Unravelling the identity of Pandora species (Bivalvia: Pandoridae) from Southern South America

Four species of Pandora have been reported from southern South America: P. cistula Gould, 1850, P. braziliensis G. B. Sowerby II, 1874, P. diffissa Mabille & Rochebrune, 1889 and P. patagonica (Dall, 1915). The group has received little taxonomic attention in this area, resulting in arbitrary and wrong usage of these names, for which several contradictory synonymies have been proposed. This study provides the first revision of Pandora species living in southern South America, including photographs of the type material and descriptions of shells, gross anatomy and living animals. Out of the four species previously mentioned, P. braziliensis is here regarded as valid, including P. patagonica and P. diffissa as synonyms. The fourth species, P. cistula, remains known only from its type specimen. In addition, a new species, P. brevirostris, is described from the shallow waters of Argentina.Fil: Güller, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales ; ArgentinaFil: Zelaya, Diego Gabriel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; Argentin

Mechanism to Generate a Two-Dimensional Electron Gas at the Surface of the Charge-Ordered Semiconductor BaBiO3

In this work, we find by means of first principle calculations a new physical mechanism to generate a two dimensional electron gas, namely, the breaking of charge ordering at the surface of a charge ordered semiconductor due to the incomplete oxygen environment of the surface ions. The emergence of the 2D gas is independent of the presence of oxygen vacancies or polar discontinuities; this is a self-doping effect. This mechanism might apply to many charge ordered systems, in particular, we study the case of BaBiO3(001). In bulk, this material is a prototype of a "forbidden valence" compound in which the formal "metallic" Bi4+ state is skipped exhibiting a charge disproportionated Bi3+ - Bi5+ ordered structure. At room temperature, this charge disproportionation together with the breathing distortions gives rise to a Peierls semiconductor with monoclinic crystal structure. At higher temperature (T > 750 K) or upon doping, it turns cubic and metallic. Interestingly, doped BaBiO3 was one of the first non-cuprate high-Tc superconductors discovered. The outer layer of the Bi-terminated simulated surface turns more cubic- like and metallic while the inner layers remain in the insulating monoclinic state. On the other hand, the metallization does not occur for the Ba termination, a fact that makes this system appealing for nanostructuring. Finally, this finding sets another possible route for future exploration: the potential scenario of 2D superconductivity at the BaBiO3 surface

Spin density wave instabilities in the NbS2 monolayer

In the present work, we study the magnetic properties of the NbS2 monolayer by first-principles calculations. The transition metal dichalcogenides (TMDC) are a family of laminar materials presenting exciting properties such as charge density waves (CDW), superconductivity and metal-insulating transitions among others. 2H-NbS2 is a particular case within the family, because it is the only one that is superconductor without exhibiting a CDW order. Although no long range magnetic order was experimentally observed in the TMDC, we show here that the single monolayer of NbS2 is on the verge of a spin density wave (SDW) phase. Our calculations indicate that a wave-like magnetic order is stabilized in the NbS2 monolayer in the presence of magnetic defects or within zig-zag nanoribbons, due to the presence of unpaired electrons. We calculate the real part of the bare electronic susceptibilty and the corresponding nesting function of the clean NbS2 monolayer, showing that there are strong electronic instabilities at the same wavevector asociated with the calculated SDWs, also corresponding with one of the main nesting vectors of the Fermi surface. We conclude that the physical mechanism behind the spin-wave instabilities are the nesting properties, accentuated by the quasi 2D character of this system, and the rather strong Coulomb interactions of the 4d band of the Nb atom. We also estimate the amplitude of the spin-fluctuations and find that they are rather large, as expected for a system on the verge of a quantum critical transition

The smallest marine bivalves from the end of the world (Tierra del Fuego, Isla de Los Estados and Burdwood Bank)

Small molluscs are known to be particularly abundant towards the poles. Although recent studies on sub-Antarctic waters of the southernmost tip of South America have begun to show a highly diversified small-sized fauna, micromolluscs have not yet received sufficient attention. Recently, samplings targeting the smallest molluscan benthic fauna have been conducted in the sub-Antarctic waters of South America, providing material of three new minute species occurring in The End of the World (Tierra del Fuego, Isla de los Estados and Burdwood Bank). The present study describes Pachykellya fuegiensis n.sp. (Neoleptonidae), Benthocardiella ituartei n.sp. and Benthocardiella finisterra n.sp. (Condylocardiidae). These are not only the smallest bivalves currently known from the area, but are also smaller than any other species thus far known from the adjacent Antarctic waters, and are included among the smallest species of their respective genera. To confirm generic placement, the type species of Pachykellya (P. edwardsi F.B. Bernard 1897) and Benthocardiella (B. pusilla Powell 1930) are studied for the first time with scanning electron microscopy. This study allows to amend the previous descriptions of hinge teeth number, morphology and arrangement for these genera. Based on these new findings, Pachykellya and Benthocardiella are here reported for the first time in South America.Fil: Güller, Marina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Zelaya, Diego Gabriel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

The families carditidae and condylocardiidae in the magellan and Perú-Chile provinces (bivalvia: Carditoidea)

Based on the study of available types and extant collections, this paper provides a systematic revision of the living species of Carditoidea occurring in the Magellan and Perú-Chile Provinces. Out of the 19 nominal species reported for the area, eight species are recognized as valid: Cyclocardia compressa, C. spurca, C. thouarsii, C. velutina, Carditella naviformis,C. semen, C. tegulata and Carditopsis flabellum. Other eight nominal species are regarded as synonyms: Cardita magellanica of Cyclocardia velutina; Carditella pallida of C. tegulata; Cardita australis and Actinobolus philippi of Carditella naviformis; Cardium pygmaeum of Carditella semen; Cardita paeteliana of Cyclocardia spurca; Carditella pallida duodecimcostata of Carditopsis flabellum; and Cardita congelascens of Cyclocardia thouarsii. Furthermore, Cardita malvinae and Cardium parvulum are nomina dubia, and the occurrence of Carditella exulata in Magellanic waters is doubtful.Fil: Güller, Marina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Zelaya, Diego Gabriel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Kundenkommunikation: Ergebnisse einer Befragung der Top-500-Unternehmen in Deutschland

In Zeiten schwieriger Wirtschaftslagen kommt einer Bezugsgruppe der Public Relations erhöhte Aufmerksamkeit zu: den Kunden. Die Ansprache der Kunden und vor allem ihre Bindung an das eigene Unternehmen werden im Wettbewerb immer schwieriger. Sehen PR-Verantwortliche in den Kunden eine Zielgruppe, bei deren Ansprache Nachholbedarf besteht? Werbung und Verkaufsförderung führen in unserer Informationsgesellschaft zu Reaktanz bei den Zielgruppen. Neue und vor allem glaubwürdige Kommunikationswege sind gefragt, um die Beziehung zum Kunden aufzubauen und vor allem zu pflegen. Die Publikation befasst sich mit Fragen rund um den Kontakt zu den Kunden als einflussreiche Bezugsgruppe der Unternehmenskommunikation: welche Ziele und Aufgaben verfolgt die Kundenkommunikation? Welche Kommunikationswege zum Kunden existieren und welche sind erfolgversprechend? Wie profitiert die PR in der Wirtschaftskrise? Ausgehend von den Einschätzungen der Top-500-Unternehmen werden die Herausforderungen der Kommunikation mit den Kunden dargestellt

Identification of the Inhibition Effects of Some Natural Antiproliferative Agents on CA-I, CA-II, and AChE Activities Isolated from Human Erythrocytes by Kinetic and Molecular Docking Studies

Nowadays the determination of inhibitors of carbonic anhydrase isoenzymes (CAs) have become one of the main goals of drug design studies, and inhibitors of CAs have taken their place in clinical applications to be used in the treatment and diagnosis of many diseases from glaucoma to cancer. On the other hand, acetylcholinesterase (AChE) inhibitors are also the main target molecules for the treatment of Alzheimer's disease. However, the unwanted side effects of existing CA and AChE inhibitors necessitate the identification of new and selective inhibitors of these enzymes. In this study, we examined the inhibition effects of some natural antiproliferative agents on CA-I, CA-II, and AChE activities isolated from human erythrocytes. Betulinic acid (I) had the strongest inhibitory effect on esterase activity of hCA-I (IC50 29.16 mu M) and hCA-II (IC50 31.82 mu M). On the other hand, sanguinarine chloride (VI) had the strongest inhibitory effect (IC50: 19.44 mu M) on hAChE activity. Molecular modeling studies were also carried out to elucidate the inhibition mechanism of betulinic acid on hCA-I and hCA-II isoenzymes and sanguinarine chloride on the hAChE enzyme. We believe that the results we obtained in this study will contribute to the design of new and natural CA and AChE inhibitors

The Teleparallel Lagrangian and Hamilton-Jacobi Formalism

We analyze the Teleparallel Equivalent of General Relativity (TEGR) from the point of view of Hamilton-Jacobi approach for singular systemsComment: 11 pages, no figures, to appear in GR

Rap in FFL classroom: a real treasure both linguistically and culturall

Ce mémoire vise à démontrer que l’utilisation des textes de rap en cours de FLE est génératrice d’un grand nombre de bénéfices. Une chanson de rap envisagée comme un instrument didactique est non seulement utile pour travailler toutes les compétences langagières mais aussi pour étudier d’autres aspects tels que l’histoire, le contexte culturel, les messages véhiculés par le texte ainsi que les différents registres de langue. Pour ce faire, il est judicieux d’avoir recours à une structure innovatrice au lieu de traditionnelle. Les bienfaits de la musique ainsi que sa place en cours de FLE constitueront un premier apport de la partie théorique suivis de l’histoire du rap et de la société française. Puis, le travail se centrera sur l’utilisation des textes de rap. Des réponses aux questions suivantes seront apportées : de quelle manière introduire le rap en cours de FLE, quels sont les critères à prendre en compte avant de choisir les textes et, quels sont les bienfaits du rap ? La défense de l’utilisation des textes de rap ainsi que l’exposition de la structure innovatrice s’opposant à celle dite traditionnelle complèteront ce cadre théorique. La partie pratique, dans un premier temps, consistera à décrire et expliquer la méthodologie utilisée à partir d’une unité didactique et d’activités mises en place lors d’un stage réalisé dans un établissement scolaire. Dans un second temps, les résultats, majoritairement concluants, seront exposés. Les points négatifs seront néanmoins décrits et seront source d’une discussion. L’utilisation de textes de rap aux méthodes innovatrices aboutira aux conclusions suivantes: l’élève développe non seulement ses compétences linguistiques et ses connaissances socio-culturelles mais sa motivation et son intérêt se voient également grandir. L’introduction des textes de rap dans les manuels de FLE se considèrera par conséquent comme fructueuse.This paper aims to show that the use of French rap texts in FFL classroom has a lot of benefits. A rap song intended as an educational instrument is not only useful for working on all language skills, but also for studying other aspects such as history, cultural context, the messages conveyed by the text, as well as the different registers of language. To do so, it is advisable to use an innovative structure instead of a traditional one. The benefits of music, as well as its role in FFL classroom, will constitute a first contribution to the theoretical part followed by the history of rap and French society. Then, the study will focus on the use of rap texts. Answers to the following questions will be provided: how to introduce rap into FFL classroom, what criteria should be considered before choosing texts and what are the benefits of rap? The defense of the use of rap texts and the exposition of the innovative structure opposed to the traditional one will complete this theoretical framework. The practical part will first consist of describing and explaining the methodology used from a didactic unit as well as the activities implemented during the teaching practice, carried out in an educational center. Secondly, the results will be presented, these being mainly positive. However, the negative points will be exposed and will be a source of discussion. The use of rap texts through innovative methods will lead to the following conclusions: the student not only develops his linguistic skills and his sociocultural knowledge, but his motivation and interest also increase. Therefore, the introduction of rap texts in FFL textbooks would be considered successful.Depto. de Didáctica de las Lenguas, Artes y Educación FísicaFac. de EducaciónTRUEunpu

Electronic structure and properties of NbS2 and TiS2 low dimensional structures

Transition metal dichalcogenides have a laminar structure, weakly bound through van der Waals interactions. Due to their technological applications in catalytic processes the bulk structure of many of them has been widely studied in the last 30 years. Some of them, such as NbTe2 and TiSe2, show superconductivity and have been, therefore, the subject of intense study. Novoselov et al. (2005) achieved to isolate not only graphene but also other bidimensional crystals, among them layers of some dichalcogenides. These bidimensional crystals preserve their monocrystallinity under normal ambient conditions, keeping the crystal structure of the bulk. In this contribution we calculate the magnetic and electronic properties of 2D layers of NbS2 (non-magnetic metal in 3D) and TiS2 (non-magnetic semimetal in 3D) as well as quasi 1D chains cut out from these layers.Fil: Güller, F.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; ArgentinaFil: Helman, Christian. Comisión Nacional de Energía Atómica. Gerencia del Área Investigaciones y Aplicaciones no Nucleares; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Llois, Ana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área Investigaciones y Aplicaciones no Nucleares; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentin