Showing papers by "James Taylor published in 2001"

3.5 W frequency-doubled fiber-based laser source at 772 nm

Abstract: A 3.5 W fiber-based laser source at 772 nm is demonstrated by using quasiphase-matched second-harmonic generation of a 40 dBm seeded ytterbium–erbium fiber amplifier in PPKTP. A 40% conversion efficiency is achieved across the entire output power range of the EDFA. No optical damage has been observed in the PPKTP over long-term high-power exposure.

Ketamine sedation for children in the emergency department.

Abstract: Objective: To introduce a protocol for dissociative sedation using ketamine for children requiring painful procedures within the emergency department. Method: A medical literature search was performed along with a review of existing ketamine-use protocols in emergency departments from Australia and the United States. Our hospital anaesthetic department and our emergency department nursing staff were closely involved in protocol design. A series of nursing education sessions were held prior to the drug being used within the emergency department. Twenty-eight children aged 1.5–12 years were administered ketamine sedation prior to undergoing a painful procedure. Ketamine was administered either i.m. (dose 3–4 mg/kg) or i.v. (dose 1.00–2.75 mg/kg) depending on physician preference. Midazolam (dose 0.02 mg/kg) and atropine (dose 0.02 mg/kg) were given as adjuncts in the majority of cases. Results: Onset of sedation was rapid (range 1–7 min) for both routes and provided excellent procedural conditions. Discharge time averaged 103 min (range 67–180 min) from time of drug administration. Side-effects included vomiting, rash, diplopia, salivation and one case of a distressing emergence reaction. On telephone follow up 1–3 days after the sedation, no delayed adverse events were reported. Conclusion: Ketamine is a safe and effective sedative agent for use in children requiring immobilization to enable performance of a painful procedure. It is important to involve both anaesthetic staff and emergency department nursing staff in sedation protocol development to ensure a smooth introduction. We present a protocol for ketamine use in children undergoing painful procedures within the emergency department. See Commentary, page 7.

Wavelength and duration tunable sub-picosecond source using adiabatic Raman compression

Abstract: A wavelength and pulse duration tunable source of subpicosecond pulses has been demonstrated at a repetition rate of 10 GHz using adiabatic Raman compression of 10 ps pulses from an external cavity laser and an electro-absorption modulator.

Multi-wavelength, continuous wave fibre Raman ring laser operating at 1.55 [micro sign]m

Abstract: A four wavelength continuous wave, fibre Raman ring laser has been demonstrated at room temperature using fibre Bragg gratings as the wavelength-selective elements with applications as a multi-wavelength source for optical fibre telecommunications. Channel spacings were /spl sim/5 nm between 1551.6 and 1565.1 nm with 14.9 dBm total output power.

Continuous-wave-pumped Raman-assisted fiber optical parametric amplifier and wavelength converter in conventional dispersion-shifted fiber.

Abstract: We present a continuous-wave-pumped fiber optical parametric amplifier, operating near 1539 nm in conventional dispersion-shifted fiber, with maximum on–off gain and wavelength-conversion efficiency of 13.7 and 13.1 dB, respectively. In addition, we show a novel configuration based on Raman amplification assistance in the parametric gain fiber that further increases the gain and wavelength-conversion efficiencies to 16.7 and 16.2 dB, respectively.

Broadband Raman gain characterisation in various optical fibres

Abstract: The Raman gain coefficient of several different types of optical fibres has been quantified using a sensitive technique based upon the measurement of backward amplified spontaneous emission. Spectral measurement of the effect of the variation of germanium doping in the fibre is also reported.

Wavelength tunable CW Raman fibre ring laser operating at 1486-1551 nm

Abstract: A continuous-wave, wavelength tunable Raman fibre ring laser has been demonstrated operating at 1485-1551 nm with peak output power of over 400 mW, pumped at 1420 nm by a 1.58 W fibre laser.

Dual wavelength pumped L- and U-band Raman amplifier

Abstract: A Raman fiber amplifier providing small signal gain of over 30dB in the U-band has been demonstrated. In addition, we present a dual wavelength pumped Raman amplifier with broad flattened gain (ripple better than 1.5 dB) over the spectral range 1600-1670nm.

The rotavirus vaccine's withdrawal and physicians' trust in vaccine safety mechanisms.

Abstract: Objective To determine how the withdrawal from the market of the rotavirus vaccine has affected physicians' trust in vaccine safety mechanisms, future adherence to vaccine recommendations, and willingness to use a new rotavirus vaccine. Design National survey mailed to 1228 randomly selected pediatricians and family physicians. Main Outcome Measures Confidence in vaccine safety mechanisms was defined by agreement with the statements that the system for determining vaccine safety before a vaccine is licensed works well and that the system for monitoring vaccine safety after vaccine licensure works well. Physicians who indicated that they would use a new rotavirus vaccine within 1 year of licensure and recommendation by professional organizations were classified as "early adopters." Logistic regression was used to assess the relationship between trust in vaccine safety mechanisms and future early adoption of new rotavirus vaccines. Results Following the withdrawal of the rotavirus vaccine, 83% of respondents believed the postlicensure surveillance system works well to monitor vaccine safety, while 22% of respondents believed the prelicensure system works well to determine vaccine safety. After adjusting for physician specialty and years in practice, respondents who believed the prelicensure vaccine safety system works well were significantly more likely to be early adopters than those with less confidence in prelicensure studies (adjusted odds ratio, 2.2 [95% confidence interval, 1.3-3.6]). Conclusions Physicians have different levels of trust in prelicensure studies that determine vaccine safety and postlicensure surveillance systems that monitor vaccine safety. Trust in prelicensure vaccine safety evaluations may be associated with early adherence to new vaccine recommendations.

Power scalability to 6 W of 770 nm source based on seeded fibre amplifier and PPKTP

Abstract: A 6 W average power at 772 nm is achieved by using a fibre integrated optical modulator for seeding of a 10 W erbium fibre amplifier followed by 64% efficient second-harmonic generation in PPKTP. The source benefits from a compact, efficient, fibre-based format and high overall efficiency.

Impact of the change to inactivated poliovirus vaccine on the immunization status of young children in the United States: a study from pediatric research in office settings and the National Medical Association.

Abstract: Objective. To determine whether the change from an all oral poliovirus vaccine (OPV) schedule to an inactivated poliovirus vaccine (IPV)-containing schedule has adversely affected the immunization status of young children in the United States. Methods. Immunization data were abstracted from the medical records of children 8 to 35 months old seen consecutively for any reason in the offices of practicing pediatricians who are members of the Pediatric Research in Office Settings network of the American Academy of Pediatrics or the National Medical Association. Data on up to 120 eligible children were collected in each practice between March 1998 and January 2000. Patients were classified as fully immunized at 8 months old if they had received 3 diphtheria-tetanus-pertussis, 2 Haemophilus influenzae type b, 2 hepatitis B, and 2 poliovirus vaccines. Study children who were ≥12 months of age at the time that data were collected were categorized as being fully immunized at 12 months if they had received the same vaccines before their first birthday. To assess the effect of type of poliovirus vaccines on these outcomes, study patients were classified as being in an IPV or OPV group based on the initial type of vaccine received. Logistic regression was used to calculate the odds ratios (ORs) and 95% confidence intervals (CIs) for IPV as a predictor of being fully immunized at 8 and 12 months of age, after adjusting for race/ethnicity of the patient, maternal education level, year of birth, and method of payment for vaccines. In addition, the effect of clustering of children within practices was accounted for by the use of generalized estimation equation techniques. Results. Data were analyzed on 13 520 children from 177 practices in 42 states; 79.4% of patients were fully immunized at 8 months of age, and 88.7% of those eligible were fully immunized at 12 months of age. A total of 6910 patients (51.1%) were classified as OPV recipients, wheras 5282 (39.1%) received IPV. In addition, 1328 children (9.8%) were documented as having received poliovirus vaccine, but the particular type could not be determined. Compared with OPV recipients and after controlling for the confounding variables and the effect of clustering within practices, children in the IPV group were as likely as were OPV recipients to be fully immunized at 8 months of age (OR: 1.04; 95% CI: 0.88,1.23). At 12 months of age, the OR for IPV as a predictor of being fully immunized was 1.08 (95% CI: 0.90,1.30). When compared with OPV recipients, adjusted ORs for children in the undetermined poliovirus vaccine type group being fully immunized at 8 and 12 months of age were 0.84 (95% CI: 0.68,1.04) and 0.84 (95% CI: 0.67,1.07), respectively. Conclusions. The results of this national study indicate that the implementation of an IPV-containing poliovirus vaccine schedule has not had an adverse effect on the immunization status of young children who were vaccinated in the offices of practicing pediatricians.

CW, multiple wavelength, room temperature, Raman fiber ring laser with external 19 channel, 10GHz pulse generation in a single electro-absorption modulator

Abstract: Simultaneous CW generation of over 24 wavelength channels with 100GHz spacing at 1550 nm has been demonstrated at room temperature in a Raman ring laser with Fabry-Perot. A single EAM was employed to simultaneously modulate 19 of the output channels at 10GHz.

Dynamic online energy loss minimisation

Abstract: An efficient method for minimisation of energy loss over intervals of time is presented. The proposed method uses different loading conditions during each given time interval instead of one single snapshot of the network. The given interval is divided into several shorter periods; the first load condition is a current snapshot and subsequent ones are forecast. By increasing the number of periods or load profiles, the dimension of the problem rises substantially. This difficulty is handled by using the generalised Benders decomposition technique. Energy and power loss minimisation are compared by simulated application to the modified IEEE 30-bus system and the New Brunswick Power network. As seen in these simulation results, the proposed method not only improves the voltage profile but also decreases the total energy loss over the given time interval.

Study of x-ray phase-shifting masks for sub-70 nm patterning

Abstract: One of the major challenges for x-ray lithography as a contender for next generation lithography lies in patterning small features—below 100 nm—with a mask-to-wafer gap greater than 20 μm. X-ray phase masks (XPM) provide an opportunity to alleviate this constraint, if the XPM can be constructed with good radiation and thermal stability for practical applications. In this article, we examine a robust silicon nitride based XPM with improved thermal and radiation stability for sub-70 nm imaging. The impact of various factors, such as exposure dose, phase-shifter thickness, sidewall slope, and mask-to-wafer gap, were studied. Phase-shifter slope and mask-to-wafer gap appeared to have a substantial impact on the printability of the XPMs. However, patterning sub-70 nm features could be achieved at a gap of 20 μm. Phase-shifter thickness variation within 10% appeared to have negligible impact on the linewidth with a synchrotron source. Extensive simulations and exposures were conducted to study the dose and gap ...

High power, seeded, fiber-amplifiers and non-linear conversion in periodically-poled crystals

Abstract: Compact, efficient sources based on seeded, high-power, cladding-pumped fiber-amplifiers have been used in c.w. and pulsed (nanosecond and picosecond) modes at average powers up to 10 W for efficient conversion to the visible in PPLN and PPKTP. With picosecond (~200ps) excitation of PPKTP up to 6W average power at 530 nm was obtained. This was used to synchronously pump a self-starting kerr lens mode locked Ti:Sapphire laser generating sub 100fs pulses.

Wavelength and duration tunable subpicosecond source using adiabatic Raman compression

Abstract: Summary form only given. Versatile infra red pulse sources with small mark-space ratios are of considerable importance to many areas of optical research from optical communication to multi-photon imaging. A wavelength and duration tunable source of sub-picosecond pulses therefore has wide appeal and many potential applications. Pulse compression in tapered optical fibers and in variants of this technique has allowed pulse compression to femtosecond durations but with considerable constraints on the system. The application of distributed Raman amplification allows considerably greater versatility, allowing both wavelength and pulse duration tunability. It should also be noted that repetition rate is also a selectable variable of the scheme that is described.

Dispersion characteristics of an AWG

Abstract: A phase-delay technique has been used to measure the group delay and dispersion of a 17/spl times/17 Arrayed Waveguide Grating (AWG) (de) multiplexer. Theoretical and experimental results have been compared and shown that dispersion is not negligible within the 10 dB transmission bandwidth.

Wavelength tunable CW Raman fiber ring laser operating at 1486-1551 nm

Abstract: Summary form only given. Erbium doped fiber lasers and amplifiers have provided a wealth of high power sources in the 1530 to 1580 nm spectral region. Other dopants such at ytterbium and thulium offer gain in other limited spectral regions but the non-linear effect of stimulated Raman scattering (SRS) provides for gain at any wavelength with the provision of a suitable pump source. Here we detail the optimization of a tunable fiber Raman ring laser with CW output between 1486 and 1551 nm, and use it to provide Raman gain over a tunable wavelength range of 1589 to 1650 nm.

Visible, multi-wavelength, fiber based Raman source

Abstract: Summary form only given. The Raman gain of silica glass can be utilized to create multi-wavelength visible sources operating in a broad range of wavelengths providing a high peak power visible pump source is employed. To date, Raman generation in the visible has usually been achieved using inefficient large frame lasers such as Ar ion, excimer or frequency doubled or tripled solid state lasers. Today's advances in parallel pumping techniques and the development of versatile format seeding sources, led to development of seeded powerful Ytterbium and Erbium fiber amplifiers which can readily replace costly, average power range, bulk solid state systems. By employing quasi-phase-matching harmonic generation in periodically poled materials, highly efficient frequency conversion and high peak powers in the visible can be readily achieved. The use of such visible fiber based systems for pumping visible Raman fiber converters can bring about fiber-delivered, compact and cost effective pulsed sources broadly operating over the visible range. We report on Raman generation in a single mode fiber pumped by 532 nm, PPKTP based, source based on a seeded Ytterbium fiber amplifier.

Skew Compensation in All Optical Bit Parallel WDM Systems

Abstract: A bit skew and dispersion compensation scheme using fibre gratings for a 10 Gb/s-channel, 2-bit, Bit Parallel WDM system over 100 km of standard single-mode fibre is presented. The combination of channelised dispersion, and additional fibre delay, is sufficient to give full compensation.