40,986 research outputs found
LASER SPECTROSCOPY OF VIBRATIONALLY-EXCITED RYDBERG STATES OF
No full textResearch supported by AFOSR and NSF L. J. Lembo, H. Helm, and D. L. Huestis, J. Chem. Phys. 90, 5299 (1989).""Author Institution: TRW; Molecular Physics Laboratory, SRI InternationalIn an earlier we observed the and states of in vibronically-allowed excitation from the metastable state. In the present work we use these 3p states as intermediate levels in two-color excitation of autoionizing vibrationally-excited Rydberg series. Rydberg states with principal quantum numbers from to are observed. The strongest transitions correspond to nd Rydberg series converging to the and states, with , of vibrationally excited . Weaker transitions are observed to nd Rydberg states converging to and levels, also with . There is also evidence for excitation of np (or nf) Rydberg states built upon , and cores. An MQDT analysis is currently in progress
SPECTROSCOPY OF THE TRIATOMIC RARE GAS HALIDES:
No full text H. H. Nakano, R. M. Hill. D. C. Lorente, D. L. Huestis, M. V. McCusker, and D. J. Eskstrom, SRI Report MP 76-99, December 1976. D. C. Lorents, R. M. Hill, D. L. Huestis, M. V. McCusker, and H. H. Nakano, Third Summer Colloquium on Electronic Transition Lasers, Snowmass-at-Aspen, Colorado, September 1976. W. R. Wadt and P. J. Hay, to be published.Author Institution: Molecular Physics Center, Stanford Research InstituteIn the course of a detailed of the energy flow kinetics in e-beam excited mixtures, strong broad emissions were observed in the region of 290 nm and 400 nm. From a characterization of the pressure and temporal behavior of these emission features it was that the radiating molecules were not the well known ArF (193 nm) or KrF (248 nm) but rather triatomic species (290 nm) and (400 nm). Recent theoretical on supports these assignments. We report here a more systematic study of the spectroscopy of the triatomic rare gas fluorides: , and chlorides , and . The wavelength shift from the diatomics is explained in terms of binding in the rare gas molecular ion in the excited state and repulsion between the neutral rare gas atoms in the ground state. These effects are illustrated using potential surfaces for calculated by the Diatomics-in-Molecules method
Pharmacodynamic effects, pharmacokinetics, and metabolism of the synthetic cannabinoid AM-2201 in male rats
No full textNovel synthetic cannabinoids are appearing in recreational drug markets worldwide. Pharmacological characterization of these new drugs is needed to inform clinicians, toxicologists, and policy makers who monitor public health. [1-(5-Fluoropentyl)-1H-indol-3-yl](1-naphthyl)methanone (AM-2201) is an abused synthetic cannabinoid that was initially created as a research tool for investigating the endocannabinoid system. Here we measured the pharmacodynamic effects of AM-2201 in rats, and simultaneously determined plasma pharmacokinetics for the parent drug and its metabolites. Male Sprague-Dawley rats were fitted with surgically implanted temperature transponders and indwelling jugular catheters under pentobarbital anesthesia. One week later, rats received subcutaneous injection of AM-2201 (0.1, 0.3, and 1.0 mg/kg) or its vehicle, and serial blood specimens were withdrawn via catheters. Core temperatures and catalepsy were measured just prior to each blood withdrawal, and plasma was assayed for drug and metabolites using liquid chromatography-tandem mass spectrometry. We found that AM-2201 produced dose-related hypothermia and catalepsy that peaked at 2 hours and lasted up to 8 hours. AM-2201 plasma concentrations rose linearly with increasing dose and ranged from 0.14 to 67.9 μg/l. Concentrations of three metabolites, AM-2201 N-(4-hydroxypentyl) (≤0.17 μg/l), naphthalen-1-yl-(1-pentylindol-3-yl)methanone (JWH-018) N-(5-hydroxypentyl) (≤1.14 μg/l), and JWH-018 N-pentanoic acid (≤0.88 μg/l) were detectable but much lower. Peak AM-2201, JWH-018 N-(5-hydroxypentyl), and JWH-018 N-pentanoic acid concentrations occurred at 1.3, 2.4, and 6.5 hours, respectively. Concentrations of AM-2201, JWH-018 N-(5-hydroxypentyl), and JWH-018 N-pentanoic acid were negatively correlated with body temperature, but, given the low concentrations of metabolites detected, AM-2201 is likely the major contributor to pharmacodynamic effects under our experimental conditions
DETERMINATION OF POTENTIAL BARRIERS: THE UPSIDE-DOWN RKR METHOD
No full text See for example R. J. LeRoy and W.-K. Liu, J. Chem. Phys. 69, 3622 (1978). See R. I. Price, Chem. Phys. 31, 309 (1978). H. Helm, P. C. Cosby, and D. L. Huestis, J. Chem Phys. 73, 2629 (1980).Author Institution:Predissociation by tunnelling through a potential barrier has been observed in many diatomic molecules. These barriers may occur in the ``rotationless’’ potential, or they may result from, the contribution of the rotational kinetic energy, . The breakoff of bound levels at high J has often been used to characterize the long-range part of the potential curve, through the limiting curve of dissociation. In the present study we consider the information about the potential curve that can be obtained directly from analysts of the lifetimes of the predissociated Levels. The semiclassical expression for the barrier tunnelling contains an integral of the same from as the JWKB quantization condition for the vibrational quantum number in the bound portion of the potential. Thus we can use the observed lifetimes to derive a quantity (-) that can he considered to be the vibrational quantum number in the barrier region, measured from the top of the. barrier. Alternately, we can consider the barrier turned upside-down, and use the observed energies, linewidths, and J assignments to determine harrier turning points using convential RKR methods. We will present results from application of this method to the quasibound levels of , and the recently quasibound levels in ). We will also discuss the limitations that result from the observation of only a few levels for each .J, and suggest some ideas on how the data can be merged
Measurement of the branching fractions for B--> D(*)+pi(-)l(-)(nu)over-bar(l) and (B)over-bar(0)-> D-(*)0 pi(+)l(-)(nu)over-bar(l)
No full textWe report on a measurement of the branching fractions for B- --> D(*)+ pi(-)l(-)(nu) over bar (l) and (B) over bar (0) --> D-(*)0 pi(+)l(-)(nu) over bar (l) with 275 x 10(6) B (B) over bar events collected at the Y(4S) resonance with the Belle detector at KEKB. Events are tagged by fully reconstructing one of the B mesons in hadronic modes. We obtain B(B- --> D(+)pi(-)l(-)(nu) over bar (l)) = (0.54 +/- 0.07 (stat) +/- 0.07(syst) +/- 0.06(BR)) x 10(-2), B(B- --> D*+pi(-) l(-) (nu) over bar (l)) (0.67 +/- 0.11 (stat) +/- 0.09(syst) +/- 0.03(BR)) x 10(-2), B((B) over bar (0) --> D(0)pi(+)l(-) (nu) over bar (l)) = (0.33 +/- 0.06(stat) +/- 0.06(syst) +/- 0.03(BR)) x 10(-2), B((B) over bar (0) -->D(*0)pi(+)l(-)(nu) over bar (l)) = (0.65 +/- 0.12(stat) +/- 0.08(syst) +/- 0.05(BR)) x 10(-2), where the third error comes from the error on (B) over bar --> D((*))l(-)(nu) over bar (l) decays. Contributions from B-0 --> D(*+)l(-)(nu) over bar (l) decays are excluded in the measurement of (B) over bar (0) --> D(0)pi(+)l-(nu) over bar (l).Astronomy & AstrophysicsPhysics, Particles & FieldsSCI(E)0ARTICLE5null7
Quantification of [1-(5-fluoropentyl)-1H-indol-3-yl](naphthalene-1-yl)methanone (AM-2201) and 13 metabolites in human and rat plasma by liquid chromatography-tandem mass spectrometry
No full textAM-2201 is a popular synthetic cannabinoid first synthesized in 2000. AM-2201 pharmacokinetic and pharmacodynamic data are scarce, requiring further investigation. We developed a sensitive method for quantifying AM-2201 and 13 metabolites in plasma to provide a tool to further metabolic, pharmacokinetic and pharmacodynamic studies. Analysis was performed by liquid chromatography-tandem mass spectrometry. Chromatographic separation was performed by gradient elution on a biphenyl column with 0.1% formic acid in water/0.1% formic acid in acetonitrile:methanol 50:50 (v/v) mobile phase. Sample preparation (75 μL) consisted of an enzymatic hydrolysis and a supported liquid extraction. The method was validated with human plasma with a 0.025 or 0.050-50 μg/L working range, and cross-validated for rat plasma. Analytical recovery was 88.8-110.1% of target concentration, and intra- (n = 30) and inter-day (n = 30) imprecision < 11.9% coefficient of variation. Method recoveries and matrix effects ranged from 58.4-84.4% and -62.1 to -15.6%, respectively. AM-2201 and metabolites were stable (±20%) at room temperature for 24 h, at 4 °C for 72 h, and after three freeze-thaw cycles, and for 72 h in the autosampler after extraction. The method was developed for pharmacodynamic and pharmacokinetic studies with controlled administration in rats but is applicable for pre-clinical and clinical research and forensic investigations. Rat plasma specimen analysis following subcutaneous AM-2201 administration demonstrated the suitability of the method. AM-2201, JWH-018 N-(5-hydroxypentyl), and JWH-018 N-pentanoic acid concentrations were 4.8 ± 1.0, 0.15 ± 0.03, and 0.34 ± 0.07 μg/L, respectively, 8 h after AM-2201 administration at 0.3 mg/kg (n = 5)
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Analysis and Interpretation of Mars Dayglow Altitude Profiles
No full textThe Mariner 4 (1965), Mariner 6 and 7 (1969), Mariner 9 (1971-72), and Viking 1 and 2 (1976-80) missions provided the first quantitative information about the structure, energetics, and dynamics of the Mars atmosphere. Not until more than 20 years later did new generations of landers and orbiters revisit the planet.
The initial Mariner dayglow observations [1] motivated numerous modeling studies and laboratory experiments. The most obvious source reaction is photodissociation and photoionization of ambient CO2, which is known in the laboratory to produce all four dayglow emitting states:
(1) hν + CO2 → O(1S), CO(a3Π), CO2+(A2Πu & B2Σu+)
If this simplest of models were sufficient, then the high altitude dayglow emissions would all share the same scale height, which would be that of CO2. The few Mariner dayglow observations [1, 2] provided weak statistics [3]. Addition of 4 months of Mars Express dayglow data [4], and including radio occultation and mass spectrometry data from other missions, have made the analyses and conclusions more robust.
The CO(a3Π) and CO2+(B2Σu+) altitude profiles are consistent with Reaction (1). In contrast, the O(1S) scale heights are much larger and are consistent with source Reaction (2).
(2) O2+ + e- → O(1S)
Both sets of scale heights change with respect to solar activity roughly as suggested by modeling studies [5, 6].
Acknowledgements: Supported by NASA Mars Data Analysis grant NNX06AE04G. SRI document MP 09-050.
References:[1] Barth C. A. et al. (1971) JGR 76, 2213-2227.[2] Stewart A. I. et al. (1972) Icarus 17, 469.[3] Huestis D. L. et al. (2008) 3rd Workshop on the Mars Atmosphere (Williamsburg, VA).[4] Leblanc F. (private communication).[5] Fox J. L. et al. (1996). Adv. Space Res. 17, (11)203.[6] Krasnopolsky V. A. (2002) JGR 107
Logarithmic variance profiles and the corresponding f-1 spectra of temperature fluctuations in turbulent Rayleigh-Bénard convection
No full textWe report experimental results for the temperature variance 2(z) and the corresponding frequency spectra P(f) in turbulent Rayleigh-Bénard convection (RBC) in a cylindrical sample of aspect ratioT= D/L = 1:00 (D = 1:12 m is the diameter and L = 1:12 m the height). The measurements were conducted in the Rayleigh-number range 1011 < Ra < 1:35 1014 and Pr ' 0:8. For Ra = 1:35x1014, 2(z) could be described well by a logarithmic dependence on the vertical position z in a range of z 1 < z < z 2 with z 1 ' 70 and z 2 = 0:1L. Here L=(2Nu) is the thickness of a thin thermal sublayer adjacent to the horizontal plate where the heat flux (denoted by the Nusselt number Nu) is carried mostly by thermal diffusion. In the log layer, we found that the temperature spectra had a significant frequency range over which P(f) f with close to 1. As Ra decreased, increased so that the log layer became thinner. At Ra = 2:05 1011, z 2 < z 1 and therefore there was no range for a log layer. Correspondingly, the temperature spectrum near the horizontal plate did not have the f1 scaling form either
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
- …
