4,766 research outputs found
A metric for rooted trees with unlabeled vertices based on nested parentheses
No full text[[abstract]]In this paper, we propose a new metric for rooted trees with unlabeled vertices based on alignments of nested parenthesis strings. We prove that the time complexity for computing this metric is NP-hard and present a 1.5-approximation algorithm for it. (C) 2010 Elsevier B.V. All rights reserved.[[note]]SC
An efficient convergent lattice algorithm for European Asian options
No full text[[abstract]]Financial options whose payoff depends critically on historical prices are called path-dependent options. Their prices are usually harder to calculate than options whose prices do not depend on past histories. Asian options are popular path-dependent derivatives, and it has been a long-standing problem to price them efficiently and accurately. No known exact pricing formulas are available to price them under the continuous-time Black-Scholes model. Although approximate pricing formulas exist, they lack accuracy guarantees. Asian options can be priced numerically on the lattice. A lattice divides the time to maturity into n equal-length time steps. The option price computed by the lattice converges to the option value under the Black-Scholes model as n -> infinity. Unfortunately, only subexponential-time algorithms are available if Asian options are to be priced on the lattice without approximations. Efficient approximation algorithms are available for the lattice. The fastest lattice algorithm published in the literature runs in O(n(3.5))-time, whereas for the related PDE method, the fastest one runs in O(n(3)) time. This paper presents a new lattice algorithm that runs in O(n(2.5)) time, the best in the literature for such methods. Our algorithm exploits the method of Lagrange multipliers to minimize the approximation error. Numerical results verify its accuracy and the excellent performance. (c) 2004 Elsevier Inc. All rights reserved.[[note]]SC
Factors associated with low bone mass in hemodialysis patients: A cross-sectional correlation study
No full text
Identifying the most efficient items from the MMSE for cognitive function assessment in older Taiwanese patients
No full textComplete Genome Sequence of the Human Herpesvirus 6A Strain AJ from Africa Resembles Strain GS from North America.
Full text linkThe genome sequence of human herpesvirus 6A (HHV-6A) strain AJ was determined in a comparison of target enrichment and long-range PCR using next-generation sequencing methodologies. The analyses show 85 predicted open reading frames (ORFs), conservation with sequenced HHV-6A reference strain U1102, and closest identity to the recently determined GS strain, despite different geographic origins (United States and Gambia)
A fast algorithm for finding the positions of all squares in a run-length encoded string
No full text[[abstract]]Squares are strings of the form win where in is any nonempty string. Main and Lorentz proposed an O(n log n)-time algorithm for finding the positions of all squares ill a string of length n. Based on their result, we show how to find the positions of all squares in a run-length encoded string in time O(N logN) where N is the number of runs in this string, provided that we do not explicitly compute at all "trivial squares" occurring within runs. The algorithm is optimal and its time complexity is independent of the length of the original uncompressed string. (C) 2009 Elsevier B.V. All rights reserved.[[note]]SC
EBUS-GS and VBN for GGO lesions
Full text linkBackground: Endobronchial ultrasonography with guide sheath (EBUS-GS) could be useful for diagnosing ground-glass opacity (GGO) predominant-type lesions in the peripheral lung. Furthermore, several studies have reported that transbronchial biopsy using EBUS-GS and virtual bronchoscopic navigation (VBN) was safe and effective for diagnosing small peripheral lung lesions. Our objectives were to diagnose solitary peripheral GGO predominant-type lesions by transbronchial biopsy using EBUS-GS and VBN under radiographic fluoroscopic guidance, and to evaluate the clinical factors associated with diagnostic yield. Methods: The medical records of 169 patients with GGO predominant-type lesions who underwent transbronchial biopsy using EBUS-GS and VBN under radiographic fluoroscopic guidance were retrospectively reviewed. Results: Endobronchial ultrasonography images could be obtained for 156 (92%) of 169 GGO predominant-type lesions, and 116 (69%) were successfully diagnosed by this method (20 of 31 pure GGO lesions [65%]; 96 of 138 mixed GGO predominant-type lesions [70%]). The mean size of diagnosed lesions was significantly larger than that of nondiagnosed lesions (22 mm versus 18 mm, p < 0.01). Regarding diagnostic yield based on computed tomography sign, cases with presence of a bronchus leading directly to a lesion had significantly higher diagnostic yield than the other lesions (p < 0.01). Conclusions: The addition of VBN to EBUS-GS could be useful in clinical practice for diagnosing GGO predominant-type lesions in the peripheral lung
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