Observation of high-energy vibrational overtones of molecules in solids: Local modes and intramolecular relaxations

In the last few years, the spectra of vibrational overtones (1) (at ~15-20,000 cm^-1) in large molecules have received considerable attention. The focus is on three problems dealing with the origin of relaxation at such high energies, the association of spectral band positions with the local modes (LM) in molecules, and the relevance of these spectra to possible selectivity in laser-induced chemistry

Non-BPS D8-branes and Dynamic Domain Walls in Massive IIA Supergravities

We study the D8-branes of the Romans massive IIA supergravity theory using the coupled supergravity and worldvolume actions. D8 branes can be regarded as domain walls with the jump in the extrinsic curvature at the brane given by the Israel matching conditions. We examine the restrictions that these conditions place on extreme and non-extreme solutions and find that they rule out some of the supersymmetric solutions given by Bergshoeff {\em et al}. We consider what happens when the dilaton varies on the worldvolume of the brane, which implies that the brane is no longer static. We obtain a family of D8-brane solutions parametrized by a non-extremality term on each side of the brane and the asymptotic values of the 10-form field. The non-extremality parameters can be related to the velocity of the brane. We also study 8-brane solutions of a massive IIA supergravity theory introduced by Howe, Lambert and West. This theory also admits a 10-form formulation, but the 10-form is not a R-R sector field and so these 8-branes are not D-branes.Comment: 23 pages REVTeX, 2 .eps figures. This paper completely replaces and extends an earlier paper (hep-th/9712112) by Chamblin and Perr

Maternal haemodynamic function differs in pre‐eclampsia when it is associated with a small‐for‐gestational‐age newborn: a prospective cohort study

Objective To describe maternal haemodynamic differences in gestational hypertension with small‐for‐gestational‐age babies (HDP + SGA), gestational hypertension with appropriate‐for‐gestational‐age babies (HDP‐only) and control pregnancies. Design Prospective cohort study. Setting Tertiary Hospital, UK. Population Women with gestational hypertension and healthy pregnant women. Methods Maternal haemodynamic indices were measured using a non‐invasive Ultrasound Cardiac Output Monitor (USCOM‐1A®) and corrected for gestational age and maternal characteristics using device‐specific reference ranges. Main outcome measures Maternal cardiac output, stroke volume, systemic vascular resistance. Results We included 114 HDP + SGA, 202 HDP‐only and 401 control pregnancies at 26–41 weeks of gestation. There was no significant difference in the mean arterial blood pressure (110 versus 107 mmHg, P = 0.445) between the two HDP groups at presentation. Pregnancies complicated by HDP + SGA had significantly lower median heart rate (76 versus 85 bpm versus 83 bpm), lower cardiac output (0.85 versus 0.98 versus 0.97 MoM) and higher systemic vascular resistance (1.4 versus 1.0 versus 1.2 MoM) compared with control and HDP‐only pregnancies, respectively (all P < 0.05). Conclusion Women with HDP + SGA present with more severe haemodynamic dysfunction than HDP‐only. Even HDP‐only pregnancies exhibit impaired haemodynamic indices compared with normal pregnancies, supporting a role of the maternal cardiovascular system in gestational hypertension irrespective of fetal size. Central haemodynamic changes may play a role in the pathogenesis of pre‐eclampsia and should be considered alongside placental aetiology

Note on restoring manifest rotational symmetry in hyperfine and fine structure in light-front QED

We study the part of the renormalized, cutoff QED light-front Hamiltonian that does not change particle number. The Hamiltonian contains interactions that must be treated in second-order bound state perturbation theory to obtain hyperfine structure. We show that a simple unitary transformation leads directly to the familiar Breit-Fermi spin-spin and tensor interactions, which can be treated in degenerate first-order bound-state perturbation theory, thus simplifying analytic light-front QED calculations. To the order in momenta we need to consider, this transformation is equivalent to a Melosh rotation. We also study how the similarity transformation affects spin-orbit interactions.Comment: 17 pages, latex fil

Thermal Lensing Spectroscopy With Picosecond Pulse Trains and a New Dual Beam Configuration

In this communication, we wish to report on the use of synchronously mode-locked picosecond lasers in a pump-probe configuration for TL spectroscopy. The peak power for these picosecond lasers is very high and, of course, the fundamental of the dye laser (red beam) can be efficiently (~10%) doubled in frequency (U.V. beam) by second harmonic generation in nonlinear crystals. We use this generated U.V. beam as a probe to monitor the very weak absorption of the red beam. An arrangement [4] of the beams involving different waist positions for the pump and probe is used. This arrangement results in an enhancement of sensitivity (at least a factor of three to seven). Also, a different dependence of the signal on the cell position compared to the single beam method is obtained. Finally, we have obtained the Δν = 5 CH-stretching overtone absorption spectrum of liquid toluene with this method (see Figure 1). Suggestions are made regarding new applications of this picosecond pulse thermal lensing technique

In-Plane Magnetolumnescence of Modulation-Doped GaAs/AlGaAs Coupled Double Quantum Wells

In-plane magnetic field photoluminescence spectra from a series of GaAs/AlGaAs coupled double quantum wells show distinctive doublet structures related to the symmetric and antisymmetric states. The magnetic field behavior of the upper transition from the antisymmetric state strongly depends on sample mobility. In lower mobility samples, the transition energy shows an $\cal N$-type kink with fields (namely a maximum followed by a minimum), whereas higher mobility samples have a linear dependence. The former is due to a homogeneous broadening of electron and hole states and the results are in good agreement with theoretical calculations.Comment: 3 pages, 4 figures, submitted to Appl. Phys. Let

A study of the usefulness of Skylab EREP data for earth resources studies in Australia

There are no author-identified significant results in this report

Control law parameterization for an aeroelastic wind-tunnel model equipped with an active roll control system and comparison with experiment

Nominal roll control laws were designed, implemented, and tested on an aeroelastically-scaled free-to-roll wind-tunnel model of an advanced fighter configuration. The tests were performed in the NASA Langley Transonic Dynamics Tunnel. A parametric study of the nominal roll control system was conducted. This parametric study determined possible control system gain variations which yielded identical closed-loop stability (roll mode pole location) and identical roll response but different maximum control-surface deflections. Comparison of analytical predictions with wind-tunnel results was generally very good