Sub-0.6 eV Inverted Metamorphic GaInAs Cells Grown on InP and GaAs Substrates for Thermophotovoltaics and Laser Power Conversion

We present inverted metamorphic Ga0.3In0.7As photovoltaic converters with sub-0.60 eV bandgaps grown on InP and GaAs substrates. The compositionally graded buffers in these devices have threading dislocation densities of 1.3x10^6 cm^-2 and 8.9x10^6 cm^-2 on InP and GaAs, respectively. The devices generate open-circuit voltages of 0.386 V and 0.383 V, respectively, at a current density of ~10 A/cm^2, yielding bandgap-voltage offsets of 0.20 and 0.21 V. We measured their broadband reflectance and used it to estimate thermophotovoltaic efficiency. The InP-based cell is estimated to yield 1.09 W/cm^2 at 1100 degrees C vs. 0.92 W/cm^2 for the GaAs-based cell, with efficiencies of 16.8 vs. 9.2%. The efficiencies of both devices are limited by sub-bandgap absorption, with power weighted sub-bandgap reflectances of 81% and 58%, respectively, which we assess largely occurs in the graded buffers. We estimate that the thermophotovoltaic efficiencies would peak at ~1100 degrees C at 24.0% and 20.7% in structures with the graded buffer removed, if previously demonstrated reflectance is achieved. These devices also have application to laser power conversion in the 2.0-2.3 micron atmospheric window. We estimate peak LPC efficiencies of 36.8% and 32.5% under 2.0 micron irradiances of 1.86 W/cm^2 and 2.81 W/cm^2, respectively.Comment: 14 pages, 6 figure

Serum testosterone levels of HbSS (sickle cell disease) male subjects in Lagos, Nigeria

<p>Abstract</p> <p>Background</p> <p>Infertility is a major problem in sickle cell disease patients, especially in males. In addition to low serum testosterone, other abnormalities involving the accessory sex organs, such as the seminal vesicles and the prostate gland, as well as marked decrease in ejaculate volume may be observed in male HbSS patients. Hence, the need to study the role of sex hormones as a cause of infertility in male HbSS patients.</p> <p>Methods</p> <p>An unmatched case-control study was performed using seventy-five consenting subjects from Lagos University Teaching Hospital. These included 47 patients with haemoglobin phenotype SS from the Sickle cell clinic and 28 volunteered medical students and members of staff with haemoglobin phenotype AA. Demographic data were obtained using a self-administered questionnaire. A total of 5 mls of blood was collected from each subject between 9.00 am & 11.am, and assayed for serum testosterone concentration.</p> <p>Results</p> <p>The concentrations of serum testosterone in HbSS patients ranged from 0.2 to 4.3 ng/ml with a mean of 1.28 ± 0.72 ng/ml whilst the values in HbAA controls ranged from 1.2 to 6.9 ng/ml with a mean of 2.63 ± 1.04 ng/ml. Seven (25.0%) of the 28 controls had serum testosterone concentration lower than the quoted reference (normal) range whereas 44 (93.6%) of the 47 HbSS subjects had serum testosterone concentration lower than the reference range.</p> <p>Conclusion</p> <p>Overall, subjects with HbSS have significantly lower mean serum testosterone than HbAA controls.</p

Hematologic Abnormalities in Treatment-naïve HIV Patients

Objectives Hematologic abnormalities, indicated by a deranged full blood count, are common manifestations and important prognostic tools for human immunodeficiency virus (HIV) infection and AIDS. This study aimed to determine the prevalence of cytopenia and its relationship to the degree of immunosupression in HIV treatment-naïve patients. Methods This was a cross-sectional study of treatment-naïve HIV-infected clients who enrolled at the HIV clinic of Lagos State University Teaching Hospital (LASUTH) between December 2009 and June 2010. Participants had samples taken for full blood count and CD4 counts, which are free routine pre-requisite and pre-treatment evaluations done for all registered HIV patients at LASUTH. They were asked to fill the structured questionnaires to obtain demographic data, with assistance if necessary. Results A total of 205 cases were reviewed: 24.2% had anemia (PCV < 30%), 26.8% had leucopenia (white blood cell <4,000/L) and 16.1% had thrombocytopenia (platelet count <150,000/L) at enrollment. The degree of cytopenia was directly related to the degree of immunosupression. Conclusion About one-fifth of HIV treatment-naïve patients were cytopenic at enrollment and the degree of cytopenia was directly related to the degree of immunosupression. It is necessary to investigate various causes of cytopenia in these patients so as to administer a specific intervention

Bolstering the Impact of Social Entrepreneurship and Poverty Alleviation for Sustainable Development in Nigeria

Social entrepreneurship has gained increasing attention as a means to address social problems, including poverty, in Nigeria. Poverty is a major challenge in Nigeria, with a poverty rate of over 40%. Poverty alleviation is critical to achieving sustainable development in the country. Social entrepreneurship can play a key role in addressing poverty by creating jobs, providing access to goods and services, and promoting economic growth. Hence, this study examines bolstering the impact of social entrepreneurship and poverty alleviation for sustainable development in Nigeria. The research focuses primarily on fostering economic, social, and environmental improvements, as well as improving people’s lives. Three hypotheses were formulated to help accomplish the primary objectives of the study. The Opportunity-Based Entrepreneurship Theory, Social Network Theory, and Schumpeterian Theory of Innovation were used to explain the objective of the study. In this study, a purposive sampling technique was used, and 300 copies of structured questionnaires were administered to selected social entrepreneurs of which 262 copies were retrieved and used for the analysis. The data were analyzed using structural and measurement models, and the path coefficient was determined using PLS-SEM. The significance level was calculated using the bootstrapping method. The results from the test of hypotheses showed that; the most significant predictor of poverty alleviation is social innovation (β = 0.376, p p p < 0.05). This study concludes that social innovation is fundamental for empowering individuals and communities to lift themselves out of poverty and achieve long-term prosperity. The study recommends that to promote sustainable social entrepreneurship and poverty alleviation in Nigeria, the government can create policies and programs that support social innovation, such as providing access to funding, business training, and mentorship. The government can also collaborate with entrepreneurs and organizations to promote their initiatives and create a supportive ecosystem for social entrepreneurship