1,071 research outputs found
Discrete Particle Swarm Optimization for the minimum labelling Steiner tree problem
Particle Swarm Optimization is an evolutionary method inspired by the
social behaviour of individuals inside swarms in nature. Solutions of the problem are
modelled as members of the swarm which fly in the solution space. The evolution is
obtained from the continuous movement of the particles that constitute the swarm
submitted to the effect of the inertia and the attraction of the members who lead the
swarm. This work focuses on a recent Discrete Particle Swarm Optimization for combinatorial optimization, called Jumping Particle Swarm Optimization. Its effectiveness is
illustrated on the minimum labelling Steiner tree problem: given an undirected labelled
connected graph, the aim is to find a spanning tree covering a given subset of nodes,
whose edges have the smallest number of distinct labels
962-61 Late Redistribution T1-201/Stress Tc-99m Sestamibi Separate Acquisition Dual Isotope Myocardial Perfusion SPECT: A Feasibility Study
Rest TI201(TI)/stress Tc-sestamibi dual isotope SPECT (DIMPS) is an efficient myocardial perfusion protocol. Patients with rest defects, however, frequently require late TI redistribution imaging the next day. Thus, we recently implemented a modified DIMPS (M-DIMPS), with 3.5 mCi TI injected at rest the night before stress testing. On the day of stress testing, 12–18 hr redistribution TI (late TI) SPECT was performed prior to stress sestamibi study. To assess image quality of late TI, we prospectively studied 107 patients who underwent M-DIMPS. For purposes of comparison between conventional DIMPS and M-DIMPS, a subset (group A, n=41) also had rest TI(25sec/stop, 60 stops) the night before M-DIMPS. Late TI used 30sec/stop. Prereconstruction processing used a 20 Butterworth filter (cut-off: 0.5/order 10 for rest TI, 0.35/order 10 for late TI). Comparisons were made for cardiac counts (counts/pixel) and quantitative heart to background ratio (H/B ratio). Image quality was assessed visually using a 5 point score (0=unacceptable, 4=excellent), based on the evaluation of image uniformity, defect clarity, left ventricular border definition and the apparent H/B ratio, Comparisons between rest TI and late TI in 41 group A patients yielded quantitative H/B ratio of 1.63±0.39 and 1.49±0,31 (p=0.002), and total myocardial counts of 41.4±18.1 and 29.3±11.6 (p<0.001), respectively. Image quality agreement between rest TI and late TI was 90%, with 31 concordant good to excellent and 6 concordant fair studies. Analysis of the 107 late TI studies by patient weight revealed:<150 Ibs (n = 31)150–200 Ibs (n = 60)>200 Ibs (n = 16)pcardiac counts30.4±9.628.9±13.828.9±7.5nsH/B ratio1.49±0.241.46±0.321.42±0.25nsquality = 3 or 490%90%63%<0.05**> 200lbs vs. the other two weight categoriesConclusionAlthough quantitatively different, late TI has acceptable count statistics and comparable visual image quality to rest TI, establishing the feasibility of late TI/stress Tc-sestamibi dual isotope SPECT in non-obese (<200 Ibs) patients. The protocol allows for final reporting on the same day as stress testing, potentially decreasing the length of hospitalization
Effective risk stratification using exercise myocardial perfusion SPECT in women: Gender-related differences in prognostic nuclear testing
AbstractObjectives. This study was designed to evaluate the incremental prognostic value over clinical and exercise variables of rest thallium-201/exercise technetium-99m sestamibi single-photon emission computed tomography (SPECT) in women compared with men and to determine whether this test can be used to effectively risk stratify patients of both genders.Background. To minimize the previously described gender-related bias in the evaluation of coronary artery disease in women, there is a need to identify a noninvasive testing strategy that is able to accurately and effectively risk stratify women.Methods. We identified 4,136 consecutive patients (2,742 men, 1,394 women) who underwent dual-isotope SPECT. The incremental value of nuclear testing was determined using both a stepwise Cox proportional hazards model and Kaplan-Meier survival analysis. Receiver operating characteristic curve analysis was performed to determine test discrimination for high risk patients in men and women.Results. The patient population was followed up for 20 ± 5 months for events (cardiac death or nonfatal myocardial infarction). During this time, 63 myocardial infarctions and 32 cardiac deaths occurred in the men, and 31 myocardial infarctions and 14 cardiac deaths occurred in the women. Nuclear testing significantly stratified both men and women irrespective of their rest electrocardiogram. Cox proportional hazards analysis revealed that nuclear testing added incremental prognostic value in both men and women after inclusion of the most predictive clinical and exercise variables (overall chi-square 89 in men vs. 120 in women, p < 0.005). Kaplan-Meier survival analysis demonstrated that nuclear testing further stratified men and women with both intermediate to high and low prescan likelihoods of coronary artery disease (p < 0.005 for all). Receiver operating characteristic curve analysis demonstrated superior discrimination for the nuclear scan results in identifying high risk women than men (area under the curve: 0.84 ± 0.03 vs. 0.71 ± 0.03 in men, p < 0.0005). The odds ratio comparing event rates in patients with abnormal versus those with normal scan results was greater in women than in men, suggesting superior stratification using nuclear testing in women.Conclusions. Dual-isotope myocardial perfusion imaging yields incremental prognostic value in both men and women. This modality identifies low risk women and men equally well but relatively high risk women more accurately than relatively high risk men and, thus, is able to stratify women more effectively than men
A Path Algorithm for Constrained Estimation
Many least squares problems involve affine equality and inequality
constraints. Although there are variety of methods for solving such problems,
most statisticians find constrained estimation challenging. The current paper
proposes a new path following algorithm for quadratic programming based on
exact penalization. Similar penalties arise in regularization in model
selection. Classical penalty methods solve a sequence of unconstrained problems
that put greater and greater stress on meeting the constraints. In the limit as
the penalty constant tends to , one recovers the constrained solution.
In the exact penalty method, squared penalties are replaced by absolute value
penalties, and the solution is recovered for a finite value of the penalty
constant. The exact path following method starts at the unconstrained solution
and follows the solution path as the penalty constant increases. In the
process, the solution path hits, slides along, and exits from the various
constraints. Path following in lasso penalized regression, in contrast, starts
with a large value of the penalty constant and works its way downward. In both
settings, inspection of the entire solution path is revealing. Just as with the
lasso and generalized lasso, it is possible to plot the effective degrees of
freedom along the solution path. For a strictly convex quadratic program, the
exact penalty algorithm can be framed entirely in terms of the sweep operator
of regression analysis. A few well chosen examples illustrate the mechanics and
potential of path following.Comment: 26 pages, 5 figure
Validation of high gradient magnetic field based drug delivery to magnetizable implants under flow
IEEE Transactions on Biomedical Engineering, 55(2): pp. 643-649.The drug-eluting stent’s increasingly frequent occurrence
late stage thrombosis have created a need for new strategies
for intervention in coronary artery disease. This paper demonstrates
further development of our minimally invasive, targeted
drug delivery system that uses induced magnetism to administer
repeatable and patient specific dosages of therapeutic agents to specific
sites in the human body. Our first aim is the use of magnetizable
stents for the prevention and treatment of coronary restenosis;
however, future applications include the targeting of tumors, vascular
defects, and other localized pathologies. Future doses can
be administered to the same site by intravenous injection. This
implant-based drug delivery system functions by placement of a
weakly magnetizable stent or implant at precise locations in the
cardiovascular system, followed by the delivery of magnetically
susceptible drug carriers. The stents are capable of applying high
local magnetic field gradients within the body, while only exposing
the body to a modest external field. The local gradients created
within the blood vessel create the forces needed to attract and hold
drug-containing magnetic nanoparticles at the implant site. Once
these particles are captured, they are capable of delivering therapeutic
agents such as antineoplastics, radioactivity, or biological
cells
SN~2012cg: Evidence for Interaction Between a Normal Type Ia Supernova and a Non-Degenerate Binary Companion
We report evidence for excess blue light from the Type Ia supernova SN 2012cg
at fifteen and sixteen days before maximum B-band brightness. The emission is
consistent with predictions for the impact of the supernova on a non-degenerate
binary companion. This is the first evidence for emission from a companion to a
SN Ia. Sixteen days before maximum light, the B-V color of SN 2012cg is 0.2 mag
bluer than for other normal SN~Ia. At later times, this supernova has a typical
SN Ia light curve, with extinction-corrected M_B = -19.62 +/- 0.02 mag and
Delta m_{15}(B) = 0.86 +/- 0.02. Our data set is extensive, with photometry in
7 filters from 5 independent sources. Early spectra also show the effects of
blue light, and high-velocity features are observed at early times. Near
maximum, the spectra are normal with a silicon velocity v_{Si} = -10,500$ km
s^{-1}. Comparing the early data with models by Kasen (2010) favors a
main-sequence companion of about 6 solar masses. It is possible that many other
SN Ia have main-sequence companions that have eluded detection because the
emission from the impact is fleeting and faint.Comment: accepted to Ap
Chronic and Acute Exposures to the World Trade Center Disaster and Lower Respiratory Symptoms: Area Residents and Workers
Objectives. We assessed associations between new-onset (post–September 11, 2001 [9/11]) lower respiratory symptoms reported on 2 surveys, administered 3 years apart, and acute and chronic 9/11-related exposures among New York City World Trade Center–area residents and workers enrolled in the World Trade Center Health Registry.
Methods. World Trade Center–area residents and workers were categorized as case participants or control participants on the basis of lower respiratory symptoms reported in surveys administered 2 to 3 and 5 to 6 years after 9/11. We created composite exposure scales after principal components analyses of detailed exposure histories obtained during face-to-face interviews. We used multivariate logistic regression models to determine associations between lower respiratory symptoms and composite exposure scales.
Results. Both acute and chronic exposures to the events of 9/11 were independently associated, often in a dose-dependent manner, with lower respiratory symptoms among individuals who lived and worked in the area of the World Trade Center.
Conclusions. Study findings argue for detailed assessments of exposure during and after events in the future from which potentially toxic materials may be released and for rapid interventions to minimize exposures and screen for potential adverse health effects
On the problem of the justification of river rights
This article aims to work out the social conditions that determine whether the
communication of river rights finds success in society. Employing the context of
hydropower development in the Mekong region, the article finds that an essentialist
strategy which claims that river rights have unlimited ‘moral’ validity regardless of any
of the decision consequences is unlikely to succeed. Instead, it is proposed that moral
conflicts over river rights may ultimately only be resolvable ‘unmorally’, that is, by
procedural legitimacy – and this is best captured by employing a methodological
framework composed of thematic, social and temporal dimension
University Physics Volume 2
University Physics is a three-volume collection that meets the scope and sequence requirements for two- and three-semester calculus-based physics courses. Volume 1 covers mechanics, sound, oscillations, and waves. Volume 2 covers thermodynamics, electricity and magnetism, and Volume 3 covers optics and modern physics. This textbook emphasizes connections between theory and application, making physics concepts interesting and accessible to students while maintaining the mathematical rigor inherent in the subject. Frequent, strong examples focus on how to approach a problem, how to work with the equations, and how to check and generalize the result.https://commons.erau.edu/oer-textbook/1002/thumbnail.jp
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