4,517 research outputs found
The Great Eruption of Eta Carinae
During the years 1838-1858, the very massive star {\eta} Carinae became the
prototype supernova impostor: it released nearly as much light as a supernova
explosion and shed an impressive amount of mass, but survived as a star.1 Based
on a light-echo spectrum of that event, Rest et al.2 conclude that "a new
physical mechanism" is required to explain it, because the gas outflow appears
cooler than theoretical expectations. Here we note that (1) theory predicted a
substantially lower temperature than they quoted, and (2) their inferred
observational value is quite uncertain. Therefore, analyses so far do not
reveal any significant contradiction between the observed spectrum and most
previous discussions of the Great Eruption and its physics.Comment: To appear in Nature, a brief communication arising in response to
Rest et al. 2012. Submitted to Nature February 17, 201
System-adapted correlation energy density functionals from effective pair interactions
We present and discuss some ideas concerning an ``average-pair-density
functional theory'', in which the ground-state energy of a many-electron system
is rewritten as a functional of the spherically and system-averaged pair
density. These ideas are further clarified with simple physical examples. We
then show that the proposed formalism can be combined with density functional
theory to build system-adapted correlation energy functionals. A simple
approximation for the unknown effective electron-electron interaction that
enters in this combined approach is described, and results for the He series
and for the uniform electron gas are briefly reviewed.Comment: to appear in Phil. Mag. as part of Conference proceedings for the
"Electron Correlations and Materials Properties", Kos Greece, July 5-9, 200
On The Potential of Minimal Flavour Violation
Assuming the Minimal Flavour Violation hypothesis, we derive the general
scalar potential for fields whose background values are the Yukawa couplings.
We analyze the minimum of the potential and discuss the fine-tuning required to
dynamically generate the mass hierarchies and the mixings between different
quark generations. Two main cases are considered, corresponding to Yukawa
interactions being effective operators of dimension five or six (or,
equivalently, resulting from bi-fundamental and fundamental scalar fields,
respectively). At the renormalizable and classical level, no mixing is
naturally induced from dimension five Yukawa operators. On the contrary, from
dimension six Yukawa operators one mixing angle and a strong mass hierarchy
among the generations result.Comment: 33 pages, 6 figures; Note added in proof on the stability of the
minima of the scalar potential; results unchanged; references adde
An integrated and coordinated approach to preventing recurrent coronary heart disease events in Australia: Policy statement from the Australian Cardiovascular Health and Rehabilitation Association
• Implementing existing knowledge about cardiac rehabilitation (CR) and heart failure management could markedly reduce mortality after acute coronary syndromes and revascularisation therapy. • Contemporary CR and secondary prevention programs are cost-effective, safe and beneficial for patients of all ages, leading to improved survival, fewer revascularisation procedures and reduced rehospitalisation. • Despite the proven benefits attributed to these secondary prevention interventions, they are not well attended by patients. • Modern programs must be flexible, culturally safe, multifaceted and integrated with the patient's primary health care provider to achieve optimal and sustainable benefits for most patients
Characterisation of urinary WFDC12 in small nocturnal basal primates, mouse lemurs (Microcebus spp.)
Mouse lemurs are basal primates that rely on chemo- and acoustic signalling for social interactions in their dispersed social systems. We examined the urinary protein content of two mouse lemurs species, within and outside the breeding season, to assess candidates used in species discrimination, reproductive or competitive communication. Urine from Microcebus murinus and Microcebus lehilahytsara contain a predominant 10 kDa protein, expressed in both species by some, but not all, males during the breeding season, but at very low levels by females. Mass spectrometry of the intact proteins confirmed the protein mass and revealed a 30 Da mass difference between proteins from the two species. Tandem mass spectrometry after digestion with three proteases and sequencing de novo defined the complete protein sequence and located an Ala/Thr difference between the two species that explained the 30 Da mass difference. The protein (mature form: 87 amino acids) is an atypical member of the whey acidic protein family (WFDC12). Seasonal excretion of this protein, species difference and male-specific expression during the breeding season suggest that it may have a function in intra- and/or intersexual chemical signalling in the context of reproduction, and could be a cue for sexual selection and species recognition
The Impact of Flavour Changing Neutral Gauge Bosons on B->X_s gamma
The branching ratio of the rare decay B->X_s gamma provides potentially
strong constraints on models beyond the Standard Model. Considering a general
scenario with new heavy neutral gauge bosons, present in particular in Z' and
gauge flavour models, we point out two new contributions to the B->X_s gamma
decay. The first one originates from one-loop diagrams mediated by gauge bosons
and heavy exotic quarks with electric charge -1/3. The second contribution
stems from the QCD mixing of neutral current-current operators generated by
heavy neutral gauge bosons and the dipole operators responsible for the B->X_s
gamma decay. The latter mixing is calculated here for the first time. We
discuss general sum rules which have to be satisfied in any model of this type.
We emphasise that the neutral gauge bosons in question could also significantly
affect other fermion radiative decays as well as non-leptonic two-body B
decays, epsilon'/epsilon, anomalous (g-2)_mu and electric dipole moments.Comment: 31 pages, 5 figures; version published on JHEP; added magic QCD
numbers for flavour-violating Z gauge boson contribution to B -> X_s gamm
Spectrum of Clinical Signs and Genetic Characterization of Gelatinous Drop-Like Corneal Dystrophy in a Colombian Family
PURPOSE: To describe the clinical signs of gelatinous drop-like corneal dystrophy (GDLD) in a consanguineous Colombian family and determine the underlying genetic cause.
METHODS: We performed ocular examination of available family members and bidirectionally Sanger sequenced the GDLD-associated gene, TACSTD2. In one individual, the presence of subepithelial amyloid was confirmed with biopsy.
RESULTS: The parents were consanguineous and 5 of their 10 children had GDLD. Typical mulberry subepithelial deposits with subepithelial vascularization were present in 3 individuals; 2 individuals only had mild polymorphic anterior stromal opacity. We identified a homozygous TACSTD2 missense mutation, c.551A>G, p.(Tyr184Cys), in the affected family members. Both parents were heterozygous for the mutation, and unaffected siblings were either heterozygous or homozygous wild-type for this allele. In the Colombian population, this mutation has a minor allele frequency of 0.53%.
CONCLUSION: The clinical presentation of GDLD in this family was variable and does not solely support an age-dependent progression of the phenotype, suggesting that environmental or other genetic factors can modify phenotypic expression. The relatively high prevalence of this mutation in the Colombian population suggests that other individuals may have undiagnosed subclinical disease
The s ---> d gamma decay in and beyond the Standard Model
The New Physics sensitivity of the s ---> d gamma transition and its
accessibility through hadronic processes are thoroughly investigated. Firstly,
the Standard Model predictions for the direct CP-violating observables in
radiative K decays are systematically improved. Besides, the magnetic
contribution to epsilon prime is estimated and found subleading, even in the
presence of New Physics, and a new strategy to resolve its electroweak versus
QCD penguin fraction is identified. Secondly, the signatures of a series of New
Physics scenarios, characterized as model-independently as possible in terms of
their underlying dynamics, are investigated by combining the information from
all the FCNC transitions in the s ---> d sector.Comment: 54 pages, 14 eps figure
Voluntary exercise can strengthen the circadian system in aged mice
Consistent daily rhythms are important to healthy aging according to studies linking disrupted circadian rhythms with negative health impacts. We studied the effects of age and exercise on baseline circadian rhythms and on the circadian system's ability to respond to the perturbation induced by an 8 h advance of the light:dark (LD) cycle as a test of the system's robustness. Mice (male, mPer2luc/C57BL/6) were studied at one of two ages: 3.5 months (n = 39) and >18 months (n = 72). We examined activity records of these mice under entrained and shifted conditions as well as mPER2::LUC measures ex vivo to assess circadian function in the suprachiasmatic nuclei (SCN) and important target organs. Age was associated with reduced running wheel use, fragmentation of activity, and slowed resetting in both behavioral and molecular measures. Furthermore, we observed that for aged mice, the presence of a running wheel altered the amplitude of the spontaneous firing rate rhythm in the SCN in vitro. Following a shift of the LD cycle, both young and aged mice showed a change in rhythmicity properties of the mPER2::LUC oscillation of the SCN in vitro, and aged mice exhibited longer lasting internal desynchrony. Access to a running wheel alleviated some age-related changes in the circadian system. In an additional experiment, we replicated the effect of the running wheel, comparing behavioral and in vitro results from aged mice housed with or without a running wheel (>21 months, n = 8 per group, all examined 4 days after the shift). The impact of voluntary exercise on circadian rhythm properties in an aged animal is a novel finding and has implications for the health of older people living with environmentally induced circadian disruption
Minimal Flavour Violation for Leptoquarks
Scalar leptoquarks, with baryon and lepton number conserving interactions,
could have TeV scale masses, and be produced at colliders or contribute to a
wide variety of rare decays. In pursuit of some insight as to the most
sensitive search channels, We assume that the leptoquark-lepton-quark coupling
can be constructed from the known mass matrices. We estimate the rates for
selected rare processes in three cases: leptoquarks carrying lepton and quark
flavour, leptoquarks with quark flavour only, and unflavoured leptoquarks. We
find that leptoquark decay to top quarks is an interesting search channel.Comment: 17 pages, 2 figures, minor changes and references adde
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