Dark matter in the inner parts of barred galaxies: The data

This paper presents surface photometry (B,V, I, J, H, K) and H_alpha rotation curves of 27 isolated spiral galaxies. The final goal is to obtain the mass distribution of a sample of isolated spiral galaxies in order to model their gas kinematics. This is then compared to the observed rotation curve, to determine the necessity of a dark halo in the inner parts (Perez et al. 2004). The azimuthally averaged radial surface brightness profiles and the integrated magnitudes obtained from ellipse fitting are given for each of the sample galaxies. The ellipse fitting technique applied to the light distribution also allowed us to obtain the size of the bar, and the inclination and position angle of the outer isophotes that allow the galaxy deprojection. Using these profiles, 1-D disk-bulge decomposition was performed to obtain the disk scale-length and the bulge effective radius for the different bands. Through the fitting of a parametric function to the observed rotation curve, the maximum rotational velocity and the corresponding radius was obtained. The correlation between the bulge and disk parameters is in agreement with previous studies (de Jong 1996a; Marquez & Moles 1999; Baggett et al. 1998). Regarding the Kormendy relation (Kormendy 1977), in agreement with de Jong, no correlation between the bulge effective radius and its surface brightness is found, possibly due to the small range of bulge magnitudes covered. We find a smaller scatter in the structural relations when compared to non-isolated samples in agreement with Marquez & Moles (1999). Finally, a correlation between the disk scale-length and the bar size is observed, possibly reflecting the rapid growth of a bar.Comment: A&A accepted. Fig. 11 and Tables 3-8 can be downloaded at: http://www.astro.rug.nl/~isa (they will also be available at http://www.edpsciences.org

Step structure on GaAs(113)A studied by scanning tunneling microscopy

The GaAs(113)A surface was prepared by molecular-beam epitaxy and in situ characterized by scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED). The occurrence of an (8×1) reconstruction as proposed by Wassermeier et al. [Phys. Rev. B 51, 14 721 (1995)] was confirmed. Overview STM images reveal a striking anisotropy in the step structure of this surface. While steps along [332¯] (the 1× direction of the reconstruction) are straight for up to 2000 Å, steps along [11¯0] are extremely rough. In this direction, kinks occur typically after less than 100 Å. The ratio of the respective lateral step densities is 8±4. This anisotropy is explained by applying the electron counting rule (ECR) to one-dimensional islands. While islands along [332¯] fulfil the ECR, it is violated by islands along [11¯0]. Thus, if structures formed additionally perpendicular to step edges along [332¯], they would be energetically unfavorable. Hence, growth occurs mainly by propagation along [332¯]. It is suggested that the determining structural element of GaAs(113)A−(8×1) is the zigzag chain of As dimers

Atomically resolved structure of InAs quantum dots

InAs was grown by molecular-beam epitaxy onto GaAs(001) until quantum dots (QDs) formed. At this point, the growth was interrupted and the uncovered QDs were investigated in situ by scanning tunneling microscopy (STM). Atomically resolved STILI images of the QDs revealed that four dominating bounding facets occur, whose Miller indices were identified to be {137}. The assignment of the facet orientation was based on experiments on planar high Miller index GaAs surfaces. In addition, the latter experiments indicated that (137) facets are thermodynamically stable only up to a certain size. This conclusion is assumed to explain the sharp size distribution of InAs QDs

Experimental evidence for a stable GaAs surface near (113)

GaAs surfaces vicinal to (113) with a continuous range of misorientation angles up to 11.5° in all azimuthal directions were created by grinding a spherical depression into (113) oriented samples. Thin homoepitaxial layers were grown onto these samples by molecular beam epitaxy (MBE), and the surfaces were in situ studied by low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). The surface quality in the depression was verified by reproducing LEED patterns of the (113) and (114) surfaces. A stable GaAs surface was found that is oriented from (113) by 9°±2° towards [11̅0̅]. STM and LEED images of this surface are presented

Enhanced Optoelectronic Response in Bilayer Lateral Heterostructures of Transition Metal Dichalcogenides

Two-dimensional lateral heterojunctions are basic components for low-power and flexible optoelectronics. In contrast to monolayers, devices based on few-layer lateral heterostructures could offer superior performance due to their lower susceptibility to environmental conditions. Here, we report the controlled synthesis of multi-junction bilayer lateral heterostructures based on MoS2-WS2 and MoSe2-WSe2, where the hetero-junctions are created via sequential lateral edge-epitaxy that happens simultaneously in both the first and the second layer. With respect to their monolayer counterparts, bilayer lateral heterostructures yield nearly one order of magnitude higher rectification currents. They also display a clear photovoltaic response, with short circuit currents ~103 times larger than those extracted from the monolayers, in addition to room-temperature electroluminescence. The superior performance of bilayer heterostructures significantly expands the functionalities of 2D crystals

Vertical fatty acid composition in the blubber of leopard seals and the implications for dietary analysis

AbstractThe analysis of blubber fatty acids (FAs) is a useful tool to infer diet of mammals that live in remote regions where year-round studies are difficult. The FA may not be distributed uniformly within the blubber, which can have implications for dietary predictive studies. The aim of this study was to determine the FA composition in the blubber core of the Antarctic leopard seal, Hydrurga leptonyx, and evaluate the potential implications of FA stratification for dietary analysis. The blubber cores of 24 seals were sub-sectioned into outer, middle and inner layers and their FA were compared to those of their potential prey species. A vertical variation in FA composition was found across the whole blubber core of the leopard seal. 17 FAs were found at greater than trace amounts (>0.5%) across all samples and the most abundant were: C18:1ω9, C16:1, C22:6ω3, C16:0 and C18:1ω7, which accounted for approximately 70% of the total FA. Almost all FAs had a continuous gradient through the blubber. Principal Component Analysis confirmed separation between inner and outer layers while the middle layer was a transition. The stratification of the leopard seal blubber was similar to the general pattern observed in a variety of marine species: monounsaturated FA (MUFA) dominated the three layers being more abundant in the outer layer, polyunsaturated (PUFA) and saturated FA (SFA) were more abundant in the inner layer. Polyunsaturated FAs are of dietary origin and SFAs are chemically inert so they can be used as a long-term reserve, which suggest that the inner layer is the site of deposition of the FA obtained from diet. The influence of prey on the composition of the leopard seals' blubber was clearer in the inner layer, although neither outer nor inner layers exactly matched the FA of the potential prey. This suggests that there are other components influencing the FA composition of this predator; therefore, in order to carry out dietary analysis it is important to consider the stratification of blubber and to use the inner layer, where the influence of diet is more evident. This has significant implications for sampling methods in the field

A compact ultrahigh-vacuum system for the in situ investigation of III/V semiconductor surfaces

A compact ultrahigh vacuum (UHV) system has been built to study growth and properties of III/V semiconductor surfaces and nanostructures. The system allows one to grow III/V semiconductor surfaces by molecular beam epitaxy (MBE) and analyze their surface by a variety of surface analysis techniques. The geometric structure is examined by scanning tunneling microscopy (STM), low-energy electron diffraction and reflection high-energy electron diffraction. The electronic properties of the surfaces are studied by angular resolved photoemission either in the laboratory using a helium discharge lamp or at the Berlin Synchrotron Radiation Facility BESSY. In order to meet the space restriction at BESSY the system dimensions are kept very small. A detailed description of the apparatus and the sample handling system is given. For the UHV-STM (Park Scientific Instruments, VP2) a new, versatile tip handling mechanism has been developed. It allows the transfer of tips out of the chamber and furthermore, the in situ tip cleaning by electron annealing. In addition, another more reliable in situ tip-preparation technique operating the STM in the field emission regime is described. The ability of the system is shown by an atomically resolved STM image of the c(4×4) reconstructed GaAs(001) surface

Potential of Computer-Aided Diagnosis to Improve CT Lung Cancer Screening

The development of low-dose spiral computed tomography (CT) has rekindled hope that effective lung cancer screening might yet be found. Screening is justified when there is evidence that it will extend lives at reasonable cost and acceptable levels of risk. A screening test should detect all extant cancers while avoiding unnecessary workups. Thus optimal screening modalities have both high sensitivity and specificity. Due to the present state of technology, radiologists must opt to increase sensitivity and rely on follow-up diagnostic procedures to rule out the incurred false positives. There is evidence in published reports that computer-aided diagnosis technology may help radiologists alter the benefit-cost calculus of CT sensitivity and specificity in lung cancer screening protocols. This review will provide insight into the current discussion of the effectiveness of lung cancer screening and assesses the potential of state-of-the-art computer-aided design developments

Conocimientos y actitudes ante la Voluntad Anticipada en profesionales de la salud del Centro Médico “Lic. Adolfo López Mateos”, Toluca, México

Introducción: La Voluntad Anticipada es una declaración mediante la cual una persona mayor de edad, con capacidad mental suficiente y libremente, expone las instrucciones que se deben tener en cuenta respecto a la atención sanitaria que desea recibir en situaciones en las cuales no pueda ya expresar personalmente su voluntad. Objetivo: Determinar el nivel de conocimientos y actitudes que tienen los profesionales de la salud de Centro Médico “Lic. Adolfo López Mateos” con respecto a la Ley de Voluntad Anticipada del Estado de México. Método y materiales: Se aplicaron 265 encuestas que incluían el conocimiento y la actitud que tienen los profesionales de la salud sobre la Ley de Voluntad Anticipada del Estado de México. Resultados: El grupo mayoritario abarcó de 25-29 años con el 31%, el turno mayoritario fue el de la Jornada Especial con 34%, el 60% de los encuestados fueron mujeres y 40% hombres, el 94% no había leído la Ley de Voluntad Anticipada inscrita en la gaceta oficial del Gobierno del Estado de México y el 6% restante respondió afirmativamente. Conclusiones: La mayoría de los y las profesionales de salud refirieron no conocer la Ley inscrita en la gaceta oficial, lo que significa que hace falta difusión y promoción del tema; a pesar de eso, tuvieron una posición favorable hacia la voluntad anticipada y demostraron tener noción sobre lo tratad