Showing papers by "James Taylor published in 2004"

Use of incident reports by physicians and nurses to document medical errors in pediatric patients.

Abstract: Objectives. To describe the proportion and types of medical errors that are stated to be reported via incident report systems by physicians and nurses who care for pediatric patients and to determine attitudes about potential interventions for increasing error reports. Methods. A survey on use of incident reports to document medical errors was sent to a random sample of 200 physicians and nurses at a large children9s hospital. Items on the survey included proportion of medical errors that were reported, reasons for underreporting medical errors, and attitudes about potential interventions for increasing error reports. In addition, the survey contained scenarios about hypothetical medical errors; the physicians and nurses were asked how likely they were to report each of the events described. Differences in use of incident reports for documenting medical errors between nurses and physicians were assessed with χ2 tests. Logistic regression was used to determine the association between health care profession type and likelihood of reporting medical errors. Results. A total of 140 surveys were returned, including 74 from physicians and 66 by nurses. Overall, 34.8% of respondents indicated that they had reported Conclusions. Medical errors in pediatric patients are significantly underreported in incident report systems, particularly by physicians. Some types of errors are less likely to be reported than others. Information in incident reports is not a representative sample of errors committed in a children9s hospital. Specific changes in the incident report system could lead to more reporting by physicians and nurses who care for pediatric patients.

Transverse myelitis as the first manifestation of systemic lupus erythematosus or lupus-like disease: good functional outcome and relevance of antiphospholipid antibodies.

Abstract: OBJECTIVE: Transverse myelitis (TM) is a rare complication of systemic lupus erythematosus (SLE). Although usually a late manifestation of SLE, it can occur at presentation. We investigated the clinical presentation, treatment and outcome of 15 patients with TM as the presenting manifestation of SLE or lupus-like disease. METHODS: All patients received corticosteroids, while 13 also received immunosuppressive therapy. Five patients were fully anticoagulated with warfarin. RESULTS: A sensory level with spastic lower limb weakness and sphincter disturbance was the most common presentation: 14/15 patients had a thoracic or cervical sensory level. Cerebrospinal fluid examination showed high protein concentrations in 3 patients and oligoclonal bands in 8. Eleven of the 15 (73%) had antiphospholipid antibodies (aPL). Of the 15 patients, 3 had complete resolution of the symptoms, 6 had good functional improvements, 5 had good to fair outcome with some functional deficit, and one patient who received corticosteroids alone later died from pneumonia. CONCLUSION: We describe 15 patients with TM as the presenting manifestation of SLE or lupus-like disease with a high prevalence of aPL. Our data support the view that early diagnosis and immunosuppressive therapy may be superior to corticosteroids alone in improving functional outcome. In those patients with aPL, antiplatelet agents and/or warfarin should also be considered.

Optical coherence tomography using a continuous-wave, high-power, Raman continuum light source

Abstract: High performance, short coherence length light sources with broad bandwidths and high output powers are critical for high-speed, ultrahigh resolution OCT imaging. We demonstrate a new, high performance light source for ultrahigh resolution OCT. Bandwidths of 140 nm at 1300 nm center wavelength with high output powers of 330 mW are generated by an all-fiber Raman light source based on a continuous-wave Yb-fiber laser-pumped microstructure fiber. The light source is compact, robust, turnkey and requires no optical alignment. In vivo, ultrahigh resolution, high-speed, time domain OCT imaging with <5 microm axial resolution is demonstrated.

Continuous-wave, totally fiber integrated optical parametric oscillator using holey fiber.

Abstract: We present, for the first time to our knowledge, a cw, all-fiber optical parametric oscillator that uses a holey fiber. The oscillator operates at 1.55 µm and can yield an oscillating parametric signal that consists of a single line with a 30-dB extinction ratio and a 10-pm linewidth or that consists of multiple lines. In addition to the signal and the idler, five other pairs of spectral lines can be observed that are due to multiple parametric interactions. The source reaches threshold for a pump power of 1.28 W and saturates for pump powers in excess of ∼1.6 W.

Smooth Transition Exponential Smoothing

Abstract: Adaptive exponential smoothing methods allow a smoothing parameter to change over time, in order to adapt to changes in the characteristics of the time series. However, these methods have tended to produce unstable forecasts and have performed poorly in empirical studies. This paper presents a new adaptive method, which enables a smoothing parameter to be modelled as a logistic function of a user-specified variable. The approach is analogous to that used to model the time-varying parameter in smooth transition models. Using simulated data, we show that the new approach has the potential to outperform existing adaptive methods and constant parameter methods when the estimation and evaluation samples both contain a level shift or both contain an outlier. An empirical study, using the monthly time series from the M3-Competition, gave encouraging results for the new approach.

All-Fiber Format Compression of Frequency Chirped Pulses in Air-Guiding Photonic Crystal Fibers

Abstract: Air-cored, photonic band-gap crystal fibers exhibiting low nonlinearity and anomalous chromatic dispersion in spectral ranges inaccessible to conventional fibers can be used in the realization of all-fiber-format pulse compressors with unprecedented peak powers and wavelength diversity. Linear compression of inherently chirped and prestretched pulses by factors ranging from 20 to 80 around 1.0 and 1.5 microm have allowed generation of pulses as short as 163 fs. The results show that totally integrated femtosecond fiber laser sources can be realized throughout the visible and near-infrared and point to the possibility of megawatt peak and tens of watt average in-fiber power levels.

A comparison of temperature density forecasts from GARCH and atmospheric models

Abstract: Density forecasts for weather variables are useful for the many industries exposed to weather risk. Weather ensemble predictions are generated from atmospheric models and consist of multiple future scenarios for a weather variable. The distribution of the scenarios can be used as a density forecast, which is needed for pricing weather derivatives. We consider one to 10-day-ahead density forecasts provided by temperature ensemble predictions. More specifically, we evaluate forecasts of the mean and quantiles of the density. The mean of the ensemble scenarios is the most accurate forecast for the mean of the density. We use quantile regression to debias the quantiles of the distribution of the ensemble scenarios. The resultant quantile forecasts compare favourably with those from a GARCH model. These results indicate the strong potential for the use of ensemble prediction in temperature density forecasting.

Temporal and noise characteristics of continuous-wave-pumped continuum generation in holey fibers around 1300nm

Abstract: The noise of continuous-wave-pumped broadband continua generated in a holey fiber is characterized in two different all-fiber configurations. An amplified spontaneous emission seeded ytterbium-doped fiber source and fiber Bragg grating based Yb laser were employed to initiate Raman-soliton continuum generation in 100m of anomalously dispersive holey fiber with spectral width of 300nm and spectral power density over 10mW/nm. Low noise operation makes these sources suitable for optical coherence tomography applications.

Multi-kilowatt, all-fiber integrated chirped-pulse amplification system yielding 40× pulse compression using air-core fiber and conventional erbium-doped fiber amplifier

Abstract: We present a totally fiber integrated chirped-pulse amplification system using air-core photonic bandgap fiber and a conventional erbium-doped fiber amplifier. ~40-ps input pulses, generated in a Mach-Zehnder modulator, were stretched and spectrally broadened in a dispersion-shifted fiber before being amplified and subsequently compressed in 10 m of anomalously-dispersive photonic bandgap fiber to yield ~960 fs pulses. The system gives multi-kilowatt peak powers while the amplifier nonlinearity threshold is as low as ~150 W. Higher peak powers could be obtained by the use of an amplifier with higher nonlinearity threshold.

Direct observation of the multisheet Fermi surface in the strongly correlated transition metal compound ZrZn2.

Abstract: The existence of flat areas of a Fermi surface (FS), predicted by electronic structure calculations and used in models of both magnetically mediated and phonon-mediated Fulde-Ferrell-Larkin-Ovchinnikov superconducting states, is reported in the paramagnetic phase of the ferromagnetic superconductor ZrZn2 using positron annihilation. The strongly mass-renormalized FS sheet, dominating the Fermi level density of states, is seen for the first time. The delocalization of the magnetization is studied using measured and calculated magnetic Compton profiles.

All-solid-state femtosecond diode-pumped Cr:LiSAF laser

Abstract: The generation of picosecond and femtosecond pulses from all-solid-state, continuous wave, diode-pumped, mode-locked Cr3+:LiSrAlF6 lasers is reported for the first time. A multiple quantum well absorber has been used in a dispersion-compensated cavity to yield cw trains of transform-limited femtosecond pulses.

7 W average power, high-beam-quality green generation in MgO-doped stoichiometric periodically poled lithium tantalate

Abstract: A periodically-poled MgO-doped stoichiometric lithium tantalate crystal is applied for single-pass, 67% peak-power efficient, 7.05W average power second-harmonic generation of a single-mode Yb-doped all-fiber fundamental source. Reduced photorefraction and green-induced infrared absorption of the material allowed to maintain a low M2 value of the high-average-power 532nm beam.

Multi-kilowatt, picosecond pulses from an all-fiber chirped pulse amplification system using air-core photonic bandgap fiber

Abstract: Multi-kilowatt, /spl sim/1 ps pulses at 1550 nm are obtained from a fully fiber integrated chirped pulse amplification system using a conventional single-mode EDFA, and an air-core photonic bandgap fiber as the compressor. /spl sim/40/spl times/ pulse compression is obtained.

1.5-2 µm, multi-Watt white-light generation in CW format in highly-nonlinear fibres

Abstract: Over 6W power, CW Raman-soliton continua are generated in a highly-nonlinear-fibre in the 1.56-2.05µm range with spectral brightness 16mW/nm and flatness <1dB peak-to-peak. Fibre-integrated pumping with single-mode, high power Yb/Er laser is employed.

High power, 775 nm, quasi-CW and CW second-harmonic-generation of linearly-polarized fiber source in PPKTP

Abstract: An Yb-Er, PM-format, narrow-line, quasi-CW fibre source is demonstrated and used for >25 W average power (>76%-efficient) SHG in PPKTP. A pure-CW operation is also demonstrated with >3 W power and possible fiber delivery in 765-785 nm range.

Low-noise, CW-pumped holey-fiber based continuum sources around 1300 nm

Abstract: We analyzed noise, temporal and spectral-power-density properties of 5.5 W, CW Raman-soliton continua with >300 nm bandwidth around 1.3 /spl mu/m generated in a holey-fibre pumped by Yb-fibre sources. Fibre-laser and MOPFA pumping configurations are compared.

Femtosecond pulse compression in air-guiding PCF

Abstract: A 22-fold pulse-duration compression around 1µm wavelength is achieved in an air-guiding, anomalously dispersive photonic-crystal-fibre. 3.6ps pulses from a Yb fibre laser are compressed to 163fs in the totally-fibre integrated format. Peak power/energy scalability is feasible.

Modeling, fabrication, and experimental application of clear x-ray phase masks

Abstract: Phase-shifting masks are widely used in optical lithography, and the question is whether the technology can be extended to much shorter wavelengths. We have extensively modeled the use of clear phase-mask materials as absorbers for x-ray exposures. Similar to the optical domain, the imaging from x-ray phase masks is highly nonlinear, and thus can be used to produce a feature reduction of 3–5× compared to the mask pattern. This observation suggests that mask fabrication might be easier, but the technique is most suited for less dense pattern requirements. In this article we review some of the salient modeling, examine the requirements for effective fabrication of the masks, and provide some experimental verification of this approach to reach the sub-50nm region. It is not essential to have exactly a 180° phase shift in the clear material, because mask feature reductions can be achieved with 45, 90, 180, and 270° shifts by choosing the appropriate thicknesses of the clear material. A mask with a 235nm featu...

Forecasting Weather Variable Densities for Weather Derivatives and Energy Prices

Abstract: Electricity markets are structurally different to other commodities, and the real-time dynamic balancing of the electricity network involves many external factors. Because of this, it is not a simple matter to transfer conventional models of financial time series analysis to wholesale electricity prices. The rationale for this compilation of chapters from international authors is, therefore, to provide econometric analysis of wholesale power markets around the world, to give greater understanding of their particular characteristics, and to assess the applicability of various methods of price modelling. Researchers and professionals in this sector will find the book an invaluable guide to the most important state-of-the-art modelling techniques, which are converging to define the special approaches necessary for unravelling and forecasting the behaviour of electricity prices. It is a high-quality synthesis of the work of financial engineering, industrial economics and power systems analysis, as they relate to the behaviour of competitive electricity markets.

Femtosecond pulse compression around 1µm wavelength in air-guiding PCF

Abstract: A 22-fold pulse-duration compression around 1µm is achieved in an air-guiding anomalously dispersive photonic-crystal-fibre. 3.6ps pulses from an Yb -fibre laser are compressed to 163fs in the totally -fibre integrated format. Peak/average power scalability is feasible.

Dispersion Measurement and Passive Mode-Locking of a Femtosecond Cr4+:YAG Laser

Abstract: The passive mode locking of a Cr4+:YAG laser generating pulses shorter than 100 fs is described. The cavity group velocity dispersion has been measured and local resonances have been observed which appear to affect the mode locking of the laser.

All-fiber integrated ∼10kW peak power ultrashort optical pulse source based on compression in aircore photonic band gap fiber

Abstract: We demonstrate an all-fiber integrated, ∼10kW peak power, ∼1ps optical pulse source at a wavelength of 1.55μm based on compression in aircore photonic band gap fiber. A 10GHz pulse train was modulated at 10MHz in a Mach–Zehnder amplitude modulator with a ∼1ns transmission window before stretching in 100m of dispersion compensating fiber, amplifying, and recompressing in 10m of aircore photonic band gap fiber. Numerical simulations show that if the aircore fiber dispersion slope could be made negligible, the achievable peak power would be increased by a factor of approximately 2.

Study of the dispersion of an air-core photonic bandgap fiber and its application as a linear chirped pulse compressor

Abstract: We study the dispersion of an air-core photonic bandgap fiber and show its application in chirped pulse amplification. ~500 fs pulses, stretched to ~ 100 ps using dispersion-compensating fiber, were re-compressed to ~1ps in 10 m of this fiber

Continuous wave, all-fibre broad-band sources for optical coherence tomography

Abstract: We demonstrate in vivo OCT imaging with < 5 um resolution in tissue at ~1.3 mum wavelength using a new compact, CW, 330 mW, 140 nm bandwidth, holey-fibre continuum light source pumped by a single-mode Yb-fibre laser

Multi-watt, 1.48-2.05 /spl mu/m range CW Raman-soliton continuum generation in highly-nonlinear fibres

Abstract: Up-to 15 W power, CW Raman-soliton continua were generated in conventional highly-nonlinear-fibres in the 1.48-2.05 /spl mu/m range with spectral brightness up-to 30 mW/nm and flatness <1 dB. All-fibre-integrated pumping with 20 W 1480 nm Raman and 10 W Yb/Er sources is employed.

Low noise, high-brightness, broadband, all-fiber CW sources for OCT around 1300nm

Abstract: We analyzed noise, coherence and spectral-power-density properties of a 5.5W, CW Raman-soliton continuum with >300nm width around 1.3µm generated in a holey-fibre pumped by Yb-fibre source. The demonstrated source is ideal for high-resolution/sensitivity OCT imaging.