Experimental results are presented for the physical origins of room-temperature photoreflectance features of a AlGaAs/GaAs single-quantum well structure. The spectra exhibit well-defined Franz–Keldysh oscillations which overlap with photoreflectance features due to the quantum well and complicate the determination of the energies of the transitions within the quantum well. The origin of the Franz–Keldysh oscillations are determined using wet chemical etching to selectively remove grown layers down to the substrate. The resulting spectra are presented as a function of etch depth which allows the magnitude of the built-in electric fields to be determined and reveals the location within the quantum well structure where the Franz–Keldysh oscillations originate.
We evaluated the utility of medium molecular weight hyaluronic acid for prolonging the local anesthetic activity of lidocaine in a rabbit model of epidural analgesia. Equiviscous formulations were prepared as either a physical mixture of lidocaine hydrochloride and sodium hyaluronate (where drug release occurred via diffusion) or as a lidocaine-hyaluronate complex (where drug release occurred via diffusional and electrostatic processes). The novel hyaluronic acid formulations were functionally evaluated, relative to lidocaine solution, in an intact, conscious rabbit model. The hyaluronate formulations were well tolerated. The duration of sensory block and loss of weight-bearing was prolonged twofold by the lidocaine-hyaluronate complex relative to the solution (P < 0.05). In terms of motor block, flaccid paresis occurred after administration of the solution formulation, whereas only partial motor block was evident after administration of the viscous formulations. Pharmacokinetic modeling of the lidocaine plasma concentration-time data indicated that the rate of drug absorption from the lidocaine-hyaluronate complex was decreased fourfold relative to the solution (P < 0.05). These observations indicate that ionic complexes of local anesthetics with medium molecular weight hyaluronic acid may offer advantages for the prolongation of epidural analgesia.
A rabbit model is described j(H the evaluation of epiduralf,v administered local anaesthetic agents. The technique involves a single injection via the readily identified lumbosacral space in conscious rabbits, with the epidural space being identified by a modified loss-of-resistance technique. The endpoints used to assess pharmacodynamic responses of the rabbit model were (/) sensory loss, (2) loss qf weight-bearing ability, and (3) /faccid paresis. The model was further characterised by investigation of endpoinr responses to changes in injection volume (0.1-0.25 mIlkg) and concentration of administered lignocaine solutions (0.5 to 2%). From these studies, a volume of 0.2 mIlkg was chosen as a standard dose and a subsequent comparison between different agents undertaken. The rank orderfor the onset of action, duration of effect and the observed phannacokinetic pf'(~/ifes after epidural administration (~f 2% lignocaine, 2% lignocaine with adrenaline (/:200,000) or 0.5% bupivacaine solutions are broadly consistent with human cfinical data. These data indicate that the rabbit is a simple (albeit limited) model for the screening evaluation of epiduralfy administered local anaesthetic agents.
Results are presented for room-temperature photoreflectance measurements on four GaAs/AI,Ga,-,As single-quantum-well structures, with x = 0.2 and x = 0.3, and nominal GaAs quantum well widths of 50 A and 100 A.However, the photoreflectance spectra of all the samples display pronounced Franz-Keldysh oscillations in the neighbourhood of both the GaAs and AI,Ga,.,As band edge energies which overlap with, and partially obscure, the photoreflectance features from the quantum well. The spectra are fitted with a model incorporating an approximate lineshape form for the Franz-Keldysh oscillations together with third-derivative functional forms. This has enabled the single-quantum-well transition energies to be determined as well as the dc electric field responsible for the Franz-Keldysh oscillations. In order to identify these transitions, the results are compared with a theoretical model for the single-quantum-well structures, which incorporates parabolic effective masses, and good agreement is obtained.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.