1,721,074 research outputs found
Crystal-fluid interactions in open-framework materials at high pressure
Full text linkThe number of experiments on the high-pressure behavior of open-framework materials increased significantly in the last decade [1,2]. The framework topology, the chemical composition and the so-called “host-guest” interactions (between the framework and the extraframework components) were found to significantly influence the response of zeolites to the applied pressure. However, the HP-behavior of zeolites may also be influenced by crystal-fluid interactions when P-transmitting fluids (PTF) are used to generate hydrostatic compression, and in particular when the PTF is “pore-penetrating”. In such a case, the P-induced penetration of PTF molecules into the zeolite structural voids leads to a change of the physical-chemical properties of the studied material, for example inducing a stiffening of the elastic behavior or leading to the hyperconfinement of supramolecular aggregates (in the zeolite channels) with functional properties [3].
In this study, we describe the HP-behavior and the crystal-fluid interactions of two synthetic zeolites with empty channels and cages, i.e. all-silica ferrierite (Si-FER) and ALPO4-5 (AlPO4), compressed with non-penetrating (silicone oil, s.o.) and potentially pore-penetrating PTF. The compression of Si-FER in s.o. evidences the remarkable flexibility of this framework: a first displacive phase transition was observed from the Pmnn to the P121/n1 space group at ~ 0.7 GPa. A second displacive phase transition, involving a significant unit-cell volume contraction, was observed at ~ 1.24 GPa from the P121/n1 to the P21/n11 space group (through an intermediate P-1 structure, “type-II” transition according to Christy [4]). The high-P P21/n11 polymorph was found to be stable at least up to 3.00(7) GPa, whereas - upon pressure release - the starting Pmnn structure was fully recovered. The three polymorphs were found to share a virtually identical bulk elastic behavior, being their average volume compressibility βV: 0.051(4), 0.056(9) and 0.055(3) GPa-1, respectively. The compression of Si-FER and ALPO-5 in potentially pore-penetrating PTF showed a lower bulk compressibility, different phase-transition paths (for Si-FER) and diverse atomic-scale deformation mechanisms with respect to the compression in silicone oil, suggesting the onset of significant crystal-fluid interactions, likely due to the P-induced penetration of PTF molecules. In addition, the HPbehavior of Si-FER is strongly influenced by the process kinetics, which was found to control the P-induced molecules intrusion phenomena and, as consequence, the P-induced phase transitions in this material.
The authors acknowledge the Italian Ministry of Education, MIUR-Project: “Futuro in Ricerca 2012 - ImPACTRBFR12CLQD”.
[1] G.D. Gatta, Y. Lee Mineral. Mag. 2014, 78, 267-291. [2] G. Vezzalini, R. Arletti, S. Quartieri Acta Cryst. 2014, B70,
444-471. [3] M. Santoro, F.A. Gorelli, R. Bini, J. Haines, A. Van der Lee Nat. Commun. 2013, 4, 1557-1563. [4] A.G.
Christy Acta Cryst. 1993, B49, 987-996
Effect of oral chronic isoflavones supplementation on male rat sexual performances and sexual hormone plasma levels.
No full textThe aim of our study was to evaluate how a chronic isoflavones oral supplementation could affect male rat sexual behavior in relationship to cause eventual change in plasma sexual hormone concentrations. Isoflavones were administered in the form of a standardized dry extract of soybeans. Three groups of 20 sexually experienced male rats were consecutively treated with saline 2 ml, or isoflavones 0.4 mg/kg−1 or 0.8 mg/kg−1 soybean dried extract via gastric tube for 40 days. No significant differences were found as regards sexual performances of the three studied groups at the baseline levels nor at the end of the study: in relationship to the base-line value, only mount frequency increased in the control group (z = −2.047, p = 0.041), while intromission frequency in the high dosage isoflavones group (z = -2.484, p = 0.13). At the base-line test 23.08% of rats in each group were not able to conclude their performance in the standard time, while at the end of the study only 15.38% of the control group rats were not able to do this. No significant difference has been observed as regards FSH, progesterone, androstenedione plasma levels, either between groups or between baseline and study end. Slight differences were found regards LH and testosterone plasma level
Behavioral and developmental outcomes of prenatal and postnatal vanadium exposure in the rat
No full textThe developmental and behavioral outcomes of uninterrupted exposure to vanadium was studied in the rat. Starting 3 days before birth and up to the 100th day of extrauterine life, rats received as drink either a water solution of vanadyl sulphate (300 mg l(-1) containing 70 mg l(-1) of vanadium element, which is equal to an ingested dose of about 10 mg kg(-1) per day of vanadium element) plus NaCl 5 g l(-1), or a water solution of NaCl 5 g l(-1), or plain water [up to weaning (25th day of extrauterine life) treatment was given to dams and offspring]. At M weaning, survivors were fewer and body weight was found to be significantly lower in the offspring of vanadium plus NaCl-treated dams than in the offspring of the other two groups. After weaning, growth retardation continued to be significant in both vanadium plus NaCl- and NaCl-treated rats. Such an effect was more pronounced in males than in females. Locomotor activity-evaluated at 1 month of; age-was not significantly different in the three groups of rats. In the open-field, male (but not female) vanadium plus NaCl-treated rats had a reduced outer ambulation, rearing posture and grooming activity, and an increased defecation, in comparison with the males of the NaCl group, and reduced rearing in comparison with control males. As concerns ingestive behaviors, the only significant datum was an increased water intake in NaCl-treated males. Finally, at the 100th day of life, working memory was significantly impaired in both vanadium plus NaCl- and NaCl-treated rats
General and cardiac toxicity of doxorubicin-loaded gelatin nanoparticles
No full textGeneral and cardiac toxicity of doxorubicin loaded gelatin nanoparticles cross-linked by glutaraldheyde were investigated in healthy rats. The rats were treated with free doxorubicin (DXR), unloaded nanoparticles (UNp), physical mixture of doxorubicin, and unloaded nanoparticles (DRX/UNp), and DXR-loaded nanoparticles (DXR-Np). Each group of animals received the same dose of DXR (3 mg/kg) via i.p. once a week. Both electrocardiogram (EGG) parameters and body weight were measured 24h before each administration. Rats treated with UNp behaved as controls. DXR/UNp provoked the same toxic effects as free DXR. On the contrary, DXR-Np resulted more toxic since significant variations of both the body weight and the ECG parameters were observed during the first week of treatment. In addition, the rats treated with DXR-Np died between the 3(rd) and the 5(th) day after the 2(nd) administration. These results demonstrate that, in these experimental conditions, the couplage of DXR to nanoparticles enhanced the cardiotoxicity of the drug. Since DXR was linked to the protein matrix of nanoparticles via glutaraldehyde, the high toxicity of DXR-loaded nanoparticles could be due to the covalent binding of the drug to the carrier
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
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