1,720,971 research outputs found
"Off-axis" metal-metal bond in Mn2(CO)10 at high pressure
Full text linkAt variance with what was previously reported, Mn2(CO)10does not transform its conformation from staggered to eclipsed in the high pressure crystal form. X-ray powder diffraction, DFT calculations and Raman spectroscopy show that the staggered conformation is retained. Instead, a rotation and a translation of the Mn(CO)5pyramidal units produce an "off-axis" and rather shorter Mn-Mn bond. This journal i
Combined Neutron and Synchrotron X-ray Diffraction investigation of the BaCe(0.85-x)Zr(x)Y(0.15)O(3-delta) (0.1 <= x <= 0.4) Proton Conductors
No full textIn this paper we investigated, by means of combined neutron and X-ray synchrotron
diffraction, the structural properties of the BaCe0.85-xZrxY0.15O3-δ solid solution as a function of
Zr-doping (0.1 e x e 0.4) and temperature. Compositions within this system have been proposed as
electrolytes for intermediate temperature solid oxide fuel cells (IT-SOFC) due to their significant
proton conductivities. However, no systematic investigations of the crystal structure evolution as a
function of temperature have been reported in the literature. In this paper, we could define the phase
stability up to 800 C for each member of the BaCe0.85-xZrxY0.15O3-δ solid solution showing that for
lower Zr-doping levels (x = 0.1 and 0.2) four different crystal structures are found in the T-range
investigated. For higher Zr-doping levels (x = 0.3 and 0.4), the samples show a more symmetric
structure already at room temperature (rhombohedral symmetry) and pass through two phase
transitions. The exact knowledge of the structural features as a function of temperature is an essential piece of information in order to assess
the possible use of these electrolyte materials in real devices
Small Angle X-Ray Scattering Data Analysis and Theoretical Modelling for the Size and Shape Characterization of Drug Delivery Systems Based on Vitamin E TPGS Micelles
No full textWe developed a simple two-dimensional/two-components theoretical model that describes the structure and functionality of a VitE-TPGS system of micelles assuming a hydrophobic inner core and an outer hydrated hydrophilic shell. We then conceptually applied the developed methodology to a simple system of VitE-TPGS micelles unloaded and loaded with an active pharmaceutical ingredient, eltrombopag, to verify if the model could reliably monitor the size change of the micelle upon loading. The fit of laboratory Small Angle X-Ray Scattering data against such model allows us to extract absolute values of the micelles size under a spherical shape hypothesis as well as the distribution within the system between components and level of hydration. The intensity scale of the SAXS experimental data needs to be normalized to a reference standard (pure water) to get absolute scattered intensities. The mathematical model which has been devel-oped under a general hypothesis of ellipsoidal micelles, is applied to our experimental data under the simpli-fied spherical assumption, which suitably fits our experimental data.(c) 2022 American Pharmacists Association. Published by Elsevier Inc. All rights reserved
Thermal, Spectroscopic, and Ab Initio Structural Characterization of Carprofen Polymorphs
No full textCommercial and recrystallized polycrystalline samples of carprofen, a nonsteroidal anti-inflammatory drug, were studied by thermal, spectroscopic, and structural techniques. Our investigations demonstrated that recrystallized sample, stable at room temperature
(RT), is a single polymorphic form of carprofen (polymorph I) that undergoes an isostructural polymorphic transformation by heating (polymorph II). Polymorph II remains then metastable
at ambient conditions. Commercial sample is instead a mixture of polymorphs I and II. The thermodynamic relationships between the two polymorphs were determined through the construction
of an energy/temperature diagram. The ab initio structural determination performed on synchrotron X-Ray powder diffraction patterns recorded at RT on both polymorphs allowed
us to elucidate, for the first time, their crystal structure. Both crystallize in the monoclinic space group type P21/c, and the unit cell similarity index and the volumetric isostructurality index
indicate that the temperature-induced polymorphic transformation I→II is isostructural. Polymorphs I and II are conformational polymorphs, sharing a very similar hydrogen bond network,
but with different conformation of the propanoic skeleton, which produces two different packing.
The small conformational change agrees with the low value of transition enthalpy obtained by differential scanning calorimetry measurements and the small internal energy computed with
density functional methods
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
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