Showing papers by "University of Utah published in 1970"

Initial Sintering with Constant Rates of Heating

Abstract: Initial sintering of several materials was studied by measuring powder compact densification at constant rates of heating (CRH). The CRH technique was extremely sensitive to the particle size distribution and other characteristics of the compacts. Although the CRH method circumvents several problems encountered in isothermal studies, it cannot be used to identify the mechanism of diffusion. Using the method on carefully prepared alumina powder compacts and assuming a grain-boundary diffusion mechanism, an activation energy of 115±10 kcal/mol was obtained. Zirconia (yttria-stabilized) and titania also exhibited a single densification mechanism with diffusion coefficients which correlate well with values obtained by isothermal measurements.

Circadian Rhythm of Gastric Acid Secretion in Man

Abstract: WE report here a circadian rhythm in human gastric acid secretion. The rate of secretion is usually greater in the evening than in the morning.

Thermal Properties of Teeth

Abstract: Recent measurements of the density and specific heat of teeth, as well as values of thermal di ff usivity based on thermal conductivity measurements, are reported. The values obtained for thermal di~usivity were within 10% (for enamel) and 25% (for dentin) of values previously reported in the literature.

Effect of TiO2 on Initial Sintering of Al2O3

Abstract: Alpha alumina with additions of TiO2 sintered more rapidly than “pure” alumina. The rate of initial sintering increased approximately exponentially with titania concentration up to a percentage beyond which the rate of sintering remained approximately constant or decreased slightly with additional titania. The concentration which produces the maximum rate of sintering is thought to be the solubility limit of TiO2 in Al2O3. For alumina particles larger than about 2 μm, the kinetic process was mainly grain-boundary diffusion. With smaller particles, volume diffusion increased. The “solubility limit” increased with decreasing particle size, indicating an excess surface concentration of TiO2. The data may be interpreted in terms of a region of enhanced diffusion at the grain boundary that increases with TiO2 concentration. With small alumina particles, this region is large enough to become a significant portion of the volume of the particle, and the small particles appear to sinter by volume diffusion kinetics, but the diffusion coefficient corresponds to an enhanced diffusion coefficient.

Dye‐sensitized photooxidation of proteins*

Abstract: In 1900, Raab' reported that living cells could be killed by illumination in the presence of certain dyes; a short time later it was found that molecular oxygen was required for this process.z Such dye-sensitized photooxidation processes are usually termed \" photodynamic \" reactions by biologist^.^ Although the killing of cells by photodynamic treatment is a rather complicated process, in the final analysis it must result from the photooxidation of critical component molecules of the cell, such as proteins and nucleic acids. The present paper is concerned with the protein aspects of this problem. The first report of photodynamic effects on proteins was in 1903 when von Tappeiner and his students showed that enzymes such as diastase, invertase and pepsin were inactivated by illumination in the presence of e o s h 4 Since that time a great deal of work has been done on the photodynamic degradation of proteins, especially enzymes. To date, over sixty crystalline proteins have been studied in this regard.3 Since this conference is devoted to singlet oxygen, it should be pointed out that not all cases of the dye-sensitized photooxidation of proteins can be interpreted in terms of a singlet-oxygen mechanism. Singlet oxygen may be involved in the inactivations sensitized by many types of dyes, such as the thiazines and the fluoresceins. However, in other cases, as with flavine and anthraquinone sensitizers, singlet oxygen appears to play only a minor role. Even with those dyes in which singlet oxygen is presumed to be involved, the evidence is only circumstantial, since studies of the effects of singlet oxygen on amino acids and proteins have not yet been reported in the literature. Since space is very limited, only the more recent references on each topic will be listed. These may be consulted for a more extensive entry into the literature on the sensitized photooxidation of proteins.

Experimental Investigation of Radiative Transfer Between Metallic Surfaces at Cryogenic Temperatures

Abstract: Radiative heat flux between two parallel copper disks at cryogenic temperature, showing dependence on emitter temperature and spacing

HOST-HOST communication protocol in the ARPA network

Abstract: The Advanced Research Projects Agency (ARPA) Computer Network (hereafter referred to as the "ARPA network") is one of the most ambitious computer networks attempted to date. The types of machines and operating systems involved in the network vary widely. For example, the computers at the first four sites are an XDS 940 (Stanford Research Institute), an IBM 360/75 (University of California, Santa Barbara), an XDS SIGMA-7 (University of California, Los Angeles), and a DEC PDP-10 (University of Utah). The only commonality among the network membership is the use of highly interactive time-sharing systems; but, of course, these are all different in external appearance and implementation. Furthermore, no one node is in control of the network. This has insured generality and reliability but complicates the software.

Normal blood leukocyte concentration values.

Abstract: Absolute blood leukocyte counts were determined in 291 normal individuals (226 Caucasian and 65 Negro), using modern, electronic leukocyte counting methods. Two hundred cell differential counts of coverslip smears stained with Wright’s stain were done. Normal mean values and 95% limits expressed as cells per cu. mm. were: band neutrophils 500 (100 to 2,100); segmented neutrophils 3,000 (1,100 to 6,050); total neutrophils 3,650 (1,830 to 7,250); lymphocytes 2,500 (1,500 to 4,000); monocytes 430 (200 to 950); eosinophils 150 (0 to 700); basophils 30 (0 to 150). No clinically significant differences between Negroes and Caucasians were found.

Increased Chloride Conductance As the Proximate Cause of Hydrogen Ion Concentration Effects in Aplysia Neurons

Abstract: A fall in extracellular pH increased membrane conductance of the giant cell in the abdominal ganglion of Aplysia californica. Chloride conductance was trebled whereas potassium conductance was increased by 50%. Half the giant cells were hyperpolarized (2–8 mv) and half were depolarized (3–10 mv) by lowering the pH. The hyperpolarizing response always became a depolarizing response in half-chloride solutions. When internal chloride was increased electrophoretically, the hyperpolarization was either decreased or changed to depolarization. The depolarizing response was reduced or became a hyperpolarizing response after soaking the cell in 10.0 mM chloride, artificial seawater solution for 1 hr. Depolarization was unaffected when either external sodium, calcium, or magnesium was omitted. A glass micropipette having an organic liquid chloride ion exchanger in its tip was used to measure intracellular chloride activity in 14 giant cells; 7 had values of 27.7 ± 1.8 mM (SEM) and 7 others 40.7 ± 1.5 mM. Three of the first group were hyperpolarized when pH was lowered and three of the second group were depolarized. In all six cells, these changes of membrane potential were in the direction of the chloride equilibrium potential. Intracellular potassium activity was measured by means of a potassium ion exchanger microelectrode.

Anistropy of the Constant-Energy Surfaces in n -Type Bi Te 3 2 and Bi 2 Se 3 from Galvanomagnetic Coefficients

Abstract: Low-field galvanomagnetic coefficients have been measured on single crystals of ${\mathrm{Bi}}_{2}$${\mathrm{Te}}_{3}$ and ${\mathrm{Bi}}_{2}$${\mathrm{Se}}_{3}$ at 76 \ifmmode^\circ\else\textdegree\fi{}K in fields to 9 kG. Using a six-valley ellipsoid model in the isotropic relaxation-time approximation, the mass parameters of the ellipsoids are calculated for both compounds. The discrepancy between previously reported galvanomagnetic data and de Haas-van Alphen data for ${\mathrm{Bi}}_{2}$${\mathrm{Te}}_{3}$ can be minimized by recalculating the mass parameters from the galvanomagnetic data and by not assuming complete degeneracy. The experimental data on ${\mathrm{Bi}}_{2}$${\mathrm{Te}}_{3}$ are in agreement with those reported earlier. There is also very good evidence of second-band effects at high electron concentrations (g ${10}^{19}$ ${\mathrm{cm}}^{\ensuremath{-}3}$), as has been previously suggested. The constant-energy surfaces undergo an apparent change in shape between low- and high-concentration samples. Data on ${\mathrm{Bi}}_{2}$${\mathrm{Se}}_{3}$ indicate that the constant-energy surfaces are more spherical than in the case of ${\mathrm{Bi}}_{2}$${\mathrm{Te}}_{3}$.

Coronary Heart Disease

Abstract: Right atrial pacing was performed in 41 subjects with coronary heart disease. Twenty developed angina pectoris during pacing, while 21 did not. The extent of coronary artery disease, as judged by selective cinearteriography, was similar in the two groups. Both had significant increases in heart rate and pressure-time per minute, but there was no significant difference in either of these parameters between groups. Among the hemodynamic parameters measured, the only statistically significant change was in the cardiac index which fell slightly but significantly in the angina group. There were no differences in myocardial oxygen extraction either within each group or between groups. In the angina group, however, 14 of 20 subjects exhibited abnormal myocardial lactate metabolism during pacing. The mean change was highly significant ( P < 0.01). In the nonangina group, eight of 21 subjects had abnormal lactate metabolism during pacing and the mean change was significant ( P < 0.05). There was no correlation between abnormal lactate metabolism and electrocardiographic evidence of myocardial ischemia in either group. Sublingual nitroglycerin, given to five subjects with angina while pacing was continued, resulted in prompt relief of symptoms, but abnormal lactate metabolism and ST-segment depression were unaffected after 10 min. By contrast, when anginal symptoms were relieved in five subjects by cessation of pacing, symptomatic improvement was accompanied by marked improvement in lactate metabolism after 10 min. Although angina pectoris appears to be related statistically to subnormal left ventricular function and abnormal lactate metabolism, there is significant individual variation.

The periodic viscous sublayer in turbulent flow

Abstract: The model of the fluctuating viscous sublayer proposed by Einstein and Li was modified by treating some of the objections to the original formulation without greatly altering the essential simplicity of the concept. The applicability of this model to the description of the important features of turbulent flow and heat transfer in ducts and of the Toms phenomenon was evaluated by comparison of predictions of the model with experimental measurements. The mean period for growth and decay of the sublayer and the magnitudes of the wall-pressure fluctuations and wall-temperature fluctuations were compared for the flow of air and liquids. Quantitative spatial features of the periodic sublayer, that is, minimum and maximum sublayer thickness and patch size in the directions normal and parallel to the flow direction, were determined.

Spontaneous rhythmic contraction of separated heart muscle cells

Abstract: Muscle cells that conitract spontaneously and rhythmically can be obtained from adult mouse myocardium. Contractions are observed immediately after homogenization in a solution that is ionically similar to intracellular fluid. Contraction frequency varies directly with temperature and decreases as a function of time after homogenization. At 16 degrees C rhythmic relaxation and contraction occur for about 20 minutes. Contractions are dependent on the presence of adenosine triphosphate in the homogenization medium.

Effect of Animal Passage on Arthritogenic and Biological Properties of Mycoplasma arthritidis.

Abstract: Determinations of the ED 50 of cultures of Mycoplasma arthritidis disclosed the existence of great diversity in the arthritogenic properties of the various strains. In most cases, the ED 50 values were lowered after passaging in rats, and a more severe arthritis with a shorter period of onset was observed. Heavy suspensions of arthritogenic M. arthritidis did not appear to induce any toxic symptoms. Prior injections of endotoxin did not enhance the toxicity of M. arthritidis suspensions. The more arthritogenic strains grew more slowly in the basal medium and remained viable for longer periods of time than those with lower arthritogenic properties. All strains were identical on the basis of complement-fixation tests. Minor differences observed between strains during gel-diffusion studies could not be correlated with arthritogenic properties. Arthritogenic strains appeared to be less susceptible to the inhibiting action of rabbit antisera than were the nonarthritogenic strains.

The fracture threshold for an adhesive interlayer

Abstract: Complementing an earlier paper which utilized an energy balance criterion for a continuum mechanics analysis of adhesive failure in a pressurized blister at the interface of an elastic material and a rigid substrate, the analysis is extended to include an additional elastic interlayer between them. An infinite lateral-length elastic plate strip bonded through a Winkler elastic foundation to a rigid substrate is assumed, in which the plate is separated from the adhesive layer by internal pressure. It is found that the important design parameters are the tensile modulus-to-thickness ratio of the adhesive layer and the adhesive fracture energy of separation of the respective materials. The results provide a basis for investigating changes in the chemical microstructure of the adhesive.