Complete Decoupling Limit of Ghost-free Massive Gravity

We present the complete form of the decoupling limit of ghost-free massive gravity with a Minkowski reference metric, including the full interactions of the helicity-1 and helicity-0 modes of the massive spin-2 field. While in the metric language the square root structure of the mass terms makes it difficult to find a simple way to write down the interactions, we show that using the vierbein formulation of massive gravity, including Stueckelberg fields for both diffeomorphism and local Lorentz symmetries, we can find an explicitly resummed expression for the helicity-1 field interactions. We clarify the equations of motion for the Lorentz Stueckelberg fields and how these generate the symmetric vierbein condition which guarantees equivalence between the vierbein and metric formulations of massive gravity.Comment: 20 pages, typos corrected, references adde

Tunable plasma wave resonant detection of optical beating in high electron mobility transistor

We report on tunable terahertz resonant detection of two 1.55 µm cw-lasers beating by plasma waves in AlGaAs/InGaAs/InP high-electron-mobility transistor. We show that the fundamental plasma resonant frequency and its odd harmonics can be tuned with the applied gate-voltage in the range 75-490 GHz. The observed frequency dependence on gate-bias is found to be in good agreement with the theoretical plasma waves dispersion law.Comment: Applied Physics Letters to be published (2006) -

Effet de la composition de différents substrats culturaux sur quelques paramètres de croissance de Gambeya lacourtiana De Wild en pépinière au nordest du Gabon

Objectif : Les connaissances en matière de gestion des ressources phytogénétiques en zone tropicale humide sont encore limitées au regard de la variabilité biologique existante. Un programme de multiplication d'espèces forestières a été entrepris au nord-est du Gabon. La simplicité des techniques et leur faible coût ont favorisé la production de milliers de plants. Nos travaux s’intègrent dans ce projet afin d’évaluer les effets de la composition de trois substrats culturaux sur quelques paramètres de croissance de Gambeya lacourtiana De Wild (Sapotacées) en pépinière.Méthodologie et résultats : Cette expérimentation en sachets de film plastique de polyéthylène a été conduite en 2010 à Ipassa (Gabon) en conditions naturelles d’éclairement, de température et d’hygrométrie. Trois substrats culturaux S1 (30% sable + 70% terre noire), S2 (20% terre noire + 70% sciure de bois + 10% sable) et S3 (70% cendre de bois + 30% sable) ont constitué le milieu de culture. Après la préparation manuelle des substrats, les sachets remplis ont été placés suivant un dispositif en blocs complément randomisés à vingt (20) unités expérimentales. Les résultats ont montré que le substrat S1 a induit le meilleur accroissement des plants. Le substrat S3 s’est révélé nocif à la croissance des plantules. La présence de sciure de bois dans le substrat S2 s’est montrée inefficace pour la germination des graines, mais ce substrat a donné des performances acceptables sur la croissance longitudinale des plantules.Conclusion et application : L’apport de matière organique serait donc plus bénéfique pour la croissance des plantules de G. lacourtiana alors qu’un milieu composé de sable et de terre humifère reste suffisant pour la germination de semences.Mots clés : multiplication végétale, substrat cultural, paramètres de croissance, Gambeya lacourtiana, Gabon.Effects of the composition of different farming substrates on some growth parameters of Gambeya lacourtiana De Wild in seedbed in north-eastern of GabonABSTRACTObjective: Knowledge in plant resources management in tropical rainfall area is still limited because of the great biological variability existing. A program of multiplication of wild species was undertaken in the northeastern of Gabon. The simplicity of the techniques and their low costs supported the production of thousands of seedlings. Our study integrates this project with a view to evaluate the effects of the composition of three farming substrates on some growth parameters of Gambeya lacourtiana De Wild (Sapotaceae) in seedbed.Methodology and Results: This experiment in polyethylene bags took place in 2010 at Ipassa (Gabon) based on natural conditions of lightness, temperature and relative humidity. Three substrates S1 (30% sand + 70% black soil), S2 (20% black soil + 70% sawdust +10% sand) and S3 (70% wood + 30% sand) were used as culture media. After manual preparation of substrate, bags filled were placed according to a complete with twenty (20) repetitions. Results show that the substrate S1 was found to induce the best increase of planlets. The chemical composition of the S3 substrate appeared to be harmful on the growth of the plantlets. The presence of sawdust in the S2 substrate was ineffective for the germination of seeds, but this substrate gave suitable performances on the longitudinal growth of the seedlings.Conclusion and Application: Organic matter is more required for the growing of plantlets of G. lacourtiana while a substrate composed by sand and black soil is efficient for the seedlings germination.Key-words: vegetative multiplication, farming substrate, growth parameters, Gambeya lacourtiana, Gabon

Cancer du testicule: particularités cliniques et limites thérapeutiques en milieu hospitalier urologique au Sénégal

RésuméButEtudier les particularités cliniques et les limites thérapeutiques de la prise en charge du cancer du testicule au Sénégal.Patients et méthodesCette étude, rétrospective, était menée sur une période de 15 ans de Janvier 1997 à Janvier 2012. Vingt-deux dossiers étaient colligés mais 17 étaient exploitables.Résultatsl’incidence annuelle moyenne était de 1,13 cas par an. L’âge moyen des patients était de 27 ans ± 9,5. La tranche d’âge la plus concernée était celle de 21 à 40 ans. Les circonstances de découverte étaient dominées par la grosse bourse (10 cas) et en cas de vacuité scrotale, la masse abdominale ou pelvienne (7 cas). L’orchidectomie a été le principal geste thérapeutique. Elle a été réalisée par voie inguinale haute (8 patients) et par voie trans-péritonéale (7 patients). Sur le plan histologique, nous avions noté une prédominance des tumeurs germinales non séminomateuses avec 10 cas de carcinome embryonnaire dont un cas de type infantile. En post opératoire, 7 cas de progression avaient été notés dans le suivi: 3 cas de carcinose péritonéale, 3 cas d’envahissement locorégionale avec des adénopathies rétropéritonéale et 1 cas de métastase pulmonaire. Avec un recul moyen de 6 mois, 9 patients étaient décédés, 4 étaient perdus de vue et les 4 autres étaient vivants.ConclusionLe cancer du testicule reste rare au Sénégal et concerne des sujets jeunes. Le diagnostic est encore posé à des stades très évolués avec une lourde mortalité.AbstractObjectiveTo investigate the clinical features and limitations of therapeutic management of testicular cancer in Senegal.Patients and methodsThis is a retrospective study over 15 years period between January 1997 and January 2012. Twenty-two cases were collected but only 17 had complete data for analysis.ResultsThe average annual incidence was 1.13 cases per year, with a mean age of 27±9.5 years. The most affected age group was between 21 and 40 years.Clinical diagnosis was suspected by the presence of a scrotal swelling in10 cases and by empty scrotum associated with abdominal or pelvic mass in the remaining 7 cases. Orchiectomy was the main treatment option, done either by high inguinal approach in 8 patients or by trans- peritoneal route in other 7 patients. Histologically, a predominance of embryonic non seminomatous germ cell carcinoma was noted in 10 cases including infantile type in one case. Seven cases developed disease progression:3 cases of peritoneal carcinmatosis, 3 other cases of locoregional invasion with retroperitoneal lymphadenopathy and one case of pulmonary metastasis. At a mean follow up of six months, nine patients died, four were lost to follow up while the remaining four cases were still alive.ConclusionTesticular cancer is a rare tumor in Senegal and usually involves young people. Clinical diagnosis is always done at very advanced stage with a very high mortality rate

Highly viscoelastic films at the water/air interface: α-Cyclodextrin with anionic surfactants

This work showcases the remarkable viscoelasticity of films consisting of α-cyclodextrin (α-CD) and anionic surfactants (S) at the water/air interface, the magnitude of which has not been observed in similar systems. The anionic surfactants employed are sodium salts of a homologous series of n-alkylsulfates (n = 8–14) and of dodecylsulfonate. Our hypothesis was that the very high viscoelasticity can be systematically related to the bulk and interfacial properties of the system. Through resolution of the bulk distribution of species using isothermal titration calorimetry, the high dilatational modulus is related to (α-CD)2:S1 inclusion complexes in the bulk with respect to both the bulk composition and temperature. Direct interfacial characterization of α-CD and sodium dodecylsulfate films at 283.15 K using ellipsometry and neutron reflectometry reveals that the most viscoelastic films consist of a highly ordered monolayer of 2:1 complexes with a minimum amount of any other component. The orientation of the complexes in the films and their driving force for adsorption are discussed in the context of results from molecular dynamics simulations. These findings open up clear potential for the design of new functional materials or molecular sensors based on films with specific mechanical, electrical, thermal, chemical, optical or even magnetic properties

Modifying of LiNi0.8Co0.2O2 Cathode Material by Chemical Vapor Deposition Coating to Improve Thermal Stability

In this paper, we tried to find answers to safety problems due to use of transition metal oxide as positive electrodes in the lithium ion batteries. The exothermic reaction at high temperature induced by the contact between positive electrode in the charged state, such as LiNi0.8Co0.2O2 and the liquid electrolyte solution based of LiPF6 (EC, DMC) is reduced by formation of ceramic oxide. Al2O3 – and ZnO-coated are synthesized on the surface of LiNi0.8Co0.2O2 particles by chemical vapor deposition. The influences of deposit on the properties of starting material, in particular the thermal stability, are characterized by using, X-ray diffraction, electrochemical measurements and differential scanning calorimeter (DSC). Al2O3-coated sample show fading specific capacity during the first cycle. However, after several cycles a retention capacity is observed. ZnO-coated LiNi0.8Co0.2O2 is inactive electrochemically as shown by X-rays diffraction pattern by the existence of two phases. With regard to DSC analysis in Al2O3-coated, one observe about 35% of reduction of heat flow during the exothermic reaction. The CVD method must be improved to obtain interesting results with regard to the electrochemical performances of treated material. Keywords: lithium-ion batteries, CVD coating; alumina, layered cathode; electrochemistry, X-ray diffraction Thermal stability

La lithotripsie extracorporelle: expérience d’un centre Sénégalais

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Metabolomic and lipidomic analysis of the colorectal adenocarcinoma cell line HT29 in hypoxia and reoxygenation

The poor availability of oxygen and nutrients in malignant tumors drives the activation of various molecular responses and metabolic reprogramming in cancer cells. Hypoxic tumor regions often exhibit resistance to chemotherapy and radiotherapy. One approach to enhance cancer therapy is to indirectly increase tumor oxygen availability through targeted metabolic reprogramming. Thus, understanding the underlying metabolic changes occurring during hypoxia and reoxygenation is crucial for improving therapy efficacy. In this study, we utilized the HT29 colorectal adenocarcinoma cell line as a hypoxia–reoxygenation model to investigate central carbon and lipid metabolism. Through quantitative NMR spectroscopy and flow injection analysis – differential mobility spectroscopy—tandem mass spectrometry (FIA-DMS-MS/MS) analysis, we observed alterations in components of mitochondrial metabolism, redox status, specific lipid classes, and structural characteristics of lipids during hypoxia and up to 24 h of reoxygenation. These findings contribute to our understanding of the metabolic changes occurring during reoxygenation and provide the basis for functional studies aimed at metabolic pathways in cancer cells.Proteomic