Reach of Segre-Veronese Manifolds

We compute the reach, extremal curvature and volume of a tubular neighborhood for the Segre-Veronese variety intersected with the unit sphere

A sensitive and rapid assay for homologous recombination in mosquito cells: impact of vector topology and implications for gene targeting

BACKGROUND: Recent progress in insect transgenesis has been dramatic but existing transposon-based approaches are constrained by position effects and potential instability. Gene targeting would bring a number of benefits, however progress requires a better understanding of the mechanisms involved. Much can be learned in vitro since extrachromosomal recombination occurs at high frequency, facilitating the study of multiple events and the impact of structural changes among the recombining molecules. We have investigated homologous recombination in mosquito cells through restoration of luciferase activity from deleted substrates. The implications of this work for the construction of insect gene targeting vectors are discussed. RESULTS: We show that linear targeting vectors are significantly more efficient than circular ones and that recombination is stimulated by introducing double-strand breaks into, or near, the region of homology. Single-strand annealing represents a very efficient pathway but may not be feasible for targeting unbroken chromosomes. Using circular plasmids to mimic chromosomal targets, one-sided invasion appears to be the predominant pathway for homologous recombination. Non-homologous end joining reactions also occur and may be utilised in gene targeting if double-strand breaks are first introduced into the target site. CONCLUSIONS: We describe a rapid, sensitive assay for extrachromosomal homologous recombination in mosquito cells. Variations in substrate topology suggest that single-strand annealing and one-sided invasion represent the predominant pathways, although non-homologous end joining reactions also occur. One-sided invasion of circular chromosomal mimics by linear vectors might therefore be used in vitro to investigate the design and efficiency of gene targeting strategies

Snowmelt Simulation

The rapid growth in recent years of a variety of demands upon available water resources has lead to an increasing interest in more fundamental approaches to the science of hydrology. Accompanying this growth has been a need for an increased understanding of the snowmelt process. A completely adequate description of the entire physical process of snowmelt under all conditions is not yet available. The complex interrelated and variable nature of the snowmelt processes that occur simultaneously complicate the problem. A preliminary mathematical model of the snowmelt process has been developed in which processes such as pack settlement rates and energy flow in the pack by means of both conduction and liquid movement are considered. Factors such as an temperature, surface albedo, and degree and direction of slope are also included. A temperature criterion is applied to predict the form of precipitation input (snow or rain) to the model. Equations of the various processes are synthesized into a dynamic model of the total system by means of an electronic analog computer. This computer was utilized primarily because of its ability to (1) perform repetitive operations at very high speeds and (2) solve directly the several time-dependent partial differential equations included in the model. Field data from snow laboraties operated by the Corps of Engineers and highly instrumented watersheds of the Agricultural Research Service are being used to test and verify the model. Inital results have indicated close agreement between observed and computed results. Sensitivity studies have been conducted, and work is continuing to further test and improve the model

Hybrid Computer Simulation of the Accumulation and Melt Processes in a Snowpack

This study represents the first phase of an investigation to develop an operational simulation model of the point snowmelt process based on a time increment of one day or less. Mathematical relationships for various phenomena involved in the snowmelt process were proposed and tested. These relationships were combined into a model which is applicable to any geographic locations by determining appropriate constants for certain relationships. The model was synthesized on a hybrid computer and calibrated using field data from the Central Sierra Snow Laboratory. It was then tested with data from other well instrumented locations. Sensitivity tests were also conducted to study the relative effects of the various basic parameters and functions upon the melting process. Initial tests of the model proved encouraging and suggested merit in perusing a proposed subsequent phase of the project to incorporate the watershed runoff hydrographs resulting from a melting snowpack will be simulated

Harnessing Electronic Health Records for Public Health Surveillance

Electronic medical record (EMR) systems are a rich potential source for detailed, timely, and efficient surveillance of large populations. We created the Electronic medical record Support for Public Health (ESP) system to facilitate and demonstrate the potential advantages of harnessing EMRs for public health surveillance. ESP organizes and analyzes EMR data for events of public health interest and transmits electronic case reports or aggregate population summaries to public health agencies as appropriate. It is designed to be compatible with any EMR system and can be customized to different states’ messaging requirements. All ESP code is open source and freely available. ESP currently has modules for notifiable disease, influenza-like illness syndrome, and diabetes surveillance. An intelligent presentation system for ESP called the RiskScape is under development. The RiskScape displays surveillance data in an accessible and intelligible format by automatically mapping results by zip code, stratifying outcomes by demographic and clinical parameters, and enabling users to specify custom queries and stratifications. The goal of RiskScape is to provide public health practitioners with rich, up-to-date views of health measures that facilitate timely identification of health disparities and opportunities for targeted interventions. ESP installations are currently operational in Massachusetts and Ohio, providing live, automated surveillance on over 1 million patients. Additional installations are underway at two more large practices in Massachusetts

Young children learn first impressions of faces through social referencing.

Previous research has demonstrated that the tendency to form first impressions from facial appearance emerges early in development. We examined whether social referencing is one route through which these consistent first impressions are acquired. In Study 1, we show that 5- to 7-year-old children are more likely to choose a target face previously associated with positive non-verbal signals as more trustworthy than a face previously associated with negative non-verbal signals. In Study 2, we show that children generalise this learning to novel faces who resemble those who have previously been the recipients of positive non-verbal behaviour. Taken together, these data show one means through which individuals within a community could acquire consistent, and potentially inaccurate, first impressions of others faces. In doing so, they highlight a route through which cultural transmission of first impressions can occur

Site-Specific Integration and Expression of an Anti-Malarial Gene in Transgenic Anopheles gambiae Significantly Reduces Plasmodium Infections

Diseases transmitted by mosquitoes have a devastating impact on global health and this is worsening due to difficulties with existing control measures and climate change. Genetically modified mosquitoes that are refractory to disease transmission are seen as having great potential in the delivery of novel control strategies. Historically the genetic modification of insects has relied upon transposable elements which have many limitations despite their successful use. To circumvent these limitations the Streptomyces phage phiC31 integrase system has been successfully adapted for site-specific transgene integration in insects. Here, we present the first site-specific transformation of Anopheles gambiae, the principal vector of human malaria. Mosquitoes were initially engineered to incorporate the phiC31 targeting site at a defined genomic location. A second phase of genetic modification then achieved site-specific integration of Vida3, a synthetic anti-malarial gene. Expression of Vida3, specifically in the midgut of bloodfed females, offered consistent and significant protection against Plasmodium yoelii nigeriensis, reducing average parasite intensity by 85%. Similar protection was observed against Plasmodium falciparum in some experiments, although protection was inconsistent. In the fight against malaria, it is imperative to establish a broad repertoire of both anti-malarial effector genes and tissue-specific promoters for their expression, enabling those offering maximum effect with minimum fitness cost to be identified. In the future, this technology will allow effective comparisons and informed choices to be made, potentially leading to complete transmission blockade

Molecular Epidemiology of Early and Acute HIV Type 1 Infections in the United States Navy and Marine Corps, 2005–2010

The U.S. military represents a unique population within the human immunodeficiency virus 1 (HIV-1) pandemic. The last comprehensive study of HIV-1 in members of the U.S. Navy and Marine Corps (Sea Services) was completed in 2000, before large-scale combat operations were taking place. Here, we present molecular characterization of HIV-1 from 40 Sea Services personnel who were identified during their seroconversion window and initially classified as HIV-1 negative during screening. Protease/reverse transcriptase (pro/rt) and envelope (env) sequences were obtained from each member of the cohort. Phylogenetic analyses were carried out on these regions to determine relatedness within the cohort and calculate the most recent common ancestor for the related sequences. We identified 39 individuals infected with subtype B and one infected with CRF01_AE. Comparison of the pairwise genetic distance of Sea Service sequences and reference sequences in the env and pro/rt regions showed that five samples were part of molecular clusters, a group of two and a group of three, confirmed by single genome amplification. Real-time molecular monitoring of new HIV-1 acquisitions in the Sea Services may have a role in facilitating public health interventions at sites where related HIV-1 infections are identified