253 research outputs found
FABRICATING POROUS METAL STRUCTURES CAPABLE OF CAPILLARY ACTION THROUGH ADDITIVE MANUFACTURING
The low-density and corrosion resistance of aluminum alloys make them useful for heat pipes in aerospace applications where heavier metals like copper and steel would be less desirable. This can be used for rapid, compact cooling of heat generating systems. However, traditional methods of manufacturing porous wicks can prove ineffective for complicated geometries, as fine aluminum wire can be difficult to produce and weave into a mesh, and sintering Al powder may leave impurities. Through liquid metal printing, a porous Al wick can be made within a fully dense structural element that is capable of capillary action without the need of additional processing. Different levels of porosity can be achieved by controlling the droplet size and jetting frequency in liquid metal printing, allowing the wick to be fine-tuned to strike the correct balance of capillary force and wick permeability.Using an ElemX metal 3D printer, we were able to 3D print wick samples made of Al-4008 alloy with cross-sectional porosities of up to 31.5%, as well as wicks that could transport 0.4734 g/min of water. The project also confirms the capability of printing multiple structures on top of one another to produce composite assemblies of different densities as well as complicated geometries. A 3-point flexure test was conducted on solid aluminum beams, porous beams, and a composite hollow structure with a solid shell and porous wick able to withstand flexural stresses of up to 290 MPa before failure.Distribution Statement A. Approved for public release: Distribution is unlimited.Lieutenant, United States Nav
The Beta Problem: A Study of Abell 262
We present an investigation of the dynamical state of the cluster A262.
Existing optical line of sight velocities for select cluster galaxies have been
augmented by new data obtained with the Automated Multi-Object Spectrograph at
Lick Observatory. We find evidence for a virialized early-type population
distinct from a late-type population infalling from the Pisces-Perseus
supercluster ridge. We also report on a tertiary population of low luminosity
galaxies whose velocity dispersion distinguishes them from both the early and
late-type galaxies. We supplement our investigation with an analysis of
archival X-ray data. A temperature is determined using ASCA GIS data and a gas
profile is derived from ROSAT HRI data. The increased statistics of our sample
results in a picture of A262 with significant differences from earlier work. A
previously proposed solution to the "beta-problem" in A262 in which the gas
temperature is significantly higher than the galaxy temperature is shown to
result from using too low a velocity dispersion for the early-type galaxies.
Our data present a consistent picture of A262 in which there is no
"beta-problem", and the gas and galaxy temperature are roughly comparable.
There is no longer any requirement for extensive galaxy-gas feedback to
drastically overheat the gas with respect to the galaxies. We also demonstrate
that entropy-floor models can explain the recent discovery that the beta values
determined by cluster gas and the cluster core radii are correlated.Comment: 31 pages, 14 figures, AAS LaTeX v5.0, Encapsulated Postscript
figures, to be published in The Astrophysical Journa
Identification and support of autistic individuals within the UK Criminal Justice System: a practical approach based upon professional consensus with input from lived experience.
Background: Autism Spectrum Disorder (hereafter referred to as autism) is characterised by difficulties with (i) social communication, social interaction, and (ii) restricted and repetitive interests and behaviours. Estimates of autism prevalence within the criminal justice system (CJS) vary considerably, but there is evidence to suggest that the condition can be missed or misidentified within this population. Autism has implications for an individualâs journey through the CJS, from police questioning and engagement in court proceedings through to risk assessment, formulation, therapeutic approaches, engagement with support services, and long-term social and legal outcomes. Methods: This consensus based on professional opinion with input from lived experience aims to provide general principles for consideration by United Kingdom (UK) CJS personnel when working with autistic individuals, focusing on autistic offenders and those suspected of offences. Principles may be transferable to countries beyond the UK. Multidisciplinary professionals and two service users were approached for their input to address the effective identification and support strategies for autistic individuals within the CJS. Results: The authors provide a consensus statement including recommendations on the general principles of effective identification, and support strategies for autistic individuals across different levels of the CJS. Conclusion: Greater attention needs to be given to this population as they navigate the CJS
Influence of bone density on implant stability parameters and implant success: a retrospective clinical study
<p>Abstract</p> <p>Background</p> <p>The aim of the present clinical study was to determine the local bone density in dental implant recipient sites using computerized tomography (CT) and to investigate the influence of local bone density on implant stability parameters and implant success.</p> <p>Methods</p> <p>A total of 300 implants were placed in 111 patients between 2003 and 2005. The bone density in each implant recipient site was determined using CT. Insertion torque and resonance frequency analysis were used as implant stability parameters. The peak insertion torque values were recorded with OsseoCare machine. The resonance frequency analysis measurements were performed with Osstell instrument immediately after implant placement, 6, and 12 months later.</p> <p>Results</p> <p>Of 300 implants placed, 20 were lost, meaning a survival rate of %. 93.3 after three years (average 3.7 ± 0.7 years). The mean bone density, insertion torque and RFA recordings of all 300 implants were 620 ± 251 HU, 36.1 ± 8 Ncm, and 65.7 ± 9 ISQ at implant placement respectively; which indicated statistically significant correlations between bone density and insertion torque values (p < 0.001), bone density and ISQ values (p < 0.001), and insertion torque and ISQ values (p < 0.001). The mean bone density, insertion torque and RFA values were 645 ± 240 HU, 37.2 ± 7 Ncm, and 67.1 ± 7 ISQ for 280 successful implants at implant placement, while corresponding values were 267 ± 47 HU, 21.8 ± 4 Ncm, and 46.5 ± 4 ISQ for 20 failed implants; which indicated statistically significant differences for each parameter (p < 0.001).</p> <p>Conclusion</p> <p>CT is a useful tool to determine the bone density in the implant recipient sites, and the local bone density has a prevailing influence on primary implant stability, which is an important determinant for implant success.</p
The state of the Martian climate
60°N was +2.0°C, relative to the 1981â2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes
Association of Inherited Variation in Toll-Like Receptor Genes with Malignant Melanoma Susceptibility and Survival
The family of Toll-like receptors (TLRs) is critical in linking innate and acquired immunity. Polymorphisms in the genes encoding TLRs have been associated with autoimmune diseases and cancer. We investigated the genetic variation of TLR genes and its potential impact on melanoma susceptibility and patient survival. The study included 763 cutaneous melanoma cases recruited in Germany and 736 matched controls that were genotyped for 47 single nucleotide polymorphisms (SNPs) in 8 TLR genes. The relationship between genotype, disease status and survival was investigated taking into account patient and tumor characteristics, and melanoma treatment. Analysis of 7 SNPs in TLR2, 7 SNPs in TLR3 and 8 SNPs in TLR4 showed statistically significant differences in distribution of inferred haplotypes between cases and controls. No individual polymorphism was associated with disease susceptibility except for the observed tendency for TLR2-rs3804099 (odds ratio OR â=â1.15, 95% CI 0.99â1.34, pâ=â0.07) and TLR4-rs2149356 (ORâ=â0.85, 95% CI 0.73â1.00, pâ=â0.06). Both polymorphisms were part of the haplotypes associated with risk modulation. An improved overall survival (Hazard ratio HR 0.53, 95% CI 0.32â0.88) and survival following metastasis (HR 0.55, 95% CI 0.34â0.91) were observed in carriers of the variant allele (D299G) of TLR4-rs4986790. In addition various TLR2, TLR4 and TLR5 haplotypes were associated with increased overall survival. Our results point to a novel association between TLR gene variants and haplotypes with melanoma survival. Our data suggest a role for the D299G polymorphism in the TLR4 gene in overall survival and a potential link with systemic treatment at stage IV of the disease. The polymorphic amino acid residue, located in the ectodomain of TLR4, can have functional consequences
Evolutionary Dynamics of Human Toll-Like Receptors and Their Different Contributions to Host Defense
Infectious diseases have been paramount among the threats to health and survival throughout human evolutionary history. Natural selection is therefore expected to act strongly on host defense genes, particularly on innate immunity genes whose products mediate the direct interaction between the host and the microbial environment. In insects and mammals, the Toll-like receptors (TLRs) appear to play a major role in initiating innate immune responses against microbes. In humans, however, it has been speculated that the set of TLRs could be redundant for protective immunity. We investigated how natural selection has acted upon human TLRs, as an approach to assess their level of biological redundancy. We sequenced the ten human TLRs in a panel of 158 individuals from various populations worldwide and found that the intracellular TLRsâactivated by nucleic acids and particularly specialized in viral recognitionâhave evolved under strong purifying selection, indicating their essential non-redundant role in host survival. Conversely, the selective constraints on the TLRs expressed on the cell surfaceâactivated by compounds other than nucleic acidsâhave been much more relaxed, with higher rates of damaging nonsynonymous and stop mutations tolerated, suggesting their higher redundancy. Finally, we tested whether TLRs have experienced spatially-varying selection in human populations and found that the region encompassing TLR10-TLR1-TLR6 has been the target of recent positive selection among non-Africans. Our findings indicate that the different TLRs differ in their immunological redundancy, reflecting their distinct contributions to host defense. The insights gained in this study foster new hypotheses to be tested in clinical and epidemiological genetics of infectious disease
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