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Ian Powell

Publications and source records attributed to Ian Powell.

7 recordsLinked to original sources
PubMed2006

Modeling of the generic spatial heterodyne spectrometer and comparison with conventional spectrometer.

We describe the modeling of the generic spatial heterodyne spectrometer. This instrument resembles a somewhat modified Michelson interferometer, in which the power spectrum of the input source is determined by performing a one-dimensional Fourier transform on the output intensity profile. Code has been developed to analyze the performance of this type of spectrometer by determining the dependence of both spectral resolution and throughput on parameters such as aperture and field of view. An example of a heterodyne spectrometer is developed to illustrate the techniques employed in the modeling and a comparison undertaken between its performance and that of a conventional spectrometer. Unlike the traditional Fourier transform infrared system, the heterodyne spectrometer has the very desirable feature of having no moving components.

Journal Article↗
PubMed2005

Wavelength-dispersive device based on a Fourier-transform Michelson-type arrayed waveguide grating.

We propose a new type of arrayed waveguide grating (AWG) device that operates as a Fourier-transform (FT) spectrometer without the need of scanning elements. The large input aperture size typical of a FT spectrometer eliminates the requirement for a narrow single-mode input waveguide while still achieving high spectral resolution with a markedly increased light-gathering capability (etendue). An example of the device with a resolution of 0.07 nm (approximately 10 GHz) and designed for a silicon-on-insulator platform is presented. The calculated spectra show no noticeable deterioration for aperture widths as large as 40 microm, yielding more than a 50-fold increase in aperture size compared with conventional AWG or echelle grating based devices at the equivalent resolution.

Journal Article↗
PubMed2002

Can psychiatric liaison reduce neuroleptic use and reduce health service utilization for dementia patients residing in care facilities.

BACKGROUND: The quality of care and overuse of neuroleptic medication in care environments are major issues in the care of elderly people with dementia. METHOD: The quality of care (Dementia Care Mapping), the severity of Behavioural and Psychological Symptoms (BPSD--Neuropsychiatric Inventory), expressive language skills (Sheffield Acquired Language Disorder scale), service utilization and use of neuroleptic drugs was compared over 9 months between six care facilities receiving a psychiatric liaison service and three facilities receiving the usual clinical support, using a single blind design. RESULTS: There was a significant reduction in neuroleptic usage in the facilities receiving the liaison service (McNemar test p<0.0001), but not amongst those receiving standard clinical support (McNemar test p=0.07). There were also significantly less GP contacts (t=3.9 p=0.0001) for residents in the facilities receiving the liaison service, and a three fold reduction in psychiatric in-patient bed usage (Bed days per person 0.6 vs. 1.5). Residents in care facilities receiving the liaison service experienced significantly less deterioration in expressive language skills (t=2.2 p=0.03), but there were no significant differences in BPSD or wellbeing. CONCLUSION: A resource efficient psychiatric liaison service can reduce neuroleptic drug use and reduce some aspects of health service utilization; but a more extensive intervention is probably required to improve the overall quality of care.

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