Showing papers by "University of Arizona published in 1973"

The cat step cycle: Hind limb joint angles and muscle lengths during unrestrained locomotion

Abstract: A cinematographic analysis of the unrestrained walking, trotting, galloping, jumping and landing movements of 11 adult cats was undertaken to provide previously unavailable information concerning the demands imposed on the nervous system for the control of low and high speed movements and the demands imposed by such natural movements on muscle performance and proprioceptive response. With due regard for the swing (F and E1) and stance (E2 and E3) phases of the step cycle of an individual limb, single frame analysis of the film permitted measurement of instantaneous angles of the lower spine, hip, knee, ankle and metatarsophalangeal joints. Appropriate lever arm measurements were also made on 50 freshly dispatched cats and 25 cadavers such that the Law of Cosines could be used to calculate instantaneous lengths of select hind limb muscles that would apply to the natural movements of adult cats of small (1.5–2.5 Kg), intermediate (2.6–3.5 Kg) and large (3.6–4.5 Kg) size. Muscle displacements were analyzed relative to maximum and minimus in situ lengths and the lengths associated with quiet standing. Use was also made of a previous electromyographic analysis of hind limb muscles during unrestrained locomotion (Engberg and Lundberg, '69). The sequential relations between the four phases of the step cycle are maintained as forward speed increases from walking ( 16 mph). There are significant differences in the time consumed by each phase, however, with a greater reduction in the E3 phase, little reduction in the E2 and E1 phases and virtually no reduction in the F phase. When each phase is expressed as a relative percentage of the duration of the total step cycle, the greatest reduction is again in E3 with little change in the E2 phase. In contrast F and E1 phases increase in the percent of time they occur in each cycle, with the greatest increase in the F phase. For all speeds, analysis of the phase relations between movements of various sections of the hind limb revealed a remarkable unity of knee and ankle joint movement. The hip joint is largely out of phase with the knee and ankle during E1 and E2, all three joints being in phase in F and E3. The digits are essentially out of phase with the other joints except in the stance phase of the gallop. Rates and extents of muscle displacement during natural movements are greater than might be anticipated when expressed in absolute mm's and mm/sec but not when considered in relation to maximum and minimum in situ length and the length associated with quiet standing (Ls). During stepping a progressive increase in forward speed results in: (a) a greater usage of muscles at lengths between Ls and maximum in situ length; (b) for knee and ankle extensors, pronounced increase in the lengthening contraction associated with the E2 (yield) phase of step; and, (c) for both flexor and extensor muscles, an increased active phase of lengthening or near isometric contraction immediately prior to periods of active shortening. In contrast to these changes in active muscle status, the change from walking to galloping has little effect on the extent and rate of passive muscle displacements, particularly the F phase stretch of extensors. For the soleus muscle, calculations were made of the relation between changes in overall muscle length during natural movements and the length of the average muscle fiber and the tendon of insertion. These measurements revealed that the increases in fiber length when passive and decreases in length during active shortening are less than would be anticipated from the extensive liteature on extirpated fibers. In contrast, the increase in fiber length when active is greater than would be expected from the admittedly sparse literature on this subject. The results of this study are discussed largely in relation to two points of neurophysiological interest: the physiological range of muscle stretch as it pertains to the responsiveness of muscle spindles and tendon organs; and those mechanical aspects of lengthening contractions that give insight into the neural control of stepping. For exciting both spindles and tendon organs passive muscle stretch and shortening contractions are shown to be relatively ineffective and lengthening and isometric contractions particularly effective movements. It is suggested that, just as recent literature has emphasized the co-activation of efferent alpha and gamma motoneurons as a muscle becomes active, so too is there a synchronous activation of afferents, particularly the Ia and group II endings of muscle spindles and Ib endings of tendon organs. Finally the thesis is advanced that, while it has been convenient to separate E2 from E3 in the description of the stance phase of the step cycle, extensor muscles are actually undergoing a single mechanical event: an active stretch-shorten cycle for knee and ankle extensors and an active isometric-shorten cycle for hip extensors. This hypothesis has significant implications for the neural control program that regulates the stepping sequence in that it emphasizes the extent to which appropriate changes must be preprogrammed in the mechanical properties of muscles for the smooth execution of stepping.

The Discovery of America The first Americans may have swept the Western Hemisphere and decimated its fauna within 1000 years

Abstract: I propose a new scenario for the discovery of America. By analogy with other successful animal invasions, one may assume that the discovery of the New World triggered a human population explosion. The invading hunters attained their highest population density along a front that swept from Canada to the Gulf of Mexico in 350 years, and on to the tip of South America in roughly 1000 years. A sharp drop in human population soon followed as major prey animals declined to extinction. Possible values for the model include an average frontal depth of 160 kilometers, an average population density of 0.4 person per square kilometer on the front and of 0.04 person per square kilometer behind the front, and an average rate of frontal advance of 16 kilometers per year. For the first two centuries the maximum rate of growth may have equaled the historic maximum of 3.4 percent annually. During the episode of faunal extinctions, the population of North America need not have exceeded 600,000 people at any one time. The model generates a population sufficiently large to overkill a biomass of Pleistocene large animals averaging 9 metric tons per square kilometer (50 animal units per section) or 2.3 x 108 metric tons in the hemisphere. It requires that on the front one person in four destroy one animal unit (450 kilograms) per week, or 26 percent of the biomass of an average section in 1 year in any one region. Extinction would occur within a decade. There was insufficient time for the fauna to learn defensive behaviors, or for more than a few kill sites to be buried and preserved for the archeologist. Should the model survive future findings, it will mean that the extinction chronology of the Pleistocene megafauna can be used to map the spread of Homo sapiens throughout the New World.

Inner-Shell Vacancy Production in Ion-Atom Collisions

Abstract: Theoretical and experimental work relevant to the creation of atomic inner-shell vacancies in collisions of ions and atoms is reviewed. The experimental data on total excitation cross sections and electron and x-ray emission spectra are discussed in some detail. Energy loss data from inelastic scattering experiments involving heavy ions are also reviewed. An attempt is made to relate the different kinds of data to one another and to the available theoretical models. Excitation by the light ions (protons, alpha particles) has been well described theoretically in terms of perturbation by an incident point charge. However, no comprehensive model yet exists for the case of incident heavier ions, although the heavy-ion data for low collision velocities support an interpretation based on the formation of a transient quasimolecule. The literature has been reviewed to about April 1972.

Multivariate Analysis of Brand Loyalty for Major Household Appliances

Abstract: Two different measures of brand loyalty are employed in an analysis of survey data by MCA in which six hypotheses are tested. A measure based on brand deliberation as well as brand repurchase appea...

Minicells of Bacillus subtilis

Abstract: After nitrosoguanidine (N-methyl-N′-nitro-N-nitrosoguanidine) mutagenesis, two Bacillus subtilis mutants (div IV-A1 and div IV-B1) were isolated that are defective in the location of division site along cell length. Both mutations were transferred into strain CU403 by transformation, and their properties were studied in the CU403 genetic background. Location of divisions in close proximity to cell pole regions in both mutants results in minicell production. Purified minicells contain a ratio of ribonucleic acid to protein comparable to that found in the parent cells. Autoradiographs of 3H-thymine incorporation into deoxyribonucleic acid (DNA), thymine-2-14C incorporation into DNA, electron micrographs, and chemical analyses for DNA all fail to demonstrate DNA in the minicells. Minicells produced by both mutants are highly motile, an indication of functional energy metabolism. Electron micrographs reveal that minicells are produced by a structurally normal division mechanism and that minicells contain a normal cell surface. The div IV-A1 mutation has been mapped by PBS1 transduction linked to ura. The div IV-B1 mutation is closely linked to pheA by both PBS1 transduction and by co-transformation.

A New Global Climatic Model.

Abstract: A global climatic model, allowing for seasonal coupling and interaction between continents and oceans, is developed, utilizing an idealized land-water distribution similar to that observed. The basic equation used is the thermodynamic energy equation averaged over time and space. It is written and solved for the mean surface temperature separately for continents and oceans. A time step of one month is used. The vertical variations of temperature, specific humidity, and the zonal and meridional components of the wind velocity are parameterized. The surface velocity components are obtained from modified forms of the first two equations of motion. The model includes variable snow and ice cover, meridional transport of heat and water vapor by mean and eddy atmospheric circulations, storage and transport of heat by the oceans, the effect of aerosols on atmospheric turbidity, and the contribution of H2O, CO2, O3, and clouds to the infrared balance. Cloud cover, the surface relative humidity, and the su...

Non-Hodgkin's lymphomas. V. Results of radiotherapy.

Abstract: Four hundred and five patients with non-Hodgkin's lymphomas, referred between 1960 and 1971, were carefully evaluated for extent of disease prior to therapy. Tumors were histologically classified according to the criteria of Rappaport et al and patients staged by the criteria of the Ann Arbor Conference. Of 234 patients, Stages I-IIIE, 215 received initial radiotherapy, 91% with a curative intent. Follow-up time ranged from 1–12 years. Calculations were made of actuarial survival and disease-free-survival for each group of patients according to initial stage, histologic type of lymphoma, and type of radiotherapy. Patients with diffuse histiocytic (DH) lymphoma exhibited a 65% probability of tumor relapse during the first year of follow-up in contrast to the 19% probability for comparably staged patients with nodular mixed histiocytic-lymphocytic (NM) and nodular lymphocytic poorly differentiated (NLPD) lymphomas. Patients with diffuse mixed (DM), diffuse lymphocytic (DLPD), and nodular histiocytic (NH) lymphomas exhibited an intermediate risk of relapse during the first year (39-45%). Patients with NM and NLPD manifested a pattern of continued late relapse whereas those with DH lymphoma seldom experienced new evidence of tumor after the first year of disease-free observation. Patients with localized extralymphatic lymphoma (IE, IIE, IIIE) demonstrated patterns of clinical behavior following radiotherapy similar to those observed in patients whose lymphomas were confined to lymphatic tissue (I, II, III). The data offer strong support for the continued use of the Rappaport et al. histologic classification and the Ann Arbor clinical staging system in the radiotherapeutic managemement of patients with the non-Hodgkin's lymphomas.

Autoimmune disorders and malignant lymphoma.

Abstract: Autoimmune disorders of the Coombs' positive hemolytic anemia (AIHA) and idiopathic thrombocytopenic purpura (ITP) types were found in 11 (2.1%) of 515 patients with the non-Hodgkin's lymphomas. Four additional patients with Hodgkin's disease and similar disorders were included for analysis. In only two instances did the autoimmune disorder precede the lymphoma. AIHA was frequently associated with splenomegaly, constitutional symptoms, and, in eight of nine instances, far-advanced lymphomas of the diffuse histiocytic and diffuse histiocytic-lymphocytic types. In contrast, three of four patients who developed ITP had no evidence of active lymphoma at the onset of thrombocytopenia. The hemolysis of AIHA was most often controlled by splenectomy or corticosteroids with concurrent chemotherapy, but in all instances of either AIHA or ITP the prognosis clearly related to the underlying lymphoma and not the autoimmune disorder. No patient died of anemia, thrombocytopenia, or complications thereof. Based on this review, therapeutic guidelines for the management of these patients are proposed.

Differential Energy Spectra of Low-Energy (<8.5 MeV per Nucleon) Heavy Cosmic Rays during Solar Quiet Times

Abstract: Explorer 47 satellite observations of carbon, oxygen, and heavier nuclei differential energy spectra below 8.5 MeV/nucleon are presented for solar quiet time periods. A dE/dx vs E method for particle identification and energy determination was used. The instrumentation telescope included an isobutane proportional counter, a surface barrier Si detector, and a cylindrical plastic scintillator anticoincidence shield. The observations were performed outside the bow-shock and in the ecliptic plane. Results show an anisotropy of about 25% at 22 degrees west of the sun with a C/O ratio of 0.5 supporting a solar origin. The low energy portions of the C and O spectra have steep negative slopes, and the corresponding power law is given. Peculiarities in the O spectrum are discussed.

Minimal structural response under random excitation using the vibration absorber

Abstract: The equations of motion are derived for the first mode response of a linear multistorey structure having a linear vibration absorber attached to the roof. Furthermore, the variance of the first mode response to a gaussian white noise lateral base acceleration (as a model of earthquake excitation) is determined. Smallest possible values of the variance of the response along with corresponding absorber parameters are established using an optimization program. It is demonstrated that the absorber is quite effective in reducing first mode response for 5- and 10-storey structures even with relatively small values of the absorber mass. Moreover, minimal responses for the randomly excited single-degree-of-freedom system have been determined, and a design example is presented. The absorber system has potential application not only in earthquake engineering but also in aerospace and terrestrial vehicle design.

Refinement of the Kudo-Weill plagioclase thermometer and its application to basaltic rocks

Abstract: The Kudo-Weill plagioclase thermometer is applied to basaltic rocks. Comparison of measured and calculated crystallization temperatures shows that the latter are generally higher than measured values. The plagioclase thermometer predicts non-ideal behavoir of plagioclase solid solution and is in close agreement with experimental work at lower temperature. New equations are generated that relate plagioclase and melt chemistries to plagioclase crystallization temperatures; and these, combined with activity coefficient corrections, result in a refinement of the plagioclase thermometer.

Biological Activity of 1α-Hydroxycholecalciferol, A Synthetic Analog of the Hormonal Form of Vitamin D3

Abstract: 1,25-Dihydroxycholecalciferol, the apparent active hormonal form of cholecalciferol (vitamin D2), is formed from cholecalciferol by specific and sequential hydroxylations of the sterol at carbons 25 and 1. Recently, 1α-hydroxycholecalciferol was synthesized and we report on its biological activity in rachitic chicks. 1α-Hydroxycholecalciferol is identical in potency to 1,25-dihydroxycholecalciferol in stimulation of intestinal calcium absorption; either sterol elicits a near maximal effect at a dose of 0.3-0.6 nmol. The time-course of action of 1α-hydroxycholecalciferol also parallels that of the active metabolite 1,25-dihydroxycholecalciferol with a maximal increase in calcium transport occurring 5-10 hr after administration of sterol to vitamin D-deficient chicks. 6.5 nmol of 1α-hydroxycholecalciferol causes a doubling in calcium absorption in only 2-3 hr, which is the most rapid physiologic response yet detected for a vitamin D-sterol. 1α-Hydroxycholecalciferol is active also in enhancing bone calcium resorption and, like 1,25-dihydroxycholecalciferol, is at least 10 times as active as cholecalciferol in mobilizing bone calcium and raising plasma calcium concentration. It is concluded that 1α-hydroxycholecalciferol represents a synthetic analog of 1,25-dihydroxycholecalciferol that can be used both to study the mechanism of action of this hormone and as a therapeutic agent in the treatment of patients with certain metabolic bone diseases.

Time Constraints for Inter-Limb Co-Ordination in the Cat During Unrestrained Locomotion

Abstract: Unrestrained walking, trotting and galloping by adult cats is analyzed cinematographically. Classical models, which have previously characterized quadrupedal gait by “idealized” footfall formulas and support durations, can be revised from the present data to specifically describe cat locomotion. The number of limbs supporting the body weight and the sequence in which they are placed on the ground are largely a function of forward speed. Even within one gait and at a given speed, however, the same cat can be observed to vary its support pattern markedly in different strides, such as a transition in mid-flight from a rotatory to a transverse gallop. On the basis of these findings we then propose that, since locomotion can thrive under a variety of conditions both across and within gaits, the locomotor control program has facultative capability.

Suppression of lex Mutations Affecting Deoxyribonucleic Acid Repair in Escherichia coli K-12 by Closely Linked Thermosensitive Mutations

Abstract: A major class of ultraviolet (UV)-resistant derivatives of lex− strains of Escherichia coli K-12 grows normally at 30 C but at 42.5 C fails to produce colonies on complete or minimal agar. At 42.5 C these thermosensitive strains form filaments without septa, due to an apparent defect in cell division. Deoxyribonucleic acid degradation in UV-irradiated cultures of the thermosensitive strains is slow, in contrast to the rapid degradation in UV-irradiated cultures of the parental lex− strains. The thermosensitive mutations (tsl) are tightly linked (less than 0.04 min on the E. coli K-12 linkage map) to the site of the lex mutation in the parental strain and could lie within the same gene. The tsl+/tsl− heterozygotes grow at 42.5 C and are UV resistant when grown at 30 or 42.5 C. The tsl mutations are, therefore, recessive in contrast to lex mutations, which are dominant. It appears likely that the tsl mutations alter the diffusible product that gives rise to the Lex− mutant phenotype. This product appears to be necessary for deoxyribonucleic acid repair and cell division.

The Allocation of Effort Under Uncertainty: The Case of Risk-Averse Behavior

Abstract: This paper analyzes the labor supply decision of a single economic agent within the expected utility framework. Two formulations of the problem are considered: pure income uncertainty and wage rate uncertainty. In each case, the effects on the labor supply decision of changes in both expected returns and the dispersion of returns (about a constant mean) are investigated. Arguments concerning the "disincentive effects" of uncertainty are shown not to be unambiguously supported by theory.