Development and characterisation of pressed packaging solutions for high-temperature high-reliability SiC power modules

SiC is a wide bandgap semiconductor with better electrothermal properties than silicon, including higher temperature of operation, higher breakdown voltage, lower losses and the ability to switch at higher frequencies. However, the power cycling performance of SiC devices in traditional silicon packaging systems is in need of further investigation since initial studies have shown reduced reliability. These traditional packaging systems have been developed for silicon, a semiconductor with different electrothermal and thermomechanical properties from SiC, hence the stresses on the different components of the package will change. Pressure packages, a packaging alternative where the weak elements of the traditional systems like wirebonds are removed, have demonstrated enhanced reliability for silicon devices however, there has not been much investigation on the performance of SiC devices in press-pack assemblies. This will be important for high power applications where reliability is critical. In this paper, SiC Schottky diodes in pressure packages have been evaluated, including the electrothermal characterisation for different clamping forces and contact materials, the thermal impedance evaluation and initial thermal cycling studies, focusing on the use of aluminium graphite as contact material

Antimicrobial susceptibility pattern of Aeromonas hydrophila among patients presented with diarrhea attending two teaching hospitals in northern, Nigeria

A total of one hundred and twenty eight (128) stool samples were collected from patients attending Ahmadu Bello University Teaching Hospital Zaria and Aminu Kano Teaching Hospital Kano, and screened for the presence of Aeromonas hydrophila infection. Out of the one hundred and twenty eight samples analyzed 4 (3.12%) were found positive for Aeromonas hydrophila infection. Antibioticsusceptibility testing of Aeromonas hydrophila isolated showed that all the 4 (100%) isolates were sensitive to Colistin and Ceftazidime, 3 (75%) to Augmentin and 2(50%) to Gentamicin and Cefuroxine. All the isolates (100%) were however resistant to Cotrimoxazole, Tetracycline, Sulphatriad, Streptomycin, Cephalothin and Ampicilin. This study confirmed that Aeromonas hydrophila as a sole enteropathogen could be responsible for diarrhea and should be considered amongst the causative agents of diarrhea. Key words: Aeromonas, diarrhoea, antibiotic, susceptibility testing, ABUTH, AKTH

Survey of the Symptoms and Viruses Associated with Cowpea (Vigna Unguiculata (L).) in the Agroecological Zones of Kwara State, Nigeria

A comprehensive field survey was carried out in 2011 spanning thirty locations within the forest and savannah agroecologies of Kwara State, Nigeria. This was with the objective of having an overview of the prevalence of virus disease symptoms and to specifically identify the viruses infecting cowpea (Vigna unguiculata .L.) in Kwara State. Data were collected on the prevalence of some peculiar virus symptoms on cowpea plants on growing on farms in each location. Symptomatic cowpea leaves were also collected from each location for virus identification in the laboratory. The serological protocol employed for virus detection in the leaf samples was the antigen – coated plate Enzyme linked immunosorbent assay (ACP–ELISA) method. The results of the field survey indicated that the symptoms observed on the cowpea plants were peculiar to those associated with virus disease infection. The symptoms observed were leaf mottling (36.8%), mosaic (24.9%), leaf curl (15.6%), necrotic spots (8.2%) and other symptoms (14.5%). The result of the laboratory assay to detect the viruses present in the leaf samples revealed the presence of four (4) different viruses. The viruses identified were, Cowpea Aphid Borne Mosaic Virus (CABMV), Cowpea Yellow Mosaic Virus (CYMV), Blackeye Cowpea Mosaic Virus (BICMV) and Cowpea Mottle Virus (CPMoV). These viruses were detected infecting the cowpea plants in mixtures of two or three. These results are indicative of the presence of viruses in all the ecological zones of Kwara State where cowpea is cultivated.Keywords: Survey, Agroecology, Cowpea, Virus, Symptoms, ACP-ELIS

Humoral immune response of chickens following vaccination with different Newcastle disease vaccines

In spite of numerous vaccines and different vaccination schedules used in the control of Newcastle disease (ND), prevention and control remain a challenge. This study evaluated three different ND vaccines. A total of one hundred and twenty, day-old brown pullets obtained from a commercial hatchery in Ibadan, Nigeria were used for the experiment. The birds were randomly assigned into 4 groups in which groups A, B and C were vaccinated on days 1, 21 and 42 of age, while group D served as unvaccinated group (control). Hitchner B1 (HB1), Clone-30 and F-Strains were used as the primers for the 3 vaccinated groups respectively. Blood samples were collected from all birds in each group on vaccination day and assayed for NDV antibody by Haemagglutination-inhibition (HI) test. Twenty five chickens from each group were challenged with virulent Newcastle disease virus (Kudu 113 strain) at 3rd week after the last vaccination. The mean antibody titres of the chickens from the vaccinated groups at 3rd week post primary vaccination showed no significant difference. However, a significant difference existed following secondary vaccination with La Sota and Komarov strains at 3rd and 6th weeks of age. A good immune response and clinical resistance were observed in group of chickens vaccinated with Hitchner B1 and Clone-30 as primers than those vaccinated using F-strain. Therefore, Hitchner B1 or Clone-30 is better primer for vaccinating chickens against Newcastle disease.Keywords: Chickens, Vaccination, antibody, Newcastle disease, Challenge viru

Is there scope for cost savings and efficiency gains in HIV services? A systematic review of the evidence from low- and middle-income countries.

OBJECTIVE: To synthesize the data available--on costs, efficiency and economies of scale and scope--for the six basic programmes of the UNAIDS Strategic Investment Framework, to inform those planning the scale-up of human immunodeficiency virus (HIV) services in low- and middle-income countries. METHODS: The relevant peer-reviewed and "grey" literature from low- and middle-income countries was systematically reviewed. Search and analysis followed Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. FINDINGS: Of the 82 empirical costing and efficiency studies identified, nine provided data on economies of scale. Scale explained much of the variation in the costs of several HIV services, particularly those of targeted HIV prevention for key populations and HIV testing and treatment. There is some evidence of economies of scope from integrating HIV counselling and testing services with several other services. Cost efficiency may also be improved by reducing input prices, task shifting and improving client adherence. CONCLUSION: HIV programmes need to optimize the scale of service provision to achieve efficiency. Interventions that may enhance the potential for economies of scale include intensifying demand-creation activities, reducing the costs for service users, expanding existing programmes rather than creating new structures, and reducing attrition of existing service users. Models for integrated service delivery--which is, potentially, more efficient than the implementation of stand-alone services--should be investigated further. Further experimental evidence is required to understand how to best achieve efficiency gains in HIV programmes and assess the cost-effectiveness of each service-delivery model

Biology of human respiratory syncytial virus: a review

Acute lower respiratory tract infection is one of the major causes of mortality and morbidity in young children worldwide. Respiratory syncytial virus (RSV) is the single most important viral cause of lower respiratory tract infection during infancy and early childhood worldwide. Respiratory syncytial virus belongs to the Pneumovirinae subfamily of the Paramyxoviridae family of enveloped single stranded negative sense RNA viruses. The virus accounts for approximately 50% of all pneumonia and up to 90% of the reported cases of bronchiolitis in infancy. It is a common community–acquired respiratory pathogen without ethnic, socioeconomic, gender, age or geographic boundaries. Moreover, the epidemiological and ecological relationships between Human Respiratory syncytial virus, man and environment have aroused increasing interest in this viral, specie. The present review looks at the nature of this virus with the view to provide more information about its biology which may be useful to the present and future researchers

Study of the Geographically Weighted Regression Application on Climate Data

This study used Geographical Weighted Regression (GWR) technique to find spatial relationship between Elevation and climate (Rainfall, Temperature) in Northern Nigeria using climate (Rainfall, Temperature) data from weather stations from 1980 – 2010 obtained from Nigerian Meteorological Agency (Nimet). From the results of the analysis it was shown that there is significant relationship between the elevation and climate variables (Rainfall, Tmax and Tmin). The study also shows that GWR has smaller residual sum of square than OLS in analysing the relationship between Elevation and Climate data. This may be due to the consideration of the spatial variation of the relationship over the study region. When mapping the results of GWR model it was observed that the effect of Elevation on climate variables appears to vary geographically Keyword: Geographical Weighted Regression (GWR), Ordinary Least square (OLS)

Necrotic enteritis and its management in 13-week old commercial pullets in Katsina, Nigeria

Necrotic enteritis is rarely reported because it is often misdiagnosed as coccidiosis due to similarity in clinical and pathological features. A field outbreak of necrotic enteritis in a flock of 13 weeks old 4,500 commercial pullets was investigated, the onset of the disease, morbidity and mortality rates were recorded. Post mortem examinations were conducted and gross lesions were documented. Tissues were collected and fixed in 10 % neutral buffered formalin and processed for histopathological examinations. Clinical signs observed were ruffled feathers, weakness, somnolence, loss of weight and diarrhoea; while the gross lesions observed were emaciated carcasses, lean abdominal fat, enlarged, pale and haemorrhagic liver; enlarged, mottled and congested spleen; mucus and diphtheritic membrane on the jejunal mucosa and enlarged kidneys. The histopathological findings of the intestine were diffused necrotic epithelial cells with marked mononuclear cells infiltration in the mucosa with severe oedema fluid. The necrotic enteritis was diagnosed based on clinical signs, pathology as well as isolation and identification of Clostridium perfringes. Triplesulfa® (sulfadimidine sodium, sulfadiazine sodium and sulfamerazine sodium); Tridox® L.A (20% Oxytetracycline long acting) and Enterocillin® (Amoxycillintrihydrate and Colistin sulphate) were ineffective, while copper sulphate at 1g/5L of drinking water was found to be effective for the treatment of the disease. The haematological values indicated lymphocytosis due to damage of the tissue caused by C. perfringes and the toxins produced. Keywords: Necrotic enteritis, Commercial pullets, Copper sulphate, Clostridium perfringen

Correlation and Path Analysis between Sorghum Yield to Growth and Yield Characters

Mutual association between characters of two sorghum varieties (ICSV III and SAMSORG 14) was determined using correlation coefficient of two years experiment. The percent contribution of growth and yield components to yield was also determined with path coefficient analysis. In both years and the average over the years, a positive and highly significant correlation was observed between sorghum yield and plant height, leaf area index and total dry matter. Likewise, sorghum yield also had a positive and highly significant interaction with panicle weight and 1000- grain weight. The highest individual contribution was made by leaf area index, followed by plant height. Total dry matter, panicle length and weight also contributed positively to the final yield. The highest combined percent contribution to yield resulted from plant height via leaf area index.  This was followed by contribution from plant height via panicle weight, panicle length via leaf area index respectively. In improving sorghum yield emphasis on breeding should be on its height, leaf area index and panicle length. Keywords: Sorghum, correlation, growth, regression and yield