Combined Influence Of Stress Research Articles

Evaluation of stress, serum and salivary cortisol, and interleukin-1β levels in smokers and non-smokers with chronic periodontitis.

Existing literature indicates a positive relationship between stress and chronic periodontitis (CP) but there is limited information on the combined influence of stress and smoking on the progression of periodontal disease. So, the objective of this study was to evaluate the effects of stress, salivary and serum, cortisol and interleukin-1β levels in smokers with CP. Seventy-five patients equally divided into three groups of healthy controls (Group I), smokers and non-smokers with CP (Group 2 and Group 3) respectively were evaluated for clinical parameters, biochemical parameters of salivary and serum cortisol and IL-1β levels via enzyme linked immunosorbent assay (ELISA). Zung's self-rating depression scale questionnaire was used to determine the stress levels amongst the patients. Smokers with CP exihibited higher values of probing pocket depth, clinical attachment level, plaque index while lower papillary bleeding index, and gingival index scores as compared to non-smokers with CP. The salivary cortisol and IL-1 β were relatively higher as compared to serum values in Group 2 than Group 3. The Group 2 patients revealed higher depression scores as compared to Group 3 patients. The depression scores positively and significantly correlated with the salivary cortisol in Group 2 patients. The results indicate that smokers with CP exhibit a significantly higher serum and salivary cortisol, IL-1β, and stress levels and thus they may show an increased risk and periodontal disease severity. Further exploration of relationships between periodontitis and stress is required.

Stress corrosion cracking of CrNi martensitic stainless steels for steam turbine blades

Stress corrosion cracking (SCC) is a delayed failure process that can occur in susceptible materials that are both under stress and in a corrosive environment. Microscopic cracks may be initiated at surface flaws, such as pits, and propagate by the combined influence of stress and corrosive attack until eventually the stress in the metal ahead of the crack exceeds that of its fracture strength, whereby component failure could occur. Steam power plants generate electricity through transforming the energy contained in steam to the rotation of a generator. The presence of condensing steam, in combination with high centrifugal stresses, provides the potential for SCC in low pressure cylinders.Laboratory samples of 12 wt% Cr martensitic stainless steels, used for low-pressure steam turbine blades, previously exposed to condensing steam at 95°C for various times, have been examined using optical and scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and electron backscatter diffraction (EBSD). The corrosion products formed within stress corrosion cracks have been analysed with the objective to devise a method of dating stress corrosion cracks by establishing links between the scale thickness and morphology and variables such as exposure time, crack length and initial stress intensity.

Вплив вихрового імпульсного магнітного поля лівого обертання на біоелектричну активність гіпоталамуса щурів за фізіологічних умов та за умов стресу

Досліджено динаміку спектральної композиції електричної активності егротропної та трофо­тропної зон гіпоталамуса щурів за умов тривалого стресу (21 тиждень) і дії лівонапрямленого вихрового імпульсного магнітного поля (МП). Виявлено, що ефекти впливу вихрового МП залежать від вихідного стану дослідженої мозкової структури та терміну впливу. За фізіологічних умов під впливом МП у спек­тральній композиції електрогіпоталамограми спостерігається синхронізація, яка виражається у підвищенні потужності тета-ритму. Під комбінованим впливом стресу та МП спостерігається формування двофазної електрогіпоталамограми у вигляді послідовної зміни явища десинхронізації синхронізацією електричної активності за рахунок представленості високочастотних компонентів.

Psychosocial Factors Associated with Adaptation in HIV-Infected Mothers

Factors associated with the mental health of 40 HIV-infected mothers were examined in a sample of primarily African-American and Latina, socioeconomically disadvantaged single mothers with histories of substance use recruited from pediatric HIV clinics. Structured questionnaires on stress, social support, family functioning, psychiatric disorder, psychological distress, and substance abuse were individually administered. Different dimensions of stressful experiences (particularly losses due to death and victimization), social support, and family functioning combined in different ways to influence the mother's mental health. The combined influence of stress and social support accounted for at least half the variance in both psychiatric symptoms and psychological distress. This study supports models of stress and protective factors in understanding the mental health of HIV+ mothers, particularly models that examine stress in different life domains and different positive and negative components of social support and family functioning.

Mechanics and mechanism of environmental crazing in a polymeric glass

The conditions have been studied for propagation of single discontinuities (cracks and crazes) in poly(methyl methacrylate) under the combined influence of stress and solvents. A series of aliphatic alcohols, water-alcohol mixtures and carbon tetrachloride were employed and temperature effects were investigated over the range 273K to 323K. Using a fracture mechanics approach, the minimum surface work J 0 required to propagate the discontinuity was estimated as a function of temperature for each solvent. J 0 varies with temperature in a consistent manner, decreasing rapidly as the temperature rises up to a characteristic temperature T c and then remaining constant at some value J ∗ 0 for T > T c . The value of J ∗ 0 is a smooth function of the difference ( δ s − δ p ) between the solubility parameters of the solvent and the polymer, both for pure solvents and water mixtures, reaching a minimum at ( δ s − δ p ) = 0. The critical temperature for pure solvents (but not solvent-water mixtures) decreases with increasing ( δ s − δ p ), probably extrapolating to T g for the plastic at ( δ s − δ p ) = 0. The behaviour of J 0 can be explained in terms of a cavitation criterion for craze formation and the necessary theory is developed. It attributes the temperature-independent value of J ∗ 0 to a polymer/solvent interfacial energy effect, and the variation of J 0 at T < T c to a yield stress effect.

Investigation of time-to-rupture of polymethyl methacrylate under the combined influence of active liquid media and ?-radiation

Time-to-rupture and creep of polymethyl methacrylate (PMM) under the combined influence of stress, active liquid media, and γ-radiation were studied. It was shown that time-to-rupture of PMM under these conditions is determined mainly by the influence of the working medium when the absorbed radiation dose is less than about 10 Mrads and that γ-radiation increases the creep rate of PMM in active liquid media.

Apparatus for investigating the creep and long-time strength of thermoplastic materials in aggressive media

A description is given of an apparatus for investigating the creep and long-time strength of thermoplastic materials under the combined influence of stress, temperature, and aggressive media.

Effects of temperature on the plastic properties of aluminium crystals

By changing the temperature of deformation, during tensile experiments on single crystals of aluminium , it has proved possible to separate reversible changes of flow stress with temperature from irreversible ones. Below 130° K the reversible change of flow stress is large; above room temperature it is hardly more than the change of elastic constants with temperature. These reversible changes are highly reproducible and, over a wide range of cold-worked states, proportional to the flow stress itself. The principal irreversible effect is a sharp yield drop, accompanied by a Lüders band, which appears when a crystal is strained plastically at a high temperature (e.g. 300° K) immediately after being heavily cold-worked at a low temperature (e.g. 90° K ). Intermediate annealing treatments reduce or eliminate this yield drop. Other experiments have proved that the yield drop is not a strain-ageing phenomenon but an extreme example of work softening, and that work hardening induced by preliminary deformation at the low temperature becomes unstable during plastic deformation at the high temperature and is rapidly removed. An explanation of the yield drop is suggested, based on recent theories of work hardening. It is proposed that, under the combined influence of stress and temperature, sessile dislocations at the heads of piled-up groups of dislocations become unlocked; the piled-up groups then partly collapse and many dislocations are released for slip. The reversible changes of flow stress are interpreted in terms of the intersection of dislocation lines.