202 research outputs found

    Double Linker Triphenylamine Dyes for Dye-Sensitized Solar Cells

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    Most organic dyes synthesized for dye-sensitized solar cells (DSC) use a single linker group to bind to the metal oxide photo-anode. Here we describe the synthesis and testing of two new triphenylamine dyes containing either two carboxylic acids 5-[2-(4-diphenylamino-phenyl)-vinyl]-isophthalic acid (10) or two cyanoacrylic acids (2Z, 2′Z)-3, 3′-(5-((E)-4-(diphenylamino) styryl)-1, 3-phenylene) bis (2-cyanoacrylic acid) (8) as linker groups. Full characterization data are reported for these dyes and their synthetic intermediates. DSC devices have been prepared from these new dyes either by passive or fast dyeing and the dyes have also been tested in co-sensitized DSC devices leading to a PCE (η = 5.4%) for the double cyanoacrylate linker dye (8) co-sensitized with D149. The dye:TiO2 surface interactions and dye excitations are interpreted using three modelling methods: density functional theory (at 0 K); molecular dynamics (at 298 K); time dependent density functional theory. The modelling results show the preferred orientation of both dyes on an anatase (1 0 1) TiO2 surface to be horizontal, and both the simulated and experimental absorption spectra of the dye molecules indicate a red shifted band for (8) compared to (10). This is in line with broader light harvesting and Jsc for (8) compared to (10)

    Novel benzothiazole half-squaraines: model chromophores to study dye–TiO2 interactions in dye-sensitized solar cells

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    We report the synthesis of 9 new half squaraine (HfSQ) dyes; 5 containing a benzothiazole moiety and 4 containing an indolenine moiety. X-ray single crystal structural and characterisation data have been correlated with device data to understand the widely reported but poorly understood influence of S heteroatoms on DSC device performance. The S heteroatom in these new dyes has also been used as an atomic probe of the dye–TiO2 interface to dye binding and orientation. Thus, for the first time, using the S heteroatom probe, angle-resolved X-ray photoelectron (AR-XPS) data have shown these dyes sit horizontally at the dye–TiO2 interface confirmed by DFT computer modelling of novel and analogous HfSQ dyes with a benzoindole backbone

    Liderazgo orientado a la gente en call centers

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    Propósito: Los call centers generan estrés y ausentismo en el personal y la literatura sugiere que el liderazgo orientado a la gente es el tipo adecuado de supervisión para tal situación. Este estudio comparó sus efectos versus los de otros tipos de liderazgo. Metodología: Datos de ausentismo de 379 representantes de servicios al cliente de un call center peruano fueron analizados y los representantes respondieron a un cuestionario sobre el Marco de Valores en Competencia y sus cuatro tipos de liderazgo. Turnos diurnos y nocturnos de trabajo fueron comparados. Resultados: Se observó que el ausentismo declina con el liderazgo orientado a la gente, aunque solo en el turno diurno, y la adición de liderazgos orientados al cambio, los resultados y el control resta validez a los modelos. Limitaciones/implicancias: Futuros estudios deberán abarcar el desempeño del trabajador. Los hallazgos sugieren una necesidad de volver a poner el foco teórico en las contingencias ambientales que afectan la eficacia del liderazgo. Originalidad/valor: Teóricos del liderazgo se preguntarán en qué circunstancias es efectivo el liderazgo múltiple. Gerentes de call centers apreciarán el valor organizacional del liderazgo orientado a la gente en el primer nivel de supervisión.Purpose: Call centers generate stress and absenteeism in staff and the literature suggests that people-oriented leadership is the right way of supervision for such a situation. This study compared its effects versus those of other types of leadership. Methodology: Absentee data of 379 representatives of customer services of a Peruvian call center were analyzed and the representatives answered a questionnaire about the Framework of Values in Competition and its four types of leadership. Day and night work shifts were compared. Results: It was observed that absenteeism declines with people-oriented leadership, although only during the day shift, and the addition of leadership oriented to change, results and control devalues models. Limitations/implications: Future studies should cover the performance of the worker. The findings suggest a need to re-focus the theoretical focus on environmental contingencies that affect leadership effectiveness. Originality/value: Leadership theorists will ask themselves in what circumstances the multiple leadership is effective. Call center managers will appreciate the organizational value of people-oriented leadership at the first level of supervision

    Liderazgo orientado a la gente en call centers

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    Purpose – Call centers generate stress and absenteeism in staff and the literature suggests that peopleoriented leadership is the right way of supervision for such a situation. This study compared its effects versus those of other types of leadership. Methodology – Absentee data of 379 representatives of customer services of a Peruvian call center were analyzed and the representatives answered a questionnaire about the Framework of Values in Competition and its four types of leadership. Day and night work shifts were compared. Results – It was observed that absenteeism declines with people-oriented leadership although only during the day shift and the addition of leadership oriented to change results and control devalues models. Limitations/implications – Future studies should cover the performance of the worker. The findings suggest a need to re-focus the theoretical focus on environmental contingencies that affect leadership effectiveness. Originality/value – Leadership theorists will ask themselves in what circumstances the multiple leadership is effective. Call center managers will appreciate the organizational value of people-oriented leadership at the first level of supervision.Propósito – Los call centers generan estrés y ausentismo en el personal y la literatura sugiere que el liderazgo orientado a la gente es el tipo adecuado de supervisión para tal situación. Este estudio comparó sus efectos versus los de otros tipos de liderazgo. Metodología – Datos de ausentismo de 379 representantes de servicios al cliente de un call center peruano fueron analizados y los representantes respondieron a un cuestionario sobre el Marco de Valores en Competencia y sus cuatro tipos de liderazgo. Turnos diurnos y  nocturnos de trabajo fueron comparados. Resultados – Se observó que el ausentismo declina con el liderazgo orientado a la gente aunque solo en el turno diurno y la adición de liderazgos orientados al cambio los resultados y el control resta validez a los modelos. Limitaciones/implicancias – Futuros estudios deberán abarcar el desempeño del trabajador. Los hallazgos sugieren una necesidad de volver a poner el foco teórico en las contingencias ambientales que afectan la eficacia del liderazgo. Originalidad/valor – Teóricos del liderazgo se preguntarán en qué circunstancias es efectivo el liderazgo múltiple. Gerentes de call centers apreciarán el valor organizacional del liderazgo orientado a la gente en el primer nivel de supervisión

    Nut production in Bertholletia excelsa across a logged forest mosaic: implications for multiple forest use

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    Although many examples of multiple-use forest management may be found in tropical smallholder systems, few studies provide empirical support for the integration of selective timber harvesting with non-timber forest product (NTFP) extraction. Brazil nut (Bertholletia excelsa, Lecythidaceae) is one of the world’s most economically-important NTFP species extracted almost entirely from natural forests across the Amazon Basin. An obligate out-crosser, Brazil nut flowers are pollinated by large-bodied bees, a process resulting in a hard round fruit that takes up to 14 months to mature. As many smallholders turn to the financial security provided by timber, Brazil nut fruits are increasingly being harvested in logged forests. We tested the influence of tree and stand-level covariates (distance to nearest cut stump and local logging intensity) on total nut production at the individual tree level in five recently logged Brazil nut concessions covering about 4000 ha of forest in Madre de Dios, Peru. Our field team accompanied Brazil nut harvesters during the traditional harvest period (January-April 2012 and January-April 2013) in order to collect data on fruit production. Three hundred and ninety-nine (approximately 80%) of the 499 trees included in this study were at least 100 m from the nearest cut stump, suggesting that concessionaires avoid logging near adult Brazil nut trees. Yet even for those trees on the edge of logging gaps, distance to nearest cut stump and local logging intensity did not have a statistically significant influence on Brazil nut production at the applied logging intensities (typically 1–2 timber trees removed per ha). In one concession where at least 4 trees ha-1 were removed, however, the logging intensity covariate resulted in a marginally significant (0.09) P value, highlighting a potential risk for a drop in nut production at higher intensities. While we do not suggest that logging activities should be completely avoided in Brazil nut rich forests, when a buffer zone cannot be observed, low logging intensities should be implemented. The sustainability of this integrated management system will ultimately depend on a complex series of socioeconomic and ecological interactions. Yet we submit that our study provides an important initial step in understanding the compatibility of timber harvesting with a high value NTFP, potentially allowing for diversification of forest use strategies in Amazonian Perù

    SN 2022joj: A Potential Double Detonation with a Thin Helium shell

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    We present photometric and spectroscopic data for SN 2022joj, a nearby peculiar Type Ia supernova (SN Ia) with a fast decline rate (Δm15,B=1.4\rm{\Delta m_{15,B}=1.4} mag). SN 2022joj shows exceedingly red colors, with a value of approximately BV1.1{B-V \approx 1.1} mag during its initial stages, beginning from 1111 days before maximum brightness. As it evolves the flux shifts towards the blue end of the spectrum, approaching BV0{B-V \approx 0} mag around maximum light. Furthermore, at maximum light and beyond, the photometry is consistent with that of typical SNe Ia. This unusual behavior extends to its spectral characteristics, which initially displayed a red spectrum and later evolved to exhibit greater consistency with typical SNe Ia. We consider two potential explanations for this behavior: double detonation from a helium shell on a sub-Chandrasekhar-mass white dwarf and Chandrasekhar-mass models with a shallow distribution of 56Ni\rm{^{56}Ni}. The shallow nickel models could not reproduce the red colors in the early light curves. Spectroscopically, we find strong agreement between SN 2022joj and double-detonation models with white dwarf masses around 1 M\rm{M_{\odot}} and thin He-shell between 0.01 and 0.02 M\rm{M_{\odot}}. Moreover, the early red colors are explained by line-blanketing absorption from iron-peak elements created by the double detonation scenario in similar mass ranges. However, the nebular spectra composition in SN 2022joj deviates from expectations for double detonation, as we observe strong [Fe III] emission instead of [Ca II] lines as anticipated from double detonation models. More detailed modeling, e.g., including viewing angle effects, is required to test if double detonation models can explain the nebular spectra

    Plasmodium falciparum heterochromatin protein 1 binds to tri-methylated histone 3 lysine 9 and is linked to mutually exclusive expression of var genes

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    Increasing experimental evidence shows a prominent role of histone modifications in the coordinated control of gene expression in the human malaria parasite Plasmodium falciparum. The search for the histone-mark-reading machinery that translates histone modifications into biological processes, such as formation of heterochromatin and antigenic variation is of foremost importance. In this work, we identified the first member of a histone modification specific recognition protein, an orthologue of heterochromatin protein 1 (PfHP1). Analysis of the PfHP1 amino-acid sequence revealed the presence of the two characteristic HP1 domains: a chromodomain (CD) and a chromo shadow domain (CSD). Recombinant CD binds to di- and tri-methylated lysine 9 from histone H3, but not to unmodified or methylated histone H3 in lysine 4. PfHP1 is able to interact with itself to form dimers, underlying its potential role in aggregating nucleosomes to form heterochromatin. Antibodies raised against PfHP1 detect this molecule in foci at the perinuclear region. ChIP analysis using anti-PfHP1 shows that this protein is linked to heterochromatin of subtelomeric non-coding repeat regions and monoallelic expression of the major virulence var gene family. This is the first report implicating an HP1 protein in the control of antigenic variation of a protozoan parasite

    No association between polymorphisms/haplotypes of the vascular endothelial growth factor gene and preeclampsia

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    <p>Abstract</p> <p>Background</p> <p>Preeclampsia (PE) is the first worldwide cause of death in pregnant women, intra-uterine growth retardation, and fetal prematurity. Some vascular endothelial grown factor gene (<it>VEGF</it>) polymorphisms have been associated to PE and other pregnancy disturbances. We evaluated the associations between <it>VEGF </it>genotypes/haplotypes and PE in Mexican women.</p> <p>Methods</p> <p>164 pregnant women were enrolled in a case-control study (78 cases and 86 normotensive pregnant controls). The rs699947 (-2578C/A), rs1570360 (-1154G/A), rs2010963 (+405G/C), and rs25648 (-7C/T), <it>VEGF </it>variants were discriminated using Polymerase Chain Reaction - Restriction Fragment Length Polymorphism (PCR-RFLP) methods or Taqman single nucleotide polymorphism (SNP) assays.</p> <p>Results</p> <p>The proportions of the minor allele for rs699947, rs1570360, rs2010963, and rs25648 <it>VEGF </it>SNPs were 0.33, 0.2, 0.39, and 0.17 in controls, and 0.39, 0.23, 0.41, and 0.15 in cases, respectively (<it>P </it>values > 0.05). The most frequent haplotypes of rs699947, rs1570360, rs2010963, and rs25648 <it>VEGF </it>SNPs, were C-G-C-C and C-G-G-C with frequencies of 0.39, 0.21 in cases and 0.37, 0.25 in controls, respectively (<it>P </it>values > 0.05)</p> <p>Conclusion</p> <p>There was no evidence of an association between <it>VEGF </it>alleles, genotypes, or haplotypes frequencies and PE in our study.</p

    Summary of session A4 at the GRG18 conference: Alternative Theories of Gravity

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    More than 50 abstracts were submitted to the A4 session on "Alternatives Theories of Gravity" at the GRG18 conference. About 30 of them were scheduled as oral presentations, that we summarize below. We do not intend to give a critical review, but rather pointers to the corresponding papers. The main topics were (i) brane models both from the mathematical and the phenomenological viewpoints; (ii) Einstein-Gauss-Bonnet gravity in higher dimensions or coupled to a scalar field; (iii) modified Newtonian dynamics (MOND); (iv) scalar-tensor and f(R) theories; (v) alternative models involving Lorentz violations, noncommutative spacetimes or Chern-Simons corrections.Comment: 9 pages, no figure; the GRG18 conference was held in Sydney, Australia, 8-13 July 200

    The Fourteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the extended Baryon Oscillation Spectroscopic Survey and from the second phase of the Apache Point Observatory Galactic Evolution Experiment

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    The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in operation since July 2014. This paper describes the second data release from this phase, and the fourteenth from SDSS overall (making this, Data Release Fourteen or DR14). This release makes public data taken by SDSS-IV in its first two years of operation (July 2014-2016). Like all previous SDSS releases, DR14 is cumulative, including the most recent reductions and calibrations of all data taken by SDSS since the first phase began operations in 2000. New in DR14 is the first public release of data from the extended Baryon Oscillation Spectroscopic Survey (eBOSS); the first data from the second phase of the Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2), including stellar parameter estimates from an innovative data driven machine learning algorithm known as "The Cannon"; and almost twice as many data cubes from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous release (N = 2812 in total). This paper describes the location and format of the publicly available data from SDSS-IV surveys. We provide references to the important technical papers describing how these data have been taken (both targeting and observation details) and processed for scientific use. The SDSS website (www.sdss.org) has been updated for this release, and provides links to data downloads, as well as tutorials and examples of data use. SDSS-IV is planning to continue to collect astronomical data until 2020, and will be followed by SDSS-V.Comment: SDSS-IV collaboration alphabetical author data release paper. DR14 happened on 31st July 2017. 19 pages, 5 figures. Accepted by ApJS on 28th Nov 2017 (this is the "post-print" and "post-proofs" version; minor corrections only from v1, and most of errors found in proofs corrected
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