Showing papers by "James Taylor published in 2006"

Zero-dispersion wavelength decreasing photonic crystal fibers for ultraviolet-extended supercontinuum generation

Abstract: We report the fabrication of photonic crystal fibers with a continuously-decreasing zero-dispersion wavelength along their length. These tapered fibers are designed to extend the generation of supercontinuum spectra from the visible into the ultraviolet. We report on their performance when pumped with both nanosecond and picosecond sources at 1.064 microm. The supercontinuum spectra have a spectral width (measured at the 10 dB points) extending from 0.372 microm to beyond 1.75 microm. In an optimal configuration a flat (3 dB) spectrum from 395 to 850 nm, with a minimum spectral power density of 2 mW/nm was achieved, with a total continuum output power of 3.5 W. We believe that the shortest wavelengths were generated by cascaded four-wave mixing: the continuous decrease of the zero dispersion wavelength along the fiber length enables the phase-matching condition to be satisfied for a wide range of wavelengths into the ultraviolet, while simultaneously increasing the nonlinear coefficient of the fiber.

Optophysiology: depth-resolved probing of retinal physiology with functional ultrahigh-resolution optical coherence tomography.

Abstract: Noncontact, depth-resolved, optical probing of retinal response to visual stimulation with a <10-μm spatial resolution, achieved by using functional ultrahigh-resolution optical coherence tomography (fUHROCT), is demonstrated in isolated rabbit retinas. The method takes advantage of the fact that physiological changes in dark-adapted retinas caused by light stimulation can result in local variation of the tissue reflectivity. fUHROCT scans were acquired from isolated retinas synchronously with electrical recordings before, during, and after light stimulation. Pronounced stimulus-related changes in the retinal reflectivity profile were observed in the inner/outer segments of the photoreceptor layer and the plexiform layers. Control experiments (e.g., dark adaptation vs. light stimulation), pharmacological inhibition of photoreceptor function, and synaptic transmission to the inner retina confirmed that the origin of the observed optical changes is the altered physiological state of the retina evoked by the light stimulus. We have demonstrated that fUHROCT allows for simultaneous, noninvasive probing of both retinal morphology and function, which could significantly improve the early diagnosis of various ophthalmic pathologies and could lead to better understanding of pathogenesis.

Oral outpatient chemotherapy medication errors in children with acute lymphoblastic leukemia.

Abstract: BACKGROUND. Although medication errors are 1 of the most common types of medical errors, their frequency in pediatric patients receiving oral outpatient chemotherapeutic agents is unknown. The prescribing, dispensing, and parental administration of these medications to children receiving treatment for acute lymphoblastic leukemia (ALL) were systematically reviewed to determine the rate and types of medication errors occurring in these patients. METHODS. During a 2-month study period, parents of children with ALL were contacted and asked to participate in the study before a regularly scheduled clinic appointment. At the visit, the parent demonstrated how each medication was administered. A pediatric oncologist reviewed the medical record to determine the correct treatment regimen for study patients. After comparing the correct treatment regimen with what was administered, a classification of “no medication error,” “medication error,” or “cannot determine” due to insufficient information was made for each indicated drug. Identified medication errors were subclassified as prescribing, dispensing, or administration errors. RESULTS. Data on 172 chemotherapeutic medications for 69 patients were analyzed. One or more errors occurred with 17 of the 172 (9.9%) medications; a classification of “cannot determine” was made for 12 (7.0%) medications. Among the 17 medication errors there were 12 (7.0%) administration errors and 5 (2.9%) prescribing errors. There were no pharmacy dispensing errors. All errors were due to incorrect dosing or failure to administer an indicated medication. At least 1 medication error occurred in 13 of the 69 (18.8%) study patients. CONCLUSIONS. Prescribing and administration medication errors occurred with nearly 10% of chemotherapeutic drugs administered to outpatient children with ALL. Systematic changes, including computerized physician order entry and simplification of treatment protocols, should be considered. Cancer 2006. © 2006 American Cancer Society.

Ytterbium gain band self-induced modulation instability laser

Abstract: We demonstrate an ytterbium gain band self-induced modulation instability laser. A highly nonlinear holey fiber is used to provide the anomalous dispersion required for bright soliton generation at 1 microm. The all-fiber integrated source yields a 40 GHz train of 4 ps pulses at a wavelength of 1064 nm.

A novel adaptive nonlinear dynamic data reconciliation and gross error detection method

Abstract: Data reconciliation is a well-known method in online process control engineering aimed at estimating the true values of corrupted measurements under constraints Most nonlinear dynamic data reconciliation methods have studied cases where the input variables are constant over relatively long periods of time separated by simple step changes (eg, set-point changes) While this scenario is not uncommon in process control, it imposes strong limitations on a method's applicability In this paper a novel adaptive nonlinear dynamic data reconciliation algorithm is presented that extends the method presented by Laylabadi and Taylor (2006) to the cases where the input variables are ramps or slow sinusoidal functions or, for that matter, any slow, smooth variation

An implementation plan for integrated control and asset management of petroleum production facilities

Abstract: This paper addresses innovative issues of asset management for the petroleum industry, which is very crucial for profitable oil and gas facilities operations and maintenance A research project was initiated to study the feasibility of an intelligent asset management system Having proposed a conceptual model for such a system in previous work [1], [2], we describe its behavior in terms of data and control flow, and pave the way for an implementation and rapid prototyping plan for such system Furthermore we discuss the required off-the-shelf development tools A simplified system prototype is introduced as a colored petri net model, which will be used to analyze the prototype logical structure and dynamic performance We finally discuss the project progress status and future work

Second-harmonic generation to the green and yellow using picosecond fiber pump sources and periodically poled waveguides

Abstract: Compact yellow (560nm) and green (532nm) picosecond pulse sources are demonstrated that utilize second-harmonic generation in periodically poled potassium titanyl phosphate waveguides. Both systems employ ytterbium-doped fiber pump sources. In the yellow case, efficient single-pass Raman scattering in 25m of dispersion-compensating fiber was additionally used to generate the 1.12μm pump. Raman gain could similarly be used in compact configurations to generate other pump wavelengths for use in frequency upconversion schemes.

Causes of pattern in plant communities where environmental change is rapid and species longevity is short

Abstract: This is a publisher's version of an article published in Journal of Vegetation Science 2006 published by Opulus Press. This version is reproduced with permission from Opulus Press. http://www.wiley.com/bw/journal.asp?ref=1100-9233

Safety, tolerability and immunogenicity of VAQTA given concomitantly versus nonconcomitantly with other pediatric vaccines in healthy 12-month-old children.

Abstract: Background The objective of this study is to assess whether hepatitis A vaccine is immunogenic and well tolerated when administered to 12-month-old children alone or concomitantly with other routinely administered pediatric vaccines. Methods Six hundred seventeen healthy 12-month-old children were randomized to receive dose 1 of hepatitis A vaccine given alone or concomitantly with measles-mumps-rubella vaccine and varicella vaccine and dose 2 of hepatitis A vaccine given alone or concomitantly with diphtheria-tetanus-acellular pertussis vaccine and optionally with oral or inactivated poliovirus vaccine. Participants were followed for clinical adverse experiences and serologic responses to all vaccine antigens. Antibody responses were compared with historical controls for some indices. Results The safety profile was generally comparable whether hepatitis A vaccine was administered alone or concomitantly with other vaccines. When administered alone, the hepatitis A seropositivity rate was 98.3% and 100% for dose 1 and dose 2, respectively, and after dose 2 was similar to historical rates and the geometric mean titers were similar between initially seropositive and initially seronegative subjects (6207 and 6810 mIU/mL, respectively). After concomitant administration with hepatitis A vaccine, antibody responses to measles, mumps, rubella, diphtheria, tetanus and filamentous hemagglutinin (98.8%, 99.6%, 100%, 98.6%, 100% and 83.3%, respectively) were similar to historical controls and response to poliovirus was demonstrated, but immune responses to varicella zoster virus (79%) and pertussis toxoid (76%) were inferior to historical controls. Conclusions Hepatitis A vaccine is highly immunogenic and generally well tolerated when administered to healthy children as young as 12 months of age regardless of initial hepatitis A serostatus and can be administered concomitantly with measles-mumps-rubella vaccine and oral or inactivated poliovirus vaccine.

A protocol for converting qualitative point soil pit survey data into continuous soil property maps

Abstract: Vineyard soil surveys to date have focused on presenting soil data in point rather than raster format. This is due to the recording of both numeric and categorical variables. A protocol, including a lookup table to transform linguistic texture values into particle size distributions, to convert point data into continuous raster maps is presented. The resulting maps are coherent with vineyard knowledge and provide a strong spatial representation of soil variability within the vineyard. Validation with an independent dataset shows an error of ~10% in prediction; however, some of this can be attributed to errors in the geo-rectification of old data. Raster maps allow the survey data to be incorporated into computer systems to better model vineyard and irrigation designs and are more readily used in day-to-day vineyard management decisions.

Generalized analysis of spatial variation in yield monitor data

Abstract: Australian lupin and cotton yield monitor data were analysed using spatial models from the Matern class of spatial covariance functions. Despite difficulties with the spatial disposition of the data, the analysis supports the statistical model in which the variation is a linear combination of white noise and the de Wijs process. The de Wijs process, also called the logarithmic covariance function, is a generalized covariance function that is conformally invariant and suggests that there is variation at all spatial scales. The present work also indicates that anisotropy and convolution are properties of yield monitor data and that it is hard to distinguish the two. The degree and causes of anisotropy require further investigation. Fitting this model is relatively easy for small, precision-agriculture datasets and open source software is available to this end. Comparing the de Wijs model with more general models in the Matern class is computationally intensive for precision-agriculture datasets.

Distribution and occurrence of Phytophthora cinnamomi at Middle Head and North Head, Sydney Harbour

Abstract: Dieback due to Phytophthora cinnamomi has significant impacts on susceptible native Australian vegetation communities and dependent fauna. Here we report the occurrence and distribution of P. cinnamomi at North Head and Middle Head, Sydney Harbour.

Chapter 33 Comparing Discriminant Analysis with Binomial Logistic Regression, Regression Kriging and Multi-Indicator Kriging for Mapping Salinity Risk in Northwest New South Wales, Australia

Abstract: In Australia, soil salinity is one of the most devastating forms of land degradation facing agricultural production. In northern New South Wales (NSW), where irrigated-cotton production is a dominant agricultural commodity, salinity even though is not currently such a serious problem, could pose a potential threat to cotton production. This chapter explores the use of discriminant analysis (DA) and other alternative models for using ancillary data to create threshold-based risk maps (rather than continuous maps) of soil salinity and compares these maps with more traditional indicator predictions. The opportunity for incorporating an error analysis into DA is also explored. The hypothesis for including the error analysis in DA and related models is that a certain level of information remains in the residuals of the initial model and that this information could be extracted and analysed to improve the final prediction. The ancillary-based models used in this chapter did not produce better predictions than a Multi-Indicator Kriging (MIK) approach that did not include the ancillary data. The DA models produced better prediction than the Multi-Variate Stepwise Linear Regression with the Kriging (MSLR-K) and Binomial Linear Regression models. A benefit of the DA approaches is the generation of probability maps, similar to MIK, that may be used in future decision making.

High Power Fibre Integrated Sources

Abstract: This presentation gives an emphasis on the development of all-fiber chirped pulse amplifier (CPA) sources. It describes both Yb and Yb-Er based CPAs, where powers of 20 kW in picosecond pulses recompressed in up to 110 m of air core photonic band gap fibre. The problem of dispersion slope, leading to incomplete recompression of the stretched pulses are also described, as well as the simple compression configuration using high efficiency transmission gratings. In the latter, frequency chirping and simultaneous amplification of a 4 ps pulse from a passively mode locked Yb fibre laser is achieved in a polarization maintaining amplifier and recompressed to obtain peak powers of 270 kW at 2.5 W average power with pulse durations of 140 fs. The limits to further power enhancement set by nonlinearity are also described. Spectral recompression as a result of nonlinearity is also demonstrated. An all fibre integrated scheme where spectral compression factors approaching times twenty have been achieved with watts average power, output pulse durations of ~7 ps and peak powers of 3-5 kW. Other schemes are also described, where transform limited operation may not be needed nor required where peak powers of up to 100 kW can be achieved and average powers up to 15 W, pulse durations selectable between 2-20 ps in a fully integrated system with a 20×30 cm footprint, 5 cm high. This laser scheme has also been applied to integrated supercontinuum generation in the ultraviolet where average powers of up to 5 mW/nm have been achieved.

Narrow-line 23W linearly polarized fiber Raman laser applied to frequency doubling to 589nm

Abstract: 23 W, single-mode linearly-polarized 0.4 nm linewidth CW generation is achieved in a polarization-maintaining fiber Raman cavity pumped by a linearly-polarized Ytterbium fiber laser and applied to 3 W 589 nm second harmonic generation in MgO-PPLN.

Pump format influence on noise characteristics and spectral extent of CW continuum generation in new low-water-loss holey fibers

Abstract: Watts-level, continuous-wave pumped supercontinua, 1.06-1.7 mum, generated in a new low OH-loss PCF exhibit distinct spectral and noise dynamics when pumped with either high or low-intensity-noise 1 um sources. Applications to ultra-low-noise mum-scale OCT are analyzed.

Aircore fiber based spectral compression of an all fiber integrated ultrashort pulse source

Abstract: We report on the spectral compression of an all fiber integrated ultrashort pulse source using both transmission grating pairs and aircore photonic bandgap fiber to provide the required negative chirp.

Holey fiber based modulation instability laser at 1.06 μm

Abstract: We report on an Ytterbium gain band, holey fiber based modulation instability laser. The all fiber integrated source produces a 40 GHz train of 4 ps pulses at a wavelength of 1064 nm.

Application of a 2W/nm all-fiber supercontinuum source to the characterization of nonlinear crystals

Abstract: We demonstrate a nanosecond all-fiber pump laser based supercontinuum source with a peak power density of 2 W/nm in the 0.5 to 1.8 mum range. The source is applied to characterization of periodically poled crystals.

Fiber integrated femtosecond soliton sources from CW noise

Abstract: We report on the development of simple, femtosecond soliton sources based on the propagation of CW noise through a highly nonlinear fiber. A method of wavelength extension to the visible is proposed.

3W CW Generation at 589nm with Narrow Line Linearly Polarized Raman Fibre Laser

Abstract: 26W, 0.4nm linewidth CW Raman generation is achieved in linearly polarized single-mode fibre and applied to efficient, over 3W 589nm generation in MgO-PPLN. Watts level generation at any wavelength 550nm to 780nm is feasible.

Blue light generation in holey fibre using frequency doubled fibre pump source

Abstract: A report is presented on the efficient generation of 18 mW of 428 nm light by propagating frequency doubled 780 nm pulses from an all-fibre integrated picosecond pulse source with kW level peak power through a length of highly nonlinear holey fibre. The wavelength conversion process is attributed to resonant coupling between solitons and dispersive radiation.

Extension of Supercontinuum Generation to the Blue in Cascaded Holey Fibers

Abstract: Combining holey-fibers with sequentially decreasing zero dispersion wavelengths, pumped with an all-fiber picosecond ytterbium laser, produced a 1.2W average power white light continuum 0.44-1.89µm. Enhancement of short wavelength generation is associated with optimized phase-matched four-wave-mixing.

Fibre-integrated high-power blue-enhanced continuum source

Abstract: Optimized cascading of HFs with shortening zero-dispersion wavelengths enabled generation of supercontinua with 1.4 W average power and significant components in the blue (10 dB) and UV from picosecond ytterbium pump sources in a totally fiber-integrated format.