friesian breed in the phase of early lactation, 30 to 40 days (on days 30, 33 and 40 following calving during the summer period, during the month of July, when there were significant variations in daily and nightly temperatures. The cows were in the second and fourth lactation, the annual milk yield was 8000 L milk per cow. The average daily milk production in the early phase of lactation ranged from 35 to 40 L. The cows were fed mixed rations (TMR twice daily. Lucerne hay in limited quantities was given to the cows prior to the mixed feed ration. The ration for this animal category was optimized on the grounds of the daily milk production. The balance of cations and anions in the feed ration stood at 95 mEq/kg DM. The results clearly demonstrate the cows' response to moderate heat stress through the defense parameters in urine (urine pH, NABE (net-acid-base-excretion, acids, bases, ammonium ion (NH4. The determination of the kidney NABE yields more correct data than the urine pH on acidotic conditions. The results of examinations of the urine pH do not show any digressions from physiological values and are approximately the same in all cows during the investigated periods. Normal NABE values are from 100-200 mmol/L. Burdening with acid products results in a NABE range from 0-100mmol/L, and metabolic acidosis results in NAB<0 mmol/L. NABE in the cows

Yield surfaces for perforated plates with square arrays of holes

International Nuclear Information System (INIS)

Bhattacharya, A.; Venkat Raj, V.

2004-01-01

A symmetric model of a perforated plate containing a 3x3 array of circular holes, arranged in a square pattern, was chosen and elastoplastic finite element analyses were carried out to determine the limit stresses for both pitch and diagonal directions of loading, for different values of biaxiality ratios. Plane stress conditions were assumed and the Tresca and von Mises yield criteria were employed to obtain two different sets of results. Yield surfaces were constructed and 'general cut-out factors' were determined for four different ligament efficiencies. The FEM results obtained by the authors using the Tresca and von Mises yield criteria were compared with the corresponding results of [J. Pressure Vessel Technol. Trans. ASME (1975) 146-154] and [J. Pressure Vessel Technol. Trans. ASME (1997) 122-126], respectively. The results based on the Tresca yield criterion obtained by the present authors and those in [J. Pressure Vessel Technol. Trans. ASME (1975) 146-154] were found to agree well with each other. In the case of the von Mises yield criterion, the agreement with [J. Pressure Vessel Technol. Trans. ASME 122-126] is generally good. The estimates based on the Tresca yield criterion are seen to result in lower values of limit stresses and cut-out factors as compared to those based on the von Mises yield criterion. The difference is attributed to the yield criterion and the flow rule chosen for the analysis. The shape as well as the size of the yield surface was found to depend on the ligament efficiency

Consolidation effects on tensile properties of an elemental Al matrix composite

Energy Technology Data Exchange (ETDEWEB)

Tang, F. [Building 4515, MS 6064, Metals and Ceramics Division, Oak Ridge National Lab, Oak Ridge, TN 37831 (United States)]. E-mail: tangf@ornl.gov; Meeks, H. [Ceracon Inc., 5150 Fairoaks Blvd. 01-330, Carmichael, CA 95628 (United States); Spowart, J.E. [UES Incorporated, AFRL/MLLM Building 655, 2230 Tenth St. Suite 1, Wright-Patterson AFB, OH 45433 (United States); Gnaeupel-Herold, T. [NIST Center for Neutron Research, 100 Bureau Dr. Stop 8562, Gaithersburg, MD 20899-8562 (United States); Prask, H. [NIST Center for Neutron Research, 100 Bureau Dr. Stop 8562, Gaithersburg, MD 20899-8562 (United States); Anderson, I.E. [Materials and Engineering Physics Program, Ames Laboratory, Iowa State University, Ames, IA 50011 (United States)

2004-11-25

In a simplified composite design, an unalloyed Al matrix was reinforced by spherical Al-Cu-Fe alloy particles (30 vol.%), using either commercial purity (99.7%) or high purity (99.99%) fine powders (diameter < 10 {mu}m). This composite material was consolidated by either vacuum hot pressing (VHP) or quasi-isostatic forging. The spatial distribution of reinforcement particles in both VHP and forged samples was shown to be almost the same by quantitative characterization with a multi-scale area fraction analysis technique. The tensile properties of all composite samples were tested and the forged materials showed significantly higher strength, while the elastic modulus values of all composite materials were close to the upper bound of theoretical predictions. Neutron diffraction measurements showed that there were high compressive residual stresses in the Al matrix of the forged samples and relatively low Al matrix residual stresses (predominantly compressive) in the VHP samples. By tensile tests and neutron diffraction measurements of the forged samples after annealing, it was shown that the high compressive residual stresses in the Al matrix were relieved and that tensile strength was also reduced to almost the same level as that of the VHP samples. Therefore, it was deduced that increased compressive residual stresses and enhanced dislocation densities in the forged composites raised the tensile strength to higher values than those of the VHP composites.

Oxidation effects on the mechanical properties of SiC fiber-reinforced reaction-bonded silicon nitride matrix composites

Science.gov (United States)

Bhatt, Ramakrishna T.

1989-01-01

The room temperature mechanical properties of SiC fiber reinforced reaction bonded silicon nitride composites were measured after 100 hrs exposure at temperatures to 1400 C in nitrogen and oxygen environments. The composites consisted of approx. 30 vol percent uniaxially aligned 142 micron diameter SiC fibers in a reaction bonded Si3N4 matrix. The results indicate that composites heat treated in a nitrogen environment at temperatures to 1400 C showed deformation and fracture behavior equivalent to that of the as-fabricated composites. Also, the composites heat treated in an oxidizing environment beyond 400 C yielded significantly lower tensile strength values. Specifically in the temperature range from 600 to 1000 C, composites retained approx. 40 percent of their as-fabricated strength, and those heat treated in the temperatures from 1200 to 1400 C retained 70 percent. Nonetheless, for all oxygen heat treatment conditions, composite specimens displayed strain capability beyond the matrix fracture stress; a typical behavior of a tough composite.

Oxidizing gel formulation for nuclear decontamination: rheological and acidic properties of the organic matrix and its ozonolysis

International Nuclear Information System (INIS)

Rouy, E.

2003-10-01

An acidic and oxidizing gel was formulated with a purely organic matrix, xanthan gum, at low concentrations (1 to 2 wt %). This polymer gel was investigated in various media (aqueous, acidic and ceric) by means of rheology: shear thinning behaviour, thixotropy, yield stress... Evidences of unexpected rheological properties in highly concentrated media show that xanthan is quite convenient for industrial projection of this type of gel on metallic walls in nuclear plants, notwithstanding its time-limited resistance to oxidation (about a few hours). Complexation mechanisms between ceric species and polar sites of the polymer led us to characterise acidic properties of our xanthan sample by potentiometric titration and 1 H NMR techniques. The matrix was finally treated by ozonolysis to suppress organic residues, as required to handle nuclear wastes. In acidic medium, ozonolysis of the gel was achieved successfully while in acidic and ceric medium this process showed limited efficiency, needing further investigation to be clarified. (author)

Analyzing coastal turbidity under complex terrestrial loads characterized by a 'stress connectivity matrix' with an atmosphere-watershed-coastal ocean coupled model

Science.gov (United States)

Yamamoto, Takahiro; Nadaoka, Kazuo

2018-04-01

Atmospheric, watershed and coastal ocean models were integrated to provide a holistic analysis approach for coastal ocean simulation. The coupled model was applied to coastal ocean in the Philippines where terrestrial sediment loads provided from several adjacent watersheds play a major role in influencing coastal turbidity and are partly responsible for the coastal ecosystem degradation. The coupled model was validated using weather and hydrologic measurement to examine its potential applicability. The results revealed that the coastal water quality may be governed by the loads not only from the adjacent watershed but also from the distant watershed via coastal currents. This important feature of the multiple linkages can be quantitatively characterized by a "stress connectivity matrix", which indicates the complex underlying structure of environmental stresses in coastal ocean. The multiple stress connectivity concept shows the potential advantage of the integrated modelling approach for coastal ocean assessment, which may also serve for compensating the lack of measured data especially in tropical basins.

Investigation of the yield process by deformation luminescence of X-ray irradiated KCl:Ca2+

International Nuclear Information System (INIS)

Nakamura, S.; Ida, K.; Ohgaku, T.

2011-01-01

It is found that deformation luminescence gives us information about the microscopic yield process of X-ray irradiated KCl:Ca 2+ . The stress-strain curve has a macroscopic yield point. But we find that luminescence appears to start before the macroscopic yield. This means that dislocation begin to move before the macroscopic yield because deformation luminescence is attributed to radiation-induced dislocation motion. The beginning of luminescence is considered to be the microscopic yield. Investigating the dependence of microscopic yield stress on strain rate and impurity concentration gives us additional information. The activation volume obtained from the dependence of microscopic yield stress on strain rate is comparable to the value estimated from the concentration of impurity. Then the dislocation starts to move overcoming impurity-vacancy dipoles as obstacles to dislocation motion. The dislocation density starts to increase at the microscopic yield point and then sharply increases to the macroscopic yield.

Thermal stress relaxation in magnesium composites during thermal cycling

Energy Technology Data Exchange (ETDEWEB)

Trojanova, Z.; Lukac, P. (Karlova Univ., Prague (Czech Republic)); Kiehn, J.; Kainer, K.U.; Mordike, B.L. (Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany))

1998-01-01

It has been shown that the internal friction of Mg - Saffil metal matrix composites can be influenced by thermal stresses, if MMCc are submitted to thermal cycling between room temperature and an upper temperature of cycling. These stresses can be accommodated by generation and motion of dislocations giving the formation of the microplastic zones. The thermal stress relaxation depends on the upper temperature of cycling, the volume fraction of reinforcement and the matrix composition and can result in plastic deformation and strain hardening of the matrix without applied stress. The internal friction measurements can be used for non destructive investigation of processes which influence the mechanical properties. (orig.)

Effects of Salinity and Nitrogen Application Methods on Yield and Yield Components of Wheat (Triticum aestivum L.

Directory of Open Access Journals (Sweden)

R Farshid

2012-07-01

Full Text Available To evaluate interaction of salinity stress and nitrogen use methods on yield and yield components, in experiment was conducted in split plot in randomized complete block with 3 replications. Treatments included: salinity of irrigation water levels 1.5, 4.4 and 7.9 ds/m as main plots, and nitrogen treatments 1. using N fertilizer at 3 stage in soil, 2. using two third N fertilizer in soil at planting and tillering and heading and one third in form of foliar application of N at tillering, 4. using and one third in form of foliar application at heading, 3. Using two third of N fertilizer in soil at planting one third of N fertilizer in soil at planting and two third in form of foliar application at tillering and heading, as sub plots. Results this study showed that increased in salt stress significant decreased total yield components such that showed decrease 41/5 kg/h in yield with increase in per unite salinity. Also methods of nitrogen application in salinity condition, have significant effects on total yield components. At the tillering, one stage of foliar with soil application of urea could increase spike no. m-2 and kernels of spike compared with other treatments. Foliar application of urea at heading stage increased kernels weight.

Comparative effectiveness of Pseudomonas and Serratia sp. containing ACC-deaminase for improving growth and yield of wheat (Triticum aestivum L.) under salt-stressed conditions.

Science.gov (United States)

Zahir, Zahir Ahmad; Ghani, Usman; Naveed, Muhammad; Nadeem, Sajid Mahmood; Asghar, Hafiz Naeem

2009-05-01

Ethylene synthesis is accelerated in response to various environmental stresses like salinity. Ten rhizobacterial strains isolated from wheat rhizosphere taken from different salt affected areas were screened for growth promotion of wheat under axenic conditions at 1, 5, 10 and 15 dS m(-1). Three strains, i.e., Pseudomonas putida (N21), Pseudomonas aeruginosa (N39) and Serratia proteamaculans (M35) showing promising performance under axenic conditions were selected for a pot trial at 1.63 (original), 5, 10 and 15 dS m(-1). Results showed that inoculation was effective even in the presence of higher salinity levels. P. putida was the most efficient strain compared to the other strains and significantly increased the plant height, root length, grain yield, 100-grain weight and straw yield up to 52, 60, 76, 19 and 67%, respectively, over uninoculated control at 15 dS m(-1). Similarly, chlorophyll content and K(+)/Na(+) of leaves also increased by P. putida over control. It is highly likely that under salinity stress, 1-aminocyclopropane-1-carboxylic acid-deaminase activity of these microbial strains might have caused reduction in the synthesis of stress (salt)-induced inhibitory levels of ethylene. The results suggested that these strains could be employed for salinity tolerance in wheat; however, P. putida may have better prospects in stress alleviation/reduction.

A matrix formulation of Frobenius power series solutions using products of 4X4 matrices

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Jeremy Mandelkern

2015-08-01

Full Text Available In Coddington and Levison [7, p. 119, Thm. 4.1] and Balser [4, p. 18-19, Thm. 5], matrix formulations of Frobenius theory, near a regular singular point, are given using 2X2 matrix recurrence relations yielding fundamental matrices consisting of two linearly independent solutions together with their quasi-derivatives. In this article we apply a reformulation of these matrix methods to the Bessel equation of nonintegral order. The reformulated approach of this article differs from [7] and [4] by its implementation of a new ``vectorization'' procedure that yields recurrence relations of an altogether different form: namely, it replaces the implicit 2X2 matrix recurrence relations of both [7] and [4] by explicit 4X4 matrix recurrence relations that are implemented by means only of 4X4 matrix products. This new idea of using a vectorization procedure may further enable the development of symbolic manipulator programs for matrix forms of the Frobenius theory.

Feeding sustains photosynthetic quantum yield of a scleractinian coral during thermal stress.

Science.gov (United States)

Borell, Esther M; Bischof, Kai

2008-10-01

Thermal resistance of the coral-zooxanthellae symbiosis has been associated with chronic photoinhibition, increased antioxidant activity and protein repair involving high demands of nitrogen and energy. While the relative importance of heterotrophy as a source of nutrients and energy for cnidarian hosts, and as a means of nitrogen acquisition for their zooxanthellae, is well documented, the effect of feeding on the thermal sensitivity of the symbiotic association has been so far overlooked. Here we examine the effect of zooplankton feeding versus starvation on the bleaching susceptibility and photosynthetic activity of photosystem II (PSII) of zooxanthellae in the scleractinian coral Stylophora pistillata in response to thermal stress (daily temperature rises of 2-3 degrees C) over 10 days, employing pulse-amplitude-modulated chlorophyll fluorometry. Fed and starved corals displayed a decrease in daily maximum potential quantum yield (F (v)/F (m)) of PSII, effective quantum yield (F/F (m)') and relative electron transport rates over the course of 10 days. However after 10 days of exposure to elevated temperature, F (v)/F (m) of fed corals was still 50-70% higher than F (v)/F (m) of starved corals. Starved corals showed strong signs of chronic photoinhibition, which was reflected in a significant decline in nocturnal recovery rates of PSII relative to fed corals. This was paralleled by the progressive inability to dissipate excess excitation energy via non-photochemical quenching (NPQ). After 10 days, NPQ of starved corals had decreased by about 80% relative to fed corals. Feeding treatment had no significant effect on chlorophyll a and c (2) concentrations and zooxanthellae densities, but the mitotic indices were significantly lower in starved than in fed corals. Collectively the results indicate that exogenous food may reduce the photophysiological damage of zooxanthellae that typically leads to bleaching and could therefore play an important role in mediating the

Explicit treatment of N-body correlations within a density-matrix formalism

International Nuclear Information System (INIS)

Shun-Jin, W.; Cassing, W.

1985-01-01

The nuclear many-body problem is reformulated in the density-matrix approach such that n-body correlations are separated out from the reduced density matrix rho/sub n/. A set of equations for the time evolution of the n-body correlations c/sub n/ is derived which allows for physically transparent truncations with respect to the order of correlations. In the stationary limit (c/sub n/ = 0) a restriction to two-body correlations yields a generalized Bethe-Goldstone equation a restriction to body correlations yields generalized Faddeev equations in the density-matrix formulation. Furthermore it can be shown that any truncation of the set of equations (c/sub n/ = 0, n>m) is compatible with conservation laws, a quality which in general is not fulfilled if higher order correlations are treated perturbatively

Sputtering yields of carbon based materials under high particle flux with low energy

Science.gov (United States)

Nakamura, K.; Nagase, A.; Dairaku, M.; Akiba, M.; Araki, M.; Okumura, Y.

1995-04-01

A new ion source which can produce high particle flux beams at low energies has been developed. This paper presents preliminary results on the sputtering yield of the carbon fiber reinforced composites (CFCs) measured with the new ion source. The sputtering yields of 1D and 2D CFCs, which are candidate materials for the divertor armour tiles, have been measured by the weight loss method under the hydrogen and deuterium particle fluxes of 2 ˜ 7 × 10 20/m 2 s at 50 ˜ 150 eV. Preferential sputtering of the matrix was observed on CFCs which included the matrix of 40 ˜ 60 w%. The energy dependence of the sputtering yields was weak. The sputtering yields of CFCs normally irradiated with deuterium beam were from 0.073 to 0.095, and were around three times larger than those with hydrogen beam.

Sputtering yields of carbon based materials under high particle flux with low energy

International Nuclear Information System (INIS)

Nakamura, K.; Nagase, A.; Dairaku, M.; Akiba, M.; Araki, M.; Okumura, Y.

1995-01-01

A new ion source which can produce high particle flux beams at low energies has been developed. This paper presents preliminary results on the sputtering yield of the carbon fiber reinforced composites (CFCs) measured with the new ion source. The sputtering yields of 1D and 2D CFCs, which are candidate materials for the divertor armour tiles, have been measured by the weight loss method under the hydrogen and deuterium particle fluxes of 2 similar 7x10 20 /m 2 s at 50 similar 150 eV. Preferential sputtering of the matrix was observed on CFCs which included the matrix of 40 similar 60 w%. The energy dependence of the sputtering yields was weak. The sputtering yields of CFCs normally irradiated with deuterium beam were from 0.073 to 0.095, and were around three times larger than those with hydrogen beam. ((orig.))

Residual stresses in plastic random systems

NARCIS (Netherlands)

Alava, M.J.; Karttunen, M.E.J.; Niskanen, K.J.

1995-01-01

We show that yielding in elastic plastic materials creates residual stresses when local disorder is present. The intensity of these stresses grows with the external stress and degree of initial disorder. The one-dimensional model we employ also yields a discontinuous transition to perfect plasticity

Evaluation of Drought Stress Effect on Growth, Essential Oil Percentage and Essential Oil Yield of Chamomile (Matricaria recutita L. Presov cultivar and Chicory (Cichorium intybus L. local cultivar in the North of Khuzestan

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roozbeh farhoudi

2017-10-01

Full Text Available Introduction: Iran’s climate is mostly arid and semi-arid, where water availability is a major problem. Water stress substantially alters plant metabolism, decreasing plant growth and photosynthesis and profoundly affecting ecosystems and agriculture, as well as human societies. Unfortunately, water deficiency is increasingly becoming a serious problem in agriculture in Iran whereas the national average annual precipitation is less than 249 mm. Recently, medicinal and aromatic plants have received much attention in several fields such as agroalimentary, perfumes, pharmaceutical industries and natural cosmetic products. Although, secondary metabolites in the medicinal and aromatic plants impressed conventionally by their genetic makeup; moreover their biosynthesis is strongly influenced by environmental factors. It means biotic and abiotic environmental factors affect growth parameter, essential oil yield and constituents. Abiotic environmental stresses like drought have the most effect on medicinal plants. In arid and semi-arid regions like south of Iran where water availability is a major limitation, using plants with low water consumption is one way to manage available water efficiently. Chamomile (Matricaria recutita L. and chicory (Cichorium intybus are annual plants belonging to Asteraceae family naturally widespread in west, northwest and south of Iran and their consumption has a long history in Iranian folklore medicine. Over 120 components have been identified in these plants essential oil, while, chamazulene, camphor, bisabolol oxides A and B, farnesene and ά- bisabolonoxide are the most important ones. Materials and Methods: This study was conducted in Research Farm of Islamic Azad University, Shoshtar Branch, Iran during 2010-2011 in order to evaluate the effects of water stress levels on growth, photosynthesis and essential oil yield of German chamomile (Matricaria recutita L. and chicory (Cichorium intybus. Two water stress

The yield drop at or below 423 K in Zr single crystals and in Ti

International Nuclear Information System (INIS)

Ferron, A.; Malik, L.M.; Dickson, J.I.

1979-01-01

Yield drops were obtained in interrupted tensile and compression tests performed on zirconium single crystals between 262 and 362 K. Near 295 K, where most tests were performed, a minimum yield drop was obtained for an aging performed near the internal stress. For positive stress relaxations and a constant aging time, this yield drop increased linearly with the stress relaxed during aging. This result indicates a significant portion of the yield drop is caused by dislocations gliding to pinning points, which are most probably forest dislocations. A similar behaviour was observed for polycrystalline titanium at 423 K. The yield drops observed in the single crystals at 295 K, after aging at zero stress, increased linearly with the logarithm of the aging time in contrast to the time-independent Haasen-Kelly effect observed in polycrystalline material. (auth)

Dimension 7 operators in the b{yields}s transition

Energy Technology Data Exchange (ETDEWEB)

Chalons, G. [Karlsruhe Univ. (T.H.) (Germany). Inst. fuer Theoretische Teilchenphysik; Domingo, F. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

2013-03-15

We extend the low-energy effective field theory relevant for b{yields}s transitions up to operators of mass-dimension 7 and compute the associated anomalous-dimension matrix. We then compare our findings to the known results for dimension 6 operators and derive a solution for the renormalization group equations involving operators of dimension 7. We finally apply our analysis to a particularly simple case where the Standard Model is extended by an electroweak-magnetic operator and consider limits on this scenario from the decays B{sub s}{yields}{mu}{sup +}{mu}{sup -} and B{yields}K{nu} anti {nu}.

Fibre-matrix bond strength studies of glass, ceramic, and metal matrix composites

Science.gov (United States)

Grande, D. H.; Mandell, J. F.; Hong, K. C. C.

1988-01-01

An indentation test technique for compressively loading the ends of individual fibers to produce debonding has been applied to metal, glass, and glass-ceramic matrix composites; bond strength values at debond initiation are calculated using a finite-element model. Results are correlated with composite longitudinal and interlaminar shear behavior for carbon and Nicalon fiber-reinforced glasses and glass-ceramics including the effects of matrix modifications, processing conditions, and high-temperature oxidation embrittlement. The data indicate that significant bonding to improve off-axis and shear properties can be tolerated before the longitudinal behavior becomes brittle. Residual stress and other mechanical bonding effects are important, but improved analyses and multiaxial interfacial failure criteria are needed to adequately interpret bond strength data in terms of composite performance.

A random matrix model of relaxation

International Nuclear Information System (INIS)

Lebowitz, J L; Pastur, L

2004-01-01

We consider a two-level system, S 2 , coupled to a general n level system, S n , via a random matrix. We derive an integral representation for the mean reduced density matrix ρ(t) of S 2 in the limit n → ∞, and we identify a model of S n which possesses some of the properties expected for macroscopic thermal reservoirs. In particular, it yields the Gibbs form for ρ(∞). We also consider an analog of the van Hove limit and obtain a master equation (Markov dynamics) for the evolution of ρ(t) on an appropriate time scale

The Effects of Drought Stress and Humic Acid on Morphological Traits, Yield and Anthocyanin of Roselle (Hibiscus sabdariffa L.

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mojgan sanjarimijani

2017-08-01

Full Text Available Introduction Roselle (Hibiscus sabdariffa L. as a medicinal plant belongs to the Malvacea family. Their active ingredient increases under water stress. Humic acid bacteria derived from humus and other natural resources have hormonal effects and can improve nutrient absorption to enhance performance especially under stress conditions . Materials and methods This experiment was conducted in the research of agricultural education centre Jiroft in 2013. Field experiment was carried out as split plot design with three replications. Water deficit stress set as main factor with three levels (A1= Irrigation after 50, A2= 100 and A3= 150 mm evaporation from pan class A and humic acid was in four manners (B1= non humic acid, B2= once with Irrigation, B3= once with Irrigation + Once spraying, B4= once with Irrigation + twice Spraying. Humic acid was used to form Irrigation spray in order to arrange with compactness (10 kg.ha-1, (250 ml/100L. In late September, which coincides with the end of the heading, plant height, inflorescence length, number of branches, stem diameter, fresh and dry weight of plant, fresh and dry weight of sepals, were examined. Wagner method was used to measure anthocyanin content sepals (Wagner, 1979. Finally, data was analyzed using SAS 9.1 and means were compared by Duncan’s multiple range test at 5% level of probability. Results and discussion The analysis of variance showed that drought stress and humic acid had significant effect on growth parameters, vegetative and generative yield and anthocyanin. Drought stress decreased plant height, inflorescence length, stem diameterand fresh and dry weight sepals. The highest values of these traits was obtained in the first level of stress (50 mm evaporation from pan class A. Due to the reduction in mentioned properties, reducing the pressure tolerance and the subsequent reduction in drought conditions was considered as division and cell enlargement. The reduction in growth parameters

Modelling of loading, stress relaxation and stress recovery in a shape memory polymer.

Science.gov (United States)

Sweeney, J; Bonner, M; Ward, I M

2014-09-01

A multi-element constitutive model for a lactide-based shape memory polymer has been developed that represents loading to large tensile deformations, stress relaxation and stress recovery at 60, 65 and 70°C. The model consists of parallel Maxwell arms each comprising neo-Hookean and Eyring elements. Guiu-Pratt analysis of the stress relaxation curves yields Eyring parameters. When these parameters are used to define the Eyring process in a single Maxwell arm, the resulting model yields at too low a stress, but gives good predictions for longer times. Stress dip tests show a very stiff response on unloading by a small strain decrement. This would create an unrealistically high stress on loading to large strain if it were modelled by an elastic element. Instead it is modelled by an Eyring process operating via a flow rule that introduces strain hardening after yield. When this process is incorporated into a second parallel Maxwell arm, there results a model that fully represents both stress relaxation and stress dip tests at 60°C. At higher temperatures a third arm is required for valid predictions. Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.

Abscisic acid, a stress hormone helps in improving water relations and yield of sunflower (helianthus annuus l.) hybrids under drought

International Nuclear Information System (INIS)

Hussain, S.; Saleem, M.F.; Cheema, M.A.; Ashraf, M.Y.; Haq, M.A.

2010-01-01

Genotypic variation in water relations under drought is an important index of studying drought tolerance of crops. Abscisic acid (ABA) application helped in mitigating drought stress by improving water relations and yield. Three sunflower hybrids viz., DK-4040 (tall stature), S-278 (medium stature) and SF-187 (short stature) were subjected to different irrigation and ABA application regimes i.e., four irrigations (25 days after sowing (DAS), at bud initiation, at flower initiation and at achene formation) and with no ABA spray, three irrigations (25 days after sowing, at flower initiation and at achene formation) and with no ABA spray, three irrigations (25 days after sowing, at flower initiation and at achene formation) and with ABA spray at bud initiation, three irrigations (25 days after sowing), at bud initiation and at achene formation) and with no ABA spray, three irrigations (25 days after sowing), at bud initiation and at achene formation) and with ABA spray at flower initiation. The experiment was laid out in randomized complete block design with split plot arrangement and had three replications. Exogenous application of ABA under drought at either stage (bud or flower initiation) was helpful in ameliorating drought stress by improving water relations and yield of sunflower hybrids; however response was better when ABA was applied under drought at bud initiation than at flower initiation stage. Sunflower hybrid DK- 4040 showed better enhancement of drought tolerance by exogenous application of ABA under drought than SF-187 and S-278 because it showed more improvement in water potential, osmotic potential, turgor pressure, relative leaf water contents and achene yield. (author)

An alternative approach for modeling strength differential effect in sheet metals with symmetric yield functions

Science.gov (United States)

Kurukuri, Srihari; Worswick, Michael J.

2013-12-01

An alternative approach is proposed to utilize symmetric yield functions for modeling the tension-compression asymmetry commonly observed in hcp materials. In this work, the strength differential (SD) effect is modeled by choosing separate symmetric plane stress yield functions (for example, Barlat Yld 2000-2d) for the tension i.e., in the first quadrant of principal stress space, and compression i.e., third quadrant of principal stress space. In the second and fourth quadrants, the yield locus is constructed by adopting interpolating functions between uniaxial tensile and compressive stress states. In this work, different interpolating functions are chosen and the predictive capability of each approach is discussed. The main advantage of this proposed approach is that the yield locus parameters are deterministic and relatively easy to identify when compared to the Cazacu family of yield functions commonly used for modeling SD effect observed in hcp materials.

Tensile and compressive behavior of Borsic/aluminum

Science.gov (United States)

Herakovich, C. T.; Davis, J. G., Jr.; Viswanathan, C. N.

1977-01-01

The results of an experimental investigation of the mechanical behavior of Borsic/aluminum are presented. Composite laminates were tested in tension and compression for monotonically increasing load and also for variable loading cycles in which the maximum load was increased in each successive cycle. It is shown that significant strain-hardening, and corresponding increase in yield stress, is exhibited by the metal matrix laminates. For matrix dominated laminates, the current yield stress is essentially identical to the previous maximum stress, and unloading is essentially linear with large permanent strains after unloading. For laminates with fiber dominated behavior, the yield stress increases with increase in the previous maximum stress, but the increase in yield stress does not keep pace with the previous maximum stress. These fiber dominated laminates exhibit smaller nonlinear strains, reversed nonlinear behavior during unloading, and smaller permanent strains after unloading. Compression results from sandwich beams and flat coupons are shown to differ considerably. Results from beam specimens tend to exhibit higher values for modulus, yield stress, and strength.

Self-consistent technique for estimating the dynamic yield strength of a shock-loaded material

International Nuclear Information System (INIS)

Asay, J.R.; Lipkin, J.

1978-01-01

A technique is described for estimating the dynamic yield stress in a shocked material. This method employs reloading and unloading data from a shocked state along with a general assumption of yield and hardening behavior to estimate the yield stress in the precompressed state. No other data are necessary for this evaluation, and, therefore, the method has general applicability at high shock pressures and in materials undergoing phase transitions. In some special cases, it is also possible to estimate the complete state of stress in a shocked state. Using this method, the dynamic yield strength of aluminum at 2.06 GPa has been estimated to be 0.26 GPa. This value agrees reasonably well with previous estimates

Yield and flow properties of aluminum alloy AA 8001

International Nuclear Information System (INIS)

Lyons, J.S.; Johnson, H.W.; Han, E.G.

1995-01-01

Aluminum alloy AA 8001 is being used at the Westinghouse Savannah River Company (WSRC) for nuclear reactor fuel and target components. The objective of this research was to determine parameters for predictive models of the compressive flow properties of AA 8001. Seventy-five true strain-rate, hot compression tests were performed. New, quantitative information about the yield and flow behavior of aluminum alloy AA 8001 was determined. Parameters were determined to use in a hyperbolic sine constitutive law so that the yield stress, the peak stress, and the peak strain can be predicted from the temperature-compensated strain-rate, Z. It was found that the onset of strain softening was more strongly dependent on Z than the onset of yielding was

Advanced Ceramic Matrix Composites with Multifunctional and Hybrid Structures

Science.gov (United States)

Singh, Mrityunjay; Morscher, Gregory N.

2004-01-01

Ceramic matrix composites are leading candidate materials for a number of applications in aeronautics, space, energy, and nuclear industries. Potential composite applications differ in their requirements for thickness. For example, many space applications such as "nozzle ramps" or "heat exchangers" require very thin (structures whereas turbine blades would require very thick parts (> or = 1 cm). Little is known about the effect of thickness on stress-strain behavior or the elevated temperature tensile properties controlled by oxidation diffusion. In this study, composites consisting of woven Hi-Nicalon (trademark) fibers a carbon interphase and CVI SiC matrix were fabricated with different numbers of plies and thicknesses. The effect of thickness on matrix crack formation, matrix crack growth and diffusion kinetics will be discussed. In another approach, hybrid fiber-lay up concepts have been utilized to "alloy" desirable properties of different fiber types for mechanical properties, thermal stress management, and oxidation resistance. Such an approach has potential for the C(sub I)-SiC and SiC(sub f)-SiC composite systems. CVI SiC matrix composites with different stacking sequences of woven C fiber (T300) layers and woven SiC fiber (Hi-Nicalon (trademark)) layers were fabricated. The results will be compared to standard C fiber reinforced CVI SiC matrix and Hi-Nicalon reinforced CVI SiC matrix composites. In addition, shear properties of these composites at different temperatures will also be presented. Other design and implementation issues will be discussed along with advantages and benefits of using these materials for various components in high temperature applications.

High-resolution mapping of yield curve shape and evolution for high porosity sandstones

Science.gov (United States)

Bedford, J. D.; Faulkner, D.; Wheeler, J.; Leclere, H.

2017-12-01

The onset of permanent inelastic deformation for porous rock is typically defined by a yield curve plotted in P-Q space, where P is the effective mean stress and Q is the differential stress. Sandstones usually have broadly elliptical shaped yield curves, with the low pressure side of the ellipse associated with localized brittle faulting (dilation) and the high pressure side with distributed ductile deformation (compaction). However recent works have shown that these curves might not be perfectly elliptical and that significant evolution in shape occurs with continued deformation. We therefore use a novel stress-probing methodology to map in high-resolution the yield curve shape for Boise and Idaho Gray sandstones (36-38% porosity) and also investigate curve evolution with increasing deformation. The data reveal yield curves with a much flatter geometry than previously recorded for porous sandstone and that the compactive side of the curve is partly comprised of a near vertical limb. The yield curve evolution is found to be strongly dependent on the nature of inelastic strain. Samples that were compacted under a deviatoric load, with a component of inelastic shear strain, were found to have yield curves with peaks that are approximately 50% higher than similar porosity samples that were hydrostatically compacted (i.e. purely volumetric strain). The difference in yield curve evolution along the different loading paths is attributed to mechanical anisotropy that develops during deviatoric loading by the closure of preferentially orientated fractures. Increased shear strain also leads to the formation of a plateau at the peak of the yield curve as samples deform along the deviatoric loading path. These results have important implications for understanding how the strength of porous rock evolves along different stress paths, including during fluid extraction from hydrocarbon reservoirs where the stress state is rarely isotropic.

Ghost peaks observed after atmospheric pressure matrix-assisted laser desorption/ionization experiments may disclose new ionization mechanism of matrix-assisted hypersonic velocity impact ionization.

Science.gov (United States)

Moskovets, Eugene

2015-08-30

Understanding the mechanisms of matrix-assisted laser desorption/ionization (MALDI) promises improvements in the sensitivity and specificity of many established applications in the field of mass spectrometry. This paper reports a serendipitous observation of a significant ion yield in a post-ionization experiment conducted after the sample had been removed from a standard atmospheric pressure (AP)-MALDI source. This post-ionization is interpreted in terms of collisions of microparticles moving with a hypersonic velocity into a solid surface. Calculations show that the thermal energy released during such collisions is close to that absorbed by the top matrix layer in traditional MALDI. The microparticles, containing both the matrix and analytes, could be detached from a film produced inside the inlet capillary during the sample ablation and accelerated by the flow rushing through the capillary. These observations contribute some new perspective to ion formation in both laser and laser-less matrix-assisted ionization. An AP-MALDI ion source hyphenated with a three-stage high-pressure ion funnel system was utilized for peptide mass analysis. After the laser had been turned off and the MALDI sample removed, ions were detected during a gradual reduction of the background pressure in the first funnel. The constant-rate pressure reduction led to the reproducible appearance of different singly and doubly charged peptide peaks in mass spectra taken a few seconds after the end of the MALDI analysis of a dried-droplet spot. The ion yield as well as the mass range of ions observed with a significant delay after a completion of the primary MALDI analysis depended primarily on the background pressure inside the first funnel. The production of ions in this post-ionization step was exclusively observed during the pressure drop. A lower matrix background and significant increase in relative yield of double-protonated ions are reported. The observations were partially consistent

Effect of Coarse Particle Volume Fraction on the Yield Stress of Muddy Sediments from Marennes Oléron Bay

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A. Pantet

2010-01-01

Full Text Available Coastal erosion results from a combination of various factors, both natural and humaninduced, which have different time and space patterns. In addition, uncertainties still remain about the interactions of the forcing agents, as well as on the significance of non-local causes of erosion. We focused about the surface sediments in the Marennes Oléron bay, after a general description of the site that has many various activities. The superficial sediments show a mechanical behavior, mainly depends on the fine fraction for a composition that contains up to 60% of sandy material. Fine sediments fraction has a typical yield stress depending naturally of concentration or water content. This yield could be modified slightly or significantly by adding silt or sand. As a result, the rheological measurement sensitivity allows us to characterize five typical sediments that correlate with solid fraction and fine fraction.

Heat stress effects on the cumulus cells surrounding the bovine oocyte during maturation: altered matrix metallopeptidase 9 and progesterone production.

Science.gov (United States)

Rispoli, L A; Payton, R R; Gondro, C; Saxton, A M; Nagle, K A; Jenkins, B W; Schrick, F N; Edwards, J L

2013-08-01

When the effects of heat stress are detrimental during maturation, cumulus cells are intimately associated with the oocyte. To determine the extent to which heat stress affects these cells, in this study, transcriptome profiles of the cumulus that surrounded control and heat-stressed oocytes (41 °C during the first 12 h only and then shifted back to 38.5 °C) during in vitro maturation (IVM) were compared using Affymetrix bovine microarrays. The comparison of cumulus-derived profiles revealed a number of transcripts whose levels were increased (n=11) or decreased (n=13) ≥ twofold after heat stress exposure (P1.7-fold decrease in the protein levels of latent matrix metallopeptidase 9 (proMMP9). Heat-induced reductions in transcript levels were noted at 6 h IVM with reductions in proMMP9 protein levels at 18 h IVM (P=0.0002). Independent of temperature, proMMP9 levels at 24 h IVM were positively correlated with the development rate of blastocysts (R²=0.36; P=0.002). The production of progesterone increased during maturation; heat-induced increases were evident by 12 h IVM (P=0.002). Both MMP9 and progesterone are associated with the developmental competence of the oocyte; thus, it seems plausible for some of the negative consequences of heat stress on the cumulus-oocyte complex to be mediated through heat-induced perturbations occurring in the surrounding cumulus.

Effect of Salinity and Silicon on Seed Yield and Yield Components of Purslane Portulaca oleracea L.(

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Z Rahimi

2011-01-01

Full Text Available Abstract In order to study the effects on salinity and silicon application on yield and yield components of purslane (Portulaca oleracea L., an experiment was conducted in a completely randomized desgin with three replications and two factors consisted of four different levels of salinity using NaCl (0, 7, 14, 21dS/m and two levels of silicon (application of one mMol sodium silicate and not application. Increasing salinity concentration significantly caused a negative effect on seed yield. But yield components such as number and weight of seed were more sensitive than number of capsul in main stem in final seed yield. Application of silicon increased seed yield in control but was not significant in salinity levels and leaves and stem biomass. Seed yield and total seed weight in branches was significantly decresed. Weight of 1000 seed in main stem and branches was not significantly different in salinity levels. As a result, purslane could be extremely tolerated to saline conditions, so it seems that it can be cultivated in saline soils and arid regions. Also applied silicon can be increase yield and plant tolerance to environmental stress. Keywords: 1000 seed, Branches, Capsul, Dry weight

Use of abrupt strain path change for determining subsequent yield surface

DEFF Research Database (Denmark)

Kuroda, Mitsutoshi; Tvergaard, Viggo

1999-01-01

is prescribed, which makes the stress point move quickly along the yield surface. It is assumed that a closed-loop testing machine is used for the experiment, so that the strain path can be prescribed according to strain gauge measurements. Relative to the standard method of determining yield surface shapes...... by probing in many different stress directions from the elastic region, using some chosen plastic strain offset, the main advantage of the proposed method is that elastic unloading is not needed prior to tracing the yield surface. The method is illustrated here by a few analyses, first for the simplest how...

On cyclic yield strength in definition of limits for characterisation of fatigue and creep behaviour

Science.gov (United States)

Gorash, Yevgen; MacKenzie, Donald

2017-06-01

This study proposes cyclic yield strength as a potential characteristic of safe design for structures operating under fatigue and creep conditions. Cyclic yield strength is defined on a cyclic stress-strain curve, while monotonic yield strength is defined on a monotonic curve. Both values of strengths are identified using a two-step procedure of the experimental stress-strain curves fitting with application of Ramberg-Osgood and Chaboche material models. A typical S-N curve in stress-life approach for fatigue analysis has a distinctive minimum stress lower bound, the fatigue endurance limit. Comparison of cyclic strength and fatigue limit reveals that they are approximately equal. Thus, safe fatigue design is guaranteed in the purely elastic domain defined by the cyclic yielding. A typical long-term strength curve in time-to-failure approach for creep analysis has two inflections corresponding to the cyclic and monotonic strengths. These inflections separate three domains on the long-term strength curve, which are characterised by different creep fracture modes and creep deformation mechanisms. Therefore, safe creep design is guaranteed in the linear creep domain with brittle failure mode defined by the cyclic yielding. These assumptions are confirmed using three structural steels for normal and high-temperature applications. The advantage of using cyclic yield strength for characterisation of fatigue and creep strength is a relatively quick experimental identification. The total duration of cyclic tests for a cyclic stress-strain curve identification is much less than the typical durations of fatigue and creep rupture tests at the stress levels around the cyclic yield strength.

Modulating the phenology and yield of camelina sativa L. by varying sowing dates under water deficit stress conditions

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Ejaz Ahmad Waraich

2017-05-01

Full Text Available Camelina (Camelina sativa L. an oilseed crop has emerged as a potential source for biofuels and bio-products. Camelina is an economic crop due to its less requirements of agronomic inputs as compared to other oilseed crops. However, it is direly required to evaluate the adaptability of camelina and characterize its production potential. Therefore, a pot experiment was carried out in rain out shelter at the Department of Agronomy, University of Agriculture, Faisalabad, Pakistan to optimize appropriate sowing date with respect to growth and yield potential of different genotypes of camelina under drought stress. Completely randomized design with factorial arrangements was adopted. Three sowing dates with the difference of 10 days (November 13 th, 23rd and December 03rd, two water regimes (100% FC and 60% FC and two camlena genotypes (611 and 618 were used in this experiment. Results indicated that camelina growth and yield related traits were significantly influenced by difference in sowing dates and water regimes. Maximum leaf area index (LAI, crop growth rate (CGR, leaf area duration (LAD, net assimilation rate (NAR and yield related traits were recorded with early sowing (13th November which was followed by sowing on 23rd November and least values of these variables were recorded in late sowing (December 03rd. Plants grown under water deficit conditions (60% FC showed the decreased values of LAI, CGR, LAD, NAR and yield related attributes as compared to normally irrigated plants (100% FC. However, the response of genotypes of camelina 611 and 618 remained statistically similar to each other.

Exogenous L-arginine reduces matrix metalloproteinase-2 and -9 activities and oxidative stress in patients with hypertension

DEFF Research Database (Denmark)

Garcia, Vinicius P; Rocha, Helena N M; Silva, Gustavo M.

2016-01-01

Aims Increased matrix metalloproteinases activity and reduced nitric oxide (NO) bioavailability contributes to development of hypertension and this may be associated with a defective L-arginine-NO pathway. Exogenous L-arginine improves endothelial function to prevent the onset of cardiovascular...... disease, but the mechanism by which this is accomplished remains unclear. We determined the effects of exogenous L-arginine infusion on vascular biomarkers in patients with hypertension. Main methods Venous blood samples were obtained from seven patients with hypertension (45 ± 5 yrs., HT group...... biomarkers between groups during the saline infusion (P > 0.05). Significance Exogenous L-arginine diminished metalloproteinase-2 and -9 activities and MMP-9/TIMP-1 ratio along with restoring the oxidative stress balance in patients with hypertension....

Matrix albedo for discrete ordinates infinite-medium boundary condition

International Nuclear Information System (INIS)

Mathews, K.; Dishaw, J.

2007-01-01

Discrete ordinates problems with an infinite exterior medium (reflector) can be more efficiently computed by eliminating grid cells in the exterior medium and applying a matrix albedo boundary condition. The albedo matrix is a discretized bidirectional reflection distribution function (BRDF) that accounts for the angular quadrature set, spatial quadrature method, and spatial grid that would have been used to model a portion of the exterior medium. The method is exact in slab geometry, and could be used as an approximation in multiple dimensions or curvilinear coordinates. We present an adequate method for computing albedo matrices and demonstrate their use in verifying a discrete ordinates code in slab geometry by comparison with Ganapol's infinite medium semi-analytic TIEL benchmark. With sufficient resolution in the spatial and angular grids and iteration tolerance to yield solutions converged to 6 digits, the conventional (scalar) albedo boundary condition yielded 2-digit accuracy at the boundary, but the matrix albedo solution reproduced the benchmark scalar flux at the boundary to all 6 digits. (authors)

Yield and Failure Behavior Investigated for Cross-Linked Phenolic Resins Using Molecular Dynamics

Science.gov (United States)

Monk, Joshua D.; Lawson, John W.

2016-01-01

Molecular dynamics simulations were conducted to fundamentally evaluate the yield and failure behavior of cross-linked phenolic resins at temperatures below the glass transition. Yield stress was investigated at various temperatures, strain rates, and degrees of cross-linking. The onset of non-linear behavior in the cross-linked phenolic structures was caused by localized irreversible molecular rearrangements through the rotation of methylene linkers followed by the formation or annihilation of neighboring hydrogen bonds. The yield stress results, with respect to temperature and strain rate, could be fit by existing models used to describe yield behavior of amorphous glasses. The degree of cross-linking only indirectly influences the maximum yield stress through its influence on glass transition temperature (Tg), however there is a strong relationship between the degree of cross-linking and the failure mechanism. Low cross-linked samples were able to separate through void formation, whereas the highly cross-linked structures exhibited bond scission.

On a novel matrix method for three-dimensional photoelasticity

International Nuclear Information System (INIS)

Theocaris, P.S.; Gdoutos, E.E.

1978-01-01

A non-destructive method for the photoelastic determination of three-dimensional stress distributions, based on the Mueller and Jones calculi, is developed. The differential equations satisfied by the Stokes and Jones vectors, when a polarized light beam passes through a photoelastic model, presenting rotation of the secondary principal stress directions, are established in matrix form. The Peano-Baker method is used for the solution of these differential equations in a matrix series form, establishing the elements of the Mueller and Jones matrices of the photoelastic model. These matrices are experimentally determined by using different wavelengths in conjunction with Jones' 'equivalence theorem'. The Neumann equations are immediately deduced from the above-mentioned differential equations. (orig.) [de

Comparison of experimental methods for estimating matrix diffusion coefficients for contaminant transport modeling

Science.gov (United States)

Telfeyan, Katherine; Ware, S. Doug; Reimus, Paul W.; Birdsell, Kay H.

2018-02-01

Diffusion cell and diffusion wafer experiments were conducted to compare methods for estimating effective matrix diffusion coefficients in rock core samples from Pahute Mesa at the Nevada Nuclear Security Site (NNSS). A diffusion wafer method, in which a solute diffuses out of a rock matrix that is pre-saturated with water containing the solute, is presented as a simpler alternative to the traditional through-diffusion (diffusion cell) method. Both methods yielded estimates of effective matrix diffusion coefficients that were within the range of values previously reported for NNSS volcanic rocks. The difference between the estimates of the two methods ranged from 14 to 30%, and there was no systematic high or low bias of one method relative to the other. From a transport modeling perspective, these differences are relatively minor when one considers that other variables (e.g., fracture apertures, fracture spacings) influence matrix diffusion to a greater degree and tend to have greater uncertainty than effective matrix diffusion coefficients. For the same relative random errors in concentration measurements, the diffusion cell method yields effective matrix diffusion coefficient estimates that have less uncertainty than the wafer method. However, the wafer method is easier and less costly to implement and yields estimates more quickly, thus allowing a greater number of samples to be analyzed for the same cost and time. Given the relatively good agreement between the methods, and the lack of any apparent bias between the methods, the diffusion wafer method appears to offer advantages over the diffusion cell method if better statistical representation of a given set of rock samples is desired.

Effect of Salicylic Acid on Yield, Component Yield and Essential Oil of Black Cumin (Nigella sativa L. under Water Deficit Stress

Directory of Open Access Journals (Sweden)

E. Rezaei Chiyaneh

2014-12-01

Full Text Available Since the production of medicinal plants can be influenced by environmental factors such as water limitation. In other hand salicylic acid as a plant regulator can enhance drought resistance in plants. In order to investigate the effect of different irrigation intervals on yield, yield components and essential oil of black cumin (Nigella sativa L., a field experiment was conducted a farm located in West Azerbaijan province- city Nagadeh, West- Azerbaijan, during growing season of 2011- 2012. The experiment was arranged as split plot based on a randomized complete block design with three replications. Irrigation intervals (6, 12 and 18 days and three levels of salicylic acid concentration (0, 0.5 and 1 mM considered as in main plots and sub-plots, respectively. Results showed that irrigation had significant effects on all characteristics such as Plant height, number of follicule per plant, number of seed per follicule, biological yield, grain yield, essential oil content and essential oil yield with the exception of 1000- seed weight. With increasing irrigation intervals from 6 to 18 days, plant height, number of follicule per plant, number of seed per follicule, biological yield, grain yield, essential oil percentage and essential oil yield were decreased up to 49, 52, 40, 35, 43, 20 and 55 %, respectively. In contrast, yield components and yield were enhanced up to treatments 0.5 mM of salicylic acid. Grain yield and essential oil yield with application of 0.5 mM salicylic acid increased up to 13 and 11 % compared to control, respectively. It seems that due to the limited sources of water in the region irrigation after 12 days and 0.5 mM salicylic acid concentration are suitable for black cumin grain production.

Matrix of transmission in structural dynamics

International Nuclear Information System (INIS)

Mukherjee, S.

1975-01-01

The problem of close-coupled systems and cantilever type buildings can be treated efficiently by means of the very general and versatile method of transmission matrix. The expression 'matrix of transmission' is used to point out the fact that the method to be described differs fundamentally from another method related to matrix calculus, and also successfully used in vibration problem. In this method, forces and displacements are introduced as the 'unknowns' of the problem. The 'matrix of transmission' relates these quantities at one point of the structure to those at the neighbouring point. The natural frequencies of a freely vibrating elastic system can be found by applying proper end conditions. The end conditions will yield the frequency determinate to zero. By using suitable numerical method, the natural frequencies and mode shapes are determined, by making a frequency sweep within the range of interest. Results of analysis of a typical nuclear building by this method show very close agreement with the results obtained by using ASKA and SAP IV Program

Mechanical properties and fracture mechanism of as-cast Mg{sub 77}TM{sub 12}Zn{sub 5}Y{sub 6} (TM = Cu, Ni) bulk amorphous matrix composites

Energy Technology Data Exchange (ETDEWEB)

Qiu, K.Q. [School of Materials Science and Engineering, Shenyang University of Technology, Shenyang 110178 (China)], E-mail: kqqiu@yahoo.com.cn; Hu, N.N.; Zhang, H.B. [School of Materials Science and Engineering, Shenyang University of Technology, Shenyang 110178 (China); Jiang, W.H. [Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37990 (United States); Ren, Y.L. [School of Materials Science and Engineering, Shenyang University of Technology, Shenyang 110178 (China); Liaw, P.K. [Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37990 (United States)

2009-06-10

Comparative investigations on the microstructures, thermal stability and mechanical properties of Mg{sub 77}Cu{sub 12}Zn{sub 5}Y{sub 6} and Mg{sub 77}Ni{sub 12}Zn{sub 5}Y{sub 6} bulk metallic glass matrix composites were carried out by using scanning electron microscopy (SEM), DSC and compressive tester. The results show that the microstructure of as-cast samples with 3 mm in diameter for Cu-containing alloy is consisted of Mg flakes and dotted Mg{sub 2}Cu phase in the amorphous matrix, while the as-cast Ni-containing alloy with the same diameter is mainly consisted of Mg flakes in the amorphous matrix. The glass transition temperature and supercooled liquid region are 413 K and 27 K for the Cu-containing, 443 K and 32 K for the Ni-containing amorphous matrix composites, respectively. The fracture strength, yield strength and plastic strain are 532 MPa, 390 MPa and 2.4% for the Cu-containing alloy, 667 MPa, 412 MPa and 7% for the Ni-containing alloy, respectively. Furthermore, the fracture mechanism for the amorphous matrix composites was discussed according to both the fracture surfaces and the stress-strain curves.

Simulations of embedded lateral stress gauge profiles in shocked targets

International Nuclear Information System (INIS)

Winter, R E; Harris, E J

2008-01-01

In principle, stress gauges mounted to measure lateral stresses in a shocked matrix allow the shear strength of the material to be determined. However, interpreting the resistance profiles from lateral stress gauges is hindered by the fact that the stress field in the vicinity of the insulating layer in which the gauges are embedded can differ significantly from the stress field that would be generated in the sample if no gauge were present. A series of high resolution Eulerian hydrocode simulations have been run which suggest that the stresses in the insulating layer vary with distance and time in a way that depends on the thickness of the layer, the shock strength and the elastic and plastic properties of both the layer and the matrix. In particular, if the shock velocity in the matrix material is high the stress at a typical gauge position initially rises to a sharp peak then falls with time, but when the shock velocity in the matrix is low the stress rises relatively gradually throughout the time of interest. The shapes of the stress versus time profiles predicted by the hydrocode compare well with the results of lateral gauge experiments on several different materials. It is concluded that lateral gauges can be used to measure the dynamic strength of materials provided high resolution computer simulation is used to take account of the perturbation of the stress field in the shocked sample caused by the gauges

Determination of the CKM matrix element vertical stroke V{sub cb} vertical stroke, the B {yields} X{sub s}{gamma} decay rate, and the b-quark mass

Energy Technology Data Exchange (ETDEWEB)

Bernlochner, Florian Urs

2011-09-15

In this work, the preliminary measurements of two fundamental parameters of the Standard Model of particles physics are presented: the CKM matrix element vertical stroke V{sub cb} vertical stroke, and the b-quark mass. The measurement of the absolute value of the CKM matrix element V{sub cb} uses the full set of recorded data of 429.06 fb{sup -1} of B anti B mesons of the BABAR experiment. The CKM matrix element is obtained by measuring the branching fractions and non-perturbative shape parameters of the two transitions into the charmed 1S ground states, B {yields} Dl{nu}{sub l} and B {yields} D{sup *}l {nu}{sub l}, respectively. The kinematic of the produced lepton is measured and the kinematics of the short-lived charmed mesons is reconstructed from kaon and pion candidates. By combining the reconstructed three-momenta of both particles with the angular information of the decay, three independent variables can be obtained. The measured distributions in these variables are analyzed in a three-dimensional global fit, which simultaneously extracts the decay parameters and branching fractions of both charmed transitions. We find that B {yields} Dl {nu}{sub l}: vertical stroke V{sub cb} vertical stroke =(36.14{+-}0.57{sub stat.}{+-}1.30{sub sys.}{+-}0.80{sub theo.}) x 10{sup -3}, B {yields} D{sup *}l {nu}{sub l}: vertical stroke V{sub cb} vertical stroke =(39.71{+-}0.26{sub stat.}{+-}0.73{sub sys.}{+-}0.74{sub theo.}) x 10{sup -3}, where the uncertainties are statistical, systematic, and theoretical, respectively. In the Standard Model, both measured values of vertical stroke V{sub cb} vertical stroke can be averaged to further minimize the uncertainties. We find Combined: vertical stroke V{sub cb} vertical stroke =(38.29{+-}0.26{sub stat.}{+-}0.64{sub sys.}{+-}0.52{sub theo.}) x 10{sup -3}. Furthermore, several scenarios are explored how possible future unquenched lattice QCD points can be incorporated into the measurement, to further reduce the uncertainty on

Rotational covariance and light-front current matrix elements

International Nuclear Information System (INIS)

Keister, B.D.

1994-01-01

Light-front current matrix elements for elastic scattering from hadrons with spin 1 or greater must satisfy a nontrivial constraint associated with the requirement of rotational covariance for the current operator. Using a model ρ meson as a prototype for hadronic quark models, this constraint and its implications are studied at both low and high momentum transfers. In the kinematic region appropriate for asymptotic QCD, helicity rules, together with the rotational covariance condition, yield an additional relation between the light-front current matrix elements

Influence of moisture stress on growth, dry matter yield and ...

African Journals Online (AJOL)

The effects of moisture stress were evaluated in four Indigofera species (I. amorphoides, I. arrecta, I. coerulea and I. vicioides) using a pot experiment under glasshouse conditions. The aim was to examine the influence of moisture-deficit stress on physiological attributes and performance of the four Indigofera species.

Matrix density effects on the mechanical properties of SiC fiber-reinforced silicon nitride matrix properties

Science.gov (United States)

Bhatt, Ramakrishna T.; Kiser, Lames D.

1990-01-01

The room temperature mechanical properties were measured for SiC fiber reinforced reaction-bonded silicon nitride composites (SiC/RBSN) of different densities. The composites consisted of approx. 30 vol percent uniaxially aligned 142 micron diameter SiC fibers (Textron SCS-6) in a reaction-bonded Si3N4 matrix. The composite density was varied by changing the consolidation pressure during RBSN processing and by hot isostatically pressing the SiC/RBSN composites. Results indicate that as the consolidation pressure was increased from 27 to 138 MPa, the average pore size of the nitrided composites decreased from 0.04 to 0.02 microns and the composite density increased from 2.07 to 2.45 gm/cc. Nonetheless, these improvements resulted in only small increases in the first matrix cracking stress, primary elastic modulus, and ultimate tensile strength values of the composites. In contrast, HIP consolidation of SiC/RBSN resulted in a fully dense material whose first matrix cracking stress and elastic modulus were approx. 15 and 50 percent higher, respectively, and ultimate tensile strength values were approx. 40 percent lower than those for unHIPed SiC/RBSN composites. The modulus behavior for all specimens can be explained by simple rule-of-mixture theory. Also, the loss in ultimate strength for the HIPed composites appears to be related to a degradation in fiber strength at the HIP temperature. However, the density effect on matrix fracture strength was much less than would be expected based on typical monolithic Si3N4 behavior, suggesting that composite theory is indeed operating. Possible practical implications of these observations are discussed.

Study of MA Effect on Yield Strength and Ductility of X80 Linepipe Steels Weld

Science.gov (United States)

Huda, Nazmul; Lazor, Robert; Gerlich, Adrian P.

2017-09-01

Multipass GMAW (Gas Metal Arc Welding) welding was used to join X80 linepipe materials using two weld metals of slightly different compositions. Welding wires with diameters of 0.984 and 0.909 mm were used while applying the same heat input in each pass. The slight difference in the wire diameters resulted in different HAZ microstructures. The microstructures in the doubly reheated HAZ of both welds were found to contain bainite-ferrite. However, etching also revealed a difference in martensite-austenite (MA) fraction in these reheated zones. The MA exhibited twice the hardness of ferrite when measured by nanoindentation. Tensile testing from the reheated zone of both welds revealed a difference in yield strength, tensile strength and elongation of the transverse weld specimens. In the reheated zone of weld A, (produced with a 0.984 mm wire) a higher fraction of MA was observed, which resulted in higher strength but lower elongation compared to weld B. The ductility of weld A was found severely impaired (to nearly half of weld B) due to formation of closely spaced voids around the MA, along with debonding of MA from the matrix, which occurs just above the yield stress.

Phase diagrams of ferroelectric nanocrystals strained by an elastic matrix

Science.gov (United States)

Nikitchenko, A. I.; Azovtsev, A. V.; Pertsev, N. A.

2018-01-01

Ferroelectric crystallites embedded into a dielectric matrix experience temperature-dependent elastic strains caused by differences in the thermal expansion of the crystallites and the matrix. Owing to the electrostriction, these lattice strains may affect polarization states of ferroelectric inclusions significantly, making them different from those of a stress-free bulk crystal. Here, using a nonlinear thermodynamic theory, we study the mechanical effect of elastic matrix on the phase states of embedded single-domain ferroelectric nanocrystals. Their equilibrium polarization states are determined by minimizing a special thermodynamic potential that describes the energetics of an ellipsoidal ferroelectric inclusion surrounded by a linear elastic medium. To demonstrate the stability ranges of such states for a given material combination, we construct a phase diagram, where the inclusion’s shape anisotropy and temperature are used as two parameters. The ‘shape-temperature’ phase diagrams are calculated numerically for PbTiO3 and BaTiO3 nanocrystals embedded into representative dielectric matrices generating tensile (silica glass) or compressive (potassium silicate glass) thermal stresses inside ferroelectric inclusions. The developed phase maps demonstrate that the joint effect of thermal stresses and matrix-induced elastic clamping of ferroelectric inclusions gives rise to several important features in the polarization behavior of PbTiO3 and BaTiO3 nanocrystals. In particular, the Curie temperature displays a nonmonotonic variation with the ellipsoid’s aspect ratio, being minimal for spherical inclusions. Furthermore, the diagrams show that the polarization orientation with respect to the ellipsoid’s symmetry axis is controlled by the shape anisotropy and the sign of thermal stresses. Under certain conditions, the mechanical inclusion-matrix interaction qualitatively alters the evolution of ferroelectric states on cooling, inducing a structural transition

Mesoporous tungsten titanate as matrix for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis of biomolecules

International Nuclear Information System (INIS)

Shan Zhe; Han Lu; Yuan Minjia; Deng Chunhui; Zhao Dongyuan; Tu Bo; Yang Pengyuan

2007-01-01

In this paper, mesoporous tungsten titanate (WTiO) with different nano-pore structures was utilized as matrix for the analysis of short peptides by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). Effect of characteristic features of mesoporous matrices on laser desorption/ionization process was investigated. Experiments showed that the ordered two-dimensional and three-dimensional mesoporous matrices were superior in performance to the non-ordered WTiO matrix. The dramatic enhancement of signal sensitivity by the ordered mesoporous matrices can be reasonably attributed to the ordered structure, which facilitated the understanding on structure-function relationship in mesoporous cavity for laser desorption process of adsorbed biomolecules. With the ordered mesoporous matrix, the short peptides are successfully detected. The presence of trace alkali metal salt effectively increased the analyte ion yields and the MALDI-TOFMS using the inorganic mesoporous matrices displayed a high salt tolerance. The developed technique also showed a satisfactory performance in peptide-mapping and amino-acid sequencing analysis

Assessment of Matrix Metalloproteinases by Gelatin Zymography.

Science.gov (United States)

Cathcart, Jillian

2016-01-01

Matrix metalloproteinases are endopeptidases responsible for remodeling of the extracellular matrix and have been identified as critical contributors to breast cancer progression. Gelatin zymography is a valuable tool which allows the analysis of MMP expression. In this approach, enzymes are resolved electrophoretically on a sodium dodecyl sulfate-polyacrylamide gel copolymerized with the substrate for the MMP of interest. Post electrophoresis, the enzymes are refolded in order for proteolysis of the incorporated substrate to occur. This assay yields valuable information about MMP isoforms or changes in activation and can be used to analyze the role of MMPs in normal versus pathological conditions.

Combining ability for maize grain yield and other agronomic ...

African Journals Online (AJOL)

Field experiments were conducted at the University of Ilorin Teaching and Research Farm in 2005 and 2006 cropping seasons with the objective to evaluate the combining ability for maize grain yield and other agronomic characters in 10 open pollinated maize varieties, which have been selected for high yield and stress ...

Effect of Foliar Application of Phosphorus and Water Deficit on Yield and Yield Components of Winter Wheat (Cultivar Alvand

Directory of Open Access Journals (Sweden)

M. Vafapour

2011-04-01

Full Text Available In order to study the effects of foliar application of phosphorus (P and water deficit on yield and yield components of winter wheat (Triticum aestivum L., cv. Alvand, a split-plot experiment, with completely randomized blocks design and three replications, was carried out at the Research Farm of Boyer Ahmad Agricultural and Natural Resources Research Station, 13 km west of Yasouj, in 2008-2009. The main plots were irrigation at three levels (1- full irrigation (control, 2- deficit irrigation from the stem elongation to booting stage, and 3- deficit irrigation from booting stage to the end of growth period and the subplots were five levels of foliar application of P fertilizer (0, 3, 6, 9 and 12 kg/ha KH2PO4. The results showed that the effects of different irrigation regimes and foliar application of P were significant on all traits, and their interaction was significant on plant height, number of grain per spike, grain yield and biological yield. Full irrigation and foliar application of 6 kg/ha P produced the highest grain and biological yield (6000 and 14170 kg/ha, respectively and deficit irrigation from the stem elongation to booting stage without foliar application of P produced the lowest grain and biological yield (2920 and 8219 kg/ha, respectively. Foliar application of P affects significantly the evaluated traits only in drought-stress treatments and its effect was not significant in full irrigation treatment. In general, foliar application of 9 kg/ha P compensated the losses in wheat due to drought stress.

Residual stresses in laser direct metal deposited Waspaloy

Energy Technology Data Exchange (ETDEWEB)

Moat, R.J., E-mail: richard.moat@manchester.ac.uk [School of Materials, University of Manchester, Grosvenor Street, Manchester M1 7HS (United Kingdom); Pinkerton, A.J.; Li, L. [Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, University of Manchester, M60 1QD (United Kingdom); Withers, P.J.; Preuss, M. [School of Materials, University of Manchester, Grosvenor Street, Manchester M1 7HS (United Kingdom)

2011-03-15

Research highlights: {yields} Neutron diffraction and the contour method show good agreement. {yields} Tensile stresses found parallel to the surfaces. {yields} Compressive stresses within the bulk of the structures. {yields} Residual stress weakly dependent on the laser pulse parameters. {yields} Maximum tensile residual stress unaffected across range of pulse parameters used. - Abstract: This paper reports a study into the effect of laser pulse length and duty cycle on the residual stress distributions in multi-track laser direct metal deposits of Waspaloy onto an Inconel 718 substrate. The residual stresses have been evaluated using neutron diffraction and the contour method, while electron microscopy and micro hardness indentation have been used to map the concomitant microstructural variation. In all cases, near the tops of the deposited walls, the longitudinal stresses are tensile towards the mid-length of the wall, while the stresses perpendicular to the substrate are negligible. By contrast near the base of the walls, the stresses along the direction of deposition are small, while the stresses perpendicular to the substrate are compressive at the centre and tensile towards the ends. Consistent with previous observations, the stresses parallel to free surfaces are tensile, balanced by compressive stresses in the interior (an inverse quench stress profile). These profiles have been found to be weakly dependent on the laser pulse parameters, most notably an increase in tensile stress gradient with increasing duty cycle, but the maximum residual stresses are largely unaffected. Furthermore, microstructural analysis has shown that the effect of laser pulse parameters on grain morphology in multi-track thick walls is less marked than previously reported for single-track wall structures.

Effect of Water Stress and Sulfur Fertilizer on Grain Yield, Chlorophyll and Nutrient Status of Black Cumin (Nigella Sativa L.)