1,322 research outputs found

    Atomic Resonance and Scattering

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    Contains research objectives, summary of research and reports on three research projects.U. S. Navy (Office of Naval Research) under Contract N00014-67-A-0204-0006Joint Services Electronics Programs (U. S. Army, U.S. Navy, and U. S. Air Force) under Contract DA 28-043-AMC-02536(E

    Atomic Resonance and Scattering

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    Contains research objectives.Joint Services Electronics Programs (U. S. Army, U.S. Navy, and U.S. Air Force) under Contract DA 36-039-AMC-03200(E)Sloan Fund for Basic Research (M.I.T. Grant 95

    Atomic Resonance and Scattering

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    Contains report on one research project.Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U. S. Air Force) under Contract DA 28-043-AMC-02536(E)Sloan Fund for Basic Research (M. I. T. Grant 170)U. S. Navy (Office of Naval Research) under Contract N00014-67-A-0204-000

    Quantifying Privacy: A Novel Entropy-Based Measure of Disclosure Risk

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    It is well recognised that data mining and statistical analysis pose a serious treat to privacy. This is true for financial, medical, criminal and marketing research. Numerous techniques have been proposed to protect privacy, including restriction and data modification. Recently proposed privacy models such as differential privacy and k-anonymity received a lot of attention and for the latter there are now several improvements of the original scheme, each removing some security shortcomings of the previous one. However, the challenge lies in evaluating and comparing privacy provided by various techniques. In this paper we propose a novel entropy based security measure that can be applied to any generalisation, restriction or data modification technique. We use our measure to empirically evaluate and compare a few popular methods, namely query restriction, sampling and noise addition.Comment: 20 pages, 4 figure

    Non-monotonic magnetic field and density dependence of in-plane magnetoresistance in dilute two-dimensional holes in GaAs/AlGaAs

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    We studied low temperature (T=50mK) in-plane magnetoresistance of a dilute two-dimensional hole system in GaAs/AlGaAs heterostructure that exhibits an apparent metal-insulator transition. We found an anisotropic magnetoresistance, which changes dramatically at high in-plane fields (B_{\parallel}\agt5T) as the hole density is varied. At high densities where the system behaves metallic at B=0B_{\parallel}=0, the transverse magnetoresistance is larger than the longitudinal magnetoresistance. With decreasing the hole density the difference becomes progressively smaller, and at densities near the "critical" density and lower, the longitudinal magnetoresistance becomes larger than the transverse magnetoresistance

    A Profile Likelihood Analysis of the Constrained MSSM with Genetic Algorithms

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    The Constrained Minimal Supersymmetric Standard Model (CMSSM) is one of the simplest and most widely-studied supersymmetric extensions to the standard model of particle physics. Nevertheless, current data do not sufficiently constrain the model parameters in a way completely independent of priors, statistical measures and scanning techniques. We present a new technique for scanning supersymmetric parameter spaces, optimised for frequentist profile likelihood analyses and based on Genetic Algorithms. We apply this technique to the CMSSM, taking into account existing collider and cosmological data in our global fit. We compare our method to the MultiNest algorithm, an efficient Bayesian technique, paying particular attention to the best-fit points and implications for particle masses at the LHC and dark matter searches. Our global best-fit point lies in the focus point region. We find many high-likelihood points in both the stau co-annihilation and focus point regions, including a previously neglected section of the co-annihilation region at large m_0. We show that there are many high-likelihood points in the CMSSM parameter space commonly missed by existing scanning techniques, especially at high masses. This has a significant influence on the derived confidence regions for parameters and observables, and can dramatically change the entire statistical inference of such scans.Comment: 47 pages, 8 figures; Fig. 8, Table 7 and more discussions added to Sec. 3.4.2 in response to referee's comments; accepted for publication in JHE

    Correlation between nucleotide composition and folding energy of coding sequences with special attention to wobble bases

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    Background: The secondary structure and complexity of mRNA influences its accessibility to regulatory molecules (proteins, micro-RNAs), its stability and its level of expression. The mobile elements of the RNA sequence, the wobble bases, are expected to regulate the formation of structures encompassing coding sequences. Results: The sequence/folding energy (FE) relationship was studied by statistical, bioinformatic methods in 90 CDS containing 26,370 codons. I found that the FE (dG) associated with coding sequences is significant and negative (407 kcal/1000 bases, mean +/- S.E.M.) indicating that these sequences are able to form structures. However, the FE has only a small free component, less than 10% of the total. The contribution of the 1st and 3rd codon bases to the FE is larger than the contribution of the 2nd (central) bases. It is possible to achieve a ~ 4-fold change in FE by altering the wobble bases in synonymous codons. The sequence/FE relationship can be described with a simple algorithm, and the total FE can be predicted solely from the sequence composition of the nucleic acid. The contributions of different synonymous codons to the FE are additive and one codon cannot replace another. The accumulated contributions of synonymous codons of an amino acid to the total folding energy of an mRNA is strongly correlated to the relative amount of that amino acid in the translated protein. Conclusion: Synonymous codons are not interchangable with regard to their role in determining the mRNA FE and the relative amounts of amino acids in the translated protein, even if they are indistinguishable in respect of amino acid coding.Comment: 14 pages including 6 figures and 1 tabl

    Enrichment analysis of Alu elements with different spatial chromatin proximity in the human genome

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    Transposable elements (TEs) have no longer been totally considered as “junk DNA” for quite a time since the continual discoveries of their multifunctional roles in eukaryote genomes. As one of the most important and abundant TEs that still active in human genome, Alu, a SINE family, has demonstrated its indispensable regulatory functions at sequence level, but its spatial roles are still unclear. Technologies based on 3C(chromosomeconformation capture) have revealed the mysterious three-dimensional structure of chromatin, and make it possible to study the distal chromatin interaction in the genome. To find the role TE playing in distal regulation in human genome, we compiled the new released Hi-C data, TE annotation, histone marker annotations, and the genome-wide methylation data to operate correlation analysis, and found that the density of Alu elements showed a strong positive correlation with the level of chromatin interactions (hESC: r=0.9, P<2.2×1016; IMR90 fibroblasts: r = 0.94, P < 2.2 × 1016) and also have a significant positive correlation withsomeremote functional DNA elements like enhancers and promoters (Enhancer: hESC: r=0.997, P=2.3×10−4; IMR90: r=0.934, P=2×10−2; Promoter: hESC: r = 0.995, P = 3.8 × 10−4; IMR90: r = 0.996, P = 3.2 × 10−4). Further investigation involving GC content and methylation status showed the GC content of Alu covered sequences shared a similar pattern with that of the overall sequence, suggesting that Alu elements also function as the GC nucleotide and CpG site provider. In all, our results suggest that the Alu elements may act as an alternative parameter to evaluate the Hi-C data, which is confirmed by the correlation analysis of Alu elements and histone markers. Moreover, the GC-rich Alu sequence can bring high GC content and methylation flexibility to the regions with more distal chromatin contact, regulating the transcription of tissue-specific genes

    Hsp90 orchestrates transcriptional regulation by Hsf1 and cell wall remodelling by MAPK signalling during thermal adaptation in a pathogenic yeast

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    Acknowledgments We thank Rebecca Shapiro for creating CaLC1819, CaLC1855 and CaLC1875, Gillian Milne for help with EM, Aaron Mitchell for generously providing the transposon insertion mutant library, Jesus Pla for generously providing the hog1 hst7 mutant, and Cathy Collins for technical assistance.Peer reviewedPublisher PD

    Similar dispersal patterns between two closely related birds with contrasting migration strategies

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    Studying dispersal is crucial to understand metapopulation and sink-source dynamics and invasion processes. The capability to disperse is especially important for species living in fragmented habitats like wetlands. We investigated the distribution of natal and breeding dispersal distances and philopatry in Spanish populations of two closely related reedbed-nesting birds, the Moustached Warbler Acrocephalus melanopogon and the Eurasian Reed Warbler Acrocephalus scirpaceus. These warblers are morphologically very similar, but differ in migration strategy and, in our study area, in population size. Our aims were to find the best model for dispersal distances and to assess the occurrence of intra- or interspecific differences in dispersal patterns. We used ringing data from the Spanish marking scheme and selected recaptures to avoid including migrating individuals. In both species, most individuals were philopatric but dispersing birds were able to cross large distances (up to more than 100 km), suggesting the capability to compensate for habitat fragmentation. We found the heavy-tailed Cauchy distribution to be the best conceptual description for our data, in all cases but natal dispersal of Moustached Warblers. Among Eurasian Reed Warblers, natal philopatry was lower than breeding philopatry. We found no significant interspecific differences. This does not confirm the hypothesis of higher dispersal ability in long distance migrants (like Eurasian Reed Warblers) than in resident/short distance migrant bird species (like Moustached Warblers). 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