1,721,809 research outputs found
The Development and Application of SPSiBox Ligands: Cu-Catalyzed Enantioselective Carbene Insertion of Ge–H Bonds
No full textA class of C2-symmetrical bisoxazoline ligands with a flexible chiral pocket has been developed, which could be readily prepared in three steps from enantiopure SPSiOLs. This type of ligands presented high level of enantioselectivity for the Cu-catalyzed asymmetric carbene insertion of Ge–H bonds with α-trifluoromethyl diazo compounds, thus providing an efficient method for the preparation of enantioenriched α-trifluoromethyl ogranogermanes. This reac-tion features a broad substrates scope, mild reaction conditions, excellent enantioselectivity, and low catalyst loading. Preliminary mechanistic studies un-veiled that this Cu-catalyzed Ge–H insertion might undergo a concerted mechanism, and computational studies unveiled the origin of chiral induction of this reaction with SPSiBox ligand
Low bandgap α-(Si,Ge):H and α-(Ge):H devices
No full textIn this research, alpha-(Si,Ge):H and alpha-(Ge):H devices are grown by electron cyclotron resonance plasma enhanced CVD technique and the electrical and optical properties of these devices under different plasma conditions are investigated;The ion bombardment during the growth can be enhanced by the low pressure, inert gas and substrate bias. The conclusion that low pressure leads to better quality of the material under hydrogen plasma because of higher ion bombardment is further verified by the space charge limited current (SCLC) method. The midgap defect density of states for the low pressure sample is lower than the one deposited under high pressure. The film properties for He-ECR films did not degrade as the pressure changed from 10mTorr to about 25mTorr, but at higher pressure (35mTorr). It's because the ion energy of He plasma is higher than that of H plasma;We also found that the negative substrate bias can provide higher ion bombardment. The effects of substrate bias on the growth rate are different for the high Ge content sample and the low Ge content sample. Under certain deposition environment, the performance of the devices can be improved when negative substrate voltage is applied. But under some conditions that the ion bombardment is already high, the effect is not so obvious;Most researchers concentrates on the alloy with Ge content >50%. In this research, we explored the properties of alpha-(Si,Ge):H alloy with Ge content <50 and found that device quality material can be obtained under the combination of low pressure, high temperature, high hydrogen dilution and ppm boron doping in i layer even for the bandgap as low as 1.16ev. Fourier transformed infrared absorptance spectroscopy (FTIR) measurement showed that the preference of Si-H to Ge-H is broken up, low pressure and high hydrogen dilution is beneficial to reduce the Ge-Ge clustering and increase the Ge-H bond so that the material is grown more homogeneously. The quality of the alpha-(Ge):H material can be further improved by provides some graded boron doping in I layer and higher ion bombardment. A fill factor of 55% and urbach energy of 40mev are obtained for alpha-(Ge):H solar cell. This is the first time ever that a good alpha-(Ge):H solar cell has been made.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
Electronic and Optical Properties of A—(Si, Ge):H Alloys
No full textAbstractWe describe the preparation and electronic and optical properties of amorphous (Si, Ge) alloys. A—(Si, Ge):H alloys were prepared by glow discharge decomposition of SiH4 and GeH4. The bandgap was varied between 1.78 and 1.42 eV by changing the GeH4:SiH4 ratio in the gas phase. We find a distinct influence of growth temperature on electronic properties. Films grown at low temperatures (200–250C) tendto have much lower photo conductivity than films grown at higher temperatures (300–325C). The electron (μ τ) products of high temperature films are general> 1X10–7 cm2/V. We also obtain very sharp valence band tails in a—(Si, Ge):H alloys, with slopes of ∼ 40 meV. The hole (μ τ) product is generally ∼1–2X10–8 cm2/V. All these properties suffer a catastrophic decline when bandgap is reduced below about 1.5 eV.</jats:p
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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