Laser-induced ultrasound transmitters for large-volume ultrasound tomography.

We present a protocol for the design, fabrication and characterisation of laser-induced ultrasound transmitters with a specific, user-defined frequency response for the purpose of ultrasound tomography of large-volume biomedical samples. Using an analytic solution to the photoacoustic equation and measurements of the optical and acoustic properties of the materials used in the transmitters, we arrive at a required mixture of carbon black and polydimethylsiloxane to achieve the desired frequency response. After an in-depth explanation of the fabrication and characterisation approaches we show the performance of the fabricated transmitter, which has a centre frequency of 0.9 MHz, 200% bandwidth and 45.8 ∘ opening angle, multi-kPa pressures over a large depth range in water.

A study of retentive filler and its use in dentistry.

OBJECTIVE: The purpose of this study was to develop a fine compound inorganic filler with special surface microstructure (called retentive filler or RF) and to investigate its use in composite resin and synthetic resin teeth. METHODS: Barium silicate glass and fine silicon dioxide or barium silicate glass were mixed and sintered, then dispersed and classified by sedimentation. The surface microstructure and the particle size distribution of retentive filler were surveyed, and the mechanical properties of the composite resin and the resin tooth material reinforced with RF were tested. RESULTS: Scanning electron microscopy showed that the surface of RF particles is distinguished for its retentive contour microstructure. The particle size of RF is smaller than 3 microns. The mechanical properties of composite resin reinforced with RF are better than that of composites containing normal fillers, and the wear resistance of the resin tooth material containing RF is better than that of normal synthetic resin. CONCLUSIONS: The RF can be successfully prepared by the technological process in this study. Because of the special surface microstructure, RF has a good bonding to the resin matrix. The testing results suggest that it is feasible to improve the mechanical properties, especially the wear resistance of the composite resin and resin teeth, by using retentive filler.

Parasympathetic ganglia: naloxone antagonizes inhibition by leucine-enkephalin and GABA.

Synaptic transmission in parasympathetic ganglia of the cat urinary bladder was depressed by low doses (0.1-10 micrograms i.a.) of Leu- or Met-enkephalin but only by larger doses (10 micrograms-1 mg i.a.) of morphine. Naloxone blocked the depressant effects of the opiates as well as the depression produced by GABA, but did not block the depressant effects of norepinephrine. Intracellular recording revealed that Leu-enkephalin reduced EPSP-amplitude and lowered the probability of synaptically evoked firing without altering postsynaptic membrane potential or resistance. These findings suggest that enkephalinergic inhibition in bladder ganglia is mediated at least in part by a presynaptic site of action on delta opiate receptors.

Cromolyn sodium nasal solution in the prophylactic treatment of pollen-induced seasonal allergic rhinitis.

A large-scale multicenter investigation was undertaken in 3 cities with comparable pollen seasons and atmospheric pollen concentrations in order to obtain more definite information about the safety and efficacy of cromolyn sodium in the treatment of pollen-induced seasonal rhinitis. The 9-wk double-blind study was conducted in 104 patiets in Pittsburgh, Pa., Cleveland, Ohio, and Louisville, Ky., during the 1975 ragweed season. It indicated that a nebulized 4% aqueous solution of cromolyn sodium is effective in reducing sneezing, rhinorrhea, nasal congestion, and ocular irritation in ragweed hay fever patients. The efficacy of the drug was notable despite the fact that patients used an average of 52 mg instead of the recommended 62.4 mg daily. Cromolyn sodium did not appear to have a significant effect on transseasonal antiragweed IgE (IgEAR) levels. Patients acceptance of the cromolyn nasal solution was good, and there were no significant adverse reactions. The side effects, which were distributed equally between the drug and placebo groups, were mild and of limited duration.