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A closed-loop control scheme for the control of intra-aortic balloon pumping has been developed and tested in dog experiments. A performance index reflecting the general objectives of balloon-assist pumping is developed and a modified steepest ascent control algorithm is utilized for the selection of a proper operating point for the balloon during its pumping cycle. This paper attempts to indicate the feasibility of closed-loop control of balloon pumping, and particularly its flexibility in achieving both diastolic augmentation of mean aortic pressure and control of the level of end-diastolic pressure (EDP)-an important factor in reducing heart work.

The purpose of this study was to determine the frequency content of intravascular pressures and their time derivatives. Pressures, recorded using catheter-tip manometers in patients undergoing diagnostic cardiac catheterization, were amplified, filtered (100 Hz) to minimize aliasing errors, and then converted to digital format at 200 samples/sec. After examination of the waveform to exclude obvious artefact, it was analyzed using a Fourier transform and then resynthesized using a decreasing number of harmonics. Peak dp/dt of both the original and resynthesized waveforms was computed until marked differences were observed.

A standardized readily reproducible experimental model has been developed to assess the relative importance of the chemical and physical configuration of sutures as determinants of early infection in contaminated wounds. The chemical structure of the suture appeared to be the most important factor in the development of surgical infection. The incidence of infection in contaminated tissues containing either polypropylene sutures or nylon sutures was lower than the infection rate of tissues subjected to any other nonabsorbable suture. Among the absorbable sutures, polyglycolic acid (PGA) sutures evoked the least inflammatory response. The infection rate of contaminated tissues containing the PGA sutures was not significantly different from the incidence of infection of tissues subjected to the least reactive nonabsorbable sutures. The physical configuration of the suture played a relatively unimportant role in the development of early infection. The infection rate of contaminated tissues containing monofilament nonabsorbable sutures did not differ significantly from the incidence of infection of tissues subjected to multifilament sutures made from the same material. Coating the multifilament suture with either silicone, wax, or Teflon did not alter the incidence of early infection in the contaminated tissue. Finally, the presence of even the least reactive suture in contaminated subdermal tissue potentiated the development of infection.

A direct-reading photoelectric reflectance meter, designed to measure true blood glucose by the glucose oxidase technic on a single drop of capillary blood was evaluated using blood samples from 149 newborn infants. The results showed excellent statistical correlation with those obtained by standard quantitative colorimetric technic. The reflectance meter has the advantages of being portable, accurate, rapid and simple to operate. During three years of routine use by the Neonatal Intensive Care Unit (5–10 determinations per day), this method has consistently demonstrated its reliability; 30–40 physicians used the machine in this period.

It has been shown that the quality of blood vessel images in cerebral angiograms can be improved either by employing radiographic magnification in conjunction with fast screens or by using slower screens and fast film without magnification. It is not known which of these methods results in better images, and under what conditions magnification used with slow screens might result in further improvement. By means of a computer, the dependence of image contrast and sharpness on magnification with various screen-film systems has been studied. One result indicates that, for blood vessel diameters less than 100 mu m and focal spot sizes of 0.3 mm or larger, the use of slow screens without magnification results in better images than those obtained with fast screens and magnification. For blood vessels larger than 300 mu m in diameter and focal spot sizes of 0.3 mm or less, fast screens with magnification can give better images than those obtained using slow screens without magnification.

A digital computer was used to generate moving patterns which were projected onto a screen to serve as an optokinetic stimulus. Patterns, speed or direction of the stimulus can be changed almost instantaneously. On-line control of the computer-generated stimulus by the eye-position signal makes it possible to produce selective stimulation of particular regions of the retina.

An apparatus, called an embolator, was designed, and its details together with tests conducted to demonstrate its efficacy are presented here. The embolator consists of two units, a timer and a fractionator, and operates by introducing air bubbles in a controlled fashion into tubing collecting systemic or hypophysial portal blood. The air bubbles separate the blood into multiple, discrete segments. Experiments under both in vitro and in vivo conditions demonstrate that the embolator can be used to prevent mixing between aliquots during a prolonged, continuous collection of blood. (Endocrinology 94: 864, 1974)

A constitutive equation for parallel-fibered elastic tissue is developed in the form of a non-linear hereditary integral. Material constants were determined from relaxation tests and these were used in the constitutive equation to predict results of constant strain rate tests, hysteresis loops and sinusoidal tests. Test speciments were obtained from the ligamentum nuchae of gross bovine specimens.

Coherent optical signal processing techniques applied to the screening of exfoliated cytologic cervical samples were evaluated. The two-dimensional Fourier spectrum of some 80 isolated cells was obtained from high resolution cell photographs and recorded. Quantitative spectrum data were collected on a training set consisting of 15 categorized malignant cells taken from slides diagnosed as malignant and 10 categorized normal cells taken from slides diagnosed as normal. A variety of transform parameters were measured and certain combinations of them were found which separated completely the normal from malignant cells. Certain parameters were shown to be functionally related to the cell diameter, nuclear diameter and nuclear density. Other parameters were found which appear to be related to other cell features such as clumping of nuclear deoxyribonucleic acid. When they were used in combination with the previous parameters, they greatly enhanced the discriminatory capabilities. Computer model studies formed the basis for our experimental design and parameter selection and have validated much of our experimental results. Although the sample size to date is admittedly small, our results have been very encouraging. The purpose of this paper is to report on the initial results obtained in a study to determine the effectiveness of coherent optical processing techniques when applied to the screening of’ exfoliated cervical cytologic samples for malignancy. These techniques rely on the diffraction properties of coherent light which are closely related to scattering techniques used by the groups at the Lawrence Livermore Laboratories and the Max-Planck Institute for cytologic screening and sample enrichment. The specific approach used in this investigation is concerned with the relationship the cell image has to its two-dimensional Fourier transform, which is generated optically by a well known method described below. The success of the screening approach depends upon the ability to measure and discriminate between the Fourier spectrum of malignant and Fourier spectrum of normal exfoliated cervical cells. In most instances the measured discriminating parameters can be functionally related to well known cytologic characteristics which are conventionally used to discriminate between malignant and normal exfoliated cervical cells.

The excess thymidine-colcemid synchronization method for mouse leukemia L5178Y was automated by deleting the removal of excess thymidine. The synchronizer adds thymidine and colcemid at predetermined times and makes the population accumulated at mitosis available at a designated time. The apparatus is inexpensive to build, easily operated and applicable to large volumes of a static suspension culture.

Following a review of the basic theories of light-diffusion, the authors endeavored to apply this technique in the determination of human platelet volume. Applying Zimm’s theory they succeeded in dete

Design aids to permit the rapid calculation of complete magnet and coil systems are presented.

Purpose: The features of the interatrial septum and its motion were studied by ultrasonocardiotomography and echocardiography. Based on the results of the above study, the detection of the ostium secundum defect of the interatrial septum was examined in the transverse and sagittal section of the ultrasonocardiotomogram. The possibility of detecting the defect by the conventional echocardiogram was also studied. Method and Materials: Ultrasonograph Model SSD-10 manufactured by Japan Radiation & Medical Electronics with a unit for synchronization with the electrocardiogram was used to record ultrasonocardiotomograms (Fig. 1). To obtain an echocardiogram in a certain direction on the tomogram, Model SSD-5 from the same manufacturer was used, connected to Model SSD-10. The frequency of ultrasound used was 2.25 MHz and the rate of the pulse repetition was 937.5 Hz. The transducers used made of barium titanate were round, 30 mm and 50 mm in diameter and concave with a radius of curvature of 20 cm. The azimuth =and distance resolving power of the both transducers was 3 mm at the distance of 20 cm. The patients were examined in the supine position. The transducer was operated in a vinyl bag on the chest wall filled with bubbleless water. The distance of the transducer from the chest wall was set at over 10 cm so that the ultrasound beam was focused nearly at the midportion of the heart and the tomogram of the heart was not disturbed by the second reflection from the chest wall. Sector scanning was mainly used and compound scanning only in cases of remarkably enlarged heart. The angle of the sector scanning was 50 in degrees and the time in one sector scanning was 0.4 sec. In order to obtain a satisfactory tomogram of the heart at a desired phase in a cardiac cycle, the synchronizing unit introduced by Kikuchi and Tanaka was adopted. The R wave of the electrocardiogram was used as a trigger and by a delaying circuit the cathode ray tube was brightened in a scheduled phase of each cardiac cycle. Setting the unblanking time of the cathode ray tube from 25 msec to 50 msec, a tomogram was completed during about twenty successive heart beats (Fig. 2). Features of the echo of the interatrial septum were examined in 7 cases of primary myocardial disease, 7 cases of ventricular septal defect, 1 case of A-V block, 6 healthy subjects and 21 cases of atrial septal defect.

An improved version of a pneumatic-tube system built by Amsco, Inc. (Erie, Pa.) and its subsidiary ATC (San Rafael, Calif.) for blood-sample transportation incorporated two innovations: The sample carrier travels at a lower speed than in the previous conventional systems, and it is decelerated gradually on arrival. This tube system was pilot tested for efficiency by running blood-filled Vacutainer tubes through the 63.6-rn (210-feet) tube 10 times, a total running distance of 636 m. Serum lactate dehydrogenase and acid phosphatase activities, and potassium, all sensitive chemical indicators of erythrocyte membrane damage, were measured in blood specimens in partially or totally filled Vacutainer tubes and the results compared with those obtained from controls. No alterations were found in serum test results after 10 or 20 repetitive cycles in the totally filled tubes, but significant changes did occur in partially filled tubes after 20 cycles. If the limitations are observed, this system appears to be suitable for blood-specimen transportation.

1. For steam sterilization of surgical instruments at 120°, we recommend an inside diameter of 160 mm and a height of 220 mm for operation in conjunction with a pressure not less than 1.2 kg/cm2 above atmospheric.

A semi-empirical graphical method to predict the performance of oxygenators using straight and parallel capillary tubes has been developed from a mathematical model and an extensive amount ofin vitro data obtained under precisely controlled conditions. This graphical technique predicts the performance of a given oxygenator for exchange of both oxygen and carbon dioxide for a wide range of blood flows and input-blood conditions, and greatly simplifies the analysis of data taken in evaluation procedures where precise control of test conditions is not achieved. Performance predictions for capillary-tube oxygenators obtained by this method are supported by preliminaryin vivo data, as well as by extensivein vitro data. The calculation also provides a simple means of designing or selecting a capillary oxygenator for application under known operating conditions. This method has indicated that, for the same blood flow rate, oxygenators staged in series are significantly more effective than when connected in parallel. This prediction has also been verified in the laboratory.

A procedure suitable for the mass screening of children for an undue body burden of lead was tested on 170 clinic patients. Capillary finger-prick blood, collected on filter paper, was analyzed for lead with an atomic absorption spectrophotometer with the Delves cup attachment. This method of analysis had first been judged to be accurate after a laboratory evaluation in which results were compared with those obtained by a dithizone procedure. In the present study, both capillary and venous bloods were obtained from the patients. Venous bloods were also analyzed by the filter paper disk method and by an atomic absorption spectrophotometric procedure requiring a 5-ml sample. Results show that the screening method described here will reliably identify those children with a significantly supranormal blood lead. Both sample collection and laboratory analysis are easier.

SUMMARY Epidermal thickness has been accurately measured on 214 samples of skin from 188 volunteers. Variations with the individual, body site, sex and age are described and discussed. An original technique of measurement has been developed which has several advantages over conventional methods. In particular, quick straight-forward measurements are possible on volunteer skin rather than post mortem material, and the method eliminates errors arising from the skin's elasticity. These improvements in accuracy have confirmed that much information in the literature on epidermal thickness, is misleading as the results are based on inaccurate techniques of measurement.

Most data indicate that cardiac output is normally controlled by the systemic circulation rather than by the heart. This manuscript extends that concept by analyzing the systemic circulation with a mathematical model comprised of two dissimilar blood flow channels. The concept and the model are not new and have, in fact, a strong anatomical and historical basis. However, re-examination using a quantitative, computerized analysis scaled to human dimensions is made in the face of new experimental data.