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Evaluating Leaf and Canopy Reflectance of Stressed Rice Plants to Monitor Arsenic Contamination
摘要： Arsenic contamination is a serious problem in rice cultivated soils of many developing countries. Hence, it is critical to monitor and control arsenic uptake in rice plants to avoid adverse effects on human health. This study evaluated the feasibility of using re?ectance spectroscopy to monitor arsenic in rice plants. Four arsenic levels were induced in hydroponically grown rice plants with application of 0, 5, 10 and 20 μmol¨ L′1 sodium arsenate. Re?ectance spectra of upper fully expanded leaves were acquired over visible and infrared (NIR) wavelengths. Additionally, canopy re?ectance for the four arsenic levels was simulated using SAIL (Scattering by Arbitrarily Inclined Leaves) model for various soil moisture conditions and leaf area indices (LAI). Further, sensitivity of various vegetative indices (VIs) to arsenic levels was assessed. Results suggest that plants accumulate high arsenic amounts causing plant stress and changes in re?ectance characteristics. All leaf spectra based VIs related strongly with arsenic with coef?cient of determination (r2) greater than 0.6 while at canopy scale, background re?ectance and LAI confounded with spectral signals of arsenic affecting the VIs’ performance. Among studied VIs, combined index, transformed chlorophyll absorption re?ectance index (TCARI)/optimized soil adjusted vegetation index (OSAVI) exhibited higher sensitivity to arsenic levels and better resistance to soil backgrounds and LAI followed by red edge based VIs (modi?ed chlorophyll absorption re?ectance index (MCARI) and TCARI) suggesting that these VIs could prove to be valuable aids for monitoring arsenic in rice ?elds.
关键词： SAIL model,spectral re?ectance,vegetative indices,arsenic uptake,leaf chlorophyll,red edge,plant stress,soil re?ectance,LAI,rice
更新于2025-09-09 09:28:46
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Identification of Heat-Induced Proteomes in Tomato Microspores Using LCM- Proteomics Analysis
摘要： Pollen development is highly susceptible to heat stress (HS) and the production of inviable pollen causes reduction in seed- and fruit-set in plants. This study was carried out to identify HS-induced pollen proteins and the associated biological processes in tomato (Solanum lycopersicum). Tomato ‘Micro-Tom’ plants were incubated under 32°C//22°C (day/night, 12/12 h) for two weeks for heat treatment, and the non-treated control plants were incubated for the same time period at 25°C /22°C. Flower buds of 5 mm in length were confirmed to contain the heat sensitive uninucleate microspores. Pollen cells were harvested using laser capture microdissection (LCM) and protein was extracted using a one-step method under high pressure and vacuum. Approximately 60,000 LCM-harvested microspore cells yielded about 18-20 μg proteins. The tandem mass tags (TMT) proteomics analysis identified a total of 6018 proteins, 4784 proteins were quantified, 37 proteins were identified as HS up-regulated significantly changed proteins (SCPs), and 83 proteins as HS down (dn)-regulated SCPs. Further analysis using the plant MetGenMap system showed that the HS up-regulated SCPs were enriched in the heat acclimation, pollen wall formation, protein folding/refolding gene ontology (GO) biological processes, and the HS dn-regulated SCPs were placed in the carbohydrate catabolism and de-novo protein biosynthesis GO terms. Biological processes such as mitosis, resistance to oxidative stresses, and carbohydrate and lipid metabolic processes contain both the HS up-, and dn-regulated SCPs. These results indicate that the LCM-TMT proteomics workflow is highly efficient in the identification of HS-induced pollen proteomes. These HS induced SCPs will be used for exploring heat tolerance of tomato pollens. The proteomics data are available via ProteomeXchange with identifier PXD010218.
关键词： Tomato,Protein functional classification,Heat stress,LCM-TMT-proteomics,Pollen,Viability,Microspores
更新于2025-09-09 09:28:46
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Stress control of tensile-strained In <sub/>1?</sub><sub/><i>x</i> </sub> Ga <sub/><i>x</i> </sub> P nanomechanical string resonators
摘要： We investigate the mechanical properties of freely suspended nanostrings fabricated from tensile-stressed, crystalline In1?xGaxP. The intrinsic strain arises during epitaxial growth as a consequence of the lattice mismatch between the thin film and the substrate, and is confirmed by x-ray diffraction measurements. The flexural eigenfrequencies of the nanomechanical string resonators reveal an orientation dependent stress with a maximum value of 650 MPa. The angular dependence is explained by a combination of anisotropic Young’s modulus and a change of elastic properties caused by defects. As a function of the crystal orientation, a stress variation of up to 50% is observed. This enables fine tuning of the tensile stress for any given Ga content x, which implies interesting prospects for the study of high Q nanomechanical systems.
关键词： In1?xGaxP,tensile-strained,defects,nanomechanical string resonators,Young’s modulus,stress control
更新于2025-09-09 09:28:46
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A Flow Cytometric Study of ER Stress and Autophagy
摘要： The mechanistic link between ER stress, autophagy, and resultant cell death was investigated by the use of drugs Thapsigargin (Tg) and Chloroquine (CQ) with prior induction and or blockade of autophagy and apoptosis which modulated the ER stress response and resultant form of cell death. All these biological processes can be measured flow cytometrically allowing the determination of the type of cell death, G1 cell cycle arrest, cell cycle dependent measurement of ER stress transducer PERK, misfolded proteins, reticulophagy, and autophagy marker LC3B. Jurkat cells after Tg or CQ treatment became necrotic and apoptotic, showed G1 cell cycle arrest, autophagy, and ER stress. Prior induction of autophagy before ER stress increased levels of necrotic and apoptotic cell death. Autophagy was further up-regulated, while PERK was reduced or abrogated. CQ showed reduced levels of misfolded proteins and reticulophagy, while Tg showed no change in misfolded protein levels but increased reticulophagy and thus displayed more ER stress. Prior blockade of apoptosis before induction of ER stress resulted in cell survival except with high Tg levels which induced necrosis. Autophagy was up-regulated with modulation of PERK and reticulophagy levels with an abrogation of the misfolded protein response. Blockade of apoptosis with induction of autophagy before ER stress showed death by necrosis with high dose drugs and cell survival with low doses of drugs. CQ induced reduced levels G1 cell cycle arrest while it was maintained with Tg. Autophagy was also maintained with reduced levels of ER stress. These data demonstrates a profound link between the processes of ER stress, autophagy, and the resultant form of cell death all of which can be modulated depending upon the sequence and concentration of drugs employed.
关键词： misfolded proteins,autophagy,PERK,ER stress,reticulophagy
更新于2025-09-09 09:28:46
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Heterogeneity governs diameter-dependent toughness and strength in SiC nanowires
摘要： Using a combination of density functional theory and molecular dynamics simulations, this paper reveals the atomistic origin of diameter-dependent extreme mechanical behavior of [111] 3C-SiC nanowires obtained from an energy-based framework. Our results suggest that heterogeneity in atomic stress and variations in diameter-dependent potential-energy density have a profound impact on extreme mechanical properties in the nanowires. The heterogeneity in stress evolves from the nonuniform bond lengths mediated by low coordinated surface atoms—and it penetrates the entire cross section in thinner nanowires and constitutes the atomistic basis for their large reduction in fracture strain, toughness, and strength. Although stress heterogeneity is substantially higher in ultrathin nanowires, its intensity drops and saturates rapidly in larger nanowires following a nonlinear dependence on diameter. The maximum stress heterogeneity in a cross section localizes crack nucleation at the core in ultrathin nanowires but near the surface in larger nanowires. Moreover results show that stiffness, toughness, strength, and fracture strain of the nanowires increase nonlinearly with increasing diameter and saturate at a lower value compared to bulk SiC. In addition to resolving wide discrepancies in the reported values of the ?rst-order elastic modulus in SiC nanowires, the ?ndings highlight heterogeneity as a critical factor for inducing diameter-dependent extreme mechanical behavior in brittle nanowires.
关键词： heterogeneity,atomic stress,strength,toughness,potential-energy density,fracture strain,SiC nanowires,diameter-dependent,mechanical properties
更新于2025-09-09 09:28:46
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Optical study of stress hormone-induced nanoscale structural alteration in brain using partial wave spectroscopic (PWS) microscopy
摘要： Chronic stress affects nano to microscale structures of the brain cells/tissues due to suppression of neural growths and reconnections, hence the neuronal activities. This results in depression, memory loss and even death of the brain cells. Our recently developed novel optical technique, partial wave spectroscopic (PWS) microscopy has nanoscale sensitivity, and hence, can detect nanoscale changes in brain tissues due to stress. In this study, we applied this technique to quantify the stress related structural changes in the corticosterone-treated mouse model of stress. Our results show that brains from corticosterone-treated mice showed higher nanoscale structural disorder in the hippocampal region as compared to the brain from normal (vehicle) mice. The increase in structural alteration correlates with the duration of the stress. We further quantified the relative changes and the spatial localization of these changes in this mouse model and found out that the maximum changes occurred nearly symmetrically in both regions of the hippocampus. The mRNA for stress-related genes, BDNF and TrkB were also significantly reduced in the hippocampus of corticosterone-treated mice compared to that in control mice. These results indicate that chronic corticosterone treatment induces nanoscale structural alterations in mouse brain that corresponds to changes in stress-related gene expression.
关键词： brain tissues,Stress,disorder strength,PWS,hippocampus,corticosterone
更新于2025-09-09 09:28:46
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(111)Si thin layers detachment by stress-induced spallation
摘要： In this work, results of controlled detachment of (111) silicon by stress induced spalling (SIS) process, which is based on a gluing on a metallic stressor layer by an epoxy adhesive on top of a silicon substrate, are presented. It is shown that silicon foils mainly (1x1) cm2 with different thicknesses (~50-170 μm) can be successfully detached using different materials (steel, copper, aluminum, nickel and titanium) as stressor layers with thicknesses ~50-500 μm. Such detachment can be realized by dipping of a stressor/glue/silicon wafer based structure into liquid nitrogen. As a result, Si foils with different thicknesses from ~50 μm to ~170 μm can be detached. An analytical and numerical approaches based on principles of linear elastic fracture mechanics is developed and they are shown that such approaches can predict general trends and conditions for the detachment of silicon foils with desired thicknesses using a stressor layer. Raman spectroscopy analysis of the residual stresses in detached silicon foils shows, that tensile stresses (up to - 36MPa) as well as higher value compressive stresses (up to ~444 MPa) are present in such foils. Moreover, optical and scanning electron microscopy (SEM) measurements show that surface of the detached foils exhibits some periodic lines originated by stresses.
关键词： Exfoliation of silicon,Thermal stress,Raman spectroscopy,Kerf-free,photovoltaics (PV)
更新于2025-09-09 09:28:46
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Recent advances in the chemical strengthening of glass
摘要： Since its development in the early 1960s till recently, applications of the glass chemical strengthening technology were limited mostly to aircraft cockpit windshields, photocopier transparencies, and hard disks. The interest has been renewed by a need to have stronger and lighter glass products, led mostly by display cover in personal mobile electronic devices, such as cell phones, and glass packaging for safe delivery of medicines in pharmaceutical applications. In this paper, I suggest that the science of the compressive stress development is nearly completely understood. The so-called “dilation anomaly” is resolved. Newer technologies are being developed, for example, thin float-produced flat glasses can be strengthened with reduced warp. Molten salt bath maintenance techniques to avoid discarding of degraded salt have been developed to some extent. In addition to more and more pharmaceutical businesses looking to strengthen the glass packaging to avoid costly recalls, interest is also high in break-resistant automobile and locomotive transparencies. Other miscellaneous topics where the use of chemically strengthened glass could bring value-added premium are also mentioned.
关键词： molten salt bath,pharmaceutical packaging,chemical strengthening,compressive stress,glass,automobile transparencies,dilation anomaly
更新于2025-09-09 09:28:46
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High-Temperature Cycle Durability of Superplastic Al-Zn Eutectoid Solder Joints with Stress Relaxation Characteristics for SiC Power Semiconductor Devices
摘要： We have developed a new high-temperature Al-Zn lead-free soldering process that utilizes superplasticity to realize SiC power devices with high-temperature cycle durability. The joining process consists of an Al-78wt.%Zn preparation being sandwiched by a SiC die and insulation substrate, an interfacial cleaning process at approximately 250-270oC, a heating stage to reach the solid-liquid coexisting temperature of 420-430oC, the ejection of low-melting-temperature β(Zn) from the joining area by press stress, and the transformation to a superplastic composition, i.e., Al-70 wt.% Zn at 270-310oC. Many lamellar phases that enable superplasticity can be formed in this microstructure. This solder joint composition was proven to have a better stress-relaxation effect than eutectic Al-95wt.%Zn, and the composition shows a much higher damping capability at the maximum operating temperature of SiC devices (200oC) than that of other joining candidates. The outstanding temperature cycle durability was verified in temperature cycle tests from -40oC to 300oC for 5000 cycles. This durability is due to the high-stress-relaxation effect from the superplasticity transformation realized by the lamellar structures in the Al-Zn alloy solder.
关键词： lamellar structure,damping capability,power semiconductor,SiC,superplasticity,temperature cycle test,Al-Zn eutectoid solder,lead-free solder,stress relaxation
更新于2025-09-09 09:28:46
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Evaluating the Reduction of Stress Intensity Factor in Center-Cracked Plates Using Piezoelectric Actuators
摘要： Active repairs using smart materials such as piezoelectric actuators can play a significant role in reducing the crack damage propagation in engineering structures. This study analytically and numerically investigated the active repair of center-cracked plates using piezoelectric actuators. First, the stress intensity factor (SIF) for a center-cracked plate due to stress produced by a piezoelectric actuator is analytically modeled. This analytical model is obtained by applying the method of weight functions. In the second step, the solution is found for the center-cracked plate due to external loading from known linear elastic fracture mechanics. These solutions are then superimposed, taking into account the superposition principle to yield the total stress intensity factor for the integrated piezoelectric actuator to the center-cracked plate. Finally, the proposed theoretical model is verified by finite element simulation. The results indicated that the relative errors of the analytical model and the FEA results are less than 5% in all the cases studied in this paper.
关键词： fracture mechanics,stress intensity factor,active repair,piezoelectric actuator
更新于2025-09-09 09:28:46