Highly anisotropic thermoelectric properties of carbon sulfide monolayers

Strain engineering applied to carbon monosulphide monolayers allows to control the bandgap, controlling electronic and thermoelectric responses. Herein, we study the semiconductor-metal phase transition of this layered material driven by strain control on the basis of first-principles calculations. We consider uniaxial and biaxial tensile strain and we find a highly anisotropic electronic and thermoelectonic responses depending on the direction of the applied strain. Our results indicate that strain-induced response could be an effective method to control the electronic response and the thermoelectric performance.Comment: 5 pages, 4 figure

Ultrashort Mn-Mn Bonds in Organometallic Complexes

Manganese metallocenes larger than the experimentally produced sandwiched MnBz$_2$ compound are studied using several density functional theory methods. First, we show that the lowest energy structures have Mn clusters surrounded by benzene molecules, in so-called rice-ball structures. We then find a strikingly short bond length of 1.8 {\AA} between pairs of Mn atoms, accompanied by magnetism depletion. The ultrashort bond lengths are related to Bz molecules caging a pair of Mn atoms, leading to a Mn-Mn triple bond. This effect is also found when replacing benzenes by other molecules such as borazine or cyclopentadiene. The stability of the Mn-Mn bond for Mn$_2$Bz$_2$ is further investigated using dissociation energy curves. For each spin configuration, the energy versus distance plot shows different spin minima with barriers, which must be overcome to synthesize larger Mn-Bz complexes.Comment: 9 pages, 8 figure

Large spin splitting in the conduction band of transition metal dichalcogenide monolayers

We study the conduction band spin splitting that arises in transition metal dichalcogenide (TMD) semiconductor monolayers such as MoS2, MoSe2, WS2, and WSe2 due to the combination of spin-orbit coupling and lack of inversion symmetry. Two types of calculation are done. First, density functional theory (DFT) calculations based on plane waves that yield large splittings, between 3 and 30 meV. Second, we derive a tight-binding model that permits to address the atomic origin of the splitting. The basis set of the model is provided by the maximally localized Wannier orbitals, obtained from the DFT calculation, and formed by 11 atomiclike orbitals corresponding to d and p orbitals of the transition metal (W, Mo) and chalcogenide (S, Se) atoms respectively. In the resulting Hamiltonian, we can independently change the atomic spin-orbit coupling constant of the two atomic species at the unit cell, which permits to analyze their contribution to the spin splitting at the high symmetry points. We find that—in contrast to the valence band—both atoms give comparable contributions to the conduction band splittings. Given that these materials are most often n-doped, our findings are important for developments in TMD spintronics.JFR acknowledges financial supported by MEC-Spain (FIS2010-21883-C02-01) and Generalitat Valenciana (ACOMP/2010/070), Prometeo. This work has been financially supported in part by FEDER funds. We acknowledge financial support by Marie-Curie-ITN 607904-SPINOGRAPH

Graphene single-electron transistor as a spin sensor for magnetic adsorbates

We study single-electron transport through a graphene quantum dot with magnetic adsorbates. We focus on the relation between the spin order of the adsorbates and the linear conductance of the device. The electronic structure of the graphene dot with magnetic adsorbates is modeled through numerical diagonalization of a tight-binding model with an exchange potential. We consider several mechanisms by which the adsorbate magnetic state can influence transport in a single-electron transistor: tuning the addition energy, changing the tunneling rate, and in the case of spin-polarized electrodes, through magnetoresistive effects. Whereas the first mechanism is always present, the others require that the electrode has to have either an energy- or spin-dependent density of states. We find that graphene dots are optimal systems to detect the spin state of a few magnetic centers.This work has been financially supported by MEC-Spain (Grant Nos. FIS2010-21883-C02-01 and CONSOLIDER CSD2007-0010) as well as Generalitat Valenciana, grant Prometeo 2012-11

TRY plant trait database – enhanced coverage and open access

Plant traits - the morphological, anatomical, physiological, biochemical and phenological characteristics of plants - determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait‐based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits - almost complete coverage for ‘plant growth form’. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait–environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives

Consideraciones preventivas para detectar la presencia del papilomavirus

The papillomavirus (HPV) is a common infection and most people contract at some point in their lives. The maximum incidence of HPV infectionoccurs in adolescence, shortly after the initiation of sexual activity, and most infections resolve spontaneously within two years, however, although there is no cure for This infection, warts, lesions and precancerous and cancerous changes caused by the virus can be treated. The objective of this research work, developed under a documentary methodology, is focused on making a review of the available scientific literature that mainly responds to what HPV is, what its types, how it is detected and what are the other technological alternatives for it. , what are considered the influential risk factors, what are the vaccines against HPV, how can infection be prevented and finally what with preventive considerations for detection, all with the purpose of providing updated material that defines these aspects. To this end, more than sixteen physical and digital sources were chosen, located in databases such as: Redalyc, Imbiomed, SciELO, Dialnet, Medlineplus, WHO, PAHO / PAHO, SCIelo, intramed, among others, which support the ideas presented here , and which consequently serve as a basis to conclude that it is still very important that programs provide information to the population in general about the prevention of HPV infection, other sexually transmitted infections and healthy sexual behaviors, However, both for those countries or governments that through their policies have already officially hosted some HPV test and for those who are still in that process, for these purposes, it is also advisable in terms of preventive considerations to detect the HPV. VPH, that take into consideration the clinicalvalidation of the test, operational and logistical aspects, in addition to the costs and benefits of the testing.O papilomavírus (HPV) é uma infecção comum e a maioria das pessoas se contrai em algum momento de suas vidas. A incidência máxima de infecção por HPV ocorre na adolescência, logo após o início da atividade sexual, e a maioria das infecções se resolve espontaneamente dentro de dois anos, embora não haja cura para essa infecção, verrugas, lesões e alterações pré-cancerosas e cancerígenas causadas pelo vírus. Pode ser tratado. O objetivo deste trabalho de pesquisa, desenvolvido sob uma metodologia documental, é focado em fazer uma revisão da literatura científica disponível que responda principalmente ao que é HPV, quais seus tipos, como é detectado e quais são as outras alternativas tecnológicas para o mesmo. , quais são os fatores de risco influentes, quais são as vacinas contra o HPV, como a infecção pode ser prevenida e, finalmente, quais as considerações preventivas para detecção, tudo com o objetivo de fornecer material atualizado que defina esses aspectos. Para tanto, foram escolhidas mais de dezesseis fontes físicas e digitais, localizadas em bases de dados como: Redalyc, Imbiomed, SciELO, Dialnet, Medlineplus, OMS, OPAS / OPAS, SCIelo, intramed, entre outras, que apóiam as ideias aqui apresentadas, e que, consequentemente, servem como base para concluir que ainda é muito importante que os programas forneçam informações à população em geral sobre a prevenção da infecção pelo HPV, outras infecções sexualmente transmissíveis e comportamentos sexuais saudáveis,no entanto, tanto para países como para governos que suas políticas já realizaram oficialmente alguns testes de HPV e, para aqueles que ainda estão nesse processo, para esses fins, também é aconselhável em termos de considerações preventivas para detectaro HPV. VPH, que leva em consideração a validação clínica do teste, aspectos operacionais e logísticos, além dos custos e benefícios dotesteEl papilomavirus (VPH) es una infección común y la mayoría de las personas contraen en algún momento de su vida. La incidencia máxima de la infección por el VPH se presenta en la adolescencia, poco después de la iniciación de la actividad sexual, y la mayoría de las infecciones se resuelven espontáneamente en un plazo de dos años, sin embargo, aunque no hay una cura para esta infección, las verrugas, lesiones y cambios precancerosos y cancerosos causados por el virus pueden ser tratados. El objetivo de este trabajo investigativo, desarrollado bajo un metodología documental, se centra en realizar una revisión a la literatura científica disponible que principalmente responda a qué es el VPH, cuáles con sus tipos, cómo se detecta y cuáles son las otras alternativas tecnológicas para ello, cuáles son considerados los fatores de riesgo influyentes, cales son las vacunas contra el VPH, cómo puede prevenirse la infección y finalmente cuales con las consideraciones preventivas para la detección, todo ello con la finalidad de proporcionar un material actualizado que defina dichos aspectos. Para ello se escogieron más de dieciséis fuentes físicas, y digitales, ubicadas en bases de datos tales como: Redalyc, Imbiomed, SciELO, Dialnet, Medlineplus, OMS, OPS/PAHO, SCIelo, intramed, entre otras, que fundamentan las ideas aquí planteadas, y que consecuentemente sirven de base para concluir que aún sigue siendo muy importante que mediante programas se brinde la información a la población en general sobre la prevención de la infección por el VPH, de las otras infecciones de transmisión sexual y de comportamientos sexuales sanos, sin embargo, tanto para aquellos países o gobiernos que mediante sus políticas ya han acogido oficialmente alguna prueba para la detección del VPH como para los que aún están en ese proceso, a tales fines, es igualmente recomendable en cuanto a las consideraciones preventivas para detectar el VPH, que tengan en consideración la validación clínica de la prueba, aspectos operacionales y logísticos, además de los costos y beneficios de la prueba