Band structures of Cu2nSnS4 and Cu2nSnSe4 from many-body methods

We calculate the band structures of kesterite and stannite Cu2ZnSnS4 and Cu2ZnSnSe4, using a state-of-the-art self-consistent GW approach. Our accurate quasiparticle states allow to discuss: the dependence of the gap on the anion displacement; the key-role of the non-locality of the exchange-correlation potential to obtain good structural parameters; the reliability of less expensive hybrid functional and GGA+U approaches. In particular, we show that even if the band gap is correctly reproduced by hybrid functionals, the band-edge corrections are in disagreement with self-consistent GW results, which has decisive implications for the positioning of the defect levels in the band gap.Comment: accepted for publication in App. Phys. Lett. (2011

Molecular systematics and patterns of morphological evolution in the Centropagidae (Copepoda: Calanoida) of Argentina

Recent studies have shown the value of complementing standard taxonomy with genetic analyses to reveal cryptic diversity and to aid in the understanding of patterns of evolution. We surveyed variation in the COI mitochondrial gene in members of the three genera of centropagid copepods from the inland waters in Argentina. In general, we found a close association between molecular and morphological systematics in this group. Similar to findings for marine calanoids, genetic distances within Boeckella species were modest ( 11%). Parabroteas is currently monotypic, although we detected cryptic genetic diversity, with two lineages showing 5.5% divergence. In contrast, Karukinka was not a valid genus, apparently representing an interesting and atavistic offshoot of B. poppei, a result reinforcing the value of considering both morphological and molecular evidence. Moreover, we used combined genetic and morphological information, analysed with maximum likelihood methods, to evaluate the common assumption that evolution tends to proceed via the loss of structures in crustaceans. Although analysis of other taxa and character types is required to evaluate fully the reduction hypothesis, our results suggest that structures may be gained readily as well as lost. © 2007 The Linnean Society of London.Fil:Menu-Marque, S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Transient Thermo-Mechanical Analysis of the TPSG4 Beam Diluter

A new extraction channel is being built in the Super Proton Synchrotron (SPS) Long Straight Section 4 (LSS4) to transfer proton beams to the Large Hadron Collider (LHC) and also to the CERN Neutrino to Gran Sasso (CNGS) target. The beam is extracted in a fast mode during a single turn. For this purpose a protection of the MSE copper septum coil, in the form of a beam diluting element placed upstream, will be required to cope with the new failure modes associated with the fast extraction operation. The present analysis focuses on the thermo-mechanical behavior of the proposed TPSG4 diluter element irradiated by a fast extracted beam (up to 4.9 x 10^13 protons per 7.2 mus pulse) from the SPS. The deposited energy densities, estimated from primary and secondary particle simulations using the high-energy particle transport code FLUKA, were converted to internal heat generation rates taken as a thermal load input for the finite-element engineering analyses code ANSYS. According to the time dependence of the extracted beam, the transient solutions were obtained for coupled heat transfer, structural deformation, and shock wave problems. The results are given for the space distribution and the time evolution of temperatures and stresses in the most critical parts of the TPSG4 beam diluting element followed by the MSE copper septum coil. In the worst case of impact of the full LHC ultimate beam, the maximum temperatures remain safely below the melting point. However, the maximum equivalent stresses may slightly exceed the elastic limit in the aluminium section of the diluter. Also, the predicted maximum temperature rise in the MSE septum coil exceeds the design value

Thermal Performance of the LHC Connection Cryostat

The 16 connection cryostats for the Large Hadron Collider (LHC) being built at CERN are designed to fill the gap existing between the dispersion suppressor zones and the standard arcs of the accelerator. The first connection cryostat was cold tested down to superfluid helium temperature in August 2005, and the measured thermal performance was as expected. This paper presents the test results and a new thermal modeling of the connection cryostat based on the measurement of the thermal resistances of the braids used for thermalisation, allowing the precise determination of cool down times and equilibrium temperatures of the shielding under various conditions such as lead heating

The Argentinean species of the genus Boeckella (Copepoda, Calanoida, Centropagidae) and related taxa

En la presente tesis se realizan sustanciales aportes al conocimiento sistemático de lacopepodofauna planctónica de aguas interiores de la Argentina, en particular de la Familia Centropagidae, perteneciente al Orden Calanoida. Esta familia abarcaespecies tanto marinas, como estuariales y de ambientes estrictamente interiores,tanto de agua dulce como salinos. De todos los miembros de la familia Centropagidaeque han logrado colonizar las aguas continentales el género Boeckella es por lejos elque ha tenido más éxito, ya sea que lo midamos en diversidad específica, en amplitudgeográfica o en abundancia. Bayly(1992a) hizo una revisión de las especiessudamericanas de Boeckella, que es aquí ampliada con la redescripción de Boeckellagibbosa (Brehm 1935) y la descripción de B. diamantina Menu-Marque y Zúñiga, 1994y B. antiqua Menu-Marque y Balseiro, 2000. La clave de determinación de lasespecies sudamericanas de Boeckella, elaborada por dicho autor sobre la base de lasquintas patas de los machos, es modificada para incluir las mencionadas especies. Seconsidera a B. titicacae (Harding, 1955) como sinónimo de B. gracilipes Daday, 1901,siguiendo el criterio de Villalobos y Zúñiga (1991). Se provee un panorama actualizado de la distribuciónde las especies de Boeckella enla Argentina, agregándose 220 nuevas citas a las que ya figuraban en la literatura. Sepresentan mapas de distribuciónde cada una de las 17 especies identificadas en la Argentina hasta el presente. Aun con la inclusión de las especies recientementehalladas y la gran cantidad de localidades citadas para especies de Boeckella desde lapublicación del clásico trabajo de Ringuelet (1958), se mantiene para la Argentinacontinental el esquema general de distribución fundamentalmente andino-patagónica "con desborde marginal por el este en el sur de la subregión vecina (en Argentina y Uruguay)" que describiera el mencionado autor. Si bien es necesario recabar másdatos sobre las localidades de Boeckella en los otros países de América del Sur, esprobable que su distribución ayude a reforzar la idea de la subregión Andina propuestasobre la base de otros taxa de artrópodos por Morrone (1996) o, más aún, su recientepropuesta de elevarla a la categoría de región biogeográfica (Morrone, 1999). Se analizan las relaciones biogeográflcas entre las especies de Boeckella de Américadel Sur utilizando un enfoque panbiogeográfico por medio de una metodología deanálisis de trazos. Para una nueva especie hallada en Tierra del Fuego, muy afín a Boeckella antiqua,pero cuyas características excepcionales en el quinto par de patas del macho laexcluyen del género Boeckella, se erige el género Karukinka, representado por Karukinka fueguina n. gen, n. sp. Los caracteres diagnósticos más sobresalientes deesta especie son referidos al quinto par de patas del macho, que en las especies delos géneros continentales Boeckella, Parabroteas, Neoboeckella, Hemiboeckella, Calamoecia, Gladioferens y en las especies marinas del género Centropages,cumplen una función estrictamente reproductiva, mientras que en el nuevo taxónconservan además función nadadora. Los rasgos más sobresalientes son la ausenciade garra en el exopodito izquierdo, la terminación de ambos exopoditos en segmentosespatulados, que del lado derecho culmina en una espina apenas curvada y, por sobretodo, la presencia de sedas nadadoras en el margen interno de ambos exopoditos. Todos éstos son considerados caracteres plesiomórficos. Se presenta una clave de identificación, basada sobre la estructura del quinto par depatas de los machos, para los géneros de Centropagidae conocidos de América del Sur. El descubrimiento de Karukinka n. gen. permite, sobre la base de un detallado estudiomorfológico, establecer comparaciones con especies del íntimamente relacionadogénero Boeckella. Se concluye que la presencia en aguas continentales deorganismos con caracteres mucho más primitivosque los de los actuales miembrosmarinos de la familia, habla a favor de la extinción del antepasado centropágido quedio origen a todos los miembros, tanto marinos como continentales de la familia. Se descartan las hipótesis de Bayly(1964) y Maly(1996) que proponen al géneromarino Centropages como el antecesor del cual derivaron todas las especies de Centropagidae que habitan aguas continentales. Se propone, en cambio, que tanto lasespecies marinas como continentales de la mencionada familia derivan de unantecesor, ya extinguido, cuyos machos poseían quintas patas con doble funciónnadadora y reproductiva. Esta hipótesis se basa sobre la morfología de la nuevaespecie hallada en un ambiente continental de agua dulce de Tierra del Fuego, Karukinka fueguina.The present thesis provides substantial knowledge on the systematics of the planktoniccopepod fauna of inland waters of Argentina, particularly of the family Centropagidae,belonging to the order Calanoida. This family includes representatives of marine, estuarine and strictly inland waters,both of freshwater and saline environments. Of all the members of the Centropagidaewhich have been able to colonize continental waters, the genus Boeckella is by far themost successful, whether we measure it by specific diversity, geographic range orabundance. Bayly (1992) published a revision of the South American species of Boeckella, which is here completed with the redescription of Boeckella gibbosa (Brehm 1935) and the detailed description of B. diamantina Menu-Marque & Zúñiga, 1994 and B. antiqua Menu-Marque & Balseiro, 2000. The identification key for the South American species of Boeckella prepared by Bayly (1992), based upon the structure ofthe male fifth legs, is here modified to include the above mentioned species. B.titicacae (Harding, 1955) is considered a junior synonym of B. gracilipes Daday, 1901,following the criterion of Villalobos & Zúñiga (1991). A complete updated list of records of the Argentinean species of Boeckella is provided,about 220 new localities are added to those previously registered from the literature. Distributional maps of the 17 species so far identified in Argentina are presented. Evenwith the inclusion of the species recently found and the large amount of new localitiescited for Boeckella species since the publication of Ringuelet's review (1958), the basicscheme for continental Argentina of an Andean-Patagonic distribution "marginallyspilling to the east on the south of the neighbouring subregion (in Argentina and Uruguay)" described by the above mentioned author still holds. Even if more data fromother South American countries are necessary, it is probable that the distribution of thespecies of Boeckella come to reinforce the idea of the Andean subregion proposed by Morrone (1996) or, still more, support his recent proposal to raise it to the category ofbiogeographical region (Morrone, 1999). The biogeographical relationships of the South American species of Boeckella areconsidered using a panbiogeographic approach based on a track analysismethodology. A new genus, Karukinka, represented by Karukinka fueguina n. gen, n. sp. is erectedto accommodate a new species very closer related to Boeckella antiqua, but whoseexceptional male fifth leg characters exclude it from the genus Boeckella. Its mostoutstanding diagnostic characters are all referred to the male fifth pair of legs, which inthe species of the continental Boeckella, Parabroteas, Neoboeckella, Hemíboeckella, Calamoecia, and Gladioferens genera and in the marine species of the genus Centropages have a strictly reproductive role, while in the new taxon they preserve aswimming function. The most important diagnostic traits are the absence of a claw inthe left exopodite, the ending of both exopodites in spatulated segments, the right ofwhich ends in a slightly curved spine which could hardly be considered a claw, andabove all, the presence of swimming setae in the inner margin of both exopodites. Allof these are considered plesiomorphic characters. A key based upon the structure of the male fifth legs is presented to identify the generaof the family Centropagidae so far known for South America. The discovery of Karukinka n. gen. permits, upon a detailed morphological study, toestablish comparisons with species of the closely related genus Boeckella. It isconcluded that the presence in inland water environments of members of the familypossessing far more primitive characters than those of their marine counterpartsspeaks in favour of the extinction of the marine ancestor which gave rise to all theextant Centropagidae, both marine and continental. The hypotheses of Bayly (1964b) and Maly(1996) which propose the marine genus Centropages as the ancestor from which all the species of Centropagidae which inhabitcontinental waters are derived, is rejected. On the contrary, it is proposed that all thespecies of this family, be them marine or continental, derive from an extinguishedancestor, whose males possessed fifth legs with both swimming and reproductivefunction. This hypothesis is based upon the morphology of Karukinka fueguina found inan ephemeral freshwater pond in Tierra del Fuego.Fil: Menu Marque, Silvina A.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Study of mechanical behavior on single use bags welding under gamma irradiation

Since a long time, biopharmaceutical industry utilizes more and more single use plastic bags due to its very easy use (long shelf-lives, mechanical properties), preparation, and storage properties (oxygen and water barriers). These plastic bags are composed of two welded multilayer polymer films. To ensure the function of the closure and the non-contamination from the external environment, welding must answer to several parameters according to norm (“ISO 15747,” 2018) and standard (F02 Committee, n.d.). In this present study, the behavior of weldings on Ethylene Vinyl Acetate (EVA) single use bags under gamma irradiation have been studied. Mechanical tests have been performed at several gamma irradiation doses (from 0 kGy to 270 kGy) and at different location of the bag (Figure 1). The first objective is to study the impact of gamma irradiation dose on the welding mechanical tensile behavior. The second objective is to evaluate the impact of the welding location on the welding tensile properties. Each tensile curve (Figure 2) has been decomposed in 6 characteristic points which were evaluated with Principal Component Analysis (PCA): Ultimate Tensile strength at break (UTS), Ultimate elongation or elongation at break, 1st Yield-Strength (Y1 Strength), 1st Yield-Strain (Y1 Strain), 2nd Yield-Strength (Y2 Strength), 2nd Yield-Strain (Y2 Strain). The study showed that weldings are never impacted during tensile testing: this evaluation reveals that in fine the film cracks before the welding modification. Its function of closure and bag content preservation from external environment is fully achieved whatever the gamma irradiation dose and the welding location. Only the multilayer film on both sides of the welding is altered after 100% elongation strain. The EVA bag showed no degradation up to 115 kGy whereas they become to be altered at 270 kGy. The welding location on EVA bag showed different film mechanical behavior correlated to the polymer film extrusion process orientation. Please click Additional Files below to see the full abstract

Short Term Effects of Hurricane Irma on the Phytoplankton of Lake Louise, Georgia, USA

Natural disturbances such as fires and severe storms can have profound impacts on the hydrology and ecology of inland waters, potentially altering the structure and function of the ecosystem for extended periods of time. Studies of the initial impacts are, however, uncommon. Here we report on the short-term impacts of Hurricane Irma in the structure of the phytoplankton association in Lake Louise, a small blackwater lake in southern Georgia. Irma hit the region on September 11, 2017, with tropical storm force winds. The event corresponded to a period during which we were conducting routine weekly monitoring of environmental conditions in the lake. Parameters monitored included temperature, dissolved oxygen, conductivity, and light from the surface to a depth of 6 m. Chlorophyll concentrations and the structure of the phytoplankton were also determined at 1 m intervals from the surface to a depth of 5 m. An increase in the overall abundance of phytoplankton in the upper meter of the lake and a decrease in the abundance of phytoplankton deeper in the water column were observed immediately after Hurricane Irma. These decreases were followed by a bloom involving several species of cyanobacteria beginning about four weeks after the passage of the hurricane. Signatures of the passage of the hurricane were erased in early December as cooler temperatures created isothermal conditions in the lake

How intramolecular hydrogen bonding (IHB) controls the C-ON bond homolysis in alkoxyamines

International audienceRecent amazing results (Nkolo et al., Org. Biomol. Chem., 2017, 6167) on the effect of solvents and polarity on the C-ON bond homolysis rate constants kd of alkoxyamine R1R2NOR3 led us to re-investigate the antagonistic effect of intramolecular hydrogen-bonding (IHB) on kd. Here, IHB is investigated both in the nitroxyl fragment R1R2NO and in the alkyl fragment R-3, as well as between fragments, that is, the donating group on the alkyl fragment and the accepting group on the nitroxyl fragment, and conversely. It appears that IHB between fragments (inter IHB) strikingly decreases the homolysis rate constant kd, whereas IHB within the fragment (intra IHB) moderately increases kd. For one alkoxyamine, the simultaneous occurrence of IHB within the nitroxyl fragment and between fragments is reported. The protonation effect is weaker in the presence than in the absence of IHB. A moderate solvent effect is also observed

High-vacuum-compatible high-power Faraday isolators for gravitational-wave interferometers

Faraday isolators play a key role in the operation of large-scale gravitational-wave detectors. Second-generation gravitational-wave interferometers such as the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and Advanced Virgo will use high-average-power cw lasers (up to 200 W) requiring specially designed Faraday isolators that are immune to the effects resulting from the laser beam absorption–degraded isolation ratio, thermal lensing, and thermally induced beam steering. In this paper, we present a comprehensive study of Faraday isolators designed specifically for high-performance operation in high-power gravitational-wave interferometers

DC-readout of a signal-recycled gravitational wave detector

All first-generation large-scale gravitational wave detectors are operated at the dark fringe and use a heterodyne readout employing radio frequency (RF) modulation-demodulation techniques. However, the experience in the currently running interferometers reveals several problems connected with a heterodyne readout, of which phase noise of the RF modulation is the most serious one. A homodyne detection scheme (DC-readout), using the highly stabilized and filtered carrier light as local oscillator for the readout, is considered to be a favourable alternative. Recently a DC-readout scheme was implemented on the GEO 600 detector. We describe the results of first measurements and give a comparison of the performance achieved with homodyne and heterodyne readout. The implications of the combined use of DC-readout and signal-recycling are considered.Comment: 11 page