Effects Of Different Stresses Research Articles

Preparation, characterization, and stability of chitosan-tremella polysaccharide layer-by-layer encapsulated astaxanthin nanoemulsion delivery system

In this study, a layer-by-layer (LBL) encapsulated astaxanthin (Ast) nanoemulsion delivery system based on chitosan (CS) and tremella polysaccharide (TP) was successfully developed. The system constructed an Ast-CS-TP emulsion with high encapsulation efficiency and an excellent stability profile by utilizing the opposite charge properties of CS and TP. This study evaluated the effects of different stresses (including temperature, salt addition, pH, UV irradiation, and centrifugal force) on the emulsion's stability. To further investigate the protective mechanism of the emulsions, we performed antioxidant activity experiments after UV treatment. Additionally, an in vitro digestion experiment was conducted to assess the behavior of Ast emulsion under simulated gastrointestinal conditions. The stability correlation coefficients were calculated using the Python database Pandas. The results showed that Ast-CS-TP emulsions exhibited turbidity and enhanced homogeneity with a small particle size of around 400 nm and a high absolute zeta potential of 35 mV and exhibited excellent stability under various stresses. The Ast-CS-TP emulsions also exhibited pH-responsive release at pH ≥ 7, consistent with pH changes in the gastrointestinal tract, and were stable in highly concentrated salt solutions. We found that the CS and TP layers significantly improved the photostability of Ast. CS and TP significantly enhanced Ast's oral bioavailability. The stability correlation coeffcients showed that pH and salt concentration were the largest factors that affected the stability of the emulsion. This study provided important insights into the encapsulation and targeting of Ast, providing a theoretical foundation and technical guidance for the comprehensive utilization of Ast.

Degradation analysis of GaN-based high–electron-mobility transistors under different stresses in semi-on state conditions

The large numbers of high-energy carriers that occur in semiconductor devices under semi-on state conditions can cause significant device degradation. The effects of different stresses on the electrical and trapping characteristics of GaN-based high-electron-mobility transistors (HEMTs) are investigated. Test results for GaN HEMTs under semi-on state conditions show that the electrical characteristics of these devices degrade to a certain extent after they are subjected to electrical pulse stress cycles with different drain voltage, frequencies, and duty cycles; a degree of degradation also occurs in the electrical characteristics of the devices when they are subjected to direct current electrical stresses. After electrical stress is applied, the absolute amplitude of the traps in the device increases, thus indicating an increase in the trap density. The results show that voltage is the main driver for device damage, with the current playing an accelerating role through its effects on device temperature or by supplying hot electrons; therefore, the drain voltage has the most significant effect on device degradation, which is mainly due to channel high-energy hot electron injection.

Facing climate change: plant stress mitigation strategies in agriculture.

Climate change poses significant challenges to global agriculture, with rising temperatures, altered precipitation patterns, and increased frequency of extreme weather events threatening crop yields. These changes exceed the adaptability thresholds of many crops, decreasing their yield and threatening food security. At plant physiological levels, climate change-induced stressors disrupt photosynthesis, growth, and reproductive processes, contributing to a reduced productivity. Furthermore, the negative impacts of climate change on agriculture are exacerbated by anthropogenic factors, with agriculture itself contributing significantly to greenhouse gas emissions. To mitigate these challenges, various approaches have been explored. This work reviews the most important physical, chemical, and biological strategies most commonly used in a broad range of agricultural crops. Among physical strategies, increasing water use efficiency without yield reduction through different irrigation strategies, and the use of foliar treatments with reflective properties to mitigate the negative effects of different stresses have been proven to be effective. Concerning chemical approaches, the exogenous treatment of plants with chemicals induces existing molecular and physiological plant defense mechanisms, enhancing abiotic stress tolerance. Regarding biological treatments, plant inoculation with mycorrhiza and plant growth-promoting rhizobacteria (PGPR) can improve enzymatic antioxidant capacity and mineral solubilization, favoring root and plant growth and enhance plant performance under stressful conditions. While these strategies provide valuable short- to medium-term solutions, there is a pressing need for new biotechnological approaches aimed at developing genotypes resistant to stressful conditions. Collaborative efforts among researchers, policymakers, and agricultural stakeholders are essential to ensure global food security in the face of ongoing climate challenges.

Winter survival in red clover: experimental evidence for interactions among stresses

BackgroundThere is a lack of knowledge on the combined effects of different stresses on plants, in particular different stresses that occur during winter in temperate climates. Perennial herbaceous plants in temperate regions are exposed to many different stresses during winter, but except for the fact that cold temperatures induce resistance to a number of them, very little is known about their interaction effects. Knowledge about stress interactions is needed in order to predict effects of climate change on both agricultural production and natural ecosystems, and to develop adaptation strategies, e.g., through plant breeding. Here, we conducted a series of experiments under controlled conditions to study the interactions between cold (low positive temperature), clover rot infection (caused by Sclerotinia trifoliorum) and freezing, in red clover (Trifolium pratense) accessions. We also compared our results with winter survival in field experiments and studied associations between stress and shoot growth.ResultsExposure to low positive temperatures (cold acclimation) induced resistance to clover rot. There was a clear negative interaction effect between freezing stress and clover rot infection, resulting in up to 37% lower survival rate compared to what would have been expected from the additive effect of freezing and infection alone. Freezing tolerance could continue to improve during incubation under artificial snow cover at 3 °C in spite of darkness, and we observed compensatory shoot growth following freezing after prolonged incubation. At the accession level, resistance to clover rot was negatively correlated with growth in the field during the previous year at a Norwegian location. It was also negatively correlated with the shoot regrowth of control plants after incubation. Clover rot resistance tests under controlled conditions showed limited correlation with clover rot resistance observed in the field, suggesting that they may reveal variation in more specific resistance mechanisms.ConclusionsWe here demonstrate, for the first time, a strong negative interaction between freezing and infection with a winter pathogen. We also characterize the effects of cold acclimation and incubation in darkness at different temperatures on winter stress tolerance, and present data that support the notion that annual cycles of growth and stress resistance are associated at the genetic level.

The Integrated-Servo-Actuator Degradation Prognosis Based on the Physical Model Combined With Data-Driven Approach

The integrated-servo-actuator (ISA) is one of the most critical subsystems of aircraft flight-control system, which controls the speed, direction, displacement, and force of load for an aircraft. The degradation state of the ISA directly influences the safety of the aircraft. Hence, it is valuable to predict the degradation of the ISA to ensure its operating reliability. However, as a kind of complex system, the degradation mechanisms and the influences of the stress cannot be fully understood. Moreover, the nonlinear degradation process brings more difficulties to establish an accurate life prognosis model. To address these challenging issues, this paper proposed a hybrid degradation prognosis method that fused the physics-based model and data-driven model for ISA. The nonlinear Wiener process (NWP) algorithm is utilized to characterize the physical degradation process of ISA. The effect of different stresses is quantitatively modeled. Furthermore, the data-driven echo-state-network (ESN) is optimized to describe the nonlinear degradation process of ISA. More degradation data are generated based on the NWP model for ESN model training. Therefore, the degradation trajectory predicting model is fused with the physics-based degradation prognosis model so that both the degradation mechanisms and time series features within the monitoring data are combined. The experimental results based on the real ISA data illustrate that the proposed method has higher prediction accuracy which is meaningful to enhance the operating reliability of the ISA.

Aluminum Nitride Based Film Bulk Acoustic Resonator With Anchor Column Structure

In order to reduce the lateral acoustic energy loss of thin film bulk acoustic resonators (FBARs), the trench structure for FBAR is generally designed to block the leakage of acoustic wave and help improving the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> -factor. One method the designers often used is etching the piezoelectric material around the active area of the FBAR to form the air-wall structure as a perfect reflection boundary condition. In this paper, the FBAR with trench structure is fabricated. The multilayer films in the FBAR with trench structure are easily warped due to excessive compressive stress. The numerical analysis and finite element simulation are used to verify the effects of different stresses on the devices. In order to avoid the degradation of FBAR performance caused by film warpage, the FBAR with anchor columns is proposed. The anchor columns are located on both sides of the FBAR, and they are designed to reduce film bending and the compressive stress of active area of the resonator. The measured results show that the Qs and Qp of the FBAR with anchor columns are increased by 55.8% and 21.1%, respectively, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k_{eff}{}^{2}$ </tex-math></inline-formula> improved from 5.6% to 6.7% compared with the FBAR without the anchor columns. [2022-0179]

Plant Growth-Promoting Rhizobacteria (PGPR): Approaches to Alleviate Abiotic Stresses for Enhancement of Growth and Development of Medicinal Plants

Plants are constantly exposed to both biotic and abiotic stresses which limit their growth and development and reduce productivity. In order to tolerate them, plants initiate a multitude of stress-specific responses which modulate different physiological, molecular and cellular mechanisms. However, many times the natural methods employed by plants for overcoming the stresses are not sufficient and require external assistance from the rhizosphere. The microbial community in the rhizosphere (known as the rhizomicrobiome) undergoes intraspecific as well as interspecific interaction and signaling. The rhizomicrobiome, as biostimulants, play a pivotal role in stimulating the growth of plants and providing resilience against abiotic stress. Such rhizobacteria which promote the development of plants and increase their yield and immunity are known as PGPR (plant growth promoting rhizobacteria). On the basis of contact, they are classified into two categories, extracellular (in soil around root, root surface and cellular space) and intracellular (nitrogen-fixing bacteria). They show their effects on plant growth directly (i.e., in absence of pathogens) or indirectly. Generally, they make their niche in concentrated form around roots, as the latter exude several nutrients, such as amino acids, lipids, proteins, etc. Rhizobacteria build a special symbiotic relationship with the plant or a section of the plant’s inner tissues. There are free-living PGPRs with the potential to work as biofertilizers. Additionally, studies show that PGPRs can ameliorate the effect of abiotic stresses and help in enhanced growth and development of plants producing therapeutically important compounds. This review focuses on the various mechanisms which are employed by PGPRs to mitigate the effect of different stresses in medicinal plants and enhance tolerance against these stress conditions.

The effects of different stress on intestinal mucosal barrier and intestinal microecology were discussed based on three typical animal models.

Recent studies have revealed that the effect of intestinal microecological disorders on organismal physiology is not limited to the digestive system, which provides new perspectives for microecological studies and new ideas for clinical diagnosis and prevention of microecology-related diseases. Stress triggers impairment of intestinal mucosal barrier function, which could be duplicated by animal models. In this paper, pathological animal models with high prevalence and typical stressors—corresponding to three major stressors of external environmental factors, internal environmental factors, and social psychological factors, respectively exemplified by burns, intestinal ischemia-reperfusion injury (IIRI), and depression models—were selected. We summarized the construction and evaluation of these typical animal models and the effects of stress on the organism and intestinal barrier, as well as systematically discussed the effects of different stresses on the intestinal mucosal barrier and intestinal microecology.

Psychosocial stress and cancer risk: a narrative review.

It is unclear which psychological factors (stressors, emotional correlates, and psychophysiological markers) induce cancer risk. This currently limits the potential for prevention strategies. The aim of this review is to bring forth evidence of stress as a determinant of cancer risk from a public health perspective, written for a broad public of practitioners and scientists. Based on a semisystematic literature search, the impact of different aspects/types of stress and the potential physiological and behavioral pathways are summarized, while highlighting further research, public health and clinical implications. Between 2007 and 2020, 65 case-control or cohort studies have been identified. Apart from overall cancer ( N = 24), 12 cancer types have been associated with psychological stress with most for breast ( N = 21), colorectal ( N = 11) and lung/prostate/pancreas cancer ( N = 8 each). Although the evidence regarding the mechanisms is still scarce, cancer development in relation to stress might be due to interacting and combined effects of different stress(or) types, but such interaction has not really been tested yet. The path from stress towards cancer incidence consists of a biological pathway with endocrinology and immunology as well as stress-induced behavioral pathways, including smoking, alcoholism, sleep disruption, an unhealthy diet, and low physical activity together with the related phenomenon of obesity. Not only the stress but also the stress-induced lifestyle should be targeted for cancer prevention and treatment. Future research should include a more diverse spectrum of cancer types (not only hormonal related like breast cancer) and of stress measures while also considering behavioral covariates.

A study on the effects of electrical and thermal stresses on void formation and migration lifetime of Sn3.0Ag0.5Cu solder joints

PurposeThe purpose of this study is to investigate the effect of electrical and thermal stresses on the void formation of the Sn3.0Ag0.5Cu (SAC305) lead-free ball grid array (BGA) solder joints and to propose a modified mean-time-to-failure (MTTF) equation when joints are subjected to coupling stress.Design/methodology/approachThe samples of the BGA package were subjected to a migration test at different currents and temperatures. Voltage variation was recorded for analysis. Scanning electron microscope and electron back-scattered diffraction were applied to achieve the micromorphological observations. Additionally, the experimental and simulation results were combined to fit the modified model parameters.FindingsVoids appeared at the corner of the cathode. The resistance of the daisy chain increased. Two stages of resistance variation were confirmed. The crystal lattice orientation rotated and became consistent and ordered. Electrical and thermal stresses had an impact on the void formation. As the current density and temperature increased, the void increased. The lifetime of the solder joint decreased as the electrical and thermal stresses increased. A modified MTTF model was proposed and its parameters were confirmed by theoretical derivation and test data fitting.Originality/valueThis study focuses on the effects of coupling stress on the void formation of the SAC305 BGA solder joint. The microstructure and macroscopic performance were studied to identify the effects of different stresses with the use of a variety of analytical methods. The modified MTTF model was constructed for application to SAC305 BGA solder joints. It was found suitable for larger current densities and larger influences of Joule heating and for the welding ball structure with current crowding.

Stress effect on the electrocaloric properties of PbTiO3 nanocylinders with the consideration of surface polarization

The refrigeration technology of electronic devices has faced severe challenges with the increasing demand for miniaturization and high frequency, and the research on the electrocaloric effect (ECE) of ferroelectric nanomaterials has made it possible to solve such problems. Due to the symmetry breaking on surfaces of a ferroelectric crystal, the polarizations on surfaces are different from those inside the crystal, which can significantly affect the electrocaloric properties of the materials. In addition, considering the electromechanical coupling between the spontaneous polarization and stress field, the applied stress has a drastic influence on the ECE of the material. In this paper, the extrapolation length is incorporated in the phase-field method based on the time-dependent Ginzburg–Landau equation to investigate the effects of different stress and surface polarization on the ECE of PbTiO3 (PTO) nanocylinders. The stress–adiabatic temperature change (ATC) curves with different extrapolation lengths are obtained through the simulations, which reveal the effect of extrapolation length and stress on the PTO nanocylinders. The results of this paper can provide theoretical guidance for the design of next-generation solid-state cooling devices.

Thermal stress and high stocking densities in poultry farms: Potential effects and mitigation strategies.

Environmental changes pose significant threats to agricultural activities particularly animal production. These changes have induced major concerns which will negatively affect the poultry health and productivity under the current climate changes. Moreover, they also alter the immunological status of the exposed birds and make them susceptible to different diseases. The adverse effects of environmental stress also include poor performance of birds (reduced feed intake, growth, feed efficiency, immunity, and egg production) and inferior product quality. The adverse effect of heat stress on different quail breeds like Japanese quail, bobwhite quail, scaled quail, and Gambel's quail ranged from decreased growth rates (11.0-14.5%), body weight (7.7-13.2%), feed intake (6.1-21.6%), feed efficiency (4.3-8.6%), and egg production (6.6-23.3%). Also, birds reared under heat stress (34°C) had significantly decreased Haugh units by 10.8% and egg weight by 14.3% in comparison with the control group (reared at 22°C). On the other hand, increasing stoking density from 30 to 45kg/m2 also negatively affected the feed intake and body weight. Recent studies have focused on evaluating the potential adverse effects of different environmental stresses on poultry performance, behavior, welfare, and reproduction. It is imperative to understand better the interaction of different environmental factors and their subsequent effects on avian physiology, to spotlights on the effective management and nutritional strategies to alleviate the adverse effects of different stresses in poultry. This review aims to present a comprehensive overview of physiological manifestations of major environmental stresses including thermal stress (heat and cold stress) and high stocking densities on poultry health and production. Moreover, we have also critically evaluated the scope and efficacy of some potential strategies to mitigate the influences of these environmental stressors in different poultry species.

Identification of Swarna x O. nivara (RPBio4918) advanced backcross lines performing well under acidic soil conditions

Aim: To evaluate a set of ABLs (Advanced Backcross Lines) to identify lines perfoming well under acidic soil and iron toxicity hydroponics conditions. Methodology: A total of 194 ABLs were randomly used in lowland field randomly following augmented experimental design. Selected lines were screened in hydroponics condition using Yoshida’s solution for iron toxicity tolerance. Results: Under field conditions, several deficiencies and toxicities often co-exist, and it becomes difficult to partition the effect of different stresses on the genotypes. Therefore, screening genotypes in artificial hydroponics conditions allows us to dissect the response of a genotype to one particular nutrient toxicity or deficiency. Based on different traits superior, average and inferior performing lines were selected from field condition. Hydroponic experiment was conducted using Yoshida’s solution for iron toxicity screening, different superior and inferior lines were identified based on the parameters like root growth, root and shoot biomass. Four lines K 408, K 455, S 304, S 203 were identified that performed well in both field and Fe toxic hydroponic conditions. Interpretation: The information generated would help to identify suitable parents for breeding program under acidic soils, and the phenotypic data on ABLs may serve as a base for future mapping of loci responsible for yield under acidic soils and iron toxic conditions. Key words: Acidic soil, Advanced backcross lines, Hydroponic condition, Iron toxicity, Seedling stage screening

Study on the Liberation of Organic Macerals in Coal by Liquid Nitrogen Quenching Pretreatment

In order to study the liberation characteristics of different macerals in coal, one must improve the liberation degree of macerals in coal and promote the utilization of macerals based on their properties. Based on the idea of quick cooling to change the brittleness and toughness of different macerals, the characteristics of macerals in coal are studied here by liquid nitrogen quenching pretreatment. In particular, coarse-grained samples (with a particle size of 1–3 mm) were. For this study, coal samples were sourced from the Yan’an Formation (J2y), a middle Jurassic coal formation in the Huangling no. 1 coal mine, located in northern Shaanxi Province, China. Firstly, we analyzed the coal properties and coal petrographic characteristics by the Chinese national standard method. Secondly, the distribution characteristics of macerals in different particle sizes (&gt;0.9, 0.5–0.9, 0.1–0.5, and &lt;0.1) were studied. Then, the samples with different particle sizes were quenched with or without liquid nitrogen to obtain the experimental group and blank group products. Finally, the differences in the liberation characteristics between the experimental group and the blank group products were studied via analyzing the micromorphology, specific surface area, pore volume, pore size and liberation degree. Our results for the particles size and liberation degree analysis indicate that inertinite and vitrinite were enriched in the coarse particles (&gt;0.5 mm) and fine particles (&lt;0.1 mm) here, respectively. Moreover, quenching pretreatment could contribute to the liberation of different macerals from coal, mainly because of the different effects of stress on the different components when they suddenly encounter cold, and this kind of liberation is mainly arc-shaped liberation between different macerals. In addition, along with the above results, this paper presents an optimized model for the liberation of macerals based on a combination of screening, liquid nitrogen quenching pretreatment and re-crushing.

Pastas: Open Source Software for the Analysis of Groundwater Time Series.

Time series analysis is an increasingly popular method to analyze heads measured in an observation well. Common applications include the quantification of the effect of different stresses (rainfall, pumping, etc.), and the detection of trends and outliers. Pastas is a new and open source Python package for the analysis of hydrogeological time series. The objective of Pastas is twofold: to provide a scientific framework to develop and test new methods, and to provide a reliable ready‐to‐use software tool for groundwater practitioners. Transfer function noise modeling is applied using predefined response functions. For example, the head response to rainfall is simulated through the convolution of measured rainfall with a Gamma response function. Pastas models are created and analyzed through scripts, ensuring reproducibility and providing a transparent report of the entire modeling process. A Pastas model can be constructed in seven simple steps: import Pastas, read the time series, create a model, specify the stresses and the types of response functions, estimate the model parameters, visualize output, and analyze the results. These seven steps, including the corresponding Python code, are applied to investigate how rainfall and reference evaporation can explain measured heads in an observation well in Kingstown, Rhode Island, USA. The second example demonstrates the use of scripts to analyze a large number of observation wells in batch to estimate the extent of the drawdown caused by a well field in the Netherlands. Pastas is free and open source software available under the MIT‐license at http://github.com/pastas/pastas.

Effect of Saccharomyces cerevisiae and Spirulina platensis on Suppressing Root-knot Nematode, Meloidogyne incognita Infecting Banana Plants under Greenhouse Conditions

Banana production is severely hindered by plant-parasitic nematodes (PPNs) worldwide. Chemical nematicide, oxamyl is a systematic compound widely applied for the control of PPNs. Because of increase pests' problems, harmful effects on human and environment caused by chemical pesticides and also increased consumer requirements for safe crops have encouraged research on bio-pesticides production. So, the effect of different stress of the yeast, Saccharomyces cerevisiae and blue green algae (cyanobacteria), Spirulina platensis were examined on banana plants infected with root-knot nematodes, Meloidogyne incognita. All tested treatments were effective methods to manage M. incognita in soil samples and banana roots. Notably, the usage of S. cerevisiae and S. platensis in combination treatment revealed the greater antagonistic action on M. incognita in potted banana. In addition it has an avail advantage over artificial nematicides by having several means to attack the RKN and mainly enhanced plant growth compared to any other treatments. Yet, the previous treatment had increased catalase (CAT) enzyme activity and reduced pectin methyl esterase (PME) activity in banana plant that leads to inhibit the count of the RKN. Generally, our results supply a novel knowledge to understand of PPNs management as a new approach for applying bio-fertilizer and bio-control of the parasitic nematodes.

Effect of stress on corrosion of high-purity magnesium in vitro and in vivo

Magnesium-based implants are subjected to complicated stresses during implantation in the human body. The stress effects on corrosion of magnesium (Mg) in vitro were investigated in previous studies, whereas in this study, the corrosion behaviors of high-purity (HP) Mg under stress were comparatively studied in vitro in Hank’s solution and in vivo in the subcutaneous environment of rats. Loading devices were designed to apply compressive stress (15.1 ± 0.5 MPa) and tensile stress (13.2 ± 0.2 MPa) on HP Mg specimens both in vitro and in vivo. Corrosion rates of HP Mg were characterized by mass and volume losses. It was shown that the applied compressive stress had no effect on in vitro corrosion behaviors and the applied tensile stress accelerated the in vitro corrosion, thereby causing severe pitting corrosions and stress corrosion cracking (SCC). However, there was no significant change for corrosion behaviors in vivo under neither compressive stress nor tensile stress. Severe pitting corrosion and SCC did not occur in vivo. Histological evaluation revealed that a fibrotic capsule induced by foreign body reaction was formed on the corrosion surfaces of HP Mg in the subcutaneous environment. It was proposed that the fibrotic capsule suppressed the effects of stress in vivo by protecting the corrosion surfaces. These results provided new insights into understanding the stress effects on the corrosion of Mg both in vitro and in vivo. Statement of SignificanceMg and its alloys have shown potential as biodegradable metallic materials. During implantation, Mg is subjected to various mechanical environments in the human body. It is necessary to have a clear understanding of different effects of stress on Mg corrosion. However, few studies were performed in vivo. It is important to analyze the effect of quantitative stress on Mg corrosion in vivo. Therefore, in this study, quantitative stresses were applied on Mg both in vitro and in vivo. The effects of stress on in vitro and in vivo corrosions of Mg were investigated and compared.

Effects of different stresses on cardiac autonomic control and cardiovascular coupling.

The objective of this study was to investigate the impacts of different stresses on time-varying autonomic reactivity and cardiovascular coupling. In total, 25 male subjects were recruited. RR intervals (RRI), systolic and diastolic blood pressure (SBP, DBP), stroke volume (SV), cardiac output (CO), and systemic vascular resistance (SVR) values were collected during rest, mental arithmetic task (MAT), and cold pressor test (CPT). Baroreflex sensitivity (BRS) was derived using the transfer function method. Continuous wavelet transformation of RRI was used to describe the time-variant patterns of autonomic neural activities. Wavelet cross correlation and phase synchronization were used to estimate the amplitude and phase coupling between RRI and SBP. MAT was characterized by increased heart rate (HR), SBP, DBP, and CO with decreased BRS attributable to prolonged parasympathetic withdrawal. Moreover, cardiovascular coupling was disrupted in MAT. These results indicated that baroreflex was depressed, and the top-down system started to take action under mental stress. In CPT, SBP, DBP, and SVR increased significantly, whereas HR and BRS remained unchanged. The increase of sympathetic activity was transient, and cardiovascular coupling did not change in CPT. Intriguingly, the frequency of the maximum cross-correlation coefficient in the low-frequency band (0.04-0.15 Hz) was significantly decreased in CPT, which may be due to the change of resonance frequency of the baroreflex loop.NEW & NOTEWORTHY The study is the first to compare the time-variant pattern of autonomic nervous activities and cardiovascular coupling between the mental arithmetic task (MAT) and the cold pressor test (CPT). Our results demonstrated that MAT and CPT elicited different time-varying patterns of autonomic neural activities and cardiovascular synchronization. Both the amplitude and phase consistency of blood pressure and heart rate decreased in MAT. CPT may affect the harmonic frequency of the baroreflex loop.

(Invited) Study of Lithium-Ion Cell Degradation Behavior Under Multiple Stresses

Cycling and storage are two typical tests in laboratory to evaluate the degradation behavior of lithium-ion cells (LIC). In real world application, however, LIC is always under the stress of multi-factors with no predefined sequence. This work addresses some of the intriguing issues in the study of the degradation behavior of LIC under multiple-stressors: the effect of different stresses on degradation rate, boundary demarcation between accelerated stress test and abuse, life prediction, path dependence, and lithium plating detection techniques, etc. The techniques developed and the insight gained are crucial to the degradation mechanism identification, charging protocol optimization, and life prediction. (1) A generic cycling profile, for which the storage is just a special case, was devised to study the main effects of the seven key stress factors, using L18(2×37) orthogonal matrix in design of experiment (DOE). Orders of the key stress factor’ impacts on capacity degradation were obtained. (2) L27(313) was employed to study the effects of the levels of three key stress factors. Close examination of the test results led to a method demarking the boundary between accelerated stress test and abuse that may lead to lithium plating. (3) Within the obtained non-abuse boundary, orthogonal regression design method with 28 tests was used to build an empirical aging model, which was validated with four independent cycling conditions. (4) Storage tests using different thermal excursion profiles were devised to evaluate path dependence characteristics of the cell capacity degradation and resistance variations. (5) Based on the degradation behaviors, three techniques were explored to evaluate whether there has been lithium plating during the cycling. The prediction was validated with the post-mortem analysis.

Effect of residual stress on the microstructure of GaN epitaxial films grown by pulsed laser deposition

The stress-free GaN epitaxial films have been directly grown by pulsed laser deposition (PLD) at 850°C, and the effect of different stress on the microstructure of as-grown GaN epitaxial films has been explored in detail. The as-grown stress-free GaN epitaxial films exhibit very smooth surface without any particles and grains, which is confirmed by the smallest surface root-mean-square roughness of 2.3nm measured by atomic force microscopy. In addition, they also have relatively high crystalline quality, which is proved by the small full-width at half maximum values of GaN(0002) and GaN(101¯2) X-ray rocking curves as 0.27° and 0.68°, respectively. However, when the growth temperature is lower or higher than 850°C, internal or thermal stress would be increased in as-grown GaN epitaxial films. To release the larger stress, a great number of dislocations are generated. Many irregular particulates, hexagonal GaN gains and pits are therefore produced on the films surface, and the crystalline quality is greatly reduced consequently. This work has demonstrated the direct growth of stress-free GaN epitaxial films with excellent surface morphology and high crystalline quality by PLD, and presented a comprehensive study on the origins and the effect of stress in GaN layer. It is instructional to achieve high-quality nitride films by PLD, and shows great potential and broad prospect for the further development of high-performance GaN-based devices.