Showing papers by "James Taylor published in 1994"
TL;DR: The prevalence of intracranial hemorrhage in children with mild closed-head injury appears to vary with the presence of neurologic abnormalities and other noncranial injuries.
128 citations
TL;DR: A novel optical fiber that consists of a chain of alternating segments of standard telecommunication fiber and dispersion-shifted fiber is proposed for the generation of a soliton pulse train based on nonlinear transformation of an optical beat signal.
Abstract: A novel optical fiber [comblike dispersion-profiled fiber (CDPF)] that consists of a chain of alternating segments of standard telecommunication fiber and dispersion-shifted fiber is proposed for the generation of a soliton pulse train based on nonlinear transformation of an optical beat signal. A totally integrated all-optical fiber source of a 59.1-GHz train of 2.2-ps solitons is demonstrated with a CDPF. For a beat signal generator we use a dual-frequency erbium fiber laser incorporating fiber grating reflectors that provides 16-kHz linewidths and a low phase noise of optical beating (<5 × 10−5). Significant suppression of stimulated Brillouin scattering, which is essential for this technique, is achieved in the CDPF.
109 citations
TL;DR: In this article, the first time the generation and compression of soliton pulses using a step-like dispersion profiled fiber has been demonstrated, and the fabrication of such fibre assemblies does not require any special facilities and relies only on conventional optical fibre technology.
Abstract: Generation of 100 GHz trains of 500-700 fs pulses using dual-frequency beat conversion in a step-like dispersion profiled fibre is reported. The authors believe that this is the first time the generation and compression of soliton pulses using such a fibre has been demonstrated. The fabrication of such fibre assemblies does not require any special facilities and relies only on conventional optical fibre technology. They believe that the use of profiling the fibre dispersion by fibre segments instead of continuously dispersion-decreasing fibre is not only possible but preferable in many applications.
77 citations
TL;DR: In this article, an 8 mm long all-fibre photo-induced chirped reflection gratings at 1560 nm were used to achieve a compression ratio of 67.
Abstract: Pulse recompression and dispersion compensation are demonstrated using 8 mm long all fibre photoinduced chirped reflection gratings at 1560 nm. Optical pulses of 400 fs at 100 Gbits/s are almost fully recompressed after undergoing broadening of approximately 30 ps in an optical fibre; a compression ratio of 67 is achieved.
71 citations
01 Jan 1994
TL;DR: The parkinsonian score, based on factor analysis from the month after treatment, was used to determine and categorize the severity of MPTP deficits and was hypothesized to predict the outcome or stability of the deficit over time.
Abstract: The neurotoxin l-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) produces parkinsonian neurochemical and functional deficits in primates, which may be useful for evaluating the effects of possible antiparkinsonian treatments. Sixty-six adult male vervet monkeys (Cercopithecus aethiops sabaeus) were treated with MPTP (0.3–0.4 mg/kg., given 4–5 doses over a 5-day period, cumulative dose 1.6–2.0 mg), and 11 were saline-treated controls. Trained observers recorded spontaneous behaviors twice daily (5 min per observation, 5 × week) for varying periods after MPTP administration. Some behaviors were recorded if they occurred any time during a 5-sec period (e.g., climb, shift, chew) or lasted for a full 5-sec duration (e.g., freeze, immobility). Behaviors were also rated on a scale of 0–5 (e.g., poverty of movement, limb and head tremor) during spontaneous behavior and after “challenges” with food or threats. Individual behaviors were analyzed, and summary factors were calculated reflecting parkinsonian, intention tremor, anxiety, arousal, and healthy behaviors. MPTP administration resulted in behavior not observed in control subjects (i.e., tremor, freezing, immobility, eating problems, delayed and poverty of movement) and reduced healthy, arousal, and anxiety-related behavior. The parkinsonian score, based on factor analysis from the month after treatment, was used to determine and categorize the severity of MPTP deficits and was hypothesized to predict the outcome or stability of the deficit over time.
56 citations
TL;DR: Self-stabilization and self-organization of the output pulse train at repetition rates from the fundamental cavity frequency of 700 kHz up to 440 MHz and report on polarization effects.
Abstract: We report what is to our knowledge the first femtosecond pulse generation at 1.3 μm in a Pr3+-doped fluoride fiber laser. After optimization of the cavity length and dispersion, the laser generated pulses as short as 620 fs. We also describe self-stabilization and self-organization of the output pulse train at repetition rates from the fundamental cavity frequency of 700 kHz up to 440 MHz and report on polarization effects.
47 citations
TL;DR: In this article, a dual-wavelength operation of a diode-pumped, passively mode-locked, ytterbium-erbium "figure-of-eight" (F8L) fiber laser has been achieved by including tunable filters and/or fiber gratings in the laser cavity.
43 citations
TL;DR: In this paper, a novel fiber Bragg transmission filter employing a fiber polarisation splitter has been fabricated and tested, which has a total insertion of 1.2 dB and potentially can be reduced below 0.5 dB.
Abstract: A novel fibre Bragg grating transmission filter employing a fibre polarisation splitter has been fabricated and tested. The device has a total insertion of 1.2 dB and potentially can be reduced below 0.5 dB. >
36 citations
TL;DR: The passive mode locking of a Cr(4+):YAG laser is reported by use of a moving mirror and the generation of pulses as short as 70 fs byUse of Kerr-lens mode locking.
Abstract: We report the passive mode locking of a Cr4+:YAG laser by use of a moving mirror and the generation of pulses as short as 70 fs by use of Kerr-lens mode locking. The intracavity dispersion has been measured, and the laser performance has been related to water absorption lines.
32 citations
TL;DR: The results suggest that the transplantation procedure was able to increase the density of transporter sites in most of the caudate nucleus, although the proportion of dopaminergic and serotonergic fibers may have been altered from normal.
27 citations
TL;DR: In this article, the results of the experimental and modeling study of a positive tone, chemically amplified photoresist, in application to x-ray lithography were presented and the effective kinetic order of the photoacid loss reaction was derived from the FTIR absorbance data obtained for different PEB times and exposure doses.
Abstract: This article presents the results of the experimental and modeling study of a positive tone, chemically amplified photoresist, in application to x‐ray lithography. Spectrophotometric titration, Fourier transform infrared spectroscopy (FTIR), and development rate monitor data were acquired and used as inputs for the modeling of the processes and pattern simulations. The exposure model assumes monomolecular decomposition upon radiation and corresponds to Dill’s model for a nonbleaching photoactive compound. The post‐exposure bake (PEB) model is based on formal kinetic equations which include a term for photoacid loss (or side reactions) during the post‐exposure bake process in a generalized way. The effective kinetic order of the photoacid loss reaction is derived from the FTIR absorbance data obtained for different PEB times and exposure doses. For patterned exposures, a diffusion term for the local photoacid concentration is included. The photoacid and tert‐butoxycarbonyloxystyrene concentration profile c...
TL;DR: While the utility of peripheral nerve as a source of dopamine graft augmentation in non-human primates remains to be demonstrated, grafted nerve has a stimulatory effect on host brain dopamine systems in adult, dopamine-depleted monkeys and that this morphological effect can be dissociated from previously hypothesized injury-induced regeneration.
TL;DR: In this paper, the reflection of constant phase pulses off photosensitive Bragg gratings in singlemode fiber was investigated using a dice-pumped erbium fiber laser and the experimental measurements showed excellent agreement with theoretical prediction.
Abstract: Picosecond soliton pulses from a stabilised figure of eight, dice-pumped erbium fibre laser have been used to investigate the reflection of constant phase pulses off photosensitive Bragg gratings in singlemode fibre. The experimental measurements have shown excellent agreement with theoretical prediction.
07 Mar 1994
TL;DR: The general hybrid systems modeling language (HSML) described here will serve two purposes: to define formally what is meant by the term "hybrid system", and to provide the basis for language-based "front ends" for hybrid system simulation environments.
Abstract: The general hybrid systems modeling language (HSML) described here will serve two purposes: to define formally what is meant by the term "hybrid system", and to provide the basis for language-based "front ends" for hybrid system simulation environments. Features of HSML include: hierarchical, modular construction of models; consistent yet distinctive definition of continuous-time, discrete-time and logic-based components; prioritized scheduling of discrete-time components; mechanisms for state-event handling; approaches for dealing with vector-field conflicts and changing order and structure; rigorous type and range checking; and a strict semantic basis that permits extensive checking and validation of the model. >
20 Feb 1994
TL;DR: A tunable diode-pumped Cr:LiSAF regenerative amplifier has been demonstrated for the first time in this paper, where femtosecond pulses have been amplified to pulse energies exceeding 1 mu J at repetition rates up to 16 kHz.
Abstract: A tunable diode-pumped Cr:LiSAF regenerative amplifier has been demonstrated for the first time. Femtosecond pulses have been amplified to pulse energies exceeding 1 mu J at repetition rates up to 16 kHz. >
20 Feb 1994
TL;DR: Narrow-linewidth erbium-doped fiber lasers of monolithic multiple linear cavity configurations that use intracore fiber grating reflectors are demonstrated and a novel multiple-cavity erBium fiber laser with simultaneous dual single-frequency lasing is demonstrated.
Abstract: Narrow-linewidth erbium-doped fiber lasers of monolithic multiple linear cavity configurations that use intracore fiber grating reflectors are demonstrated. Robust single-frequency operation of a miniature coupled-cavity fiber laser with a linewidth of 30 kHz is reported. A novel multiple-cavity erbium fiber laser with simultaneous dual single-frequency lasing is also demonstrated. A 16-kHz linewidth and a frequency separation of 59 GHz with a stability of better than 3 MHz were achieved in this dual-frequency laser.
TL;DR: In this article, a sub-100 fs pulse generation from a Kerr lens modelocked Cr/sup 4+/:YAG laser was demonstrated, yielding femtosecond pulses tunable from 1.49 to 1.56 mu m with pulses as short as 90 fs obtained at 1.53 mu m.
Abstract: Sub-100 fs pulse generation from a Kerr lens modelocked Cr/sup 4+/:YAG laser has been demonstrated for the first time, yielding femtosecond pulses tunable from 1.49 to 1.56 mu m with pulses as short as 90 fs obtained at 1.53 mu m.
TL;DR: In this paper, the authors report Kerr lens modelocking of the Pr3+:YLF laser, operating at 639 nm, initiated through the use of a solid state saturable absorber, generating pulsewidths of 8 ps at repetition rates around 100 MHz.
Abstract: The authors report Kerr lens modelocking of the Pr3+:YLF laser, operating at 639 nm, initiated through the use of a solid state saturable absorber, generating pulsewidths of 8 ps at repetition rates around 100 MHz.
TL;DR: Using intensity-dependent polarization rotation as a passive mode-locking mechanism, pulses as short as 350 fs have been generated in an erbium fiber loop laser as discussed by the authors, and the response of the soliton structures to the periodic amplification gave rise to the now characteristic spectral side bands.
Abstract: Using intensity-dependent polarization rotation as a passive mode-locking mechanism, pulses as short as 350 fs have been generated in an erbium fibre loop laser. Even in the cavities optimized for minimum-pulse-width generation, the response of the soliton structures to the periodic amplification gave rise to the now characteristic spectral side bands.
28 Aug 1994
TL;DR: In this article, the authors reported the first ultrafast Cr":YAG laser, which was actively mode-locked with an acoustooptic modulator to yield 26 ps pulses.
Abstract: The rapid development of ultrafast tunable solid-state lasers has extended to the near infrared with the demonstration of mode-locked Cr4':Forsterite' and Cr4+: YAG lasers? Previously we reported the first ultrafast Cr":YAG laser, which was actively mode-locked with an acoustooptic modulator to yield 26 ps pulses.' Subsequent refinements have reduced the pulse duration to 10 ps and we have also generated 20 ps pulses using synchronous mode-locking. We now report on passive mode-locking of this laser medium. We have observed that, although mode-locking was achieved across almost the full laser tuning range (coating-limited to 1.37-1.58 Fm), femtosecond operation was only possible above 1.49 pm. Following a measurement of the intracavity group velocity dispersion (GVD), we attribute this to the deletirious effects of water absorption lines. Our attempts to actively initiate KLM with active loss/gain modulation were initially unsuccessful for the spectral region 1.37-1.49 nm (the tuning range permitted by our first dielectric mirror coating). Using moving mirror mode-locking3 with a simple four mirror astigmatically compensated cw laser cavity and with an external cavity configuration, we gener3RNING
TL;DR: In this article, the spectral and temporal evolution of a Cr3+:LiSrAlF6 laser, passively mode-locked using a multiple quantum well saturable absorber, was investigated to elucidate the self-starting behaviour.
TL;DR: In this paper, the authors used real-time Fourier transform infrared spectrometry (RT•FTIR) to monitor changes in resist chemistry during the bake steps using in situ using real time FTIR.
Abstract: Currently, the major approach to improving the performance of chemically amplified resists is by means of statistical design methods. These methods do not make use of information about the underlying chemical processes, information which could be useful in expediting the optimization process. We have developed techniques and equipment to monitor changes in resist chemistry during the bake steps using in situ using real time Fourier transform infrared spectrometry (RT‐FTIR). Using the Shipley SAL 605 negative chemically amplified resist, we monitored exposed resist as it was being baked at 110 °C; we were thus able to see several peaks change, including the growth of a peak at 982 cm−1 which we associate with the formation of an ether linkage during cross‐linking. When the height of this peak is plotted over time from the start of the bake, it shows several things, among them (a) the reaction being monitored takes much longer to reach its final level of completion (≳300 s) than the statistically derived op...
TL;DR: An XRS 200 model 2M X-ray stepper has been installed at the Center for Xray Lithography (CXrL) as mentioned in this paper, and the performance of the stepper gives with respect to the dose control and the mask/wafer alignment.
Abstract: An XRS 200 model 2M X-ray stepper has been installed at the Center for X-ray Lithography. This paper describes the capability of the machine and its installation. Of greater interest is the performance the stepper gives with respect to the dose control and the mask/wafer alignment. How robust a process is depends on the latitude of each process parameter and the control tolerance accorded the machines and materials that affect each one. The dose repeatabillty and uniformity is determined by the optical elements in the beamline, the helium delivery system, and the accuracy of the scanning stage. Test results are reported for dose control using three separate methods. The scan speed is measured using Suss supplied equipment and is verified separately by CXrL's own technique. The dose delivered is analysed by the response of radiachromic film. Also important is the behavior and performance of the ALX-100 alignment system. The optical set-up is described as a model that includes the ALX hardware and illumination as well as the mask and wafer. The signal and contrast from the mask and wafer are compared to data for several substrates. A figure of merit is discussed for determining which membranes will give the best overlay.
TL;DR: In this paper, the dissolution characteristics of a positive chemically amplified photoresist, AZ-PF514 from Hoechst Celanese, have been studied and development rate monitor data for different developer concentrations are analyzed.
Abstract: Dissolution characteristics of a positive chemically amplified photoresist, AZ-PF514 from Hoechst Celanese, have been studied. Development rate monitor data for different developer concentrations are analyzed. The experimental dissolution rates of the X-ray-exposed photoresist are examined in view of the dissolution model proposed earlier by Reiser. Parameters of Reiser's model associated with the diffusion of an aqueous base through a thin penetration layer and solubility of a phenolate complex in an aqueous base solution are derived for different X-ray exposure conditions. Reiser's dissolution model was used to simulate the developed photoresist pattern profile. An example of 0.25 µm pattern development simulation using a dose-dependent coefficient for diffusion of a developer base into polymer is demonstrated.
Proceedings Article•
08 May 1994
07 Mar 1994
TL;DR: This brief note reviews five papers which were presented at the 1993 IFAC World Congress, on the theme 'standards and guidelines for computer-aided control engineering (CACE), to note the substantial progress that was made.
Abstract: This brief note reviews five papers which were presented at the 1993 IFAC World Congress, on the theme 'standards and guidelines for computer-aided control engineering (CACE)'. This session was organized as part of the CACE Software Standardization Initiative, a combined effort of the IFAC and IEEE Control System Society committees on standards. The motivation of this report is to note the substantial progress that was made in this initiative, and to provide the basis for further discussion and work. The papers under review were concerned with integrated design environments, the use of the EXPRESS language for defining standard data structures, database management, user interfaces, and the modeling and simulation of hybrid systems. >
08 May 1994
TL;DR: The phase dispersion of multilayer dielectric mirrors provides a unique and extremely powerful means of controlling and manipulating optical pulses of the order of 1Ofs or shorter in this article.
Abstract: prism pair, will provide a simple and powerful means of recompressing the stretched pulses to their original shape and duration. Our results suggest that engineering the phase dispersion of multilayer dielectric mirrors provides a unique and extremely powerful means of controlling and manipulating optical pulses of the order of 1Ofs or shorter. ‘Optical Coating Laborato y, Research Institute for Solid State Physics, H-1521 Budapest, POB 49, Hunga y 1. Ch. Spielmann, P. F. Curley, T. Brabec, E. Wintner, F. Krausz, Electron. Lett. 28, 1532 (1992). M. Asaki, C. Huang, D. Garvey, J. Zhou, H. C. Kapteyn, M. M. Murnane, Opt. Lett. 18, 977 (1993). R. Szipocs, K. Ferncz, Ch. Spielmann, F. Krausz, Opt. Lett. 19, 1. Feb (1994). A. Stingl, Ch. Spielmann, R. Szipocs, F. Krausz, Opt. Lett. 19, 1. Feb (1994). 2.