Thermal Expansion of 3C-SiC Obtained from In-Situ X-ray Diffraction at High Temperature and First-Principal Calculations

In situ X-ray crystallography powder diffraction studies on beta silicon carbide (3C-SiC) in the temperature range 25–800 °C at the maximum peak (111) are reported. At 25 °C, it was found that the lattice parameter is 4.596 Å, and coefficient thermal expansion (CTE) is 2.4 ×10−6/°C. The coefficient of thermal expansion along a-direction was established to follow a second order polynomial relationship with temperature (α11=−1.423×10−12T2+4.973×10−9T+2.269×10−6). CASTEP codes were utilized to calculate the phonon frequency of 3C-SiC at various pressures using density function theory. Using the Gruneisen formalism, the computational coefficient of thermal expansion was found to be 2.2 ×10−6/°C. The novelty of this work lies in the adoption of two-step thermal expansion determination for 3C-SiC using both experimental and computational techniques.     

Biliary dyskinesia in children

Biliary dyskinesia (BD) is a well-recognized cause of chronic abdominal pain in adults, but is less common in children. We reviewed our experience with the diagnosis, treatment, and follow-up in a group of children treated with cholecystectomy from March 1995 to October 2000. We identified children with chronic upper abdominal pain, normal ultrasonography (US), and delayed cholecystokinin (CCK)-stimulated gallbladder emptying (<35%). All other diagnostic tests for their abdominal pain were reviewed. Their treatment, surgical intervention, and outcome were recorded. During the study period, 74 cholecystectomies were performed in our institution, 10 (13.5%) of them for BD. The duration of symptoms ranged between 1 and 60 months (mean 22). All patients had a normal plain abdominal radiograph, normal US, and delayed gallbladder ejection fraction (EF). All were treated by elective laparoscopic cholecystectomy. Symptoms were completely relieved in all patients during the follow-up period, which ranged between 9 and 24 months (mean 12.8). Cholecystectom should be considered in children with chronic upper-abdominal pain and delayed EF on CCK-HIDA scintigraphy. Laparoscopic cholecystectomy is the procedure of choice in these patients.     

Relationships between the electroretinogram a-wave,b-wave and oscillatory potentials and their application to clinical diagnosis

The electroretinogram is the electrical response of the retina to a light stimulus. The amplitude and temporal pattern of its components, the a-wave, the b-wave and the oscillatory potentials, depend on the functional integrity of the retina, on the intensity of test flash reaching the retina and on the ambient illumination. The latter contributions to the normal variability in the electroretinogram can be circumvented by constructing the relationships between the different electroretinogram waves. The electroretinogram responses were recorded from 18 dark-adapted subjects with normal vision. The slope of the a-wave and the amplitude of the b-waves were measured in the time domain. The oscillatory potentials were isolated by a digital filter and were transformed to the frequency domain for quantitative measurement. The relationship between each pair of variables could be fitted by linear segments. Our findings suggest that this mode of electroretinogram analysis can be useful in localizing the site of action of retinal disorders and that the relationship between the a-wave slope and the power density of the oscillatory potentials is a useful index for identifying disorders of the inner retina.     

Estimating the incubation period of paediatric AIDS in Rwanda.

OBJECTIVE: To estimate the distribution of the incubation period of paediatric AIDS in Rwanda. DESIGN: Data were collected between February 1984 and December 1990 at the Centre Hospitalier de Kigali (CHK), the capital city of Rwanda, Central Africa. PATIENTS: We used a sample of 685 AIDS cases registered consecutively in the Department of Paediatrics of the CHK, in which the proportion of perinatally acquired HIV-1 infection was estimated to be 98.6%. METHODS: We performed both non-parametric and parametric analyses. The methods of estimation were adapted to truncated data, using essentially the same methods as Auger et al. in their analysis of data from the New York City and the New York State AIDS case registries in 1988. RESULTS: We found that a double Weibull model fitted the data very well and that the risk of developing AIDS was high for subjects under 18 months of age, but lower for older subjects. CONCLUSIONS: Our results were qualitatively similar to those of Auger et al.. There were quantitative differences between the two studies, but it was not possible to compare median survival periods. Parameters such as median or mean survival times cannot be validly estimated using only data from registers because these data exclude infected subjects who have not yet developed AIDS.     

The epidemiology of measles in a partially vaccinated population in an African city: implications for immunization programs

A large outbreak of measles was reported in Pointe-Noire, Congo, between October 1984 and March 1985. An investigation was conducted to determine the epidemiology of measles in this community in which, in 1985, 54% of the children 12-23 months of age had documented evidence of vaccination against measles. The investigation included hospital and clinic record reviews and a community survey. Measles has been continuously transmitted in Pointe-Noire since at least 1979, with seasonal epidemics. In early 1984, the expected epidemic did not occur, and at least 1,000 measles hospital admissions and 100 measles deaths were prevented. Between October 1984 and March 1985, 1,942 measles cases were hospitalized, of which 306 (15.8%) died. During the epidemic, the proportion of nonpreventable cases (cases occurring before nine months of age) was 17%, reflecting the change in age distribution of measles cases in childhood since the immunization program started in Pointe-Noire in 1982. From the community survey, it was estimated that 13% of all children under age five years acquired measles in Pointe-Noire in 1985. Vaccine efficacy was calculated from community and hospital samples to be between 78% and 87%. Our findings suggest that increasing vaccination coverage levels to well above 50% is necessary to substantially reduce measles morbidity and mortality in African cities.     

Hepatitis C virus: The role of molecular mimicry in response to interferon treatment

Chronic hepatitis C virus (HCV) infection is one of the major causes of chronic liver disease worldwide. In order for HCV to persist, the virus must escape immune recognition or inhibit the host immune response. The NS5A protein contains the interferon sensitivity‐determining region (ISDR) and is able to repress dsRNA‐dependent protein kinase (PKR) thus influencing the response to interferon (IFN) therapy. Patients who respond to IFN therapy have stronger antibody reactivity against the NS5A compared to IFN non‐responders. Therefore, given the possible role for the ISDR in IFN resistance and differential antibody reactivity, it is possible that variation in ISDR may be involved in viral immune escape and development of persistent HCV infection employing aspects of host mimicry. In this study, pre‐treatment samples obtained from HCV infected patients were used to investigate the effect of different NS5A ISDR variants on the IFN antiviral response and their involvement in immune evasion. The NS5A was identified as a homologue of the variable region of immunoglobulins (Ig). The IFN resistant genotypes had higher levels of similarity to Ig compared to IFN sensitive genotypes. Expression of NS5A‐6003 (HCV genotype 1b) and NS5A‐6074 (HCV genotype 2a) was able to rescue vesicular stomatitis virus (VSV) from IFN inhibition and restore luciferase activity. A correlation between Ig‐like NS5A structure and also antibody response with the outcome of IFN treatment was observed. J. Med. Virol. 84:1571–1585, 2012. © 2012 Wiley Periodicals, Inc.