Electron-Scale Reconnection in Three-Dimensional Shock Turbulence.

Magnetic reconnection has been observed in the transition region of quasi-parallel shocks. In this work, the particle-in-cell method is used to simulate three-dimensional reconnection in a quasi-parallel shock. The shock transition region is turbulent, leading to the formation of reconnecting current sheets with various orientations. Two reconnection sites with weak and strong guide fields are studied, and it is shown that reconnection is fast and transient. Reconnection sites are characterized using diagnostics including electron flows and magnetic flux transport. In contrast to two-dimensional simulations, weak guide field reconnection is realized. Furthermore, the current sheets in these events form in a direction almost perpendicular to those found in two-dimensional simulations, where the reconnection geometry is constrained.

Modeling Kelvin-Helmholtz Instability at the High-Latitude Boundary Layer in a Global Magnetosphere Simulation.

The Kelvin-Helmholtz instability at the magnetospheric boundary plays a crucial role in solar wind-magnetosphere-ionosphere coupling, particle entry, and energization. The full extent of its impact has remained an open question due, in part, to global models without sufficient resolution to capture waves at higher latitudes. Using global magnetohydrodynamic simulations, we investigate an event when the Magnetospheric Multiscale (MMS) mission observed periodic low-frequency waves at the dawn-flank, high-latitude boundary layer. We show the layer to be unstable, even though the slow solar wind with the draped interplanetary magnetic field is seemingly unfavorable for wave generation. The simulated velocity shear at the boundary is thin ( ∼ 0.65 R E ) and requires commensurately high spatial resolution. These results, together with MMS observations, confirm for the first time in fully three-dimensional global geometry that KH waves can grow in this region and thus can be an important process for energetic particle acceleration, dynamics, and transport.

Imaging findings in MR imaging-guided focused ultrasound treatment for patients with essential tremor.

BACKGROUND AND PURPOSE: MR imaging-guided focused sonography surgery is a new stereotactic technique that uses high-intensity focused sonography to heat and ablate tissue. The goal of this study was to describe MR imaging findings pre- and post-ventralis intermedius nucleus lesioning by MR imaging-guided focused sonography as a treatment for essential tremor and to determine whether there was an association between these imaging features and the clinical response to MR imaging-guided focused sonography. MATERIALS AND METHODS: Fifteen patients with medication-refractory essential tremor prospectively gave consent; were enrolled in a single-site, FDA-approved pilot clinical trial; and were treated with transcranial MR imaging-guided focused sonography. MR imaging studies were obtained on a 3T scanner before the procedure and 24 hours, 1 week, 1 month, and 3 months following the procedure. RESULTS: On T2-weighted imaging, 3 time-dependent concentric zones were seen at the site of the focal spot. The inner 2 zones showed reduced ADC values at 24 hours in all patients except one. Diffusion had pseudonormalized by 1 month in all patients, when the cavity collapsed. Very mild postcontrast enhancement was seen at 24 hours and again at 1 month after MR imaging-guided focused sonography. The total lesion size and clinical response evolved inversely compared with each other (coefficient of correlation = 0.29, P value = .02). CONCLUSIONS: MR imaging-guided focused sonography can accurately ablate a precisely delineated target, with typical imaging findings seen in the days, weeks, and months following the treatment. Tremor control was optimal early when the lesion size and perilesional edema were maximal and was less later when the perilesional edema had resolved.

HIV risk and prevention in emergency-affected populations: a review.

While basic guidelines on HIV prevention in emergencies have been available for several years, international agencies involved in the provision of health services have not placed sufficient priority on the prevention of the human immune deficiency virus (HIV) and other sexually transmitted infections (STIs) in complex emergencies. This paper reviews the factors that may increase the risk of HIV transmission in populations affected by complex emergencies and outlines recommendations for research and programmes. Research into the most appropriate methods of carrying out HIV surveillance and interventions in these settings is needed. In the post-emergency phase programmes need to be far more extensive than those offered under the Minimal Initial Services Package (MISP). While the potential for stigmatization represents an important constraint, there is a need to prioritize HIV/STI interventions in order to prevent HIV transmission in emergency-affected populations themselves, as well as to contribute to regional control of the epidemic.

Two new mutations in the human E1 beta subunit of branched chain alpha-ketoacid dehydrogenase associated with maple syrup urine disease.

Maple syrup urine disease (MSUD) is an autosomal recessive disorder caused by defective function of the mitochondrial branched chain alpha-ketoacid dehydrogenase (BCKD) complex. Mutations in both alleles of any of three genes for component proteins result in the clinical phenotype. Two discrete mutant alleles for the E1 beta subunit of the decarboxylase component in a proband with MSUD are defined and parental origin of each allele identified. The maternal mutation, an A to T transversion at nucleotide 526 in the coding sequence, potentiates an asparagine to tyrosine change at position 126 (N126Y). The paternal mutant allele contains a C to T transition at nucleotide 970 introducing a stop codon (R274 ). Western blot analysis revealed a 75% reduction in the E1 beta-N126Y protein and an absence of the R274* truncated protein in proband cells. Both mutant proteins could be synthesized, imported into mitochondria, and processed in vitro. Functional analysis of the mutant proteins provided new information on the role of E1 beta in the activity of BCKD. In vivo the E1 beta-N126Y protein associated into macromolecular complexes indistinguishable from those formed with the wild type E1 beta protein. However, catalytic activity of these complexes in proband cells was < 1% of wild type activity. Alignment comparisons with other thiamin pyrophosphate-requiring enzymes suggests the N126Y substitution could interfere with interactions of the protein with the cofactor causing inactivity. The truncated E1 beta-R274* protein is unstable and not found in mitochondria from the patient derived cells.

Prevalence of and risk factors for antibody to hepatitis E virus seroreactivity among blood donors in Northern California.

To evaluate antibody to hepatitis E virus (anti-HEV) seroreactivity, 5000 US blood donors were tested for anti-HEV by two EIAs: a mosaic protein assay (MPr-EIA) and a recombinant protein assay (RPr-EIA). Overall, 59 (1.2%) were seroreactive by MPr-EIA and 70 (1.4%) were seroreactive by RPr-EIA. The overall concordance between tests was 98.5% (4925/5000); the concordance among reactive sera by either test was only 27% (27/102). In a case-control study, seroreactive persons were more likely than seronegative persons to have traveled to countries in which HEV is endemic (odds ratio [OR] for MPr-EIA = 4.3, P < .001; OR for RPr-EIA = 2.5, P = .005), but 31% of MPr-EIA anti-HEV-reactive persons and 38% of RPr-EIA anti-HEV-reactive persons had no history of international travel. These findings suggest that travelers to regions in which HEV is endemic can acquire subclinical HEV infection. The significance of anti-HEV seroreactivity among persons without an international travel history needs to be determined.

Protection in a gerbil model of amebiasis by oral immunization with Salmonella expressing the galactose/N-acetyl D-galactosamine inhibitable lectin of Entamoeba histolytica.

Infection with the enteric parasite Entamoeba histolytica can result in colitis and dysentery as well as abscesses at extra-intestinal sites. An effective vaccine must be able to protect against both mucosal and systemic disease. In this study an attenuated Salmonella strain that expressed a portion of the GalNAc lectin of E, histolytica was used to orally immunize gerbils. Animals were challenged by intrahepatic injection of amebic trophozoites. A significant decrease in size of amebic liver abscesses was observed in orally immunized animals. Oral immunization with a Salmonella-based vaccine was as effective as systemic immunization for protection against systemic challenge.

When chaos reigns: responding to complex emergencies.

PIP: This article discusses the impact of Complex Humanitarian Emergencies on the delivery of humanitarian aids. Complex emergencies were the results of long-term political and social disputes. Its impact brings about public health crises like epidemics, malnutrition, and even widespread desperation. In fact, there are four aspects of these crises which complicate public health programs: 1) emergencies are long and recurring; 2) access to the most vulnerable population is often restricted; 3) restructuring health systems in complex emergencies can be futile; and 4) complex emergencies often result in mass forced migration. What makes matters worse is the breakdown of health networks which collapse early in complex emergencies, leading to extensive losses of human health resources. Not only that, health facilities and transportation, infrastructure are often decimated in complex emergencies, and regional hospitals, district health posts, laboratories, and primary care outposts are similarly abandoned or destroyed. Moreover, because it is difficult to predict the course of these emergencies, ascertaining the optimal time to intervene and to invest in materials and facilities that could be lost to renewed fighting can be impossible. To solve this problem requires a coordinated effort. It should also focus on resources, early warning systems, preparedness measures, ongoing career training of relief workers, and prepositioning of relief supplies.^ieng

Nosocomial transmission of hepatitis A in a pediatric hospital traced to an anti-hepatitis A virus-negative patient with immunodeficiency.

From July through October 1991, an outbreak of hepatitis A virus (HAV) infection involving 26 hospital staff, inpatients and household contacts occurred in a pediatric hospital. All ill staff members had cared for one inpatient who had profuse diarrhea with gross fecal contamination of the environment, negative HAV serology and idiopathic immunodeficiency. HAV infection in this patient was later confirmed by polymerase chain reaction. Among hospital staff HAV attack rates were highest in nursing personnel (15%). A retrospective cohort study of nurses found that the risk of infection was greatest in those who handled the source patient's soiled bed pad (relative risk, 6.7; 95% confidence intervals, 1.6, 27.8), diaper (relative risk, 5.4; 95% confidence intervals, 0.8, 39.2) or gown (relative risk, 2.9; 95% confidence intervals, 1.1, 7.8). Glove use during these activities was not associated with a lower risk of infection, possibly because of gross environmental contamination or less use than reported. This situation was unusual because the patient was HAV-infected but had negative serology, probably because of immunodeficiency. In situations of potentially extensive environmental contamination, such as with a diapered or incontinent patient with suspected or confirmed hepatitis A, careful attention to frequent handwashing is an essential protective measure; in addition strict glove use whenever entering the patient's room should be followed to provide additional protection.

Prevention of hepatitis B virus infection.

Hepatitis B virus infection is the most important cause of acute and chronic liver disease worldwide. The Immunization Practices Advisory Committee has proposed a comprehensive strategy to eliminate the transmission of hepatitis B virus in the United States. The three phases of this strategy are prevention of perinatal transmission of the hepatitis B virus, universal vaccination of all infants against hepatitis B virus infection and selected vaccination of high-risk adolescents and adults. Because family physicians provide obstetric, perinatal, adolescent and adult care, they can have a major influence on the success of this strategy.

The cariogenic potential of several snack foods.

The use of the animal model and the Konig-Hofer program-feeding machine is a valuable tool in the research effort to identify the factors contributing to dental caries. As this methodology provides uniform host, microflora, and frequency components, the food is the variable being evaluated. The relative cariogenicity of food is dependent on variations in the composition, texture, solubility, retentiveness, and ability to stimulate saliva flow. The results of these experiments indicated the equal importance of all food-related parameters on dental caries formation. If the composition of foods was solely responsible for dental caries formation, all three of the granola bars should have had similar relative cariogenicity values. This was not true. Granola bar no. 3, which was crispier in texture and less moist, had a third the relative cariogenicity value of granola bars nos. 1 and 2. As reported by other dental researchers, the production of dental caries is food related, but not simplistic in nature. Dental caries is the outcome of complicated interactions, all of which are equally important in the progress of this disease.

Mutations Altering Chloroplast Ribosome Phenotype in Chlamydomonas, II. A New Mendelian Mutation.

A new mutation of Chlamydomonas reinhardi, cr-1, is characterized. The mutation exhibits Mendelian inheritance and affects the sedimentation velocity and formation of intact chloroplast ribosomes. The mutant grows reasonably well when supplied with sodium acetate as a carbon source, but poorly when forced to grow photosynthetically using carbon dioxide. Since the mutant cr-1 accumulates large subunits of the chloroplast ribosome, we postulate that it is blocked in the formation of the small subunit. A tentative model explaining the behavior of the several mutants in Chlamydomonas now known to have altered chloroplast ribosomal phenotypes is presented.

Mutations altering chloroplast ribosome phenotype in Chlamydomonas. I. Non-mendelian mutations.

Uniparentally inherited mutations to antibiotic resistance and dependence in Chlamydomonas reinhardi exhibit an altered chloroplast ribosome phenotype. Genetic studies demonstrate an absolute correlation between the drug resistance or dependence and the ribosome phenotype in two such mutants.