Strategy for Enhancing the Dielectric Constant of Organic Semiconductors Without Sacrificing Charge Carrier Mobility and Solubility

Current organic semiconductors for organic photovoltaics (OPV) have relative dielectric constants (relative permittivities, epsilon(r)) in the range of 2-4. As a consequence, Coulombically bound electron-hole pairs (excitons) are produced upon absorption of light, giving rise to limited power conversion efficiencies. We introduce a strategy to enhance epsilon(r) of well-known donors and acceptors without breaking conjugation, degrading charge carrier mobility or altering the transport gap. The ability of ethylene glycol (EG) repeating units to rapidly reorient their dipoles with the charge redistributions in the environment was proven via density functional theory (DFT) calculations. Fullerene derivatives functionalized with triethylene glycol side chains were studied for the enhancement of epsilon(r) together with poly(p-phenylene vinylene) and diketo-pyrrolopyrrole based polymers functionalized with similar side chains. The polymers showed a doubling of epsilon(r) with respect to their reference polymers in identical backbone. Fullerene derivatives presented enhancements up to 6 compared with phenyl-C-61-butyric acid methyl ester (PCBM) as the reference. Importantly, the applied modifications did not affect the mobility of electrons and holes and provided excellent solubility in common organic solvents.

Heterogeneity in Dye-TiO2 Interactions Dictate Charge Transfer Efficiencies for Diketopyrrolopyrrole-Based Polymer Sensitized Solar Cells

Power conversion efficiency of a solar cell is a complex parameter which usually hides the molecular details of the charge generation process. For rationally tailoring the overall device efficiency of the dye-sensitized solar cell, detailed molecular understanding of photoinduced reactions at the dye-TiO2 interface has to be achieved. Recently, near-IR absorbing diketopyrrolopyrrole-based (DPP) low bandgap polymeric dyes with enhanced photostabilities have been used for TiO2 sensitization with moderate efficiencies. To improve the reported device performances, a critical analysis of the polymerTiO(2) interaction and electron transfer dynamics is imperative. Employing a combination of time-resolved optical measurements complemented by low temperature EPR and steady-state Raman spectroscopy on polymerTiO(2) conjugates, we provide direct evidence for photoinduced electron injection from the TDPP-BBT polymer singlet state into TiO2 through the C-O group of the DPP-core. A detailed excited state description of the electron transfer process in films reveals instrument response function (IRF) limited (<110 fs) charge injection from a minor polymer fraction followed by a picosecond recombination. The major fraction of photoexcited polymers, however, does not show injection indicating pronounced ground state heterogeneity induced due to nonspecific polymerTiO(2) interactions. Our work therefore underscores the importance of gathering molecular-level insight into the competitive pathways of ultrafast charge generation along with probing the chemical heterogeneity at the nanoscale within the polymerTiO2 films for optimizing photovoltaic device efficiencies.

Surface Freshwater Storage Variations in the Orinoco Floodplains Using Multi-Satellite Observations

Variations in surface water extent and storage are poorly characterized from regional to global scales. In this study, a multi-satellite approach is proposed to estimate the water stored in the floodplains of the Orinoco Basin at a monthly time-scale using remotely-sensed observations of surface water from the Global Inundation Extent Multi-Satellite (GIEMS) and stages from Envisat radar altimetry. Surface water storage variations over 2003-2007 exhibit large interannual variability and a strong seasonal signal, peaking during summer, and associated with the flood pulse. The volume of surface water storage in the Orinoco Basin was highly correlated with the river discharge at Ciudad Bolivar (R = 0.95), the closest station to the mouth where discharge was estimated, although discharge lagged one month behind storage. The correlation remained high (R = 0.73) after removing seasonal effects. Mean annual variations in surface water volume represented similar to 170 km(3), contributing to similar to 45% of the Gravity Recovery and Climate Experiment (GRACE)-derived total water storage variations and representing similar to 13% of the total volume of water that flowed out of the Orinoco Basin to the Atlantic Ocean.

Room-temperature bandlike transport and Hall effect in a high-mobility ambipolar polymer

The advent of a new class of high-mobility semiconducting polymers opens up a window to address fundamental issues in electrical transport mechanism such as transport between localized states versus extended state conduction. Here, we investigate the origin of the ultralow degree of disorder (E-a similar to 16 meV) and the ``bandlike'' negative temperature (T) coefficient of the field effect electron mobility: mu(e)(FET) (T) in a high performance (mu(e)(FET) > 2.5 cm(2) V-1 s(-1)) diketopyrrolopyrrole based semiconducting polymer. Models based on the framework of mobility edge with exponential density of states are invoked to explain the trends in transport. The temperature window over which the system demonstrates delocalized transport was tuned by a systematic introduction of disorder at the transport interface. Additionally, the Hall mobility (mu(e)(Hall)) extracted from Hall voltage measurements in these devices was found to be comparable to field effect mobility (mu(e)(FET)) in the high T bandlike regime. Comprehensive studies with different combinations of dielectrics and semiconductors demonstrate the effectiveness of rationale molecular design, which emphasizes uniform-energetic landscape and low reorganization energy.

A comparative phase 1 clinical trial to identify anti-infective mechanisms of vitamin D in people with HIV infection

Objectives:To determine if there is a biological mechanism that explains the association between HIV disease progression and increased mortality with low circulating vitamin D levels; specifically, to determine if restoring vitamin D levels induced T-cell functional changes important for antiviral immunity.Design:This was a pilot, open-label, three-arm prospective phase 1 study.Methods:We recruited 28 patients with low plasma vitamin D (<50nmol/l 25-hydroxyvitamin D3), comprising 17 HIV+ patients (11 on HAART, six treatment-naive) and 11 healthy controls, who received a single dose of 200000IU oral cholecalciferol. Advanced T-cell flow cytometry methods measured CD4(+) T-cell function associated with viral control in blood samples at baseline and 1-month after vitamin D supplementation.Results:One month of vitamin D supplementation restored plasma levels to sufficiency (>75nmol/l) in 27 of 28 patients, with no safety issues. The most striking change was in HIV+ HAART+ patients, where increased frequencies of antigen-specific T cells expressing macrophage inflammatory protein (MIP)-1 - an important anti-HIV blocking chemokine - were observed, with a concomitant increase in plasma MIP-1, both of which correlated significantly with vitamin D levels. In addition, plasma cathelicidin - a vitamin D response gene with broad antimicrobial activity - was enhanced.Conclusion:Vitamin D supplementation modulates disease-relevant T-cell functions in HIV-infected patients, and may represent a useful adjunct to HAART therapy. Copyright (C) 2015 Wolters Kluwer Health, Inc. All rights reserved.

Emergent photophenomena in three dimensional van der Waals heterostructures

We report on the fabrication and observation of emergent opto-electronic phenomena in three dimensional, micron-sized van der Waals heterostructures self-assembled from atomic layers of graphene and hexagonal boron nitride in varying ratios.

Toward a High-Resolution Monitoring of Continental Surface Water Extent and Dynamics, at Global Scale: from GIEMS (Global Inundation Extent from Multi-Satellites) to SWOT (Surface Water Ocean Topography)

Up to now, high-resolution mapping of surface water extent from satellites has only been available for a few regions, over limited time periods. The extension of the temporal and spatial coverage was difficult, due to the limitation of the remote sensing technique e.g., the interaction of the radiation with vegetation or cloud for visible observations or the temporal sampling with the synthetic aperture radar (SAR)]. The advantages and the limitations of the various satellite techniques are reviewed. The need to have a global and consistent estimate of the water surfaces over long time periods triggered the development of a multi-satellite methodology to obtain consistent surface water all over the globe, regardless of the environments. The Global Inundation Extent from Multi-satellites (GIEMS) combines the complementary strengths of satellite observations from the visible to the microwave, to produce a low-resolution monthly dataset () of surface water extent and dynamics. Downscaling algorithms are now developed and applied to GIEMS, using high-spatial-resolution information from visible, near-infrared, and synthetic aperture radar (SAR) satellite images, or from digital elevation models. Preliminary products are available down to 500-m spatial resolution. This work bridges the gaps and prepares for the future NASA/CNES Surface Water Ocean Topography (SWOT) mission to be launched in 2020. SWOT will delineate surface water extent estimates and their water storage with an unprecedented spatial resolution and accuracy, thanks to a SAR in an interferometry mode. When available, the SWOT data will be adopted to downscale GIEMS, to produce a long time series of water surfaces at global scale, consistent with the SWOT observations.

El lenguaje místico en Santa Catalina de Siena

Resumen: El lenguaje místico posee características propias, una de ellas es la inefabilidad. En este artículo la autora, basándose en los conceptos elaborados por M. De Certeau, analiza en primer lugar los rasgos que posee este lenguaje en la obra de Santa Catalina de Siena. En segundo lugar el artículo explora la matriz epistolar que posee Il Dialogo della Divina Provvidenza, la obra más importante de la santa. Aquí se observa de qué manera una gramática hablada conserva las entonaciones propias de la meditación que le da origen. Teniendo su origen en una carta Il Dialogo no sólo manifiesta el lenguaje oral usado en su época sino su estatuto privado y público a la vez.

La precarite de l’emploi et ses multiples impacts a la lumière du genre

Résumé: A l’heure où l’on évoque une “génération précaire” il est intéressant de s’interroger sur l’accroissement de la précarité de l’emploi en France et d’étudier ses éventuels effets sur les salariés. L’objectif de la présente recherche était d’observer les impacts causés par la précarité de l’emploi sur une population de référence et voir si ces effets différaient selon le sexe du salarié soumis à la précarité. Pour ce faire, nous avons soumis un questionnaire à deux groupes de travailleurs. Ce dernier portait sur la précarité de l’emploi et ses impacts en termes de stress, consommation de substances et impacts sur la sphère privée. Les résultats font apparaître des effets significatifs et des tendances qui existent sur certaines des dimensions interrogées (stress et consommation) entre le groupe de travailleurs précaires et non précaires. De plus, des effets entre hommes et femmes ont également été relevés. Par contre, nous n’avons pas d’effets observés sur la sphère privée de l’individu. Suite à l’absence d’effet constaté nous interrogeons la spécificité de la population. Aussi, nous envisageons de prolonger cette étude sur la recherche d’indicateurs concernant la précarité enseignante. Mots clés: précarité professionnelle, précarité du travail, précarité de l’emploi, travailleurs précaires, inégalités hommes femmes, stress, substances addictives, impact vie hors travail

STREAM Journal, Vol. 1, No. 4, pp 1-16. October-December 2002

CONTENTS: Hon Mun MPA Pilot Project on community-based natural resources management, by Nguyen Thi Hai Yen and Bernard Adrien. An experience with participatory research in Tam Giang Lagoon, Thua Thien-Hue, by Ton That Chat. Experiences and benefits of livelihoods analysis, by Michael Reynaldo, Orlando Arciaga, Fernando Gervacio and Catherine Demesa. Lessons learnt in implementing PRA in livelihoods analysis, by Nguyen Thi Thuy. Lessons learnt from livelihoods analysis and PRA in the Trao Reef Marine Reserve, by Nguyen Viet Vinh. Using the findings from a participatory poverty assessment in Tra Vinh Province, by Le Quang Binh.

Voyage dans le district des Diamans et sur le littoral du Brésil : suivi de notes sur quelques plantes caracteristiques et d'un precis de l'histoire des revolutions de l'empire bresilien, depuis le commencement du regne de Jean vi jusqu'a l'abdication de D. Pedro

As Voyages... são estudos completos, abrangendo todos os aspectos das regiões percorridas; servem de subsídio ao estudo das condições de vida no Brasil no século passado. "Fonte primordial de informações sobre os prédios coloniais do Rio de Janeiro, Minas Gerais, São Paulo, Santa Catarina e Goiás. Poucas obras no gênero atingem o valor de Saint-Hilarire. São clássicas e indispensáveis para o estudo do sul do Brasil, antes da Independência" segundo Borba de Moraes

Viagem a provincia de Santa Catharina : 1820

Auguste de Saint-Hilaire foi membro da Academia de Sciencias do Instituto de França. Professor da Faculdade de Sciencias de Patis. Do Instituto Historico e Geographlco Brasileiro, da Socie.dade de Medicina do Rio de Janeiro, etc .

Viagem às nascentes do rio S. Francisco e pela província de Goyaz

As Voyages... são estudos completos, abrangendo todos os aspectos das regiões percorridas; servem de subsídio ao estudo das condições de vida no Brasil no século passado. "Fonte primordial de informações sobre os prédios coloniais do Rio de Janeiro, Minas Gerais, São Paulo, Santa Catarina e Goiás. Poucas obras no gênero atingem o valor de Saint-Hilarire. São clássicas e indispensáveis para o estudo do sul do Brasil, antes da Independência" segundo Borba de Moraes.

Segunda viagem ao interior do Brasil : Espirito Santo

As Voyages... são estudos completos, abrangendo todos os aspectos das regiões percorridas; servem de subsídio ao estudo das condições de vida no Brasil no século passado. "Fonte primordial de informações sobre os prédios coloniais do Rio de Janeiro, Minas Gerais, São Paulo, Santa Catarina e Goiás. Poucas obras no gênero atingem o valor de Saint-Hilarire. São clássicas e indispensáveis para o estudo do sul do Brasil, antes da Independência" segundo Borba de Moraes.