Browsing by Subject "stress"
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Item A methodology for memory chip stress levels prediction(Texas A&M University, 2006-10-30) Sharma, KartikThe reliability of electronic component plays an important role in proper functioning of the electronic devices. The manufacturer tests electronic components before they are used by end users. Still at times electronic devices fail due to undue stresses existing inside the microelectronic components such as memory chips, microcontrollers, resistors etc. The stresses can be caused by variation in the operating voltage, variation in the usage frequency of the particular chip and other factors. This variation leads to variation in chip temperature, which can be made evident from thermal profiles of these chips. In this thesis, effort was made to study two different kind of stress existing in the electronic board, namely signal stress based on variation in duty cycle/frequency of chip usage and the voltage stress. Memory chips were stressed using these stresses causing change in heating rates, which were captured by infrared camera. This data was then extracted and plotted to obtain different curves for the heating rate. The same experiment was done time and again for a large number of chips to get heating rate data. This data consisting of average heating rate for large number of chips was used to build Neural Network model (NN). Back Propagation algorithm was used for modeling because of its advantage of converging to solution faster compared to other algorithms. To develop a prediction model, data sets were divided into two-third and one-third parts. This two-thirds of the data was used to build the prediction model and remaining one third was used to evaluate the model. The designed model would predict the stress levels existing in the chips based on the heating rates of the chips. Results obtained suggested 1. There is difference in heating rate for chips stressed at different stress levels. 2. Accuracy of the model to predict the stress is high (greater than 90 %). 3. Model is robust enough that is it can yield efficient results even if there is presence of noise in the data. 4. Generic methodology can be proposed based on the experiments. This work is a progress in direction of making predictive model, for a complete electronic device, which can predict the stress level existing on any component in the device and will provide an opportunity to either protect the data or removal of the defected components timely before it even fails.Item A Structurally Based Investigation of Abdominal Aortic Aneurysms in Mouse Models(2012-02-14) Collins, MelissaUnderstanding the mechanical properties of Abdominal Aortic Aneurysms is paramount to improving treatment of this deadly condition. Here, we present work that makes strides in understanding not only the mechanical behavior and constitutive parameters of the two vessels that experience AAAs in different models, but also the effects of three major components of AAA formation. Biaxial mechanical tests were performed using a modified computer- controlled device. We examined the solid mechanics of the infrarenal and suprarenal aorta to examine why non-targeted models of AAAs (like Ang-II infusion) form exclusively in the suprarenal aorta whereas in humans the lesions preferentially form in the infrarenal aorta. The major difference between the two vessels is the elastin content and lamellar thickness in the suprarenal aorta. We analyzed the mechanical and constitutive effects of an acute loss of functional elastin via intraluminal exposure to elastase. We found that after elastase exposure, vessels were less distensible and experienced non-uniform, but modest dilatation. The constitutive parameters reflect elastin loss and increased collagen loading. We detailed the loss of smooth muscle cell contractility as found in human lesions that form in the thoracic aorta. We examined wild-type (WT), heterozygous (HET), and null (KO) a-smooth muscle actin (a-SMA) mice. The data and associated constitutive parameters were nearly identical amongst the three groups. We studied the biaxial mechanical tests on Angiotensin-II-infused ApoE-/- mice. This model is common model of AAA; however, instead of dilation and a thinning of the wall as in AAAs, Ang-II results in a dissecting aneurysm with adventitial growth. The pressure-diameter curves show a lack of sigmoidal shape attributed to elastin, there is some distensibility. The pressure-force behavior of these vessels is similar to a native vessel, unlike the pressure-force behavior of the elastase vessels. We have added a piece to the puzzle in understanding why AAAs occur preferentially in the suprarenal in mice as opposed to the infrarenal in humans. Our work with the a-SMA mice, introduces the idea that missense mutations in the ACTA2 gene, rather than the knocking out of the gene, leads to vascular diseases. We have increased the knowledge of the Ang-II infusion model by presenting biaxial mechanical data of the resulting dilatations. We have also further explored this widely used AAA model via histology to determine that in it is not a model for aneurysm development, but is a dissecting adventitial disease.Item An atypical approach to officer safety: the importance of counseling programs for the assistance of the law enforcement professional(Law Enforcement Management Institute of Texas (LEMIT), 2015) Zaragoza, RobertItem Complementary Vasoactivity and Matrix Remodeling in Arteries: Theoretical Foundations and Predicted Trends(2010-10-12) Valentin, Auturo IIIArteries possess the ability to grow and remodel in response to sustained alterations in biomechanical loading, likely via mechanisms that are similarly involved in diverse arterial pathologies and responses to treatment. In particular, myriad experminental observations suggest that cell and matrix turnover within vasoaltered states enable arteries to adapt to sustained changes in mechanical stimuli. The goal herein is to show explicitly how altered smooth muscle contractility and matrix growth and remodeling work together to adapt the geometry, structure, stiffness, and function of a representative basilar artery. This work seeks to illustrate the importance of complementary vasoactivity and matrix remodeling for basilar arteries in response to sustained alterations in mechanical stimuli. Toward this end, an extended constrained mixture model of the arterial wall is employed whereby the mass fractions, material properties, and natural configurations of individual constituents can evolve separately and thereby dictate overall growth and remodeling. This approach accounts for fundamentally important behaviors. Simulations provide important intuition and insight regarding constitutive functional forms and model parameters.Item Determining Salt Tolerance Among Sunflower Genotypes(2012-02-14) Masor, Laura LeeCrop lands around the world are becoming more salt-affected due to natural processes and agricultural practices. Due to this increase of salinization, acquisition of saline tolerant germplasm for breeding purposes is becoming a priority. Although cultivated sunflower is classified as a moderately salt tolerant crop, highly tolerant germplasm may be of value. The goal of this study was to screen Helianthus spp. in order to determine the salt tolerance of different genotypes. To accomplish this goal, a novel method of rapid screening was developed. Screening for tolerance at initial growth stages was accomplished by germinating seeds in varying concentrations of NaCl solution in petri dishes. Radicle lengths were measured as an indicator of tolerance. This method identified genotypes that are more tolerant than others during germination. Greenhouse trials were also conducted to ascertain morphological measurements during vegetative stages. Two field locations were chosen to screen germplasm for tolerance through physiological maturity; College Station, TX with low salt concentrations and Pecos, TX with high concentrations of salt in the soil and water. Vegetative growth measurements showed a significant genotype by environment interaction. Due to insect infestation in both locations, yields could not be accurately measured and thus compared between sites in 2010. Yields between locations in 2011 showed significant differences and identified germplasm more suited for cropping in salt affected soil. Seed oil content was determined with Fourier Transform Near-Infrared Spectroscopy. Seed oil content was not significantly different between locations, but was highly significant between genotypes. These screenings identified genotypes that are more salt tolerant than others.Item Evaluation of a Bovine Temperament Model for Endophenotypes Associated with Hypothalamic-Pituitary-Adrenal Axis Dysfunction(2012-07-16) Curley, KevinDynamic interactions of behavior-related traits and the physiological stress response bear upon the beef industry by impacting animal welfare, health, and productivity. The specific mechanisms of hypothalamic-pituitary-adrenal (HPA) axis dysfunction as related to cattle temperament remain unclear. To further characterize endophenotypes associated with the complex interaction of environment and genotype, the following experiments focused on stimulation and regulation of the pituitary gland in cattle of differing genetic background and temperament. Using serial blood sampling, via jugular cannula, the pituitary and subsequent adrenal response to exogenous vasopressin (VP) was characterized for steers of an excitable or calm temperament. Exit velocity (EV) measured at weaning was used to determine steer temperament. Endocrine parameters were measured for 6 h before and 6 h after the VP administration to quantify the stress response to both the handling associated with the experimental procedures and pharmacological challenge. Elevated concentrations of cortisol in excitable steers during the pre-challenge period reflected an increased initial adrenal reactivity to interactions with humans. Subsequent acclimation to the experimental surroundings yielded greater baseline cortisol concentrations in the cattle with an excitable temperament. Pituitary stimulation with VP resulted in a greater adrenocorticotropic hormone (ACTH) output from the excitable compared to the calm animals. A separate experiment employed the same 12-h blood sampling protocol with a different pituitary secretagogue, corticotrophin-releasing hormone (CRH), in order to evaluate pituitary-adrenal responsiveness in cattle with differing temperaments and genetic backgrounds. Measures of EV at weaning identified the calmest and most excitable steers from two separate calf crops; one Angus and the other Brahman. Within breed, adrenal medullary response to initial handling was influenced by temperament as concentrations of epinephrine and norepinephrine were higher in the excitable steers of both breedtypes. Additionally, concentrations of cortisol also differed by temperament in the Angus steers at this time point. An effect of temperament on pituitary responsiveness to exogenous CRH was observed in the Angus but not the Brahman steers. Unlike what was observed with the previously described VP challenge, the pituitary responsiveness to CRH was blunted in the excitable steers. The specific endophenotypes which have been identified or reinforced through these experiments suggest that there are aspects of HPA dysfunction associated with bovine temperament.Item Evaluation of Stress Before, During, and After Transport in Naive Yearling Horses(2010-07-14) Garey, Shannon M.Recently, the European Union published regulations regarding the welfare of horses during transport requiring that horses be transported in individual stalls separated by partitions. The objective of this study was to determine if concentrations of cortisol, corticosterone, or dehydroepiandrosterone (DHEA) differed among horses with no prior transport experience when transported in individual stalls versus loose groups. Twenty na?ve yearlings were assigned to either individual stalls or a loose group, then transported for 6 hours. Ten horses were transported per day (5 in stalls and 5 in a loose group) over a two day trial. The experiment was replicated with a second trial 35 days later, and utilized a switchback design where the horses exchanged treatments between trials. Blood samples were collected and analyzed for cortisol, corticosterone, and DHEA concentrations at pre-transport, 2, 4, and 6 h of transport, and at 2 and 4 h after unloading. After Trial 2, the horses? changed housing from group paddocks to stalls and a follow-up experiment was conducted. The data were analyzed using a mixed model repeated measures ANOVA with the animal as the subject, with trial, treatment, sample time, and treatment-sample time interaction in the model with unstructured covariance (SAS 9.1). Differences between sample times within each trial, and pre-transport concentrations between trials, were analyzed using paired t-tests (SPSS 12.0.1). No significant differences were found in hormone concentrations for horses transported in individual stalls versus in loose groups. Horses exhibited a significant elevation in cortisol and corticosterone during transport which returned to pre-transport concentrations by 2 hr after transport (P < 0.01). Mean pre-transport cortisol concentrations rose significantly in Trial 3 (7.87 ng/ml) from Trials 1 (2.71 ng/ml) and 2 (2.84 ng/ml) (P < 0.001). Pre-transport concentrations of DHEA in Trials 1 (482 pg/ml) and 2 (392 pg/ml) also rose significantly in Trial 3 (1607 pg/ml) (P < 0.01). Changes in cortisol and DHEA indicated that transportation was a significant stressor for horses, however, being transported in a loose group versus individual stalls was not different. Also, housing changes from paddocks to stalls resulted in significant increases in pre-transport concentrations of stress-related compounds.Item Evaluation of the inter-relationships of temperament, stress responsiveness and immune function in beef calves(Texas A&M University, 2006-08-16) Oliphint, Ryan AllanA series of in vivo and in vitro approaches were followed to assess the inter-relationships of temperament, stress responsiveness and immune function in beef bulls and steers. In experiment one, Brahman bull calves were weaned at approximately six months of age when pen score and exit velocity were measured to sort calves into groups with extremes in temperament (calm n = 10 and temperamental n = 10). The calves were vaccinated on day 0 and 42 of the study with serial blood samples colleted for 11 weeks. Calm calves tended to have higher primary and secondary immune responses as indicated by increased serum concentrations of immunoglobulin G following Clostridial vaccination. In vitro lymphocyte cultures were performed on day 0 and 42 to measure proliferation and IgM production. Calm calves had significantly higher proliferative responses on both day 0 and 42. Lymphocyte IgM production was significantly higher in calm calves on day 0 and tended to be higher on day 42 than temperamental calves. In experiment two, weaned and yearling steers were arrayed by pen score and exit velocity, to assign steers to groups with extremes in temperament (trial 1: calm n = 7 and temperamental n = 5; trial 2: calm n = 5 and temperamental n = 5). In both trials, temperamental steers had higher proliferative responses than calm steers. Immunoglobulin M production did not differ in either trial. The effects of stress responsiveness on animal performance and health are considerable because they affect the profitability of the cattle industry. Investigations into animal temperament can help cattle producers identify animals that may be more susceptible to decreased performance and immunosuppression. The effectiveness of vaccines given to calves is important in conferring immunity to common diseases at times when they are at a higher risk for infection. If we can identify temperamental animals that will not perform as well as their cohorts, management procedures can be altered to reduce the risks associated with decreased performance and morbidity.Item Gender differences in psychopathology examined under an expanded transactional theory of stress framework(2009-05-15) Lee, Jillian AprilPrevalence rates of many types of psychopathology are lower for men than they are for women, but the causes of these discrepancies are not known. This paper focuses on two such psychopathology groups ? eating disorders and depressive disorders ? and examines gender differences within a transactional theory of stress that takes into account levels of cognitive processing (an expanded transactional theory of stress). Both studies found that men are more physiologically reactive to disorder-relevant, stressful stimuli and stressful events. The study on depression also found that different cognitive processes may be depressogenic for men and women: deployment of attentional resources toward negative stimuli was associated with depression in men, while deployment of attentional resources away from positive stimuli was associated with depression in women. These findings have significant implications for choosing appropriate treatment options for men and women.Item Impacts of Castration and Docking Method on Lamb Stress and PerformanceBodenchuk, Leigh Ann .; Salisbury, Michael W; Scott, Cody B; Runyan, Chase A; Osterhout, John JThe objectives of this study were to determine which method of castration and docking causes more stress to lambs and subsequent effects on performance. For this study 60 crossbred lambs, 31 females and 29 males, were assigned to one of two treatment groups. Female lambs were docked while male lambs were castrated. Lambs were docked or castrated with either an All-in-One tool or by elastrator rubber band. Ewe lambs docked with an elastrator band were more restless than lambs docked with an All-in-One (p < 0.01). There were no differences in mean 93 day weight between ewe treatments (p = 0.93). Male lambs castrated with an elastrator band vocalized more (p = 0.03) and were more restless than lambs castrated with an All-in-One (p = 0.05). Mean 93 day weight was affected by treatment with banded males weighing more than All-in-One castrated males (p = 0.03). Results suggest that castration method can affect performance while docking method does not.Item Investigating the Relation Between Stress and Marital Satisfaction: The Interaction Effects of Dyadic Coping and Communication(2013-07-30) Gasbarrini, Molly FThis study examined the role that communication and coping skills play in the relation between stress and marital satisfaction in a community sample of 119 married, heterosexual couples in Italy. Hierarchical regression models were used to test for communication or coping skills as a moderator of the relation between an external or internal stressor and relationship satisfaction. Results from regression analyses showed that actor reports of both coping and communication significantly contributed to relationship satisfaction above and beyond contributions from external/internal stressors for both husbands and wives. There was a significant interaction effect of poor communication and internal stress on relationship satisfaction for both husbands and wives. There was also a significant interaction effect of coping skills and internal stress on relationship satisfaction for wives. Additionally, there was a significant interaction effect of husbands? coping and wives? internal stress on relationship satisfaction. Implications of these findings for prevention and intervention strategies for relationship distress and for further research are discussed.Item Leadership Skills and StressRussell, Whitney Marie; van Ittersum, Kyle; Brewer, Steven; Stenmark, Cheryl; Solomon, MarvaThe present study induced stress in order to examine the relationship between leadership skills and stress. The study evaluated leadership skills, personality, and affect in order to measure the differences between perceived stress and physiological stress. Physiological stress was measured by salivary Cortisol samples that were taken before and after the stressor. The participants were exposed to the Trier Social Stress Test (TSST) as the stressor. A stepwise regression found that the personality factor, Neuroticism, was a significant predictor of Cortisol reactivity (R2 = .081, F(1, 68) = 5.966, p < .05) and self-reports of stress (R2 = .057, F(1, 68) = 4.113, p < .05). These findings suggest that individuals who are high in neuroticism might not be the best candidates for high stress jobs or workplaces.Item Media induced anxiety in the active duty medical clinic setting: A pilot study(2009-05-21) Jonathan Michael Strobel; Laura Rudkin; Ruth Levine; Dan FreemanMedia stimuli have long been used in the research community to evaluate autonomic responses among subpopulations. Prior to the terrorist attacks of 9/11, the majority of research had been focused on war veterans, rape/crime victims, and vehicle accident victims. Post- 9/11, a new surge of research has been focused on survivors, eyewitnesses, and media watchers to the extraordinary events that occurred on that historic day. The current news media stimuli of violent activities and economic and political turmoil are potential stressors for active duty soldiers who have faced or will face similar events in the near future. These types of media stressors could potentially lead to unnecessary autonomic response in the active duty soldiers who are a susceptible population. Currently there is no policy is in place to regulate what is being shown in the waiting rooms of clinics attended by these soldiers. The aims of this Capstone are twofold. The first aim is to assess the impact of current news media coverage on the anxiety levels of active duty soldiers in the clinical setting. The second aim is to propose recommendations regarding the types of media that should be restricted in the military medical clinic setting.Item Nutritional modulation of immunity and physiological responses in beef calves(Texas A&M University, 2004-11-15) Kurz, Michael WayneTwenty-four crossbred steer calves (235 + 6 kg initial BW) were weaned, adapted to a growing diet, trained to use Calan feeders and assigned to one of four treatments in a 2 x 2 factorial arrangement as follows: (1) no transit stress and saline injection, (2) no transit stress and trace mineral and vitamin E (TM/VitE) injections, (3) transit stress and saline injection and (4) transit stress and TM/VitE injection. TM/VitE injections consisted of MultiminTM to provide 0.3, 0.6, 0.15 and 0.6 mg of Cu, Mn, Se, and Zn/kg BW, respectively, and Vita ETM to provide 9 IU of VitE/kg BW on d 0 and 21 of the study. On d 24, transit-stressed steers were subjected to a three-d, 2000-km, transportation period. During the 56-d experiment, liver and serum samples were assayed to assess trace mineral status, antibody titers to keyhole limpet hemocyanin (KLH) measured to assess humoral immunity and phytohemagglutinin(PHA)- and ovalbumin(OVA)-induced skin swelling and lymphocyte proliferation measured to assess cellular immunity. TM/VitE-injected steers grew slower (P < 0.05) over the first 24 d of the experiment and tended (P = 0.10) to grow slower after transit. TM/VitE injections increased (P < 0.05) liver Cu and Zn concentrations 135 and 21 % by d 30, respectively. TM/VitE-injected steers had increased (P < 0.05) serum Cu on d 24 and 26, but decreased (P < 0.05) serum Zn and whole blood Se compared to saline-injected steers on d 24 and 56. TM/VitE injections increased serum α-tocopherol concentrations. TM/VitE injections did not affect humoral immunity, but decreased (P < 0.05) skin-swelling responses to PHA on d 21, and decreased (P < 0.05) lymphocyte proliferation to OVA and KLH. Transit-stressed steers had higher (P < 0.05) serum Cu on d 26, and higher (P < 0.05) liver Cu concentrations on d 56 than non-transit-stressed steers. Transit stress did not affect serum Zn or whole blood Se concentrations. Injections of TM/VitE increased Cu, Zn and vitamin E, but not Se status. The TM/VitE treatment suppressed growth and cellular immune function suggesting that levels of trace minerals used in this study were too high.Item Psychological Well-Being and Spinal Cord Injury Recovery: A Two-Way Street?(2014-08-26) Maldonado, SiouiSpinal cord injury (SCI) leads to increased anxiety and depression in as many as 60% of patients. Yet despite extensive clinical research focused on understanding the variables influencing psychological well-being following SCI, risk factors that decrease psychological well-being remain unclear. We hypothesized that excitation of the immune system, inherent to SCI, may contribute to the decrease in well-being. We used a battery of established behavioral tests to assess depression and anxiety in contused rats and (1) characterized psychological well-being as a function of SCI severity, (2) examined peripheral (serum) and central (hippocampi and spinal cord) inflammation in relation to psychological well-being post SCI, and (3) explored whether social enrichment, as a modulator of psychological well-being, could improve overall recovery post SCI, by housing contused animals either alone, or with an injured or an intact cagemate. Following SCI, the contused subjects showed one of three profiles: depression-like, depression- and anxiety-like, or no signs of decreased psychological well-being. Subjects exhibiting a purely depression-like profile showed higher levels of pro-inflammatory cytokines peripherally, whereas subjects exhibiting a depression- and anxiety-like profile showed higher levels of pro-inflammatory cytokines centrally (hippocampi and spinal cord). These changes in inflammation were not associated with injury severity; suggesting that the association between inflammation and the expression of behaviors characteristic of decreased psychological well-being was not confounded by differential impairments in motor ability. Social enrichment, in the form of group housing, did not improve psychological well-being post SCI. Depression- and anxiety-like signs were found in all group housing conditions. Unexpectedly, we found that the intact animals housed with contused subjects showed depression- and anxiety-like signs similar to those of contused subjects, indicating that their psychological well-being was affected by the presence of an injured cagemate. This is reminiscent of the caregiver effect in humans, specifically the manifestation of symptoms of depression in individuals who care for patients suffering with a chronic illness, such as SCI. These experiments demonstrate that the depression and anxiety patients experience following spinal cord injury is not due solely to psychosocial factors, but may also, in part, result from increased immune activation following the injury.Item Psychoneuroimmunology of Interleukin-10(2006-07-14) Huolin Tu; Thomas K. Hughes, Ph.D.; S David Hudnall, M.D; Peter L. Rady, M.D., Ph.D; John F. Sheridan, Ph.D; Eric M. Smith, Ph.DAppropriate interactions between the neuroendocrine and immune systems are important for optimal host defense and homeostasis. Pro-inflammatory cytokines such as interleukin-1, interleukin-6 and tumor necrosis factor-alpha, arising from disease processes, can activate the hypothalamic-pituitary-adrenal (HPA) axis. Interleukin-10, as a prominent anti-inflammatory cytokine in the immune system, has been shown to be expressed in both the central nervous system and neuroendocrine system. Little is known, however, about IL-10's functions in the HPA axis. We hypothesize that IL-10 contributes to the homeostasis of the HPA axis. In order to examine this hypothesis, we conducted in vitro and in vivo experiments. In our in vitro studies, we found the following: IL-10 induces the production of corticotropin-releasing hormone (CRH) from the hypothalamus; IL-10 induces the production of adrenocorticotropic hormone (ACTH) from AtT-20 cells derived from pituitary; and IL-10 inhibits glucocorticoid (GCS) production in Y-1 cells in the presence of ACTH. In our in vivo studies, we found that serum corticosterone in IL-10 knockout mice is significantly higher than in wild type mice under basal conditions and following immune and physiologic stress. In our microarry analysis, we determined gene expression profiles regulated by IL-10 and interferon (IFN)-gamma in cells derived from the HPA axis. The results showed that quorums of genes are modulated by IL-10 and IFN-gamma in these neuroendocrine cells, which provides a valuable repository to aid in understanding cytokine functions in the HPA axis at the molecular level. In addition, we found that endogenous IL-10 contributes to pain behavior in response to a noxious thermal stimulus as well as Capsaicin induced pain behaviors. Moreover, we found that cytokines such as IFN-¦Ã and IL-10 are able to regulate indoleamine 2, 3-dioxygenase (IDO) expression in cells of hypothalamic and pituitary origin. The capability of IL-10 to suppress IFN-¦Ã induced IDO expression implies that IL-10 has a putative neuroprotective role in the HPA axis. These novel data strongly suggest that IL-10 plays a potential role in the homeostasis of the HPA axis and has a complicated role in pain perception.Item Relationships among Perceived Working Hours, General Stress, Work Centrality, Job Control, Job Demands, and Work Condition Constraints(2014-06-27) Kim, Se HoonAlthough working hours are generally regarded as a major indicator of stress, little exploration has been done about how working hours influence stress with the relevant individual and job characteristics. The purpose of this study was to examine the relationships among perceived working hours, general stress, work centrality, job control, job demands, and work condition constraints for full-time employees in the United States and Korea. A self-administered questionnaire survey approach was used to collect data which were utilized to reflect six variables of this study. The sample size was 805 (U.S.: 397, Korea: 408). As the results from the measurement invariance test indicated that the measurement model was not invariant by country, statistical examinations were conducted separately for each country to test hypotheses. In the path analysis, for the U.S. sample, Job Demands was significantly associated with Perceived Working Hours. Job Demands and Work Condition Constraints were significantly related to General Stress. There was a significant relationship between Work Condition Constraints and Job Demands. There were significant mediation effects for the relationships between Work Condition Constraints and Perceived Working Hours via Job Demands and between Work Condition Constraints and General Stress via Job Demands. For the Korean sample, in the path analysis, Work Centrality and Job Demands were significantly associated with Perceived Working Hours. Job Demands, Job Control, and Work Condition Constraints were significantly associated with General Stress. There was a significant relationship between Work Condition Constraints and Job Demands. All the hypothesized mediation effects were significant: from Job Demands via Perceived Working Hours to General Stress, from Work Condition Constraints via Job Demands to Perceived Working Hours, and Work Condition Constraints via Job Demands to General Stress. It was found that this study overall supported the selected theories and related research. The significance of this study includes contributions to work-life/work-family balance studies that are an emerging research area in HRD, practical implications for sound work-settings, and cultural validations of the theories related to working hours and stress. Limitations, implications for theories, research, and practices were also discussed.Item Stress in Hispanic women enrolled in selected medical schools in Texas(Texas A&M University, 2005-02-17) Anita, Connelly NicholsonLittle uniquely identifiable information about Hispanic women who gain entrance into medical school is known. A few studies that focus just on stress in Hispanic women in medical school have found ?unique? stressors. This research examines stress in Hispanic women students (all four years) at Texas A&M University System ? Health Science Center ? College of Medicine (TAMUS-HSC) at College Station and at the University of Texas Medical Branch (UTMB) at Galveston, Texas. Twenty- four women took part in this project. Data was gathered using a packet of questionnaires, incorporating Sheridan and Radmacher?s Comprehensive Scale of Stress Assessment and the Personal Style Inventory (1987 and 1991) and The Community Oriented Primary Care (COPC) Student Project: Stress in First-Year Medical Students (Lensky, Noori, Matsukuma, Melamud & Chen, 1999). Each woman was personally interviewed. The results suggest increased stress and ?unique? stressors found by others who have researched Hispanic women in medical school. The intensity of medical school coupled with the stress that engulfs them from fear and sometimes anger (two stress emotions) stemming from worry about failure in school and worry about student loans that they are fearful they may not be able to repay causes high stress. Social, ethnic, and cultural bias and norms barriers to which they struggle to overcome anger them. Results from investigation of coping strategies suggest the women are coping as well as can be expected and are joyous over what they are doing. They rely on social groups to give them support. The knowledge they have obtained that there is prejudice toward their academic qualifications seems to make them more determined. They appear to be non-traditional and strong women who feel they are destined to become medical doctors This research should add valuable information to future research in this area. It is suggested by this author that there is a need for substantial, active, immediate and constant support for all minority students in Texas medicine. It is of necessity that minority mentors be trained and efforts made to put in place a program that works to support the women who are struggling and in fear of failing out.Item Stress response effects on growth, carcass characteristics, and tenderness in Bonsmara-influenced steers(Texas A&M University, 2006-08-16) Falkenberg, Shollie MarieHalf-blood Bonsmara steers were evaluated for temperament during stressful situations to discover the relationships between behavioral stress responses, growth, carcass characteristics and tenderness. Two experiments were conducted to evaluate behavioral stress responses at different stages in the U.S. beef production system with growth, carcass characteristics and tenderness. The first experiment evaluated stress responses at both time of weaning and at the beginning of the feedlot period on half-blood Bonsmara X Beefmaster steers. Steers (n=156) were weaned and paired to destinations of either Uvalde or Overton for winter grazing. At weaning cattle were weighed, and temperament measurements were recorded. After grazing winter pastures, cattle entered the feedlot and were measured for temperament, weight, and condition and frame scores. Cattle were harvested in two groups; each group was selected for harvest when they reached a backfat of approximately 7 mm. Backfat endpoints were determined by visual assessment and ultrasound. Carcass data were recorded approximately 36 hrs post-mortem, and 2.5cm steaks were removed from the 13th rib for Warner-Bratzler shear force determination. The second experiment involved Bonsmara X Angus (n=207) steers grazed on wheat pasture and fed at Cattletown feedlot near Hereford, TX. The steers were evaluated near the beginning and end of the finishing phase for performance and temperament. They were harvested in two groups; each group was selected for harvest when they reached approximately 7 mm of backfat as determined by visual assessment and ultrasound. In experiments 1 and 2, behavioral or temperament measures and hormonal responses were related to each other. It appeared as cattle become acclimated to the production system, temperament measures lose their predictive ability. In Experiment 1, weaning exit velocity appeared to be more related to economically important traits such as ADG (r = -0.26), ribeye area (r = -0.37), and Warner Bratzler shear force (r = 0.27), although beginning feedlot exit velocity was associated with feedlot weights (r = -0.30). In Experiment 2, end feedlot measurements tended to be more associated with feedlot weight (r = -0.20), but there did not seem to be any high relationships with carcass characteristics and tenderness.Item Stress-dependent permeability on tight gas reservoirs(Texas A&M University, 2005-02-17) Rodriguez, Cesar AlexanderPeople in the oil and gas industry sometimes do not consider pressure-dependent permeability in reservoir performance calculations. It basically happens due to lack of lab data to determine level of dependency. This thesis attempts to evaluate the error introduced in calculations when a constant permeability is assumed in tight gas reservoir. It is desired to determine how accurate are conventional pressure analysis calculations when the reservoir has a strong pressure-dependent permeability. The analysis considers the error due to effects of permeability and skin factor. Also included is the error associated when calculating Original Gas in Place in the reservoir. The mathematical model considers analytical and numerical solutions of radial and linear flow of gas through porous media. The model includes both the conventional method, which assumes a constant permeability (pressure-independent), and a numerical method that incorporates a pressure-dependent permeability. Analysis focuses on different levels of pressure draw down in a well located in the center of a homogeneous reservoir considering two types of flow field geometries: radial and linear. Two different producing control modes for the producer well are considered: constant rate and constant bottom hole pressure. Methodology consists of simulated tight gas well production with k(p) included. Then, we analyze results as though k(p) effects were ignored and finally, observe errors in determining permeability (k) and skin factor (s). Additionally, we calculate pore volume and OGIP in the reservoir. Analysis demonstrates that incorporation of pressure-dependence of permeability k(p) is critical in order to avoid inference of erroneous values of permeability, skin factor and OGIP from well test analysis of tight gas reservoirs. Estimation of these parameters depends on draw down in the reservoir. The great impact of permeability, skin factor and OGIP calculations are useful in business decisions and profitability for the oil company. Miscalculation of permeability and skin factor can lead to wrong decisions regarding well stimulation, which reduces well profitability. In most cases the OGIP calculated is underestimated. Calculated values are lower than the correct value. It can be taken as an advantage if we consider that additional gas wells and reserves would be incorporated in the exploitation plan.