3,874 research outputs found
Smooth Regression Analysis
No full textWatson GS. Smooth Regression Analysis. Sankhyā: The Indian Journal of Statistics; Series A. 1964;26:359-372
Complete Genome Sequence of the Human Herpesvirus 6A Strain AJ from Africa Resembles Strain GS from North America.
No full textThe 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)
Analysis of Recombinative Algorithms on a Non-Separable Building-Block Problem
No full textEvolution by natural selection is a process of variation and selection acting on replicating units. These units are often assumed to be individuals, but in a sexual population, the largest reliably-replicated unit on which selection can act is a small section of chromosome – hence, the ‘selfish gene’ model. However, the scale of unit at which variation by spontaneous mutation occurs is different from the scale of unit at which variation by recombination occurs. I suggest that the action of recombinative variation and mutational variation together can enable local optimization to occur at two different scales simultaneously. I adapt a recent model illustrating a benefit of sexual recombination to illustrate conditions for two scales of optimization in natural populations, and show that the operation of natural selection in this scenario cannot be understood by considering either scale alone
EBUS-GS and VBN for GGO lesions
No full textBackground: 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
Quantum random walks
No full textAfter a short review of the notion of a quantum Markov chain,
a particular class
of such chains, generalizing in a natural way the usual random walks,
is introduced. In Section (5) a limit theorem for quantum random walks
is proved showing that the diffusion limit of the continuous coherent
chain is an abelian extension of the Fock quantum Brownian motion on
Markov states of the quantum electromagnetic field
No full textA translation-invariant state (a quantum Markov chain) is associated with a nearest-neighbor interaction
on a one-dimensional lattice by a new technique which provides closed forms for all the
correlation functions. When applied to an Ising-type perturbation of a chain of harmonic oscillators,
the dynamics can be computed explicitly. The resulting translation-invariant distribution is
substantially different from the Planck distribution when the temperature and the coupling constant
are large. For the evolution of the field operators on a given mode, we obtain a natural nonlinear
generalization of the theorem which states that the free evolution of the field operators is obtained
by second quantization of the classical free evolution
Solution structure of a DNA decanter duplex containing the stable 3 T center dot G base pair of the pyrimidine(6-4)pyrimidone photoproduct [(6-4) adduct]: Implications for the highly specific 3 T -> C transition of the (6-4) adduct
No full textThe pyrimidine(6-4)pyrimidone photoproduct [(6-4) adduct] is one of the major photoproducts induced by UV irradiation of DNA and occurs at TpT sites. The (6-4) adduct is highly mutagenic and leads most often to a 3' T --> C transition with 85% replicating error frequency [LeClerc, J E,, Borden, A. & Lawrence, C, W, (1991) Proc. Natl, Acad, Sci, USA 88, 9685-9689]. To determine the origin of the specific 3' T --> C transition of the (6-4) adduct, we have used experimental NMR restraints and molecular dynamics to determine the solution structure of a (6-4)-lesion DNA decamer duplex that contains a mismatched base pair between the 3' T residue and an opposed G residue. Normal Watson-Crick-type hydrogen bonding is retained at the 5' T of the lesion site. The O2 carbonyl of the 3' T residue forms hydrogen bonds with the imino and amino protons of the opposed C residue. This potential hydrogen bonding stabilizes the overall helix and restores the highly distorted conformation of the (6-4) adduct to the typical B-form-like DNA structure. This structural feature can explain the marked preference for the insertion of an A residue opposite the 5' T and a G residue opposite the 3' T of the (6-4) lesion during trans-lesion synthesis. Thus these insertions yield the predominant 3' T --> C transition
The solution structure of a psoralen cross-linked DNA duplex by NMR and relaxation matrix refinement
No full text(T)he three dimensional structure of the DNA oligomer d(5'-GGGTACCC-3')(2) cross-linked with 4'-aminomethyl-4,5',8-trimethylpsoralen (AMT) has been determined by two-dimensional NMR and a relaxation matrix refinement method. NMR data and structural calculation establish that the cross-linking of the psoralen in the B-DNA duplex retains Watson-Crick type hydrogen bonding throughout the duplex, although the thymine residue which is cross-linked with psoralen forms a weaker hydrogen bond. The psoralen cross-linking in DNA duplex induces significant change of the local DNA structure, but has no important effect on overall DNA helix. Our observation places an upper limit of 10 degrees on overall DNA bending by psoralen cross-linking, which is consistent with the result of HMT-octamer cross Link [Spielmann, H. P., Dwyer, T. J., Sastry, S. S., Hearst, J. E., and Wemmer, D. E., (1995) Proc. Natl. Acad. Sci. USA 92, 2345-2349] and gel electrophoretic study [Haran,T. E., and Crothers, D. E. (1988) Biochemistry 27, 6967-6971]. (C) 1996 Academic Press, Inc
Symbiotic Composition and Evolvability
No full textSeveral of the Major Transitions in natural evolution, such as the symbiogenic origin of eukaryotes from prokaryotes, share the feature that existing entities became the components of composite entities at a higher level of organisation. This composition of pre-adapted extant entities into a new whole is a fundamentally different source of variation from the gradual accumulation of small random variations, and it has some interesting consequences for issues of evolvability. In this paper we present a very abstract model of 'symbiotic composition' to explore its possible impact on evolvability. A particular adaptive landscape is used to exemplify a class where symbiotic composition has an adaptive advantage with respect to evolution under mutation and sexual recombination. Whilst innovation using conventional evolutionary algorithms becomes increasingly more difficult as evolution continues in this problem, innovation via symbiotic composition continues through successive hierarchical levels unimpeded. <br/
Some stationary Markov processes in discrete time for unit vectors
No full textSome simple parametric models are given for stationary sequences of unit vectors. Their behaviour is mainly shown by simulations. One process is reminescent of the changing polarity of the earth's magnetic field. Some extensions are suggested
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