Two-Particle Resonant States in a Many-Body Mean Field

A formalism to evaluate the resonant states produced by two particles moving outside a closed shell core is presented. The two particle states are calculated by using a single particle representation consisting of bound states, Gamow resonances and scattering states in the complex energy plane (Berggren representation). Two representative cases are analysed corresponding to whether the Fermi level is below or above the continuum threshold. It is found that long lived two-body states (including bound states) are mostly determined by either bound single-particle states or by narrow Gamow resonances. However, they can be significantly affected by the continuum part of the spectrum.Comment: 11 pages, 4 figure

Effects of resonant single-particle states on pairing correlations

Effects of resonant single-particle (s.p.) states on the pairing correlations are investigated by an exact treatment of the pairing Hamiltonian on the Gamow shell model basis. We introduce the s.p. states with complex energies into the Richardson equations. The solution shows the property that the resonant s.p. states with large widths are less occupied. The importance of many-body correlations between bound and resonant prticle pairs is shown.Comment: 4 pages, 3 figures, to be published in Phys. Rev.

Discovery of dipolar chromospheres in two white dwarfs

This paper reports the ULTRACAM discovery of dipolar surface spots in two cool magnetic white dwarfs with Balmer emission lines, while a third system exhibits a single spot, similar to the prototype GD 356. The light curves are modelled with simple, circular, isothermal dark spots, yielding relatively large regions with minimum angular radii of 20°. For those stars with two light-curve minima, the dual spots are likely observed at high inclination (or colatitude); however, identical and antipodal spots cannot simultaneously reproduce both the distinct minima depths and the phases of the light-curve maxima. The amplitudes of the multiband photometric variability reported here are all several times larger than that observed in the prototype GD 356; nevertheless, all DAHe stars with available data appear to have light-curve amplitudes that increase towards the blue in correlated ratios. This behaviour is consistent with cool spots that produce higher contrasts at shorter wavelengths, with remarkably similar spectral properties given the diversity of magnetic field strengths and rotation rates. These findings support the interpretation that some magnetic white dwarfs generate intrinsic chromospheres as they cool, and that no external source is responsible for the observed temperature inversion. Spectroscopic time-series data for DAHe stars is paramount for further characterization, where it is important to obtain well-sampled data, and consider wavelength shifts, equivalent widths, and spectropolarimetry

Deepening subwavelength acoustic resonance via metamaterials with universal broadband elliptical microstructure

Slow sound is a frequently exploited phenomenon that metamaterials can induce in order to permit wave energy compression, redirection, imaging, sound absorption, and other special functionalities. Generally, however, such slow sound structures have a poor impedance match to air, particularly at low frequencies and consequently exhibit strong transmission only in narrow frequency ranges. This therefore strongly restricts their application in wave manipulation devices. In this work, we design a slow sound medium that halves the effective speed of sound in air over a wide range of low frequencies (hence our referral to the microstructure as “broadband”), whilst simultaneously maintaining a near impedance match to air. This is achieved with a rectangular array of acoustically rigid cylinders of elliptical cross section, a microstructure that is motivated by combining transformation acoustics with homogenization. Microstructural parameters are optimized in order to provide the required anisotropic material properties as well as near impedance matching. We then employ this microstructure in order to halve the size of a quarter-wavelength resonator (QWR) or equivalently to halve the resonant frequency of a QWR of a given size. This provides significant space savings in the context of low-frequency tonal noise attenuation in confined environments where the absorbing material is adjacent to the region in which sound propagates, such as in a duct. We employ the term “universal” since we envisage that this microstructure may be employed in a number of diverse applications involving sound manipulation.EPSRC Grant EP/K033208/I and EP/R014604/

Diabetic Muscle Infarction: A Rare Complication of Long-Standing and Poorly Controlled Diabetes Mellitus

Objective. To report a case of diabetic muscle infarction (DMI), a rare complication of long-standing poorly controlled diabetes mellitus. Methods. We describe a case of a 45-year-old male with an approximately 8-year history of poorly controlled type 2 diabetes mellitus with multiple microvascular complications who presented with the sudden onset of left thigh pain and swelling. He had a swollen left thigh and a CK of 1670 U/L. He was initially treated with intravenous antibiotics for a presumptive diagnosis of pyomyositis or necrotizing fasciitis with no improvement. A diagnosis of diabetic muscle infarction was considered. Results. An MRI of the thigh demonstrated diffuse edema in the anterior compartment. A muscle biopsy demonstrated coagulation necrosis in skeletal muscle and inflammation and infarction in the walls of small blood vessels. These studies confirmed the final diagnosis of DMI. He was treated with supportive care and gradually improved. Conclusion. DMI is a rare complication of diabetes that is often mistaken for infections such as pyomyositis and necrotizing fasciitis or thrombophlebitis. Treatment is supportive. Although the short-term prognosis is good in these patients, the long-term prognosis is poor

Iterative Approximate Consensus in the presence of Byzantine Link Failures

This paper explores the problem of reaching approximate consensus in synchronous point-to-point networks, where each directed link of the underlying communication graph represents a communication channel between a pair of nodes. We adopt the transient Byzantine link failure model [15, 16], where an omniscient adversary controls a subset of the directed communication links, but the nodes are assumed to be fault-free. Recent work has addressed the problem of reaching approximate consen- sus in incomplete graphs with Byzantine nodes using a restricted class of iterative algorithms that maintain only a small amount of memory across iterations [22, 21, 23, 12]. However, to the best of our knowledge, we are the first to consider approximate consensus in the presence of Byzan- tine links. We extend our past work that provided exact characterization of graphs in which the iterative approximate consensus problem in the presence of Byzantine node failures is solvable [22, 21]. In particular, we prove a tight necessary and sufficient condition on the underlying com- munication graph for the existence of iterative approximate consensus algorithms under transient Byzantine link model. The condition answers (part of) the open problem stated in [16].Comment: arXiv admin note: text overlap with arXiv:1202.609

Carbon-enhanced stars with short orbital and spin periods

Many characteristics of dwarf carbon stars are broadly consistent with a binary origin, including mass transfer from an evolved companion. While the population overall appears to have old-disc or halo kinematics, roughly 2 per cent of these stars exhibit Hα emission, which in low-mass main-sequence stars is generally associated with rotation and relative youth. Its presence in an older population therefore suggests either irradiation or spin-up. This study presents time-series analyses of photometric and radial-velocity data for seven dwarf carbon stars with Hα emission. All are shown to have photometric periods in the range 0.2–5.2 d, and orbital periods of similar length, consistent with tidal synchronisation. It is hypothesised that dwarf carbon stars with emission lines are the result of close-binary evolution, indicating that low-mass, metal-weak or metal-poor stars can accrete substantial material prior to entering a common-envelope phase

Gamow Shell Model description of Li isotopes and their mirror partners

Background: Weakly bound and unbound nuclei close to particle drip lines are laboratories of new nuclear structure physics at the extremes of neutron/proton excess. The comprehensive description of these systems requires an open quantum system framework that is capable of treating resonant and nonresonant many-body states on equal footing. Purpose: In this work, we construct the minimal complex-energy configuration interaction approach to describe binding energies and spectra of selected 5 $\leq$ A $\leq$ 11 nuclei. Method: We employ the complex-energy Gamow shell model (GSM) assuming a rigid $^4$He core. The effective Hamiltonian, consisting of a core-nucleon Woods-Saxon potential and a simplified version of the Furutani-Horiuchi-Tamagaki interaction with the mass-dependent scaling, is optimized in the sp space. To diagonalize the Hamiltonian matrix, we employ the Davidson method and the Density Matrix Renormalization Group technique. Results: Our optimized GSM Hamiltonian offers a good reproduction of binding energies and spectra with the root-mean-square (rms) deviation from experiment of 160 keV. Since the model performs well when used to predict known excitations that have not been included in the fit, it can serve as a reliable tool to describe poorly known states. A case in point is our prediction for the pair of unbound mirror nuclei $^{10}$Li-$^{10}$N in which a huge Thomas-Ehrman shift dramatically alters the pattern of low-energy excitations. Conclusion: The new model will enable comprehensive studies of structure and reactions aspects of light drip-line nuclei.Comment: 11 pages, 3 figure

Advanced prostate cancer experimental radioactive treatment-clinical trial decision making: patient experiences.

ObjectivesNested qualitative studies within clinical trials provide the opportunity to better understand participant experiences of participation and identify areas where improved support is required. The purpose of this qualitative study is to describe the lived experiences of men with advanced prostate cancer participating in the TheraP trial; a randomised trial of 177Lu-PSMA-617 compared with cabazitaxel chemotherapy.MethodsFifteen men with advanced prostate cancer were recruited from the TheraP clinical trial and interviewed at three time points during the trial. Interviews were inductively analysed using thematic analysis. This research paper reports the results from the baseline interview at commencement of the trial, focusing specifically on participants' enrolment experiences.ResultsFour themes were identified representing the lived experiences of men with advanced prostate cancer deciding to participate in the TheraP trial: (1) hoping to survive; (2) needing to feel informed; (3) choosing to participate and (4) being randomised. The process of deciding to enrol in a clinical trial is filled with indecision, emotional difficulties and focused on a desire to live.ConclusionsFor men with advanced prostate cancer, the experience of deciding to enrol in a clinical trial is principally driven by a desire to survive but interlinked with the need to make an informed decision as participants in this study expressed a preference for allocation to the experimental arm. Men seeking to enrol in clinical trials of new prostate cancer treatments would benefit from improved informational and decision support.Trial registration numberNCT03392428, ANZUP1603