Statistical Properties of Fano Resonances in Atomic and Molecular Photoabsorption

Statistical properties of Fano resonances occurring in photoabsorption to highly excited atomic or molecular states are derived. The situation with one open and one closed channel is analyzed when the classical motion of the excited complex in the closed channel is chaotic. The closed channel subspace is modeled by random matrix theory. The probability distribution of the Fano parameter is derived both for the case of time reversal symmetry (TRS) and broken time reversal symmetry. For the TRS case the area distribution under a resonance profile relevant for low resolution experiments is discussed in detail.Comment: 4 pages, 4 figure

Momentum resolved spin dynamics of bulk and surface excited states in the topological insulator Bi2Se3\mathrm{Bi_{2}Se_{3}}

The prospective of optically inducing a spin polarized current for spintronic devices has generated a vast interest in the out-of-equilibrium electronic and spin structure of topological insulators (TIs). In this Letter we prove that only by measuring the spin intensity signal over several order of magnitude in spin, time and angle resolved photoemission spectroscopy (STAR-PES) experiments is it possible to comprehensively describe the optically excited electronic states in TIs materials. The experiments performed on $\mathrm{Bi_{2}Se_{3}}$ reveal the existence of a Surface-Resonance-State in the 2nd bulk band gap interpreted on the basis of fully relativistic ab-initio spin resolved photoemission calculations. Remarkably, the spin dependent relaxation of the hot carriers is well reproduced by a spin dynamics model considering two non-interacting electronic systems, derived from the excited surface and bulk states, with different electronic temperatures.Comment: 5 pages and 4 figure

New mobilities across the lifecourse: A framework for analysing demographically-linked drivers of migration

Date of acceptance: 17/02/2015Taking the life course as the central concern, the authors set out a conceptual framework and define some key research questions for a programme of research that explores how the linked lives of mobile people are situated in time–space within the economic, social, and cultural structures of contemporary society. Drawing on methodologically innovative techniques, these perspectives can offer new insights into the changing nature and meanings of migration across the life course.Publisher PDFPeer reviewe

Fistulotomy and drainage of deep postanal space abscess in the treatment of posterior horseshoe fistula

BACKGROUND: Posterior horseshoe fistula with deep postanal space abscess is a complex disease. Most patients have a history of anorectal abscess drainage or surgery for fistula-in-ano. METHODS: Twenty-five patients who underwent surgery for posterior horseshoe fistula with deep postanal space abscess were analyzed retrospectively with respect to age, gender, previous surgery for fistula-in-ano, number of external openings, diagnostic studies, concordance between preoperative studies and operative findings for the extent of disease, operating time, healing time, complications, and recurrence. RESULTS: There were 22 (88%) men and 3 (12%) women with a median age of 37 (range, 25–58) years. The median duration of disease was 13 (range, 3–96) months. There was one external opening in 12 (48%) patients, 2 in 8 (32%), 3 in 4 (16%), and 4 in 1 (4%). Preoperative diagnosis of horseshoe fistula was made by contrast fistulography in 4 (16%) patients, by ultrasound in 3 (12%), by magnetic resonance imaging in 6 (24%), and by physical examination only in the remainder (48%). The mean ± SD operating time was 47 ± 10 min. The mean ± SD healing time was 12 ± 3 weeks. Three of the 25 patients (12%) had diabetes mellitus type II. Nineteen (76%) patients had undergone previous surgery for fistula-in-ano, while five (20%) had only perianal abscess drainage. Neither morbidity nor mortality developed. All patients were followed up for a median of 35 (range, 6–78) months and no recurrence was observed. CONCLUSIONS: Fistulotomy of the tracts along the arms of horseshoe fistula and drainage of the deep postanal space abscess with posterior midline incision that severs both the lower edge of the internal sphincter and the subcutaneous external sphincter and divides the superficial external sphincter into halves gives excellent results with no recurrence. When it is necessary, severing the halves of the superficial external sphincter unilaterally or even bilaterally in the same session does not result in anal incontinence. Close follow-up of patients until the wounds completely healed is essential in the prevention of premature wound closure and recurrence

Orbital state and magnetic properties of LiV_2 O_4

LiV_2 O_4 is one of the most puzzling compounds among transition metal oxides because of its heavy fermion like behavior at low temperatures. In this paper we present results for the orbital state and magnetic properties of LiV_2 O_4 obtained from a combination of density functional theory within the local density approximation and dynamical mean-field theory (DMFT). The DMFT equations are solved by quantum Monte Carlo simulations. The trigonal crystal field splits the V 3d orbitals such that the a_{1g} and e_{g}^{pi} orbitals cross the Fermi level, with the former being slightly lower in energy and narrower in bandwidth. In this situation, the d-d Coulomb interaction leads to an almost localization of one electron per V ion in the a_{1g} orbital, while the e_{g}^{pi} orbitals form relatively broad bands with 1/8 filling. 2The theoretical high-temperature paramagnetic susceptibility chi(T) follows a Curie-Weiss law with an effective paramagnetic moment p_{eff}=1.65 in agreement with the experimental results.Comment: 11 pages, 10 figures, 2 table

Non-supersymmetric heterotic model building

We investigate orbifold and smooth Calabi-Yau compactifications of the non-supersymmetric heterotic SO(16)xSO(16) string. We focus on such Calabi-Yau backgrounds in order to recycle commonly employed techniques, like index theorems and cohomology theory, to determine both the fermionic and bosonic 4D spectra. We argue that the N=0 theory never leads to tachyons on smooth Calabi-Yaus in the large volume approximation. As twisted tachyons may arise on certain singular orbifolds, we conjecture that such tachyonic states are lifted in the full blow-up. We perform model searches on selected orbifold geometries. In particular, we construct an explicit example of a Standard Model-like theory with three generations and a single Higgs field.Comment: 1+30 pages latex, 11 tables; v2: references and minor revisions added, matches version published in JHE

A Solvable Regime of Disorder and Interactions in Ballistic Nanostructures, Part I: Consequences for Coulomb Blockade

We provide a framework for analyzing the problem of interacting electrons in a ballistic quantum dot with chaotic boundary conditions within an energy $E_T$ (the Thouless energy) of the Fermi energy. Within this window we show that the interactions can be characterized by Landau Fermi liquid parameters. When $g$, the dimensionless conductance of the dot, is large, we find that the disordered interacting problem can be solved in a saddle-point approximation which becomes exact as $g\to\infty$ (as in a large-N theory). The infinite $g$ theory shows a transition to a strong-coupling phase characterized by the same order parameter as in the Pomeranchuk transition in clean systems (a spontaneous interaction-induced Fermi surface distortion), but smeared and pinned by disorder. At finite $g$, the two phases and critical point evolve into three regimes in the $u_m-1/g$ plane -- weak- and strong-coupling regimes separated by crossover lines from a quantum-critical regime controlled by the quantum critical point. In the strong-coupling and quantum-critical regions, the quasiparticle acquires a width of the same order as the level spacing $\Delta$ within a few $\Delta$'s of the Fermi energy due to coupling to collective excitations. In the strong coupling regime if $m$ is odd, the dot will (if isolated) cross over from the orthogonal to unitary ensemble for an exponentially small external flux, or will (if strongly coupled to leads) break time-reversal symmetry spontaneously.Comment: 33 pages, 14 figures. Very minor changes. We have clarified that we are treating charge-channel instabilities in spinful systems, leaving spin-channel instabilities for future work. No substantive results are change

Role of calcium channel blocking agents in the prevention of atherosclerosis

Calcium channel blocking agents, although effective and widely used in the symptomatic therapy of hypertension and ischemic heart disease, have an uncertain effect on the development of coronary atherosclerosis, plaque rupture, and postrupture thrombosis. Both nifedipine and nicardipine have been shown to prevent the development of new coronary lesions but not the progression of existing lesions in prospective randomized angiographic studies. Verapamil, in contrast, failed to prevent the development of new coronary lesions and had no significant effect on the progression of existing lesions. Diltiazem, although not studied in patients with coronary atheroscleroses, has been shown to prevent the development of post-transplant coronary vascular disease. Despite the beneficial effects of nifedipine and nicardipine on new coronary lesion development, they have not been shown to reduce the incidence of recurrent ischemic events or mortality in the prospective randomized studies that demonstrated their effect on new coronary lesion development. A relatively new dihydropyridine calcium channel blocking agent, amlodipine, is hypothesized to prevent atherosclerosis due to its calcium channel blocking properties as well as by mechanisms independent of its calcium channel blocking properties. This agent has been selected for evaluation in the Prospective Randomized Evaluation of the Vascular Effects of Norvasc Trial (PREVENT) to explore whether the use of amlodipine over 3 years will reduce the incidence of early atherosclerotic lesions and, possibly, the progression of existing lesions in both the coronary and carotid arterial beds. Amlodipine could play an important future role in the secondary prevention of ischemic heart disease, but further study and a demonstration of a beneficial effect on recurrent ischemic events is required before any final conclusions concerning its effectiveness are reached.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44649/1/10557_2004_Article_BF00878569.pd

Assessing learning and memory in pigs

In recent years, there has been a surge of interest in (mini) pigs (Sus scrofa) as species for cognitive research. A major reason for this is their physiological and anatomical similarity with humans. For example, pigs possess a well-developed, large brain. Assessment of the learning and memory functions of pigs is not only relevant to human research but also to animal welfare, given the nature of current farming practices and the demands they make on animal health and behavior. In this article, we review studies of pig cognition, focusing on the underlying processes and mechanisms, with a view to identifying. Our goal is to aid the selection of appropriate cognitive tasks for research into pig cognition. To this end, we formulated several basic criteria for pig cognition tests and then applied these criteria and knowledge about pig-specific sensorimotor abilities and behavior to evaluate the merits, drawbacks, and limitations of the different types of tests used to date. While behavioral studies using (mini) pigs have shown that this species can perform learning and memory tasks, and much has been learned about pig cognition, results have not been replicated or proven replicable because of the lack of validated, translational behavioral paradigms that are specially suited to tap specific aspects of pig cognition. We identified several promising types of tasks for use in studies of pig cognition, such as versatile spatial free-choice type tasks that allow the simultaneous measurement of several behavioral domains. The use of appropriate tasks will facilitate the collection of reliable and valid data on pig cognition