124,790 research outputs found
A Modular Sampling Standard for Quantum Traceable Power Measurements: Comparison and Perspectives
No full textA power frequency modular digital sampling power standard (DSPS) is developed and extensively characterized at the Istituto Nazionale di Ricerca Metrologica (INRiM) for accurate electric power measurement with a relative uncertainty (k = 1) better than 8 mu W/VA. The calibration strategy employed allows to link its key constituents to electrical quantum standards with a relative uncertainty (k = 1) within 3 x 10(-6). Comparison measurements against the national power standard at 53 Hz agree well within the respective measurement uncertainties and did not exceed 10 mu W/VA at 240 V and 5 A and any power factor. The various novelties introduced make the DSPS a versatile metrological grade measurement setup, which lends well to further improvements and accurate evaluation of electrical parameters involved in power quality measurements. This article reports the standard, its traceability chain and calibration strategy, comparison measurements, and uncertainty budget
Asynchronous Phase Comparator for Characterization of Devices for PMUs Calibrator
No full textThis paper reports recent progress in developing a new asynchronous digital phase comparator for the precision measurement of phase difference of voltage ratio devices and calibration of functional elements of phasor measurement units (PMUs) calibrator. The phase error of the proposed digital comparator is below 300 nrad at 50 Hz and 100 μrad at 100 kHz with applied voltages ranging between 500 mV and 3 V, whereas the phase error of cables and connectors was estimated to be 4 μrad at 1 MHz. Besides resistive dividers, the phase comparator has been employed for the characterization of frequency behavior of phase difference between the output and input of voltage and transconductance amplifiers for a PMUs calibrator. The system can also be an important tool for phase-frequency characterization of devices employed for specific wideband power measurements
Sub-Golgi distribution in rat liver of CMP-NeuAc: GM3- and CMP-NeuAc: GT1b alpha2-8 sialyltransferases and comparison with the distribution the other glycosyltransferase activities involved in ganglioside biosynthesis
No full textGoing 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
Towards a He-Free Source of Arbitrary Quantum Voltage Signals
No full textThe Josephson effect is worldwide exploited as the basis for constant reference voltages in National Metrological Institutes (NMIs) and in industry calibration laboratories. Lately, voltage metrology research has been mainly directed towards the application of Josephson effect for the synthesis of very accurate ac and arbitrary voltage signals: pulse-driven Josephson arrays represent the most promising way for linking ac voltage calibrations to a quantum phenomenon. Furthermore, an easy and secure cooling system based on cryocoolers is desirable in order to allow the spread of Josephson standards outside NMIs. A Gifford-McMahon cryocooler is currently in use at INRiM for the operation of ac-Josephson Voltage Standards (JVSs). We employed pulse-driven JVSs for synthesizing sine waves with frequency in the kHz range and amplitudes in the mV range, with distortion around 80 dBc. In this report we present a detailed description of this technique and of the refrigeration system employed
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
Francesco Trinchera e la Scienza della ricchezza. Il ruolo sociale dell’economia politica
No full textITConosciuto soprattutto per il suo contributo alla diffusione di alcune importanti correnti di pensiero nel campo giuridico, filosofico ed economico, Francesco Trinchera è stato trascurato come autore di diversi discorsi e opere di contenuto economico. Questo paper si concentra sui seguenti aspetti: a) il ruolo significativo di Francesco Trinchera come economista e storico del pensiero economico; b) il suo coinvolgimento nel dibattito metodologico sul ruolo dell’Economia politica; c) il suo impegno riguardo alla definizione di un progetto di sviluppo economico e sociale dell’Italia Unita.EnFrancesco Trinchera, well known above all for his contribution to the spread of some important European schools of thought in the juridical, philosophical and economic fields, has been neglected as the author of various economic works and speeches. This paper focuses on the following aspects: a) the significant role of Francesco Trinchera as an economist and historian of economic thought; b) his involvement in the methodological debate of his time about the role of Political Economy; c) his commitment to the process of economic and social development of the United Kingdom of Italy
Comparative analysis of retroviral and native promoters driving expression of β1,3-galactosyltransferase β3Gal-T5 in human and mouse tissues
No full textβ1,3-Galactosyltransferase β3Gal-T5 is highly expressed in the colons of humans and certain primates due to a retroviral long terminal repeat (LTR) acting as a strong promoter. Because this promoter is inactive in other human tissues or mice, we attempted to understand how adoption of a retrotransposon allowed the gene to acquire tissue-specific expression. We identified three novel 5′-UTRs of 3Gal-T5 mRNA, types A, B, and C, and found wide-spread expression of the type A transcript at much lower levels than the LTR transcript, the expression of which is restricted to organs of the gastrointestinal tract. Expression of the type C 5′-UTR transcript was mostly restricted to the ileum, where it was expressed at high levels. We cloned the 5′-flanking regions of both types A and B 5′-UTRs, found deletion constructs functionally active as promoters, and identified CCAAT-binding factor (CBF) and hepatocyte nuclear factor 1 (HNF-1) as the principal nuclear factors controlling the promoters of types A and B 5′-UTR transcripts, respectively. The CCAAT-binding factor binding site and the entire downstream sequence driving the expression of type A transcripts in humans are structurally and functionally conserved in mice, where they constitute a unique β3Gal-T5 promoter that appears to be the ancestral promoter of the gene. The HNF-1 binding motif of the second human promoter is identical to the HNF-1/Cdx binding motif of the LTR promoter but is in the antisense orientation, resulting in much lower binding affinity and promoter strength. These data may explain the successful insertion of the transposon during evolution
Complementary use of carbohydrate antigens lewis a, lewis b, and sialyl-lewis a (Ca19.9 epitope) in gastrointestinal cancers: Biological rationale towards a personalized clinical application
No full textCarbohydrate antigen 19.9 (CA19.9) is used as a tumor marker for clinical and research purposes assuming that it is abundantly produced by gastrointestinal cancer cells due to a cancer-associated aberrant glycosylation favoring its synthesis. Recent data has instead suggested a different picture, where immunodetection on tissue sections matches biochemical and molecular data. In addition to CA19.9, structurally related carbohydrate antigens Lewis a and Lewis b are, in fact, undetectable in colon cancer, due to the down-regulation of a galactosyltransferase necessary for their synthesis. In the pancreas, no differential expression of CA19.9 or cognate glycosyltransferases occurs in cancer. Ductal cells only express such Lewis antigens in a pattern affected by the relative levels of each glycosyltransferase, which are genetically and epigenetically determined. The elevation of circulating antigens seems to depend on the obstruction of neoplastic ducts and loss of polarity occurring in malignant ductal cells. Circulating Lewis a and Lewis b are indeed promising candidates for monitoring pancreatic cancer patients that are negative for CA19.9, but not for improving the low diagnostic performance of such an antigen. Insufficient biological data are available for gastric and bile duct cancer. Studying each patient in a personalized manner determining all Lewis antigens in the surgical specimens and in the blood, together with the status of the tissue-specific glycosylation machinery, promises fruitful advances in translational research and clinical practice
Comparison of a Planar Thin-Film Thermal AC Voltage Standard up to 1 MHz
No full textThis paper presents results of a trilateral comparison with a traveling ac voltage standard comprising a planar thin-film thermal converter. The ac–dc voltage transfer difference of the standard was measured at 1 V and at selected frequencies from 20 Hz to 1 MHz against primary thermal ac voltage standards at the Silesian University of Technology, Istituto Nazionale di Ricerca Metrologica, and Trescal
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