Mid-infrared intersubband absorption from p-Ge quantum wells grown on Si substrates

Mid-infrared intersubband absorption from p-Ge quantum wells with Si0.5Ge0.5 barriers grown on a Si substrate is demonstrated from 6 to 9 μm wavelength at room temperature and can be tuned by adjusting the quantum well thickness. Fourier transform infra-red transmission and photoluminescence measurements demonstrate clear absorption peaks corresponding to intersubband transitions among confined hole states. The work indicates an approach that will allow quantum well intersubband photodetectors to be realized on Si substrates in the important atmospheric transmission window of 8–13 μm

Mid-Infrared Intersubband Absorption from P-Ge Quantum Wells on Si

Mid-infrared intersubband absorption from p-Ge quantum wells with Si0.5Ge0.5 barriers grown on a Si substrate is demonstrated from 6 to 9 μm wavelength at room temperature and can be tuned by adjusting the quantum well thickness. Fourier transform infra-red spectroscopy measurements demonstrate clear absorption peaks corresponding to intersubband transitions among confined hole states. The work indicates an approach that will allow quantum well intersubband photodetectors to be realized on Si substrates in the important atmospheric transmission window of 8–13 μm

A constant dark matter halo surface density in galaxies

We confirm and extend the recent finding that the central surface density r_0*rho_0 galaxy dark matter halos, where r_0 and rho_0 are the halo core radius and central density, is nearly constant and independent of galaxy luminosity. Based on the co-added rotation curves of about 1000 spiral galaxies, mass models of individual dwarf irregular and spiral galaxies of late and early types with high-quality rotation curves and, galaxy-galaxy weak lensing signals from a sample of spiral and elliptical galaxies, we find that log(r_0*rho_0) = 2.15 +- 0.2, in units of log(Msol/pc^2). We also show that the observed kinematics of Local Group dwarf spheroidal galaxies are consistent with this value. Our results are obtained for galactic systems spanning over 14 magnitudes, belonging to different Hubble Types, and whose mass profiles have been determined by several independent methods. In the same objects, the approximate constancy of rho_0*r_0 is in sharp contrast to the systematical variations, by several orders of magnitude, of galaxy properties, including rho_0 and central stellar surface density.Comment: Accepted for publication in MNRAS. 9 pages, 4 figure

Radiación infrarroja atmosférica en Salta y posible influencia urbana

Las medidas de radiación IR realizadas en Salta en el período marzo-agosto de 2012 y mayo-julio de 2013 muestran valores comprendidos entre 252 y 431 W/m2 que, para superficies con emisividad 0,95, representan un potencial de enfriamiento  (radiación  útil) entre 0  y  171  W/m2.  La correlación  entre emisividad  y  temperatura de rocío  obtenida anteriormente para cielo claro sigue siendo buena con una dispersión menor al 4%. La influencia del ambiente urbano parece manifestarse no sólo en un aumento de las temperaturas sino también en un aumento de la radiación de cielo, de la temperatura de cielo, de la emisividad y una disminución de la radiación útil disponible como potencial de enfriamiento pasivo.IR measurements performed at Salta in the periods march-august 2012 and may-july 2013 show values between 252 and 431 W/m2 that for surfaces with emisivity 0,95 represent a cooling potential (useful radiation) of 0 to 171 W/m 2 . The correlation between emisivity and dew point obtained before for clear skies is still valid with a dispersion less than 4%. The first measurements suggest that the influence of urban environment manifests not only through the rising of temperatures but also through a rise of sky radiation, sky temperature and emisivity, and a diminution of the useful radiation available for passive cooling.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Putting the squeeze on plasmodesmata- a role for reticulons in primary plasmodesmata formation

Primary plasmodesmata (PD) arise at cytokinesis when the new cell plate forms. During this process, fine strands of endoplasmic reticulum are laid down between enlarging Golgi-derived vesicles to form nascent PD, each pore containing a desmotubule, a membranous rod derived from the cortical ER. Little is known about the forces that model the ER during cell-plate formation. Here we show that members of the reticulon (RTNLB) family of ER-tubulating proteins may play a role in formation of the desmotubule. RTNLB3 and RTNLB6, two RTNLBs present in the PD proteome, are recruited to the cell plate at late telophase, when primary PD are formed, and remain associated with primary PD in the mature cell wall. Both RTNLBs showed significant co-localisation at PD with the viral movement protein of tobacco mosaic virus while super-resolution imaging (3D-SIM) of primary PD revealed the central desmotubule to be labelled by RTNLB6. FRAP studies showed that these RTNLBs are mobile at the edge of the developing cell plate, where new wall materials are being delivered, but significantly less mobile at its centre where PD are forming. A truncated RTNLB3, unable to constrict the ER, was not recruited to the cell plate at cytokinesis. We discuss the potential roles of RTNLBs in desmotubule formatio

Minimizing Higgs Potentials via Numerical Polynomial Homotopy Continuation

The study of models with extended Higgs sectors requires to minimize the corresponding Higgs potentials, which is in general very difficult. Here, we apply a recently developed method, called numerical polynomial homotopy continuation (NPHC), which guarantees to find all the stationary points of the Higgs potentials with polynomial-like nonlinearity. The detection of all stationary points reveals the structure of the potential with maxima, metastable minima, saddle points besides the global minimum. We apply the NPHC method to the most general Higgs potential having two complex Higgs-boson doublets and up to five real Higgs-boson singlets. Moreover the method is applicable to even more involved potentials. Hence the NPHC method allows to go far beyond the limits of the Gr\"obner basis approach.Comment: 9 pages, 4 figure

Seasonality fluctuations recorded in fossil bivalves during the early Pleistocene: implications for climate change

Understanding the transformations of the climate system may help to predict and reduce the effects of global climate change. The geological record provides a unique archive that documents the long-term fluctuations of environmental variables, such as seasonal change. Here, we investigate how seasonal variation in seawater temperatures varied in the Mediterranean Sea during the early Pleistocene, approaching the Early-Middle Pleistocene Transition (EMPT) and the beginning of precession-driven Quaternary-style glacial–interglacial cycles. We performed whole-shell and sclerochemical stable isotope analyses (δ18O, δ13C) on bivalves, collected from the lower Pleistocene Arda River marine succession (northern Italy), after checking shell preservation. Our results indicate that seawater temperature seasonality was the main variable of climate change in the Mediterranean area during the early Pleistocene, with the Northern Hemisphere Glaciation (NHG) exerting a control on the Mediterranean climate. We show that strong seasonality (14.4–16.0 °C range) and low winter paleotemperatures (0.8–1.6 °C) were likely the triggers leading to the establishment of widespread populations of so called “northern guests” (i.e., cold water taxa) in the Mediterranean Sea around 1.80 Ma. The shells postdating the arrival of the “northern guests” record a return to lower seasonal variations and higher seawater paleotemperatures, with seasonality increasing again approaching the EMPT; the latter, however, is not associated with a corresponding cooling of mean seawater paleotemperatures, showing that the observed seasonality variation represents a clear signal of progressive climate change in the Mediterranean Sea

L-Carnitine: An Antioxidant Remedy for the Survival of Cardiomyocytes under Hyperglycemic Condition

Background: Metabolic alterations as hyperglycemia and inflammation induce myocardial molecular events enhancing oxidative stress and mitochondrial dysfunction. Those alterations are responsible for a progressive loss of cardiomyocytes, cardiac stem cells, and consequent cardiovascular complications. Currently, there are no effective pharmacological measures to protect the heart from these metabolic modifications, and the development of new therapeutic approaches, focused on improvement of the oxidative stress condition, is pivotal. The protective effects of levocarnitine (LC) in patients with ischemic heart disease are related to the attenuation of oxidative stress, but LC mechanisms have yet to be fully understood. Objective: The aim of this work was to investigate LC's role in oxidative stress condition, on ROS production and mitochondrial detoxifying function in H9c2 rat cardiomyocytes during hyperglycemia. Methods: H9c2 cells in the hyperglycemic state (25\u2009mmol/L glucose) were exposed to 0.5 or 5\u2009mM LC for 48 and 72\u2009h: LC effects on signaling pathways involved in oxidative stress condition were studied by Western blot and immunofluorescence analysis. To evaluate ROS production, H9c2 cells were exposed to H2O2 after LC pretreatment. Results: Our in vitro study indicates how LC supplementation might protect cardiomyocytes from oxidative stress-related damage, preventing ROS formation and activating antioxidant signaling pathways in hyperglycemic conditions. In particular, LC promotes STAT3 activation and significantly increases the expression of antioxidant protein SOD2. Hyperglycemic cardiac cells are characterized by impairment in mitochondrial dysfunction and the CaMKII signal: LC promotes CaMKII expression and activation and enhancement of AMPK protein synthesis. Our results suggest that LC might ameliorate metabolic aspects of hyperglycemic cardiac cells. Finally, LC doses herein used did not modify H9c2 growth rate and viability. Conclusions: Our novel study demonstrates that LC improves the microenvironment damaged by oxidative stress (induced by hyperglycemia), thus proposing this nutraceutical compound as an adjuvant in diabetic cardiac regenerative medicine

Neutrino masses and mixing: Singular mass matrices and Quark-lepton symmetry

We suggest an approach to explain the observed pattern of the neutrino masses and mixing which employs the weakly broken quark-lepton symmetry and does not require introduction of an ad hoc symmetry of the neutrino sector. The mass matrices are nearly equal for all quarks and leptons. They have very small determinants and hierarchical form with expansion parameter lambda = 0.26. The latter can be realized, e.g., in the model with U(1) family symmetry. The symmetry is broken at the lambda^2 level. Large lepton mixing appears as a result of summation of the neutrino and charged lepton rotations which diagonalize the mass matrices in contrast with quark sector where the up quarks and down quarks rotations cancel each other. We show that the flip of the sign of rotation in the lepton sector is a result of the seesaw mechanism which also enhances the neutrino mixing. In this approach one expects, in general, deviation of the 2-3 mixing from maximal, s_{13} \sim (1-3) lambda^2, hierarchical neutrino mass spectrum, and m_{ee} < 10^{-2} eV. The scenario is consistent with the thermal leptogenesis and (in SUSY context) bounds on lepton number violating processes, like mu to e gamma.Comment: 25 pages, one figure, ReVTeX4, Nucl. Phys. B versio