Inelastic lifetimes of hot electrons in real metals

We report a first-principles description of inelastic lifetimes of excited electrons in real Cu and Al, which we compute, within the GW approximation of many-body theory, from the knowledge of the self-energy of the excited quasiparticle. Our full band-structure calculations indicate that actual lifetimes are the result of a delicate balance between localization, density of states, screening, and Fermi-surface topology. A major contribution from $d$-electrons participating in the screening of electron-electron interactions yields lifetimes of excited electrons in copper that are larger than those of electrons in a free-electron gas with the electron density equal to that of valence ($4s^1$) electrons. In aluminum, a simple metal with no $d$-bands, splitting of the band structure over the Fermi level results in electron lifetimes that are smaller than those of electrons in a free-electron gas.Comment: 4 papes, 2 figures, to appear in Phys. Rev. Let

Non-trace full-F gyro-fluid interchange impurity advection

A full-F isothermal gyro-fluid model and code (which is based on the full distribution function F compared to only small fluctuations) is extended to handle self-consistent coupling of multiple quasi-neutral ion species via the polarisation equation in the long wavelength approximation. The numerical model is used to determine two-dimensional interchange driven ‘blob’ transport in a plasma with intrinsic impurity content for a range of impurity parameters. With the same model, the self-consistent advective interaction of a main plasma species blob with a non-trace impurity cloud is studied. For homogeneous impurity distributions an increased effective mass reduces blob transport, whereas it is found that localised impurity clouds can lead either to acceleration or slowing down of blob propagation depending on the alignment of the impurity density gradient during the acceleration phase of the main ion species blob

Nonlinear interfacial waves in a constant-vorticity planar flow over variable depth

Exact Lagrangian in compact form is derived for planar internal waves in a two-fluid system with a relatively small density jump (the Boussinesq limit taking place in real oceanic conditions), in the presence of a background shear current of constant vorticity, and over arbitrary bottom profile. Long-wave asymptotic approximations of higher orders are derived from the exact Hamiltonian functional in a remarkably simple way, for two different parametrizations of the interface shape.Comment: revtex, 4.5 pages, minor corrections, summary added, accepted to JETP Letter

NiO/ZrO2nanocomposites as photocathodes of tandem DSCs with higher photoconversion efficiency with respect to parent single-photoelectrode p-DSCs

The nanocomposites of nickel oxide (NiO) and zirconia (ZrO2) (NZNCs) are particularly effective photocathodic materials in p-type dye-sensitized solar cells (p-DSCs) and tandem DSCs (t-DSCs). The t-DSCs obtained from P1-sensitized NZNC as photocathode and nanostructured titania (TiO2) sensitized with squaraine VG10-C8 as photoanode display overall efficiencies of ca. 2% at their best and, more importantly, produced photocurrents that surpassed systematically the values obtained from the parent devices having one photoelectrochemical interface. Such a finding is a consequence of the diminished resistance of the electrolyte the thickness of which is systematically smaller in t-DSCs with respect to parent DSCs with a single photoelectrochemical junction and same interelectrodic separation. The results here reported demonstrate that a careful combination of photoelectroactive electrodes can lead to an increase in current density of more than 15% in the t-DSC with respect to single-junction DSCs employing the same photoelectrodes provided that the whole thickness of the t-DSC is the same as in the single photoelectrode DSC and the photoelectrodes in the t-DSC do not incur in short-circuit phenomena through the electrolyte. For the successful realization of t-DSCs another important aspect is the complementarity of the absorption properties of the chosen colorants with the sensitized electrodes having similar absorbance in their respective ranges of optical absorption. The latter condition in t-DSCs makes possible the achievement of photoactivity spectra with a uniform efficiency of conversion in the whole visible range. For the attainment of efficient t-DSCs the two different photoelectrodes from parent DSCs (i.e. the devices at a single photoeletrochemical interface), should generate anodic and cathodic photocurrent densities with very similar values. Such a matching of photocurrents requires a careful selection of the thickness values for the photoelectrodes especially in case of materials with considerably different characteristics of charge injection. The approach here considered is a promising one for the assembly of quasi-transparent photoelectrochemical tandem devices operating as smart windows that convert light into electrical power

Dose-finding study and pharmacogenomic analysis of fixed-rate infusion of gemcitabine, irinotecan and bevacizumab in pretreated metastatic colorectal cancer patients

BACKGROUND: To determine the dose-limiting toxicity (DLT), maximum tolerated dose, recommended dose (RD) and preliminary evidence of activity of escalating doses of irinotecan (CPT-11) fixed-dose-rate infusional gemcitabine (FDR-GMB) and bevacizumab in pretreated metastatic colorectal cancer (mCRC) patients. Pharmacogenomic analysis was performed to investigate the association between VEGF single-nucleotide polymorphisms and clinical outcome. PATIENTS AND METHODS: A total of 89 mCRC patients were recruited in a two-step study design; 28 were included in the dose-finding study and 59 in the pharmacogenomic analysis. The FDR-GMB of 1000 mg m⁻², bevacizumab 5 mg kg⁻¹ and CPT-11 doses ranging from 100 to 160 mg m⁻² were explored. The VEGF protein serum levels were quantified by EIA. Allelic discrimination was performed to genotype polymorphisms in the VEGF gene. RESULTS: CPT-11 RD was 150 mg m⁻². Diarrhoea and neutropenia were the DLT. After a median follow-up of 42 months, the median time to progression (TTP) and overall survival were 5.2 and 19.9 months, respectively. VEGF levels were significantly correlated with VEGF-2578AA and VEGF-460CC genotypes, and a trend was observed with VEGF+405GG genotype. The presence of any of these genotypes correlated with a longer median TTP (8.8 vs 4.5 months, P=0.04). CONCLUSION: The triplet combination tested in this study is effective and well tolerated. A possible predictive role for VEGF gene polymorphisms and baseline VEGF circulating levels is suggested

Estimación de los factores de emisión de las fuentes Móviles de la ciudad de bogotá

Se seleccionó, adaptó y aplicó una metodología práctica y económica para determinar las emisiones del parque automotor de la ciudad de Bogotá. La metodología está basada en mediciones de calidad de aire, parámetros meteorológicos, conteos de vehículos y la aplicación inversa de un modelo de calidad de aire. Se presentan los resultados de un estudio de trazadores con el cual se validó la aplicación del modelo empleado. Se reportan los factores de emisión promedio de los contaminantes evaluados para vehículos livianos, pesados y para todos los vehículos. Las emisiones de los vehículos pesados son considerablemente mayores a las de los vehículos livianos.

Combining chemotherapy and targeted therapies in metastatic colorectal cancer

Colorectal cancer remains one of the major causes of cancer death worldwide. During the past years, the development of new effective treatment options has led to a considerable improvement in the outcome of this disease. The advent of agents such as capecitabine, irinotecan, oxaliplatin, cetuximab and bevacizumab has translated into median survival times in the range of 2 years. Intense efforts have focused on identifying novel agents targeting specific growth factor receptors, critical signal transduction pathways or mediators of angiogenesis. In addition, several clinical trials have suggested that some of these molecularly targeted drugs can be safely and effectively used in combination with conventional chemotherapy. In this article we review various treatment options combining cytotoxic and targeted therapies currently available for patients with metastatic colorectal cancer

Boltzmann equation and hydrodynamic fluctuations

We apply the method of invariant manifolds to derive equations of generalized hydrodynamics from the linearized Boltzmann equation and determine exact transport coefficients, obeying Green-Kubo formulas. Numerical calculations are performed in the special case of Maxwell molecules. We investigate, through the comparison with experimental data and former approaches, the spectrum of density fluctuations and address the regime of finite Knudsen numbers and finite frequencies hydrodynamics.Comment: This is a more detailed version of a related paper: I.V. Karlin, M. Colangeli, M. Kroger, PRL 100 (2008) 214503, arXiv:0801.2932. It contains comparison between predictions and experiment, in particular. 11 pages, 6 figures, 2 table

Altered interaction with environmental reinforcers in major depressive disorder: Relationship to anhedonia

Anhedonia—defined as loss of interest or pleasure—is one of two core symptoms of major depressive disorder (MDD). Anhedonia may involve decreased enjoyment of potentially rewarding activities and decreased motivation to engage in such activities. Increased engagement with reinforcers—activities with the potential to be positive experiences—is a frequent target of cognitive-behavioral therapies. Nevertheless, how environmental reinforcers are perceived, and how decisions to approach or avoid them are made by individuals with MDD, is largely unknown. We developed an experimental Behavioral Approach Motivation Paradigm to study how activities are evaluated and approached in MDD. Twenty-one MDD participants and 23 healthy controls performed an experimental task that rated activity words for their hedonic value, then engaged in an approach-avoidance joystick task with each individual’s unique set of ‘liked’ and ‘disliked’ activity words. A negative correlation was observed between anhedonia and the number of ‘liked’ activities across participants. No significant difference between approach and avoidance behavior was found in direct comparisons between healthy controls and MDD participants; however, weaker avoidance and greater approach toward ‘disliked’ activities was found in MDD participants. This suggests negative bias in selecting environmental opportunities, potentially further compromising access to hedonic experiences in MDD