322,892 research outputs found
Equilibrium Constants for Ionisation and Enolisation of 3-Nitrobutan-2-one
No full textThe equilibrium constant for the keto-enol tautomerism of 3-nitrobutan-2-one K-T = [enol]/[ketone] has been measured in water as 4.57 x 10(-3) (pK(T) = 2.34) by combining the rate constants for ketonisation of the enolate form and pK(a) of the ketone at 25 degrees C. The rates of ketonisation were measured by a rapid kinetic technique and the pK(a) was determined spectrophotometrically and potentiometrically as 5.15. A comparison with 2-butanone and acetone shows a strong influence of the nitro group in enhancing the acidity of the substrate and in stabilizing the enol relative to the keto tautomer. By means of semiempirical AM1 calculations, good correlations were found between the atomic charge on the acidic hydrogens and the pK(a) tin water at 25 degrees C) of both tautomeric forms for a number of simple ketones whose pK(a)s and pK(T)s are available in the literature. The agreement of experimental acidity constants of the enol, pK(a)(EH), th, ketone, pK(a)(KH), and the tautomeric constant, pK(T) with predicted values is satisfactory
Enlarged vestibular aqueduct: Audiological and genetical features in children and adolescents
No full textBackground Enlarged Vestibular Aqueduct (EVA) is one of the most common congenital malformations associated with sensorineural or mixed hearing loss. The association between hearing loss and EVA is described in syndromic (i.e. Pendred Syndrome, BOR, Waardenburg) and non-syndromic disorders, as isolate or familiar mutations of the SLC26A4 gene. The audiological phenotype of the EVA syndrome is heterogeneous, the type and entity of hearing loss may vary and vertigo episodes might also be present. Objective The aim of this retrospective study was to describe the clinical and genetic features of a group of adolescent subjects presenting an EVA clinical profile, considering the presence of SLC26A4 gene mutations. Methods 14 Caucasian patients were assessed (24 ears in total; 4 patients presented a monolateral EVA), 10 females and 4 males. Their age at the time of diagnosis was between 1 and 6 years (mean age 2.5 years). Subjects were assessed by an ENT microscopy evaluation with a complete audiometric assessment, CT & MRI scans and genetic tests for the evaluation of the pendrin gene mutations (SLC26A4). Results Considering the presence of SLC26A4 mutations and thyroid function, we could identify three sub-groups of patients: group 1, non syndromic EVA (ns EVA, no SLC26A4 mutation and no thyroid dysfunction); group 2, EVA with DFNB4 (single SLC26A4 gene mutation and no thyroid dysfunction); group 3, EVA with Pendred Syndrome (two pathological mutation of SLC26A4 and thyromegaly with thyroid dysfunction). Patients of group 1 (ns-EVA) showed various degrees of hearing loss from mild (55%) to severe-profound (45%). In groups 2 (DFNB4) and 3 (PDS), the degree of hearing loss is severe to profound in 70–75% of the cases; middle and high frequencies are mainly involved. Conclusions The phenotypic expressions associated with the EVA clinical profile are heterogeneous. From the available data, it was not possible to identify a representative audiological profile, in any of the three sub-groups. The data suggest that: (i) a later onset of hearing loss is usually related to EVA, in absence of SLC26A4 gene mutations; and (ii) hearing loss is more severe in patients with SLC26A4 gene mutations (groups 2 and 3 of this study)
Diffusive author(s), cohesive author: Analysis of S/N (1994)
No full textThis study indicates the ways in which various aspects of the author(s) are brought forth in Dumb type’s performance art, the S/N production. Previous research has suggested a non-hierarchical organization of Dumb type and the absence of a “privileged author” in Dumb type’s collaborative work, S/N. However, the results that I have investigated from member’s interviews on the creative process of S/N along with my analysis of the recorded images of S/N, indicate a different aspect of the author(s). First, S/N was created through, so to speak, the collective ideas of the members of Dumb type. Further, S/N has at least nine quotations from previous performances, installations, and printed writings, besides the work-in-progress technique. Explicating one of the “author functions” as given by Michel Foucault, each text has plural subjects of the author. However, it has been revealed from members’ interviews that Teiji Furuhashi had a decision-making role in selecting the members’ ideas within the performance. Since then, S/N has had plural subjects of creation; however, Furuhashi is one of the subjects of creation along with the “privileged author.” S/N has plural authors (diffusive authors) yet at the same time, it has a “privileged author,” Teiji Furuhashi (cohesive author)
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
An effective simulation of aqueous micellar aggregates by computational models
No full textWe have computationally studied the interaction modes, localization and orientation of a benzene (Bz) molecule on the surface of micelles formed by cetyltrimethylammonium salts CTAX. Experimental H-1-NMR data on complexation shifts induced by Bz on the polar head hydrogens and on the adjacent methylene hydrogens of CTAX have been interpreted using a computational approach that combines an automatic molecular docking procedure with a calculation module that accounts for NMR complexation shifts due to ring current diamagnetic anisotropy. Three different models were used to reduce the complexity of the micellar system. Computational results, in good agreement with available experimental data, point to a preferential localization of the Bz molecule along the CTAX alkyl tail, about 3.9 angstrom away from the charged nitrogen. The Bz molecular plane is predicted perpendicular to the C-H bonds of the alkyl tail. The good results obtained with the simplest model suggest that it could be used to study more complex systems involving surfactants endowed with molecular recognition or catalytic abilities
Multidirectional migrations from a major nesting area in Turkey support the widespread distribution of foraging sites for loggerhead turtles in the Mediterranean
No full textSatellite tracking studies have identified some of the migratory corridors and foraging sites of Mediterranean loggerhead sea turtle (Caretta caretta) rookeries over the past few decades. However, due to a lack of information for breeding rookeries in Libya and Turkey, our understanding of the distribution and connectivity of adult loggerheads is limited. We satellite-tracked 17 female loggerhead turtles breeding in one of the main nesting areas in Turkey to identify (1) migratory pathways, and (2) their foraging areas. Females were tracked for 96-657 d (mean: 271 d), and followed 3 general migratory directions (southeast, southwest and northwest/west). While migrating, individuals alternated oceanic and neritic movements, generally travelling significantly slower when in neritic waters (average speed reduction: 20%). Five turtles stopped between 1 to 3 times in stopover sites for 6 d before resuming their migration. While 1 turtle resided in oceanic foraging areas, the remaining 16 loggerheads settled in 12 distinct neritic foraging grounds; 2 turtles shared one site and 4 turtles shared another site. The identified foraging grounds were widely distributed across the Eastern and Central basin, in locations known to be frequented by loggerhead turtles from other rookeries. The present findings reveal links between foraging areas and one of the main breeding sites in Turkey, providing useful information for species conservation.Turkish Ministry of Environment and Urbanization; RAC-SPA; Baku-Tbilisi-Ceyhan Pipeline Company; TUI Care Foundation; MAVA Foundation; US Fish and Wildlife Ser vice under the Marine Turtle Conservation Act [PL 108-266]; University of PisaWe thank Dr. Flegra Bentivegna, Dr. Fulvio Maffucci and all DEKAMER volunteers for their help during field activities. Dr. Cheryl Sanchez (Pisa, IT) kindly revised the English text. Funding was provided by the Turkish Ministry of Environment and Urbanization, RAC-SPA, Baku-Tbilisi-Ceyhan Pipeline Company, TUI Care Foundation, MAVA Foundation, the US Fish and Wildlife Ser vice under the Marine Turtle Conservation Act (award no. PL 108-266), and the University of Pisa
Patent Foramen Ovale as Possible Cause of Sudden Sensorineural Hearing Loss: A Case Report
No full text<b><i>Objective:</i></b> To present a case of sudden sensorineural hearing loss (SSNHL) and the related diagnostic workup. <b><i>Clinical Presentation and Intervention:</i></b> A 54-year-old man presented with a unilateral SSNHL episode and vertigo. A severe patent foramen ovale (PFO) that included a complete ear nose and throat, audiological, and neurological examination was discovered during the diagnostic workup. Audiometry, blood, and serological tests were performed. Magnetic resonance imaging and color Doppler echography of the supra-aortic trunks and lower limbs were carried out. Finally, transthoracic followed by transesophageal echocardiography and transcranial Doppler were performed in order to confirm the diagnosis of PFO. Medical therapy with systemic steroid and antiplatelet drugs was administered. <b><i>Conclusions:</i></b> This case showed a small PFO associated with an aneurysmatic interatrial septum. The PFO and paradoxical thromboembolism could be involved in the pathogenesis of SSNHL.</jats:p
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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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