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Damping information is required to analyse heat exchangers for flow-induced vibration. The most important energy dissipation mechanisms in heat exchanger tubes are related to the dynamic interaction between tube and support. In liquids, squeeze-film damping is dominant. Simple experiments were carried out on a two-span tube with one intermediate support to investigate the effects of support parameters, such as: support thickness, diametral clearance, tube eccentricity, tube span length, location of tube support, and nature of dynamic interaction between tube and support. The results show that squeeze-film damping is much larger for lateral-type motion than for the rocking-type motion at the support. Eccentricity was found to be very important. Diametral clearance, support thickness and frequency are also very relevant. The experimental results were compared to existing theories. A semi-empirical expression to formulate squeeze-film damping is proposed.

In this letter we propose a method to represent the decision region in pattern recognition by a set of open parallelpipes within each of which some statistical property is satisfied. The proposed method has the following advantages: 1) it results in a great reduction of classification time, and 2) a priori knowledge can be easily incorporated in the decision rule.

Actinobacillus actinomycetemcomitans is a very uncommon cause of infectious endocarditis. The organism was first described in 1912.1 Thjotta and Sydnes2 reported its isolation in pure culture from a long standing abscess which had developed after tooth extraction. Subsequently this organism was found to be part of the normal flora, and the organism was defined as a slow growing, fastidious gram negative bacillus.3 Carbon dioxide is essential for the growth of A. actinomycetemcomitans. Approximately 50 cases of endocartitis due to A. actinomycetemcomitans have been reported4 since the first case reported in 1964.5 The purpose of this report is to document a case of endocarditis due to A. actinomycetemcomitans and to stress the value of the echocardiogram in the assessment of patients with endocarditis.

A radionuclide angiogram in a patient with Ebstein's anomaly showed a very dilated right atrium with a minimally enlarged right ventricle and a normal sized left ventricle. This study led to the establishment of a definitive diagnosis by means of an echocardiogram. Late close of the tricuspid valve was demon strated. In addition prolapse of the tricuspid and mitral valves was docu mented. A tricuspid valve prolapse has never been reported in this condition.

Analytic results from inviscid hypersonic small-disturbance theory for axisymmetric conical flow are used to generate waverider configurations valid for all values of Kb ^A/^5, where d is the semi vertex angle of the basic cone. By means of the calculus of variations, those configurations are sought that yield the maximum lift-todrag ratio subject to suitable constraints, such as fixed lift, fixed volume, fixed base area, fixed planform area, and so on. The inviscid analysis accounts for wave drag only, but the effects of viscous drag are discussed. For the fixed-lift constraint, two types of optimized configurations are found: types with pointed noses, and types with round noses with sharp leading edges. The results are analytic in nature and particularly suitable for studying the various tradeoffs that are involved in missile design. Comparison of the results with other types of lifting bodies suggests that properly selected cone-derived waveriders are among the best producers of large liftto-drag ratios.

Primary cultures of adult rat hepatocytes (Fischer 344) were used as an in vitro metabolic activation system in immunotoxicological assays. Rat hepatocytes were isolated by a collagenase perfusion technique and cultured for 20 to 24 hr to allow the formation of a monolayer on collagen-coated plastic petri dishes. Spleen cells isolated from (C57BL/6 × C3H)F1 mice were cocultured with the hepatocytes along with the chemicals. Cyclophosphamide (CP) and Aflatoxin B1 (AFB1) were effectively activated in this coculture system and produced a dose-related suppression of the in vitro antibody responses to LPS, DNP-Ficoll, and SRBC in 3 hr. Neither CP (1 m m ) nor AFB1 (10−4 m ) cultured with spleen cells alone produced any effects. Both CP and AFB1 also produced a dose-related suppression of the proliferative responses to LPS, Con A, and PHA. In contrast, up to 100 m m of N-nitrosodimethylamine (DMN) did not suppress any of these assays after a 3-hr incubation in the coculture system. These results indicate that a coculture system can be used to characterize the activity of immunosuppressive chemicals requiring metabolic activation.

A first-pass nuclear angiogram and a multiple-gated acquisition study were obtained in 10 normal physicians and in 10 patients with a 7-to-10 day old transmural myocardial infarction. After the scan the subjects drank 2 oz. of whiskey. After 60 minutes, the multiple-gated acquisition study was repeated. In the normal group the left ventricular ejection fraction was 68% before and 72% after alcohol. The left ventricular end-diastolic volume increased from 89 to 97 ml while the left ventricular end-systolic volume decreased from 29 to 27 ml. The stroke volume rose from 61 to 70 ml/beat (p less than 0.05). The cardiac output increased from 4.0 to 5.0 l/min (p less than 0.05). In the infarction group, the left ventricular ejection fraction was 58% before and 56% after alcohol administration. The left ventricular end-diastolic volume fell from 111 to 96 ml, while the left ventricular end-systolic volume declined from 50 to 44 ml. The stroke volume fell from 61 to 52 ml/beat, while the cardiac output fell from 4.5 to 3.8 l/min. In the left ventricular infarction zones, alcohol produced in 9 of the 10 cardiac patients a decline in the left ventricular regional ejection fraction. In the normal group, alcohol produced no significant changes in the regional ejection fraction. The normal and the postinfarction patients responded differently to alcohol.