Showing papers by "University of Notre Dame published in 1968"

Inverses of Linear Sequential Circuits

Abstract: —This paper states the necessary and sufficient conditions for the existence of a feedforward inverse for a feedforward linear sequential circuit and gives an implicit procedure for constructing such inverses. It then goes on to give the necessary and sufficient conditions for the existence of general inverses with finite delay and gives procedures for constructing a class of such inverses. The discussion considers both the transfer function matrix description and the structural matrix description of the linear sequential circuit, together with the complementary nature of the results obtained from these two viewpoints. Finally, a large part of the work is motivated by results and techniques which have been applied in the study of continuous-time linear dynamical systems and thus serves to point out the advantages which may accrue through simultaneous study of both continuous-time systems and linear sequential circuits.

Histological and ultrastructural study of the muscular and nervous systems in Hydra. II. Nervous system.

Abstract: Nerve cells in hydra have been studied with the light and electron microscopes. Techniques for observing bi-polar, tri-polar, multi-polar and sensory cells are described. Evidence is presented that these cells form a major part of the nervous system in hydra. The ultrastructural studies indicate the following: (1) There are three types of nerve cells: ganglionic, sensory and neurosecretory. (2) Nerve cells are concentrated at the base of tentacles, hypostome and basal regions. (3) Nerve cells are situated adjacent to the muscle fibers of the epithelio-muscular cells. Criteria for identification of nerve cells at the ultrastructural level are presented. The nerve cells in hydra appear to be structurally different from similar cells in higher invertebrates and vertebrates. An important distinction is the lack of specialized synaptic vesicles in hydra. The appearance, dimensions, and location of secretory droplets in cells identified as neurosecretory cells are discussed. The droplets resemble closely neurosecretory droplets in nerve cells of higher invertebrates and vertebrates. The mechanism for the release of neurosecretory material in hydra appears to be similar to that suggested for higher organisms. It is suggested that one type of secretory droplet in hydra nerve cells may represent a growth stimulating principle that is believed to control growth and differentiation (Burnett, '66). The relationship of nerve cells to muscle processes is discussed.

What do Physical Models Tell us

Abstract: Publisher Summary This chapter focuses on the inferences that are drawn from physical models. It is this rather hazy separation between the descriptive and the explanatory aspects of science, between the functions of observational terms and of theoretical terms that has provided the material for much of the recent discussion in the philosophy of science. Three different levels of question can be asked about this, as about any other problem in philosophy of science. It is important to separate these levels, because the techniques used in answering them are significantly different. The aim is to begin from ordinary usage and when stipulation becomes necessary to choose those stipulations that will, so far as is possible, support those conceptual distinctions that are latent in actual scientific practice. A theory is something put forward to account for one or more empirical laws that are already known. It is not just a singular hypothesis but has some degree of generality. But it is something more than a mere higher-order generalization.

Convergent systems

Abstract: An equivalent relationship has been established between the problems of convergence or zero-input convergence of nonlinear systems and the problem of zero-input convergence of linear systems. A special feature is that the formulation of the problem and the analysis are done directly on a component-connection model instead of the usual input-output state model. As a consequence, the results obtained can be easily interpreted in terms of given practical systems.

Optical Properties of Some Transition Metals

Abstract: Optical properties of Mo, Ta W and Re by reflectance vs incidence angle method, stressing dielectric constants

Some basic viscous flows in micropolar fluids

Abstract: This paper analyzes some basic viscous flows of micropolar fluids. The problems ofCouette andPoiseuille flows between two parallel plates and a rotating fluid with a free surface, are solved using the theory of micropolar fluids. The results are presented graphically and compared with the classical ones, and the differences are discussed.

Cecal enlargement, cardiac output, and O2 consumption in germfree rats.

Abstract: SummaryGerm free rats have cardiac output and O2 consumption values respectively 30% and 24% lower than found in comparable conventional rats. Surgical removal of the enlarged cecum typical for these animals resulted in cardiac output values similar to those obtained with conventional rats, while O2 consumption increased significantly to levels only slightly lower than seen in the conventional control group. No significant difference in body temperature was found between comparable groups of germfree and conventional rats.

An ultrastructural examination of the mesoglea of Hydra.

Abstract: The survey of the mesoglea of four species of Hydra indicates a basic similarity of structure. In each species the mesoglea consists of an amorphous ground substance with three different types of fibers and particulate material dispersed in this matrix. A probable interpretation of the fine structure of the mesoglea is that collagen-like protein demonstrated by other investigators, forms all or part of the “beaded” fibers. Acid mucopolysaccharide which can be demonstrated histochemically probably corresponds to the amorphous ground substance in which the mesogleal fibers are dispersed. The role of the mesoglea as an extra-cellular skeleton and cementing substance is discussed.

Efficiency of digestion in germ-free and conventional rabbits.

Abstract: 1. Germ-free (GF) and conventional (CV) rabbits wearing collars to prevent coprophagy were fed an autoclaved diet with added cellulose. Their faecal excretion was analysed to determine nutrient digestibility.2. Clearly distinguishable hard faeces were excreted by the GF rabbit only if the diet contained at least 15% cellulose. Unlike CV rabbits, the GF rabbits did not consume their soft faeces even when permitted to do so. Soft faeces made up a larger proportion of the total output of GF than of CV rabbits. Food intake and total dry-matter excretion per kg body-weight were similar in both groups.3. Although digestibility of dry matter was similar in the two groups, in the GF rabbits there was a higher digestibility of crude fat and true protein and a lower digestibility of crude fibre and nitrogen-free extract. GF rabbits excreted a higher percentage of ingested calcium and phosphorus in the urine than did CV rabbits.4. The results suggest that intestinal microbes, even without the enhancing effect of coprophagy, aid in the digestion of carbohydrate by rabbits. The greater faecal excretion of crude fat and true protein by CV rabbits could result from poorer digestion and absorption, but could also represent nutrients synthesized by microbes from simpler materials. The reingestion of faecal crude fat and true protein might therefore improve the quality of the total nutrient intake. The results suggest ways of assuring an adequate dietary intake by GF rabbits in the absence of contributions from an intestinal microflora.

Heat transfer response of laminar free-convection boundary layers along a vertical heated plate to surface-temperature oscillations

Abstract: Die Warmeubertragung durch freie Konvektion von der laminaren Grenzschicht einer vertikalen erhitzten Platte wird mittels einer linearisierten Theorie fur den Fall einer schwingenden Oberflachentemperatur studiert. Die Oberflachentemperatur wird als Potenzn des Abstands zur Plattenvorderkante angenommen. Furn=1 ergeben sich genaue Losungen uber den ganzen Frequenzbereich. Furn<1 werden asymptotische Reihenlosungen bei niederen und hohen Frequenzen abgeleitet. Ausfuhrliche numerische Rechnungen wurden uber den gesamten Frequenzbereich furn=0, 0.2 und 1.0 bei Prandtlzahlen 0.72, 1.0 und 10.0 durchgefuhrt. Eine physikalische Deutung der durch die Schwingung der Oberflachentemperatur bedingten Amplituden und Phasen des Warmeflusses wird gegeben.

Mechanical and Electrical Activity in the Indirect Flight Muscles of the Honey Bee

Abstract: 1. Recordings were made from single elements in the indirect flight muscles of the honey bee with the usual insulated metal electrodes uninsulated at the tip. With the “indifferent” electrode in the head few neighboring elements showed up. All recorded elements had random phase differences. 2. In the dorsoventral (DV) muscles about 80% of the spikes are not followed by striking junctional components, 20% are. Practically all spikes from the dorsolongitudinal (DL) muscles have a junctional component following. 3. The DV-muscles in the intact animal shorten linearily with increasing action potential frequency (Fig. 6). The DL-muscles are stretched slightly. 4. Approximately 50 to 100 msec before the onset of oscillations the action potential frequency in both groups of muscles (DV and DL) increases to 30–60 Hz for 2 to 4 action potentials. The DV-muscles shorten (evidently isotonically) about 20 to 40 μ and start oscillations with a lengthening. An experiment performed by Boettiger (p. 438) might explain the events that start the oscillations. The oscillations end about 180 to 200 msec after the ending of the action potentials. The DV-muscles return to their resting length in the next 200 to 1,000 msec. 5. The duration of the action potentials depends strongly on the temperature (Fig. 4). 6. The wingbeat frequency increases with the action potential frequency (Fig. 10).

The phase diagram of the system tellurium/arsenic

Abstract: Thermal analysis, metallographic and X-ray procedures have been used to investigate the system tellurium/arsenic. As2Te3 is the only binary compound present. It melts at 381° C and forms a eutectic with tellurium at 18.5 wt % As/81.5 wt % Te and at a temperature of 363° C. The As2Te3 and As also produce a eutectic at 31.5 wt % As/68.5 wt % Te, with a melting point of 380°C. The solid solubilities at the As and Te ends of ths phase diagram are too small to detect by the methods used, and the compositional range of the As2Te3 is very restricted.

An analysis of external respiration in man

Abstract: An analytical model of the external respiratory system is presented that embodies the important aspects of the previous capillary and gas side studies. The capillary bed is represented by a set of distributed-parameter flow-forced diffusional tubes, while the lungs are divided into two compartments—a dead space and a gas exchange space. Based upon realistic physiological properties, the concentrations of oxygen and carbon dioxide are determined as functions of time and position in the capillary bed, and as functions of time in the dead space and gas exchange regions under both normal and abnormal environmental conditions. The results provide a number of insights into the behavior of the respiratory system and the relative importance of some of the variables that affect it.

Wide distribution of leukaemia virus in strains of laboratory mice.

Abstract: LABORATORY mice of defined genetic qualities and, more recently, so-called germ-free (gnotobiotic, axenic) mice have become available to investigators. Electron microscopy has revealed, however, that the so-called germ-free mice (AKR, Balb/c, C3Hf, CFW, ICR and Swiss-Webster strains) were not virus-free1–3. Virus-like particles were observed in the thymic tissues of prenatal, neonatal and mature “germ-free” mice3. Moreover, significant numbers of mice from each strain developed lymphatic leukaemia after whole-body exposure to X-rays, which served to identify some of the virus particles in their tissues4. The development of a virus-free mouse strain would be very useful for determining the exclusive causal role of virus in leukaemogenesis. We have therefore examined additional conventional mouse strains for leukaemia virus by electron microscopy and some also for host-response to the leukaemogenic action of whole-body irradiation.

Controlled Recovery of Payloads at Large Glide Distances, Using the Para-Foil

Abstract: Recent progress of Sandia Laboratory in the development of a small guidance and control system and by the University of Notre Dame on the Para-Foil has indicated that the design of a system capable of recovering a 150-Ib payload from altitudes greater than 300,000 ft and ranges of from three to five times the deployment height (60,000 ft) is quite feasible. The Para-Foil is a completely nonrigid, self-inflating flying wing, capable of being packed and deployed like a conventional parachute and able to glide large distances. The guidance package is an electromechanical control system employing a direction-finding antenna to control the direction of the Para-Foil's glide path with respect to a ground or shipboard transmitter. The recovery system design program includes such parameters as size and weight of the recovery unit, size of the payload (W/S wing loading), glide ratio and wind structure, and flare-out capabilities in the recovery area. The full-scale recovery program includes numerous packing, deployment, and glide tests. These tests demonstrated successful deployment, excellent gliding performance (JL/D = 3.88) and dynamic flight stability, and very low impact velocities during the final recovery phases. Recent guidance and control tests also demonstrated excellent response in maneuverability of the Para-Foil. This paper summarizes the design program and the results of full-scale deployment and guided recovery flight tests and demonstrates the potential of the Para-Foil for use in many space-age recovery programs.

Compilation of π − p Data at 4 GeV/ c : Backward Resonance Production and π π Scattering

Abstract: In ${\ensuremath{\pi}}^{\ensuremath{-}}p$ single-pion-production reactions near 4 GeV/c, we observe several interesting features. Backward ${\ensuremath{\rho}}^{0}$ production is seen to occur with $\frac{d\ensuremath{\sigma}}{\mathrm{du}}=63\ifmmode\pm\else\textpm\fi{}21$ \ensuremath{\mu}b/${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$ at 180\ifmmode^\circ\else\textdegree\fi{}. Backward ${\ensuremath{\rho}}^{\ensuremath{-}}$ production is less prominent. We see evidence for production at small $u$ of ${N}^{*0}$ ($p{\ensuremath{\pi}}^{\ensuremath{-}}$ near 1700 MeV) and ${\ensuremath{\Delta}}^{\ensuremath{-}}$ ($n{\ensuremath{\pi}}^{\ensuremath{-}}$ at 1236 MeV), and possible evidence for other $n{\ensuremath{\pi}}^{\ensuremath{-}}$ structure at about 1800 MeV. The density-matrix elements for peripheral ${\ensuremath{\rho}}^{0}$ production are presented in the Jackson and in the helicity frame. The ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ elastic cross section is obtained by extrapolation of the data to the mass shell. The $S$-wave $\ensuremath{\pi}\ensuremath{\pi}$ phase shifts are calculated by two methods and compared with previous results. We find evidence in the dipion decay angular distribution for the ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ decay mode of the ${S}^{*}(1070)$.

Effect of ionizing radiation on a series of saturated polyesters

Abstract: The effect of ionizing radiation on a series of saturated linear polyesters containing the repeating unit in which R1 and R2 are linear or branched alkylene groups, is reported. Cross-linking and scission were shown to be influenced greatly by the structural features of R1 and R2 and the intrinsic viscosities of the polymers. A dose-rate independence was observed for the polymers in vacuo, whereas in air, degradation was related to diffusion of the gas into the polymer. Amorphous polymers were shown to cross-link more readily than the crystalline and oriented polyesters; trapped radicals in the crystalline polymers cause delayed cross-linking when the polymers were subsequently heated.