10,008 research outputs found

    UHF flows and the flip automorphism

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    A UHF flow is an infinite tensor product type action of the reals on a UHF algebra AA and the flip automorphism is an automorphism of A⊗AA\otimes A sending x⊗yx\otimes y into y⊗xy\otimes x. If α\alpha is an inner perturbation of a UHF flow on AA, there is a sequence (un)(u_n) of unitaries in A⊗AA\otimes A such that αt⊗αt(un)−un\alpha_t\otimes \alpha_t(u_n)-u_n converges to zero and the flip is the limit of \Ad u_n. We consider here whether the converse holds or not and solve it with an additional assumption: If A⊗A≅AA\otimes A\cong A and α\alpha absorbs any UHF flow β\beta (i.e., α⊗β\alpha\otimes\beta is cocycle conjugate to α\alpha), then the converse holds; in this case α\alpha is what we call a universal UHF flow.Comment: 18 page

    Search for associations containing young stars (SACY). V. Is multiplicity universal? Tight multiple systems

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    Context: Dynamically undisrupted, young populations of stars are crucial to study the role of multiplicity in relation to star formation. Loose nearby associations provide us with a great sample of close (<<150 pc) Pre-Main Sequence (PMS) stars across the very important age range (≈\approx5-70 Myr) to conduct such research. Aims: We characterize the short period multiplicity fraction of the SACY (Search for Associations Containing Young stars) accounting for any identifiable bias in our techniques and present the role of multiplicity fractions of the SACY sample in the context of star formation. Methods: Using the cross-correlation technique we identified double-lined spectroscopic systems (SB2), in addition to this we computed Radial Velocity (RV) values for our subsample of SACY targets using several epochs of FEROS and UVES data. These values were used to revise the membership of each association then combined with archival data to determine significant RV variations across different data epochs characteristic of multiplicity; single-lined multiple systems (SB1). Results: We identified 7 new multiple systems (SB1s: 5, SB2s: 2). We find no significant difference between the short period multiplicity fraction (FmF_\mathrm{m}) of the SACY sample and that of nearby star forming regions (≈\approx1-2 Myr) and the field (Fm≤F_\mathrm{m}\leq10%) both as a function of age and as a function of primary mass, M1M_1, in the ranges PP [1:200 day] and M2M_2 [0.08 M⊙M_{\odot}-M1 M_1]. Conclusions: Our results are consistent with the picture of universal star formation, when compared to the field and nearby star forming regions (SFRs). We comment on the implications of the relationship between increasing multiplicity fraction with primary mass, within the close companion range, in relation to star formation.Comment: 14 pages, 18 figures, published, A&A http://dx.doi.org/10.1051/0004-6361/20142385

    Search for associations containing young stars (SACY). VI. Is multiplicity universal? Stellar multiplicity in the range 3-1000 au from adaptive-optics observations

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    Context. Young loose nearby associations are unique samples of close (<150 pc), young (approx 5-100 Myr) pre-main sequence (PMS) stars. A significant number of members of these associations have been identified in the SACY collaboration. We can use the proximity and youth of these members to investigate key ingredients in star formation processes, such as multiplicity. Aims. We present the statistics of identified multiple systems from 113 confirmed SACY members. We derive multiplicity frequencies, mass-ratio, and physical separation distributions in a consistent parameter space, and compare our results to other PMS populations and the field. Methods. We have obtained adaptive-optics assisted near-infrared observations with NACO (ESO/VLT) and IRCAL (Lick Observatory) for at least one epoch of all 113 SACY members. We have identified multiple systems using co-moving proper-motion analysis and using contamination estimates. We have explored ranges in projected separation and mass-ratio of a [3-1000 au], and q [0.1-1], respectively. Results. We have identified 31 multiple systems (28 binaries and 3 triples). We derive a multiplicity frequency (MF) of MF_(3-1000au)=28.4 +4.7, -3.9% and a triple frequency (TF) of TF_(3-1000au)=2.8 +2.5, -0.8% in the separation range of 3-1000 au. We do not find any evidence for an increase in the MF with primary mass. The estimated mass-ratio of our statistical sample (with power-law index gamma=-0.04 +/- 0.14) is consistent with a flat distribution (gamma = 0). Conclusions. We show further similarities (but also hints of discrepancies) between SACY and the Taurus region: flat mass-ratio distributions and statistically similar MF and TF values. We also compared the SACY sample to the field (in the separation range of 19-100 au), finding that the two distributions are indistinguishable, suggesting a similar formation mechanism.Comment: 16 Pages, accepted in A&A 28 May 201

    Search for associations containing young stars (SACY) VII. New stellar and substellar candidate members in the young associations

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    The young associations offer us one of the best opportunities to study the properties of young stellar and substellar objects and to directly image planets thanks to their proximity (<<200 pc) and age (≈\approx5-150 Myr). However, many previous works have been limited to identifying the brighter, more active members (≈\approx1 M⊙_\odot) owing to photometric survey sensitivities limiting the detections of lower mass objects. We search the field of view of 542 previously identified members of the young associations to identify wide or extremely wide (1000-100,000 au in physical separation) companions. We combined 2MASS near-infrared photometry (JJ, HH, KK) with proper motion values (from UCAC4, PPMXL, NOMAD) to identify companions in the field of view of known members. We collated further photometry and spectroscopy from the literature and conducted our own high-resolution spectroscopic observations for a subsample of candidate members. This complementary information allowed us to assess the efficiency of our method. We identified 84 targets (45: 0.2-1.3 M⊙_\odot, 17: 0.08-0.2 M⊙_\odot, 22: <<0.08 M⊙_\odot) in our analysis, ten of which have been identified from spectroscopic analysis in previous young association works. For 33 of these 84, we were able to further assess their membership using a variety of properties (X-ray emission, UV excess, Hα_\alpha, lithium and K I equivalent widths, radial velocities, and CaH indices). We derive a success rate of 76-88% for this technique based on the consistency of these properties. Once confirmed, the targets identified in this work would significantly improve our knowledge of the lower mass end of the young associations. Additionally, these targets would make an ideal new sample for the identification and study of planets around nearby young stars.Comment: 28 pages, 24 figures, accepted in A&

    Nambu-Goldstone Modes in Gravitational Theories with Spontaneous Lorentz Breaking

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    Spontaneous breaking of Lorentz symmetry has been suggested as a possible mechanism that might occur in the context of a fundamental Planck-scale theory, such as string theory or a quantum theory of gravity. However, if Lorentz symmetry is spontaneously broken, two sets of questions immediately arise: what is the fate of the Nambu-Goldstone modes, and can a Higgs mechanism occur? A brief summary of some recent work looking at these questions is presented here.Comment: 6 pages. Presented at the meeting "From Quantum to Cosmos," Washington, D.C., May 2006; published in Int. J. Mod. Phys. D16:2357-2363, 200

    Spatial Modulation Microscopy for Real-Time Imaging of Plasmonic Nanoparticles and Cells

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    Spatial modulation microscopy is a technique originally developed for quantitative spectroscopy of individual nano-objects. Here, a parallel implementation of the spatial modulation microscopy technique is demonstrated based on a line detector capable of demodulation at kHz frequencies. The capabilities of the imaging system are shown using an array of plasmonic nanoantennas and dendritic cells incubated with gold nanoparticles.Comment: 3 pages, 4 figure

    Dynamical approach to chains of scatterers

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    Linear chains of quantum scatterers are studied in the process of lengthening, which is treated and analysed as a discrete dynamical system defined over the manifold of scattering matrices. Elementary properties of such dynamics relate the transport through the chain to the spectral properties of individual scatterers. For a single-scattering channel case some new light is shed on known transport properties of disordered and noisy chains, whereas translationally invariant case can be studied analytically in terms of a simple deterministic dynamical map. The many-channel case was studied numerically by examining the statistical properties of scatterers that correspond to a certain type of transport of the chain i.e. ballistic or (partially) localised.Comment: 16 pages, 7 figure

    Measuring the Impact of Oesophagectomy on Physical Functioning and Physical Activity Participation: a Prospective Study

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    Background: Oesophagectomy remains the only curative intervention for oesophageal cancer, with defined nutritional and health-related quality of life (HR-QOL) consequences. It follows therefore that there is a significant risk of decline in physical wellbeing with oesophagectomy however this has been inadequately quantified. This study prospectively examines change in physical functioning and habitual physical activity participation, from presurgery through 6-months post-oesophagectomy. Methods: Patients scheduled for oesophagectomy with curative intent were recruited. Key domains of physical functioning including exercise tolerance (six-minute walk test (6MWT)) and muscle strength (hand-grip strength), and habitual physical activity participation, including sedentary behaviour (accelerometry) were measured presurgery (T0) and repeated at 1-month (T1) and 6-months (T2) post-surgery. HR-QOL was measured using the EORTC-QOL C30. Results: Thirty-six participants were studied (mean age 62.4 (8.8) years, n = 26 male, n = 26 transthoracic oesophagectomy). Mean 6MWT distance decreased significantly from T0 to T1 (p = 0.006) and returned to T0 levels between T1 and T2 (p \u3c 0.001). Percentage time spent sedentary increased throughout recovery (p \u3c 0.001) and remained significantly higher at T2 in comparison to T0 (p = 0.003). In contrast, percentage time spent engaged in either light or moderate-to-vigorous intensity activity, all reduced significantly (p \u3c 0.001 for both) and remained significantly lower at T2 in comparison to T0 (p = 0.009 and p = 0.01 respectively). Patients reported deficits in multiple domains of HR-QOL during recovery including global health status (p = 0.04), physical functioning (p \u3c 0.001) and role functioning (p \u3c 0.001). Role functioning remained a clinically important 33-points lower than preoperative values at T2. Conclusion: Habitual physical activity participation remains significantly impaired at 6-months postoesophagectomy. Physical activity is a measurable and modifiable target for physical rehabilitation, which is closely aligned with patient-reported deficits in role functioning. Rehabilitation aimed at optimising physical health in oesophageal cancer survivorship is warranted

    Canine chronic kidney disease in UK veterinary practices: prevalence, risk factors and survival

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    Analyses covering 107,214 dogs attending 89 UK practices aimed to estimate the prevalence and identify risk factors associated with canine chronic kidney disease (CKD) diagnosis and survival. The apparent prevalence (AP) was estimated using a cross-sectional approach while the true prevalence (TP) was estimated using Bayesian analysis. A nested case-control study design was used to evaluate risk factors. Survival analysis was conducted using the Kaplan-Meier survival curve method and multivariable Cox proportional hazards regression modelling. CKD AP was estimated at 0.21% and TP at 0.37%. CKD risk factors included increasing age, being insured and certain breeds. The median survival time was 226 days. IRIS stage and blood urea nitrogen concentration at diagnosis were significantly associated with hazard of CKD death. This study of a clinically important condition indicates the increasing importance of electronic patient records (EPRs) to evaluate diseases in companion animals

    Sub MeV Particles Detection and Identification in the MUNU detector ((1)ISN, IN2P3/CNRS-UJF, Grenoble, France, (2)Institut de Physique, Neuch\^atel, Switzerland, (3) INFN, Padova Italy, (4) Physik-Institut, Z\"{u}rich, Switzerland)

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    We report on the performance of a 1 m3^{3} TPC filled with CF4_{4} at 3 bar, immersed in liquid scintillator and viewed by photomultipliers. Particle detection, event identification and localization achieved by measuring both the current signal and the scintillation light are presented. Particular features of α\alpha particle detection are also discussed. Finally, the 54{54}Mn photopeak, reconstructed from the Compton scattering and recoil angle is shown.Comment: Latex, 19 pages, 20 figure
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