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O NE of the outstanding scientific advances of this decade in the field of electro-optics has been the development of the laser beam. The state of the art has progressed so rapidly that laser devices with pulsed powers of 1 billion watts or with continuous wave (CW) power of 1000 watts are available. By focusing the laser beam, power-densities of 10 ~2 W/cm: of pulsed energy and 10 ~ W / c m 2 of CW energy are available for experimentation. Because we need to know the effects of laser energy on biological tissues from the point of view of public health hazard as well as biomedical application, the following studies were carried out. The principles of laser physics and engineering have been described in earlier publications3-S, 12 Following the demonstration by McGuff ~5 and Minton ~6 tha t pulsed laser radiation destroyed cancer tissue, Rosomoff ~7 applied a similar technique to malignant, hunmn brain neoplasms exposed surgically in the operating room. The patients and animals subjected to pulsed laser radiation in their experiments appeared unharmed. On the other hand, Fine, et a l . , 5 found that a laser pulse of 100 joules (J)++ at 694 nanometer (nm)w

THE independent metabolic activities of some of the obligate intracellular bacteria, such as rickettsiae and chlamydiae1, have been extensively investigated2. Such work has rarely included Rickettsia rickettsi, the agent of Rocky Mountain spotted fever, because of the difficulty of obtaining sufficient material of adequate purity and stability. The only data on respiration of R. rickettsi are those given in a preliminary report by Price3, who carried out his experiments with the collection from several thousand infected yolk sacs and tested the micro-organisms immediately after the final step of purification.

This study of the effect of laser radiation on the brain was made to further our understanding of the interaction of light with living matter and to provide a basis for the possible uses of laser energy in biology and medicine. The physics and engineering aspects of lasers are adequately treated elsewhere (1–3). Light produced by lasers differs from that of conventional sources in that it is strongly coherent and emitted in a narrow, collimated monochromatic beam which can be focused to produce high energy and power densities which are destructive to tissues. The ability to produce sharply circumscribed superficial lesions has been demonstrated (4) and suggests the application as an ablative tool in neurosurgery and neurophysiological research. Using equipment similar to ours, Fine et al. (4, 5) found that 75 per cent of mice died within 24 hours when a single 1-millisecond focused or unfocused laser pulse of about 100 joules struck the brain of the mouse through the intact scalp and skull. In earlier experiments we (G) were able to kill nearly every mouse within a few minutes, using only a single 1-millisecond, 20-joule pulse focused within the brain through the scalp and skull. The lethal mechanism was not explained by the small focal lesions. The occurrence of isolated hemorrhages in the base of the brain away from the site of impact had been thought to be an artifact produced during the removal of the brain from the cranium. If laser light had actually penetrated to that depth in sufficient intensity to produce hemorrhage, a continuous lesion would be expected.

Clinical reports and certain experimental studies have indicated that ethylenediaminetetraacetate and diethylenetriaminepentaacetate are nephrotoxic. Since these compounds have a very high order of physiologic and biochemical specificity, studies were performed in the expectation that insights of a mechanistic nature might be obtained. It was found that the tubular vacuolization produced in the rat by intraperitoneal injection of the chelates daily for 10 days was not accompanied by significant elevation of serum creatinine or urea nitrogen. In addition, there was no impairment in renal excretion of the 14C-labeled chelates or in the ability of slices of the renal cortex to accumulate p-aminohippurate. The results with labeled compounds indicated that the vacuoles were not simple repositories of accumulated chelate, and metal analyses of the kidney indicated that vacuolization could occur independent of changes in the metal spectrum. Kidneys with preexisting or evolving damage due to vitamin D2 or lead intoxication did not appear to be more vulnerable to the action of the chelates. Advice to the effect that renal function should be followed in patients receiving these chelates is consistent with good medical practice, but the label “nephrotoxin” is unjustified. There are similarities between the vacuoles produced by these chelates and those observed with sucrose and mannitol. The driving forces in these morphologic events appear to center on the moiety of these materials that gain entrance to the cell rather than on the number of osmotically active particles in the filtrate or urine volume. Observations and thoughts concerning the origin and fate of the vacuoles are discussed.

The renal cortices of rats were examined for changes in lysosomal enzymes 2 and 24 hr after the administration of 1·0 and 2·5 g of calcium disodium ethylene-diaminetetraacetic acid per kg. The enzymes measured were aryl sulfatase, acid phosphatase, and acid ribonuclease. Though vacuolization occurred at both time intervals with both doses, enzymatic changes were observed only at the 24-hr interval. The changes were manifested as a decrease in the concentration of the three enzymes in the nuclear-weight fractions. It is suggested that part of the chelate enters the cell via pinocytosis, resulting in the formation of a vacuole analogous to the phagosome described by previous investigators. A subsequent combination of the vacuoles with lysosomes is proposed.

There has been considerable interest recently in the use of Doppler shifted signal information as a technique for passive acoustic localization. An investigation of this phenomenon using conventional techniques, however, rapidly becomes complicated by the large number of parameters and geometrical configurations that must be considered. In particular, it is especially difficult to determine the sensitivity of the technique to measurement errors. As an alternative, this paper treats the Doppler profile in terms of its inherent information content and indicates how such information may be utilized to obtain both qualitative and quantitative results. By invoking Fourier transform and sampling techniques, the limitations of Doppler localization are viewed in terms of conventional filter bandwidth and aliasing problems. Furthermore, measurement sensitivity is treated as a generalized S/N ratio enhancement problem. Utilizing the methods of this paper, a more generalized and complete understanding of the Doppler phenomena is achieved when compared to the specialized results of conventional methods.

The time waveforms of the underwater acoustic transients under consideration may be described as noise‐corrupted pulses with varying risetimes and fall times, varying durations, and varying levels. In the past, these transients have been experimentally obtained using omnidirectional hydrophones and recorded on analog magnetic tape. The fact that these transients have been properly recorded is aurally verified before any spectral analysis is commenced. In order to perform the preanalysis detection of the transients at a faster rate and at adverse signal‐to‐noise ratios, an effort was initiated to develop an automatic system for the detection of this particular class of underwater acoustic transient. The development program consisted of three phases. First, the general class of transient was studied in detail to determine recognizable and repeatable attributes fo the signal. Using these attributes, a mask of the transient was constructed. A cross‐correlation detector was developed that used the mask in conjunction with a general prupose computer and a specially designed analog system. Finally, the automated detector was used to locate transients which had previously gone undetected by direct aural means. This paper describes the metamorphosis of the development program. Examples of the detector output are also given. [Work supported by ONR.]