Glass-clad single-crystal germanium optical fiber.

Long lengths (250 meters) of a flexible 150 microm diameter glass-clad optical fiber containing a 15 microm diameter crystalline and phase-pure germanium core was fabricated using conventional optical fiber draw techniques. X-ray diffraction and spontaneous Raman scattering measurements showed the core to be very highly crystalline germanium with no observed secondary phases. Elemental analysis confirmed a very well-defined core-clad interface with a step-profile in composition and nominally 4 weight-percent oxygen having diffused into the germanium core from the glass cladding. For this proof-of-concept fiber, polycrystalline n-type germanium of unknown dopant concentration was used. The measured infrared transparency of the starting material was poor and, as a likely outcome, the attenuation of the resultant fiber was too high to be measured. However, the larger Raman cross-section, infrared and terahertz transparency of germanium over silicon should make these fibers of significant value for fiber-based mid- to long-wave infrared and terahertz waveguides and Raman-shifted infrared light sources once high-purity, high-resistivity germanium is employed.

Silicon optical fiber.

Described herein are initial experimental details and properties of a silicon core, silica glass-clad optical fiber fabricated using conventional optical fiber draw methods. Such semiconductor core fibers have potential to greatly influence the fields of nonlinear fiber optics, infrared and THz power delivery. More specifically, x-ray diffraction and Raman spectroscopy showed the core to be highly crystalline silicon. The measured propagation losses were 4.3 dB/m at 2.936 microm, which likely are caused by either microcracks in the core arising from the large thermal expansion mismatch with the cladding or to SiO(2) precipitates formed from oxygen dissolved in the silicon melt. Suggestions for enhancing the performance of these semiconductor core fibers are provided. Here we show that lengths of an optical fiber containing a highly crystalline semiconducting core can be produced using scalable fiber fabrication techniques.

Abundance of leptin mRNA in fetal adipose tissue is related to fetal body weight.

Leptin mRNA was measured in adipose tissue of fetal sheep by reverse transcription polymerase chain reaction (RTPCR). Abundance of leptin mRNA relative to b-actin mRNA in fetal perirenal adipose tissue increased (P<0.02) with gestation, being higher at 144 d (0.73 +/- 0. 10, n=5) than at 90-91 d (0.40 +/- 0.08, n=6) or 125 d (0.40 +/- 0. 04, n=5) gestation (term approximately 147- 150 d). There was a positive relationship between relative abundance of leptin mRNA (y) and fetal body weight (x)between 90 and 144 d gestation (r 2 =0.27, P<0.01). The slope of the linear dependence of leptin mRNA on fetal weight was 15-fold greater (P<0.001) at 90-91d (y = 2.81x - 1.1, n=6, r 2 =0.71, P<0.025) than between 125-144 d gestation (y = 0.195x - 0.15, n=16, r 2 =0.39, P<0.01). Thus the leptin synthetic capacity of fetal adipose tissue appears to increase in late gestation but this is accompanied by constraint of its sensitivity to fetal body weight. We hypothesise that leptin synthesis in fetal adipose tissue is related to fetal nutrient supply and growth rate.

Perceived benefit from child sexual abuse.

People often report perceptions of benefit from adverse life experiences. In this study, adult perceptions of benefit from child sexual abuse were examined in a sample of 154 low-income women who were sexually abused as children. Almost half reported some perceived benefit. The benefits fell into 4 main categories: protecting children from abuse, self-protection, increased knowledge of child sexual abuse, and having a stronger personality. Degree of perceived benefit was associated with several indicators of adult adjustment. In addition, those who perceived themselves as stronger had higher self-esteem, and those who perceived increased sexual abuse knowledge viewed others more favorably and were more comfortable getting close to others, when compared with other respondents.

Untangling the impact of sexual abuse on HIV risk behaviors among youths in foster care.

This study investigates the interrelationships among childhood sexual abuse, other types of child maltreatment, emotional and behavioral problems, and HIV risk behaviors in a sample of 167 adolescents, aged 15-19, participating in an independent living preparation program in one midwestern county. Thirty-three percent of the youths identified as white and 67% as youths of color. The sample was almost evenly split by gender (51% male and 49% female). Thirty-five percent of the youths (n = 59) reported some form of sexual abuse; 21 reported unwanted touching, with no unwanted intercourse, and 38 reported unwanted intercourse. Multivariate analyses demonstrated a significant relationship between the severity of sexual abuse and youths' recent HIV risk behaviors, after accounting for the contribution of other childhood trauma and emotional and behavioral problems. The findings support the need for HIV prevention programs targeting sexually abused youths.

Positive by-products of the struggle with chemical dependency.

Focus groups were conducted to identify ways persons in recovery from chemical dependence think they have benefited from their struggles with addiction. Categories of positive by-products were identified independently by two sets of readers. Several of the positive by-products discussed by the focus group participants are commonly reported from other kinds of challenging life experiences. These include increases in self-efficacy, family closeness, closeness with others, compassion and spirituality, and changes in life priorities. Additional positive by-products were discussed by the focus group participants that may be more unique to substance abuse and other similar stressors, including increased self-knowledge, enhanced ability to help offspring with substance abuse-related issues, and decreased naïveté. Ways to incorporate knowledge about these positive by-products into substance abuse treatment programs are introduced.

Concrete strategies for sensitizing youth-serving agencies to the needs of gay, lesbian, and other sexual minority youths.

In the past few years, several authors have detailed the needs of gay and lesbian youths and the obstacles youth-serving agencies face in addressing their needs. How administrators and practitioners can make changes in agencies that are not adequately serving sexual minority youths has been unclear. This article uses the experiences of two youth-serving agencies to offer recommendations on agency philosophies concerning the social realities of sexual minority youths and on several ways of creating a safe, welcoming, and productive environment.