1,551 research outputs found
Centennial-scale vegetation and North Atlantic Oscillation changes during the Late Holocene in the southern Iberia
High-reso CE to lution pollen analysis, charcoal, non-pollen palynomorphs and magnetic susceptibility have been analyzed in the sediment record of a peat bog in Sierra Nevada in southern Iberia. The study of these proxies provided the reconstruction of vegetation, climate, fire and human activity of the last ∼4500 cal yr BP. A progressive trend towards aridification during the late Holocene is observed in this record. This trend is interrupted by millennial- and centennial-scale variability of relatively more humid and arid periods. Arid conditions are recorded between ∼4000 and 3100 cal yr BP, being characterized by a decline in arboreal pollen and with a spike in magnetic susceptibility. This is followed by a relatively humid period from ∼3100 to 1600 cal yr BP, coinciding partially with the Iberian-Roman Humid Period, and is indicated by the increase of Pinus and the decrease in xerophytic taxa. The last 1500 cal yr BP are characterized by several centennial-scale climatic oscillations. Generally arid conditions from ∼450 to 1300 CE, depicted by a decrease in Pinus and an increase in Artemisia, comprise the Dark Ages and the Medieval Climate Anomaly. Since ∼ 1300 to 1850 CE pronounced oscillations occur between relatively humid and arid conditions. Four periods depicted by relatively higher Pinus coinciding with the beginning and end of the Little Ice Age are interrupted by three arid events characterized by an increase in Artemisia. These alternating arid and humid shifts could be explained by centennial-scale changes in the North Atlantic Oscillation and solar activity
Thin Al 1− Ga As 0.56 Sb 0.44 diodes with extremely weak temperature dependence of avalanche breakdown
When using avalanche photodiodes (APDs) in applications, temperature dependence of avalanche breakdown voltage is one of the performance parameters to be considered. Hence, novel materials developed for APDs require dedicated experimental studies. We have carried out such a study on thin Al1–xGaxAs0.56Sb0.44 p–i–n diode wafers (Ga composition from 0 to 0.15), plus measurements of avalanche gain and dark current. Based on data obtained from 77 to 297 K, the alloys Al1−xGaxAs0.56Sb0.44 exhibited weak temperature dependence of avalanche gain and breakdown voltage, with temperature coefficient approximately 0.86–1.08 mV K−1, among the lowest values reported for a number of semiconductor materials. Considering no significant tunnelling current was observed at room temperature at typical operating conditions, the alloys Al1−xGaxAs0.56Sb0.44 (Ga from 0 to 0.15) are suitable for InP substrates-based APDs that require excellent temperature stability without high tunnelling current
Asymptotics and zeros of Sobolev orthogonal polynomials on unbounded supports
In this paper we present a survey about analytic properties of polynomials
orthogonal with respect to a weighted Sobolev inner product such that the
vector of measures has an unbounded support. In particular, we are focused in
the study of the asymptotic behaviour of such polynomials as well as in the
distribution of their zeros. Some open problems as well as some new directions
for a future research are formulated.Comment: Changed content; 34 pages, 41 reference
Electron Spin Resonance Above Tc In Layered Manganites
We have performed electron spin resonance (ESR) and dc magnetization measurements on single crystals of La2(1-x)Sr1+2xMn2O7 up to 800 K with special emphasis on the x = 0.4 composition. The ESR linewidth shows behavior similar to that observed in the three-dimensional perovskites and above ∼500 K can be described by a universal expression ΔHpp(T)=[C/Tχ(T)]ΔHpp (∞). The linewidth and the resonance field become anisotropic below ∼500 K. The anisotropy in the resonance field is proportional to the magnetization M, and we concluded that it is intrinsic to the system. We show that demagnetization effects can explain only part of the anisotropy. The remainder arises from short-range uniaxial terms in the Hamiltonian that are associated with the crystal field and Dzialozhinsky-Moriya interactions. The anisotropy in the linewidth is attributed to the easy-plane ferromagnetic ordering, which also arises from the short-range anisotropy.631717441311744136Ruddlesden, S.N., Popper, P., (1958) Acta Crystallogr., 11, p. 54Moritomo, Y., Asamitsu, A., Kuwahara, H., Tokura, Y., (1996) Nature (London), 380, p. 141Causa, M.T., Tovar, M., Caneiro, A., Prado, F., Ibanez, G., Ramos, C.A., Butera, A., Oseroff, S.B., (1998) Phys. Rev. B, 58, p. 3233Causa, M.T., Alejandro, G., Tovar, M., Pagliuso, P.G., Rettori, C., Oseroff, S.B., Subramanian, M.A., (1999) J. Appl. Phys., 85, p. 5408Huber, D.L., Alejandro, G., Caneiro, A., Causa, M.T., Prado, F., Tovar, M., Oseroff, S.B., (1999) Phys. Rev. B, 60, p. 12155Oseroff, S.B., Moreno, N.O., Pagliuso, P.G., Rettori, C., Huber, D.L., Gardner, J.S., Sarrao, J.L., Alascio, B.R., (2000) J. Appl. Phys., 87, p. 5810Seehra, M.S., Ibrahim, M.M., Babu, V.S., Srinivasan, G., (1996) J. Phys.: Condens. Matter, 8, p. 11283Dominguez, M., Lofland, S.E., Bhagat, S.M., Raychaudhuri, A.K., Ju, H.L., Venkates, T., Greene, R.L., (1996) Solid State Commun., 97, p. 193Lofland, S.E., Kim, P., Dahiroc, P., Bhagat, S.M., Tyagi, S.D., Karabashev, S.G., Shultyatev, D.A., Mukovskii, Y., (1997) Phys. Lett. A, 233, p. 476Kimura, T., Tomioka, Y., Kuwahara, H., Asamitsu, A., Tamura, M., Tokura, Y., (1996) Science, 274, p. 1698Perring, T.G., Aeppli, G., Moritomo, Y., Tokura, Y., (1997) Phys. Rev. Lett., 78, p. 3197Zhou, J.-S., Goodenough, J.B., Mitchell, J.F., (1998) Phys. Rev. B, 58, p. 579Zhou, J.-S., Goodenough, J.B., (1998) Phys. Rev. Lett., 80, p. 2665Kelley, T.M., Argyriou, D.N., Robinson, R.A., Nakotte, H., Mitchell, J.F., Osbron, R., Jorgensen, J.D., (1998) Physica B, 241-243, p. 439Heffner, R.H., MacLaughlin, D.E., Nieuwenhuys, G.J., Kimura, T., Luke, G.M., Tokura, Y., Uemura, Y.J., (1998) Phys. Rev. Lett., 81, p. 1706Potter, C.D., Swiatek, M., Bader, S.D., Argyriou, D.N., Mitchell, J.F., Miller, D.J., Hinks, D.G., Jorgensen, J.D., (1998) Phys. Rev. B, 57, p. 72Chauvet, O., Goglio, G., Molinie, P., Corraze, B., Brohan, L., (1998) Phys. Rev. Lett., 81, p. 1102Hirota, K., Moritomo, Y., Fujioka, H., Kubota, M., Yoshizawa, H., Endoh, Y., (1998) J. Phys. Soc. Jpn., 67, p. 3380Li, J.Q., Matsui, Y., Kimura, T., Tokura, Y., (1998) Phys. Rev. B, 57, pp. R3205Kimura, T., Kumai, R., Tokura, Y., Li, J.Q., Matsui, Y., (1998) Phys. Rev. B, 58, p. 11081Hayashi, T., Miura, N., Tokunaga, M., Kimura, T., Tokura, Y., (1998) J. Phys.: Condens. Matter, 10, p. 11525Suryanarayanan, R., Dhalenne, G., Revcolevschi, A., Prellier, W., Renard, J.P., Dupas, C., Caliebe, W., Chatterji, T., (2000) Solid State Commun., 113, p. 267Kubota, M., Fujioka, H., Ohoyama, K., Hirota, K., Moritomo, Y., Yoshizawa, H., Endoh, Y., (1999) J. Phys. Chem. Solids, 60, p. 116Bhagat, S.M., Lofland, S.E., Mitchell, J.F., (1999) Phys. Lett. A, 259, p. 326Kittel, C., (1997) Introduction to Solid State Physics, , Wiley, New YorkOkochi, M., (1970) J. Phys. Soc. Jpn., 28, p. 897Victoria, C., Barker, R.C., Yelon, A., (1967) Phys. Rev. Lett., 19, p. 792Nagata, K., (1976) J. Phys. Soc. Jpn., 40, p. 1209Nagata, K., Yamamoto, I., Takano, H., Yokozawa, Y., (1977) J. Phys. Soc. Jpn., 43, p. 857. , and references thereinHuber, D.L., Seehra, M.S., (1976) Phys. Status Solidi B, 74, p. 145Stanger, J.-L., Andre, J.-J., Turek, P., Hosokoshi, Y., Tamura, M., Kinoshita, M., Rey, P., Veciana, J., (1997) Phys. Rev. B, 55, p. 8398Van Vleck, J.H., (1950) Phys. Rev., 78, p. 266Kittel, C., (1948) Phys. Rev., 73, p. 15
Magnetic Structure Of Cerhin5 As A Function Of Pressure And Temperature
We report magnetic neutron-diffraction and electrical resistivity studies on single crystals of the heavy-fermion antiferromagnet CeRhIn5 at pressures up to 2.3 GPa. These experiments show that the staggered moment of Ce and the incommensurate magnetic structure change weakly with applied pressure up to 1.63 GPa, where resistivity, specific heat and nuclear quadrupole resonance measurements confirm the presence of bulk superconductivity. This work places important constraints on an interpretation of the relationship between antiferromagnetism and unconventional superconductivity in CeRhIn 5.692244031244036Heffner, R.H., Norman, M.R., (1996) Comments Condens. Matter Phys., 17, p. 361Stewart, G.R., (2001) Rev. Mod. 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Detection of prostate cancer-specific transcripts in extracellular vesicles isolated from post-DRE urine
Background: The measurement of gene expression in post-digital rectal examination (DRE) urine specimens provides a non-invasive method to determine a patient’s risk of prostate cancer. Many currently available assays use whole urine or cell pellets for the analysis of prostate cancer-associated genes, although the use of extracellular vesicles (EVs) has also recently been of interest. We investigated the expression of prostate-, kidney-, and bladder- specific transcripts and known prostate cancer biomarkers in urine EVs. Methods: Cell pellets and EVs were recovered from post-DRE urine specimens, with the total RNA yield and quality determined by Bioanalyzer. The levels of prostate, kidney, and bladder- associated transcripts in EVs were assessed by TaqMan qPCR and targeted sequencing. Results: RNA was more consistently recovered from the urine EV specimens, with over 80% of the patients demonstrating higher RNA yields in the EV fraction as compared to urine cell pellets. The median EV RNA yield of 36.4 ng was significantly higher than the median urine cell pellet RNA yield of 4.8 ng. Analysis of the post-DRE urine EVs indicated that prostate-specific transcripts were more abundant than kidney- or bladder-specific transcripts. Additionally, patients with prostate cancer had significantly higher levels of the prostate cancer-associated genes PCA3 and ERG. Conclusions: Post-DRE urine EVs are a viable source of prostate-derived RNAs for biomarker discovery and prostate cancer status can be distinguished from analysis of these specimens. Continued analysis of urine EVs offers the potential discovery of novel biomarkers for pre- biopsy prostate cancer detection
Neutrino Zero Modes on Electroweak Strings
Zero modes of massive standard model fermions have been found on electroweak
Z-strings. A zero mode solution for a massless left-handed neutrino is also
known, but was thought to be non-normalizable. Here we show that although this
mode is not discretely normalizable, it is delta-function normalizable and the
correct interpretation of this solution is within the framework of the
continuum spectrum. We also analyze an extension of the standard model
including right-handed neutrinos in which neutrinos have Dirac masses, arising
from a Yukawa coupling to the usual SU(2) Higgs doublet, and right-handed
Majorana masses. The Majorana mass terms are taken to be spatially homogeneous
and are presumed to arise from the vacuum expectation value of some field
acquired in a phase transition well above the electroweak phase transition. The
resulting zero energy equations have a discrete zero mode.Comment: 5 pages, 1 figures, version to appear in Phys. Rev.
Spreading lengths of Hermite polynomials
The Renyi, Shannon and Fisher spreading lengths of the classical or
hypergeometric orthogonal polynomials, which are quantifiers of their
distribution all over the orthogonality interval, are defined and investigated.
These information-theoretic measures of the associated Rakhmanov probability
density, which are direct measures of the polynomial spreading in the sense of
having the same units as the variable, share interesting properties: invariance
under translations and reflections, linear scaling and vanishing in the limit
that the variable tends towards a given definite value. The expressions of the
Renyi and Fisher lengths for the Hermite polynomials are computed in terms of
the polynomial degree. The combinatorial multivariable Bell polynomials, which
are shown to characterize the finite power of an arbitrary polynomial, play a
relevant role for the computation of these information-theoretic lengths.
Indeed these polynomials allow us to design an error-free computing approach
for the entropic moments (weighted L^q-norms) of Hermite polynomials and
subsequently for the Renyi and Tsallis entropies, as well as for the Renyi
spreading lengths. Sharp bounds for the Shannon length of these polynomials are
also given by means of an information-theoretic-based optimization procedure.
Moreover, it is computationally proved the existence of a linear correlation
between the Shannon length (as well as the second-order Renyi length) and the
standard deviation. Finally, the application to the most popular
quantum-mechanical prototype system, the harmonic oscillator, is discussed and
some relevant asymptotical open issues related to the entropic moments
mentioned previously are posed.Comment: 16 pages, 4 figures. Journal of Computational and Applied Mathematics
(2009), doi:10.1016/j.cam.2009.09.04
Alexithymia and depression in elderly people that get directed physical activity
La relación entre la alexitimia y la depresión y los factores sociodemográficos ha sido estudiada en personas mayores. Sin embargo, el papel atenuador del ejercicio en estas afecciones aún debe ser determinado. En el presente estudio se mide el grado de alexitimia y depresión en adultos mayores, comparando una muestra sedentaria con una de practicantes de actividad fÃsica. Se utilizó un diseño descriptivo transversal con una muestra compuesta por 27 participantes, 9 hombres y 18 mujeres de más de 60 años (64 ± 5.1 años), con objeto de medir el grado de alexitimia y depresión que presentaban en el momento de la recogida de datos. Los instrumentos utilizados fueron la escala de depresión de Yesavage, la Escala de Alexitimia de Toronto (TAS-20) y el Cuestionario de Salud SF-12. Los resultados mostraron que los practicantes de actividad fÃsica presentaban puntuaciones más bajas en alexitimia y depresión que los sujetos sedentarios, sin que éstas variables estuvieran relacionadas en función del género y la edad. A tenor de los resultados, el ejercicio pudiera jugar algún papel en la modulación de las alteraciones psicológicas
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