Super-optimal approximation by meromorphic functions.

Let G be a matrix function of type m × n and suppose that G is expressible as the sum of an H∞ function and a continuous function on the unit circle. Suppose also that the (k – 1)th singular value of the Hankel operator with symbol G is greater than the kth singular value. Then there is a unique superoptimal approximant to G in : that is, there is a unique matrix function Q having at most k poles in the open unit disc which minimizes s∞(G – Q) or, in other words, which minimizes the sequence with respect to the lexicographic ordering, where and Sj(·) denotes the jth singular value of a matrix. This result is due to the present authors [PY1] in the case k = 0 (when the hypothesis on the Hankel singular values is vacuous) and to S. Treil[T2] in general. In this paper we give a proof of uniqueness by a diagonalization argument, a high level algorithm for the computation of the superoptimal approximant and a recursive parametrization of the set of all optimal solutions of a matrix Nehari—Takagi problem

Smoking and ethnic group, not epidural use, determine breast feeding outcome

No abstract available

Art Museum attendance and the public realm: The agency of visitor information in Tate's organisational practices of making the art museum's audiences

This study presents an original contribution to knowledge in its investigation of Tate’s strategic practices of audience, via materially-traced networks of action. In recent years, museological literature has examined issues of access and evaluation, their relation to cultural policy, and the wider framework of value delivery within the public realm. The present study employs ethnographic observation over a fifteen month period, combined with a theoretical approach, to trace and describe the social construction of Tate’s understandings of its audiences. The study provides insights into how the visitor information is generated, distributed, mediated, valued and applied across the various departments of the museum, and in what forms it exerts agency upon the daily practices of the art museum. This study advances understandings of audiences within museological discourse by moving beyond the customary calls for the generation of more data, or improved data-collection methods, to consider the effects of the application of visitor information in the formation of audiences, and the significance of this agency in terms of structures of power

A site-controlled quantum dot system offering both high uniformity and spectral purity

In this paper we report on the optical properties of site controlled InGaAs dots with GaAs barriers grown in pyramidal recesses by metalorganic vapour phase epitaxy. The inhomogeneous broadening of excitonic emission from an ensemble of quantum dots is found to be unusually narrow, with a standard deviation of 1.19 meV, and spectral purity of emission lines from individual dots is found to be very high (18-30 ueV), in contrast with other site-controlled systems.Comment: 12 pages, 3 figure

Spectral properties of a limit-periodic Schr\"odinger operator in dimension two

We study Schr\"{o}dinger operator $H=-\Delta+V(x)$ in dimension two, $V(x)$ being a limit-periodic potential. We prove that the spectrum of $H$ contains a semiaxis and there is a family of generalized eigenfunctions at every point of this semiaxis with the following properties. First, the eigenfunctions are close to plane waves $e^{i\langle \vec k,\vec x\rangle }$ at the high energy region. Second, the isoenergetic curves in the space of momenta $\vec k$ corresponding to these eigenfunctions have a form of slightly distorted circles with holes (Cantor type structure). Third, the spectrum corresponding to the eigenfunctions (the semiaxis) is absolutely continuous.Comment: 89 pages, 6 figure

Where do hands go? An audit of sequential hand-touch events on a hospital ward

Reservoirs of pathogens could establish themselves at forgotten sites on a ward, posing a continued risk for transmission to patients via unwashed hands. To track potential spread of organisms between surfaces and patients, and to gaina greater understanding into transmission pathways of pathogens during patient care. Hand-touch activities were audited covertly for 40 30 min sessions during summer and winter, and included hand hygiene on entry; contact with near-patient sites; patient contact; contact with clinical equipment; hand hygiene on exit; and contact with sites outside the room. There were 104 entries overall: 77 clinical staff (59 nurses; 18 doctors), 21 domestic staff, one pharmacist and five relatives. Hand-hygiene compliance among clinical staff before and after entry was 25% (38/154), with higher compliance during 20 summer periods [47%; 95% confidence interval (CI): 35.6e58.8] than during 20 winter periods (7%; 95% CI: 3.2e14.4; P < 0.0001). More than half of the staff (58%; 45/77) touched the patient. Staff were more likely to clean their hands prior to contact with a patient [odds ratio (OR): 3.44; 95% CI: 0.94e16.0); P ¼ 0.059] and sites beside the patient (OR: 6.76; 95% CI: 1.40e65.77; P ¼ 0.0067). Nearly half (48%; 37/77) handled patient notes and 25% touched the bed. Most frequently handled equipment inside the room were intravenous drip (30%) and blood pressure stand (13%), and computer (26%), notes trolley (23%) and telephone (21%) outside the room. Hand-hygiene compliance remains poor during covert observation; understanding the most frequent interactions between hands and surfaces could target sites for cleaning

A comprehensive analysis of cavitation and liquid impingement erosion data

Cavitation-erosion experimental data previously covering several materials tested in a rotating disk device and a magnetostriction apparatus were analyzed using new normalization and curve-fitting techniques. From this process a universal approach is derived which can include data from cavitation and liquid impingement studies for specific materials from different test devices