89 research outputs found
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An efficient technique for excess loop delay compensation in continuous-time ΔΣ modulators
A highly-digital technique is proposed for excess loop delay (ELD)
compensation in multi-bit continuous-time ΔΣ modulators. A digitally
controlled reference switching matrix is used to replace the power-hungry
signal adder and extra DAC driving the quantizer, which are
commonly used in ELD compensation. With the proposed technique,
the feedback DAC is embedded in the quantizer and implemented by a
few switches. Thus it allows low voltage and low-power operation.This paper is a postprint of a paper submitted to and accepted for publication in Electronics Letters and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at IET Digital Library. It can be found at: http://digital-library.theiet.org/content/journals/el
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Teraohm on-chip resistance realisation using switched capacitor topologies
Two large-resistance realisation schemes are proposed using switched-capacitor
circuits. The equivalent resistance of the array realisation
increases as the third power of the number of capacitor pairs, and
that of the ladder realisation increases exponentially. The equivalent
resistance for the ladder scheme also grows with the capacitance
ratio. Using these schemes, large resistances can be fabricated with
standard CMOS process in an affordable chip area. Simulation
results show that very low pole frequency (~ 9 Hz in the example)
can be achieved with practical element values, and with a capacitance
spread of only 10 in a three-stage ladder.This is the author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the Institution of Engineering and Technology and can be found at: http://digital-library.theiet.org/content/journals/el
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Multi-Step Extended-Counting Analog-to- Digital Converters
Extended-counting A/D converters are proposed which achieve a high
accuracy by performing the conversion in several cycles. During the
first cycle, the circuit performs as an incremental ADC, while during the
remaining ones it acts as a multi-slope counting converter. With only
one opamp and a single-slope ADC, the accuracy is comparable to that
of a second-order incremental ADC. A three-step A/D converter using
only a single opamp and a two-slope ADC achieves an accuracy
comparable to that of a third-order incremental ADC, but with much
higher power efficiency.Keywords: second-order incremental ADC, analogue-digital conversion, operational amplifiers, third-order incremental ADC, multislope counting converter, multistep extended-counting analogue-to-digital converters, counting circuits, single-slope ADC, single opamp, two-slope ADC, circuit performance, extended-counting A-D converters, three-step A/D converter, power efficiencyThis is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by IEEE-Institute of Electrical and Electronics Engineers and can be found at: http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=2220. ©2013 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works
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Noise-Shaping SAR ADC Using Three Capacitors
In this letter, a simple and highly efficient successive-approximation
Registers (SAR) ADC realization is proposed. It requires an op-amp,
a comparator and only three equal-valued capacitors. The proposed
scheme is insensitive to the capacitor parasitics, and has a small
capacitance spread. With an oversampled scheme, it also allows
noise-shaping the remaining quantization error. It is well-suited for
low-frequency instrumentation and measurement applications, and for
use in extended-counting ADCs.This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by IEEE-Institute of Electrical and Electronics Engineers and can be found at: http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=2220. ©2013 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works
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A Two-Step Incremental Analog-to-Digital Converter
A new incremental ADC is proposed which extends the order of a
conventional incremental ADC from N to (2N-1) by way of a two-step
operation. For a given conversion time, the duration of each step can be
optimized. For an Nth-order IADC, the performance is equivalent to that
of a (2N-1)-order converter. However, it only needs the same circuitry
as the Nth-order one. The new IADC is hence more accurate, and also
much more power-efficient than the conventional ones.This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by IEEE-Institute of Electrical and Electronics Engineers and can be found at: http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=2220. ©2013 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.Keywords: two-step incremental analogue-to-digital converter, power-efficient IADC, analogue-digital conversion, incremental ADC, two-step operatio
Flavour Changing Neutral Higgs Boson Decays from Squark - Gluino Loops
We study the flavour changing neutral Higgs boson decays that can be induced
from genuine supersymmetric particles at the one-loop level and within the
context of the Minimal Supersymmetric Standard Model. We consider all the
possible flavour changing decay channels of the three neutral Higgs bosons into
second and third generation quarks, and focus on the Supersymmetric-QCD
corrections from squark-gluino loops which are expected to provide the dominant
contributions. We assume here the more general hypothesis for flavour mixing,
where there is misalignment between the quark and squark sectors, leading to a
flavour non-diagonal squark mass matrix. The form factors involved, and the
corresponding Higgs partial decay widths and branching ratios, are computed
both analytically and numerically, and their behaviour with the parameters of
the Minimal Supersymmetric Standard Model and with the squark mass mixing are
analyzed in full detail. The large rates found, are explained in terms of the
non-decoupling behaviour of these squark-gluino loop corrections in the
scenario with very large supersymmetric mass parameters. Our results show that
if these decays are seen in future colliders they could provide clear indirect
signals of supersymmetry.Comment: 32 Pages and 12 PostScript Level 2 Figures. Some references adde
Pan-cancer analysis of whole genomes identifies driver rearrangements promoted by LINE-1 retrotransposition.
About half of all cancers have somatic integrations of retrotransposons. Here, to characterize their role in oncogenesis, we analyzed the patterns and mechanisms of somatic retrotransposition in 2,954 cancer genomes from 38 histological cancer subtypes within the framework of the Pan-Cancer Analysis of Whole Genomes (PCAWG) project. We identified 19,166 somatically acquired retrotransposition events, which affected 35% of samples and spanned a range of event types. Long interspersed nuclear element (LINE-1; L1 hereafter) insertions emerged as the first most frequent type of somatic structural variation in esophageal adenocarcinoma, and the second most frequent in head-and-neck and colorectal cancers. Aberrant L1 integrations can delete megabase-scale regions of a chromosome, which sometimes leads to the removal of tumor-suppressor genes, and can induce complex translocations and large-scale duplications. Somatic retrotranspositions can also initiate breakage-fusion-bridge cycles, leading to high-level amplification of oncogenes. These observations illuminate a relevant role of L1 retrotransposition in remodeling the cancer genome, with potential implications for the development of human tumors
Productive Parvovirus B19 Infection of Primary Human Erythroid Progenitor Cells at Hypoxia Is Regulated by STAT5A and MEK Signaling but not HIFα
Human parvovirus B19 (B19V) causes a variety of human diseases. Disease outcomes of bone marrow failure in patients with high turnover of red blood cells and immunocompromised conditions, and fetal hydrops in pregnant women are resulted from the targeting and destruction of specifically erythroid progenitors of the human bone marrow by B19V. Although the ex vivo expanded erythroid progenitor cells recently used for studies of B19V infection are highly permissive, they produce progeny viruses inefficiently. In the current study, we aimed to identify the mechanism that underlies productive B19V infection of erythroid progenitor cells cultured in a physiologically relevant environment. Here, we demonstrate an effective reverse genetic system of B19V, and that B19V infection of ex vivo expanded erythroid progenitor cells at 1% O2 (hypoxia) produces progeny viruses continuously and efficiently at a level of approximately 10 times higher than that seen in the context of normoxia. With regard to mechanism, we show that hypoxia promotes replication of the B19V genome within the nucleus, and that this is independent of the canonical PHD/HIFα pathway, but dependent on STAT5A and MEK/ERK signaling. We further show that simultaneous upregulation of STAT5A signaling and down-regulation of MEK/ERK signaling boosts the level of B19V infection in erythroid progenitor cells under normoxia to that in cells under hypoxia. We conclude that B19V infection of ex vivo expanded erythroid progenitor cells at hypoxia closely mimics native infection of erythroid progenitors in human bone marrow, maintains erythroid progenitors at a stage conducive to efficient production of progeny viruses, and is regulated by the STAT5A and MEK/ERK pathways
Pan-cancer analysis of whole genomes identifies driver rearrangements promoted by LINE-1 retrotransposition
About half of all cancers have somatic integrations of retrotransposons. Here, to characterize their role in oncogenesis, we analyzed the patterns and mechanisms of somatic retrotransposition in 2,954 cancer genomes from 38 histological cancer subtypes within the framework of the Pan-Cancer Analysis of Whole Genomes (PCAWG) project. We identified 19,166 somatically acquired retrotransposition events, which affected 35% of samples and spanned a range of event types. Long interspersed nuclear element (LINE-1; L1 hereafter) insertions emerged as the first most frequent type of somatic structural variation in esophageal adenocarcinoma, and the second most frequent in head-and-neck and colorectal cancers. Aberrant L1 integrations can delete megabase-scale regions of a chromosome, which sometimes leads to the removal of tumor-suppressor genes, and can induce complex translocations and large-scale duplications. Somatic retrotranspositions can also initiate breakage–fusion–bridge cycles, leading to high-level amplification of oncogenes. These observations illuminate a relevant role of L1 retrotransposition in remodeling the cancer genome, with potential implications for the development of human tumors
Pan-cancer analysis of whole genomes
Cancer is driven by genetic change, and the advent of massively parallel sequencing has enabled systematic documentation of this variation at the whole-genome scale(1-3). Here we report the integrative analysis of 2,658 whole-cancer genomes and their matching normal tissues across 38 tumour types from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA). We describe the generation of the PCAWG resource, facilitated by international data sharing using compute clouds. On average, cancer genomes contained 4-5 driver mutations when combining coding and non-coding genomic elements; however, in around 5% of cases no drivers were identified, suggesting that cancer driver discovery is not yet complete. Chromothripsis, in which many clustered structural variants arise in a single catastrophic event, is frequently an early event in tumour evolution; in acral melanoma, for example, these events precede most somatic point mutations and affect several cancer-associated genes simultaneously. Cancers with abnormal telomere maintenance often originate from tissues with low replicative activity and show several mechanisms of preventing telomere attrition to critical levels. Common and rare germline variants affect patterns of somatic mutation, including point mutations, structural variants and somatic retrotransposition. A collection of papers from the PCAWG Consortium describes non-coding mutations that drive cancer beyond those in the TERT promoter(4); identifies new signatures of mutational processes that cause base substitutions, small insertions and deletions and structural variation(5,6); analyses timings and patterns of tumour evolution(7); describes the diverse transcriptional consequences of somatic mutation on splicing, expression levels, fusion genes and promoter activity(8,9); and evaluates a range of more-specialized features of cancer genomes(8,10-18).Peer reviewe
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