Microscale Analysis of Spacecraft Heat Shields

Imagine entering Earths atmosphere after returning from the outer solar system. A heat shield less than 2 inches thick protects you from temperatures up to 2,900 Celsius (5,252 Fahrenheit). Such conditions were experienced by NASAs Stardust capsule during reentry in 2006. The only materials capable of providing the necessary protection are composites with complex microstructures. Evaluating these materials is difficult, requiring precise knowledge of their properties. To this end, NASA scientists are developing research codes to compute material properties and simulate ablation at the microscale using agency supercomputers. Utilizing these tools, along with experiments, researchers are working to push the limits of spaceflight, allowing for greater flexibility in future space missions

Distribution of \u3ci\u3eEscherichia coli\u3c/i\u3e Passaged through Processing Equipment during Ground Beef Production Using Inoculated Trimmings

The contamination of raw ground beef by Escherichia coli O157:H7 is not only a public health issue but also an economic concern to meat processors. When E. coli O157:H7 is detected in a ground beef sample, the product lots made immediately before and after the lot represented by the positive sample are discarded or diverted to lethality treatment. However, there is little data to base decisions on how much product must be diverted. Therefore, five 2,000-lb (907-kg) combo bins of beef trimmings were processed into 10-lb (4.54-kg) chubs of raw ground beef, wherein the second combo of meat was contaminated with a green fluorescent protein (GFP)–expressing strain of E. coli. This was performed at two different commercial ground beef processing facilities, and at a third establishment where ground beef chubs from the second grinding establishment were mechanically split and repackaged into 3-lb (1.36-kg) loaves in trays. The GFP E. coli was tracked through the production of 10-lb (4.54-kg) chubs and the strain could not be detected after 26.5% more material (500 lb or 227 kg) and 87.8% more material (1,840 lb or 835 kg) followed the contaminated combo at each establishment, respectively. Three-pound (1.36-kg) loaves were no longer positive after just 8.6% more initially noncontaminated material (72 lb or 33 kg) was processed. The GFP strain could not be detected postprocessing in any residual meat or fat collected from the equipment used in the three trials. These results indicate that diversion to a safe end point (lethality or rendering) of the positive lot of ground beef, plus the lot before and lot after should remove contaminated ground beef, and as such provides support for the current industry practice. Further, the distribution and flow of E. coli on beef trimmings through various commercial equipment was different; thus, each establishment needs to consider this data when segregating lots of ground beef and establishing sampling protocols to monitor production

Micro-scale Artificial Weave Generation Capabilities for Thermal Protection System Material Modeling

Thermal Protection System (TPS) modeling requires accurate representation and prediction of the thermomechanical behavior of ablative materials. State-of-the-art TPS materials such as Phenolic Impregnated Carbon Ablator (PICA) have a proven flight record and demonstrate exceptional capabilities for handling extreme aerothermal heating conditions. The constant push for lightweight materials that are flexible in their design and performance, and hence allow for a wide range of mission profiles, has led NASA over the past years to develop its Heatshield for Extreme Entry Environment Technology (HEEET). HEEET is based primarily on a dual layer woven carbon fiber architecture and the technology has successfully been tested in arc-jet facilities. These recent developments have sparked interest in the accurate micro-scale modeling of composite weave architectures, to predict the structural response of macro-scale heatshields upon atmospheric entry. This effort can be extended to incorporate in-depth failure mechanics analyses as a result of local thermal gradients or high-velocity particle impact

The Porous Microstructure Analysis (PuMA) Software for High-Temperature Microscale Modeling

No abstract availabl

Genome Diversification in Phylogenetic Lineages I and II of \u3ci\u3eListeria monocytogenes\u3c/i\u3e: Identification of Segments Unique to Lineage II Populations

Thirteen different serotypes of Listeria monocytogenes can be distinguished on the basis of variation in somatic and flagellar antigens. Although the known virulence genes are present in all serotypes, greater than 90% of human cases of listeriosis are caused by serotypes 1/2a, 1/2b, and 4b and nearly all outbreaks of food-borne listeriosis have been caused by serotype 4b strains. Phylogenetic analysis of these three common clinical serotypes places them into two different lineages, with serotypes 1/2b and 4b belonging to lineage I and 1/2a belonging to lineage II. To begin examining evolution of the genome in these serotypes, DNA microarray analysis was used to identify lineage-specific and serotype-specific differences in genome content. A set of 44 strains representing serotypes 1/2a, 1/2b, and 4b was probed with a shotgun DNA microarray constructed from the serotype 1/2a strain 10403s. Clones spanning 47 different genes in 16 different contiguous segments relative to the lineage II 1/2a genome were found to be absent in all lineage I strains tested (serotype 4b and 1/2b) and an additional nine were altered exclusively in 4b strains. Southern hybridization confirmed that conserved alterations were, in all but two loci, due to absence of the segments from the genome. Genes within these contiguous segments comprise five functional categories, including genes involved in synthesis of cell surface molecules and regulation of virulence gene expression. Phylogenetic reconstruction and examination of compositional bias in the regions of difference are consistent with a model in which the ancestor of the two lineages had the 1/2 somatic serotype and the regions absent in the lineage I genome arose by loss of ancestral sequences

Configurable LDPC Decoder Architecture for Regular and Irregular Codes

Low Density Parity Check (LDPC) codes are one of the best error correcting codes that enable the future generations of wireless devices to achieve higher data rates with excellent quality of service. This paper presents two novel flexible decoder architectures. The first one supports (3, 6) regular codes of rate 1/2 that can be used for different block lengths. The second decoder is more general and supports both regular and irregular LDPC codes with twelve combinations of code lengths −648, 1296, 1944-bits and code rates-1/2, 2/3, 3/4, 5/6- based on the IEEE 802.11n standard. All codes correspond to a block-structured parity check matrix, in which the sub-blocks are either a shifted identity matrix or a zero matrix. Prototype architectures for both LDPC decoders have been implemented and tested on a Xilinx field programmable gate array.NokiaNational Science Foundatio

Factors affecting age-appropriate timeliness of vaccination coverage among children in Lebanon [version 1; referees: 2 approved]

Background: The effect of immunization does not only depend on its completeness, but also on its timely administration. Routine childhood vaccinations schedules recommend that children receive the vaccine doses at specific ages. This article attempts to assess timeliness of routine vaccination coverage among a sub-sample of children from a survey conducted in 2016. Methods: This analysis was based on data from a cross-sectional multistage cluster survey conducted between December 2015 and June 2016 among caregivers of children aged 12-59 months in all of Lebanon using a structured survey questionnaire. The analysis used Kaplan–Meier curves and logistic regression to identify the predictors of age-appropriate immunization. Results: Among the 493 randomly selected children, timely administration of the third dose of polio vaccine, diphtheria-tetanus-pertussis (DTP)-containing vaccine and hepatitis B (HepB) vaccine occurred in about one-quarter of children. About two-thirds of children received the second dose of a measles-containing vaccine (MCV) within the age interval recommended by the Expanded Programme on Immunization (EPI). Several factors including socio-demographic, knowledge, beliefs and practices were found to be associated with age-appropriate vaccination; however, this association differed between the types and doses of vaccine. Important factors associated with timely vaccination included being Lebanese as opposed to Syrian and being born in a hospital for hepatitis B birth dose; believing that vaccination status was up-to-date was related to untimely vaccination. Conclusions: The results suggest that there is reason for concern over the timeliness of vaccination in Lebanon. Special efforts need to be directed towards the inclusion of timeliness of vaccination as another indicator of the performance of the EPI in Lebanon

Building capacity for HIV/AIDS program leadership and management in Uganda through mentored Fellowships

Background: Around the world, health professionals and program managers are leading and managing public and private health organizations with little or no formal management and leadership training and experience. Objective: To describe an innovative 2-year, long-term apprenticeship Fellowship training program implemented by Makerere University School of Public Health (MakSPH) to strengthen capacity for leadership and management of HIV/AIDS programs in Uganda. Implementation process: The program, which began in 2002, is a 2-year, full-time, non-degree Fellowship. It is open to Ugandan nationals with postgraduate training in health-related disciplines. Enrolled Fellows are attached to host institutions implementing HIV/AIDS programs and placed under the supervision of host institution and academic mentors. Fellows spend 75% of their apprenticeship at the host institutions while the remaining 25% is dedicated to didactic short courses conducted at MakSPH to enhance their knowledge base. Achievements: Overall, 77 Fellows have been enrolled since 2002. Of the 57 Fellows who were admitted between 2002 and 2008, 94.7% (54) completed the Fellowship successfully and 50 (92.3%) are employed in senior leadership and management positions in Uganda and internationally. Eighty-eight percent of those employed (44/54) work in institutions registered in Uganda, indicating a high level of in-country retention. Nineteen of the 20 Fellows who were admitted between 2009 and 2010 are still undergoing training. A total of 67 institutions have hosted Fellows since 2002. The host institutions have benefited through staff training and technical expertise from the Fellows as well as through grant support to Fellows to develop and implement innovative pilot projects. The success of the program hinges on support from mentors, stakeholder involvement, and the hands-on approach employed in training. Conclusion: The Fellowship Program offers a unique opportunity for hands-on training in HIV/AIDS program leadership and management for both Fellows and host institutions

Diagnostic and Imaging Approaches to Chest Wall Lesions

Chest wall lesions are relatively uncommon and may be challenging once they are encountered on images. Radiologists may detect these lesions incidentally at examinations performed for other indications, or they may be asked specifically to evaluate a suspicious lesion. While many chest wall lesions have characteristic imaging findings that can result in an accurate diagnosis with use of imaging alone, other entities are difficult to distinguish at imaging because there is significant overlap among them. The interpreting radiologist should be familiar with the imaging features of both "do not touch" benign entities (which can be confidently diagnosed with imaging only, with no need for biopsy or resection unless the patient is symptomatic) and lesions that cannot be confidently characterized and thus require further workup. CT and MRI are the main imaging modalities used to assess the chest wall, with each having different benefits and drawbacks. Chest wall lesions can be classified according to their predominant composition: fat, calcification and ossification, soft tissue, or fluid. The identification or predominance of signal intensities or attenuation for these findings, along with the patient age, clinical history, and lesion location, can help establish the appropriate differential diagnosis. In addition, imaging findings in other organs, such as the lungs or upper abdomen, can at times provide clues to the underlying diagnosis. The authors review different chest wall lesions classified on the basis of their composition and highlight the imaging findings that can assist the radiologist in narrowing the differential diagnosis and guiding management