Minimal Stress Research Articles

Wall Shear Stress and Flow Patterns in Unruptured and Ruptured Anterior Communicating Artery Aneurysms Using Computational Fluid Dynamics.

ObjectiveThe goal of this study was to compare several parameters, including wall shear stress (WSS) and flow pattern, between unruptured and ruptured anterior communicating artery (ACoA) aneurysms using patient-specific aneurysm geometry. MethodsIn total, 18 unruptured and 24 ruptured aneurysms were analyzed using computational fluid dynamics (CFD) models. Minimal, average, and maximal wall shear stress were calculated based on CFD simulations. Aneurysm height, ostium diameter, aspect ratio, and area of aneurysm were measured. Aneurysms were classified according to flow complexity (simple or complex) and inflow jet (concentrated or diffused). Statistical analyses were performed to ascertain differences between the aneurysm groups. ResultsAverage wall shear stress of the ruptured group was greater than that of the unruptured group (9.42% for aneurysm and 10.38% for ostium). The average area of ruptured aneurysms was 31.22% larger than unruptured aneurysms. Simple flow was observed in 14 of 18 (78%) unruptured aneurysms, while all ruptured aneurysms had complex flow (p<0.001). Ruptured aneurysms were more likely to have a concentrated inflow jet (63%), while unruptured aneurysms predominantly had a diffused inflow jet (83%, p=0.004). ConclusionRuptured aneurysms tended to have a larger geometric size and greater WSS compared to unruptured aneurysms, but the difference was not statistically significant. Flow complexity and inflow jet were significantly different between unruptured and ruptured ACoA aneurysms.

A novel automated system to acquire biometric and morphological measurements and predict body weight of pigs via 3D computer vision.

Computer vision applications in livestock are appealing since they enable measurement of traits of interest without the need to directly interact with the animals. This allows the possibility of multiple measurements of traits of interest with minimal animal stress. In the current study, an automated computer vision system was devised and evaluated for extraction of features of interest, as body measurements and shape descriptors, and prediction of body weight in pigs. From the 655 pigs that had data collected 580 had more than 5 frames recorded and were used for development of the predictive models. The cross-validation for the models developed with data from nursery and finishing pigs presented an R2 ranging from 0.86 (random selected image) to 0.94 (median of images truncated on the third quartile), whereas with the dataset without nursery pigs, the R2 estimates ranged from 0.70 (random selected image) to 0.84 (median of images truncated on the third quartile). However, overall the mean absolute error was lower for the models fitted without data on nursery animals. From the body measures extracted from the image, body volume, area, and length were the most informative for prediction of body weight. The inclusion of the remaining body measurements (width and heights) or shape descriptors to the model promoted significant improvement of the predictions, whereas the further inclusion of sex and line effects were not significant.

Green-Kubo stress correlation function at the atomic scale and a long-range bond-orientational ordering in a model liquid

Recently there have been several considerations by different authors of viscosity and the Green-Kubo stress correlation function from the microscopic perspective. In most of these and earlier works the atomic level stress is the minimal element of stress. It is also possible to consider, for pairwise interaction potentials, as the minimal elements of stress, the stress tensors associated with the pairs of interacting particles. From this perspective, the atomic level stress is not the minimal stress element, but a sum of all pair stress elements in which involved a selected particle. In this paper, we consider the Green-Kubo stress correlation function from a microscopic perspective using the stress tensors of interacting pairs as the basic stress elements. The obtained results show the presence of a long-range bond-orientational order in the studied model liquid and naturally elucidate the connection of the bond-orientational order with viscosity. It turns out that the long-range bond-orientational order is more clearly expressed in the pairs' stress correlation function than in the atomic-stress correlation function. On the other hand, previously observed stress waves are much better expressed in the atomic-stress correlation functions. We also address the close connection of our approach with the previous bond-orientational order considerations. Finally, we consider the probability distributions for the bond-stress and atomic-stress correlation products at selected distances. The character of the obtained probability distributions raises questions about the meaning of the average correlation functions at large distances.

EEG and autonomic responses to nociceptive stimulation in disorders of consciousness

Since behavioral responses to external stimuli of patients presenting disorders of consciousness (DoC) are often difficult to qualify, covert physiological correlates of responsivity are deemed as potentially valuable tools to help assessment procedures. While noxious stimuli seem good candidates to explore DoC patients’ responsivity, autonomic and electrophysiological correlates of pain detection in DoC patients are still debated. This research aims at investigating autonomic and cortical activation as covert measure of residual somatosensory and nociceptive processes in patients in vegetative state. Twenty-one patients received touch- and pain-related stimulations while autonomic and cortical measures were recorded, with minimal stress for them. Results showed an increased frontal and parietal activation in response to both touch and pain stimuli. Pain-related stimulation was however associated with greater delta parietal response, lower left frontal activation, and increased electrodermal and heart rate measures. Present findings suggest that both somatic stimulations could induce measurable central responses, which might mirror basic attention orientation and perceptual processes. Nonetheless, the nociceptive stimulation in particular seemed to induce a more consistent and informative pattern of covert response even if we used a mild pain-induction procedure.

Efficacy of Hot Yoga as a Heat Stress Technique for Enhancing Plasma Volume and Cardiovascular Performance in Elite Female Field Hockey Players.

Perrotta, AS, White, MD, Koehle, MS, Taunton, JE, and Warburton, DER. Efficacy of hot yoga as a heat stress technique for enhancing plasma volume and cardiovascular performance in elite female field hockey players. J Strength Cond Res 32(10): 2878-2887, 2018-This investigation examined the efficacy of hot yoga as an alternative heat stress technique for enhancing plasma volume percentage (PV%) and cardiovascular performance. Ten international caliber female field hockey players completed six 60-minute hot yoga sessions using permissive dehydration over 6 days, followed by a 6-day national team camp. Changes in PV% were examined throughout the intervention and postintervention period. A graded maximal exercise test was performed in a thermoneutral environment (23.2 ± 1.0° C) 24 hours before and 24 hours after intervention. Six days of hot yoga initiated a moderate state of hypovolemia (PV% = -3.5%, 90% confidence limit [CL] [-6.9 to -0.13]), trivial improvements in maximal aerobic power (V[Combining Dot Above]O2max) (effect size [ES] = 0.06, 90% CL [-0.16 to 0.28]), and run time to exhaustion (ES = 0.11, 90% CL [-0.07 to 0.29]). Small meaningful improvements were observed in running speed (km·h) at ventilatory threshold (VT1) (ES = 0.34, 90% CL [-0.08 to 0.76]), VT2 (ES = 0.53, 90% CL [-0.05 to 1.1]), along with adaptations in the respiratory exchange ratio during high-intensity exercise (ES = -0.25, 90% CL [-0.62 to 0.12]). A large plasma volume expansion transpired 72 hours after intervention (PV% = 5.0%, 90% CL [1.3-8.7]) that contracted to a small expansion after 6 days (PV% = 1.6%, 90% CL [-1.0 to 4.2]). This investigation provides practitioners an alternative heat stress technique conducive for team sport, involving minimal exercise stress that can preserve maximal cardiovascular performance over periodized rest weeks within the yearly training plan. Furthermore, improvements in submaximal performance and a delayed hypervolemic response may provide a performance-enhancing effect when entering a 6-day competition period.

Large-area diamond thin film on Q-carbon coated crystalline sapphire by HFCVD

The growth of diamond on transparent substrates like sapphire presents a great challenge because of the large thermal misfit between the film and the substrate, absence of any carbide layer during diamond growth, and low nucleation density during chemical vapor deposition (CVD) growth process. In this study, we report on the use and the role of Q-carbon as an intermediate layer to successfully deposit large-area diamond film on c-sapphire by hot filament chemical vapor deposition (HFCVD). The Q-carbon consists of very high-density diamond tetrahedra which act as the embryo for diamond nucleation. Different techniques such as X-ray diffraction, scanning electron microscopy, and Raman spectroscopy show that continuous diamond films with good crystallinity and without any impurity phase can be deposited on the Q-carbon coated single crystal sapphire substrate. The Q-carbon layer is very adherent and it negates the thermal mismatch between the diamond film and the sapphire substrate. A small blue shift in the Raman peak of the diamond from its equilibrium position suggests the deposition of the CVD diamond film with minimal stress (1.14 GPa). This technique of growing large-area continuous diamond thin film with excellent crystalline quality on a single crystal sapphire substrate can serve as a platform for the development of next-generation corrosion and erosion resistant infrared windows, state-of-the-art optoelectronic devices, and advanced scanning probe microscopy systems.

Dual offset metaphyseal-filling stems in primary total hip arthroplasty in dysplastic hips after a minimum follow-up of ten years

The aim of this study was to assess the long-term performance of tapered one-third proximally coated stems in dysplastic hips. This study included 135 dysplasia patients (150 hips) who underwent a total hip arthroplasty and had a minimum follow-up of ten years. Single design tapered stems were used in all patients. There were 112 women (83%) and 23 men (17%) with a mean age of 45years (23 to 72) at the time of surgery. The mean follow-up was 14.7years (10 to 16.8). For clinical evaluation, the Harris Hip Score and Merle D'Aubigne scale were used pre-operatively and at the final follow-up. Implant survival was calculated using Kaplan-Meier survivorship analysis, with failure defined as a component revision for any reason. Overall, one stem was revised for a deep infection. There were no other femoral stem revisions secondary to loosening, wear, periprosthetic fracture, or instability. Radiographic evaluation showed excellent stem osteointegration in all cases. Kaplan-Meier survivorship, with stem revision for any reason as the end point, was 98% at 14years (95% confidence interval 92.5 to 99.8). This study demonstrates that a dual offset tapered stem achieved excellent survivorship and stability, as well as good clinical outcome scores with minimal thigh pain and stress shielding in patients with arthritis and developmental dysplasia of the hip; a dual offset tapered stem may be a suitable option for primary total hip arthroplasty in this group.

The Promise of Sustainable Magnesium Composite Technology for Greener Future

Ethical research that ensures the enhancement of quality of human life for present and future generations is the need of the day. This inherits the typical requirement to impose zero or minimal stress on the environment. Currently, planet earth is witnessing global warming and largely unpredictable weather changes, primarily due to greenhouse gas emissions. Transportation sector is one of the major engineering sectors contributing to greenhouse gas emissions. One way to mitigate/minimize these emissions is to use lightweight materials in the construction of vehicles for use in land, water, aerospace and space applications. Towards this, magnesium based materials are viable options which are suitable to replace aluminum based materials allowing ~ 35% weight saving on a component basis. As magnesium is abundant in nature and is a nutritional element, its availability and recyclability is not an issue. Accordingly, this paper will focus on the development of magnesium based nanocomposites capable of replacing conventional materials in multiple engineering and biomedical applications.

The Cessation Threshold of Nonsuspended Sediment Transport Across Aeolian and Fluvial Environments

Using particle‐scale simulations of nonsuspended sediment transport for a large range of Newtonian fluids driving transport, including air and water, we determine the bulk transport cessation threshold by extrapolating the transport load as a function of the dimensionless fluid shear stress (Shields number) Θ to the vanishing transport limit. In this limit, the simulated steady states of continuous transport can be described by simple analytical model equations relating the average transport layer properties to the law of the wall flow velocity profile. We use this model to calculate for arbitrary environments and derive a general Shields‐like threshold diagram in which a Stokes‐like number replaces the particle Reynolds number. Despite the simplicity of our hydrodynamic description, the predicted cessation threshold, both from the simulations and analytical model, quantitatively agrees with measurements for transport in air and viscous and turbulent liquids despite not being fitted to these measurements. We interpret the analytical model as a description of a continuous rebound motion of transported particles and thus as the minimal fluid shear stress needed to compensate the average energy loss of transported particles during an average rebound at the bed surface. This interpretation, supported by simulations near , implies that entrainment mechanisms are needed to sustain transport above . While entrainment by turbulent events sustains intermittent transport, entrainment by particle‐bed impacts sustains continuous transport. Combining our interpretations with the critical energy criterion for incipient motion by Valyrakis and coworkers, we put forward a new conceptual picture of sediment transport intermittency.

Flow development and interface sculpting in stable lubricated pipeline transport

In Sarmadi et al. (2017) [1] we introduced a novel methodology for efficient transport of heavy oil via a triple-layer core-annular flow. Pumping pressures are significantly reduced by concentrating high shear rates to a lubricating layer, while ideas from Visco-plastic lubrication are used to eliminate the possibility of interfacial instabilities. Specifically, we purposefully position a shaped unyielded skin of a visco-plastic fluid between the transported oil and the lubricating fluid layer. The shaping of the skin layer allows for lubrication forces to develop as the core settles under the action of transverse buoyancy forces: adopting an eccentric position where buoyancy and lubrication forces balance. In Sarmadi et al. (2017) [1] we focused on a steady periodic length of established flow, to establish feasibility for the pipelining application. Here we address the equally important issue of how in practice to develop a triple layer flow with a sculpted/shaped viscoplastic skin, all within a concentric inflow manifold. First, we use a simple 1D model to control layer thickness via flow rates of the individual fluids. This is used to give the input flow rates for an axisymmetric triple-layer computation using a finite element discretization with the augmented Lagrangian method to represent the yield surface behavior accurately and a Piecewise Linear Interface Calculation (PLIC) method to track the interface motion. This establishes that these flows may be stably established in a controlled way with a desired interface shape. The shaped interface induces extensional stresses in the skin layer. We study this directly by developing a long-wavelength/quasi-steady analysis of the extensional flow. This allows us to predict the minimal yield stress required to maintain the skin rigid, for a given shape, all while maintaining a constant flow rate of the transported oil.

Determination of optimal temperature(s) in juvenile red‐spotted grouperEpinephelusakaara(Temminck &amp; Schlegel) based on growth performance and stress responses

This study sought to determine the optimal temperature(s) for aquaculture of juvenile red-spotted grouper Epinephelus akaara (Temminck & Schlegel) (mean initial BW: 3.1 g). Growth performance, insulin-like growth factor 1 (IGF-1) expression and thermal stress responses (plasma cortisol, glucose, and hepatic heat shock protein 60 expression) were evaluated at three constant temperatures (24°C, 26°C and 28°C) in a 2-week trial. At the end of the trial, final BW was significantly higher at 26°C and 28°C than at 24°C (p < 0.05); a quadratic regression analysis of final BW showed the optimum temperature for growth was 27.5°C (p < 0.05, R2 = 0.806). The highest hepatic IGF-1 expression was observed at 26°C (p < 0.05). On the other hand, hepatic heat shock protein 60 expression was highest at 28°C (p < 0.05), suggesting thermal stress. In conclusion, temperature optima, which support excellent growth but induce minimal thermal stress, was 26°C. This fine information within a narrow temperature range is expected to give empirical information for red-spotted grouper farmers to sustain maximal production efficiency with avoiding thermal stress and to determine the future location of production, especially in consideration of arising seawater temperatures.

Symptom Based Clustering of Women in the LURN Observational Cohort Study

Women with lower urinary tract symptoms are often diagnosed based on a predefined symptom complex or a predominant symptom. There are many limitations to this paradigm as often patients present with multiple urinary symptoms which do not perfectly fit the preestablished diagnoses. We used cluster analysis to identify novel, symptom based subtypes of women with lower urinary tract symptoms. We analyzed baseline urinary symptom questionnaire data obtained from 545 care seeking female participants enrolled in the LURN (Symptoms of Lower Urinary Tract Dysfunction Research Network) Observational Cohort Study. Symptoms were measured with the LUTS (lower urinary tract symptoms) Tool and the AUA SI (American Urological Association Symptom Index), and analyzed using a probability based consensus clustering algorithm. Four clusters were identified. The 138 women in cluster F1 did not report incontinence but experienced post-void dribbling, frequency and voiding symptoms. The 80 women in cluster F2 reported urgency incontinence as well as urgency and frequency but minimal voiding symptoms or stress incontinence. Cluster F3 included 244 women who reported all types of incontinence, urgency, frequency and mild voiding symptoms. The 83 women in cluster F4 reported all lower urinary tract symptoms at uniformly high levels. All but 2 of 44 LUTS Tool and 8 AUA SI questions significantly differed between at least 2 clusters (p<0.05). All clusters contained at least 1 member from each conventional group, including continence, and stress, urgency, mixed and other incontinence. Women seeking care for lower urinary tract symptoms cluster into 4 distinct symptom groups which differ from conventional clinical diagnostic groups. Further validation is needed to determine whether management improves using this new classification.

Abstract 5040: Perfusion air culture of tissue slices: A new method to cultivate tumor tissue with minimal culture-dependent tissue stress

Abstract Cultivation of tumor tissue slices provides an ex vivo model capturing both tumor heterogeneity and its native microenvironment. Slices are commonly cultured either free-floating in medium or filter-supported. These conditions lead both to culture-dependent stress (free-floating culture condition) and intra-slice gradients regarding proliferation, marker expression and oxygen supply (filter-supported culture condition) (Davies et al Sci Rep (2015) 10.1038/srep17178). To facilitate homogenous supply with nutrients and oxygen, we developed a new method to culture tumor tissue slices. The precision-cut tissue slices (150µm to 300µm thickness) are kept in-between two organotypic supports and fixed in a special chamber allowing continuous perfusion with medium and drugs. The chamber is settled vertically inside of a 50 ml tube with air exchange capacity and connected with a syringe pump via a silicon tube. The whole system is cultured inside the cell culture incubator. Several different types of mouse xenografts (MCF-7, H1437) and primary human tumor (lung and ovarian cancer) tissue slices have been cultured with this new system and compared with the commonly used filter-support culture. Both breast and lung xenograft tissues slices showed a gradient of proliferation, HIF-1α and hormone receptor (ER) expression in the filter-supported culture condition but not with the new perfusion air culture system. The same results were obtained with primary tumor samples. Primary lung tumor and ovarian cancer tissue slices also showed a gradient of HIF-1α expression after cultivation in the filter-supported system but not in the new perfusion air culture system when cotton membranes are used as scaffold. In addition, the choice of the material of the organotypic support allows a variety of biological studies. Scaffolds from de-cellularized porcine intestine provide niches for migrating cells and are suited for studying tumor invasiveness. When used as organotypic support, primary ovarian cancer can be cultured up to 7 days with good tissue morphology and structure and migrating cells into the scaffold can be counted as a measure of invasiveness. When the tissues are sandwiched between polycarbonate membranes (pore size: 12 µm), oxygen gradients can be generated similar to gradients observed around vessels in vivo. Our perfusion air culture system facilitates the cultivation of tumor tissue slices due to its flexibility and adjustability of all culture conditions such as oxygen, scaffolds and flow rate parameters. It allows studying tumor slices under conditions closely resembling the in vivo situation. Citation Format: Kathrin Boepple, Meng Dong, Emma Davis, Julia Schueler, Heike Walles, John Hickman, Walter E. Aulitzky, Heiko van der Kuip. Perfusion air culture of tissue slices: A new method to cultivate tumor tissue with minimal culture-dependent tissue stress [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5040.

Adaptation to reef habitats through selection on the coral animal and its associated microbiome.

Spatially adjacent habitats on coral reefs can represent highly distinct environments, often harbouring different coral communities. Yet, certain coral species thrive across divergent environments. It is unknown whether the forces of selection are sufficiently strong to overcome the counteracting effects of the typically high gene flow over short distances, and for local adaptation to occur. We screened the coral genome (using restriction site-associated sequencing) and characterized both the dinoflagellate photosymbiont- and tissue-associated prokaryote microbiomes (using metabarcoding) of a reef flat and slope population of the reef-building coral, Pocillopora damicornis, at two locations on Heron Island in the southern Great Barrier Reef. Reef flat and slope populations were separated by <100m horizontally and ~5m vertically, and the two study locations were separated by ~1km. For the coral host, genetic divergence between habitats was much greater than between locations, suggesting limited gene flow between the flat and slope populations. Consistent with environmental selection, outlier loci primarily belonged to the conserved, minimal cellular stress response, likely reflecting adaptation to the different temperature and irradiance regimes on the reef flat and slope. The prokaryote community differed across both habitat and, to a lesser extent, location, whereas the dinoflagellate photosymbionts differed by habitat but not location. The observed intraspecific diversity associated with divergent habitats supports that environmental adaptation involves multiple members of the coral holobiont. Adaptive alleles or microbial associations present in coral populations from the environmentally variable reef flat may provide a source of adaptive variation for assisted evolution approaches, through assisted gene flow, artificial cross-breeding or probiotic inoculations, with the aim to increase climate resilience in the slope populations.

Comparison between the Behavior, Productive Performance and Stress Level of Different Weaning Ages of Young Rabbits

Thirty six, New-Zealand, white growing rabbits of both sexes were divided into three equal groups (12 animals / group) according to the weaning age (21, 28 and 35 day). The mean duration of the behavioral patterns and productive parameters were measured weekly. Concerning the behavior of growing rabbit, the mean duration of food consumption (min.) and drinking (min.) increased significantly (P ≤ 0.01) in 28 day weaning than 21 and 35 day. The mean duration of resting (min.) increased significantly (P ≤ 0.05) while, the mean duration of locomotory behavior (min.) decreased significantly (P ≤ 0.01) in later weaned groups (35 day) than early weaning (21 day). Concerning the productive performance of growing rabbits, the highest body weight (g) and daily weight gain (g) were obtained in later weaning age group (35 day). The lowest daily weight gain (g) was noted in the third week of growing. The highest mortality rate (%) was observed in rabbits weaned at 21 days of age. Cortisol hormone levels (ng/ml) increased significantly (P ≤ 0.01) in early (21, 28 day) than later (35 day) weaned rabbits at weaning and at slaughtering. Our results suggest that later weaning of young rabbits at 35 day improves the growth rate, behaviors and allows young rabbits to live with minimal stress levels during the growing period.

Educational stress and coping strategies in school going adolescents

Background: Academic pressure are one of the main causes of stress for young people and this stress is a significant catalyst and precursor to depression. This research uses to assist the teaching units in understanding the related problems of stress of students of modern teaching technology, thereby proceeding to provide assistance and preventive measures. Current study was aimed to find out prevalence of educational stress among school going adolescents and associated factors. In addition to study the use of stress coping strategies.Methods: It was Cross-sectional study carried out during 2016-2017 at Government and Private Schools of Gwalior. 1400 students were selected randomly. Prepared questionnaire in Hindi and English language adapted from. Educational Stress Scale for Adolescent (ESSA) and Academic Stress Scale (ASC). Scales are modified according to our settings.Results: We found that 43% children have minimal stress, 56.6% moderate stress, 0.4% have highly stress. Female adolescents have more stress than male. 63% adolescents of government school have moderate stress as compared to private school which has 50.9% moderate stress. 11th and 12th standard students have more stress than 9th and 10th standard which is highly significant (p value &lt;0.01). 20.4% adolescents use occasionally coping and 55.3% adolescents used sometimes coping and 23.5% used frequently coping strategies.Conclusions: The present study reveals that the school going adolescents are having educational stress and which is affected by age, gender, socioeconomic status, examinations, parents expectation and peer and also found that adolescents uses different coping strategies to cope up with educational stress.

Trap modification and mechanoluminescence improvement by Si substitution for Sn in Sr2SnO4:Sm3+ ceramics

A series of Sr[Formula: see text]Sn[Formula: see text]SixO4:0.04Sm[Formula: see text] ([Formula: see text], 0.1, 0.15, 0.2, 0.3, 0.4) were synthesized from solid-state reaction. The mechanoluminescence (ML) performance of Sr[Formula: see text]SnO4:0.04Sm[Formula: see text] was greatly enhanced by partial Si[Formula: see text] substitution for Sn[Formula: see text], and the sample of Sr[Formula: see text]Sn[Formula: see text]Si[Formula: see text]O4:0.04Sm[Formula: see text] showed weaker afterglow and twice stronger ML intensity than that in Sr[Formula: see text] SnO4:0.04Sm[Formula: see text]. The stress response of Sr[Formula: see text]Sn[Formula: see text]Si[Formula: see text]O4:0.04Sm[Formula: see text] ranged from 250 to 1200 N, and its linearity was greatly restored. Particularly, it was very sensitive in the minimal stress response range. These properties of no load threshold for stress sensing and weak afterglow make Sr[Formula: see text]Sn[Formula: see text]Si[Formula: see text]O4:0.04Sm[Formula: see text] superior to other excellent ML materials. The introduction of Si[Formula: see text] caused lattice distortion and promoted defect formation in the system. The trap level energy greatly increased and the trap depth changed, which enhanced the trap ability and therefore improved effectively the ML properties.

Visual and psychological stress during computer work in healthy, young females\u2014physiological responses

PurposeAmong computer workers, visual complaints, and neck pain are highly prevalent. This study explores how occupational simulated stressors during computer work, like glare and psychosocial stress, affect physiological responses in young females with normal vision.MethodsThe study was a within-subject laboratory experiment with a counterbalanced, repeated design. Forty-three females performed four 10-min computer-work sessions with different stress exposures: (1) minimal stress; (2) visual stress (direct glare); (3) psychological stress; and (4) combined visual and psychological stress. Muscle activity and muscle blood flow in trapezius, muscle blood flow in orbicularis oculi, heart rate, blood pressure, blink rate and postural angles were continuously recorded. Immediately after each computer-work session, fixation disparity was measured and a questionnaire regarding perceived workstation lighting and stress was completed.ResultsExposure to direct glare resulted in increased trapezius muscle blood flow, increased blink rate, and forward bending of the head. Psychological stress induced a transient increase in trapezius muscle activity and a more forward-bent posture. Bending forward towards the computer screen was correlated with higher productivity (reading speed), indicating a concentration or stress response. Forward bent posture was also associated with changes in fixation disparity. Furthermore, during computer work per se, trapezius muscle activity and blood flow, orbicularis oculi muscle blood flow, and heart rate were increased compared to rest.ConclusionsExposure to glare and psychological stress during computer work were shown to influence the trapezius muscle, posture, and blink rate in young, healthy females with normal binocular vision, but in different ways. Accordingly, both visual and psychological factors must be taken into account when optimizing computer workstations to reduce physiological responses that may cause excessive eyestrain and musculoskeletal load.

(Invited) Bio-Inspired Helical Coil Network for Soft, Wireless Electronics

Coils are made of elastic materials formed into the shape of helixes which return to their natural length when unloaded. With its unique geometry, the helix coil structure is one of the most stretchable forms among all kinds of shapes in man-made systems and nature. I employed the coil mechanics to modern stretchable electronics to archive an extreme level of elastic stretchability, which cannot be accomplished with existing technologies. Compared to typical 2D filamentary serpentines fully bonded onto soft planar elastomeric substrates, the proposed 3D helix structures are designed to be uniformly bent with compressive buckling with minimally defined bonding sites. The constructed helix coil interconnections can be naturally deformed along the coil direction under tensile stress with minimal stress concentration. As a result, these structures exhibit extreme elastic stretchability up to ~100%. Currently, I am building extremely stretchable biomedical devices as a system-level demo.

Simultaneous assessment of cognitive function, circadian rhythm, and spontaneous activity in aging mice.

Cognitive function declines substantially with age in both humans and animal models. In humans, this decline is associated with decreases in independence and quality of life. Although the methodology for analysis of cognitive function in human models is relatively well established, similar analyses in animal models have many technical issues (e.g., unintended experimenter bias, motivational issues, stress, and testing during the light phase of the light dark cycle) that limit interpretation of the results. These caveats, and others, potentially bias the interpretation of studies in rodents and prevent the application of current tests of learning and memory as part of an overall healthspan assessment in rodent models of aging. The goal of this study was to establish the methodology to assess cognitive function in aging animals that addresses many of these concerns. Here, we use a food reward-based discrimination procedure with minimal stress in C57Bl/6J male mice at 6, 21, and 27months of age, followed by a reversal task to assess behavioral flexibility. Importantly, the procedures minimize issues related to between-experimenter confounds and are conducted during both the dark and light phases of the light dark cycle in a home-cage setting. During cognitive testing, we were able to assess multiple measures of spontaneous movement and diurnal activity in young and aged mice including, distance moved, velocity, and acceleration over a 90-h period. Both initial discrimination and reversal learning significantly decreased with age and, similar to rats and humans, not all old mice demonstrated impairments in learning with age. These results permitted classification of animals based on their cognitive status. Analysis of movement parameters indicated decreases in distance moved as well as velocity and acceleration with increasing age. Based on these data, we developed preliminary models indicating, as in humans, a close relationship exists between age-related movement parameters and cognitive ability. Our results provide a reliable method for assessing cognitive performance with minimal stress and simultaneously provide key information on movement and diurnal activity. These methods represent a novel approach to developing non-invasive healthspan measures in rodent models that allow standardization across laboratories.