Confinement-induced metal-to-insulator transition in strained LaNiO3_3/LaAlO3_3 superlattices

Using density functional theory calculations including a Hubbard $U$ term we explore the effect of strain and confinement on the electronic ground state of superlattices containing the band insulator LaAlO$_3$ and the correlated metal LaNiO$_3$. Besides a suppression of holes at the apical oxygen, a central feature is the asymmetric response to strain in single unit cell superlattices: For tensile strain a band gap opens due to charge disproportionation at the Ni sites with two distinct magnetic moments of 1.45$\mu_{\rm B}$ and 0.71$\mu_{\rm B}$. Under compressive stain, charge disproportionation is nearly quenched and the band gap collapses due to overlap of $d_{3z^2-r^2}$ bands through a semimetallic state. This asymmetry in the electronic behavior is associated with the difference in octahedral distortions and rotations under tensile and compressive strain. The ligand hole density and the metallic state are quickly restored with increasing thickness of the (LaAlO$_3$)$_n$/(LaNiO$_3$)$_n$ superlattice from $n=1$ to $n=3$.Comment: 7 pages, 10 Figure

Non-unitary representations of the SU(2) algebra in the Dirac equation with a Coulomb potential

A novel realization of the classical SU(2) algebra is introduced for the Dirac relativistic hydrogen atom defining a set of operators that, besides, allow the factorization of the problem. An extra phase is needed as a new variable in order to define the algebra. We take advantage of the operators to solve the Dirac equation using algebraic methods. To acomplish this, a similar path to the one used in the angular momentum case is employed; hence, the radial eigenfuntions calculated comprise non unitary representations of the algebra. One of the interesting properties of such non unitary representations is that they are not labeled by integer nor by half-integer numbers as happens in the usual angular momentum representation.Comment: 20 pages 1 eps figure in a single zipped file, submitted to J. Math. Phy

The contrasting activity of iodido versus chlorido ruthenium and osmium arene azo- and imino-pyridine anticancer complexes : control of cell selectivity, cross-resistance, p53 dependence, and apoptosis pathway

Organometallic half-sandwich complexes [M(p-cymene)(azo/imino-pyridine)X]+ where M = RuII or OsII and X ═ Cl or I, exhibit potent antiproliferative activity toward a range of cancer cells. Not only are the iodido complexes more potent than the chlorido analogues, but they are not cross-resistant with the clinical platinum drugs cisplatin and oxaliplatin. They are also more selective for cancer cells versus normal cells (fibroblasts) and show high accumulation in cell membranes. They arrest cell growth in G1 phase in contrast to cisplatin (S phase) with a high incidence of late-stage apoptosis. The iodido complexes retain potency in p53 mutant colon cells. All complexes activate caspase 3. In general, antiproliferative activity is greatly enhanced by low levels of the glutathione synthase inhibitor l-buthionine sulfoxime. The work illustrates how subtle changes to the design of low-spin d6 metal complexes can lead to major changes in cellular metabolism and to potent complexes with novel mechanisms of anticancer activity

Whole body interaction

In this workshop we explore the notation of whole body interaction. We bring together different disciplines to create a new research direction for study of this emerging form of interaction

Can we measure hospital quality from physicians' choices?

In this paper, we propose an alternative methodology for ranking hospitals based on the choices of Medical School graduates over hospital training vacancies. Our methodology is therefore a revealed preference approach. Our methodology for measuring relative hospital quality has the following desirable properties: a) robust to manipulation from hospital administrators; b) conditional on having enough observations, it allows for differences in quality across specialties within a hospital; c) inexpensive in terms of data requirements, d) not subject to selection bias from patients nor hospital screening of patients; and e) unlike other rankings based on experts' evaluations, it does not require physicians to provide a complete ranking of all hospitals. We apply our methodology to the Spanish case and find, among other results, the following: First, the probability of choosing the best hospital relative to the worst hospital is statistically significantly different from zero. Second, physicians value proximity and nearby hospitals are seen as more substitutable. Third, observable time-invariant city characteristics are unrelated to results. Finally, our estimates for physicians' hospital valuations are significantly correlated to more traditional hospital quality measures

A methodology to measure hospital quality using physicians' choices over training vacancies

In this paper, we propose an alternative methodology to rank hospitals based on the choices of Medical Schools graduates over training vacancies. We argue that our measure of relative hospital quality has the following desirable properties: a) robustness to manipulation from the hospital's administrators; b) comprehensiveness in the scope of the services analyzed; c) inexpensive in terms of data requirements, and d) not subject to selection biases. Accurate measures of health provider quality are needed in order to establish incentive mechanisms, to assess the need for quality improvement, or simply to increase market transparency and competition. Public report cards in certain US states and the NHS ranking system in the UK are two attempts at constructing quality rankings of health care providers. Although the need for such rankings is widely recognized, the criticisms at these attempts reveal the difficulties involved in this task. Most criticisms alert to the inadequate risk-adjustment and the potential for perverse consequences such as patient selection. The recent literature, using sophisticated econometric models is capable of controlling for case-mix, hospital and patient selection, and measurement error. The detailed data needed for these evaluations is, however, often unavailable to researchers. In those countries, such as Spain, where there is neither public hospital rankings nor public data on hospital output measures such as mortality rates our methodology is a valid alternative. We develop this methodology for the Spanish case. In a follow-up paper we will present results using Spanish data. In Spain graduates choose hospital training vacancies in a sequential manner that depends on their average grade. Our framework relies on three assumptions. First, high quality hospitals provide high quality training. Second, graduates are well informed decision makers who are well qualified to assess hospital quality. Third, they prefer to choose a high quality vacancy rather than a low quality one ceteris paribus. If these assumptions hold, then the first physicians to choose are likely to grab the best vacancies while the ones who choose last are stuck with the worst available. Thus, it is possible to infer from physicans' choices quality differentials amongst hospitals. We model the physician's decision as a nested-logit a la McFadden. Unlike in standard applications of McFadden's model, in our application the choice set is not constant across physicians but it shrinks along the sequential hospital choice proces

Modeling TeV gamma-rays from LS 5039: An active OB star at the extreme

Perhaps the most extreme examples of "Active OB stars" are the subset of high-mass X-ray binaries -- consisting of an OB star plus compact companion -- that have recently been observed by Fermi and ground-based Cerenkov telescopes like HESS to be sources of very high energy (VHE; up to 30 TeV) gamma-rays. This paper focuses on the prominent gamma-ray source, LS5039, which consists of a massive O6.5V star in a 3.9-day-period, mildly elliptical (e = 0.24) orbit with its companion, assumed here to be a black-hole or unmagnetized neutron star. Using 3-D SPH simulations of the Bondi-Hoyle accretion of the O-star wind onto the companion, we find that the orbital phase variation of the accretion follows very closely the simple Bondi-Hoyle-Lyttleton (BHL) rate for the local radius and wind speed. Moreover, a simple model, wherein intrinsic emission of gamma-rays is assumed to track this accretion rate, reproduces quite well Fermi observations of the phase variation of gamma-rays in the energy range 0.1-10 GeV. However for the VHE (0.1-30 TeV) radiation observed by the HESS Cerenkov telescope, it is important to account also for photon-photon interactions between the gamma-rays and the stellar optical/UV radiation, which effectively attenuates much of the strong emission near periastron. When this is included, we find that this simple BHL accretion model also quite naturally fits the HESS light curve, thus making it a strong alternative to the pulsar-wind-shock models commonly invoked to explain such VHE gamma-ray emission in massive-star binaries.Comment: To appear in "Active OB Stars: Structure, Evolution, Mass Loss & Critical Limits", Proceedings of IAUS 272, held July 2010 in Paris, France. 7 pages; 3 figures. This version 2 corrects an alignment error in figure