112 research outputs found
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High power wide bandgap cascode switching circuits
Emerging wide bandgap (WBG) power transistors are capable of improving the efficiency of mains voltage power electronic circuits. Several commercial WBG transistors are now available, but all exhibit undesirable gate drive characteristics. The cascode circuit has been suggested as a solution to this problem: WBG cascodes improve the switching speed, gate characteristics and noise immunity of devices, at the expense of greater on-state resistance. WBG cascodes have not, however, been widely accepted in commercial applications. Previous research has typically been too application-specific, with little practical information available for design engineers wishing to use them. This thesis addresses these shortcomings through a comprehensive investigation of practical design considerations for switch-mode cascode circuits. A SPICE simulation and simplified mathematical model are developed as design tools to give a detailed insight into cascode hard-switching behaviour and to aid cascode optimisation and device selection. The effects of the cascode configuration on static (DC) device performance are quantified for a silicon super-junction (SJ) metal-oxide-semiconductor field-effect transistor (MOSFET), silicon carbide (SiC) junction field-effect transistor JFET and SiC MOSFET. The on-state resistance penalty of the cascode configuration is shown to be modest and potentially mitigated by careful selection of HV transistor gate bias. There are few advantages to using silicon SJ MOSFETs in a cascode configuration, but both SiC MOSFET and JFET cascodes benefit from improved gate drive, reverse conduction and switching characteristics. SiC MOSFETs are shown to be better suited to efficient high temperature operation, while SiC JFETs are more appropriate for high current applications. Cascode switching losses are shown to be reduced compared to standalone devices, although reverse recovery losses can counteract this. Methods of controlling switching transients using gate resistors or feedback capacitors are investigated and shown to be effective. The effects of stray inductance on cascode switching are quantified experimentally for the first time. This corroborates other work and informs the layout of cascode circuits. The resilience of cascodes to severe is also demonstrated. The findings of this thesis are summarised in a practical design guide aimed at design engineers who wish to use this useful circuit
LHCb Upgraded RICH 1 Engineering Design Review Report
During the Long Shutdown 2 of the LHC, the LHCb collaboration will replace the upstream
Ring Imaging Cherenkov detector (RICH 1). The magnetic shield of the current RICH 1
will be modified, new spherical and plane mirrors will be installed and a new gas enclosure
will be manufactured. New photon detectors (multianode photomultiplier tubes) will be
used and these, together with their readout electronics, require a new mechanical support
system. This document describes the new optical arrangement of RICH 1, its engineering
design, installation and alignment. A summary of the project schedule and institute
responsibilities is provided
LHCb Upgraded RICH 1 Engineering Design Review Report
During the Long Shutdown 2 of the LHC, the LHCb collaboration will replace the upstream
Ring Imaging Cherenkov detector (RICH 1). The magnetic shield of the current RICH 1
will be modified, new spherical and plane mirrors will be installed and a new gas enclosure
will be manufactured. New photon detectors (multianode photomultiplier tubes) will be
used and these, together with their readout electronics, require a new mechanical support
system. This document describes the new optical arrangement of RICH 1, its engineering
design, installation and alignment. A summary of the project schedule and institute
responsibilities is provided
Les droits disciplinaires des fonctions publiques : « unification », « harmonisation » ou « distanciation ». A propos de la loi du 26 avril 2016 relative à la déontologie et aux droits et obligations des fonctionnaires
The production of tt‾ , W+bb‾ and W+cc‾ is studied in the forward region of proton–proton collisions collected at a centre-of-mass energy of 8 TeV by the LHCb experiment, corresponding to an integrated luminosity of 1.98±0.02 fb−1 . The W bosons are reconstructed in the decays W→ℓν , where ℓ denotes muon or electron, while the b and c quarks are reconstructed as jets. All measured cross-sections are in agreement with next-to-leading-order Standard Model predictions.The production of , and is studied in the forward region of proton-proton collisions collected at a centre-of-mass energy of 8 TeV by the LHCb experiment, corresponding to an integrated luminosity of 1.98 0.02 \mbox{fb}^{-1}. The bosons are reconstructed in the decays , where denotes muon or electron, while the and quarks are reconstructed as jets. All measured cross-sections are in agreement with next-to-leading-order Standard Model predictions
Observation of D⁰ Meson Decays to Π⁺π⁻μ⁺μ⁻ and K⁺K⁻μ⁺μ⁻ Final States
The first observation of the D⁰→π⁺π⁻μ⁺μ⁻ and D⁰→K⁺K⁻μ⁺μ⁻ decays is reported using a sample of proton-proton collisions collected by LHCb at a center-of-mass energy of 8 TeV, and corresponding to 2 fb⁻¹ of integrated luminosity. The corresponding branching fractions are measured using as normalization the decay D⁰→K⁻π⁺[μ⁺μ⁻][subscript ρ⁰/ω], where the two muons are consistent with coming from the decay of a ρ⁰ or ω meson. The results are B(D⁰→π⁺π⁻μ⁺μ⁻)=(9.64±0.48±0.51±0.97)×10⁻⁷ and B(D⁰→K⁺K⁻μ⁺μ⁻)=(1.54±0.27±0.09±0.16)×10⁻⁷, where the uncertainties are statistical, systematic, and due to the limited knowledge of the normalization branching fraction. The dependence of the branching fraction on the dimuon mass is also investigated
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Genomic footprints of activated telomere maintenance mechanisms in cancer
Abstract: Cancers require telomere maintenance mechanisms for unlimited replicative potential. They achieve this through TERT activation or alternative telomere lengthening associated with ATRX or DAXX loss. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, we dissect whole-genome sequencing data of over 2500 matched tumor-control samples from 36 different tumor types aggregated within the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium to characterize the genomic footprints of these mechanisms. While the telomere content of tumors with ATRX or DAXX mutations (ATRX/DAXXtrunc) is increased, tumors with TERT modifications show a moderate decrease of telomere content. One quarter of all tumor samples contain somatic integrations of telomeric sequences into non-telomeric DNA. This fraction is increased to 80% prevalence in ATRX/DAXXtrunc tumors, which carry an aberrant telomere variant repeat (TVR) distribution as another genomic marker. The latter feature includes enrichment or depletion of the previously undescribed singleton TVRs TTCGGG and TTTGGG, respectively. Our systematic analysis provides new insight into the recurrent genomic alterations associated with telomere maintenance mechanisms in cancer
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Genomic footprints of activated telomere maintenance mechanisms in cancer
Abstract: Cancers require telomere maintenance mechanisms for unlimited replicative potential. They achieve this through TERT activation or alternative telomere lengthening associated with ATRX or DAXX loss. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, we dissect whole-genome sequencing data of over 2500 matched tumor-control samples from 36 different tumor types aggregated within the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium to characterize the genomic footprints of these mechanisms. While the telomere content of tumors with ATRX or DAXX mutations (ATRX/DAXXtrunc) is increased, tumors with TERT modifications show a moderate decrease of telomere content. One quarter of all tumor samples contain somatic integrations of telomeric sequences into non-telomeric DNA. This fraction is increased to 80% prevalence in ATRX/DAXXtrunc tumors, which carry an aberrant telomere variant repeat (TVR) distribution as another genomic marker. The latter feature includes enrichment or depletion of the previously undescribed singleton TVRs TTCGGG and TTTGGG, respectively. Our systematic analysis provides new insight into the recurrent genomic alterations associated with telomere maintenance mechanisms in cancer
Recommended from our members
Genomic footprints of activated telomere maintenance mechanisms in cancer
Abstract: Cancers require telomere maintenance mechanisms for unlimited replicative potential. They achieve this through TERT activation or alternative telomere lengthening associated with ATRX or DAXX loss. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, we dissect whole-genome sequencing data of over 2500 matched tumor-control samples from 36 different tumor types aggregated within the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium to characterize the genomic footprints of these mechanisms. While the telomere content of tumors with ATRX or DAXX mutations (ATRX/DAXXtrunc) is increased, tumors with TERT modifications show a moderate decrease of telomere content. One quarter of all tumor samples contain somatic integrations of telomeric sequences into non-telomeric DNA. This fraction is increased to 80% prevalence in ATRX/DAXXtrunc tumors, which carry an aberrant telomere variant repeat (TVR) distribution as another genomic marker. The latter feature includes enrichment or depletion of the previously undescribed singleton TVRs TTCGGG and TTTGGG, respectively. Our systematic analysis provides new insight into the recurrent genomic alterations associated with telomere maintenance mechanisms in cancer
High-coverage whole-genome analysis of 1220 cancers reveals hundreds of genes deregulated by rearrangement-mediated cis-regulatory alterations.
The impact of somatic structural variants (SVs) on gene expression in cancer is largely unknown. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole-genome sequencing data and RNA sequencing from a common set of 1220 cancer cases, we report hundreds of genes for which the presence within 100 kb of an SV breakpoint associates with altered expression. For the majority of these genes, expression increases rather than decreases with corresponding breakpoint events. Up-regulated cancer-associated genes impacted by this phenomenon include TERT, MDM2, CDK4, ERBB2, CD274, PDCD1LG2, and IGF2. TERT-associated breakpoints involve ~3% of cases, most frequently in liver biliary, melanoma, sarcoma, stomach, and kidney cancers. SVs associated with up-regulation of PD1 and PDL1 genes involve ~1% of non-amplified cases. For many genes, SVs are significantly associated with increased numbers or greater proximity of enhancer regulatory elements near the gene. DNA methylation near the promoter is often increased with nearby SV breakpoint, which may involve inactivation of repressor elements
Measurement of the J/ψ pair production cross-section in pp collisions at TeV
The production cross-section of J/ψ pairs is measured using a data sample of pp collisions collected by the LHCb experiment at a centre-of-mass energy of TeV, corresponding to an integrated luminosity of 279 ±11 pb. The measurement is performed for J/ψ mesons with a transverse momentum of less than 10 GeV/c in the rapidity range 2.0 < y < 4.5. The production cross-section is measured to be 15.2 ± 1.0 ± 0.9 nb. The first uncertainty is statistical, and the second is systematic. The differential cross-sections as functions of several kinematic variables of the J/ψ pair are measured and compared to theoretical predictions.The production cross-section of pairs is measured using a data sample of collisions collected by the LHCb experiment at a centre-of-mass energy of , corresponding to an integrated luminosity of . The measurement is performed for mesons with a transverse momentum of less than in the rapidity range . The production cross-section is measured to be . The first uncertainty is statistical, and the second is systematic. The differential cross-sections as functions of several kinematic variables of the pair are measured and compared to theoretical predictions
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