Development of Innovative Heat Sinks for Power Electronics Cooling within the More Electrical Aircraft

Peer ReviewedPostprint (published version

Phytoplankton and particle size spectra indicate intense mixotrophic dinoflagellates grazing from summer to winter

Abstract Mixotrophic dinoflagellates (MTD) are a diverse group of organisms often responsible for the formation of harmful algal blooms. However, the development of dinoflagellate blooms and their effects on the plankton community are still not well explored. Here we relate the species succession of MTD with parallel changes of phytoplankton size spectra during periods of MTD dominance. We used FlowCAM analysis to acquire size spectra in the range 2–200 μm every one or two weeks from July to December 2007 at Helgoland Roads (Southern North Sea). Most size spectra of dinoflagellates were bimodal, whereas for other groups, e.g. diatoms and autotrophic flagellates, the spectra were unimodal, which indicates different resource use strategies of autotrophs and mixotrophs. The biomass lost in the size spectrum correlates with the potential grazing pressure of MTD. Based on size-based analysis of trophic linkages, we suggest that mixotrophy, including detritivory, drives species succession and facilitates the formation of bimodal size spectra. Bimodality in particular indicates niche differentiation through grazing of large MTD on smaller MTD. Phagotrophy of larger MTD may exceed one of the smaller MTD since larger prey was more abundant than smaller prey. Under strong light limitation, a usually overlooked refuge strategy may derive from detritivory. The critical role of trophic links of MTD as a central component of the plankton community may guide future observational and theoretical research.</jats:p

Diseño de un modelo de gestión empresarial para aumentar la productividad en la Corporación Saona S.A.C., Chimbote 2023

El objetivo de la presente tesis fue Diseñar un modelo de gestión empresarial para aumentar la productividad en la CORPORACIÓN SAONA S.A.C., Chimbote 2023. La metodología fue de tipo aplicada, cuantitativa, de diseño pre – experimental. La muestra fue aplicada a 08 empleados, se les hizo una encuesta para conocer los datos de la gestión empresarial y la productividad. En los resultados mostraron que, en el pre – test la gestión empresarial obtuvo una puntuación de 64.79% y la productividad un 67.19%; después, en el post – test la gestión empresarial obtuvo una puntuación de 94.06% y la productividad un 97.92%. En conclusión, un nuevo modelo de gestión empresarial logró aumentar la productividad de la CORPORACIÓN SAONA S.A.C

Resonant Raman scattering based approaches for the quantitative assessment of nanometric ZnMgO layers in high efficiency chalcogenide solar cells

This work reports a detailed resonant Raman scattering analysis of ZnMgO solid solution nanometric layers that are being developed for high efficiency chalcogenide solar cells. This includes layers with thicknesses below 100 nm and compositions corresponding to Zn/(Zn + Mg) content rations in the range between 0% and 30%. The vibrational characterization of the layers grown with different compositions and thicknesses has allowed deepening in the knowledge of the sensitivity of the different Raman spectral features on the characteristics of the layers, corroborating the viability of resonant Raman scattering based techniques for their non-destructive quantitative assessment. This has included a deeper analysis of different experimental approaches for the quantitative assessment of the layer thickness, based on (a) the analysis of the intensity of the ZnMgO main Raman peak; (b) the evaluation of the changes of the intensity of the main Raman peak from the subjacent layer located below the ZnMgO one; and (c) the study of the changes in the relative intensity of the first to second/third order ZnMgO peaks. In all these cases, the implications related to the presence of quantum confinement effects in the nanocrystalline layers grown with different thicknesses have been discussed and evaluated

Structural and vibrational properties of α- and π-SnS polymorphs for photovoltaic applications

Tin sulphide (SnS) has attracted the attention of the photovoltaic (PV) community due to the combination of desirable optical properties, and its binary and earth abundant elemental composition, which should lead to relatively simple synthesis. However, currently the best SnS based PV device efficiency remains at 4.36%. Limited performance of this material is attributed to band gap alignment issues, deviations in doping concentration and poor film morphology. In this context Raman spectroscopy (RS) analysis can be useful as it facilitates the accurate evaluation of material properties. In this study we present a RS study, supported by X-ray diffraction and wavelength dispersive X-ray measurements, of α- and π-SnS thin films. In particular a complete description of SnS vibrational properties is made using six excitation wavelengths, including excitation energies coupled with certain optical band to band transitions, which leads to close to resonance measurement conditions. This study describes an in-depth analysis of the Raman spectra of both SnS structural polymorphs, including the differences in the number of observed peaks, with their relative intensities and Raman shift. Additionally, we evaluate the impact of low temperature heat treatment on SnS. These results explicitly present how the variation of the [S]/[Sn] ratio in samples deposited by different methods can lead to significant and correlated shifts in the relative positions of Raman peaks, which is only observed in the α-SnS phase. Furthermore, we discuss the suitability of using Raman spectroscopy based methodologies to extract fine stoichiometric variations in different α-SnS samples.</p

The importance of back contact modification in Cu2ZnSnSe4 solar cells: The role of a thin MoO2 layer

Cu2ZnSn(SxSe1-x)4 (CZTSSe) photovoltaic absorbers could be the earth-abundant and low toxicity replacement for the already commercialized CuIn1-xGaxSe2 (CIGS) thin film technology. In order to make this possible, specific research efforts applied to the bulk, front and back interfaces must be performed with the aim of improving CZTSSe performance. In this paper the importance of back contact modification to obtain high efficiency Cu2ZnSnSe4 (CZTSe) solar cells and to increase a paramount and limiting parameter such as VOC is highlighted. Several Mo configurations (monolayer, bi-layer and tri-layer) with different electrical and morphological properties are investigated in CZTSe solar cells. An optimum tri-layer configuration in order to minimize overselenization of the back contact during thermal annealing while keeping reasonable electrical features is defined. Additionally, a thin intermediate MoO2 layer that results in a very effective barrier against selenization and innovative way to efficiently assist in the CZTSe absorber sintering is introduced. The use of this layer enhances grain growth and subsequently the efficiency of solar cells increases via major VOC and FF improvement. An efficiency increase from 7.2% to 9.5% is obtained using a Mo tri-layer with a 20 nm intermediate MoO2 layerThis research was supported by the Framework 7 program under the project KESTCELLS (FP7-PEOPLE-2012-ITN-316488), by MINECO (Ministerio de Economía y Competitividad de España) under the SUNBEAM project (ENE2013-49136-C4-1-R), and by European Regional Development Founds (ERDF, FEDER Programa Competitivitat de Catalunya 2007–2013). Authors from IREC and the University of Barcelona belong to the M-2E (Electronic Materials for Energy) Consolidated Research Group and the XaRMAE Network of Excellence on Materials for Energy of the “Generalitat de Catalunya”. M.E-R. thanks the MINECO for the FPI-MINECO (BES-2011-045774), Y.S. for the PTA fellowship (PTA2012-7852-A), SG for the FPI fellowship (BES-2014-068533), M.P. for the MINECO postdoctoral fellow (FPDI-2013-18968), E.S. and R.C. for the “Ramon y Cajal” fellowship (RYC-2011-09212) and (RYC-2011-08521) respectively, and H.X. thanks the “China Scholarship Council” fellowship (CSC Nº 201206340113

Structural and vibrational properties of α- and π-SnS polymorphs for photovoltaic applications

Tin sulphide (SnS) has attracted the attention of the photovoltaic (PV) community due to the combination of desirable optical properties, and its binary and earth abundant elemental composition, which should lead to relatively simple synthesis. However, currently the best SnS based PV device efficiency remains at 4.36%. Limited performance of this material is attributed to band gap alignment issues, deviations in doping concentration and poor film morphology. In this context Raman spectroscopy (RS) analysis can be useful as it facilitates the accurate evaluation of material properties. In this study we present a RS study, supported by X-ray diffraction and wavelength dispersive X-ray measurements, of α- and π-SnS thin films. In particular a complete description of SnS vibrational properties is made using six excitation wavelengths, including excitation energies coupled with certain optical band to band transitions, which leads to close to resonance measurement conditions. This study describes an in-depth analysis of the Raman spectra of both SnS structural polymorphs, including the differences in the number of observed peaks, with their relative intensities and Raman shift. Additionally, we evaluate the impact of low temperature heat treatment on SnS. These results explicitly present how the variation of the [S]/[Sn] ratio in samples deposited by different methods can lead to significant and correlated shifts in the relative positions of Raman peaks, which is only observed in the α-SnS phase. Furthermore, we discuss the suitability of using Raman spectroscopy based methodologies to extract fine stoichiometric variations in different α-SnS samples.</p

CoFlex TOP: A Teleoperation System for Flexible Ureteroscopy

In flexible ureteroscopy (fURS) for kidney stones, the renal collecting system is inspected and stones are removed with a flexible ureteroscope (FU). One alternative to the fragmentation of stones and their removal with the help of graspers or extraction baskets is the dusting of stones with laser light. To support a single surgeon during a fURS procedure, in particular with the fine manipulation during dusting, we developed the CoFlex TOP system for the teleoperation of a handheld FU with three degrees of freedom. This paper describes the overall structure of the system, its kinematics and the hardware and software components. Sub- sequently, the system properties and its position repeatability are investigated and the system's feasibility for a tip positioning task in virtual reality is evaluated in a user study. Finally, we discuss the implications of the evaluation and sketch possible foci of a user study with urology surgeons

Soil fertility and drought interact to determine large variations in wood production for a hyperdominant Amazonian tree species

Introduction: The productivity of the Amazon Rainforest is related to climate and soil fertility. However, the degrees to which these interactions influence multiannual to decadal variations in tree diameter growth are still poorly explored. Methods: To fill this gap, we used radiocarbon measurements to evaluate the variation in tree growth rates over the past decades in an important hyperdominant species, Eschweilera coriacea (Lecythidaceae), from six sites in the Brazilian Amazon that span a range of soil properties and climate. Results: Using linear mixed-effects models, we show that temporal variations in mean annual diameter increment evaluated over a specific time period reflect interactions between soil fertility and the drought index (SPEI-Standardized Precipitation and Evapotranspiration Index). Discussion: Our results indicate that the growth response of trees to drought is strongly dependent on soil conditions, a facet of forest productivity that is still underexplored, and which has great potential for improving predictions of future tropical tree growth in the face of projected climate change

Tectono-thermal history of an exhumed thrust-sheet-top basin : an example from the south Pyrenean thrust belt

This paper presents a new balanced structural cross-section of the Jaca thrust-sheet-top basin of the southern Pyrenees combined with paleo-thermometry and apatite fission track (AFT) thermochronology data. The cross-section, based on field data and interpretation of industrial seismic reflection profiles, allows refinement of previous interpretations of the south-directed thrust system, involving the identification of new thrust faults, and of the kinematic relationships between basement and cover thrusts from the middle Eocene to the early Miocene. AFT analysis shows a southward decrease in the level of fission track resetting, from totally reset Paleozoic rocks and lower Eocene turbidites (indicative of heating to Tmax>~120°C), to partially reset middle Eocene turbidites and no/very weak resetting in the upper Eocene-lower Oligocene molasse (Tmax<~60°C). AFT results indicate a late Oligocene-early Miocene cooling event throughout the Axial Zone and Jaca Basin. Paleo-maximum temperatures determined by vitrinite reflectance measurements and Raman spectroscopy of carbonaceous material reach up to ~240°C at the base of the turbidite succession. Inverse modelling of AFT and vitrinite reflectance data with the QTQt software for key samples show compatibility between vitrinite-derived Tmax and the AFT reset level for most of the samples. However, they also suggest that the highest temperatures determined in the lowermost turbidites correspond to a thermal anomaly rather than burial heating, possibly due to fluid circulation during thrust activity. From these results, we propose a new sequential restoration of the south Pyrenean thrust system propagation and related basin evolution