1,721,070 research outputs found
A high-pressure cubic-to-tetragonal phase-transition in melanophlogite, a SiO2 clathrate phase
No full textSystems and Synthetic biology: tackling genetic networks and complex diseases
No full textIn the era of post-genomic research two new disciplines, Systems and Synthetic biology, act in a complementary way to shed light on the ever-increasing amount of data produced by novel high-throughput techniques. Systems biology aims at developing a formal understanding of biological processes through the development of quantitative mathematical models (bottom-up approach) and of 'reverse engineering' (top-down approach), whose aim is to infer the interactions among genes and proteins from experimental observations (gene regulatory networks). Synthetic biology on the other hand uses mathematical models to design novel biological 'circuits' (synthetic networks) able to perform specific tasks (for example, periodic expression of a gene of interest), or able to change the behavior of a biological process in a desired way (for example, modify metabolism to produce a specific compound of interest). The use of a pioneering approach that combines biology and engineering, to describe and/or invent new behaviors, could represent a valuable resource for studying complex diseases and design novel therapies. The identification of regulatory networks will help in identifying hundreds of genes that are responsible for most genetic diseases and that could serve as a starting point for therapeutic intervention. Here we present some of the main genetics and medical applications of these two emerging fields
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
Anomalous elastic behavior and high-pressure structural evolution of zeolite levyne
No full textElastic behavior and high-pressure (HP) structural evolution of a natural zeolite levyne,(Ca0.5,Na,K)6(Al6Si12O36) 18H2O, has been investigated up to 5 GPa by means of in situ single-crystal X-ray diffraction with a diamond-anvil cell using a non-penetrating pressure-transmitting medium. Peculiar elastic behavior has been observed in the range 0Œ1 GPa: the c parameter decreases between 0 and 0.2 GPa, then increases up to 0.5-0.6 GPa. Above this P-value, the parameter decreases as expected. Anomalous behavior is also shown by the a-parameter, which first increases up to 0.2 GPa,
then decreases as expected. However, these anomalous lattice variations are only slightly reflected in the cell volume behavior. The low-P trend (P < 1 GPa) is also followed by the lattice parameters
in decompression. The isothermal Equation-of-State (EoS) at P > 1 GPa, refined with a second-order Birch-Murnaghan EoS, yields the following parameters: V0 = 3539(3) Å3 and KT0 = 48(1) GPa. Comparison of structural refinements performed at 0.0001, 0.79(5), and 3.00(5) GPa highlights two distinct
deformation mechanisms of the Si/Al-framework, one predominant at low pressures (0-1 GPa) and the other at high pressures (1-5 GPa).The extra-framework content does not show any evident modification within the pressure range investigated
Vibrational characterization of the new gemstone Pezzottaite
No full textPezzottaite is a rare Cs-bearing mineral with ideal composition Cs(Be2Li)Al2Si6O18, discovered in November 2002. Pezzottaite is probably the only new mineral species with some relevance in gemology, thanks to its optical properties, rarity and beauty.
It is considered as a member of the “beryl group”, along with beryl sensu-scricto (Be3Al2Si6O18;), bazzite (Be3Sc2Si6O18), stoppaniite (Be3Fe2Si6O18) and indialite (Mg2Al3(AlSi5O18)).
The chemical composition and the spectroscopic features of pezzottaite from Ambatovita (central Madagascar) and a Cs-rich beryl from Monte Capanne (Isola d’Elba, Italy) were investigated by standard gemmological analysis, electron microprobe analysis in wavelength dispersive mode (EMPA-WDS), X-ray diffraction and micro-Raman spectroscopy.
The density and the refractive index of pezzottaite were found to be higher than those of beryl due to the entrance of a large amount of alkali. However, an unambiguous distinction between pezzottaite and Cs-rich beryl cannot be done only on the basis of density and optical properties.
Pezzottaite and Cs-rich beryl are usually distinguished on the basis of chemical analysis, considering a conventional upper-limit of caesium in Cs-rich beryl of Cs2O ~ 9 wt%, or by X-ray diffraction, as pezzottaite has different symmetry. In any case, the discrimination is not easy and requires advanced and expensive techniques.
Chemical analysis of our samples showed an high amount of cesium (Cs2O 12.91 wt%) for pezzottaite, while the Cs-beryl has 1.27 wt%.
The crystal structure of the samples has been investigated through X-ray diffraction. The pezzottaite has a trigonal symmetry (space group R-3c, with a~15.9 and c~27.8 Å), while beryl is hexagonal (space group P6/mcc, with a~9.2 and c~9.2 Å). The increase of cell parameters is due to the entrance of lithium, that replaces beryllium in the tethaedra. The replacement causes a positive charge deficit neutralized by cesium in the channels.
The samples of pezzottaite and Cs-rich beryl were investigated by micro-Raman spectroscopy, a non-destructive and rapid tool of investigation. The un-polarized Raman spectrum of pezzottaite over the extended region 100-3650 cm-1 was collected for the first time, and compared with the spectrum of a Cs-beryl (Figure 1 and 2). In particular, Cs-beryl has showed only a intense peak at 3604 cm-1, ascribable to H2O stretching vibrations. On the other hand, two weak Raman bands at 3,591 and 3,545 cm-1, ascribable to the fundamental H2O or OH stretching vibrations respectively, were observed, despite the mineral should be nominally anhydrous. The Raman spectroscopy was useful to understand the type of water (type “I” or type “II”) and then to evaluate presence of alkali in the channels.
In addition, the Raman spectrum of pezzottaite shows two intense and characteristic bands at 110-112 cm-1 and 1100 cm-1, which are not present in the beryl spectrum (Figure 1).
Even if the true nature of the two bands is not completely understood, Raman spectroscopy appears to be a promising and inexpensive tool for a quicker identification of pezzottaite.
Figure 1: Raman spectra of pezzottaite (above) and Cs-beryl (below) in the region 100-1,200 cm-1.
Figure 2: Raman spectra of pezzottaite (above) and Cs-beryl (below) in the region 3,500-3,650 cm-1
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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