Thermodynamics of zinc insertion in CuGaS2:Ti, used as a modulator agent in an intermediate-band photovoltaic material

An intermediate-bandphotovoltaicmaterial, which has an isolated metallic band located between the top of the valence band and bottom of the conduction band of some semiconductors, has been proposed as third generation solar cell to be used in photovoltaic applications. Density functional theory calculations of Zn in CuGaS2:Ti have previously shown that, the intermediate-band position can be modulated in proportion of Zn insertion in such a way that increasing Zn concentration can lead to aband-gap reduction, and an adjustment of the intermediate-band position. This could be interesting in the formation of an intermediate-bandmaterial, that has the maximum efficiency theoretically predicted for the intermediate-band solar cell. In this work, the energetics of several reaction schemes that could lead to the decomposition of the modulated intermediate-bandphotovoltaicmaterial, CuGaS2:Ti:Zn, is studied in order to assess the thermodynamic stability of this material. Calculations of the total free energy and disorder entropy have been taken into account, to get the reaction energy and free energy of the compound decomposition, which is found to be thermodynamically favorabl

Vortex matter in mesoscopic superconductors

Superconducting mesoscopic devices in magnetic fields present novel properties which can only be accounted for by both the quantum confinement of the Cooper pairs and by the interaction between the magnetic-field-induced vortices. Sub-micrometer disks, much the same as their semiconductor counterparts known as quantum dots, are being subject to experimental investigation by measuring their conducting properties and, more recently, their magnetization by using state-of-the-art ballistic Hall magnetometry. In this work I review the main results obtained in these two types of experiments as well as the current theoretical developments which are contributing to our understanding of the superconducting condensate in these systems.Comment: 16 pages, 4 figures. Invited presentation at the 13th International Conference on High Magnetic Fields in Semiconductor Physics to appear in Physica

Freedom can also be productive: The historical inversions of "the conduct of conduct"

The Foucauldian conception of power as ‘productive’ has left us so far with a residual conception of freedom. The article examines a number of historical cases in which ‘relationships of freedom’ have potentially come into existence within Western culture, from ‘revolution’ and ‘political truth-telling’ to ‘cynicism’ and ‘civility’. But the argument is not just about demonstrating that there have in fact been many historical inversions of ‘the conduct of conduct’. It is about theorizing how freedom can be ‘productive’ or give rise to cultural norms if any such inversion can only come into being as an event in itself

Mitochondrial Replacement Techniques and Mexico’s Rule of Law: On the Legality of the First Maternal Spindle Transfer Case

News about the first baby born after a mitochondrial replacement technique (MRT; specifically maternal spindle transfer) broke on September 27, 2016 and, in a matter of hours, went global. Of special interest was the fact that the mitochondrial replacement procedure happened in Mexico. One of the scientists behind this world first was quoted as having said that he and his team went to Mexico to carry out the procedure because, in Mexico, there are no rules. In this paper, we explore Mexico's rule of law in relation to mitochondrial replacement techniques and show that, in fact, certain instances of MRTs are prohibited at the federal level and others are prohibited at the state level. According to our interpretation of the law, the scientists behind this first successful MRT procedure broke federal regulations regarding assisted fertilization research

Origin of the quasi-universality of the graphene minimal conductivity

It is a fact that the minimal conductivity $\sigma_0$ of most graphene samples is larger than the well-established universal value for ideal graphene $4e^2/\pi h$; in particular, larger by a factor $\gtrsim\pi$. Despite intense theoretical activity, this fundamental issue has eluded an explanation so far. Here we present fully atomistic quantum mechanical estimates of the graphene minimal conductivity where electron-electron interactions are considered in the framework of density functional theory. We show the first conclusive evidence of the dominant role on the minimal conductivity of charged impurities over ripples, which have no visible effect. Furthermore, in combination with the logarithmic scaling law for diffusive metallic graphene, we ellucidate the origin of the ubiquitously observed minimal conductivity in the range $8e^2/h > \sigma_0 \gtrsim 4e^2/h$.Comment: 6 pages, expanded version to appear in PR

A plasmonic accuracy biosensor using a single laser diode

A theoretical model was implemented to obtain the total specular reflection of a variable external multicavity for out of normal incidence and different polarisations. The model was theoretically and experimentally validated and a further analysis was applied to the study of the stability of the SMI signal. It was found that out of normal incidence, or the use of different polarisations does not affect the quality of the signal in a relevant manner

Chimeras intended for human gamete production: an ethical alternative?

Human eggs for basic, fertility and stem-cell research are in short supply. Many experiments that require their use cannot be carried out at present, and, therefore, the benefits that could emerge from these are either delayed or never materialise. This state of affairs is problematic for scientists and patients worldwide, and it is a matter that needs our attention. Recent advances in chimera research have opened the possibility of creating human/non-human animal chimeras intended for human gamete production (chimeras-IHGP). In this paper, I examine four arguments against the creation of such chimeras and prove that all of them are found wanting. I conclude by showing that there is a strong moral reason for scientists to pursue this research avenue

Mexico and mitochondrial replacement techniques: what a mess

Abstract Background The first live birth following the use of a new reproductive technique, maternal spindle transfer (MST), which is a mitochondrial replacement technique (MRT), was accomplished by dividing the execution of the MST procedure between two countries, the USA and Mexico. This was done in order to avoid US legal restrictions on this technique. Sources of data Academic articles, news articles, documents obtained through freedom of information requests, laws, regulations and national reports. Areas of agreement MRTs are new reproductive techniques that present novel ethical and legal challenges, since genetic material from three people is employed to create a child. Areas of controversy Could the first MST procedure that culminated in a live birth negatively impact reproductive medicine in Mexico? Growing points The USA and Mexico need specific and clear legislation on MRTs, in order for such techniques not to be governed by prior existing legislation on assisted reproduction that is inadequate for dealing with the new challenges that these techniques present. Areas timely for developing research There is a pressing need for work to be done on the international governance of new reproductive techniques