Showing papers by "University of Florida published in 1976"

Properties and management of soils in the tropics.

Abstract: The long-awaited second edition of this classic textbook expands on the first edition to include advances made in the last four decades, bringing the topic completely up to date. The book addresses critical issues such as whether humanity can feed itself, and whether it can do so in environmentally sound and sustainable ways. Written from agronomic, environmental, and ecological standpoints, the textbook employs a multidisciplinary approach, including policymaking and plant genetic improvements, as well as ecosystem services, climate change, biodiversity, sustainability and resilience. New chapters in this second edition focus on organic carbon in soil, soil biology, soils in relation to livestock production and forestry, and agroforestry. The new edition will again be the go-to textbook for courses on tropical soils, and a reference textbook for soil and agricultural scientists and development professionals working in the tropics.

A Modified Sine Wave Method for Calculating Degree Days

Abstract: A FORTRAN program is described which uses maximum and minimum temperatures to compute heating and cooling degree days (between and below thresholds, respectively). The temperature cycle is assumed to be a sine wave in which the 1st and 2nd minimum are not necessarily the same. The method is compared With actual planimeter measurements from hygrothermograph charts from Alaska, Arizona, Florida, and Michigan. The data suggest that the bias incurred from the sine wave assumption is somewhat specific to geographical areas. No effect of day length was observed, but in Florida the sine wave method tended to overestimate degree days. A method of correcting for local bias using linear regression is described.

Plant tissue culture media.

Abstract: Plant tissue culture techniques have become vitally important for pursuing a wide range of fundamental and applied problems in research and development. The techniques encompass a variety of procedures used for specific purposes. The growing of masses of unorganized cells (callus) on agar or in liquid suspension is widely employed in biochemical and growth studies (1-5). The culture of segments of stems, roots, leaves or of callus provides systems to study differentiation, morphogenesis and plant regeneration (6, 7). Shoot apex culture methods leading to plant regeneration have been adopted for plant propagation and production of virusfree stock (8). The culture of anthers and pollen provides new approaches to haploid plant formation (9). Recently the technology has been extended to include the isolation and culture of plant protoplasts which are employed in fusion and somatic cell hybridization (10-13). The development of the various types of tissue culture has been based on empirical approaches, and some of the observations recorded in the literature may not be typical for plant cells. Differences in medium, environment, age, cell origin, and growth rates may explain the behavior of a particular line and need not represent a general characteristic of plant cells in culture. More uniformity in conditions of culture would assist in making data and observations more comparable.

The unwillingness‐to‐communicate scale: Development and validation

Abstract: The construct of unwillingness to communicate represents a global predisposition to avoid communication, whether due to apprehension, alienation, low self‐esteem, introversion, or other causes. The lines of research supporting the existence of the construct are discussed. The program of research leading to the present form of the Unwillingness‐to‐Communicate Scale is reported, including results of two studies that have provided reliability and validity data. Based on factor analysis results, a 20‐item instrument with two factors, reward and approach‐avoidance, is recommended for research use.

Patterns of recurrence following surgery alone for adenocarcinoma of the colon and rectum

Abstract: Two hundred and eighty patients with previously untreated large bowel adenocarcinoma were retrospectively evaluated following complete primary resection to determine patterns of recurrence. One hundred and five patients (37%) subsequently developed recurrent disease. Sixty percent (63/105) presented with local recurrence alone, 14% (15/105) with concomitant local recurrence and distant metastases, and 26% (27/105) with distant metastases alone. Ninety-two percent of local recurrences developed in structures contiguous to the operative area of the incision. The degree of tumor anaplasia and depth of tumor penetration into the bowel wall influenced the rate of local recurrence. Through 5 years, local recurrence without clinical evidence of distant metastases was the most common cause of death. Plans for adjuvant radiation therapy are discussed.

Origin and early evolution of angiosperms

Abstract: Contributions from paleobotany, phylogenetics, genomics, developmental biology, and developmental genetics have yielded tremendous insight into Darwin’s “abominable mystery”—the origin and rapid diversification of the angiosperms. Analyses of morphological and molecular data reveal a revised “anthophyte clade” consisting of the fossils glossopterids, Pentoxylon, Bennettitales, and Caytonia as sister to angiosperms. Molecular estimates of the age of crown group angiosperms have converged on 140– 180 million years ago (Ma), older than the oldest fossils (132 Ma), suggesting that older fossils remain to be discovered. Whether the first angiosperms were forest shrubs (darkand-disturbed hypothesis) or aquatic herbs (wet-and-wild hypothesis) remains unclear. The near-basal phylogenetic position of Nymphaeales (water lilies), which may include the well-known fossil Archaefructus, certainly indicates that the aquatic habit arose early. After initial, early “experiments,” angiosperms radiated rapidly (≤5 million years [Myr]), yielding the five lineages of Mesangiospermae (magnoliids and Chloranthaceae as sisters to a clade of monocots and eudicots + Ceratophyllaceae). This radiation ultimately produced approximately 97% of all angiosperm species. Updated estimates of divergence times across the angiosperms conducted using nonparametric rate smoothing, with one or multiple fossils, were older than previous reports, whereas estimates using PATHd8 were typically younger. Virtually all angiosperm genomes show evidence of whole-genome duplication, indicating that polyploidy may have been an important catalyst in angiosperm evolution. Although the flower is the central feature of the angiosperms, its origin and subsequent diversification remain major questions. Variation in spatial expression of floral regulators may control major differences in floral morphology between basal angiosperms and eudicot models.

Body weight, diet and home range area in primates

Abstract: Primates show a strong positive relationship between body weight and home range area. Dietary habits also influence home range area. Folivorous primates occupy smaller home range areas for their body weight than do frugivores and omnivores. Primates generally require smaller home range area per individual than solitary terrestrial mammals, but primates living in social groups have much larger total home range than individual solitary mammals. This trend may necessitate higher expenditures of energy in food-gathering or modifications in movement patterns.

Comparison of the photosynthetic characteristics of three submersed aquatic plants.

Abstract: Light- and CO(2)-saturated photosynthetic rates of the submersed aquatic plants Hydrilla verticillata, Ceratophyllum demersum, and Myriophyllum spicatum were 50 to 60 mumol O(2)/mg Chl.hr at 30 C. At air levels of CO(2), the rates were less than 5% of those achieved by terrestrial C(3) plants. The low photosynthetic rates correlated with low activities of the carboxylation enzymes. In each species, ribulose 1,5-diphosphate carboxylase was the predominant carboxylation enzyme. The apparent K(m)(CO(2)) values for photosynthesis were 150 to 170 mum at pH 4, and 75 to 95 mum at pH 8. The K(m)(CO(2)) of Hydrilla ribulose 1,5-diphosphate carboxylase was 45 mum at pH 8. Optimum temperatures for the photosynthesis of Hydrilla, Myriophyllum, and Ceratophyllum were 36.5, 35.0, and 28.5 C, respectively. The apparent ability of each species to use HCO(3) (-) ions for photosynthesis was similar, but at saturating free CO(2) levels, there was no indication of HCO(3) (-) use. Increasing the pH from 3.1 to 9.2 affected the photosynthetic rate indirectly, by decreasing the free CO(2). With saturating free CO(2) (0.5 mm), the maximum photosynthetic rates were similar at pH 4 and 8. Carbonic anhydrase activity, although much lower than in terrestrial C(3) plants, was still in excess of that required to support HCO(3) (-) utilization.Hydrilla and Ceratophyllum had CO(2) compensation points of 44 and 41 mul/l, respectively, whereas the value for Myriophyllum was 19. Relatively high CO(2) compensation points under 1% O(2) indicated that some "dark" respiration occurred in the light. The inhibition of photosynthesis by O(2) was less than with terrestrial C(3) plants. Glycolate oxidase activity was 12.3 to 27.5 mumol O(2)/mg Chl.hr, as compared to 78.4 for spinach. Light saturation of photosynthesis occurred at 600 to 700 mueinsteins/m(2).sec in each species grown under full sunlight. Hydrilla had the lowest light compensation point, and required the least irradiance to achieve the half-maximal photosynthetic rate.Field measurements in a Hydrilla mat indicated that in the afternoon, free CO(2) dropped to zero, and O(2) rose to over 200% air saturation. Most photosynthetic activity occurred in the morning when the free CO(2) was highest and O(2) and solar radiation lowest. The low light requirement of Hydrilla probably provides a competitive advantage under these field conditions.

Toward a theory of personal space expectations and their violations

Abstract: Proxemics literature is synthesized and placed in a theoretical framework based on norms and expectations. Two major and three subordinate propositions are supported, and a model for predicting effects of violations of proxemic expectations is advanced. A sample of hypotheses generated from the model is included.

A Gated, Wideband Magnetic Direction Finder for Lightning Return Strokes

Abstract: A magnetic direction finder has been developed which utilizes only the initial few microseconds of wideband return stroke waveforms to provide accurate directions to the channel bases of lightning discharges to ground. Bearing errors are minimized because, near the ground, most channels tend to be straight and vertical with no large branches or horizontal sections. Tests on a number of lightning storms at distances of 10 to 100 km indicate the angular resolution is in the range 1-2 deg, with little or no systematic dependence on azimuth or distance.

The influence of surface chemistry on implant interface histology: a theoretical basis for implant materials selection.

Abstract: A theory is proposed stating that an ideal implant material must have a dynamic surface chemistry that induces histological changes at the implant interface which would normally occur if the implant were not present. Evidence for the validity of this theory is provided with a series of bone-implant studies which result in stable interfacial osteogenesis under specific implant surface chemistry conditions. Insufficient or excess surface ion concentrations produce negative osteogenesis and fixation results. Implantation of osteogenic implants in soft tissues also produces undesirable histological responses as proposed in the theory. A variety of surface chemical analyses of the implant are reviewed which provide a scientific basis for the implant surface theory.

Clinical Evaluation of Freeze-dried Bone Allografts in Periodontal Osseous Defects*, †

Abstract: Freeze-dried cortical bone allografts of a fine particle size were implanted into wide three-wall, two-wall, one-wall, combination, and furcation defects. Of the 97 defects treated, 23 manifested complete bone regeneration; 39 showed greater than 50%; and 24, less than 50% osseous repair. Twelve defects failed to demonstrate any bony regeneration, of which nine were furcation involvements. From the preliminary data available, there is strong evidence which indicates that freeze-dried bone allografts have definite potential as grafting material in certain periodontal osseous defects. However, final determination must await the outcome of a larger number of cases and also histologic evidence.

Unstable angina pectoris: National cooperative study group to compare medical and surgical therapy

Abstract: A preliminary report is presented of a prospective randomized trial conducted by eight cooperative institutions under the auspices of the National Heart and Lung Institute to compare the effectiveness of medical and surgical therapy in the management of the acute stages of unstable angina pectoris. To date 150 patients have been included in the randomized trial, 80 assigned to medical and 70 to surgical therapy; the clinical presentation, coronary arterial anatomy and left ventricular function in the two groups are similar. Some physicians have been reluctant to prescribe medical or surgical therapy by a random process, and the ethical basis of the trial has been questioned. Since there are no hard data regarding the natural history and outcome of therapy for unstable angina pectoris, randomization appears to provide a rational way of selecting therapy. Furthermore, subsets of patients at high risk may emerge during the process of randomization. The design of this randomized trial is compared with that of another reported trial. Thus far, the study has shown that it is possible to conduct a randomized trial in patients with unstable angina pectoris, and that the medical and surgical groups have been similar in relation to the variables examined. The group as a whole presented with severe angina pectoris, either as a crescendo pattern or as new onset of angina at rest, and 84 percent had recurrence of pain while in the coronary care unit and receiving vigorous medical therapy. It is anticipated that sufficient patients will have been entered into the trial within the next 12 months to determine whether medical or surgical therapy is superior in the acute stages of unstable angina pectoris.

Auger Spectroscopic Analysis of Bioglass Corrosion Films

Abstract: Auger spectroscopy and ion beam milling were used to determine surface compositional profiles on a series of bioglass implant materials after exposure to simulated body conditions. Four glasses were examined, a soda-lime-silica glass and 3 compositions produced by adding 3, 6, and 12 wt% P2O5 to the ternary glass. An SiO2-rich layer is formed on the surface of all glasses investigated. As P2O5 is added to the bulk composition, a second film rich in Ca and P forms at the SiO2-rich film-water interface. The rate of formation of the Ca-P film increases as the P2O5 content of the bulk glass increases. When glasses are corroded under identical conditions, the thickness of the Ca-P layer increases as the P2O5 content of the bulk composition is increased.

Heat inactivation temperature‐time relationships for pectinesterase inactivation in citrus juices

Abstract: The necessary pasteurization temperature, F and z values for pectinesterase inactivation were developed for three varieties of orange juices and one grapefruit juice. Since common commercial practice involves blending various orange varieties, the recommended conditions are those for the most heat resistant variety. For an FT=1.0 min, the recommended processes are T = 194°F with z = 12.2 for orange juice and T = 186°F with z = 9.3 for grapefruit juice.

On Invariants, Canonical Forms and Moduli for Linear, Constant, Finite Dimensional, Dynamical Systems

Abstract: A linear, constant, finite dimensional dynamical system is thought of as being represented by a triple of matrices (F,G,H), where F is an n × n matrix, G an n × m matrix, and H an p × n matrix; i.e. there are m inputs, p outputs and the state space dimension is n. The dynamical system itself is $$ \mathop {\text{x}}\limits^. = {\text{Fx}}\;{\text{ + }}\;{\text{Gu,}}\;{\text{y}}\;{\text{ = }}\;{\text{Hx}} $$ (1.1) or, if one prefers discrete time systems $$ {{\text{x}}_{{\text{t}} + 1}} = {\text{F}}{{\text{x}}_{\text{t}}}\;{\text{ + }}\;{\text{G}}{{\text{u}}_{\text{t}}}{\text{,}}\;{{\text{y}}_{\text{t}}}\;{\text{ = }}\;{\text{H}}{{\text{x}}_{\text{t}}} $$ (1.2) A change of coordinates in state space changes the triple of matrices (F,G,H) into the triple (SFS-1, SG, HS-1). Let DS denote the space of all triples (F,G,H); i.e. DS is affine space of dimension np + n2 + nm.

Nitrogen Fixation in Grasses Inoculated with Spirillum lipoferum

Abstract: Field-grown pearl millet (Pennisetum americanum) and guinea grass (Panicum maximum), lightly fertilized and inoculated with Spirillum lipoferum, produced significantly higher yields of dry matter than did uninoculated controls. Up to 42 and 39 kilograms of nitrogen per hectare were replaced by inoculation for pearl millet and guinea grass, respectively. The data demonstrate that nitrogen fixation by these grass-Spirillum systems is efficient and is achieved at a reasonable energy cost to the plant.

Inhibition by anions of human red cell carbonic anhydrase B: physiological and biochemical implications.

Abstract: The hydration rate of CO2 catalyzed by human red cell carbonic anhydrase B is 92 percent reduced by the normal concentrations of chloride and bicarbonate in red cells. This reflects a general sensitivity of this reaction to halides and other anions, up to 87 times greater than the effect on red cell carbonic anhydrase C. The catalytic hydration of CO2 is generally more (up to 24 times) sensitive to inhibition by anions and sulfonamides than the dehydration of HCO3-, probably reflecting different mechanisms. The sensitivity of enzyme B to anion inhibition also depends upon the substrate, being much greater for CO2 than for certain esters. On the basis of the very low catalytic activity of B for CO2 in the presence of physiological concentration of chloride, and the fact that carbonic anhydrase C is effective for CO2 hydration (in the presence of chloride) at a rate 340 times greater than that of CO2 output from tissues, it appears that the biological role of enzyme B is not that of a carbonic anhydrase.

Chemical and mechanical behavior of bioglass-coated alumina.

Abstract: This work has shown that it is possible to produce a bioglass-coated, high-strength, fully dense alumina implant system with a variable surface reactivity. Furthermore, it has been demonstrated that this system will bond with bone. These two factors, plus the inherent strength of the dense alumina, make this system an attractive candidate as a new prosthetic material.

Ecology of a Pleistocene Relict, the Western Big-Eared Rat (Plecotus townsendii), in the Southern Great Plains

Abstract: In karst regions of western Oklahoma and Kansas, Plecotus townsendii is locally ubiquitous but low in density. Natality is low but reproductive effort and preweaning survival of young are comparatively high. Movement data show no consistent pattern of dispersal that would account for a low density. P. townsendii uses nursery roosts that are marginal or uninhabitable for locally sympatric cave-dwelling species. Reproductive success depends on the ability of individuals in small nursery colonies to maintain a high degree of thermal exchange during pregnancy and lactation. This is facilitated by the formation of dense clusters in which metabolic heat is shared directly by body contact. In our judgment, the selection of intrinsically warm nursery sites is essential for reproductive success. In early and late winter most P. townsendii are absent from caves; presumably they occupy alternate roosts and forage on warm evenings. These bats seem to require relatively cold temperatures to hibernate. In autumn and early winter some individuals hibernate singly near cave entrances where ambient temperatures are variable but cool cave rock stabilizes body temperatures. By midwinter, these sites reach subfreezing temperatures and many bats move deep into caves, where they may form clusters. Both sexes lose over half their body weight before spring. Owing to this large weight loss, susceptibility to predation in midwinter, and probable late winter foraging efforts, we suspect substantial winter mortality as the prevailing limiting factor. The relictual nature of populations in the southern plains is made comprehensible by the species' reproductive, dispersal, and hibernating performance. From this ecological performance we infer that P. townsendii occurred across the southern United States during the Wisconsin glaciation, when numerous trees grew on the southern plains and the climate was moist with short, cool summers and long, mild winters. The present isolated taxa use caves as refugia from intolerable post-Pleistocene winters. The small size of P. townsendii populations, rather severe ecological limitations, and high sensitivity to disturbance lead us to conclude that visitation of nurseries by humans could threaten the species' survival in the Great Plains.