On a linear program for minimum-weight triangulation

Minimum-weight triangulation (MWT) is NP-hard. It has a polynomial-time constant-factor approximation algorithm, and a variety of effective polynomial-time heuristics that, for many instances, can find the exact MWT. Linear programs (LPs) for MWT are well-studied, but previously no connection was known between any LP and any approximation algorithm or heuristic for MWT. Here we show the first such connections: For an LP formulation due to Dantzig, Hoffman, and Hu [Math. Programming, 31 (1985), pp. 1-14], (i) the integrality gap is constant, and (ii) given any instance, if the aforementioned heuristics find the MWT, then so does the LP. © 2014 Society for Industrial and Applied Mathematics

On a Linear Program for Minimum-Weight Triangulation

Minimum-weight triangulation (MWT) is NP-hard. It has a polynomial-time constant-factor approximation algorithm, and a variety of effective polynomial- time heuristics that, for many instances, can find the exact MWT. Linear programs (LPs) for MWT are well-studied, but previously no connection was known between any LP and any approximation algorithm or heuristic for MWT. Here we show the first such connections: for an LP formulation due to Dantzig et al. (1985): (i) the integrality gap is bounded by a constant; (ii) given any instance, if the aforementioned heuristics find the MWT, then so does the LP.Comment: To appear in SICOMP. Extended abstract appeared in SODA 201

The long-term prognostic significance of 6-minute walk test distance in patients with chronic heart failure

Background. The 6-minute walk test (6-MWT) is used to assess patients with chronic heart failure (CHF). The prognostic significance of the 6-MWT distance during long-term followup ( > 5 years) is unclear. Methods. 1,667 patients (median [inter-quartile range, IQR]) (age 72 [65-77] ; 75% males) with heart failure due to left ventricular systolic impairment undertook a 6-MWT as part of their baseline assessment and were followed up for 5 years. Results. At 5 years' followup, those patients who died (n = 959) were older at baseline and had a higher log NT pro-BNP than those who survived to 5 years (n = 708). 6-MWT distance was lower in those who died [163 (153) m versus 269 (160) m; P 360 m. 6-MWT distance was a predictor of all-cause mortality (HR 0.97; 95% CI 0.96-0.97; Chi-square = 184.1; P < 0.0001). Independent predictors of all-cause mortality were decreasing 6-MWT distance, increasing age, increasing NYHA classification, increasing log NT pro-BNP, decreasing diastolic blood pressure, decreasing sodium, and increasing urea. Conclusion. The 6-MWT is an important independent predictor of all-cause mortality following long-term followup in patients with CHF. © 2014 Lee Ingle et al

Cardiorespiratory requirements of the 6-min walk test in patients with left ventricular systolic disfunction and no major structural heart disease

The six-minute walk test (6-MWT) is widely used to assess functional status in patients with chronic heart failure (CHF). The aims of the present study were: (1) to compare metabolic gas exchange during the 6-MWT in older patients with left ventricular systolic dysfunction (LVSD) and in breathless patients with no major structural heart disease (MSHD); (2) to determine the exercise intensity of the 6-MWT relative to peak oxygen uptake; (3) to establish the accuracy and reproducibility of the Metamax 3B ergospirometer during an incremental workload. Twenty four older patients with LVSD (19 male; age 76 ± 5 years; BMI 27 ± 4), and 18 patients with no MSHD (12 male; age 75 ± 8 years; BMI 27 ± 4) attended on consecutive days at the same time. Patients completed a 6-MWT with metabolic gas exchange measurements using the Metamax 3B portable ergospirometer, and an incremental cycle ergometry test using both the Metamax 3B and Oxycon Pro metabolic cart. Patients returned and performed a second 6-MWT and an incremental treadmill test, metabolic gas exchange was measured with the Metamax 3B. In patients with LVSD, the 6-MWT was performed at a higher fraction of maximal exercise capacity (p = 0.02). The 6-MWT was performed below the anaerobic threshold in patients with LVSD (83 %) and in patients with no MSHD (61 %). The Metamax 3B showed satisfactory to high accuracy at 10 W and 20 W in patients with LVSD (r = 0.77 - 0.97, p < 0.05), and no MSHD (r = 0.76 - 0.94, p < 0.05). Metabolic gas exchange variables measured during the 6-MWT showed satisfactory to high day-to-day reproducibility in patients with LVSD (ICC = 0.75 - 0.98), but a higher variability was evident in participants with no MSHD (ICC = 0.62 - 0.97). The Metamax 3B portable ergospirometer is an accurate and reproducible device during submaximal, fixed rate exercise in older patients with LVSD and no MSHD. In elderly patients with LVSD and no MSHD, the 6-MWT should not be considered a maximal test of exercise capacity but rather a test of submaximal exercise performance. Our study demonstrates that the 6-MWT takes place at a higher proportion of peak oxygen uptake in patients with LVSD compared to those with no MSHD, and may be one reason why fatigue is a more prominent symptom in these patients

A Combinatorial Algorithm for All-Pairs Shortest Paths in Directed Vertex-Weighted Graphs with Applications to Disc Graphs

We consider the problem of computing all-pairs shortest paths in a directed graph with real weights assigned to vertices. For an $n\times n$ 0-1 matrix $C,$ let $K_{C}$ be the complete weighted graph on the rows of $C$ where the weight of an edge between two rows is equal to their Hamming distance. Let $MWT(C)$ be the weight of a minimum weight spanning tree of $K_{C}.$ We show that the all-pairs shortest path problem for a directed graph $G$ on $n$ vertices with nonnegative real weights and adjacency matrix $A_G$ can be solved by a combinatorial randomized algorithm in time $$\widetilde{O}(n^{2}\sqrt {n + \min\{MWT(A_G), MWT(A_G^t)\}})$$ As a corollary, we conclude that the transitive closure of a directed graph $G$ can be computed by a combinatorial randomized algorithm in the aforementioned time. $\widetilde{O}(n^{2}\sqrt {n + \min\{MWT(A_G), MWT(A_G^t)\}})$ We also conclude that the all-pairs shortest path problem for uniform disk graphs, with nonnegative real vertex weights, induced by point sets of bounded density within a unit square can be solved in time $\widetilde{O}(n^{2.75})$

Predictions for LHC from SO(4) MWT

We investigate the vector, axial and pseudo scalar mass spectrum of an SO(4) - MWT gauge theory with fermions in the vector representation of SO(4). Here we present the preliminary lattice results for the masses of vector and axial vector meson using Wilson fermions. These spectra are crucial for the discovery and to guide the searches of composite dynamics at the LHC.Comment: 7 pages, 5 figures, presented at the 31st International Symposium on Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz, German

Evaluasi Kemampuan Sistem Menara Pendingin Reaktor Rsg-gas

EVALUASI KEMAMPUAN SISTEM MENARA PENDINGIN REAKTOR RSG-GAS. Saat ini, pengoperasian reaktor telah berlangsung selama 29 tahun. Meskipun selama ini masih dapat beroperasi secara aman. Namun analisis terkini kemampuan sistem pendingin reaktor RSG-GAS sangat penting untuk dilakukan. Hal ini perlu disampaikan kepada badan pengawas untuk mendapatkan persetujuan perpanjangan izin operasi RSG-GAS. Sistem pendingin RSG-GAS adalah pendingin primer dan sekunder. Unit komponen operasi yang berperan mentransfer panas adalah pompa penukar panas dan menara pendingin, dari 7 unit menara pendingin yang ada, dapat dioperasikan sesuai dengan beban panas dari reaktor. Tujuan makalah ini adalah menganalisis kemampuan sistem menara pendingin RSG-GAS pada daya operasi reaktor 20 MWt, 25 MWt dan 30 MWt. Uji verifikasi dikerjakan dengan mengukur temperatur pendingin keluar menara pendingin dan masuk ke reaktor pada operasi reaktor daya 15 MWt dengan moda operasi 4, 5 dan 6 unit menara pendingin. Selanjutnya analisis kemampuan menara pendingin pada daya reaktor 20 MWt, 25 MWt dan 30 MWt dianalisis menggunakan software ChemCAD. Hasil evaluasi menunjukkan bahwa dari aspek keselamatan, reaktor RSG-GAS daya 15 MWt dapat dioperasikan secara aman. Dari analisis operasi 4 dan 5 menara pendingin pada daya 30 MWt mengindikasikan bahwa temperatur pendingin ke reaktor mendekati batas sistem proteksi reaktor yang sebaiknya dihindari, oleh karena itu dianjurkan penggunaan 6 menara pendingin untuk operasi steady state pada daya 30 MWt

Estimation of genetic parameters for preweaning and postweaning growth traits in the Gudali beef cattle using multiple trait derivative free restricted maximum likelihood

Records on pedigree information and growth traits of Gudali beef calves were obtained from the Institute of Agricultural Research for Development, Cameroon. Data were edited to have complete information on calf, sire and dam identity, sex, dates and season of birth, herd and weights at birth (BWT), 6 months (6 MWT), weaning (WWT), 12 months (12 MWT), yearling (YWT), 18 months (18 MWT), 24 months (24 MWT) and 36 months (36 MWT). Genetic parameters were estimated using multiple trait derivative free restricted maximum likelihood (MTDFRML) program. The estimated direct (h2a) and maternal (h2m) heritabilities for BWT, 6 MWT, WWT, YWT, 18 MWT, 24 MWT and 36 MWT obtained were 0.39, 0.10, 0.25, 0.21, 0.18, 0.25, 0.18 and 0.05, 0.07, 0.11, 0.10, 0.05, 0.09, 0.07, respectively. Estimates of maternal genetic variance and corresponding heritabilities (h2m) were lower than estimates for direct additive variance and heritability (h2a). The genetic correlation between direct and maternal influence were negative. The across-trait direct and maternal genetic correlation estimates were medium to high with the exception of BWT and 18 MWT; BWT and 36 MWT, had negative values. The positive values reported for the additive and maternal correlations between the growth parameters indicate that selection for one trait resulted in genetic improvement in the other. The moderate values of heritabilities indicate that selection for growth traits was effective.Key words: Covariance, heritability, genetic correlation, growth traits

Bond degradation and reduced cover in concrete with transverse reinforcement

Corrosion of the internal steel reinforcement is among the main causes of deterioration in concrete bridges. The expansive nature of corrosion products can lead to cracking, delamination or complete spalling of the concrete cover. The subsequent reduction in reinforcement anchorage is difficult to assess accurately. To study the effects of spalling on the steel-to-concrete bond, pull-out tests were carried out on half-joint cantilever specimens. Spalling was simulated with progressively reduced cover. This led to degradation of bond and anchorage of the longitudinal bars. However, the presence of transverse confining reinforcement had beneficial effects, limiting bond degradation and avoiding brittle failures where splitting occurred