Degrees Intervals Research Articles

Clinical Evaluation of Stenosis of the Carotid Bifurcation With Magnetic Resonance Angiographic Techniques

We evaluated the images of 60 carotid artery bifurcations in 31 patients suspected to have carotid artery disease who underwent invasive carotid angiography and combined two-dimensional, phase-sensitive and a gradient-echo magnetic resonance angiography. The phase scans consisted of seven serial projections that were obtained at 20 degrees intervals (11.0 minutes) around the carotid bifurcation; the gradient-echo (GRASS) scans were composed of 11 axial images (2.4 minutes) acquired through the bifurcation. The two magnetic resonance angiographic techniques yielded complementary pieces of information and were used together to compare magnetic resonance angiography with invasive angiography. Comparison of magnetic resonance and invasive angiograms of the 60 carotid arteries shows that the sensitivity (86%) and specificity (92%) of the magnetic resonance angiographic techniques we used to diagnose clinically significant carotid stenosis approach but do not reach those of invasive angiography.

Absolute determination of electrolytic conductivity for primary standard KCl solutions from 0 to 50�C

An absolute determination of aqueous electrolytic conductivity has been made for primary standards 0.01D and 0.1D (demal) potassium chloride solutions over the temperature range of 0 to 50°C in 5 degree intervals. A cell with a removable center section of accurately known length and area was used for the measurements. Values were adjusted to be in conformity with the ITS-90 temperature scale. The overall uncertainty over the entire temperature range is estimated to be 0.03%. Values at 25°C for 0.01D and 0.1D KCl solutions are 0.0014086 and 0.012852 S-cm−1, respectively.

Proposed New Electrolytic Conductivity Primary Standards for KCl Solutions.

An absolute determination of aqueous electrolytic conductivity has been made for 0.01 molal (m) and 0.1 m potassium cliloride solutions, over the temperature range of 0 to 50 °C in 5 degree intervals. A cell with a removable center section of accurately known length and area was used for the measurements. Values were adjusted to be in conformity with the ITS-90 temperature scale. The overall uncertainty over the entire temperature range is estimated to be 0.03%. Values at 25 °C for 0.01 and 0.1 m are 0.00140823 and 0.0128246 S/cm, respectively. It is proposed that these values be adopted as primary standards for aqueous electrolytic conductivity, replacing the demal scale.

A three-phase PWM strategy using a stepped reference waveform (invertor drives)

The theoretical derivation of a carrier-based three phase pulse-width-modulated (PWM) technique for invertor drives using a stepped reference waveform is presented. The reference waveform is divided into 30 degrees intervals, with each interval being controlled individually to control the magnitude of the fundamental harmonic. This process contrasts with the commonly used approach of amplitude modulating the entire reference waveform to control the fundamental harmonic. The resultant PWM technique is shown to be similar to a square-wave strategy but with a lower current distortion being obtained at high fundamental magnitudes and high carrier frequencies. The practical realization of the PWM technique is described using performance criteria such as minimum pulse widths, peak carrier frequencies, and the current distortion.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Multisensory Integration in the Human Vestibular Velocity Storage Mechanism?

To test the hypothesis that auditory inputs can interact with the optokinetically or vestibularly-charged human VSM, we examined the effects of sound on rotational nystagmus and HOKAN. Subjects were rotated at 60 degrees/s, in either clockwise (CW) or counterclockwise (CCV) direction, for a total of 3 min. After 1 min of constant rotation, the optokinetic surround (7 ft dia., 2 degrees stripes at 18 degrees intervals) was illuminated for 60 s and the ensuing HOKAN was recorded for 60 s (standard DCEOG). The chair was stopped 60 s later and the post-rotatory nystagmus (PRN) was recorded. The acoustic stimulus (4/s, 10 ms pulses) was presented to the subject by a loudspeaker in 4 randomized test conditions: (1) fixed to the surround-on during OKN, off during OKAN (2) fixed to the surround-off during OKN, on during OKAN (3) rotating with the subject-on during OKN, off during OKAN (4) rotating with the subject-off during OKN, on during OKAN. In all conditions, the sound was on during per- and post-rotatory nystagmus. Each test was performed on a different day and consisted of 4 randomized control and test trials (CW and CCW). Under none of the above conditions was the rotatory or optokinetic decay affected by the presence of stationary or rotating sound. This absence of alteration of PRN by sound cues contradicts that reported by Kollar et al. (1988). Our evidence that neither HOKAN nor post rotatory nystagmus decay is affected by sound cues supports the conclusion that, under our conditions, multisensory interaction does not occur in the human VSM.

A Comparison of Four Computerized Methods for Measuring Vertebral Rotation

The ability to measure vertebral rotation is particularly important in the assessment and treatment of scoliosis. We determined the accuracy and precision of four methods that may be used with routine anteroposterior (AP) spine radiographs. Two vertebrae were radiographed at 0 degrees and at 5 degrees intervals to 20 degrees and at 30 degrees, to the right and left. The radiographs were distributed to three members of the staff who marked the 14 points required for calculating rotation with the four methods. The points were digitized, and rotation calculated by computer. The results showed no significant difference in the calculated rotation of the two vertebrae, or between the results of the three markers. Stokes's method was significantly the least accurate. The other three methods were not significantly different but Bunnell's method appeared to give more consistent results.

Cerebellar neuronal activity related to whole-arm reaching movements in the monkey.

1. Three monkeys were trained to make whole-arm reaching movements from a common central starting position toward eight radially arranged targets disposed at 45 degrees intervals. A sample of 312 cerebellar neurons with proximal-arm receptive fields or discharge related to shoulder or elbow movements was studied in the task. The sample included 69 Purkinje cells, 115 unidentified cortical cells, 65 interpositus neurons, and 63 dentate units. 2. The reaching task was divided into three movement-related epochs: a reaction time, a movement time, and holding over the target. All neurons demonstrated significant changes in discharge during one or more of these three epochs. Almost all of the cells (95%) showed a significant change in activity during the movement, whereas 68-69% of the cells showed significant changes from premovement activity during the reaction time and holding periods. 3. During the combined reaction time-movement period, 231/312 cells were strongly active in the task. Of these, 151 cells (65.4%) demonstrated unimodal directional responses. Sixty-three had a reciprocal relation to movement direction, whereas 88 showed only graded increases or decreases in activity. A further 37 cells (16.0%) were nondirectional, with statistically uniform changes in discharge in all eight directions. The remaining 43 cells (18.6%) showed significant differences in activity for different directions of movement, but their response patterns were not readily classifiable. 4. The proportion of directional versus nondirectional cells was consistent across the four cell populations. However, graded response patterns were more common and reciprocal responses less common among Purkinje and dentate neurons than among unidentified cortical cells and interpositus neurons. 5. The distribution of preferred directions of the population of cerebellar neurons covered all possible movement directions away from the common central starting position in the horizontal plane. When the preferred direction of each cell in the sample population was aligned, the mean direction-related activity of the cerebellar population formed a bell-shaped tuning curve for the activity recorded during both the reaction time and the movement, as well as during the time the arm maintained a fixed posture over the targets. A vector representation also showed that the overall activity of the cerebellar population during normal reaching arm movements generated a signal that varied with movement direction. 6. These results demonstrate that the cerebellum generates a signal that varies with the direction of movement of the proximal arm during normal aimed reaching movements and is consistent with a role in the control of the activity of muscles or muscle groups generating these movements.

Vector electron paramagnetic resonance spectroscopy with first and second harmonic displays of ferrihemoglobin

Superimposed plots of electron paramagnetic resonance spectra with the first and second harmonic displays of ferrihemoglobin at pH 9.1 and 90 K were measured at 20 degree intervals of phase angle using a phase-sensitive detector. The high spin signal in the g = 6 region was observed in both displays, and a small splitting of the signal was found in the calculated amplitude spectrum of the second harmonic display, with g values of 5.95 and 6.05. Low spin signals were observed at g = 2.55, 2.25 and 1.82 in both harmonic displays. A signal in the g = 2.05 region was observed only in the second harmonic display. The signal is probably associated with the low spin spectrum; however, its origin is obscure.

Tomographic reconstruction from energy-filtered images of thick biological sections.

Energy filtration makes it possible to image an approximately 0.5 microm biological section at 80 kV in the electron microscope. Based on spectra taken at different tilt angles, we chose the most probable energy loss, deltaEp +/- 10eV for each tilt angle, as the imaging energy window. A complete tilt series from +60 degrees to -60 degrees at 2.5 degree intervals was collected on the Zeiss EM902 and used in a tomographic reconstruction of transcriptionally active chromatin in the Balbiani ring of Chironomus tentans.

Response of a Brachytherapy Model Using 125 I in a Murine Tumor System

The effects of low-dose-rate irradiation (brachytherapy) were investigated in vivo using a murine mammary adenocarcinoma (MTG-B) growing in the flank of C3H mice. For local tumor irradiations, a noninvasive cap was devised to cover the tumor and house three 125I seeds (average apparent activity 5.2 mCi each) located at 120 degree intervals around the circumference of the hemispherical cap (13 mm i.d.). Mice were secured during treatment in a tube allowing limited mobility while restricting access to the seeds. Tumors were exposed to a series of dose rates ranging from 14-40 cGy/h, and the total dose over the treatment interval (48 or 72 h) ranged from 830 to 2378 cGy. A total of nine experiments were conducted using the caps over a 10-week interval. In each experiment three groups (irradiated tumors, sham controls, and untreated controls) were analyzed, each containing 8-15 mice (N = 34, untreated control; N = 46, sham control; N = 91, brachytherapy irradiation). The brachytherapy results are compared to the effects of external beam irradiation in the same tumor system. A linear relationship was observed between the total radiation dose and doubling volume growth delay (GDDV) or treatment volume growth delay (GDTV) for the brachytherapy and external beam irradiation. The slopes of the dose-response curves are steeper for the acute dose (517 cGy/min) external beam irradiation (0.0072 day/cGy, GDDV; 0.00695 day/cGy, GDTV) than for the brachytherapy (0.0050 day/cGy, GDDV; 0.0057 day/cGy, GDTV) using both GDTV and GDDV end points. Comparison of the tumor volume regrowth slopes indicates that the tumor bed effect is larger for external beam irradiation than for brachytherapy, suggesting that the tumor bed effect may be dose-rate dependent.

Specificity of joint angle in isometric training.

Six healthy women (21.8 +/- 0.4 y) did isometric strength training of the left plantarflexors at an ankle joint angle of 90 degrees. Training sessions, done 3 times per week for 6 weeks, consisted of 2 sets of ten 5 s maximal voluntary contractions. Prior to and following the training, and in random order, voluntary and evoked isometric contraction strength was measured at the training angle and at additional angles: 5 degrees, 10 degrees, 15 degrees, and 20 degrees intervals in the plantarflexion and dorsiflexion directions. Evoked contraction strength was measured as the peak torque of maximal twitch contractions of triceps surae. Training increased voluntary strength at the training angle and the two adjacent angles only (p less than 0.05). Time to peak twitch torque was not affected by training. Twitch half relaxation time increased after training (p = 0.013), but the increase was not specific to the training angle. There was a small (1.1%, p less than 0.05) increase in calf circumference after training. Evoked twitch torque did not increase significantly at any joint angle. It was therefore concluded that a neural mechanism is responsible for the specificity of joint angle observed in isometric training.

Thermal enhancement of low dose rate irradiation in a murine tumour system

The effects of localized hyperthermia (HT) in combination with low dose rate irradiation (brachytherapy) have been investigated in vivo using a murine mammary adenocarcinoma. Flank tumours were grown to 0.45-0.70 cm3 in volume, at which time their treatment course was initiated. Tumours were locally heated in a water bath for 15 min at either 44 or 45 degrees C. For tumour irradiations a non-invasive cap was devised to permanently house three iodine-125 sealed sources located at 120 degree intervals around the circumference of the hemispherical cap. During treatment, mice were secured in a modified syringe tube allowing mobility while restricting access to the cap which was placed over the tumour. Calculated dose rates ranged from 15 to 40 cGy/h. Brachytherapy (BT) was delivered for 48 or 72 h to obtain a dose range of 830-2378 cGy. Mice were randomized into one of 10 treatment protocols: BT alone, HT-BT, BT-HT, HT-BT-HT, 1/2BT-HT-1/2BT, four control groups of HT alone and a sham treatment group. Normalized tumour doubling volume growth delays (GDDv) were used to calculate the thermal enhancement ratios (TER). In the 44 degrees C experiments, HT before BT (TER = 1.33 +/- 0.071) was more efficacious than HT after BT (TER = 1.07 +/- 0.042). Two HT treatments, one given before and one after BT (TER = 1.38 +/- 0.152), were not different from a single HT treatment given before BT. However, a single HT treatment given in the middle of an interrupted course of BT resulted in the greatest thermal enhancement (TER = 1.64 +/- 0.072) compared to any other treatment sequence. These data suggest that potentiation of low dose rate irradiation by a single heat treatment may be maximized if the HT is given either in the middle of, or simultaneously with, the BT.

A 17-tesla magnet with multiple radial access ports

A description is given of the design and construction of a magnet generating over 17 T with multiple radial access ports to allow water cooling. There are seven ports, 19-mm high, at 30 degrees intervals around half the circumference of the magnet midplane. The magnet consists of a split pair of coils of 330 mm (outer diameter) and 100-mm length spaced 23 mm apart. Together they consume approximately 8.5 MW. They are Bitter coils with cooling provided by water flowing outward through shallow passages etched in the plates. Heat fluxes are as high as 700 W/cm/sup 2/. In an unusual overall configuration, hydraulics, coil clamping, support, and electrical connections were all made as unobtrusive as possible.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Three-dimensional reconstruction of a human metaphase chromosome from electron micrographs

A complete human metaphase chromosome has been reconstructed from a series of electron microscopical projections obtained by tilting the specimen stage at 3 degree intervals from -60 to +60 degrees. The reconstructed structure is about 3.0 microns long, 1.6 micron wide, and 0.8 micron thick. The mass distribution was fairly homogeneous within the chromatids and neither a hollow nor a dense core was observed. The distribution and course of fibers observed are most consistent with a looping model of chromosome structure.

The analysing powers of medium-mass nuclei for 3 MeV neutrons

The analysing powers of Cd, Sn, Sb, Te and I for the elastic scattering of 3 MeV neutrons have been measured at 7 degrees intervals from 20 degrees to 167 degrees . The differential cross sections have also been measured. Scattering samples of natural isotopic abundance were used. The measured values are compared with the results of optical model and Hauser-Feshbach calculations based on parameters proposed recently for low-energy neutron scattering in this mass region. Optical model parameters which give a best fit to the data are also found and discussed. It is found that the spin-orbit potential in this region is less deep and less diffuse than that usually employed.

Chain Flail Used to Clean Encrusted Water Mains

This article describes a chain flail that was invented for cleaning an 8‐inch water main. The flail consists of a center shaft drilled to fit on the root cutter driver of a high‐velocity‐jet sewer cleaner. Three steel ball bearings, 1 3/4 inch (35 mm) in diameter, are welded to a 3/8 inch × 1 3/8 inch (0.38 mm × 35 mm) chain at 120 degree intervals around the shaft. The diameter of the flail arc is 8.5 inches (220 mm). The root cutter drives the flail at speeds of 600–800 rpm. The flail is inserted into the main through a 2‐foot (0.6 m) cut‐out section. The flail travels forward at 20–25 fpm (0.10–0.13 m/s), and is withdrawn at about 10 fpm (0.05 m/s). Suggestions for use of the flail are presented.

Carotid bifurcation atherosclerosis. Quantitative correlation of plaque localization with flow velocity profiles and wall shear stress: Zarins CK, Giddens DP, Bharadvaj BK, et al. Circ Res 1983;53:502–514

The distribution of nonstenosing, asymptomatic intimal plaques in 12 adult human carotid bifurcations obtained at autopsy was compared with the distribution of flow streamline patterns, flow velocity profiles, and shear stresses in corresponding scale models. The postmortem specimens were fixed while distended to restore normal in vivo length, diameter, and configuration. Angiograms were used to measure branch angles and diameters, and transverse histological sections were studied at five standard sampling levels. Intimal thickness was determined at 15 degrees intervals around the circumference of the vessel sections from contour tracings of images projected onto a digitizing plate. In the models, laser-Doppler anemometry was used to determine flow velocity profiles and shear stresses at levels corresponding to the standard specimen sampling sites under conditions of steady flow at Reynolds numbers of 400, 800, and 1200, and flow patterns were visualized by hydrogen bubble and dye-washout techniques. Inti...

Butylcyanoacrylate adhesives in microvascular surgery: an experimental pilot study.

An investigation was undertaken to examine the effects of the butylcyanoacrylate adhesives (Histoacryl) on vascular tissue. Using a rat femoral artery model, 18 vessels were prepared. End-to-end anastomoses were completed using three stay sutures of 10-0 nylon inserted at 120 degrees intervals around the vessels, followed by direct application of Histoacryl glue. Results showed a patency rate of 73 percent, the vessels being inspected between two and 14 weeks after anastomosis. Histological examination of the vessels showed an early marked foreign body granulomatous response with giant cell formation, and later extreme thinning of the vessel wall, splitting of the elastic lamina, and calcification of the media. It was concluded that the histologic results of butylcyanoacrylate tissue adhesives on the vessel wall preclude their use on human subjects.

The Motion of Interplanetary Dust Particles

AbstractRadial velocity measurements on the solar MgI 5183.618Å Fraunhofer absorption line in the Zodiacal Light spectrum have been made with a microprocessor-controlled servo-stabilised Fabry-Perot interferometer. Observations were made at 5 and 10 degree intervals in the ecliptic plane between morning and evening elongations of 25 degrees. These new data are of much greater precision and coverage than any previously obtained. Obtained over a two year period, the observations show a consistent evening/morning asymmetry in the radial velocity curve with the Gegenschein receding from the Earth at 4 Km/sec. These data do not support the hypothesis that the majority of interplanetary dust grains are in hyperbolic trajectories.

Computerized quantitative analysis of left ventricular wall motion by two-dimensional echocardiography.

Quantitative detection of left ventricular segmental wall motion abnormalities by any modality depends on the reference system used because of the dynamic geometry of contraction and cardiac motion within the thorax. To assess the feasibility and accuracy of quantitative analysis of left ventricular wall motion by two-dimensional echocardiography, we studied 61 subjects with the use of 44 different reference methods in each of three echocardiographic views: the parasternal short-axis view at the levels of the mitral valve and of the papillary muscles and an apical four-chamber view. The three major groups of reference systems used were those with a fixed external reference, a floating reference correcting for translation, and systems correcting for both translation and rotation. In the first part of this study the end-diastolic and end-systolic outlines of 20 normal subjects were stored in a computer and composite data of these 20 subjects were plotted to obtain a 95% confidence interval for measured normal fractional change for each reference method. In the second part of the project an additional prospective group of 10 normal subjects and a group of 31 "abnormal" patients had their left ventricular wall motion analyzed by similar methods and the results were compared with all the confidence intervals. One reference method was selected for each two-dimensional echocardiographic view based on the highest sensitivity and specificity found by statistical analysis; a floating-reference system including translation was found to be optimal for the apical four-chamber and parasternal short-axis views at the level of the mitral valve and a fixed external reference system was optimal for the short-axis view at the papillary level. The percent fractional shortening of radial dimensions (radial methods) and the percent fractional change in area measurements (area methods) during the cardiac cycle were also calculated at 5, 10, 20, 30 and 45 degree intervals around the outline perimeter for each subject according to each of the 44 different methods. Area methods yielded the same specificity and sensitivity as radial dimension analysis methods at 5 to 45 degree intervals. Ten normal subjects underwent repeat echocardiography within 2 days of their first study to examine day-to-day variation. Average change in mean contraction from day to day was 7% to 9% for radial methods and 9% to 13% for area methods. In conclusion, we present a computerized system for unbiased selection of optimal methods of analysis of left ventricular wall motion by two-dimensional echocardiography.(ABSTRACT TRUNCATED AT 400 WORDS)