131,692 research outputs found
Vitamin D: metabolism and biological effects
No full textАдрес за кореспонденция: Д-р Росен Михайлов, УМБАЛ „Царица Йоанна – ИСУЛ“, ул. „Бяло
море“ № 8, 1527 София ***** Address for correspondence: Rossen Mihaylov, M.D., Clinical Laboratory, University Hospital “Tzaritza Joanna – ISUL”, 8, Byalo more St., Bg – 1527 SofiaРезюме: Витамин D е открит през 1782 г., но е изолиран през 1920 г. Човешкият ор-
ганизъм си доставя този витамин по два пътя: а) ендогенно – чрез синтез в
кожата с помощта на ултравиолетовите В лъчи (UVB), и б) екзогенно –
чрез животинска и растителна храна. От червата посредством хиломикро-
ните и от кожата мастноразтворимият витамин D постъпва в лимфата и
след това във венозната циркулация. Тук той се свързва с протеини: 85-
90% с витамин D свързващи протеини (DBP), 10-15% с албумин и само под
1% се намира в свободна форма. От циркулацията витамин D постъпва за
хидроксилиране до 25-хидроксивитамин D (25-OH-D или калцидиол). Tова
е главният циркулиращ метаболит на витамин D. Част от циркулиращия
калцидиол се хидроксилира в проксималните тубули на бъбреците до 1,25-
хидрокси витамин D (1,25-ОН-2D3 или 1,25 (ОН)2D), известен като калцит-
риол, хормонално активен метаболит на витамин D. Локалeн синтез на
калцитриол се среща в много клетки и тъкани. За вътреклетъчното си
действие, витамин D използва ядрени рецептори (ВДР), открити през 1988
г. Сега се знае, че витамин D не е само “витамин на костите“, но участва в
регулацията на клетъчната пролиферация и диференциация, възпалител-
ните процеси, реакциите на имунната и ендокринната система, включително RAS, инсулиновата резистентност и липидния метаболизъм. Дискутира се ролята му при редица социалнозначими заболявания. ***** Summary: Vitamin D was discovered in 1782 but isolated in 1920. The human body provides
this vitamin in two ways: a) endogenously – via synthesis in the skin by
ultraviolet B rays (UVB) and b) exogenously – through animal and plant food.
From the intestines through the chylomicrons and from the skin the fat-soluble
vitamin D enters the lymph and then the venous circulation. Here it binds to proteins:
85-90% with vitamin D binding proteins (DBP), 10-15% with albumin and
only less than 1% is in a free form. Coming from the circulation Vitamin D is hydroxylated
to 25-hydroxyvitamin D (25-OH-D or calcidiol). This is the major circulating
metabolite of vitamin D. Some of the circulating calcidiol is hydroxylated
in the proximal tubules of the kidney to 1,25-hydroxy vitamin D (1,25-OH-2D3 or
1,25 (OH)2D) known as calcitriol, hormonally active metabolite of vitamin D. Local
synthesis of calcitriol is also found in many cells and tissues. For its intracellular
action vitamin D uses nuclear receptors (VDR) found in 1988. Now it is
known that vitamin D is not only "bone vitamin", but it is involved in the regulation
of cell proliferation and differentiation, inflammation, immune system and
endocrine system, including RAS, insulin resistance and lipid metabolism
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Precise Measurement of Neutrino and Anti-neutrino Differential Cross Sections on Iron
No full textThis thesis will present a precise measurement of the differentialcross section for charged current neutrino and anti-neutrino scatteringfrom iron. The NuTeV experiment took data during 1996-97 and collected and charged-current (CC) interactions. The experiment combines sign-selected neutrino andantineutrino beams and the upgraded CCFR iron-scintillator neutrinodetector. A precision continuous calibration beam was used to determinethe muon and hadron energy scales to a precision of about a factor of two better thanprevious experiments. The structure functions and are extracted and compared with theory and previous measurements
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Experimental Investigation of Dapped Ends with Diagonal Reinforcement
No full textReinforced concrete dapped-end connections are susceptible to formation of inclined cracks at the reentrant corner under service conditions. As these connections also work with high shear stresses, they require a high amount of reinforcement to ensure sufficient load-bearing capacity. To deepen the understanding of this topic, an experimental campaign of eight large-scale dapped-end connections featuring diagonal reinforcement is presented. These specimens, which are among the largest available in the literature, are similar in size to the dapped ends typically used in bridges. The test series captures both flexural and shear failures of dapped ends. The crack displacements, crack patterns, and elongation of main reinforcement are reported, with 56 continuous measurements of deformations. The test results of this study are used in conjunction with a similar study on specimens with orthogonal reinforcement to investigate the impact of reinforcement layout. For the same amount of dapped-end reinforcement, specimens with diagonal reinforcement are considerably stronger than the corresponding connections with orthogonal reinforcement. For both reinforcement layouts, the crack widths exceeded typical code provisions under service conditions.Financial assistance for this research was provided by the grant BOF 2018: Doctoraatsfonds i.s.m. ULiège: Chathura Rajapakse [Grant Number BOF 2018 – BOF18DOCLI02 – cofin UHasselt-ULiege]. The authors would like to express their gratitude to the Applicatiecentrum Beton en Bouw (structural laboratory) at Hasselt University, where the tests were conducted. The excellent support of D. Dragan in conducting the tests and R. Steensels during the design and procurement of the specimens
is greatly appreciated
Scholarly Communication and Publishing Lunch and Learn Talk #11: The ULS Open Access Author Fee Fund
No full textAt the May 2014 talk, you will learn about the ULS Open Access Author Fee Fund--what it is, why we do it, how it works, and how the program is going so far
Belgium
No full textpeer reviewedDeep beams with shear span-to-depth ratios a/d ≤ 2.5 are used to resist large shear forces due to their ability to develop direct strut action. To further enhance the shear strength and crack control of such members, researchers have studied the use of fibre-reinforced concrete (FRC). However, while this solution is promising, there is a need for rational mechanical models capable of predicting the shear strength of FRC deep beams in a sufficiently simple manner. This paper proposes such a mod-el based on first principles: kinematics, equilibrium and consti-tutive relationships. The proposed model simplifies an earlier two-parameter kinematic theory (2PKT) for the complete shear behavior of FRC deep beams, to predict the shear strength and components of shear resistance in a straightforward manner. The new simplified method (S2PKT) is validated by compar-ing the predicted results to 22 tests from the literature, as well as to FEM and 2PKT predictions. It is shown that the proposed simplified kinematic approach predicts well the shear strength with an average experimental-to-predicted shear strength ratio of 1.12 and a coefficient of variation of 12.9%. Furthermore, the model is used to discuss the effect of shear span-to-depth ratio and fibre volumetric ratio on the shear strength of FRC deep beams
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