5,897 research outputs found

    Blueprint for a high-performance biomaterial: full-length spider dragline silk genes.

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    Spider dragline (major ampullate) silk outperforms virtually all other natural and manmade materials in terms of tensile strength and toughness. For this reason, the mass-production of artificial spider silks through transgenic technologies has been a major goal of biomimetics research. Although all known arthropod silk proteins are extremely large (>200 kiloDaltons), recombinant spider silks have been designed from short and incomplete cDNAs, the only available sequences. Here we describe the first full-length spider silk gene sequences and their flanking regions. These genes encode the MaSp1 and MaSp2 proteins that compose the black widow's high-performance dragline silk. Each gene includes a single enormous exon (>9000 base pairs) that translates into a highly repetitive polypeptide. Patterns of variation among sequence repeats at the amino acid and nucleotide levels indicate that the interaction of selection, intergenic recombination, and intragenic recombination governs the evolution of these highly unusual, modular proteins. Phylogenetic footprinting revealed putative regulatory elements in non-coding flanking sequences. Conservation of both upstream and downstream flanking sequences was especially striking between the two paralogous black widow major ampullate silk genes. Because these genes are co-expressed within the same silk gland, there may have been selection for similarity in regulatory regions. Our new data provide complete templates for synthesis of recombinant silk proteins that significantly improve the degree to which artificial silks mimic natural spider dragline fibers

    Sensitive Radio Survey of Obscured Quasar Candidates

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    We study the radio properties of moderately obscured quasars over a range of redshifts to understand the role of radio activity in accretion using the Jansky Very Large Array (JVLA) at 6.0GHz and 1.4GHz. Our z~2.5 sample consists of optically-selected obscured quasar candidates, all of which are radio-quiet, with typical radio luminosities of νLν\nu L_{\nu}[1.4 GHz] < 104010^{40} erg s−1^{-1}. Only a single source is individually detected in our deep (rms~10 μ\muJy) exposures. This population would not be identified by radio-based selection methods used for distinguishing dusty star-forming galaxies and obscured active nuclei. In our pilot A-array study of z~0.5 radio-quiet quasars, we spatially resolve four of five objects on scales ~ 5 kpc and find they have steep spectral indices. Therefore, radio emission in these sources could be due to jet-driven or radiatively driven bubbles interacting with interstellar material on the scale of the host galaxy. Finally, we also study the population of ~ 200 faint (~40 μ\muJy - 40 mJy) radio sources observed over ~ 120 arcmin2^2 of our data. 60% of these detections are matched in the SDSS and/or WISE and are, in roughly equal shares, active nuclei at a broad range of redshifts, passive galaxies with no other signs of nuclear activity and IR-bright but optically faint sources. Spectroscopically or photometrically confirmed star-forming galaxies constitute only a small minority of the matches. Such sensitive radio surveys allow us to address important questions of AGN evolution and evaluate the AGN contribution to the radio-quiet sky.Comment: 18 pages, submitted to MNRA

    Internet and Social Media Access Among Youth Experiencing Homelessness: Mixed-Methods Study.

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    BACKGROUND: Youth experiencing homelessness are at a risk for a variety of adverse outcomes. Given the widespread use of the internet and social media, these new technologies may be used to address their needs and for outreach purposes. However, little is known about how this group uses these resources. OBJECTIVE: This study investigated how homeless adolescents use these technologies for general and health-related purposes, whether the scope of their use changes with housing status, and their interest in a website dedicated to youth experiencing homelessness. METHODS: A convenience sample of youth aged 18 to 21 years was recruited from a youth-specific homeless shelter. All participants completed a 47-item survey, with 10 individuals completing a semistructured interview. Descriptive statistics, exact testing, logistic regression, and generalized estimating equation modeling was performed for quantitative data analysis. Interviews were transcribed verbatim, and NVivo 10 (QSR International) was employed to facilitate double coding and thematic analysis. RESULTS: A total of 87 participants completed the survey with a mean age of 19.4 (SD 1.1) years. While experiencing homelessness, 56% (49/87) accessed the internet at least once a day, with 86% (75/87) accessing once a week. Access to a smartphone was associated with a 3.03 greater odds of accessing the internet and was the most frequently used device (66% of participants, 57/87). While experiencing homelessness, subjects reported a 68% decreased odds in internet access frequency (odds ratio [OR] 0.32, P\u3c.001), 75% decreased odds in spending greater amounts of time on the internet (OR 0.25, P\u3c.001), and an 87% decreased odds of social media use (OR 0.13, P=.01). Ten participants completed the semistructured interview. Several themes were identified, including (1) changes in internet behaviors while experiencing homelessness, (2) health status as a major concern and reason for Internet use, and (3) interest in a website dedicated to youth experiencing homelessness. While experiencing homelessness, participants indicated their behaviors were more goal-oriented and less focused on leisure or entertainment activities. CONCLUSIONS: While homeless youth experience changes in the frequency, amount of time, and specific uses of the internet and social media, study participants were able to access the internet regularly. The internet was used to search health-related topics. Given the importance of smartphones in accessing the internet, mobile-optimized websites may be an effective method for reaching this group

    Reconocimiento óptico de fuentes en inglés en documentos de imágenes utilizando eigenfaces

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    Introduction: In this paper, a system for recognizing fonts has been designed and implemented. The system is based on the Eigenfaces method. Because font recognition works in conjunction with other methods like Optical Character Recognition (OCR), we used Decapod and OCRopus software as a framework to present the method. Materials and Methods: In our experiments, text typeset with three English fonts (Comic Sans MS, DejaVu Sans Condensed,Times New Roman) have been used. Results and Discussion: The system is tested thoroughly using synthetic and degraded data. The experimental results show that Eigenfaces algorithm is very good at recognizing fonts of synthetic clean data as well as degraded data. The correct recognition rate for synthetic data for Eigenfaces is 99% based on Euclidean Distance. The overall accuracy of Eigenfaces is 97% based on 6144 degraded samples and considering Euclidean Distance performance criterion. Conclusions: It is concluded from the experimental results that the Eigenfaces method is suitable for font recognition of degraded documents. The three percentage incorrect classification can be mediated by relying on intra-word font information
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