The Cosmic Lens All-Sky Survey parent population - I. Sample selection and number counts

We present the selection of the Jodrell Bank Flat-spectrum (JBF) radio source sample, which is designed to reduce the uncertainties in the Cosmic Lens All-Sky Survey (CLASS) gravitational lensing statistics arising from the lack of knowledge about the parent population luminosity function. From observations at 4.86 GHz with the Very Large Array, we have selected a sample of 117 flat-spectrum radio sources with flux densities greater than 5 mJy. These sources were selected in a similar manner to the CLASS complete sample and are therefore representative of the parent population at low flux densities. The vast majority (~90 per cent) of the JBF sample are found to be compact on the arcsecond scales probed here and show little evidence of any extended radio jet emission. Using the JBF and CLASS complete samples we find the differential number counts slope of the parent population above and below the CLASS 30 mJy flux density limit to be -2.07+/-0.02 and -1.96+/-0.12, respectively.Comment: 10 pages, 4 figures, accepted for publication in MNRA

Elastic moduli approximation of higher symmetry for the acoustical properties of an anisotropic material

The issue of how to define and determine an optimal acoustical fit to a set of anisotropic elastic constants is addressed. The optimal moduli are defined as those which minimize the mean squared difference in the acoustical tensors between the given moduli and all possible moduli of a chosen higher material symmetry. The solution is shown to be identical to minimizing a Euclidean distance function, or equivalently, projecting the tensor of elastic stiffness onto the appropriate symmetry. This has implications for how to best select anisotropic constants to acoustically model complex materials.Comment: 20 page

Current cosmological constraints from a 10 parameter CMB analysis

We compute the constraints on a ``standard'' 10 parameter cold dark matter (CDM) model from the most recent CMB and data and other observations, exploring 30 million discrete models and two continuous parameters. Our parameters are the densities of CDM, baryons, neutrinos, vacuum energy and curvature, the reionization optical depth, and the normalization and tilt for both scalar and tensor fluctuations. Our strongest constraints are on spatial curvature, -0.24 < Omega_k < 0.38, and CDM density, h^2 Omega_cdm <0.3, both at 95%. Including SN 1a constraints gives a positive cosmological constant at high significance. We explore the robustness of our results to various assumptions. We find that three different data subsets give qualitatively consistent constraints. Some of the technical issues that have the largest impact are the inclusion of calibration errors, closed models, gravity waves, reionization, nucleosynthesis constraints and 10-dimensional likelihood interpolation.Comment: Replaced to match published ApJ version. More details added. 13 ApJ pages. CMB movies and color figs at http://www.hep.upenn.edu/~max/10par_frames.html or from [email protected]

Poly-MTO, {(CH_3)_{0.92} Re O_3}_\infty, a Conducting Two-Dimensional Organometallic Oxide

Polymeric methyltrioxorhenium, {(CH_{3})_{0.92}ReO_{3}}_{\infty} (poly-MTO), is the first member of a new class of organometallic hybrids which adopts the structural pattern and physical properties of classical perovskites in two dimensions (2D). We demonstrate how the electronic structure of poly-MTO can be tailored by intercalation of organic donor molecules, such as tetrathiafulvalene (TTF) or bis-(ethylendithio)-tetrathiafulvalene (BEDT-TTF), and by the inorganic acceptor SbF$_3$. Integration of donor molecules leads to a more insulating behavior of poly-MTO, whereas SbF$_3$ insertion does not cause any significant change in the resistivity. The resistivity data of pure poly-MTO is remarkably well described by a two-dimensional electron system. Below 38 K an unusual resistivity behavior, similar to that found in doped cuprates, is observed: The resistivity initially increases approximately as $\rho \sim$ ln$(1/T$) before it changes into a $\sqrt{T}$ dependence below 2 K. As an explanation we suggest a crossover from purely two-dimensional charge-carrier diffusion within the \{ReO$_2$\}$_{\infty}$ planes at high temperatures to three-dimensional diffusion at low temperatures in a disorder-enhanced electron-electron interaction scenario (Altshuler-Aronov correction). Furthermore, a linear positive magnetoresistance was found in the insulating regime, which is caused by spatial localization of itinerant electrons at some of the Re atoms, which formally adopt a $5d^1$ electronic configuration. X-ray diffraction, IR- and ESR-studies, temperature dependent magnetization and specific heat measurements in various magnetic fields suggest that the electronic structure of poly-MTO can safely be approximated by a purely 2D conductor.Comment: 15 pages, 16 figures, 2 table

E-government and the digital divide: A study of English-as-a-Second-Language Users' Information Behaviour

Internet-based technologies are increasingly used by organisations and governments to offer services to consumers and the public in a quick and efficient manner, removing the need for face-to-face conversations and human advisors. Despite their obvious benefits for most users, these online systems may present barriers of access to certain groups in society which may lead to information poverty. In this study we consider the information behaviour of ten ESL (English as a Second Language) participants as they conduct four search tasks designed to reflect actual information seeking situations. Our results suggest that, despite a perception that they have a good understanding of English, they often choose documents that are only partially or tangentially relevant. There were significant differences in the behaviour of participants given their perceived confidence in using English to perform search tasks. Those who were confident took riskier strategies and were less thorough, leading to them bookmarking a larger proportion of non-relevant documents. The results of this work have potentially profound repercussions for how e-government services are provided and how second-language speakers are assisted in their use of these

Non-linear phenomena in time-dependent density-functional theory: What Rabi physics can teach us

Through the exact solution of a two-electron system interacting with a monochromatic laser we prove that all adiabatic density functionals within time-dependent density-functional theory are not able to discern between resonant and non-resonant (detuned) Rabi oscillations. This is rationalized in terms of a fictitious dynamical exchange-correlation (xc) detuning of the resonance while the laser is acting. The non-linear dynamics of the Kohn-Sham system shows the characteristic features of detuned Rabi oscillations even if the exact resonant frequency is used. We identify the source of this error in a contribution from the xc-functional to the non-linear equations describing the electron dynamics in an effective two-level system. The constraint of preventing the detuning introduces a new strong condition to be satisfied by approximate xc-functionals

Quality management: reduction of waiting time and efficiency enhancement in an ENT-university outpatients' department

Background Public health systems are confronted with constantly rising costs. Furthermore, diagnostic as well as treatment services become more and more specialized. These are the reasons for an interdisciplinary project on the one hand aiming at simplification of planning and scheduling patient appointments, on the other hand at fulfilling all requirements of efficiency and treatment quality. Methods As to understanding procedure and problem solving activities, the responsible project group strictly proceeded with four methodical steps: actual state analysis, analysis of causes, correcting measures, and examination of effectiveness. Various methods of quality management, as for instance opinion polls, data collections, and several procedures of problem identification as well as of solution proposals were applied. All activities were realized according to the requirements of the clinic's ISO 9001:2000 certified quality management system. The development of this project is described step by step from planning phase to inauguration into the daily routine of the clinic and subsequent control of effectiveness. Results Five significant problem fields could be identified. After an analysis of causes the major remedial measures were: installation of a patient telephone hotline, standardization of appointment arrangements for all patients, modification of the appointments book considering the reason for coming in planning defined working periods for certain symptoms and treatments, improvement of telephonic counselling, and transition to flexible time planning by daily updates of the appointments book. After implementation of these changes into the clinic's routine success could be demonstrated by significantly reduced waiting times and resulting increased patient satisfaction. Conclusion Systematic scrutiny of the existing organizational structures of the outpatients' department of our clinic by means of actual state analysis and analysis of causes revealed the necessity of improvement. According to rules of quality management correcting measures and subsequent examination of effectiveness were performed. These changes resulted in higher satisfaction of patients, referring colleagues and clinic staff the like. Additionally the clinic is able to cope with an increasing demand for appointments in outpatients' departments, and the clinic's human resources are employed more effectively

Photodynamische Therapie bei altersbedingter Makuladegeneration am schlechteren und besseren Auge

Zusammenfassung: Hintergrund: Die PDT ist die Standardbehandlung vieler Formen der exsudativen bzw. neovaskulären Makuladegeneration (AMD). Trotz Therapie fällt die Sehschärfe häufig in den Low-vision-Bereich ab. Die Kosteneffizienz der Therapie am schlechteren Auge wird daher kontrovers diskutiert. Patienten und Methoden: Retrospektive Fallkontrollstudie aller Patienten, welche zwischen September 1999 und November 2004 am Universitätsspital Zürich eine PDT erhalten haben. Die Situation bei Präsentation und der Verlauf unter Therapie wurden bei ersten (schlechteren) und zweiten (besseren) Augen verglichen. Ergebnisse: In 117/228Fällen (51,3%) war der Visus am behandelten Auge bei Präsentation besser (oder gleich) als der Visus am Partnerauge. Der Visus vor Behandlung betrug bei den besseren Augen im Mittel 0,58±0,27logMAR [Snellen: 0,26 (0,14-0,49)] und 0,69±0,4logMAR [Snellen 0,20 (0,08-0,51)] bei den schlechteren Augen (p=0,015). Nach Behandlung bestand zwischen den Gruppen weder bezüglich Visus bzw. Visusveränderung noch bezüglich Membrangröße bzw. Größenveränderung der Membran ein signifikanter Unterschied. Schlussfolgerung: Die Resultate nach PDT sind beim zweiten (bzw. besseren) Auge nicht signifikant besser als beim ersten (bzw. schlechteren) Aug

Boson stars in massive dilatonic gravity

We study equilibrium configurations of boson stars in the framework of a class scalar-tensor theories of gravity with massive gravitational scalar (dilaton). In particular we investigate the influence of the mass of the dilaton on the boson star structure. We find that the masses of the boson stars in presence of dilaton are close to those in general relativity and they are sensitive to the ratio of the boson mass to the dilaton mass within a typical few percent. It turns out also that the boson star structure is mainly sensitive to the mass term of the dilaton potential rather to the exact form of the potential.Comment: 9 pages, latex, 9 figures, one figure dropped, new comments added, new references added, typos correcte

Measuring Cosmological Parameters with the JVAS and CLASS Gravitational Lens Surveys

The JVAS (Jodrell Bank-VLA Astrometric Survey) and CLASS (Cosmic Lens All-Sky Survey) are well-defined surveys containing about ten thousand flat-spectrum radio sources. For many reasons, flat-spectrum radio sources are particularly well-suited as a population from which one can obtain unbiased samples of gravitational lenses. These are by far the largest gravitational (macro)lens surveys, and particular attention was paid to constructing a cleanly-defined sample for the survey itself and for the underlying luminosity function. Here we present the constraints on cosmological parameters, particularly the cosmological constant, derived from JVAS and combine them with constraints from optical gravitational lens surveys, `direct' measurements of $\Omega_{0}$, $H_{0}$ and the age of the universe, and constraints derived from CMB anisotropies, before putting this final result into the context of the latest results from other, independent cosmological tests.Comment: LaTeX, 9 pages, 6 PostScript figures, uses texas.sty. To appear in the Proceedings of the 19th Texas Symposium on Relativistic Astrophysics and Cosmology (CD-ROM). Paper version available on request. Actual poster (A0 and A4 versions) available from http://multivac.jb.man.ac.uk:8000/helbig/research/publications/info/ texas98.htm