4 resultados para equivalent stress intensity factor
em Digital Commons at Florida International University
Resumo:
The purpose of this study was threefold. The primary purpose was to develop a stress profile for teachers in private schools. This study also addressed two exploratory issues. The first, consisted of an examination of the possible differences in the levels of on-the-job stress among teachers in different types of private schools. A second issue was to discuss the findings on private school in light of the extant literature on public schools, specifically using the data collected by Fimain to develop the Teacher Stress Inventory. This study was conducted utilizing 316 full time teachers from seven schools from six different states.^ The instrument employed in this study was the Teacher Stress Inventory (TSI) developed by Fimian (1988). The TSI is a 10 factor, 49 item self-report measure. The 10 factors consist of five Stress Sources and five Stress measure. The 10 factors consist of five Stress Sources and five Stress Manifestations subscales. The mean for these 10 factors yields the stress construct termed "Total Stress." Of the 437 surveys mailed, 316 usable surveys, i.e., 72.3%, were returned.^ The results suggest that private school teachers experience moderate levels of stress. The mean score was 2.27 indicating a lower than average stress level as measured by the TSI. Comparisons between types of private schools revealed that there were no significant differences between the stress levels of teachers in boarding and nonboarding schools. Teachers in large schools experience significantly higher levels of stress than teachers in small and medium size schools. However, the measurable difference between them translates into a very small difference in terms of the real stress levels of these teachers in their professional lives. A significant difference was also found between the stress levels of public $(M=2.60)$ and private school teachers $(M=2.27).$ Both means fall within the moderate range, however, while private school teachers experience lower than average levels of stress, the stress levels of teachers in public schools falls in the higher than average range.^ Recommendations for reducing stress levels in both private and public schools are presented as well as suggestions for future research. ^
Resumo:
Somatic growth in fishes is regulated by a variety of hormones. A central step in this hormonal network is the growth hormone-insulin-like growth factor-I (IGF-I) axis. Studies conducted evaluated the relationship of hepatic IGF-I (hIGF-1) mRNA with growth as affected by feeding regimes (satiation or restricted level; daily or alternate-day feeding), temperatures (high, ambient, low) and by social stress. To develop a cellular means for the quantification of hIGF-I mRNA levels in O. niloticus, hIGF-I cDNA was isolated and cloned. The partial sequence of IGF-I cDNA encodes for signal peptide, mature protein and a portion of the E-domain. A sensitive TaqMan quantitative reverse transcription-polymerase chain reaction (qRT-PCR) assay was developed based on the mature IGF-I. Using the developed qRT-PCR assay a significant positive correlation was observed between hIGF-I mRNA levels and growth rate of fish reared under different feeding regimes (r = 0.64) and temperature conditions (r = 0.64). On the dynamics of hIGF-I gene expression in response to elevated temperature, hIGF-I mRNA levels were significantly elevated after at least 2 days of exposure to warm temperature. This validates the concept that hIGF-I gene expressions are sufficiently sensitive to be used as a rapid growth rate indicator for O. niloticus. The hIGF-I levels have a significant positive correlation with specific growth rate (length; r = 0.92), and with condition factor (r = 0.55). On the effect of social stress, differential alterations in growth rates between the dominant and subordinates were observed which was attributed more to behavioral changes as transduced by physiological regulators. The fish's relative position in the social hierarchy was consistently reflected in the levels of hIGF-I mRNA and the eye color pattern. Subordination depressed hIGF-I levels while dominance stimulated it. These findings have shown that hGF-I level remained positively correlated to growth rate as affected by feeding regime, temperature and social stress. This suggests that hIGF-I plays a key role in controlling growth in O. niloticus and indicates that IGF-I mRNA quantification could prove useful for the rapid assessment of growth rate in this species of fish.
Resumo:
Isotope signatures of mangrove leaves can vary depending on discrimination associated with plant response to environmental stressors defined by gradients of resources (such as water and nutrient limitation) and regulators (such as salinity and sulfide toxicity). We tested the variability of mangrove isotopic signatures (d13C and d15N) across a stress gradient in south Florida, using green leaves from four mangrove species collected at six sites. Mangroves across the landscape studied are stressed by resource and regulator gradients represented by limited phosphorus concentrations combined with high sulfide concentrations, respectively. Foliar d13C ratios exhibited a range from 24.6 to –32.7‰, and multiple regression analysis showed that 46% of the variability in mangrove d13C composition could be explained by the differences in dissolved inorganic nitrogen, soluble reactive phosphorus, and sulfide porewater concentrations. 15N discrimination in mangrove species ranged from –0.1 to 7.7‰, and porewater N, salinity, and leaf N:Pa ratios accounted for 41% of this variability in mangrove leaves. The increase in soil P availability reduced 15N discrimination due to higher N demand. Scrub mangroves (<1.5 m tall) are more water-use efficient, as indicated by higher d13C; and have greater nutrient use efficiency ratios of P than do tall mangroves (5 to 10 m tall) existing in sites with greater soil P concentrations. The high variability of mangrove d13C and d15N across these resource and regulator gradients could be a confounding factor obscuring the linkages between mangrove wetlands and estuarine food webs. These results support the hypothesis that landscape factors may control mangrove structure and function, so that nutrient biogeochemistry and mangrove-based food webs in adjacent estuaries should account for watershed-specific organic inputs.
Resumo:
The adaptation process to a new land can be an arduous transition for families who migrate from their countries in an attempt to evade negative life conditions. Family-based immigration has been the cornerstone of immigration policy for the U.S. However, there has been a relative lack of attention given in immigration studies to the impact of immigration particularly on parents. Furthermore, little is known about their adjustment to their post-migration circumstances, particularly the initial phase of migration, where the psychological impact of immigration tends to be concentrated. It is even rarer that investigators have addressed longitudinally the dynamic process of parents' adaptation to a new ecology, which can shed a great deal of light on its mechanisms. In this dissertation, changes over time in levels of stress, adjustment (affect balance and life satisfaction), and the factors (social support, economic hardship, and discrimination) contributing to stress and adjustment were examined in newly immigrant parents from Argentina, Colombia, Cuba, Haiti, and the West Indies. Moderating effects of gender and country-of-origin were examined as well. This study also aimed to investigate to what extent the contributing factors impacted stress and adjustment, not only concurrently, but also over the first three years of post-migration. Analysis of variance results showed that both affect balance and social support increased whereas life satisfaction decreased over time. There was no significant change in stress, however. Both gender and group effects were also observed. Mothers experienced higher stress whereas fathers experienced higher discrimination. Among groups, Haitians appeared at the greatest risk in terms of stress, discrimination, and economic hardship. A structural equation modeling analysis showed that the relative importance of contributing factors changed over time in the process of immigrants' adaptation. Yet, social support emerged as a powerful protective factor in that its effects carried over time, and discrimination was a primary mediator through which other predictors were related to stress and adjustment. These findings shed light on the "hows and whys" of the immigration-adaptation process, by demonstrating the significance of specific conditions of life change to psychological outcomes as newly immigrant parents adapt to their post-migration ecology.