Design, fabrication and evaluation of chalcogenide glass Luneburg lenses for LiNbO3 integrated optical devices

Optical waveguide Luneburg lenses of arsenic trisulfide glass are described. The lenses are formed by thermal evaporation of As2S3 through suitably placed masks onto the surface of LiNbO3:Ti indiffused waveguides. The lenses are designed for input apertures up to 1 cm and for speeds of f/5 or better. They are designed to focus the TM sub 0 guided mode of a beam of wavelength, external to the guide, of 633 nm. The refractive index of the As2S3 films and the changes induced in the refractive index by exposure to short wavelength light were measured. Some correlation between film thickness and optical properties was noted. The short wavelength photosensitivity was used to shorten the lens focal length from the as deposited value. Lenses of rectangular shape, as viewed from above the guide, as well as conventional circular Luneburg lenses, were made. Measurements made on the lenses include thickness profile, general optical quality, focal length, quality of focal spot, and effect of ultraviolet irradiation on optical properties

The few-body problem for trapped bosons with large scattering length

We calculate energy levels of two and three bosons trapped in a harmonic oscillator potential with oscillator length $a_{\mathrm osc}$. The atoms are assumed to interact through a short-range potential with a scattering length $a$, and the short-distance behavior of the three-body wave function is characterized by a parameter $\theta$. For large positive $a/a_{\mathrm osc}$, the energies of states which, in the absence of the trap, correspond to three free atoms approach values independent of $a$ and $\theta$. For other states the $\theta$ dependence of the energy is strong, but the energy is independent of $a$ for $|a/a_{\mathrm osc}|\gg1$.Comment: 4 pages, 3 figure

Multidisciplinary integrated parent and child centres in Amsterdam: a qualitative study

Background: In several countries centres for the integrated delivery of services to the parent and child have been established. In the Netherlands family health care service centres, called Parent and Child Centres (PCCs) involve multidisciplinary teams. Here doctors, nurses, midwives, maternity help professionals and educationists are integrated into multidisciplinary teams in neighbourhood-based centres. To date there has been little research on the implementation of service delivery in these centres. Study Design: A SWOT analysis was performed by use of triangulation data; this took place by integrating all relevant published documents on the origin and organization of the PCCs and the results from interviews with PCC experts and with PCC professionals (N=91). Structured interviews were performed with PCC-professionals (health care professionals (N=67) and PCC managers N=12)) and PCC-experts (N=12) in Amsterdam and qualitatively analysed thematically. The interview themes were based on a pre-set list of codes, derived from a prior documentation study and a focus group with PCC experts. Results: Perceived advantages of PCCs were more continuity of care, shorter communication lines, low-threshold contact between professionals and promising future perspectives. Perceived challenges included the absence of uniform multidisciplinary guidelines, delays in communication with hospitals and midwives, inappropriate accommodation for effective professional integration, differing expectations regarding the PCC-manager role among PCC-partners and the danger of professionals' needs dominating clients' needs. Conclusions: Professionals perceive PCCs as a promising development in the integration of services. Remaining challenges involved improvements at the managerial and organizational level. Quantitative research into the improvements in quality of care and child health is recommended

Strongly Incompatible Quantum Devices

The fact that there are quantum observables without a simultaneous measurement is one of the fundamental characteristics of quantum mechanics. In this work we expand the concept of joint measurability to all kinds of possible measurement devices, and we call this relation compatibility. Two devices are incompatible if they cannot be implemented as parts of a single measurement setup. We introduce also a more stringent notion of incompatibility, strong incompatibility. Both incompatibility and strong incompatibility are rigorously characterized and their difference is demonstrated by examples.Comment: 27 pages (AMSart), 6 figure

Chaotic Scattering with Resonance Enhancement

The passage of light or of electrons through a disordered medium is modified in the presence of resonances. We describe a simple model for this problem, and present first results.Comment: 13 pages, 2 figures, REVTEX. To appear in Nucl. Phys. A (1996

Solid-state memcapacitive system with negative and diverging capacitance

We suggest a possible realization of a solid-state memory capacitive (memcapacitive) system. Our approach relies on the slow polarization rate of a medium between plates of a regular capacitor. To achieve this goal, we consider a multi-layer structure embedded in a capacitor. The multi-layer structure is formed by metallic layers separated by an insulator so that non-linear electronic transport (tunneling) between the layers can occur. The suggested memcapacitor shows hysteretic charge-voltage and capacitance-voltage curves, and both negative and diverging capacitance within certain ranges of the field. This proposal can be easily realized experimentally, and indicates the possibility of information storage in memcapacitive devices