3,941 research outputs found
The Bias of the Gini Coefficient due to Grouping
We propose a first order bias correction term for the Gini index to reduce the bias due to grouping. The first order correction term is obtained from studying the estimator of the Gini index within a measurement error framework. In addition, it reveals an intuitive formula for the remaining second order bias which is useful in empirical analyses. We analyze the empirical performance of our first order correction term using income data for 15 European countries and the US, and show that it reduces a considerable share of the bias due to grouping
E-QED: Electrical Bug Localization During Post-Silicon Validation Enabled by Quick Error Detection and Formal Methods
During post-silicon validation, manufactured integrated circuits are
extensively tested in actual system environments to detect design bugs. Bug
localization involves identification of a bug trace (a sequence of inputs that
activates and detects the bug) and a hardware design block where the bug is
located. Existing bug localization practices during post-silicon validation are
mostly manual and ad hoc, and, hence, extremely expensive and time consuming.
This is particularly true for subtle electrical bugs caused by unexpected
interactions between a design and its electrical state. We present E-QED, a new
approach that automatically localizes electrical bugs during post-silicon
validation. Our results on the OpenSPARC T2, an open-source
500-million-transistor multicore chip design, demonstrate the effectiveness and
practicality of E-QED: starting with a failed post-silicon test, in a few hours
(9 hours on average) we can automatically narrow the location of the bug to
(the fan-in logic cone of) a handful of candidate flip-flops (18 flip-flops on
average for a design with ~ 1 Million flip-flops) and also obtain the
corresponding bug trace. The area impact of E-QED is ~2.5%. In contrast,
deter-mining this same information might take weeks (or even months) of mostly
manual work using traditional approaches
Zeeman smearing of the Coulomb blockade
Charge fluctuations of a large quantum dot coupled to a two-dimensional lead
via a single-mode good Quantum Point Contact (QPC) and capacitively coupled to
a back-gate, are investigated in the presence of a parallel magnetic field. The
Zeeman term induces an asymmetry between transmission probabilities for the
spin-up and spin-down channels at the QPC, producing noticeable effects on the
quantization of the grain charge already at low magnetic fields. Performing a
quantitative analysis, I show that the capacitance between the gate and the
lead exhibits - instead of a logarithmic singularity - a reduced peak as a
function of gate voltage. Experimental applicability is discussed.Comment: 5 pages, 3 figures (Final version
Capacitance of a quantum dot from the channel-anisotropic two-channel Kondo model
We investigate the charge fluctuations of a large quantum dot coupled to a
two-dimensional electron gas via a quantum point contact following the work of
Matveev. We limit our discussion to the case where exactly two channels enter
the dot and we discuss the role of an anisotropy between the transmission
coefficients (for these two channels) at the constriction. Experimentally, a
channel-anisotropy can be introduced applying a relatively weak in-plane
magnetic field to the system when only one ``orbital'' channel is open. The
magnetic field leads to different transmission amplitudes for spin-up and
spin-down electrons.
In a strong magnetic field the anisotropic two-channel limit corresponds to
two (spin-polarized) orbital channels entering the dot.
The physics of the charge fluctuations can be captured using a mapping on the
channel-anisotropic two-channel Kondo model. For the case of weak reflection at
the point contact this has already briefly been stressed by one of us in PRB
{\bf 64}, 161302R (2001). This mapping is also appropriate to discuss the
conductance behavior of a two-contact set-up in strong magnetic field.
Here, we elaborate on this approach and also discuss an alternative solution
using a mapping on a channel-isotropic Kondo model. In addition we consider the
limit of weak transmission.
We show that the Coulomb-staircase behavior of the charge in the dot as a
function of the gate voltage, is already smeared out by a small
channel-anisotropy both in the weak- and strong transmission limits.Comment: 17 pages, 4 figures, 1 Table; Expands cond-mat/0101126; Sec. VI on
2-contact setup added (Final version for PRB
Anderson-Yuval approach to the multichannel Kondo problem
We analyze the structure of the perturbation expansion of the general
multichannel Kondo model with channel anisotropic exchange couplings and in the
presence of an external magnetic field, generalizing to this case the
Anderson-Yuval technique. For two channels, we are able to map the Kondo model
onto a generalized resonant level model. Limiting cases in which the equivalent
resonant level model is solvable are identified. The solution correctly
captures the properties of the two channel Kondo model, and also allows an
analytic description of the cross-over from the non Fermi liquid to the Fermi
liquid behavior caused by the channel anisotropy.Comment: 23 pages, ReVTeX, 4 figures av. on reques
Kondo effect in crossed Luttinger liquids
We study the Kondo effect in two crossed Luttinger liquids, using Boundary
Conformal Field Theory. We predict two types of critical behaviors: either a
two-channel Kondo fixed point with a nonuniversal Wilson ratio, or a new theory
with an anomalous response identical to that found by Furusaki and Nagaosa (for
the Kondo effect in a single Luttinger liquid). Moreover, we discuss the
relevance of perturbations like channel anisotropy, and we make links with the
Kondo effect in a two-band Hubbard system modeled by a channel-dependent
Luttinger Hamiltonian. The suppression of backscattering off the impurity
produces a model similar to the four-channel Kondo theory.Comment: 7 pages, RevteX, to be published in Physical Review
The impact of loco-regional recurrences on metastatic progression in early-stage breast cancer: a multistate model
To study whether the effects of prognostic factors associated with the occurrence of distant metastases (DM) at primary diagnosis change after the incidence of loco-regional recurrences (LRR) among women treated for invasive stage I or II breast cancer. The study population consisted of 3,601 women, enrolled in EORTC trials 10801, 10854, or 10902 treated for early-stage breast cancer. Data were analysed in a multivariate, multistate model by using multivariate Cox regression models, including a state-dependent covariate. The presence of a LRR in itself is a significant prognostic risk factor (HR: 3.64; 95%-CI: 2.02-6.5) for the occurrence of DM. Main prognostic risk factors for a DM are young age at diagnosis (</=40: HR: 1.79; 95%-CI: 1.28-2.51), larger tumour size (HR: 1.58; 95%-CI: 1.35-1.84) and node positivity (HR: 2.00; 95%-CI: 1.74-2.30). Adjuvant chemotherapy is protective for a DM (HR: 0.66; 95%-CI: 0.55-0.80). After the occurrence of a LRR the latter protective effect has disappeared (P = 0.009). The presence of LRR in itself is a significant risk factor for DM. For patients who are at risk of developing LRR, effective local control should be the main target of therapy
Dynamic Scaling of Magnetic Flux Noise Near the KTB Transition in Overdamped Josephson Junction Arrays
We have used a dc Superconducting QUantum Interference Device to measure the
magnetic flux noise generated by the equilibrium vortex density fluctuations
associated with the Kosterlitz-Thouless-Berezinskii (KTB) transition in an
overdamped Josephson junction array. At temperatures slightly above the KTB
transition temperature, the noise is white for and scales as
for . Here , where is the correlation
length and is the dynamic exponent. Moreover, when all frequencies are
scaled by , data for different temperatures and frequencies collapse on
to a single curve. In addition, we have extracted the dynamic exponent and
found .Comment: 5 pages, LaTeX (REVTeX) format, requires epsfig and amstex style
files. 3 figures included. Tentatively scheduled for publication in Physical
Review Letters, 18 March, 199
Caspase I-related protease inhibition retards the execution of okadaic acid- and camptothecin-induced apoptosis and PAI-2 cleavage, but not commitment to cell death in HL-60 cells
We have previously reported that the putative cytoprotective protease inhibitor, plasminogen activator inhibitor type 2 (PAI-2), is specifically cleaved during okadaic acid-induced apoptosis in a myeloid leukaemic cell line (Br J Cancer (1994) 70: 834–840). HL-60 cells exposed to okadaic acid and camptothecin underwent morphological and biochemical changes typical of apoptosis, including internucleosomal DNA fragmentation and PAI-2 cleavage. Significant endogenous PAI-2 cleavage was observed 9 h after exposure to okadaic acid; thus correlating with other signs of macromolecular degradation, like internucleosomal DNA fragmentation. In camptothecin-treated cells, PAI-2 cleavage was an early event, detectable after 2 h of treatment, and preceding internucleosomal DNA fragmentation. The caspase I selective protease inhibitor, YVAD-cmk, inhibited internucleosomal DNA fragmentation and PAI-2 cleavage of okadaic acid and camptothecin-induced apoptotic cells. YVAD-cmk rather sensitively and non-toxically inhibited camptothecin-induced morphology, but not okadaic acid-induced morphology. In in vitro experiments recombinant PAI-2 was not found to be a substrate for caspase I. The results suggest that caspase I selective protease inhibition could antagonize parameters coupled to the execution phase of okadaic acid- and camptothecin-induced apoptosis, but not the commitment to cell death. © 1999 Cancer Research Campaig
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