430 research outputs found

    Quantum effects on Higgs-strahlung events at Linear Colliders within the general 2HDM

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    The associated production of neutral Higgs bosons with the Z gauge boson is investigated in the context of the future linear colliders, such as the ILC and CLIC, within the general two-Higgs-doublet model (2HDM). We compute the corresponding production cross-sections at one-loop, in full consistency with the available theoretical and phenomenological constraints. We find that the wave-function renormalization corrections to the external Higgs fields are the dominant source of the quantum effects, which turn out to be large and negative, and located predominantly in the region around \tan\beta=1 and moderate values of the parameter \lambda_5 (being \lambda_5 < 0). This behavior can be ultimately traced back to the enhancement potential of the triple Higgs boson self-couplings, a trademark feature of the 2HDM with no counterpart in the Higgs sector of the Minimal Supersymmetric Standard Model. The predicted Higgs-strahlung rates comfortably reach a few tens of femtobarn, which means barely 10^3 - 10^4 events per 500 inverse femtobarn of integrated luminosity. Due to their great complementarity, we argue that the combined analysis of the Higgs-strahlung events and the previously computed one-loop Higgs-pair production processes could be instrumental to probe the structure of the Higgs sector at future linac facilities.Comment: LaTeX, 16 pages, 9 Figures, 2 Tables. Extended discussion, references added, matches published version in Phys. Rev.

    Threading Through Macrocycles Enhances the Performance of Carbon Nanotubes as Polymer Fillers

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    In this work we study the reinforcement of polymers by mechanically interlocked derivatives of single-walled carbon nanotubes (SWNTs). We compare the mechanical properties of fibers made of polymers and of composites with pristine single-walled carbon nanotubes (SWNTs), mechanically interlocked derivatives of SWNTs (MINTs) and the corresponding supramolecular models. Improvements of both Young's modulus and tensile strength of up to 200 % were observed for the polystyrene-MINTs samples with an optimized loading of just 0.01 wt.%, while the supramolecular models with identical chemical composition and loading showed negligible or even detrimental influence. This behavior is found for three different types of SWNTs and two types of macrocycles. Molecular dynamics simulations show that the polymer adopts an elongated conformation parallel to the SWNT when interacting with MINT fillers, irrespective of the macrocycle chemical nature, whereas a more globular structure is taken upon facing with either pristine SWNTs or supramolecular models. The MINT composite architecture thus leads to a more efficient exploitation of the axial properties of the SWNTs and of the polymer chain at the interface, in agreement with experimental results. Our findings demonstrate that the mechanical bond imparts distinctive advantageous properties to SWNT derivatives as polymer fillers.Comment: 39 pages, 19 figure

    PTGER1 and PTGER2 receptors mediate regulation of progesterone synthesis and type 1 11β-hydroxysteroid dehydrogenase activity by prostaglandin E2 in human granulosa–lutein cells

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    In luteinizing granulosa cells, prostaglandin E2 (PGE2) can exert luteotrophic actions, apparently via the cAMP signalling pathway. In addition to stimulating progesterone synthesis, PGE2 can also stimulate oxidation of the physiological glucocorticoid, cortisol, to its inactive metabolite, cortisone, by the type 1 11β-hydroxysteroid dehydrogenase (11βHSD1) enzyme in human granulosa–lutein cells. Having previously shown these human ovarian cells to express functional G-protein coupled, E-series prostaglandin (PTGER)1, PTGER2 and PTGER4 receptors, the aim of this study was to delineate the roles of PTGER1 and PTGER2 receptors in mediating the effects of PGE2 on steroidogenesis and cortisol metabolism in human granulosa–lutein cells. PGE2-stimulated concentration-dependent increases in both progesterone production and cAMP accumulation (by 1·9±0·1- and 18·7±6·8-fold respectively at 3000 nM PGE2). While a selective PTGER1 antagonist, SC19220, could partially inhibit the steroidogenic response to PGE2 (by 55·9±4·1% at 1000 nM PGE2), co-treatment with AH6809, a mixed PTGER1/PTGER2 receptor antagonist, completely abolished the stimulation of progesterone synthesis at all tested concentrations of PGE2 and suppressed the stimulation of cAMP accumulation. Both PGE2 and butaprost (a preferential PTGER2 receptor agonist) stimulated concentration-dependent increases in cortisol oxidation by 11βHSD1 (by 42·5±3·1 and 40·0±3·0% respectively, at PGE2 and butaprost concentrations of 1000 nM). Co-treatment with SC19220 enhanced the ability of both PGE2 and butaprost to stimulate 11βHSD1 activity (by 30·2±0·2 and 30·5±0·6% respectively), whereas co-treatment with AH6809 completely abolished the 11βHSD1 responses to PGE2 and butaprost. These findings implicate the PTGER2 receptor–cAMP signalling pathway in the stimulation of progesterone production and 11βHSD1 activity by PGE2 in human granulosa–lutein cells

    Applications of Direct Injection Soft Chemical Ionisation-Mass Spectrometry for the Detection of Pre-blast Smokeless Powder Organic Additives

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    Analysis of smokeless powders is of interest from forensics and security perspectives. This article reports the detection of smokeless powder organic additives (in their pre-detonation condition), namely the stabiliser diphenylamine and its derivatives 2-nitrodiphenylamine and 4-nitrodiphenylamine, and the additives (used both as stabilisers and plasticisers) methyl centralite and ethyl centralite, by means of swab sampling followed by thermal desorption and direct injection soft chemical ionisation-mass spectrometry. Investigations on the product ions resulting from the reactions of the reagent ions H3O+ and O2+ with additives as a function of reduced electric field are reported. The method was comprehensively evaluated in terms of linearity, sensitivity and precision. For H3O+, the limits of detection (LoD) are in the range of 41-88 pg of additive, for which the accuracy varied between 1.5 and 3.2%, precision varied between 3.7 and 7.3% and linearity showed R20.9991. For O2+, LoD are in the range of 72 to 1.4 ng, with an accuracy of between 2.8 and 4.9% and a precision between 4.5 and 8.6% and R20.9914. The validated methodology was applied to the analysis of commercial pre-blast gun powders from different manufacturers.(VLID)4826148Accepted versio

    Sistema combinado UASB+MBR para la eliminación biológica de contaminantes emergentes, materia orgánica y nutrientes en aguas residuales urbanas

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    Conventional treatment systems can be inefficient in removing and / or degradation of emerging contaminants (ECs) present in urban wastewater. Although aerobic biological technologies such as membrane bioreactors (MBR) have proven to be very effective, certain compounds are highly removed by anaerobic biological systems. This research focuses on the study of a system that combines the advantages of biological treatment aerobic and anaerobic in order to optimize the removal of ECs, organic matter and nutrients. For this have been analyzed the operation of a pilot plant consists of an Upflow Anaerobic Sludge Blanket (UASB) followed by a submerged MBR external configuration. The research was carried out in the first phase with aerobic biomass in suspension and in a second phase with supported biomass. The results confirm the synergy of both systems, achieving high removal efficiencies of the most persistent pollutants such as carbamazepine, diazepam, diclofenac, simazine, atrazine, linuron and terbuthylazine. Regarding the elimination of organic matter, nitrogen and phosphorous, overall yields were close to 97%, 45% y 35% respectively, being particularly high when biomass was supported.Los sistemas convencionales de depuración pueden ser poco eficientes en la eliminación y/o degradación de contaminantes emergentes (ECs) presentes en las aguas residuales urbanas. Aunque tecnologías biológicas aerobias como los biorreactores de membranas (MBR) han demostrado ser muy eficaces, determinados compuestos se eliminan en mayor grado mediante sistemas biológicos anaerobios. Esta investigación se centra en el estudio de un sistema que reune las ventajas de la depuración biológica aerobia y de la anaerobia con el fin de optimizar la eliminación de ECs, materia orgánica y nutrientes. Para ello se ha analizado el funcionamiento de una planta piloto compuesta por un reactor anaerobio de lechos fluidizados de flujo ascendente (UASB) seguido de un MBR en configuración externa sumergida. La investigación se ha realizado en una primera fase con la biomasa aerobia en suspensión y en una segunda fase con biomasa soportada. Los resultados confirman el efecto sinérgico de ambos sistemas, alcanzándose altos rendimientos de eliminación de los contaminantes más persistentes como carbamazepina, diazepam, diclofenaco, simazina, atrazina, linurón y terbutilazina. En cuanto a la eliminación de materia orgánica, nitrógeno y fósforo, los rendimientos globales fueron cercanos al 97%, 45 % y 35% respectivamente, siendo especialmente altos en la fase de biomasa soportada.Esta investigación ha sido desarrollada en el Instituto del Agua y las Ciencias Ambientales de la Universidad de Alicante en el marco del Proyecto CTM 2013-46669: Eliminación y/o degradación de contaminantes emergentes en aguas mediante tratamientos combinados, del Ministerio de Economía y Competitividad de España

    Confort ambiental en vivienda de interés social en Cali.

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    Los escritores realizan un análisis de la situación de confort a nivel urbano y de VIS en la ciudad de Cali. Presentan en forma condensada la información de vientos, insolación e isotermas típicas, y determinan las islas de calor. Un examen critico indica que la planeación urbana es deficiente en términos de sostenibilidad y confort, y que podría mejorarse potenciado micro climas reguladores de altas temperaturas, y diseño paisajística urbano. Respecto a las VIS, muestran estadísticas y ediciones que conforman la percepción común de in confortabilidad dándole un carácter científico a esta creencia. Los autores respaldan técnicamente la evaluación del confort y muestran el método, e indican que la oferta de urbanizaciones VIS no posee respaldo científico en sus pretensiones de sostenibilidad. Finalmente demuestran, con una aplicación práctica, que es posible mejorar la VIS hasta lograr en confort de manera económica siguiendo una secuencia lógica y académica.El confort ambiental y el clima en la vivienda de interés social (VIS) -- Fenomenología energética del edificio -- Relación del paisaje y del contexto urbano de la vivienda de interés social con el confort -- Caso de estudio- indagaciones -- Vivienda de interés social (VIS) sostenible - propuesta de mejoramient

    Field analysis of solar PV-based collective systems for rural electrification.

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    This article analyses the long-term performance of collective off-grid photovoltaic (PV) systems in rural areas. The use of collective PV systems for the electrification of small medium-size villages in developing countries has increased in the recent years. They are basically set up as stand-alone installations (diesel hybrid or pure PV) with no connection with other electrical grids. Their particular conditions (isolated) and usual installation places (far from commercial/industrial centers) require an autonomous and reliable technology. Different but related factors affect their performance and the energy supply; some of them are strictly technical but others depend on external issues like the solar energy resource and users’ energy and power consumption. The work presented is based on field operation of twelve collective PV installations supplying the electricity to off-grid villages located in the province of Jujuy, Argentina. Five of them have PV generators as unique power source while other seven include the support of diesel groups. Load demand evolution, energy productivity and fuel consumption are analyzed. Besides, energy generation strategies (PV/diesel) are also discussed

    Wanting to become PE teachers in Spain: connections between previous experiences and particular beliefs about school Physical Education and the development of professional teacher identities

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    Physical Education (PE) teachers have previous experiences that both shape their particular beliefs about the role and purpose of this school subject as well as their pedagogical practice. The present study aims to examine and deepen our knowledge of future Spanish PE teachers’ previous experiences of and beliefs about PE that condition their pedagogical practice and intentionality within this school subject. The data reported on in this paper were generated through questionnaires, life-history stories and semi-structured interviews with 24 initial teacher education students in the second year of a degree specialising in PE at a Spanish university. The data was analysed using content and narrative (thematic) analysis. The students, far from being tabula rasa, in their responses show how their previous socialisation period, their subjectivities and identities constitute particular beliefs about PE teaching. More specifically, the results reveal four key themes in the student teachers’ experiences and beliefs that represent four different factors influencing future PE teacher identities: (1) ‘Sport’; (2) ‘PE for health’; (3) ‘A focus on pedagogy’; and (4) ‘A critical orientation’. In conclusion, the study reaffirms the need for further reflection on how previous experiences and beliefs influence the development of professional teacher identities as part of initial teacher education in PE

    Preparation of hcp and fcc Ni and Ni/NiO Nanoparticles Using a Citric Acid Assisted Pechini-Type Method

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    The preparation and characterization of hcp and fcc Ni and Ni/NiO nanoparticles is reported. Ni and Ni/NiO nanoparticles were obtained starting from a precursor material prepared using a citric assisted Pechini-type method and, then, followed by a calcination of the precursor in air at either 400 or 600°C for different times. The precursor was analyzed using thermogravimetric and differential thermal methods (TGA-DTA), and the resulting nanoparticles were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and vibrational sample magnetometry. Nanoparticles showed a phase transformation for Ni from hcp to fcc and/or to fcc NiO structure as the calcination time increased. The influence of the phase transition and the formation of NiO on the magnetic properties of the samples are discussed
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