407 research outputs found

    Assessment for the mean value total dressing method: Comparison with coupled cluster including triples methods for BF, NO+, CN+, C2, BeO, NH3, CH2, H2O, BH, HF, SiH2, Li2, LiNa, LiBe+, NeH+, and O3

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    Limited previous experience with the mean value total dressing (MVTD) method had shown that MVTD energies for closed shell systems are generally better than CCSD(T) ones compared to FCI. The method, previously published as total dressing 2′(td-2′), is based on the single reference intermediate Hamiltonian theory. It is not a CC method but deals in a great part with the same physical effects that CC methods that incorporate amplitudes of triples such as CCSDT or its CCSDT-1n approaches. A number of test calculations comparing to diverse CC methods, as well as FCI and experiment when available, have been performed. The tests concern equilibrium energies in NH3 and CH2, equilibrium energies and distances in some diatomics (BF, NO+, CN+, C2, BeO), different bond breaking situations (H2O, BH, HF, SiH2) and spectroscopic properties of different bonding conditions (Li2, LiNa, LiBe+, NeH+, and O3). The results are in general closer to the full CCSDT ones in the equilibrium regions and close to CCSDT-1 along most dissociation curves. A few exceptions to this rule are analyzed with the help of an approach to MVTD that does not take into account the effects of linked quadriexcitations. Such analysis suggests the interest of improving the treatment of effects of linked triples in the MVTD model. The separate contributions of linked and unlinked triples and quadruples are also analyzed for some of the above diatomics representing different behaviors of bond breaking. The interest of such analysis is illustrated in the NeH+ molecule. The MVTD results show, in general, a high quality, provided that the nature of the correlation problem does not become largely multiconfigurational, as occurs in multiple bond dissociation or in the asymmetric stretching of [email protected] ; [email protected] ; [email protected]

    Les osteomes des sinus de la face

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    Introduction : Le but de notre travail est préciser le profil épidémio-clinique de cette pathologie, l’apport de l’imagerie dans le diagnostic, et discuter les modalités de l’exérèse chirurgicale et l’apport de la voie endoscopique.Patients et méthode : il s’agit d’une étude rétrospective de 18 patients porteurs d’ostéomes des sinus paranasaux opérés entre 1993 à 2010. Ont été exclus les patients non opérés et les malades perdus de vue.Résultats : il s’agit de 18 patients porteurs d’un ostéome symptomatique des sinus de la face, d’âge moyen 40 ans, sex ratio 0,38. La localisation la plus fréquente était le sinus frontal dans 55.5% des cas. Le traitement chirurgical était de mise pour les patients symptomatiques. La voie endonasale était indiquée dans 6 cas.la récidive a intéressé deux patients (11%) ayant un ostéome frontal et fronto-ethmoïdal. Pour le reste des malades l’évolution était favorable avec un recul moyen de 36 mois.Conclusion : L’ostéome des sinus paranasaux reste longtemps asymptomatique mais peut se compliquer par extension orbitaire ou cérébrale. L’abord endonasal a permis d’améliorer la prise en charge.Mots clés : Ostéome, sinus de la face, tomodensitométrie, chirurgie, voie endonasaleObjective : Lymph node infection is the most frequent localization of extrapulmonary tuberculosis. The treatment does not make general agreement. The aim of this study is to specify, from a review of the literature, the different ways of antimicrobial treatment and the indications of surgery.Patients and methods : il is about a retrospective study including 18 patients with paranasal sinus osteomas operated between 1993 and 2010. Were excluded unoperated and lost patients.Results : in this group of 18 patients with symptomatic sinus osteoma of the face, the mean age was 40 years, sex ratio was 0.38. the frontal sinus was the most affected, 55.5% of cases. Surgical treatment was set for symptomatic patients. The endonasal route was indicated in 6 cases. Recurrence was observed in two patients (11%) having a frontal osteoma and fronto-ethmoid. Outcomes were favorable in the remaining patients, mean follow-up was 36 months.Conclusion: Paranasal sinuses osteoma is a long asymptomatic tumor, but it may be complicated with orbital extending or stroke. Endonasal approach contributed to improve the treatment.Keyswords : Osteoma, paranasal sinus, computed tomography, surgery, endonasal approac

    Otospongiose : a propos de 149 cas

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    Introduction : L’otospongiose est une ostéodystrophie de la capsule otique se traduisant par une surdité de transmission ou plus rarement une surdité mixte d’apparition progressive. Le but de notre travail est d’analyser les caractéristiques épidémiologiques, cliniques, paracliniques et comparer les résultats en fonction de l’âge, du stade de l’ostéodystrophie, de la technique chirurgicale et de la prothèse.Patients et méthodes : notre étude est rétrospective portant sur 124 patients (149 oreilles) colligés sur une période de 9 ans (2000-2008).Résultats : notre population a comporté 86 femmes et 38 hommes. La moyenne d’âge à l’intervention était de 39,82 ans. La surdité était bilatérale dans 61,3% des cas et unilatérale dans 38,3%. Les seuils moyens préopératoires de la conduction osseuse et aérienne étaient respectivement de 17,33 dB et 52,52 dB, le rinne moyen était de 35,19 dB. La tomodensitométrie a été réalisée chez 63 patients. On a réalisé 21 platinectomie totale, 24 platinectomie partielle et 101 platinotomie calibrée. Selon la classification de Portmann, on a trouvé une répartition sensiblement égale entre les stades II, III et IV. On a utilisé un piston téflon 6/10 mm dans 119 cas et 4/10 mm dans 27 cas. Le rinne moyen postopératoire était de 15,95 dB. a 1 an, le rinne était de 14,81 dB avec un résultat satisfaisant de 94,2%.Conclusion : Il ressort de notre travail que certains facteurs semblent prédictifs de bons résultats et qui sont : le sexe féminin, l’âge <50 ans, le stade chirurgical< stade IV, la platinotomie, et le piston 0,4 mm.Mots clés : otospongiose, conduction osseuse, conduction aérienne, platinotomie, platinectomie.Objective : Otosclerosis is a common disorder of the otic capsule characterized by the presence of a progressive conductive or rarely mixed hearing loss. The aims of this study were to analyses the epidemiologic, clinical, paraclinical characteristic and compare our results according to age, stage, surgical technique and prosthesis. Patients et méthodes : Our study is retrospective about 124 patients (149 ears) in the period of 9 years (2000-2008).Results: Our population included 86 female and 38 male patients. mean age at intervention time was 39,82 years. The hearing loss was bilateral in 61,3% of cases and unilateral in 38,3%. The bone and air conduction threshold was 17.33 dB and 52,52 dB, the air-bone gap was 35,19 dB. The CT scan was realized in 63 patients. We have realized 21stapedectomy, 24 partial stapedectomy and 101 stapedotomy. In accordance with Portmann classification, the distribution between II, III and IV stages was almost equal. We used 6/10 mm Teflon piston prosthesis in 119 cases and 4/10 mm in 27 cases. The postoperative air-bone gap was 15,95 dB. after 1 year, the air-bone gap was 14,81 dB with a satisfying results in 94,2%.Conclusion: it seems that some factors are predictive for good results like a female sex, age<50 years, stage< stage IV, platinotomy and piston 4/10 mm.Keyswords : otosclerosis, bone conduction, air conduction, stapedectomy, stapedotom

    Size-consistent self-consistent configuration interaction from a complete active space : Excited states

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    The self-consistent size consistent on a complete active space singly and doubly configuration interaction (SC)2CAS-SDCI method is applied to excited states. The (SC)2 correction is performed on a closed shell state, and the excited states are obtained by diagonalization of the dressed matrix. A theoretical justification of the transferability of the improvement concerning the dressing state to all roots of the matrix is presented. The method is tested by three tests on the spectrum of small [email protected] ; [email protected]

    Composition and Anticoagulant Potential of Chondroitin Sulfate and Dermatan Sulfate from Inedible Parts of Garfish (Belone belone)

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    Glycosaminoglycans (GAGs) play a crucial role due to their significant biomedical functions. Chondroitin sulfate (CS) and dermatan sulfate (DS), the main representative family of GAGs, were extracted and purified from garfish (Belone belone) by-products, i.e., skin (GSB), bones (GCB), and heads (GHB), and their composition and anticoagulant activity were investigated. CS/DS were purified by ion-exchange chromatography with yields of 8.1% for heads, 3.7% for skin, and 1.4% for bones. Cellulose acetate electrophoresis was also explored for analyzing the extracted CS/DS. Interestingly, GHB, GSB, and GCB possessed sulfate contents of 21 ± 2%, 20 ± 1%, and 20 ± 1.5%, respectively. Physico-chemical analysis showed that there were no significant differences (p > 0.05) between the variances for sulfate, uronic acid, and total sugars in the GAGs extracted from the different parts of fish. Disaccharide analysis by SAX-HPLC showed that the GSB and GCB were predominately composed of ΔDi-4S [ΔUA-GalNAc 6S] (74.78% and 69.22%, respectively) and ΔDi-2,4S [ΔUA2S-GalNAc 4S] (10.92% and 6.55%, respectively). However, the GHB consisted of 25.55% ΔDi-6S [ΔUA-GalNAc 6S] and 6.28% ΔDi-2,6S [ΔUA2S-GalNAc 4S]. Moreover, classical anticoagulation tests were also used to measure their anticoagulant properties in vitro, which included the activated partial thromboplastin time, prothrombin time, and thrombin time. The CS/DS isolated from garfish by-products exhibited potent anticoagulant effects. The purified CS/DS showed exceptional anticoagulant properties according to this research and can be considered as a new agent with anticoagulant properties

    Local character of magnetic coupling in ionic solids

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    Magnetic interactions in ionic solids are studied using parameter-free methods designed to provide accurate energy differences associated with quantum states defining the Heisenberg constant J. For a series of ionic solids including KNiF3, K2NiF4, KCuF3, K2CuF4, and high- Tc parent compound La2CuO4, the J experimental value is quantitatively reproduced. This result has fundamental implications because J values have been calculated from a finite cluster model whereas experiments refer to infinite solids. The present study permits us to firmly establish that in these wide-gap insulators, J is determined from strongly local electronic interactions involving two magnetic centers only thus providing an ab initio support to commonly used model Hamiltonians

    Novel, Meso-Substituted Cationic Porphyrin Molecule for Photo-Mediated Larval Control of the Dengue Vector Aedes aegypti

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    Dengue is a life-threatening viral disease of growing importance, transmitted by Aedes mosquito vectors. The control of mosquito larvae is crucial to contain or prevent disease outbreaks, and the discovery of new larvicides able to increase the efficacy and the flexibility of the vector control approach is highly desirable. Porphyrins are a class of molecules which generate reactive oxygen species if excited by visible light, thus inducing oxidative cell damage and cell death. In this study we aimed at assessing the potential of this photo-mediated cytotoxic mechanism to kill Aedes (Stegomyia) aegypti mosquito larvae. The selected porphyrin molecule, meso-tri(N-methylpyridyl),meso-mono(N-tetradecylpyridyl)porphine (C14 for simplicity), killed the larvae at doses lower than 1 µM, and at light intensities 50–100 times lower than those typical of natural sunlight, by damaging their intestinal tissues. The physicochemical properties of C14 make it easily adsorbed into organic material, and we exploited this feature to prepare an ‘insecticidal food’ which efficiently killed the larvae and remained active for at least 14 days after its dispersion in water. This study demonstrated that photo-sensitizing agents are promising tools for the development of new larvicides against mosquito vectors of dengue and other human and animal diseases

    Possibilistic classifiers for numerical data

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    International audienceNaive Bayesian Classifiers, which rely on independence hypotheses, together with a normality assumption to estimate densities for numerical data, are known for their simplicity and their effectiveness. However, estimating densities, even under the normality assumption, may be problematic in case of poor data. In such a situation, possibility distributions may provide a more faithful representation of these data. Naive Possibilistic Classifiers (NPC), based on possibility theory, have been recently proposed as a counterpart of Bayesian classifiers to deal with classification tasks. There are only few works that treat possibilistic classification and most of existing NPC deal only with categorical attributes. This work focuses on the estimation of possibility distributions for continuous data. In this paper we investigate two kinds of possibilistic classifiers. The first one is derived from classical or flexible Bayesian classifiers by applying a probability–possibility transformation to Gaussian distributions, which introduces some further tolerance in the description of classes. The second one is based on a direct interpretation of data in possibilistic formats that exploit an idea of proximity between data values in different ways, which provides a less constrained representation of them. We show that possibilistic classifiers have a better capability to detect new instances for which the classification is ambiguous than Bayesian classifiers, where probabilities may be poorly estimated and illusorily precise. Moreover, we propose, in this case, an hybrid possibilistic classification approach based on a nearest-neighbour heuristics to improve the accuracy of the proposed possibilistic classifiers when the available information is insufficient to choose between classes. Possibilistic classifiers are compared with classical or flexible Bayesian classifiers on a collection of benchmarks databases. The experiments reported show the interest of possibilistic classifiers. In particular, flexible possibilistic classifiers perform well for data agreeing with the normality assumption, while proximity-based possibilistic classifiers outperform others in the other cases. The hybrid possibilistic classification exhibits a good ability for improving accuracy

    Proposal of an extended t-J Hamiltonian for high-Tc cuprates from ab initio calculations on embedded clusters

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    A series of accurate ab initio calculations on Cu_pO-q finite clusters, properly embedded on the Madelung potential of the infinite lattice, have been performed in order to determine the local effective interactions in the CuO_2 planes of La_{2-x}Sr_xCuO_4 compounds. The values of the first-neighbor interactions, magnetic coupling (J_{NN}=125 meV) and hopping integral (t_{NN}=-555 meV), have been confirmed. Important additional effects are evidenced, concerning essentially the second-neighbor hopping integral t_{NNN}=+110meV, the displacement of a singlet toward an adjacent colinear hole, h_{SD}^{abc}=-80 meV, a non-negligible hole-hole repulsion V_{NN}-V_{NNN}=0.8 eV and a strong anisotropic effect of the presence of an adjacent hole on the values of the first-neighbor interactions. The dependence of J_{NN} and t_{NN} on the position of neighbor hole(s) has been rationalized from the two-band model and checked from a series of additional ab initio calculations. An extended t-J model Hamiltonian has been proposed on the basis of these results. It is argued that the here-proposed three-body effects may play a role in the charge/spin separation observed in these compounds, that is, in the formation and dynamic of stripes.Comment: 24 pages, 4 figures, submitted to Phys. Rev.
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