Showing papers by "University of California, Davis published in 1983"

Incidence of Visual Field Loss in 20,000 Eyes and Its Relationship to Driving Performance

Abstract: Automated visual field screening of 10,000 volunteers (20,000 eyes) showed the incidence of visual field loss was 30% to 35% for persons aged 16 to 60 years but was approximately 130% for those older than 65 years Approximately half of the persons with abnormal visual fields were previously unaware of any problem with peripheral vision Follow-up results suggested that the most common causes of visual field loss were glaucoma, retinal disorders, and cataracts Drivers with binocular visual field loss had accident and conviction rates twice as high as those with normal visual fields Drivers with monocular visual field loss had accident and conviction rates equivalent to those of a control group Our results have important implications for mass visual field screening to detect eye diseases and for vision-related factors in traffic safety

Chloroplast DNA evolution and the origin of amphidiploid Brassica species.

Abstract: The origin and evolution of a hybrid species complex in the genus Brassica (cabbage, turnip, mustard, rapeseed oil) has been explored through mutational analysis of the maternally inherited chloroplast genome. A detailed chloroplast DNA phylogeny enables identification of the maternal parent for most of the amphidiploids examined and permits quantitative resolution of the relative time of hybridization as well as the relative divergence of the diploid parents. Contradictory chloroplast and nuclear phylogenies obtained for two accessions of the amphidiploid B. napus (rapeseed oil) lead to the hypothesis that introgressive hybridization has also figured in their recent evolution.

Nonequilibrium molecular dynamics via Gauss's principle of least constraint

Abstract: Gauss's principle of least constraint is used to develop nonequilibrium molecular-dynamics algo­ rithms for systems SUbject to constraints. The treatment not only includes "nonholonomic" constraints-those involving velocities-but it also provides a basis for simulating nonequilibrium steady states. We describe two applications of this new use of Gauss's principle. The first of these examples, the isothermal molecular dynamics of a three-particle chain, can be treated analytically. The second, the steady-state diffusiort~of a Lennard-Jones liquid, near its triple point, is studied nu­ merically. The measured diffusion coefficient agrees with inaependent estimates from eqUilibrium fluctuation theory and from Hamiltonian external fields. I. INTRODUCTION

Active damping in road vehicle suspension systems

Abstract: Low order, linearized dynamic models of road vehicle suspension systems are analyzed to provide insight into the benefits of suspensions incorporating generalized velocity feedback compared with conventional passive suspensions. Damping forces from passive dampers are supplemented by forces generated by an active element requiring a power supply. A simple criterion is developed which indicates whether or not the introduction of activedamping forces will result in significant benefit for pneumatic tired vehicles. An extended active suspension concept involving a high-gain load leveler as well as active damping is analyzed. The realization of active or semi-active damping forces through electrical or hydraulic means is briefly discussed.

Thermodynamic binding constants for gallium transferrin.

Abstract: Gallium-67 is widely used as an imaging agent for tumors and inflammatory abscesses. It is well established that Ga3+ travels through the circulatory system bound to the serum iron transport protein transferrin and that this protein binding is an essential step in tumor localization. However, there have been conflicting reports on the magnitude of the gallium-transferrin binding constants. Therefore, thermodynamic binding constants for gallium complexation at the two specific metal binding sites of human serum transferrin at pH 7.4 and 5 mM NaHCO3 have been determined by UV difference spectroscopy. The conditional constants calculated for 27 mM NaHCO3 are log K1 = 20.3 and log K2 = 19.3. These results are discussed in relation to the thermodynamics of transferrin binding of Fe3+ and to previous reports on gallium binding. The strength of transferrin complexation is also compared to that of a series of low molecular weight ligands by using calculated pM values (pM = -log [Ga-(H2O)6]) to express the effective binding strength at pH 7.4.

Testing the stochastic structure of production: a flexible moment-based approach

Abstract: Conventional production function specifications are shown to impose restrictions on the probability distribution of output that cannot be tested with the conventional models. These restrictions have important implications for firm behavior under uncertainty. A flexible representation of a firm's stochastic technology is developed based on the moments of the probability distribution of output. These moments are a unique representation of the technology and are functions of inputs. Large-sample estimators are developed for a linear moment model that is sufficiently flexible to test the restrictions implied by conventional production function specifications. The flexible moment-based approach is applied to milk production data. The first three moments of output are statistically significant functions of inputs. The cross-moment restrictions implied by conventional models are rejected.

English Workers’Living Standards During the Industrial Revolution: A New Look*

Abstract: T he politically charged debate over workers' living standards during the Industrial Revolution' deserves renewal with the appearance of fresh data or new perspectives. This paper mines an expanding data base and emerges with a far clearer picture of workers' fortunes after I750. While optimists and pessimists can both draw support from the enterprise, the pessimists' case emerges with the greater need for redirection and repair. The evidence suggests that material gains were even bigger after I 820 than optimists had previously claimed, even if the concept of material well-being is expanded

The light environment and growth of C3 and C4 tree species in the understory of a Hawaiian forest.

Abstract: The light environment in the understory of a Hawaiian forest containing a C4 tree species, Euphorbia forbesii, was characterized using photosynthetic photon flux density sensors connected to portable data acquisition systems and a strip chart recorder, and hemispherical “fisheye” photographs of the canopy During July 1980, 86 μmol cm2 day1 was received in the understory of which approximately 40% was contributed by sunflecks The understory received 24% of the light reaching the top of the canopy Nearly all sunflecks had peak photon flux densities greater than 250 μmol m2 s1, but two-thirds were less than 05 min in length The number of minutes of sunflecks received per day at any site was highly variable, depending on cloudiness and the overstory canopy structure On a relatively clear day a 10-fold difference in the number of minutes of sunflecks was observed between sample sites Estimates obtained from hemispherical photographs were used to calculate the annual mean potential number of minutes of sunflecks per day received by saplings of Euphorbia and a C3 tree species, Claoxylon sandwicense The growth of saplings of both species was highly correlated with the estimates of the minutes of sunflecks and was similar for both species Although C4 photosynthesis is usually found in plants native to high-light environments, it does not appear to confer any disadvantage in terms of growth to Euphorbia forbesii in the low-light conditions of the forest understory

Hydrogen isotopic evidence of rhyolitic magma degassing during shallow intrusion and eruption

Abstract: Deuterium and water contents of rhyolite obsidian tephra clasts and lava flows sampled in the western USA decrease within each eruptive sequence, from D- and H2O-rich, explosive (Plinian) eruptions, to D- and H2O-depleted lava flows. These changes result not from volatile gradients in the magma, but rather from progressive in situ degassing; involvement of meteoric water is excluded.

Structure of the Reynolds Stress in a Canopy Layer

Abstract: The u, w velocity covariance above and within a plant canopy (Zea mays L) was examined using the technique of quadrant analysis to separate the momentum transport into events classified as sweep, ejection, and outward and inward interactions. A hyperbolic hole of variable size acted as an excluded region in the u, w domain to asses the relative importance of short-lived events of large magnitude. The results of the analysis were a reasonably close match to rough-wall wind tunnel studies but differed in some respects from a similar experiment performed elsewhere in a flexible wheat canopy. Generally, sweeps exceeded ejections in their contribution to the Reynolds stress, especially at mid-canopy, while the interaction events were of minor importance. Sweeps that were large in magnitude relative to the time-averaged stress were evident at all levels and were intermittent in character. Compared with the layers above, the effect of the canopy was to increase the dominance of sweeps over ejections and...

The Mineralogy, Chemistry, and Physics of Tropical Soils With Variable Charge Clays

Abstract: This book is the culmination of an effort started in 1974 when the senior author started assembling information for a tropical soils course that he taught while on sabbatical leave at North Carolina State University. The literature cited throughout the book was current when the book went to press. Soil systems contain mineral and organic materials that have constant or permanent surface charges, such as montmorillonite, or constant surface potentials, usually referred to as variable charge materials. Most soil systems contain some of both kinds. In the tropics, most of the minerals with permanent charge have been severely weathered. Consequently, the surface charge of the remaining material results from adsorption of potential determining ions. This book treats the mineralogy, chemistry, and physics of the variable charge minerals and soil organic matter.

Clumping Patterns of Fruit and Arthropods in Cotton, with Implications for Binomial Sampling

Abstract: A binomial model is presented which enables the clumping patterns of different species or categories of cotton arthropods and plant parts to be compared, accounting for the effect of their densities. Estimates of the proportion of infested sample units derived with this model are compared with those derived with three other binomial models. Statistical comparison is made, using as a criterion the degree to which each model fit field values of the proportion of infested sample units collected by three sampling methods (visual whole-plant examination, a bag method, and sweep-net). Those models which fail to incorporate the effect of density on clumping behavior fit the data less well. Estimates of sample sizes derived by a binomial sample size equation and a numerical sample size equation both of which incorporate species clumping behavior are also compared. The sample size estimates from the two equations are most similar at low densities and for species whose distributions appear closest to random; and although binomial sampling requires a larger sample size at higher densities, less time is required to sample each unit (leaf, plant, etc.).

The timing and sequence of events in the development of the human reproductive system during the embryonic period proper

Abstract: A documented scheme of the early development of the human reproductive system is presented. It is based on (1) reports of workers who personally studied staged embryos, and (2) personal observations and confirmations. The necessity of using staged embryos in order to determine the precise sequence of developmental events is stressed.

Nonequilibrium Molecular Dynamics

Abstract: MOLECULAR DYNAMICS has been generalized in order to stimulate a variety of NONEQUILIBRIUM systems This generalization has been achieved by adopting microscopic mechanical definitions of macroscopic thermodynamic and hydrodynamic variables, such as temperature and stress Some of the problems already treated include rapid plastic deformation, intense heat conduction, strong shockwaves simulation, and far-from-equilibrium phase transformations Continuing advances in technique and in the modeling of interatomic forces, coupled with qualitative improvements in computer hardware, are enabling such simulations to approximate real-world microscale and nanoscale experiments

Potassium Transport in Corn Roots : II. The Significance of the Root Periphery.

Abstract: The relative transport capabilities of the cells of the root periphery and cortex were investigated using a variety of experimental techniques. Brief (30 seconds to 1 minute) exposures with the penetrating sulfhydryl reagent, N-ethyl maleimide (NEM), and the impermeant reagent, p-chloromercuribenzene sulfonic acid (PCMBS), dramatically reduced (86)Rb(+) (0.2 millimolar RbCl) uptake into 2 centimeter corn (Zea mays [A632 x (C3640 x Oh43)]) root segments. Autoradiographic localization studies with [(3)H]NEM and [(203)Hg]PCMBS demonstrated that, during short term exposures with either reagent, sulfhydryl binding occurred almost exclusively in the cells of the root periphery.Corn root cortical protoplasts were isolated, and exhibited significant K(+)((86)Rb(+)) influx. The kinetics for K(+) uptake were studied; the influx isotherms were smooth, nonsaturating curves that approached linearity at higher K(+)(Rb(+)) concentrations (above 1 millimolar K(+)). These kinetics were identical in shape to the complex kinetics previously observed for K(+) uptake in corn roots (Kochian, Lucas 1982 Plant Physiol 70: 1723-1731), and could be resolved into a saturable and a first order kinetic component.The existence of a hypodermal apoplastic barrier was investigated. The apoplastic, cell wall binding dye, Calcofluor White M2R, appeared to be excluded from the cortex by the hypodermis. However, experiments with damaged roots indicated that this result may be an artifact resulting from the binding of dye to the epidermal cell walls. Furthermore, [(203)Hg] PCMBS autoradiography demonstrated that the hypodermis was not a barrier to apoplastic movement of PCMBS.These results suggest that although cortical cells possess the capacity to absorb ions, K(+) influx at low concentrations is limited to the root periphery. Cortical cell uptake appears to be repressed under these conditions. At higher concentrations, cortical cells may function to absorb K(+). Such a model may involve regulation of cortical cell ion transport capacity.

Algae-grazing minnows (Campostoma anomalum), piscivorous bass (Micropterus spp.), and the distribution of attached algae in a small prairie-margin stream

Abstract: Campostoma anomalum is an algae-grazing minnow, abundant in many streams of the central and eastern United States. In a small stream in south-central Oklahoma, Campostoma has a marked impact on standing crops of attached algae. Pools with schools of Campostoma are barren, while pools in which Campostoma are apparently excluded by bass (Micropterus salmoides or M. punctulatus) support large standing crops of filamentous green algae (predominantly Spirogyra sp. and Rhizoclonium sp.). Campostoma grazed actively on algae-covered cobbles transferred into their pools, and visibly reduced standing crops within one hour. After 24 h of exposure to Campostoma, standing crops of attached algae on cobbles were reduced from 22.0 to 6.3 mg ash-free dry weight cm-2. When a largemouth bass was tethered in a pool with Campostoma, the minnows did not graze on algae-covered cobbles within 30-50 cm of the bass, but fed actively on cobbles that were more than 1.3 m away. These results indicate that interactions of Campostoma and their predators may be an important factor contributing to pool-to-pool variation in attached algae in small streams of the central and eastern United States.

Convex Bodies of Constant Width

Abstract: A spherical ball obviously has the property that it can be arbitrarily rotated between two fixed parallel planes without losing contact with either plane. It has been known for a long time, certainly since the time of Euler, that there are other convex bodies with the same property. Such bodies are called convex bodies of constant width. Other names that have also been used are ‘convex bodies of constant breadth’, ‘equiwide convex bodies’, ‘orbiforms’ and ‘spheroforms’ (in the two and three-dimensional case, respectively) and several more; the occasionally used German ‘Gleichdick’ being one of the most charming.