488 research outputs found

    Studies in partition theory

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    A 83Krm Source for Use in Low-background Liquid Xenon Time Projection Chambers

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    We report the testing of a charcoal-based Kr-83m source for use in calibrating a low background two-phase liquid xenon detector. Kr-83m atoms produced through the decay of Rb-83 are introduced into a xenon detector by flowing xenon gas past the Rb-83 source. 9.4 keV and 32.1 keV transitions from decaying 83Krm nuclei are detected through liquid xenon scintillation and ionization. The characteristics of the Kr-83m source are analyzed and shown to be appropriate for a low background liquid xenon detector. Introduction of Kr-83m allows for quick, periodic calibration of low background noble liquid detectors at low energy.Comment: Updated to version submitted to JINS

    Calibration of a Liquid Xenon Detector with Kr-83m

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    We report the preparation of a Kr-83m source and its subsequent use in calibrating a liquid xenon detector. Kr-83m atoms were produced through the decay of Rb-83 atoms trapped in zeolite molecular sieve and were then introduced into liquid xenon. Decaying Kr-83m nuclei were detected through liquid xenon scintillation. Conversion electrons with energies of 9.4 keV and 32.1 keV from the decay of Kr-83m were both observed. This calibration source will allow the characterization of the scintillation and ionization response of noble liquid detectors at low energies, highly valuable for the search for WIMP dark matter. Kr-83m may also be useful for measuring fluid flow dynamics, both to understand purification in noble liquid-based particle detectors, as well as for studies of classical and quantum turbulence in superfluid helium.Comment: Minor edits to match published versio

    Electromyography and muscle biopsy in paediatric neuromuscular disorders – Evaluation of current practice and literature review

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    The conduct and interpretation of electromyography in children is considered difficult and therefore often avoided. We assessed the diagnostic accuracy of the paediatric electromyography protocol used in our tertiary reference centre and compared it to muscle biopsy results and clinical diagnosis. Electromyography was performed in unsedated children with suspected neuromuscular diseases between January 2010 and September 2017 and was analysed quantitatively. Muscle pathology was classified into seven groups based on existing histopathology reports. The clinical diagnosis, including myopathic, neurogenic and non-neuromuscular categories was used as the gold standard. 171 children between the age of 12 days to 17.4 years were included in the analysis. 41 children (24%) were under the age of 2 years at the time of electromyography. 98 (57%) children were diagnosed with a myopathic disorder, 18 (11%) with a neurogenic disease and 55 (32%) as not having a primary neuromuscular disorder. In detecting myopathic disease, electromyography performed as well as muscle biopsy (sensitivity 87.8% for electromyography vs. 84.5% for muscle biopsy; specificity 75.7% vs. 86.4%). This also applied to children under the age of 2 years (sensitivity 81.8% vs. 86.4%). Quantitative analysis of a limited electromyography protocol performed in unsedated children is a very valuable diagnostic tool

    Knowledge Mobilization for Agri-Food Supply Chain Decisions: Identification of Knowledge Boundaries and Categorization of Boundary-Spanning Mechanisms

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    The current world business environment is characterized by increasing uncertainties, complexities, and risks, which require agri-food supply chain (AFSC) managers to respond and act quickly in a context full of instability and unpredictability. Increasing pressure placed on AFSC managers intensifies the need to combine knowledge management (KM) and decision support that rapidly overcome knowledge boundaries. It has been recognized that the research issue related to the knowledge mobilization crossing boundaries in the AFSC needs to be addressed. This paper investigates knowledge boundaries and boundary-spanning mechanisms by collecting data from experienced AFSC practitioners. Empirical results verify that knowledge boundaries such as syntactic boundaries, semantic boundaries, and pragmatic boundaries could be effectively tackled by four specific boundary-spanning mechanisms: boundary spanners, boundary objects, boundary practices, and boundary discourses

    SIGMAR1 mutation associated with autosomal recessive Silver-like syndrome

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    OBJECTIVE: To describe the genetic and clinical features of a simplex patient with distal hereditary motor neuropathy (dHMN) and lower limb spasticity (Silver-like syndrome) due to a mutation in the sigma nonopioid intracellular receptor-1 gene (SIGMAR1) and review the phenotypic spectrum of mutations in this gene. METHODS: We used whole-exome sequencing to investigate the proband. The variants of interest were investigated for segregation in the family using Sanger sequencing. Subsequently, a larger cohort of 16 unrelated dHMN patients was specifically screened for SIGMAR1 mutations. RESULTS: In the proband, we identified a homozygous missense variant (c.194T>A, p.Leu65Gln) in exon 2 of SIGMAR1 as the probable causative mutation. Pathogenicity is supported by evolutionary conservation, in silico analyses, and the strong phenotypic similarities with previously reported cases carrying coding sequence mutations in SIGMAR1. No other mutations were identified in 16 additional patients with dHMN. CONCLUSIONS: We suggest that coding sequence mutations in SIGMAR1 present clinically with a combination of dHMN and pyramidal tract signs, with or without spasticity, in the lower limbs. Preferential involvement of extensor muscles of the upper limbs may be a distinctive feature of the disease. These observations should be confirmed in future studies

    Synthesis, Spectroscopic Characterization, Structural Studies, and in Vitro Antitumor Activities of Pyridine-3-carbaldehyde Thiosemicarbazone Derivatives

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    Eight new thiosemicarbazone derivatives, 6-(1-trifluoroethoxy)pyridine-3-carbaldehyde thiosemicarbazone (1), 6-(4'-fluorophenyl)pyridine-3-carbaldehyde thiosemicarbazone (2), 5-chloro-pyridine-3-carbaldehyde thiosemicarbazone (3), 2-chloro-5-bromo-pyridine-3-carbaldehyde thiosemicarbazone (4), 6-(3',4'-dimethoxyphenyl)pyridine-3-carbaldehyde thiosemicarbazone (5), 2-chloro-5-fluor-pyridine-3-carbaldehyde thiosemicarbazone, (6), 5-iodo-pyridine-3-carbaldehyde thiosemicarbazone (7), and 6-(3',5'-dichlorophenyl)pyridine-3-carbaldehyde thiosemicarbazone (8) were synthesized, from the reaction of the corresponding pyridine-3-carbaldehyde with thiosemicarbazide. The synthesized compounds were characterized by ESI-Mass, UV-Vis, IR, and NMR (1H, 13C, 19F) spectroscopic techniques. Molar mass values and spectroscopic data are consistent with the proposed structural formulas. The molecular structure of 7 has been also confirmed by single crystal X-ray diffraction. In the solid state 7 exists in the E conformation about the N2-N3 bond; 7 also presents the E conformation in solution, as evidenced by 1H NMR spectroscopy. The in vitro antitumor activity of the synthesized compounds was studied on six human tumor cell lines: H460 (lung large cell carcinoma), HuTu80 (duodenum adenocarcinoma), DU145 (prostate carcinoma), MCF-7 (breast adenocarcinoma), M-14 (amelanotic melanoma), and HT-29 (colon adenocarcinoma). Furthermore, toxicity studies in 3T3 normal cells were carried out for the prepared compounds. The results were expressed as IC50 and the selectivity index (SI) was calculated. Biological studies revealed that 1 (IC50 = 3.36 to 21.35 µM) displayed the highest antiproliferative activity, as compared to the other tested thiosemicarbazones (IC50 = 40.00 to >582.26 µM) against different types of human tumor cell lines. 1 was found to be about twice as cytotoxic (SI = 1.82) than 5-fluorouracile (5-FU) against the M14 cell line, indicating its efficiency in inhibiting the cell growth even at low concentrations. A slightly less efficient activity was shown by 1 towards the HuTu80 and MCF7 tumor cell lines, as compared to that of 5-FU. Therefore, 1 can be considered as a promising candidate to be used as a pharmacological agent, since it presents significant activity and was found to be more innocuous than the 5-FU anticancer drug against the 3T3 mouse embryo fibroblast cells

    Efecto de las características psicográficas en la intención de compra de marcas privadas en Chile

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    Private Labels are steadily but slowly included in Chileans´ consumption baskets. However, they have not reached the market share and penetration levels of European countries. The main objective of this article is to study how customers` psychographics affect private labels buying intentions. A shopping center intercept study was conducted, interviewing 300 female shoppers, regarding 14 psychographic variables and private labels purchase intentions. Nine product categories were used, in order to improve the generalizability of findings. Using discriminant analysis, the relative importance of each psychographic variable to explain private labels´ purchasing intentions was assessed, in order to help retailers and manufacturers optimize their marketing efforts of private labels.Las marcas privadas se han incorporado estable, pero lentamente en las canastas de compra de los chilenos. Sin embargo, ellas no han alcanzado los niveles de participación de mercado y penetración que se observan en países europeos. El principal objetivo de este artículo es estudiar cómo las características psicográficas de los consumidores pueden afectar la intención de compra de las marcas privadas. Para ello, se realizó una encuesta de intercepción de mall a 300 compradoras, en relación a 14 variables psicográficas y a la intención de compra de marcas privadas. Se usaron nueve categorías de productos como una manera de aumentar la posibilidad de generalización de los resultados. Utilizando la técnica de análisis discriminante, se estableció la importancia de cada variable para explicar las intenciones de compra de marcas privadas y así orientar de mejor forma los esfuerzos de marketing de marcas privadas por parte de detallistas y fabricantes
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