Isolation of a Ru(IV) side-on peroxo intermediate in the water oxidation reaction

The electrons that nature uses to reduce CO2 during photosynthesis come from water oxidation at the oxygen-evolving complex of photosystem II. Molecular catalysts have served as models to understand its mechanism, in particular the O-O bond-forming reaction, which is still not fully understood. Here we report a Ru(IV) side-on peroxo complex that serves as a 'missing link' for the species that form after the rate-determining O-O bond-forming step. The Ru(IV) side-on peroxo complex (eta(2)-1(IV)-OO) is generated from the isolated Ru(IV) oxo complex (1(IV)=O) in the presence of an excess of oxidant. The oxidation (IV) and spin state (singlet) of eta(2)-1(IV)-OO were determined by a combination of experimental and theoretical studies. O-18- and H-2-labelling studies evidence the direct evolution of O-2 through the nucleophilic attack of a H2O molecule on the highly electrophilic metal-oxo species via the formation of eta(2)-1(IV)-OO. These studies demonstrate water nucleophilic attack as a viable mechanism for O-O bond formation, as previously proposed based on indirect evidence

Snow Chemistry Across Antarctica

An updated compilation of published and new data of major-ion (Ca, Cl, K, Mg, Na, NO3, SO4) and methylsulfonate (MS) concentrations in snow from 520 Antarctic sites is provided by the national ITASE (International Trans-Antarctic Scientific Expedition) programmes of Australia, Brazil, China, Germany, Italy, Japan, Korea, New Zealand, Norway, the United Kingdom, the United States and the national Antarctic programme of Finland. The comparison shows that snow chemistry concentrations vary by up to four orders of magnitude across Antarctica and exhibit distinct geographical patterns. The Antarctic-wide comparison of glaciochemical records provides a unique opportunity to improve our understanding of the fundamental factors that ultimately control the chemistry of snow or ice samples. This paper aims to initiate data compilation and administration in order to provide a framework for facilitation of Antarctic-wide snow chemistry discussions across all ITASE nations and other contributing groups. The data are made available through the ITASE web page (http:// www2.umaine.edu/itase/content/syngroups/snowchem.html) and will be updated with new data as they are provided. In addition, recommendations for future research efforts are summarized

Email forensic tools : A roadmap to email header analysis through a cybercrime use case

Email is one of the primary sources of numerous criminal activities, on the Internet, of which some threaten human lives. Email analysis is challenging due to not only various fields that can be forged by hackers or the wide range email applications in use, but also due to imposed law restrictions in the analysis of email body. Despite this being a relatively new area, a number of both open source and proprietary forensic tools, with varying possibilities and versatility, have been developed aiding use by practitioners. In this paper, we review existing email forensic tools for email header analysis, as part of email investigation, with emphasis on aspects related to online crime while still considering legal constraints. Through our analysis, we investigate a common case of cybercrime and examine the breadth of information one may gain solely through email forensics analysis. Additionally, a roadmap for email forensic analysis is presented, combining features and functionality already available, to assist the process of digital forensic analysis

The quartile benefit plot: a middle ear surgery benefit assessment scheme.

International audienceOBJECTIVE: The purpose of this study is to present a new method for the assessment of hearing improvement following stapes surgery, taking into account additional, previously omitted evaluation criteria. STUDY DESIGN: Retrospective. METHODS: A quartile plot, based on the currently used Glasgow benefit plot, is structured to include two additional criteria of hearing assessment, namely the absence of postoperative sensorineural hearing loss and the closure of the air-bone gap to <10 dB. Pre- and postoperative hearing results of 132 patients diagnosed with bilateral otosclerosis and treated with bilateral stapes surgery were plotted on both the classical Glasgow benefit plot and the new quartile benefit plot. The difference in success assessment due to stricter assessment criteria is demonstrated. RESULTS: Functional success rate following bilateral stapes surgery as plotted on the traditional Glasgow benefit plot was 51.5%. Success rate for bilateral stapes surgery assessed on the new quartile plot with the addition of the two new criteria was 38.64%. The difference in success rates was found to be statistically significant. CONCLUSION: The basis of benefit assessment in stapes surgery solely on the mean deficit in air conduction results in overestimation of success rate. This study demonstrates that results that appear satisfactory when judged by the Glasgow benefit plot are of modest success when assessed by the new quartile plot. The quartile benefit plot presented in this paper provides a strict measure of presentation and evaluation of stapes surgery results

Unilateral cochleovestibular nerve compression syndrome in a patient with bilateral IAC osteoma

International audienceIntroductionOsteomas of the internal auditory canal are rarely reported in the literature. Patients may complain of disabling symptoms of dizziness, hearing loss, and vestibular dysfunction. We report the case of a patient with bilateral osteomas of the internal auditory canal (IAC) associated with bilateral neurovascular compression mainly affecting the right cochleovestibular nerve (VIII) and right anterior inferior cerebellar artery (AICA).ObservationThis 75-year-old woman patient complained of disabling paroxysmal vertigo, typewriter tinnitus and hearing loss of the right ear. Temporal bone computed tomography showed bilateral osteoma arising from the posterior superior wall of the IAC. MRI sequences of the right VIII demonstrated compression by the right AICA against the inferior wall of the narrowed IAC. Treatment with oxcarbazepine allowed marked and lasting improvement of the patient's symptoms.ConclusionTo our knowledge, this is the first description of an ipsilateral neurovascular compression syndrome of the VIII secondary to the presence of an osteoma narrowing the IAC

Paroxysmies vestibulaires et ostéome bilatéral du CAI

International audienceIntroductionL’ostéome du conduit auditif interne (CAI) est une tumeur osseuse rarement retrouvée ; les patients présentent souvent une symptomatologie variée, comportant des acouphènes, une surdité de perception et une dysfonction vestibulaire. Nous rapportons ici le cas d’une patiente présentant un ostéome bilatéral des CAI coexistant avec un conflit neurovasculaire bilatéral incriminant principalement le nerf cochléovestibulaire droit (VIII) et l’artère cérébelleuse antéro-inférieure droite (ACAI).ObservationUne patiente de 75 ans présentait une symptomatologie associant paroxysmies vestibulaires, acouphènes et hypoacousie droite. La tomodensitométrie des os temporaux montrait un ostéome bilatéral se développant sur la paroi postérosupérieure des CAI. Sur les séquences IRM le VIII droit apparaissait comprimé contre la paroi inférieure du CAI sténosé par l’ACAI droite. Un traitement par oxcarbazépine a été proposé et a permis une amélioration franche et durable des symptômes.ConclusionIl s’agit à notre connaissance de la première description d’un cas où existe dans le cadre d’une double pathologie un syndrome de compression neurovasculaire sur le VIII secondaire à l’existence d’un ostéome sténosant le CAI

Magnetic and transport properties of nanocrystalline titanium carbide in carbon matrix

Samples of titanium carbide (TiCx) in a carbon matrix have been prepared by the nonhydrolytic sol-gel process. The nanocomposite powder samples containing one the TiCx of average size ca. 30 nm encapsulated in carbon cages of 3 wt.% and other the TiCx in carbon matrix (ca. 10 wt.%) have been obtained. The temperature dependence of the EPR spectra of titanium carbide has shown coexistence of two different paramagnetic centers, one arising from conducting electrons and the other from trivalent titanium ion complexes. Comparison with a similar titanium nitride (TiNx) is made, where no EPR spectra of trivalent titanium ions exist. The titanium nitride has shown only the EPR spectra arising from magnetic localized centers and not from trivalent titanium ion complexes. The magnetic ordering and superconducting states are observed in titanium carbide in the low temperature region, while in titanium nitride only the later state is recorded. The titanium nitride is a good conducting material while the titanium carbide shows an extraordinary behaviour, especially in the higher temperature region where a sharp jump in conductivity is recorded about 250 K. It is suggested that the disorder-order processes are more intense in the nonstoichiometric titanium carbide. © 2009 Springer Netherlands