4,859 research outputs found
Computational Study of Tunneling Transistor Based on Graphene Nanoribbon
Tunneling field-effect transistors (FETs) have been intensely explored
recently due to its potential to address power concerns in nanoelectronics. The
recently discovered graphene nanoribbon (GNR) is ideal for tunneling FETs due
to its symmetric bandstructure, light effective mass, and monolayer-thin body.
In this work, we examine the device physics of p-i-n GNR tunneling FETs using
atomistic quantum transport simulations. The important role of the edge bond
relaxation in the device characteristics is identified. The device, however,
has ambipolar I-V characteristics, which are not preferred for digital
electronics applications. We suggest that using either an asymmetric
source-drain doping or a properly designed gate underlap can effectively
suppress the ambipolar I-V. A subthreshold slope of 14mV/dec and a
significantly improved on-off ratio can be obtained by the p-i-n GNR tunneling
FETs
Testing the performance of a blind burst statistic
In this work we estimate the performance of a method for the detection of
burst events in the data produced by interferometric gravitational wave
detectors. We compute the receiver operating characteristics in the specific
case of a simulated noise having the spectral density expected for Virgo, using
test signals taken from a library of possible waveforms emitted during the
collapse of the core of Type II Supernovae.Comment: 8 pages, 6 figures, Talk given at the GWDAW2002 worksho
Quasiparticle bandgap engineering of graphene and graphone on hexagonal boron nitride substrate
Graphene holds great promise for post-silicon electronics, however, it faces
two main challenges: opening up a bandgap and finding a suitable substrate
material. In principle, graphene on hexagonal boron nitride (hBN) substrate
provides potential system to overcome these challenges. Recent theoretical and
experimental studies have provided conflicting results: while theoretical
studies suggested a possibility of a finite bandgap of graphene on hBN, recent
experimental studies find no bandgap. Using the first-principles density
functional method and the many-body perturbation theory, we have studied
graphene on hBN substrate. A Bernal stacked graphene on hBN has a bandgap on
the order of 0.1 eV, which disappears when graphene is misaligned with respect
to hBN. The latter is the likely scenario in realistic devices. In contrast, if
graphene supported on hBN is hydrogenated, the resulting system (graphone)
exhibits bandgaps larger than 2.5 eV. While the bandgap opening in graphene/hBN
is due to symmetry breaking and is vulnerable to slight perturbation such as
misalignment, the graphone bandgap is due to chemical functionalization and is
robust in the presence of misalignment. The bandgap of graphone reduces by
about 1 eV when it is supported on hBN due to the polarization effects at the
graphone/hBN interface. The band offsets at graphone/hBN interface indicate
that hBN can be used not only as a substrate but also as a dielectric in the
field effect devices employing graphone as a channel material. Our study could
open up new way of bandgap engineering in graphene based nanostructures.Comment: 8 pages, 4 figures; Nano Letters, Publication Date (Web): Oct. 25
2011, http://pubs.acs.org/doi/abs/10.1021/nl202725
Use of Surrogate end points in HTA
The different actors involved in health system decision-making and regulation have to deal with the question which are valid parameters to assess the health value of health technologies
Development and psychometric properties of the Suicidality:Treatment Occurring in Paediatrics (STOP) Suicidality Assessment Scale (STOP-SAS) in children and adolescents
Background: To create a self-reported, internet-based questionnaire for the assessment of suicide risk in children and adolescents.Methods: As part of the EU project `Suicidality: Treatment Occurring in Paediatrics' (STOP project), we developed web-based Patient Reported Outcome Measures (PROMs) for children and adolescents and for proxy reports by parents and clinicians in order to assess suicidality. Based on a literature review, expert panels and focus groups of patients, we developed the items of the STOP Suicidality Assessment Scale (STOP-SAS) in Spanish and English, translated it into four more languages, and optimized it for web-based presentation using the HealthTracker (TM) platform. Of the total 19 questions developed for the STOP-SAS, four questions that assess low-level suicidality were identified as screening questions (three of them for use with children, and all four for use with adolescents, parents and clinicians). A total of 395 adolescents, 110 children, 637 parents and 716 clinicians completed the questionnaire using the HealthTracker (TM), allowing us to evaluate the internal consistency and convergent validity of the STOP-SAS with the clinician-rated Columbia Suicide Severity Rating Scale (C-SSRS). Validity was also assessed with the receiver operating characteristic (ROC) area of the STOP-SAS with the C-SSRS.Results: The STOP-SAS comprises 19 items in its adolescent, parent, and clinician versions, and 14 items in its children's version. Good internal consistency was found for adolescents (Cronbach's alpha: 0.965), children (Cronbach's alpha: 0.922), parents (Cronbach's alpha: 0.951) and clinicians (Cronbach's alpha: 0.955) versions. A strong correlation was found between the STOP-SAS and the C-SSRS for adolescents (r:0.670), parents (r:0.548), clinicians (r:0.863) and children (r:0.654). The ROC area was good for clinicians' (0.917), adolescents' (0.834) and parents' (0.756) versions but only fair (0.683) for children's version.Conclusions: The STOP-SAS is a comprehensive, web-based PROM developed on the HealthTracker (TM) platform, and co-designed for use by adolescents, children, parents and clinicians. It allows the evaluation of aspects of suicidality and shows good reliability and validity.</p
Study of Thermal Properties of Graphene-Based Structures Using the Force Constant Method
The thermal properties of graphene-based materials are theoretically
investigated. The fourth-nearest neighbor force constant method for phonon
properties is used in conjunction with both the Landauer ballistic and the
non-equilibrium Green's function techniques for transport. Ballistic phonon
transport is investigated for different structures including graphene, graphene
antidot lattices, and graphene nanoribbons. We demonstrate that this particular
methodology is suitable for robust and efficient investigation of phonon
transport in graphene-based devices. This methodology is especially useful for
investigations of thermoelectric and heat transport applications.Comment: 23 pages, 9 figures, 1 tabl
International alliance of Urolithiasis (IAU) guideline on percutaneous nephrolithotomy
The International Alliance of Urolithiasis (IAU) would like to release the latest guideline on percutaneous nephrolithotomy (PCNL) and to provide a clinical framework for surgeons performing PCNL. These recommendations were collected and appraised from a systematic review and assessment of the literature covering all aspects of PCNLs from the PubMed database between January 1, 1976, and July 31, 2021. Each generated recommendation was graded using a modified GRADE methodology. The quality of the evidence was graded using a classification system modified from the Oxford Center for Evidence-Based Medicine Levels of Evidence. Forty-seven recommendations were summarized and graded, which covered the following issues, indications and contraindications, stone complexity evaluation, preoperative imaging, antibiotic strategy, management of antithrombotic therapy, anesthesia, position, puncture, tracts, dilation, lithotripsy, intraoperative evaluation of residual stones, exit strategy, postoperative imaging and stone-free status evaluation, complications. The present guideline on PCNL was the first in the IAU series of urolithiasis management guidelines. The recommendations, tips and tricks across the PCNL procedures would provide adequate guidance for urologists performing PCNLs to ensure safety and efficiency in PCNLs
Measurement of Rapidity Distribution for High Mass Drell-Yan ee Pairs at CDF
We report on the first measurement of the rapidity distribution dsigma/dy
over nearly the entire kinematic region of rapidity for e^+e^- pairs in the
Z-boson region of 66116 GeV/c^2.
The data sample consists of 108 pb^{-1} of ppbar collisions at \sqrt{s}=1.8 TeV
taken by the Collider Detector at Fermilab during 1992--1995. The total cross
section in the -boson region is measured to be 252 +- 11 pb. The measured
total cross section and d\sigma/dy are compared with quantum chromodynamics
calculations in leading and higher orders.Comment: 7 pages, 3 figures. Submitted to Physical Review Letter
Search for the Supersymmetric Partner of the Top-Quark in Collisions at
We report on a search for the supersymmetric partner of the top quark (stop)
produced in events using of
collisions at recorded with the Collider Detector at
Fermilab. In the case of a light stop squark, the decay of the top quark into
stop plus the lightest supersymmetric particle (LSP) could have a significant
branching ratio. The observed events are consistent with Standard Model production and decay. Hence, we set limits on the branching ratio of
the top quark decaying into stop plus LSP, excluding branching ratios above 45%
for a LSP mass up to 40 {\rm GeV/c}.Comment: 11 pages, 4 figure
Inclusive Search for Anomalous Production of High-pT Like-Sign Lepton Pairs in Proton-Antiproton Collisions at sqrt{s}=1.8 TeV
We report on a search for anomalous production of events with at least two
charged, isolated, like-sign leptons with pT > 11 GeV/c using a 107 pb^-1
sample of 1.8 TeV ppbar collisions collected by the CDF detector. We define a
signal region containing low background from Standard Model processes. To avoid
bias, we fix the final cuts before examining the event yield in the signal
region using control regions to test the Monte Carlo predictions. We observe no
events in the signal region, consistent with an expectation of
0.63^(+0.84)_(-0.07) events. We present 95% confidence level limits on new
physics processes in both a signature-based context as well as within a
representative minimal supergravity (tanbeta = 3) model.Comment: 15 pages, 4 figures. Minor textual changes, cosmetic improvements to
figures and updated and expanded reference
- …