2,227 research outputs found
Characterization of the non-classical nature of conditionally prepared single photons
A reliable single photon source is a prerequisite for linear optical quantum
computation and for secure quantum key distribution. A criterion yielding a
conclusive test of the single photon character of a given source, attainable
with realistic detectors, is therefore highly desirable. In the context of
heralded single photon sources, such a criterion should be sensitive to the
effects of higher photon number contributions, and to vacuum introduced through
optical losses, which tend to degrade source performance. In this paper we
present, theoretically and experimentally, a criterion meeting the above
requirements.Comment: 4 pages; 3 figure
The Role of in Determining the Weak Phase
The decay rates for , , and the
charge-conjugate processes were found to provide information on the weak phase
when the ratio of weak tree and penguin
amplitudes was taken from data on or semileptonic
decays. We show here that the rates for and can provide the necessary information on , and estimate the
statistical accuracy of forthcoming measurements at the Fermilab Tevatron.Comment: 8 pages, LaTeX, no figures, submitted to Physics Letters B,
corrections to discussion of SU(3) breaking adde
Exploring the Longitudinal Relationship Between Short Sleep Duration, Temperament and Attention Deficit Hyperactivity Disorder Symptoms in a Biethnic Population of Children Aged Between 6 and 61 Months:A Born in Bradford Study
Objective: Examine the association between sleep duration, temperament and symptoms of Attention Deficit Hyperactivity Disorder (ADHD) in a biethnic child-population from The Born in Bradford cohort. Method: Parent-report sleep duration categorized children as: early short, late short, consistently short or consistently normal sleepers between 6 and 36 months. Temperament was measured using the Infant Characteristics Questionnaire at 6 months. The Strengths and Difficulties Questionnaire assessed symptoms of ADHD at 37, 54, and 61 months. Results: Normal sleepers before 18 months had significantly fewer ADHD symptoms at 37 months compared with consistently short sleepers. Fussiness at 6 months was significantly positively associated with ADHD symptoms at 37 and 54 months; but does not appear to mediate the relationship between sleep duration and ADHD symptoms. Conclusion: Awareness of the relationship between short sleep duration and fussiness in infancy and later ADHD symptomatology may support earlier identification of arising difficulties in children
Entanglement in an expanding spacetime
We show that a dynamical spacetime generates entanglement between modes of a
quantum field. Conversely, the entanglement encodes information concerning the
underlying spacetime structure, which hints at the prospect of applications of
this observation to cosmology. Here we illustrate this point by way of an
analytically exactly soluble example, that of a scalar quantum field on a
two-dimensional asymptotically flat Robertson-Walker expanding spacetime. We
explicitly calculate the entanglement in the far future, for a quantum field
residing in the vacuum state in the distant past. In this toy universe, it is
possible to fully reconstruct the parameters of the cosmic history from the
entanglement entropy.Comment: 4 pages, no figures; I. F-S published previously under Fuentes-Gurid
Use of short-tandem repeat (STR) fingerprinting to validate sample origins in hepatitis C virus molecular epidemiology studies
Sequence analysis is used to define the molecular epidemiology and evolution of the hepatitis C virus. Whilst most studies have shown that individual patients harbour viruses that are derived from a limited number of highly related strains, some recent reports have shown that some patients can be co-infected with very distinct variants whose frequency can fluctuate greatly. Whilst co-infection with highly divergent strains is possible, an alternative explanation is that such data represent contamination or sample mix-up. In this study, we have shown that DNA fingerprinting techniques can accurately assess sample provenance and differentiate between samples that are truly exhibiting mixed infection from those that harbour distinct virus populations due to sample mix-up. We have argued that this approach should be adopted routinely in virus sequence analyses to validate sample provenance
Final-State Phases in Baryon-Antibaryon Decays
The recent observation of the decay \ob \to \Lambda_c^+ \bar p suggests
that related decays may soon be visible at colliders. It is shown how
these decays can shed light on strong final-state phases and amplitudes
involving the spectator quark, both of which are normally expected to be small
in B decays.Comment: 14 pages, LaTeX, 2 figures, submitted to Phys. Rev. D, references and
discussion of helicity amplitudes adde
Phylogeny and biogeography of southern African spoon-winged lacewings (Neuroptera : Nemopteridae : Nemopterinae)
Nemopteridae are a charismatic family of lacewings characterised by uniquely extended hind wings.They
are an ancient widespread group in the drier regions of the world. The family comprises two subfamilies,
Crocinae (thread-wings) and Nemopterinae (spoon- and ribbon-wings). The present distribution of the
family has been largely influenced by the vicariant events of plate tectonics, resulting in relict populations
in some parts of the world and extensive evolutionary radiations in others, particularly southern Africa
where the vast majority of the species are endemic to the Western and Northern Cape Provinces of South
Africa. This study aimed to establish the validity of the 11 currently recognised genera and infer their
biogeographic history using molecular sequence data from four gene regions. The hypothesis that the
Cape nemopterines co-evolved with certain taxa in the Cape Floristic Region was also tested.
Phylogenetic analysis supports seven of the 11 currently recognised genera. The crown age of the
Nemopterinae is estimated to be at ca. 145.6 Mya, indicating that the group has been present since the
late Jurassic. Most of the genera appear to have diversified during the middle Eocene and into the middle
Miocene (ca. 44 - 11 Mya) with recent rapid radiation of several of the genera occurring during the late
Miocene (ca. 6 - 4.5 Mya). While these data support an initial radiation with the Rushioideae (Aizoaceae)
it is recommended that further study including observations and gut content be carried out. [238]Funding for the genetic analysis was provided through the National Research Foundation (NRF) with additional private funding from J.B. Ball.www.elsevier.com/locate/ympevhb2013ab201
A diverse panel of hepatitis C virus glycoproteins for use in vaccine research reveals extremes of monoclonal antibody neutralization resistance
Despite significant advances in the treatment of hepatitis C virus (HCV) infection, the need to develop preventative vaccines remains. Identification of the best vaccine candidates and evaluation of their performance in preclinical and clinical development will require appropriate neutralization assays utilizing diverse HCV isolates. We aimed to generate and characterize a panel of HCVE1E2 glycoproteins suitable for subsequent use in vaccine and therapeutic antibody testing. Full-length E1E2 clones were PCR amplified from patient- derived serum samples, cloned into an expression vector, and used to generate viral pseudoparticles (HCVpp). In addition, some of these clones were used to generate cell culture infectious (HCVcc) clones. The infectivity and neutralization sensitivity of these viruses were then determined. Bioinformatic and HCVpp infectivity screening of approximately 900 E1E2 clones resulted in the assembly of a panel of 78 functional E1E2 proteins representing distinct HCV genotypes and different stages of infection. These HCV glycoproteins differed markedly in their sensitivity to neutralizing antibodies. We used this panel to predict antibody efficacy against circulating HCV strains, highlighting the likely reason why some monoclonal antibodies failed in previous clinical trials. This study provides the first objective categorization of cross-genotype patient-derived HCVE1E2 clones according to their sensitivity to antibody neutralization. It has shown that HCV isolates have clearly distinguishable neutralization-sensitive, -resistant, or -intermediate phenotypes, which are independent of genotype. The panel provides a systematic means for characterization of the neutralizing response elicited by candidate vaccines and for defining the therapeutic potential of monoclonal antibodies
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