Recent developments in vibrating-plate macrosonic transducers.

As is known, the stepped-plate transducer [Ultrasonics 16 (6) (1978) 267] represents an optimum system for the efficient generation of high-intensity sonic and ultrasonic radiation in fluid media. Nevertheless, the design of this transducer may be difficult to adapt to some specific problems. Such is the case of the treatment of large volumes in industrial installations. A solution is the enlargement of the surface of the radiating plate. However, that means to work at high-order vibration modes which implies numerous practical problems. Another case is the application of the stepped-plate transducer for the generation at sonic frequencies where the height of the steps of the radiating plate, which has to be half a wavelength of the radiation, becomes too high and it makes the transducer construction impractical. To face these specific situations a series of new designs in transducer development have been recently carried out. This paper presents the characteristics of two new transducer devices, one for the treatment of large industrial volumes and the other for low-frequency sonic applications. Both devices are based on vibrating-plate radiators and represent a novel approach to practical existing problems.

A macrosonic system for industrial processing

The development of high-power applications of sonic and ultrasonic energy in industrial processing requires a great variety of practical systems with characteristics which are dependent on the effect to be exploited. Nevertheless, the majority of systems are basically constituted of a treatment chamber and one or several transducers coupled to it. Therefore, the feasibility of the application mainly depends on the efficiency of the transducer-chamber system. This paper deals with a macrosonic system which is essentially constituted of a high-power transducer with a double stepped-plate radiator coupled to a chamber of square section. The radiator, which has a rectangular shape, is placed on one face of the chamber in order to drive the inside fluid volume. The stepped profile of the radiator allows a piston-like radiation to be obtained. The radiation from the back face of the radiator is also applied to the chamber by using adequate reflectors. Transducer-chamber systems for sonic and ultrasonic frequencies have been developed with power capacities up to about 5 kW for the treatment of fluid volumes of several cubic meters. The characteristics of these systems are presented in this paper.

[Research on osteoarthritis in Latin America]. / La investigación latinoamericana sobre osteoartritis.

To evaluate the investigative approach towards osteoarthritis of latinamerican physicians, we reviewed the literature. After a manual and electronic search of Latin american medical publications (1980 to 1990) and of 9 Mexican medical journals (1976 to 1990), we reviewed all papers about osteoarthritis. We found 60 such papers (40 from Mexico and 20 from 7 other countries) and analyzed their goals and methods. The common subject was "treatment with nonsteroidal antiinflammatory drugs" (52%), followed by "quality of attention" (25%); "other treatments" (12%) and "epidemiology" (10%). The most common methodologic design was "series of cases" (28%), followed by "editorials" (17%); "controlled clinical trials" (17%), "interview collected data" (17%), "monographies" (10%) and "comparative cohorts" (8%). An innovative and positive aspect is the presence of 25% of studies on "quality of life", "cost-benefits" and "quality of attention". Most studies used insufficiently valid designs and we did not find studies designed to establish causality or to look for the validation of diagnostic tests or prognostic factors, which we propose as methods and fields to study from now on.

Effects of lithium carbonate on leucocytes of hepatic cirrhosis patients.

So as to assess the effects of lithium carbonate on peripheral leucocyte levels of hepatic cirrhosis patients, 10 cirrhotic patients were studied with less than 4,500 leukocytes per cubic ml and without contraindications for lithium salts that were administered for three weeks at a dose of 90 mg daily. At the end of each week total peripheral leukocytes, differential formula, platelet count and serum lithium concentration determinations were made. In the basal stage, total leukocyte average was 3,400 +/- 527 (X +/- DE) and granulocyte average was 2,090 +/- 341. After the first week of lithium treatment a significant increase was observed in total leukocyte and granulocyte levels whose averages at the end of the third week of treatment were 4,800 +/- 1,052 (p less than 0.01) and 3,694 +/- 1,003 (p less than 0.001) respectively. There was no correlation between the magnitude of leukocyte increase and serum lithium levels obtained that ranged from 0.28 and 1.32 mEq/l. Three patients showed transient gross tremor and two suffered hepatic coma. We can conclude that lithium carbonate increases peripheral leucocytes at the expense of neutrophilia in patients with secondary granulocytopenia and hypersplenism resulting in liver cirrhosis.

[Protocol drafting of laparotomy in the diagnosis of the cause of fever of unknown origin]. / Laparotomía protocolizada en el diagnóstico de las causas de fiebre de origen oscuro.

Eighteen patients with fever of unknown origin in whom other diagnostic procedures had failed, underwent exploratory laparotomy with splenectomy, hepatic biopsies and biopsies of lymph nodes, muscle and bone, while bile, urine and intestinal content were cultured. In all patients, inspection and palpation of abdominal cavity doesn't give any diagnostic orientation. With histologic examination and cultures, precise diagnosis was made in 13 cases (72 per cent). Predominant diagnosis was Hodgkin's disease. One patient died with complications of surgery.