1,005 research outputs found

    Comparison of hand laid-up tape and filament wound composite cylinders and panels with and without impact damage

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    The results of this experimental comparison of filament wound control (unimpacted) cylinders loaded to failure in axial compression indicates that one fiber cross-over location has no effect on the failure mode or strain in thick walled filament wound graphite-epoxy specimens with stacking sequence (plus or minus 45/90) sub 3s. A comparison between filament wound and hand laid-up tape control cylinders indicates that there is little or no difference in the response of cylinders constructed by using two different fabrication methods, however, unimpacted panels with many fiber cross-overs fail at up to 15 percent lower strains than panels with no fiber cross-overs. A comparison of samples subjected to low speed impact damage prior to compressive loading indicates that impact damage reduces the strain at failure by over 60 percent in tape and filament wound graphite-epoxy cylinders and in tape flat panels. The presence of fiber cross-overs was observed to reduce the strength of filament wound impact-damaged panels, but to have no significant effect on the strength of filament wound impact-damaged cylinders

    Optimal Influencer Marketing Campaign Under Budget Constraints Using Frank-Wolfe

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    Influencer marketing has become a thriving industry with a global market value expected to reach 15 billion dollars by 2022. The advertising problem that such agencies face is the following: given a monetary budget find a set of appropriate influencers that can create and publish posts of various types (e.g. text, image, video) for the promotion of a target product. The campaign's objective is to maximize across one or multiple online social platforms some impact metric of interest, e.g. number of impressions, sales (ROI), or audience reach. In this work, we present an original continuous formulation of the budgeted influencer marketing problem as a convex program. We further propose an efficient iterative algorithm based on the Frank-Wolfe method, that converges to the global optimum and has low computational complexity. We also suggest a simpler near-optimal rule of thumb, which can perform well in many practical scenarios. We test our algorithm and the heuristic against several alternatives from the optimization literature as well as standard seed selection methods and validate the superior performance of Frank-Wolfe in execution time and memory, as well as its capability to scale well for problems with very large number (millions) of social users.Comment: accepted in IEEE Transactions on Network Science and Engineering, 16 pages, double column, 4 figure

    Do Word Of Mouth And Advertising Messages On Social Networks Influence The Purchasing Behavior Of College Students?

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    Many online advertisers are exploring the use of Internet social networking to build brand awareness and loyalty. Social networking is particularly popular among the younger, 15-24 year- old generation, who is more computer savvy and spends more time on the Internet than adults. While this generation has substantial potential, they also represent a challenge to advertisers. This group is notoriously skeptical of being “advertised at.” They expect a more personal, interactive experience. The purpose of this research is to determine which types of social networks are used most by college students and what types of online marketing impact their purchasing choices. In carrying out this research, the following research questions were addressed: which social networks are used most by college students; do factors such as student and/or parent income, student age, classification, gender, marital status, or employment status influence use of social networks; do ads on social networks impact purchasing decisions; does advice from other users of social networks impact purchasing decisions; and do online games, scavenger hunts, and contests influence purchasing decisions? The research provides a better understanding of social network use and provides insight into effective online advertising to college students

    Streptomycin-induced inflammation enhances Escherichia coli gut colonization through nitrate respiration.

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    UnlabelledTreatment with streptomycin enhances the growth of human commensal Escherichia coli isolates in the mouse intestine, suggesting that the resident microbial community (microbiota) can inhibit the growth of invading microbes, a phenomenon known as "colonization resistance." However, the precise mechanisms by which streptomycin treatment lowers colonization resistance remain obscure. Here we show that streptomycin treatment rendered mice more susceptible to the development of chemically induced colitis, raising the possibility that the antibiotic might lower colonization resistance by changing mucosal immune responses rather than by preventing microbe-microbe interactions. Investigation of the underlying mechanism revealed a mild inflammatory infiltrate in the cecal mucosa of streptomycin-treated mice, which was accompanied by elevated expression of Nos2, the gene that encodes inducible nitric oxide synthase. In turn, this inflammatory response enhanced the luminal growth of E. coli by nitrate respiration in a Nos2-dependent fashion. These data identify low-level intestinal inflammation as one of the factors responsible for the loss of resistance to E. coli colonization after streptomycin treatment.ImportanceOur intestine is host to a complex microbial community that confers benefits by educating the immune system and providing niche protection. Perturbation of intestinal communities by streptomycin treatment lowers "colonization resistance" through unknown mechanisms. Here we show that streptomycin increases the inflammatory tone of the intestinal mucosa, thereby making the bowel more susceptible to dextran sulfate sodium treatment and boosting the Nos2-dependent growth of commensal Escherichia coli by nitrate respiration. These data point to the generation of alternative electron acceptors as a by-product of the inflammatory host response as an important factor responsible for lowering resistance to colonization by facultative anaerobic bacteria such as E. coli

    Donor IFNL4 Genotype Is Associated with Early Post-Transplant Fibrosis in Recipients with Hepatitis C

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    Background and Aims Early post-transplant hepatic fibrosis is associated with poor outcomes and may be influenced by donor/recipient genetic factors. The rs368234815 IFNL4 polymorphism is related to the previously described IL28B polymorphism, which predicts etiology-independent hepatic fibrosis. The aim of this study was to identify the impact of donor and/or recipient IFNL4 genotype on early fibrosis among patients transplanted for hepatitis C (HCV). Methods Clinical data were collected for 302 consecutive patients transplanted for HCV. 116 patients who had available liver biopsies and donor/recipient DNA were included. 28% of these patients with stage 2 fibrosis or greater were compared to patients without significant post-transplant fibrosis with respect to clinical features as well as donor/recipient IFNL4 genotype. Results The IFNL4 TT/TT genotype was found in 26.0% of recipients and 38.6% of donors. Patients who developed early post-transplant fibrosis had a 3.45 adjusted odds of having donor IFNL4 TT/TT genotype (p = 0.012). Donor IFNL4 TT/TT genotype also predicted decreased overall survival compared to non-TT/TT genotypes (p = 0.016). Conclusions Donor IFNL4 TT/TT genotype, a favorable predictor of spontaneous HCV clearance pre-transplant, is associated with increased early post-transplant fibrosis and decreased survival

    Health literacy and its association with adherence in pediatric liver transplant recipients and their parents

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    ObjectiveNon- adherence to pediatric regimens is a common concern. Low health literacy is correlated with poor outcomes in adults but is understudied in pediatrics. The current project aimed to determine the relationship between health literacy, adherence, and outcomes in pediatric liver transplant recipients. Hypotheses included a) parent and patient health literacy would be positively correlated; and b) low patient and/or parent health literacy would be negatively correlated with adherence and health outcomes.Patients and MethodsEligible participants were recruited during routine follow- up visits in a pediatric liver transplant clinic. Parents and patients (>13 years old) completed 2 measures of health literacy. Patients - „18 years completed health literacy measures without corresponding parent surveys. Adherence variables and health outcomes were obtained from medical records.ResultsSeventy- nine patients across two sites completed the study. Variance in classification of health literacy between measures was observed; however, most parents (82%- 100%) scored within an - adequate literacy- range. More adolescents scored in lower health literacy ranges relative to the parents. Markers of SES were positively correlated with health literacy. Parent health literacy was negatively associated with biopsy- proven rejection episodes and the number of hospitalizations; however, it was not associated with measures of tacrolimus adherence. There were no relationships observed between parent and adolescent health literacy.ConclusionsHealth literacy is an important consideration in managing patient care; however, available measures demonstrate variability in capturing the skills of patients. Effective communication strategies may ameliorate admittedly small, but negative, impacts of limited health literacy on outcomes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156215/2/petr13726_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156215/1/petr13726.pd

    Gene Expression and Functional Analyses of Odorant Receptors in Small Hive Beetles (Aethina tumida).

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    Olfaction is key to many insects. Odorant receptors (ORs) stand among the key chemosensory receptors mediating the detection of pheromones and kairomones. Small hive beetles (SHBs), Aethina tumida, are parasites of social bee colonies and olfactory cues are especially important for host finding. However, how interactions with their hosts may have shaped the evolution of ORs in the SHB remains poorly understood. Here, for the first time, we analyzed the evolution of SHB ORs through phylogenetic and positive selection analyses. We then tested the expression of selected OR genes in antennae, heads, and abdomens in four groups of adult SHBs: colony odor-experienced/-naive males and females. The results show that SHBs experienced both OR gene losses and duplications, thereby providing a first understanding of the evolution of SHB ORs. Additionally, three candidate ORs potentially involved in host finding and/or chemical communication were identified. Significantly different downregulations of ORs between the abdomens of male and female SHBs exposed to colony odors may reflect that these expression patterns might also reflect other internal events, e.g., oviposition. Altogether, these results provide novel insights into the evolution of SHB ORs and provide a valuable resource for analyzing the function of key genes, e.g., for developing biological control. These results will also help in understanding the chemosensory system in SHBs and other beetles

    An updated genetic marker for detection of Lake Sinai Virus and metagenetic applications

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    Background. Lake Sinai Viruses (LSV) are common RNA viruses of honey bees (Apis mellifera) that frequently reach high abundance but are not linked to overt disease. LSVs are genetically heterogeneous and collectively widespread, but despite frequent detection in surveys, the ecological and geographic factors structuring their distribution in A. mellifera are not understood. Even less is known about their distribution in other species. Better understanding of LSV prevalence and ecology have been hampered by high sequence diversity within the LSV clade. Methods. Here we report a new polymerase chain reaction (PCR) assay that is compatible with currently known lineages with minimal primer degeneracy, producing an expected 365 bp amplicon suitable for end-point PCR and metagenetic sequencing. Using the Illumina MiSeq platform, we performed pilot metagenetic assessments of three sample sets, each representing a distinct variable that might structure LSV diversity (geography, tissue, and species). Results. The first sample set in our pilot assessment compared cDNA pools from managed A. mellifera hives in California (n = 8) and Maryland (n = 6) that had previously been evaluated for LSV2, confirming that the primers co-amplify divergent lineages in real-world samples. The second sample set included cDNA pools derived from different tissues (thorax vs. abdomen, n = 24 paired samples), collected from managed A. mellifera hives in North Dakota. End-point detection of LSV frequently differed between the two tissue types; LSV metagenetic composition was similar in one pair of sequenced samples but divergent in a second pair. Overall, LSV1 and intermediate lineages were common in these samples whereas variants clustering with LSV2 were rare. The third sample set included cDNA from individual pollinator specimens collected from diverse landscapes in the vicinity of Lincoln, Nebraska. We detected LSV in the bee Halictus ligatus (four of 63 specimens tested, 6.3%) at a similar rate as A. mellifera (nine of 115 specimens, 7.8%), but only one H. ligatus sequencing library yielded sufficient data for compositional analysis. Sequenced samples often contained multiple divergent LSV lineages, including individual specimens. While these studies were exploratory rather than statistically powerful tests of hypotheses, they illustrate the utility of high-throughput sequencing for understanding LSV transmission within and among species

    Dynamic evolution in the key honey bee pathogen deformed wing virus: Novel insights into virulence and competition using reverse genetics

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    The impacts of invertebrate RNA virus population dynamics on virulence and infection out- comes are poorly understood. Deformed wing virus (DWV), the main viral pathogen of honey bees, negatively impacts bee health, which can lead to colony death. Despite previ- ous reports on the reduction of DWV diversity following the arrival of the parasitic mite Var- roa destructor, the key DWV vector, we found high genetic diversity of DWV in infested United States honey bee colonies. Phylogenetic analysis showed that divergent US DWV genotypes are of monophyletic origin and were likely generated as a result of diversification after a genetic bottleneck. To investigate the population dynamics of this divergent DWV, we designed a series of novel infectious cDNA clones corresponding to coexisting DWV genotypes, thereby devising a reverse-genetics system for an invertebrate RNA virus qua- sispecies. Equal replication rates were observed for all clone-derived DWV variants in single infections. Surprisingly, individual clones replicated to the same high levels as their mixtures and even the parental highly diverse natural DWV population, suggesting that complemen- tation between genotypes was not required to replicate to high levels. Mixed clone–derived infections showed a lack of strong competitive exclusion, suggesting that the DWV geno- types were adapted to coexist. Mutational and recombination events were observed across clone progeny, providing new insights into the forces that drive and constrain virus diversifi- cation. Accordingly, our results suggest that Varroa influences DWV dynamics by causing an initial selective sweep, which is followed by virus diversification fueled by negative fre- quency-dependent selection for new genotypes. We suggest that this selection might reflect the ability of rare lineages to evade host defenses, specifically antiviral RNA interference (RNAi). In support of this hypothesis, we show that RNAi induced against one DWV strain is less effective against an alternate strain from the same population
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