Quark deconfinement in neutron star cores: The effects of spin-down

We study the role of spin-down in driving quark deconfinement in the high density core of isolated neutron stars. Assuming spin-down to be solely due to magnetic braking, we obtain typical timescales to quark deconfinement for neutron stars that are born with Keplerian frequencies. Employing different equations of state (EOS), we determine the minimum and maximum neutron star masses that will allow for deconfinement via spin-down only. We find that the time to reach deconfinement is strongly dependent on the magnetic field and that this time is least for EOS that support the largest minimum mass at zero spin, unless rotational effects on stellar structure are large. For a fiducial critical density of $5\rho_0$ for the transition to the quark phase ($\rho_0=2.5\times10^{14}$g/cm$^3$ is the saturation density of nuclear matter), we find that neutron stars lighter than $1.5M_{\odot}$ cannot reach a deconfined phase. Depending on the EOS, neutron stars of more than $1.5M_{\odot}$ can enter a quark phase only if they are spinning faster than about 3 milliseconds as observed now, whereas larger spin periods imply that they are either already quark stars or will never become one.Comment: 4 pages, 4 figures, submitted to ApJ

Casimir Energies for Spherically Symmetric Cavities

A general calculation of Casimir energies --in an arbitrary number of dimensions-- for massless quantized fields in spherically symmetric cavities is carried out. All the most common situations, including scalar and spinor fields, the electromagnetic field, and various boundary conditions are treated with care. The final results are given as analytical (closed) expressions in terms of Barnes zeta functions. A direct, straightforward numerical evaluation of the formulas is then performed, which yields highly accurate numbers of, in principle, arbitrarily good precision.Comment: 18 pages, LaTeX, sub. Ann. Phy

Soil quality assessment based on soil organic matter pools under long‐term tillage systems and following tillage conversion in a semi‐humid region

A field study was conducted to assess the long-term effects of no-tillage (NT) and conventional tillage (CT), and the short-term effects following tillage conversion -from CT to NT (NTn) and from NT to CT (CTn) on soil quality (SQ) indicators in a semi-humid climate. First, plots of a long-term tillage experiment on a Luvic Phaeozem initiated in 1986, were split into two subplots in 2012, yielding four treatments: NT, CT, NTn and CTn. In 2015, composite soil samples were collected from each treatment and from a natural site (Ref) at depths 0-5, 5-10, 10-20 and 0-20 cm. Several indicators were determined: soil organic carbon (SOC) and nitrogen (SON); particulate organic C (POM-C) and N (POM-N); potential N mineralization (PMN) and soil respiration (Rs). Moreover, bulk density was determined in long-term tillage systems. Different ratios between indicators were calculated, with emphasis on its function in the agroecosystem, i.e. functional indicators. Significant differences in SOC, SON and PMN were found between CT and NT at most depths. In contrast, three years after tillage conversion, only a part of the SQ indicators studied were modified mainly at the 0-10 cm depth. The functional indicators showed differences between tillage systems in the long-term and after short-term tillage conversion depending on the depth; however, the PMN/SON ratio demonstrated differences at all depths. Under these conditions, this ratio -related to easily mineralizable N fraction- proved to be a promising indicator for assessing SQ under contrasting tillage systems regardless of the sampling depth.Fil: Martinez, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; ArgentinaFil: Galantini, Juan Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; ArgentinaFil: Duval, Matias Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: López, Fernando Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentin

IntCal09 and Marine09 radiocarbon age calibration curves, 0-50,000yeats cal BP

The IntCal04 and Marine04 radiocarbon calibration curves have been updated from 12 cal kBP (cal kBP is here defined as thousands of calibrated years before AD 1950), and extended to 50 cal kBP, utilizing newly available data sets that meet the IntCal Working Group criteria for pristine corals and other carbonates and for quantification of uncertainty in both the 14C and calendar timescales as established in 2002. No change was made to the curves from 0–12 cal kBP. The curves were constructed using a Markov chain Monte Carlo (MCMC) implementation of the random walk model used for IntCal04 and Marine04. The new curves were ratified at the 20th International Radiocarbon Conference in June 2009 and are available in the Supplemental Material at www.radiocarbon.org

Significance of Soil Lightness Versus Physicochemical Soil Properties in Semiarid Areas

This is an author's accepted manuscript of an article published in " Arid Land Research and Management"; Volume 28, Issue 4, 2014; copyright Taylor & Francis; available online at: http://www.tandfonline.com/doi/abs/10.1080/15324982.2014.882871Modern agriculture aims to encompass all soil attributes to optimize soil use and minimize environmental impacts. One of those attributes is soil color, which allows determining important soil variables for crop management and soil conservation. In this study, the relationships between lightness and several pedologic, topographic, and soil management variables were determined. One hundred and ten topsoil points were sampled in an area where the Mediterranean climate is the only homogeneous soil forming factor. Soil samples were air dried, crushed, and sieved, and lightness measurements were made using a trichromatic colorimeter. The relationships between lightness and soil-related parameters were carried out by means of bivariate linear correlation, and Mann-Witney and Kruskal-Wallis tests. Soil textural fractions (sand and silt), electrical conductivity and carbonates were statistically significant (p<0.001) and exhibited moderate correlation coefficients (0.32 0.45). Topographic variables (slope and aspect), soil organic carbon, iron, nitrogen, pH, and parent material (marls) exhibited lower effect on lightness. The response of lightness to clay content was highly conditioned by iron content. Stoniness, phosphorous, elevation, and soil management variables (irrigation and land use) were not statistically significant. The results obtained with calcareous samples from semiarid areas showed that soil lightness behavior agree with findings in developed soils, despite of the large differences in soil composition and the heterogeneity of the study area.Moreno-Ramón, H.; Marqués-Mateu, Á.; Ibañez Asensio, S. (2014). Significance of Soil Lightness Versus Physicochemical Soil Properties in Semiarid Areas. Arid Land Research and Management. 28(4):371-382. doi:10.1080/15324982.2014.882871S371382284Al-Mahawili , S. M. H. , M. F. Baumgardner , R. A. Weismiller , and W. N. Melhorn . 1983 . Satellite image interpretation and laboratory spectral reflectance measurements of saline and gypsiferous soils of West Baghdad, Iraq.LARS Technical Reports. Paper 104.Barrett, L. R. (2002). Spectrophotometric color measurement in situ in well drained sandy soils. Geoderma, 108(1-2), 49-77. doi:10.1016/s0016-7061(02)00121-0Bogrekci, I., & Lee, W. S. (2005). Spectral Phosphorus Mapping using Diffuse Reflectance of Soils and Grass. Biosystems Engineering, 91(3), 305-312. doi:10.1016/j.biosystemseng.2005.04.015Buol, S. W., Southard, R. J., Graham, R. C., & McDaniel, P. A. (2011). Soil Genesis and Classification. doi:10.1002/9780470960622Christensen, L. K., Bennedsen, B. S., Jørgensen, R. N., & Nielsen, H. (2004). Modelling Nitrogen and Phosphorus Content at Early Growth Stages in Spring Barley using Hyperspectral Line Scanning. Biosystems Engineering, 88(1), 19-24. doi:10.1016/j.biosystemseng.2004.02.006Doi, R., Wachrinrat, C., Teejuntuk, S., Sakurai, K., & Sahunalu, P. (2009). Semiquantitative color profiling of soils over a land degradation gradient in Sakaerat, Thailand. Environmental Monitoring and Assessment, 170(1-4), 301-309. doi:10.1007/s10661-009-1233-xDuiker, S. W., Rhoton, F. E., Torrent, J., Smeck, N. E., & Lal, R. (2003). Iron (Hydr)Oxide Crystallinity Effects on Soil Aggregation. Soil Science Society of America Journal, 67(2), 606. doi:10.2136/sssaj2003.0606Ehsani, M. R., Upadhyaya, S. K., Slaughter, D., Shafii, S., & Pelletier, M. (1999). Precision Agriculture, 1(2), 219-236. doi:10.1023/a:1009916108990Gunal, H., Ersahin, S., Yetgin, B., & Kutlu, T. (2008). Use of Chromameter‐Measured Color Parameters in Estimating Color‐Related Soil Variables. Communications in Soil Science and Plant Analysis, 39(5-6), 726-740. doi:10.1080/00103620701879422Ibarra-F., F. A., Martin-R., M. H., Cox, J. R., Crowl, T. A., Post, D. F., Miller, R. W., & Rasmussen, G. A. (1995). Relationship between Buffelgrass Survival, Organic Carbon, and Soil Color in Mexico. Soil Science Society of America Journal, 59(4), 1120. doi:10.2136/sssaj1995.03615995005900040025xKonen, M. E., Burras, C. L., & Sandor, J. A. (2003). Organic Carbon, Texture, and Quantitative Color Measurement Relationships for Cultivated Soils in North Central Iowa. Soil Science Society of America Journal, 67(6), 1823. doi:10.2136/sssaj2003.1823Mouazen, A. M., Maleki, M. R., De Baerdemaeker, J., & Ramon, H. (2007). On-line measurement of some selected soil properties using a VIS–NIR sensor. Soil and Tillage Research, 93(1), 13-27. doi:10.1016/j.still.2006.03.009Pan, G., Xu, X., Smith, P., Pan, W., & Lal, R. (2010). An increase in topsoil SOC stock of China’s croplands between 1985 and 2006 revealed by soil monitoring. Agriculture, Ecosystems & Environment, 136(1-2), 133-138. doi:10.1016/j.agee.2009.12.011Sánchez-Marañón, M., Martín-García, J. M., & Delgado, R. (2011). Effects of the fabric on the relationship between aggregate stability and color in a Regosol–Umbrisol soilscape. Geoderma, 162(1-2), 86-95. doi:10.1016/j.geoderma.2011.01.008Sánchez-Marañón, M., Ortega, R., Miralles, I., & Soriano, M. (2007). Estimating the mass wetness of Spanish arid soils from lightness measurements. Geoderma, 141(3-4), 397-406. doi:10.1016/j.geoderma.2007.07.005Sánchez-Marañón, M., Delgado, G., Melgosa, M., Hita, E., & Delgado, R. (1997). CIELAB COLOR PARAMETERS AND THEIR RELATIONSHIP TO SOIL CHARACTERISTICS IN MEDITERRANEAN RED SOILS. Soil Science, 162(11), 833-842. doi:10.1097/00010694-199711000-00007Singleton, P. (1991). Water tables and soil colour as an indicator of saturation in some soils of the Waikato, New Zealand. Soil Research, 29(4), 467. doi:10.1071/sr9910467Spielvogel, S., Knicker, H., & Kögel-Knabner, I. (2004). Soil organic matter composition and soil lightness. Journal of Plant Nutrition and Soil Science, 167(5), 545-555. doi:10.1002/jpln.200421424Viscarra Rossel, R. A., Minasny, B., Roudier, P., & McBratney, A. B. (2006). Colour space models for soil science. Geoderma, 133(3-4), 320-337. doi:10.1016/j.geoderma.2005.07.017Webster, R., & Oliver, M. A. (2007). Geostatistics for Environmental Scientists. Statistics in Practice. doi:10.1002/978047051727

Incremental dimension reduction of tensors with random index

We present an incremental, scalable and efficient dimension reduction technique for tensors that is based on sparse random linear coding. Data is stored in a compactified representation with fixed size, which makes memory requirements low and predictable. Component encoding and decoding are performed on-line without computationally expensive re-analysis of the data set. The range of tensor indices can be extended dynamically without modifying the component representation. This idea originates from a mathematical model of semantic memory and a method known as random indexing in natural language processing. We generalize the random-indexing algorithm to tensors and present signal-to-noise-ratio simulations for representations of vectors and matrices. We present also a mathematical analysis of the approximate orthogonality of high-dimensional ternary vectors, which is a property that underpins this and other similar random-coding approaches to dimension reduction. To further demonstrate the properties of random indexing we present results of a synonym identification task. The method presented here has some similarities with random projection and Tucker decomposition, but it performs well at high dimensionality only (n>10^3). Random indexing is useful for a range of complex practical problems, e.g., in natural language processing, data mining, pattern recognition, event detection, graph searching and search engines. Prototype software is provided. It supports encoding and decoding of tensors of order >= 1 in a unified framework, i.e., vectors, matrices and higher order tensors.Comment: 36 pages, 9 figure

Klotho, APOEε4, cognitive ability, brain size, atrophy and survival : A study in the Aberdeen Birth Cohort of 1936

We thank the cohort participants who contributed to these studies. The study was supported by the University of Aberdeen Development Trust; the UK’s Biotechnology and Biological Sciences Research Council (BBSRC); the Wellcome Trust; the Chief Scientist Office (Scotland); and the Alzheimer’s Research Trust (now ARUK).Peer reviewedPostprin

Iron and Calcium Biomineralizations in the Pampean Coastal Plains, Argentina: Their Role in the Environmental Reconstruction of the Holocene

Biomineralizations are biogenic composites, crystalline or amorphous,produced by the metabolic activity of organisms distributed all over the world. Theaim of this work was to evaluate the presence of iron and calcium biomineralizationsand their influence in the physicochemical and mineralochemical variations inpaleo and actual pedosedimentary sequences of the coastal plains in Mar Chiquita.The complex interaction of calcium with iron biomineralizations, as framboidal andpoliframboidal pyrites associated with gypsum, barite, calcite, halite, and iron oxyhydroxides,have demonstrated the active and complex biogeochemistry that occursin the temperate?wet paleoesturaries and estuaries of the coastal Pampean Plains.Particularly the consequences that different human activities could have.Fil: Osterrieth, Margarita Luisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Frayssinet, Celia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Geología de Costas y del Cuaternario. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Geología de Costas y del Cuaternario; ArgentinaFil: Frayssinet, Lucrecia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentin

Fermions scattering in a three dimensional extreme black hole background

The absorption cross section for scattering of fermions off an extreme BTZ black hole is calculated. It is shown that, as in the case of scalar particles, an extreme BTZ black hole exhibits a vanishing absorption cross section, which is consistent with the vanishing entropy of such object. Additionally, we give a general argument to prove that the particle flux near the horizon is zero. Finally we show that the {\it reciprocal space} introduced previously in \cite{gm} gives rise to the same result and, therefore, it could be considered as the space where the scattering process takes place in an AdS spacetime.Comment: 15 pages, RevTex4. Revised version. To be published in Class. Quantum. Gra

Cannonballs in the context of Gamma Ray Bursts: Formation sites ?

We investigate possible formation sites of the cannonballs (in the gamma ray bursts context) by calculating their physical parameters, such as density, magnetic field and temperature close to the origin. Our results favor scenarios where the cannonballs form as instabilities (knots) within magnetized jets from hyperaccreting disks. These instabilities would most likely set in beyond the light cylinder where flow velocity with Lorentz factors as high as 2000 can be achieved. Our findings challenge the cannonball model of gamma ray bursts if these indeed form inside core-collapse supernovae (SNe) as suggested in the literature; unless hyperaccreting disks and the corresponding jets are common occurrences in core-collapse SNe.Comment: 10 pages, 12 figure