Influence of siblings on adolescent sexual behavior.

There has been recent attention in the research literature to the influence of friends on adolescent sexual behavior. This study extends that interest to the family environment and considers the influence that siblings can have on adolescent sexual behavior. We use a popular and powerful adolescent sexuality dataset—the {adsex} data, collected in two different metropolitan areas of the Southeast United States—and study previously unused family information contained therein. By considering the previous literature and possible effects of sibling influence, we made several predictions about the patterns we expected to find in the sibling data. We also specify several possible artifactual conclusions that may be ruled out by capitalizing on the longitudinal structure of the dataset. Analysis of the {adsex} data shows that younger siblings have consistently higher levels of sexual activity at a given age than their older siblings. The effect does not interact with race or with the sex-match of the siblings. A sibling influence interpretation seems the most plausible explanation for this result; the only other contenders are within-family processes that also act to make siblings systematically different at a given age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Quantum transport of p-type GaAs/(AlGa)As heterostructures grown on non-(100) substrates by molecular beam epitaxy

We report on a series of Be-doped GaAs/(AlGa)As two-dimensional hole gas (2DHG) structures grown on (110), (111)B, (211)B and (311)B oriented substrates and compare their properties with high mobility samples grown on (311)A using Si doping. The samples were prepared and grown under the same conditions in order to render them comparable. They are found to have mobilities which are strongly anisotropic within the plane. All the samples show strong low-field positive magnetoresistance with resistance increases of up to 30% at magnetic fields of only 0.1 T. The presence of this feature on all the different planes shows that it does not depend upon the details of the band structure. It is identified with the lifting of the degeneracy of the spin sub-bands by the asymmetrical potential giving rise to a classical two-band magnetoresistance.

The modulation-doped GaAs/(AlGa)As heterostructures grown on the (311)A GaAs surface using silicon as the acceptor produced 2DHGs with low-temperature hole mobility exceeding 1.2 × 10⁶ cm² V⁻¹ s⁻¹ with carrier concentrations as low as 0.8 × 10¹¹ cm⁻². This hole mobility is the highest ever observed at such low densities by any growth technique. These 2DHG samples show for the first time the persistent photoconductivity effect. This effect is normally absent in 2DHG systems. An analysis of the number density and temperature dependence of the mobility leads us to conclude that the mobility is limited by phonon scattering above 4 K and interface scattering at lower temperatures.     

Plasma protein profiles and prognosis in gastric cancer

In 104 patients with gastric cancer the serum proteins carcinoembryonic antigen (CEA), C-reactive protein (CRP), alpha 1-acid glycoprotein (AGP) (orosomucoid) and alpha 1-antichymotrypsin (ACT) were measured pre-operatively. The estimated median survival of patients with both raised CEA and ACT was only 5 weeks in contrast to 64 weeks for those with both proteins normal. An intermediary group with one of these proteins raised and the other normal had an estimated median survival of 15 weeks. Similar results were obtained by considering a combination of CEA with either AGP or CRP. For these data the results were not explicable in terms of associations between survival time and patient's age, stage, operative procedure, histological classification or site of primary tumour.     

Reliability of pressure-sensitive adhesive tapes for heat sink attachment in air-cooled electronic assemblies

This study investigates the reliability of commercially available pressure-sensitive adhesive (PSA) tapes used for electronic component-to-heat sink attachment. It is found that creep can affect the PSA reliability. Therefore, creep is experimentally characterized using isothermal, constant load, double lap shear measurements in conditions representative of vertically oriented heat sink applications. PSA joint life predictions are derived from the accelerated creep characteristics using a secondary creep model. The creep resistance of a laminated silicone/aluminum/acrylic PSA tape is found to be significantly lower than that of a single-layer acrylic tape. This suggests that the potential impact of tape creep on joint reliability should be carefully evaluated as a function of tape chemistry/construction and application environment. Furthermore, the sensitivity of PSA creep characteristics to both operating temperature and heat sink weight highlights the need for thermally optimized, least-weight heat sink designs.     

Preventing Thin Film Dewetting via Graphene Capping

A monolayer 2D capping layer with high Young's modulus is shown to be able to effectively suppress the dewetting of underlying thin films of small organic semiconductor molecule, polymer, and polycrystalline metal, respectively. To verify the universality of this capping layer approach, the dewetting experiments are performed for single‐layer graphene transferred onto polystyrene (PS), semiconducting thienoazacoronene (EH‐TAC), gold, and also MoS₂ on PS. Thermodynamic modeling indicates that the exceptionally high Young's modulus and surface conformity of 2D capping layers such as graphene and MoS₂ substantially suppress surface fluctuations and thus dewetting. As long as the uncovered area is smaller than the fluctuation wavelength of the thin film in a dewetting process via spinodal decomposition, the dewetting should be suppressed. The 2D monolayer‐capping approach opens up exciting new possibilities to enhance the thermal stability and expands the processing parameters for thin film materials without significantly altering their physical properties.     

Transforming growth factor-beta1 induces apoptotic cell death in cultured retinal endothelial cells but not pericytes: association with decreased expression of p21waf1/cip1

Building on earlier work by Pascual-Leone (1970) and Case (1985), Olson (1989; 1993) set out a theory showing how a series of incremental changes in capacity for "holding in mind" could account, in part, for children's acquisition of a theory of mind. Following Piaget (1951) infants were said to employ schemata for maintaining relations with objects and events in the presence of those events. At about 18 months children became capable of holding in mind an object so as to free the perceptual system to perceive a second object and form a relation between the two, allowing for what Piaget called the "symbolic function" and what Olson described as predication. At around 4 years, the period examined in the present study, children were said to acquire the ability to represent that predicative relation as a belief or as true or false. That was the stage at which children were said to possess a theory of mind. The present study tested the hypothesized relation between development of a theory of mind and increasing computational resources. Three-, four-, and five-year-old children's performance on a pair of theory of mind tasks was compared with that on a pair of dual processing tasks designed on the basis of Baddeley's (1986) model of working memory. The resulting correlations, as high as r = .64 between the tasks, suggest that changes in capacity to hold in mind allow the expression of, and arguably the formation of, a theory of mind.     

Curriculum trends in nurse-midwifery education. Views of program directors

The purpose of this study was to determine the extent to which nurse-midwifery education programs are addressing the practice competencies that have been recommended by the Pew Health Professions Commission and others as essential for effective practice in the 21st century. This study was part of a larger survey of eleven health professions education programs. The 56 nurse-midwifery program directors whose names and addresses were provided by the American College of Nurse-Midwives were surveyed by mailed questionnaire, with a response rate of 59% (n = 33). The study sought to identify current and ideal emphasis placed on 33 broad topics, most important curriculum topics, and barriers to curriculum change as perceived by respondents. Findings revealed that nurse-midwifery program directors would like to see greater emphasis placed on every topic except one (tertiary/quaternary care). Desired increases ranged from .04 to 1.36. The overall mean rating for all topics was 3.51 for current emphasis (5-point scale) and 4.18 for ideal emphasis, both of which were higher than any other survey group. The greatest desired increases (> 1.00) were for "primary care," "managed care," "use of electronic information systems," and "business management of practice." Respondents identified "primary care," "health promotion/disease prevention," and "accountability for cost-effectiveness and patient outcomes" as the most important topics. The top three barriers to curriculum change were identified as "already crowded curriculum," "inadequate funding," and "limited availability of clinical learning sites," the last being statistically significant compared with other survey groups. Findings indicate that nurse-midwifery program directors perceived that they are adequately addressing most of the curriculum topics, while continuing to focus on the need for curriculum change as the health care environment changes.     

Air-borne laser induced fluorescence system for measuring OH and other trace gases in the parts-per-quadrillion to parts-per-trillion range

Described in detail is a laser induced fluorescence system which has been successfully interfaced with two aircraft sampling platforms (i.e., Sabreliner jet and an L-188C Electra). This system, which has been under development for four years, presently consists of the following major components: (1) a Nd-Yag laser driven oscillator-amplifier dye laser; (2) a sampling manifold with associated fluorescence detection optics; (3) an OH calibration chamber; (4) a laser beam steering assembly; and (5) sampling electronics and data processing hardware. During the last three years, this system has been flown some 50 000 air miles making tropospheric OH radical measurements over the latitude range of 70 degrees N to 57 degrees S. OH concentrations measured during these flights have ranged from 30 parts-per-quadrillion (3.7x10(5) molecules/cm(3)) at altitudes of 6 km to 0.8 parts-per-trillion (2.0x10(7) molecules/cm(3)) at 0.5 km. Computations have been completed which indicate that the existing aircraft system with modest modifications should also be capable of detecting natural tropospheric levels of NO, SO(2), CH(2)O, NO(2), HNO(2), NO(3), H(2)O(2), and CS(2) by using both conventional laser-induced fluorescence methodology and multiphoton techniques.