PLASMA CONCENTRATIONS OF METHADONE DURING POSTOPERATIVE PATIENT-CONTROLLED EXTRADURAL ANALGESIA

Plasma concentrations of methadone were measured by gas chromatography in 16 patients receiving extradural methadone by continuous infusion for relief of postoperative pain. Venous blood samples were taken after a loading dose of extradural methadone 2 mg and during infusion of 0.46 mg h−1 plus patient-controlled increments of 0.2-1 mg. Mean (SD) plasma concentration of methadone was 9.8 (2.1) ng ml−1 at 15 min; this did not change significantly during the first 2 h, after which it increased gradually to 32.2 (4.6) ng ml−1 (P < 0.001) at the end of 24 h. The mean quantity of extradural methadone required to produce effective analgesia was 10.3 (1.8) mg during the first 12 h after operation and 6 (1.0) mg for the subsequent 12 h. The mean amount of methadone for effective analgesia on the second day was 7.6 (1.1) mg. No adverse effects were detected during the 2-3 days of methadone therapy. Plasma concentration of methadone increased significantly during patient-controlled infusion of extradural methadone in the first 24 h after operation, suggesting rapid vascular uptake. Systemic activity of the drug contributes to the analgesic effect of extradural methadon

Effective suppression of parametric instabilities with decoupled broadband lasers in plasma

A theoretical analysis for the stimulated Raman scattering (SRS) instability driven by two laser beams with certain frequency difference is presented. It is found that strong coupling and enhanced SRS take place only when the unstable regions for each beam are overlapped in the wavenumber space. Hence a threshold of the beam frequency difference for their decoupling is found as a function of their intensity and plasma density. Based upon this, a strategy to suppress the SRS instability with decoupled broadband lasers (DBLs) is proposed. A DBL can be composed of tens or even hundreds of beamlets, where the beamlets are distributed uniformly in a broad spectrum range such as over 10% of the central frequency. Decoupling among the beamlets is found due to the limited beamlet energy and suitable frequency difference between neighboring beamlets. Particle-in-cell simulations demonstrate that SRS can be almost completely suppressed with DBLs under the laser intensity ∼ 1015 W/cm2. Moreover, stimulated Brillouin scattering (SBS) will be suppressed simultaneously with DBLs can be attractive for driving inertial confined fusion

A 750 mW, continuous-wave, solid-state laser source at 313 nm for cooling and manipulating trapped 9Be+ ions

We present a solid-state laser system that generates 750 mW of continuous-wave single-frequency output at 313 nm. Sum-frequency generation with fiber lasers at 1550 nm and 1051 nm produces up to 2 W at 626 nm. This visible light is then converted to UV by cavity-enhanced second-harmonic generation. The laser output can be tuned over a 495 GHz range, which includes the 9Be+ laser cooling and repumping transitions. This is the first report of a narrow-linewidth laser system with sufficient power to perform fault-tolerant quantum-gate operations with trapped 9Be+ ions by use of stimulated Raman transitions.Comment: 9 pages, 4 figure

Landmine policy in the near-term: a framework for technology analysis and action

Any effective solution to the problem of leftover landmines and other post-conflict unexploded ordnance (UXO) must take into account the real capabilities of demining technologies and the availability of sufficient resources to carry out demining operations. Economic and operational factors must be included in analyses of humanitarian demining. These factors will provide a framework for using currently available resources and technologies to complete this task in a time frame that is both practical and useful. Since it is likely that reliable advanced technologies for demining are still several years away, this construct applies to the intervening period. It may also provide a framework for utilizing advanced technologies as they become available. This study is an economic system model for demining operations carried out by the developed nations that clarifies the role and impact of technology on the economic performance and viability of these operations. It also provides a quantitative guide to assess the performance penalties arising from gaps in current technology, as well as the potential advantages and desirable features of new technologies that will significantly affect the international community`s ability to address this problem. Implications for current and near-term landmine and landmine technology policies are drawn

Use of alternating-Z doubling in high-dynamic-range tripling: design and evaluation of an optimized prototype tripler

We designed and tested an alternating-Z tripler that consisted of two detuned, Type-1, potassium dihydrogen phosphate (KD*P) doublers and one KD*P mixer. The crystal thicknesses were, respectively, 13, 10 and 10 mm, and the detunings of the doublers were +420 and -520 µrad. All three crystals were fabricated from 80% deuterated KDP. Conversion efficiency was measured and calculated for input 1053- nm pulses with approximately rectangular waveforms and durations of either 1 or 6 ns, and for 20-ns pulses that exhibited intensity variation by a factor of 10. The measured peak conversion efficiency was more than 80%, and energy conversion efficiencies ranged from 62-80% depending on the waveform of the input pulse. The expected large dynamic range in input intensity, 9-10, was observed, and the measured and calculated efficiencies were in excellent agreement

Research on nonlinear optical materials: an assessment

The seven papers making up this assessment are based on the Workshop on Nonlinear Optical Materials held in April 1986

Science and Technology Review September 1999

This review consists of the following titles; The Laboratory in the News; Life Performance of Complex Systems; A Better Picture of Aging Materials; Researchers Determine Chernobyl Liquidators' Exposure; and Target Chamber's Dedication Marks a Giant Milestone

Science and Technology Review, November 1998

Lawrence Livermore National Laboratory is operated by the University of California for the Department of Energy. At Livermore, we focus science and technology on assuring our nationÕs security. We also apply that expertise to solve other important national problems in energy, bioscience, and the environment. Science & Technology Review is published 10 times a year to communicate, to a broad audience, the LaboratoryÕs scientific and technological accomplishments in fulfilling its primary missions. The publicationÕs goal is to help readers understand these accomplishments and appreciate their value to the individual citizen, the nation, and the world

Science and Technology Review May 1999

The following two abstracts are for the 2 feature stories in this issue of ''Science and Technology Review''. (1) ''Leveraging Science and Technology in the National Interest''--A sampling of current projects at Lawrence Livermore demonstrates the many ways in which the Laboratory's science and technology support Department of Defense missions. These projects range from engineering and fabricating munitions and explosives to developing the advanced computer codes that optimize warhead design or assess their hazards. The Penetration Augmented Munition is a portable, multistage weapon that not only provides offensive capability for diminishing adversaries' mobility and capability but also gives US soldiers an additional margin of security in a hostile encounter. Livermore's fiber-composite sabot makes weapons more lethal and is particularly effective in tank warfare. The GLO (global local optimizer) code optimizes the design of shaped-charge warheads, while the CHEETAH thermochemical code improves explosives formulation. CALE, a multiuse mechanical code, is used to help the Air Force assess missile launch site safety and in particular to predict hazards from propellant that falls to the ground when rockets misfire. ALE3D, now being upgraded, will increase the capability of codes to assess safety hazards. (2) ''Extracting Valuable Information from Acoustic Waves''--Lawrence Livermore researchers are developing advanced techniques for interpreting acoustic signals, focusing on complex algorithms that at times mimic the reasoning processes of the human brain. Three current acoustic signal-processing projects, involving heart valve classification, oil exploration, and large-structure analysis, demonstrate the wide range of acoustic signal usefulness. To determine whether an artificial heart valve is intact or needs replacing, a suite of Livermore algorithms sift through heart and body sounds to isolate the telltale signals of a faulty artificial heart valve. If successful, the new technique would spare patients from surgery to determine if their artificial valve needs replacement. Livermore experts and colleagues from Shell Oil are automating a key procedure used for locating undersea oil deposits. The procedure uses acoustic signals from underwater explosions that are detected by hydrophones. The project's goal is to reduce manual analysis of the signals to only about 0.1 percent of the data processed, thereby saving millions of dollars in oil exploration costs. Finally, a Livermore team is using acoustic wave vibrations to assess the integrity of several large structures in northern California. The goal is to develop a fast and reliable method to check for damage after earthquakes or other destructive events. A scale-model building at the Nevada Test Site is serving as a testbed for the project