178,077 research outputs found
Kinetics and Equilibria of Nickel(II)-Schiff Base Adducts Formation
No full textThe interactions between Ni-II cations and bidentate Schiff base ligands, N-alkyl-5-X-salicylaldimine HL (X = H; R = Et, nPr, tBu; X = Cl, OMe, NO2; R = nPr), and bis(N-n-alkyl-5-X-salicylaldiminato)nickel(II) complexes [NiL2] (X = H; R = Et, nPr, nBu; X = Cl, OMe, Me; R = nPr) were investigated by UV/Vis spectrophotometry in acetonitrile. The kinetics for the formation of Ni-II/HL 1:1 adducts was studied by stopped-flow techniques, which showed that the process followed a two-consecutive mechanism, Experimental evidence and theoretical calculations indicated the formation of an unidentate intermediate in the first step, according to a dissociative interchange mechanism. Ring-closure occurs in the second step and its rate is slower for electron-withdrawing-substituted Schiff bases. Nickel(II) cations interact with [NiL2] affording [NiL](+) and [Ni2L3](+) species; the associated equilibrium constants were found to be related to the electronic effects of the 5-X ligand substituents
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
THE TRIGGER SYSTEM OF THE MAGIC TELESCOPE: ON-LINE SELECTION STRATEGIES FOR CHERENKOV TELESCOPES
No full textThe Major Atmospheric Gamma-ray Imaging Cherenkov Telescope aims at the detection of very low energy gamma-rays (E > 10 GeV) through the atmospheric emission of Cherenkov light. The high background rate originated by various sources sets a serious challenge to this goal. Application of topological selection cuts at trigger level can contribute to the background reduction, allowing the telescope to operate at lower thresholds and reducing the minimum detectable energy
"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.
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
Letter from R. R. Zellick, Assistant Trust Officer, Anglo California National Bank of San Francisco, to Joseph R. Goodman, October 2, 1942
No full textLetter from R. R. Zellick, Assistant Trust Officer at The Anglo California National Bank of San Francisco, to Joseph R. Goodman, regarding property owned by Dave Tatsuno. Zellick mentions a dispute between current tenants and Tatsuno, and that Tatsuno has asked Goodman to help locate trustworthy tenants.Personal correspondence, organizational records, government documents, publications, and other papers created or collected by Joseph R. Goodman documenting the forced removal and incarceration of Japanese Americans during World War II, as well as organized resistance to incarceration. Included in the collection are records of the Japanese Young Men's Christian Association and the Japanese American Citizens' League in San Francisco, including papers of the Japanese YMCA's executive secretary Lincoln Kanai; Sakai family papers; Goodman's correspondence to and from Japanese American incarcerees, organizations opposing forced removal and incarceration of Japanese Americans, the War Relocation Authority, and others; publications, photographs, and ephemera from the Topaz Relocation Center, where Goodman taught high school; War Relocation Authority records and publications; and newspaper clippings, pamphlets, and reports about forced removal and incarceration created by various government, religious, and civic organizations, in California and nationwide
Performance of the Domino Ring Sampler in the MAGIC experiment
No full textWe present a waveform digitizing system based on the Domino Ring Sampler (DRS) chip and its implementation in a mezzanine card. This system is suitable for experiments in which the waveform sampling of high-speed PMT signals is crucial. The analog waveform is stored in an array of 1024 capacitive sampling cells fabricated in a 0.25 mu m CMOS process and is read out at 40 MHz with an external 12 bit flash ADC. The DRS sampling frequency can be chosen between 1.5 and 4.5 GHz and is locked to an external low-frequency reference clock. The design is optimized for a multi-channel board with parallel sampling of 32 input channels triggered by a common pulse. In November 2004 the system was tested in La Palma on the magic telescope experiment and a preliminary measurement of the night sky background was performed. This is the first of a series of measurements that we are scheduling for a better understanding of the telescope performance. (c) 2006 Published by Elsevier B.V
The trigger system of the MAGIC telescope
No full textThe MAGIC telescope aims at the detection of very low energy gamma rays (E > 30 GeV) through the atmospheric emission of Cherenkov light. The high background rate originating from the night sky background, muons, hadronic showers and bright stars sets a serious challenge to this goal. Application of topological selection cuts at trigger level can have a big impact on background reduction allowing the telescope to operate at lower thresholds and reducing the minimum detectable energy. The trigger of the MAGIC telescope is a two-level system following a pipeline philosophy, similar to those adopted in high energy physics experiments. Operative since October 2002, the trigger system has been a key point in the commissioning of the MAGIC telescope that is now taking data. The trigger hardware is described in detail
The DRS VME board: a low power digitizing system in the GHz range
No full textWe present a waveform digitizing system based on the Domino Sampling Chip and its implementation in a Mezzanine Card. This system is suitable for experiments in which the waveform sampling of high-speed PMT signals is crucial. The principle of operation, the test and the performance of the system are described. The Domino ring capacitors are sampling input signals up to a maximum frequency of 4.5 GHz and are locked to an external low frequency clock. The analog waveform is stored in capacitive sampling cells fabricated in a 0.25 mu m CMOS process and read out at 40 MHz with an external 12 bit flash ADC. The design is optimized for a multi-channel VME board with parallel sampling of 16 input channels upon a common trigger pulse
The trigger system of the MAGIC telescope
No full textThe MAGIC telescope aims at the detection of very low energy gamma rays (E > 30 GeV) through the atmospheric emission of Cherenkov light. The high background rate originating from the night sky background, muons, hadronic showers and bright stars sets a serious challenge to this goal. Application of topological selection cuts at trigger level can have a big impact on background reduction allowing the telescope to operate at lower thresholds and reducing the minimum detectable energy. The trigger of the MAGIC telescope is a two-level system following a pipeline philosophy, similar to those adopted in high energy physics experiments. Operative since October 2002, the trigger system has been a key point in the commissioning of the MAGIC telescope that is now taking data. The trigger hardware is described in detail
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