2,362 research outputs found

    Measurements and TCAD simulation of novel ATLAS planar pixel detector structures for the HL-LHC upgrade

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    The LHC accelerator complex will be upgraded between 2020-2022, to the High-Luminosity-LHC, to considerably increase statistics for the various physics analyses. To operate under these challenging new conditions, and maintain excellent performance in track reconstruction and vertex location, the ATLAS pixel detector must be substantially upgraded and a full replacement is expected. Processing techniques for novel pixel designs are optimised through characterisation of test structures in a clean room and also through simulations with Technology Computer Aided Design (TCAD). A method to study non-perpendicular tracks through a pixel device is discussed. Comparison of TCAD simulations with Secondary Ion Mass Spectrometry (SIMS) measurements to investigate the doping profile of structures and validate the simulation process is also presented.Comment: 9 pages, 7 figures, PIXEL201

    Imaging and Dynamics of Light Atoms and Molecules on Graphene

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    Observing the individual building blocks of matter is one of the primary goals of microscopy. The invention of the scanning tunneling microscope [1] revolutionized experimental surface science in that atomic-scale features on a solid-state surface could finally be readily imaged. However, scanning tunneling microscopy has limited applicability due to restrictions, for example, in sample conductivity, cleanliness, and data aquisition rate. An older microscopy technique, that of transmission electron microscopy (TEM) [2, 3] has benefited tremendously in recent years from subtle instrumentation advances, and individual heavy (high atomic number) atoms can now be detected by TEM [4 - 7] even when embedded within a semiconductor material [8, 9]. However, detecting an individual low atomic number atom, for example carbon or even hydrogen, is still extremely challenging, if not impossible, via conventional TEM due to the very low contrast of light elements [2, 3, 10 - 12]. Here we demonstrate a means to observe, by conventional transmision electron microscopy, even the smallest atoms and molecules: On a clean single-layer graphene membrane, adsorbates such as atomic hydrogen and carbon can be seen as if they were suspended in free space. We directly image such individual adatoms, along with carbon chains and vacancies, and investigate their dynamics in real time. These techniques open a way to reveal dynamics of more complex chemical reactions or identify the atomic-scale structure of unknown adsorbates. In addition, the study of atomic scale defects in graphene may provide insights for nanoelectronic applications of this interesting material.Comment: 9 pages manuscript and figures, 9 pages supplementary informatio

    In-situ grown Cu dendrites plasmonically enhance electrocatalytic hydrogen evolution on facet-engineered Cu₂O

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    Electrocatalytic hydrogen evolution reaction (HER) is widely regarded as one of the most efficient and sustainable strategies for hydrogen production. Up to now, most electrocatalysis research related to HER mainly focuses on stand-alone electrocatalysis and fails to pay attention to the integration of other driving forces such as light. Herein, Cu2 O nanostructures with different exposed crystal facets were synthesized by wet chemical methods for electrocatalytic HER, and it was found that the octahedral Cu2 O nanostructures with exposed crystal planes of (111) (O-Cu2 O) had the best hydrogen evolution performance. Density functional theory (DFT) calculations found that the better HER performance on Cu2 O (111) facets was attributed to the lower energy barrier in the Heyrovsky step. Operando Raman spectroscopy and ex-situ characterization techniques showed that Cu2 O was reduced during HER, in which Cu dendrites were grown on the surface of the Cu2 O nanostructures, resulting in the better HER performance of O-Cu2 O after HER (O-Cu2 O-A) compared with that of the as-prepared O-Cu2 O. DFT calculations indicated that the charge transfer at the Cu2 O/Cu interface enhanced its surface electron concentration. Under illumination, the onset potential of O-Cu2 O-A is ca. 52 mV positive than that of O-Cu2 O, which is induced by the plasmon-activated electrochemical system consisting of Cu2 O and the in-situ generated Cu dendrites. Incident photon-to-current efficiency (IPCE) measurements, ultraviolet-visible (UV-Vis) spectroscopy and X-ray photoelectron spectroscopy (XPS) demonstrate the hot electron injection (HEI) from Cu dendrites to Cu2 O. Ab initio nonadiabatic molecular dynamics (NAMD) simulations revealed that the transfer of photogenerated electrons (27 fs) from Cu dendrites to Cu2 O nanostructures is faster than electron relaxation (170 fs), enhancing its surface plasmons activity, and the HEI of Cu dendrites increases the charge density of Cu2 O. These make the energy level of the catalyst be closer to that of H+ /H2 , evidenced by the plasmon-enhanced HER electrocatalytic activity. This article is protected by copyright. All rights reserved

    Variants Within TSC2 Exons 25 and 31 Are Very Unlikely to Cause Clinically Diagnosable Tuberous Sclerosis

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    Inactivating mutations in TSC1 and TSC2 cause tuberous sclerosis complex (TSC). The 2012 international consensus meeting on TSC diagnosis and management agreed that the identification of a pathogenic TSC1 or TSC2 variant establishes a diagnosis of TSC, even in the absence of clinical signs. However, exons 25 and 31 of TSC2 are subject to alternative splicing. No variants causing clinically diagnosed TSC have been reported in these exons, raising the possibility that such variants would not cause TSC. We present truncating and in‐frame variants in exons 25 and 31 in three individuals unlikely to fulfil TSC diagnostic criteria and examine the importance of these exons in TSC using different approaches. Amino acid conservation analysis suggests significantly less conservation in these exons compared with the majority of TSC2 exons, and TSC2 expression data demonstrates that the majority of TSC2 transcripts lack exons 25 and/or 31 in many human adult tissues. In vitro assay of both exons shows that neither exon is essential for TSC complex function. Our evidence suggests that variants in TSC2 exons 25 or 31 are very unlikely to cause classical TSC, although a role for these exons in tissue/stage specific development cannot be excluded

    PAK2 is an effector of TSC1/2 signaling independent of mTOR and a potential therapeutic target for Tuberous Sclerosis Complex

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    Tuberous sclerosis complex (TSC) is caused by inactivating mutations in either TSC1 or TSC2 and is characterized by uncontrolled mTORC1 activation. Drugs that reduce mTOR activity are only partially successful in the treatment of TSC, suggesting that mTOR-independent pathways play a role in disease development. Here, kinome profiles of wild-type and Tsc2-/- mouse embryonic fibroblasts (MEFs) were generated, revealing a prominent role for PAK2 in signal transduction downstream of TSC1/2. Further investigation showed that the effect of the TSC1/2 complex on PAK2 is mediated through RHEB, but is independent of mTOR and p21RAC. We also demonstrated that PAK2 over-activation is likely responsible for the migratory and cell cycle abnormalities observed in Tsc2-/- MEFs. Finally, we detected high levels of PAK2 activation in giant cells in the brains of TSC patients. These results show that PAK2 is a direct effector of TSC1-TSC2-RHEB signaling and a new target for rational drug therapy in TSC

    Estudo de caso : avaliação do impacto no desempenho e satisfação da força de trabalho com a reestruturação organizacional do departamento de gestão integrada (DGI) - UFRGS

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    A administração pública no Brasil é um tema bastante estudado e criticado por diversos autores, pois ainda está imersa em dúvidas acerca das melhores governanças, práticas de gestão e estruturas organizacionais que impactem positivamente o desempenho e, consequentemente, promova o crescimento e vigor dessas instituições. O setor da administração pública em nosso país é constantemente criticado pela disfunção da burocracia pertinente ao sistema, bem como a dificuldade de acompanhar as mudanças que são vivenciadas pelo setor privado, por exemplo. No presente trabalho, é realizado um estudo de caso no Departamento de Gestão Integrada (DGI) da PROPLAN – UFRGS (Universidade Federal do Rio Grande do Sul), que passou por mudanças na sua atuação e função como departamento perante a instituição. As modificações que foram propostas ao departamento podem ser divididas em dois campos. O primeiro em relação à orientação e função do departamento como um todo, que também influenciou uma mudança de mesmo teor em suas divisões internas. O segundo campo, pelo qual as modificações passaram, é o da força de trabalho, ou seja, pessoas. Em outras palavras, uma realocação de funções que promovesse um melhor aproveitamento das competências dos membros foi promovida. O presente estudo traça um paralelo entre o período anterior as modificações em contraste com o período após as modificações, verificando, junto ao departamento, questões ligadas ao desempenho e satisfação das pessoas que trabalham nesse espaço. Com os resultados, foi possível concluir que houve um aumento na satisfação geral dos membros, bem como aspectos relativos ao desempenho foram impactados positivamente pelas mudanças promovidas no DGI.Public administration in Brazil is a theme widely studied and criticized by authors in this area, because it stills immerged in doubts concerning the best managing practices, governance and organizational structures that impact positively the performance and, as a result, generate growth in this kind of institutions. The public administration sector in Brazil is constantly criticized by its burocracy disfunction related to the system it is involved, as well as a strong effort to be up to date with the changes that happen in the private sector of the economy. In this study, its presented a case study in the “Departamento de Gestão Integrada - (DGI)” which can be understood as the department responsible for the strategy deployment in the institution, that has been under several changes in its function an operation towards the university (Universidade Federal do Rio Grande do Sul – UFRGS). The changes on the department can be split in two, in order to be easily understood. The first is related to the orientation and function of the entire department, that influenced changes in its intern divisions. The second point in which the changes went through is people functions in the department. In other words, shifts in personal roles in the department aiming a better exploitation of each ones capacities and competences was implemented. This case study draws a parallel between the period before the changes and after them, verifying issues linked to the department’s overall performance and personal satisfaction with the role each person has in the organization. Analyzing the results, it was possible to conclude an increase in people satisfaction and aspects related to the department’s performance

    Prototype ATLAS IBL Modules using the FE-I4A Front-End Readout Chip

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    The ATLAS Collaboration will upgrade its semiconductor pixel tracking detector with a new Insertable B-layer (IBL) between the existing pixel detector and the vacuum pipe of the Large Hadron Collider. The extreme operating conditions at this location have necessitated the development of new radiation hard pixel sensor technologies and a new front-end readout chip, called the FE-I4. Planar pixel sensors and 3D pixel sensors have been investigated to equip this new pixel layer, and prototype modules using the FE-I4A have been fabricated and characterized using 120 GeV pions at the CERN SPS and 4 GeV positrons at DESY, before and after module irradiation. Beam test results are presented, including charge collection efficiency, tracking efficiency and charge sharing.Comment: 45 pages, 30 figures, submitted to JINS
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