Showing papers by "University of Illinois at Chicago published in 1977"

Free convection about a vertical flat plate embedded in a porous medium with application to heat transfer from a dike

Abstract: An analysis is made for steady free convection about a vertical flat plate embedded in a saturated porous medium at high Rayleigh numbers. Within the framework of boundary layer approximations, similarity solutions are obtained for a class of problems where wall temperature varies as xλ, i.e., a power function of distance from the origin where wall temperature begins to deviate from that of the surrounding fluids. Analytical expressions are obtained for boundary layer thickness, local and overall surface heat flux, and local and average heat transfer coefficients. Application to convective heat transfer about an isothermal dike intruded in an aquifer is discussed.

Arrhythmias documented by 24 hour continuous electrocardiographic monitoring in 50 male medical students without apparent heart disease.

Abstract: Results are reported of portable 24 hour dynamic electrocardiographic monitoring in 50 male medical students without cardiovascular disease, as defined by normal clinical and noninvasive cardiovascular examination. During waking periods, maximal sinus rates ranged from 107 to 180 beats/min (mean ± standard deviation 141 ± 17) and minimal rates from 37 to 65 beats/min (mean 53 ± 6). Maximal and minimal observed sleeping rates were, respectively, 70 to 115 (mean 86 ± 9) and 33 to 55 (mean 43 ± 5). Twenty-five subjects (50 percent) had episodes of marked sinus arrhythmia as defined by spontaneous changes in adjacent cycle lengths of 100 percent or more. Fourteen subjects (28 percent) had sinus pauses of more than 1.75 seconds, usually during sinus arrhythmia. Transient nocturnal type I second degree atrioventricular (A-V) block was noted in three subjects (6 percent). Of 28 patients (56 percent) having atrial premature beats, only 1 (2 percent) had more than 100 such beats (141) in 24 hours. Of 25 patients (50 percent) having premature ventricular contractions, only 1 (2 percent) had more than 50 such contractions (86) in 24 hours. In conclusion, frequent atrial and ventricular premature beats are unusual in a young adult male population. In contrast, bradyarrhythmias (including marked sinus arrhythmia with sinus pauses, sinus bradycardia and nocturnal A-V block) are common. These findings are useful in evaluating the clinical significance of arrhythmias detected with portable monitoring.

In Vivo Labeling of Red Blood Cells with 99mTc: A New Approach to Blood Pool Visualization

Abstract: A simple and rapid procedure for in vivo labeling of red blood cells (RBC) is presented. The labeling is done with two consecutive intravenous injections, first of "cold" stannous pyrophosphate (Sn-PYP) and then of 99mTc-pertechnetate. Experimentally, a lag time of 30 min between the two injections was found to result in a mean RBC labeling of greater than 95% during the first hour after pertechnetate injection. A total of 75 patients have been explored by scintillation camera imaging of brain, heart, great vessels, aortic bifurcation, testicles, and lower extremities using the technique outlined. High-quality images were obtained.

Mars and Earth: Origin and Abundance of Volatiles

Abstract: Mars, like Earth, may have received its volatiles in the final stages of accretion, as a veneer of volatile-rich material similar to C3V carbonaceous chondrites. The high (40)Ar/(36)Ar ratio and low (36)Ar abundance on Mars, compared to data for other differentiated planets, suggest that Mars is depleted in volatiles relative to Earth-by a factor of 1.7 for K and 14 other moderately volatile elements and by a factor of 35 for (36)Ar and 15 other highly volatile elements. Using these two scaling factors, we have predicted martian abundances of 31 elements from terrestrial abundances. Comparison with the observed (36)Ar abundance suggests that outgassing on Mars has been about four times less complete than on Earth. Various predictions of the model can be checked against observation. The initial abundance of N, prior to escape, was about ten times the present value of 0.62 ppb, in good agreement with an independent estimate based on the observed enhancement in the martian (15)N/(14)N ratio (78,79). The initial water content corresponds to a 9-m layer, close to the value of >/=13 m inferred from the lack of an (18)O/(16)O fractionation (75). The predicted crustal Cl/S ratio of 0.23 agrees exactly with the value measured for martian dust (67); we estimate the thickness of this dust layer to be about 70 m. The predicted surface abundance of carbon, 290 g/cm(2), is 70 times greater than the atmospheric CO(2) value, but the CaCO(3) content inferred for martian dust (67) could account for at least one-quarter of the predicted value. The past atmospheric pressure, prior to formation of carbonates, could have been as high as 140 mbar, and possibly even 500 mbar. Finally, the predicted (129)Xe/(132)Xe ratio of 2.96 agrees fairly well with the observed value of 2.5(+2)(-1) (85). From the limited data available thus far, a curious dichotomy seems to be emerging among differentiated planets in the inner solar system. Two large planets (Earth and Venus) are fairly rich in volatiles, whereas three small planets (Mars, the moon, and the eucrite parent body-presumably the asteroid 4 Vesta) are poorer in volatiles by at least an order of magnitude. None of the obvious mechanisms seems capable of explaining this trend, and so we can only speculate that the same mechanism that stunted the growth of the smaller bodies prevented them from collecting their share of volatiles. But why then did the parent bodies of the chondrites and shergottites fare so much better? One of the driving forces behind the exploration of the solar system has always been the realization that these studies can provide essential clues to the intricate network of puzzles associated with the origin of life and its prevalence in the universe. In our own immediate neighborhood, Mars has always seemed to be the planet most likely to harbor extraterrestrial life, so the environment we have found in the vicinity of the two Viking landers is rather disappointing in this context. But the perspective we have gained through the present investigation suggests that this is not a necessary condition for planets at the distance of Mars from a solar-type central star. In other words, if it turns out that Mars is completely devoid of life, this does not mean that the zones around stars in which habitable planets can exist are much narrower than has been thought (114). Suppose Mars had been a larger planet-the size of Earth or Venus-and therefore had accumulated a thicker veneer and had also developed global tectonic activity on the scale exhibited by Earth. A much larger volatile reservoir would now be available, there would be repeated opportunities for tapping that reservoir, and the increased gravitational field would limit escape from the upper atmosphere. Such a planet could have produced and maintained a much thicker atmosphere, which should have permitted at least an intermittently clement climate to exist. How different would such a planet be from the present Mars? Could a stable, warm climate be maintained? It seems conceivable that an increase in the size of Mars might have compensated for its greater distance from the sun and that the life zone around our star would have been enlarged accordingly.

Patterns of Student-Faculty Informal Interaction beyond the Classroom and Voluntary Freshman Attrition

Abstract: In a test of Tinto's theoretical model of attrition, this study investigated the pattern of relationships between different types of student-faculty interaction beyond the classroom and college persistence during the freshman year. After controlling for student sex, academic aptitude and personality attributes, freshman persisters were found to have a significantly higher (p < .01) frequency of interactions along six dimensions than were voluntary leavers. Discriminant analysis indicated that student-faculty interactions focusing on discussion of intellectual or course related concerns contributed most to group discrimination.

Group Combustion of Liquid Droplets

Abstract: Quasi steady “external group combustion” of droplet cloud with non-uniform droplet size distributions has been developed to assess the group burning behavior of fuel sprays in industrial and jet engine combustors. The exact solutions for the perturbation equation for power law droplet size distributions are obtained. Numerical analysis pertaining to the initial phase of group combustion with mean droplet size approximation is also presented. The study reveals that current spray burners are operating at high group combustion number regime, wherein the burning mechanism coincides with external group burning mode as previously predicted by Suzuki and Chiu. A spray with a higher group combustion number is also featured by a “sheath vaporization” which is localized in a thin layer located in the outermost region of the cloud. Sprays at lower group combustion number regime cease to burn with external combustion modes when the group combustion number is less than the critical value which is determined b...

Large displacement, transient analysis of space frames

Abstract: A formulation is presented for the transient analysis of space frames in large displacement, small strain problems. For purposes of treating arbitrarily large rotations, node orientations are described by unit vectors and deformable elements are treated by a co-rotational (rigid-convected) description. Deformable elements may be connected either to nodes directly or through rigid bodies. The equations of motion are integrated by an explicit procedure. Sample results are presented on the snap-through of an arch-type structure and an idealization of a vehicle-barrier impact.

Optic disc edema in raised intracranial pressure. IV. Axoplasmic transport in experimental papilledema.

Abstract: • Tritiated leucine was Injected intravitreously into the eyes of rhesus monkeys that had developed papilledema secondary to implantation of intracranial balloons Autoradiographic studies of the optic nerve head showed that six hours after intravitreous injection of the isotope the fast component of axoplasmic transport accumulated in the regions of the lamina choroidalis and lamina scleralis The slow component arrived at the optic nerve head two to four days after injection, and the swollen axons of the entire optic nerve head were filled with radioactive isotopes Twelve days after injection of isotope, the axons in the optic nerve head were still diffusely labeled Disturbance of axoplasmic transport was one of the primary events resulting in swelling of axons in papilledema The pattern of axoplasmic disturbances in papilledema secondary to raised intracranial pressure was similar to that observed in papilledema secondary to ocular hypotony or increased intraocular pressure Ocular hypotony, raised intracranial pressure, and increased intraocular pressure appear to share a final common pathway All these conditions apparently converge into this final common pathway of disturbance of axoplasmic transport to give rise to papilledema (Arch Ophthalmol95:1458-1462, 1977)

Learning Disabled Children's Comprehension of Nonverbal Communication

Abstract: A problem shared by many learning disabled youngsters which confounds their academic difficulties is adequate social adjustment. Frequently, inadequate social adjustment among the learning disabled is conceived of as derived from their academic failure, mediated by lowered self-confidence. Various psychodynamic and social-psychological explanations for this phenomenon are widely known. In this article, Bryan poses an alternative, that the learning disabled child may be less sensitive to social cues and, hence, may be more apt to misinterpret them, the result being inappropriate, maladaptive social behavior. While confirmation of this hypothesis in no way disproves the fact that some children may show inappropriate social behavior for other reasons, the demonstration that some learning disabled children do have less accurate social perceptions has distinctive remedial implications which Bryan discusses. — G.M.S.

Temporal dioecism: an alternative to dioecism?

Abstract: The maintenance of genetic variation in natural populations is usually considered to be important in maintaining ecological plasticity and evolutionary success. In most plants, including autogamous ones, there are adaptations that facilitate outcrossing (Cruden, 1977). Outcrossing is obligatory or virtually so in self-incompatible and dioecious species, but self-compatible xenogamous species, especially those with many flowers open at a time, are liable to varying degrees of selfing through geitonogamy (cross pollinations between flowers of the same plant). Selfing in xenogamous plants may result in inbreeding depression (Antonovics, 1968; Darwin, 1895; Watts, 1965). In xenogamous, selfcompatible plants, therefore, any adaptation that decreased selfing should help maximize fitness. Below we describe a breeding system, which we call temporal dioecism, that permits little geitonogamy regardless of the number of open flowers, even in self-compatible, protogynous species. Temporal dioecism is, in essence, a flowering sequence which is synchronized so there is little or no overlap between staminate and pistillate phases of an individual plant. Umbelliferae offer good examples of this system. Our observations on protandrous species of Ammi, Angelica, Cicuta, Eryngiumn, Heracleum, Pastinaca, and Sium, and protogynous Donnellsmithia, Thaspium and Zizia are consistent with Ponomarev's (1960) description of flowering in Libanotis intermedia Rupr. and seven other species. Regardless of the number of umbels, overlap between the staminate and pistillate phases, either within or between umbels (Table 1), is minimal. In protandrous species, in each umbel, the flowers open and the anthers dehisce centripetally over a period of several days. After the last anther has dehisced, and only then, all the stigmas become receptive. Synchrony of flowering within a plant is well illustrated by Pastinaca sativa L. The primary umbels (terminal umbels of Bell, 1971) are staminate for approximately 6 days, then pistillate for one and one-half to two days before the first flowers of each secondary umbel open. The latter are staminate for approximately seven days and are then pistillate for two days before the tertiary umbels become staminate. The ultimate expression of temporal dioecism occurs in Peucedanum lubimenkoanum Kot. in which all the umbels, both primary and secondary, pass through the staminate phase together, then become pistillate (Ponomarev, 1960). The difference between the lengths of the staminate and pistillate phases in protandrous Umbelliferae results in a disproportionate number of "staminate" plants in a population at any given time. In the species studied extensively over many days (Table 1), the ratio is approximately four "staminate" plants to each "pistillate" plant. Such biased ratios are not observed in all temporally dioecious species (Table 2). Geitonogamous pollinations may occur in unusual situations, for example when 1) branches or stems of a plant are not in synchrony (Ponomarev, 1960); 2) polli-

Optic Disc Edema in Raised Intracranial Pressure: III. A Pathologic Study of Experimental Papilledema

Abstract: Optic nerve heads of 21 eyes from 13 rhesus monkeys that had developed papilledema secondary to chronically raised intracranial pressure from balloon implantation in the subarachnoid space were studied by light and electron microscopy. Nine eyes were also examined with the horseradish peroxidase tracer technique. The pathologic changes in the optic nerve head included severe axonal changes and mild interstitial edema. Axonal alteration ranged from axonal swelling to formation of cytoid bodies. Interstitial edema and vascular leakage of horseradish peroxidase were noted in the posterior lamina retinalis, lamina choroidalis and lamina scleralis (prelaminar and lamina cribrosa regions), as well as in the retrolaminar myelinated optic nerve. No intracellular edema of the glial elements was noted. Axonal swelling was so prominent that it appeared to be primarily responsible for the overall swelling of the optic disc observed ophthalmoscopically.

The System Zirconia-Scandia

Abstract: The system zirconia-scandia was investigated using X-ray diffraction analysis, differential thermal analysis, metallographic analysis, and melting point studies. Results reveal the monoclinic α1 phase (0 to 2 mol% Sc2O3), the tetragonal α2’phase (5 to 8% Sc2O3), the rhombohedral β phase (9 to 13% Sc2O3), the rhombohedral γ phase (15 to 23% Sc2O3), the rhombohedral δ phase (24 to 40% Sc2O3), and the cubic % phase (77.5 to 100% Sc2O3). The monoclinic α1 phase and the tetragonal α2’phase were found to transform to the tetragonal α2 phase over a wide temperature range depending on composition. The β, γ, and α phases transformed to a cubic phase at temperatures of %600%, 1100%, and 1300%C, respectively. A maximum melting point of %2870%C was found at %10% Sc2O3 and a eutectic at %2400%C at 55% Sc2O3.

An unusual variety of atrioventricular nodal re-entry due to retrograde dual atrioventricular nodal pathways.

Abstract: Three patients with paroxysmal supraventricular tachycardia (PSVT) had discontinuous ventriculo-artrial conduction curves (V1-V2, A1-A2), suggesting dual A-V nodal pathways. Ventricular echoes occurred simultaneously with sudden increase of V-A interval. These echoes were characterized by retrograde P waves occurring in front of QRS, suggesting utilization of a slow pathway for retrograde conduction and a fast pathway for antegrade conduction. In case one, atropine improved retrograde slow pathway and antegrade fast pathway conduction and made A-V nodal re-entry sustained, resulting in PSVT (with retrograde P in front of the QRS). In cases 2 and 3, atropine markedly shortened retrograde fast pathway refractory period and slightly improved antegrade slow pathway conduction. The discontinuous V1-V2, A1-A2 curves and echoes were no longer demonstrable. However, with improvement of retrograde fast pathway and antegrade slow pathway conduction, A-V nodal re-entrant echoes and PSVT were observed, utilizing the slow pathway for antegrade conduction and the fast pathway for retrograde conduction (P simultaneous with QRS).

Sudden Death in Patients With Chronic Bifascicular Block

Abstract: Prospective follow-up studies of 277 patients with chronic bifascicular block showed that 30 patients developed sudden cardiac death (SCD). Cumulative one-, two-, and three-year SCD mortality was computed. The patients that developed SCD were compared with the remaining patients (209 alive and 38 dead). The groups were similar in regard to age, sex, AH, and HV intervals. The following were more frequent in the SCD group ( P ( Arch Intern Med 137:1005-1010, 1977)

Arrhythmias documented by 24-hour continuous electrocardiographic monitoring in 50 male medical students without apparent heart disease

Abstract: Results are reported of portable 24 hour dynamic electrocardiographic monitoring in 50 male medical students without cardiovascular disease, as defined by normal clinical and noninvasive cardiovascular examination. During waking periods, maximal sinus rates ranged from 107 to 180 beats/min (mean ± standard deviation 141 ± 17) and minimal rates from 37 to 65 beats/min (mean 53 ± 6). Maximal and minimal observed sleeping rates were, respectively, 70 to 115 (mean 86 ± 9) and 33 to 55 (mean 43 ± 5). Twenty-five subjects (50 percent) had episodes of marked sinus arrhythmia as defined by spontaneous changes in adjacent cycle lengths of 100 percent or more. Fourteen subjects (28 percent) had sinus pauses of more than 1.75 seconds, usually during sinus arrhythmia. Transient nocturnal type I second degree atrioventricular (A-V) block was noted in three subjects (6 percent). Of 28 patients (56 percent) having atrial premature beats, only 1 (2 percent) had more than 100 such beats (141) in 24 hours. Of 25 patients (50 percent) having premature ventricular contractions, only 1 (2 percent) had more than 50 such contractions (86) in 24 hours. In conclusion, frequent atrial and ventricular premature beats are unusual in a young adult male population. In contrast, bradyarrhythmias (including marked sinus arrhythmia with sinus pauses, sinus bradycardia and nocturnal A-V block) are common. These findings are useful in evaluating the clinical significance of arrhythmias detected with portable monitoring.

Mapping the locus of the H-Y gene on the human Y chromosome.

Abstract: The H-Y locus is on the short arm of the human Y chromosome in most individuals but on the long arm in at least one of 17 individuals with structural abnormalities of the Y.

Gamma Benzene Hexachloride Toxicity: A Review

Abstract: Scabies major health problem. Currently, the most frequently used antiscabetic substance is a lotion containing 1% of the pesticide, gamma benzene hexachloride (lindane). Because of its widespread use in humans and because of some anecdotal communications suggesting that toxic reactions may have been observed in children treated for scabies with gamma benzene hexachloride, we felt it would be of interest to review toxicity of the substance and examine the indications and methods currently recommended for its use. Gamma benzene hexachloride is the y isomer of 1,2,3,4,5,6-hexachlorocyclohexane (HCCH). It is the chlorine analogue of muco-inositol. 1 It is a nonaromatic compound whose physical properties are given in the Figure. Gamma benzene hexachloride is present in several products sold under a number of trade names. Although gamma benzene hexachloride was probably first synthesized by Michael Faraday in 1825, the pure alpha, beta, gamma, and delta isomers were not prepared until 1943 by

Oscillation of the human ankle joint in response to applied sinusoidal torque on the foot.

Abstract: 1. Low-frequency (3-30 Hz) oscillatory rotation of the ankle joint in plantarflexion—dorsiflexion was generated with a torque motor. Torque, rotation about the ankle and electromyograms (e.m.g.s) for the gastrocnemius—soleus and the anterior tibial muscles were recorded. 2. Fourier coefficients at each drive frequency were used to calculate the effective compliance (ratio of rotation and torque). The compliance has a sharp resonance when tonic, voluntary muscle activity is present. 3. The resonant frequency of compliance is between 3 and 8 Hz. The location of the resonant frequency and the magnitude of the compliance at resonance depend upon both the degree of tonic muscle activity and the amplitude of the driving torque. The resonant frequency increases with increasing tonic activity. 4. With tonic muscle activity, the compliance in the frequency range below resonance increases with increasing amplitudes of driving torque. 5. The e.m.g., when evoked by the rhythmic stretch, lags the start of stretching by between 50 and 70 msec. 6. When tonic muscle activity is present, the resonant frequency of the stretch reflex is between 5 and 6·5 Hz. 7. Following the start of driven oscillation at frequencies near resonance, slowly increasing amplitudes of angular rotation (to a limit) are observed. 8. Distortion (from the sinusoidal wave shape) of angular rotation is frequently observed with drive frequencies between 8 and 12 Hz during which there sometimes occur spontaneous recurrences of oscillation at the drive frequency. For the angular rotation, a significant portion of the power may be in subharmonic frequency components of the drive frequency when that frequency is between 8 and 12 Hz. 9. Self-sustaining oscillation (clonus) near the resonant frequency of the compliance is sometimes observed after the modulation signal to the motor is turned off. This is most often seen when the gastrocnemius—soleus muscles are fatigued. Clonus may be evoked by driven oscillation at any frequency. 10. The hypothesis that physiological tremor, which occurs between 8 and 12 Hz, is a consequence of stretch reflex servo properties seems to be at odds with the observations of resonance in the compliance and of self-generated clonus both occurring in the 5-8 Hz region.

Critical exponents for percolation conductivity in resistor networks

Abstract: The conductivity of two-dimensional and of three-dimensional cubic binary random resistor networks is shown to obey a power-law dependence on the conductivity ratio at the percolation threshold. The relation recently derived by Straley between the exponent of this power law and the other two critical exponents of the conductivity above and below the percolation threshold is accurately obeyed. Extension of the scaling laws for a complex dielectric function of a binary network is provided.

Electrophysiological studies with multiple drugs in patients with atrioventricular re-entrant tachycardias utilizing an extranodal pathway.

Abstract: Eleven patients with recurrent paroxysmal tachycardia (PSVT) underwent electrophysiological studies. In each patient, initial study revealed re-entrant PSVT with antegrade conduction via the normal pathway and retrograde conduction via an extranodal pathway (Kent bundle). A temporary electrode catheter was left at the conclusion of initial study and PSVT induction was performed on subsequent days before and after the following intravenous drugs: ouabain 0.01 mg/kg (OU), propranolol 0.1 mg/kg (PRO), ouabain + propranolol (OU + PRO) and procainamide 750 mg (PA). In all patients, control studies prior to drug administration revealed the ability to induce sustained PSVT. In five patients, OU, PRO, or OU + PRO prevented induction of sustained PSVT by increasing atrioventricular (A-V) nodal refractoriness. In four of the patients, (including one of the above), PA prevented induction of sustained PSVT: in one, by increasing His-Purkinje refractoriness, and in three by increasing refractoriness in the Kent bundle. Oral drug therapy based upon the above studies (8 pts) prevented recurrent sustained PSVT for a mean follow-up period of 9 ± 5 months. In the remaining three patients, all drugs failed to prevent induction of sustained PSVT. These patients were either treated with radiofrequency pacemakers or surgery. In conclusion, drug responses in patients with recurrent PSVT utilizing a Kent bundle are variable. Antiarrhythmic drugs may interfere with circus movements at the A-V node, His-Purkinje system, or Kent bundle. Chronic oral drug therapy based upon responses to electrophysiological studies with multiple drugs prevents recurrent sustained PSVT over a short-term followup period.

Postsynaptic supersensitivity in schizophrenia

Abstract: In the context ofthe dopamine hypothesis of schizophrenia , the authors examined postsynaptic dopamine (DA) receptor sensitivity in schizophrenic patients by means ofa neuroendocrine strategy using the DA receptor agonist apomorphine and growth hormone (GH) release as the measurable postsynaptic event. The activity ofplatelet adenylate cyclase, an enzyme intimate/v associated with catecholamine receptor activity , was also studied following stimulation by prostaglandin E1 (PGEI). Patients diagnosed as having acute schizophrenia had significant/v higher GH responses and adenylate cyclase activity than normal control subjects and patients diagnosed as having chronic schizophrenia. Chronic schizophrenic patients with and without tardive dyskinesia showed GH responses slightly lower than but not significant/v differentfrom those of