Weak Localization and Antilocalization in Topological Insulator Thin Films with Coherent Bulk-Surface Coupling

We evaluate quantum corrections to conductivity in an electrically gated thin film of a three-dimensional (3D) topological insulator (TI). We derive approximate analytical expressions for the low-field magnetoresistance as a function of bulk doping and bulk-surface tunneling rate. Our results reveal parameter regimes for both weak localization and weak antilocalization, and include diffusive Weyl semimetals as a special case.Comment: After publication, we have noticed and corrected two small but potentially misleading typographic errors in Eqs. (2.27) and (2.29), where the definitions of \tau_s and \tau_v were mistakenly switched. Once these typographic errors are fixed, all the results remain unchanged. An Erratum will be published in PR

Development of thermally formed glass optics for astronomical hard x-ray telescopes

The next major observational advance in hard X-ray/soft gamma-ray astrophysics will come with the implementation of telescopes capable of focusing 10-200 keV radiation. Focusing allows high signal-to-noise imaging and spectroscopic observations of many sources in this band for the first time. The recent development of depth-graded multilayer coatings has made the design of telescopes for this bandpass practical, however the ability to manufacture inexpensive substrates with appropriate surface quality and figure to achieve sub-arcminute performance has remained an elusive goal. In this paper, we report on new, thermally-formed glass micro-sheet optics capable of meeting the requirements of the next-generation of astronomical hard X-ray telescopes

Interplay between Symmetric Exchange Anisotropy, Uniform Dzyaloshinskii-Moriya Interaction and Magnetic Fields in the Phase Diagram of Quantum Magnets and Superconductors

We theoretically study the joint influence of uniform Dzyaloshinskii-Moriya (DM) interactions, symmetric exchange anisotropy (with its axis parallel to the DM vector) and arbitrarily oriented magnetic fields on one-dimensional spin 1/2 antiferromagnets. We show that the zero-temperature phase diagram contains three competing phases: (i) an antiferromagnet with Neel vector in the plane spanned by the DM vector and the magnetic field, (ii) a {\em dimerized} antiferromagnet with Neel vector perpendicular to both the DM vector and the magnetic field, and (iii) a gapless Luttinger liquid. Phase (i) is destroyed by a small magnetic field component along the DM vector and is furthermore unstable beyond a critical value of easy-plane anisotropy, which we estimate using Abelian and non-Abelian bosonization along with perturbative renormalization group. We propose a mathematical equivalent of the spin model in a one-dimensional Josephson junction (JJ) array located in proximity to a bulk superconductor. We discuss the analogues of the magnetic phases in the superconducting context and comment on their experimental viability.Comment: 20 pages, 16 figures; submitted to Phys. Rev.

Swift monitoring of Cygnus X-2: investigating the NUV-X-ray connection

The neutron star X-ray binary (NSXRB) Cygnus X-2 was observed by the Swift satellite 51 times over a 4 month period in 2008 with the XRT, UVOT, and BAT instruments. During this campaign, we observed Cyg X-2 in all three branches of the Z track (horizontal, normal, and flaring branches). We find that the NUV emission is uncorrelated with the soft X-ray flux detected with the XRT, and is anticorrelated with the BAT X-ray flux and the hard X-ray color. The observed anticorrelation is inconsistent with simple models of reprocessing as the source of the NUV emission. The anticorrelation may be a consequence of the high inclination angle of Cyg X-2, where NUV emission is preferentially scattered by a corona that expands as the disk is radiatively heated. Alternatively, if the accretion disk thickens as Cyg X-2 goes down the normal branch toward the flaring branch, this may be able to explain the observed anticorrelation. In these models the NUV emission may not be a good proxy for $\dot m$ in the system. We also discuss the implications of using Swift/XRT to perform spectral modeling of the continuum emission of NSXRBs.Comment: 10 pages, 8 figures. ApJ Accepte

Modelling Nutrient Uptake of Sweet Pepper

Models simulating dry matter production have been developed for a large number of greenhouse crops during the past decades. This paper describes how plant-nutrient relationships can be incorporated in a model for greenhouse crops, with sweet pepper as an example. Based on climatic data, the model simulates the growth of plant organs, transpiration, water uptake and uptake of the various macro nutrients. A mechanistic photosynthesis-driven model is used to simulate dry matter production. For each plant organ its required concentrations of the various macro nutrients are calculated, which depend on the ontogenetic age of the organ. The required nutrient uptake is calculated from these required concentrations and the dry weights of the organs. If there is no limitation in availability at the root surface the actual uptake will equal the required uptake. When the root system cannot fulfil the demand, uptake will be less, plant nutrient concentration will drop and crop production is potentially reduced. The model was tested on data from two different climatic regions (France and Spain). The model was also used to show some effects of the greenhouse climate on water and nutrient uptake. The rate of water uptake per unit radiation as well as the EC of the water taken up by plants was shown to vary considerably. Finally, the utilization of the model in an integrated control and monitoring system is discusse

Li-rich pegmatites and related peraluminous granites of the Fregeneda-Almendra field (Spain-Portugal): A case study of magmatic signature for Li enrichment

Based on field and petrographic observations, mineralogical, geochemical (whole-rock by ICP-MS, ICP-OES, ISE and PGNAA) and geochronological (Ar[sbnd]Ar on mica and U[sbnd]Pb on columbite) data, ten pegmatite types and one type of cassiterite-rich quartz hydrothermal veins have been distinguished in the Fregeneda-Almendra field (FA) (Central Iberian Zone), some of them highly enriched in Li (included in petalite, spodumene and Li-rich mica). The pegmatites and the veins mostly intrude Neoproterozoic to Cambrian rocks from the Schist-Greywacke Complex. Felsic igneous magmatism during syn- to late-D3 stages ( 320295 Ma) of the Variscan orogeny was important and nearly continuous in the area, with the overlap of different granitic units of highly peraluminous S-type composition. The most important in outcrop corresponds to the Mêda-Escalhão-Penedono-Lumbrales granitic complex (MEPL), which belongs to a two-mica leucogranitic series. The other granitic units (Saucelle, Feli and East-MEPL granites) are younger and belong to a P-rich, Ca-poor monzogranitic series. Spatial relationships, together with chemical, mineralogical and geochronological data, indicate that all the pegmatite types and the cassiterite-rich quartz hydrothermal veins are not cogenetic, being related to three different magmatic events: (i) ( 319313 Ma) includes the syn-D3 MEPL granite and three types of barren pegmatites (intragranitic, quartz+andalusite layers and simple concordant pegmatites); (ii) ( 305300 Ma) corresponds to the late to post-D3 Feli granite, related to a group of cassiterite-rich quartz veins; and, (iii) ( 300298 Ma) represents the late- to post-D3 East-MEPL and Saucelle granites, likely parental of some barren aplitic-pegmatitic apophyses and the discordant intermediate and Li-rich pegmatites. These latter form part of a general granite-pegmatite fractionation trend. (c) 2023 The Author

Albumina e índice neutrófilo-linfocito como predictores de estadío tumoral en pacientes con cáncer gástrico: Albumin and neutrophil to lymphocyte ratio as predictors of tumor stage in patients with gastric cancer

Introduction: Gastric cancer is a public health problem worldwide. Objective: To determine the association between albumin, inflammatory markers and tumor stage of gastric cancer patients in a National Hospital of Peru. Methods: An observational, analytical and retrospective study corresponding to the 2017 and 2018 years. The frequencies and distribution of the variables were evaluated: clinical stage according to the AJCC 2018, albumin as a nutrition indicator and Neutrophil Lymphocyte-Ratio (NLR) as an indicator of inflammatory and immune response. The value 2.44 was taken as the cut-off point for high NLR. Results: Were included 96 patients. The average age was 63.5 years ± 12.8, the male: female ratio was 1: 1, 80.2% came from the region of the coast of Peru; 70.8% had an advanced clinical stage and 85.4% corresponded to tumor size T3 and T4. 64% presented undifferentiated histological grade and 30.1 showed evidence of metastasis. The mean NLR was 2.94 ± 1.7, and albumin was 3.64 g / dl ± 0.6. In the bivariate analysis, a significant association was found between the high level of NLR and the advanced clinical stage (OR: 4.46 95% CI 1.65-13.27 p <0.001), and between low levels of serum albumin with advanced stage (OR: 13.02 95% CI 1.78-563.36 p <0.005). Conclusion: A late diagnosis was found in 70% of the patients. High NLR as an indicator of inflammatory response and low albumin as an indicator of nutrition are predictors of advanced clinical stage in gastric cancer.Introducción: El cáncer gástrico es un problema de salud pública a nivel mundial. Objetivo: Determinar la asociación entre albumina, marcadores inflamatorios y el estadío tumoral de los pacientes con cáncer gástrico en un Hospital Nacional del Perú. Métodos: Estudio de tipo observacional, analítico y retrospectivo correspondiente a los años 2017 y 2018. Se evaluaron las frecuencias y distribucion de las variables de estadío clínico según el AJCC 2018, albúmina como indicador de nutricion e Índice-Neutrófilo Linfocito (INL) como indicador de respuesta inflamatoria-inmunológica. Se consideró 2,44 como el punto de corte para INL elevado. Resultados: Fueron incluidos 96 pacientes. La edad promedio fue de 63,5 años ±12,8, la relacion hombre:mujer fue de 1:1, 80,2% provenían de la region de la costa del Perú; 70,8% tuvieron un estadío clínico avanzado y 85,4% correspondió a tamaño tumoral T3 y T4. El 64% presento grado histológico indiferenciado y un 30,1 mostró evdiencia de metástasis. La media de INL fue 2,94 ± 1,7, y de albúmina fue 3,64 g/dl ± 0,6, En el análisis bivariado se encontró una asociación significativa entre el nivel elevado de INL y el estadío clínico avanzado (OR: 4,46 IC 95% 1,65-13,27 p<0,001), y entre os niveles bajos de albúmina sérica con estadio avanzado (OR: 13,02 IC 95% 1,78-5,36 p<0,005). Conclusión: Se encontró un diagnóstico tardío en el 70% de los pacientes. El INL elevado como indicador de respuesta inflamatoria y la albúmina baja como indicador de nutricion son factores predictivos de estadio clínico avanzado en cáncer gástrico

Compositional Variations in Apatite and Petrogenetic Significance: Examples from Peraluminous Granites and Related Pegmatites and Hydrothermal Veins from the Central Iberian Zone (Spain and Portugal)

Apatite can be used as an archive of processes occurring during the evolution of granitic magmas and as a pegmatite exploration tool. With this aim, a detailed compositional study of apatite was performed on different Variscan granites, pegmatites and quartz veins from the Central Iberian Zone. Manganese in granitic apatite increases with increasing evolution degree. Such Mn increase would not be related to changes in the fO(2) during evolution but rather to a higher proportion of Mn in residual melts, joined to an increase in SiO2 content and peraluminosity. In the case of pegmatitic apatite, the fO(2) and the polymerization degree of the melts seem not to have influenced the Mn and Fe contents but the higher availability of these transition elements and/or the lack of minerals competing for them. The subrounded Fe-Mn phosphate nodules, where apatite often occurs in P-rich pegmatites and P-rich quartz dykes, probably crystallized from a P-rich melt exsolved from the pegmatitic melt and where Fe, Mn and Cl would partition. The low Mn and Fe contents in the apatite from the quartz veins may be attributed either to the low availability of these elements in the late hydrothermal fluids derived from the granitic and pegmatitic melts, or to a high fO(2). The Rare Earth Elements, Sr and Y are the main trace elements of the studied apatites. The REE contents of apatite decrease with the evolution of their hosting rocks. The REE patterns show in general strong tetrad effects that are probably not related to the fluids' activity in the system. On the contrary, the fluids likely drive the non-CHARAC behavior of apatite from the most evolved granitic and pegmatitic units. Low fO(2) conditions seem to be related to strong Eu anomalies observed for most of the apatites associated with different granitic units, barren and P-rich pegmatites. The positive Eu anomalies in some apatites from leucogranites and Li-rich pegmatites could reflect their early character, prior to the crystallization of feldspars. The increase in the Sr content in apatite from Li-rich pegmatites and B-P +/- F-rich leucogranites could be related to problems in accommodating this element in the albite structure, favoring its incorporation into apatite. The triangular plots sigma REE-Sr-Y and U-Th-Pb of apatites, as well as the Eu anomaly versus the TE1,3 diagram, seem to be potentially good as petrogenetic indicators, mainly for pegmatites and, to a lesser extent, for granites from the CIZ