270 research outputs found
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Library support for an academic medical center's institutional animal care and use committee (IACUC)
Building a communication network between an academic medical centerâs library and its Institutional Animal Care and Use Committee (IACUC) can lead to specialized reference services that aid institutions in meeting the information requirements of the Animal Welfare Act
Mass spectrometric study of volatile components in mould powders
The mass spectrometric Knudsen effusion method was applied for the study of vaporization processes of mould powders. All measurements were performed in vacuum conditions in the temperature range between 100 and 1550°C, the standard rate of temperature elevation being 100°C/hour. Mould powders were selected from those used in continuous casting at Saarstahl AG (Völklingen, Germany) to represent the variety of types and compositions. In addition to SiO2, CaO, Al2O3 and MgO they contained 0.4-14.3 wt% Na2O, 0.3-1.0 wt% K2O, 0.1-3.6 wt% Fe2O3, 2.6-7.6 wt% fluorine and 3.4-9.1 wt% carbon.
With such complex mixtures as mould powders only a half-quantitative analysis of vaporization curves could be carried out. Mass spectra were interpreted with the help of isotopic abundance ratios and equilibrium constants for the gas phase components. Hence, they were not deciphered in full and the main results are given as time/temperature dependences of ion currents.
The results confirm that fluorides dominate in the gas phase. Vaporization (sublimation) occurs mainly in the form of NaF, Na2F2, KF, SiF4 and CaF2, while gaseous AlF3, MgF2, AlOF are generated in smaller amounts and depend on the slag composition. Yet, in the given experimental conditions, the gas phase was found to be richer in molecular species than found previously. Analysis of the NaF/Na2F2 ratio proved the existence of Na(g). Some components of the mass spectra indicate the presence of significant amounts of SiF2 and SiO in the vapour. The relative intensities of Mg+ and MgF+ ion currents suggest that Mg in vapour is present in the form of Mg(g) and its fluorides. The extra gaseous components observed in this study could be explained by the presence of carbon in the samples. This was confirmed by comparison with the vapour phase composition of the decarburised sample of a mould powder. CO could be registered in the vapour up to temperatures 1400-1500°C. In the temperature interval between 100 and 600°C, the gas phase was formed by H2O and CO2. In addition, numerous ion currents of small intensities were recorded between 100 and 450°C but their origin remained unclear. They were attributed to impurities, though some of them may have included components of the assay, such as K2O or Na2O. HF(g) could not be detected in the vapour.
The thesis is partly based on the work done within the European Coal and Steel Community Project concerning emissions of hazardous substances (the data related to pre-melted slags, fluorine free mixtures, Li2O substituted compositions).reviewe
Identification of a novel proliferationâinducing determinant using lentiviral expression cloning
One of the major challenges in the postâgenome era is the correlation between genes and function or phenotype. We have pioneered a strategy for screening of cDNA libraries, which is based on sequential combination of lentiviral and oncoretroviral expression systems and can be used to identify proliferationâmodulating genes. Screening of a lentiviral expression library derived from adult human brain cDNA resulted in cloning of the potent proliferationâinducing determinant termed pi1 (proliferation inducer 1). Transduction experiments using GFPâexpressing oncoretroviruses to target proliferationâcompetent cells suggested that overexpression of pi1 initiates proliferation of human umbilical vein endothelial cells (HUVECs). Growth induction of HUVECs as well as Swiss3T3 fibroblasts was confirmed by Brdâuridine incorporation assays, which correlated increased DNA synthesis with expression of pi1. The identified pi1 cDNA is 297 bp long and encodes a 10 kDa polypeptide. Since deregulation of proliferation control accounts for a number of today's untreatable human diseases such as neurodegenerative disorders and cancer, discovery of novel proliferationâmodulating genes is essential for developing new strategies for gene therapy and tissue engineerin
KSNet-Approach to Knowledge Fusion from Distributed Sources
The rapidity of the decision making process is an important factor in different branches of the human life (business, healthcare, industry, military applications etc.). Since responsible persons make decisions using available knowledge, it is important for knowledge management systems to deliver necessary and timely information. Knowledge logistics is a new direction in the knowledge management addressing this. Technology of knowledge fusion, based on the synergistic use of knowledge from multiple distributed sources, is a basis for these activities. The paper presents an overview of a Knowledge Source Network configuration approach (KSNet-approach) to knowledge fusion, multi-agent architecture and research prototype of the KSNet knowledge fusion system based on this approach
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Updating reference services statistics collection techniques for the 21st century
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Library Toolkit : pathophysiology--dentistry
A case study describing the creation of a library toolkit for a pathophysiology course for Columbia dental students
A Systematic Review of Proton Therapy for the Management of Nasopharyngeal Cancer
PURPOSE: With improved technology, more patients with nasopharyngeal cancer (NPC) are receiving definitive treatment with proton therapy, which allows greater sparing of dose to normal tissues without compromising efficacy. As there is no randomized data, the purpose of this study was to systematically review the available literature on proton therapy in this setting, focusing on the toxicity endpoints. MATERIALS AND METHODS: A systematic search using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines was conducted in 5 databases: PubMed, Embase, SCOPUS, Web of Science, and the Cochrane Central Register of Controlled Trials. A total of 491 studies were found on the topic of NPC and proton therapy. Following independent study selection by 2 investigators, 9 studies were found to have sufficient focus and relevance to be incorporated into the systematic review. RESULTS: All 9 studies were retrospective and examined only NPC patients except for one that also included paranasal sinus cancer. One study was a reirradiation study. Four studies used 3D or double scatter technique, while all others used intensity-modulated proton therapy. Oncologic outcomes were similar to intensity-modulated radiation therapy (IMRT) rates, with 2-year local and regional progression-free survival (LRFS) ranging from 84% to 100%, 2-year progression-free survival (PFS) ranging from 75% to 88.9%, and 2-year overall survival (OS) ranging from 88% to 95% in the up-front setting. Four comparison studies with IMRT found significantly lower feeding tube rates (20% versus 65%, Pâ=â.015; and 14% versus 85%, Pâ<â.001) with proton therapy as well as lower mucositis (G2 46% versus 70%, Pâ=â.019; and G3 11% versus 76%, Pâ=â.0002). All other acute and late effects were largely improved with proton therapy but not statistically significant. CONCLUSIONS: NPC patients receiving proton therapy maintain good outcomes with improved toxicity profile, likely due to sparing of dose to normal structures. Prospective studies are ongoing to better quantify the magnitude
Subretinal fluid may protect against macular atrophy in neovascular ageârelated macular degeneration: 5âyears of followâup from Fight Retinal Blindness registry
PurposeThe purpose of the study was to assess the association of macular atrophy (MA) according to the activity of macular neovascularization (MNV) (inactive, only subretinal fluid [SRFL], or active, i.e. including intraretinal fluid [IRFL]) using optical coherence tomography (OCT) in patients with neovascular ageârelated macular degeneration (nAMD).MethodsMulticentric observational study. TreatmentânaĂŻve nAMD eyes without subfoveal MA or subretinal fibrosis (SF) at baseline were included since 1st January 2010 and 30th September 2016 to allow up to 5âyears of treatment followâup. Eyes were grouped based on their predominant activity status as: (1) mostly inactive, (2) mostly active nonâSRFL only [IRFL] or (3) mostly activeâSRFL only [onlySRFL]. KaplanâMeier survival curves estimated the time to development of MA or SF. Cox proportional hazards models evaluated predictors of developing subfoveal MA or SF. The main outcome measure was the risk of developing MA according to predominant MNV activity.ResultsA total of 973 eyes were eligible for analysis. OnlySRFL eyes had lower risk of developing subfoveal MA (HR [95% CI]: 0.56 [0.36, 0.88]; p =â0.024) and extrafoveal MA (HR [95% CI]: 0.41 [0.27, 0.61]; p <â0.001) than IRFL eyes. IRFL eyes had lower visual acuity (VA) (54.5 letters) and the highest proportion of eyes with vision â€35 letters (25%) at 5âyears while onlySRFL eyes had comparable 5âyear VA (63.7 letters) to inactive eyes (63.7 letters).ConclusionSubretinal fluid appears to protect against MA. Distinguishing the compartment of retinal fluid and understanding its relationship with MA and SF can guide the management of nAMD
Loss of mtDNA activates astrocytes and leads to spongiotic encephalopathy
Mitochondrial dysfunction manifests as different neurological diseases, but the mechanisms underlying the clinical variability remain poorly understood. To clarify whether different brain cells have differential sensitivity to mitochondrial dysfunction, we induced mitochondrial DNA (mtDNA) depletion in either neurons or astrocytes of mice, by inactivating Twinkle (TwKO), the replicative mtDNA helicase. Here we show that astrocytes, the most abundant cerebral cell type, are chronically activated upon mtDNA loss, leading to early-onset spongiotic degeneration of brain parenchyma, microgliosis and secondary neurodegeneration. Neuronal mtDNA loss does not, however, cause symptoms until 8 months of age. Findings in astrocyte-TwKO mimic neuropathology of Alpers syndrome, infantile-onset mitochondrial spongiotic encephalopathy caused by mtDNA maintenance defects. Our evidence indicates that (1) astrocytes are dependent on mtDNA integrity; (2) mitochondrial metabolism contributes to their activation; (3) chronic astrocyte activation has devastating consequences, underlying spongiotic encephalopathy; and that (4) astrocytes are a potential target for interventions.Peer reviewe
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