Effect of the spin-orbit interaction on the thermodynamic properties of crystals: The specific heat of bismuth

In recent years, there has been increasing interest in the specific heat $C$ of insulators and semiconductors because of the availability of samples with different isotopic masses and the possibility of performing \textit{ab initio} calculations of its temperature dependence $C(T)$ using as a starting point the electronic band structure. Most of the crystals investigated are elemental (e.g., germanium) or binary (e.g., gallium nitride) semiconductors. The initial electronic calculations were performed in the local density approximation and did not include spin-orbit interaction. Agreement between experimental and calculated results was usually found to be good, except for crystals containing heavy atoms (e.g., PbS) for which discrepancies of the order of 20% existed at the low temperature maximum found for $C/T^3$. It has been conjectured that this discrepancies result from the neglect of spin-orbit interaction which is large for heavy atoms ($\Delta_0\sim$1.3eV for the $p$ valence electrons of atomic lead). Here we discuss measurements and \textit{ab initio} calculations of $C(T)$ for crystalline bismuth ($\Delta_0\sim$1.7 eV), strictly speaking a semimetal but in the temperature region accessible to us ($T >$ 2K) acting as a semiconductor. We extend experimental data available in the literature and notice that the \textit{ab initio} calculations without spin-orbit interaction exhibit a maximum at $\sim$8K, about 20% lower than the measured one. Inclusion of spin-orbit interaction decreases the discrepancy markedly: The maximum of $C(T)$ is now only 7% larger than the measured one. Exact agreement is obtained if the spin-orbit hamiltonian is reduced by a factor of $\sim$0.8.Comment: 4 pages, 3 figure

S-Nav: Semantic-Geometric Planning for Mobile Robots

Path planning is a basic capability of autonomous mobile robots. Former approaches in path planning exploit only the given geometric information from the environment without leveraging the inherent semantics within the environment. The recently presented S-Graphs constructs 3D situational graphs incorporating geometric, semantic, and relational aspects between the elements to improve the overall scene understanding and the localization of the robot. But these works do not exploit the underlying semantic graphs for improving the path planning for mobile robots. To that aim, in this paper, we present S-Nav a novel semantic-geometric path planner for mobile robots. It leverages S-Graphs to enable fast and robust hierarchical high-level planning in complex indoor environments. The hierarchical architecture of S-Nav adds a novel semantic search on top of a traditional geometric planner as well as precise map reconstruction from S-Graphs to improve planning speed, robustness, and path quality. We demonstrate improved results of S-Nav in a synthetic environment.Comment: 6 pages, 4 figure

Using Chemical Modeling to Asses Water Quality in the Raigón Aquifer System in Southern Uruguay

The Raigón aquifer is an important groundwater system in southern Uruguay. The increasing use of groundwater resources in the last decades has provoked changes in the concentration of many elements which are strongly related to anthropogenic pollution sources. Concentration levels are useful to detect changes in reservoir status but it is also necessary to analyze their chemical significance in order to make an accurate assessment of the sources of contamination and the causes of changes. In this work we use the available thermodynamic data to calculate chemical speciation on these groundwater samples. Trace elements present as anions, in particular Se and Mo, are especially focused to show the chemical modeling possibilities. Both elements form anionic species, predominantly MoO42- and SeO42-. Results show that these anions interact in solution and are greatly influenced by the concentration of the abundant calcium ion. Localized changes in pH can strongly affect the situation. The same is observed with the pE parameter, but only in the case of Se. Chemical speciation of trace elements is in general highly dependent on pH, pE and concentration of major elements. In consequence, for a fixed analytical total concentration, these parameters can markedly change the situation, affecting the mobility, the bioavailability and environmental fate of these elements. The strategy employed in this work can also be extended to the study of many other environmental water scenarios

A Lightweight Universal Gripper with Low Activation Force for Aerial Grasping

Soft robotic grippers have numerous advantages that address challenges in dynamic aerial grasping. Typical multi-fingered soft grippers recently showcased for aerial grasping are highly dependent on the direction of the target object for successful grasping. This study pushes the boundaries of dynamic aerial grasping by developing an omnidirectional system for autonomous aerial manipulation. In particular, the paper investigates the design, fabrication, and experimental verification of a novel, highly integrated, modular, sensor-rich, universal jamming gripper specifically designed for aerial applications. Leveraging recent developments in particle jamming and soft granular materials, the presented gripper produces a substantial holding force while being very lightweight, energy-efficient and only requiring a low activation force. We show that the holding force can be improved by up to 50% by adding an additive to the membrane's silicone mixture. The experiments show that our lightweight gripper can develop up to 15N of holding force with an activation force as low as 2.5N, even without geometric interlocking. Finally, a pick and release task is performed under real-world conditions by mounting the gripper onto a multi-copter. The developed aerial grasping system features many useful properties, such as resilience and robustness to collisions and the inherent passive compliance which decouples the UAV from the environment.Comment: 21 pages, 19 figures; corrected affiliation

Respuestas fisiológicas y productivas en olivo (Olea europaea L.) cv. Frantoio bajo riego deficitario controlado en condiciones de un clima mediterráneo semiárido (Cholqui, Valle del Maipo, Chile)

The objective of the present study was to determine the Regulated Deficit Irrigation (RDI) effect on the cv. Frantoio olive tree, under semiarid mediterranean weather condtions (8 months dry period). The trial was established in the “El Oliveto" farm (33°48' S, 71°05' W) Cholqui, Melipilla, Metropolitan Region, Chile, and considered five irrigation treatments: 100% of crop evapotranspiration (ETc) (T1), 85% ETc (T2), 75% ETc (T3), 70% ETc (T4), and 65% ETc (T5) applied between February (endocarp lignification) to May (harvest) of 2011. Periodic plant measurements were conducted, which included physiological parameters (midday stem water potential, photosynthesis and stomatal conductance) and production indices (mean fruit weight, maturity index and total production). The results obtained indicate that to a less irrigation water, the water potential, the stomatal conductance and the photosynthesis are decreased when compared to the 100% ETc. As others have quoted, it was also noticed that the less irrigation water had no effect on yield and fruit oil content.El objetivo del presente estudio fue determinar el efecto del riego deficitario controlado (RDC) en el olivo cv. Frantoio, bajo condiciones de un clima mediterráneo semiárido (8 meses secos). El ensayo se estableció en el fundo "El Oliveto" (33°48' S 71°05' O) localidad de Cholqui, comuna de Melipilla, Región Metropolitana, Chile y consistió en 5 tratamientos de reposición hídrica equivalentes a: 100% evapotranspiración de cultivo (ETc) (T1), 85% ETc (T2), 75% ETc (T3), 70% ETc (T4), y 65% ETc (T5) aplicados entre febrero (lignificacion del endocarpo) y mayo (cosecha) de 2011. Se realizaron mediciones periódicas a la planta, las que abarcaron variables fisiológicas (potencial hídrico xilemático, fotosíntesis y conductancia estomática) y de producción (peso promedio de fruto, índice de madurez y producción total). Los resultados obtenidos indican que a menor restitución hídrica, el potencial hídrico, la conductancia estomática y la fotosíntesis se ven disminuidos comparados con el 100% de ETc. Tal como señalaron otros autores, se observó que la menor reposición hídrica no afectó ni la producción, ni el contenido de aceite en el fruto.Fil: Kremer, Cristian. Universidad de Chile. Facultad de Ciencias Agronómicas.Fil: Reyes, Luis. Universidad de Chile. Facultad de Ciencias Agronómicas.Fil: Fichet, Thomas. Universidad de Chile. Facultad de Ciencias Agronómicas.Fil: García de Cortázar, Víctor. Universidad de Chile. Facultad de Ciencias Agronómicas.Fil: Haberland, Julio. Universidad de Chile. Facultad de Ciencias Agronómicas

Phantom cosmologies and fermions

Form invariance transformations can be used for constructing phantom cosmologies starting with conventional cosmological models. In this work we reconsider the scalar field case and extend the discussion to fermionic fields, where the "phantomization" process exhibits a new class of possible accelerated regimes. As an application we analyze the cosmological constant group for a fermionic seed fluid.Comment: 5 pages, version which was accepted for publication in CQ

Tachyonization of the \LaCDM cosmological model

In this work a tachyonization of the $\Lambda$CDM model for a spatially flat Friedmann-Robertson-Walker space-time is proposed. A tachyon field and a cosmological constant are considered as the sources of the gravitational field. Starting from a stability analysis and from the exact solutions for a standard tachyon field driven by a given potential, the search for a large set of cosmological models which contain the $\Lambda$CDM model is investigated. By the use of internal transformations two new kinds of tachyon fields are derived from the standard tachyon field, namely, a complementary and a phantom tachyon fields. Numerical solutions for the three kinds of tachyon fields are determined and it is shown that the standard and complementary tachyon fields reproduces the $\Lambda$CDM model as a limiting case. The standard tachyon field can also describe a transition from an accelerated to a decelerated regime, behaving as an inflaton field at early times and as a matter field at late times. The complementary tachyon field always behaves as a matter field. The phantom tachyon field is characterized by a rapid expansion where its energy density increases with time.Comment: Version accepted for publication in GR

Detection of hepatitis C virus (HCV) in body fluids from HCV monoinfected and HCV/HIV coinfected patients

The possibility of the non-parenteral Hepatitis C Virus (HCV) transmission is supported by the demonstration that the actual virus is present in several body fluids. In this study, we investigated the relationship between the detection of HCV RNA in body fluids (saliva, cervical smears, seminal fluid and peripheral blood mononuclear cells) from chronically HCV-infected patients and several viral and host factors. METHODOLOGY: This study comprised 16 HIV/HCV coinfected and 21 HCV monoinfected patients with a median age of 38 and 45 years, respectively. HCV-RNA was detected in serum and fluids samples by reverse transcription-nested polymerase chain reaction. Genotypes were determined by using RFLP and direct nucleotide sequencing of the PCR products and plasma viral loads by using NASBA HCV-QT. RESULTS: When compared on the basis of the results of the detection of HCV-RNA in fluids, patients did not differ significantly in relation to viral load, genotype, HCV-HIV coinfection, HCV/HIV coinfection and epidemiological host factors. Our data suggest that HCV can be detected in body fluids of chronically HCV-infected patients independent of these cofactors, including circulating HCV load. Studies on HCV dynamics are needed to gain insights into nonparenteral transmission of HCV.Fil: Farías, Adrián Alejandro. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología Dr. J. M. Vanella; ArgentinaFil: Ré, Viviana Elizabeth. Universidad Nacional de Cordoba. Facultad de Medicina. Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mengarelli, Silvia Estela. Gobierno de la Provincia de Córdoba. Nuevo Hospital San Roque; ArgentinaFil: Kremer, Luis. Gobierno de la Provincia de Cordoba. Hospital de Clinicas.; ArgentinaFil: Pisano, María Belén. Universidad Nacional de Cordoba. Facultad de Medicina. Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Allende, Luis Ramón. Gobierno de la Provincia de Cordoba. Hospital de Clinicas.; ArgentinaFil: Nicolás, Juan Carlos. Universidad Católica de Córdoba; ArgentinaFil: Elbarcha, Osvaldo. Universidad Católica de Córdoba; ArgentinaFil: Contigiani de Minio, Marta Silvia. Universidad Nacional de Cordoba. Facultad de Medicina. Instituto de Virología; Argentin

Detection of hepatitis C virus (HCV) in body fluids from HCV monoinfected and HCV/HIV coinfected patients

The possibility of the non-parenteral Hepatitis C Virus (HCV) transmission is supported by the demonstration that the actual virus is present in several body fluids. In this study, we investigated the relationship between the detection of HCV RNA in body fluids (saliva, cervical smears, seminal fluid and peripheral blood mononuclear cells) from chronically HCV-infected patients and several viral and host factors. METHODOLOGY: This study comprised 16 HIV/HCV coinfected and 21 HCV monoinfected patients with a median age of 38 and 45 years, respectively. HCV-RNA was detected in serum and fluids samples by reverse transcription-nested polymerase chain reaction. Genotypes were determined by using RFLP and direct nucleotide sequencing of the PCR products and plasma viral loads by using NASBA HCV-QT. RESULTS: When compared on the basis of the results of the detection of HCV-RNA in fluids, patients did not differ significantly in relation to viral load, genotype, HCV-HIV coinfection, HCV/HIV coinfection and epidemiological host factors. Our data suggest that HCV can be detected in body fluids of chronically HCV-infected patients independent of these cofactors, including circulating HCV load. Studies on HCV dynamics are needed to gain insights into nonparenteral transmission of HCV.Fil: Farías, Adrián Alejandro. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología Dr. J. M. Vanella; ArgentinaFil: Ré, Viviana Elizabeth. Universidad Nacional de Cordoba. Facultad de Medicina. Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mengarelli, Silvia Estela. Gobierno de la Provincia de Córdoba. Nuevo Hospital San Roque; ArgentinaFil: Kremer, Luis. Gobierno de la Provincia de Cordoba. Hospital de Clinicas.; ArgentinaFil: Pisano, María Belén. Universidad Nacional de Cordoba. Facultad de Medicina. Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Allende, Luis Ramón. Gobierno de la Provincia de Cordoba. Hospital de Clinicas.; ArgentinaFil: Nicolás, Juan Carlos. Universidad Católica de Córdoba; ArgentinaFil: Elbarcha, Osvaldo. Universidad Católica de Córdoba; ArgentinaFil: Contigiani de Minio, Marta Silvia. Universidad Nacional de Cordoba. Facultad de Medicina. Instituto de Virología; Argentin

Cosmological model with interactions in the dark sector

A cosmological model is proposed for the current Universe consisted of non-interacting baryonic matter and interacting dark components. The dark energy and dark matter are coupled through their effective barotropic indexes, which are considered as functions of the ratio between their energy densities. It is investigated two cases where the ratio is asymptotically stable and their parameters are adjusted by considering best fits to Hubble function data. It is shown that the deceleration parameter, the densities parameters, and the luminosity distance have the correct behavior which is expected for a viable present scenario of the Universe.Comment: 6 pages, 8 figure