Uniform semiclassical wave function for coherent 2D electron flow

We find a uniform semiclassical (SC) wave function describing coherent branched flow through a two-dimensional electron gas (2DEG), a phenomenon recently discovered by direct imaging of the current using scanned probed microscopy. The formation of branches has been explained by classical arguments, but the SC simulations necessary to account for the coherence are made difficult by the proliferation of catastrophes in the phase space. In this paper, expansion in terms of "replacement manifolds" is used to find a uniform SC wave function for a cusp singularity. The method is then generalized and applied to calculate uniform wave functions for a quantum-map model of coherent flow through a 2DEG. Finally, the quantum-map approximation is dropped and the method is shown to work for a continuous-time model as well.Comment: 9 pages, 7 figure

Potencialidad de la cosecha y rendimiento industrial de bosques de Nothofagus antarctica en Tierra del Fuego (Argentina)

Martínez Pastur, G.; Lencinas, M.V. CADIC-CONICET. Casilla 92 (9410) Ushuaia, Argentina. Cellini, J.M. Cátedra de Biometría. Universidad Nacional de La Plata, La Plata, Argentina. Peri, P. UNPA-INTA-CONICET, Río Gallegos, Argentina.La propuesta silvícola para bosques de Nothofagus antarctica es el manejo silvopastoril, siendo la limitante para su implementación la falta de mercado para los productos madereros generados durante su aplicación. En Tierra del Fuego (Argentina) existen más de 180 mil ha, de las cuales 23% pertenecen a sitios medio-altos (>11,5 m de altura). El potencial de cosecha y el rendimiento industrial fueron analizados en 12 parcelas de 500 m², cuya área basal fue 58,7±11,5 m².ha-1 (promedio ± desvío estándar) con un remanente de 29,9±7,6 m².ha-1 luego de la aplicación de raleos. El volumen cosechado fue 102,2±29,0 m3.ha-1. El rendimiento en aserradero (127 trozas en 20 paquetes de muestreo) varió con la calidad y el tamaño de las trozas. Trozas >30 cm presentaron rendimientos del 34, 10, y 4% para calidades alta, media y baja, respectivamente. Trozas <30 cm de alta calidad presentaron rendimientos del 27%, y 10% para la de calidad media. Las trozas >30 cm de mejor calidad produjeron 9% de tablones, 21% de tablas, 49% de tirantes, 5% de madera corta y 16% de madera para pallet y las trozas <30 cm produjeron 0-1, 8-11%, 30-53%, 7- 16% y 32-43%, respectivamente. Los rendimientos sugieren la posibilidad de incorporar al aserrado solo trozas de alta calidad de cualquier diámetro, lo que representa rendimientos de cosecha de 50,0±27,9 m3.ha-1 para bosques de calidad de sitio media-alta. Considerando solo el punto de vista maderero, los rendimientos obtenidos pueden solventar la aplicación de los tratamientos silvopastoriles con ingresos brutos de hasta U$S 3500 por hectárea.Proyecto PID2005 35648 (SECYT-Argentina

Factores que influyen en la floración y el establecimiento de la regeneración en bosques primarios y manejados de Nothofagus pumilio

Martínez Pastur, G.; Lencinas, M. V. y Soler Esteban, R.CADIC-CONICET. Av. Houssay 200 (9410) Ushuaia, Argentina. E-mail: [email protected]. Cellini, J. M. UNLP, La Plata, Argentina.El manejo forestal de los bosques de Nothofagus pumilio se basa en su regeneración natural, pudiendo existir factores internos o externos, bióticos o abióticos que influyan sobre la misma. Para determinar los factores limitantes es necesario realizar una aproximación al ciclo completo. En este trabajo se analizaron patrones de floración, fructificación y establecimiento de la regeneración durante una estación de crecimiento en bosques primarios (BP) y manejados con retención agregada (RA) y dispersa (RD). Del total de flores femeninas producidas (BP=21,5 mill.ha-1, RA=6,5 mill.ha-1 y RD=2,9 mill.ha1) el 95%-97% produjo frutos. De estos, entre el 72%-79% llegó a semillas maduras, ocasionándose la pérdida por abscisión de frutos inmaduros (14%-20%), ataque de insectos (1,3%-4,9%) o consumo por aves (1,6%-3,5%). De las semillas maduras que llegaron al suelo, muchas no eran viables o estaban vacías (20%-31%). Durante la estratificación invernal también disminuyó la viabilidad (16%-33%), mientras que la pérdida por consumo de ratones y aves en este período fue menor en RA y BP (1,6%-2,3%) que en RD (7,4%). Las flores que formaron semillas disponibles para germinar variaron entre tratamientos: BP=23,5%, RA=23,5% y RD=19,3% del total de flores, siendo el establecimiento efectivo de plántulas del BP=2,6%, RA=1,8% y RD=0,7%. La principal limitante del ciclo fue la pérdida de viabilidad, durante la maduración del fruto (principalmente en los bosques manejados) y la estratificación invernal, así como la instalación de nuevas plántulas, tanto en BP como en RD. Estudios a largo plazo son necesarios para establecer las variaciones de estos ciclos en años con diferente producción de semillas.Estudio financiado por el proyecto PAE2004 22428 (SECYT-Argentina), y gracias a la colaboración del Aserradero Kareken (Tierra del Fuego - Argentina)

Uso de fotos hemiesféricas para la elaboración de modelos de altura de la regeneración en Nothofagus pumilio

Martínez Pastur, G.; Lencinas, M.V.; Soler Esteban, R. CADIC-CONICET. Casilla 92 (9410) Ushuaia, Argentina. [email protected]. Cellini, J.M.; Barrera, M. Universidad Nacional de La Plata, La Plata. Argentina. Peri, P. UNPA-INTA-CONICET, Río Gallegos, Argentina.El crecimiento en altura de la regeneración es la principal variable empleada para caracterizar la continuidad de bosques primarios y manejados. Entre los condicionantes bióticos y abióticos, la cobertura del dosel determina la cantidad de luz disponible. Se desarrollaron modelos de predicción de altura de regeneración de Nothofagus pumilio en relación con parámetros de cobertura y radiación obtenidos mediante fotos hemiesféricas, para bosques primarios y manejados. Se emplearon 3700 pares de datos (edad-altura) obtenidos durante 2002-2007 en parcelas permanentes de muestreo (n=16), caracterizadas con fotos hemiesféricas empleando un lente Sigma 8mm y analizadas usando el programa Gap Light Analyzer v.2.0. Se ajustaron modelos (Altura=a.Edadb.(c+d.X+e.X²)) por medio de técnicas de regresión no-linear que utilizaron como variables independientes a la altura y la edad de las plántulas, y como variables dependientes a la cobertura de copas (CC), el índice de área foliar efectivo (IAF), la radiación global (RG) y el porcentaje de radiación global incidente (PRG). Los modelos ajustados tuvieron un ajuste aceptable (r²=61%-63%) generando curvas polimórficas donde H aumentó hasta un máximo (20-25 cm en plántulas de 6 en CC 55%, LAI 1.0, GR 12.0 W.m² o PGR 50%) para luego decrecer en todas las edades analizadas con mayores o menores valores de dichas variables. Los bosques primarios presentaron CC=89.5%, LAI=2.6, GR=3.5 W.m² y PGR=14.3%, mientras que la corta de protección presentó CC=56.5%, LAI=0.8, GR=14.1 W.m² and PGR= 57.2%. El desarrollo de estos modelos es una herramienta útil para diseñar nuevas estrategias de manejo forestal al predecir la respuesta de la regeneración.Estudio financiado por el proyecto PAE2004 22428 (SECYT-Argentina), y gracias a la colaboración de la Consultora “Servicios Forestales” y el Aserradero Los Castores (Tierra del Fuego - Argentina)

Are Comorbidities Associated With Overall Survival in Patients With Oral Squamous Cell Carcinoma?

Purpose: Oral squamous cell carcinoma (OSCC) is a highly prevalent type of immunogenic cancer with a low survival rate in patients with comorbidities owing to toxic habits. Materials and Methods: A retrospective cohort study was conducted of patients with resectable OSCC at a tertiary Spanish hospital from 2011 to 2014. The primary predictor variables were comorbidity and immune biomarkers. Comorbidity was assessed using the Adult Comorbidity Evaluation–27 (ACE-27) and scored from 1 to 3 (mild to severe decompensation, respectively). The immune biomarkers were neutrophil-to-lymphocyte ratio (NLR), derived NLR (dNLR), platelet-to-lymphocyte ratio (PLR), and lymphocyte-to-monocyte ratio (LMR). The primary outcome variable was 5-year overall survival (OS). Other study variables were stage, margin, and neck management. Receiver operating characteristic curves were built for each ratio. For the survey of immune biomarkers, area under the curve was computed to determine cutoff points and investigate their association with OS. Kaplan-Meier estimates of survival and Cox proportional hazards models were used for longitudinal analysis. Results: Overall 215 patients were identified (median age, 67 yr; range, 32 to 96 yr; median follow-up, 31 months; range, 7 to 78 months); 159 patients had at least 1 comorbid condition. Results showed that a severe comorbidity (according to the ACE-27) increased the risk of death by 4 times in patients with OSCC regardless of stage. NLR, dNLR, LMR, and PLR were associated with OS in the univariate study. Cutoff points to predict increased mortality were 3, 1.9, 2.6, and 66 for NLR, dNLR, LMR, and PLR, respectively. Age, comorbidity, stage, margins, and management of the neck were important independent predictors of decreased OS in OSCC. PLR was marginally associated with OS in the multivariate model. Conclusion: These results suggest that comorbidity and NLR, dNLR, LMR, and PLR are associated with 5-year OS in patients with resectable OSCC

A nano-luciferase expressing human coronavirus OC43 for countermeasure development

The genetic diversity of the coronavirus (CoV) family poses a significant challenge for drug discovery and development. Traditional antiviral drugs often target specific viral proteins from specific viruses which limits their use, especially against novel emerging viruses. Antivirals with broad-spectrum activity overcome this limitation by targeting highly conserved regions or catalytic domains within viral proteins that are essential for replication. For rapid identification of small molecules with broad antiviral activity, assays with viruses representing family-wide genetic diversity are needed. Viruses engineered to express a reporter gene (i.e. luminescence, fluorescence, etc.) can increase the efficiency, sensitivity or precision of drug screening over classical measures of replication like observation of cytopathic effect or measurement of infectious titers. We have previously developed reporter virus systems for multiple other endemic, pandemic, epidemic and enzootic CoV. Human CoV OC43 (HCoV-OC43) is a human endemic CoV that causes respiratory infection with age-related exacerbations of pathogenesis. Here, we describe the development of a novel recombinant HCoV-OC43 reporter virus that expresses nano-luciferase (HCoV-OC43 nLuc), and its potential application for screening of antivirals against CoV

Floquet scattering in parametric electron pumps

A Floquet scattering approach to parametric electron pumps is presented and compared with Brouwer's adiabatic scattering approach [Phys. Rev. B 58, R10135 (1998)] for a simple scattering model with two harmonically oscillating delta-function barriers. For small strength of oscillating potentials these two approaches give exactly equivalent results while for large strength, these clearly deviate from each other. The validity of the adiabatic theory is also discussed by using the Wigner delay time obtained from the Floquet scattering matrix.Comment: 10 pages, 7 figure

General Adiabatic Evolution with a Gap Condition

We consider the adiabatic regime of two parameters evolution semigroups generated by linear operators that are analytic in time and satisfy the following gap condition for all times: the spectrum of the generator consists in finitely many isolated eigenvalues of finite algebraic multiplicity, away from the rest of the spectrum. The restriction of the generator to the spectral subspace corresponding to the distinguished eigenvalues is not assumed to be diagonalizable. The presence of eigenilpotents in the spectral decomposition of the generator forbids the evolution to follow the instantaneous eigenprojectors of the generator in the adiabatic limit. Making use of superadiabatic renormalization, we construct a different set of time-dependent projectors, close to the instantaneous eigeprojectors of the generator in the adiabatic limit, and an approximation of the evolution semigroup which intertwines exactly between the values of these projectors at the initial and final times. Hence, the evolution semigroup follows the constructed set of projectors in the adiabatic regime, modulo error terms we control

Effective dynamics for particles coupled to a quantized scalar field

We consider a system of N non-relativistic spinless quantum particles (``electrons'') interacting with a quantized scalar Bose field (whose excitations we call ``photons''). We examine the case when the velocity v of the electrons is small with respect to the one of the photons, denoted by c (v/c= epsilon << 1). We show that dressed particle states exist (particles surrounded by ``virtual photons''), which, up to terms of order (v/c)^3, follow Hamiltonian dynamics. The effective N-particle Hamiltonian contains the kinetic energies of the particles and Coulomb-like pair potentials at order (v/c)^0 and the velocity dependent Darwin interaction and a mass renormalization at order (v/c)^{2}. Beyond that order the effective dynamics are expected to be dissipative. The main mathematical tool we use is adiabatic perturbation theory. However, in the present case there is no eigenvalue which is separated by a gap from the rest of the spectrum, but its role is taken by the bottom of the absolutely continuous spectrum, which is not an eigenvalue. Nevertheless we construct approximate dressed electrons subspaces, which are adiabatically invariant for the dynamics up to order (v/c)\sqrt{\ln (v/c)^{-1}}. We also give an explicit expression for the non adiabatic transitions corresponding to emission of free photons. For the radiated energy we obtain the quantum analogue of the Larmor formula of classical electrodynamics.Comment: 67 pages, 2 figures, version accepted for publication in Communications in Mathematical Physic