Life stress and adjustment: Effects of life events experienced by young adolescents and their parents.

A longitudinal design was used to test the effects of life events experienced by young adolescents and their parents. The criteria were the adolescents' depression, anxiety, and self-esteem. The longitudinal analysis revealed a significant effect for the adolescents' controllable, but not uncontrollable, negative events. However, causal analyses revealed that this effect was the result of the significant relation between initial adjustment and the subsequent occurrence of controllable life stress (e.g., school suspension). The longitudinal analysis also revealed the stress-protective role of positive events, but only with respect to girls' self-esteem. There was no longitudinal support for the role of the parents' negative life events. These findings do not support the etiological importance of an accumulation of relatively discrete negative events experienced by early adolescents and their parents, but they do suggest the need (a) to conceptualize (controllable) life stress as a dependent variable in future research on developmental psychopathology; (b) to examine gender differences in early adolescent life stress; and (c) to develop more sophisticated measures of family life stress. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Extremum-seeking with variable gain control for intensifying biogas production in anaerobic fermentation.

A state-dependent variable-gain control system is implemented to follow the characteristics of a laboratory-scale up-flow anaerobic fixed-bed reactor dynamically. The transition from one state to another is determined on an hourly basis, depending on difference between the setpoint of the reactor pH and its true value. Considerable improvement of the process stability--reduction of oscillation in both the reactor pH and biogas production rate during high-rate operation, has been achieved, although the control structure is simple and intuitive.     

Changing the hydrogen content of alloy steel in relation to the technology used to cool cast slabs

Results are reported from the production of two trial heats of alloy steel in which the cast slabs were cooled in a thermostatted chamber and in a dense stack. It is shown that cooling slabs in such a chamber makes it possible to reduce the hydrogen content of the steel 30% compared to slabs that are cooled while stacked.     

A contribution to the theory of parametric excitation of thermomechanical oscillations

The conditions for a rather fast increase in parametric thermomechanical oscillations have been revealed by using numerical solutions of some types of Hill's equation. It is shown that the occurrence of a real parametric resonance is essentially determined by the character of thermal modulations. It is hypothesized that the indicated trends are observed in oscillations of any physical nature.Stavropol State Pedagogical Institute, Stavropol. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 63, No. 3, pp. 294–298, September, 1992.     

Methods to assess physical activity with special reference tomotion sensors and accelerometers

Motion sensors may be applied for the assessment of physical activity. This paper reviews the evolution of these instruments from the mechanical pedometer to the electronic accelerometer. We conclude that for accurate assessment of physical activity under free living conditions the recently introduced accelerometer looks most promising, although little information was available regarding the reliability of these instruments. Subsequently, reliability of an accelerometer with a three-directional sensor was examined. Intrainstrument variation in a bench test was less than 8% during four measurements over a week. Interinstrument variation during treadmill experiments while subjects wore two accelerometers at the same time was on average 22% and was not improved after adjustment for differences found in the bench test. Reproducibility in the treadmill experiment was approximately 76, 85, and 95% at 3, 5, and 7 km/h, respectively. Bench testing revealed that the sensitivity of a piezoelectric element is prone to shifts, probably due to mechanical, electromagnetic, and/or temperature shock, which may be encountered during outdoor application. However, the relevance of the bench test in this study may be questioned, as results did not correspond with the findings in subjects. This needs further investigation.     

A note on computing environments and network reliability

Interest has increased during recent years in using microcomputers for implementation of network reliability algorithms. There are indications that some implementations suffer severe restrictions imposed by such a computing environment, whereas some other results indicate otherwise. This brief note attempts to clarify the apparently contradictory conclusions that would be naturally drawn from recent papers that treat this subject.     

Preparation,structure and properties of transition metal trichalcogenides

In recent years, the transition metal trichalcogenides (TX₃) of Group IVB, VB and VIB have received much more attention because of the considerable diversity in their physical properties. The most striking feature of these compounds is that the structure here may be classified into three types depending on the number of different TX₃ chains present in the unit cell. Thus ZrSe₃, TaSe₃ and NbSe₃ are the representative compounds having one, two and three types of chain based on the different bond lengths for the (X₂)^2– pairs in the base of the TX₃ trigonal prismatic framework. A similar model is also applicable in the case of NbS₃, with the addition of a 2b-superstructure associated with the formation of niobium pairs. The chain structure also facilitates the process of intercalation which has been most effectively used in secondary batteries. These compounds exhibit the superconductivity phenomena and charge density wave, etc. and also find application in photoelectrochemical cells. An attempt has been made here to review the up-to-date chemistry of transition metal trichalcogenides related with their preparation, structure and properties such as physical and chemical, thermodynamic, electrical, magnetic and optical properties, intercalation and use in the photoelectrochemical cells. 93     

Use of liquid sealants to protect still-waste-containing tanks-settling basins from corrosion

Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 10, pp. 29–31, October, 1992.     

Cimaterol and clenbuterol residue analysis by HPLC-HPTLC in liver.

A method has been developed for the analysis of cimaterol and clenbuterol residues in liver, with detection limits of 0.25 micrograms/kg and 0.5 micrograms/kg, respectively. The recovery varied from 55% to 60%. After extraction, a clean-up procedure with Baker-spe C-18 columns was performed. The two chemical compounds of interest were eluted with methanol. Cimaterol and clenbuterol were quantitatively determined by high-performance liquid chromatography (HPLC) using an RP-Select B (5 microns) column and a post-column reaction procedure. The positive results were confirmed by high-performance thin-layer chromatography (HPTLC) as this technique reaches the same level of sensitivity as the HPLC method.