An optical fibre switch employing a Sagnac interferometer

Local area networks and high-bit-rate telecommunications demand fast switches for modulators, re-routing and demultiplexing. Optically-driven nonlinear optical switches based on intensity-dependent phase shifts in an optical fibre have been demonstrated at femtosecond switching speeds. An all optical switch has the benefit of compatibility with the rest of the optical network and its availability would considerably enhance the capabilities of optical transmission systems. An optical fibre switch which exploits the non-linearity in silica fibre may be polarimetric or interferometric. However, most configurations are very environmentally unstable and suffer large phase shifts due to temperature and vibration. The exception is the Sagnac interferometer, which uses the same path for both interfering beams and is therefore only sensitive to perturbations that occur in a time less than the loop transit time. We describe here the basic theory of operation of the Sagnac fibre switch, followed by an experimental demonstration of a stable switch operating on a picosecond time scale

Localised spherical-wave basis set for O(N) total-energy pseudopotential calculations

Accepted versio

The Maine Patient Centered Medical Home (PCMH) Pilot: Implementation Evaluation

The purpose of this Maine Patient Centered Medical Home (PCMH) Pilot is to improve quality of care, efficiency, and patient/family satisfaction provided by primary care practices. Its premise is that the resources provided to practices through the Pilot (including enhanced payments, training, consultation, and learning collaborative) will help them transform themselves and reach a higher level of functionality as medical homes, which in turn will lead to improvements in quality of care, efficiency, and patient/family satisfaction. The three-year Pilot was convened by MaineCare, the Maine Quality Forum, and Quality Counts. The participating payers are MaineCare (Maine Medicaid), Aetna, Anthem, and Harvard Pilgrim Health Care. Three aspects of the Pilot are being evaluated by the Muskie School of Public Service: 1) patient’s experiences; 2) the implementation process and interim results during Year 1; and 3) changes in the quality and efficiency of primary care. This report focuses on findings from the implementation evaluation. A national evaluation of a PCMH demonstration concluded that several factors, including practices’ workplace culture and resilience (or “adaptive reserve,” including communication, leadership, learning culture, teamwork and work environment) were major determinants in the degree to which practices could transform themselves into medical homes. The implementation evaluation describes the processes the Pilot practices engaged in during the first year and profiles adaptive reserve and several other factors that may contribute to their success in achieving the Pilot’s objectives. The objectives of the implementation evaluation are to Profile the characteristics of the Pilot practices Describe the practices’ objectives and strategies for implementing the Pilot Describe the implementation process during Year 1 Provide practical guidance to the practices, the Pilot conveners, and MaineCare Develop profiles of the Pilot practices for use in the quality and efficiency evaluation Make recommendations for use by evaluators of other PCMH pilot

Comment on ``Local dimer-adatom stacking fault structures from 3x3 to 13x13 along Si(111)-7x7 domain boundaries''

Zhao et al. [Phys.Rev.B 58, 13824 (1998)] depicted several atomic structures of domain boundaries on a Si(111) surface and criticized the article by the present author and the co-workers. I will point out that their criticism is incorrect and their structure models have no consistency.Comment: 2 pages. Physical Review B, to appea

Modified conjugated gradient method for diagonalising large matrices

We present an iterative method to diagonalise large matrices. The basic idea is the same as the conjugated gradient (CG) method, i.e, minimizing the Rayleigh quotient via its gradient and avoiding reintroduce errors to the directions of previous gradients. Each iteration step is to find lowest eigenvector of the matrix in a subspace spanned by the current trial vector and the corresponding gradient of the Rayleigh quotient, as well as some previous trial vectors. The gradient, together with the previous trail vectors, play a similar role of the conjugated gradient of the original CG algorithm. Our numeric tests indicate that this method converges significantly faster than the original CG method. And the computational cost of one iteration step is about the same as the original CG method. It is suitably for first principle calculations.Comment: 6 Pages, 2EPS figures. (To appear in Phys. Rev. E

Healthy IDEAS for Caregivers of People with Dementia in Maine: Evaluation Report

The overall goal of the Maine Healthy IDEAS program was to improve and expand the care and support provided to people with Alzheimer’s disease and their caregivers. The objectives of the program were: To improve the health and wellness of caregivers To improve access to services To enhance the knowledge of care coordinators about caring for people with dementia The desired outcomes were improved health and mental health status of caregivers; increased rate of referral to services; high participation and completion rates for the evidence-based programs; and greater consumer choice and control

Dislocation constriction and cross-slip in Al and Ag: an ab initio study

A novel model based on the Peierls framework of dislocations is developed. The new theory can deal with a dislocation spreading at more than one slip planes. As an example, we study dislocation cross-slip and constriction process of two fcc metals, Al and Ag. The energetic parameters entering the model are determined from ab initio calculations. We find that the screw dislocation in Al can cross-slip spontaneously in contrast with that in Ag, which splits into partials and cannot cross-slip without first being constricted. The dislocation response to an external stress is examined in detail. We determine dislocation constriction energy and critical stress for cross-slip, and from the latter, we estimate the cross-slip energy barrier for the straight screw dislocations

quasiharmonic equations of state for dynamically-stabilized soft-mode materials

We introduce a method for treating soft modes within the analytical framework of the quasiharmonic equation of state. The corresponding double-well energy-displacement relation is fitted to a functional form that is harmonic in both the low- and high-energy limits. Using density-functional calculations and statistical physics, we apply the quasiharmonic methodology to solid periclase. We predict the existence of a B1--B2 phase transition at high pressures and temperatures

Optical properties of the vibrations in charged C60_{60} molecules

The transition strengths for the four infrared-active vibrations of charged C$_{60}$ molecules are evaluated in self-consistent density functional theory using the local density approximation. The oscillator strengths for the second and fourth modes are strongly enhanced relative to the neutral C$_{60}$ molecule, in good agreement with the experimental observation of ``giant resonances'' for those two modes. Previous theory, based on a ``charged phonon'' model, predicted a quadratic dependence of the oscillator strength on doping, but this is not borne out in our calculations.Comment: 10 pages, RevTeX3.

Optical Spectra of SNR Candidates in NGC 300

We present moderate-resolution (<5A) long-slit optical spectra of 51 nebular objects in the nearby Sculptor Group galaxy NGC 300 obtained with the 2.3 meter Advanced Technology Telescope at Siding Spring Observatory, Australia. Adopting the criterion of [SII]/Ha>=0.4 to confirm supernova remnants (SNRs) from optical spectra, we find that of 28 objects previously proposed as SNRs from optical observations, 22 meet this criterion with six showing [SII]/Ha of less than 0.4. Of 27 objects suggested as SNRs from radio data, four are associated with the 28 previously proposed SNRs. Of these four, three (included in the 22 above) meet the criterion. In all, 22 of the 51 nebular objects meet the [SII]/Ha criterion as SNRs while the nature of the remaining 29 objects remains undetermined by these observations.Comment: Accepted for publication in Astrophysics & Space Scienc