On Drazin invertibility Aiena, Pietro; Biondi, Maria T.; Carpintero, Carlos
Proceedings of the American Mathematical Society,
08/2008, Letnik:
136, Številka:
8
Journal Article
Recenzirano
Odprti dostop
The left Drazin spectrum and the Drazin spectrum coincide with the upper semi-B-Browder spectrum and the B-Browder spectrum, respectively. We also prove that some spectra coincide whenever T or ...T^\ast satisfies the single-valued extension property.
The evaluation and management of prostate cancer (PCa) are based mainly on parameters such as the serum prostate-specific antigen level, clinical stage, and pathologic findings at biopsy or after ...surgery. The aim of this paper was to review the current roles of conventional imaging and multiparametric magnetic resonance imaging (mpMRI) techniques in the diagnosis of PCa. A non systematic literature search using the Medline and Cochrane Library databases was performed up to January 2012. Bibliographies of retrieved articles and review articles were also examined. Only those articles reporting complete data with clinical relevance for the present review (i.e., diagnosis, staging) were selected. The advent of a high performance (1.5T) and higher fields strength (3T), and thus, higher spatial resolution, increased the potentiality and the diffusion of MR examinations. Intense research has focused on the use of complementary techniques to improve the detection, characterization, and staging of PCa by MRI. This review article is divided into two major parts: the first one considers the technical aspects of mpMRI; the second part is intended to provide the impact of this technique on patients with PCa. Published data indicate an emerging role for MRI (particularly mpMRI combining T2 weighted imaging, diffusion weighted imaging, contrast enhanced MR, and spectroscopy) as the most sensitive and specific tool available for imaging PCa. MpMRI can provide metabolic information, characterize tissue and tumor vascularity, as well as tissue cellularity and correlate with tumor aggressiveness.
The analysis and modeling of monolithic stacked transformers fabricated in a high-speed silicon bipolar technology is addressed. On-wafer experimental measurements are employed to investigate the ...effect of layout scaling on transformer performance parameters (i.e., self-resonance frequency, magnetic coupling coefficient, and insertion loss). Based on this analysis, a wideband lumped model is developed, whose parameters are related to layout and technological data through closed-form expressions. Model accuracy is demonstrated by comparing simulated and measured S-parameters, coil inductance, magnetic coupling coefficient, and maximum available gain of several transformers with scaled layout geometry. The self-resonance frequency is also employed as a figure-of-merit to demonstrate model accuracy at very high frequency.
A lumped scalable model for spiral inductors in silicon bipolar technology has been developed. The effect of three different cross sections on inductor performance was first investigated by comparing ...experimental measurements. Using both the results of this analysis and three-dimensional electromagnetic simulation guidelines, several circular inductors were integrated on a radial patterned ground shield for model validation purposes. The model employs a novel equation for series resistance with only one fitting parameter extracted from experimental measurements. All other model elements were related to technological and geometrical data by using rigorous analytical equations. The model was validated using one- and two-port measured performance parameters of 45 integrated inductors, and excellent agreement was found for all considered geometries up to frequencies well above self-resonance.
This paper reports a technique for generating a lumped-element distributed model for silicon power devices that takes into account the effect of layout parasitics. The proposed methodology exploits ...the high-frequency modeling approach of microstrips and striplines to describe both the passive parts of the device and elementary transistor cells. A semi-empirical model for the elementary transistor cells of the power device is also proposed. Parameter extraction is described and validated by direct comparison with device simulations of an actual device. The proposed modeling approach is employed to investigate the internal current distribution of a high-voltage silicon power MOSFET supplied by STMicroelectronics during the turnoff transient. The tradeoff that must be accomplished between accuracy and complexity is discussed. The effect of increased switching frequency on the device current distribution is also reported explaining how it may lead to performance degradation and device failure.
Property ( w) and perturbations III Aiena, Pietro; Biondi, Maria T.; Villafañe, Fernando
Journal of mathematical analysis and applications,
05/2009, Letnik:
353, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The property (
w) is a variant of Weyl's theorem, for a bounded operator
T acting on a Banach space. In this note we consider the preservation of property (
w) under a finite rank perturbation ...commuting with
T, whenever
T is polaroid, or
T has analytical core
K
(
λ
0
I
−
T
)
=
{
0
}
for some
λ
0
∈
C
. The preservation of property (
w) is also studied under commuting nilpotent or under injective quasi-nilpotent perturbations. The theory is exemplified in the case of some special classes of operators.
Sub-nH inductor modeling for RFIC design Biondi, T.; Scuderi, A.; Ragonese, E. ...
IEEE microwave and wireless components letters,
2005-Dec., 2005-12-00, 20051201, Letnik:
15, Številka:
12
Journal Article
Recenzirano
This letter presents the modeling of sub-nH radial patterned ground shield circular inductors fabricated in a silicon bipolar technology for radio frequency applications. Based on both ...electromagnetic simulations and experimental measurements, the well-known current sheet expression for circular spirals is revised and modified to improve its accuracy at lower inductance values. The proposed expression is also extended to inductors with polygonal geometries showing significant improvements with respect to the state-of-the-art. Finally, the original and modified expressions are employed in a lumped scalable model for silicon spiral inductors. Comparisons with measured data revealed that the modified expression allows error reductions as large as 20% with respect to the original one, on both inductance and quality factor simulations.
Results of a first-stage Sea Urchin Genome Project are summarized here. The species chosen was Strongylocentrotus purpuratus, a research model of major importance in developmental and molecular ...biology. A virtual map of the genome was constructed by sequencing the ends of 76,020 bacterial artificial chromosome (BAC) recombinants (average length, 125 kb). The BAC-end sequence tag connectors (STCs) occur an average of 10 kb apart, and, together with restriction digest patterns recorded for the same BAC clones, they provide immediate access to contigs of several hundred kilobases surrounding any gene of interest. The STCs survey >5% of the genome and provide the estimate that this genome contains ≈ 27,350 protein-coding genes. The frequency distribution and canonical sequences of all middle and highly repetitive sequence families in the genome were obtained from the STCs as well. The 500-kb Hox gene complex of this species is being sequenced in its entirety. In addition, arrayed cDNA libraries of > 105clones each were constructed from every major stage of embryogenesis, several individual cell types, and adult tissues and are available to the community. The accumulated STC data and an expanding expressed sequence tag database (at present including >12,000 sequences) have been reported to GenBank and are accessible on public web sites.
The low-voltage power capabilities of a low-cost high-performance silicon bipolar process were investigated. By optimizing the emitter finger layout, epilayer thickness, and collector doping level, ...efficiency values up to 83% were achieved by on-wafer load-pull measurements on a single-cell test device operating at 1.8 GHz and 2.7-V power supply. The detrimental effect of the emitter distributed resistance on the current capability of long-emitter bipolar transistors was also considered.. An analytical model for a proper device design was derived and experimentally validated. Using the optimized unit power device, a 1.8-GHz 2.7-V three-stage monolithic power amplifier was implemented, which provides a 57% power-added efficiency and a 33-dB gain while delivering a 34-dBm output power to the load.
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