Stress and smoking in adolescence: A test of directional hypotheses.

The authors conducted a comparative test of the hypotheses that (a) stress is an etiological factor for smoking and (b) cigarette smoking causes increases in stress (A. C. Parrott, 1999). Participants were a sample of 1,364 adolescents, initially surveyed at mean age 12.4 years and followed at 3 yearly intervals. Measures of negative affect, negative life events, and cigarette smoking were obtained at all 4 assessments. Latent growth modeling showed negative affect was related to increase in smoking over time; there was no path from initial smoking to change in negative affect. Comparable results were found for negative life events, with no evidence for reverse causation. Results are discussed with respect to theoretical models of nicotine effects and implications for prevention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A longitudinal study of the moderating role of extraversion: Leader-member exchange, performance, and turnover during new executive development.

Identifying factors that help or hinder new executives in "getting up to speed" quickly and remaining with an organization is vital to maximizing the effectiveness of executive development. The current study extends past research by examining extraversion as a moderator of relationships between leader-member exchange (LMX) and performance, turnover intentions, and actual turnover for an executive sample. The sample consisted of 116 new executives who were surveyed prior to starting their employment and at 3 months postentry. A total of 67 senior executives rated these new executives in terms of overall performance at 6 months postentry. Turnover data were gathered from company records 3 1/2 years later. Hierarchical regression results showed that LMX was not related to performance or turnover intentions for those high in extraversion; but for individuals low in extraversion, there was a relation between LMX, performance, and turnover intentions. Furthermore, survival analyses showed that LMX was only related to turnover-hazard rate for individuals low in extraversion. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Effects of injurious compression on matrix turnover around individual cells in calf articular cartilage explants

The effects of mechanical injury on the metabolism of cartilage matrix are of interest for understanding the pathogenesis of osteoarthrosis and the development of strategies for cartilage repair. The purpose of the present study was to examine the effects of injury on matrix turnover in a calf articular cartilage explant system for which the effects of mechanical loading on cell activity and the cell-mediated pathways of matrix metabolism are already well characterized. New methods of quantitative autoradiography were used in combination with established biochemical and biomechanical techniques for the analysis of cell and matrix responses to acute mechanical injury, with particular attention to the processes of localized matrix turnover in the cell-associated matrices of individual chondrocytes. Matrix deposition and turnover around cells in control explants was spatially dependent, with the highest rates of proteoglycan deposition and turnover and the lowest rates of collagen deposition (as indicated by [3H]proline autoradiography) occurring in the pericellular matrix. Injurious compression was associated with (a) an abrupt decrease in the tensile load-carrying capacity of the collagen matrix, apparently associated with mechanical failure of the tissue, (b) a considerable but subtotal decrease in cell viability, marked by the emergence of an apparently inactive cell population interspersed within catabolically active but abnormally large cells, and (c) sustained, elevated rates of proteoglycan turnover, particularly in the cell-associated matrices of apparently viable cells, which involved the increased release of aggregating species in addition to a spectrum of degradation fragments that were also in controls. These results may represent an in vitro model for the responses of chondrocytes and the cartilage extracellular matrix to mechanical injury.     

Heterogeneity in the families of sons of alcoholics: The impact of familial vulnerability type on offspring characteristics.

In 2 samples of sons of alcoholics (family history positive for alcoholism; FHP: N?=?74 & N?=?72), cluster analyses identified 3 subtypes of familial vulnerability: 1 with low levels of familial psychopathology (FHP-LP) and moderate levels of familial alcoholism; a 2nd with high levels of familial antisocial personality (FHP-ASP), violence, and alcoholism; and a 3rd with high levels of familial depression (FHP-DEP), mania, anxiety disorder, and alcoholism. Compared with family history negative (FHN) participants (N?=?106), FHP offspring had higher levels of alcohol problems. FHP-ASP offspring had elevated levels of antisocial traits and negative affect. Compared with FHN participants, FHP-DEP offspring elevated levels of antisocial traits, hypomania, and experience seeking. FHP-LP offspring had moderate levels of antisocial traits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

iNOEX:超声波科技实现便捷轻松的薄层检测

汽车行业、地热行业及其它多个行业对多层供给管材的性能有严格的要求,因此,诸如汽车刹车管和地热管之类多层管材的生产工艺是非常复杂的。为满足特定的机械或化学性能要求,多层管的生产中经常需要用到超     

A highly compact packaging concept for ultrasound transducer arrays embedded in neurosurgical needles

Microsystem Technologies - State-of-the-art neurosurgery intervention relies heavily on information from tissue imaging taken at a pre-operative stage. However, the data retrieved prior to...     

Mathematical optimization of multilayer piezoelectric devices with nonuniform layers by simulated annealing

Multilayer ultrasonic transducers with layers of uniform design are in common use. It is also possible to devise such transducers in which the layer design is nonuniform. However, this adds many degrees of freedom to the transducer design, and conventional design techniques are inadequate to realize desired behavior or even to assess potential benefits. In this paper, a theoretical investigation of multilayer piezoelectric structures with nonuniform layers is reported. Results are presented from a study using computer code to solve the one-dimensional wave equation. It is first shown how multilayer structures with nonuniform layer thicknesses generate even and odd harmonics in their frequency response, suggesting that frequency response can be controlled by choice of layer thickness. However, this choice is complicated and it is impossible to analyze all possible combinations of layer thicknesses. Hence, use of the stochastic optimization technique of simulated annealing is reported. Two optimized transducer designs illustrate this. The first design maximizes uniformity of the fundamental, second, and third harmonics of pressure output, achieved to approximately +/-3%. The results suggest additional bandwidth can be achieved for practical applications, as the presence of a finite response at the second harmonic frequency avoids the null usually associated with this frequency. This is further illustrated with the second optimized transducer design in the form of a three-layer 1-3 connectivity piezo-composite transducer for underwater operation.     

Scheduling with Conflicts on Bipartite and Interval Graphs

In this paper, we consider the on-line scheduling of jobs that may be competing for mutually exclusive resources. We model the conflicts between jobs with a conflict graph, so that the set of all concurrently running jobs must form an independent set in the graph. This model is natural and general enough to have applications in a variety of settings; however, we are motivated by the following two specific applications: traffic intersection control and session scheduling in high speed local area networks with spatial reuse. Our results focus on two special classes of graphs motivated by our applications: bipartite graphs and interval graphs. The cost function we use is maximum response time. In all of the upper bounds, we devise algorithms which maintain a set of invariants which bound the accumulation of jobs on cliques (in the case of bipartite graphs, edges) in the graph. The lower bounds show that the invariants maintained by the algorithms are tight to within a constant factor. For a specific graph which arises in the traffic intersection control problem, we show a simple algorithm which achieves the optimal competitive ratio.